helper/bwrap: separate sequential/static args

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

helper/bwrap.go

@@ -20,7 +20,7 @@ type bubblewrap struct {
 	name string
 
 	// bwrap pipes
-	p *pipes
+	control *pipes
 	// sync pipe
 	sync *os.File
 	// returns an array of arguments passed directly
@@ -29,7 +29,7 @@ type bubblewrap struct {
 
 	// pipes received by the child
 	// nil if no pipes are required
-	cp *pipes
+	controlPt *pipes
 
 	lock sync.RWMutex
 	*exec.Cmd
@@ -39,7 +39,7 @@ func (b *bubblewrap) StartNotify(ready chan error) error {
 	b.lock.Lock()
 	defer b.lock.Unlock()
 
-	if ready != nil && b.cp == nil {
+	if ready != nil && b.controlPt == nil {
 		panic("attempted to start with status monitoring on a bwrap child initialised without pipes")
 	}
 
@@ -50,16 +50,16 @@ func (b *bubblewrap) StartNotify(ready chan error) error {
 	}
 
 	// prepare bwrap pipe and args
-	if argsFD, _, err := b.p.prepareCmd(b.Cmd); err != nil {
+	if argsFD, _, err := b.control.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 {
+	if b.controlPt != nil {
-		b.cp.ready = ready
+		b.controlPt.ready = ready
-		if argsFD, statFD, err := b.cp.prepareCmd(b.Cmd); err != nil {
+		if argsFD, statFD, err := b.controlPt.prepareCmd(b.Cmd); err != nil {
 			return err
 		} else {
 			b.Cmd.Args = append(b.Cmd.Args, b.argF(argsFD, statFD)...)
@@ -70,7 +70,7 @@ func (b *bubblewrap) StartNotify(ready chan error) error {
 
 	if ready != nil {
 		b.Cmd.Env = append(b.Cmd.Env, FortifyHelper+"=1", FortifyStatus+"=1")
-	} else if b.cp != nil {
+	} else if b.controlPt != nil {
 		b.Cmd.Env = append(b.Cmd.Env, FortifyHelper+"=1", FortifyStatus+"=0")
 	} else {
 		b.Cmd.Env = append(b.Cmd.Env, FortifyHelper+"=1", FortifyStatus+"=-1")
@@ -85,13 +85,13 @@ func (b *bubblewrap) StartNotify(ready chan error) error {
 	}
 
 	// write bwrap args first
-	if err := b.p.readyWriteArgs(); err != nil {
+	if err := b.control.readyWriteArgs(); err != nil {
 		return err
 	}
 
 	// write child args if enabled
-	if b.cp != nil {
+	if b.controlPt != nil {
-		if err := b.cp.readyWriteArgs(); err != nil {
+		if err := b.controlPt.readyWriteArgs(); err != nil {
 			return err
 		}
 	}
@@ -100,11 +100,11 @@ func (b *bubblewrap) StartNotify(ready chan error) error {
 }
 
 func (b *bubblewrap) Close() error {
-	if b.cp == nil {
+	if b.controlPt == nil {
 		panic("attempted to close bwrap child initialised without pipes")
 	}
 
-	return b.cp.closeStatus()
+	return b.controlPt.closeStatus()
 }
 
 func (b *bubblewrap) Start() error {
@@ -136,14 +136,14 @@ func NewBwrap(conf *bwrap.Config, wt io.WriterTo, name string, argF func(argsFD,
 	if args, err := NewCheckedArgs(conf.Args()); err != nil {
 		return nil, err
 	} else {
-		b.p = &pipes{args: args}
+		b.control = &pipes{args: args}
 	}
 
 	b.sync = conf.Sync()
 	b.argF = argF
 	b.name = name
 	if wt != nil {
-		b.cp = &pipes{args: wt}
+		b.controlPt = &pipes{args: wt}
 	}
 	b.Cmd = execCommand(BubblewrapName)
 

