release: 0.2.5

Signed-off-by: Ophestra Umiker <cat@ophivana.moe>

.gitea/workflows/nix.yml

@@ -0,0 +1,46 @@
+name: Nix
+
+on:
+  - push
+  - pull_request
+
+jobs:
+  tests:
+    name: NixOS tests
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+
+      - name: Install Nix
+        uses: cachix/install-nix-action@08dcb3a5e62fa31e2da3d490afc4176ef55ecd72 # v30
+        with:
+          # explicitly enable sandbox
+          install_options: --daemon
+          extra_nix_config: |
+            sandbox = true
+            system-features = nixos-test benchmark big-parallel kvm
+          enable_kvm: true
+
+      - name: Ensure environment
+        run: >-
+          apt-get update && apt-get install -y sqlite3
+        if: ${{ runner.os == 'Linux' }}
+
+      - name: Restore Nix store
+        uses: nix-community/cache-nix-action@v5
+        with:
+          primary-key: nix-${{ runner.os }}-${{ hashFiles('**/*.nix') }}
+          restore-prefixes-first-match: nix-${{ runner.os }}-
+
+      - name: Run tests
+        run: |
+          nix --print-build-logs --experimental-features 'nix-command flakes' flake check --all-systems
+          nix build --out-link "result" --print-out-paths --print-build-logs .#checks.x86_64-linux.nixos-tests
+
+      - name: Upload test output
+        uses: actions/upload-artifact@v3
+        with:
+          name: "result"
+          path: result/*
+          retention-days: 1

.gitea/workflows/release.yml

@@ -1,4 +1,4 @@
-name: release
+name: Create distribution
 
 on:
   push:
@@ -7,32 +7,47 @@ on:
 
 jobs:
   release:
+    name: Release
     runs-on: ubuntu-latest
+    container:
+      image: node:16-bookworm-slim
     steps:
+      - name: Get dependencies
+        run: >-
+          echo 'deb http://deb.debian.org/debian bookworm-backports main' >> /etc/apt/sources.list.d/backports.list &&
+          apt-get update &&
+          apt-get install -y
+          acl
+          git
+          gcc
+          pkg-config
+          libwayland-dev
+          wayland-protocols/bookworm-backports
+          libxcb1-dev
+          libacl1-dev
+        if: ${{ runner.os == 'Linux' }}
+
       - name: Checkout
         uses: actions/checkout@v4
         with:
           fetch-depth: 0
-      - name: Set up go
+
+      - name: Setup go
         uses: https://github.com/actions/setup-go@v5
         with:
-          go-version: '>=1.20.1'
+          go-version: '>=1.23.0'
-      - name: Get dependencies
+
+      - name: Go generate
         run: >-
-          sudo apt-get update &&
+          go generate ./...
-          sudo apt-get install -y
+
-          gcc
+      - name: Build for release
-          pkg-config
+        run: FORTIFY_VERSION='${{ github.ref_name }}' ./dist/release.sh
-          libacl1-dev
+
-        if: ${{ runner.os == 'Linux' }}
-      - name: Build for Linux
-        run: >-
-          sh -c "go build -v -ldflags '-s -w -X main.Version=${{ github.ref_name }}' -o bin/ego &&
-          sha256sum --tag -b bin/ego > bin/ego.sha256"
       - name: Release
         id: use-go-action
         uses: https://gitea.com/actions/release-action@main
         with:
           files: |-
-            bin/**
+            dist/fortify-**
           api_key: '${{secrets.RELEASE_TOKEN}}'

.gitea/workflows/test.yml

@@ -0,0 +1,62 @@
+name: Tests
+
+on:
+  - push
+  - pull_request
+
+jobs:
+  test:
+    name: Go tests
+    runs-on: ubuntu-latest
+    container:
+      image: node:16-bookworm-slim
+    steps:
+      - name: Enable backports
+        run: >-
+          echo 'deb http://deb.debian.org/debian bookworm-backports main' >> /etc/apt/sources.list.d/backports.list
+        if: ${{ runner.os == 'Linux' }}
+
+      - name: Ensure environment
+        run: >-
+          apt-get update && apt-get install -y curl wget sudo libxml2
+        if: ${{ runner.os == 'Linux' }}
+
+      - name: Get dependencies
+        uses: awalsh128/cache-apt-pkgs-action@latest
+        with:
+          packages: acl git gcc pkg-config libwayland-dev wayland-protocols/bookworm-backports libxcb1-dev libacl1-dev
+          version: 1.0
+          #execute_install_scripts: true
+        if: ${{ runner.os == 'Linux' }}
+
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Setup go
+        uses: https://github.com/actions/setup-go@v5
+        with:
+          go-version: '>=1.23.0'
+
+      - name: Go generate
+        run: >-
+          go generate ./...
+
+      - name: Run tests
+        run: >-
+          go test ./...
+
+      - name: Build for test
+        id: build-test
+        run: >-
+          FORTIFY_VERSION="$(git rev-parse --short HEAD)"
+          bash -c './dist/release.sh &&
+          echo "rev=$FORTIFY_VERSION" >> $GITHUB_OUTPUT'
+
+      - name: Upload test build
+        uses: actions/upload-artifact@v3
+        with:
+          name: "fortify-${{ steps.build-test.outputs.rev }}"
+          path: dist/fortify-*
+          retention-days: 1

.gitignore

@@ -4,7 +4,7 @@
 *.dll
 *.so
 *.dylib
-/ego
+/fortify
 
 # Test binary, built with `go test -c`
 *.test
@@ -23,3 +23,9 @@ go.work.sum
 .env
 .idea
 .vscode
+
+# go generate
+security-context-v1-protocol.*
+
+# release
+/dist/fortify-*

README.md

@@ -1,83 +1,162 @@
-ego (the Go side)
+Fortify
-=================
+=======
 
-[![Go Reference](https://pkg.go.dev/badge/git.ophivana.moe/cat/ego.svg)](https://pkg.go.dev/git.ophivana.moe/cat/ego)
+[![Go Reference](https://pkg.go.dev/badge/git.gensokyo.uk/security/fortify.svg)](https://pkg.go.dev/git.gensokyo.uk/security/fortify)
+[![Go Report Card](https://goreportcard.com/badge/git.gensokyo.uk/security/fortify)](https://goreportcard.com/report/git.gensokyo.uk/security/fortify)
 
-> Do all your games need access to your documents, browser history, SSH private keys?
+Lets you run graphical applications as another user in a confined environment with a nice NixOS
->
+module to configure target users and provide launchers and desktop files for your privileged user.
-> ... No? Just run `ego steam`!
 
-**Ego** is a tool to run Linux desktop applications under a different local user. Currently
+Why would you want this?
-integrates with Wayland, Xorg, PulseAudio and xdg-desktop-portal. You may think of it as `xhost`
-for Wayland and PulseAudio. This is done using filesystem ACLs and X11 host access control.
 
-Disclaimer: **DO NOT RUN UNTRUSTED PROGRAMS VIA EGO.** However, using ego is more secure than
+- It protects the desktop environment from applications.
-running applications directly under your primary user.
 
-Differences
+- It protects applications from each other.
------------
-* Written in Go
-* Tracks process states
-* Cleans up after last process exits
-* Argv preservation in machinectl mode
-* Has no dependencies other than the two C libraries
 
-Manual setup
+- It provides UID isolation on top of the standard application sandbox.
-------------
-Ego aims to come with sane defaults and be easy to set up.
 
-**Requirements:**
+If you have a flakes-enabled nix environment, you can try out the tool by running:
-* Sudo
-* A C compiler
-* [Go](https://go.dev/doc/install)
-* `libacl.so` library (Debian/Ubuntu: libacl1-dev; Fedora: libacl-devel; Arch: acl)
-* `libxcb.so` library (Debian/Ubuntu: libxcb1-dev; Fedora: libxcb-devel; Arch: libxcb)
 
