diff options
Diffstat (limited to 'cryptfs/file.go')
-rw-r--r-- | cryptfs/file.go | 148 |
1 files changed, 0 insertions, 148 deletions
diff --git a/cryptfs/file.go b/cryptfs/file.go deleted file mode 100644 index 5645f3c..0000000 --- a/cryptfs/file.go +++ /dev/null @@ -1,148 +0,0 @@ -package cryptfs - -import ( - "fmt" - "os" - "io" - "errors" - "crypto/cipher" -) - -type CryptFile struct { - file *os.File - gcm cipher.AEAD - plainBS int64 - cipherBS int64 -} - -// readCipherBlock - Read ciphertext block number "blockNo", decrypt, -// return plaintext -func (be *CryptFile) readCipherBlock(blockNo int64) ([]byte, error) { - off := blockNo * int64(be.cipherBS) - buf := make([]byte, be.cipherBS) - - readN, err := be.file.ReadAt(buf, off) - - if err != nil && err != io.EOF { - return nil, err - } - - // Truncate buffer to actually read bytes - buf = buf[:readN] - - // Empty block?file:///home/jakob/go/src/github.com/rfjakob/gocryptfs-bazil/backend/backend.go - - if len(buf) == 0 { - return buf, nil - } - - if len(buf) < NONCE_LEN { - warn.Printf("readCipherBlock: Block is too short: %d bytes\n", len(buf)) - return nil, errors.New("Block is too short") - } - - // Extract nonce - nonce := buf[:NONCE_LEN] - buf = buf[NONCE_LEN:] - - // Decrypt - var plainBuf []byte - plainBuf, err = be.gcm.Open(plainBuf, nonce, buf, nil) - if err != nil { - fmt.Printf("gcm.Open() failed: %d\n", err) - return nil, err - } - - return plainBuf, nil -} - -// 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 -} - -// Split a plaintext byte range into (possible partial) blocks -func (be *CryptFile) splitRange(offset int64, length int64) []intraBlock { - var b intraBlock - var parts []intraBlock - - for length > 0 { - 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 - } - return parts -} - -func (be *CryptFile) min64(x int64, y int64) int64 { - if x < y { - return x - } - return y -} - -// writeCipherBlock - Encrypt plaintext and write it to file block "blockNo" -func (be *CryptFile) writeCipherBlock(blockNo int64, plain []byte) error { - - if int64(len(plain)) > be.plainBS { - panic("writeCipherBlock: Cannot write block that is larger than plainBS") - } - - // Get fresh nonce - nonce := gcmNonce.Get() - // Encrypt data and append to nonce - cipherBuf := be.gcm.Seal(nonce, nonce, plain, nil) - - // WriteAt retries short writes autmatically - written, err := be.file.WriteAt(cipherBuf, blockNo * be.cipherBS) - - debug.Printf("writeCipherBlock: wrote %d ciphertext bytes to block %d\n", - written, blockNo) - - return err -} - -// 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)) { - panic("Length mismatch") - } - - 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) - var newBlock []byte - - // Write goes beyond the old block and grows the file? - // Must create a bigger newBlock - if newBlockLen > int64(len(oldBlock)) { - newBlock = make([]byte, newBlockLen) - } else { - newBlock = make([]byte, len(oldBlock)) - } - - // Fill with old data - copy(newBlock, oldBlock) - // Then overwrite the relevant parts with new data - copy(newBlock[b.offset:b.offset + b.length], data) - - // Actual write - err = be.writeCipherBlock(b.blockNo, newBlock) - - if err != nil { - // An incomplete write to a ciphertext block means that the whole block - // is destroyed. - fmt.Printf("rmwWrite: Write error: %s\n", err) - } - - return err -} |