Merge pull request #157 from reaperhulk/hmac

HMAC support

1 files changed, 59 insertions, 0 deletions

diff --git a/cryptography/hazmat/primitives/hmac.py b/cryptography/hazmat/primitives/hmac.py
new file mode 100644
index 00000000..4da0cc3f
--- /dev/null
+++ b/cryptography/hazmat/primitives/hmac.py
@@ -0,0 +1,59 @@
+# 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
+
+import binascii
+
+import six
+
+
+class HMAC(object):
+    def __init__(self, key, msg=None, digestmod=None, ctx=None, backend=None):
+        super(HMAC, self).__init__()
+        if backend is None:
+            from cryptography.hazmat.bindings import _default_backend
+            backend = _default_backend
+
+        if digestmod is None:
+            raise TypeError("digestmod is a required argument")
+
+        self._backend = backend
+        self.digestmod = digestmod
+        self.key = key
+        if ctx is None:
+            self._ctx = self._backend.hmacs.create_ctx(key, self.digestmod)
+        else:
+            self._ctx = ctx
+
+        if msg is not None:
+            self.update(msg)
+
+    def update(self, msg):
+        if isinstance(msg, six.text_type):
+            raise TypeError("Unicode-objects must be encoded before hashing")
+        self._backend.hmacs.update_ctx(self._ctx, msg)
+
+    def copy(self):
+        return self.__class__(self.key, digestmod=self.digestmod,
+                              backend=self._backend, ctx=self._copy_ctx())
+
+    def digest(self):
+        return self._backend.hmacs.finalize_ctx(self._copy_ctx(),
+                                                self.digestmod.digest_size)
+
+    def hexdigest(self):
+        return str(binascii.hexlify(self.digest()).decode("ascii"))
+
+    def _copy_ctx(self):
+        return self._backend.hmacs.copy_ctx(self._ctx)