-**Recommended:** (Not needed when using `--sudo` mode, but some desktop functionality may not work).
+```shell
-* `machinectl` command (Debian/Ubuntu/Fedora: systemd-container; Arch: systemd)
+nix run git+https://git.gensokyo.uk/security/fortify -- help
-* `xdg-desktop-portal-gtk` (Debian/Ubuntu/Fedora/Arch: xdg-desktop-portal-gtk)
-
-**Installation:**
-
-1. Run in repository worktree:
-
-       go build -v -ldflags '-s -w'
-       sudo cp ego /usr/local/bin/
-
-2. Create local user named "ego": <sup>[1]</sup>
-
-       sudo useradd ego --uid 155 --create-home
-
-3. That's all, try it:
-
-       ego xdg-open .
-
-[1] No extra groups are needed by the ego user.
-UID below 1000 hides this user on the login screen.
-
-### Avoid password prompt
-If using "machinectl" mode (default if available), you need the rather new systemd version >=247
-and polkit >=0.106 to do this securely.
-
-Create file `/etc/polkit-1/rules.d/50-ego-machinectl.rules`, polkit will automatically load it
-(replace `$USER` with your own username):
-
-```js
-polkit.addRule(function(action, subject) {
-    if (action.id == "org.freedesktop.machine1.host-shell" &&
-        action.lookup("user") == "ego" &&
-        subject.user == "$USER") {
-            return polkit.Result.YES;
-    }
-});
 ```
 
-##### sudo mode
+## Module usage
-For sudo, add the following to `/etc/sudoers` (replace `$USER` with your own username):
 
-    $USER ALL=(ego) NOPASSWD:ALL
+The NixOS module currently requires home-manager to function correctly.
 
-Appendix
+Full module documentation can be found [here](options.md).
---------
+
-Ego is licensed under the MIT License (see the `LICENSE` file).
+To use the module, import it into your configuration with
-The original Ego was created by Marti Raudsepp under the repository https://github.com/intgr/ego
+
+```nix
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.05";
+
+    fortify = {
+      url = "git+https://git.gensokyo.uk/security/fortify";
+
+      # Optional but recommended to limit the size of your system closure.
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs = { self, nixpkgs, fortify, ... }:
+  {
+    nixosConfigurations.fortify = nixpkgs.lib.nixosSystem {
+      system = "x86_64-linux";
+      modules = [
+        fortify.nixosModules.fortify
+      ];
+    };
+  };
+}
+```
+
+This adds the `environment.fortify` option:
+
+```nix
+{ pkgs, ... }:
+
+{
+  environment.fortify = {
+    enable = true;
+    stateDir = "/var/lib/persist/module/fortify";
+    users = {
+      alice = 0;
+      nixos = 10;
+    };
+
+    apps = [
+      {
+        name = "chromium";
+        id = "org.chromium.Chromium";
+        packages = [ pkgs.chromium ];
+        userns = true;
+        mapRealUid = true;
+        dbus = {
+          system = {
+            filter = true;
+            talk = [
+              "org.bluez"
+              "org.freedesktop.Avahi"
+              "org.freedesktop.UPower"
+            ];
+          };
+          session =
+            f:
+            f {
+              talk = [
+                "org.freedesktop.FileManager1"
+                "org.freedesktop.Notifications"
+                "org.freedesktop.ScreenSaver"
+                "org.freedesktop.secrets"
+                "org.kde.kwalletd5"
+                "org.kde.kwalletd6"
+              ];
+              own = [
+                "org.chromium.Chromium.*"
+                "org.mpris.MediaPlayer2.org.chromium.Chromium.*"
+                "org.mpris.MediaPlayer2.chromium.*"
+              ];
+              call = { };
+              broadcast = { };
+            };
+        };
+      }
+      {
+        name = "claws-mail";
+        id = "org.claws_mail.Claws-Mail";
+        packages = [ pkgs.claws-mail ];
+        gpu = false;
+        capability.pulse = false;
+      }
+      {
+        name = "weechat";
+        packages = [ pkgs.weechat ];
+        capability = {
+          wayland = false;
+          x11 = false;
+          dbus = true;
+          pulse = false;
+        };
+      }
+      {
+        name = "discord";
+        id = "dev.vencord.Vesktop";
+        packages = [ pkgs.vesktop ];
+        share = pkgs.vesktop;
+        command = "vesktop --ozone-platform-hint=wayland";
+        userns = true;
+        mapRealUid = true;
+        capability.x11 = true;
+        dbus = {
+          session =
+            f:
+            f {
+              talk = [ "org.kde.StatusNotifierWatcher" ];
+              own = [ ];
+              call = { };
+              broadcast = { };
+            };
+          system.filter = true;
+        };
+      }
+      {
+        name = "looking-glass-client";
+        groups = [ "plugdev" ];
+        extraPaths = [
+          {
+            src = "/dev/shm/looking-glass";
+            write = true;
+          }
+        ];
+        extraConfig = {
+          programs.looking-glass-client.enable = true;
+        };
+      }
+    ];
+  };
+}
+```

acl.go

@@ -1,176 +0,0 @@
-package main
-
-import (
-	"errors"
-	"fmt"
-	"syscall"
-	"unsafe"
-)
-
-//#include <stdlib.h>
-//#include <sys/acl.h>
-//#include <acl/libacl.h>
-//#cgo linux LDFLAGS: -lacl
-import "C"
-
-const (
-	aclRead    = C.ACL_READ
-	aclWrite   = C.ACL_WRITE
-	aclExecute = C.ACL_EXECUTE
-
-	aclTypeDefault = C.ACL_TYPE_DEFAULT
-	aclTypeAccess  = C.ACL_TYPE_ACCESS
-
-	aclUndefinedTag = C.ACL_UNDEFINED_TAG
-	aclUserObj      = C.ACL_USER_OBJ
-	aclUser         = C.ACL_USER
-	aclGroupObj     = C.ACL_GROUP_OBJ
-	aclGroup        = C.ACL_GROUP
-	aclMask         = C.ACL_MASK
-	aclOther        = C.ACL_OTHER
-)
-
-type acl struct {
-	val   C.acl_t
-	freed bool
-}
-
-func aclUpdatePerm(path string, uid int, perms ...C.acl_perm_t) error {
-	// read acl from file
-	a, err := aclGetFile(path, aclTypeAccess)
-	if err != nil {
-		return err
-	}
-	// free acl on return if get is successful
-	defer a.free()
-
-	// remove existing entry
-	if err = a.removeEntry(aclUser, uid); err != nil {
-		return err
-	}
-
-	// create new entry if perms are passed
-	if len(perms) > 0 {
-		// create new acl entry
-		var e C.acl_entry_t
-		if _, err = C.acl_create_entry(&a.val, &e); err != nil {
-			return err
-		}
-
-		// get perm set of new entry
-		var p C.acl_permset_t
-		if _, err = C.acl_get_permset(e, &p); err != nil {
-			return err
-		}
-
-		// add target perms
-		for _, perm := range perms {
-			if _, err = C.acl_add_perm(p, perm); err != nil {
-				return err
-			}
-		}
-
-		// set perm set to new entry
-		if _, err = C.acl_set_permset(e, p); err != nil {
-			return err
-		}
-
-		// set user tag to new entry
-		if _, err = C.acl_set_tag_type(e, aclUser); err != nil {
-			return err
-		}
-
-		// set qualifier (uid) to new entry
-		if _, err = C.acl_set_qualifier(e, unsafe.Pointer(&uid)); err != nil {
-			return err
-		}
-	}
-
-	// calculate mask after update
-	if _, err = C.acl_calc_mask(&a.val); err != nil {
-		return err
-	}
-
-	// write acl to file
-	return a.setFile(path, aclTypeAccess)
-}
-
-func aclGetFile(path string, t C.acl_type_t) (*acl, error) {
-	p := C.CString(path)
-	a, err := C.acl_get_file(p, t)
-	C.free(unsafe.Pointer(p))
-
-	if errors.Is(err, syscall.ENODATA) {
-		err = nil
-	}
-	return &acl{val: a, freed: false}, err
-}
-
-func (a *acl) setFile(path string, t C.acl_type_t) error {
-	if C.acl_valid(a.val) != 0 {
-		return fmt.Errorf("invalid acl")
-	}
-
-	p := C.CString(path)
-	_, err := C.acl_set_file(p, t, a.val)
-	C.free(unsafe.Pointer(p))
-	return err
-}
-
-func (a *acl) removeEntry(tt C.acl_tag_t, tq int) error {
-	var e C.acl_entry_t
-
-	// get first entry
-	if r, err := C.acl_get_entry(a.val, C.ACL_FIRST_ENTRY, &e); err != nil {
-		return err
-	} else if r == 0 {
-		// return on acl with no entries
-		return nil
-	}
-
-	for {
-		if r, err := C.acl_get_entry(a.val, C.ACL_NEXT_ENTRY, &e); err != nil {
-			return err
-		} else if r == 0 {
-			// return on drained acl
-			return nil
-		}
-
-		var (
-			q int
-			t C.acl_tag_t
-		)
-
-		// get current entry tag type
-		if _, err := C.acl_get_tag_type(e, &t); err != nil {
-			return err
-		}
-
-		// get current entry qualifier
-		if rq, err := C.acl_get_qualifier(e); err != nil {
-			// neither ACL_USER nor ACL_GROUP
-			if errors.Is(err, syscall.EINVAL) {
-				continue
-			}
-
-			return err
-		} else {
-			q = *(*int)(rq)
-			C.acl_free(rq)
-		}
-
-		// delete on match
-		if t == tt && q == tq {
-			_, err := C.acl_delete_entry(a.val, e)
-			return err
-		}
-	}
-}
-
-func (a *acl) free() {
-	if a.freed {
-		panic("acl already freed")
-	}
-	C.acl_free(unsafe.Pointer(a.val))
-	a.freed = true
-}

acl/acl.go

@@ -0,0 +1,19 @@
+// Package acl implements simple ACL manipulation via libacl.
+package acl
+
+type Perms []Perm
+
+func (ps Perms) String() string {
+	var s = []byte("---")
+	for _, p := range ps {
+		switch p {
+		case Read:
+			s[0] = 'r'
+		case Write:
+			s[1] = 'w'
+		case Execute:
+			s[2] = 'x'
+		}
+	}
+	return string(s)
+}

acl/acl_getfacl_test.go

@@ -0,0 +1,156 @@
+package acl_test
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"os/exec"
+	"strconv"
+)
+
+type (
+	getFAclInvocation struct {
+		cmd *exec.Cmd
+		val []*getFAclResp
+		pe  []error
+	}
+
+	getFAclResp struct {
+		typ  fAclType
+		cred int32
+		val  fAclPerm
+
+		raw []byte
+	}
+
+	fAclPerm uintptr
+	fAclType uint8
+)
+
+const fAclBufSize = 16
+
+const (
+	fAclPermRead fAclPerm = 1 << iota
+	fAclPermWrite
+	fAclPermExecute
+)
+
+const (
+	fAclTypeUser fAclType = iota
+	fAclTypeGroup
+	fAclTypeMask
+	fAclTypeOther
+)
+
+func (c *getFAclInvocation) run(name string) error {
+	if c.cmd != nil {
+		panic("attempted to run twice")
+	}
+
+	c.cmd = exec.Command("getfacl", "--omit-header", "--absolute-names", "--numeric", name)
+
+	scanErr := make(chan error, 1)
+	if p, err := c.cmd.StdoutPipe(); err != nil {
+		return err
+	} else {
+		go c.parse(p, scanErr)
+	}
+
+	if err := c.cmd.Start(); err != nil {
+		return err
+	}
+
+	return errors.Join(<-scanErr, c.cmd.Wait())
+}
+
+func (c *getFAclInvocation) parse(pipe io.Reader, scanErr chan error) {
+	c.val = make([]*getFAclResp, 0, 4+fAclBufSize)
+
+	s := bufio.NewScanner(pipe)
+	for s.Scan() {
+		fields := bytes.SplitN(s.Bytes(), []byte{':'}, 3)
+		if len(fields) != 3 {
+			continue
+		}
+
+		resp := getFAclResp{}
+
+		switch string(fields[0]) {
+		case "user":
+			resp.typ = fAclTypeUser
+		case "group":
+			resp.typ = fAclTypeGroup
+		case "mask":
+			resp.typ = fAclTypeMask
+		case "other":
+			resp.typ = fAclTypeOther
+		default:
+			c.pe = append(c.pe, fmt.Errorf("unknown type %s", string(fields[0])))
+			continue
+		}
+
+		if len(fields[1]) == 0 {
+			resp.cred = -1
+		} else {
+			if cred, err := strconv.Atoi(string(fields[1])); err != nil {
+				c.pe = append(c.pe, err)
+				continue
+			} else {
+				resp.cred = int32(cred)
+				if resp.cred < 0 {
+					c.pe = append(c.pe, fmt.Errorf("credential %d out of range", resp.cred))
+					continue
+				}
+			}
+		}
+
+		if len(fields[2]) != 3 {
+			c.pe = append(c.pe, fmt.Errorf("invalid perm length %d", len(fields[2])))
+			continue
+		} else {
+			switch fields[2][0] {
+			case 'r':
+				resp.val |= fAclPermRead
+			case '-':
+			default:
+				c.pe = append(c.pe, fmt.Errorf("invalid perm %v", fields[2][0]))
+				continue
+			}
+			switch fields[2][1] {
+			case 'w':
+				resp.val |= fAclPermWrite
+			case '-':
+			default:
+				c.pe = append(c.pe, fmt.Errorf("invalid perm %v", fields[2][1]))
+				continue
+			}
+			switch fields[2][2] {
+			case 'x':
+				resp.val |= fAclPermExecute
+			case '-':
+			default:
+				c.pe = append(c.pe, fmt.Errorf("invalid perm %v", fields[2][2]))
+				continue
+			}
+		}
+
+		resp.raw = make([]byte, len(s.Bytes()))
+		copy(resp.raw, s.Bytes())
+		c.val = append(c.val, &resp)
+	}
+	scanErr <- s.Err()
+}
+
+func (r *getFAclResp) String() string {
+	if r.raw != nil && len(r.raw) > 0 {
+		return string(r.raw)
+	}
+
+	return "(user-initialised resp value)"
+}
+
+func (r *getFAclResp) equals(typ fAclType, cred int32, val fAclPerm) bool {
+	return r.typ == typ && r.cred == cred && r.val == val
+}

acl/acl_test.go

@@ -0,0 +1,125 @@
+package acl_test
+
+import (
+	"errors"
+	"os"
+	"path"
+	"reflect"
+	"testing"
+
+	"git.gensokyo.uk/security/fortify/acl"
+)
+
+const testFileName = "acl.test"
+
+var (
+	uid  = os.Geteuid()
+	cred = int32(os.Geteuid())
+)
+
+func TestUpdatePerm(t *testing.T) {
+	if os.Getenv("GO_TEST_SKIP_ACL") == "1" {
+		t.Log("acl test skipped")
+		t.SkipNow()
+	}
+
+	testFilePath := path.Join(t.TempDir(), testFileName)
+
+	if f, err := os.Create(testFilePath); err != nil {
+		t.Fatalf("Create: error = %v", err)
+	} else {
+		if err = f.Close(); err != nil {
+			t.Fatalf("Close: error = %v", err)
+		}
+	}
+	defer func() {
+		if err := os.Remove(testFilePath); err != nil {
+			t.Fatalf("Remove: error = %v", err)
+		}
+	}()
+
+	cur := getfacl(t, testFilePath)
+
+	t.Run("default entry count", func(t *testing.T) {
+		if len(cur) != 3 {
+			t.Fatalf("unexpected test file acl length %d", len(cur))
+		}
+	})
+
+	t.Run("default clear mask", func(t *testing.T) {
+		if err := acl.UpdatePerm(testFilePath, uid); err != nil {
+			t.Fatalf("UpdatePerm: error = %v", err)
+		}
+		if cur = getfacl(t, testFilePath); len(cur) != 4 {
+			t.Fatalf("UpdatePerm: %v", cur)
+		}
+	})
+
+	t.Run("default clear consistency", func(t *testing.T) {
+		if err := acl.UpdatePerm(testFilePath, uid); err != nil {
+			t.Fatalf("UpdatePerm: error = %v", err)
+		}
+		if val := getfacl(t, testFilePath); !reflect.DeepEqual(val, cur) {
+			t.Fatalf("UpdatePerm: %v, want %v", val, cur)
+		}
+	})
+
+	testUpdate(t, testFilePath, "r--", cur, fAclPermRead, acl.Read)
+	testUpdate(t, testFilePath, "-w-", cur, fAclPermWrite, acl.Write)
+	testUpdate(t, testFilePath, "--x", cur, fAclPermExecute, acl.Execute)
+	testUpdate(t, testFilePath, "-wx", cur, fAclPermWrite|fAclPermExecute, acl.Write, acl.Execute)
+	testUpdate(t, testFilePath, "r-x", cur, fAclPermRead|fAclPermExecute, acl.Read, acl.Execute)
+	testUpdate(t, testFilePath, "rw-", cur, fAclPermRead|fAclPermWrite, acl.Read, acl.Write)
+	testUpdate(t, testFilePath, "rwx", cur, fAclPermRead|fAclPermWrite|fAclPermExecute, acl.Read, acl.Write, acl.Execute)
+}
+
+func testUpdate(t *testing.T, testFilePath, name string, cur []*getFAclResp, val fAclPerm, perms ...acl.Perm) {
+	t.Run(name, func(t *testing.T) {
+		t.Cleanup(func() {
+			if err := acl.UpdatePerm(testFilePath, uid); err != nil {
+				t.Fatalf("UpdatePerm: error = %v", err)
+			}
+			if v := getfacl(t, testFilePath); !reflect.DeepEqual(v, cur) {
+				t.Fatalf("UpdatePerm: %v, want %v", v, cur)
+			}
+		})
+
+		if err := acl.UpdatePerm(testFilePath, uid, perms...); err != nil {
+			t.Fatalf("UpdatePerm: error = %v", err)
+		}
+		r := respByCred(getfacl(t, testFilePath), fAclTypeUser, cred)
+		if r == nil {
+			t.Fatalf("UpdatePerm did not add an ACL entry")
+		}
+		if !r.equals(fAclTypeUser, cred, val) {
+			t.Fatalf("UpdatePerm(%s) = %s", name, r)
+		}
+	})
+}
+
+func getfacl(t *testing.T, name string) []*getFAclResp {
+	c := new(getFAclInvocation)
+	if err := c.run(name); err != nil {
+		t.Fatalf("getfacl: error = %v", err)
+	}
+	if len(c.pe) != 0 {
+		t.Errorf("errors encountered parsing getfacl output\n%s", errors.Join(c.pe...).Error())
+	}
+	return c.val
+}
+
+func respByCred(v []*getFAclResp, typ fAclType, cred int32) *getFAclResp {
+	j := -1
+	for i, r := range v {
+		if r.typ == typ && r.cred == cred {
+			if j != -1 {
+				panic("invalid acl")
+			}
+			j = i
+		}
+	}
+	if j == -1 {
+		return nil
+	}
+	return v[j]
+}

acl/c.go

@@ -0,0 +1,196 @@
+package acl
+
+import "C"
+import (
+	"errors"
+	"runtime"
+	"syscall"
+	"unsafe"
+)
+
+/*
+#cgo linux pkg-config: libacl
+
+#include <stdlib.h>
+#include <sys/acl.h>
+#include <acl/libacl.h>
+
+static acl_t _go_acl_get_file(const char *path_p, acl_type_t type) {
+	acl_t acl = acl_get_file(path_p, type);
+	free((void *)path_p);
+	return acl;
+}
+
+static int _go_acl_set_file(const char *path_p, acl_type_t type, acl_t acl) {
+	if (acl_valid(acl) != 0) {
+		return -1;
+	}
+
+	int ret = acl_set_file(path_p, type, acl);
+	free((void *)path_p);
+	return ret;
+}
+*/
+import "C"
+
+func getFile(name string, t C.acl_type_t) (*ACL, error) {
+	a, err := C._go_acl_get_file(C.CString(name), t)
+	if errors.Is(err, syscall.ENODATA) {
+		err = nil
+	}
+
+	return newACL(a), err
+}
+
+func (acl *ACL) setFile(name string, t C.acl_type_t) error {
+	_, err := C._go_acl_set_file(C.CString(name), t, acl.acl)
+	return err
+}
+
+func newACL(a C.acl_t) *ACL {
+	acl := &ACL{a}
+	runtime.SetFinalizer(acl, (*ACL).free)
+	return acl
+}
+
+type ACL struct {
+	acl C.acl_t
+}
+
+func (acl *ACL) free() {
+	C.acl_free(unsafe.Pointer(acl.acl))
+
+	// no need for a finalizer anymore
+	runtime.SetFinalizer(acl, nil)
+}
+
+const (
+	Read    = C.ACL_READ
+	Write   = C.ACL_WRITE
+	Execute = C.ACL_EXECUTE
+
+	TypeDefault = C.ACL_TYPE_DEFAULT
+	TypeAccess  = C.ACL_TYPE_ACCESS
+
+	UndefinedTag = C.ACL_UNDEFINED_TAG
+	UserObj      = C.ACL_USER_OBJ
+	User         = C.ACL_USER
+	GroupObj     = C.ACL_GROUP_OBJ
+	Group        = C.ACL_GROUP
+	Mask         = C.ACL_MASK
+	Other        = C.ACL_OTHER
+)
+
+type (
+	Perm C.acl_perm_t
+)
+
+func (acl *ACL) removeEntry(tt C.acl_tag_t, tq int) error {
+	var e C.acl_entry_t
+
+	// get first entry
+	if r, err := C.acl_get_entry(acl.acl, C.ACL_FIRST_ENTRY, &e); err != nil {
+		return err
+	} else if r == 0 {
+		// return on acl with no entries
+		return nil
+	}
+
+	for {
+		if r, err := C.acl_get_entry(acl.acl, C.ACL_NEXT_ENTRY, &e); err != nil {
+			return err
+		} else if r == 0 {
+			// return on drained acl
+			return nil
+		}
+
+		var (
+			q int
+			t C.acl_tag_t
+		)
+
+		// get current entry tag type
+		if _, err := C.acl_get_tag_type(e, &t); err != nil {
+			return err
+		}
+
+		// get current entry qualifier
+		if rq, err := C.acl_get_qualifier(e); err != nil {
+			// neither ACL_USER nor ACL_GROUP
+			if errors.Is(err, syscall.EINVAL) {
+				continue
+			}
+
+			return err
+		} else {
+			q = *(*int)(rq)
+			C.acl_free(rq)
+		}
+
+		// delete on match
+		if t == tt && q == tq {
+			_, err := C.acl_delete_entry(acl.acl, e)
+			return err
+		}
+	}
+}
+
+func UpdatePerm(name string, uid int, perms ...Perm) error {
+	// read acl from file
+	a, err := getFile(name, TypeAccess)
+	if err != nil {
+		return err
+	}
+	// free acl on return if get is successful
+	defer a.free()
+
+	// remove existing entry
+	if err = a.removeEntry(User, uid); err != nil {
+		return err
+	}
+
+	// create new entry if perms are passed
+	if len(perms) > 0 {
+		// create new acl entry
+		var e C.acl_entry_t
+		if _, err = C.acl_create_entry(&a.acl, &e); err != nil {
+			return err
+		}
+
+		// get perm set of new entry
+		var p C.acl_permset_t
+		if _, err = C.acl_get_permset(e, &p); err != nil {
+			return err
+		}
+
+		// add target perms
+		for _, perm := range perms {
+			if _, err = C.acl_add_perm(p, C.acl_perm_t(perm)); err != nil {
+				return err
+			}
+		}
+
+		// set perm set to new entry
+		if _, err = C.acl_set_permset(e, p); err != nil {
+			return err
+		}
+
+		// set user tag to new entry
+		if _, err = C.acl_set_tag_type(e, User); err != nil {
+			return err
+		}
+
+		// set qualifier (uid) to new entry
+		if _, err = C.acl_set_qualifier(e, unsafe.Pointer(&uid)); err != nil {
+			return err
+		}
+	}
+
+	// calculate mask after update
+	if _, err = C.acl_calc_mask(&a.acl); err != nil {
+		return err
+	}
+
+	// write acl to file
+	return a.setFile(name, TypeAccess)
+}

cli.go

@@ -1,50 +0,0 @@
-package main
-
-import (
-	"errors"
-	"flag"
-	"fmt"
-	"os"
-	"os/user"
-)
-
-var (
-	userName     string
-	methodFlags  [2]bool
-	printVersion bool
-	mustPulse    bool
-)
-
-func init() {
-	flag.StringVar(&userName, "u", "ego", "Specify a username")
-	flag.BoolVar(&methodFlags[0], "sudo", false, "Use 'sudo' to change user")
-	flag.BoolVar(&methodFlags[1], "bare", false, "Use 'machinectl' but skip xdg-desktop-portal setup")
-	flag.BoolVar(&mustPulse, "pulse", false, "Treat unavailable PulseAudio as fatal")
-	flag.BoolVar(&verbose, "v", false, "Verbose output")
-	flag.BoolVar(&printVersion, "V", false, "Print version")
-}
-
-func copyArgs() {
-	tryLauncher()
-	tryVersion()
-	tryLicense()
-
-	command = flag.Args()
-
-	if u, err := user.Lookup(userName); err != nil {
-		if errors.As(err, new(user.UnknownUserError)) {
-			fmt.Println("unknown user", userName)
-		} else {
-			// unreachable
-			panic(err)
-		}
-
-		os.Exit(1)
-	} else {
-		ego = u
-	}
-
-	if verbose {
-		fmt.Println("Running as user", ego.Username, "("+ego.Uid+"),", "command:", command)
-	}
-}

cmd/finit/ipc/payload.go

@@ -0,0 +1,13 @@
+package init0
+
+const Env = "FORTIFY_INIT"
+
+type Payload struct {
+	// target full exec path
+	Argv0 string
+	// child full argv
+	Argv []string
+
+	// verbosity pass through
+	Verbose bool
+}

cmd/finit/main.go

@@ -0,0 +1,174 @@
+package main
+
+import (
+	"errors"
+	"os"
+	"os/exec"
+	"os/signal"
+	"path"
+	"syscall"
+	"time"
+
+	init0 "git.gensokyo.uk/security/fortify/cmd/finit/ipc"
+	"git.gensokyo.uk/security/fortify/internal"
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+	"git.gensokyo.uk/security/fortify/internal/proc"
+)
+
+const (
+	// time to wait for linger processes after death of initial process
+	residualProcessTimeout = 5 * time.Second
+)
+
+// everything beyond this point runs within pid namespace
+// proceed with caution!
+
+func main() {
+	// sharing stdout with shim
+	// USE WITH CAUTION
+	fmsg.SetPrefix("init")
+
+	// setting this prevents ptrace
+	if err := internal.PR_SET_DUMPABLE__SUID_DUMP_DISABLE(); err != nil {
+		fmsg.Fatalf("cannot set SUID_DUMP_DISABLE: %s", err)
+		panic("unreachable")
+	}
+
+	if os.Getpid() != 1 {
+		fmsg.Fatal("this process must run as pid 1")
+		panic("unreachable")
+	}
+
+	// re-exec
+	if len(os.Args) > 0 && (os.Args[0] != "finit" || len(os.Args) != 1) && path.IsAbs(os.Args[0]) {
+		if err := syscall.Exec(os.Args[0], []string{"finit"}, os.Environ()); err != nil {
+			fmsg.Println("cannot re-exec self:", err)
+			// continue anyway
+		}
+	}
+
+	// receive setup payload
+	var (
+		payload    init0.Payload
+		closeSetup func() error
+	)
+	if f, err := proc.Receive(init0.Env, &payload); err != nil {
+		if errors.Is(err, proc.ErrInvalid) {
+			fmsg.Fatal("invalid config descriptor")
+		}
+		if errors.Is(err, proc.ErrNotSet) {
+			fmsg.Fatal("FORTIFY_INIT not set")
+		}
+
+		fmsg.Fatalf("cannot decode init setup payload: %v", err)
+		panic("unreachable")
+	} else {
+		fmsg.SetVerbose(payload.Verbose)
+		closeSetup = f
+
+		// child does not need to see this
+		if err = os.Unsetenv(init0.Env); err != nil {
+			fmsg.Printf("cannot unset %s: %v", init0.Env, err)
+			// not fatal
+		} else {
+			fmsg.VPrintln("received configuration")
+		}
+	}
+
+	// die with parent
+	if err := internal.PR_SET_PDEATHSIG__SIGKILL(); err != nil {
+		fmsg.Fatalf("prctl(PR_SET_PDEATHSIG, SIGKILL): %v", err)
+	}
+
+	cmd := exec.Command(payload.Argv0)
+	cmd.Stdin, cmd.Stdout, cmd.Stderr = os.Stdin, os.Stdout, os.Stderr
+	cmd.Args = payload.Argv
+	cmd.Env = os.Environ()
+
+	if err := cmd.Start(); err != nil {
+		fmsg.Fatalf("cannot start %q: %v", payload.Argv0, err)
+	}
+	fmsg.Suspend()
+
+	// close setup pipe as setup is now complete
+	if err := closeSetup(); err != nil {
+		fmsg.Println("cannot close setup pipe:", err)
+		// not fatal
+	}
+
+	sig := make(chan os.Signal, 2)
+	signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
+
+	type winfo struct {
+		wpid    int
+		wstatus syscall.WaitStatus
+	}
+	info := make(chan winfo, 1)
+	done := make(chan struct{})
+
+	go func() {
+		var (
+			err     error
+			wpid    = -2
+			wstatus syscall.WaitStatus
+		)
+
+		// keep going until no child process is left
+		for wpid != -1 {
+			if err != nil {
+				break
+			}
+
+			if wpid != -2 {
+				info <- winfo{wpid, wstatus}
+			}
+
+			err = syscall.EINTR
+			for errors.Is(err, syscall.EINTR) {
+				wpid, err = syscall.Wait4(-1, &wstatus, 0, nil)
+			}
+		}
+		if !errors.Is(err, syscall.ECHILD) {
+			fmsg.Println("unexpected wait4 response:", err)
+		}
+
+		close(done)
+	}()
+
+	// closed after residualProcessTimeout has elapsed after initial process death
+	timeout := make(chan struct{})
+
+	r := 2
+	for {
+		select {
+		case s := <-sig:
+			fmsg.VPrintln("received", s.String())
+			fmsg.Resume() // output could still be withheld at this point, so resume is called
+			fmsg.Exit(0)
+		case w := <-info:
+			if w.wpid == cmd.Process.Pid {
+				// initial process exited, output is most likely available again
+				fmsg.Resume()
+
+				switch {
+				case w.wstatus.Exited():
+					r = w.wstatus.ExitStatus()
+				case w.wstatus.Signaled():
+					r = 128 + int(w.wstatus.Signal())
+				default:
+					r = 255
+				}
+
+				go func() {
+					time.Sleep(residualProcessTimeout)
+					close(timeout)
+				}()
+			}
+		case <-done:
+			fmsg.Exit(r)
+		case <-timeout:
+			fmsg.Println("timeout exceeded waiting for lingering processes")
+			fmsg.Exit(r)
+		}
+	}
+}

cmd/fshim/ipc/payload.go

@@ -0,0 +1,21 @@
+package shim0
+
+import (
+	"git.gensokyo.uk/security/fortify/helper/bwrap"
+)
+
+const Env = "FORTIFY_SHIM"
+
+type Payload struct {
+	// child full argv
+	Argv []string
+	// bwrap, target full exec path
+	Exec [2]string
+	// bwrap config
+	Bwrap *bwrap.Config
+	// sync fd
+	Sync *uintptr
+
+	// verbosity pass through
+	Verbose bool
+}

cmd/fshim/ipc/shim/shim.go

@@ -0,0 +1,137 @@
+package shim
+
+import (
+	"encoding/gob"
+	"errors"
+	"os"
+	"os/exec"
+	"os/signal"
+	"strconv"
+	"strings"
+	"syscall"
+	"time"
+
+	shim0 "git.gensokyo.uk/security/fortify/cmd/fshim/ipc"
+	"git.gensokyo.uk/security/fortify/internal"
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+	"git.gensokyo.uk/security/fortify/internal/proc"
+)
+
+const shimSetupTimeout = 5 * time.Second
+
+// used by the parent process
+
+type Shim struct {
+	// user switcher process
+	cmd *exec.Cmd
+	// uid of shim target user
+	uid uint32
+	// string representation of application id
+	aid string
+	// string representation of supplementary group ids
+	supp []string
+	// fallback exit notifier with error returned killing the process
+	killFallback chan error
+	// shim setup payload
+	payload *shim0.Payload
+}
+
+func New(uid uint32, aid string, supp []string, payload *shim0.Payload) *Shim {
+	return &Shim{uid: uid, aid: aid, supp: supp, payload: payload}
+}
+
+func (s *Shim) String() string {
+	if s.cmd == nil {
+		return "(unused shim manager)"
+	}
+	return s.cmd.String()
+}
+
+func (s *Shim) Unwrap() *exec.Cmd {
+	return s.cmd
+}
+
+func (s *Shim) WaitFallback() chan error {
+	return s.killFallback
+}
+
+func (s *Shim) Start() (*time.Time, error) {
+	// start user switcher process and save time
+	var fsu string
+	if p, ok := internal.Check(internal.Fsu); !ok {
+		fmsg.Fatal("invalid fsu path, this copy of fshim is not compiled correctly")
+		panic("unreachable")
+	} else {
+		fsu = p
+	}
+	s.cmd = exec.Command(fsu)
+
+	var encoder *gob.Encoder
+	if fd, e, err := proc.Setup(&s.cmd.ExtraFiles); err != nil {
+		return nil, fmsg.WrapErrorSuffix(err,
+			"cannot create shim setup pipe:")
+	} else {
+		encoder = e
+		s.cmd.Env = []string{
+			shim0.Env + "=" + strconv.Itoa(fd),
+			"FORTIFY_APP_ID=" + s.aid,
+		}
+	}
+
+	if len(s.supp) > 0 {
+		fmsg.VPrintf("attaching supplementary group ids %s", s.supp)
+		s.cmd.Env = append(s.cmd.Env, "FORTIFY_GROUPS="+strings.Join(s.supp, " "))
+	}
+	s.cmd.Stdin, s.cmd.Stdout, s.cmd.Stderr = os.Stdin, os.Stdout, os.Stderr
+	s.cmd.Dir = "/"
+
+	// pass sync fd if set
+	if s.payload.Bwrap.Sync() != nil {
+		fd := proc.ExtraFile(s.cmd, s.payload.Bwrap.Sync())
+		s.payload.Sync = &fd
+	}
+
+	fmsg.VPrintln("starting shim via fsu:", s.cmd)
+	fmsg.Suspend() // withhold messages to stderr
+	if err := s.cmd.Start(); err != nil {
+		return nil, fmsg.WrapErrorSuffix(err,
+			"cannot start fsu:")
+	}
+	startTime := time.Now().UTC()
+
+	// kill shim if something goes wrong and an error is returned
+	s.killFallback = make(chan error, 1)
+	killShim := func() {
+		if err := s.cmd.Process.Signal(os.Interrupt); err != nil {
+			s.killFallback <- err
+		}
+	}
+	defer func() { killShim() }()
+
+	// take alternative exit path on signal
+	sig := make(chan os.Signal, 2)
+	signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
+	go func() {
+		v := <-sig
+		fmsg.Printf("got %s after program start", v)
+		s.killFallback <- nil
+		signal.Ignore(syscall.SIGINT, syscall.SIGTERM)
+	}()
+
+	shimErr := make(chan error)
+	go func() { shimErr <- encoder.Encode(s.payload) }()
+
+	select {
+	case err := <-shimErr:
+		if err != nil {
+			return &startTime, fmsg.WrapErrorSuffix(err,
+				"cannot transmit shim config:")
+		}
+		killShim = func() {}
+	case <-time.After(shimSetupTimeout):
+		return &startTime, fmsg.WrapError(errors.New("timed out waiting for shim"),
+			"timed out waiting for shim")
+	}
+
+	return &startTime, nil
+}

cmd/fshim/main.go

@@ -0,0 +1,145 @@
+package main
+
+import (
+	"errors"
+	"os"
+	"path"
+	"strconv"
+	"syscall"
+
+	init0 "git.gensokyo.uk/security/fortify/cmd/finit/ipc"
+	shim "git.gensokyo.uk/security/fortify/cmd/fshim/ipc"
+	"git.gensokyo.uk/security/fortify/helper"
+	"git.gensokyo.uk/security/fortify/internal"
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+	"git.gensokyo.uk/security/fortify/internal/proc"
+)
+
+// everything beyond this point runs as unconstrained target user
+// proceed with caution!
+
+func main() {
+	// sharing stdout with fortify
+	// USE WITH CAUTION
+	fmsg.SetPrefix("shim")
+
+	// setting this prevents ptrace
+	if err := internal.PR_SET_DUMPABLE__SUID_DUMP_DISABLE(); err != nil {
+		fmsg.Fatalf("cannot set SUID_DUMP_DISABLE: %s", err)
+		panic("unreachable")
+	}
+
+	// re-exec
+	if len(os.Args) > 0 && (os.Args[0] != "fshim" || len(os.Args) != 1) && path.IsAbs(os.Args[0]) {
+		if err := syscall.Exec(os.Args[0], []string{"fshim"}, os.Environ()); err != nil {
+			fmsg.Println("cannot re-exec self:", err)
+			// continue anyway
+		}
+	}
+
+	// check path to finit
+	var finitPath string
+	if p, ok := internal.Path(internal.Finit); !ok {
+		fmsg.Fatal("invalid finit path, this copy of fshim is not compiled correctly")
+	} else {
+		finitPath = p
+	}
+
+	// receive setup payload
+	var (
+		payload    shim.Payload
+		closeSetup func() error
+	)
+	if f, err := proc.Receive(shim.Env, &payload); err != nil {
+		if errors.Is(err, proc.ErrInvalid) {
+			fmsg.Fatal("invalid config descriptor")
+		}
+		if errors.Is(err, proc.ErrNotSet) {
+			fmsg.Fatal("FORTIFY_SHIM not set")
+		}
+
+		fmsg.Fatalf("cannot decode shim setup payload: %v", err)
+		panic("unreachable")
+	} else {
+		fmsg.SetVerbose(payload.Verbose)
+		closeSetup = f
+	}
+
+	if payload.Bwrap == nil {
+		fmsg.Fatal("bwrap config not supplied")
+	}
+
+	// restore bwrap sync fd
+	if payload.Sync != nil {
+		payload.Bwrap.SetSync(os.NewFile(*payload.Sync, "sync"))
+	}
+
+	// close setup socket
+	if err := closeSetup(); err != nil {
+		fmsg.Println("cannot close setup pipe:", err)
+		// not fatal
+	}
+
+	var ic init0.Payload
+
+	// resolve argv0
+	ic.Argv = payload.Argv
+	if len(ic.Argv) > 0 {
+		// looked up from $PATH by parent
+		ic.Argv0 = payload.Exec[1]
+	} else {
+		// no argv, look up shell instead
+		var ok bool
+		if payload.Bwrap.SetEnv == nil {
+			fmsg.Fatal("no command was specified and environment is unset")
+		}
+		if ic.Argv0, ok = payload.Bwrap.SetEnv["SHELL"]; !ok {
+			fmsg.Fatal("no command was specified and $SHELL was unset")
+		}
+
+		ic.Argv = []string{ic.Argv0}
+	}
+
+	conf := payload.Bwrap
+
+	var extraFiles []*os.File
+
+	// serve setup payload
+	if fd, encoder, err := proc.Setup(&extraFiles); err != nil {
+		fmsg.Fatalf("cannot pipe: %v", err)
+	} else {
+		conf.SetEnv[init0.Env] = strconv.Itoa(fd)
+		go func() {
+			fmsg.VPrintln("transmitting config to init")
+			if err = encoder.Encode(&ic); err != nil {
+				fmsg.Fatalf("cannot transmit init config: %v", err)
+			}
+		}()
+	}
+
+	helper.BubblewrapName = payload.Exec[0] // resolved bwrap path by parent
+	if b, err := helper.NewBwrap(conf, nil, finitPath,
+		func(int, int) []string { return make([]string, 0) }); err != nil {
+		fmsg.Fatalf("malformed sandbox config: %v", err)
+	} else {
+		cmd := b.Unwrap()
+		cmd.Stdin, cmd.Stdout, cmd.Stderr = os.Stdin, os.Stdout, os.Stderr
+		cmd.ExtraFiles = extraFiles
+
+		if fmsg.Verbose() {
+			fmsg.VPrintln("bwrap args:", conf.Args())
+		}
+
+		// run and pass through exit code
+		if err = b.Start(); err != nil {
+			fmsg.Fatalf("cannot start target process: %v", err)
+		} else if err = b.Wait(); err != nil {
+			fmsg.VPrintln("wait:", err)
+		}
+		if b.Unwrap().ProcessState != nil {
+			fmsg.Exit(b.Unwrap().ProcessState.ExitCode())
+		} else {
+			fmsg.Exit(127)
+		}
+	}
+}

cmd/fsu/main.go

@@ -0,0 +1,154 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"log"
+	"os"
+	"path"
+	"slices"
+	"strconv"
+	"strings"
+	"syscall"
+)
+
+const (
+	compPoison  = "INVALIDINVALIDINVALIDINVALIDINVALID"
+	fsuConfFile = "/etc/fsurc"
+	envShim     = "FORTIFY_SHIM"
+	envAID      = "FORTIFY_APP_ID"
+	envGroups   = "FORTIFY_GROUPS"
+
+	PR_SET_NO_NEW_PRIVS = 0x26
+)
+
+var (
+	Fmain = compPoison
+	Fshim = compPoison
+)
+
+func main() {
+	log.SetFlags(0)
+	log.SetPrefix("fsu: ")
+	log.SetOutput(os.Stderr)
+
+	if os.Geteuid() != 0 {
+		log.Fatal("this program must be owned by uid 0 and have the setuid bit set")
+	}
+
+	puid := os.Getuid()
+	if puid == 0 {
+		log.Fatal("this program must not be started by root")
+	}
+
+	var fmain, fshim string
+	if p, ok := checkPath(Fmain); !ok {
+		log.Fatal("invalid fortify path, this copy of fsu is not compiled correctly")
+	} else {
+		fmain = p
+	}
+	if p, ok := checkPath(Fshim); !ok {
+		log.Fatal("invalid fshim path, this copy of fsu is not compiled correctly")
+	} else {
+		fshim = p
+	}
+
+	pexe := path.Join("/proc", strconv.Itoa(os.Getppid()), "exe")
+	if p, err := os.Readlink(pexe); err != nil {
+		log.Fatalf("cannot read parent executable path: %v", err)
+	} else if strings.HasSuffix(p, " (deleted)") {
+		log.Fatal("fortify executable has been deleted")
+	} else if p != fmain {
+		log.Fatal("this program must be started by fortify")
+	}
+
+	// uid = 1000000 +
+	//   fid * 10000 +
+	//           aid
+	uid := 1000000
+
+	// authenticate before accepting user input
+	if fid, ok := parseConfig(fsuConfFile, puid); !ok {
+		log.Fatalf("uid %d is not in the fsurc file", puid)
+	} else {
+		uid += fid * 10000
+	}
+
+	// allowed aid range 0 to 9999
+	if as, ok := os.LookupEnv(envAID); !ok {
+		log.Fatal("FORTIFY_APP_ID not set")
+	} else if aid, err := parseUint32Fast(as); err != nil || aid < 0 || aid > 9999 {
+		log.Fatal("invalid aid")
+	} else {
+		uid += aid
+	}
+
+	// pass through setup fd to shim
+	var shimSetupFd string
+	if s, ok := os.LookupEnv(envShim); !ok {
+		// fortify requests target uid
+		// print resolved uid and exit
+		fmt.Print(uid)
+		os.Exit(0)
+	} else if len(s) != 1 || s[0] > '9' || s[0] < '3' {
+		log.Fatal("FORTIFY_SHIM holds an invalid value")
+	} else {
+		shimSetupFd = s
+	}
+
+	// supplementary groups
+	var suppGroups, suppCurrent []int
+
+	if gs, ok := os.LookupEnv(envGroups); ok {
+		if cur, err := os.Getgroups(); err != nil {
+			log.Fatalf("cannot get groups: %v", err)
+		} else {
+			suppCurrent = cur
+		}
+
+		// parse space-separated list of group ids
+		gss := bytes.Split([]byte(gs), []byte{' '})
+		suppGroups = make([]int, len(gss)+1)
+		for i, s := range gss {
+			if gid, err := strconv.Atoi(string(s)); err != nil {
+				log.Fatalf("cannot parse %q: %v", string(s), err)
+			} else if gid > 0 && gid != uid && gid != os.Getgid() && slices.Contains(suppCurrent, gid) {
+				suppGroups[i] = gid
+			} else {
+				log.Fatalf("invalid gid %d", gid)
+			}
+		}
+		suppGroups[len(suppGroups)-1] = uid
+	} else {
+		suppGroups = []int{uid}
+	}
+
+	// final bounds check to catch any bugs
+	if uid < 1000000 || uid >= 2000000 {
+		panic("uid out of bounds")
+	}
+
+	// careful! users in the allowlist is effectively allowed to drop groups via fsu
+
+	if err := syscall.Setresgid(uid, uid, uid); err != nil {
