Add EME filename encryption & enable it by default

Documentation/MANPAGE.md

@@ -42,6 +42,9 @@ Options:
 **-diriv**
 :	Use per-directory file name IV (default true)
 
+**-emenames**
+:	Use EME filename encryption (default true). This option implies diriv.
+
 **-extpass string**
 :	Use an external program (like ssh-askpass) for the password prompt.
 The program should return the password on stdout, a trailing newline is

cryptfs/config_file.go

@@ -12,10 +12,6 @@ const (
 	// The dot "." is not used in base64url (RFC4648), hence
 	// we can never clash with an encrypted file.
 	ConfDefaultName = "gocryptfs.conf"
-	// Understood Feature Flags
-	// Also teach isFeatureFlagKnown() about any additions
-	FlagPlaintextNames = "PlaintextNames"
-	FlagDirIV          = "DirIV"
 )
 
 type ConfFile struct {
@@ -37,7 +33,7 @@ type ConfFile struct {
 // CreateConfFile - create a new config with a random key encrypted with
 // "password" and write it to "filename".
 // Uses scrypt with cost parameter logN.
-func CreateConfFile(filename string, password string, plaintextNames bool, logN int) error {
+func CreateConfFile(filename string, password string, plaintextNames bool, logN int, EMENames bool) error {
 	var cf ConfFile
 	cf.filename = filename
 
@@ -50,11 +46,13 @@ func CreateConfFile(filename string, password string, plaintextNames bool, logN
 
 	// Set defaults
 	cf.Version = HEADER_CURRENT_VERSION
-	cf.FeatureFlags = []string{FlagDirIV}
 
 	// Set values chosen by the user
 	if plaintextNames {
 		cf.FeatureFlags = append(cf.FeatureFlags, FlagPlaintextNames)
+	} else {
+		cf.FeatureFlags = append(cf.FeatureFlags, FlagDirIV)
+		cf.FeatureFlags = append(cf.FeatureFlags, FlagEMENames)
 	}
 
 	// Write file to disk
@@ -157,10 +155,18 @@ func (cf *ConfFile) WriteFile() error {
 	return nil
 }
 
+const (
+	// Understood Feature Flags.
+	// Also teach isFeatureFlagKnown() about any additions
+	FlagPlaintextNames = "PlaintextNames"
+	FlagDirIV          = "DirIV"
+	FlagEMENames       = "EMENames"
+)
+
 // Verify that we understand a feature flag
 func (cf *ConfFile) isFeatureFlagKnown(flag string) bool {
 	switch flag {
-	case FlagPlaintextNames, FlagDirIV:
+	case FlagPlaintextNames, FlagDirIV, FlagEMENames:
 		return true
 	default:
 		return false

cryptfs/config_test.go

@@ -59,7 +59,7 @@ func TestLoadV2StrangeFeature(t *testing.T) {
 }
 
 func TestCreateConfFile(t *testing.T) {
-	err := CreateConfFile("config_test/tmp.conf", "test", false, 0)
+	err := CreateConfFile("config_test/tmp.conf", "test", false, 10, true)
 	if err != nil {
 		t.Fatal(err)
 	}

cryptfs/cryptfs.go

@@ -25,7 +25,6 @@ type CryptFS struct {
 	cipherBS    uint64
 	// Stores an all-zero block of size cipherBS
 	allZeroBlock   []byte
-	plaintextNames bool
 	// DirIV cache for filename encryption
 	DirIVCacheEnc DirIVCache
 }
@@ -59,7 +58,6 @@ func NewCryptFS(key []byte, useOpenssl bool, plaintextNames bool) *CryptFS {
 		plainBS:        DEFAULT_PLAINBS,
 		cipherBS:       uint64(cipherBS),
 		allZeroBlock:   make([]byte, cipherBS),
-		plaintextNames: plaintextNames,
 	}
 }
 

