Use block number as authentication data
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45ea8aa546
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a3d286069f
@ -39,7 +39,7 @@ func CreateConfFile(filename string, password string) error {
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// Lock master key using password-based key
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cfs := NewCryptFS(scryptHash, false)
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cf.EncryptedKey = cfs.EncryptBlock(key)
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cf.EncryptedKey = cfs.EncryptBlock(key, 0)
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// Write file to disk
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err := cf.WriteFile()
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@ -73,7 +73,7 @@ func LoadConfFile(filename string, password string) ([]byte, error) {
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// We use stock go GCM instead of OpenSSL here as speed is not important
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// and we get better error messages
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cfs := NewCryptFS(scryptHash, false)
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key, err := cfs.DecryptBlock(cf.EncryptedKey)
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key, err := cfs.DecryptBlock(cf.EncryptedKey, 0)
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if err != nil {
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Warn.Printf("Failed to unlock master key: %s\n", err.Error())
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return nil, err
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@ -13,7 +13,6 @@ const (
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KEY_LEN = 32 // AES-256
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NONCE_LEN = 12
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AUTH_TAG_LEN = 16
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FILEID_LEN = 16
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)
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type CryptFS struct {
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@ -3,6 +3,7 @@ package cryptfs
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// File content encryption / decryption
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import (
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"encoding/binary"
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"bytes"
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"crypto/cipher"
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"crypto/md5"
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@ -29,18 +30,19 @@ type CryptFile struct {
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}
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// DecryptBlocks - Decrypt a number of blocks
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func (be *CryptFS) DecryptBlocks(ciphertext []byte) ([]byte, error) {
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func (be *CryptFS) DecryptBlocks(ciphertext []byte, firstBlockNo uint64) ([]byte, error) {
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cBuf := bytes.NewBuffer(ciphertext)
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var err error
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var pBuf bytes.Buffer
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for cBuf.Len() > 0 {
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cBlock := cBuf.Next(int(be.cipherBS))
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var pBlock []byte
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pBlock, err = be.DecryptBlock(cBlock)
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pBlock, err = be.DecryptBlock(cBlock, firstBlockNo)
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if err != nil {
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break
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}
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pBuf.Write(pBlock)
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firstBlockNo++
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}
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return pBuf.Bytes(), err
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}
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@ -49,7 +51,7 @@ func (be *CryptFS) DecryptBlocks(ciphertext []byte) ([]byte, error) {
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//
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// Corner case: A full-sized block of all-zero ciphertext bytes is translated
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// to an all-zero plaintext block, i.e. file hole passtrough.
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func (be *CryptFS) DecryptBlock(ciphertext []byte) ([]byte, error) {
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func (be *CryptFS) DecryptBlock(ciphertext []byte, blockNo uint64) ([]byte, error) {
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// Empty block?
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if len(ciphertext) == 0 {
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@ -74,7 +76,8 @@ func (be *CryptFS) DecryptBlock(ciphertext []byte) ([]byte, error) {
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// Decrypt
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var plaintext []byte
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aData := make([]byte, 8)
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binary.BigEndian.PutUint64(aData, blockNo)
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plaintext, err := be.gcm.Open(plaintext, nonce, ciphertext, nil)
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if err != nil {
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@ -87,7 +90,7 @@ func (be *CryptFS) DecryptBlock(ciphertext []byte) ([]byte, error) {
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}
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// encryptBlock - Encrypt and add MAC using GCM
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func (be *CryptFS) EncryptBlock(plaintext []byte) []byte {
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func (be *CryptFS) EncryptBlock(plaintext []byte, blockNo uint64) []byte {
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// Empty block?
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if len(plaintext) == 0 {
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@ -98,6 +101,8 @@ func (be *CryptFS) EncryptBlock(plaintext []byte) []byte {
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nonce := gcmNonce.Get()
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// Encrypt plaintext and append to nonce
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aData := make([]byte, 8)
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binary.BigEndian.PutUint64(aData, blockNo)
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ciphertext := be.gcm.Seal(nonce, nonce, plaintext, nil)
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return ciphertext
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@ -63,10 +63,6 @@ func (be opensslGCM) Seal(dst, nonce, plaintext, data []byte) []byte {
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// The ciphertext and dst may alias exactly or not at all.
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func (be opensslGCM) Open(dst, nonce, ciphertext, data []byte) ([]byte, error) {
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if len(data) > 0 {
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panic("Extra data is not supported")
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}
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l := len(ciphertext)
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tag := ciphertext[l-AUTH_TAG_LEN : l]
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ciphertext = ciphertext[0 : l-AUTH_TAG_LEN]
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@ -76,6 +72,10 @@ func (be opensslGCM) Open(dst, nonce, ciphertext, data []byte) ([]byte, error) {
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if err != nil {
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return nil, err
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}
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err = dctx.ExtraData(data)
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if err != nil {
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return nil, err
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}
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part, err := dctx.DecryptUpdate(ciphertext)
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if err != nil {
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return nil, err
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@ -90,10 +90,6 @@ func (be opensslGCM) Open(dst, nonce, ciphertext, data []byte) ([]byte, error) {
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return nil, err
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}
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plainBuf.Write(part)
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err = dctx.ExtraData(data)
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if err != nil {
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return nil, err
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}
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return plainBuf.Bytes(), nil
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}
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@ -80,13 +80,12 @@ func (f *file) doRead(off uint64, length uint64) ([]byte, fuse.Status) {
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}
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// Truncate ciphertext buffer down to actually read bytes
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ciphertext = ciphertext[0:n]
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{
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blockNo := alignedOffset / f.cfs.CipherBS()
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cryptfs.Debug.Printf("ReadAt offset=%d bytes (%d blocks), want=%d, got=%d\n", alignedOffset, blockNo, alignedLength, n)
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}
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blockNo := alignedOffset / f.cfs.CipherBS()
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cryptfs.Debug.Printf("ReadAt offset=%d bytes (%d blocks), want=%d, got=%d\n", alignedOffset, blockNo, alignedLength, n)
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// Decrypt it
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plaintext, err := f.cfs.DecryptBlocks(ciphertext)
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plaintext, err := f.cfs.DecryptBlocks(ciphertext, blockNo)
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if err != nil {
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blockNo := (alignedOffset + uint64(len(plaintext))) / f.cfs.PlainBS()
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cipherOff := blockNo * f.cfs.CipherBS()
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@ -159,7 +158,7 @@ func (f *file) doWrite(data []byte, off int64) (uint32, fuse.Status) {
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// Write
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blockOffset, _ := b.CiphertextRange()
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blockData = f.cfs.EncryptBlock(blockData)
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blockData = f.cfs.EncryptBlock(blockData, b.BlockNo)
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cryptfs.Debug.Printf("ino%d: Writing %d bytes to block #%d, md5=%s\n", f.ino, len(blockData), b.BlockNo, cryptfs.Debug.Md5sum(blockData))
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if len(blockData) != int(f.cfs.CipherBS()) {
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cryptfs.Debug.Printf("ino%d: Writing partial block #%d (%d bytes)\n", f.ino, b.BlockNo, len(blockData))
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