+		log.Fatalf("cannot set gid: %v", err)
+	}
+	if err := syscall.Setgroups(suppGroups); err != nil {
+		log.Fatalf("cannot set supplementary groups: %v", err)
+	}
+	if err := syscall.Setresuid(uid, uid, uid); err != nil {
+		log.Fatalf("cannot set uid: %v", err)
+	}
+	if _, _, errno := syscall.AllThreadsSyscall(syscall.SYS_PRCTL, PR_SET_NO_NEW_PRIVS, 1, 0); errno != 0 {
+		log.Fatalf("cannot set no_new_privs flag: %s", errno.Error())
+	}
+	if err := syscall.Exec(fshim, []string{"fshim"}, []string{envShim + "=" + shimSetupFd}); err != nil {
+		log.Fatalf("cannot start shim: %v", err)
+	}
+
+	panic("unreachable")
+}
+
+func checkPath(p string) (string, bool) {
+	return p, p != compPoison && p != "" && path.IsAbs(p)
+}

cmd/fsu/parse.go

@@ -0,0 +1,77 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"log"
+	"os"
+	"strings"
+	"syscall"
+)
+
+func parseUint32Fast(s string) (int, error) {
+	sLen := len(s)
+	if sLen < 1 {
+		return -1, errors.New("zero length string")
+	}
+	if sLen > 10 {
+		return -1, errors.New("string too long")
+	}
+
+	n := 0
+	for i, ch := range []byte(s) {
+		ch -= '0'
+		if ch > 9 {
+			return -1, fmt.Errorf("invalid character '%s' at index %d", string([]byte{ch}), i)
+		}
+		n = n*10 + int(ch)
+	}
+	return n, nil
+}
+
+func parseConfig(p string, puid int) (fid int, ok bool) {
+	// refuse to run if fsurc is not protected correctly
+	if s, err := os.Stat(p); err != nil {
+		log.Fatal(err)
+	} else if s.Mode().Perm() != 0400 {
+		log.Fatal("bad fsurc perm")
+	} else if st := s.Sys().(*syscall.Stat_t); st.Uid != 0 || st.Gid != 0 {
+		log.Fatal("fsurc must be owned by uid 0")
+	}
+
+	if r, err := os.Open(p); err != nil {
+		log.Fatal(err)
+		return -1, false
+	} else {
+		s := bufio.NewScanner(r)
+		var line int
+		for s.Scan() {
+			line++
+
+			// <puid> <fid>
+			lf := strings.SplitN(s.Text(), " ", 2)
+			if len(lf) != 2 {
+				log.Fatalf("invalid entry on line %d", line)
+			}
+
+			var puid0 int
+			if puid0, err = parseUint32Fast(lf[0]); err != nil || puid0 < 1 {
+				log.Fatalf("invalid parent uid on line %d", line)
+			}
+
+			ok = puid0 == puid
+			if ok {
+				// allowed fid range 0 to 99
+				if fid, err = parseUint32Fast(lf[1]); err != nil || fid < 0 || fid > 99 {
+					log.Fatalf("invalid fortify uid on line %d", line)
+				}
+				return
+			}
+		}
+		if err = s.Err(); err != nil {
+			log.Fatalf("cannot read fsurc: %v", err)
+		}
+		return -1, false
+	}
+}

cmd/fuserdb/main.go

@@ -0,0 +1,69 @@
+package main
+
+import (
+	"bytes"
+	"errors"
+	"flag"
+	"fmt"
+	"os"
+	"path"
+	"strconv"
+
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+)
+
+func main() {
+	fmsg.SetPrefix("fuserdb")
+
+	const varEmpty = "/var/empty"
+
+	out := flag.String("o", "userdb", "output directory")
+	homeDir := flag.String("d", varEmpty, "parent of home directories")
+	shell := flag.String("s", "/sbin/nologin", "absolute path to subordinate user shell")
+	flag.Parse()
+
+	type user struct {
+		name string
+		fid  int
+	}
+
+	users := make([]user, len(flag.Args()))
+	for i, s := range flag.Args() {
+		f := bytes.SplitN([]byte(s), []byte{':'}, 2)
+		if len(f) != 2 {
+			fmsg.Fatalf("invalid entry at index %d", i)
+		}
+		users[i].name = string(f[0])
+		if fid, err := strconv.Atoi(string(f[1])); err != nil {
+			fmsg.Fatal(err.Error())
+		} else {
+			users[i].fid = fid
+		}
+	}
+
+	if err := os.MkdirAll(*out, 0755); err != nil && !errors.Is(err, os.ErrExist) {
+		fmsg.Fatalf("cannot create output: %v", err)
+	}
+
+	for _, u := range users {
+		fidString := strconv.Itoa(u.fid)
+		for aid := 0; aid < 10000; aid++ {
+			userName := fmt.Sprintf("u%d_a%d", u.fid, aid)
+			uid := 1000000 + u.fid*10000 + aid
+			us := strconv.Itoa(uid)
+			realName := fmt.Sprintf("Fortify subordinate user %d (%s)", aid, u.name)
+			var homeDirectory string
+			if *homeDir != varEmpty {
+				homeDirectory = path.Join(*homeDir, "u"+fidString, "a"+strconv.Itoa(aid))
+			} else {
+				homeDirectory = varEmpty
+			}
+
+			writeUser(userName, uid, us, realName, homeDirectory, *shell, *out)
+			writeGroup(userName, uid, us, nil, *out)
+		}
+	}
+
+	fmsg.Printf("created %d entries", len(users)*2*10000)
+	fmsg.Exit(0)
+}

cmd/fuserdb/payload.go

@@ -0,0 +1,64 @@
+package main
+
+import (
+	"encoding/json"
+	"os"
+	"path"
+
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+)
+
+type payloadU struct {
+	UserName      string   `json:"userName"`
+	Uid           int      `json:"uid"`
+	Gid           int      `json:"gid"`
+	MemberOf      []string `json:"memberOf,omitempty"`
+	RealName      string   `json:"realName"`
+	HomeDirectory string   `json:"homeDirectory"`
+	Shell         string   `json:"shell"`
+}
+
+func writeUser(userName string, uid int, us string, realName, homeDirectory, shell string, out string) {
+	userFileName := userName + ".user"
+	if f, err := os.OpenFile(path.Join(out, userFileName), os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644); err != nil {
+		fmsg.Fatalf("cannot create %s: %v", userName, err)
+	} else if err = json.NewEncoder(f).Encode(&payloadU{
+		UserName:      userName,
+		Uid:           uid,
+		Gid:           uid,
+		RealName:      realName,
+		HomeDirectory: homeDirectory,
+		Shell:         shell,
+	}); err != nil {
+		fmsg.Fatalf("cannot serialise %s: %v", userName, err)
+	} else if err = f.Close(); err != nil {
+		fmsg.Printf("cannot close %s: %v", userName, err)
+	}
+	if err := os.Symlink(userFileName, path.Join(out, us+".user")); err != nil {
+		fmsg.Fatalf("cannot link %s: %v", userName, err)
+	}
+}
+
+type payloadG struct {
+	GroupName string   `json:"groupName"`
+	Gid       int      `json:"gid"`
+	Members   []string `json:"members,omitempty"`
+}
+
+func writeGroup(groupName string, gid int, gs string, members []string, out string) {
+	groupFileName := groupName + ".group"
+	if f, err := os.OpenFile(path.Join(out, groupFileName), os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644); err != nil {
+		fmsg.Fatalf("cannot create %s: %v", groupName, err)
+	} else if err = json.NewEncoder(f).Encode(&payloadG{
+		GroupName: groupName,
+		Gid:       gid,
+		Members:   members,
+	}); err != nil {
+		fmsg.Fatalf("cannot serialise %s: %v", groupName, err)
+	} else if err = f.Close(); err != nil {
+		fmsg.Printf("cannot close %s: %v", groupName, err)
+	}
+	if err := os.Symlink(groupFileName, path.Join(out, gs+".group")); err != nil {
+		fmsg.Fatalf("cannot link %s: %v", groupName, err)
+	}
+}

comp/_fortify

@@ -0,0 +1,51 @@
+#compdef fortify
+
+_fortify_app() {
+  _path_files -g "*.(json|ftfy)"
+}
+
+_fortify_run() {
+  _arguments \
+    '--id[App ID, leave empty to disable security context app_id]:id' \
+    '-a[Fortify application ID]: :_numbers' \
+    '-g[Groups inherited by the app process]: :_groups' \
+    '-d[Application home directory]: :_files -/' \
+    '-u[Passwd name within sandbox]: :_users' \
+    '--wayland[Share Wayland socket]' \
+    '-X[Share X11 socket and allow connection]' \
+    '--dbus[Proxy D-Bus connection]' \
+    '--pulse[Share PulseAudio socket and cookie]' \
+    '--dbus-config[Path to D-Bus proxy config file]: :_files -g "*.json"' \
+    '--dbus-system[Path to system D-Bus proxy config file]: :_files -g "*.json"' \
+    '--mpris[Allow owning MPRIS D-Bus path]' \
+    '--dbus-log[Force logging in the D-Bus proxy]'
+}
+
+(( $+functions[_fortify_commands] )) || _fortify_commands()
+{
+  local -a _fortify_cmds
+  _fortify_cmds=(
+    "app:Launch app defined by the specified config file"
+    "run:Configure and start a permissive default sandbox"
+    "ps:List active apps and their state"
+    "version:Show fortify version"
+    "license:Show full license text"
+    "template:Produce a config template"
+    "help:Show help message"
+  )
+  if (( CURRENT == 1 )); then
+    _describe -t commands 'fortify command' _fortify_cmds || compadd "$@"
+  else
+    local curcontext="$curcontext"
+    cmd="${${_fortify_cmds[(r)$words[1]:*]%%:*}}"
+    if (( $+functions[_fortify_$cmd] )); then
+      _fortify_$cmd
+    else
+      _message "no more options"
+    fi
+  fi
+}
+
+_arguments -C \
+  '-v[Verbose output]' \
+  '*::fortify command:_fortify_commands'

dbus/config.go

@@ -0,0 +1,105 @@
+package dbus
+
+import (
+	"encoding/json"
+	"errors"
+	"io"
+	"os"
+)
+
+type Config struct {
+	// See set 'see' policy for NAME (--see=NAME)
+	See []string `json:"see"`
+	// Talk set 'talk' policy for NAME (--talk=NAME)
+	Talk []string `json:"talk"`
+	// Own set 'own' policy for NAME (--own=NAME)
+	Own []string `json:"own"`
+
+	// Call set RULE for calls on NAME (--call=NAME=RULE)
+	Call map[string]string `json:"call"`
+	// Broadcast set RULE for broadcasts from NAME (--broadcast=NAME=RULE)
+	Broadcast map[string]string `json:"broadcast"`
+
+	Log    bool `json:"log,omitempty"`
+	Filter bool `json:"filter"`
+}
+
+func (c *Config) Args(bus [2]string) (args []string) {
+	argc := 2 + len(c.See) + len(c.Talk) + len(c.Own) + len(c.Call) + len(c.Broadcast)
+	if c.Log {
+		argc++
+	}
+	if c.Filter {
+		argc++
+	}
+
+	args = make([]string, 0, argc)
+	args = append(args, bus[0], bus[1])
+	if c.Filter {
+		args = append(args, "--filter")
+	}
+	for _, name := range c.See {
+		args = append(args, "--see="+name)
+	}
+	for _, name := range c.Talk {
+		args = append(args, "--talk="+name)
+	}
+	for _, name := range c.Own {
+		args = append(args, "--own="+name)
+	}
+	for name, rule := range c.Call {
+		args = append(args, "--call="+name+"="+rule)
+	}
+	for name, rule := range c.Broadcast {
+		args = append(args, "--broadcast="+name+"="+rule)
+	}
+	if c.Log {
+		args = append(args, "--log")
+	}
+
+	return
+}
+
+func (c *Config) Load(r io.Reader) error {
+	return json.NewDecoder(r).Decode(&c)
+}
+
+// NewConfigFromFile opens the target config file at path and parses its contents into *Config.
+func NewConfigFromFile(path string) (*Config, error) {
+	if f, err := os.Open(path); err != nil {
+		return nil, err
+	} else {
+		c := new(Config)
+		err1 := c.Load(f)
+		err = f.Close()
+
+		return c, errors.Join(err1, err)
+	}
+}
+
+// NewConfig returns a reference to a Config struct with optional defaults.
+// If id is an empty string own defaults are omitted.
+func NewConfig(id string, defaults, mpris bool) (c *Config) {
+	c = &Config{
+		Call:      make(map[string]string),
+		Broadcast: make(map[string]string),
+
+		Filter: true,
+	}
+
+	if defaults {
+		c.Talk = []string{"org.freedesktop.DBus", "org.freedesktop.Notifications"}
+
+		c.Call["org.freedesktop.portal.*"] = "*"
+		c.Broadcast["org.freedesktop.portal.*"] = "@/org/freedesktop/portal/*"
+
+		if id != "" {
+			c.Own = []string{id + ".*"}
+			if mpris {
+				c.Own = append(c.Own, "org.mpris.MediaPlayer2."+id+".*")
+			}
+		}
+	}
+
+	return
+}

dbus/config_test.go

@@ -0,0 +1,159 @@
+package dbus_test
+
+import (
+	"errors"
+	"os"
+	"path"
+	"reflect"
+	"slices"
+	"strings"
+	"testing"
+
+	"git.gensokyo.uk/security/fortify/dbus"
+)
+
+func TestConfig_Args(t *testing.T) {
+	for _, tc := range testCases() {
+		if tc.wantErr {
+			// args does not check for nulls
+			continue
+		}
+
+		t.Run("build arguments for "+tc.id, func(t *testing.T) {
+			if got := tc.c.Args(tc.bus); !slices.Equal(got, tc.want) {
+				t.Errorf("Args(%q) = %v, want %v",
+					tc.bus,
+					got, tc.want)
+			}
+		})
+	}
+}
+
+func TestNewConfigFromFile(t *testing.T) {
+	for _, tc := range testCases() {
+		name := new(strings.Builder)
+		name.WriteString("parse configuration file for application ")
+		name.WriteString(tc.id)
+		if tc.wantErr {
+			name.WriteString(" with unexpected results")
+		}
+
+		samplePath := path.Join("testdata", tc.id+".json")
+
+		t.Run(name.String(), func(t *testing.T) {
+			got, err := dbus.NewConfigFromFile(samplePath)
+			if errors.Is(err, os.ErrNotExist) != tc.wantErrF {
+				t.Errorf("NewConfigFromFile(%q) error = %v, wantErrF %v",
+					samplePath,
+					err, tc.wantErrF)
+				return
+			}
+
+			if tc.wantErrF {
+				return
+			}
+
+			if !tc.wantErr && !reflect.DeepEqual(got, tc.c) {
+				t.Errorf("NewConfigFromFile(%q) got = %v, want %v",
+					samplePath,
+					got, tc.c)
+			}
+			if tc.wantErr && reflect.DeepEqual(got, tc.c) {
+				t.Errorf("NewConfigFromFile(%q) got = %v, wantErr %v",
+					samplePath,
+					got, tc.wantErr)
+			}
+		})
+	}
+}
+
+func TestNewConfig(t *testing.T) {
+	ids := [...]string{"org.chromium.Chromium", "dev.vencord.Vesktop"}
+
+	type newTestCase struct {
+		id   string
+		args [2]bool
+		want *dbus.Config
+	}
+
+	// populate tests from IDs in generic tests
+	tcs := make([]newTestCase, 0, (len(ids)+1)*4)
+	// tests for defaults without id
+	tcs = append(tcs,
+		newTestCase{"", [2]bool{false, false}, &dbus.Config{
+			Call:      make(map[string]string),
+			Broadcast: make(map[string]string),
+			Filter:    true,
+		}},
+		newTestCase{"", [2]bool{false, true}, &dbus.Config{
+			Call:      make(map[string]string),
+			Broadcast: make(map[string]string),
+			Filter:    true,
+		}},
+		newTestCase{"", [2]bool{true, false}, &dbus.Config{
+			Talk:      []string{"org.freedesktop.DBus", "org.freedesktop.Notifications"},
+			Call:      map[string]string{"org.freedesktop.portal.*": "*"},
+			Broadcast: map[string]string{"org.freedesktop.portal.*": "@/org/freedesktop/portal/*"},
+			Filter:    true,
+		}},
+		newTestCase{"", [2]bool{true, true}, &dbus.Config{
+			Talk:      []string{"org.freedesktop.DBus", "org.freedesktop.Notifications"},
+			Call:      map[string]string{"org.freedesktop.portal.*": "*"},
+			Broadcast: map[string]string{"org.freedesktop.portal.*": "@/org/freedesktop/portal/*"},
+			Filter:    true,
+		}},
+	)
+	for _, id := range ids {
+		tcs = append(tcs,
+			newTestCase{id, [2]bool{false, false}, &dbus.Config{
+				Call:      make(map[string]string),
+				Broadcast: make(map[string]string),
+				Filter:    true,
+			}},
+			newTestCase{id, [2]bool{false, true}, &dbus.Config{
+				Call:      make(map[string]string),
+				Broadcast: make(map[string]string),
+				Filter:    true,
+			}},
+			newTestCase{id, [2]bool{true, false}, &dbus.Config{
+				Talk:      []string{"org.freedesktop.DBus", "org.freedesktop.Notifications"},
+				Own:       []string{id + ".*"},
+				Call:      map[string]string{"org.freedesktop.portal.*": "*"},
+				Broadcast: map[string]string{"org.freedesktop.portal.*": "@/org/freedesktop/portal/*"},
+				Filter:    true,
+			}},
+			newTestCase{id, [2]bool{true, true}, &dbus.Config{
+				Talk:      []string{"org.freedesktop.DBus", "org.freedesktop.Notifications"},
+				Own:       []string{id + ".*", "org.mpris.MediaPlayer2." + id + ".*"},
+				Call:      map[string]string{"org.freedesktop.portal.*": "*"},
+				Broadcast: map[string]string{"org.freedesktop.portal.*": "@/org/freedesktop/portal/*"},
+				Filter:    true,
+			}},
+		)
+	}
+
+	for _, tc := range tcs {
+		name := new(strings.Builder)
+		name.WriteString("create new configuration struct")
+
+		if tc.args[0] {
+			name.WriteString(" with builtin defaults")
+			if tc.args[1] {
+				name.WriteString(" (mpris)")
+			}
+		}
+
+		if tc.id != "" {
+			name.WriteString(" for application ID ")
+			name.WriteString(tc.id)
+		}
+
+		t.Run(name.String(), func(t *testing.T) {
+			if gotC := dbus.NewConfig(tc.id, tc.args[0], tc.args[1]); !reflect.DeepEqual(gotC, tc.want) {
+				t.Errorf("NewConfig(%q, %t, %t) = %v, want %v",
+					tc.id, tc.args[0], tc.args[1],
+					gotC, tc.want)
+			}
+		})
+	}
+}

dbus/dbus.go

@@ -0,0 +1,40 @@
+// Package dbus wraps xdg-dbus-proxy and implements configuration and sandboxing of the underlying helper process.
+package dbus
+
+import (
+	"fmt"
+	"os"
+	"sync"
+)
+
+const (
+	SessionBusAddress = "DBUS_SESSION_BUS_ADDRESS"
+	SystemBusAddress  = "DBUS_SYSTEM_BUS_ADDRESS"
+)
+
+var (
+	addresses   [2]string
+	addressOnce sync.Once
+)
+
+func Address() (session, system string) {
+	addressOnce.Do(func() {
+		// resolve upstream session bus address
+		if addr, ok := os.LookupEnv(SessionBusAddress); !ok {
+			// fall back to default format
+			addresses[0] = fmt.Sprintf("unix:path=/run/user/%d/bus", os.Getuid())
+		} else {
+			addresses[0] = addr
+		}
+
+		// resolve upstream system bus address
+		if addr, ok := os.LookupEnv(SystemBusAddress); !ok {
+			// fall back to default hardcoded value
+			addresses[1] = "unix:path=/run/dbus/system_bus_socket"
+		} else {
+			addresses[1] = addr
+		}
+	})
+
+	return addresses[0], addresses[1]
+}

dbus/dbus_test.go

@@ -0,0 +1,215 @@
+package dbus_test
+
+import (
+	"errors"
+	"strings"
+	"testing"
+
+	"git.gensokyo.uk/security/fortify/dbus"
+	"git.gensokyo.uk/security/fortify/helper"
+)
+
+func TestNew(t *testing.T) {
+	for _, tc := range [][2][2]string{
+		{
+			{"unix:path=/run/user/1971/bus", "/tmp/fortify.1971/1ca5d183ef4c99e74c3e544715f32702/bus"},
+			{"unix:path=/run/dbus/system_bus_socket", "/tmp/fortify.1971/1ca5d183ef4c99e74c3e544715f32702/system_bus_socket"},
+		},
+		{
+			{"unix:path=/run/user/1971/bus", "/tmp/fortify.1971/881ac3796ff3f3bf0a773824383187a0/bus"},
+			{"unix:path=/run/dbus/system_bus_socket", "/tmp/fortify.1971/881ac3796ff3f3bf0a773824383187a0/system_bus_socket"},
+		},
+		{
+			{"unix:path=/run/user/1971/bus", "/tmp/fortify.1971/3d1a5084520ef79c0c6a49a675bac701/bus"},
+			{"unix:path=/run/dbus/system_bus_socket", "/tmp/fortify.1971/3d1a5084520ef79c0c6a49a675bac701/system_bus_socket"},
+		},
+		{
+			{"unix:path=/run/user/1971/bus", "/tmp/fortify.1971/2a1639bab712799788ea0ff7aa280c35/bus"},
+			{"unix:path=/run/dbus/system_bus_socket", "/tmp/fortify.1971/2a1639bab712799788ea0ff7aa280c35/system_bus_socket"},
+		},
+	} {
+		t.Run("create instance for "+tc[0][0]+" and "+tc[1][0], func(t *testing.T) {
+			if got := dbus.New(tc[0], tc[1]); !got.CompareTestNew(tc[0], tc[1]) {
+				t.Errorf("New(%q, %q) = %v",
+					tc[0], tc[1],
+					got)
+			}
+		})
+	}
+}
+
+func TestProxy_Seal(t *testing.T) {
+	t.Run("double seal panic", func(t *testing.T) {
+		defer func() {
+			want := "dbus proxy sealed twice"
+			if r := recover(); r != want {
+				t.Errorf("Seal: panic = %q, want %q",
+					r, want)
+			}
+		}()
+
+		p := dbus.New([2]string{}, [2]string{})
+		_ = p.Seal(dbus.NewConfig("", true, false), nil)
+		_ = p.Seal(dbus.NewConfig("", true, false), nil)
+	})
+
+	ep := dbus.New([2]string{}, [2]string{})
+	if err := ep.Seal(nil, nil); !errors.Is(err, dbus.ErrConfig) {
+		t.Errorf("Seal(nil, nil) error = %v, want %v",
+			err, dbus.ErrConfig)
+	}
+
+	for id, tc := range testCasePairs() {
+		t.Run("create seal for "+id, func(t *testing.T) {
+			p := dbus.New(tc[0].bus, tc[1].bus)
+			if err := p.Seal(tc[0].c, tc[1].c); (errors.Is(err, helper.ErrContainsNull)) != tc[0].wantErr {
+				t.Errorf("Seal(%p, %p) error = %v, wantErr %v",
+					tc[0].c, tc[1].c,
+					err, tc[0].wantErr)
+				return
+			}
+
+			// rest of the tests happen for sealed instances
+			if tc[0].wantErr {
+				return
+			}
+
+			// build null-terminated string from wanted args
+			want := new(strings.Builder)
+			args := append(tc[0].want, tc[1].want...)
+			for _, arg := range args {
+				want.WriteString(arg)
+				want.WriteByte('\x00')
+			}
+
+			wt := p.AccessTestProxySeal()
+			got := new(strings.Builder)
+			if _, err := wt.WriteTo(got); err != nil {
+				t.Errorf("p.seal.WriteTo(): %v", err)
+			}
+
+			if want.String() != got.String() {
+				t.Errorf("Seal(%p, %p) seal = %v, want %v",
+					tc[0].c, tc[1].c,
+					got.String(), want.String())
+			}
+		})
+	}
+}
+
+func TestProxy_Start_Wait_Close_String(t *testing.T) {
+	t.Run("sandboxed", func(t *testing.T) {
+		testProxyStartWaitCloseString(t, true)
+	})
+	t.Run("direct", func(t *testing.T) {
+		testProxyStartWaitCloseString(t, false)
+	})
+}
+
+func testProxyStartWaitCloseString(t *testing.T, sandbox bool) {
+	for id, tc := range testCasePairs() {
+		// this test does not test errors
+		if tc[0].wantErr {
+			continue
+		}
+
+		t.Run("string for nil proxy", func(t *testing.T) {
+			var p *dbus.Proxy
+			want := "(invalid dbus proxy)"
+			if got := p.String(); got != want {
+				t.Errorf("String() = %v, want %v",
+					got, want)
+			}
+		})
+
+		t.Run("proxy for "+id, func(t *testing.T) {
+			helper.InternalReplaceExecCommand(t)
+			p := dbus.New(tc[0].bus, tc[1].bus)
+			output := new(strings.Builder)
+
+			t.Run("unsealed behaviour of "+id, func(t *testing.T) {
+				t.Run("unsealed string of "+id, func(t *testing.T) {
+					want := "(unsealed dbus proxy)"
+					if got := p.String(); got != want {
+						t.Errorf("String() = %v, want %v",
+							got, want)
+						return
+					}
+				})
+
+				t.Run("unsealed start of "+id, func(t *testing.T) {
+					want := "proxy not sealed"
+					if err := p.Start(nil, nil, sandbox); err == nil || err.Error() != want {
+						t.Errorf("Start() error = %v, wantErr %q",
+							err, errors.New(want))
+						return
+					}
+				})
+
+				t.Run("unsealed wait of "+id, func(t *testing.T) {
+					wantErr := "proxy not started"
+					if err := p.Wait(); err == nil || err.Error() != wantErr {
+						t.Errorf("Wait() error = %v, wantErr %v",
+							err, wantErr)
+					}
+				})
+			})
+
+			t.Run("seal with "+id, func(t *testing.T) {
+				if err := p.Seal(tc[0].c, tc[1].c); err != nil {
+					t.Errorf("Seal(%p, %p) error = %v, wantErr %v",
+						tc[0].c, tc[1].c,
+						err, tc[0].wantErr)
+					return
+				}
+			})
+
+			t.Run("sealed behaviour of "+id, func(t *testing.T) {
+				want := strings.Join(append(tc[0].want, tc[1].want...), " ")
+				if got := p.String(); got != want {
+					t.Errorf("String() = %v, want %v",
+						got, want)
+					return
+				}
+
+				t.Run("sealed start of "+id, func(t *testing.T) {
+					if err := p.Start(nil, output, sandbox); err != nil {
+						t.Errorf("Start(nil, nil) error = %v",
+							err)
+					}
+
+					t.Run("started string of "+id, func(t *testing.T) {
+						wantSubstr := dbus.ProxyName + " --args="
+						if got := p.String(); !strings.Contains(got, wantSubstr) {
+							t.Errorf("String() = %v, want %v",
+								p.String(), wantSubstr)
+							return
+						}
+					})
+
+					t.Run("sealed closing of "+id+" without status", func(t *testing.T) {
+						wantPanic := "attempted to close helper with no status pipe"
+						defer func() {
+							if r := recover(); r != wantPanic {
+								t.Errorf("Close() panic = %v, wantPanic %v",
+									r, wantPanic)
+							}
+						}()
+
+						if err := p.Close(); err != nil {
+							t.Errorf("Close() error = %v",
+								err)
+						}
+					})
+
+					t.Run("started wait of "+id, func(t *testing.T) {
+						if err := p.Wait(); err != nil {
+							t.Errorf("Wait() error = %v\noutput: %s",
+								err, output.String())
+						}
+					})
+				})
+			})
+		})
+	}
+}

dbus/export_test.go

@@ -0,0 +1,13 @@
+package dbus
+
+import "io"
+
+// CompareTestNew provides TestNew with comparison access to unexported Proxy fields.
+func (p *Proxy) CompareTestNew(session, system [2]string) bool {
+	return session == p.session && system == p.system
+}
+
+// AccessTestProxySeal provides TestProxy_Seal with access to unexported Proxy seal field.
+func (p *Proxy) AccessTestProxySeal() io.WriterTo {
+	return p.seal
+}

dbus/proxy.go

@@ -0,0 +1,105 @@
+package dbus
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"sync"
+
+	"git.gensokyo.uk/security/fortify/helper"
+	"git.gensokyo.uk/security/fortify/helper/bwrap"
+)
+
+// ProxyName is the file name or path to the proxy program.
+// Overriding ProxyName will only affect Proxy instance created after the change.
+var ProxyName = "xdg-dbus-proxy"
+
+// Proxy holds references to a xdg-dbus-proxy process, and should never be copied.
+// Once sealed, configuration changes will no longer be possible and attempting to do so will result in a panic.
+type Proxy struct {
+	helper helper.Helper
+	bwrap  *bwrap.Config
+
+	name    string
+	session [2]string
+	system  [2]string
+
+	seal io.WriterTo
+	lock sync.RWMutex
+}
+
+func (p *Proxy) Session() [2]string {
+	return p.session
+}
+
+func (p *Proxy) System() [2]string {
+	return p.system
+}
+
+func (p *Proxy) Sealed() bool {
+	p.lock.RLock()
+	defer p.lock.RUnlock()
+
+	return p.seal != nil
+}
+
+var (
+	ErrConfig = errors.New("no configuration to seal")
+)
+
+func (p *Proxy) String() string {
+	if p == nil {
+		return "(invalid dbus proxy)"
+	}
+
+	p.lock.RLock()
+	defer p.lock.RUnlock()
+
+	if p.helper != nil {
+		return p.helper.Unwrap().String()
+	}
+
+	if p.seal != nil {
+		return p.seal.(fmt.Stringer).String()
+	}
+
+	return "(unsealed dbus proxy)"
+}
+
+func (p *Proxy) Bwrap() []string {
+	return p.bwrap.Args()
+}
+
+// Seal seals the Proxy instance.
+func (p *Proxy) Seal(session, system *Config) error {
+	p.lock.Lock()
+	defer p.lock.Unlock()
+
+	if p.seal != nil {
+		panic("dbus proxy sealed twice")
+	}
+
+	if session == nil && system == nil {
+		return ErrConfig
+	}
+
+	var args []string
+	if session != nil {
+		args = append(args, session.Args(p.session)...)
+	}
+	if system != nil {
+		args = append(args, system.Args(p.system)...)
+	}
+	if seal, err := helper.NewCheckedArgs(args); err != nil {
+		return err
+	} else {
+		p.seal = seal
+	}
+
+	return nil
+}
+
+// New returns a reference to a new unsealed Proxy.
+func New(session, system [2]string) *Proxy {
+	return &Proxy{name: ProxyName, session: session, system: system}
+}

dbus/run.go

@@ -0,0 +1,140 @@
+package dbus
+
+import (
+	"errors"
+	"io"
+	"os/exec"
+	"path"
+	"path/filepath"
+	"strconv"
+	"strings"
+
+	"git.gensokyo.uk/security/fortify/helper"
+	"git.gensokyo.uk/security/fortify/helper/bwrap"
+	"git.gensokyo.uk/security/fortify/ldd"
+)
+
+// Start launches the D-Bus proxy and sets up the Wait method.
+// ready should be buffered and must only be received from once.
+func (p *Proxy) Start(ready chan error, output io.Writer, sandbox bool) error {
+	p.lock.Lock()
+	defer p.lock.Unlock()
+
+	if p.seal == nil {
+		return errors.New("proxy not sealed")
+	}
+
+	var (
+		h   helper.Helper
+		cmd *exec.Cmd
+
+		argF = func(argsFD, statFD int) []string {
+			if statFD == -1 {
+				return []string{"--args=" + strconv.Itoa(argsFD)}
+			} else {
+				return []string{"--args=" + strconv.Itoa(argsFD), "--fd=" + strconv.Itoa(statFD)}
+			}
+		}
+	)
+
+	if !sandbox {
+		h = helper.New(p.seal, p.name, argF)
+		cmd = h.Unwrap()
+		// xdg-dbus-proxy does not need to inherit the environment
+		cmd.Env = []string{}
+	} else {
+		// look up absolute path if name is just a file name
+		toolPath := p.name
+		if filepath.Base(p.name) == p.name {
+			if s, err := exec.LookPath(p.name); err == nil {
+				toolPath = s
+			}
+		}
+
+		// resolve libraries by parsing ldd output
+		var proxyDeps []*ldd.Entry
+		if path.IsAbs(toolPath) {
+			if l, err := ldd.Exec(toolPath); err != nil {
+				return err
+			} else {
+				proxyDeps = l
+			}
+		}
+
+		bc := &bwrap.Config{
+			Unshare:       nil,
+			Hostname:      "fortify-dbus",
+			Chdir:         "/",
+			Clearenv:      true,
+			NewSession:    true,
+			DieWithParent: true,
+		}
+
+		// resolve proxy socket directories
+		bindTarget := make(map[string]struct{}, 2)
+		for _, ps := range []string{p.session[1], p.system[1]} {
+			if pd := path.Dir(ps); len(pd) > 0 {
+				if pd[0] == '/' {
+					bindTarget[pd] = struct{}{}
+				}
+			}
+		}
+		for k := range bindTarget {
+			bc.Bind(k, k, false, true)
+		}
+
+		roBindTarget := make(map[string]struct{}, 2+1+len(proxyDeps))
+
+		// xdb-dbus-proxy bin and dependencies
+		roBindTarget[path.Dir(toolPath)] = struct{}{}
+		for _, ent := range proxyDeps {
+			if path.IsAbs(ent.Path) {
+				roBindTarget[path.Dir(ent.Path)] = struct{}{}
+			}
+		}
+
+		// resolve upstream bus directories
+		for _, as := range []string{p.session[0], p.system[0]} {
+			if len(as) > 0 && strings.HasPrefix(as, "unix:path=/") {
+				// leave / intact
+				roBindTarget[path.Dir(as[10:])] = struct{}{}
+			}
+		}
+
+		for k := range roBindTarget {
+			bc.Bind(k, k)
+		}
+
+		h = helper.MustNewBwrap(bc, p.seal, toolPath, argF)
+		cmd = h.Unwrap()
+		p.bwrap = bc
+	}
+
+	if output != nil {
+		cmd.Stdout = output
+		cmd.Stderr = output
+	}
+	if err := h.StartNotify(ready); err != nil {
+		return err
+	}
+
+	p.helper = h
+	return nil
+}
+
+// Wait waits for xdg-dbus-proxy to exit or fault.
+func (p *Proxy) Wait() error {
+	p.lock.RLock()
+	defer p.lock.RUnlock()
+
+	if p.helper == nil {
+		return errors.New("proxy not started")
+	}
+
+	return p.helper.Wait()
+}
+
+// Close closes the status file descriptor passed to xdg-dbus-proxy, causing it to stop.
+func (p *Proxy) Close() error {
+	return p.helper.Close()
+}

dbus/samples_test.go

@@ -0,0 +1,221 @@
+package dbus_test
+
+import (
+	"sync"
+
+	"git.gensokyo.uk/security/fortify/dbus"
+)
+
+var samples = []dbusTestCase{
+	{
+		"org.chromium.Chromium", &dbus.Config{
+			See: nil,
+			Talk: []string{"org.freedesktop.Notifications", "org.freedesktop.FileManager1", "org.freedesktop.ScreenSaver",
+				"org.freedesktop.secrets", "org.kde.kwalletd5", "org.kde.kwalletd6", "org.gnome.SessionManager"},
+			Own: []string{"org.chromium.Chromium.*", "org.mpris.MediaPlayer2.org.chromium.Chromium.*",
+				"org.mpris.MediaPlayer2.chromium.*"},
+			Call:      map[string]string{"org.freedesktop.portal.*": "*"},
+			Broadcast: map[string]string{"org.freedesktop.portal.*": "@/org/freedesktop/portal/*"},
+			Log:       false,
+			Filter:    true,
+		}, false, false,
+		[2]string{"unix:path=/run/user/1971/bus", "/tmp/fortify.1971/12622d846cc3fe7b4c10359d01f0eb47/bus"},
+		[]string{
+			"unix:path=/run/user/1971/bus",
+			"/tmp/fortify.1971/12622d846cc3fe7b4c10359d01f0eb47/bus",
+			"--filter",
+			"--talk=org.freedesktop.Notifications",
+			"--talk=org.freedesktop.FileManager1",
+			"--talk=org.freedesktop.ScreenSaver",
+			"--talk=org.freedesktop.secrets",
+			"--talk=org.kde.kwalletd5",
+			"--talk=org.kde.kwalletd6",
+			"--talk=org.gnome.SessionManager",
+			"--own=org.chromium.Chromium.*",
+			"--own=org.mpris.MediaPlayer2.org.chromium.Chromium.*",
+			"--own=org.mpris.MediaPlayer2.chromium.*",
+			"--call=org.freedesktop.portal.*=*",
+			"--broadcast=org.freedesktop.portal.*=@/org/freedesktop/portal/*",
+		},
+	},
+	{
+		"org.chromium.Chromium+", &dbus.Config{
+			See:       nil,
+			Talk:      []string{"org.bluez", "org.freedesktop.Avahi", "org.freedesktop.UPower"},
+			Own:       nil,
+			Call:      nil,
+			Broadcast: nil,
+			Log:       false,
+			Filter:    true,
+		}, false, false,
+		[2]string{"unix:path=/run/dbus/system_bus_socket", "/tmp/fortify.1971/12622d846cc3fe7b4c10359d01f0eb47/system_bus_socket"},
+		[]string{"unix:path=/run/dbus/system_bus_socket",
+			"/tmp/fortify.1971/12622d846cc3fe7b4c10359d01f0eb47/system_bus_socket",
+			"--filter",
+			"--talk=org.bluez",
+			"--talk=org.freedesktop.Avahi",
+			"--talk=org.freedesktop.UPower",
+		},
+	},
+
+	{
+		"dev.vencord.Vesktop", &dbus.Config{
+			See:       nil,
+			Talk:      []string{"org.freedesktop.Notifications", "org.kde.StatusNotifierWatcher"},
+			Own:       []string{"dev.vencord.Vesktop.*", "org.mpris.MediaPlayer2.dev.vencord.Vesktop.*"},
+			Call:      map[string]string{"org.freedesktop.portal.*": "*"},
+			Broadcast: map[string]string{"org.freedesktop.portal.*": "@/org/freedesktop/portal/*"},
+			Log:       false,
+			Filter:    true,
+		}, false, false,
+		[2]string{"unix:path=/run/user/1971/bus", "/tmp/fortify.1971/34c24f16a0d791d28835ededaf446033/bus"},
+		[]string{
+			"unix:path=/run/user/1971/bus",
+			"/tmp/fortify.1971/34c24f16a0d791d28835ededaf446033/bus",
+			"--filter",
+			"--talk=org.freedesktop.Notifications",
+			"--talk=org.kde.StatusNotifierWatcher",
+			"--own=dev.vencord.Vesktop.*",
+			"--own=org.mpris.MediaPlayer2.dev.vencord.Vesktop.*",
+			"--call=org.freedesktop.portal.*=*",
+			"--broadcast=org.freedesktop.portal.*=@/org/freedesktop/portal/*"},
+	},
+
+	{
+		"moe.ophivana.CrashTestDummy", &dbus.Config{
+			See:       []string{"moe.ophivana.CrashTestDummy1"},
+			Talk:      []string{"org.freedesktop.Notifications"},
+			Own:       []string{"moe.ophivana.CrashTestDummy.*", "org.mpris.MediaPlayer2.moe.ophivana.CrashTestDummy.*"},
+			Call:      map[string]string{"org.freedesktop.portal.*": "*"},
+			Broadcast: map[string]string{"org.freedesktop.portal.*": "@/org/freedesktop/portal/*"},
+			Log:       true,
+			Filter:    true,
+		}, false, false,
+		[2]string{"unix:path=/run/user/1971/bus", "/tmp/fortify.1971/5da7845287a936efbc2fa75d7d81e501/bus"},
+		[]string{
+			"unix:path=/run/user/1971/bus",
+			"/tmp/fortify.1971/5da7845287a936efbc2fa75d7d81e501/bus",
+			"--filter",
+			"--see=moe.ophivana.CrashTestDummy1",
+			"--talk=org.freedesktop.Notifications",
+			"--own=moe.ophivana.CrashTestDummy.*",
+			"--own=org.mpris.MediaPlayer2.moe.ophivana.CrashTestDummy.*",
+			"--call=org.freedesktop.portal.*=*",
+			"--broadcast=org.freedesktop.portal.*=@/org/freedesktop/portal/*",
+			"--log"},
+	},
+	{
+		"moe.ophivana.CrashTestDummy1", &dbus.Config{
+			See:       []string{"moe.ophivana.CrashTestDummy"},
+			Talk:      []string{"org.freedesktop.Notifications"},
+			Own:       []string{"moe.ophivana.CrashTestDummy1.*", "org.mpris.MediaPlayer2.moe.ophivana.CrashTestDummy1.*"},
+			Call:      map[string]string{"org.freedesktop.portal.*": "*"},
+			Broadcast: map[string]string{"org.freedesktop.portal.*": "@/org/freedesktop/portal/*"},
+			Log:       true,
+			Filter:    true,
+		}, false, true,
+		[2]string{"unix:path=/run/user/1971/bus", "/tmp/fortify.1971/5da7845287a936efbc2fa75d7d81e501/bus"},
+		[]string{
+			"unix:path=/run/user/1971/bus",
+			"/tmp/fortify.1971/5da7845287a936efbc2fa75d7d81e501/bus",
+			"--filter",
+			"--see=moe.ophivana.CrashTestDummy",
+			"--talk=org.freedesktop.Notifications",
+			"--own=moe.ophivana.CrashTestDummy1.*",
+			"--own=org.mpris.MediaPlayer2.moe.ophivana.CrashTestDummy1.*",
+			"--call=org.freedesktop.portal.*=*",
+			"--broadcast=org.freedesktop.portal.*=@/org/freedesktop/portal/*",
+			"--log"},
+	},
+}
+
+type dbusTestCase struct {
+	id       string
+	c        *dbus.Config
+	wantErr  bool
+	wantErrF bool
+	bus      [2]string
+	want     []string
+}
+
+var (
+	testCasesV     []dbusTestCase
+	testCasePairsV map[string][2]dbusTestCase
+
+	testCaseOnce sync.Once
+)
+
+func testCases() []dbusTestCase {
+	testCaseOnce.Do(testCaseGenerate)
+	return testCasesV
+}
+
+func testCasePairs() map[string][2]dbusTestCase {
+	testCaseOnce.Do(testCaseGenerate)
+	return testCasePairsV
+}
+
+func injectNulls(t *[]string) {
+	f := make([]string, len(*t))
+	for i := range f {
+		f[i] = "\x00" + (*t)[i] + "\x00"
+	}
+	*t = f
+}
+
+func testCaseGenerate() {
+	// create null-injected test cases
+	testCasesV = make([]dbusTestCase, len(samples)*2)
+	for i := range samples {
+		testCasesV[i] = samples[i]
+		testCasesV[len(samples)+i] = samples[i]
+		testCasesV[len(samples)+i].c = new(dbus.Config)
+		*testCasesV[len(samples)+i].c = *samples[i].c
+
+		// inject nulls
+		fi := &testCasesV[len(samples)+i]
+		fi.wantErr = true
+
+		injectNulls(&fi.c.See)
+		injectNulls(&fi.c.Talk)
+		injectNulls(&fi.c.Own)
+	}
+
+	// enumerate test case pairs
+	var pc int
+	for _, tc := range samples {
+		if tc.id != "" {
+			pc++
+		}
+	}
+	testCasePairsV = make(map[string][2]dbusTestCase, pc)
+	for i, tc := range testCasesV {
+		if tc.id == "" {
+			continue
+		}
+
+		// skip already enumerated system bus test
+		if tc.id[len(tc.id)-1] == '+' {
+			continue
+		}
+
+		ftp := [2]dbusTestCase{tc}
+
+		// system proxy tests always place directly after its user counterpart with id ending in +
+		if i+1 < len(testCasesV) && testCasesV[i+1].id[len(testCasesV[i+1].id)-1] == '+' {
+			// attach system bus config
+			ftp[1] = testCasesV[i+1]
+
+			// check for misplaced/mismatching tests
+			if ftp[0].wantErr != ftp[1].wantErr || ftp[0].id+"+" != ftp[1].id {
+				panic("mismatching session/system pairing")
+			}
+		}
+
+		k := tc.id
+		if tc.wantErr {
+			k = "malformed_" + k
+		}
+		testCasePairsV[k] = ftp
+	}
+}

dbus/stub_test.go

@@ -0,0 +1,11 @@
+package dbus_test
+
+import (
+	"testing"
+
+	"git.gensokyo.uk/security/fortify/helper"
+)
+
+func TestHelperChildStub(t *testing.T) {
+	helper.InternalChildStub()
+}

dbus/testdata/dev.vencord.Vesktop.json

@@ -0,0 +1,18 @@
+{