cryptfs/filter.go

@@ -1,15 +0,0 @@
-package cryptfs
-
-// IsFiltered - check if "path" should be forbidden
-//
-// Used to prevent name clashes with gocryptfs.conf
-// when file names are not encrypted
-func (be *CryptFS) IsFiltered(path string) bool {
-	// gocryptfs.conf in the root directory is forbidden
-	if be.plaintextNames == true && path == ConfDefaultName {
-		Warn.Printf("The name /%s is reserved when -plaintextnames is used\n",
-			ConfDefaultName)
-		return true
-	}
-	return false
-}

cryptfs/log.go

@@ -3,6 +3,7 @@ package cryptfs
 import (
 	"fmt"
 	"strings"
+	"encoding/json"
 )
 
 type logChannel struct {
@@ -26,6 +27,18 @@ func (l *logChannel) Dump(d []byte) {
 	fmt.Println(strings.Replace(s, "\000", "\\0", -1))
 }
 
+func (l *logChannel) JSONDump(obj interface{}) {
+	if !l.enabled {
+		return
+	}
+	b, err := json.MarshalIndent(obj, "", "\t")
+	if err != nil {
+		fmt.Println(err)
+	} else {
+		fmt.Println(string(b))
+	}
+}
+
 func (l *logChannel) Enable() {
 	l.enabled = true
 }

cryptfs/names_core.go

@@ -1,6 +1,6 @@
 package cryptfs
 
-// Filename encryption / decryption function
+// Filename encryption / decryption functions
 
 import (
 	"crypto/aes"
@@ -8,16 +8,22 @@ import (
 	"encoding/base64"
 	"errors"
 	"fmt"
-	"strings"
-)
 
-const (
+	"github.com/rfjakob/eme"
-	OpEncrypt = iota
-	OpDecrypt
 )
 
 // DecryptName - decrypt base64-encoded encrypted filename "cipherName"
-func (be *CryptFS) DecryptName(cipherName string, iv []byte) (string, error) {
+// The used encryption is either CBC or EME, depending on the "EMENames" argument.
+//
+// This function is exported because it allows for a very efficient readdir
+// implementation (read IV once, decrypt all names using this function).
+func (be *CryptFS) DecryptName(cipherName string, iv []byte, EMENames bool) (string, error) {
+	return be.decryptName(cipherName, iv, EMENames)
+}
+
+// decryptName - decrypt base64-encoded encrypted filename "cipherName".
+// The used encryption is either CBC or EME, depending on the "EMENames" argument.
+func (be *CryptFS) decryptName(cipherName string, iv []byte, EMENames bool) (string, error) {
 
 	// Make sure relative symlinks still work after encryption
 	// by passing these through unchanged
@@ -34,8 +40,12 @@ func (be *CryptFS) DecryptName(cipherName string, iv []byte) (string, error) {
 		return "", fmt.Errorf("Decoded length %d is not a multiple of the AES block size", len(bin))
 	}
 
-	cbc := cipher.NewCBCDecrypter(be.blockCipher, iv)
+	if EMENames {
-	cbc.CryptBlocks(bin, bin)
+		bin = eme.Transform(be.blockCipher, iv, bin, eme.DirectionDecrypt)
+	} else {
+		cbc := cipher.NewCBCDecrypter(be.blockCipher, iv)
+		cbc.CryptBlocks(bin, bin)
+	}
 
 	bin, err = be.unPad16(bin)
 	if err != nil {
@@ -46,8 +56,9 @@ func (be *CryptFS) DecryptName(cipherName string, iv []byte) (string, error) {
 	return plain, err
 }
 
-// EncryptName - encrypt filename
+// encryptName - encrypt "plainName", return base64-encoded "cipherName64"
-func (be *CryptFS) encryptName(plainName string, iv []byte) string {
+// The used encryption is either CBC or EME, depending on the "EMENames" argument.
+func (be *CryptFS) encryptName(plainName string, iv []byte, EMENames bool) (cipherName64 string) {
 
