diff options
Diffstat (limited to 'crypto/key_store_passphrase.go')
| -rw-r--r-- | crypto/key_store_passphrase.go | 49 |
1 files changed, 28 insertions, 21 deletions
diff --git a/crypto/key_store_passphrase.go b/crypto/key_store_passphrase.go index ee383584c..4cfb1851b 100644 --- a/crypto/key_store_passphrase.go +++ b/crypto/key_store_passphrase.go @@ -28,24 +28,25 @@ the private key is encrypted and on disk uses another JSON encoding. Cryptography: -1. Encryption key is scrypt derived key from user passphrase. Scrypt parameters +1. Encryption key is first 16 bytes of SHA3-256 of first 16 bytes of + scrypt derived key from user passphrase. Scrypt parameters (work factors) [1][2] are defined as constants below. -2. Scrypt salt is 32 random bytes from CSPRNG. It is appended to ciphertext. -3. Checksum is SHA3 of the private key bytes. -4. Plaintext is concatenation of private key bytes and checksum. -5. Encryption algo is AES 256 CBC [3][4] -6. CBC IV is 16 random bytes from CSPRNG. It is appended to ciphertext. +2. Scrypt salt is 32 random bytes from CSPRNG. + It's stored in plain next to ciphertext in key file. +3. MAC is SHA3-256 of concatenation of ciphertext and last 16 bytes of scrypt derived key. +4. Plaintext is the EC private key bytes. +5. Encryption algo is AES 128 CBC [3][4] +6. CBC IV is 16 random bytes from CSPRNG. + It's stored in plain next to ciphertext in key file. 7. Plaintext padding is PKCS #7 [5][6] Encoding: -1. On disk, ciphertext, salt and IV are encoded in a nested JSON object. +1. On disk, the ciphertext, MAC, salt and IV are encoded in a nested JSON object. cat a key file to see the structure. 2. byte arrays are base64 JSON strings. 3. The EC private key bytes are in uncompressed form [7]. They are a big-endian byte slice of the absolute value of D [8][9]. -4. The checksum is the last 32 bytes of the plaintext byte array and the - private key is the preceeding bytes. References: @@ -124,21 +125,25 @@ func (ks keyStorePassphrase) StoreKey(key *Key, auth string) (err error) { return err } + encryptKey := Sha3(derivedKey[:16])[:16] + keyBytes := FromECDSA(key.PrivateKey) - keyBytesHash := Sha3(keyBytes) - toEncrypt := PKCS7Pad(append(keyBytes, keyBytesHash...)) + toEncrypt := PKCS7Pad(keyBytes) - AES256Block, err := aes.NewCipher(derivedKey) + AES128Block, err := aes.NewCipher(encryptKey) if err != nil { return err } iv := randentropy.GetEntropyCSPRNG(aes.BlockSize) // 16 - AES256CBCEncrypter := cipher.NewCBCEncrypter(AES256Block, iv) + AES128CBCEncrypter := cipher.NewCBCEncrypter(AES128Block, iv) cipherText := make([]byte, len(toEncrypt)) - AES256CBCEncrypter.CryptBlocks(cipherText, toEncrypt) + AES128CBCEncrypter.CryptBlocks(cipherText, toEncrypt) + + mac := Sha3(derivedKey[16:32], cipherText) cipherStruct := cipherJSON{ + mac, salt, iv, cipherText, @@ -177,6 +182,7 @@ func DecryptKey(ks keyStorePassphrase, keyAddr []byte, auth string) (keyBytes [] err = json.Unmarshal(fileContent, keyProtected) keyId = keyProtected.Id + mac := keyProtected.Crypto.MAC salt := keyProtected.Crypto.Salt iv := keyProtected.Crypto.IV cipherText := keyProtected.Crypto.CipherText @@ -186,15 +192,16 @@ func DecryptKey(ks keyStorePassphrase, keyAddr []byte, auth string) (keyBytes [] if err != nil { return nil, nil, err } - plainText, err := aesCBCDecrypt(derivedKey, cipherText, iv) - if err != nil { + + calculatedMAC := Sha3(derivedKey[16:32], cipherText) + if !bytes.Equal(calculatedMAC, mac) { + err = errors.New("Decryption failed: MAC mismatch") return nil, nil, err } - keyBytes = plainText[:len(plainText)-32] - keyBytesHash := plainText[len(plainText)-32:] - if !bytes.Equal(Sha3(keyBytes), keyBytesHash) { - err = errors.New("Decryption failed: checksum mismatch") + + plainText, err := aesCBCDecrypt(Sha3(derivedKey[:16])[:16], cipherText, iv) + if err != nil { return nil, nil, err } - return keyBytes, keyId, err + return plainText, keyId, err } |