From a1ec262a3596dbba4ff82ff7d05c4f265f794359 Mon Sep 17 00:00:00 2001
From: Paul Kehrer <paul.l.kehrer@gmail.com>
Date: Wed, 11 Sep 2013 09:38:45 -0500
Subject: CFB support

This requires a bit of explanation. OpenSSL has methods that implement
standard CFB, 1-bit CFB (cfb1), and 8-bit CFB (cfb8). Unfortunately,
while old (read: 0.9.7) versions of OpenSSL appear to test these
variants, newer versions have a comment stating that cfb{1,8} are
unsupported. Accordingly, I've backed out any support for the variants
for now. We can add it back into the CFB class if and when we gain a
backend that supports arbitrary s for 1 <= s <= block_size
---
 cryptography/primitives/block/modes.py |  9 +++++++
 tests/primitives/test_nist.py          | 47 ++++++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+)

diff --git a/cryptography/primitives/block/modes.py b/cryptography/primitives/block/modes.py
index 62a1c2c9..0f17a1a5 100644
--- a/cryptography/primitives/block/modes.py
+++ b/cryptography/primitives/block/modes.py
@@ -36,5 +36,14 @@ class OFB(object):
         self.nonce = nonce
 
 
+class CFB(object):
+    name = "CFB"
+
+    def __init__(self, initialization_vector):
+        super(CFB, self).__init__()
+        self.initialization_vector = initialization_vector
+
+
 interfaces.ModeWithInitializationVector.register(CBC)
 interfaces.ModeWithNonce.register(OFB)
+interfaces.ModeWithInitializationVector.register(CFB)
diff --git a/tests/primitives/test_nist.py b/tests/primitives/test_nist.py
index 0e16cc9c..1e5d2396 100644
--- a/tests/primitives/test_nist.py
+++ b/tests/primitives/test_nist.py
@@ -180,3 +180,50 @@ class TestAES_OFB(object):
         actual_ciphertext = cipher.encrypt(binascii.unhexlify(plaintext))
         actual_ciphertext += cipher.finalize()
         assert binascii.hexlify(actual_ciphertext) == ciphertext
+
+
+class TestAES_CFB(object):
+    @parameterize_encrypt_test(
+        "AES", "KAT",
+        ("key", "iv", "plaintext", "ciphertext"),
+        [
+            "CFB128GFSbox128.rsp",
+            "CFB128GFSbox192.rsp",
+            "CFB128GFSbox256.rsp",
+            "CFB128KeySbox128.rsp",
+            "CFB128KeySbox192.rsp",
+            "CFB128KeySbox256.rsp",
+            "CFB128VarKey128.rsp",
+            "CFB128VarKey192.rsp",
+            "CFB128VarKey256.rsp",
+            "CFB128VarTxt128.rsp",
+            "CFB128VarTxt192.rsp",
+            "CFB128VarTxt256.rsp",
+        ]
+    )
+    def test_KAT(self, key, iv, plaintext, ciphertext):
+        cipher = BlockCipher(
+            ciphers.AES(binascii.unhexlify(key)),
+            modes.CFB(binascii.unhexlify(iv))
+        )
+        actual_ciphertext = cipher.encrypt(binascii.unhexlify(plaintext))
+        actual_ciphertext += cipher.finalize()
+        assert binascii.hexlify(actual_ciphertext) == ciphertext
+
+    @parameterize_encrypt_test(
+        "AES", "MMT",
+        ("key", "iv", "plaintext", "ciphertext"),
+        [
+            "CFB128MMT128.rsp",
+            "CFB128MMT192.rsp",
+            "CFB128MMT256.rsp",
+        ]
+    )
+    def test_MMT(self, key, iv, plaintext, ciphertext):
+        cipher = BlockCipher(
+            ciphers.AES(binascii.unhexlify(key)),
+            modes.CFB(binascii.unhexlify(iv))
+        )
+        actual_ciphertext = cipher.encrypt(binascii.unhexlify(plaintext))
+        actual_ciphertext += cipher.finalize()
+        assert binascii.hexlify(actual_ciphertext) == ciphertext
-- 
cgit v1.2.3


From 4223df72cf3d3566ae8ccbce7d31dbae7ee25cdd Mon Sep 17 00:00:00 2001
From: Paul Kehrer <paul.l.kehrer@gmail.com>
Date: Wed, 11 Sep 2013 09:48:04 -0500
Subject: add CFB to documentation

---
 docs/primitives/symmetric-encryption.rst | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/docs/primitives/symmetric-encryption.rst b/docs/primitives/symmetric-encryption.rst
index c4f78a79..be86229b 100644
--- a/docs/primitives/symmetric-encryption.rst
+++ b/docs/primitives/symmetric-encryption.rst
@@ -79,6 +79,19 @@ Modes
                         of the cipher.  Reuse of a ``nonce`` with a given
                         ``key`` can allow recovery of the original plaintext.
 
+.. class:: cryptography.primitives.block.modes.CFB(initialization_vector)
+
+    CFB (Cipher Feedback) is a mode of operation for block ciphers. It
+    transforms a block cipher into a stream cipher.
+
+    :param bytes initialization_vector: Must be random bytes. They do not need
+                                        to be kept secret (they can be included
+                                        in a transmitted message). Must be the
+                                        same number of bytes as the
+                                        ``block_size`` of the cipher. Do not
+                                        reuse an ``initialization_vector`` with
+                                        a given ``key``.
+
 
 Insecure Modes
 --------------
-- 
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