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path: root/cryptfs/cryptfs_content.go
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Diffstat (limited to 'cryptfs/cryptfs_content.go')
-rw-r--r--cryptfs/cryptfs_content.go20
1 files changed, 13 insertions, 7 deletions
diff --git a/cryptfs/cryptfs_content.go b/cryptfs/cryptfs_content.go
index 7a1859a..03253d3 100644
--- a/cryptfs/cryptfs_content.go
+++ b/cryptfs/cryptfs_content.go
@@ -30,14 +30,14 @@ type CryptFile struct {
}
// DecryptBlocks - Decrypt a number of blocks
-func (be *CryptFS) DecryptBlocks(ciphertext []byte, firstBlockNo uint64) ([]byte, error) {
+func (be *CryptFS) DecryptBlocks(ciphertext []byte, firstBlockNo uint64, fileId []byte) ([]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, firstBlockNo)
+ pBlock, err = be.DecryptBlock(cBlock, firstBlockNo, fileId)
if err != nil {
break
}
@@ -51,7 +51,7 @@ func (be *CryptFS) DecryptBlocks(ciphertext []byte, firstBlockNo uint64) ([]byte
//
// 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, blockNo uint64) ([]byte, error) {
+func (be *CryptFS) DecryptBlock(ciphertext []byte, blockNo uint64, fileId []byte) ([]byte, error) {
// Empty block?
if len(ciphertext) == 0 {
@@ -77,6 +77,7 @@ func (be *CryptFS) DecryptBlock(ciphertext []byte, blockNo uint64) ([]byte, erro
// Decrypt
var plaintext []byte
aData := make([]byte, 8)
+ aData = append(aData, fileId...)
binary.BigEndian.PutUint64(aData, blockNo)
plaintext, err := be.gcm.Open(plaintext, nonce, ciphertext, aData)
@@ -89,8 +90,8 @@ func (be *CryptFS) DecryptBlock(ciphertext []byte, blockNo uint64) ([]byte, erro
return plaintext, nil
}
-// encryptBlock - Encrypt and add MAC using GCM
-func (be *CryptFS) EncryptBlock(plaintext []byte, blockNo uint64) []byte {
+// encryptBlock - Encrypt and add IV and MAC
+func (be *CryptFS) EncryptBlock(plaintext []byte, blockNo uint64, fileId []byte) []byte {
// Empty block?
if len(plaintext) == 0 {
@@ -103,6 +104,7 @@ func (be *CryptFS) EncryptBlock(plaintext []byte, blockNo uint64) []byte {
// Encrypt plaintext and append to nonce
aData := make([]byte, 8)
binary.BigEndian.PutUint64(aData, blockNo)
+ aData = append(aData, fileId...)
ciphertext := be.gcm.Seal(nonce, nonce, plaintext, aData)
return ciphertext
@@ -118,6 +120,7 @@ func (be *CryptFS) SplitRange(offset uint64, length uint64) []intraBlock {
for length > 0 {
b.BlockNo = offset / be.plainBS
b.Skip = offset % be.plainBS
+ // Minimum of remaining data and remaining space in the block
b.Length = be.minu64(length, be.plainBS-b.Skip)
parts = append(parts, b)
offset += b.Length
@@ -134,6 +137,9 @@ func (be *CryptFS) PlainSize(size uint64) uint64 {
return 0
}
+ // Account for header
+ size -= HEADER_LEN
+
overhead := be.cipherBS - be.plainBS
nBlocks := (size + be.cipherBS - 1) / be.cipherBS
if nBlocks*overhead > size {
@@ -171,7 +177,7 @@ func (be *CryptFS) CiphertextRange(offset uint64, length uint64) (alignedOffset
firstBlockNo := offset / be.plainBS
lastBlockNo := (offset + length - 1) / be.plainBS
- alignedOffset = firstBlockNo * be.cipherBS
+ alignedOffset = HEADER_LEN + firstBlockNo * be.cipherBS
alignedLength = (lastBlockNo - firstBlockNo + 1) * be.cipherBS
skipBytes = int(skip)
@@ -232,5 +238,5 @@ func (be *CryptFS) BlockNoPlainOff(plainOffset uint64) uint64 {
// Get the block number at ciphter-text offset
func (be *CryptFS) BlockNoCipherOff(cipherOffset uint64) uint64 {
- return cipherOffset / be.cipherBS
+ return (cipherOffset - HEADER_LEN) / be.cipherBS
}