app: run in native sandbox

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

internal/app/shim/main.go

@@ -7,18 +7,26 @@ import (
 	"os"
 	"os/exec"
 	"os/signal"
-	"path"
-	"strconv"
 	"syscall"
+	"time"
 
-	"git.gensokyo.uk/security/fortify/fst"
-	"git.gensokyo.uk/security/fortify/helper"
 	"git.gensokyo.uk/security/fortify/internal"
-	"git.gensokyo.uk/security/fortify/internal/app/init0"
 	"git.gensokyo.uk/security/fortify/internal/fmsg"
 	"git.gensokyo.uk/security/fortify/sandbox"
 )
 
+const Env = "FORTIFY_SHIM"
+
+type Params struct {
+	// finalised container params
+	Container *sandbox.Params
+	// path to outer home directory
+	Home string
+
+	// verbosity pass through
+	Verbose bool
+}
+
 // everything beyond this point runs as unconstrained target user
 // proceed with caution!
 
@@ -27,17 +35,15 @@ func Main() {
 	// USE WITH CAUTION
 	fmsg.Prepare("shim")
 
-	// setting this prevents ptrace
 	if err := sandbox.SetDumpable(sandbox.SUID_DUMP_DISABLE); err != nil {
 		log.Fatalf("cannot set SUID_DUMP_DISABLE: %s", err)
 	}
 
-	// receive setup payload
 	var (
-		payload    Payload
+		params     Params
 		closeSetup func() error
 	)
-	if f, err := sandbox.Receive(Env, &payload, nil); err != nil {
+	if f, err := sandbox.Receive(Env, &params, nil); err != nil {
 		if errors.Is(err, sandbox.ErrInvalid) {
 			log.Fatal("invalid config descriptor")
 		}
@@ -45,32 +51,26 @@ func Main() {
 			log.Fatal("FORTIFY_SHIM not set")
 		}
 
-		log.Fatalf("cannot decode shim setup payload: %v", err)
+		log.Fatalf("cannot receive shim setup params: %v", err)
 	} else {
-		internal.InstallFmsg(payload.Verbose)
+		internal.InstallFmsg(params.Verbose)
 		closeSetup = f
 	}
 
-	if payload.Bwrap == nil {
-		log.Fatal("bwrap config not supplied")
-	}
-
-	// restore bwrap sync fd
-	var syncFd *os.File
-	if payload.Sync != nil {
-		syncFd = os.NewFile(*payload.Sync, "sync")
+	if params.Container == nil || params.Container.Ops == nil {
+		log.Fatal("invalid container params")
 	}
 
 	// close setup socket
 	if err := closeSetup(); err != nil {
-		log.Println("cannot close setup pipe:", err)
+		log.Printf("cannot close setup pipe: %v", err)
 		// not fatal
 	}
 
 	// ensure home directory as target user
-	if s, err := os.Stat(payload.Home); err != nil {
+	if s, err := os.Stat(params.Home); err != nil {
 		if os.IsNotExist(err) {
-			if err = os.Mkdir(payload.Home, 0700); err != nil {
+			if err = os.Mkdir(params.Home, 0700); err != nil {
 				log.Fatalf("cannot create home directory: %v", err)
 			}
 		} else {
@@ -79,72 +79,37 @@ func Main() {
 
 		// home directory is created, proceed
 	} else if !s.IsDir() {
-		log.Fatalf("data path %q is not a directory", payload.Home)
+		log.Fatalf("path %q is not a directory", params.Home)
 	}
 
-	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 {
-			log.Fatal("no command was specified and environment is unset")
-		}
-		if ic.Argv0, ok = payload.Bwrap.SetEnv["SHELL"]; !ok {
-			log.Fatal("no command was specified and $SHELL was unset")
-		}
-
-		ic.Argv = []string{ic.Argv0}
+	var name string
+	if len(params.Container.Args) > 0 {
+		name = params.Container.Args[0]
 	}
-
-	conf := payload.Bwrap
-
-	var extraFiles []*os.File
-
-	// serve setup payload
-	if fd, encoder, err := sandbox.Setup(&extraFiles); err != nil {
-		log.Fatalf("cannot pipe: %v", err)
-	} else {
-		conf.SetEnv[init0.Env] = strconv.Itoa(fd)
-		go func() {
-			fmsg.Verbose("transmitting config to init")
-			if err = encoder.Encode(&ic); err != nil {
-				log.Fatalf("cannot transmit init config: %v", err)
-			}
-		}()
-	}
-
-	helper.BubblewrapName = payload.Exec[0] // resolved bwrap path by parent
-
 	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
 	defer stop() // unreachable
-	if b, err := helper.NewBwrap(
-		ctx, path.Join(fst.Tmp, "sbin/init0"),
-		nil, false,
-		func(int, int) []string { return make([]string, 0) },
-		func(cmd *exec.Cmd) { cmd.Stdin, cmd.Stdout, cmd.Stderr = os.Stdin, os.Stdout, os.Stderr },
-		extraFiles,
-		conf, syncFd,
-	); err != nil {
-		log.Fatalf("malformed sandbox config: %v", err)
-	} else {
-		// run and pass through exit code
-		if err = b.Start(); err != nil {
-			log.Fatalf("cannot start target process: %v", err)
-		} else if err = b.Wait(); err != nil {
-			var exitError *exec.ExitError
-			if !errors.As(err, &exitError) {
-				log.Printf("wait: %v", err)
-				internal.Exit(127)
-				panic("unreachable")
+	container := sandbox.New(ctx, name)
+	container.Params = *params.Container
+	container.Stdin, container.Stdout, container.Stderr = os.Stdin, os.Stdout, os.Stderr
+	container.Cancel = func(cmd *exec.Cmd) error { return cmd.Process.Signal(os.Interrupt) }
+	container.WaitDelay = 2 * time.Second
+
+	if err := container.Start(); err != nil {
+		fmsg.PrintBaseError(err, "cannot start container:")
+		os.Exit(1)
+	}
+	if err := container.Serve(); err != nil {
+		fmsg.PrintBaseError(err, "cannot configure container:")
+	}
+	if err := container.Wait(); err != nil {
+		var exitError *exec.ExitError
+		if !errors.As(err, &exitError) {
+			if errors.Is(err, context.Canceled) {
+				os.Exit(2)
 			}
-			internal.Exit(exitError.ExitCode())
-			panic("unreachable")
+			log.Printf("wait: %v", err)
+			os.Exit(127)
 		}
+		os.Exit(exitError.ExitCode())
 	}
 }

