diff options
| -rw-r--r-- | cryptography/hazmat/bindings/openssl/backend.py | 31 | ||||
| -rw-r--r-- | cryptography/hazmat/bindings/openssl/err.py | 7 | ||||
| -rw-r--r-- | docs/exceptions.rst | 1 | ||||
| -rw-r--r-- | docs/hazmat/primitives/padding.rst | 8 | ||||
| -rw-r--r-- | docs/hazmat/primitives/symmetric-encryption.rst | 12 | ||||
| -rw-r--r-- | tests/hazmat/bindings/test_openssl.py | 4 | ||||
| -rw-r--r-- | tests/hazmat/primitives/test_block.py | 16 |
7 files changed, 76 insertions, 3 deletions
diff --git a/cryptography/hazmat/bindings/openssl/backend.py b/cryptography/hazmat/bindings/openssl/backend.py index db4d18e7..9f8ea939 100644 --- a/cryptography/hazmat/bindings/openssl/backend.py +++ b/cryptography/hazmat/bindings/openssl/backend.py @@ -193,6 +193,33 @@ class Backend(object): def create_symmetric_decryption_ctx(self, cipher, mode): return _CipherContext(self, cipher, mode, _CipherContext._DECRYPT) + def _handle_error(self): + code = self.lib.ERR_get_error() + assert code != 0 + lib = self.lib.ERR_GET_LIB(code) + func = self.lib.ERR_GET_FUNC(code) + reason = self.lib.ERR_GET_REASON(code) + return self._handle_error_code(lib, func, reason) + + def _handle_error_code(self, lib, func, reason): + if lib == self.lib.ERR_LIB_EVP: + if func == self.lib.EVP_F_EVP_ENCRYPTFINAL_EX: + if reason == self.lib.EVP_R_DATA_NOT_MULTIPLE_OF_BLOCK_LENGTH: + raise ValueError( + "The length of the provided data is not a multiple of " + "the block length" + ) + elif func == self.lib.EVP_F_EVP_DECRYPTFINAL_EX: + if reason == self.lib.EVP_R_DATA_NOT_MULTIPLE_OF_BLOCK_LENGTH: + raise ValueError( + "The length of the provided data is not a multiple of " + "the block length" + ) + + raise SystemError( + "Unknown error code from OpenSSL, you should probably file a bug." + ) + class GetCipherByName(object): def __init__(self, fmt): @@ -268,7 +295,9 @@ class _CipherContext(object): buf = self._backend.ffi.new("unsigned char[]", self._cipher.block_size) outlen = self._backend.ffi.new("int *") res = self._backend.lib.EVP_CipherFinal_ex(self._ctx, buf, outlen) - assert res != 0 + if res == 0: + self._backend._handle_error() + res = self._backend.lib.EVP_CIPHER_CTX_cleanup(self._ctx) assert res == 1 return self._backend.ffi.buffer(buf)[:outlen[0]] diff --git a/cryptography/hazmat/bindings/openssl/err.py b/cryptography/hazmat/bindings/openssl/err.py index 6a36dee0..3dac6948 100644 --- a/cryptography/hazmat/bindings/openssl/err.py +++ b/cryptography/hazmat/bindings/openssl/err.py @@ -21,6 +21,13 @@ struct ERR_string_data_st { const char *string; }; typedef struct ERR_string_data_st ERR_STRING_DATA; + +static const int ERR_LIB_EVP; + +static const int EVP_F_EVP_ENCRYPTFINAL_EX; +static const int EVP_F_EVP_DECRYPTFINAL_EX; + +static const int EVP_R_DATA_NOT_MULTIPLE_OF_BLOCK_LENGTH; """ FUNCTIONS = """ diff --git a/docs/exceptions.rst b/docs/exceptions.rst index ab1b28fe..c6f5a7cc 100644 --- a/docs/exceptions.rst +++ b/docs/exceptions.rst @@ -12,4 +12,3 @@ Exceptions This is raised when a backend doesn't support the requested algorithm (or combination of algorithms). - diff --git a/docs/hazmat/primitives/padding.rst b/docs/hazmat/primitives/padding.rst index aebb4d4d..4d79ac8f 100644 --- a/docs/hazmat/primitives/padding.rst +++ b/docs/hazmat/primitives/padding.rst @@ -25,8 +25,14 @@ multiple of the block size. >>> padder = padding.PKCS7(128).padder() >>> padder.update(b"1111111111") '' - >>> padder.finalize() + >>> padded_data = padder.finalize() + >>> padded_data '1111111111\x06\x06\x06\x06\x06\x06' + >>> unpadder = padding.PKCS7(128).unpadder() + >>> unpadder.update(padded_data) + '' + >>> unpadder.finalize() + '1111111111' :param block_size: The size of the block in bits that the data is being padded to. diff --git a/docs/hazmat/primitives/symmetric-encryption.rst b/docs/hazmat/primitives/symmetric-encryption.rst index eef359d6..732af33c 100644 --- a/docs/hazmat/primitives/symmetric-encryption.rst +++ b/docs/hazmat/primitives/symmetric-encryption.rst @@ -75,6 +75,15 @@ an "encrypt-then-MAC" formulation as `described by Colin Percival`_. everything into the context. Once that is done call ``finalize()`` to finish the operation and obtain the remainder of the data. + Block ciphers require that plaintext or ciphertext always be a multiple of + their block size, because of that **padding** is often required to make a + message the correct size. ``CipherContext`` will not automatically apply + any padding; you'll need to add your own. For block ciphers the reccomended + padding is :class:`cryptography.hazmat.primitives.padding.PKCS7`. If you + are using a stream cipher mode (such as + :class:`cryptography.hazmat.primitives.modes.CTR`) you don't have to worry + about this. + .. method:: update(data) :param bytes data: The data you wish to pass into the context. @@ -90,6 +99,9 @@ an "encrypt-then-MAC" formulation as `described by Colin Percival`_. .. method:: finalize() :return bytes: Returns the remainder of the data. + :raises ValueError: This is raised when the data provided isn't + correctly padded to be a multiple of the + algorithm's block size. Once ``finalize`` is called this object can no longer be used and :meth:`update` and :meth:`finalize` will raise diff --git a/tests/hazmat/bindings/test_openssl.py b/tests/hazmat/bindings/test_openssl.py index 9f27aab7..7ad1ea75 100644 --- a/tests/hazmat/bindings/test_openssl.py +++ b/tests/hazmat/bindings/test_openssl.py @@ -70,3 +70,7 @@ class TestOpenSSL(object): ) with pytest.raises(UnsupportedAlgorithm): cipher.encryptor() + + def test_handle_unknown_error(self): + with pytest.raises(SystemError): + backend._handle_error_code(0, 0, 0) diff --git a/tests/hazmat/primitives/test_block.py b/tests/hazmat/primitives/test_block.py index 9460c53d..ea40127e 100644 --- a/tests/hazmat/primitives/test_block.py +++ b/tests/hazmat/primitives/test_block.py @@ -108,3 +108,19 @@ class TestCipherContext(object): with pytest.raises(UnsupportedAlgorithm): cipher.decryptor() + + def test_incorrectly_padded(self, backend): + cipher = Cipher( + algorithms.AES(b"\x00" * 16), + modes.CBC(b"\x00" * 16), + backend + ) + encryptor = cipher.encryptor() + encryptor.update(b"1") + with pytest.raises(ValueError): + encryptor.finalize() + + decryptor = cipher.decryptor() + decryptor.update(b"1") + with pytest.raises(ValueError): + decryptor.finalize() |