Merge pull request #1177 from reaperhulk/split-openssl-backend-cipher

Split OpenSSL backend into separate files (cipher contexts)

2 files changed, 223 insertions, 201 deletions

diff --git a/cryptography/hazmat/backends/openssl/backend.py b/cryptography/hazmat/backends/openssl/backend.py
index 183f29f7..d08cd3e4 100644
--- a/cryptography/hazmat/backends/openssl/backend.py
+++ b/cryptography/hazmat/backends/openssl/backend.py
@@ -21,13 +21,16 @@ import six
 
 from cryptography import utils
 from cryptography.exceptions import (
-    InternalError, InvalidTag, UnsupportedAlgorithm, _Reasons
+    InternalError, UnsupportedAlgorithm, _Reasons
 )
 from cryptography.hazmat.backends.interfaces import (
     CMACBackend, CipherBackend, DSABackend, EllipticCurveBackend, HMACBackend,
     HashBackend, PBKDF2HMACBackend, PKCS8SerializationBackend, RSABackend,
     TraditionalOpenSSLSerializationBackend
 )
+from cryptography.hazmat.backends.openssl.ciphers import (
+    _AESCTRCipherContext, _CipherContext
+)
 from cryptography.hazmat.backends.openssl.dsa import (
     _DSASignatureContext, _DSAVerificationContext
 )
@@ -1168,206 +1171,6 @@ class GetCipherByName(object):
         return backend._lib.EVP_get_cipherbyname(cipher_name.encode("ascii"))
 
 
-@utils.register_interface(interfaces.CipherContext)
-@utils.register_interface(interfaces.AEADCipherContext)
-@utils.register_interface(interfaces.AEADEncryptionContext)
-class _CipherContext(object):
-    _ENCRYPT = 1
-    _DECRYPT = 0
-
-    def __init__(self, backend, cipher, mode, operation):
-        self._backend = backend
-        self._cipher = cipher
-        self._mode = mode
-        self._operation = operation
-        self._tag = None
-
-        if isinstance(self._cipher, interfaces.BlockCipherAlgorithm):
-            self._block_size = self._cipher.block_size
-        else:
-            self._block_size = 1
-
-        ctx = self._backend._lib.EVP_CIPHER_CTX_new()
-        ctx = self._backend._ffi.gc(
-            ctx, self._backend._lib.EVP_CIPHER_CTX_free
-        )
-
-        registry = self._backend._cipher_registry
-        try:
-            adapter = registry[type(cipher), type(mode)]
-        except KeyError:
-            raise UnsupportedAlgorithm(
-                "cipher {0} in {1} mode is not supported "
-                "by this backend.".format(
-                    cipher.name, mode.name if mode else mode),
-                _Reasons.UNSUPPORTED_CIPHER
-            )
-
-        evp_cipher = adapter(self._backend, cipher, mode)
-        if evp_cipher == self._backend._ffi.NULL:
-            raise UnsupportedAlgorithm(
-                "cipher {0} in {1} mode is not supported "
-                "by this backend.".format(
-                    cipher.name, mode.name if mode else mode),
-                _Reasons.UNSUPPORTED_CIPHER
-            )
-
-        if isinstance(mode, interfaces.ModeWithInitializationVector):
-            iv_nonce = mode.initialization_vector
-        elif isinstance(mode, interfaces.ModeWithNonce):
-            iv_nonce = mode.nonce
-        else:
-            iv_nonce = self._backend._ffi.NULL
-        # begin init with cipher and operation type
-        res = self._backend._lib.EVP_CipherInit_ex(ctx, evp_cipher,
-                                                   self._backend._ffi.NULL,
-                                                   self._backend._ffi.NULL,
-                                                   self._backend._ffi.NULL,
-                                                   operation)
-        assert res != 0
-        # set the key length to handle variable key ciphers
-        res = self._backend._lib.EVP_CIPHER_CTX_set_key_length(
-            ctx, len(cipher.key)
-        )
-        assert res != 0
-        if isinstance(mode, GCM):
-            res = self._backend._lib.EVP_CIPHER_CTX_ctrl(
-                ctx, self._backend._lib.EVP_CTRL_GCM_SET_IVLEN,
-                len(iv_nonce), self._backend._ffi.NULL
-            )
-            assert res != 0
-            if operation == self._DECRYPT:
-                res = self._backend._lib.EVP_CIPHER_CTX_ctrl(
-                    ctx, self._backend._lib.EVP_CTRL_GCM_SET_TAG,
-                    len(mode.tag), mode.tag
-                )
-                assert res != 0
-
-        # pass key/iv
-        res = self._backend._lib.EVP_CipherInit_ex(
-            ctx,
-            self._backend._ffi.NULL,
-            self._backend._ffi.NULL,
-            cipher.key,
-            iv_nonce,
-            operation
-        )
-        assert res != 0
-        # We purposely disable padding here as it's handled higher up in the
-        # API.
