diff options
Diffstat (limited to 'cryptfs')
| -rw-r--r-- | cryptfs/cryptfile.go | 100 |
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 |