release: 0.3.2

Signed-off-by: Ophestra <cat@gensokyo.uk>

.gitea/workflows/test.yml

@@ -22,6 +22,57 @@ jobs:
           path: result/*
           retention-days: 1
 
+  race:
+    name: Fortify (race detector)
+    runs-on: nix
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Run NixOS test
+        run: nix build --out-link "result" --print-out-paths --print-build-logs .#checks.x86_64-linux.race
+
+      - name: Upload test output
+        uses: actions/upload-artifact@v3
+        with:
+          name: "fortify-race-vm-output"
+          path: result/*
+          retention-days: 1
+
+  sandbox:
+    name: Sandbox
+    runs-on: nix
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Run NixOS test
+        run: nix build --out-link "result" --print-out-paths --print-build-logs .#checks.x86_64-linux.sandbox
+
+      - name: Upload test output
+        uses: actions/upload-artifact@v3
+        with:
+          name: "sandbox-vm-output"
+          path: result/*
+          retention-days: 1
+
+  sandbox-race:
+    name: Sandbox (race detector)
+    runs-on: nix
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Run NixOS test
+        run: nix build --out-link "result" --print-out-paths --print-build-logs .#checks.x86_64-linux.sandbox-race
+
+      - name: Upload test output
+        uses: actions/upload-artifact@v3
+        with:
+          name: "sandbox-race-vm-output"
+          path: result/*
+          retention-days: 1
+
   fpkg:
     name: Fpkg
     runs-on: nix
@@ -39,29 +90,14 @@ jobs:
           path: result/*
           retention-days: 1
 
-  race:
-    name: Data race detector
-    runs-on: nix
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-
-      - name: Run NixOS test
-        run: nix build --out-link "result" --print-out-paths --print-build-logs .#checks.x86_64-linux.race
-
-      - name: Upload test output
-        uses: actions/upload-artifact@v3
-        with:
-          name: "fortify-race-vm-output"
-          path: result/*
-          retention-days: 1
-
   check:
     name: Flake checks
     needs:
       - fortify
-      - fpkg
       - race
+      - sandbox
+      - sandbox-race
+      - fpkg
     runs-on: nix
     steps:
       - name: Checkout

dbus/dbus_test.go

@@ -8,6 +8,7 @@ import (
 	"os"
 	"os/exec"
 	"strings"
+	"syscall"
 	"testing"
 	"time"
 
@@ -71,7 +72,7 @@ func TestProxy_Seal(t *testing.T) {
 	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 {
+			if err := p.Seal(tc[0].c, tc[1].c); (errors.Is(err, syscall.EINVAL)) != tc[0].wantErr {
 				t.Errorf("Seal(%p, %p) error = %v, wantErr %v",
 					tc[0].c, tc[1].c,
 					err, tc[0].wantErr)

flake.nix

@@ -58,12 +58,19 @@
         in
         {
           fortify = callPackage ./test { inherit system self; };
-          fpkg = callPackage ./cmd/fpkg/test { inherit system self; };
           race = callPackage ./test {
             inherit system self;
             withRace = true;
           };
 
+          sandbox = callPackage ./test/sandbox { inherit self; };
+          sandbox-race = callPackage ./test/sandbox {
+            inherit self;
+            withRace = true;
+          };
+
+          fpkg = callPackage ./cmd/fpkg/test { inherit system self; };
+
           formatting = runCommandLocal "check-formatting" { nativeBuildInputs = [ nixfmt-rfc-style ]; } ''
             cd ${./.}
 

fst/sandbox.go

@@ -97,6 +97,10 @@ func (s *SandboxConfig) ToContainer(sys SandboxSys, uid, gid *int) (*sandbox.Par
 		Seccomp:  s.Seccomp,
 	}
 
+	if s.Multiarch {
+		container.Seccomp |= seccomp.FlagMultiarch
+	}
+
 	/* this is only 4 KiB of memory on a 64-bit system,
 	permissive defaults on NixOS results in around 100 entries
 	so this capacity should eliminate copies for most setups */

helper/args.go

@@ -1,38 +1,17 @@
 package helper
 
 import (
-	"errors"
+	"bytes"
 	"io"
-	"strings"
+	"syscall"
 )
 
-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
-}
+type argsWt [][]byte
 
 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"))
+		n, err := w.Write(arg)
 		nt += n
 
 		if err != nil {
@@ -44,18 +23,32 @@ func (a argsWt) WriteTo(w io.Writer) (int64, error) {
 }
 
 func (a argsWt) String() string {
-	return strings.Join(a, " ")
+	return string(
+		bytes.TrimSuffix(
+			bytes.ReplaceAll(
+				bytes.Join(a, nil),
+				[]byte{0}, []byte{' '},
+			),
+			[]byte{' '},
+		),
+	)
 }
 