-        self._backend._lib.EVP_CIPHER_CTX_set_padding(ctx, 0)
-        self._ctx = ctx
-
-    def update(self, data):
-        # OpenSSL 0.9.8e has an assertion in its EVP code that causes it
-        # to SIGABRT if you call update with an empty byte string. This can be
-        # removed when we drop support for 0.9.8e (CentOS/RHEL 5). This branch
-        # should be taken only when length is zero and mode is not GCM because
-        # AES GCM can return improper tag values if you don't call update
-        # with empty plaintext when authenticating AAD for ...reasons.
-        if len(data) == 0 and not isinstance(self._mode, GCM):
-            return b""
-
-        buf = self._backend._ffi.new("unsigned char[]",
-                                     len(data) + self._block_size - 1)
-        outlen = self._backend._ffi.new("int *")
-        res = self._backend._lib.EVP_CipherUpdate(self._ctx, buf, outlen, data,
-                                                  len(data))
-        assert res != 0
-        return self._backend._ffi.buffer(buf)[:outlen[0]]
-
-    def finalize(self):
-        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)
-        if res == 0:
-            errors = self._backend._consume_errors()
-
-            if not errors and isinstance(self._mode, GCM):
-                raise InvalidTag
-
-            assert errors
-
-            if errors[0][1:] == (
-                self._backend._lib.ERR_LIB_EVP,
-                self._backend._lib.EVP_F_EVP_ENCRYPTFINAL_EX,
-                self._backend._lib.EVP_R_DATA_NOT_MULTIPLE_OF_BLOCK_LENGTH
-            ) or errors[0][1:] == (
-                self._backend._lib.ERR_LIB_EVP,
-                self._backend._lib.EVP_F_EVP_DECRYPTFINAL_EX,
-                self._backend._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."
-                )
-            else:
-                raise self._backend._unknown_error(errors[0])
-
-        if (isinstance(self._mode, GCM) and
-           self._operation == self._ENCRYPT):
-            block_byte_size = self._block_size // 8
-            tag_buf = self._backend._ffi.new(
-                "unsigned char[]", block_byte_size
-            )
-            res = self._backend._lib.EVP_CIPHER_CTX_ctrl(
-                self._ctx, self._backend._lib.EVP_CTRL_GCM_GET_TAG,
-                block_byte_size, tag_buf
-            )
-            assert res != 0
-            self._tag = self._backend._ffi.buffer(tag_buf)[:]
-
-        res = self._backend._lib.EVP_CIPHER_CTX_cleanup(self._ctx)
-        assert res == 1
-        return self._backend._ffi.buffer(buf)[:outlen[0]]
-
-    def authenticate_additional_data(self, data):
-        outlen = self._backend._ffi.new("int *")
-        res = self._backend._lib.EVP_CipherUpdate(
-            self._ctx, self._backend._ffi.NULL, outlen, data, len(data)
-        )
-        assert res != 0
-
-    @property
-    def tag(self):
-        return self._tag
-
-
-@utils.register_interface(interfaces.CipherContext)
-class _AESCTRCipherContext(object):
-    """
-    This is needed to provide support for AES CTR mode in OpenSSL 0.9.8. It can
-    be removed when we drop 0.9.8 support (RHEL5 extended life ends 2020).
