diff options
| -rw-r--r-- | docs/hazmat/primitives/aead.rst | 18 | ||||
| -rw-r--r-- | src/cryptography/hazmat/primitives/ciphers/aead.py | 30 | ||||
| -rw-r--r-- | tests/hazmat/primitives/test_aead.py | 38 |
3 files changed, 41 insertions, 45 deletions
diff --git a/docs/hazmat/primitives/aead.rst b/docs/hazmat/primitives/aead.rst index 94b08f0a..6b13edc1 100644 --- a/docs/hazmat/primitives/aead.rst +++ b/docs/hazmat/primitives/aead.rst @@ -78,7 +78,7 @@ also support providing integrity for associated data which is not encrypted. when the ciphertext has been changed, but will also occur when the key, nonce, or associated data are wrong. -.. class:: AESCCM(key) +.. class:: AESCCM(key, tag_length=16) .. versionadded:: 2.0 @@ -93,6 +93,10 @@ also support providing integrity for associated data which is not encrypted. cipher utilizing Counter with CBC-MAC (CCM) (specified in :rfc:`3610`). :param bytes key: A 128, 192, or 256-bit key. This **must** be kept secret. + :param int tag_length: The length of the authentication tag. This + defaults to 16 bytes and it is **strongly** recommended that you + do not make it shorter unless absolutely necessary. Valid tag + lengths are 4, 6, 8, 12, 14, and 16. :raises cryptography.exceptions.UnsupportedAlgorithm: If the version of OpenSSL does not support AES-CCM. @@ -119,7 +123,7 @@ also support providing integrity for associated data which is not encrypted. :returns bytes: The generated key. - .. method:: encrypt(nonce, data, associated_data, tag_length=16) + .. method:: encrypt(nonce, data, associated_data) .. warning:: @@ -138,13 +142,9 @@ also support providing integrity for associated data which is not encrypted. :param bytes data: The data to encrypt. :param bytes associated_data: Additional data that should be authenticated with the key, but is not encrypted. Can be ``None``. - :param int tag_length: The length of the authentication tag. This - defaults to 16 bytes and it is **strongly** recommended that you - do not make it shorter unless absolutely necessary. Valid tag - lengths are 4, 6, 8, 12, 14, and 16. :returns bytes: The ciphertext bytes with the tag appended. - .. method:: decrypt(nonce, data, associated_data, tag_length=16) + .. method:: decrypt(nonce, data, associated_data) Decrypts the ``data`` and authenticates the ``associated_data``. If you called encrypt with ``associated_data`` you must pass the same @@ -156,10 +156,6 @@ also support providing integrity for associated data which is not encrypted. :param bytes data: The data to decrypt (with tag appended). :param bytes associated_data: Additional data to authenticate. Can be ``None`` if none was passed during encryption. - :param int tag_length: The length of the authentication tag. This - defaults to 16 bytes. You only need to change this if your existing - ciphertext has a shorter tag. Valid tag lengths are 4, 6, 8, 12, - 14, and 16. :returns bytes: The original plaintext. :raises cryptography.exceptions.InvalidTag: If the authentication tag doesn't validate this exception will be raised. This will occur diff --git a/src/cryptography/hazmat/primitives/ciphers/aead.py b/src/cryptography/hazmat/primitives/ciphers/aead.py index 189cb5b1..e2c5e381 100644 --- a/src/cryptography/hazmat/primitives/ciphers/aead.py +++ b/src/cryptography/hazmat/primitives/ciphers/aead.py @@ -56,12 +56,20 @@ class ChaCha20Poly1305(object): class AESCCM(object): - def __init__(self, key): + def __init__(self, key, tag_length=16): utils._check_bytes("key", key) if len(key) not in (16, 24, 32): raise ValueError("AESCCM key must be 128, 192, or 256 bits.") self._key = key + if not isinstance(tag_length, int): + raise TypeError("tag_length must be an integer") + + if tag_length not in (4, 6, 8, 12, 14, 16): + raise ValueError("Invalid tag_length") + + self._tag_length = tag_length + if not backend.aead_cipher_supported(self): raise exceptions.UnsupportedAlgorithm( "AESCCM is not supported by this version of OpenSSL", @@ -78,23 +86,23 @@ class AESCCM(object): return os.urandom(bit_length // 8) - def encrypt(self, nonce, data, associated_data, tag_length=16): + def encrypt(self, nonce, data, associated_data): if associated_data is None: associated_data = b"" - self._check_params(nonce, data, associated_data, tag_length) + self._check_params(nonce, data, associated_data) self._validate_lengths(nonce, len(data)) return aead._encrypt( - backend, self, nonce, data, associated_data, tag_length + backend, self, nonce, data, associated_data, self._tag_length ) - def decrypt(self, nonce, data, associated_data, tag_length=16): + def decrypt(self, nonce, data, associated_data): if associated_data is None: associated_data = b"" - self._check_params(nonce, data, associated_data, tag_length) + self._check_params(nonce, data, associated_data) return aead._decrypt( - backend, self, nonce, data, associated_data, tag_length + backend, self, nonce, data, associated_data, self._tag_length ) def _validate_lengths(self, nonce, data_len): @@ -104,13 +112,7 @@ class AESCCM(object): if 2 ** (8 * l) < data_len: raise ValueError("Nonce too long for data") - def _check_params(self, nonce, data, associated_data, tag_length): - if not isinstance(tag_length, int): - raise TypeError("tag_length must be an integer") - - if tag_length not in (4, 6, 8, 12, 14, 16): - raise ValueError("Invalid tag_length") - + def _check_params(self, nonce, data, associated_data): utils._check_bytes("nonce", nonce) utils._check_bytes("data", data) utils._check_bytes("associated_data", associated_data) diff --git a/tests/hazmat/primitives/test_aead.py b/tests/hazmat/primitives/test_aead.py index 9700a1ab..27374da9 100644 --- a/tests/hazmat/primitives/test_aead.py +++ b/tests/hazmat/primitives/test_aead.py @@ -178,14 +178,14 @@ class TestAESCCM(object): def test_invalid_tag_length(self, backend): key = AESCCM.generate_key(128) - aesccm = AESCCM(key) - pt = b"hello" - nonce = os.urandom(12) with pytest.raises(ValueError): - aesccm.encrypt(nonce, pt, None, tag_length=7) + AESCCM(key, tag_length=7) with pytest.raises(ValueError): - aesccm.encrypt(nonce, pt, None, tag_length=2) + AESCCM(key, tag_length=2) + + with pytest.raises(TypeError): + AESCCM(key, tag_length="notanint") def test_invalid_nonce_length(self, backend): key = AESCCM.generate_key(128) @@ -217,14 +217,14 @@ class TestAESCCM(object): adata = binascii.unhexlify(vector["adata"])[:vector["alen"]] ct = binascii.unhexlify(vector["ct"]) pt = binascii.unhexlify(vector["payload"])[:vector["plen"]] - aesccm = AESCCM(key) + aesccm = AESCCM(key, vector["tlen"]) if vector.get('fail'): with pytest.raises(InvalidTag): - aesccm.decrypt(nonce, ct, adata, vector["tlen"]) + aesccm.decrypt(nonce, ct, adata) else: - computed_pt = aesccm.decrypt(nonce, ct, adata, vector["tlen"]) + computed_pt = aesccm.decrypt(nonce, ct, adata) assert computed_pt == pt - assert aesccm.encrypt(nonce, pt, adata, vector["tlen"]) == ct + assert aesccm.encrypt(nonce, pt, adata) == ct def test_roundtrip(self, backend): key = AESCCM.generate_key(128) @@ -232,8 +232,8 @@ class TestAESCCM(object): pt = b"encrypt me" ad = b"additional" nonce = os.urandom(12) - ct = aesccm.encrypt(nonce, pt, ad, 16) - computed_pt = aesccm.decrypt(nonce, ct, ad, 16) + ct = aesccm.encrypt(nonce, pt, ad) + computed_pt = aesccm.decrypt(nonce, ct, ad) assert computed_pt == pt def test_nonce_too_long(self, backend): @@ -243,23 +243,21 @@ class TestAESCCM(object): # pt can be no more than 65536 bytes when nonce is 13 bytes nonce = os.urandom(13) with pytest.raises(ValueError): - aesccm.encrypt(nonce, pt, None, 16) + aesccm.encrypt(nonce, pt, None) @pytest.mark.parametrize( - ("nonce", "data", "associated_data", "tag_length"), + ("nonce", "data", "associated_data"), [ - [object(), b"data", b"", 16], - [b"0" * 12, object(), b"", 16], - [b"0" * 12, b"data", object(), 16], - [b"0" * 12, b"data", b"", object()] + [object(), b"data", b""], + [b"0" * 12, object(), b""], + [b"0" * 12, b"data", object()], ] ) - def test_params_not_bytes(self, nonce, data, associated_data, tag_length, - backend): + def test_params_not_bytes(self, nonce, data, associated_data, backend): key = AESCCM.generate_key(128) aesccm = AESCCM(key) with pytest.raises(TypeError): - aesccm.encrypt(nonce, data, associated_data, tag_length) + aesccm.encrypt(nonce, data, associated_data) def test_bad_key(self, backend): with pytest.raises(TypeError): |