crypt: add suffix option to set a custom suffix for encrypted files - fixes #6392

backend/crypt/cipher.go

@@ -38,7 +38,6 @@ const (
 	blockHeaderSize     = secretbox.Overhead
 	blockDataSize       = 64 * 1024
 	blockSize           = blockHeaderSize + blockDataSize
-	encryptedSuffix     = ".bin" // when file name encryption is off we add this suffix to make sure the cloud provider doesn't process the file
 )
 
 // Errors returned by cipher
@@ -54,8 +53,9 @@ var (
 	ErrorEncryptedBadBlock       = errors.New("failed to authenticate decrypted block - bad password?")
 	ErrorBadBase32Encoding       = errors.New("bad base32 filename encoding")
 	ErrorFileClosed              = errors.New("file already closed")
-	ErrorNotAnEncryptedFile      = errors.New("not an encrypted file - no \"" + encryptedSuffix + "\" suffix")
+	ErrorNotAnEncryptedFile      = errors.New("not an encrypted file - does not match suffix")
 	ErrorBadSeek                 = errors.New("Seek beyond end of file")
+	ErrorSuffixMissingDot        = errors.New("suffix config setting should include a '.'")
 	defaultSalt                  = []byte{0xA8, 0x0D, 0xF4, 0x3A, 0x8F, 0xBD, 0x03, 0x08, 0xA7, 0xCA, 0xB8, 0x3E, 0x58, 0x1F, 0x86, 0xB1}
 	obfuscQuoteRune              = '!'
 )
@@ -180,6 +180,7 @@ type Cipher struct {
 	cryptoRand      io.Reader // read crypto random numbers from here
 	dirNameEncrypt  bool
 	passBadBlocks   bool // if set passed bad blocks as zeroed blocks
+	encryptedSuffix string
 }
 
 // newCipher initialises the cipher.  If salt is "" then it uses a built in salt val
@@ -189,6 +190,7 @@ func newCipher(mode NameEncryptionMode, password, salt string, dirNameEncrypt bo
 		fileNameEnc:     enc,
 		cryptoRand:      rand.Reader,
 		dirNameEncrypt:  dirNameEncrypt,
+		encryptedSuffix: ".bin",
 	}
 	c.buffers.New = func() interface{} {
 		return new([blockSize]byte)
@@ -200,6 +202,19 @@ func newCipher(mode NameEncryptionMode, password, salt string, dirNameEncrypt bo
 	return c, nil
 }
 
+// setEncryptedSuffix set suffix, or an empty string
+func (c *Cipher) setEncryptedSuffix(suffix string) {
+	if strings.EqualFold(suffix, "none") {
+		c.encryptedSuffix = ""
+		return
+	}
+	if !strings.HasPrefix(suffix, ".") {
+		fs.Errorf(nil, "crypt: bad suffix: %v", ErrorSuffixMissingDot)
+		suffix = "." + suffix
+	}
+	c.encryptedSuffix = suffix
+}
+
 // Call to set bad block pass through
 func (c *Cipher) setPassBadBlocks(passBadBlocks bool) {
 	c.passBadBlocks = passBadBlocks
@@ -512,7 +527,7 @@ func (c *Cipher) encryptFileName(in string) string {
 // EncryptFileName encrypts a file path
 func (c *Cipher) EncryptFileName(in string) string {
 	if c.mode == NameEncryptionOff {
-		return in + encryptedSuffix
+		return in + c.encryptedSuffix
 	}
 	return c.encryptFileName(in)
 }
@@ -572,8 +587,8 @@ func (c *Cipher) decryptFileName(in string) (string, error) {
 // DecryptFileName decrypts a file path
 func (c *Cipher) DecryptFileName(in string) (string, error) {
 	if c.mode == NameEncryptionOff {
-		remainingLength := len(in) - len(encryptedSuffix)
+		remainingLength := len(in) - len(c.encryptedSuffix)
-		if remainingLength == 0 || !strings.HasSuffix(in, encryptedSuffix) {
+		if remainingLength == 0 || !strings.HasSuffix(in, c.encryptedSuffix) {
 			return "", ErrorNotAnEncryptedFile
 		}
 		decrypted := in[:remainingLength]