 	// Make sure relative symlinks still work after encryption
 	// by passing these trough unchanged
@@ -58,50 +69,17 @@ func (be *CryptFS) encryptName(plainName string, iv []byte) string {
 	bin := []byte(plainName)
 	bin = be.pad16(bin)
 
-	cbc := cipher.NewCBCEncrypter(be.blockCipher, iv)
+	if EMENames {
-	cbc.CryptBlocks(bin, bin)
+		bin = eme.Transform(be.blockCipher, iv, bin, eme.DirectionEncrypt)
+	} else {
+		cbc := cipher.NewCBCEncrypter(be.blockCipher, iv)
+		cbc.CryptBlocks(bin, bin)
+	}
 
-	cipherName64 := base64.URLEncoding.EncodeToString(bin)
+	cipherName64 = base64.URLEncoding.EncodeToString(bin)
 	return cipherName64
 }
 
-// TranslatePathZeroIV - encrypt or decrypt path using CBC with a constant all-zero IV.
-// Just splits the string on "/" and hands the parts to encryptName() / decryptName()
-func (be *CryptFS) TranslatePathZeroIV(path string, op int) (string, error) {
-	var err error
-
-	// Empty string means root directory
-	if path == "" {
-		return path, err
-	}
-
-	zeroIV := make([]byte, DIRIV_LEN)
-
-	// Run operation on each path component
-	var translatedParts []string
-	parts := strings.Split(path, "/")
-	for _, part := range parts {
-		if part == "" {
-			// This happens on "/foo/bar/" on the front and on the end.
-			// Don't panic.
-			translatedParts = append(translatedParts, "")
-			continue
-		}
-		var newPart string
-		if op == OpEncrypt {
-			newPart = be.encryptName(part, zeroIV)
-		} else {
-			newPart, err = be.DecryptName(part, zeroIV)
-			if err != nil {
-				return "", err
-			}
-		}
-		translatedParts = append(translatedParts, newPart)
-	}
-
-	return strings.Join(translatedParts, "/"), err
-}
-
 // pad16 - pad filename to 16 byte blocks using standard PKCS#7 padding
 // https://tools.ietf.org/html/rfc5652#section-6.3
 func (be *CryptFS) pad16(orig []byte) (padded []byte) {

cryptfs/names_diriv.go

@@ -73,11 +73,8 @@ func WriteDirIV(dir string) error {
 	return ioutil.WriteFile(file, iv, 0444)
 }
 
-// EncryptPathDirIV - encrypt path using CBC with DirIV
+// EncryptPathDirIV - encrypt path using CBC or EME with DirIV
-func (be *CryptFS) EncryptPathDirIV(plainPath string, rootDir string) (string, error) {
+func (be *CryptFS) EncryptPathDirIV(plainPath string, rootDir string, eme bool) (cipherPath string, err error) {
-	if be.plaintextNames {
-		return plainPath, nil
-	}
 	// Empty string means root directory
 	if plainPath == "" {
 		return plainPath, nil
@@ -88,36 +85,32 @@ func (be *CryptFS) EncryptPathDirIV(plainPath string, rootDir string) (string, e
 	if found {
 		//fmt.Print("h")
 		baseName := filepath.Base(plainPath)
-		cBaseName := be.encryptName(baseName, iv)
+		cBaseName := be.encryptName(baseName, iv, eme)
-		cPath := cParentDir + "/" + cBaseName
+		cipherPath = cParentDir + "/" + cBaseName
-		return cPath, nil
+		return cipherPath, nil
 	}
 	// Walk the directory tree
 	var wd = rootDir
 	var encryptedNames []string
-	var err error
 	plainNames := strings.Split(plainPath, "/")
 	for _, plainName := range plainNames {
 		iv, err = be.ReadDirIV(wd)
 		if err != nil {
 			return "", err
 		}
-		encryptedName := be.encryptName(plainName, iv)
+		encryptedName := be.encryptName(plainName, iv, eme)
 		encryptedNames = append(encryptedNames, encryptedName)
 		wd = filepath.Join(wd, encryptedName)
 	}
 	// Cache the final DirIV
-	cPath := strings.Join(encryptedNames, "/")
+	cipherPath = strings.Join(encryptedNames, "/")
-	cParentDir = filepath.Dir(cPath)
+	cParentDir = filepath.Dir(cipherPath)
 	be.DirIVCacheEnc.store(parentDir, iv, cParentDir)
-	return cPath, nil
+	return cipherPath, nil
 }
 