-// 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()
+// NewCheckedArgs returns a checked null-terminated argument writer for a copy of args.
+func NewCheckedArgs(args []string) (wt io.WriterTo, err error) {
+	a := make(argsWt, len(args))
+	for i, arg := range args {
+		a[i], err = syscall.ByteSliceFromString(arg)
+		if err != nil {
+			return
+		}
+	}
+	wt = a
+	return
 }
 
-// MustNewCheckedArgs returns a checked argument writer for args and panics if check fails.
-// Callers must not retain any references to args.
+// MustNewCheckedArgs returns a checked null-terminated argument writer for a copy of args.
+// If s contains a NUL byte this function panics instead of returning an error.
 func MustNewCheckedArgs(args []string) io.WriterTo {
 	a, err := NewCheckedArgs(args)
 	if err != nil {

helper/args_test.go

@@ -4,34 +4,33 @@ import (
 	"errors"
 	"fmt"
 	"strings"
+	"syscall"
 	"testing"
 
 	"git.gensokyo.uk/security/fortify/helper"
 )
 
-func Test_argsFd_String(t *testing.T) {
+func TestArgsString(t *testing.T) {
 	wantString := strings.Join(wantArgs, " ")
 	if got := argsWt.(fmt.Stringer).String(); got != wantString {
-		t.Errorf("String(): got %v; want %v",
+		t.Errorf("String: %q, want %q",
 			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)
+	if _, err := helper.NewCheckedArgs(args); !errors.Is(err, syscall.EINVAL) {
+		t.Errorf("NewCheckedArgs: error = %v, wantErr %v",
+			err, syscall.EINVAL)
 	}
 
 	t.Run("must panic", func(t *testing.T) {
 		badPayload := []string{"\x00"}
 		defer func() {
-			wantPanic := "argument contains null character"
+			wantPanic := "invalid argument"
 			if r := recover(); r != wantPanic {
-				t.Errorf("MustNewCheckedArgs(%q) panic = %v, wantPanic %v",
-					badPayload,
+				t.Errorf("MustNewCheckedArgs: panic = %v, wantPanic %v",
 					r, wantPanic)
 			}
 		}()

internal/app/seal.go

@@ -8,7 +8,6 @@ import (
 	"fmt"
 	"io"
 	"io/fs"
-	"maps"
 	"os"
 	"path"
 	"regexp"
@@ -505,7 +504,13 @@ func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *fst.Co
 
 	// flatten and sort env for deterministic behaviour
 	seal.container.Env = make([]string, 0, len(seal.env))
-	maps.All(seal.env)(func(k string, v string) bool { seal.container.Env = append(seal.container.Env, k+"="+v); return true })
+	for k, v := range seal.env {
+		if strings.IndexByte(k, '=') != -1 {
+			return fmsg.WrapError(syscall.EINVAL,
+				fmt.Sprintf("invalid environment variable %s", k))
+		}
+		seal.container.Env = append(seal.container.Env, k+"="+v)
+	}
 	slices.Sort(seal.container.Env)
 
 	fmsg.Verbosef("created application seal for uid %s (%s) groups: %v, argv: %s",

internal/state/multi.go

@@ -33,10 +33,10 @@ func (s *multiStore) Do(aid int, f func(c Cursor)) (bool, error) {
 
 	// load or initialise new backend
 	b := new(multiBackend)
+	b.lock.Lock()
 	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

internal/sys/interface.go

@@ -47,7 +47,7 @@ type State interface {
 	Uid(aid int) (int, error)
 }
 
-// CopyPaths is a generic implementation of [System.Paths].
+// CopyPaths is a generic implementation of [fst.Paths].
 func CopyPaths(os State, v *fst.Paths) {
 	v.SharePath = path.Join(os.TempDir(), "fortify."+strconv.Itoa(os.Getuid()))
 

nixos.nix

@@ -201,9 +201,11 @@ in
                   ${copy "${pkg}/share/icons"}
                   ${copy "${pkg}/share/man"}
 
-                  substituteInPlace $out/share/applications/* \
-                    --replace-warn '${pkg}/bin/' "" \
-                    --replace-warn '${pkg}/libexec/' ""
+                  if test -d "$out/share/applications"; then
+                    substituteInPlace $out/share/applications/* \
+                      --replace-warn '${pkg}/bin/' "" \
+                      --replace-warn '${pkg}/libexec/' ""
+                  fi
                 ''
               )
               ++ acc

options.md

@@ -35,7 +35,7 @@ package
 
 
 *Default:*
-` <derivation fortify-static-x86_64-unknown-linux-musl-0.3.1> `
+` <derivation fortify-static-x86_64-unknown-linux-musl-0.3.2> `
 