helper/bwrap/arg.static.awkward.go

@@ -1,23 +0,0 @@
-package bwrap
-
-const (
-	Tmpfs = iota
-	Dir
-	Symlink
-
-	OverlaySrc
-	Overlay
-	TmpOverlay
-	ROOverlay
-)
-
-var awkwardArgs = [...]string{
-	Tmpfs:   "--tmpfs",
-	Dir:     "--dir",
-	Symlink: "--symlink",
-
-	OverlaySrc: "--overlay-src",
-	Overlay:    "--overlay",
-	TmpOverlay: "--tmp-overlay",
-	ROOverlay:  "--ro-overlay",
-}

helper/bwrap/arg.static.bool.go

@@ -1,81 +0,0 @@
-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

@@ -1,47 +0,0 @@
-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

@@ -1,73 +0,0 @@
-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

@@ -1,65 +0,0 @@
-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/builder.go

@@ -39,46 +39,60 @@ func (c *Config) Bind(src, dest string, opts ...bool) *Config {
 
 	if dev {
 		if try {
-			c.Filesystem = append(c.Filesystem, &pairF{pairArgs[DevBindTry], src, dest})
+			c.Filesystem = append(c.Filesystem, &pairF{DevBindTry.Unwrap(), src, dest})
 		} else {
-			c.Filesystem = append(c.Filesystem, &pairF{pairArgs[DevBind], src, dest})
+			c.Filesystem = append(c.Filesystem, &pairF{DevBind.Unwrap(), src, dest})
 		}
 		return c
 	} else if write {
 		if try {
-			c.Filesystem = append(c.Filesystem, &pairF{pairArgs[BindTry], src, dest})
+			c.Filesystem = append(c.Filesystem, &pairF{BindTry.Unwrap(), src, dest})
 		} else {
-			c.Filesystem = append(c.Filesystem, &pairF{pairArgs[Bind], src, dest})
+			c.Filesystem = append(c.Filesystem, &pairF{Bind.Unwrap(), src, dest})
 		}
 		return c
 	} else {
 		if try {
-			c.Filesystem = append(c.Filesystem, &pairF{pairArgs[ROBindTry], src, dest})
+			c.Filesystem = append(c.Filesystem, &pairF{ROBindTry.Unwrap(), src, dest})
 		} else {
-			c.Filesystem = append(c.Filesystem, &pairF{pairArgs[ROBind], src, dest})
+			c.Filesystem = append(c.Filesystem, &pairF{ROBind.Unwrap(), src, dest})
 		}
 		return c
 	}
 }
 
+// Dir create dir in sandbox
+// (--dir DEST)
+func (c *Config) Dir(dest string) *Config {
+	c.Filesystem = append(c.Filesystem, &stringF{Dir.Unwrap(), 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})
+	c.Filesystem = append(c.Filesystem, &stringF{RemountRO.Unwrap(), 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})
+	c.Filesystem = append(c.Filesystem, &stringF{Procfs.Unwrap(), 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})
+	c.Filesystem = append(c.Filesystem, &stringF{DevTmpfs.Unwrap(), dest})
+	return c
+}
+
+// Mqueue mount new mqueue in sandbox
+// (--mqueue DEST)
+func (c *Config) Mqueue(dest string) *Config {
+	c.Filesystem = append(c.Filesystem, &stringF{Mqueue.Unwrap(), dest})
 	return c
 }
 
@@ -121,20 +135,6 @@ func (c *Config) Persist(dest, rwsrc, workdir string, src ...string) *Config {
 	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{awkwardArgs[Dir], dest})
-	return c
-}
-
 // Symlink create symlink within sandbox
 // (--symlink SRC DEST)
 func (c *Config) Symlink(src, dest string, perm ...os.FileMode) *Config {

helper/bwrap/config.go

@@ -1,17 +1,9 @@
 package bwrap
 
 import (
-	"encoding/gob"
 	"os"
-	"strconv"
 )
 
