diriv: Convert filename encryption users to diriv

3 files changed, 88 insertions, 33 deletions

diff --git a/cryptfs/cryptfs_names.go b/cryptfs/cryptfs_names.go
index 1282f53..37a769f 100644
--- a/cryptfs/cryptfs_names.go
+++ b/cryptfs/cryptfs_names.go
@@ -12,15 +12,15 @@ import (
 )
 
 const (
-	ENCRYPT = true
-	DECRYPT = false
+	OpEncrypt = iota
+	OpDecrypt
 )
 
-// DecryptName - decrypt filename
-func (be *CryptFS) decryptName(cipherName string) (string, error) {
+// DecryptName - decrypt base64-encoded encrypted filename "cipherName"
+func (be *CryptFS) decryptName(cipherName string, iv []byte) (string, error) {
 
 	// Make sure relative symlinks still work after encryption
-	// by passing these trough unchanged
+	// by passing these through unchanged
 	if cipherName == "." || cipherName == ".." {
 		return cipherName, nil
 	}
@@ -34,7 +34,6 @@ func (be *CryptFS) decryptName(cipherName string) (string, error) {
 		return "", fmt.Errorf("Decoded length %d is not a multiple of the AES block size", len(bin))
 	}
 
-	iv := make([]byte, aes.BlockSize) // TODO ?
 	cbc := cipher.NewCBCDecrypter(be.blockCipher, iv)
 	cbc.CryptBlocks(bin, bin)
 
@@ -48,7 +47,7 @@ func (be *CryptFS) decryptName(cipherName string) (string, error) {
 }
 
 // EncryptName - encrypt filename
-func (be *CryptFS) encryptName(plainName string) string {
+func (be *CryptFS) encryptName(plainName string, iv []byte) string {
 
 	// Make sure relative symlinks still work after encryption
 	// by passing these trough unchanged
@@ -59,7 +58,6 @@ func (be *CryptFS) encryptName(plainName string) string {
 	bin := []byte(plainName)
 	bin = be.pad16(bin)
 
-	iv := make([]byte, 16) // TODO ?
 	cbc := cipher.NewCBCEncrypter(be.blockCipher, iv)
 	cbc.CryptBlocks(bin, bin)
 
@@ -67,9 +65,10 @@ func (be *CryptFS) encryptName(plainName string) string {
 	return cipherName64
 }
 
-// TranslatePath - encrypt or decrypt path. Just splits the string on "/"
-// and hands the parts to EncryptName() / DecryptName()
-func (be *CryptFS) translatePath(path string, op bool) (string, error) {
+
+// 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
@@ -77,6 +76,8 @@ func (be *CryptFS) translatePath(path string, op bool) (string, error) {
 		return path, err
 	}
 
+	zeroIV := make([]byte, DIRIV_LEN)
+
 	// Run operation on each path component
 	var translatedParts []string
 	parts := strings.Split(path, "/")
@@ -88,10 +89,10 @@ func (be *CryptFS) translatePath(path string, op bool) (string, error) {
 			continue
 		}
 		var newPart string
-		if op == ENCRYPT {
-			newPart = be.encryptName(part)
+		if op == OpEncrypt {
+			newPart = be.encryptName(part, zeroIV)
 		} else {
-			newPart, err = be.decryptName(part)
+			newPart, err = be.decryptName(part, zeroIV)
 			if err != nil {
 				return "", err
 			}
@@ -102,23 +103,6 @@ func (be *CryptFS) translatePath(path string, op bool) (string, error) {
 	return strings.Join(translatedParts, "/"), err
 }
 
-// EncryptPath - encrypt filename or path. Just hands it to translatePath().
-func (be *CryptFS) EncryptPath(path string) string {
-	if be.plaintextNames {
-		return path
-	}
-	newPath, _ := be.translatePath(path, ENCRYPT)
-	return newPath
-}
-
-// DecryptPath - decrypt filename or path. Just hands it to translatePath().
-func (be *CryptFS) DecryptPath(path string) (string, error) {
-	if be.plaintextNames {
-		return path, nil
-	}
-	return be.translatePath(path, DECRYPT)
-}
-
 // 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) {
@@ -171,3 +155,5 @@ func (be *CryptFS) unPad16(orig []byte) ([]byte, error) {
 	}
 	return orig[0:newLen], nil
 }
+
+
diff --git a/cryptfs/names_diriv.go b/cryptfs/names_diriv.go
new file mode 100644
index 0000000..c9debab
--- /dev/null
+++ b/cryptfs/names_diriv.go
@@ -0,0 +1,69 @@
+package cryptfs
+
+import (
+	"path/filepath"
+	"io/ioutil"
+	"fmt"
+	"strings"
+)
+
+// readDirIV - read the "gocryptfs.diriv" file from "dir" (absolute path)
+func (be *CryptFS) readDirIV(dir string) (iv []byte, err error) {
+		ivfile := filepath.Join(dir, DIRIV_FILENAME)
+		iv, err = ioutil.ReadFile(ivfile)
+		if err != nil {
+			Warn.Printf("readDirIV: %v\n", err)
+			return nil, err
+		}
+		if len(iv) != DIRIV_LEN {
+			return nil, fmt.Errorf("readDirIV: Invalid length %d\n", len(iv))
+		}
+		return iv, nil
+}
+
+// EncryptPathDirIV - encrypt path using CBC with DirIV
+func (be *CryptFS) EncryptPathDirIV(plainPath string, rootDir string) (string, error) {
+	if be.plaintextNames {
+		return plainPath, nil
+	}
+	// Empty string means root directory
+	if plainPath == "" {
+		return plainPath, nil
+	}
+	var wd = rootDir
+	var encryptedNames []string
+	plainNames := strings.Split(plainPath, "/")
+	for _, plainName := range plainNames {
+		iv, err := be.readDirIV(wd)
+		if err != nil {
+			return "", err
+		}
+		encryptedName := be.encryptName(plainName, iv)
+		encryptedNames = append(encryptedNames, encryptedName)
+		wd = filepath.Join(wd, encryptedName)
+	}
+	return filepath.Join(encryptedNames...), nil
+}
+
+// DecryptPathDirIV - encrypt path using CBC with DirIV
+func (be *CryptFS) DecryptPathDirIV(encryptedPath string, rootDir string) (string, error) {
+	if be.plaintextNames {
+		return encryptedPath, nil
+	}
+	var wd = rootDir
+	var plainNames []string
+	encryptedNames := strings.Split(encryptedPath, "/")
+	for _, encryptedName := range encryptedNames {
+		iv, err := be.readDirIV(wd)
+		if err != nil {
+			return "", err
+		}
+		plainName, err := be.decryptName(encryptedName, iv)
+		if err != nil {
+			return "", err
+		}
+		plainNames = append(plainNames, plainName)
+		wd = filepath.Join(wd, encryptedName)
+	}
+	return filepath.Join(plainNames...), nil
+}
diff --git a/cryptfs/names_test.go b/cryptfs/names_test.go
index ccf08df..1ad3391 100644
--- a/cryptfs/names_test.go
+++ b/cryptfs/names_test.go
@@ -15,8 +15,8 @@ func TestTranslatePath(t *testing.T) {
 	fs := NewCryptFS(key, true, false)
 
 	for _, n := range s {
-		c := fs.EncryptPath(n)
-		d, err := fs.DecryptPath(c)
+		c, err := fs.TranslatePathZeroIV(n, OpEncrypt)
+		d, err := fs.TranslatePathZeroIV(c, OpDecrypt)
 		if err != nil {
 			t.Errorf("Got error from DecryptName: %s", err)
 		}