Added support for HMAC backend

1 files changed, 15 insertions, 1 deletions

diff --git a/cryptography/hazmat/backends/multibackend.py b/cryptography/hazmat/backends/multibackend.py
index 210efbe8..035517ea 100644
--- a/cryptography/hazmat/backends/multibackend.py
+++ b/cryptography/hazmat/backends/multibackend.py
@@ -15,11 +15,14 @@ from __future__ import absolute_import, division, print_function
 
 from cryptography import utils
 from cryptography.exceptions import UnsupportedAlgorithm
-from cryptography.hazmat.backends.interfaces import CipherBackend, HashBackend
+from cryptography.hazmat.backends.interfaces import (
+    CipherBackend, HashBackend, HMACBackend
+)
 
 
 @utils.register_interface(CipherBackend)
 @utils.register_interface(HashBackend)
+@utils.register_interface(HMACBackend)
 class PrioritizedMultiBackend(object):
     name = "multibackend"
 
@@ -55,3 +58,14 @@ class PrioritizedMultiBackend(object):
             except UnsupportedAlgorithm:
                 pass
         raise UnsupportedAlgorithm
+
+    def hmac_supported(self, algorithm):
+        return any(b.hmac_supported(algorithm) for b in self._backends)
+
+    def create_hmac_ctx(self, key, algorithm):
+        for b in self._backends:
+            try:
+                return b.create_hmac_ctx(key, algorithm)
+            except UnsupportedAlgorithm:
+                pass
+        raise UnsupportedAlgorithm