Make sure the backend implementatinos of various interfaces have verify() methods.

Also make the frontend versions actually use them

1 files changed, 7 insertions, 5 deletions

diff --git a/cryptography/hazmat/primitives/hmac.py b/cryptography/hazmat/primitives/hmac.py
index 22a31391..47a048ff 100644
--- a/cryptography/hazmat/primitives/hmac.py
+++ b/cryptography/hazmat/primitives/hmac.py
@@ -15,10 +15,10 @@ from __future__ import absolute_import, division, print_function
 
 from cryptography import utils
 from cryptography.exceptions import (
-    AlreadyFinalized, InvalidSignature, UnsupportedAlgorithm, _Reasons
+    AlreadyFinalized, UnsupportedAlgorithm, _Reasons
 )
 from cryptography.hazmat.backends.interfaces import HMACBackend
-from cryptography.hazmat.primitives import constant_time, interfaces
+from cryptography.hazmat.primitives import interfaces
 
 
 @utils.register_interface(interfaces.MACContext)
@@ -71,6 +71,8 @@ class HMAC(object):
     def verify(self, signature):
         if not isinstance(signature, bytes):
             raise TypeError("signature must be bytes.")
-        digest = self.finalize()
-        if not constant_time.bytes_eq(digest, signature):
-            raise InvalidSignature("Signature did not match digest.")
+        if self._ctx is None:
+            raise AlreadyFinalized("Context was already finalized.")
+
+        ctx, self._ctx = self._ctx, None
+        ctx.verify(signature)