-// DecryptPathDirIV - encrypt path using CBC with DirIV
+// DecryptPathDirIV - encrypt path using CBC or EME with DirIV
-func (be *CryptFS) DecryptPathDirIV(encryptedPath string, rootDir string) (string, error) {
+func (be *CryptFS) DecryptPathDirIV(encryptedPath string, rootDir string, eme bool) (string, error) {
-	if be.plaintextNames {
-		return encryptedPath, nil
-	}
 	var wd = rootDir
 	var plainNames []string
 	encryptedNames := strings.Split(encryptedPath, "/")
@@ -127,7 +120,7 @@ func (be *CryptFS) DecryptPathDirIV(encryptedPath string, rootDir string) (strin
 		if err != nil {
 			return "", err
 		}
-		plainName, err := be.DecryptName(encryptedName, iv)
+		plainName, err := be.decryptName(encryptedName, iv, eme)
 		if err != nil {
 			return "", err
 		}

cryptfs/names_noiv.go

@@ -0,0 +1,63 @@
+package cryptfs
+
+import (
+	"strings"
+)
+
+const (
+	OpEncrypt = iota
+	OpDecrypt
+)
+
+// DecryptPathNoIV - decrypt path using CBC without any IV.
+// This function is deprecated by the the more secure DirIV variant and only retained
+// for compatability with old filesystems.
+func (be *CryptFS) DecryptPathNoIV(cipherPath string) (plainPath string, err error) {
+	plainPath, err = be.translatePathNoIV(cipherPath, OpDecrypt)
+	return plainPath, err
+}
+
+// EncryptPathNoIV - decrypt path using CBC without any IV.
+// This function is deprecated by the the more secure DirIV variant and only retained
+// for compatability with old filesystems.
+func (be *CryptFS) EncryptPathNoIV(plainPath string) (cipherPath string) {
+	cipherPath, _ = be.translatePathNoIV(plainPath, OpEncrypt)
+	return cipherPath
+}
+
+// translatePathZeroIV - encrypt or decrypt path using CBC with an all-zero IV.
+// Just splits the string on "/" and hands the parts to encryptName() / decryptName()
+func (be *CryptFS) translatePathNoIV(path string, op int) (string, error) {
+	var err error
+
+	// Empty string means root directory
+	if path == "" {
+		return path, err
+	}
+
+	zeroIV := make([]byte, DIRIV_LEN)
+
+	// Run operation on each path component
+	var translatedParts []string
+	parts := strings.Split(path, "/")
+	for _, part := range parts {
+		if part == "" {
+			// This happens on "/foo/bar/" on the front and on the end.
+			// Don't panic.
+			translatedParts = append(translatedParts, "")
+			continue
+		}
+		var newPart string
+		if op == OpEncrypt {
+			newPart = be.encryptName(part, zeroIV, false)
+		} else {
+			newPart, err = be.decryptName(part, zeroIV, false)
+			if err != nil {
+				return "", err
+			}
+		}
+		translatedParts = append(translatedParts, newPart)
+	}
+
+	return strings.Join(translatedParts, "/"), err
+}

cryptfs/names_test.go

@@ -5,7 +5,7 @@ import (
 	"testing"
 )
 