-func init() {
-	gob.Register(new(PermConfig[SymlinkConfig]))
-	gob.Register(new(PermConfig[*TmpfsConfig]))
-	gob.Register(new(OverlayConfig))
-}
-
 type Config struct {
 	// unshare every namespace we support by default if nil
 	// (--unshare-all)
@@ -124,153 +116,3 @@ type UnshareConfig struct {
 	// 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 OverlayConfig struct {
-	/*
-		read files from SRC in the following overlay
-		(--overlay-src SRC)
-	*/
-	Src []string `json:"src,omitempty"`
-
-	/*
-		mount overlayfs on DEST, with RWSRC as the host path for writes and
-		WORKDIR an empty directory on the same filesystem as RWSRC
-		(--overlay RWSRC WORKDIR DEST)
-
-		if nil, mount overlayfs on DEST, with writes going to an invisible tmpfs
-		(--tmp-overlay DEST)
-
-		if either strings are empty, mount overlayfs read-only on DEST
-		(--ro-overlay DEST)
-	*/
-	Persist *[2]string `json:"persist,omitempty"`
-
-	/*
-		--overlay RWSRC WORKDIR DEST
-
-		--tmp-overlay DEST
-
-		--ro-overlay DEST
-	*/
-	Dest string `json:"dest"`
-}
-
-func (o *OverlayConfig) Path() string {
-	return o.Dest
-}
-
-func (o *OverlayConfig) Len() int {
-	// (--tmp-overlay DEST) or (--ro-overlay DEST)
-	p := 2
-	// (--overlay RWSRC WORKDIR DEST)
-	if o.Persist != nil && o.Persist[0] != "" && o.Persist[1] != "" {
-		p = 4
-	}
-
-	return p + len(o.Src)*2
-}
-
-func (o *OverlayConfig) Append(args *[]string) {
-	// --overlay-src SRC
-	for _, src := range o.Src {
-		*args = append(*args, awkwardArgs[OverlaySrc], src)
-	}
-
-	if o.Persist != nil {
-		if o.Persist[0] != "" && o.Persist[1] != "" {
-			// --overlay RWSRC WORKDIR
-			*args = append(*args, awkwardArgs[Overlay], o.Persist[0], o.Persist[1])
-		} else {
-			// --ro-overlay
-			*args = append(*args, awkwardArgs[ROOverlay])
-		}
-	} else {
-		// --tmp-overlay
-		*args = append(*args, awkwardArgs[TmpOverlay])
-	}
-
-	// DEST
-	*args = append(*args, o.Dest)
-}
-
-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_test.go

@@ -1,6 +1,7 @@
 package bwrap_test
 
 import (
+	"os"
 	"slices"
 	"testing"
 