internal/app/shim/payload.go

@@ -1,23 +0,0 @@
-package shim
-
-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
-	// path to outer home directory
-	Home string
-	// sync fd
-	Sync *uintptr
-
-	// verbosity pass through
-	Verbose bool
-}

internal/app/shim/proc.go

@@ -8,9 +8,9 @@ import (
 	"os/exec"
 	"strconv"
 	"strings"
+	"syscall"
 	"time"
 
-	"git.gensokyo.uk/security/fortify/helper/proc"
 	"git.gensokyo.uk/security/fortify/internal"
 	"git.gensokyo.uk/security/fortify/internal/fmsg"
 	"git.gensokyo.uk/security/fortify/sandbox"
@@ -25,10 +25,11 @@ type Shim struct {
 	killFallback chan error
 	// monitor to shim encoder
 	encoder *gob.Encoder
-	// bwrap --sync-fd value
-	sync *uintptr
 }
 
+func (s *Shim) Unwrap() *exec.Cmd    { return s.cmd }
+func (s *Shim) Fallback() chan error { return s.killFallback }
+
 func (s *Shim) String() string {
 	if s.cmd == nil {
 		return "(unused shim manager)"
@@ -36,21 +37,9 @@ func (s *Shim) String() string {
 	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(
-	// string representation of application id
 	aid string,
-	// string representation of supplementary group ids
 	supp []string,
-	// bwrap --sync-fd
-	syncFd *os.File,
 ) (*time.Time, error) {
 	// prepare user switcher invocation
 	fsuPath := internal.MustFsuPath()
@@ -76,12 +65,6 @@ func (s *Shim) Start(
 	s.cmd.Stdin, s.cmd.Stdout, s.cmd.Stderr = os.Stdin, os.Stdout, os.Stderr
 	s.cmd.Dir = "/"
 
-	// pass sync fd if set
-	if syncFd != nil {
-		fd := proc.ExtraFile(s.cmd, syncFd)
-		s.sync = &fd
-	}
-
 	fmsg.Verbose("starting shim via fsu:", s.cmd)
 	// withhold messages to stderr
 	fmsg.Suspend()
@@ -90,10 +73,11 @@ func (s *Shim) Start(
 			"cannot start fsu:")
 	}
 	startTime := time.Now().UTC()
+
 	return &startTime, nil
 }
 
-func (s *Shim) Serve(ctx context.Context, payload *Payload) error {
+func (s *Shim) Serve(ctx context.Context, params *Params) error {
 	// kill shim if something goes wrong and an error is returned
 	s.killFallback = make(chan error, 1)
 	killShim := func() {
@@ -103,9 +87,8 @@ func (s *Shim) Serve(ctx context.Context, payload *Payload) error {
 	}
 	defer func() { killShim() }()
 
-	payload.Sync = s.sync
 	encodeErr := make(chan error)
-	go func() { encodeErr <- s.encoder.Encode(payload) }()
+	go func() { encodeErr <- s.encoder.Encode(params) }()
 
 	select {
 	// encode return indicates setup completion
@@ -121,11 +104,11 @@ func (s *Shim) Serve(ctx context.Context, payload *Payload) error {
 	case <-ctx.Done():
 		err := ctx.Err()
 		if errors.Is(err, context.Canceled) {
-			return fmsg.WrapError(errors.New("shim setup canceled"),
+			return fmsg.WrapError(syscall.ECANCELED,
 				"shim setup canceled")
 		}
 		if errors.Is(err, context.DeadlineExceeded) {
-			return fmsg.WrapError(errors.New("deadline exceeded waiting for shim"),
+			return fmsg.WrapError(syscall.ETIMEDOUT,
 				"deadline exceeded waiting for shim")
 		}
 		// unreachable