main: accept -dev, -nodev, -suid, -nosuid, -exec, -noexec

When mounted via /etc/fstab like this,

  /a /b fuse.gocryptfs default 0 0

we always get extra options passed. As reported by @mahkoh
at #233 :

  mount passes `-o noexec` if `-o user` is set and `-o exec` is not set.
  If both `-o user` and `-o exec` are set, it passes `-o exec`.

Make these options work, and in addtion, also make -suid and -rw
work the same way.

Reported-by: @mahkoh

cli_args.go

@@ -20,9 +20,11 @@ import (
 type argContainer struct {
 	debug, init, zerokey, fusedebug, openssl, passwd, fg, version,
 	plaintextnames, quiet, nosyslog, wpanic,
-	longnames, allow_other, ro, reverse, aessiv, nonempty, raw64,
+	longnames, allow_other, reverse, aessiv, nonempty, raw64,
 	noprealloc, speed, hkdf, serialize_reads, forcedecode, hh, info,
 	sharedstorage, devrandom, fsck bool
+	// Mount options with opposites
+	dev, nodev, suid, nosuid, exec, noexec, rw, ro bool
 	masterkey, mountpoint, cipherdir, cpuprofile, extpass,
 	memprofile, ko, passfile, ctlsock, fsname, force_owner, trace string
 	// Configuration file name override
@@ -121,7 +123,6 @@ func parseCliOpts() (args argContainer) {
 	flagSet.BoolVar(&args.longnames, "longnames", true, "Store names longer than 176 bytes in extra files")
 	flagSet.BoolVar(&args.allow_other, "allow_other", false, "Allow other users to access the filesystem. "+
 		"Only works if user_allow_other is set in /etc/fuse.conf.")
-	flagSet.BoolVar(&args.ro, "ro", false, "Mount the filesystem read-only")
 	flagSet.BoolVar(&args.reverse, "reverse", false, "Reverse mode")
 	flagSet.BoolVar(&args.aessiv, "aessiv", false, "AES-SIV encryption")
 	flagSet.BoolVar(&args.nonempty, "nonempty", false, "Allow mounting over non-empty directories")
@@ -137,6 +138,17 @@ func parseCliOpts() (args argContainer) {
 	flagSet.BoolVar(&args.sharedstorage, "sharedstorage", false, "Make concurrent access to a shared CIPHERDIR safer")
 	flagSet.BoolVar(&args.devrandom, "devrandom", false, "Use /dev/random for generating master key")
 	flagSet.BoolVar(&args.fsck, "fsck", false, "Run a filesystem check on CIPHERDIR")
+
+	// Mount options with opposites
+	flagSet.BoolVar(&args.dev, "dev", false, "Allow device files")
+	flagSet.BoolVar(&args.nodev, "nodev", false, "Deny device files")
+	flagSet.BoolVar(&args.suid, "suid", false, "Allow suid binaries")
+	flagSet.BoolVar(&args.nosuid, "nosuid", false, "Deny suid binaries")
+	flagSet.BoolVar(&args.exec, "exec", false, "Allow executables")
+	flagSet.BoolVar(&args.noexec, "noexec", false, "Deny executables")
+	flagSet.BoolVar(&args.rw, "rw", false, "Mount the filesystem read-write")
+	flagSet.BoolVar(&args.ro, "ro", false, "Mount the filesystem read-only")
+
 	flagSet.StringVar(&args.masterkey, "masterkey", "", "Mount with explicit master key")
 	flagSet.StringVar(&args.cpuprofile, "cpuprofile", "", "Write cpu profile to specified file")
 	flagSet.StringVar(&args.memprofile, "memprofile", "", "Write memory profile to specified file")
@@ -152,12 +164,6 @@ func parseCliOpts() (args argContainer) {
 		"successful mount - used internally for daemonization")
 	flagSet.IntVar(&args.scryptn, "scryptn", configfile.ScryptDefaultLogN, "scrypt cost parameter logN. Possible values: 10-28. "+
 		"A lower value speeds up mounting and reduces its memory needs, but makes the password susceptible to brute-force attacks")
-	// Ignored otions
-	var dummyBool bool
-	ignoreText := "(ignored for compatibility)"
-	flagSet.BoolVar(&dummyBool, "rw", false, ignoreText)
-	flagSet.BoolVar(&dummyBool, "nosuid", false, ignoreText)
-	flagSet.BoolVar(&dummyBool, "nodev", false, ignoreText)
 	var dummyString string
 	flagSet.StringVar(&dummyString, "o", "", "For compatibility with mount(1), options can be also passed as a comma-separated list to -o on the end.")
 	// Actual parsing