-func TestTranslatePath(t *testing.T) {
+func TestEncryptPathNoIV(t *testing.T) {
 	var s []string
 	s = append(s, "foo")
 	s = append(s, "foo12312312312312312313123123123")
@@ -15,15 +15,14 @@ func TestTranslatePath(t *testing.T) {
 	fs := NewCryptFS(key, true, false)
 
 	for _, n := range s {
-		c, err := fs.TranslatePathZeroIV(n, OpEncrypt)
+		c := fs.EncryptPathNoIV(n)
-		d, err := fs.TranslatePathZeroIV(c, OpDecrypt)
+		d, err := fs.DecryptPathNoIV(c)
 		if err != nil {
-			t.Errorf("Got error from DecryptName: %s", err)
+			t.Errorf("Got error from DecryptPathNoIV: %s", err)
 		}
 		if d != n {
-			t.Errorf("Content mismatch, n=\"%s\" d=\"%s\"", n, d)
+			t.Errorf("Content mismatch, n != d: n=%s c=%s d=%s", n, c, d)
 		}
-		//fmt.Printf("n=%s c=%s d=%s\n", n, c, d)
 	}
 }
 

integration_tests/example_filesystems_test.go

@@ -57,7 +57,7 @@ func TestExampleFsV04(t *testing.T) {
 	checkExampleContent(t, pDir)
 	unmount(pDir)
 	mount(cDir, pDir, "-masterkey", "74676e34-0b47c145-00dac61a-17a92316-"+
-		"bb57044c-e205b71f-65f4fdca-7cabd4b3", "-diriv=false")
+		"bb57044c-e205b71f-65f4fdca-7cabd4b3", "-diriv=false", "-emenames=false")
 	checkExampleContent(t, pDir)
 	unmount(pDir)
 	err = os.Remove(pDir)
@@ -79,7 +79,7 @@ func TestExampleFsV05(t *testing.T) {
 	checkExampleContent(t, pDir)
 	unmount(pDir)
 	mount(cDir, pDir, "-masterkey", "199eae55-36bff4af-83b9a3a2-4fa16f65-"+
-		"1549ccdb-2d08d1f0-b1b26965-1b61f896")
+		"1549ccdb-2d08d1f0-b1b26965-1b61f896", "-emenames=false")
 	checkExampleContent(t, pDir)
 	unmount(pDir)
 	err = os.Remove(pDir)