@@ -13,6 +14,83 @@ func TestConfig_Args(t *testing.T) {
 		conf *bwrap.Config
 		want []string
 	}{
+		{
+			name: "bind",
+			conf: (new(bwrap.Config)).
+				Bind("/etc", "/.fortify/etc").
+				Bind("/etc", "/.fortify/etc", true).
+				Bind("/run", "/.fortify/run", false, true).
+				Bind("/sys/devices", "/.fortify/sys/devices", true, true).
+				Bind("/dev/dri", "/.fortify/dev/dri", false, true, true).
+				Bind("/dev/dri", "/.fortify/dev/dri", true, true, true),
+			want: []string{
+				"--unshare-all", "--unshare-user",
+				"--disable-userns", "--assert-userns-disabled",
+				// Bind("/etc", "/.fortify/etc")
+				"--ro-bind", "/etc", "/.fortify/etc",
+				// Bind("/etc", "/.fortify/etc", true)
+				"--ro-bind-try", "/etc", "/.fortify/etc",
+				// Bind("/run", "/.fortify/run", false, true)
+				"--bind", "/run", "/.fortify/run",
+				// Bind("/sys/devices", "/.fortify/sys/devices", true, true)
+				"--bind-try", "/sys/devices", "/.fortify/sys/devices",
+				// Bind("/dev/dri", "/.fortify/dev/dri", false, true, true)
+				"--dev-bind", "/dev/dri", "/.fortify/dev/dri",
+				// Bind("/dev/dri", "/.fortify/dev/dri", true, true, true)
+				"--dev-bind-try", "/dev/dri", "/.fortify/dev/dri",
+			},
+		},
+		{
+			name: "dir remount-ro proc dev mqueue",
+			conf: (new(bwrap.Config)).
+				Dir("/.fortify").
+				RemountRO("/home").
+				Procfs("/proc").
+				DevTmpfs("/dev").
+				Mqueue("/dev/mqueue"),
+			want: []string{
+				"--unshare-all", "--unshare-user",
+				"--disable-userns", "--assert-userns-disabled",
+				// Dir("/.fortify")
+				"--dir", "/.fortify",
+				// RemountRO("/home")
+				"--remount-ro", "/home",
+				// Procfs("/proc")
+				"--proc", "/proc",
+				// DevTmpfs("/dev")
+				"--dev", "/dev",
+				// Mqueue("/dev/mqueue")
+				"--mqueue", "/dev/mqueue",
+			},
+		},
+		{
+			name: "tmpfs",
+			conf: (new(bwrap.Config)).
+				Tmpfs("/run/user", 8192).
+				Tmpfs("/run/dbus", 8192, 0755),
+			want: []string{
+				"--unshare-all", "--unshare-user",
+				"--disable-userns", "--assert-userns-disabled",
+				// Tmpfs("/run/user", 8192)
+				"--size", "8192", "--tmpfs", "/run/user",
+				// Tmpfs("/run/dbus", 8192, 0755)
+				"--perms", "755", "--size", "8192", "--tmpfs", "/run/dbus",
+			},
+		},
+		{
+			name: "symlink",
+			conf: (new(bwrap.Config)).
+				Symlink("/.fortify/sbin/init", "/sbin/init").
+				Symlink("/.fortify/sbin/init", "/sbin/init", 0755),
+			want: []string{
+				"--unshare-all", "--unshare-user",
+				"--disable-userns", "--assert-userns-disabled",
+				// Symlink("/.fortify/sbin/init", "/sbin/init")
+				"--symlink", "/.fortify/sbin/init", "/sbin/init",
+				// Symlink("/.fortify/sbin/init", "/sbin/init", 0755)
+				"--perms", "755", "--symlink", "/.fortify/sbin/init", "/sbin/init",
+			},
+		},
 		{
 			name: "overlayfs",
 			conf: (new(bwrap.Config)).
@@ -32,6 +110,64 @@ func TestConfig_Args(t *testing.T) {
 				"--overlay", "/data/data/org.chromium.Chromium/overlay/rwsrc", "/data/data/org.chromium.Chromium/workdir", "/nix",
 			},
 		},
+		{
+			name: "unshare",
+			conf: &bwrap.Config{Unshare: &bwrap.UnshareConfig{
+				User:   false,
+				IPC:    false,
+				PID:    false,
+				Net:    false,
+				UTS:    false,
+				CGroup: false,
+			}},
+			want: []string{"--disable-userns", "--assert-userns-disabled"},
+		},
+		{
+			name: "uid gid sync",
+			conf: (new(bwrap.Config)).
+				SetUID(1971).
+				SetGID(100).
+				SetSync(os.Stdin),
+			want: []string{
+				"--unshare-all", "--unshare-user",
+				"--disable-userns", "--assert-userns-disabled",
+				// SetUID(1971)
+				"--uid", "1971",
+				// SetGID(100)
+				"--gid", "100",
+				// SetSync(os.Stdin)
+				// this is set when the process is created
+			},
+		},
+		{
+			name: "hostname chdir setenv unsetenv lockfile chmod",
+			conf: &bwrap.Config{
+				Hostname: "fortify",
+				Chdir:    "/.fortify",
+				SetEnv:   map[string]string{"FORTIFY_INIT": "/.fortify/sbin/init"},
+				UnsetEnv: []string{"HOME", "HOST"},
+				LockFile: []string{"/.fortify/lock"},
+				Chmod:    map[string]os.FileMode{"/.fortify/sbin/init": 0755},
+			},
+			want: []string{
+				"--unshare-all", "--unshare-user",
+				"--disable-userns", "--assert-userns-disabled",
+				// Hostname: "fortify"
+				"--hostname", "fortify",
+				// Chdir: "/.fortify"
+				"--chdir", "/.fortify",
+				// UnsetEnv: []string{"HOME", "HOST"}
+				"--unsetenv", "HOME",
+				"--unsetenv", "HOST",
+				// LockFile: []string{"/.fortify/lock"},
+				"--lock-file", "/.fortify/lock",
+				// SetEnv: map[string]string{"FORTIFY_INIT": "/.fortify/sbin/init"}
+				"--setenv", "FORTIFY_INIT", "/.fortify/sbin/init",
+				// Chmod: map[string]os.FileMode{"/.fortify/sbin/init": 0755}
+				"--chmod", "755", "/.fortify/sbin/init",
+			},
+		},
+
 		{
 			name: "xdg-dbus-proxy constraint sample",
 			conf: (&bwrap.Config{
@@ -90,148 +226,6 @@ func TestConfig_Args(t *testing.T) {
 				"--ro-bind", "/etc", "/etc",
 			},
 		},
-		{
-			name: "fortify permissive default nixos",
-			conf: (&bwrap.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 {
@@ -241,4 +235,21 @@ func TestConfig_Args(t *testing.T) {
 			}
 		})
 	}
+
+	// test persist validation
+	t.Run("invalid persist", func(t *testing.T) {
+		defer func() {
+			wantPanic := "persist called without required paths"
+			if r := recover(); r != wantPanic {
+				t.Errorf("Persist() panic = %v; wantPanic %v", r, wantPanic)
+			}
+		}()
+		(new(bwrap.Config)).Persist("/run", "", "")
+	})
+
+	t.Run("sync file", func(t *testing.T) {
+		if s := (new(bwrap.Config)).SetSync(os.Stdout).Sync(); s != os.Stdout {
+			t.Errorf("Sync() = %v", s)
+		}
+	})
 }