-    """
-    def __init__(self, backend, cipher, mode):
-        self._backend = backend
-
-        self._key = self._backend._ffi.new("AES_KEY *")
-        assert self._key != self._backend._ffi.NULL
-        res = self._backend._lib.AES_set_encrypt_key(
-            cipher.key, len(cipher.key) * 8, self._key
-        )
-        assert res == 0
-        self._ecount = self._backend._ffi.new("char[]", 16)
-        self._nonce = self._backend._ffi.new("char[16]", mode.nonce)
-        self._num = self._backend._ffi.new("unsigned int *", 0)
-
-    def update(self, data):
-        buf = self._backend._ffi.new("unsigned char[]", len(data))
-        self._backend._lib.AES_ctr128_encrypt(
-            data, buf, len(data), self._key, self._nonce,
-            self._ecount, self._num
-        )
-        return self._backend._ffi.buffer(buf)[:]
-
-    def finalize(self):
-        self._key = None
-        self._ecount = None
-        self._nonce = None
-        self._num = None
-        return b""
-
-
 @utils.register_interface(interfaces.HashContext)
 class _HashContext(object):
     def __init__(self, backend, algorithm, ctx=None):
diff --git a/cryptography/hazmat/backends/openssl/ciphers.py b/cryptography/hazmat/backends/openssl/ciphers.py
new file mode 100644
index 00000000..c3a5499a
--- /dev/null
+++ b/cryptography/hazmat/backends/openssl/ciphers.py
@@ -0,0 +1,219 @@
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import absolute_import, division, print_function
+
+from cryptography import utils
+from cryptography.exceptions import InvalidTag, UnsupportedAlgorithm, _Reasons
+from cryptography.hazmat.primitives import interfaces
+from cryptography.hazmat.primitives.ciphers.modes import GCM
+
+
+@utils.register_interface(interfaces.CipherContext)
+@utils.register_interface(interfaces.AEADCipherContext)
+@utils.register_interface(interfaces.AEADEncryptionContext)
+class _CipherContext(object):
+    _ENCRYPT = 1
+    _DECRYPT = 0
+
+    def __init__(self, backend, cipher, mode, operation):
+        self._backend = backend
+        self._cipher = cipher
+        self._mode = mode
+        self._operation = operation
+        self._tag = None
+
+        if isinstance(self._cipher, interfaces.BlockCipherAlgorithm):
+            self._block_size = self._cipher.block_size
+        else:
+            self._block_size = 1
+
+        ctx = self._backend._lib.EVP_CIPHER_CTX_new()
+        ctx = self._backend._ffi.gc(
+            ctx, self._backend._lib.EVP_CIPHER_CTX_free
+        )
+
+        registry = self._backend._cipher_registry
+        try:
+            adapter = registry[type(cipher), type(mode)]
+        except KeyError:
+            raise UnsupportedAlgorithm(
+                "cipher {0} in {1} mode is not supported "
+                "by this backend.".format(
+                    cipher.name, mode.name if mode else mode),
+                _Reasons.UNSUPPORTED_CIPHER
+            )
+
+        evp_cipher = adapter(self._backend, cipher, mode)
+        if evp_cipher == self._backend._ffi.NULL:
+            raise UnsupportedAlgorithm(
+                "cipher {0} in {1} mode is not supported "
+                "by this backend.".format(
+                    cipher.name, mode.name if mode else mode),
+                _Reasons.UNSUPPORTED_CIPHER
+            )
+
+        if isinstance(mode, interfaces.ModeWithInitializationVector):
+            iv_nonce = mode.initialization_vector
+        elif isinstance(mode, interfaces.ModeWithNonce):
+            iv_nonce = mode.nonce
+        else:
+            iv_nonce = self._backend._ffi.NULL
+        # begin init with cipher and operation type
+        res = self._backend._lib.EVP_CipherInit_ex(ctx, evp_cipher,
+                                                   self._backend._ffi.NULL,
+                                                   self._backend._ffi.NULL,
+                                                   self._backend._ffi.NULL,
+                                                   operation)
+        assert res != 0
+        # set the key length to handle variable key ciphers
+        res = self._backend._lib.EVP_CIPHER_CTX_set_key_length(
+            ctx, len(cipher.key)
+        )
+        assert res != 0
+        if isinstance(mode, GCM):
+            res = self._backend._lib.EVP_CIPHER_CTX_ctrl(
+                ctx, self._backend._lib.EVP_CTRL_GCM_SET_IVLEN,
+                len(iv_nonce), self._backend._ffi.NULL
+            )
+            assert res != 0
+            if operation == self._DECRYPT:
+                res = self._backend._lib.EVP_CIPHER_CTX_ctrl(
+                    ctx, self._backend._lib.EVP_CTRL_GCM_SET_TAG,
+                    len(mode.tag), mode.tag
+                )
+                assert res != 0
+
+        # pass key/iv
+        res = self._backend._lib.EVP_CipherInit_ex(
+            ctx,
+            self._backend._ffi.NULL,
+            self._backend._ffi.NULL,
+            cipher.key,
+            iv_nonce,
+            operation
+        )
+        assert res != 0
+        # We purposely disable padding here as it's handled higher up in the
+        # API.