main.go

@@ -35,7 +35,7 @@ const (
 
 type argContainer struct {
 	debug, init, zerokey, fusedebug, openssl, passwd, foreground, version,
-	plaintextnames, quiet, diriv bool
+	plaintextnames, quiet, diriv, emenames bool
 	masterkey, mountpoint, cipherdir, cpuprofile, config, extpass string
 	notifypid, scryptn                                            int
 }
@@ -55,7 +55,7 @@ func initDir(args *argContainer) {
 	// Create gocryptfs.conf
 	cryptfs.Info.Printf("Choose a password for protecting your files.\n")
 	password := readPasswordTwice(args.extpass)
-	err = cryptfs.CreateConfFile(args.config, password, args.plaintextnames, args.scryptn)
+	err = cryptfs.CreateConfFile(args.config, password, args.plaintextnames, args.scryptn, args.emenames)
 	if err != nil {
 		fmt.Println(err)
 		os.Exit(ERREXIT_INIT)
@@ -146,6 +146,7 @@ func main() {
 		"file names")
 	flagSet.BoolVar(&args.quiet, "q", false, "Quiet - silence informational messages")
 	flagSet.BoolVar(&args.diriv, "diriv", true, "Use per-directory file name IV")
+	flagSet.BoolVar(&args.emenames, "emenames", true, "Use EME filename encryption. This option implies diriv.")
 	flagSet.StringVar(&args.masterkey, "masterkey", "", "Mount with explicit master key")
 	flagSet.StringVar(&args.cpuprofile, "cpuprofile", "", "Write cpu profile to specified file")
 	flagSet.StringVar(&args.config, "config", "", "Use specified config file instead of CIPHERDIR/gocryptfs.conf")
@@ -262,7 +263,7 @@ func main() {
 		printMasterKey(masterkey)
 	}
 	// Initialize FUSE server
-	cryptfs.Debug.Printf("args: %v\n", args)
+	cryptfs.Debug.Printf("cli args: %v\n", args)
 	srv := pathfsFrontend(masterkey, args, confFile)
 	cryptfs.Info.Println("Filesystem ready.")
 	// We are ready - send USR1 signal to our parent
@@ -289,13 +290,26 @@ func pathfsFrontend(key []byte, args argContainer, confFile *cryptfs.ConfFile) *
 		OpenSSL:        args.openssl,
 		PlaintextNames: args.plaintextnames,
 		DirIV:          args.diriv,
+		EMENames:       args.emenames,
 	}
 	// confFile is nil when "-zerokey" or "-masterkey" was used
 	if confFile != nil {
 		// Settings from the config file override command line args
 		frontendArgs.PlaintextNames = confFile.IsFeatureFlagSet(cryptfs.FlagPlaintextNames)
 		frontendArgs.DirIV = confFile.IsFeatureFlagSet(cryptfs.FlagDirIV)
+		frontendArgs.EMENames = confFile.IsFeatureFlagSet(cryptfs.FlagEMENames)
 	}
+	// EMENames implies DirIV, both on the command line and in the config file.
+	if frontendArgs.EMENames {
+		frontendArgs.DirIV = true
+	}
+	// PlainTexnames disables both EMENames and DirIV
+	if frontendArgs.PlaintextNames {
+		frontendArgs.DirIV = false
+		frontendArgs.EMENames = false
+	}
+	cryptfs.Debug.Printf("frontendArgs: ")
+	cryptfs.Debug.JSONDump(frontendArgs)
 
 	finalFs := pathfs_frontend.NewFS(frontendArgs)
 	pathFsOpts := &pathfs.PathNodeFsOptions{ClientInodes: true}

pathfs_frontend/args.go

@@ -7,4 +7,5 @@ type Args struct {
 	OpenSSL        bool
 	PlaintextNames bool
 	DirIV          bool
+	EMENames       bool
 }

pathfs_frontend/fs.go

@@ -48,7 +48,7 @@ func (fs *FS) getBackingPath(relPath string) (string, error) {
 
 func (fs *FS) GetAttr(name string, context *fuse.Context) (*fuse.Attr, fuse.Status) {
 	cryptfs.Debug.Printf("FS.GetAttr('%s')\n", name)
-	if fs.CryptFS.IsFiltered(name) {
+	if fs.isFiltered(name) {
 		return nil, fuse.EPERM
 	}
 	cName, err := fs.encryptPath(name)
@@ -103,7 +103,7 @@ func (fs *FS) OpenDir(dirName string, context *fuse.Context) ([]fuse.DirEntry, f
 			continue
 		}
 		var name string
-		name, err = fs.CryptFS.DecryptName(cName, cachedIV)
+		name, err = fs.CryptFS.DecryptName(cName, cachedIV, fs.args.EMENames)
 		if err != nil {
 			cryptfs.Warn.Printf("Invalid name \"%s\" in dir \"%s\": %s\n", cName, dirName, err)
 			continue
@@ -128,7 +128,7 @@ func (fs *FS) mangleOpenFlags(flags uint32) (newFlags int, writeOnly bool) {
 }
 
 func (fs *FS) Open(path string, flags uint32, context *fuse.Context) (fuseFile nodefs.File, status fuse.Status) {
-	if fs.CryptFS.IsFiltered(path) {
+	if fs.isFiltered(path) {
 		return nil, fuse.EPERM
 	}
 	iflags, writeOnly := fs.mangleOpenFlags(flags)
@@ -147,7 +147,7 @@ func (fs *FS) Open(path string, flags uint32, context *fuse.Context) (fuseFile n
 }
 