 
 
@@ -73,6 +73,25 @@ list of package
 
 
 
+## environment\.fortify\.apps\.\*\.args
+
+
+
+Custom args\.
+Setting this to null will default to script name\.
+
+
+
+*Type:*
+null or (list of string)
+
+
+
+*Default:*
+` null `
+
+
+
 ## environment\.fortify\.apps\.\*\.capability\.dbus
 
 
@@ -486,6 +505,25 @@ boolean
 
 
 
+## environment\.fortify\.apps\.\*\.path
+
+
+
+Custom executable path\.
+Setting this to null will default to the start script\.
+
+
+
+*Type:*
+null or string
+
+
+
+*Default:*
+` null `
+
+
+
 ## environment\.fortify\.apps\.\*\.script
 
 
@@ -606,7 +644,7 @@ package
 
 
 *Default:*
-` <derivation fortify-fsu-0.3.1> `
+` <derivation fortify-fsu-0.3.2> `
 
 
 

package.nix

@@ -31,7 +31,7 @@
 
 buildGoModule rec {
   pname = "fortify";
-  version = "0.3.1";
+  version = "0.3.2";
 
   src = builtins.path {
     name = "${pname}-src";

sandbox/container.go

@@ -99,6 +99,8 @@ type (
 		// Permission bits of newly created parent directories.
 		// The zero value is interpreted as 0755.
 		ParentPerm os.FileMode
+		// Retain CAP_SYS_ADMIN.
+		Privileged bool
 
 		Flags HardeningFlags
 	}

sandbox/init.go

@@ -223,17 +223,30 @@ func Init(prepare func(prefix string), setVerbose func(verbose bool)) {
 	if _, _, errno := syscall.Syscall(PR_SET_NO_NEW_PRIVS, 1, 0, 0); errno != 0 {
 		log.Fatalf("prctl(PR_SET_NO_NEW_PRIVS): %v", errno)
 	}
+
 	if _, _, errno := syscall.Syscall(syscall.SYS_PRCTL, PR_CAP_AMBIENT, PR_CAP_AMBIENT_CLEAR_ALL, 0); errno != 0 {
 		log.Fatalf("cannot clear the ambient capability set: %v", errno)
 	}
 	for i := uintptr(0); i <= LastCap(); i++ {
+		if params.Privileged && i == CAP_SYS_ADMIN {
+			continue
+		}
 		if _, _, errno := syscall.Syscall(syscall.SYS_PRCTL, syscall.PR_CAPBSET_DROP, i, 0); errno != 0 {
 			log.Fatalf("cannot drop capability from bonding set: %v", errno)
 		}
 	}
+
+	var keep [2]uint32
+	if params.Privileged {
+		keep[capToIndex(CAP_SYS_ADMIN)] |= capToMask(CAP_SYS_ADMIN)
+
+		if _, _, errno := syscall.Syscall(syscall.SYS_PRCTL, PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_SYS_ADMIN); errno != 0 {
+			log.Fatalf("cannot raise CAP_SYS_ADMIN: %v", errno)
+		}
+	}
 	if err := capset(
 		&capHeader{_LINUX_CAPABILITY_VERSION_3, 0},
-		&[2]capData{{0, 0, 0}, {0, 0, 0}},
+		&[2]capData{{0, keep[0], keep[0]}, {0, keep[1], keep[1]}},
 	); err != nil {
 		log.Fatalf("cannot capset: %v", err)
 	}

sandbox/seccomp/export_test.go

@@ -73,6 +73,16 @@ func TestExport(t *testing.T) {
 			0x80, 0x8b, 0x1a, 0x6f, 0x84, 0xf3, 0x2b, 0xbd,
 			0xe1, 0xaa, 0x02, 0xae, 0x30, 0xee, 0xdc, 0xfa,
 		}, false},
+		{"fortify default", seccomp.FlagExt | seccomp.FlagDenyDevel, []byte{
+			0xc6, 0x98, 0xb0, 0x81, 0xff, 0x95, 0x7a, 0xfe,
+			0x17, 0xa6, 0xd9, 0x43, 0x74, 0x53, 0x7d, 0x37,
+			0xf2, 0xa6, 0x3f, 0x6f, 0x9d, 0xd7, 0x5d, 0xa7,
+			0x54, 0x65, 0x42, 0x40, 0x7a, 0x9e, 0x32, 0x47,
+			0x6e, 0xbd, 0xa3, 0x31, 0x2b, 0xa7, 0x78, 0x5d,
+			0x7f, 0x61, 0x85, 0x42, 0xbc, 0xfa, 0xf2, 0x7c,
+			0xa2, 0x7d, 0xcc, 0x2d, 0xdd, 0xba, 0x85, 0x20,
+			0x69, 0xd2, 0x8b, 0xcf, 0xe8, 0xca, 0xd3, 0x9a,
+		}, false},
 	}
 
 	buf := make([]byte, 8)

sandbox/seccomp/seccomp.go

@@ -1,3 +1,4 @@
+// Package seccomp provides filter presets and high level wrappers around libseccomp.
 package seccomp
 
