Add known weak ciphers to blacklisted calls

The following are known to be weak.
  - Crypto.Cipher.ARC2
  - Crypto.Cipher.ARC4
  - Crypto.Cipher.Blowfish
  - Crypto.Cipher.DES
  - Crypto.Cipher.XOR
  - cryptography.hazmat.primitives.ciphers.algorithms.ARC4
  - cryptography.hazmat.primitives.ciphers.algorithms.Blowfish
  - cryptography.hazmat.primitives.ciphers.algorithms.IDEA

Change-Id: Ied7910b95ccf1f674ccece4f2f9b0992030952a3

bandit/config/bandit.yaml

@@ -103,6 +103,20 @@ blacklist_calls:
                 - Crypto.Hash.MD5.new
                 - cryptography.hazmat.primitives.hashes.MD5
             message: Use of insecure MD2, MD4, or MD5 hash function.
+        - ciphers:
+            qualnames:
+                - Crypto.Cipher.ARC2.new
+                - Crypto.Cipher.ARC4.new
+                - Crypto.Cipher.Blowfish.new
+                - Crypto.Cipher.DES.new
+                - Crypto.Cipher.XOR.new
+                - cryptography.hazmat.primitives.ciphers.algorithms.ARC4
+                - cryptography.hazmat.primitives.ciphers.algorithms.Blowfish
+                - cryptography.hazmat.primitives.ciphers.algorithms.IDEA
+            message: >
+                Use of insecure cipher {func}. Replace with a known secure
+                cipher such as AES.
+            level: HIGH
         - mktemp_q:
             qualnames: [tempfile.mktemp]
             message: Use of insecure and deprecated function (mktemp).

examples/ciphers.py

@@ -0,0 +1,58 @@
+from Crypto.Cipher import ARC2
+from Crypto.Cipher import ARC4
+from Crypto.Cipher import Blowfish
+from Crypto.Cipher import DES
+from Crypto.Cipher import XOR
+from Crypto.Hash import SHA
+from Crypto import Random
+from Crypto.Util import Counter
+from cryptography.hazmat.primitives.ciphers import Cipher
+from cryptography.hazmat.primitives.ciphers import algorithms
+from cryptography.hazmat.primitives.ciphers import modes
+from cryptography.hazmat.backends import default_backend
+from struct import pack
+
+key = b'Sixteen byte key'
+iv = Random.new().read(ARC2.block_size)
+cipher = ARC2.new(key, ARC2.MODE_CFB, iv)
+msg = iv + cipher.encrypt(b'Attack at dawn')
+
+key = b'Very long and confidential key'
+nonce = Random.new().read(16)
+tempkey = SHA.new(key+nonce).digest()
+cipher = ARC4.new(tempkey)
+msg = nonce + cipher.encrypt(b'Open the pod bay doors, HAL')
+
+bs = Blowfish.block_size
+key = b'An arbitrarily long key'
+iv = Random.new().read(bs)
+cipher = Blowfish.new(key, Blowfish.MODE_CBC, iv)
+plaintext = b'docendo discimus '
+plen = bs - divmod(len(plaintext),bs)[1]
+padding = [plen]*plen
+padding = pack('b'*plen, *padding)
+msg = iv + cipher.encrypt(plaintext + padding)
+
+key = b'-8B key-'
+nonce = Random.new().read(DES.block_size/2)
+ctr = Counter.new(DES.block_size*8/2, prefix=nonce)
+cipher = DES.new(key, DES.MODE_CTR, counter=ctr)
+plaintext = b'We are no longer the knights who say ni!'
+msg = nonce + cipher.encrypt(plaintext)
+
+key = b'Super secret key'
+cipher = XOR.new(key)
+plaintext = b'Encrypt me'
+msg = cipher.encrypt(plaintext)
+
+cipher = Cipher(algorithms.ARC4(key), mode=None, backend=default_backend())
+encryptor = cipher.encryptor()
+ct = encryptor.update(b"a secret message")
+
+cipher = Cipher(algorithms.Blowfish(key), mode=None, backend=default_backend())
+encryptor = cipher.encryptor()
+ct = encryptor.update(b"a secret message")
+
+cipher = Cipher(algorithms.IDEA(key), mode=None, backend=default_backend())
+encryptor = cipher.encryptor()
+ct = encryptor.update(b"a secret message")

tests/functional/test_functional.py

@@ -92,6 +92,11 @@ class FunctionalTests(testtools.TestCase):
         expect = {'SEVERITY': {'MEDIUM': 8}, 'CONFIDENCE': {'HIGH': 8}}
         self.check_example('crypto-md5.py', expect)
 
+    def test_ciphers(self):
+        '''Test the `Crypto.Cipher` example.'''
+        expect = {'SEVERITY': {'LOW': 1, 'HIGH': 8}, 'CONFIDENCE': {'HIGH': 9}}
+        self.check_example('ciphers.py', expect)
+
     def test_eval(self):
         '''Test the `eval` example.'''
         expect = {'SEVERITY': {'MEDIUM': 3}, 'CONFIDENCE': {'HIGH': 3}}