 func (fs *FS) Create(path string, flags uint32, mode uint32, context *fuse.Context) (fuseFile nodefs.File, code fuse.Status) {
-	if fs.CryptFS.IsFiltered(path) {
+	if fs.isFiltered(path) {
 		return nil, fuse.EPERM
 	}
 	iflags, writeOnly := fs.mangleOpenFlags(flags)
@@ -163,7 +163,7 @@ func (fs *FS) Create(path string, flags uint32, mode uint32, context *fuse.Conte
 }
 
 func (fs *FS) Chmod(path string, mode uint32, context *fuse.Context) (code fuse.Status) {
-	if fs.CryptFS.IsFiltered(path) {
+	if fs.isFiltered(path) {
 		return fuse.EPERM
 	}
 	cPath, err := fs.encryptPath(path)
@@ -174,7 +174,7 @@ func (fs *FS) Chmod(path string, mode uint32, context *fuse.Context) (code fuse.
 }
 
 func (fs *FS) Chown(path string, uid uint32, gid uint32, context *fuse.Context) (code fuse.Status) {
-	if fs.CryptFS.IsFiltered(path) {
+	if fs.isFiltered(path) {
 		return fuse.EPERM
 	}
 	cPath, err := fs.encryptPath(path)
@@ -185,7 +185,7 @@ func (fs *FS) Chown(path string, uid uint32, gid uint32, context *fuse.Context)
 }
 
 func (fs *FS) Mknod(path string, mode uint32, dev uint32, context *fuse.Context) (code fuse.Status) {
-	if fs.CryptFS.IsFiltered(path) {
+	if fs.isFiltered(path) {
 		return fuse.EPERM
 	}
 	cPath, err := fs.encryptPath(path)
@@ -201,7 +201,7 @@ func (fs *FS) Truncate(path string, offset uint64, context *fuse.Context) (code
 }
 
 func (fs *FS) Utimens(path string, Atime *time.Time, Mtime *time.Time, context *fuse.Context) (code fuse.Status) {
-	if fs.CryptFS.IsFiltered(path) {
+	if fs.isFiltered(path) {
 		return fuse.EPERM
 	}
 	cPath, err := fs.encryptPath(path)
@@ -244,7 +244,7 @@ func (fs *FS) Readlink(path string, context *fuse.Context) (out string, status f
 }
 
 func (fs *FS) Mkdir(relPath string, mode uint32, context *fuse.Context) (code fuse.Status) {
-	if fs.CryptFS.IsFiltered(relPath) {
+	if fs.isFiltered(relPath) {
 		return fuse.EPERM
 	}
 	encPath, err := fs.getBackingPath(relPath)
@@ -275,7 +275,7 @@ func (fs *FS) Mkdir(relPath string, mode uint32, context *fuse.Context) (code fu
 }
 
 func (fs *FS) Unlink(path string, context *fuse.Context) (code fuse.Status) {
-	if fs.CryptFS.IsFiltered(path) {
+	if fs.isFiltered(path) {
 		return fuse.EPERM
 	}
 	cPath, err := fs.getBackingPath(path)
@@ -349,7 +349,7 @@ func (fs *FS) Rmdir(name string, context *fuse.Context) (code fuse.Status) {
 
 func (fs *FS) Symlink(target string, linkName string, context *fuse.Context) (code fuse.Status) {
 	cryptfs.Debug.Printf("Symlink(\"%s\", \"%s\")\n", target, linkName)
-	if fs.CryptFS.IsFiltered(linkName) {
+	if fs.isFiltered(linkName) {
 		return fuse.EPERM
 	}
 	cPath, err := fs.getBackingPath(linkName)
@@ -376,7 +376,7 @@ func (fs *FS) Symlink(target string, linkName string, context *fuse.Context) (co
 }
 