 /*

sandbox/syscall.go

@@ -11,6 +11,7 @@ const (
 	PR_SET_NO_NEW_PRIVS = 0x26
 
 	CAP_SYS_ADMIN = 0x15
+	CAP_SETPCAP   = 0x8
 )
 
 const (
@@ -30,10 +31,9 @@ func SetDumpable(dumpable uintptr) error {
 const (
 	_LINUX_CAPABILITY_VERSION_3 = 0x20080522
 
-	PR_CAP_AMBIENT           = 47
-	PR_CAP_AMBIENT_CLEAR_ALL = 4
-
-	CAP_SETPCAP = 8
+	PR_CAP_AMBIENT           = 0x2f
+	PR_CAP_AMBIENT_RAISE     = 0x2
+	PR_CAP_AMBIENT_CLEAR_ALL = 0x4
 )
 
 type (
@@ -49,6 +49,12 @@ type (
 	}
 )
 
+// See CAP_TO_INDEX in linux/capability.h:
+func capToIndex(cap uintptr) uintptr { return cap >> 5 }
+
+// See CAP_TO_MASK in linux/capability.h:
+func capToMask(cap uintptr) uint32 { return 1 << uint(cap&31) }
+
 func capset(hdrp *capHeader, datap *[2]capData) error {
 	if _, _, errno := syscall.Syscall(syscall.SYS_CAPSET,
 		uintptr(unsafe.Pointer(hdrp)),

test/configuration.nix

@@ -4,17 +4,6 @@
   config,
   ...
 }:
-let
-  testCases = import ./sandbox/case {
-    inherit (pkgs)
-      lib
-      callPackage
-      writeText
-      foot
-      ;
-    inherit (config.environment.fortify.package) version;
-  };
-in
 {
   users.users = {
     alice = {
@@ -113,10 +102,6 @@ in
     home-manager = _: _: { home.stateVersion = "23.05"; };
 
     apps = [
-      testCases.preset
-      testCases.tty
-      testCases.mapuid
-
       {
         name = "ne-foot";
         verbose = true;

test/sandbox/assert.go

@@ -7,10 +7,15 @@ in the public sandbox/vfs package. Files in this package are excluded by the bui
 package sandbox
 
 import (
+	"crypto/sha512"
+	"encoding/hex"
 	"encoding/json"
+	"errors"
 	"io/fs"
 	"log"
 	"os"
+	"syscall"
+	"time"
 )
 
 var (
@@ -116,7 +121,7 @@ func (t *T) MustCheck(want *TestCase) {
 	}
 
 	if want.Seccomp {
-		if TrySyscalls() != nil {
+		if trySyscalls() != nil {
 			os.Exit(1)
 		}
 	} else {
@@ -124,6 +129,81 @@ func (t *T) MustCheck(want *TestCase) {
 	}
 }
 
+func MustCheckFilter(pid int, want string) {
+	err := CheckFilter(pid, want)
+	if err == nil {
+		return
+	}
+
+	var perr *ptraceError
+	if !errors.As(err, &perr) {
+		fatalf("%s", err)
+	}
+	switch perr.op {
+	case "PTRACE_ATTACH":
+		fatalf("cannot attach to process %d: %v", pid, err)
+	case "PTRACE_SECCOMP_GET_FILTER":
+		if perr.errno == syscall.ENOENT {
+			fatalf("seccomp filter not installed for process %d", pid)
+		}
+		fatalf("cannot get filter: %v", err)
+	default:
+		fatalf("cannot check filter: %v", err)
+	}
+
+	*(*int)(nil) = 0 // not reached
+}
+
+func CheckFilter(pid int, want string) error {
+	if err := ptraceAttach(pid); err != nil {
+		return err
+	}
+	defer func() {
+		if err := ptraceDetach(pid); err != nil {
+			printf("cannot detach from process %d: %v", pid, err)
+		}
+	}()
+
+	h := sha512.New()
+	{
+	getFilter:
+		buf, err := getFilter[[8]byte](pid, 0)
+		/* this is not how ESRCH should be handled: the manpage advises the
+		use of waitpid, however that is not applicable for attaching to an
+		arbitrary process, and spawning target process here is not easily
+		possible under the current testing framework;
+
+		despite checking for /proc/pid/status indicating state t (tracing stop),
+		it does not appear to be directly related to the internal state used to
+		determine whether a process is ready to accept ptrace operations, it also
+		introduces a TOCTOU that is irrelevant in the testing vm; this behaviour
+		is kept anyway as it reduces the average iterations required here;
+
+		since this code is only ever compiled into the test program, whatever
+		implications this ugliness might have should not hurt anyone */
+		if errors.Is(err, syscall.ESRCH) {
+			time.Sleep(100 * time.Millisecond)
+			goto getFilter
+		}
+
+		if err != nil {
+			return err
+		}
+
+		for _, b := range buf {
+			h.Write(b[:])
+		}
+	}
+
+	if got := hex.EncodeToString(h.Sum(nil)); got != want {
+		printf("[FAIL] %s", got)
+		return syscall.ENOTRECOVERABLE
+	} else {
+		printf("[ OK ] %s", got)
+		return nil
+	}
+}
+
 func mustDecode(wantFilePath string, v any) {
 	if f, err := os.Open(wantFilePath); err != nil {
 		fatalf("cannot open %q: %v", wantFilePath, err)

