make _CipherContext in backend.py compliant with AEADCipherContext

* Might make more sense to split it into _CipherContext and
  _AEADCipherContext like we do in base.py, but there would be quite a
  bit of duplicate code.

2 files changed, 6 insertions, 1 deletions

diff --git a/cryptography/hazmat/bindings/openssl/backend.py b/cryptography/hazmat/bindings/openssl/backend.py
index 1a534011..4d9a8ce5 100644
--- a/cryptography/hazmat/bindings/openssl/backend.py
+++ b/cryptography/hazmat/bindings/openssl/backend.py
@@ -237,6 +237,7 @@ class GetCipherByName(object):
 
 
 @utils.register_interface(interfaces.CipherContext)
+@utils.register_interface(interfaces.AEADCipherContext)
 class _CipherContext(object):
     _ENCRYPT = 1
     _DECRYPT = 0
@@ -343,6 +344,10 @@ class _CipherContext(object):
         )
         assert res != 0
 
+    @property
+    def tag(self):
+        return self._tag
+
 
 @utils.register_interface(interfaces.HashContext)
 class _HashContext(object):
diff --git a/cryptography/hazmat/primitives/ciphers/base.py b/cryptography/hazmat/primitives/ciphers/base.py
index 252a9feb..a6f06b82 100644
--- a/cryptography/hazmat/primitives/ciphers/base.py
+++ b/cryptography/hazmat/primitives/ciphers/base.py
@@ -85,7 +85,7 @@ class _AEADCipherContext(object):
         if self._ctx is None:
             raise AlreadyFinalized("Context was already finalized")
         data = self._ctx.finalize()
-        self._tag = self._ctx._tag
+        self._tag = self._ctx.tag
         self._ctx = None
         return data