1 files changed, 78 insertions, 0 deletions
diff --git a/src/cryptography/hazmat/primitives/hmac.py b/src/cryptography/hazmat/primitives/hmac.py
new file mode 100644
index 00000000..47a048ff
--- /dev/null
+++ b/src/cryptography/hazmat/primitives/hmac.py
@@ -0,0 +1,78 @@
+# 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 (
+    AlreadyFinalized, UnsupportedAlgorithm, _Reasons
+)
+from cryptography.hazmat.backends.interfaces import HMACBackend
+from cryptography.hazmat.primitives import interfaces
+
+
+@utils.register_interface(interfaces.MACContext)
+@utils.register_interface(interfaces.HashContext)
+class HMAC(object):
+    def __init__(self, key, algorithm, backend, ctx=None):
+        if not isinstance(backend, HMACBackend):
+            raise UnsupportedAlgorithm(
+                "Backend object does not implement HMACBackend.",
+                _Reasons.BACKEND_MISSING_INTERFACE
+            )
+
+        if not isinstance(algorithm, interfaces.HashAlgorithm):
+            raise TypeError("Expected instance of interfaces.HashAlgorithm.")
+        self._algorithm = algorithm
+
+        self._backend = backend
+        self._key = key
+        if ctx is None:
+            self._ctx = self._backend.create_hmac_ctx(key, self.algorithm)
+        else:
+            self._ctx = ctx
+
+    algorithm = utils.read_only_property("_algorithm")
+
+    def update(self, data):
+        if self._ctx is None:
+            raise AlreadyFinalized("Context was already finalized.")
+        if not isinstance(data, bytes):
+            raise TypeError("data must be bytes.")
+        self._ctx.update(data)
+
+    def copy(self):
+        if self._ctx is None:
+            raise AlreadyFinalized("Context was already finalized.")
+        return HMAC(
+            self._key,
+            self.algorithm,
+            backend=self._backend,
+            ctx=self._ctx.copy()
+        )
+
+    def finalize(self):
+        if self._ctx is None:
+            raise AlreadyFinalized("Context was already finalized.")
+        digest = self._ctx.finalize()
+        self._ctx = None
+        return digest
+
+    def verify(self, signature):
+        if not isinstance(signature, bytes):
+            raise TypeError("signature must be bytes.")
+        if self._ctx is None:
+            raise AlreadyFinalized("Context was already finalized.")
+
+        ctx, self._ctx = self._ctx, None
+        ctx.verify(signature)