test/sandbox/assert.nix

@@ -1,30 +0,0 @@
-{
-  writeText,
-  buildGoModule,
-  pkg-config,
-  util-linux,
-
-  version,
-}:
-buildGoModule {
-  pname = "check-sandbox";
-  inherit version;
-
-  src = ../.;
-  vendorHash = null;
-
-  buildInputs = [ util-linux ];
-  nativeBuildInputs = [ pkg-config ];
-
-  preBuild = ''
-    go mod init git.gensokyo.uk/security/fortify/test >& /dev/null
-    cp ${writeText "main.go" ''
-      package main
-
-      import "os"
-      import "git.gensokyo.uk/security/fortify/test/sandbox"
-
-      func main() { (&sandbox.T{FS: os.DirFS("/")}).MustCheckFile(os.Args[1], "/tmp/sandbox-ok") }
-    ''} main.go
-  '';
-}

test/sandbox/case/default.nix

@@ -1,11 +1,4 @@
-{
-  lib,
-  callPackage,
-  writeText,
-  foot,
-
-  version,
-}:
+lib: testProgram:
 let
   fs = mode: dir: data: {
     mode = lib.fromHexString mode;
@@ -30,8 +23,6 @@ let
       ;
   };
 
-  checkSandbox = callPackage ../assert.nix { inherit version; };
-
   callTestCase =
     path:
     let
@@ -47,12 +38,12 @@ let
       name = "check-sandbox-${tc.name}";
       verbose = true;
       inherit (tc) tty mapRealUid;
-      share = foot;
+      share = testProgram;
       packages = [ ];
-      path = "${checkSandbox}/bin/test";
+      path = "${testProgram}/bin/fortify-test";
       args = [
         "test"
-        (toString (writeText "fortify-${tc.name}-want.json" (builtins.toJSON tc.want)))
+        (toString (builtins.toFile "fortify-${tc.name}-want.json" (builtins.toJSON tc.want)))
       ];
     };
 in

test/sandbox/case/mapuid.nix

@@ -97,7 +97,6 @@
         "pki" = fs "80001ff" null null;
         "polkit-1" = fs "80001ff" null null;
         "profile" = fs "80001ff" null null;
-        "profiles" = fs "80001ff" null null;
         "protocols" = fs "80001ff" null null;
         "resolv.conf" = fs "80001ff" null null;
         "resolvconf.conf" = fs "80001ff" null null;

test/sandbox/case/preset.nix

@@ -97,7 +97,6 @@
         "pki" = fs "80001ff" null null;
         "polkit-1" = fs "80001ff" null null;
         "profile" = fs "80001ff" null null;
-        "profiles" = fs "80001ff" null null;
         "protocols" = fs "80001ff" null null;
         "resolv.conf" = fs "80001ff" null null;
         "resolvconf.conf" = fs "80001ff" null null;

test/sandbox/case/tty.nix

@@ -98,7 +98,6 @@
         "pki" = fs "80001ff" null null;
         "polkit-1" = fs "80001ff" null null;
         "profile" = fs "80001ff" null null;
-        "profiles" = fs "80001ff" null null;
         "protocols" = fs "80001ff" null null;
         "resolv.conf" = fs "80001ff" null null;
         "resolvconf.conf" = fs "80001ff" null null;