+  "talk":[
+    "org.freedesktop.Notifications",
+    "org.kde.StatusNotifierWatcher"
+  ],
+  "own":[
+    "dev.vencord.Vesktop.*",
+    "org.mpris.MediaPlayer2.dev.vencord.Vesktop.*"
+  ],
+  "call":{
+    "org.freedesktop.portal.*":"*"
+  },
+  "broadcast":{
+    "org.freedesktop.portal.*":"@/org/freedesktop/portal/*"
+  },
+
+  "filter":true
+}

dbus/testdata/moe.ophivana.CrashTestDummy.json

@@ -0,0 +1,21 @@
+{
+  "see": [
+    "moe.ophivana.CrashTestDummy1"
+  ],
+  "talk":[
+    "org.freedesktop.Notifications"
+  ],
+  "own":[
+    "moe.ophivana.CrashTestDummy.*",
+    "org.mpris.MediaPlayer2.moe.ophivana.CrashTestDummy.*"
+  ],
+  "call":{
+    "org.freedesktop.portal.*":"*"
+  },
+  "broadcast":{
+    "org.freedesktop.portal.*":"@/org/freedesktop/portal/*"
+  },
+
+  "log": true,
+  "filter":true
+}

dbus/testdata/org.chromium.Chromium+.json

@@ -0,0 +1,9 @@
+{
+  "talk":[
+    "org.bluez",
+    "org.freedesktop.Avahi",
+    "org.freedesktop.UPower"
+  ],
+
+  "filter":true
+}

dbus/testdata/org.chromium.Chromium.json

@@ -0,0 +1,24 @@
+{
+  "talk":[
+    "org.freedesktop.Notifications",
+    "org.freedesktop.FileManager1",
+    "org.freedesktop.ScreenSaver",
+    "org.freedesktop.secrets",
+    "org.kde.kwalletd5",
+    "org.kde.kwalletd6",
+    "org.gnome.SessionManager"
+  ],
+  "own":[
+    "org.chromium.Chromium.*",
+    "org.mpris.MediaPlayer2.org.chromium.Chromium.*",
+    "org.mpris.MediaPlayer2.chromium.*"
+  ],
+  "call":{
+    "org.freedesktop.portal.*":"*"
+  },
+  "broadcast":{
+    "org.freedesktop.portal.*":"@/org/freedesktop/portal/*"
+  },
+
+  "filter":true
+}

dist/fsurc.default

@@ -0,0 +1 @@
+1000 0

dist/install.sh

@@ -0,0 +1,10 @@
+#!/bin/sh
+cd "$(dirname -- "$0")" || exit 1
+
+install -vDm0755 "bin/fortify" "${FORTIFY_INSTALL_PREFIX}/usr/bin/fortify"
+install -vDm0755 "bin/fshim" "${FORTIFY_INSTALL_PREFIX}/usr/libexec/fortify/fshim"
+install -vDm0755 "bin/finit" "${FORTIFY_INSTALL_PREFIX}/usr/libexec/fortify/finit"
+install -vDm0755 "bin/fuserdb" "${FORTIFY_INSTALL_PREFIX}/usr/libexec/fortify/fuserdb"
+
+install -vDm6511 "bin/fsu" "${FORTIFY_INSTALL_PREFIX}/usr/bin/fsu"
+install -vDm0400 "fsurc.default" "${FORTIFY_INSTALL_PREFIX}/etc/fsurc"

dist/release.sh

@@ -0,0 +1,19 @@
+#!/bin/sh -e
+cd "$(dirname -- "$0")/.."
+VERSION="${FORTIFY_VERSION:-untagged}"
+pname="fortify-${VERSION}"
+out="dist/${pname}"
+
+mkdir -p "${out}"
+cp "README.md" "dist/fsurc.default" "dist/install.sh" "${out}"
+
+go build -v -o "${out}/bin/" -ldflags "-s -w
+  -X git.gensokyo.uk/security/fortify/internal.Version=${VERSION}
+  -X git.gensokyo.uk/security/fortify/internal.Fsu=/usr/bin/fsu
+  -X git.gensokyo.uk/security/fortify/internal.Finit=/usr/libexec/fortify/finit
+  -X main.Fmain=/usr/bin/fortify
+  -X main.Fshim=/usr/libexec/fortify/fshim" ./...
+
+rm -f "./${out}.tar.gz" && tar -C dist -czf "${out}.tar.gz" "${pname}"
+rm -rf "./${out}"
+sha512sum "${out}.tar.gz" > "${out}.tar.gz.sha512"

error.go

@@ -0,0 +1,55 @@
+package main
+
+import (
+	"errors"
+
+	"git.gensokyo.uk/security/fortify/internal/app"
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+)
+
+func logWaitError(err error) {
+	var e *fmsg.BaseError
+	if !fmsg.AsBaseError(err, &e) {
+		fmsg.Println("wait failed:", err)
+	} else {
+		// Wait only returns either *app.ProcessError or *app.StateStoreError wrapped in a *app.BaseError
+		var se *app.StateStoreError
+		if !errors.As(err, &se) {
+			// does not need special handling
+			fmsg.Print(e.Message())
+		} else {
+			// inner error are either unwrapped store errors
+			// or joined errors returned by *appSealTx revert
+			// wrapped in *app.BaseError
+			var ej app.RevertCompoundError
+			if !errors.As(se.InnerErr, &ej) {
+				// does not require special handling
+				fmsg.Print(e.Message())
+			} else {
+				errs := ej.Unwrap()
+
+				// every error here is wrapped in *app.BaseError
+				for _, ei := range errs {
+					var eb *fmsg.BaseError
+					if !errors.As(ei, &eb) {
+						// unreachable
+						fmsg.Println("invalid error type returned by revert:", ei)
+					} else {
+						// print inner *app.BaseError message
+						fmsg.Print(eb.Message())
+					}
+				}
+			}
+		}
+	}
+}
+
+func logBaseError(err error, message string) {
+	var e *fmsg.BaseError
+
+	if fmsg.AsBaseError(err, &e) {
+		fmsg.Print(e.Message())
+	} else {
+		fmsg.Println(message, err)
+	}
+}

flake.lock

@@ -1,23 +1,45 @@
 {
   "nodes": {
+    "home-manager": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1733951536,
+        "narHash": "sha256-Zb5ZCa7Xj+0gy5XVXINTSr71fCfAv+IKtmIXNrykT54=",
+        "owner": "nix-community",
+        "repo": "home-manager",
+        "rev": "1318c3f3b068cdcea922fa7c1a0a1f0c96c22f5f",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "ref": "release-24.11",
+        "repo": "home-manager",
+        "type": "github"
+      }
+    },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1717179513,
+        "lastModified": 1734298236,
-        "narHash": "sha256-vboIEwIQojofItm2xGCdZCzW96U85l9nDW3ifMuAIdM=",
+        "narHash": "sha256-aWhhqY44xBjMoO9r5fyPp5u8tqUNWRZ/m/P+abMSs5c=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "63dacb46bf939521bdc93981b4cbb7ecb58427a0",
+        "rev": "eb919d9300b6a18f8583f58aef16db458fbd7bec",
         "type": "github"
       },
       "original": {
         "owner": "NixOS",
-        "ref": "24.05",
+        "ref": "nixos-24.11-small",
         "repo": "nixpkgs",
         "type": "github"
       }
     },
     "root": {
       "inputs": {
+        "home-manager": "home-manager",
         "nixpkgs": "nixpkgs"
       }
     }

flake.nix

@@ -1,56 +1,152 @@
 {
-  description = "ego development environment";
+  description = "fortify sandbox tool and nixos module";
 
   inputs = {
-    nixpkgs.url = "github:NixOS/nixpkgs/24.05";
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.11-small";
+
+    home-manager = {
+      url = "github:nix-community/home-manager/release-24.11";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
   };
 
   outputs =
-    { self, nixpkgs }:
+    {
+      self,
+      nixpkgs,
+      home-manager,
+    }:
     let
-      supportedSystems = [ "x86_64-linux" ];
+      supportedSystems = [
-      forAllSystems = f: nixpkgs.lib.genAttrs supportedSystems (system: f system);
+        "aarch64-linux"
+        "i686-linux"
+        "x86_64-linux"
+      ];
+
+      forAllSystems = nixpkgs.lib.genAttrs supportedSystems;
+      nixpkgsFor = forAllSystems (system: import nixpkgs { inherit system; });
     in
     {
-      devShells = forAllSystems (
+      nixosModules.fortify = import ./nixos.nix;
+
+      checks = forAllSystems (
         system:
         let
-          pkgs = import nixpkgs { inherit system; };
+          pkgs = nixpkgsFor.${system};
-        in
+
-        {
-          default =
-            let
           inherit (pkgs)
-                mkShell
+            runCommandLocal
-                buildGoModule
+            callPackage
-                acl
+            nixfmt-rfc-style
-                xorg
+            deadnix
+            statix
             ;
         in
-            mkShell {
+        {
-              packages = [
+          check-formatting =
-                (buildGoModule rec {
+            runCommandLocal "check-formatting" { nativeBuildInputs = [ nixfmt-rfc-style ]; }
-                  pname = "ego";
+              ''
-                  version = "0.0.0-flake";
+                cd ${./.}
 
-                  src = ./.;
+                echo "running nixfmt..."
-                  vendorHash = null; # we have no dependencies :3
+                nixfmt --check .
 
-                  ldflags = [
+                touch $out
-                    "-s"
+              '';
-                    "-w"
-                    "-X"
-                    "main.Version=v${version}"
-                  ];
 
-                  buildInputs = [
+          check-lint =
-                    acl
+            runCommandLocal "check-lint"
-                    xorg.libxcb
+              {
+                nativeBuildInputs = [
+                  deadnix
+                  statix
                 ];
-                })
+              }
-              ];
+              ''
-            };
+                cd ${./.}
+
+                echo "running deadnix..."
+                deadnix --fail
+
+                echo "running statix..."
+                statix check .
+
+                touch $out
+              '';
+
+          nixos-tests = callPackage ./test.nix { inherit system self home-manager; };
         }
       );
+
+      packages = forAllSystems (
+        system:
+        let
+          pkgs = nixpkgsFor.${system};
+        in
+        {
+          default = self.packages.${system}.fortify;
+
+          fortify = pkgs.callPackage ./package.nix { };
+        }
+      );
+
+      devShells = forAllSystems (system: {
+        default = nixpkgsFor.${system}.mkShell {
+          buildInputs = with nixpkgsFor.${system}; self.packages.${system}.fortify.buildInputs;
+        };
+
+        fhs = nixpkgsFor.${system}.buildFHSEnv {
+          pname = "fortify-fhs";
+          inherit (self.packages.${system}.fortify) version;
+          targetPkgs =
+            pkgs: with pkgs; [
+              go
+              gcc
+              pkg-config
+              acl
+              wayland
+              wayland-scanner
+              wayland-protocols
+              xorg.libxcb
+            ];
+          extraOutputsToInstall = [ "dev" ];
+          profile = ''
+            export PKG_CONFIG_PATH="/usr/share/pkgconfig:$PKG_CONFIG_PATH"
+          '';
+        };
+
+        withPackage = nixpkgsFor.${system}.mkShell {
+          buildInputs =
+            with nixpkgsFor.${system};
+            self.packages.${system}.fortify.buildInputs ++ [ self.packages.${system}.fortify ];
+        };
+
+        generateDoc =
+          let
+            pkgs = nixpkgsFor.${system};
+            inherit (pkgs) lib;
+
+            doc =
+              let
+                eval = lib.evalModules {
+                  specialArgs = {
+                    inherit pkgs;
+                  };
+                  modules = [ ./options.nix ];
+                };
+                cleanEval = lib.filterAttrsRecursive (n: _: n != "_module") eval;
+              in
+              pkgs.nixosOptionsDoc { inherit (cleanEval) options; };
+            docText = pkgs.runCommand "fortify-module-docs.md" { } ''
+              cat ${doc.optionsCommonMark} > $out
+              sed -i '/*Declared by:*/,+1 d' $out
+            '';
+          in
+          nixpkgsFor.${system}.mkShell {
+            shellHook = ''
+              exec cat ${docText} > options.md
+            '';
+          };
+      });
     };
 }

fst/config.go

@@ -0,0 +1,242 @@
+package fst
+
+import (
+	"errors"
+
+	"git.gensokyo.uk/security/fortify/dbus"
+	"git.gensokyo.uk/security/fortify/helper/bwrap"
+	"git.gensokyo.uk/security/fortify/internal/linux"
+	"git.gensokyo.uk/security/fortify/internal/system"
+)
+
+const fTmp = "/fortify"
+
+// Config is used to seal an *App
+type Config struct {
+	// D-Bus application ID
+	ID string `json:"id"`
+	// value passed through to the child process as its argv
+	Command []string `json:"command"`
+
+	// child confinement configuration
+	Confinement ConfinementConfig `json:"confinement"`
+}
+
+// ConfinementConfig defines fortified child's confinement
+type ConfinementConfig struct {
+	// numerical application id, determines uid in the init namespace
+	AppID int `json:"app_id"`
+	// list of supplementary groups to inherit
+	Groups []string `json:"groups"`
+	// passwd username in the sandbox, defaults to chronos
+	Username string `json:"username,omitempty"`
+	// home directory in sandbox, empty for outer
+	Inner string `json:"home_inner"`
+	// home directory in init namespace
+	Outer string `json:"home"`
+	// bwrap sandbox confinement configuration
+	Sandbox *SandboxConfig `json:"sandbox"`
+
+	// reference to a system D-Bus proxy configuration,
+	// nil value disables system bus proxy
+	SystemBus *dbus.Config `json:"system_bus,omitempty"`
+	// reference to a session D-Bus proxy configuration,
+	// nil value makes session bus proxy assume built-in defaults
+	SessionBus *dbus.Config `json:"session_bus,omitempty"`
+
+	// child capability enablements
+	Enablements system.Enablements `json:"enablements"`
+}
+
+// SandboxConfig describes resources made available to the sandbox.
+type SandboxConfig struct {
+	// unix hostname within sandbox
+	Hostname string `json:"hostname,omitempty"`
+	// userns availability within sandbox
+	UserNS bool `json:"userns,omitempty"`
+	// share net namespace
+	Net bool `json:"net,omitempty"`
+	// share all devices
+	Dev bool `json:"dev,omitempty"`
+	// do not run in new session
+	NoNewSession bool `json:"no_new_session,omitempty"`
+	// map target user uid to privileged user uid in the user namespace
+	MapRealUID bool `json:"map_real_uid"`
+	// direct access to wayland socket
+	DirectWayland bool `json:"direct_wayland,omitempty"`
+
+	// final environment variables
+	Env map[string]string `json:"env"`
+	// sandbox host filesystem access
+	Filesystem []*FilesystemConfig `json:"filesystem"`
+	// symlinks created inside the sandbox
+	Link [][2]string `json:"symlink"`
+	// automatically set up /etc symlinks
+	AutoEtc bool `json:"auto_etc"`
+	// paths to override by mounting tmpfs over them
+	Override []string `json:"override"`
+}
+
+type FilesystemConfig struct {
+	// mount point in sandbox, same as src if empty
+	Dst string `json:"dst,omitempty"`
+	// host filesystem path to make available to sandbox
+	Src string `json:"src"`
+	// write access
+	Write bool `json:"write,omitempty"`
+	// device access
+	Device bool `json:"dev,omitempty"`
+	// exit if unable to share
+	Must bool `json:"require,omitempty"`
+}
+
+// Bwrap returns the address of the corresponding bwrap.Config to s.
+// Note that remaining tmpfs entries must be queued by the caller prior to launch.
+func (s *SandboxConfig) Bwrap(os linux.System) (*bwrap.Config, error) {
+	if s == nil {
+		return nil, errors.New("nil sandbox config")
+	}
+
+	var uid int
+	if !s.MapRealUID {
+		uid = 65534
+	} else {
+		uid = os.Geteuid()
+	}
+
+	conf := (&bwrap.Config{
+		Net:           s.Net,
+		UserNS:        s.UserNS,
+		Hostname:      s.Hostname,
+		Clearenv:      true,
+		SetEnv:        s.Env,
+		NewSession:    !s.NoNewSession,
+		DieWithParent: true,
+		AsInit:        true,
+
+		// initialise map
+		Chmod: make(bwrap.ChmodConfig),
+	}).
+		SetUID(uid).SetGID(uid).
+		Procfs("/proc").
+		Tmpfs(fTmp, 4*1024)
+
+	if !s.Dev {
+		conf.DevTmpfs("/dev").Mqueue("/dev/mqueue")
+	} else {
+		conf.Bind("/dev", "/dev", false, true, true)
+	}
+
+	if !s.AutoEtc {
+		conf.Dir("/etc")
+	}
+
+	for _, c := range s.Filesystem {
+		if c == nil {
+			continue
+		}
+		src := c.Src
+		dest := c.Dst
+		if c.Dst == "" {
+			dest = c.Src
+		}
+		conf.Bind(src, dest, !c.Must, c.Write, c.Device)
+	}
+
+	for _, l := range s.Link {
+		conf.Symlink(l[0], l[1])
+	}
+
+	if s.AutoEtc {
+		conf.Bind("/etc", fTmp+"/etc")
+
+		// link host /etc contents to prevent passwd/group from being overwritten
+		if d, err := os.ReadDir("/etc"); err != nil {
+			return nil, err
+		} else {
+			for _, ent := range d {
+				name := ent.Name()
+				switch name {
+				case "passwd":
+				case "group":
+
+				case "mtab":
+					conf.Symlink("/proc/mounts", "/etc/"+name)
+				default:
+					conf.Symlink(fTmp+"/etc/"+name, "/etc/"+name)
+				}
+			}
+		}
+	}
+
+	return conf, nil
+}
+
+// Template returns a fully populated instance of Config.
+func Template() *Config {
+	return &Config{
+		ID: "org.chromium.Chromium",
+		Command: []string{
+			"chromium",
+			"--ignore-gpu-blocklist",
+			"--disable-smooth-scrolling",
+			"--enable-features=UseOzonePlatform",
+			"--ozone-platform=wayland",
+		},
+		Confinement: ConfinementConfig{
+			AppID:    9,
+			Groups:   []string{"video"},
+			Username: "chronos",
+			Outer:    "/var/lib/persist/home/org.chromium.Chromium",
+			Inner:    "/var/lib/fortify",
+			Sandbox: &SandboxConfig{
+				Hostname:      "localhost",
+				UserNS:        true,
+				Net:           true,
+				NoNewSession:  true,
+				MapRealUID:    true,
+				Dev:           true,
+				DirectWayland: false,
+				// example API credentials pulled from Google Chrome
+				// DO NOT USE THESE IN A REAL BROWSER
+				Env: map[string]string{
+					"GOOGLE_API_KEY":               "AIzaSyBHDrl33hwRp4rMQY0ziRbj8K9LPA6vUCY",
+					"GOOGLE_DEFAULT_CLIENT_ID":     "77185425430.apps.googleusercontent.com",
+					"GOOGLE_DEFAULT_CLIENT_SECRET": "OTJgUOQcT7lO7GsGZq2G4IlT",
+				},
+				Filesystem: []*FilesystemConfig{
+					{Src: "/nix/store"},
+					{Src: "/run/current-system"},
+					{Src: "/run/opengl-driver"},
+					{Src: "/var/db/nix-channels"},
+					{Src: "/home/chronos", Write: true, Must: true},
+					{Src: "/dev/dri", Device: true},
+				},
+				Link:     [][2]string{{"/run/user/65534", "/run/user/150"}},
+				AutoEtc:  true,
+				Override: []string{"/var/run/nscd"},
+			},
+			SystemBus: &dbus.Config{
+				See:       nil,
+				Talk:      []string{"org.bluez", "org.freedesktop.Avahi", "org.freedesktop.UPower"},
+				Own:       nil,
+				Call:      nil,
+				Broadcast: nil,
+				Log:       false,
+				Filter:    true,
+			},
+			SessionBus: &dbus.Config{
+				See: nil,
+				Talk: []string{"org.freedesktop.Notifications", "org.freedesktop.FileManager1", "org.freedesktop.ScreenSaver",
+					"org.freedesktop.secrets", "org.kde.kwalletd5", "org.kde.kwalletd6", "org.gnome.SessionManager"},
+				Own: []string{"org.chromium.Chromium.*", "org.mpris.MediaPlayer2.org.chromium.Chromium.*",
+					"org.mpris.MediaPlayer2.chromium.*"},
+				Call:      map[string]string{"org.freedesktop.portal.*": "*"},
+				Broadcast: map[string]string{"org.freedesktop.portal.*": "@/org/freedesktop/portal/*"},
+				Log:       false,
+				Filter:    true,
+			},
+			Enablements: system.EWayland.Mask() | system.EDBus.Mask() | system.EPulse.Mask(),
+		},
+	}
+}

fst/id.go

@@ -0,0 +1,48 @@
+package fst
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"errors"
+	"fmt"
+)
+
+type ID [16]byte
+
+var (
+	ErrInvalidLength = errors.New("string representation must have a length of 32")
+)
+
+func (a *ID) String() string {
+	return hex.EncodeToString(a[:])
+}
+
+func NewAppID(id *ID) error {
+	_, err := rand.Read(id[:])
+	return err
+}
+
+func ParseAppID(id *ID, s string) error {
+	if len(s) != 32 {
+		return ErrInvalidLength
+	}
+
+	for i, b := range s {
+		if b < '0' || b > 'f' {
+			return fmt.Errorf("invalid char %q at byte %d", b, i)
+		}
+
+		v := uint8(b)
+		if v > '9' {
+			v = 10 + v - 'a'
+		} else {
+			v -= '0'
+		}
+		if i%2 == 0 {
+			v <<= 4
+		}
+		id[i/2] += v
+	}
+
+	return nil
+}

fst/id_test.go

@@ -0,0 +1,63 @@
+package fst_test
+
+import (
+	"errors"
+	"testing"
+
+	"git.gensokyo.uk/security/fortify/fst"
+)
+
+func TestParseAppID(t *testing.T) {
+	t.Run("bad length", func(t *testing.T) {
+		if err := fst.ParseAppID(new(fst.ID), "meow"); !errors.Is(err, fst.ErrInvalidLength) {
+			t.Errorf("ParseAppID: error = %v, wantErr =  %v", err, fst.ErrInvalidLength)
+		}
+	})
+
+	t.Run("bad byte", func(t *testing.T) {
+		wantErr := "invalid char '\\n' at byte 15"
+		if err := fst.ParseAppID(new(fst.ID), "02bc7f8936b2af6\n\ne2535cd71ef0bb7"); err == nil || err.Error() != wantErr {
+			t.Errorf("ParseAppID: error = %v, wantErr =  %v", err, wantErr)
+		}
+	})
+
+	t.Run("fuzz 16 iterations", func(t *testing.T) {
+		for i := 0; i < 16; i++ {
+			testParseAppIDWithRandom(t)
+		}
+	})
+}
+
+func FuzzParseAppID(f *testing.F) {
+	for i := 0; i < 16; i++ {
+		id := new(fst.ID)
+		if err := fst.NewAppID(id); err != nil {
+			panic(err.Error())
+		}
+		f.Add(id[0], id[1], id[2], id[3], id[4], id[5], id[6], id[7], id[8], id[9], id[10], id[11], id[12], id[13], id[14], id[15])
+	}
+
+	f.Fuzz(func(t *testing.T, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, b10, b11, b12, b13, b14, b15 byte) {
+		testParseAppID(t, &fst.ID{b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, b10, b11, b12, b13, b14, b15})
+	})
+}
+
+func testParseAppIDWithRandom(t *testing.T) {
+	id := new(fst.ID)
+	if err := fst.NewAppID(id); err != nil {
+		t.Fatalf("cannot generate app ID: %v", err)
+	}
+	testParseAppID(t, id)
+}
+
+func testParseAppID(t *testing.T, id *fst.ID) {
+	s := id.String()
+	got := new(fst.ID)
+	if err := fst.ParseAppID(got, s); err != nil {
+		t.Fatalf("cannot parse app ID: %v", err)
+	}
+
+	if *got != *id {
+		t.Fatalf("ParseAppID(%#v) = \n%#v, want \n%#v", s, got, id)
+	}
+}

fst/shared.go

@@ -0,0 +1,2 @@
+// Package fst exports shared fortify types.
+package fst

go.mod

@@ -1,3 +1,3 @@
-module git.ophivana.moe/cat/ego
+module git.gensokyo.uk/security/fortify
 
 go 1.22

helper/args.go

@@ -0,0 +1,66 @@
+package helper
+
+import (
+	"errors"
+	"io"
+	"strings"
+)
+
+var (
+	ErrContainsNull = errors.New("argument contains null character")
+)
+
+type argsWt []string
+
+// checks whether any element contains the null character
+// must be called before args use and args must not be modified after call
+func (a argsWt) check() error {
+	for _, arg := range a {
+		for _, b := range arg {
+			if b == '\x00' {
+				return ErrContainsNull
+			}
+		}
+	}
+
+	return nil
+}
+
+func (a argsWt) WriteTo(w io.Writer) (int64, error) {
+	// assuming already checked
+
+	nt := 0
+	// write null terminated arguments
+	for _, arg := range a {
+		n, err := w.Write([]byte(arg + "\x00"))
+		nt += n
+
+		if err != nil {
+			return int64(nt), err
+		}
+	}
+
+	return int64(nt), nil
+}
+
+func (a argsWt) String() string {
+	return strings.Join(a, " ")
+}
+
+// NewCheckedArgs returns a checked argument writer for args.
+// Callers must not retain any references to args.
+func NewCheckedArgs(args []string) (io.WriterTo, error) {
+	a := argsWt(args)
+	return a, a.check()
+}
+
+// MustNewCheckedArgs returns a checked argument writer for args and panics if check fails.
+// Callers must not retain any references to args.
+func MustNewCheckedArgs(args []string) io.WriterTo {
+	a, err := NewCheckedArgs(args)
+	if err != nil {
+		panic(err.Error())
+	}
+
+	return a
+}

helper/args_test.go

@@ -0,0 +1,40 @@
+package helper_test
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+	"testing"
+
+	"git.gensokyo.uk/security/fortify/helper"
+)
+
+func Test_argsFD_String(t *testing.T) {
+	wantString := strings.Join(wantArgs, " ")
+	if got := argsWt.(fmt.Stringer).String(); got != wantString {
+		t.Errorf("String(): got %v; want %v",
+			got, wantString)
+	}
+}
+
+func TestNewCheckedArgs(t *testing.T) {
+	args := []string{"\x00"}
+	if _, err := helper.NewCheckedArgs(args); !errors.Is(err, helper.ErrContainsNull) {
+		t.Errorf("NewCheckedArgs(%q) error = %v, wantErr %v",
+			args,
+			err, helper.ErrContainsNull)
+	}
+
+	t.Run("must panic", func(t *testing.T) {
+		badPayload := []string{"\x00"}
+		defer func() {
+			wantPanic := "argument contains null character"
+			if r := recover(); r != wantPanic {
+				t.Errorf("MustNewCheckedArgs(%q) panic = %v, wantPanic %v",
+					badPayload,
+					r, wantPanic)
+			}
+		}()
+		helper.MustNewCheckedArgs(badPayload)
+	})
+}

helper/bwrap.go

@@ -0,0 +1,151 @@
+package helper
+
+import (
+	"errors"
+	"io"
+	"os"
+	"os/exec"
+	"strconv"
+	"sync"
+
+	"git.gensokyo.uk/security/fortify/helper/bwrap"
+	"git.gensokyo.uk/security/fortify/internal/proc"
+)
+
+// BubblewrapName is the file name or path to bubblewrap.
+var BubblewrapName = "bwrap"
+
+type bubblewrap struct {
+	// bwrap child file name
+	name string
+
+	// bwrap pipes
+	p *pipes
+	// sync pipe
+	sync *os.File
+	// returns an array of arguments passed directly
+	// to the child process spawned by bwrap
+	argF func(argsFD, statFD int) []string
+
+	// pipes received by the child
+	// nil if no pipes are required
+	cp *pipes
+
+	lock sync.RWMutex
+	*exec.Cmd
+}
+
+func (b *bubblewrap) StartNotify(ready chan error) error {
+	b.lock.Lock()
+	defer b.lock.Unlock()
+
+	if ready != nil && b.cp == nil {
+		panic("attempted to start with status monitoring on a bwrap child initialised without pipes")
+	}
+
+	// Check for doubled Start calls before we defer failure cleanup. If the prior
+	// call to Start succeeded, we don't want to spuriously close its pipes.
+	if b.Cmd.Process != nil {
+		return errors.New("exec: already started")
+	}
+
+	// prepare bwrap pipe and args
+	if argsFD, _, err := b.p.prepareCmd(b.Cmd); err != nil {
+		return err
+	} else {
+		b.Cmd.Args = append(b.Cmd.Args, "--args", strconv.Itoa(argsFD), "--", b.name)
+	}
+
+	// prepare child args and pipes if enabled
+	if b.cp != nil {
+		b.cp.ready = ready
+		if argsFD, statFD, err := b.cp.prepareCmd(b.Cmd); err != nil {
+			return err
+		} else {
+			b.Cmd.Args = append(b.Cmd.Args, b.argF(argsFD, statFD)...)
+		}
+	} else {
+		b.Cmd.Args = append(b.Cmd.Args, b.argF(-1, -1)...)
+	}
+
+	if ready != nil {
+		b.Cmd.Env = append(b.Cmd.Env, FortifyHelper+"=1", FortifyStatus+"=1")
+	} else if b.cp != nil {
+		b.Cmd.Env = append(b.Cmd.Env, FortifyHelper+"=1", FortifyStatus+"=0")
+	} else {
+		b.Cmd.Env = append(b.Cmd.Env, FortifyHelper+"=1", FortifyStatus+"=-1")
+	}
+
+	if b.sync != nil {
+		b.Cmd.Args = append(b.Cmd.Args, "--sync-fd", strconv.Itoa(int(proc.ExtraFile(b.Cmd, b.sync))))
+	}
+
+	if err := b.Cmd.Start(); err != nil {
+		return err
+	}
+
+	// write bwrap args first
+	if err := b.p.readyWriteArgs(); err != nil {
+		return err
+	}
+
+	// write child args if enabled
+	if b.cp != nil {
+		if err := b.cp.readyWriteArgs(); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (b *bubblewrap) Close() error {
+	if b.cp == nil {
+		panic("attempted to close bwrap child initialised without pipes")
+	}
+
+	return b.cp.closeStatus()
+}
+
+func (b *bubblewrap) Start() error {
+	return b.StartNotify(nil)
+}
+
+func (b *bubblewrap) Unwrap() *exec.Cmd {
+	return b.Cmd
+}
+
+// MustNewBwrap initialises a new Bwrap instance with wt as the null-terminated argument writer.
+// If wt is nil, the child process spawned by bwrap will not get an argument pipe.
+// Function argF returns an array of arguments passed directly to the child process.
+func MustNewBwrap(conf *bwrap.Config, wt io.WriterTo, name string, argF func(argsFD, statFD int) []string) Helper {
+	b, err := NewBwrap(conf, wt, name, argF)
+	if err != nil {
+		panic(err.Error())
+	} else {
+		return b
+	}
+}
+
+// NewBwrap initialises a new Bwrap instance with wt as the null-terminated argument writer.
+// If wt is nil, the child process spawned by bwrap will not get an argument pipe.
+// Function argF returns an array of arguments passed directly to the child process.
+func NewBwrap(conf *bwrap.Config, wt io.WriterTo, name string, argF func(argsFD, statFD int) []string) (Helper, error) {
+	b := new(bubblewrap)
+
+	if args, err := NewCheckedArgs(conf.Args()); err != nil {
+		return nil, err
+	} else {
+		b.p = &pipes{args: args}
+	}
+
+	b.sync = conf.Sync()
+	b.argF = argF
+	b.name = name
+	if wt != nil {
+		b.cp = &pipes{args: wt}
+	}
+	b.Cmd = execCommand(BubblewrapName)
+
+	return b, nil
+}

helper/bwrap/arg.go

@@ -0,0 +1,77 @@
+package bwrap
+
+import "encoding/gob"
+
+type Builder interface {
+	Len() int
+	Append(args *[]string)
+}
+
+type FSBuilder interface {
+	Path() string
+	Builder
+}
+
+func init() {
+	gob.Register(new(pairF))
+	gob.Register(new(stringF))
+}
+
+type pairF [3]string
+
+func (p *pairF) Path() string {
+	return p[2]
+}
+
+func (p *pairF) Len() int {
+	return len(p) // compiler replaces this with 3
+}
+
+func (p *pairF) Append(args *[]string) {
+	*args = append(*args, p[0], p[1], p[2])
+}
+
+type stringF [2]string
+
+func (s stringF) Path() string {
+	return s[1]
+}
+
+func (s stringF) Len() int {
+	return len(s) // compiler replaces this with 2
+}
+
+func (s stringF) Append(args *[]string) {
+	*args = append(*args, s[0], s[1])
+}
+
+// Args returns a slice of bwrap args corresponding to c.
+func (c *Config) Args() (args []string) {
+	builders := []Builder{
+		c.boolArgs(),
+		c.intArgs(),
+		c.stringArgs(),
+		c.pairArgs(),
+	}
+
+	// copy FSBuilder slice to builder slice
+	fb := make([]Builder, len(c.Filesystem)+1)
+	for i, f := range c.Filesystem {
+		fb[i] = f
+	}
+	fb[len(fb)-1] = c.Chmod
+	builders = append(builders, fb...)
+
+	// accumulate arg count
+	argc := 0
+	for _, b := range builders {
+		argc += b.Len()
+	}
+
+	args = make([]string, 0, argc)
+	for _, b := range builders {
+		b.Append(&args)
+	}
+
+	return
+}

helper/bwrap/arg.static.awkward.go

@@ -0,0 +1,13 @@
+package bwrap
+
+const (
+	Tmpfs = iota
+	Dir
+	Symlink
+)
+
+var awkwardArgs = [...]string{
+	Tmpfs:   "--tmpfs",
+	Dir:     "--dir",
+	Symlink: "--symlink",
+}

helper/bwrap/arg.static.bool.go

@@ -0,0 +1,81 @@
+package bwrap
+
+const (
+	UnshareAll = iota
+	UnshareUser
+	UnshareIPC
+	UnsharePID
+	UnshareNet
+	UnshareUTS
+	UnshareCGroup
+	ShareNet
+
+	UserNS
+	Clearenv
+
+	NewSession
+	DieWithParent
+	AsInit
+)
+
+var boolArgs = [...][]string{
+	UnshareAll:    {"--unshare-all", "--unshare-user"},
+	UnshareUser:   {"--unshare-user"},
+	UnshareIPC:    {"--unshare-ipc"},
+	UnsharePID:    {"--unshare-pid"},
+	UnshareNet:    {"--unshare-net"},
+	UnshareUTS:    {"--unshare-uts"},
+	UnshareCGroup: {"--unshare-cgroup"},
+	ShareNet:      {"--share-net"},
+
+	UserNS:   {"--disable-userns", "--assert-userns-disabled"},
+	Clearenv: {"--clearenv"},
+
+	NewSession:    {"--new-session"},
+	DieWithParent: {"--die-with-parent"},
+	AsInit:        {"--as-pid-1"},
+}
+
+func (c *Config) boolArgs() Builder {
+	b := boolArg{
+		UserNS:   !c.UserNS,
+		Clearenv: c.Clearenv,
+
+		NewSession:    c.NewSession,
+		DieWithParent: c.DieWithParent,
+		AsInit:        c.AsInit,
+	}
+
+	if c.Unshare == nil {
+		b[UnshareAll] = true
+		b[ShareNet] = c.Net
+	} else {
+		b[UnshareUser] = c.Unshare.User
+		b[UnshareIPC] = c.Unshare.IPC
+		b[UnsharePID] = c.Unshare.PID
+		b[UnshareNet] = c.Unshare.Net
+		b[UnshareUTS] = c.Unshare.UTS
+		b[UnshareCGroup] = c.Unshare.CGroup
+	}
+
+	return &b
+}
+
+type boolArg [len(boolArgs)]bool
+
+func (b *boolArg) Len() (l int) {
+	for i, v := range b {
+		if v {
+			l += len(boolArgs[i])
+		}
+	}
+	return
+}
+
+func (b *boolArg) Append(args *[]string) {
+	for i, v := range b {
+		if v {
+			*args = append(*args, boolArgs[i]...)
+		}
+	}
+}

helper/bwrap/arg.static.int.go

@@ -0,0 +1,47 @@
+package bwrap
+
+import "strconv"
+
+const (
+	UID = iota
+	GID
+	Perms
+	Size
+)
+
+var intArgs = [...]string{
+	UID:   "--uid",
+	GID:   "--gid",
+	Perms: "--perms",
+	Size:  "--size",
+}
+
+func (c *Config) intArgs() Builder {
+	// Arg types:
+	//   Perms
+	// are handled by the sequential builder
+
+	return &intArg{
+		UID: c.UID,
+		GID: c.GID,
+	}
+}
+
+type intArg [len(intArgs)]*int
+
+func (n *intArg) Len() (l int) {
+	for _, v := range n {
+		if v != nil {
+			l += 2
+		}
+	}
+	return
+}
+
+func (n *intArg) Append(args *[]string) {
+	for i, v := range n {
+		if v != nil {
+			*args = append(*args, intArgs[i], strconv.Itoa(*v))
+		}
+	}
+}

helper/bwrap/arg.static.pair.go

@@ -0,0 +1,73 @@
+package bwrap
+
+import (
+	"slices"
+)
+
+const (
+	SetEnv = iota
+
+	Bind
+	BindTry
+	DevBind
+	DevBindTry
+	ROBind
+	ROBindTry
+
+	Chmod
+)
+
+var pairArgs = [...]string{
+	SetEnv: "--setenv",
+
+	Bind:       "--bind",
+	BindTry:    "--bind-try",
+	DevBind:    "--dev-bind",
+	DevBindTry: "--dev-bind-try",
+	ROBind:     "--ro-bind",
+	ROBindTry:  "--ro-bind-try",
+
+	Chmod: "--chmod",
+}
+
+func (c *Config) pairArgs() Builder {
+	var n pairArg
+	n[SetEnv] = make([][2]string, len(c.SetEnv))
+	keys := make([]string, 0, len(c.SetEnv))
+	for k := range c.SetEnv {
+		keys = append(keys, k)
+	}
+	slices.Sort(keys)
+	for i, k := range keys {
+		n[SetEnv][i] = [2]string{k, c.SetEnv[k]}
+	}
+
+	// Arg types:
+	//   Bind
+	//   BindTry
+	//   DevBind
+	//   DevBindTry
+	//   ROBind
+	//   ROBindTry
+	//   Chmod
+	// are handled by the sequential builder
+
+	return &n
+}
+
+type pairArg [len(pairArgs)][][2]string
+
+func (p *pairArg) Len() (l int) {
+	for _, v := range p {
+		l += len(v) * 3
+	}
+	return
+}
+
+func (p *pairArg) Append(args *[]string) {
+	for i, arg := range p {
+		for _, v := range arg {
+			*args = append(*args, pairArgs[i], v[0], v[1])
+		}
+	}
+}

helper/bwrap/arg.static.string.go

@@ -0,0 +1,65 @@
+package bwrap
+
+const (
+	Hostname = iota
+	Chdir
+	UnsetEnv
+	LockFile
+
+	RemountRO
+	Procfs
+	DevTmpfs
+	Mqueue
+)
+
+var stringArgs = [...]string{
+	Hostname: "--hostname",
+	Chdir:    "--chdir",
+	UnsetEnv: "--unsetenv",
+	LockFile: "--lock-file",
+
+	RemountRO: "--remount-ro",
+	Procfs:    "--proc",
+	DevTmpfs:  "--dev",
+	Mqueue:    "--mqueue",
+}
+
+func (c *Config) stringArgs() Builder {
+	n := stringArg{
+		UnsetEnv: c.UnsetEnv,
+		LockFile: c.LockFile,
+	}
+
+	if c.Hostname != "" {
+		n[Hostname] = []string{c.Hostname}
+	}
+	if c.Chdir != "" {
+		n[Chdir] = []string{c.Chdir}
+	}
+
+	// Arg types:
+	// 	 RemountRO
+	//   Procfs
+	//   DevTmpfs
+	//   Mqueue
+	// are handled by the sequential builder
+
+	return &n
+}
+
+type stringArg [len(stringArgs)][]string
+
+func (s *stringArg) Len() (l int) {
+	for _, arg := range s {
+		l += len(arg) * 2
+	}
+	return
+}
+
+func (s *stringArg) Append(args *[]string) {
+	for i, arg := range s {
+		for _, v := range arg {
+			*args = append(*args, stringArgs[i], v)
+		}
+	}
+}

helper/bwrap/config.go

@@ -0,0 +1,205 @@
+package bwrap
+
+import (
+	"encoding/gob"
+	"os"
+	"strconv"
+)
+
+func init() {
+	gob.Register(new(PermConfig[SymlinkConfig]))
+	gob.Register(new(PermConfig[*TmpfsConfig]))
+}
+
+type Config struct {
+	// unshare every namespace we support by default if nil
+	// (--unshare-all)
+	Unshare *UnshareConfig `json:"unshare,omitempty"`
+	// retain the network namespace (can only combine with nil Unshare)
+	// (--share-net)
+	Net bool `json:"net"`
+
+	// disable further use of user namespaces inside sandbox and fail unless
+	// further use of user namespace inside sandbox is disabled if false
+	// (--disable-userns) (--assert-userns-disabled)
+	UserNS bool `json:"userns"`
+
+	// custom uid in the sandbox, requires new user namespace
+	// (--uid UID)
+	UID *int `json:"uid,omitempty"`
+	// custom gid in the sandbox, requires new user namespace
+	// (--gid GID)
+	GID *int `json:"gid,omitempty"`
+	// custom hostname in the sandbox, requires new uts namespace
+	// (--hostname NAME)
+	Hostname string `json:"hostname,omitempty"`
+
+	// change directory
+	// (--chdir DIR)
+	Chdir string `json:"chdir,omitempty"`
+	// unset all environment variables
+	// (--clearenv)
+	Clearenv bool `json:"clearenv"`
+	// set environment variable
+	// (--setenv VAR VALUE)
+	SetEnv map[string]string `json:"setenv,omitempty"`
+	// unset environment variables
+	// (--unsetenv VAR)
+	UnsetEnv []string `json:"unsetenv,omitempty"`
+
+	// take a lock on file while sandbox is running
+	// (--lock-file DEST)
+	LockFile []string `json:"lock_file,omitempty"`
+
+	// ordered filesystem args
+	Filesystem []FSBuilder
+
+	// change permissions (must already exist)
+	// (--chmod OCTAL PATH)
+	Chmod ChmodConfig `json:"chmod,omitempty"`
+
+	// create a new terminal session
+	// (--new-session)
+	NewSession bool `json:"new_session"`
+	// kills with SIGKILL child process (COMMAND) when bwrap or bwrap's parent dies.
+	// (--die-with-parent)
+	DieWithParent bool `json:"die_with_parent"`
+	// do not install a reaper process with PID=1
+	// (--as-pid-1)
+	AsInit bool `json:"as_init"`
+
+	// keep this fd open while sandbox is running
+	// (--sync-fd FD)
+	sync *os.File
+
+	/* unmapped options include:
+	    --unshare-user-try           Create new user namespace if possible else continue by skipping it
+	    --unshare-cgroup-try         Create new cgroup namespace if possible else continue by skipping it
+	    --userns FD                  Use this user namespace (cannot combine with --unshare-user)
+	    --userns2 FD                 After setup switch to this user namespace, only useful with --userns
+	    --pidns FD                   Use this pid namespace (as parent namespace if using --unshare-pid)