helper/bwrap/sequential.go

@@ -0,0 +1,223 @@
+package bwrap
+
+import (
+	"encoding/gob"
+	"os"
+	"strconv"
+)
+
+func init() {
+	gob.Register(new(PermConfig[SymlinkConfig]))
+	gob.Register(new(PermConfig[*TmpfsConfig]))
+	gob.Register(new(OverlayConfig))
+}
+
+type PositionalArg int
+
+func (p PositionalArg) Unwrap() string {
+	return positionalArgs[p]
+}
+
+const (
+	Tmpfs PositionalArg = iota
+	Symlink
+
+	Bind
+	BindTry
+	DevBind
+	DevBindTry
+	ROBind
+	ROBindTry
+
+	Chmod
+	Dir
+	RemountRO
+	Procfs
+	DevTmpfs
+	Mqueue
+
+	Perms
+	Size
+
+	OverlaySrc
+	Overlay
+	TmpOverlay
+	ROOverlay
+)
+
+var positionalArgs = [...]string{
+	Tmpfs:   "--tmpfs",
+	Symlink: "--symlink",
+
+	Bind:       "--bind",
+	BindTry:    "--bind-try",
+	DevBind:    "--dev-bind",
+	DevBindTry: "--dev-bind-try",
+	ROBind:     "--ro-bind",
+	ROBindTry:  "--ro-bind-try",
+
+	Chmod:     "--chmod",
+	Dir:       "--dir",
+	RemountRO: "--remount-ro",
+	Procfs:    "--proc",
+	DevTmpfs:  "--dev",
+	Mqueue:    "--mqueue",
+
+	Perms: "--perms",
+	Size:  "--size",
+
+	OverlaySrc: "--overlay-src",
+	Overlay:    "--overlay",
+	TmpOverlay: "--tmp-overlay",
+	ROOverlay:  "--ro-overlay",
+}
+
+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, Perms.Unwrap(), 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, Size.Unwrap(), strconv.Itoa(t.Size))
+	}
+	*args = append(*args, Tmpfs.Unwrap(), t.Dir)
+}
+
+type OverlayConfig struct {
+	/*
+		read files from SRC in the following overlay
+		(--overlay-src SRC)
+	*/
+	Src []string `json:"src,omitempty"`
+
+	/*
+		mount overlayfs on DEST, with RWSRC as the host path for writes and
+		WORKDIR an empty directory on the same filesystem as RWSRC
+		(--overlay RWSRC WORKDIR DEST)
+
+		if nil, mount overlayfs on DEST, with writes going to an invisible tmpfs
+		(--tmp-overlay DEST)
+
+		if either strings are empty, mount overlayfs read-only on DEST
+		(--ro-overlay DEST)
+	*/
+	Persist *[2]string `json:"persist,omitempty"`
+
+	/*
+		--overlay RWSRC WORKDIR DEST
+
+		--tmp-overlay DEST
+
+		--ro-overlay DEST
+	*/
+	Dest string `json:"dest"`
+}
+
+func (o *OverlayConfig) Path() string {
+	return o.Dest
+}
+
+func (o *OverlayConfig) Len() int {
+	// (--tmp-overlay DEST) or (--ro-overlay DEST)
+	p := 2
+	// (--overlay RWSRC WORKDIR DEST)
+	if o.Persist != nil && o.Persist[0] != "" && o.Persist[1] != "" {
+		p = 4
+	}
+
+	return p + len(o.Src)*2
+}
+
+func (o *OverlayConfig) Append(args *[]string) {
+	// --overlay-src SRC
+	for _, src := range o.Src {
+		*args = append(*args, OverlaySrc.Unwrap(), src)
+	}
+
+	if o.Persist != nil {
+		if o.Persist[0] != "" && o.Persist[1] != "" {
+			// --overlay RWSRC WORKDIR
+			*args = append(*args, Overlay.Unwrap(), o.Persist[0], o.Persist[1])
+		} else {
+			// --ro-overlay
+			*args = append(*args, ROOverlay.Unwrap())
+		}
+	} else {
+		// --tmp-overlay
+		*args = append(*args, TmpOverlay.Unwrap())
+	}
+
+	// DEST
+	*args = append(*args, o.Dest)
+}
+
+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, Symlink.Unwrap(), 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, Chmod.Unwrap(), strconv.FormatInt(int64(mode), 8), path)
+	}
+}

