Added auto decryption of invalid file names

Changed invalid file decoding and decryption. Function
DecryptName now shortens the filename until the filename is
decodable and decryptable. Will work with valid **and**
invalid Base64URL delimiter (valid delimiter [0-9a-zA-z_\\-].
If the filename is not decryptable at all, it returns the
original cipher name with flag suffix Changed cli tests to
generate decryptable and undecryptable file names with correct
encrypted content. Replacing #474, extends #393

1 files changed, 8 insertions, 1 deletions

diff --git a/internal/nametransform/names.go b/internal/nametransform/names.go
index e9f9346..675ed34 100644
--- a/internal/nametransform/names.go
+++ b/internal/nametransform/names.go
@@ -61,7 +61,14 @@ func (n *NameTransform) DecryptName(cipherName string, iv []byte) (string, error
 		for _, pattern := range n.BadnamePatterns {
 			match, err := filepath.Match(pattern, cipherName)
 			if err == nil && match { // Pattern should have been validated already
-				return "GOCRYPTFS_BAD_NAME " + cipherName, nil
+				//find longest decryptable substring
+				for charpos := len(cipherName) - 1; charpos > 0; charpos-- {
+					res, err = n.decryptName(cipherName[:charpos], iv)
+					if err == nil {
+						return res + cipherName[charpos:] + " GOCRYPTFS_BAD_NAME", nil
+					}
+				}
+				return cipherName + " GOCRYPTFS_BAD_NAME", nil
 			}
 		}
 	}