+	    --exec-label LABEL           Exec label for the sandbox
+	    --file-label LABEL           File label for temporary sandbox content
+	    --file FD DEST               Copy from FD to destination DEST
+	    --bind-data FD DEST          Copy from FD to file which is bind-mounted on DEST
+	    --ro-bind-data FD DEST       Copy from FD to file which is readonly bind-mounted on DEST
+	    --seccomp FD                 Load and use seccomp rules from FD (not repeatable)
+	    --add-seccomp-fd FD          Load and use seccomp rules from FD (repeatable)
+	    --block-fd FD                Block on FD until some data to read is available
+	    --userns-block-fd FD         Block on FD until the user namespace is ready
+	    --info-fd FD                 Write information about the running container to FD
+	    --json-status-fd FD          Write container status to FD as multiple JSON documents
+	    --cap-add CAP                Add cap CAP when running as privileged user
+	    --cap-drop CAP               Drop cap CAP when running as privileged user
+
+	among which --args is used internally for passing arguments */
+}
+
+// Sync keep this fd open while sandbox is running
+// (--sync-fd FD)
+func (c *Config) Sync() *os.File {
+	return c.sync
+}
+
+type UnshareConfig struct {
+	// (--unshare-user)
+	// create new user namespace
+	User bool `json:"user"`
+	// (--unshare-ipc)
+	// create new ipc namespace
+	IPC bool `json:"ipc"`
+	// (--unshare-pid)
+	// create new pid namespace
+	PID bool `json:"pid"`
+	// (--unshare-net)
+	// create new network namespace
+	Net bool `json:"net"`
+	// (--unshare-uts)
+	// create new uts namespace
+	UTS bool `json:"uts"`
+	// (--unshare-cgroup)
+	// create new cgroup namespace
+	CGroup bool `json:"cgroup"`
+}
+
+type PermConfig[T FSBuilder] struct {
+	// set permissions of next argument
+	// (--perms OCTAL)
+	Mode *os.FileMode `json:"mode,omitempty"`
+	// path to get the new permission
+	// (--bind-data, --file, etc.)
+	Inner T `json:"path"`
+}
+
+func (p *PermConfig[T]) Path() string {
+	return p.Inner.Path()
+}
+
+func (p *PermConfig[T]) Len() int {
+	if p.Mode != nil {
+		return p.Inner.Len() + 2
+	} else {
+		return p.Inner.Len()
+	}
+}
+
+func (p *PermConfig[T]) Append(args *[]string) {
+	if p.Mode != nil {
+		*args = append(*args, intArgs[Perms], strconv.FormatInt(int64(*p.Mode), 8))
+	}
+	p.Inner.Append(args)
+}
+
+type TmpfsConfig struct {
+	// set size of tmpfs
+	// (--size BYTES)
+	Size int `json:"size,omitempty"`
+	// mount point of new tmpfs
+	// (--tmpfs DEST)
+	Dir string `json:"dir"`
+}
+
+func (t *TmpfsConfig) Path() string {
+	return t.Dir
+}
+
+func (t *TmpfsConfig) Len() int {
+	if t.Size > 0 {
+		return 4
+	} else {
+		return 2
+	}
+}
+
+func (t *TmpfsConfig) Append(args *[]string) {
+	if t.Size > 0 {
+		*args = append(*args, intArgs[Size], strconv.Itoa(t.Size))
+	}
+	*args = append(*args, awkwardArgs[Tmpfs], t.Dir)
+}
+
+type SymlinkConfig [2]string
+
+func (s SymlinkConfig) Path() string {
+	return s[1]
+}
+
+func (s SymlinkConfig) Len() int {
+	return 3
+}
+
+func (s SymlinkConfig) Append(args *[]string) {
+	*args = append(*args, awkwardArgs[Symlink], s[0], s[1])
+}
+
+type ChmodConfig map[string]os.FileMode
+
+func (c ChmodConfig) Len() int {
+	return len(c)
+}
+
+func (c ChmodConfig) Append(args *[]string) {
+	for path, mode := range c {
+		*args = append(*args, pairArgs[Chmod], strconv.FormatInt(int64(mode), 8), path)
+	}
+}

helper/bwrap/config.set.go

@@ -0,0 +1,145 @@
+package bwrap
+
+import "os"
+
+/*
+Bind binds mount src on host to dest in sandbox.
+
+Bind(src, dest) bind mount host path readonly on sandbox
+(--ro-bind SRC DEST).
+Bind(src, dest, true) equal to ROBind but ignores non-existent host path
+(--ro-bind-try SRC DEST).
+
+Bind(src, dest, false, true) bind mount host path on sandbox.
+(--bind SRC DEST).
+Bind(src, dest, true, true) equal to Bind but ignores non-existent host path
+(--bind-try SRC DEST).
+
+Bind(src, dest, false, true, true) bind mount host path on sandbox, allowing device access
+(--dev-bind SRC DEST).
+Bind(src, dest, true, true, true) equal to DevBind but ignores non-existent host path
+(--dev-bind-try SRC DEST).
+*/
+func (c *Config) Bind(src, dest string, opts ...bool) *Config {
+	var (
+		try   bool
+		write bool
+		dev   bool
+	)
+
+	if len(opts) > 0 {
+		try = opts[0]
+	}
+	if len(opts) > 1 {
+		write = opts[1]
+	}
+	if len(opts) > 2 {
+		dev = opts[2]
+	}
+
+	if dev {
+		if try {
+			c.Filesystem = append(c.Filesystem, &pairF{pairArgs[DevBindTry], src, dest})
+		} else {
+			c.Filesystem = append(c.Filesystem, &pairF{pairArgs[DevBind], src, dest})
+		}
+		return c
+	} else if write {
+		if try {
+			c.Filesystem = append(c.Filesystem, &pairF{pairArgs[BindTry], src, dest})
+		} else {
+			c.Filesystem = append(c.Filesystem, &pairF{pairArgs[Bind], src, dest})
+		}
+		return c
+	} else {
+		if try {
+			c.Filesystem = append(c.Filesystem, &pairF{pairArgs[ROBindTry], src, dest})
+		} else {
+			c.Filesystem = append(c.Filesystem, &pairF{pairArgs[ROBind], src, dest})
+		}
+		return c
+	}
+}
+
+// RemountRO remount path as readonly; does not recursively remount
+// (--remount-ro DEST)
+func (c *Config) RemountRO(dest string) *Config {
+	c.Filesystem = append(c.Filesystem, &stringF{stringArgs[RemountRO], dest})
+	return c
+}
+
+// Procfs mount new procfs in sandbox
+// (--proc DEST)
+func (c *Config) Procfs(dest string) *Config {
+	c.Filesystem = append(c.Filesystem, &stringF{stringArgs[Procfs], dest})
+	return c
+}
+
+// DevTmpfs mount new dev in sandbox
+// (--dev DEST)
+func (c *Config) DevTmpfs(dest string) *Config {
+	c.Filesystem = append(c.Filesystem, &stringF{stringArgs[DevTmpfs], dest})
+	return c
+}
+
+// Tmpfs mount new tmpfs in sandbox
+// (--tmpfs DEST)
+func (c *Config) Tmpfs(dest string, size int, perm ...os.FileMode) *Config {
+	tmpfs := &PermConfig[*TmpfsConfig]{Inner: &TmpfsConfig{Dir: dest}}
+	if size >= 0 {
+		tmpfs.Inner.Size = size
+	}
+	if len(perm) == 1 {
+		tmpfs.Mode = &perm[0]
+	}
+	c.Filesystem = append(c.Filesystem, tmpfs)
+	return c
+}
+
+// Mqueue mount new mqueue in sandbox
+// (--mqueue DEST)
+func (c *Config) Mqueue(dest string) *Config {
+	c.Filesystem = append(c.Filesystem, &stringF{stringArgs[Mqueue], dest})
+	return c
+}
+
+// Dir create dir in sandbox
+// (--dir DEST)
+func (c *Config) Dir(dest string) *Config {
+	c.Filesystem = append(c.Filesystem, &stringF{stringArgs[Dir], dest})
+	return c
+}
+
+// Symlink create symlink within sandbox
+// (--symlink SRC DEST)
+func (c *Config) Symlink(src, dest string, perm ...os.FileMode) *Config {
+	symlink := &PermConfig[SymlinkConfig]{Inner: SymlinkConfig{src, dest}}
+	if len(perm) == 1 {
+		symlink.Mode = &perm[0]
+	}
+	c.Filesystem = append(c.Filesystem, symlink)
+	return c
+}
+
+// SetUID sets custom uid in the sandbox, requires new user namespace (--uid UID).
+func (c *Config) SetUID(uid int) *Config {
+	if uid >= 0 {
+		c.UID = &uid
+	}
+	return c
+}
+
+// SetGID sets custom gid in the sandbox, requires new user namespace (--gid GID).
+func (c *Config) SetGID(gid int) *Config {
+	if gid >= 0 {
+		c.GID = &gid
+	}
+	return c
+}
+
+// SetSync sets the sync pipe kept open while sandbox is running
+// (--sync-fd FD)
+func (c *Config) SetSync(s *os.File) *Config {
+	c.sync = s
+	return c
+}

helper/bwrap/config_test.go

@@ -0,0 +1,223 @@
+package bwrap
+
+import (
+	"slices"
+	"testing"
+)
+
+func TestConfig_Args(t *testing.T) {
+	testCases := []struct {
+		name string
+		conf *Config
+		want []string
+	}{
+		{
+			name: "xdg-dbus-proxy constraint sample",
+			conf: (&Config{
+				Unshare:       nil,
+				UserNS:        false,
+				Clearenv:      true,
+				DieWithParent: true,
+			}).
+				Symlink("usr/bin", "/bin").
+				Symlink("var/home", "/home").
+				Symlink("usr/lib", "/lib").
+				Symlink("usr/lib64", "/lib64").
+				Symlink("run/media", "/media").
+				Symlink("var/mnt", "/mnt").
+				Symlink("var/opt", "/opt").
+				Symlink("sysroot/ostree", "/ostree").
+				Symlink("var/roothome", "/root").
+				Symlink("usr/sbin", "/sbin").
+				Symlink("var/srv", "/srv").
+				Bind("/run", "/run", false, true).
+				Bind("/tmp", "/tmp", false, true).
+				Bind("/var", "/var", false, true).
+				Bind("/run/user/1971/.dbus-proxy/", "/run/user/1971/.dbus-proxy/", false, true).
+				Bind("/boot", "/boot").
+				Bind("/dev", "/dev").
+				Bind("/proc", "/proc").
+				Bind("/sys", "/sys").
+				Bind("/sysroot", "/sysroot").
+				Bind("/usr", "/usr").
+				Bind("/etc", "/etc"),
+			want: []string{
+				"--unshare-all", "--unshare-user",
+				"--disable-userns", "--assert-userns-disabled",
+				"--clearenv", "--die-with-parent",
+				"--symlink", "usr/bin", "/bin",
+				"--symlink", "var/home", "/home",
+				"--symlink", "usr/lib", "/lib",
+				"--symlink", "usr/lib64", "/lib64",
+				"--symlink", "run/media", "/media",
+				"--symlink", "var/mnt", "/mnt",
+				"--symlink", "var/opt", "/opt",
+				"--symlink", "sysroot/ostree", "/ostree",
+				"--symlink", "var/roothome", "/root",
+				"--symlink", "usr/sbin", "/sbin",
+				"--symlink", "var/srv", "/srv",
+				"--bind", "/run", "/run",
+				"--bind", "/tmp", "/tmp",
+				"--bind", "/var", "/var",
+				"--bind", "/run/user/1971/.dbus-proxy/", "/run/user/1971/.dbus-proxy/",
+				"--ro-bind", "/boot", "/boot",
+				"--ro-bind", "/dev", "/dev",
+				"--ro-bind", "/proc", "/proc",
+				"--ro-bind", "/sys", "/sys",
+				"--ro-bind", "/sysroot", "/sysroot",
+				"--ro-bind", "/usr", "/usr",
+				"--ro-bind", "/etc", "/etc",
+			},
+		},
+		{
+			name: "fortify permissive default nixos",
+			conf: (&Config{
+				Unshare:  nil,
+				Net:      true,
+				UserNS:   true,
+				Clearenv: true,
+				SetEnv: map[string]string{
+					"HOME":              "/home/chronos",
+					"TERM":              "xterm-256color",
+					"FORTIFY_INIT":      "3",
+					"XDG_RUNTIME_DIR":   "/run/user/150",
+					"XDG_SESSION_CLASS": "user",
+					"XDG_SESSION_TYPE":  "tty",
+					"SHELL":             "/run/current-system/sw/bin/zsh",
+					"USER":              "chronos",
+				},
+				DieWithParent: true,
+				AsInit:        true,
+			}).SetUID(65534).SetGID(65534).
+				Procfs("/proc").DevTmpfs("/dev").Mqueue("/dev/mqueue").
+				Bind("/bin", "/bin", false, true).
+				Bind("/boot", "/boot", false, true).
+				Bind("/etc", "/etc", false, true).
+				Bind("/home", "/home", false, true).
+				Bind("/lib", "/lib", false, true).
+				Bind("/lib64", "/lib64", false, true).
+				Bind("/nix", "/nix", false, true).
+				Bind("/root", "/root", false, true).
+				Bind("/srv", "/srv", false, true).
+				Bind("/sys", "/sys", false, true).
+				Bind("/usr", "/usr", false, true).
+				Bind("/var", "/var", false, true).
+				Bind("/run/NetworkManager", "/run/NetworkManager", false, true).
+				Bind("/run/agetty.reload", "/run/agetty.reload", false, true).
+				Bind("/run/binfmt", "/run/binfmt", false, true).
+				Bind("/run/booted-system", "/run/booted-system", false, true).
+				Bind("/run/credentials", "/run/credentials", false, true).
+				Bind("/run/cryptsetup", "/run/cryptsetup", false, true).
+				Bind("/run/current-system", "/run/current-system", false, true).
+				Bind("/run/host", "/run/host", false, true).
+				Bind("/run/keys", "/run/keys", false, true).
+				Bind("/run/libvirt", "/run/libvirt", false, true).
+				Bind("/run/libvirtd.pid", "/run/libvirtd.pid", false, true).
+				Bind("/run/lock", "/run/lock", false, true).
+				Bind("/run/log", "/run/log", false, true).
+				Bind("/run/lvm", "/run/lvm", false, true).
+				Bind("/run/mount", "/run/mount", false, true).
+				Bind("/run/nginx", "/run/nginx", false, true).
+				Bind("/run/nscd", "/run/nscd", false, true).
+				Bind("/run/opengl-driver", "/run/opengl-driver", false, true).
+				Bind("/run/pppd", "/run/pppd", false, true).
+				Bind("/run/resolvconf", "/run/resolvconf", false, true).
+				Bind("/run/sddm", "/run/sddm", false, true).
+				Bind("/run/syncoid", "/run/syncoid", false, true).
+				Bind("/run/systemd", "/run/systemd", false, true).
+				Bind("/run/tmpfiles.d", "/run/tmpfiles.d", false, true).
+				Bind("/run/udev", "/run/udev", false, true).
+				Bind("/run/udisks2", "/run/udisks2", false, true).
+				Bind("/run/utmp", "/run/utmp", false, true).
+				Bind("/run/virtlogd.pid", "/run/virtlogd.pid", false, true).
+				Bind("/run/wrappers", "/run/wrappers", false, true).
+				Bind("/run/zed.pid", "/run/zed.pid", false, true).
+				Bind("/run/zed.state", "/run/zed.state", false, true).
+				Bind("/tmp/fortify.1971/tmpdir/150", "/tmp", false, true).
+				Tmpfs("/tmp/fortify.1971", 1048576).
+				Tmpfs("/run/user", 1048576).
+				Tmpfs("/run/user/150", 8388608).
+				Bind("/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/passwd", "/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/passwd").
+				Bind("/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/group", "/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/group").
+				Bind("/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/passwd", "/etc/passwd").
+				Bind("/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/group", "/etc/group").
+				Tmpfs("/var/run/nscd", 8192),
+			want: []string{
+				"--unshare-all", "--unshare-user", "--share-net",
+				"--clearenv", "--die-with-parent", "--as-pid-1",
+				"--uid", "65534",
+				"--gid", "65534",
+				"--setenv", "FORTIFY_INIT", "3",
+				"--setenv", "HOME", "/home/chronos",
+				"--setenv", "SHELL", "/run/current-system/sw/bin/zsh",
+				"--setenv", "TERM", "xterm-256color",
+				"--setenv", "USER", "chronos",
+				"--setenv", "XDG_RUNTIME_DIR", "/run/user/150",
+				"--setenv", "XDG_SESSION_CLASS", "user",
+				"--setenv", "XDG_SESSION_TYPE", "tty",
+				"--proc", "/proc", "--dev", "/dev",
+				"--mqueue", "/dev/mqueue",
+				"--bind", "/bin", "/bin",
+				"--bind", "/boot", "/boot",
+				"--bind", "/etc", "/etc",
+				"--bind", "/home", "/home",
+				"--bind", "/lib", "/lib",
+				"--bind", "/lib64", "/lib64",
+				"--bind", "/nix", "/nix",
+				"--bind", "/root", "/root",
+				"--bind", "/srv", "/srv",
+				"--bind", "/sys", "/sys",
+				"--bind", "/usr", "/usr",
+				"--bind", "/var", "/var",
+				"--bind", "/run/NetworkManager", "/run/NetworkManager",
+				"--bind", "/run/agetty.reload", "/run/agetty.reload",
+				"--bind", "/run/binfmt", "/run/binfmt",
+				"--bind", "/run/booted-system", "/run/booted-system",
+				"--bind", "/run/credentials", "/run/credentials",
+				"--bind", "/run/cryptsetup", "/run/cryptsetup",
+				"--bind", "/run/current-system", "/run/current-system",
+				"--bind", "/run/host", "/run/host",
+				"--bind", "/run/keys", "/run/keys",
+				"--bind", "/run/libvirt", "/run/libvirt",
+				"--bind", "/run/libvirtd.pid", "/run/libvirtd.pid",
+				"--bind", "/run/lock", "/run/lock",
+				"--bind", "/run/log", "/run/log",
+				"--bind", "/run/lvm", "/run/lvm",
+				"--bind", "/run/mount", "/run/mount",
+				"--bind", "/run/nginx", "/run/nginx",
+				"--bind", "/run/nscd", "/run/nscd",
+				"--bind", "/run/opengl-driver", "/run/opengl-driver",
+				"--bind", "/run/pppd", "/run/pppd",
+				"--bind", "/run/resolvconf", "/run/resolvconf",
+				"--bind", "/run/sddm", "/run/sddm",
+				"--bind", "/run/syncoid", "/run/syncoid",
+				"--bind", "/run/systemd", "/run/systemd",
+				"--bind", "/run/tmpfiles.d", "/run/tmpfiles.d",
+				"--bind", "/run/udev", "/run/udev",
+				"--bind", "/run/udisks2", "/run/udisks2",
+				"--bind", "/run/utmp", "/run/utmp",
+				"--bind", "/run/virtlogd.pid", "/run/virtlogd.pid",
+				"--bind", "/run/wrappers", "/run/wrappers",
+				"--bind", "/run/zed.pid", "/run/zed.pid",
+				"--bind", "/run/zed.state", "/run/zed.state",
+				"--bind", "/tmp/fortify.1971/tmpdir/150", "/tmp",
+				"--size", "1048576", "--tmpfs", "/tmp/fortify.1971",
+				"--size", "1048576", "--tmpfs", "/run/user",
+				"--size", "8388608", "--tmpfs", "/run/user/150",
+				"--ro-bind", "/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/passwd", "/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/passwd",
+				"--ro-bind", "/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/group", "/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/group",
+				"--ro-bind", "/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/passwd", "/etc/passwd",
+				"--ro-bind", "/tmp/fortify.1971/67a97cc824a64ef789f16b20ca6ce311/group", "/etc/group",
+				"--size", "8192", "--tmpfs", "/var/run/nscd",
+			},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := tc.conf.Args(); !slices.Equal(got, tc.want) {
+				t.Errorf("Args() = %#v, want %#v", got, tc.want)
+			}
+		})
+	}
+}

helper/bwrap_test.go

@@ -0,0 +1,112 @@
+package helper_test
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"strings"
+	"testing"
+
+	"git.gensokyo.uk/security/fortify/helper"
+	"git.gensokyo.uk/security/fortify/helper/bwrap"
+)
+
+func TestBwrap(t *testing.T) {
+	sc := &bwrap.Config{
+		Unshare:       nil,
+		Net:           true,
+		UserNS:        false,
+		Hostname:      "localhost",
+		Chdir:         "/nonexistent",
+		Clearenv:      true,
+		NewSession:    true,
+		DieWithParent: true,
+		AsInit:        true,
+	}
+
+	t.Run("nonexistent bwrap name", func(t *testing.T) {
+		bubblewrapName := helper.BubblewrapName
+		helper.BubblewrapName = "/nonexistent"
+		t.Cleanup(func() {
+			helper.BubblewrapName = bubblewrapName
+		})
+
+		h := helper.MustNewBwrap(sc, argsWt, "fortify", argF)
+
+		if err := h.Start(); !errors.Is(err, os.ErrNotExist) {
+			t.Errorf("Start() error = %v, wantErr %v",
+				err, os.ErrNotExist)
+		}
+	})
+
+	t.Run("valid new helper nil check", func(t *testing.T) {
+		if got := helper.MustNewBwrap(sc, argsWt, "fortify", argF); got == nil {
+			t.Errorf("MustNewBwrap(%#v, %#v, %#v) got nil",
+				sc, argsWt, "fortify")
+			return
+		}
+	})
+
+	t.Run("invalid bwrap config new helper panic", func(t *testing.T) {
+		defer func() {
+			wantPanic := "argument contains null character"
+			if r := recover(); r != wantPanic {
+				t.Errorf("MustNewBwrap: panic = %q, want %q",
+					r, wantPanic)
+			}
+		}()
+
+		helper.MustNewBwrap(&bwrap.Config{Hostname: "\x00"}, nil, "fortify", argF)
+	})
+
+	t.Run("start notify without pipes panic", func(t *testing.T) {
+		defer func() {
+			wantPanic := "attempted to start with status monitoring on a bwrap child initialised without pipes"
+			if r := recover(); r != wantPanic {
+				t.Errorf("StartNotify: panic = %q, want %q",
+					r, wantPanic)
+			}
+		}()
+
+		panic(fmt.Sprintf("unreachable: %v",
+			helper.MustNewBwrap(sc, nil, "fortify", argF).StartNotify(make(chan error))))
+	})
+
+	t.Run("start without pipes", func(t *testing.T) {
+		helper.InternalReplaceExecCommand(t)
+
+		h := helper.MustNewBwrap(sc, nil, "crash-test-dummy", argFChecked)
+		cmd := h.Unwrap()
+
+		stdout, stderr := new(strings.Builder), new(strings.Builder)
+		cmd.Stdout, cmd.Stderr = stdout, stderr
+
+		t.Run("close without pipes panic", func(t *testing.T) {
+			defer func() {
+				wantPanic := "attempted to close bwrap child initialised without pipes"
+				if r := recover(); r != wantPanic {
+					t.Errorf("Close: panic = %q, want %q",
+						r, wantPanic)
+				}
+			}()
+
+			panic(fmt.Sprintf("unreachable: %v",
+				h.Close()))
+		})
+
+		if err := h.Start(); err != nil {
+			t.Errorf("Start() error = %v",
+				err)
+			return
+		}
+
+		if err := h.Wait(); err != nil {
+			t.Errorf("Wait() err = %v stderr = %s",
+				err, stderr)
+		}
+	})
+
+	t.Run("implementation compliance", func(t *testing.T) {
+		testHelper(t, func() helper.Helper { return helper.MustNewBwrap(sc, argsWt, "crash-test-dummy", argF) })
+	})
+}

helper/direct.go

@@ -0,0 +1,93 @@
+package helper
+
+import (
+	"errors"
+	"io"
+	"os/exec"
+	"sync"
+)
+
+// direct wraps *exec.Cmd and manages status and args fd.
+// Args is always 3 and status if set is always 4.
+type direct struct {
+	// helper pipes
+	// cannot be nil
+	p *pipes
+
+	// returns an array of arguments passed directly
+	// to the helper process
+	argF func(argsFD, statFD int) []string
+
+	lock sync.RWMutex
+	*exec.Cmd
+}
+
+func (h *direct) StartNotify(ready chan error) error {
+	h.lock.Lock()
+	defer h.lock.Unlock()
+
+	// Check for doubled Start calls before we defer failure cleanup. If the prior
+	// call to Start succeeded, we don't want to spuriously close its pipes.
+	if h.Cmd.Process != nil {
+		return errors.New("exec: already started")
+	}
+
+	h.p.ready = ready
+	if argsFD, statFD, err := h.p.prepareCmd(h.Cmd); err != nil {
+		return err
+	} else {
+		h.Cmd.Args = append(h.Cmd.Args, h.argF(argsFD, statFD)...)
+	}
+
+	if ready != nil {
+		h.Cmd.Env = append(h.Cmd.Env, FortifyHelper+"=1", FortifyStatus+"=1")
+	} else {
+		h.Cmd.Env = append(h.Cmd.Env, FortifyHelper+"=1", FortifyStatus+"=0")
+	}
+
+	if err := h.Cmd.Start(); err != nil {
+		return err
+	}
+	if err := h.p.readyWriteArgs(); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (h *direct) Wait() error {
+	h.lock.RLock()
+	defer h.lock.RUnlock()
+
+	if h.Cmd.Process == nil {
+		return errors.New("exec: not started")
+	}
+	defer h.p.mustClosePipes()
+	if h.Cmd.ProcessState != nil {
+		return errors.New("exec: Wait was already called")
+	}
+
+	return h.Cmd.Wait()
+}
+
+func (h *direct) Close() error {
+	return h.p.closeStatus()
+}
+
+func (h *direct) Start() error {
+	return h.StartNotify(nil)
+}
+
+func (h *direct) Unwrap() *exec.Cmd {
+	return h.Cmd
+}
+
+// New initialises a new direct Helper instance with wt as the null-terminated argument writer.
+// Function argF returns an array of arguments passed directly to the child process.
+func New(wt io.WriterTo, name string, argF func(argsFD, statFD int) []string) Helper {
+	if wt == nil {
+		panic("attempted to create helper with invalid argument writer")
+	}
+
+	return &direct{p: &pipes{args: wt}, argF: argF, Cmd: execCommand(name)}
+}

helper/direct_test.go

@@ -0,0 +1,44 @@
+package helper_test
+
+import (
+	"errors"
+	"os"
+	"testing"
+
+	"git.gensokyo.uk/security/fortify/helper"
+)
+
+func TestDirect(t *testing.T) {
+	t.Run("start non-existent helper path", func(t *testing.T) {
+		h := helper.New(argsWt, "/nonexistent", argF)
+
+		if err := h.Start(); !errors.Is(err, os.ErrNotExist) {
+			t.Errorf("Start() error = %v, wantErr %v",
+				err, os.ErrNotExist)
+		}
+	})
+
+	t.Run("valid new helper nil check", func(t *testing.T) {
+		if got := helper.New(argsWt, "fortify", argF); got == nil {
+			t.Errorf("New(%q, %q) got nil",
+				argsWt, "fortify")
+			return
+		}
+	})
+
+	t.Run("invalid new helper panic", func(t *testing.T) {
+		defer func() {
+			wantPanic := "attempted to create helper with invalid argument writer"
+			if r := recover(); r != wantPanic {
+				t.Errorf("New: panic = %q, want %q",
+					r, wantPanic)
+			}
+		}()
+
+		helper.New(nil, "fortify", argF)
+	})
+
+	t.Run("implementation compliance", func(t *testing.T) {
+		testHelper(t, func() helper.Helper { return helper.New(argsWt, "crash-test-dummy", argF) })
+	})
+}

helper/helper.go

@@ -0,0 +1,36 @@
+// Package helper runs external helpers with optional sandboxing and manages their status/args pipes.
+package helper
+
+import (
+	"errors"
+	"os/exec"
+)
+
+var (
+	ErrStatusFault = errors.New("generic status pipe fault")
+	ErrStatusRead  = errors.New("unexpected status response")
+)
+
+const (
+	// FortifyHelper is set for the process launched by Helper.
+	FortifyHelper = "FORTIFY_HELPER"
+	// FortifyStatus is 1 when sync fd is enabled and 0 otherwise.
+	FortifyStatus = "FORTIFY_STATUS"
+)
+
+type Helper interface {
+	// StartNotify starts the helper process.
+	// A status pipe is passed to the helper if ready is not nil.
+	StartNotify(ready chan error) error
+	// Start starts the helper process.
+	Start() error
+	// Close closes the status pipe.
+	// If helper is started without the status pipe, Close panics.
+	Close() error
+	// Wait calls wait on the child process and cleans up pipes.
+	Wait() error
+	// Unwrap returns the underlying exec.Cmd instance.
+	Unwrap() *exec.Cmd
+}
+
+var execCommand = exec.Command

helper/helper_test.go

@@ -0,0 +1,167 @@
+package helper_test
+
+import (
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+
+	"git.gensokyo.uk/security/fortify/helper"
+)
+
+var (
+	wantArgs = []string{
+		"unix:path=/run/dbus/system_bus_socket",
+		"/tmp/fortify.1971/12622d846cc3fe7b4c10359d01f0eb47/system_bus_socket",
+		"--filter",
+		"--talk=org.bluez",
+		"--talk=org.freedesktop.Avahi",
+		"--talk=org.freedesktop.UPower",
+	}
+
+	wantPayload = strings.Join(wantArgs, "\x00") + "\x00"
+	argsWt      = helper.MustNewCheckedArgs(wantArgs)
+)
+
+func argF(argsFD, statFD int) []string {
+	if argsFD == -1 {
+		panic("invalid args fd")
+	}
+
+	return argFChecked(argsFD, statFD)
+}
+
+func argFChecked(argsFD, statFD int) []string {
+	if statFD == -1 {
+		return []string{"--args", strconv.Itoa(argsFD)}
+	} else {
+		return []string{"--args", strconv.Itoa(argsFD), "--fd", strconv.Itoa(statFD)}
+	}
+}
+
+// this function tests an implementation of the helper.Helper interface
+func testHelper(t *testing.T, createHelper func() helper.Helper) {
+	helper.InternalReplaceExecCommand(t)
+
+	t.Run("start helper with status channel and wait", func(t *testing.T) {
+		h := createHelper()
+		ready := make(chan error, 1)
+		cmd := h.Unwrap()
+
+		stdout, stderr := new(strings.Builder), new(strings.Builder)
+		cmd.Stdout, cmd.Stderr = stdout, stderr
+
+		t.Run("wait not yet started helper", func(t *testing.T) {
+			wantErr := "exec: not started"
+			if err := h.Wait(); err != nil && err.Error() != wantErr {
+				t.Errorf("Wait(%v) error = %v, wantErr %v",
+					ready,
+					err, wantErr)
+				return
+			}
+		})
+
+		t.Log("starting helper stub")
+		if err := h.StartNotify(ready); err != nil {
+			t.Errorf("StartNotify(%v) error = %v",
+				ready,
+				err)
+			return
+		}
+
+		t.Run("start already started helper", func(t *testing.T) {
+			wantErr := "exec: already started"
+			if err := h.StartNotify(ready); err != nil && err.Error() != wantErr {
+				t.Errorf("StartNotify(%v) error = %v, wantErr %v",
+					ready,
+					err, wantErr)
+				return
+			}
+		})
+
+		t.Log("waiting on status channel with timeout")
+		select {
+		case <-time.NewTimer(5 * time.Second).C:
+			t.Errorf("never got a ready response")
+			t.Errorf("stdout:\n%s", stdout.String())
+			t.Errorf("stderr:\n%s", stderr.String())
+			if err := cmd.Process.Kill(); err != nil {
+				panic(err.Error())
+			}
+			return
+		case err := <-ready:
+			if err != nil {
+				t.Errorf("StartNotify(%v) latent error = %v",
+					ready,
+					err)
+			}
+		}
+
+		t.Log("closing status pipe")
+		if err := h.Close(); err != nil {
+			t.Errorf("Close() error = %v",
+				err)
+		}
+
+		t.Log("waiting on helper")
+		if err := h.Wait(); err != nil {
+			t.Errorf("Wait() err = %v stderr = %s",
+				err, stderr)
+		}
+
+		t.Run("wait already finalised helper", func(t *testing.T) {
+			wantErr := "exec: Wait was already called"
+			if err := h.Wait(); err != nil && err.Error() != wantErr {
+				t.Errorf("Wait(%v) error = %v, wantErr %v",
+					ready,
+					err, wantErr)
+				return
+			}
+		})
+
+		if got := stdout.String(); !strings.HasPrefix(got, wantPayload) {
+			t.Errorf("StartNotify(%v) stdout = %v, want %v",
+				ready,
+				got, wantPayload)
+		}
+	})
+
+	t.Run("start helper and wait", func(t *testing.T) {
+		h := createHelper()
+		cmd := h.Unwrap()
+
+		stdout, stderr := new(strings.Builder), new(strings.Builder)
+		cmd.Stdout, cmd.Stderr = stdout, stderr
+
+		if err := h.Start(); err != nil {
+			t.Errorf("Start() error = %v",
+				err)
+			return
+		}
+
+		t.Run("close helper without status pipe", func(t *testing.T) {
+			defer func() {
+				wantPanic := "attempted to close helper with no status pipe"
+				if r := recover(); r != wantPanic {
+					t.Errorf("Close() panic = %v, wantPanic %v",
+						r, wantPanic)
+				}
+			}()
+			if err := h.Close(); err != nil {
+				t.Errorf("Close() error = %v",
+					err)
+				return
+			}
+		})
+
+		if err := h.Wait(); err != nil {
+			t.Errorf("Wait() err = %v stderr = %s",
+				err, stderr)
+		}
+
+		if got := stdout.String(); !strings.HasPrefix(got, wantPayload) {
+			t.Errorf("Start() stdout = %v, want %v",
+				got, wantPayload)
+		}
+	})
+}

helper/pipe.go

@@ -0,0 +1,149 @@
+package helper
+
+import (
+	"errors"
+	"io"
+	"os"
+	"os/exec"
+
+	"git.gensokyo.uk/security/fortify/internal/proc"
+)
+
+type pipes struct {
+	args io.WriterTo
+
+	statP [2]*os.File
+	argsP [2]*os.File
+
+	ready chan error
+
+	cmd *exec.Cmd
+}
+
+func (p *pipes) pipe() error {
+	if p.statP[0] != nil || p.statP[1] != nil ||
+		p.argsP[0] != nil || p.argsP[1] != nil {
+		panic("attempted to pipe twice")
+	}
+	if p.args == nil {
+		panic("attempted to pipe without args")
+	}
+
+	// create pipes
+	if pr, pw, err := os.Pipe(); err != nil {
+		return err
+	} else {
+		p.argsP[0], p.argsP[1] = pr, pw
+	}
+
+	// create status pipes if ready signal is requested
+	if p.ready != nil {
+		if pr, pw, err := os.Pipe(); err != nil {
+			return err
+		} else {
+			p.statP[0], p.statP[1] = pr, pw
+		}
+	}
+
+	return nil
+}
+
+// calls pipe to create pipes and sets them up as ExtraFiles, returning their fd
+func (p *pipes) prepareCmd(cmd *exec.Cmd) (argsFd, statFd int, err error) {
+	argsFd, statFd = -1, -1
+	if err = p.pipe(); err != nil {
+		return
+	}
+
+	// save a reference of cmd for future use
+	p.cmd = cmd
+
+	argsFd = int(proc.ExtraFile(cmd, p.argsP[0]))
+	if p.ready != nil {
+		statFd = int(proc.ExtraFile(cmd, p.statP[1]))
+	}
+
+	return
+}
+
+func (p *pipes) readyWriteArgs() error {
+	statsP, argsP := p.statP[0], p.argsP[1]
+
+	// write arguments and close args pipe
+	if _, err := p.args.WriteTo(argsP); err != nil {
+		if err1 := p.cmd.Process.Kill(); err1 != nil {
+			// should be unreachable
+			panic(err1.Error())
+		}
+		return err
+	} else {
+		if err = argsP.Close(); err != nil {
+			if err1 := p.cmd.Process.Kill(); err1 != nil {
+				// should be unreachable
+				panic(err1.Error())
+			}
+			return err
+		}
+	}
+
+	if p.ready != nil {
+		// monitor stat pipe
+		go func() {
+			n, err := statsP.Read(make([]byte, 1))
+			switch n {
+			case -1:
+				if err1 := p.cmd.Process.Kill(); err1 != nil {
+					// should be unreachable
+					panic(err1.Error())
+				}
+				// ensure error is not nil
+				if err == nil {
+					err = ErrStatusFault
+				}
+				p.ready <- err
+			case 0:
+				// ensure error is not nil
+				if err == nil {
+					err = ErrStatusRead
+				}
+				p.ready <- err
+			case 1:
+				p.ready <- nil
+			default:
+				panic("unreachable") // unexpected read count
+			}
+		}()
+	}
+
+	return nil
+}
+
+func (p *pipes) mustClosePipes() {
+	if err := p.argsP[0].Close(); err != nil && !errors.Is(err, os.ErrClosed) {
+		// unreachable
+		panic(err.Error())
+	}
+	if err := p.argsP[1].Close(); err != nil && !errors.Is(err, os.ErrClosed) {
+		// unreachable
+		panic(err.Error())
+	}
+
+	if p.ready != nil {
+		if err := p.statP[0].Close(); err != nil && !errors.Is(err, os.ErrClosed) {
+			// unreachable
+			panic(err.Error())
+		}
+		if err := p.statP[1].Close(); err != nil && !errors.Is(err, os.ErrClosed) {
+			// unreachable
+			panic(err.Error())
+		}
+	}
+}
+
+func (p *pipes) closeStatus() error {
+	if p.ready == nil {
+		panic("attempted to close helper with no status pipe")
+	}
+
+	return p.statP[0].Close()
+}

helper/pipe_test.go

@@ -0,0 +1,42 @@
+package helper
+
+import (
+	"testing"
+)
+
+func Test_pipes_pipe_mustClosePipes(t *testing.T) {
+	p := new(pipes)
+
+	t.Run("pipe without args", func(t *testing.T) {
+		defer func() {
+			wantPanic := "attempted to pipe without args"
+			if r := recover(); r != wantPanic {
+				t.Errorf("pipe() panic = %v, wantPanic %v",
+					r, wantPanic)
+			}
+		}()
+		_ = p.pipe()
+	})
+
+	p.args = MustNewCheckedArgs(make([]string, 0))
+	t.Run("obtain pipes", func(t *testing.T) {
+		if err := p.pipe(); err != nil {
+			t.Errorf("pipe() error = %v",
+				err)
+			return
+		}
+	})
+
+	t.Run("pipe twice", func(t *testing.T) {
+		defer func() {
+			wantPanic := "attempted to pipe twice"
+			if r := recover(); r != wantPanic {
+				t.Errorf("pipe() panic = %v, wantPanic %v",
+					r, wantPanic)
+			}
+		}()
+		_ = p.pipe()
+	})
+
+	p.mustClosePipes()
+}

helper/stub.go

@@ -0,0 +1,175 @@
+package helper
+
+import (
+	"flag"
+	"io"
+	"os"
+	"os/exec"
+	"strconv"
+	"strings"
+	"syscall"
+	"testing"
+
+	"git.gensokyo.uk/security/fortify/helper/bwrap"
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+)
+
+// InternalChildStub is an internal function but exported because it is cross-package;
+// it is part of the implementation of the helper stub.
+func InternalChildStub() {
+	// this test mocks the helper process
+	if os.Getenv(FortifyHelper) != "1" ||
+		os.Getenv(FortifyStatus) == "-1" { // this indicates the stub is being invoked as a bwrap child without pipes
+		return
+	}
+
+	argsFD := flag.Int("args", -1, "")
+	statFD := flag.Int("fd", -1, "")
+	_ = flag.CommandLine.Parse(os.Args[4:])
+
+	switch os.Args[3] {
+	case "bwrap":
+		bwrapStub(argsFD, statFD)
+	default:
+		genericStub(argsFD, statFD)
+	}
+
+	fmsg.Exit(0)
+}
+
+// InternalReplaceExecCommand is an internal function but exported because it is cross-package;
+// it is part of the implementation of the helper stub.
+func InternalReplaceExecCommand(t *testing.T) {
+	t.Cleanup(func() {
+		execCommand = exec.Command
+	})
+
+	// replace execCommand to have the resulting *exec.Cmd launch TestHelperChildStub
+	execCommand = func(name string, arg ...string) *exec.Cmd {
+		// pass through nonexistent path
+		if name == "/nonexistent" && len(arg) == 0 {
+			return exec.Command(name)
+		}
+
+		return exec.Command(os.Args[0], append([]string{"-test.run=TestHelperChildStub", "--", name}, arg...)...)
+	}
+}
+
+func genericStub(argsFD, statFD *int) {
+	// simulate args pipe behaviour
+	func() {
+		if *argsFD == -1 {
+			panic("attempted to start helper without passing args pipe fd")
+		}
+
+		f := os.NewFile(uintptr(*argsFD), "|0")
+		if f == nil {
+			panic("attempted to start helper without args pipe")
+		}
+
+		if _, err := io.Copy(os.Stdout, f); err != nil {
+			panic("cannot read args: " + err.Error())
+		}
+	}()
+
+	var wait chan struct{}
+
+	// simulate status pipe behaviour
+	if os.Getenv(FortifyStatus) == "1" {
+		if *statFD == -1 {
+			panic("attempted to start helper with status reporting without passing status pipe fd")
+		}
+
+		wait = make(chan struct{})
+		go func() {
+			f := os.NewFile(uintptr(*statFD), "|1")
+			if f == nil {
+				panic("attempted to start with status reporting without status pipe")
+			}
+
+			if _, err := f.Write([]byte{'x'}); err != nil {
+				panic("cannot write to status pipe: " + err.Error())
+			}
+
+			// wait for status pipe close
+			var epoll int
+			if fd, err := syscall.EpollCreate1(0); err != nil {
+				panic("cannot open epoll fd: " + err.Error())
+			} else {
+				defer func() {
+					if err = syscall.Close(fd); err != nil {
+						panic("cannot close epoll fd: " + err.Error())
+					}
+				}()
+				epoll = fd
+			}
+			if err := syscall.EpollCtl(epoll, syscall.EPOLL_CTL_ADD, int(f.Fd()), &syscall.EpollEvent{}); err != nil {
+				panic("cannot add status pipe to epoll: " + err.Error())
+			}
+			events := make([]syscall.EpollEvent, 1)
+			if _, err := syscall.EpollWait(epoll, events, -1); err != nil {
+				panic("cannot poll status pipe: " + err.Error())
+			}
+			if events[0].Events != syscall.EPOLLERR {
+				panic(strconv.Itoa(int(events[0].Events)))
+
+			}
+			close(wait)
+		}()
+	}
+
+	if wait != nil {
+		<-wait
+	}
+}
+
+func bwrapStub(argsFD, statFD *int) {
+	// the bwrap launcher does not ever launch with sync fd
+	if *statFD != -1 {
+		panic("attempted to launch bwrap with status monitoring")
+	}
+
+	// test args pipe behaviour
+	func() {
+		if *argsFD == -1 {
+			panic("attempted to start bwrap without passing args pipe fd")
+		}
+
+		f := os.NewFile(uintptr(*argsFD), "|0")
+		if f == nil {
+			panic("attempted to start helper without args pipe")
+		}
+
+		got, want := new(strings.Builder), new(strings.Builder)
+