helper/bwrap/static.go

@@ -0,0 +1,249 @@
+package bwrap
+
+import (
+	"slices"
+	"strconv"
+)
+
+/*
+	static boolean args
+*/
+
+type BoolArg int
+
+func (b BoolArg) Unwrap() []string {
+	return boolArgs[b]
+}
+
+const (
+	UnshareAll BoolArg = 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, BoolArg(i).Unwrap()...)
+		}
+	}
+}
+
+/*
+	static integer args
+*/
+
+type IntArg int
+
+func (i IntArg) Unwrap() string {
+	return intArgs[i]
+}
+
+const (
+	UID IntArg = iota
+	GID
+)
+
+var intArgs = [...]string{
+	UID: "--uid",
+	GID: "--gid",
+}
+
+func (c *Config) intArgs() 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, IntArg(i).Unwrap(), strconv.Itoa(*v))
+		}
+	}
+}
+
+/*
+	static string args
+*/
+
+type StringArg int
+
+func (s StringArg) Unwrap() string {
+	return stringArgs[s]
+}
+
+const (
+	Hostname StringArg = iota
+	Chdir
+	UnsetEnv
+	LockFile
+)
+
+var stringArgs = [...]string{
+	Hostname: "--hostname",
+	Chdir:    "--chdir",
+	UnsetEnv: "--unsetenv",
+	LockFile: "--lock-file",
+}
+
+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}
+	}
+
+	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, StringArg(i).Unwrap(), v)
+		}
+	}
+}
+
+/*
+	static pair args
+*/
+
+type PairArg int
+
+func (p PairArg) Unwrap() string {
+	return pairArgs[p]
+}
+
+const (
+	SetEnv PairArg = iota
+)
+
+var pairArgs = [...]string{
+	SetEnv: "--setenv",
+}
+
+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]}
+	}
+
+	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, PairArg(i).Unwrap(), v[0], v[1])
+		}
+	}
+}