test/sandbox/configuration.nix

@@ -0,0 +1,76 @@
+{
+  lib,
+  pkgs,
+  config,
+  ...
+}:
+let
+  testProgram = pkgs.callPackage ./tool/package.nix { inherit (config.environment.fortify.package) version; };
+  testCases = import ./case lib testProgram;
+in
+{
+  users.users = {
+    alice = {
+      isNormalUser = true;
+      description = "Alice Foobar";
+      password = "foobar";
+      uid = 1000;
+    };
+  };
+
+  home-manager.users.alice.home.stateVersion = "24.11";
+
+  # Automatically login on tty1 as a normal user:
+  services.getty.autologinUser = "alice";
+
+  environment = {
+    systemPackages = with pkgs; [
+      # For checking seccomp outcome:
+      testProgram
+    ];
+
+    variables = {
+      SWAYSOCK = "/tmp/sway-ipc.sock";
+      WLR_RENDERER = "pixman";
+    };
+  };
+
+  # Automatically configure and start Sway when logging in on tty1:
+  programs.bash.loginShellInit = ''
+    if [ "$(tty)" = "/dev/tty1" ]; then
+      set -e
+
+      mkdir -p ~/.config/sway
+      (sed s/Mod4/Mod1/ /etc/sway/config &&
+      echo 'output * bg ${pkgs.nixos-artwork.wallpapers.simple-light-gray.gnomeFilePath} fill' &&
+      echo 'output Virtual-1 res 1680x1050') > ~/.config/sway/config
+
+      sway --validate
+      systemd-cat --identifier=session sway && touch /tmp/sway-exit-ok
+    fi
+  '';
+
+  programs.sway.enable = true;
+
+  virtualisation.qemu.options = [
+    # Need to switch to a different GPU driver than the default one (-vga std) so that Sway can launch:
+    "-vga none -device virtio-gpu-pci"
+
+    # Increase performance:
+    "-smp 8"
+  ];
+
+  environment.fortify = {
+    enable = true;
+    stateDir = "/var/lib/fortify";
+    users.alice = 0;
+
+    home-manager = _: _: { home.stateVersion = "23.05"; };
+
+    apps = [
+      testCases.preset
+      testCases.tty
+      testCases.mapuid
+    ];
+  };
+}

test/sandbox/default.nix

@@ -0,0 +1,39 @@
+{
+  lib,
+  nixosTest,
+
+  self,
+  withRace ? false,
+}:
+
+nixosTest {
+  name = "fortify-sandbox" + (if withRace then "-race" else "");
+  nodes.machine =
+    { options, pkgs, ... }:
+    {
+      # Run with Go race detector:
+      environment.fortify = lib.mkIf withRace rec {
+        # race detector does not support static linking
+        package = (pkgs.callPackage ../../package.nix { }).overrideAttrs (previousAttrs: {
+          GOFLAGS = previousAttrs.GOFLAGS ++ [ "-race" ];
+        });
+        fsuPackage = options.environment.fortify.fsuPackage.default.override { fortify = package; };
+      };
+
+      imports = [
+        ./configuration.nix
+
+        self.nixosModules.fortify
+        self.inputs.home-manager.nixosModules.home-manager
+      ];
+    };
+
+  # adapted from nixos sway integration tests
+
+  # testScriptWithTypes:49: error: Cannot call function of unknown type
+  #           (machine.succeed if succeed else machine.execute)(
+  #           ^
+  # Found 1 error in 1 file (checked 1 source file)
+  skipTypeCheck = true;
+  testScript = builtins.readFile ./test.py;
+}