+		if _, err := io.Copy(got, f); err != nil {
+			panic("cannot read args: " + err.Error())
+		}
+
+		// hardcoded bwrap configuration used by test
+		if _, err := MustNewCheckedArgs((&bwrap.Config{
+			Unshare:       nil,
+			Net:           true,
+			UserNS:        false,
+			Hostname:      "localhost",
+			Chdir:         "/nonexistent",
+			Clearenv:      true,
+			NewSession:    true,
+			DieWithParent: true,
+			AsInit:        true,
+		}).Args()).WriteTo(want); err != nil {
+			panic("cannot read want: " + err.Error())
+		}
+
+		if len(flag.CommandLine.Args()) > 0 && flag.CommandLine.Args()[0] == "crash-test-dummy" && got.String() != want.String() {
+			panic("bad bwrap args\ngot: " + got.String() + "\nwant: " + want.String())
+		}
+	}()
+
+	if err := syscall.Exec(
+		os.Args[0],
+		append([]string{os.Args[0], "-test.run=TestHelperChildStub", "--"}, flag.CommandLine.Args()...),
+		os.Environ()); err != nil {
+		panic("cannot start general stub: " + err.Error())
+	}
+}

helper/stub_test.go

@@ -0,0 +1,11 @@
+package helper_test
+
+import (
+	"testing"
+
+	"git.gensokyo.uk/security/fortify/helper"
+)
+
+func TestHelperChildStub(t *testing.T) {
+	helper.InternalChildStub()
+}

internal/app/app.go

@@ -0,0 +1,97 @@
+package app
+
+import (
+	"sync"
+	"sync/atomic"
+
+	"git.gensokyo.uk/security/fortify/cmd/fshim/ipc/shim"
+	"git.gensokyo.uk/security/fortify/fst"
+	"git.gensokyo.uk/security/fortify/internal/linux"
+)
+
+type App interface {
+	// ID returns a copy of App's unique ID.
+	ID() fst.ID
+	// Start sets up the system and starts the App.
+	Start() error
+	// Wait waits for App's process to exit and reverts system setup.
+	Wait() (int, error)
+	// WaitErr returns error returned by the underlying wait syscall.
+	WaitErr() error
+
+	Seal(config *fst.Config) error
+	String() string
+}
+
+type app struct {
+	// single-use config reference
+	ct *appCt
+
+	// application unique identifier
+	id *fst.ID
+	// operating system interface
+	os linux.System
+	// shim process manager
+	shim *shim.Shim
+	// child process related information
+	seal *appSeal
+	// error returned waiting for process
+	waitErr error
+
+	lock sync.RWMutex
+}
+
+func (a *app) ID() fst.ID {
+	return *a.id
+}
+
+func (a *app) String() string {
+	if a == nil {
+		return "(invalid fortified app)"
+	}
+
+	a.lock.RLock()
+	defer a.lock.RUnlock()
+
+	if a.shim != nil {
+		return a.shim.String()
+	}
+
+	if a.seal != nil {
+		return "(sealed fortified app as uid " + a.seal.sys.user.us + ")"
+	}
+
+	return "(unsealed fortified app)"
+}
+
+func (a *app) WaitErr() error {
+	return a.waitErr
+}
+
+func New(os linux.System) (App, error) {
+	a := new(app)
+	a.id = new(fst.ID)
+	a.os = os
+	return a, fst.NewAppID(a.id)
+}
+
+// appCt ensures its wrapped val is only accessed once
+type appCt struct {
+	val  *fst.Config
+	done *atomic.Bool
+}
+
+func (a *appCt) Unwrap() *fst.Config {
+	if !a.done.Load() {
+		defer a.done.Store(true)
+		return a.val
+	}
+	panic("attempted to access config reference twice")
+}
+
+func newAppCt(config *fst.Config) (ct *appCt) {
+	ct = new(appCt)
+	ct.done = new(atomic.Bool)
+	ct.val = config
+	return ct
+}

internal/app/app_nixos_test.go

@@ -0,0 +1,225 @@
+package app_test
+
+import (
+	"git.gensokyo.uk/security/fortify/acl"
+	"git.gensokyo.uk/security/fortify/dbus"
+	"git.gensokyo.uk/security/fortify/fst"
+	"git.gensokyo.uk/security/fortify/helper/bwrap"
+	"git.gensokyo.uk/security/fortify/internal/system"
+)
+
+var testCasesNixos = []sealTestCase{
+	{
+		"nixos chromium direct wayland", new(stubNixOS),
+		&fst.Config{
+			ID:      "org.chromium.Chromium",
+			Command: []string{"/nix/store/yqivzpzzn7z5x0lq9hmbzygh45d8rhqd-chromium-start"},
+			Confinement: fst.ConfinementConfig{
+				AppID: 1, Groups: []string{}, Username: "u0_a1",
+				Outer: "/var/lib/persist/module/fortify/0/1",
+				Sandbox: &fst.SandboxConfig{
+					UserNS: true, Net: true, MapRealUID: true, DirectWayland: true, Env: nil,
+					Filesystem: []*fst.FilesystemConfig{
+						{Src: "/bin", Must: true}, {Src: "/usr/bin", Must: true},
+						{Src: "/nix/store", Must: true}, {Src: "/run/current-system", Must: true},
+						{Src: "/sys/block"}, {Src: "/sys/bus"}, {Src: "/sys/class"}, {Src: "/sys/dev"}, {Src: "/sys/devices"},
+						{Src: "/run/opengl-driver", Must: true}, {Src: "/dev/dri", Device: true},
+					}, AutoEtc: true,
+					Override: []string{"/var/run/nscd"},
+				},
+				SystemBus: &dbus.Config{
+					Talk:   []string{"org.bluez", "org.freedesktop.Avahi", "org.freedesktop.UPower"},
+					Filter: true,
+				},
+				SessionBus: &dbus.Config{
+					Talk: []string{
+						"org.freedesktop.FileManager1", "org.freedesktop.Notifications",
+						"org.freedesktop.ScreenSaver", "org.freedesktop.secrets",
+						"org.kde.kwalletd5", "org.kde.kwalletd6",
+					},
+					Own: []string{
+						"org.chromium.Chromium.*",
+						"org.mpris.MediaPlayer2.org.chromium.Chromium.*",
+						"org.mpris.MediaPlayer2.chromium.*",
+					},
+					Call: map[string]string{}, Broadcast: map[string]string{},
+					Filter: true,
+				},
+				Enablements: system.EWayland.Mask() | system.EDBus.Mask() | system.EPulse.Mask(),
+			},
+		},
+		fst.ID{
+			0x8e, 0x2c, 0x76, 0xb0,
+			0x66, 0xda, 0xbe, 0x57,
+			0x4c, 0xf0, 0x73, 0xbd,
+			0xb4, 0x6e, 0xb5, 0xc1,
+		},
+		system.New(1000001).
+			Ensure("/tmp/fortify.1971", 0711).
+			Ephemeral(system.Process, "/tmp/fortify.1971/8e2c76b066dabe574cf073bdb46eb5c1", 0711).
+			Ensure("/tmp/fortify.1971/tmpdir", 0700).UpdatePermType(system.User, "/tmp/fortify.1971/tmpdir", acl.Execute).
+			Ensure("/tmp/fortify.1971/tmpdir/1", 01700).UpdatePermType(system.User, "/tmp/fortify.1971/tmpdir/1", acl.Read, acl.Write, acl.Execute).
+			Ensure("/run/user/1971/fortify", 0700).UpdatePermType(system.User, "/run/user/1971/fortify", acl.Execute).
+			Ensure("/run/user/1971", 0700).UpdatePermType(system.User, "/run/user/1971", acl.Execute). // this is ordered as is because the previous Ensure only calls mkdir if XDG_RUNTIME_DIR is unset
+			Ephemeral(system.Process, "/run/user/1971/fortify/8e2c76b066dabe574cf073bdb46eb5c1", 0700).UpdatePermType(system.Process, "/run/user/1971/fortify/8e2c76b066dabe574cf073bdb46eb5c1", acl.Execute).
+			WriteType(system.Process, "/tmp/fortify.1971/8e2c76b066dabe574cf073bdb46eb5c1/passwd", "u0_a1:x:1971:1971:Fortify:/var/lib/persist/module/fortify/0/1:/run/current-system/sw/bin/zsh\n").
+			WriteType(system.Process, "/tmp/fortify.1971/8e2c76b066dabe574cf073bdb46eb5c1/group", "fortify:x:1971:\n").
+			Link("/run/user/1971/wayland-0", "/run/user/1971/fortify/8e2c76b066dabe574cf073bdb46eb5c1/wayland").
+			UpdatePermType(system.EWayland, "/run/user/1971/wayland-0", acl.Read, acl.Write, acl.Execute).
+			Link("/run/user/1971/pulse/native", "/run/user/1971/fortify/8e2c76b066dabe574cf073bdb46eb5c1/pulse").
+			CopyFile("/tmp/fortify.1971/8e2c76b066dabe574cf073bdb46eb5c1/pulse-cookie", "/home/ophestra/xdg/config/pulse/cookie").
+			MustProxyDBus("/tmp/fortify.1971/8e2c76b066dabe574cf073bdb46eb5c1/bus", &dbus.Config{
+				Talk: []string{
+					"org.freedesktop.FileManager1", "org.freedesktop.Notifications",
+					"org.freedesktop.ScreenSaver", "org.freedesktop.secrets",
+					"org.kde.kwalletd5", "org.kde.kwalletd6",
+				},
+				Own: []string{
+					"org.chromium.Chromium.*",
+					"org.mpris.MediaPlayer2.org.chromium.Chromium.*",
+					"org.mpris.MediaPlayer2.chromium.*",
+				},
+				Call: map[string]string{}, Broadcast: map[string]string{},
+				Filter: true,
+			}, "/tmp/fortify.1971/8e2c76b066dabe574cf073bdb46eb5c1/system_bus_socket", &dbus.Config{
+				Talk: []string{
+					"org.bluez",
+					"org.freedesktop.Avahi",
+					"org.freedesktop.UPower",
+				},
+				Filter: true,
+			}).
+			UpdatePerm("/tmp/fortify.1971/8e2c76b066dabe574cf073bdb46eb5c1/bus", acl.Read, acl.Write).
+			UpdatePerm("/tmp/fortify.1971/8e2c76b066dabe574cf073bdb46eb5c1/system_bus_socket", acl.Read, acl.Write),
+		(&bwrap.Config{
+			Net:      true,
+			UserNS:   true,
+			Chdir:    "/var/lib/persist/module/fortify/0/1",
+			Clearenv: true,
+			SetEnv: map[string]string{
+				"DBUS_SESSION_BUS_ADDRESS": "unix:path=/run/user/1971/bus",
+				"DBUS_SYSTEM_BUS_ADDRESS":  "unix:path=/run/dbus/system_bus_socket",
+				"HOME":                     "/var/lib/persist/module/fortify/0/1",
+				"PULSE_COOKIE":             "/tmp/fortify.1971/8e2c76b066dabe574cf073bdb46eb5c1/pulse-cookie",
+				"PULSE_SERVER":             "unix:/run/user/1971/pulse/native",
+				"SHELL":                    "/run/current-system/sw/bin/zsh",
+				"TERM":                     "xterm-256color",
+				"USER":                     "u0_a1",
+				"WAYLAND_DISPLAY":          "/run/user/1971/wayland-0",
+				"XDG_RUNTIME_DIR":          "/run/user/1971",
+				"XDG_SESSION_CLASS":        "user",
+				"XDG_SESSION_TYPE":         "tty",
+			},
+			Chmod:         make(bwrap.ChmodConfig),
+			NewSession:    true,
+			DieWithParent: true,
+			AsInit:        true,
+		}).SetUID(1971).SetGID(1971).
+			Procfs("/proc").
+			Tmpfs("/fortify", 4096).
+			DevTmpfs("/dev").Mqueue("/dev/mqueue").
+			Bind("/bin", "/bin").
+			Bind("/usr/bin", "/usr/bin").
+			Bind("/nix/store", "/nix/store").
+			Bind("/run/current-system", "/run/current-system").
+			Bind("/sys/block", "/sys/block", true).
+			Bind("/sys/bus", "/sys/bus", true).
+			Bind("/sys/class", "/sys/class", true).
+			Bind("/sys/dev", "/sys/dev", true).
+			Bind("/sys/devices", "/sys/devices", true).
+			Bind("/run/opengl-driver", "/run/opengl-driver").
+			Bind("/dev/dri", "/dev/dri", true, true, true).
+			Bind("/etc", "/fortify/etc").
+			Symlink("/fortify/etc/alsa", "/etc/alsa").
+			Symlink("/fortify/etc/bashrc", "/etc/bashrc").
+			Symlink("/fortify/etc/binfmt.d", "/etc/binfmt.d").
+			Symlink("/fortify/etc/dbus-1", "/etc/dbus-1").
+			Symlink("/fortify/etc/default", "/etc/default").
+			Symlink("/fortify/etc/ethertypes", "/etc/ethertypes").
+			Symlink("/fortify/etc/fonts", "/etc/fonts").
+			Symlink("/fortify/etc/fstab", "/etc/fstab").
+			Symlink("/fortify/etc/fuse.conf", "/etc/fuse.conf").
+			Symlink("/fortify/etc/host.conf", "/etc/host.conf").
+			Symlink("/fortify/etc/hostid", "/etc/hostid").
+			Symlink("/fortify/etc/hostname", "/etc/hostname").
+			Symlink("/fortify/etc/hostname.CHECKSUM", "/etc/hostname.CHECKSUM").
+			Symlink("/fortify/etc/hosts", "/etc/hosts").
+			Symlink("/fortify/etc/inputrc", "/etc/inputrc").
+			Symlink("/fortify/etc/ipsec.d", "/etc/ipsec.d").
+			Symlink("/fortify/etc/issue", "/etc/issue").
+			Symlink("/fortify/etc/kbd", "/etc/kbd").
+			Symlink("/fortify/etc/libblockdev", "/etc/libblockdev").
+			Symlink("/fortify/etc/locale.conf", "/etc/locale.conf").
+			Symlink("/fortify/etc/localtime", "/etc/localtime").
+			Symlink("/fortify/etc/login.defs", "/etc/login.defs").
+			Symlink("/fortify/etc/lsb-release", "/etc/lsb-release").
+			Symlink("/fortify/etc/lvm", "/etc/lvm").
+			Symlink("/fortify/etc/machine-id", "/etc/machine-id").
+			Symlink("/fortify/etc/man_db.conf", "/etc/man_db.conf").
+			Symlink("/fortify/etc/modprobe.d", "/etc/modprobe.d").
+			Symlink("/fortify/etc/modules-load.d", "/etc/modules-load.d").
+			Symlink("/proc/mounts", "/etc/mtab").
+			Symlink("/fortify/etc/nanorc", "/etc/nanorc").
+			Symlink("/fortify/etc/netgroup", "/etc/netgroup").
+			Symlink("/fortify/etc/NetworkManager", "/etc/NetworkManager").
+			Symlink("/fortify/etc/nix", "/etc/nix").
+			Symlink("/fortify/etc/nixos", "/etc/nixos").
+			Symlink("/fortify/etc/NIXOS", "/etc/NIXOS").
+			Symlink("/fortify/etc/nscd.conf", "/etc/nscd.conf").
+			Symlink("/fortify/etc/nsswitch.conf", "/etc/nsswitch.conf").
+			Symlink("/fortify/etc/opensnitchd", "/etc/opensnitchd").
+			Symlink("/fortify/etc/os-release", "/etc/os-release").
+			Symlink("/fortify/etc/pam", "/etc/pam").
+			Symlink("/fortify/etc/pam.d", "/etc/pam.d").
+			Symlink("/fortify/etc/pipewire", "/etc/pipewire").
+			Symlink("/fortify/etc/pki", "/etc/pki").
+			Symlink("/fortify/etc/polkit-1", "/etc/polkit-1").
+			Symlink("/fortify/etc/profile", "/etc/profile").
+			Symlink("/fortify/etc/protocols", "/etc/protocols").
+			Symlink("/fortify/etc/qemu", "/etc/qemu").
+			Symlink("/fortify/etc/resolv.conf", "/etc/resolv.conf").
+			Symlink("/fortify/etc/resolvconf.conf", "/etc/resolvconf.conf").
+			Symlink("/fortify/etc/rpc", "/etc/rpc").
+			Symlink("/fortify/etc/samba", "/etc/samba").
+			Symlink("/fortify/etc/sddm.conf", "/etc/sddm.conf").
+			Symlink("/fortify/etc/secureboot", "/etc/secureboot").
+			Symlink("/fortify/etc/services", "/etc/services").
+			Symlink("/fortify/etc/set-environment", "/etc/set-environment").
+			Symlink("/fortify/etc/shadow", "/etc/shadow").
+			Symlink("/fortify/etc/shells", "/etc/shells").
+			Symlink("/fortify/etc/ssh", "/etc/ssh").
+			Symlink("/fortify/etc/ssl", "/etc/ssl").
+			Symlink("/fortify/etc/static", "/etc/static").
+			Symlink("/fortify/etc/subgid", "/etc/subgid").
+			Symlink("/fortify/etc/subuid", "/etc/subuid").
+			Symlink("/fortify/etc/sudoers", "/etc/sudoers").
+			Symlink("/fortify/etc/sysctl.d", "/etc/sysctl.d").
+			Symlink("/fortify/etc/systemd", "/etc/systemd").
+			Symlink("/fortify/etc/terminfo", "/etc/terminfo").
+			Symlink("/fortify/etc/tmpfiles.d", "/etc/tmpfiles.d").
+			Symlink("/fortify/etc/udev", "/etc/udev").
+			Symlink("/fortify/etc/udisks2", "/etc/udisks2").
+			Symlink("/fortify/etc/UPower", "/etc/UPower").
+			Symlink("/fortify/etc/vconsole.conf", "/etc/vconsole.conf").
+			Symlink("/fortify/etc/X11", "/etc/X11").
+			Symlink("/fortify/etc/zfs", "/etc/zfs").
+			Symlink("/fortify/etc/zinputrc", "/etc/zinputrc").
+			Symlink("/fortify/etc/zoneinfo", "/etc/zoneinfo").
+			Symlink("/fortify/etc/zprofile", "/etc/zprofile").
+			Symlink("/fortify/etc/zshenv", "/etc/zshenv").
+			Symlink("/fortify/etc/zshrc", "/etc/zshrc").
+			Bind("/tmp/fortify.1971/tmpdir/1", "/tmp", false, true).
+			Tmpfs("/tmp/fortify.1971", 1048576).
+			Tmpfs("/run/user", 1048576).
+			Tmpfs("/run/user/1971", 8388608).
+			Bind("/var/lib/persist/module/fortify/0/1", "/var/lib/persist/module/fortify/0/1", false, true).
+			Bind("/tmp/fortify.1971/8e2c76b066dabe574cf073bdb46eb5c1/passwd", "/etc/passwd").
+			Bind("/tmp/fortify.1971/8e2c76b066dabe574cf073bdb46eb5c1/group", "/etc/group").
+			Bind("/run/user/1971/fortify/8e2c76b066dabe574cf073bdb46eb5c1/wayland", "/run/user/1971/wayland-0").
+			Bind("/run/user/1971/fortify/8e2c76b066dabe574cf073bdb46eb5c1/pulse", "/run/user/1971/pulse/native").
+			Bind("/tmp/fortify.1971/8e2c76b066dabe574cf073bdb46eb5c1/pulse-cookie", "/tmp/fortify.1971/8e2c76b066dabe574cf073bdb46eb5c1/pulse-cookie").
+			Bind("/tmp/fortify.1971/8e2c76b066dabe574cf073bdb46eb5c1/bus", "/run/user/1971/bus").
+			Bind("/tmp/fortify.1971/8e2c76b066dabe574cf073bdb46eb5c1/system_bus_socket", "/run/dbus/system_bus_socket").
+			Tmpfs("/var/run/nscd", 8192),
+	},
+}

internal/app/app_pd_test.go

@@ -0,0 +1,452 @@
+package app_test
+
+import (
+	"git.gensokyo.uk/security/fortify/acl"
+	"git.gensokyo.uk/security/fortify/dbus"
+	"git.gensokyo.uk/security/fortify/fst"
+	"git.gensokyo.uk/security/fortify/helper/bwrap"
+	"git.gensokyo.uk/security/fortify/internal/system"
+)
+
+var testCasesPd = []sealTestCase{
+	{
+		"nixos permissive defaults no enablements", new(stubNixOS),
+		&fst.Config{
+			Command: make([]string, 0),
+			Confinement: fst.ConfinementConfig{
+				AppID:    0,
+				Username: "chronos",
+				Outer:    "/home/chronos",
+			},
+		},
+		fst.ID{
+			0x4a, 0x45, 0x0b, 0x65,
+			0x96, 0xd7, 0xbc, 0x15,
+			0xbd, 0x01, 0x78, 0x0e,
+			0xb9, 0xa6, 0x07, 0xac,
+		},
+		system.New(1000000).
+			Ensure("/tmp/fortify.1971", 0711).
+			Ephemeral(system.Process, "/tmp/fortify.1971/4a450b6596d7bc15bd01780eb9a607ac", 0711).
+			Ensure("/tmp/fortify.1971/tmpdir", 0700).UpdatePermType(system.User, "/tmp/fortify.1971/tmpdir", acl.Execute).
+			Ensure("/tmp/fortify.1971/tmpdir/0", 01700).UpdatePermType(system.User, "/tmp/fortify.1971/tmpdir/0", acl.Read, acl.Write, acl.Execute).
+			Ensure("/run/user/1971/fortify", 0700).UpdatePermType(system.User, "/run/user/1971/fortify", acl.Execute).
+			Ensure("/run/user/1971", 0700).UpdatePermType(system.User, "/run/user/1971", acl.Execute). // this is ordered as is because the previous Ensure only calls mkdir if XDG_RUNTIME_DIR is unset
+			Ephemeral(system.Process, "/run/user/1971/fortify/4a450b6596d7bc15bd01780eb9a607ac", 0700).UpdatePermType(system.Process, "/run/user/1971/fortify/4a450b6596d7bc15bd01780eb9a607ac", acl.Execute).
+			WriteType(system.Process, "/tmp/fortify.1971/4a450b6596d7bc15bd01780eb9a607ac/passwd", "chronos:x:65534:65534:Fortify:/home/chronos:/run/current-system/sw/bin/zsh\n").
+			WriteType(system.Process, "/tmp/fortify.1971/4a450b6596d7bc15bd01780eb9a607ac/group", "fortify:x:65534:\n"),
+		(&bwrap.Config{
+			Net:      true,
+			UserNS:   true,
+			Clearenv: true,
+			Chdir:    "/home/chronos",
+			SetEnv: map[string]string{
+				"HOME":              "/home/chronos",
+				"SHELL":             "/run/current-system/sw/bin/zsh",
+				"TERM":              "xterm-256color",
+				"USER":              "chronos",
+				"XDG_RUNTIME_DIR":   "/run/user/65534",
+				"XDG_SESSION_CLASS": "user",
+				"XDG_SESSION_TYPE":  "tty"},
+			Chmod:         make(bwrap.ChmodConfig),
+			DieWithParent: true,
+			AsInit:        true,
+		}).SetUID(65534).SetGID(65534).
+			Procfs("/proc").
+			Tmpfs("/fortify", 4096).
+			DevTmpfs("/dev").Mqueue("/dev/mqueue").
+			Bind("/bin", "/bin", false, true).
+			Bind("/boot", "/boot", false, true).
+			Bind("/home", "/home", false, true).
+			Bind("/lib", "/lib", false, true).
+			Bind("/lib64", "/lib64", false, true).
+			Bind("/nix", "/nix", false, true).
+			Bind("/root", "/root", false, true).
+			Bind("/srv", "/srv", false, true).
+			Bind("/sys", "/sys", false, true).
+			Bind("/usr", "/usr", false, true).
+			Bind("/var", "/var", false, true).
+			Bind("/run/agetty.reload", "/run/agetty.reload", false, true).
+			Bind("/run/binfmt", "/run/binfmt", false, true).
+			Bind("/run/booted-system", "/run/booted-system", false, true).
+			Bind("/run/credentials", "/run/credentials", false, true).
+			Bind("/run/cryptsetup", "/run/cryptsetup", false, true).
+			Bind("/run/current-system", "/run/current-system", false, true).
+			Bind("/run/host", "/run/host", false, true).
+			Bind("/run/keys", "/run/keys", false, true).
+			Bind("/run/libvirt", "/run/libvirt", false, true).
+			Bind("/run/libvirtd.pid", "/run/libvirtd.pid", false, true).
+			Bind("/run/lock", "/run/lock", false, true).
+			Bind("/run/log", "/run/log", false, true).
+			Bind("/run/lvm", "/run/lvm", false, true).
+			Bind("/run/mount", "/run/mount", false, true).
+			Bind("/run/NetworkManager", "/run/NetworkManager", false, true).
+			Bind("/run/nginx", "/run/nginx", false, true).
+			Bind("/run/nixos", "/run/nixos", false, true).
+			Bind("/run/nscd", "/run/nscd", false, true).
+			Bind("/run/opengl-driver", "/run/opengl-driver", false, true).
+			Bind("/run/pppd", "/run/pppd", false, true).
+			Bind("/run/resolvconf", "/run/resolvconf", false, true).
+			Bind("/run/sddm", "/run/sddm", false, true).
+			Bind("/run/store", "/run/store", false, true).
+			Bind("/run/syncoid", "/run/syncoid", false, true).
+			Bind("/run/system", "/run/system", false, true).
+			Bind("/run/systemd", "/run/systemd", false, true).
+			Bind("/run/tmpfiles.d", "/run/tmpfiles.d", false, true).
+			Bind("/run/udev", "/run/udev", false, true).
+			Bind("/run/udisks2", "/run/udisks2", false, true).
+			Bind("/run/utmp", "/run/utmp", false, true).
+			Bind("/run/virtlogd.pid", "/run/virtlogd.pid", false, true).
+			Bind("/run/wrappers", "/run/wrappers", false, true).
+			Bind("/run/zed.pid", "/run/zed.pid", false, true).
+			Bind("/run/zed.state", "/run/zed.state", false, true).
+			Bind("/etc", "/fortify/etc").
+			Symlink("/fortify/etc/alsa", "/etc/alsa").
+			Symlink("/fortify/etc/bashrc", "/etc/bashrc").
+			Symlink("/fortify/etc/binfmt.d", "/etc/binfmt.d").
+			Symlink("/fortify/etc/dbus-1", "/etc/dbus-1").
+			Symlink("/fortify/etc/default", "/etc/default").
+			Symlink("/fortify/etc/ethertypes", "/etc/ethertypes").
+			Symlink("/fortify/etc/fonts", "/etc/fonts").
+			Symlink("/fortify/etc/fstab", "/etc/fstab").
+			Symlink("/fortify/etc/fuse.conf", "/etc/fuse.conf").
+			Symlink("/fortify/etc/host.conf", "/etc/host.conf").
+			Symlink("/fortify/etc/hostid", "/etc/hostid").
+			Symlink("/fortify/etc/hostname", "/etc/hostname").
+			Symlink("/fortify/etc/hostname.CHECKSUM", "/etc/hostname.CHECKSUM").
+			Symlink("/fortify/etc/hosts", "/etc/hosts").
+			Symlink("/fortify/etc/inputrc", "/etc/inputrc").
+			Symlink("/fortify/etc/ipsec.d", "/etc/ipsec.d").
+			Symlink("/fortify/etc/issue", "/etc/issue").
+			Symlink("/fortify/etc/kbd", "/etc/kbd").
+			Symlink("/fortify/etc/libblockdev", "/etc/libblockdev").
+			Symlink("/fortify/etc/locale.conf", "/etc/locale.conf").
+			Symlink("/fortify/etc/localtime", "/etc/localtime").
+			Symlink("/fortify/etc/login.defs", "/etc/login.defs").
+			Symlink("/fortify/etc/lsb-release", "/etc/lsb-release").
+			Symlink("/fortify/etc/lvm", "/etc/lvm").
+			Symlink("/fortify/etc/machine-id", "/etc/machine-id").
+			Symlink("/fortify/etc/man_db.conf", "/etc/man_db.conf").
+			Symlink("/fortify/etc/modprobe.d", "/etc/modprobe.d").
+			Symlink("/fortify/etc/modules-load.d", "/etc/modules-load.d").
+			Symlink("/proc/mounts", "/etc/mtab").
+			Symlink("/fortify/etc/nanorc", "/etc/nanorc").
+			Symlink("/fortify/etc/netgroup", "/etc/netgroup").
+			Symlink("/fortify/etc/NetworkManager", "/etc/NetworkManager").
+			Symlink("/fortify/etc/nix", "/etc/nix").
+			Symlink("/fortify/etc/nixos", "/etc/nixos").
+			Symlink("/fortify/etc/NIXOS", "/etc/NIXOS").
+			Symlink("/fortify/etc/nscd.conf", "/etc/nscd.conf").
+			Symlink("/fortify/etc/nsswitch.conf", "/etc/nsswitch.conf").
+			Symlink("/fortify/etc/opensnitchd", "/etc/opensnitchd").
+			Symlink("/fortify/etc/os-release", "/etc/os-release").
+			Symlink("/fortify/etc/pam", "/etc/pam").
+			Symlink("/fortify/etc/pam.d", "/etc/pam.d").
+			Symlink("/fortify/etc/pipewire", "/etc/pipewire").
+			Symlink("/fortify/etc/pki", "/etc/pki").
+			Symlink("/fortify/etc/polkit-1", "/etc/polkit-1").
+			Symlink("/fortify/etc/profile", "/etc/profile").
+			Symlink("/fortify/etc/protocols", "/etc/protocols").
+			Symlink("/fortify/etc/qemu", "/etc/qemu").
+			Symlink("/fortify/etc/resolv.conf", "/etc/resolv.conf").
+			Symlink("/fortify/etc/resolvconf.conf", "/etc/resolvconf.conf").
+			Symlink("/fortify/etc/rpc", "/etc/rpc").
+			Symlink("/fortify/etc/samba", "/etc/samba").
+			Symlink("/fortify/etc/sddm.conf", "/etc/sddm.conf").
+			Symlink("/fortify/etc/secureboot", "/etc/secureboot").
+			Symlink("/fortify/etc/services", "/etc/services").
+			Symlink("/fortify/etc/set-environment", "/etc/set-environment").
+			Symlink("/fortify/etc/shadow", "/etc/shadow").
+			Symlink("/fortify/etc/shells", "/etc/shells").
+			Symlink("/fortify/etc/ssh", "/etc/ssh").
+			Symlink("/fortify/etc/ssl", "/etc/ssl").
+			Symlink("/fortify/etc/static", "/etc/static").
+			Symlink("/fortify/etc/subgid", "/etc/subgid").
+			Symlink("/fortify/etc/subuid", "/etc/subuid").
+			Symlink("/fortify/etc/sudoers", "/etc/sudoers").
+			Symlink("/fortify/etc/sysctl.d", "/etc/sysctl.d").
+			Symlink("/fortify/etc/systemd", "/etc/systemd").
+			Symlink("/fortify/etc/terminfo", "/etc/terminfo").
+			Symlink("/fortify/etc/tmpfiles.d", "/etc/tmpfiles.d").
+			Symlink("/fortify/etc/udev", "/etc/udev").
+			Symlink("/fortify/etc/udisks2", "/etc/udisks2").
+			Symlink("/fortify/etc/UPower", "/etc/UPower").
+			Symlink("/fortify/etc/vconsole.conf", "/etc/vconsole.conf").
+			Symlink("/fortify/etc/X11", "/etc/X11").
+			Symlink("/fortify/etc/zfs", "/etc/zfs").
+			Symlink("/fortify/etc/zinputrc", "/etc/zinputrc").
+			Symlink("/fortify/etc/zoneinfo", "/etc/zoneinfo").
+			Symlink("/fortify/etc/zprofile", "/etc/zprofile").
+			Symlink("/fortify/etc/zshenv", "/etc/zshenv").
+			Symlink("/fortify/etc/zshrc", "/etc/zshrc").
+			Bind("/tmp/fortify.1971/tmpdir/0", "/tmp", false, true).
+			Tmpfs("/tmp/fortify.1971", 1048576).
+			Tmpfs("/run/user", 1048576).
+			Tmpfs("/run/user/65534", 8388608).
+			Bind("/home/chronos", "/home/chronos", false, true).
+			Bind("/tmp/fortify.1971/4a450b6596d7bc15bd01780eb9a607ac/passwd", "/etc/passwd").
+			Bind("/tmp/fortify.1971/4a450b6596d7bc15bd01780eb9a607ac/group", "/etc/group").
+			Tmpfs("/var/run/nscd", 8192),
+	},
+	{
+		"nixos permissive defaults chromium", new(stubNixOS),
+		&fst.Config{
+			ID:      "org.chromium.Chromium",
+			Command: []string{"/run/current-system/sw/bin/zsh", "-c", "exec chromium "},
+			Confinement: fst.ConfinementConfig{
+				AppID:    9,
+				Groups:   []string{"video"},
+				Username: "chronos",
+				Outer:    "/home/chronos",
+				SessionBus: &dbus.Config{
+					Talk: []string{
+						"org.freedesktop.Notifications",
+						"org.freedesktop.FileManager1",
+						"org.freedesktop.ScreenSaver",
+						"org.freedesktop.secrets",
+						"org.kde.kwalletd5",
+						"org.kde.kwalletd6",
+						"org.gnome.SessionManager",
+					},
+					Own: []string{
+						"org.chromium.Chromium.*",
+						"org.mpris.MediaPlayer2.org.chromium.Chromium.*",
+						"org.mpris.MediaPlayer2.chromium.*",
+					},
+					Call: map[string]string{
+						"org.freedesktop.portal.*": "*",
+					},
+					Broadcast: map[string]string{
+						"org.freedesktop.portal.*": "@/org/freedesktop/portal/*",
+					},
+					Filter: true,
+				},
+				SystemBus: &dbus.Config{
+					Talk: []string{
+						"org.bluez",
+						"org.freedesktop.Avahi",
+						"org.freedesktop.UPower",
+					},
+					Filter: true,
+				},
+				Enablements: system.EWayland.Mask() | system.EDBus.Mask() | system.EPulse.Mask(),
+			},
+		},
+		fst.ID{
+			0xeb, 0xf0, 0x83, 0xd1,
+			0xb1, 0x75, 0x91, 0x17,
+			0x82, 0xd4, 0x13, 0x36,
+			0x9b, 0x64, 0xce, 0x7c,
+		},
+		system.New(1000009).
+			Ensure("/tmp/fortify.1971", 0711).
+			Ephemeral(system.Process, "/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c", 0711).
+			Ensure("/tmp/fortify.1971/tmpdir", 0700).UpdatePermType(system.User, "/tmp/fortify.1971/tmpdir", acl.Execute).
+			Ensure("/tmp/fortify.1971/tmpdir/9", 01700).UpdatePermType(system.User, "/tmp/fortify.1971/tmpdir/9", acl.Read, acl.Write, acl.Execute).
+			Ensure("/run/user/1971/fortify", 0700).UpdatePermType(system.User, "/run/user/1971/fortify", acl.Execute).
+			Ensure("/run/user/1971", 0700).UpdatePermType(system.User, "/run/user/1971", acl.Execute). // this is ordered as is because the previous Ensure only calls mkdir if XDG_RUNTIME_DIR is unset
+			Ephemeral(system.Process, "/run/user/1971/fortify/ebf083d1b175911782d413369b64ce7c", 0700).UpdatePermType(system.Process, "/run/user/1971/fortify/ebf083d1b175911782d413369b64ce7c", acl.Execute).
+			WriteType(system.Process, "/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/passwd", "chronos:x:65534:65534:Fortify:/home/chronos:/run/current-system/sw/bin/zsh\n").
+			WriteType(system.Process, "/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/group", "fortify:x:65534:\n").
+			Ensure("/tmp/fortify.1971/wayland", 0711).
+			Wayland("/tmp/fortify.1971/wayland/ebf083d1b175911782d413369b64ce7c", "/run/user/1971/wayland-0", "org.chromium.Chromium", "ebf083d1b175911782d413369b64ce7c").
+			Link("/run/user/1971/pulse/native", "/run/user/1971/fortify/ebf083d1b175911782d413369b64ce7c/pulse").
+			CopyFile("/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/pulse-cookie", "/home/ophestra/xdg/config/pulse/cookie").
+			MustProxyDBus("/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/bus", &dbus.Config{
+				Talk: []string{
+					"org.freedesktop.Notifications",
+					"org.freedesktop.FileManager1",
+					"org.freedesktop.ScreenSaver",
+					"org.freedesktop.secrets",
+					"org.kde.kwalletd5",
+					"org.kde.kwalletd6",
+					"org.gnome.SessionManager",
+				},
+				Own: []string{
+					"org.chromium.Chromium.*",
+					"org.mpris.MediaPlayer2.org.chromium.Chromium.*",
+					"org.mpris.MediaPlayer2.chromium.*",
+				},
+				Call: map[string]string{
+					"org.freedesktop.portal.*": "*",
+				},
+				Broadcast: map[string]string{
+					"org.freedesktop.portal.*": "@/org/freedesktop/portal/*",
+				},
+				Filter: true,
+			}, "/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/system_bus_socket", &dbus.Config{
+				Talk: []string{
+					"org.bluez",
+					"org.freedesktop.Avahi",
+					"org.freedesktop.UPower",
+				},
+				Filter: true,
+			}).
+			UpdatePerm("/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/bus", acl.Read, acl.Write).
+			UpdatePerm("/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/system_bus_socket", acl.Read, acl.Write),
+		(&bwrap.Config{
+			Net:      true,
+			UserNS:   true,
+			Chdir:    "/home/chronos",
+			Clearenv: true,
+			SetEnv: map[string]string{
+				"DBUS_SESSION_BUS_ADDRESS": "unix:path=/run/user/65534/bus",
+				"DBUS_SYSTEM_BUS_ADDRESS":  "unix:path=/run/dbus/system_bus_socket",
+				"HOME":                     "/home/chronos",
+				"PULSE_COOKIE":             "/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/pulse-cookie",
+				"PULSE_SERVER":             "unix:/run/user/65534/pulse/native",
+				"SHELL":                    "/run/current-system/sw/bin/zsh",
+				"TERM":                     "xterm-256color",
+				"USER":                     "chronos",
+				"WAYLAND_DISPLAY":          "/run/user/65534/wayland-0",
+				"XDG_RUNTIME_DIR":          "/run/user/65534",
+				"XDG_SESSION_CLASS":        "user",
+				"XDG_SESSION_TYPE":         "tty",
+			},
+			Chmod:         make(bwrap.ChmodConfig),
+			DieWithParent: true,
+			AsInit:        true,
+		}).SetUID(65534).SetGID(65534).
+			Procfs("/proc").
+			Tmpfs("/fortify", 4096).
+			DevTmpfs("/dev").Mqueue("/dev/mqueue").
+			Bind("/bin", "/bin", false, true).
+			Bind("/boot", "/boot", false, true).
+			Bind("/home", "/home", false, true).
+			Bind("/lib", "/lib", false, true).
+			Bind("/lib64", "/lib64", false, true).
+			Bind("/nix", "/nix", false, true).
+			Bind("/root", "/root", false, true).
+			Bind("/srv", "/srv", false, true).
+			Bind("/sys", "/sys", false, true).
+			Bind("/usr", "/usr", false, true).
+			Bind("/var", "/var", false, true).
+			Bind("/run/agetty.reload", "/run/agetty.reload", false, true).
+			Bind("/run/binfmt", "/run/binfmt", false, true).
+			Bind("/run/booted-system", "/run/booted-system", false, true).
+			Bind("/run/credentials", "/run/credentials", false, true).
+			Bind("/run/cryptsetup", "/run/cryptsetup", false, true).
+			Bind("/run/current-system", "/run/current-system", false, true).
+			Bind("/run/host", "/run/host", false, true).
+			Bind("/run/keys", "/run/keys", false, true).
+			Bind("/run/libvirt", "/run/libvirt", false, true).
+			Bind("/run/libvirtd.pid", "/run/libvirtd.pid", false, true).
+			Bind("/run/lock", "/run/lock", false, true).
+			Bind("/run/log", "/run/log", false, true).
+			Bind("/run/lvm", "/run/lvm", false, true).
+			Bind("/run/mount", "/run/mount", false, true).
+			Bind("/run/NetworkManager", "/run/NetworkManager", false, true).
+			Bind("/run/nginx", "/run/nginx", false, true).
+			Bind("/run/nixos", "/run/nixos", false, true).
+			Bind("/run/nscd", "/run/nscd", false, true).
+			Bind("/run/opengl-driver", "/run/opengl-driver", false, true).
+			Bind("/run/pppd", "/run/pppd", false, true).
+			Bind("/run/resolvconf", "/run/resolvconf", false, true).
+			Bind("/run/sddm", "/run/sddm", false, true).
+			Bind("/run/store", "/run/store", false, true).
+			Bind("/run/syncoid", "/run/syncoid", false, true).
+			Bind("/run/system", "/run/system", false, true).
+			Bind("/run/systemd", "/run/systemd", false, true).
+			Bind("/run/tmpfiles.d", "/run/tmpfiles.d", false, true).
+			Bind("/run/udev", "/run/udev", false, true).
+			Bind("/run/udisks2", "/run/udisks2", false, true).
+			Bind("/run/utmp", "/run/utmp", false, true).
+			Bind("/run/virtlogd.pid", "/run/virtlogd.pid", false, true).
+			Bind("/run/wrappers", "/run/wrappers", false, true).
+			Bind("/run/zed.pid", "/run/zed.pid", false, true).
+			Bind("/run/zed.state", "/run/zed.state", false, true).
+			Bind("/dev/dri", "/dev/dri", true, true, true).
+			Bind("/etc", "/fortify/etc").
+			Symlink("/fortify/etc/alsa", "/etc/alsa").
+			Symlink("/fortify/etc/bashrc", "/etc/bashrc").
+			Symlink("/fortify/etc/binfmt.d", "/etc/binfmt.d").
+			Symlink("/fortify/etc/dbus-1", "/etc/dbus-1").
+			Symlink("/fortify/etc/default", "/etc/default").
+			Symlink("/fortify/etc/ethertypes", "/etc/ethertypes").
+			Symlink("/fortify/etc/fonts", "/etc/fonts").
+			Symlink("/fortify/etc/fstab", "/etc/fstab").
+			Symlink("/fortify/etc/fuse.conf", "/etc/fuse.conf").
+			Symlink("/fortify/etc/host.conf", "/etc/host.conf").
+			Symlink("/fortify/etc/hostid", "/etc/hostid").
+			Symlink("/fortify/etc/hostname", "/etc/hostname").
+			Symlink("/fortify/etc/hostname.CHECKSUM", "/etc/hostname.CHECKSUM").
+			Symlink("/fortify/etc/hosts", "/etc/hosts").
+			Symlink("/fortify/etc/inputrc", "/etc/inputrc").
+			Symlink("/fortify/etc/ipsec.d", "/etc/ipsec.d").
+			Symlink("/fortify/etc/issue", "/etc/issue").
+			Symlink("/fortify/etc/kbd", "/etc/kbd").
+			Symlink("/fortify/etc/libblockdev", "/etc/libblockdev").
+			Symlink("/fortify/etc/locale.conf", "/etc/locale.conf").
+			Symlink("/fortify/etc/localtime", "/etc/localtime").
+			Symlink("/fortify/etc/login.defs", "/etc/login.defs").
+			Symlink("/fortify/etc/lsb-release", "/etc/lsb-release").
+			Symlink("/fortify/etc/lvm", "/etc/lvm").
+			Symlink("/fortify/etc/machine-id", "/etc/machine-id").
+			Symlink("/fortify/etc/man_db.conf", "/etc/man_db.conf").
+			Symlink("/fortify/etc/modprobe.d", "/etc/modprobe.d").
+			Symlink("/fortify/etc/modules-load.d", "/etc/modules-load.d").
+			Symlink("/proc/mounts", "/etc/mtab").
+			Symlink("/fortify/etc/nanorc", "/etc/nanorc").
+			Symlink("/fortify/etc/netgroup", "/etc/netgroup").
+			Symlink("/fortify/etc/NetworkManager", "/etc/NetworkManager").
+			Symlink("/fortify/etc/nix", "/etc/nix").
+			Symlink("/fortify/etc/nixos", "/etc/nixos").
+			Symlink("/fortify/etc/NIXOS", "/etc/NIXOS").
+			Symlink("/fortify/etc/nscd.conf", "/etc/nscd.conf").
+			Symlink("/fortify/etc/nsswitch.conf", "/etc/nsswitch.conf").
+			Symlink("/fortify/etc/opensnitchd", "/etc/opensnitchd").
+			Symlink("/fortify/etc/os-release", "/etc/os-release").
+			Symlink("/fortify/etc/pam", "/etc/pam").
+			Symlink("/fortify/etc/pam.d", "/etc/pam.d").
+			Symlink("/fortify/etc/pipewire", "/etc/pipewire").
+			Symlink("/fortify/etc/pki", "/etc/pki").
+			Symlink("/fortify/etc/polkit-1", "/etc/polkit-1").
+			Symlink("/fortify/etc/profile", "/etc/profile").
+			Symlink("/fortify/etc/protocols", "/etc/protocols").
+			Symlink("/fortify/etc/qemu", "/etc/qemu").
+			Symlink("/fortify/etc/resolv.conf", "/etc/resolv.conf").
+			Symlink("/fortify/etc/resolvconf.conf", "/etc/resolvconf.conf").
+			Symlink("/fortify/etc/rpc", "/etc/rpc").
+			Symlink("/fortify/etc/samba", "/etc/samba").
+			Symlink("/fortify/etc/sddm.conf", "/etc/sddm.conf").
+			Symlink("/fortify/etc/secureboot", "/etc/secureboot").
+			Symlink("/fortify/etc/services", "/etc/services").
+			Symlink("/fortify/etc/set-environment", "/etc/set-environment").
+			Symlink("/fortify/etc/shadow", "/etc/shadow").
+			Symlink("/fortify/etc/shells", "/etc/shells").
+			Symlink("/fortify/etc/ssh", "/etc/ssh").
+			Symlink("/fortify/etc/ssl", "/etc/ssl").
+			Symlink("/fortify/etc/static", "/etc/static").
+			Symlink("/fortify/etc/subgid", "/etc/subgid").
+			Symlink("/fortify/etc/subuid", "/etc/subuid").
+			Symlink("/fortify/etc/sudoers", "/etc/sudoers").
+			Symlink("/fortify/etc/sysctl.d", "/etc/sysctl.d").
+			Symlink("/fortify/etc/systemd", "/etc/systemd").
+			Symlink("/fortify/etc/terminfo", "/etc/terminfo").
+			Symlink("/fortify/etc/tmpfiles.d", "/etc/tmpfiles.d").
+			Symlink("/fortify/etc/udev", "/etc/udev").
+			Symlink("/fortify/etc/udisks2", "/etc/udisks2").
+			Symlink("/fortify/etc/UPower", "/etc/UPower").
+			Symlink("/fortify/etc/vconsole.conf", "/etc/vconsole.conf").