backend/crypt/cipher_test.go

@@ -405,6 +405,13 @@ func TestNonStandardEncryptFileName(t *testing.T) {
 	// Off mode
 	c, _ := newCipher(NameEncryptionOff, "", "", true, nil)
 	assert.Equal(t, "1/12/123.bin", c.EncryptFileName("1/12/123"))
+	// Off mode with custom suffix
+	c, _ = newCipher(NameEncryptionOff, "", "", true, nil)
+	c.setEncryptedSuffix(".jpg")
+	assert.Equal(t, "1/12/123.jpg", c.EncryptFileName("1/12/123"))
+	// Off mode with empty suffix
+	c.setEncryptedSuffix("none")
+	assert.Equal(t, "1/12/123", c.EncryptFileName("1/12/123"))
 	// Obfuscation mode
 	c, _ = newCipher(NameEncryptionObfuscated, "", "", true, nil)
 	assert.Equal(t, "49.6/99.23/150.890/53.!!lipps", c.EncryptFileName("1/12/123/!hello"))
@@ -483,21 +490,27 @@ func TestNonStandardDecryptFileName(t *testing.T) {
 			in             string
 			expected       string
 			expectedErr    error
+			customSuffix   string
 		}{
-			{NameEncryptionOff, true, "1/12/123.bin", "1/12/123", nil},
+			{NameEncryptionOff, true, "1/12/123.bin", "1/12/123", nil, ""},
-			{NameEncryptionOff, true, "1/12/123.bix", "", ErrorNotAnEncryptedFile},
+			{NameEncryptionOff, true, "1/12/123.bix", "", ErrorNotAnEncryptedFile, ""},
-			{NameEncryptionOff, true, ".bin", "", ErrorNotAnEncryptedFile},
+			{NameEncryptionOff, true, ".bin", "", ErrorNotAnEncryptedFile, ""},
-			{NameEncryptionOff, true, "1/12/123-v2001-02-03-040506-123.bin", "1/12/123-v2001-02-03-040506-123", nil},
+			{NameEncryptionOff, true, "1/12/123-v2001-02-03-040506-123.bin", "1/12/123-v2001-02-03-040506-123", nil, ""},
-			{NameEncryptionOff, true, "1/12/123-v1970-01-01-010101-123-v2001-02-03-040506-123.bin", "1/12/123-v1970-01-01-010101-123-v2001-02-03-040506-123", nil},
+			{NameEncryptionOff, true, "1/12/123-v1970-01-01-010101-123-v2001-02-03-040506-123.bin", "1/12/123-v1970-01-01-010101-123-v2001-02-03-040506-123", nil, ""},
-			{NameEncryptionOff, true, "1/12/123-v1970-01-01-010101-123-v2001-02-03-040506-123.txt.bin", "1/12/123-v1970-01-01-010101-123-v2001-02-03-040506-123.txt", nil},
+			{NameEncryptionOff, true, "1/12/123-v1970-01-01-010101-123-v2001-02-03-040506-123.txt.bin", "1/12/123-v1970-01-01-010101-123-v2001-02-03-040506-123.txt", nil, ""},
-			{NameEncryptionObfuscated, true, "!.hello", "hello", nil},
+			{NameEncryptionOff, true, "1/12/123.jpg", "1/12/123", nil, ".jpg"},
-			{NameEncryptionObfuscated, true, "hello", "", ErrorNotAnEncryptedFile},
+			{NameEncryptionOff, true, "1/12/123", "1/12/123", nil, "none"},
-			{NameEncryptionObfuscated, true, "161.\u00e4", "\u00a1", nil},
+			{NameEncryptionObfuscated, true, "!.hello", "hello", nil, ""},
-			{NameEncryptionObfuscated, true, "160.\u03c2", "\u03a0", nil},
+			{NameEncryptionObfuscated, true, "hello", "", ErrorNotAnEncryptedFile, ""},
-			{NameEncryptionObfuscated, false, "1/12/123/53.!!lipps", "1/12/123/!hello", nil},
+			{NameEncryptionObfuscated, true, "161.\u00e4", "\u00a1", nil, ""},
-			{NameEncryptionObfuscated, false, "1/12/123/53-v2001-02-03-040506-123.!!lipps", "1/12/123/!hello-v2001-02-03-040506-123", nil},
+			{NameEncryptionObfuscated, true, "160.\u03c2", "\u03a0", nil, ""},
+			{NameEncryptionObfuscated, false, "1/12/123/53.!!lipps", "1/12/123/!hello", nil, ""},
+			{NameEncryptionObfuscated, false, "1/12/123/53-v2001-02-03-040506-123.!!lipps", "1/12/123/!hello-v2001-02-03-040506-123", nil, ""},
 		} {
 			c, _ := newCipher(test.mode, "", "", test.dirNameEncrypt, enc)
+			if test.customSuffix != "" {
+				c.setEncryptedSuffix(test.customSuffix)
+			}
 			actual, actualErr := c.DecryptFileName(test.in)
 			what := fmt.Sprintf("Testing %q (mode=%v)", test.in, test.mode)
 			assert.Equal(t, test.expected, actual, what)

backend/crypt/crypt.go

@@ -48,7 +48,7 @@ func init() {
 					Help:  "Very simple filename obfuscation.",
 				}, {
 					Value: "off",
-					Help:  "Don't encrypt the file names.\nAdds a \".bin\" extension only.",
+					Help:  "Don't encrypt the file names.\nAdds a \".bin\", or \"suffix\" extension only.",
 				},
 			},
 		}, {
@@ -151,6 +151,14 @@ length and if it's case sensitive.`,
 				},
 			},
 			Advanced: true,
+		}, {
+			Name: "suffix",
+			Help: `If this is set it will override the default suffix of ".bin".
+
+Setting suffix to "none" will result in an empty suffix. This may be useful 
+when the path length is critical.`,
+			Default:  ".bin",
+			Advanced: true,
 		}},
 	})
 }
@@ -183,6 +191,7 @@ func newCipherForConfig(opt *Options) (*Cipher, error) {
 	if err != nil {
 		return nil, fmt.Errorf("failed to make cipher: %w", err)
 	}
+	cipher.setEncryptedSuffix(opt.Suffix)
 	cipher.setPassBadBlocks(opt.PassBadBlocks)
 	return cipher, nil
 }
@@ -274,6 +283,7 @@ type Options struct {
 	ShowMapping             bool   `config:"show_mapping"`
 	PassBadBlocks           bool   `config:"pass_bad_blocks"`
 	FilenameEncoding        string `config:"filename_encoding"`
+	Suffix                  string `config:"suffix"`
 }
 
 // Fs represents a wrapped fs.Fs