test/sandbox/ptrace.go

@@ -0,0 +1,119 @@
+package sandbox
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+	"syscall"
+	"time"
+	"unsafe"
+)
+
+const (
+	NULL = 0
+
+	PTRACE_ATTACH             = 16
+	PTRACE_DETACH             = 17
+	PTRACE_SECCOMP_GET_FILTER = 0x420c
+)
+
+type ptraceError struct {
+	op    string
+	errno syscall.Errno
+}
+
+func (p *ptraceError) Error() string { return fmt.Sprintf("%s: %v", p.op, p.errno) }
+
+func (p *ptraceError) Unwrap() error {
+	if p.errno == 0 {
+		return nil
+	}
+	return p.errno
+}
+
+func ptrace(op uintptr, pid, addr int, data unsafe.Pointer) (r uintptr, errno syscall.Errno) {
+	r, _, errno = syscall.Syscall6(syscall.SYS_PTRACE, op, uintptr(pid), uintptr(addr), uintptr(data), NULL, NULL)
+	return
+}
+
+func ptraceAttach(pid int) error {
+	const (
+		statePrefix = "State:"
+		stateSuffix = "t (tracing stop)"
+	)
+
+	var r io.ReadSeekCloser
+	if f, err := os.Open(fmt.Sprintf("/proc/%d/status", pid)); err != nil {
+		return err
+	} else {
+		r = f
+	}
+
+	if _, errno := ptrace(PTRACE_ATTACH, pid, 0, nil); errno != 0 {
+		return &ptraceError{"PTRACE_ATTACH", errno}
+	}
+
+	// ugly! but there does not appear to be another way
+	for {
+		time.Sleep(10 * time.Millisecond)
+
+		if _, err := r.Seek(0, io.SeekStart); err != nil {
+			return err
+		}
+		s := bufio.NewScanner(r)
+
+		var found bool
+		for s.Scan() {
+			found = strings.HasPrefix(s.Text(), statePrefix)
+			if found {
+				break
+			}
+		}
+		if err := s.Err(); err != nil {
+			return err
+		}
+
+		if !found {
+			return syscall.EBADE
+		}
+
+		if strings.HasSuffix(s.Text(), stateSuffix) {
+			break
+		}
+	}
+
+	return nil
+}
+
+func ptraceDetach(pid int) error {
+	if _, errno := ptrace(PTRACE_DETACH, pid, 0, nil); errno != 0 {
+		return &ptraceError{"PTRACE_DETACH", errno}
+	}
+	return nil
+}
+
+type sockFilter struct { /* Filter block */
+	code uint16 /* Actual filter code */
+	jt   uint8  /* Jump true */
+	jf   uint8  /* Jump false */
+	k    uint32 /* Generic multiuse field */
+}
+
+func getFilter[T comparable](pid, index int) ([]T, error) {
+	if s := unsafe.Sizeof(*new(T)); s != 8 {
+		panic(fmt.Sprintf("invalid filter block size %d", s))
+	}
+
+	var buf []T
+	if n, errno := ptrace(PTRACE_SECCOMP_GET_FILTER, pid, index, nil); errno != 0 {
+		return nil, &ptraceError{"PTRACE_SECCOMP_GET_FILTER", errno}
+	} else {
+		buf = make([]T, n)
+	}
+	if _, errno := ptrace(PTRACE_SECCOMP_GET_FILTER, pid, index, unsafe.Pointer(&buf[0])); errno != 0 {
+		return nil, &ptraceError{"PTRACE_SECCOMP_GET_FILTER", errno}
+	}
+	return buf, nil
+}

test/sandbox/seccomp.go

@@ -10,9 +10,7 @@ import (
 */
 import "C"
 
-const NULL = 0
-
-func TrySyscalls() error {
+func trySyscalls() error {
 	testCases := []struct {
 		name  string
 		errno syscall.Errno

test/sandbox/test.py

@@ -0,0 +1,71 @@
+import json
+import shlex
+
+q = shlex.quote
+
+
+def swaymsg(command: str = "", succeed=True, type="command"):
+    assert command != "" or type != "command", "Must specify command or type"
+    shell = q(f"swaymsg -t {q(type)} -- {q(command)}")
+    with machine.nested(
+            f"sending swaymsg {shell!r}" + " (allowed to fail)" * (not succeed)
+    ):
+        ret = (machine.succeed if succeed else machine.execute)(
+            f"su - alice -c {shell}"
+        )
+
+    # execute also returns a status code, but disregard.
+    if not succeed:
+        _, ret = ret
+
+    if not succeed and not ret:
+        return None
+
+    parsed = json.loads(ret)
+    return parsed
+
+
+start_all()
+machine.wait_for_unit("multi-user.target")
+
+# To check fortify's version:
+print(machine.succeed("sudo -u alice -i fortify version"))
+
+# Wait for Sway to complete startup:
+machine.wait_for_file("/run/user/1000/wayland-1")
+machine.wait_for_file("/tmp/sway-ipc.sock")
+
+# Check seccomp outcome:
+swaymsg("exec fortify run cat")
+pid = int(machine.wait_until_succeeds("pgrep -U 1000000 -x cat", timeout=5))
+print(machine.succeed(f"fortify-test filter {pid} c698b081ff957afe17a6d94374537d37f2a63f6f9dd75da7546542407a9e32476ebda3312ba7785d7f618542bcfaf27ca27dcc2dddba852069d28bcfe8cad39a &>/dev/stdout", timeout=5))
+machine.succeed(f"kill -TERM {pid}")
+
+# Verify capabilities/securebits in user namespace:
+print(machine.succeed("sudo -u alice -i fortify run capsh --print"))
+print(machine.succeed("sudo -u alice -i fortify run capsh --has-no-new-privs"))
+print(machine.fail("sudo -u alice -i fortify run capsh --has-a=CAP_SYS_ADMIN"))
+print(machine.fail("sudo -u alice -i fortify run capsh --has-b=CAP_SYS_ADMIN"))
+print(machine.fail("sudo -u alice -i fortify run capsh --has-i=CAP_SYS_ADMIN"))
+print(machine.fail("sudo -u alice -i fortify run capsh --has-p=CAP_SYS_ADMIN"))
+print(machine.fail("sudo -u alice -i fortify run umount -R /dev"))
+
+# Check sandbox outcome:
+check_offset = 0
+def check_sandbox(name):
+    global check_offset
+    check_offset += 1
+    swaymsg(f"exec script /dev/null -E always -qec check-sandbox-{name}")
+    machine.wait_for_file(f"/tmp/fortify.1000/tmpdir/{check_offset}/sandbox-ok", timeout=15)
+
+
+check_sandbox("preset")
+check_sandbox("tty")
+check_sandbox("mapuid")
+
+# Exit Sway and verify process exit status 0:
+swaymsg("exit", succeed=False)
+machine.wait_for_file("/tmp/sway-exit-ok")
+
+# Print fortify runDir contents:
+print(machine.succeed("find /run/user/1000/fortify"))