+			Symlink("/fortify/etc/X11", "/etc/X11").
+			Symlink("/fortify/etc/zfs", "/etc/zfs").
+			Symlink("/fortify/etc/zinputrc", "/etc/zinputrc").
+			Symlink("/fortify/etc/zoneinfo", "/etc/zoneinfo").
+			Symlink("/fortify/etc/zprofile", "/etc/zprofile").
+			Symlink("/fortify/etc/zshenv", "/etc/zshenv").
+			Symlink("/fortify/etc/zshrc", "/etc/zshrc").
+			Bind("/tmp/fortify.1971/tmpdir/9", "/tmp", false, true).
+			Tmpfs("/tmp/fortify.1971", 1048576).
+			Tmpfs("/run/user", 1048576).
+			Tmpfs("/run/user/65534", 8388608).
+			Bind("/home/chronos", "/home/chronos", false, true).
+			Bind("/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/passwd", "/etc/passwd").
+			Bind("/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/group", "/etc/group").
+			Bind("/tmp/fortify.1971/wayland/ebf083d1b175911782d413369b64ce7c", "/run/user/65534/wayland-0").
+			Bind("/run/user/1971/fortify/ebf083d1b175911782d413369b64ce7c/pulse", "/run/user/65534/pulse/native").
+			Bind("/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/pulse-cookie", "/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/pulse-cookie").
+			Bind("/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/bus", "/run/user/65534/bus").
+			Bind("/tmp/fortify.1971/ebf083d1b175911782d413369b64ce7c/system_bus_socket", "/run/dbus/system_bus_socket").
+			Tmpfs("/var/run/nscd", 8192),
+	},
+}

internal/app/app_stub_test.go

@@ -0,0 +1,153 @@
+package app_test
+
+import (
+	"fmt"
+	"io"
+	"io/fs"
+	"os/user"
+	"strconv"
+
+	"git.gensokyo.uk/security/fortify/internal/linux"
+)
+
+// fs methods are not implemented using a real FS
+// to help better understand filesystem access behaviour
+type stubNixOS struct {
+	lookPathErr map[string]error
+	usernameErr map[string]error
+}
+
+func (s *stubNixOS) Geteuid() int {
+	return 1971
+}
+
+func (s *stubNixOS) LookupEnv(key string) (string, bool) {
+	switch key {
+	case "SHELL":
+		return "/run/current-system/sw/bin/zsh", true
+	case "TERM":
+		return "xterm-256color", true
+	case "WAYLAND_DISPLAY":
+		return "wayland-0", true
+	case "PULSE_COOKIE":
+		return "", false
+	case "HOME":
+		return "/home/ophestra", true
+	case "XDG_CONFIG_HOME":
+		return "/home/ophestra/xdg/config", true
+	default:
+		panic(fmt.Sprintf("attempted to access unexpected environment variable %q", key))
+	}
+}
+
+func (s *stubNixOS) TempDir() string {
+	return "/tmp"
+}
+
+func (s *stubNixOS) LookPath(file string) (string, error) {
+	if s.lookPathErr != nil {
+		if err, ok := s.lookPathErr[file]; ok {
+			return "", err
+		}
+	}
+
+	switch file {
+	case "sudo":
+		return "/run/wrappers/bin/sudo", nil
+	case "machinectl":
+		return "/home/ophestra/.nix-profile/bin/machinectl", nil
+	default:
+		panic(fmt.Sprintf("attempted to look up unexpected executable %q", file))
+	}
+}
+
+func (s *stubNixOS) Executable() (string, error) {
+	return "/home/ophestra/.nix-profile/bin/fortify", nil
+}
+
+func (s *stubNixOS) LookupGroup(name string) (*user.Group, error) {
+	switch name {
+	case "video":
+		return &user.Group{Gid: "26", Name: "video"}, nil
+	default:
+		return nil, user.UnknownGroupError(name)
+	}
+}
+
+func (s *stubNixOS) ReadDir(name string) ([]fs.DirEntry, error) {
+	switch name {
+	case "/":
+		return stubDirEntries("bin", "boot", "dev", "etc", "home", "lib",
+			"lib64", "nix", "proc", "root", "run", "srv", "sys", "tmp", "usr", "var")
+	case "/run":
+		return stubDirEntries("agetty.reload", "binfmt", "booted-system",
+			"credentials", "cryptsetup", "current-system", "dbus", "host", "keys",
+			"libvirt", "libvirtd.pid", "lock", "log", "lvm", "mount", "NetworkManager",
+			"nginx", "nixos", "nscd", "opengl-driver", "pppd", "resolvconf", "sddm",
+			"store", "syncoid", "system", "systemd", "tmpfiles.d", "udev", "udisks2",
+			"user", "utmp", "virtlogd.pid", "wrappers", "zed.pid", "zed.state")
+	case "/etc":
+		return stubDirEntries("alsa", "bashrc", "binfmt.d", "dbus-1", "default",
+			"ethertypes", "fonts", "fstab", "fuse.conf", "group", "host.conf", "hostid",
+			"hostname", "hostname.CHECKSUM", "hosts", "inputrc", "ipsec.d", "issue", "kbd",
+			"libblockdev", "locale.conf", "localtime", "login.defs", "lsb-release", "lvm",
+			"machine-id", "man_db.conf", "modprobe.d", "modules-load.d", "mtab", "nanorc",
+			"netgroup", "NetworkManager", "nix", "nixos", "NIXOS", "nscd.conf", "nsswitch.conf",
+			"opensnitchd", "os-release", "pam", "pam.d", "passwd", "pipewire", "pki", "polkit-1",
+			"profile", "protocols", "qemu", "resolv.conf", "resolvconf.conf", "rpc", "samba",
+			"sddm.conf", "secureboot", "services", "set-environment", "shadow", "shells", "ssh",
+			"ssl", "static", "subgid", "subuid", "sudoers", "sysctl.d", "systemd", "terminfo",
+			"tmpfiles.d", "udev", "udisks2", "UPower", "vconsole.conf", "X11", "zfs", "zinputrc",
+			"zoneinfo", "zprofile", "zshenv", "zshrc")
+	default:
+		panic(fmt.Sprintf("attempted to read unexpected directory %q", name))
+	}
+}
+
+func (s *stubNixOS) Stat(name string) (fs.FileInfo, error) {
+	switch name {
+	case "/var/run/nscd":
+		return nil, nil
+	case "/run/user/1971/pulse":
+		return nil, nil
+	case "/run/user/1971/pulse/native":
+		return stubFileInfoMode(0666), nil
+	case "/home/ophestra/.pulse-cookie":
+		return stubFileInfoIsDir(true), nil
+	case "/home/ophestra/xdg/config/pulse/cookie":
+		return stubFileInfoIsDir(false), nil
+	default:
+		panic(fmt.Sprintf("attempted to stat unexpected path %q", name))
+	}
+}
+
+func (s *stubNixOS) Open(name string) (fs.File, error) {
+	switch name {
+	default:
+		panic(fmt.Sprintf("attempted to open unexpected file %q", name))
+	}
+}
+
+func (s *stubNixOS) Exit(code int) {
+	panic("called exit on stub with code " + strconv.Itoa(code))
+}
+
+func (s *stubNixOS) Stdout() io.Writer {
+	panic("requested stdout")
+}
+
+func (s *stubNixOS) Paths() linux.Paths {
+	return linux.Paths{
+		SharePath:   "/tmp/fortify.1971",
+		RuntimePath: "/run/user/1971",
+		RunDirPath:  "/run/user/1971/fortify",
+	}
+}
+
+func (s *stubNixOS) Uid(aid int) (int, error) {
+	return 1000000 + 0*10000 + aid, nil
+}
+
+func (s *stubNixOS) SdBooted() bool {
+	return true
+}

internal/app/app_test.go

@@ -0,0 +1,135 @@
+package app_test
+
+import (
+	"io/fs"
+	"reflect"
+	"testing"
+	"time"
+
+	"git.gensokyo.uk/security/fortify/fst"
+	"git.gensokyo.uk/security/fortify/helper/bwrap"
+	"git.gensokyo.uk/security/fortify/internal/app"
+	"git.gensokyo.uk/security/fortify/internal/linux"
+	"git.gensokyo.uk/security/fortify/internal/system"
+)
+
+type sealTestCase struct {
+	name      string
+	os        linux.System
+	config    *fst.Config
+	id        fst.ID
+	wantSys   *system.I
+	wantBwrap *bwrap.Config
+}
+
+func TestApp(t *testing.T) {
+	testCases := append(testCasesPd, testCasesNixos...)
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			a := app.NewWithID(tc.id, tc.os)
+
+			if !t.Run("seal", func(t *testing.T) {
+				if err := a.Seal(tc.config); err != nil {
+					t.Errorf("Seal: error = %v", err)
+				}
+			}) {
+				return
+			}
+
+			gotSys, gotBwrap := app.AppSystemBwrap(a)
+
+			t.Run("compare sys", func(t *testing.T) {
+				if !gotSys.Equal(tc.wantSys) {
+					t.Errorf("Seal: sys = %#v, want %#v",
+						gotSys, tc.wantSys)
+				}
+			})
+
+			t.Run("compare bwrap", func(t *testing.T) {
+				if !reflect.DeepEqual(gotBwrap, tc.wantBwrap) {
+					t.Errorf("seal: bwrap = %#v, want %#v",
+						gotBwrap, tc.wantBwrap)
+				}
+			})
+		})
+	}
+}
+
+func stubDirEntries(names ...string) (e []fs.DirEntry, err error) {
+	e = make([]fs.DirEntry, len(names))
+	for i, name := range names {
+		e[i] = stubDirEntryPath(name)
+	}
+	return
+}
+
+type stubDirEntryPath string
+
+func (p stubDirEntryPath) Name() string {
+	return string(p)
+}
+
+func (p stubDirEntryPath) IsDir() bool {
+	panic("attempted to call IsDir")
+}
+
+func (p stubDirEntryPath) Type() fs.FileMode {
+	panic("attempted to call Type")
+}
+
+func (p stubDirEntryPath) Info() (fs.FileInfo, error) {
+	panic("attempted to call Info")
+}
+
+type stubFileInfoMode fs.FileMode
+
+func (s stubFileInfoMode) Name() string {
+	panic("attempted to call Name")
+}
+
+func (s stubFileInfoMode) Size() int64 {
+	panic("attempted to call Size")
+}
+
+func (s stubFileInfoMode) Mode() fs.FileMode {
+	return fs.FileMode(s)
+}
+
+func (s stubFileInfoMode) ModTime() time.Time {
+	panic("attempted to call ModTime")
+}
+
+func (s stubFileInfoMode) IsDir() bool {
+	panic("attempted to call IsDir")
+}
+
+func (s stubFileInfoMode) Sys() any {
+	panic("attempted to call Sys")
+}
+
+type stubFileInfoIsDir bool
+
+func (s stubFileInfoIsDir) Name() string {
+	panic("attempted to call Name")
+}
+
+func (s stubFileInfoIsDir) Size() int64 {
+	panic("attempted to call Size")
+}
+
+func (s stubFileInfoIsDir) Mode() fs.FileMode {
+	panic("attempted to call Mode")
+}
+
+func (s stubFileInfoIsDir) ModTime() time.Time {
+	panic("attempted to call ModTime")
+}
+
+func (s stubFileInfoIsDir) IsDir() bool {
+	return bool(s)
+}
+
+func (s stubFileInfoIsDir) Sys() any {
+	panic("attempted to call Sys")
+}

internal/app/export_test.go

@@ -0,0 +1,20 @@
+package app
+
+import (
+	"git.gensokyo.uk/security/fortify/fst"
+	"git.gensokyo.uk/security/fortify/helper/bwrap"
+	"git.gensokyo.uk/security/fortify/internal/linux"
+	"git.gensokyo.uk/security/fortify/internal/system"
+)
+
+func NewWithID(id fst.ID, os linux.System) App {
+	a := new(app)
+	a.id = &id
+	a.os = os
+	return a
+}
+
+func AppSystemBwrap(a App) (*system.I, *bwrap.Config) {
+	v := a.(*app)
+	return v.seal.sys.I, v.seal.sys.bwrap
+}

internal/app/seal.go

@@ -0,0 +1,242 @@
+package app
+
+import (
+	"errors"
+	"fmt"
+	"io/fs"
+	"path"
+	"regexp"
+	"strconv"
+
+	"git.gensokyo.uk/security/fortify/dbus"
+	"git.gensokyo.uk/security/fortify/fst"
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+	"git.gensokyo.uk/security/fortify/internal/linux"
+	"git.gensokyo.uk/security/fortify/internal/state"
+	"git.gensokyo.uk/security/fortify/internal/system"
+)
+
+var (
+	ErrConfig = errors.New("no configuration to seal")
+	ErrUser   = errors.New("invalid aid")
+	ErrHome   = errors.New("invalid home directory")
+	ErrName   = errors.New("invalid username")
+)
+
+var posixUsername = regexp.MustCompilePOSIX("^[a-z_]([A-Za-z0-9_-]{0,31}|[A-Za-z0-9_-]{0,30}\\$)$")
+
+// appSeal seals the application with child-related information
+type appSeal struct {
+	// app unique ID string representation
+	id string
+	// dbus proxy message buffer retriever
+	dbusMsg func(f func(msgbuf []string))
+
+	// freedesktop application ID
+	fid string
+	// argv to start process with in the final confined environment
+	command []string
+	// persistent process state store
+	store state.Store
+
+	// process-specific share directory path
+	share string
+	// process-specific share directory path local to XDG_RUNTIME_DIR
+	shareLocal string
+
+	// pass-through enablement tracking from config
+	et system.Enablements
+	// wayland socket direct access
+	directWayland bool
+
+	// prevents sharing from happening twice
+	shared bool
+	// seal system-level component
+	sys *appSealSys
+
+	linux.Paths
+
+	// protected by upstream mutex
+}
+
+// Seal seals the app launch context
+func (a *app) Seal(config *fst.Config) error {
+	a.lock.Lock()
+	defer a.lock.Unlock()
+
+	if a.seal != nil {
+		panic("app sealed twice")
+	}
+
+	if config == nil {
+		return fmsg.WrapError(ErrConfig,
+			"attempted to seal app with nil config")
+	}
+
+	// create seal
+	seal := new(appSeal)
+
+	// fetch system constants
+	seal.Paths = a.os.Paths()
+
+	// pass through config values
+	seal.id = a.id.String()
+	seal.fid = config.ID
+	seal.command = config.Command
+
+	// create seal system component
+	seal.sys = new(appSealSys)
+
+	// mapped uid
+	if config.Confinement.Sandbox != nil && config.Confinement.Sandbox.MapRealUID {
+		seal.sys.mappedID = a.os.Geteuid()
+	} else {
+		seal.sys.mappedID = 65534
+	}
+	seal.sys.mappedIDString = strconv.Itoa(seal.sys.mappedID)
+	seal.sys.runtime = path.Join("/run/user", seal.sys.mappedIDString)
+
+	// validate uid and set user info
+	if config.Confinement.AppID < 0 || config.Confinement.AppID > 9999 {
+		return fmsg.WrapError(ErrUser,
+			fmt.Sprintf("aid %d out of range", config.Confinement.AppID))
+	} else {
+		seal.sys.user = appUser{
+			aid:      config.Confinement.AppID,
+			as:       strconv.Itoa(config.Confinement.AppID),
+			data:     config.Confinement.Outer,
+			home:     config.Confinement.Inner,
+			username: config.Confinement.Username,
+		}
+		if seal.sys.user.username == "" {
+			seal.sys.user.username = "chronos"
+		} else if !posixUsername.MatchString(seal.sys.user.username) {
+			return fmsg.WrapError(ErrName,
+				fmt.Sprintf("invalid user name %q", seal.sys.user.username))
+		}
+		if seal.sys.user.data == "" || !path.IsAbs(seal.sys.user.data) {
+			return fmsg.WrapError(ErrHome,
+				fmt.Sprintf("invalid home directory %q", seal.sys.user.data))
+		}
+		if seal.sys.user.home == "" {
+			seal.sys.user.home = seal.sys.user.data
+		}
+
+		// invoke fsu for full uid
+		if u, err := a.os.Uid(seal.sys.user.aid); err != nil {
+			return fmsg.WrapErrorSuffix(err,
+				"cannot obtain uid from fsu:")
+		} else {
+			seal.sys.user.uid = u
+			seal.sys.user.us = strconv.Itoa(u)
+		}
+
+		// resolve supplementary group ids from names
+		seal.sys.user.supp = make([]string, len(config.Confinement.Groups))
+		for i, name := range config.Confinement.Groups {
+			if g, err := a.os.LookupGroup(name); err != nil {
+				return fmsg.WrapError(err,
+					fmt.Sprintf("unknown group %q", name))
+			} else {
+				seal.sys.user.supp[i] = g.Gid
+			}
+		}
+	}
+
+	// map sandbox config to bwrap
+	if config.Confinement.Sandbox == nil {
+		fmsg.VPrintln("sandbox configuration not supplied, PROCEED WITH CAUTION")
+
+		// permissive defaults
+		conf := &fst.SandboxConfig{
+			UserNS:       true,
+			Net:          true,
+			NoNewSession: true,
+			AutoEtc:      true,
+		}
+		// bind entries in /
+		if d, err := a.os.ReadDir("/"); err != nil {
+			return err
+		} else {
+			b := make([]*fst.FilesystemConfig, 0, len(d))
+			for _, ent := range d {
+				p := "/" + ent.Name()
+				switch p {
+				case "/proc":
+				case "/dev":
+				case "/run":
+				case "/tmp":
+				case "/mnt":
+				case "/etc":
+
+				default:
+					b = append(b, &fst.FilesystemConfig{Src: p, Write: true, Must: true})
+				}
+			}
+			conf.Filesystem = append(conf.Filesystem, b...)
+		}
+		// bind entries in /run
+		if d, err := a.os.ReadDir("/run"); err != nil {
+			return err
+		} else {
+			b := make([]*fst.FilesystemConfig, 0, len(d))
+			for _, ent := range d {
+				name := ent.Name()
+				switch name {
+				case "user":
+				case "dbus":
+				default:
+					p := "/run/" + name
+					b = append(b, &fst.FilesystemConfig{Src: p, Write: true, Must: true})
+				}
+			}
+			conf.Filesystem = append(conf.Filesystem, b...)
+		}
+		// hide nscd from sandbox if present
+		nscd := "/var/run/nscd"
+		if _, err := a.os.Stat(nscd); !errors.Is(err, fs.ErrNotExist) {
+			conf.Override = append(conf.Override, nscd)
+		}
+		// bind GPU stuff
+		if config.Confinement.Enablements.Has(system.EX11) || config.Confinement.Enablements.Has(system.EWayland) {
+			conf.Filesystem = append(conf.Filesystem, &fst.FilesystemConfig{Src: "/dev/dri", Device: true})
+		}
+
+		config.Confinement.Sandbox = conf
+	}
+	seal.directWayland = config.Confinement.Sandbox.DirectWayland
+	if b, err := config.Confinement.Sandbox.Bwrap(a.os); err != nil {
+		return err
+	} else {
+		seal.sys.bwrap = b
+	}
+	seal.sys.override = config.Confinement.Sandbox.Override
+	if seal.sys.bwrap.SetEnv == nil {
+		seal.sys.bwrap.SetEnv = make(map[string]string)
+	}
+
+	// open process state store
+	// the simple store only starts holding an open file after first action
+	// store activity begins after Start is called and must end before Wait
+	seal.store = state.NewMulti(seal.RunDirPath)
+
+	// initialise system interface with full uid
+	seal.sys.I = system.New(seal.sys.user.uid)
+
+	// pass through enablements
+	seal.et = config.Confinement.Enablements
+
+	// this method calls all share methods in sequence
+	if err := seal.shareAll([2]*dbus.Config{config.Confinement.SessionBus, config.Confinement.SystemBus}, a.os); err != nil {
+		return err
+	}
+
+	// verbose log seal information
+	fmsg.VPrintf("created application seal for uid %s (%s) groups: %v, command: %s",
+		seal.sys.user.us, seal.sys.user.username, config.Confinement.Groups, config.Command)
+
+	// seal app and release lock
+	a.seal = seal
+	a.ct = newAppCt(config)
+	return nil
+}

internal/app/share.dbus.go

@@ -0,0 +1,44 @@
+package app
+
+import (
+	"path"
+
+	"git.gensokyo.uk/security/fortify/acl"
+	"git.gensokyo.uk/security/fortify/dbus"
+	"git.gensokyo.uk/security/fortify/internal/system"
+)
+
+const (
+	dbusSessionBusAddress = "DBUS_SESSION_BUS_ADDRESS"
+	dbusSystemBusAddress  = "DBUS_SYSTEM_BUS_ADDRESS"
+)
+
+func (seal *appSeal) shareDBus(config [2]*dbus.Config) error {
+	if !seal.et.Has(system.EDBus) {
+		return nil
+	}
+
+	// downstream socket paths
+	sessionPath, systemPath := path.Join(seal.share, "bus"), path.Join(seal.share, "system_bus_socket")
+
+	// configure dbus proxy
+	if f, err := seal.sys.ProxyDBus(config[0], config[1], sessionPath, systemPath); err != nil {
+		return err
+	} else {
+		seal.dbusMsg = f
+	}
+
+	// share proxy sockets
+	sessionInner := path.Join(seal.sys.runtime, "bus")
+	seal.sys.bwrap.SetEnv[dbusSessionBusAddress] = "unix:path=" + sessionInner
+	seal.sys.bwrap.Bind(sessionPath, sessionInner)
+	seal.sys.UpdatePerm(sessionPath, acl.Read, acl.Write)
+	if config[1] != nil {
+		systemInner := "/run/dbus/system_bus_socket"
+		seal.sys.bwrap.SetEnv[dbusSystemBusAddress] = "unix:path=" + systemInner
+		seal.sys.bwrap.Bind(systemPath, systemInner)
+		seal.sys.UpdatePerm(systemPath, acl.Read, acl.Write)
+	}
+
+	return nil
+}

internal/app/share.display.go

@@ -0,0 +1,81 @@
+package app
+
+import (
+	"errors"
+	"path"
+
+	"git.gensokyo.uk/security/fortify/acl"
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+	"git.gensokyo.uk/security/fortify/internal/linux"
+	"git.gensokyo.uk/security/fortify/internal/system"
+)
+
+const (
+	term    = "TERM"
+	display = "DISPLAY"
+
+	// https://manpages.debian.org/experimental/libwayland-doc/wl_display_connect.3.en.html
+	waylandDisplay = "WAYLAND_DISPLAY"
+)
+
+var (
+	ErrWayland  = errors.New(waylandDisplay + " unset")
+	ErrXDisplay = errors.New(display + " unset")
+)
+
+func (seal *appSeal) shareDisplay(os linux.System) error {
+	// pass $TERM to launcher
+	if t, ok := os.LookupEnv(term); ok {
+		seal.sys.bwrap.SetEnv[term] = t
+	}
+
+	// set up wayland
+	if seal.et.Has(system.EWayland) {
+		var wp string
+		if wd, ok := os.LookupEnv(waylandDisplay); !ok {
+			return fmsg.WrapError(ErrWayland,
+				"WAYLAND_DISPLAY is not set")
+		} else {
+			wp = path.Join(seal.RuntimePath, wd)
+		}
+
+		w := path.Join(seal.sys.runtime, "wayland-0")
+		seal.sys.bwrap.SetEnv[waylandDisplay] = w
+
+		if seal.directWayland {
+			// hardlink wayland socket
+			wpi := path.Join(seal.shareLocal, "wayland")
+			seal.sys.Link(wp, wpi)
+			seal.sys.bwrap.Bind(wpi, w)
+
+			// ensure Wayland socket ACL (e.g. `/run/user/%d/wayland-%d`)
+			seal.sys.UpdatePermType(system.EWayland, wp, acl.Read, acl.Write, acl.Execute)
+		} else {
+			wc := path.Join(seal.SharePath, "wayland")
+			wt := path.Join(wc, seal.id)
+			seal.sys.Ensure(wc, 0711)
+			appID := seal.fid
+			if appID == "" {
+				// use instance ID in case app id is not set
+				appID = "moe.ophivana.fortify." + seal.id
+			}
+			seal.sys.Wayland(wt, wp, appID, seal.id)
+			seal.sys.bwrap.Bind(wt, w)
+		}
+	}
+
+	// set up X11
+	if seal.et.Has(system.EX11) {
+		// discover X11 and grant user permission via the `ChangeHosts` command
+		if d, ok := os.LookupEnv(display); !ok {
+			return fmsg.WrapError(ErrXDisplay,
+				"DISPLAY is not set")
+		} else {
+			seal.sys.ChangeHosts("#" + seal.sys.user.us)
+			seal.sys.bwrap.SetEnv[display] = d
+			seal.sys.bwrap.Bind("/tmp/.X11-unix", "/tmp/.X11-unix")
+		}
+	}
+
+	return nil
+}

internal/app/share.pulse.go

@@ -0,0 +1,117 @@
+package app
+
+import (
+	"errors"
+	"fmt"
+	"io/fs"
+	"path"
+
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+	"git.gensokyo.uk/security/fortify/internal/linux"
+	"git.gensokyo.uk/security/fortify/internal/system"
+)
+
+const (
+	pulseServer = "PULSE_SERVER"
+	pulseCookie = "PULSE_COOKIE"
+
+	home          = "HOME"
+	xdgConfigHome = "XDG_CONFIG_HOME"
+)
+
+var (
+	ErrPulseCookie = errors.New("pulse cookie not present")
+	ErrPulseSocket = errors.New("pulse socket not present")
+	ErrPulseMode   = errors.New("unexpected pulse socket mode")
+)
+
+func (seal *appSeal) sharePulse(os linux.System) error {
+	if !seal.et.Has(system.EPulse) {
+		return nil
+	}
+
+	// check PulseAudio directory presence (e.g. `/run/user/%d/pulse`)
+	pd := path.Join(seal.RuntimePath, "pulse")
+	ps := path.Join(pd, "native")
+	if _, err := os.Stat(pd); err != nil {
+		if !errors.Is(err, fs.ErrNotExist) {
+			return fmsg.WrapErrorSuffix(err,
+				fmt.Sprintf("cannot access PulseAudio directory %q:", pd))
+		}
+		return fmsg.WrapError(ErrPulseSocket,
+			fmt.Sprintf("PulseAudio directory %q not found", pd))
+	}
+
+	// check PulseAudio socket permission (e.g. `/run/user/%d/pulse/native`)
+	if s, err := os.Stat(ps); err != nil {
+		if !errors.Is(err, fs.ErrNotExist) {
+			return fmsg.WrapErrorSuffix(err,
+				fmt.Sprintf("cannot access PulseAudio socket %q:", ps))
+		}
+		return fmsg.WrapError(ErrPulseSocket,
+			fmt.Sprintf("PulseAudio directory %q found but socket does not exist", pd))
+	} else {
+		if m := s.Mode(); m&0o006 != 0o006 {
+			return fmsg.WrapError(ErrPulseMode,
+				fmt.Sprintf("unexpected permissions on %q:", ps), m)
+		}
+	}
+
+	// hard link pulse socket into target-executable share
+	psi := path.Join(seal.shareLocal, "pulse")
+	p := path.Join(seal.sys.runtime, "pulse", "native")
+	seal.sys.Link(ps, psi)
+	seal.sys.bwrap.Bind(psi, p)
+	seal.sys.bwrap.SetEnv[pulseServer] = "unix:" + p
+
+	// publish current user's pulse cookie for target user
+	if src, err := discoverPulseCookie(os); err != nil {
+		return err
+	} else {
+		dst := path.Join(seal.share, "pulse-cookie")
+		seal.sys.bwrap.SetEnv[pulseCookie] = dst
+		seal.sys.CopyFile(dst, src)
+		seal.sys.bwrap.Bind(dst, dst)
+	}
+
+	return nil
+}
+
+// discoverPulseCookie attempts various standard methods to discover the current user's PulseAudio authentication cookie
+func discoverPulseCookie(os linux.System) (string, error) {
+	if p, ok := os.LookupEnv(pulseCookie); ok {
+		return p, nil
+	}
+
+	// dotfile $HOME/.pulse-cookie
+	if p, ok := os.LookupEnv(home); ok {
+		p = path.Join(p, ".pulse-cookie")
+		if s, err := os.Stat(p); err != nil {
+			if !errors.Is(err, fs.ErrNotExist) {
+				return p, fmsg.WrapErrorSuffix(err,
+					fmt.Sprintf("cannot access PulseAudio cookie %q:", p))
+			}
+			// not found, try next method
+		} else if !s.IsDir() {
+			return p, nil
+		}
+	}
+
+	// $XDG_CONFIG_HOME/pulse/cookie
+	if p, ok := os.LookupEnv(xdgConfigHome); ok {
+		p = path.Join(p, "pulse", "cookie")
+		if s, err := os.Stat(p); err != nil {
+			if !errors.Is(err, fs.ErrNotExist) {
+				return p, fmsg.WrapErrorSuffix(err,
+					fmt.Sprintf("cannot access PulseAudio cookie %q:", p))
+			}
+			// not found, try next method
+		} else if !s.IsDir() {
+			return p, nil
+		}
+	}
+
+	return "", fmsg.WrapError(ErrPulseCookie,
+		fmt.Sprintf("cannot locate PulseAudio cookie (tried $%s, $%s/pulse/cookie, $%s/.pulse-cookie)",
+			pulseCookie, xdgConfigHome, home))
+}

internal/app/share.runtime.go

@@ -0,0 +1,39 @@
+package app
+
+import (
+	"path"
+
+	"git.gensokyo.uk/security/fortify/acl"
+	"git.gensokyo.uk/security/fortify/internal/system"
+)
+
+const (
+	xdgRuntimeDir   = "XDG_RUNTIME_DIR"
+	xdgSessionClass = "XDG_SESSION_CLASS"
+	xdgSessionType  = "XDG_SESSION_TYPE"
+)
+
+// shareRuntime queues actions for sharing/ensuring the runtime and share directories
+func (seal *appSeal) shareRuntime() {
+	// mount tmpfs on inner runtime (e.g. `/run/user/%d`)
+	seal.sys.bwrap.Tmpfs("/run/user", 1*1024*1024)
+	seal.sys.bwrap.Tmpfs(seal.sys.runtime, 8*1024*1024)
+
+	// point to inner runtime path `/run/user/%d`
+	seal.sys.bwrap.SetEnv[xdgRuntimeDir] = seal.sys.runtime
+	seal.sys.bwrap.SetEnv[xdgSessionClass] = "user"
+	seal.sys.bwrap.SetEnv[xdgSessionType] = "tty"
+
+	// ensure RunDir (e.g. `/run/user/%d/fortify`)
+	seal.sys.Ensure(seal.RunDirPath, 0700)
+	seal.sys.UpdatePermType(system.User, seal.RunDirPath, acl.Execute)
+
+	// ensure runtime directory ACL (e.g. `/run/user/%d`)
+	seal.sys.Ensure(seal.RuntimePath, 0700) // ensure this dir in case XDG_RUNTIME_DIR is unset
+	seal.sys.UpdatePermType(system.User, seal.RuntimePath, acl.Execute)
+
+	// ensure process-specific share local to XDG_RUNTIME_DIR (e.g. `/run/user/%d/fortify/%s`)
+	seal.shareLocal = path.Join(seal.RunDirPath, seal.id)
+	seal.sys.Ephemeral(system.Process, seal.shareLocal, 0700)
+	seal.sys.UpdatePerm(seal.shareLocal, acl.Execute)
+}

internal/app/share.system.go

@@ -0,0 +1,77 @@
+package app
+
+import (
+	"path"
+
+	"git.gensokyo.uk/security/fortify/acl"
+	"git.gensokyo.uk/security/fortify/internal/linux"
+	"git.gensokyo.uk/security/fortify/internal/system"
+)
+
+const (
+	shell = "SHELL"
+)
+
+// shareSystem queues various system-related actions
+func (seal *appSeal) shareSystem() {
+	// ensure Share (e.g. `/tmp/fortify.%d`)
+	// acl is unnecessary as this directory is world executable
+	seal.sys.Ensure(seal.SharePath, 0711)
+
+	// ensure process-specific share (e.g. `/tmp/fortify.%d/%s`)
+	// acl is unnecessary as this directory is world executable
+	seal.share = path.Join(seal.SharePath, seal.id)
+	seal.sys.Ephemeral(system.Process, seal.share, 0711)
+
+	// ensure child tmpdir parent directory (e.g. `/tmp/fortify.%d/tmpdir`)
+	targetTmpdirParent := path.Join(seal.SharePath, "tmpdir")
+	seal.sys.Ensure(targetTmpdirParent, 0700)
+	seal.sys.UpdatePermType(system.User, targetTmpdirParent, acl.Execute)
+
+	// ensure child tmpdir (e.g. `/tmp/fortify.%d/tmpdir/%d`)
+	targetTmpdir := path.Join(targetTmpdirParent, seal.sys.user.as)
+	seal.sys.Ensure(targetTmpdir, 01700)
+	seal.sys.UpdatePermType(system.User, targetTmpdir, acl.Read, acl.Write, acl.Execute)
+	seal.sys.bwrap.Bind(targetTmpdir, "/tmp", false, true)
+
+	// mount tmpfs on inner shared directory (e.g. `/tmp/fortify.%d`)
+	seal.sys.bwrap.Tmpfs(seal.SharePath, 1*1024*1024)
+}
+
+func (seal *appSeal) sharePasswd(os linux.System) {
+	// look up shell
+	sh := "/bin/sh"
+	if s, ok := os.LookupEnv(shell); ok {
+		seal.sys.bwrap.SetEnv[shell] = s
+		sh = s
+	}
+
+	// generate /etc/passwd
+	passwdPath := path.Join(seal.share, "passwd")
+	username := "chronos"
+	if seal.sys.user.username != "" {
+		username = seal.sys.user.username
+	}
+	homeDir := "/var/empty"
+	if seal.sys.user.home != "" {
+		homeDir = seal.sys.user.home
+	}
+
+	// bind home directory
+	seal.sys.bwrap.Bind(seal.sys.user.data, homeDir, false, true)
+	seal.sys.bwrap.Chdir = homeDir
+
+	seal.sys.bwrap.SetEnv["USER"] = username
+	seal.sys.bwrap.SetEnv["HOME"] = homeDir
+
+	passwd := username + ":x:" + seal.sys.mappedIDString + ":" + seal.sys.mappedIDString + ":Fortify:" + homeDir + ":" + sh + "\n"
+	seal.sys.Write(passwdPath, passwd)
+
+	// write /etc/group
+	groupPath := path.Join(seal.share, "group")
+	seal.sys.Write(groupPath, "fortify:x:"+seal.sys.mappedIDString+":\n")
+
+	// bind /etc/passwd and /etc/group
+	seal.sys.bwrap.Bind(passwdPath, "/etc/passwd")
+	seal.sys.bwrap.Bind(groupPath, "/etc/group")
+}

internal/app/start.go

@@ -0,0 +1,265 @@
+package app
+
+import (
+	"errors"
+	"fmt"
+	"os/exec"
+	"path/filepath"
+	"strings"
+
+	shim0 "git.gensokyo.uk/security/fortify/cmd/fshim/ipc"
+	"git.gensokyo.uk/security/fortify/cmd/fshim/ipc/shim"
+	"git.gensokyo.uk/security/fortify/helper"
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+	"git.gensokyo.uk/security/fortify/internal/state"
+	"git.gensokyo.uk/security/fortify/internal/system"
+)
+
+// Start selects a user switcher and starts shim.
+// Note that Wait must be called regardless of error returned by Start.
+func (a *app) Start() error {
+	a.lock.Lock()
+	defer a.lock.Unlock()
+
+	// resolve exec paths
+	shimExec := [2]string{helper.BubblewrapName}
+	if len(a.seal.command) > 0 {
+		shimExec[1] = a.seal.command[0]
+	}
+	for i, n := range shimExec {
+		if len(n) == 0 {
+			continue
+		}
+		if filepath.Base(n) == n {
+			if s, err := exec.LookPath(n); err == nil {
+				shimExec[i] = s
+			} else {
+				return fmsg.WrapError(err,
+					fmt.Sprintf("executable file %q not found in $PATH", n))
+			}
+		}
+	}
+
+	// construct shim manager
+	a.shim = shim.New(
+		uint32(a.seal.sys.UID()),
+		a.seal.sys.user.as,
+		a.seal.sys.user.supp,
+		&shim0.Payload{
+			Argv:  a.seal.command,
+			Exec:  shimExec,
+			Bwrap: a.seal.sys.bwrap,
+
+			Verbose: fmsg.Verbose(),
+		},
+	)
+
+	// startup will go ahead, commit system setup
+	if err := a.seal.sys.Commit(); err != nil {
+		return err
+	}
+	a.seal.sys.needRevert = true
+
+	// export sync pipe from sys
+	a.seal.sys.bwrap.SetSync(a.seal.sys.Sync())
+
+	if startTime, err := a.shim.Start(); err != nil {
+		return err
+	} else {
+		// shim start and setup success, create process state
+		sd := state.State{
+			ID:     *a.id,
+			PID:    a.shim.Unwrap().Process.Pid,
+			Config: a.ct.Unwrap(),
+			Time:   *startTime,
+		}
+
+		// register process state
+		var err0 = new(StateStoreError)
+		err0.Inner, err0.DoErr = a.seal.store.Do(a.seal.sys.user.aid, func(c state.Cursor) {
+			err0.InnerErr = c.Save(&sd)
+		})
+		a.seal.sys.saveState = true
+		return err0.equiv("cannot save process state:")
+	}
+}
+
+// StateStoreError is returned for a failed state save
+type StateStoreError struct {
+	// whether inner function was called
+	Inner bool
+	// error returned by state.Store Do method
+	DoErr error
+	// error returned by state.Backend Save method
+	InnerErr error
+	// any other errors needing to be tracked
+	Err error
+}
+
+func (e *StateStoreError) equiv(a ...any) error {
+	if e.Inner && e.DoErr == nil && e.InnerErr == nil && e.Err == nil {
+		return nil
+	} else {
+		return fmsg.WrapErrorSuffix(e, a...)
+	}
+}
+
+func (e *StateStoreError) Error() string {
+	if e.Inner && e.InnerErr != nil {
+		return e.InnerErr.Error()
+	}
+
+	if e.DoErr != nil {
+		return e.DoErr.Error()
+	}
+
+	if e.Err != nil {
+		return e.Err.Error()
+	}
+
+	return "(nil)"
+}
+
+func (e *StateStoreError) Unwrap() (errs []error) {
+	errs = make([]error, 0, 3)
+	if e.DoErr != nil {
+		errs = append(errs, e.DoErr)
+	}
+	if e.InnerErr != nil {
+		errs = append(errs, e.InnerErr)
+	}
+	if e.Err != nil {
+		errs = append(errs, e.Err)
+	}
+	return
+}
+
+type RevertCompoundError interface {
+	Error() string
+	Unwrap() []error
+}
+
+func (a *app) Wait() (int, error) {
+	a.lock.Lock()
+	defer a.lock.Unlock()
+
+	if a.shim == nil {
+		fmsg.VPrintln("shim not initialised, skipping cleanup")
+		return 1, nil
+	}
+
+	var r int
+
+	if cmd := a.shim.Unwrap(); cmd == nil {
+		// failure prior to process start
+		r = 255
+	} else {
+		wait := make(chan error, 1)
+		go func() { wait <- cmd.Wait() }()
+
+		select {
+		// wait for process and resolve exit code
+		case err := <-wait:
+			if err != nil {
+				var exitError *exec.ExitError
+				if !errors.As(err, &exitError) {
+					// should be unreachable
+					a.waitErr = err
+				}
+
+				// store non-zero return code
+				r = exitError.ExitCode()
+			} else {
+				r = cmd.ProcessState.ExitCode()
+			}
+			fmsg.VPrintf("process %d exited with exit code %d", cmd.Process.Pid, r)
+
+		// alternative exit path when kill was unsuccessful
+		case err := <-a.shim.WaitFallback():
+			r = 255
+			if err != nil {
+				fmsg.Printf("cannot terminate shim on faulted setup: %v", err)
+			} else {
+				fmsg.VPrintln("alternative exit path selected")
+			}
+		}
+	}
+
+	// child process exited, resume output
+	fmsg.Resume()
+
+	// print queued up dbus messages
+	if a.seal.dbusMsg != nil {
+		a.seal.dbusMsg(func(msgbuf []string) {
+			for _, msg := range msgbuf {
+				fmsg.Println(msg)
+			}
+		})
+	}
+
+	// update store and revert app setup transaction
+	e := new(StateStoreError)
+	e.Inner, e.DoErr = a.seal.store.Do(a.seal.sys.user.aid, func(b state.Cursor) {
+		e.InnerErr = func() error {
+			// destroy defunct state entry
+			if cmd := a.shim.Unwrap(); cmd != nil && a.seal.sys.saveState {
+				if err := b.Destroy(*a.id); err != nil {
+					return err
+				}
+			}
+
+			// enablements of remaining launchers
+			rt, ec := new(system.Enablements), new(system.Criteria)
+			ec.Enablements = new(system.Enablements)
+			ec.Set(system.Process)
+			if states, err := b.Load(); err != nil {
+				return err
+			} else {
+				if l := len(states); l == 0 {
+					// cleanup globals as the final launcher
+					fmsg.VPrintln("no other launchers active, will clean up globals")
+					ec.Set(system.User)
+				} else {
+					fmsg.VPrintf("found %d active launchers, cleaning up without globals", l)
+				}
+
+				// accumulate capabilities of other launchers
+				for i, s := range states {
+					if s.Config != nil {
+						*rt |= s.Config.Confinement.Enablements
+					} else {
+						fmsg.Printf("state entry %d does not contain config", i)
+					}
+				}
+			}
+			// invert accumulated enablements for cleanup
+			for i := system.Enablement(0); i < system.Enablement(system.ELen); i++ {
+				if !rt.Has(i) {
+					ec.Set(i)
+				}
+			}
+			if fmsg.Verbose() {
+				labels := make([]string, 0, system.ELen+1)
+				for i := system.Enablement(0); i < system.Enablement(system.ELen+2); i++ {
+					if ec.Has(i) {
+						labels = append(labels, system.TypeString(i))
+					}
+				}
+				if len(labels) > 0 {
+					fmsg.VPrintln("reverting operations labelled", strings.Join(labels, ", "))
+				}
+			}
+
+			if a.seal.sys.needRevert {
+				if err := a.seal.sys.Revert(ec); err != nil {
+					return err.(RevertCompoundError)
+				}
+			}
+
+			return nil
+		}()
+	})
+
+	e.Err = a.seal.store.Close()
+	return r, e.equiv("error returned during cleanup:", e)
+}

internal/app/system.go

@@ -0,0 +1,87 @@
+package app
+
+import (
+	"git.gensokyo.uk/security/fortify/dbus"
+	"git.gensokyo.uk/security/fortify/helper/bwrap"
+	"git.gensokyo.uk/security/fortify/internal/linux"
+	"git.gensokyo.uk/security/fortify/internal/system"
+)
+
+// appSealSys encapsulates app seal behaviour with OS interactions
+type appSealSys struct {
+	bwrap *bwrap.Config
+	// paths to override by mounting tmpfs over them
+	override []string
+
+	// default formatted XDG_RUNTIME_DIR of User
+	runtime string
+	// target user sealed from config
+	user appUser
+
+	// mapped uid and gid in user namespace
+	mappedID int
+	// string representation of mappedID
+	mappedIDString string
+
+	needRevert bool
+	saveState  bool
+	*system.I
+
+	// protected by upstream mutex
+}
+
+type appUser struct {
+	// full uid resolved by fsu
+	uid int
+	// string representation of uid
+	us string
+
+	// supplementary group ids
+	supp []string
+
+	// application id
+	aid int
+	// string representation of aid
+	as string
+
+	// home directory host path
+	data string
+	// app user home directory
+	home string
+	// passwd database username
+	username string
+}
+
+// shareAll calls all share methods in sequence
+func (seal *appSeal) shareAll(bus [2]*dbus.Config, os linux.System) error {
+	if seal.shared {
+		panic("seal shared twice")
+	}
+	seal.shared = true
+
+	seal.shareSystem()
+	seal.shareRuntime()
+	seal.sharePasswd(os)
+	if err := seal.shareDisplay(os); err != nil {
+		return err
+	}
+	if err := seal.sharePulse(os); err != nil {
+		return err
+	}
+
+	// ensure dbus session bus defaults
+	if bus[0] == nil {
+		bus[0] = dbus.NewConfig(seal.fid, true, true)
+	}
+
+	if err := seal.shareDBus(bus); err != nil {
+		return err
+	}
+
+	// queue overriding tmpfs at the end of seal.sys.bwrap.Filesystem
+	for _, dest := range seal.sys.override {
+		seal.sys.bwrap.Tmpfs(dest, 8*1024)
+	}
+
+	return nil
+}

internal/comp.go

@@ -0,0 +1,12 @@
+package internal
+
+const compPoison = "INVALIDINVALIDINVALIDINVALIDINVALID"
+