 func (fs *FS) Rename(oldPath string, newPath string, context *fuse.Context) (code fuse.Status) {
-	if fs.CryptFS.IsFiltered(newPath) {
+	if fs.isFiltered(newPath) {
 		return fuse.EPERM
 	}
 	cOldPath, err := fs.getBackingPath(oldPath)
@@ -396,7 +396,7 @@ func (fs *FS) Rename(oldPath string, newPath string, context *fuse.Context) (cod
 }
 
 func (fs *FS) Link(oldPath string, newPath string, context *fuse.Context) (code fuse.Status) {
-	if fs.CryptFS.IsFiltered(newPath) {
+	if fs.isFiltered(newPath) {
 		return fuse.EPERM
 	}
 	cOldPath, err := fs.getBackingPath(oldPath)
@@ -411,7 +411,7 @@ func (fs *FS) Link(oldPath string, newPath string, context *fuse.Context) (code
 }
 
 func (fs *FS) Access(path string, mode uint32, context *fuse.Context) (code fuse.Status) {
-	if fs.CryptFS.IsFiltered(path) {
+	if fs.isFiltered(path) {
 		return fuse.EPERM
 	}
 	cPath, err := fs.getBackingPath(path)

pathfs_frontend/names.go

@@ -6,20 +6,47 @@ import (
 	"github.com/rfjakob/gocryptfs/cryptfs"
 )
 
-func (fs *FS) encryptPath(plainPath string) (string, error) {
+// isFiltered - check if plaintext "path" should be forbidden
-	if !fs.args.DirIV {
+//
-		return fs.CryptFS.TranslatePathZeroIV(plainPath, cryptfs.OpEncrypt)
+// Prevents name clashes with internal files when file names are not encrypted
+func (fs *FS) isFiltered(path string) bool {
+	if !fs.args.PlaintextNames {
+		return false
 	}
-	fs.dirIVLock.RLock()
+	// gocryptfs.conf in the root directory is forbidden
-	defer fs.dirIVLock.RUnlock()
+	if path == cryptfs.ConfDefaultName {
-	return fs.CryptFS.EncryptPathDirIV(plainPath, fs.args.Cipherdir)
+		cryptfs.Warn.Printf("The name /%s is reserved when -plaintextnames is used\n",
+			cryptfs.ConfDefaultName)
+		return true
+	}
+	// Note: gocryptfs.diriv is NOT forbidden because diriv and plaintextnames
+	// are exclusive
+	return false
 }
 
-func (fs *FS) decryptPath(cipherPath string) (string, error) {
+
+// encryptPath - encrypt relative plaintext path
+func (fs *FS) encryptPath(plainPath string) (string, error) {
+	if fs.args.PlaintextNames {
+		return plainPath, nil
+	}
 	if !fs.args.DirIV {
-		return fs.CryptFS.TranslatePathZeroIV(cipherPath, cryptfs.OpDecrypt)
+		return fs.CryptFS.EncryptPathNoIV(plainPath), nil
 	}
 	fs.dirIVLock.RLock()
 	defer fs.dirIVLock.RUnlock()
-	return fs.CryptFS.DecryptPathDirIV(cipherPath, fs.args.Cipherdir)
+	return fs.CryptFS.EncryptPathDirIV(plainPath, fs.args.Cipherdir, fs.args.EMENames)
+}
+
+// decryptPath - decrypt relative ciphertext path
+func (fs *FS) decryptPath(cipherPath string) (string, error) {
+	if fs.args.PlaintextNames {
+		return cipherPath, nil
+	}
+	if !fs.args.DirIV {
+		return fs.CryptFS.DecryptPathNoIV(cipherPath)
+	}
+	fs.dirIVLock.RLock()
+	defer fs.dirIVLock.RUnlock()
+	return fs.CryptFS.DecryptPathDirIV(cipherPath, fs.args.Cipherdir, fs.args.EMENames)
 }