split commoncrypto backend - hmac

2 files changed, 59 insertions, 40 deletions

diff --git a/cryptography/hazmat/backends/commoncrypto/backend.py b/cryptography/hazmat/backends/commoncrypto/backend.py
index d22db1da..6147a996 100644
--- a/cryptography/hazmat/backends/commoncrypto/backend.py
+++ b/cryptography/hazmat/backends/commoncrypto/backend.py
@@ -20,6 +20,7 @@ from cryptography.exceptions import (
     InternalError, InvalidTag, UnsupportedAlgorithm, _Reasons
 )
 from cryptography.hazmat.backends.commoncrypto.hashes import _HashContext
+from cryptography.hazmat.backends.commoncrypto.hmac import _HMACContext
 from cryptography.hazmat.backends.interfaces import (
     CipherBackend, HMACBackend, HashBackend, PBKDF2HMACBackend
 )
@@ -416,44 +417,4 @@ class _GCMCipherContext(object):
         return self._tag
 
 
-@utils.register_interface(interfaces.HashContext)
-class _HMACContext(object):
-    def __init__(self, backend, key, algorithm, ctx=None):
-        self.algorithm = algorithm
-        self._backend = backend
-        if ctx is None:
-            ctx = self._backend._ffi.new("CCHmacContext *")
-            try:
-                alg = self._backend._supported_hmac_algorithms[algorithm.name]
-            except KeyError:
-                raise UnsupportedAlgorithm(
-                    "{0} is not a supported HMAC hash on this backend.".format(
-                        algorithm.name),
-                    _Reasons.UNSUPPORTED_HASH
-                )
-
-            self._backend._lib.CCHmacInit(ctx, alg, key, len(key))
-
-        self._ctx = ctx
-        self._key = key
-
-    def copy(self):
-        copied_ctx = self._backend._ffi.new("CCHmacContext *")
-        # CommonCrypto has no APIs for copying HMACs, so we have to copy the
-        # underlying struct.
-        copied_ctx[0] = self._ctx[0]
-        return _HMACContext(
-            self._backend, self._key, self.algorithm, ctx=copied_ctx
-        )
-
-    def update(self, data):
-        self._backend._lib.CCHmacUpdate(self._ctx, data, len(data))
-
-    def finalize(self):
-        buf = self._backend._ffi.new("unsigned char[]",
-                                     self.algorithm.digest_size)
-        self._backend._lib.CCHmacFinal(self._ctx, buf)
-        return self._backend._ffi.buffer(buf)[:]
-
-
 backend = Backend()
diff --git a/cryptography/hazmat/backends/commoncrypto/hmac.py b/cryptography/hazmat/backends/commoncrypto/hmac.py
new file mode 100644
index 00000000..ec3a878b
--- /dev/null
+++ b/cryptography/hazmat/backends/commoncrypto/hmac.py
@@ -0,0 +1,58 @@
+# 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 UnsupportedAlgorithm, _Reasons
+from cryptography.hazmat.primitives import interfaces
+
+
+@utils.register_interface(interfaces.HashContext)
+class _HMACContext(object):
+    def __init__(self, backend, key, algorithm, ctx=None):
+        self.algorithm = algorithm
+        self._backend = backend
+        if ctx is None:
+            ctx = self._backend._ffi.new("CCHmacContext *")
+            try:
+                alg = self._backend._supported_hmac_algorithms[algorithm.name]
+            except KeyError:
+                raise UnsupportedAlgorithm(
+                    "{0} is not a supported HMAC hash on this backend.".format(
+                        algorithm.name),
+                    _Reasons.UNSUPPORTED_HASH
+                )
+
+            self._backend._lib.CCHmacInit(ctx, alg, key, len(key))
+
+        self._ctx = ctx
+        self._key = key
+
+    def copy(self):
+        copied_ctx = self._backend._ffi.new("CCHmacContext *")
+        # CommonCrypto has no APIs for copying HMACs, so we have to copy the
+        # underlying struct.
+        copied_ctx[0] = self._ctx[0]
+        return _HMACContext(
+            self._backend, self._key, self.algorithm, ctx=copied_ctx
+        )
+
+    def update(self, data):
+        self._backend._lib.CCHmacUpdate(self._ctx, data, len(data))
+
+    def finalize(self):
+        buf = self._backend._ffi.new("unsigned char[]",
+                                     self.algorithm.digest_size)
+        self._backend._lib.CCHmacFinal(self._ctx, buf)
+        return self._backend._ffi.buffer(buf)[:]