+        self._backend._lib.EVP_CIPHER_CTX_set_padding(ctx, 0)
+        self._ctx = ctx
+
+    def update(self, data):
+        # OpenSSL 0.9.8e has an assertion in its EVP code that causes it
+        # to SIGABRT if you call update with an empty byte string. This can be
+        # removed when we drop support for 0.9.8e (CentOS/RHEL 5). This branch
+        # should be taken only when length is zero and mode is not GCM because
+        # AES GCM can return improper tag values if you don't call update
+        # with empty plaintext when authenticating AAD for ...reasons.
+        if len(data) == 0 and not isinstance(self._mode, GCM):
+            return b""
+
+        buf = self._backend._ffi.new("unsigned char[]",
+                                     len(data) + self._block_size - 1)
+        outlen = self._backend._ffi.new("int *")
+        res = self._backend._lib.EVP_CipherUpdate(self._ctx, buf, outlen, data,
+                                                  len(data))
+        assert res != 0
+        return self._backend._ffi.buffer(buf)[:outlen[0]]
+
+    def finalize(self):
+        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)
+        if res == 0:
+            errors = self._backend._consume_errors()
+
+            if not errors and isinstance(self._mode, GCM):
+                raise InvalidTag
+
+            assert errors
+
+            if errors[0][1:] == (
+                self._backend._lib.ERR_LIB_EVP,
+                self._backend._lib.EVP_F_EVP_ENCRYPTFINAL_EX,
+                self._backend._lib.EVP_R_DATA_NOT_MULTIPLE_OF_BLOCK_LENGTH
+            ) or errors[0][1:] == (
+                self._backend._lib.ERR_LIB_EVP,
+                self._backend._lib.EVP_F_EVP_DECRYPTFINAL_EX,
+                self._backend._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."
+                )
+            else:
+                raise self._backend._unknown_error(errors[0])
+
+        if (isinstance(self._mode, GCM) and
+           self._operation == self._ENCRYPT):
+            block_byte_size = self._block_size // 8
+            tag_buf = self._backend._ffi.new(
+                "unsigned char[]", block_byte_size
+            )
+            res = self._backend._lib.EVP_CIPHER_CTX_ctrl(
+                self._ctx, self._backend._lib.EVP_CTRL_GCM_GET_TAG,
+                block_byte_size, tag_buf
+            )
+            assert res != 0
+            self._tag = self._backend._ffi.buffer(tag_buf)[:]
+
+        res = self._backend._lib.EVP_CIPHER_CTX_cleanup(self._ctx)
+        assert res == 1
+        return self._backend._ffi.buffer(buf)[:outlen[0]]
+
+    def authenticate_additional_data(self, data):
+        outlen = self._backend._ffi.new("int *")
+        res = self._backend._lib.EVP_CipherUpdate(
+            self._ctx, self._backend._ffi.NULL, outlen, data, len(data)
+        )
+        assert res != 0
+
+    @property
+    def tag(self):
+        return self._tag
+
+
+@utils.register_interface(interfaces.CipherContext)
+class _AESCTRCipherContext(object):
+    """
+    This is needed to provide support for AES CTR mode in OpenSSL 0.9.8. It can
+    be removed when we drop 0.9.8 support (RHEL5 extended life ends 2020).
+    """
+    def __init__(self, backend, cipher, mode):
+        self._backend = backend
+
+        self._key = self._backend._ffi.new("AES_KEY *")
+        assert self._key != self._backend._ffi.NULL
+        res = self._backend._lib.AES_set_encrypt_key(
+            cipher.key, len(cipher.key) * 8, self._key
+        )
+        assert res == 0
+        self._ecount = self._backend._ffi.new("char[]", 16)
+        self._nonce = self._backend._ffi.new("char[16]", mode.nonce)
+        self._num = self._backend._ffi.new("unsigned int *", 0)
+
+    def update(self, data):
+        buf = self._backend._ffi.new("unsigned char[]", len(data))
+        self._backend._lib.AES_ctr128_encrypt(
+            data, buf, len(data), self._key, self._nonce,
+            self._ecount, self._num
+        )
+        return self._backend._ffi.buffer(buf)[:]
+
+    def finalize(self):
+        self._key = None
+        self._ecount = None
+        self._nonce = None
+        self._num = None
+        return b""