add ECB support to create_block_cipher_context

* This is a basic refactor to support ECB and CBC mode in this method.
  We can use this as a starting point to discuss a better solution.

1 files changed, 13 insertions, 1 deletions

diff --git a/cryptography/bindings/openssl/api.py b/cryptography/bindings/openssl/api.py
index 54a74d03..17823786 100644
--- a/cryptography/bindings/openssl/api.py
+++ b/cryptography/bindings/openssl/api.py
@@ -74,9 +74,11 @@ class API(object):
         assert evp_cipher != self._ffi.NULL
         # TODO: only use the key and initialization_vector as needed. Sometimes
         # this needs to be a DecryptInit, when?
+        iv = self._get_iv(mode)
+
         res = self._lib.EVP_EncryptInit_ex(
             ctx, evp_cipher, self._ffi.NULL, cipher.key,
-            mode.initialization_vector
+            iv
         )
         assert res != 0
 
@@ -85,6 +87,16 @@ class API(object):
         self._lib.EVP_CIPHER_CTX_set_padding(ctx, 0)
         return ctx
 
+    def _get_iv(self, mode):
+        # TODO: refactor this to visitor pattern
+        klass_name = mode.__class__.__name__
+        if klass_name == 'CBC':
+            return mode.initialization_vector
+        elif klass_name == 'ECB':
+            return self._ffi.NULL
+        else:
+            raise NotImplementedError
+
     def update_encrypt_context(self, ctx, plaintext):
         buf = self._ffi.new("unsigned char[]", len(plaintext))
         outlen = self._ffi.new("int *")