daemonize.go

@@ -37,7 +37,7 @@ func forkChild() int {
 	exitOnUsr1()
 	err := c.Start()
 	if err != nil {
-		tlog.Fatal.Printf("forkChild: starting %s failed: %v\n", name, err)
+		tlog.Fatal.Printf("forkChild: starting %s failed: %v", name, err)
 		return exitcodes.ForkChild
 	}
 	err = c.Wait()
@@ -47,7 +47,7 @@ func forkChild() int {
 				os.Exit(waitstat.ExitStatus())
 			}
 		}
-		tlog.Fatal.Printf("forkChild: wait returned an unknown error: %v\n", err)
+		tlog.Fatal.Printf("forkChild: wait returned an unknown error: %v", err)
 		return exitcodes.ForkChild
 	}
 	// The child exited with 0 - let's do the same.

mount.go

@@ -314,17 +314,33 @@ func initGoFuse(fs pathfs.FileSystem, args *argContainer) *fuse.Server {
 	if args.reverse {
 		mOpts.Name += "-reverse"
 	}
-
 	// Add a volume name if running osxfuse. Otherwise the Finder will show it as
 	// something like "osxfuse Volume 0 (gocryptfs)".
 	if runtime.GOOS == "darwin" {
 		mOpts.Options = append(mOpts.Options, "volname="+path.Base(args.mountpoint))
 	}
-
 	// The kernel enforces read-only operation, we just have to pass "ro".
 	// Reverse mounts are always read-only.
 	if args.ro || args.reverse {
 		mOpts.Options = append(mOpts.Options, "ro")
+	} else if args.rw {
+		mOpts.Options = append(mOpts.Options, "rw")
+	}
+	// If both "nosuid" and "suid" were passed, the safer option wins.
+	if args.nosuid {
+		mOpts.Options = append(mOpts.Options, "nosuid")
+	} else if args.suid {
+		mOpts.Options = append(mOpts.Options, "suid")
+	}
+	if args.nodev {
+		mOpts.Options = append(mOpts.Options, "nodev")
+	} else if args.dev {
+		mOpts.Options = append(mOpts.Options, "dev")
+	}
+	if args.noexec {
+		mOpts.Options = append(mOpts.Options, "noexec")
+	} else if args.exec {
+		mOpts.Options = append(mOpts.Options, "exec")
 	}
 	// Add additional mount options (if any) after the stock ones, so the user has
 	// a chance to override them.

tests/cli/cli_test.go

@@ -449,6 +449,30 @@ func TestMultipleOperationFlags(t *testing.T) {
 	}
 }
 
+func TestNoexec(t *testing.T) {
+	dir := test_helpers.InitFS(t)
+	mnt := dir + ".mnt"
+	err := os.Mkdir(mnt, 0700)
+	if err != nil {
+		t.Fatal(err)
+	}
+	test_helpers.MountOrFatal(t, dir, mnt, "-extpass=echo test", "-noexec")
+	defer test_helpers.UnmountPanic(mnt)
+	sh := mnt + "/x.sh"
+	content := `#!/bin/bash
+echo hello
+`
+	err = ioutil.WriteFile(sh, []byte(content), 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = exec.Command(sh).Run()
+	exitCode := test_helpers.ExtractCmdExitCode(err)
+	if exitCode != int(syscall.EACCES) {
+		t.Errorf("got exitcode %d instead of EPERM (%d)", exitCode, syscall.EPERM)
+	}
+}
+
 // Test that a missing argument to "-o" triggers exit code 1.
 // See also cli_args_test.go for comprehensive tests of "-o" parsing.
 func TestMissingOArg(t *testing.T) {

tests/test_helpers/helpers.go

@@ -433,9 +433,14 @@ func ExtractCmdExitCode(err error) int {
 		return 0
 	}
 	// OMG this is convoluted
-	err2 := err.(*exec.ExitError)
-	code := err2.Sys().(syscall.WaitStatus).ExitStatus()
-	return code
+	if err2, ok := err.(*exec.ExitError); ok {
+		return err2.Sys().(syscall.WaitStatus).ExitStatus()
+	}
+	if err2, ok := err.(*os.PathError); ok {
+		return int(err2.Err.(syscall.Errno))
+	}
+	log.Panicf("could not decode error %#v", err)
+	return 0
 }
 
 // ListFds lists our open file descriptors.