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

Also make the frontend versions actually use them

5 files changed, 39 insertions, 14 deletions

diff --git a/cryptography/hazmat/backends/commoncrypto/hmac.py b/cryptography/hazmat/backends/commoncrypto/hmac.py
index c2b6c379..ee7e3abb 100644
--- a/cryptography/hazmat/backends/commoncrypto/hmac.py
+++ b/cryptography/hazmat/backends/commoncrypto/hmac.py
@@ -14,8 +14,10 @@
 from __future__ import absolute_import, division, print_function
 
 from cryptography import utils
-from cryptography.exceptions import UnsupportedAlgorithm, _Reasons
-from cryptography.hazmat.primitives import interfaces
+from cryptography.exceptions import (
+    InvalidSignature, UnsupportedAlgorithm, _Reasons
+)
+from cryptography.hazmat.primitives import constant_time, interfaces
 
 
 @utils.register_interface(interfaces.MACContext)
@@ -59,3 +61,8 @@ class _HMACContext(object):
                                      self.algorithm.digest_size)
         self._backend._lib.CCHmacFinal(self._ctx, buf)
         return self._backend._ffi.buffer(buf)[:]
+
+    def verify(self, signature):
+        digest = self.finalize()
+        if not constant_time.bytes_eq(digest, signature):
+            raise InvalidSignature("Signature did not match digest.")
diff --git a/cryptography/hazmat/backends/openssl/cmac.py b/cryptography/hazmat/backends/openssl/cmac.py
index 6a844cdc..1ad6055b 100644
--- a/cryptography/hazmat/backends/openssl/cmac.py
+++ b/cryptography/hazmat/backends/openssl/cmac.py
@@ -15,8 +15,10 @@ from __future__ import absolute_import, division, print_function
 
 
 from cryptography import utils
-from cryptography.exceptions import UnsupportedAlgorithm, _Reasons
-from cryptography.hazmat.primitives import interfaces
+from cryptography.exceptions import (
+    InvalidSignature, UnsupportedAlgorithm, _Reasons
+)
+from cryptography.hazmat.primitives import constant_time, interfaces
 from cryptography.hazmat.primitives.ciphers.modes import CBC
 
 
@@ -80,3 +82,8 @@ class _CMACContext(object):
         return _CMACContext(
             self._backend, self._algorithm, ctx=copied_ctx
         )
+
+    def verify(self, signature):
+        digest = self.finalize()
+        if not constant_time.bytes_eq(digest, signature):
+            raise InvalidSignature("Signature did not match digest.")
diff --git a/cryptography/hazmat/backends/openssl/hmac.py b/cryptography/hazmat/backends/openssl/hmac.py
index d5300ea0..c324bd8c 100644
--- a/cryptography/hazmat/backends/openssl/hmac.py
+++ b/cryptography/hazmat/backends/openssl/hmac.py
@@ -15,8 +15,10 @@ from __future__ import absolute_import, division, print_function
 
 
 from cryptography import utils
-from cryptography.exceptions import UnsupportedAlgorithm, _Reasons
-from cryptography.hazmat.primitives import interfaces
+from cryptography.exceptions import (
+    InvalidSignature, UnsupportedAlgorithm, _Reasons
+)
+from cryptography.hazmat.primitives import constant_time, interfaces
 
 
 @utils.register_interface(interfaces.MACContext)
@@ -81,3 +83,8 @@ class _HMACContext(object):
         assert outlen[0] == self.algorithm.digest_size
         self._backend._lib.HMAC_CTX_cleanup(self._ctx)
         return self._backend._ffi.buffer(buf)[:outlen[0]]
+
+    def verify(self, signature):
+        digest = self.finalize()
+        if not constant_time.bytes_eq(digest, signature):
+            raise InvalidSignature("Signature did not match digest.")
diff --git a/cryptography/hazmat/primitives/cmac.py b/cryptography/hazmat/primitives/cmac.py
index 7ae5c118..d5e26a57 100644
--- a/cryptography/hazmat/primitives/cmac.py
+++ b/cryptography/hazmat/primitives/cmac.py
@@ -59,9 +59,11 @@ class CMAC(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)
 
     def copy(self):
         if self._ctx is None:
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)