+var (
+	Version = compPoison
+)
+
+// Check validates string value set at compile time.
+func Check(s string) (string, bool) {
+	return s, s != compPoison && s != ""
+}

internal/fmsg/defer.go

@@ -0,0 +1,97 @@
+package fmsg
+
+import (
+	"os"
+	"sync"
+	"sync/atomic"
+)
+
+var (
+	wstate   atomic.Bool
+	dropped  atomic.Uint64
+	withhold = make(chan struct{}, 1)
+	msgbuf   = make(chan dOp, 64) // these ops are tiny so a large buffer is allocated for withholding output
+
+	dequeueOnce sync.Once
+	queueSync   sync.WaitGroup
+)
+
+func dequeue() {
+	go func() {
+		for {
+			select {
+			case op := <-msgbuf:
+				op.Do()
+				queueSync.Done()
+			case <-withhold:
+				<-withhold
+			}
+		}
+	}()
+}
+
+// queue submits ops to msgbuf but drops messages
+// when the buffer is full and dequeue is withholding
+func queue(op dOp) {
+	queueSync.Add(1)
+
+	select {
+	case msgbuf <- op:
+	default:
+		// send the op anyway if not withholding
+		// as dequeue will get to it eventually
+		if !wstate.Load() {
+			msgbuf <- op
+		} else {
+			queueSync.Done()
+			// increment dropped message count
+			dropped.Add(1)
+		}
+	}
+}
+
+type dOp interface{ Do() }
+
+func Exit(code int) {
+	queueSync.Wait()
+	os.Exit(code)
+}
+
+func Suspend() {
+	dequeueOnce.Do(dequeue)
+	if wstate.CompareAndSwap(false, true) {
+		queueSync.Wait()
+		withhold <- struct{}{}
+	}
+}
+
+func Resume() {
+	dequeueOnce.Do(dequeue)
+	if wstate.CompareAndSwap(true, false) {
+		withhold <- struct{}{}
+		if d := dropped.Swap(0); d != 0 {
+			Printf("dropped %d messages during withhold", d)
+		}
+	}
+}
+
+type dPrint []any
+
+func (v dPrint) Do() {
+	std.Print(v...)
+}
+
+type dPrintf struct {
+	format string
+	v      []any
+}
+
+func (d *dPrintf) Do() {
+	std.Printf(d.format, d.v...)
+}
+
+type dPrintln []any
+
+func (v dPrintln) Do() {
+	std.Println(v...)
+}

internal/fmsg/errors.go

@@ -0,0 +1,72 @@
+package fmsg
+
+import (
+	"fmt"
+	"reflect"
+)
+
+// baseError implements a basic error container
+type baseError struct {
+	Err error
+}
+
+func (e *baseError) Error() string {
+	return e.Err.Error()
+}
+
+func (e *baseError) Unwrap() error {
+	return e.Err
+}
+
+// BaseError implements an error container with a user-facing message
+type BaseError struct {
+	message string
+	baseError
+}
+
+// Message returns a user-facing error message
+func (e *BaseError) Message() string {
+	return e.message
+}
+
+// WrapError wraps an error with a corresponding message.
+func WrapError(err error, a ...any) error {
+	if err == nil {
+		return nil
+	}
+	return wrapError(err, fmt.Sprintln(a...))
+}
+
+// WrapErrorSuffix wraps an error with a corresponding message with err at the end of the message.
+func WrapErrorSuffix(err error, a ...any) error {
+	if err == nil {
+		return nil
+	}
+	return wrapError(err, fmt.Sprintln(append(a, err)...))
+}
+
+// WrapErrorFunc wraps an error with a corresponding message returned by f.
+func WrapErrorFunc(err error, f func(err error) string) error {
+	if err == nil {
+		return nil
+	}
+	return wrapError(err, f(err))
+}
+
+func wrapError(err error, message string) *BaseError {
+	return &BaseError{message, baseError{err}}
+}
+
+var (
+	baseErrorType = reflect.TypeFor[*BaseError]()
+)
+
+func AsBaseError(err error, target **BaseError) bool {
+	v := reflect.ValueOf(err)
+	if !v.CanConvert(baseErrorType) {
+		return false
+	}
+
+	*target = v.Convert(baseErrorType).Interface().(*BaseError)
+	return true
+}

internal/fmsg/fmsg.go

@@ -0,0 +1,40 @@
+// Package fmsg provides various functions for output messages.
+package fmsg
+
+import (
+	"log"
+	"os"
+)
+
+var std = log.New(os.Stderr, "fortify: ", 0)
+
+func SetPrefix(prefix string) {
+	prefix += ": "
+	std.SetPrefix(prefix)
+	std.SetPrefix(prefix)
+}
+
+func Print(v ...any) {
+	dequeueOnce.Do(dequeue)
+	queue(dPrint(v))
+}
+
+func Printf(format string, v ...any) {
+	dequeueOnce.Do(dequeue)
+	queue(&dPrintf{format, v})
+}
+
+func Println(v ...any) {
+	dequeueOnce.Do(dequeue)
+	queue(dPrintln(v))
+}
+
+func Fatal(v ...any) {
+	Print(v...)
+	Exit(1)
+}
+
+func Fatalf(format string, v ...any) {
+	Printf(format, v...)
+	Exit(1)
+}

internal/fmsg/verbose.go

@@ -0,0 +1,25 @@
+package fmsg
+
+import "sync/atomic"
+
+var verbose = new(atomic.Bool)
+
+func Verbose() bool {
+	return verbose.Load()
+}
+
+func SetVerbose(v bool) {
+	verbose.Store(v)
+}
+
+func VPrintf(format string, v ...any) {
+	if verbose.Load() {
+		Printf(format, v...)
+	}
+}
+
+func VPrintln(v ...any) {
+	if verbose.Load() {
+		Println(v...)
+	}
+}

internal/linux/interface.go

@@ -0,0 +1,70 @@
+package linux
+
+import (
+	"io"
+	"io/fs"
+	"os/user"
+	"path"
+	"strconv"
+
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+)
+
+// System provides safe access to operating system resources.
+type System interface {
+	// Geteuid provides [os.Geteuid].
+	Geteuid() int
+	// LookupEnv provides [os.LookupEnv].
+	LookupEnv(key string) (string, bool)
+	// TempDir provides [os.TempDir].
+	TempDir() string
+	// LookPath provides [exec.LookPath].
+	LookPath(file string) (string, error)
+	// Executable provides [os.Executable].
+	Executable() (string, error)
+	// LookupGroup provides [user.LookupGroup].
+	LookupGroup(name string) (*user.Group, error)
+	// ReadDir provides [os.ReadDir].
+	ReadDir(name string) ([]fs.DirEntry, error)
+	// Stat provides [os.Stat].
+	Stat(name string) (fs.FileInfo, error)
+	// Open provides [os.Open]
+	Open(name string) (fs.File, error)
+	// Exit provides [os.Exit].
+	Exit(code int)
+	// Stdout provides [os.Stdout].
+	Stdout() io.Writer
+
+	// Paths returns a populated [Paths] struct.
+	Paths() Paths
+	// Uid invokes fsu and returns target uid.
+	Uid(aid int) (int, error)
+}
+
+// Paths contains environment dependent paths used by fortify.
+type Paths struct {
+	// path to shared directory e.g. /tmp/fortify.%d
+	SharePath string `json:"share_path"`
+	// XDG_RUNTIME_DIR value e.g. /run/user/%d
+	RuntimePath string `json:"runtime_path"`
+	// application runtime directory e.g. /run/user/%d/fortify
+	RunDirPath string `json:"run_dir_path"`
+}
+
+// CopyPaths is a generic implementation of [System.Paths].
+func CopyPaths(os System, v *Paths) {
+	v.SharePath = path.Join(os.TempDir(), "fortify."+strconv.Itoa(os.Geteuid()))
+
+	fmsg.VPrintf("process share directory at %q", v.SharePath)
+
+	if r, ok := os.LookupEnv(xdgRuntimeDir); !ok || r == "" || !path.IsAbs(r) {
+		// fall back to path in share since fortify has no hard XDG dependency
+		v.RunDirPath = path.Join(v.SharePath, "run")
+		v.RuntimePath = path.Join(v.RunDirPath, "compat")
+	} else {
+		v.RuntimePath = r
+		v.RunDirPath = path.Join(v.RuntimePath, "fortify")
+	}
+
+	fmsg.VPrintf("runtime directory at %q", v.RunDirPath)
+}

internal/linux/std.go

@@ -0,0 +1,88 @@
+package linux
+
+import (
+	"io"
+	"io/fs"
+	"os"
+	"os/exec"
+	"os/user"
+	"strconv"
+	"sync"
+
+	"git.gensokyo.uk/security/fortify/internal"
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+)
+
+// Std implements System using the standard library.
+type Std struct {
+	paths     Paths
+	pathsOnce sync.Once
+
+	uidOnce sync.Once
+	uidCopy map[int]struct {
+		uid int
+		err error
+	}
+	uidMu sync.RWMutex
+}
+
+func (s *Std) Geteuid() int                                 { return os.Geteuid() }
+func (s *Std) LookupEnv(key string) (string, bool)          { return os.LookupEnv(key) }
+func (s *Std) TempDir() string                              { return os.TempDir() }
+func (s *Std) LookPath(file string) (string, error)         { return exec.LookPath(file) }
+func (s *Std) Executable() (string, error)                  { return os.Executable() }
+func (s *Std) LookupGroup(name string) (*user.Group, error) { return user.LookupGroup(name) }
+func (s *Std) ReadDir(name string) ([]os.DirEntry, error)   { return os.ReadDir(name) }
+func (s *Std) Stat(name string) (fs.FileInfo, error)        { return os.Stat(name) }
+func (s *Std) Open(name string) (fs.File, error)            { return os.Open(name) }
+func (s *Std) Exit(code int)                                { fmsg.Exit(code) }
+func (s *Std) Stdout() io.Writer                            { return os.Stdout }
+
+const xdgRuntimeDir = "XDG_RUNTIME_DIR"
+
+func (s *Std) Paths() Paths {
+	s.pathsOnce.Do(func() { CopyPaths(s, &s.paths) })
+	return s.paths
+}
+
+func (s *Std) Uid(aid int) (int, error) {
+	s.uidOnce.Do(func() {
+		s.uidCopy = make(map[int]struct {
+			uid int
+			err error
+		})
+	})
+
+	s.uidMu.RLock()
+	if u, ok := s.uidCopy[aid]; ok {
+		s.uidMu.RUnlock()
+		return u.uid, u.err
+	}
+
+	s.uidMu.RUnlock()
+	s.uidMu.Lock()
+	defer s.uidMu.Unlock()
+
+	u := struct {
+		uid int
+		err error
+	}{}
+	defer func() { s.uidCopy[aid] = u }()
+
+	u.uid = -1
+	if fsu, ok := internal.Check(internal.Fsu); !ok {
+		fmsg.Fatal("invalid fsu path, this copy of fshim is not compiled correctly")
+		panic("unreachable")
+	} else {
+		cmd := exec.Command(fsu)
+		cmd.Path = fsu
+		cmd.Stderr = os.Stderr // pass through fatal messages
+		cmd.Env = []string{"FORTIFY_APP_ID=" + strconv.Itoa(aid)}
+		cmd.Dir = "/"
+		var p []byte
+		if p, u.err = cmd.Output(); u.err == nil {
+			u.uid, u.err = strconv.Atoi(string(p))
+		}
+		return u.uid, u.err
+	}
+}

internal/path.go

@@ -0,0 +1,12 @@
+package internal
+
+import "path"
+
+var (
+	Fsu   = compPoison
+	Finit = compPoison
+)
+
+func Path(p string) (string, bool) {
+	return p, p != compPoison && p != "" && path.IsAbs(p)
+}

internal/prctl.go

@@ -0,0 +1,20 @@
+package internal
+
+import "syscall"
+
+func PR_SET_DUMPABLE__SUID_DUMP_DISABLE() error {
+	// linux/sched/coredump.h
+	if _, _, errno := syscall.RawSyscall(syscall.SYS_PRCTL, syscall.PR_SET_DUMPABLE, 0, 0); errno != 0 {
+		return errno
+	}
+
+	return nil
+}
+
+func PR_SET_PDEATHSIG__SIGKILL() error {
+	if _, _, errno := syscall.AllThreadsSyscall(syscall.SYS_PRCTL, syscall.PR_SET_PDEATHSIG, uintptr(syscall.SIGKILL), 0); errno != 0 {
+		return errno
+	}
+
+	return nil
+}

internal/proc/fd.go

@@ -0,0 +1,42 @@
+package proc
+
+import (
+	"encoding/gob"
+	"errors"
+	"os"
+	"strconv"
+)
+
+var (
+	ErrNotSet  = errors.New("environment variable not set")
+	ErrInvalid = errors.New("bad file descriptor")
+)
+
+func Setup(extraFiles *[]*os.File) (int, *gob.Encoder, error) {
+	if r, w, err := os.Pipe(); err != nil {
+		return -1, nil, err
+	} else {
+		fd := 3 + len(*extraFiles)
+		*extraFiles = append(*extraFiles, r)
+		return fd, gob.NewEncoder(w), nil
+	}
+}
+
+func Receive(key string, e any) (func() error, error) {
+	var setup *os.File
+
+	if s, ok := os.LookupEnv(key); !ok {
+		return nil, ErrNotSet
+	} else {
+		if fd, err := strconv.Atoi(s); err != nil {
+			return nil, err
+		} else {
+			setup = os.NewFile(uintptr(fd), "setup")
+			if setup == nil {
+				return nil, ErrInvalid
+			}
+		}
+	}
+
+	return func() error { return setup.Close() }, gob.NewDecoder(setup).Decode(e)
+}

internal/proc/files.go

@@ -0,0 +1,13 @@
+package proc
+
+import (
+	"os"
+	"os/exec"
+)
+
+func ExtraFile(cmd *exec.Cmd, f *os.File) (fd uintptr) {
+	// ExtraFiles: If non-nil, entry i becomes file descriptor 3+i.
+	fd = uintptr(3 + len(cmd.ExtraFiles))
+	cmd.ExtraFiles = append(cmd.ExtraFiles, f)
+	return
+}

internal/state/multi.go

@@ -0,0 +1,292 @@
+package state
+
+import (
+	"encoding/gob"
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+	"path"
+	"strconv"
+	"sync"
+	"syscall"
+
+	"git.gensokyo.uk/security/fortify/fst"
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+)
+
+// fine-grained locking and access
+type multiStore struct {
+	base string
+
+	// initialised backends
+	backends *sync.Map
+
+	lock sync.RWMutex
+}
+
+func (s *multiStore) Do(aid int, f func(c Cursor)) (bool, error) {
+	s.lock.RLock()
+	defer s.lock.RUnlock()
+
+	// load or initialise new backend
+	b := new(multiBackend)
+	if v, ok := s.backends.LoadOrStore(aid, b); ok {
+		b = v.(*multiBackend)
+	} else {
+		b.lock.Lock()
+		b.path = path.Join(s.base, strconv.Itoa(aid))
+
+		// ensure directory
+		if err := os.MkdirAll(b.path, 0700); err != nil && !errors.Is(err, fs.ErrExist) {
+			s.backends.CompareAndDelete(aid, b)
+			return false, err
+		}
+
+		// open locker file
+		if l, err := os.OpenFile(b.path+".lock", os.O_RDWR|os.O_CREATE, 0600); err != nil {
+			s.backends.CompareAndDelete(aid, b)
+			return false, err
+		} else {
+			b.lockfile = l
+		}
+		b.lock.Unlock()
+	}
+
+	// lock backend
+	if err := b.lockFile(); err != nil {
+		return false, err
+	}
+
+	// expose backend methods without exporting the pointer
+	c := new(struct{ *multiBackend })
+	c.multiBackend = b
+	f(b)
+	// disable access to the backend on a best-effort basis
+	c.multiBackend = nil
+
+	// unlock backend
+	return true, b.unlockFile()
+}
+
+func (s *multiStore) List() ([]int, error) {
+	var entries []os.DirEntry
+
+	// read base directory to get all aids
+	if v, err := os.ReadDir(s.base); err != nil && !errors.Is(err, os.ErrNotExist) {
+		return nil, err
+	} else {
+		entries = v
+	}
+
+	aidsBuf := make([]int, 0, len(entries))
+	for _, e := range entries {
+		// skip non-directories
+		if !e.IsDir() {
+			fmsg.VPrintf("skipped non-directory entry %q", e.Name())
+			continue
+		}
+
+		// skip non-numerical names
+		if v, err := strconv.Atoi(e.Name()); err != nil {
+			fmsg.VPrintf("skipped non-aid entry %q", e.Name())
+			continue
+		} else {
+			if v < 0 || v > 9999 {
+				fmsg.VPrintf("skipped out of bounds entry %q", e.Name())
+				continue
+			}
+
+			aidsBuf = append(aidsBuf, v)
+		}
+	}
+
+	return append([]int(nil), aidsBuf...), nil
+}
+
+func (s *multiStore) Close() error {
+	s.lock.Lock()
+	defer s.lock.Unlock()
+
+	var errs []error
+	s.backends.Range(func(_, value any) bool {
+		b := value.(*multiBackend)
+		errs = append(errs, b.close())
+		return true
+	})
+
+	return errors.Join(errs...)
+}
+
+type multiBackend struct {
+	path string
+
+	// created/opened by prepare
+	lockfile *os.File
+
+	lock sync.RWMutex
+}
+
+func (b *multiBackend) filename(id *fst.ID) string {
+	return path.Join(b.path, id.String())
+}
+
+func (b *multiBackend) lockFileAct(lt int) (err error) {
+	op := "LockAct"
+	switch lt {
+	case syscall.LOCK_EX:
+		op = "Lock"
+	case syscall.LOCK_UN:
+		op = "Unlock"
+	}
+
+	for {
+		err = syscall.Flock(int(b.lockfile.Fd()), lt)
+		if !errors.Is(err, syscall.EINTR) {
+			break
+		}
+	}
+	if err != nil {
+		return &fs.PathError{
+			Op:   op,
+			Path: b.lockfile.Name(),
+			Err:  err,
+		}
+	}
+	return nil
+}
+
+func (b *multiBackend) lockFile() error {
+	return b.lockFileAct(syscall.LOCK_EX)
+}
+
+func (b *multiBackend) unlockFile() error {
+	return b.lockFileAct(syscall.LOCK_UN)
+}
+
+// reads all launchers in simpleBackend
+// file contents are ignored if decode is false
+func (b *multiBackend) load(decode bool) (Entries, error) {
+	b.lock.RLock()
+	defer b.lock.RUnlock()
+
+	// read directory contents, should only contain files named after ids
+	var entries []os.DirEntry
+	if pl, err := os.ReadDir(b.path); err != nil {
+		return nil, err
+	} else {
+		entries = pl
+	}
+
+	// allocate as if every entry is valid
+	// since that should be the case assuming no external interference happens
+	r := make(Entries, len(entries))
+
+	for _, e := range entries {
+		if e.IsDir() {
+			return nil, fmt.Errorf("unexpected directory %q in store", e.Name())
+		}
+
+		id := new(fst.ID)
+		if err := fst.ParseAppID(id, e.Name()); err != nil {
+			return nil, err
+		}
+
+		// run in a function to better handle file closing
+		if err := func() error {
+			// open state file for reading
+			if f, err := os.Open(path.Join(b.path, e.Name())); err != nil {
+				return err
+			} else {
+				defer func() {
+					if f.Close() != nil {
+						// unreachable
+						panic("foreign state file closed prematurely")
+					}
+				}()
+
+				s := new(State)
+				r[*id] = s
+
+				// append regardless, but only parse if required, used to implement Len
+				if decode {
+					if err = gob.NewDecoder(f).Decode(s); err != nil {
+						return err
+					}
+
+					if s.ID != *id {
+						return fmt.Errorf("state entry %s has unexpected id %s", id, &s.ID)
+					}
+				}
+
+				return nil
+			}
+		}(); err != nil {
+			return nil, err
+		}
+	}
+
+	return r, nil
+}
+
+// Save writes process state to filesystem
+func (b *multiBackend) Save(state *State) error {
+	b.lock.Lock()
+	defer b.lock.Unlock()
+
+	if state.Config == nil {
+		return errors.New("state does not contain config")
+	}
+
+	statePath := b.filename(&state.ID)
+
+	// create and open state data file
+	if f, err := os.OpenFile(statePath, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0600); err != nil {
+		return err
+	} else {
+		defer func() {
+			if f.Close() != nil {
+				// unreachable
+				panic("state file closed prematurely")
+			}
+		}()
+		// encode into state file
+		return gob.NewEncoder(f).Encode(state)
+	}
+}
+
+func (b *multiBackend) Destroy(id fst.ID) error {
+	b.lock.Lock()
+	defer b.lock.Unlock()
+
+	return os.Remove(b.filename(&id))
+}
+
+func (b *multiBackend) Load() (Entries, error) {
+	return b.load(true)
+}
+
+func (b *multiBackend) Len() (int, error) {
+	// rn consists of only nil entries but has the correct length
+	rn, err := b.load(false)
+	return len(rn), err
+}
+
+func (b *multiBackend) close() error {
+	b.lock.Lock()
+	defer b.lock.Unlock()
+
+	err := b.lockfile.Close()
+	if err == nil || errors.Is(err, os.ErrInvalid) || errors.Is(err, os.ErrClosed) {
+		return nil
+	}
+	return err
+}
+
+// NewMulti returns an instance of the multi-file store.
+func NewMulti(runDir string) Store {
+	b := new(multiStore)
+	b.base = path.Join(runDir, "state")
+	b.backends = new(sync.Map)
+	return b
+}

internal/state/multi_test.go

@@ -0,0 +1,11 @@
+package state_test
+
+import (
+	"testing"
+
+	"git.gensokyo.uk/security/fortify/internal/state"
+)
+
+func TestMulti(t *testing.T) {
+	testStore(t, state.NewMulti(t.TempDir()))
+}

internal/state/print.go

@@ -0,0 +1,118 @@
+package state
+
+import (
+	"fmt"
+	"os"
+	"strings"
+	"text/tabwriter"
+	"time"
+
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+	"git.gensokyo.uk/security/fortify/internal/system"
+)
+
+// MustPrintLauncherStateSimpleGlobal prints active launcher states of all simple stores
+// in an implementation-specific way.
+func MustPrintLauncherStateSimpleGlobal(w **tabwriter.Writer, runDir string) {
+	now := time.Now().UTC()
+	s := NewMulti(runDir)
+
+	// read runtime directory to get all UIDs
+	if aids, err := s.List(); err != nil {
+		fmsg.Fatal("cannot list store:", err)
+	} else {
+		for _, aid := range aids {
+			// print states belonging to this store
+			s.(*multiStore).mustPrintLauncherState(aid, w, now)
+		}
+	}
+
+	// mustPrintLauncherState causes store activity so store needs to be closed
+	if err := s.Close(); err != nil {
+		fmsg.Printf("cannot close store: %v", err)
+	}
+}
+
+func (s *multiStore) mustPrintLauncherState(aid int, w **tabwriter.Writer, now time.Time) {
+	var innerErr error
+
+	if ok, err := s.Do(aid, func(c Cursor) {
+		innerErr = func() error {
+			// read launcher states
+			states, err := c.Load()
+			if err != nil {
+				return err
+			}
+
+			// initialise tabwriter if nil
+			if *w == nil {
+				*w = tabwriter.NewWriter(os.Stdout, 0, 1, 4, ' ', 0)
+
+				// write header when initialising
+				if !fmsg.Verbose() {
+					_, _ = fmt.Fprintln(*w, "\tPID\tApp\tUptime\tEnablements\tCommand")
+				} else {
+					// argv is emitted in body when verbose
+					_, _ = fmt.Fprintln(*w, "\tPID\tApp\tArgv")
+				}
+			}
+
+			// print each state
+			for _, state := range states {
+				// skip nil states
+				if state == nil {
+					_, _ = fmt.Fprintln(*w, "\tnil state entry")
+					continue
+				}
+
+				// build enablements and command string
+				var (
+					ets *strings.Builder
+					cs  = "(No command information)"
+				)
+
+				// check if enablements are provided
+				if state.Config != nil {
+					ets = new(strings.Builder)
+					// append enablement strings in order
+					for i := system.Enablement(0); i < system.Enablement(system.ELen); i++ {
+						if state.Config.Confinement.Enablements.Has(i) {
+							ets.WriteString(", " + i.String())
+						}
+					}
+
+					cs = fmt.Sprintf("%q", state.Config.Command)
+				}
+				if ets != nil {
+					// prevent an empty string
+					if ets.Len() == 0 {
+						ets.WriteString("(No enablements)")
+					}
+				} else {
+					ets = new(strings.Builder)
+					ets.WriteString("(No confinement information)")
+				}
+
+				if !fmsg.Verbose() {
+					_, _ = fmt.Fprintf(*w, "\t%d\t%d\t%s\t%s\t%s\n",
+						state.PID, aid, now.Sub(state.Time).Round(time.Second).String(), strings.TrimPrefix(ets.String(), ", "), cs)
+				} else {
+					// emit argv instead when verbose
+					_, _ = fmt.Fprintf(*w, "\t%d\t%d\t%s\n",
+						state.PID, aid, state.ID)
+				}
+			}
+
+			return nil
+		}()
+	}); err != nil {
+		fmsg.Printf("cannot perform action on app %d: %v", aid, err)
+		if !ok {
+			fmsg.Fatal("store faulted before printing")
+		}
+	}
+
+	if innerErr != nil {
+		fmsg.Fatalf("cannot print launcher state of app %d: %s", aid, innerErr)
+	}
+}

internal/state/state.go

@@ -0,0 +1,44 @@
+package state
+
+import (
+	"time"
+
+	"git.gensokyo.uk/security/fortify/fst"
+)
+
+type Entries map[fst.ID]*State
+
+type Store interface {
+	// Do calls f exactly once and ensures store exclusivity until f returns.
+	// Returns whether f is called and any errors during the locking process.
+	// Cursor provided to f becomes invalid as soon as f returns.
+	Do(aid int, f func(c Cursor)) (ok bool, err error)
+
+	// List queries the store and returns a list of aids known to the store.
+	// Note that some or all returned aids might not have any active apps.
+	List() (aids []int, err error)
+
+	// Close releases any resources held by Store.
+	Close() error
+}
+
+// Cursor provides access to the store
+type Cursor interface {
+	Save(state *State) error
+	Destroy(id fst.ID) error
+	Load() (Entries, error)
+	Len() (int, error)
+}
+
+// State is the on-disk format for a fortified process's state information
+type State struct {
+	// fortify instance id
+	ID fst.ID `json:"instance"`
+	// child process PID value
+	PID int `json:"pid"`
+	// sealed app configuration
+	Config *fst.Config `json:"config"`
+
+	// process start time
+	Time time.Time
+}

internal/state/state_test.go

@@ -0,0 +1,126 @@
+package state_test
+
+import (
+	"math/rand/v2"
+	"reflect"
+	"slices"
+	"testing"
+	"time"
+
+	"git.gensokyo.uk/security/fortify/fst"
+	"git.gensokyo.uk/security/fortify/internal/state"
+)
+
+func testStore(t *testing.T, s state.Store) {
+	t.Run("list empty store", func(t *testing.T) {
+		if aids, err := s.List(); err != nil {
+			t.Fatalf("List: error = %v", err)
+		} else if len(aids) != 0 {
+			t.Fatalf("List: aids = %#v", aids)
+		}
+	})
+
+	const (
+		insertEntryChecked = iota
+		insertEntryNoCheck
+		insertEntryOtherApp
+
+		tl
+	)
+
+	var tc [tl]state.State
+	for i := 0; i < tl; i++ {
+		makeState(t, &tc[i])
+	}
+
+	do := func(aid int, f func(c state.Cursor)) {
+		if ok, err := s.Do(aid, f); err != nil {
+			t.Fatalf("Do: ok = %v, error = %v", ok, err)
+		}
+	}
+
+	insert := func(i, aid int) {
+		do(aid, func(c state.Cursor) {
+			if err := c.Save(&tc[i]); err != nil {
+				t.Fatalf("Save(&tc[%v]): error = %v", i, err)
+			}
+		})
+	}
+
+	check := func(i, aid int) {
+		do(aid, func(c state.Cursor) {
+			if entries, err := c.Load(); err != nil {
+				t.Fatalf("Load: error = %v", err)
+			} else if got, ok := entries[tc[i].ID]; !ok {
+				t.Fatalf("Load: entry %s missing",
+					&tc[i].ID)
+			} else {
+				got.Time = tc[i].Time
+				if !reflect.DeepEqual(got, &tc[i]) {
+					t.Fatalf("Load: entry %s got %#v, want %#v",
+						&tc[i].ID, got, &tc[i])
+				}
+			}
+		})
+	}
+
+	t.Run("insert entry checked", func(t *testing.T) {
+		insert(insertEntryChecked, 0)
+		check(insertEntryChecked, 0)
+	})
+
+	t.Run("insert entry unchecked", func(t *testing.T) {
+		insert(insertEntryNoCheck, 0)
+	})
+
+	t.Run("insert entry different aid", func(t *testing.T) {
+		insert(insertEntryOtherApp, 1)
+		check(insertEntryOtherApp, 1)
+	})
+
+	t.Run("check previous insertion", func(t *testing.T) {
+		check(insertEntryNoCheck, 0)
+	})
+
+	t.Run("list aids", func(t *testing.T) {
+		if aids, err := s.List(); err != nil {
+			t.Fatalf("List: error = %v", err)
+		} else {
+			slices.Sort(aids)
+			want := []int{0, 1}
+			if slices.Compare(aids, want) != 0 {
+				t.Fatalf("List() = %#v, want %#v", aids, want)
+			}
+		}
+	})
+
+	t.Run("clear aid 1", func(t *testing.T) {
+		do(1, func(c state.Cursor) {
+			if err := c.Destroy(tc[insertEntryOtherApp].ID); err != nil {
+				t.Fatalf("Destroy: error = %v", err)
+			}
+		})
+		do(1, func(c state.Cursor) {
+			if l, err := c.Len(); err != nil {
+				t.Fatalf("Len: error = %v", err)
+			} else if l != 0 {
+				t.Fatalf("Len() = %d, want 0", l)
+			}
+		})
+	})
+
+	t.Run("close store", func(t *testing.T) {
+		if err := s.Close(); err != nil {
+			t.Fatalf("Close: error = %v", err)
+		}
+	})
+}
+
+func makeState(t *testing.T, s *state.State) {
+	if err := fst.NewAppID(&s.ID); err != nil {
+		t.Fatalf("cannot create dummy state: %v", err)
+	}
+	s.Config = fst.Template()
+	s.PID = rand.Int()
+	s.Time = time.Now()
+}

internal/system/acl.go

@@ -0,0 +1,70 @@
+package system
+
+import (
+	"fmt"
+	"slices"
+
+	"git.gensokyo.uk/security/fortify/acl"
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+)
+
+// UpdatePerm appends an ephemeral acl update Op.
+func (sys *I) UpdatePerm(path string, perms ...acl.Perm) *I {
+	sys.UpdatePermType(Process, path, perms...)
+
+	return sys
+}
+
+// UpdatePermType appends an acl update Op.
+func (sys *I) UpdatePermType(et Enablement, path string, perms ...acl.Perm) *I {
+	sys.lock.Lock()
+	defer sys.lock.Unlock()
+
+	sys.ops = append(sys.ops, &ACL{et, path, perms})
+
+	return sys
+}
+
+type ACL struct {
+	et    Enablement
+	path  string
+	perms acl.Perms
+}
+
+func (a *ACL) Type() Enablement {
+	return a.et
+}
+
+func (a *ACL) apply(sys *I) error {
+	fmsg.VPrintln("applying ACL", a)
+	return fmsg.WrapErrorSuffix(acl.UpdatePerm(a.path, sys.uid, a.perms...),
+		fmt.Sprintf("cannot apply ACL entry to %q:", a.path))
+}
+
+func (a *ACL) revert(sys *I, ec *Criteria) error {
+	if ec.hasType(a) {
+		fmsg.VPrintln("stripping ACL", a)
+		return fmsg.WrapErrorSuffix(acl.UpdatePerm(a.path, sys.uid),
+			fmt.Sprintf("cannot strip ACL entry from %q:", a.path))
+	} else {
+		fmsg.VPrintln("skipping ACL", a)
+		return nil
+	}
+}
+
+func (a *ACL) Is(o Op) bool {
+	a0, ok := o.(*ACL)
+	return ok && a0 != nil &&
+		a.et == a0.et &&
+		a.path == a0.path &&
+		slices.Equal(a.perms, a0.perms)
+}
+
+func (a *ACL) Path() string {
+	return a.path
+}
+
+func (a *ACL) String() string {
+	return fmt.Sprintf("%s type: %s path: %q",
+		a.perms, TypeString(a.et), a.path)
+}

internal/system/acl_test.go

@@ -0,0 +1,90 @@
+package system
+
+import (
+	"testing"
+
+	"git.gensokyo.uk/security/fortify/acl"
+)
+
+func TestUpdatePerm(t *testing.T) {
+	testCases := []struct {
+		path  string
+		perms []acl.Perm
+	}{
+		{"/run/user/1971/fortify", []acl.Perm{acl.Execute}},
+		{"/tmp/fortify.1971/tmpdir/150", []acl.Perm{acl.Read, acl.Write, acl.Execute}},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.path+permSubTestSuffix(tc.perms), func(t *testing.T) {
+			sys := New(150)
+			sys.UpdatePerm(tc.path, tc.perms...)
+			(&tcOp{Process, tc.path}).test(t, sys.ops, []Op{&ACL{Process, tc.path, tc.perms}}, "UpdatePerm")
+		})
+	}
+}
+
+func TestUpdatePermType(t *testing.T) {
+	testCases := []struct {
+		perms []acl.Perm
+		tcOp
+	}{
+		{[]acl.Perm{acl.Execute}, tcOp{User, "/tmp/fortify.1971/tmpdir"}},
+		{[]acl.Perm{acl.Read, acl.Write, acl.Execute}, tcOp{User, "/tmp/fortify.1971/tmpdir/150"}},
+		{[]acl.Perm{acl.Execute}, tcOp{Process, "/run/user/1971/fortify/fcb8a12f7c482d183ade8288c3de78b5"}},
+		{[]acl.Perm{acl.Read}, tcOp{Process, "/tmp/fortify.1971/fcb8a12f7c482d183ade8288c3de78b5/passwd"}},
+		{[]acl.Perm{acl.Read}, tcOp{Process, "/tmp/fortify.1971/fcb8a12f7c482d183ade8288c3de78b5/group"}},
+		{[]acl.Perm{acl.Read, acl.Write, acl.Execute}, tcOp{EWayland, "/run/user/1971/wayland-0"}},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.path+"_"+TypeString(tc.et)+permSubTestSuffix(tc.perms), func(t *testing.T) {
+			sys := New(150)
+			sys.UpdatePermType(tc.et, tc.path, tc.perms...)
+			tc.test(t, sys.ops, []Op{&ACL{tc.et, tc.path, tc.perms}}, "UpdatePermType")
+		})
+	}
+}
+
+func TestACL_String(t *testing.T) {
+	testCases := []struct {
+		want  string
+		et    Enablement
+		perms []acl.Perm
+	}{
+		{`--- type: Process path: "/nonexistent"`, Process, []acl.Perm{}},
+		{`r-- type: User path: "/nonexistent"`, User, []acl.Perm{acl.Read}},
+		{`-w- type: Wayland path: "/nonexistent"`, EWayland, []acl.Perm{acl.Write}},
+		{`--x type: X11 path: "/nonexistent"`, EX11, []acl.Perm{acl.Execute}},
+		{`rw- type: D-Bus path: "/nonexistent"`, EDBus, []acl.Perm{acl.Read, acl.Write}},
+		{`r-x type: PulseAudio path: "/nonexistent"`, EPulse, []acl.Perm{acl.Read, acl.Execute}},
+		{`rwx type: User path: "/nonexistent"`, User, []acl.Perm{acl.Read, acl.Write, acl.Execute}},
+		{`rwx type: Process path: "/nonexistent"`, Process, []acl.Perm{acl.Read, acl.Write, acl.Write, acl.Execute}},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.want, func(t *testing.T) {
+			a := &ACL{et: tc.et, perms: tc.perms, path: "/nonexistent"}
+			if got := a.String(); got != tc.want {
+				t.Errorf("String() = %v, want %v",
+					got, tc.want)
+			}
+		})
+	}
+}
+
+func permSubTestSuffix(perms []acl.Perm) (suffix string) {
+	for _, perm := range perms {
+		switch perm {
+		case acl.Read:
+			suffix += "_read"
+		case acl.Write:
+			suffix += "_write"
+		case acl.Execute:
+			suffix += "_execute"
+		default:
+			panic("unreachable")
+		}
+	}
+	return
+}

internal/system/dbus.go

@@ -0,0 +1,202 @@
+package system
+
+import (
+	"bytes"
+	"errors"
+	"os"
+	"strings"
+	"sync"
+
+	"git.gensokyo.uk/security/fortify/dbus"
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+)
+
+var (
+	ErrDBusConfig = errors.New("dbus config not supplied")
+)
+
+func (sys *I) MustProxyDBus(sessionPath string, session *dbus.Config, systemPath string, system *dbus.Config) *I {
+	if _, err := sys.ProxyDBus(session, system, sessionPath, systemPath); err != nil {
+		panic(err.Error())
+	} else {
+		return sys
+	}
+}
+
+func (sys *I) ProxyDBus(session, system *dbus.Config, sessionPath, systemPath string) (func(f func(msgbuf []string)), error) {
+	d := new(DBus)
+
+	// used by waiting goroutine to notify process exit
+	d.done = make(chan struct{})
+
+	// session bus is mandatory
+	if session == nil {
+		return nil, fmsg.WrapError(ErrDBusConfig,
+			"attempted to seal message bus proxy without session bus config")
+	}
+
+	// system bus is optional
+	d.system = system == nil
+
+	// upstream address, downstream socket path
+	var sessionBus, systemBus [2]string
+
+	// resolve upstream bus addresses
+	sessionBus[0], systemBus[0] = dbus.Address()
+
+	// set paths from caller
+	sessionBus[1], systemBus[1] = sessionPath, systemPath
+
+	// create proxy instance
+	d.proxy = dbus.New(sessionBus, systemBus)
+
+	defer func() {
+		if fmsg.Verbose() && d.proxy.Sealed() {
+			fmsg.VPrintln("sealed session proxy", session.Args(sessionBus))
+			if system != nil {
+				fmsg.VPrintln("sealed system proxy", system.Args(systemBus))
+			}
+			fmsg.VPrintln("message bus proxy final args:", d.proxy)
+		}
+	}()
+
+	// queue operation
+	sys.ops = append(sys.ops, d)
+
+	// seal dbus proxy
+	d.out = &scanToFmsg{msg: new(strings.Builder)}
+	return d.out.F, fmsg.WrapErrorSuffix(d.proxy.Seal(session, system),
+		"cannot seal message bus proxy:")
+}
+
+type DBus struct {
+	proxy *dbus.Proxy
+
+	out *scanToFmsg
+	// whether system bus proxy is enabled
+	system bool
+	// notification from goroutine waiting for dbus.Proxy
+	done chan struct{}
+}
+
+func (d *DBus) Type() Enablement {
+	return Process
+}
+
+func (d *DBus) apply(_ *I) error {
+	fmsg.VPrintf("session bus proxy on %q for upstream %q", d.proxy.Session()[1], d.proxy.Session()[0])
+	if d.system {
+		fmsg.VPrintf("system bus proxy on %q for upstream %q", d.proxy.System()[1], d.proxy.System()[0])
+	}
+
+	// ready channel passed to dbus package
+	ready := make(chan error, 1)
+
+	// background dbus proxy start
+	if err := d.proxy.Start(ready, d.out, true); err != nil {
+		return fmsg.WrapErrorSuffix(err,
+			"cannot start message bus proxy:")
+	}
+	fmsg.VPrintln("starting message bus proxy:", d.proxy)
+	if fmsg.Verbose() { // save the extra bwrap arg build when verbose logging is off
+		fmsg.VPrintln("message bus proxy bwrap args:", d.proxy.Bwrap())
+	}
+
+	// background wait for proxy instance and notify completion
+	go func() {
+		if err := d.proxy.Wait(); err != nil {
+			fmsg.Println("message bus proxy exited with error:", err)
+			go func() { ready <- err }()
+		} else {
+			fmsg.VPrintln("message bus proxy exit")
+		}
+
+		// ensure socket removal so ephemeral directory is empty at revert
+		if err := os.Remove(d.proxy.Session()[1]); err != nil && !errors.Is(err, os.ErrNotExist) {
+			fmsg.Println("cannot remove dangling session bus socket:", err)
+		}
+		if d.system {
+			if err := os.Remove(d.proxy.System()[1]); err != nil && !errors.Is(err, os.ErrNotExist) {
+				fmsg.Println("cannot remove dangling system bus socket:", err)
+			}
+		}
+
+		// notify proxy completion
+		close(d.done)
+	}()
+
+	// ready is not nil if the proxy process faulted
+	if err := <-ready; err != nil {
+		// note that err here is either an I/O error or a predetermined unexpected behaviour error
+		return fmsg.WrapErrorSuffix(err,
+			"message bus proxy fault after start:")
+	}
+	fmsg.VPrintln("message bus proxy ready")
+
+	return nil
+}
+
+func (d *DBus) revert(_ *I, _ *Criteria) error {
+	// criteria ignored here since dbus is always process-scoped
+	fmsg.VPrintln("terminating message bus proxy")
+
+	if err := d.proxy.Close(); err != nil {
+		if errors.Is(err, os.ErrClosed) {
+			return fmsg.WrapError(err,
+				"message bus proxy already closed")
+		} else {
+			return fmsg.WrapErrorSuffix(err,
+				"cannot stop message bus proxy:")
+		}
+	}
+
+	// block until proxy wait returns
+	<-d.done
+	return nil
+}
+
+func (d *DBus) Is(o Op) bool {
+	d0, ok := o.(*DBus)
+	return ok && d0 != nil &&
+		((d.proxy == nil && d0.proxy == nil) ||
+			(d.proxy != nil && d0.proxy != nil && d.proxy.String() == d0.proxy.String()))
+}
+
+func (d *DBus) Path() string {
+	return "(dbus proxy)"
+}
+
+func (d *DBus) String() string {
+	return d.proxy.String()
+}
+
+type scanToFmsg struct {
+	msg    *strings.Builder
+	msgbuf []string
+
+	mu sync.RWMutex
+}
+
+func (s *scanToFmsg) Write(p []byte) (n int, err error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.write(p, 0)
+}
+
+func (s *scanToFmsg) write(p []byte, a int) (int, error) {
+	if i := bytes.IndexByte(p, '\n'); i == -1 {
+		n, _ := s.msg.Write(p)
+		return a + n, nil
+	} else {
+		n, _ := s.msg.Write(p[:i])
+		s.msgbuf = append(s.msgbuf, s.msg.String())
+		s.msg.Reset()
+		return s.write(p[i+1:], a+n+1)
+	}
+}
+
+func (s *scanToFmsg) F(f func(msgbuf []string)) {
+	s.mu.RLock()
+	f(s.msgbuf)
+	s.mu.RUnlock()
+}

internal/system/enablement.go

@@ -0,0 +1,49 @@
+package system
+
+type (
+	// Enablement represents an optional system resource
+	Enablement uint8
+	// Enablements represents optional system resources to share
+	Enablements uint64
+)
+
+const (
+	EWayland Enablement = iota
+	EX11
+	EDBus
+	EPulse
+)
+
+var enablementString = [...]string{
+	EWayland: "Wayland",
+	EX11:     "X11",
+	EDBus:    "D-Bus",
+	EPulse:   "PulseAudio",
+}
+
+const ELen = len(enablementString)
+
+func (e Enablement) String() string {
+	if int(e) >= ELen {
+		return "<invalid enablement>"
+	}
+	return enablementString[e]
+}
+
+func (e Enablement) Mask() Enablements {
+	return 1 << e
+}
+
+// Has returns whether a feature is enabled
+func (es *Enablements) Has(e Enablement) bool {
+	return *es&e.Mask() != 0
+}
+
+// Set enables a feature
+func (es *Enablements) Set(e Enablement) {
+	if es.Has(e) {
+		panic("enablement " + e.String() + " set twice")
+	}
+
+	*es |= e.Mask()
+}