ARC4 support

2 files changed, 25 insertions, 1 deletions

diff --git a/cryptography/hazmat/bindings/openssl/backend.py b/cryptography/hazmat/bindings/openssl/backend.py
index 0c3d22d5..1cb886dc 100644
--- a/cryptography/hazmat/bindings/openssl/backend.py
+++ b/cryptography/hazmat/bindings/openssl/backend.py
@@ -21,7 +21,7 @@ import cffi
 from cryptography.exceptions import UnsupportedAlgorithm
 from cryptography.hazmat.primitives import interfaces
 from cryptography.hazmat.primitives.ciphers.algorithms import (
-    AES, Blowfish, Camellia, CAST5, TripleDES,
+    AES, Blowfish, Camellia, CAST5, TripleDES, ARC4,
 )
 from cryptography.hazmat.primitives.ciphers.modes import (
     CBC, CTR, ECB, OFB, CFB
@@ -254,6 +254,11 @@ class Ciphers(object):
             ECB,
             GetCipherByName("cast5-ecb")
         )
+        self.register_cipher_adapter(
+            ARC4,
+            type(None),
+            GetCipherByName("rc4")
+        )
 
     def create_encrypt_ctx(self, cipher, mode):
         return _CipherContext(self._backend, cipher, mode,
diff --git a/cryptography/hazmat/primitives/ciphers/algorithms.py b/cryptography/hazmat/primitives/ciphers/algorithms.py
index 8046bd26..cbfaceb8 100644
--- a/cryptography/hazmat/primitives/ciphers/algorithms.py
+++ b/cryptography/hazmat/primitives/ciphers/algorithms.py
@@ -116,3 +116,22 @@ class CAST5(object):
     @property
     def key_size(self):
         return len(self.key) * 8
+
+
+class ARC4(object):
+    name = "RC4"
+    key_sizes = frozenset([40, 56, 64, 80, 128, 192, 256])
+
+    def __init__(self, key):
+        super(ARC4, self).__init__()
+        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