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path: root/cryptfs/cryptfile.go
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Diffstat (limited to 'cryptfs/cryptfile.go')
-rw-r--r--cryptfs/cryptfile.go100
1 files changed, 82 insertions, 18 deletions
diff --git a/cryptfs/cryptfile.go b/cryptfs/cryptfile.go
index 5645f3c..0cd11da 100644
--- a/cryptfs/cryptfile.go
+++ b/cryptfs/cryptfile.go
@@ -15,6 +15,50 @@ type CryptFile struct {
cipherBS int64
}
+// decryptBlock - Verify and decrypt GCM block
+func (be *CryptFS) DecryptBlock(ciphertext []byte) ([]byte, error) {
+
+ // Empty block?
+ if len(ciphertext) == 0 {
+ return ciphertext, nil
+ }
+
+ if len(ciphertext) < NONCE_LEN {
+ warn.Printf("decryptBlock: Block is too short: %d bytes\n", len(ciphertext))
+ return nil, errors.New("Block is too short")
+ }
+
+ // Extract nonce
+ nonce := ciphertext[:NONCE_LEN]
+ ciphertext = ciphertext[NONCE_LEN:]
+
+ // Decrypt
+ var plaintext []byte
+ plaintext, err := be.gcm.Open(plaintext, nonce, ciphertext, nil)
+ if err != nil {
+ return nil, err
+ }
+
+ return plaintext, nil
+}
+
+// encryptBlock - Encrypt and add MAC using GCM
+func (be *CryptFS) EncryptBlock(plaintext []byte) []byte {
+
+ // Empty block?
+ if len(plaintext) == 0 {
+ return plaintext
+ }
+
+ // Get fresh nonce
+ nonce := gcmNonce.Get()
+
+ // Encrypt plaintext and append to nonce
+ ciphertext := be.gcm.Seal(nonce, nonce, plaintext, nil)
+
+ return ciphertext
+}
+
// readCipherBlock - Read ciphertext block number "blockNo", decrypt,
// return plaintext
func (be *CryptFile) readCipherBlock(blockNo int64) ([]byte, error) {
@@ -30,8 +74,7 @@ func (be *CryptFile) readCipherBlock(blockNo int64) ([]byte, error) {
// Truncate buffer to actually read bytes
buf = buf[:readN]
- // Empty block?file:///home/jakob/go/src/github.com/rfjakob/gocryptfs-bazil/backend/backend.go
-
+ // Empty block?
if len(buf) == 0 {
return buf, nil
}
@@ -58,28 +101,49 @@ func (be *CryptFile) readCipherBlock(blockNo int64) ([]byte, error) {
// intraBlock identifies a part of a file block
type intraBlock struct {
- blockNo int64 // Block number in file
- offset int64 // Offset into block plaintext
- length int64 // Length of data from this block
+ BlockNo int64 // Block number in file
+ Offset int64 // Offset into block plaintext
+ Length int64 // Length of data from this block
+ fs *CryptFS
+}
+
+// isPartial - is the block partial? This means we have to do read-modify-write.
+func (ib *intraBlock) IsPartial() bool {
+ if ib.Offset > 0 || ib.Length < ib.fs.plainBS {
+ return true
+ }
+ return false
+}
+
+// ciphertextRange - get byte range in ciphertext file corresponding to BlockNo
+func (ib *intraBlock) CiphertextRange() (offset int64, length int64) {
+ return ib.BlockNo * ib.fs.cipherBS, ib.fs.cipherBS
+}
+
+// CropBlock - crop a full plaintext block down to the relevant part
+func (ib *intraBlock) CropBlock(d []byte) []byte{
+ return d[ib.Offset:ib.Offset+ib.Length]
}
// Split a plaintext byte range into (possible partial) blocks
-func (be *CryptFile) splitRange(offset int64, length int64) []intraBlock {
+func (be *CryptFS) SplitRange(offset int64, length int64) []intraBlock {
var b intraBlock
var parts []intraBlock
+ b.fs = be
+
for length > 0 {
- b.blockNo = offset / be.plainBS
- b.offset = offset % be.plainBS
- b.length = be.min64(length, be.plainBS - b.offset)
+ b.BlockNo = offset / be.plainBS
+ b.Offset = offset % be.plainBS
+ b.Length = be.min64(length, be.plainBS - b.Offset)
parts = append(parts, b)
- offset += b.length
- length -= b.length
+ offset += b.Length
+ length -= b.Length
}
return parts
}
-func (be *CryptFile) min64(x int64, y int64) int64 {
+func (be *CryptFS) min64(x int64, y int64) int64 {
if x < y {
return x
}
@@ -110,16 +174,16 @@ func (be *CryptFile) writeCipherBlock(blockNo int64, plain []byte) error {
// Perform RMW cycle on block
// Write "data" into file location specified in "b"
func (be *CryptFile) rmwWrite(b intraBlock, data []byte, f *os.File) error {
- if b.length != int64(len(data)) {
+ if b.Length != int64(len(data)) {
panic("Length mismatch")
}
- oldBlock, err := be.readCipherBlock(b.blockNo)
+ oldBlock, err := be.readCipherBlock(b.BlockNo)
if err != nil {
return err
}
- newBlockLen := b.offset + b.length
- debug.Printf("newBlockLen := %d + %d\n", b.offset, b.length)
+ newBlockLen := b.Offset + b.Length
+ debug.Printf("newBlockLen := %d + %d\n", b.Offset, b.Length)
var newBlock []byte
// Write goes beyond the old block and grows the file?
@@ -133,10 +197,10 @@ func (be *CryptFile) rmwWrite(b intraBlock, data []byte, f *os.File) error {
// Fill with old data
copy(newBlock, oldBlock)
// Then overwrite the relevant parts with new data
- copy(newBlock[b.offset:b.offset + b.length], data)
+ copy(newBlock[b.Offset:b.Offset + b.Length], data)
// Actual write
- err = be.writeCipherBlock(b.blockNo, newBlock)
+ err = be.writeCipherBlock(b.BlockNo, newBlock)
if err != nil {
// An incomplete write to a ciphertext block means that the whole block