Merge pull request #108 from alex/triple-des

[WIP] Add TripleDES

2 files changed, 31 insertions, 1 deletions

diff --git a/cryptography/bindings/openssl/api.py b/cryptography/bindings/openssl/api.py
index 7d189d62..3d92c144 100644
--- a/cryptography/bindings/openssl/api.py
+++ b/cryptography/bindings/openssl/api.py
@@ -19,7 +19,7 @@ import sys
 import cffi
 
 from cryptography.primitives import interfaces
-from cryptography.primitives.block.ciphers import AES, Camellia
+from cryptography.primitives.block.ciphers import AES, Camellia, TripleDES
 from cryptography.primitives.block.modes import CBC, CTR, ECB, OFB, CFB
 
 
@@ -135,6 +135,12 @@ class API(object):
                 mode_cls,
                 GetCipherByName("{cipher.name}-{cipher.key_size}-{mode.name}")
             )
+        for mode_cls in [CBC, CFB, OFB]:
+            self.register_cipher_adapter(
+                TripleDES,
+                mode_cls,
+                GetCipherByName("des-ede3-{mode.name}")
+            )
 
     def create_block_cipher_context(self, cipher, mode):
         ctx = self.lib.EVP_CIPHER_CTX_new()
diff --git a/cryptography/primitives/block/ciphers.py b/cryptography/primitives/block/ciphers.py
index 4ac150a4..4143b89d 100644
--- a/cryptography/primitives/block/ciphers.py
+++ b/cryptography/primitives/block/ciphers.py
@@ -52,3 +52,27 @@ class Camellia(object):
     @property
     def key_size(self):
         return len(self.key) * 8
+
+
+class TripleDES(object):
+    name = "3DES"
+    block_size = 64
+    key_sizes = frozenset([64, 128, 192])
+
+    def __init__(self, key):
+        super(TripleDES, self).__init__()
+        if len(key) == 8:
+            key += key + key
+        elif len(key) == 16:
+            key += key[:8]
+        self.key = key
+
+        # Verify that the key size matches the expected key size
+        if self.key_size not in self.key_sizes:
+            raise ValueError("Invalid key size ({0}) for {1}".format(
+                self.key_size, self.name
+            ))
+
+    @property
+    def key_size(self):
+        return len(self.key) * 8