test/sandbox/tool/main.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+	"log"
+	"os"
+	"strconv"
+	"strings"
+
+	"git.gensokyo.uk/security/fortify/test/sandbox"
+)
+
+func main() {
+	log.SetFlags(0)
+	log.SetPrefix("test: ")
+
+	if len(os.Args) < 2 {
+		log.Fatal("invalid argument")
+	}
+
+	switch os.Args[1] {
+	case "filter":
+		if len(os.Args) != 4 {
+			log.Fatal("invalid argument")
+		}
+
+		if pid, err := strconv.Atoi(strings.TrimSpace(os.Args[2])); err != nil {
+			log.Fatalf("%s", err)
+		} else if pid < 1 {
+			log.Fatalf("%d out of range", pid)
+		} else {
+			sandbox.MustCheckFilter(pid, os.Args[3])
+			return
+		}
+
+	default:
+		(&sandbox.T{FS: os.DirFS("/")}).MustCheckFile(os.Args[1], "/tmp/sandbox-ok")
+		return
+	}
+}

test/sandbox/tool/package.nix

@@ -0,0 +1,30 @@
+{
+  lib,
+  buildGoModule,
+  pkg-config,
+  util-linux,
+
+  version,
+}:
+buildGoModule rec {
+  pname = "check-sandbox";
+  inherit version;
+
+  src = builtins.path {
+    name = "${pname}-src";
+    path = lib.cleanSource ../.;
+    filter = path: type: (type == "directory") || (type == "regular" && lib.hasSuffix ".go" path);
+  };
+  vendorHash = null;
+
+  buildInputs = [ util-linux ];
+  nativeBuildInputs = [ pkg-config ];
+
+  preBuild = ''
+    go mod init git.gensokyo.uk/security/fortify/test/sandbox >& /dev/null
+  '';
+
+  postInstall = ''
+    mv $out/bin/tool $out/bin/fortify-test
+  '';
+}

test/test.py

@@ -99,34 +99,15 @@ print(denyOutputVerbose)
 # Fail direct fsu call:
 print(machine.fail("sudo -u alice -i fsu"))
 
-# Verify capabilities/securebits in user namespace:
-print(machine.succeed("sudo -u alice -i fortify run capsh --print"))
-print(machine.succeed("sudo -u alice -i fortify run capsh --has-no-new-privs"))
-print(machine.fail("sudo -u alice -i fortify run capsh --has-a=CAP_SYS_ADMIN"))
-print(machine.fail("sudo -u alice -i fortify run capsh --has-b=CAP_SYS_ADMIN"))
-print(machine.fail("sudo -u alice -i fortify run capsh --has-i=CAP_SYS_ADMIN"))
-print(machine.fail("sudo -u alice -i fortify run capsh --has-p=CAP_SYS_ADMIN"))
-print(machine.fail("sudo -u alice -i fortify run umount -R /dev"))
-
 # Verify PrintBaseError behaviour:
 if denyOutput != "fsu: uid 1001 is not in the fsurc file\n":
     raise Exception(f"unexpected deny output:\n{denyOutput}")
 if denyOutputVerbose != "fsu: uid 1001 is not in the fsurc file\nfortify: *cannot obtain uid from fsu: permission denied\n":
     raise Exception(f"unexpected deny verbose output:\n{denyOutputVerbose}")
 
-# Check sandbox outcome:
 check_offset = 0
-def check_sandbox(name):
-    global check_offset
-    check_offset += 1
-    swaymsg(f"exec script /dev/null -E always -qec check-sandbox-{name}")
-    machine.wait_for_file(f"/tmp/fortify.1000/tmpdir/{check_offset}/sandbox-ok", timeout=15)
 
 
-check_sandbox("preset")
-check_sandbox("tty")
-check_sandbox("mapuid")
-
 def aid(offset):
     return 1+check_offset+offset