diff options
| -rw-r--r-- | cryptography/hazmat/backends/commoncrypto/ciphers.py | 12 | ||||
| -rw-r--r-- | cryptography/hazmat/backends/openssl/ciphers.py | 8 | ||||
| -rw-r--r-- | tests/hazmat/primitives/test_aes.py | 35 |
3 files changed, 54 insertions, 1 deletions
diff --git a/cryptography/hazmat/backends/commoncrypto/ciphers.py b/cryptography/hazmat/backends/commoncrypto/ciphers.py index 525500c8..6d3ba863 100644 --- a/cryptography/hazmat/backends/commoncrypto/ciphers.py +++ b/cryptography/hazmat/backends/commoncrypto/ciphers.py @@ -151,6 +151,12 @@ class _GCMCipherContext(object): len(mode.initialization_vector) ) self._backend._check_cipher_response(res) + # CommonCrypto has a bug where calling update without at least one + # call to authenticate_additional_data will result in null byte output + # for ciphertext. The following empty byte string call prevents the + # issue, which is present in at least 10.8 and 10.9. + # Filed as rdar://18314544 + self.authenticate_additional_data(b"") def update(self, data): buf = self._backend._ffi.new("unsigned char[]", len(data)) @@ -164,6 +170,12 @@ class _GCMCipherContext(object): return self._backend._ffi.buffer(buf)[:] def finalize(self): + # CommonCrypto has a yet another bug where you must make at least one + # call to update. If you pass just AAD and call finalize without a call + # to update you'll get null bytes for tag. The following update call + # prevents this issue, which is present in at least 10.8 and 10.9. + # Filed as rdar://18314580 + self.update(b"") tag_size = self._cipher.block_size // 8 tag_buf = self._backend._ffi.new("unsigned char[]", tag_size) tag_len = self._backend._ffi.new("size_t *", tag_size) diff --git a/cryptography/hazmat/backends/openssl/ciphers.py b/cryptography/hazmat/backends/openssl/ciphers.py index c3a5499a..d37bb014 100644 --- a/cryptography/hazmat/backends/openssl/ciphers.py +++ b/cryptography/hazmat/backends/openssl/ciphers.py @@ -128,6 +128,14 @@ class _CipherContext(object): return self._backend._ffi.buffer(buf)[:outlen[0]] def finalize(self): + # OpenSSL 1.0.1 on Ubuntu 12.04 (and possibly other distributions) + # appears to have a bug where you must make at least one call to update + # even if you are only using authenticate_additional_data or the + # GCM tag will be wrong. An (empty) call to update resolves this + # and is harmless for all other versions of OpenSSL. + if isinstance(self._mode, GCM): + self.update(b"") + buf = self._backend._ffi.new("unsigned char[]", self._block_size) outlen = self._backend._ffi.new("int *") res = self._backend._lib.EVP_CipherFinal_ex(self._ctx, buf, outlen) diff --git a/tests/hazmat/primitives/test_aes.py b/tests/hazmat/primitives/test_aes.py index 5bde7d3c..e8e0eee4 100644 --- a/tests/hazmat/primitives/test_aes.py +++ b/tests/hazmat/primitives/test_aes.py @@ -18,7 +18,7 @@ import os import pytest -from cryptography.hazmat.primitives.ciphers import algorithms, modes +from cryptography.hazmat.primitives.ciphers import algorithms, base, modes from .utils import generate_aead_test, generate_encrypt_test from ...utils import load_nist_vectors @@ -228,3 +228,36 @@ class TestAESModeGCM(object): algorithms.AES, modes.GCM, ) + + def test_gcm_tag_with_only_aad(self, backend): + key = binascii.unhexlify(b"5211242698bed4774a090620a6ca56f3") + iv = binascii.unhexlify(b"b1e1349120b6e832ef976f5d") + aad = binascii.unhexlify(b"b6d729aab8e6416d7002b9faa794c410d8d2f193") + tag = binascii.unhexlify(b"0f247e7f9c2505de374006738018493b") + + cipher = base.Cipher( + algorithms.AES(key), + modes.GCM(iv), + backend=backend + ) + encryptor = cipher.encryptor() + encryptor.authenticate_additional_data(aad) + encryptor.finalize() + assert encryptor.tag == tag + + def test_gcm_ciphertext_with_no_aad(self, backend): + key = binascii.unhexlify(b"e98b72a9881a84ca6b76e0f43e68647a") + iv = binascii.unhexlify(b"8b23299fde174053f3d652ba") + ct = binascii.unhexlify(b"5a3c1cf1985dbb8bed818036fdd5ab42") + tag = binascii.unhexlify(b"23c7ab0f952b7091cd324835043b5eb5") + pt = binascii.unhexlify(b"28286a321293253c3e0aa2704a278032") + + cipher = base.Cipher( + algorithms.AES(key), + modes.GCM(iv), + backend=backend + ) + encryptor = cipher.encryptor() + computed_ct = encryptor.update(pt) + encryptor.finalize() + assert computed_ct == ct + assert encryptor.tag == tag |