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libgocryptfs
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Use block number as authentication data

This commit is contained in:
Jakob Unterwurzacher 2015-10-06 22:27:37 +02:00
parent 45ea8aa546
commit a3d286069f
5 changed files with 21 additions and 22 deletions
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4
cryptfs/config_file.go
View File

@ -39,7 +39,7 @@ func CreateConfFile(filename string, password string) error {
// Lock master key using password-based key
cfs := NewCryptFS(scryptHash, false)
cf.EncryptedKey = cfs.EncryptBlock(key)
cf.EncryptedKey = cfs.EncryptBlock(key, 0)
// Write file to disk
err := cf.WriteFile()
@ -73,7 +73,7 @@ func LoadConfFile(filename string, password string) ([]byte, error) {
// We use stock go GCM instead of OpenSSL here as speed is not important
// and we get better error messages
cfs := NewCryptFS(scryptHash, false)
key, err := cfs.DecryptBlock(cf.EncryptedKey)
key, err := cfs.DecryptBlock(cf.EncryptedKey, 0)
if err != nil {
Warn.Printf("Failed to unlock master key: %s\n", err.Error())
return nil, err

1
cryptfs/cryptfs.go
View File

@ -13,7 +13,6 @@ const (
KEY_LEN = 32 // AES-256
NONCE_LEN = 12
AUTH_TAG_LEN = 16
FILEID_LEN = 16
)
type CryptFS struct {

15
cryptfs/cryptfs_content.go
View File

@ -3,6 +3,7 @@ package cryptfs
// File content encryption / decryption
import (
"encoding/binary"
"bytes"
"crypto/cipher"
"crypto/md5"
@ -29,18 +30,19 @@ type CryptFile struct {
}
// DecryptBlocks - Decrypt a number of blocks
func (be *CryptFS) DecryptBlocks(ciphertext []byte) ([]byte, error) {
func (be *CryptFS) DecryptBlocks(ciphertext []byte, firstBlockNo uint64) ([]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)
pBlock, err = be.DecryptBlock(cBlock, firstBlockNo)
if err != nil {
break
}
pBuf.Write(pBlock)
firstBlockNo++
}
return pBuf.Bytes(), err
}
@ -49,7 +51,7 @@ func (be *CryptFS) DecryptBlocks(ciphertext []byte) ([]byte, error) {
//
// 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) ([]byte, error) {
func (be *CryptFS) DecryptBlock(ciphertext []byte, blockNo uint64) ([]byte, error) {
// Empty block?
if len(ciphertext) == 0 {
@ -74,7 +76,8 @@ func (be *CryptFS) DecryptBlock(ciphertext []byte) ([]byte, error) {
// Decrypt
var plaintext []byte
aData := make([]byte, 8)
binary.BigEndian.PutUint64(aData, blockNo)
plaintext, err := be.gcm.Open(plaintext, nonce, ciphertext, nil)
if err != nil {
@ -87,7 +90,7 @@ func (be *CryptFS) DecryptBlock(ciphertext []byte) ([]byte, error) {
}
// encryptBlock - Encrypt and add MAC using GCM
func (be *CryptFS) EncryptBlock(plaintext []byte) []byte {
func (be *CryptFS) EncryptBlock(plaintext []byte, blockNo uint64) []byte {
// Empty block?
if len(plaintext) == 0 {
@ -98,6 +101,8 @@ func (be *CryptFS) EncryptBlock(plaintext []byte) []byte {
nonce := gcmNonce.Get()
// Encrypt plaintext and append to nonce
aData := make([]byte, 8)
binary.BigEndian.PutUint64(aData, blockNo)
ciphertext := be.gcm.Seal(nonce, nonce, plaintext, nil)
return ciphertext

12
cryptfs/openssl_aead.go
View File

@ -63,10 +63,6 @@ func (be opensslGCM) Seal(dst, nonce, plaintext, data []byte) []byte {
// The ciphertext and dst may alias exactly or not at all.
func (be opensslGCM) Open(dst, nonce, ciphertext, data []byte) ([]byte, error) {
if len(data) > 0 {
panic("Extra data is not supported")
}
l := len(ciphertext)
tag := ciphertext[l-AUTH_TAG_LEN : l]
ciphertext = ciphertext[0 : l-AUTH_TAG_LEN]
@ -76,6 +72,10 @@ func (be opensslGCM) Open(dst, nonce, ciphertext, data []byte) ([]byte, error) {
if err != nil {
return nil, err
}
err = dctx.ExtraData(data)
if err != nil {
return nil, err
}
part, err := dctx.DecryptUpdate(ciphertext)
if err != nil {
return nil, err
@ -90,10 +90,6 @@ func (be opensslGCM) Open(dst, nonce, ciphertext, data []byte) ([]byte, error) {
return nil, err
}
plainBuf.Write(part)
err = dctx.ExtraData(data)
if err != nil {
return nil, err
}
return plainBuf.Bytes(), nil
}

11
pathfs_frontend/file.go
View File

@ -80,13 +80,12 @@ func (f *file) doRead(off uint64, length uint64) ([]byte, fuse.Status) {
}
// Truncate ciphertext buffer down to actually read bytes
ciphertext = ciphertext[0:n]
{
blockNo := alignedOffset / f.cfs.CipherBS()
cryptfs.Debug.Printf("ReadAt offset=%d bytes (%d blocks), want=%d, got=%d\n", alignedOffset, blockNo, alignedLength, n)
}
blockNo := alignedOffset / f.cfs.CipherBS()
cryptfs.Debug.Printf("ReadAt offset=%d bytes (%d blocks), want=%d, got=%d\n", alignedOffset, blockNo, alignedLength, n)
// Decrypt it
plaintext, err := f.cfs.DecryptBlocks(ciphertext)
plaintext, err := f.cfs.DecryptBlocks(ciphertext, blockNo)
if err != nil {
blockNo := (alignedOffset + uint64(len(plaintext))) / f.cfs.PlainBS()
cipherOff := blockNo * f.cfs.CipherBS()
@ -159,7 +158,7 @@ func (f *file) doWrite(data []byte, off int64) (uint32, fuse.Status) {
// Write
blockOffset, _ := b.CiphertextRange()
blockData = f.cfs.EncryptBlock(blockData)
blockData = f.cfs.EncryptBlock(blockData, b.BlockNo)
cryptfs.Debug.Printf("ino%d: Writing %d bytes to block #%d, md5=%s\n", f.ino, len(blockData), b.BlockNo, cryptfs.Debug.Md5sum(blockData))
if len(blockData) != int(f.cfs.CipherBS()) {
cryptfs.Debug.Printf("ino%d: Writing partial block #%d (%d bytes)\n", f.ino, b.BlockNo, len(blockData))