Use block number as authentication data

4 files changed, 16 insertions, 16 deletions

diff --git a/cryptfs/config_file.go b/cryptfs/config_file.go
index 74eb3b2..82f7e72 100644
--- a/cryptfs/config_file.go
+++ b/cryptfs/config_file.go
@@ -39,7 +39,7 @@ func CreateConfFile(filename string, password string) error {
 
 	// Lock master key using password-based key
 	cfs := NewCryptFS(scryptHash, false)
-	cf.EncryptedKey = cfs.EncryptBlock(key)
+	cf.EncryptedKey = cfs.EncryptBlock(key, 0)
 
 	// Write file to disk
 	err := cf.WriteFile()
@@ -73,7 +73,7 @@ func LoadConfFile(filename string, password string) ([]byte, error) {
 	// We use stock go GCM instead of OpenSSL here as speed is not important
 	// and we get better error messages
 	cfs := NewCryptFS(scryptHash, false)
-	key, err := cfs.DecryptBlock(cf.EncryptedKey)
+	key, err := cfs.DecryptBlock(cf.EncryptedKey, 0)
 	if err != nil {
 		Warn.Printf("Failed to unlock master key: %s\n", err.Error())
 		return nil, err
diff --git a/cryptfs/cryptfs.go b/cryptfs/cryptfs.go
index d7d1516..1556757 100644
--- a/cryptfs/cryptfs.go
+++ b/cryptfs/cryptfs.go
@@ -13,7 +13,6 @@ const (
 	KEY_LEN         = 32 // AES-256
 	NONCE_LEN       = 12
 	AUTH_TAG_LEN    = 16
-	FILEID_LEN      = 16
 )
 
 type CryptFS struct {
diff --git a/cryptfs/cryptfs_content.go b/cryptfs/cryptfs_content.go
index 6444b8b..cb309ea 100644
--- a/cryptfs/cryptfs_content.go
+++ b/cryptfs/cryptfs_content.go
@@ -3,6 +3,7 @@ package cryptfs
 // File content encryption / decryption
 
 import (
+	"encoding/binary"
 	"bytes"
 	"crypto/cipher"
 	"crypto/md5"
@@ -29,18 +30,19 @@ type CryptFile struct {
 }
 
 // DecryptBlocks - Decrypt a number of blocks
-func (be *CryptFS) DecryptBlocks(ciphertext []byte) ([]byte, error) {
+func (be *CryptFS) DecryptBlocks(ciphertext []byte, firstBlockNo uint64) ([]byte, error) {
 	cBuf := bytes.NewBuffer(ciphertext)
 	var err error
 	var pBuf bytes.Buffer
 	for cBuf.Len() > 0 {
 		cBlock := cBuf.Next(int(be.cipherBS))
 		var pBlock []byte
-		pBlock, err = be.DecryptBlock(cBlock)
+		pBlock, err = be.DecryptBlock(cBlock, firstBlockNo)
 		if err != nil {
 			break
 		}
 		pBuf.Write(pBlock)
+		firstBlockNo++
 	}
 	return pBuf.Bytes(), err
 }
@@ -49,7 +51,7 @@ func (be *CryptFS) DecryptBlocks(ciphertext []byte) ([]byte, error) {
 //
 // Corner case: A full-sized block of all-zero ciphertext bytes is translated
 // to an all-zero plaintext block, i.e. file hole passtrough.
-func (be *CryptFS) DecryptBlock(ciphertext []byte) ([]byte, error) {
+func (be *CryptFS) DecryptBlock(ciphertext []byte, blockNo uint64) ([]byte, error) {
 
 	// Empty block?
 	if len(ciphertext) == 0 {
@@ -74,7 +76,8 @@ func (be *CryptFS) DecryptBlock(ciphertext []byte) ([]byte, error) {
 
 	// Decrypt
 	var plaintext []byte
-
+	aData := make([]byte, 8)
+	binary.BigEndian.PutUint64(aData, blockNo)
 	plaintext, err := be.gcm.Open(plaintext, nonce, ciphertext, nil)
 
 	if err != nil {
@@ -87,7 +90,7 @@ func (be *CryptFS) DecryptBlock(ciphertext []byte) ([]byte, error) {
 }
 
 // encryptBlock - Encrypt and add MAC using GCM
-func (be *CryptFS) EncryptBlock(plaintext []byte) []byte {
+func (be *CryptFS) EncryptBlock(plaintext []byte,  blockNo uint64) []byte {
 
 	// Empty block?
 	if len(plaintext) == 0 {
@@ -98,6 +101,8 @@ func (be *CryptFS) EncryptBlock(plaintext []byte) []byte {
 	nonce := gcmNonce.Get()
 
 	// Encrypt plaintext and append to nonce
+	aData := make([]byte, 8)
+	binary.BigEndian.PutUint64(aData, blockNo)
 	ciphertext := be.gcm.Seal(nonce, nonce, plaintext, nil)
 
 	return ciphertext
diff --git a/cryptfs/openssl_aead.go b/cryptfs/openssl_aead.go
index 9baa6d5..1ec7c48 100644
--- a/cryptfs/openssl_aead.go
+++ b/cryptfs/openssl_aead.go
@@ -63,10 +63,6 @@ func (be opensslGCM) Seal(dst, nonce, plaintext, data []byte) []byte {
 // The ciphertext and dst may alias exactly or not at all.
 func (be opensslGCM) Open(dst, nonce, ciphertext, data []byte) ([]byte, error) {
 
-	if len(data) > 0 {
-		panic("Extra data is not supported")
-	}
-
 	l := len(ciphertext)
 	tag := ciphertext[l-AUTH_TAG_LEN : l]
 	ciphertext = ciphertext[0 : l-AUTH_TAG_LEN]
@@ -76,6 +72,10 @@ func (be opensslGCM) Open(dst, nonce, ciphertext, data []byte) ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
+	err = dctx.ExtraData(data)
+	if err != nil {
+		return nil, err
+	}
 	part, err := dctx.DecryptUpdate(ciphertext)
 	if err != nil {
 		return nil, err
@@ -90,10 +90,6 @@ func (be opensslGCM) Open(dst, nonce, ciphertext, data []byte) ([]byte, error) {
 		return nil, err
 	}
 	plainBuf.Write(part)
-	err = dctx.ExtraData(data)
-	if err != nil {
-		return nil, err
-	}
 
 	return plainBuf.Bytes(), nil
 }