add test to verify AES CTR is always available in 0.9.8+, comment updates

1 files changed, 6 insertions, 1 deletions

diff --git a/tests/hazmat/backends/test_openssl.py b/tests/hazmat/backends/test_openssl.py
index 154af00f..fb2ca19f 100644
--- a/tests/hazmat/backends/test_openssl.py
+++ b/tests/hazmat/backends/test_openssl.py
@@ -22,7 +22,7 @@ from cryptography.hazmat.primitives import hashes, interfaces
 from cryptography.hazmat.primitives.asymmetric import dsa, padding, rsa
 from cryptography.hazmat.primitives.ciphers import Cipher
 from cryptography.hazmat.primitives.ciphers.algorithms import AES
-from cryptography.hazmat.primitives.ciphers.modes import CBC
+from cryptography.hazmat.primitives.ciphers.modes import CBC, CTR
 from cryptography.hazmat.primitives.interfaces import BlockCipherAlgorithm
 
 from ...utils import raises_unsupported_algorithm
@@ -64,6 +64,11 @@ class TestOpenSSL(object):
     def test_supports_cipher(self):
         assert backend.cipher_supported(None, None) is False
 
+    def test_aes_ctr_always_available(self):
+        # AES CTR should always be available in both 0.9.8 and 1.0.0+
+        assert backend.cipher_supported(AES(b"\x00" * 16),
+                                        CTR(b"\x00" * 16)) is True
+
     def test_register_duplicate_cipher_adapter(self):
         with pytest.raises(ValueError):
             backend.register_cipher_adapter(AES, CBC, None)