Check key and iv length. Handle variable key length ciphers

diff --git a/ctypescrypto/cipher.py b/ctypescrypto/cipher.py
index 1ea4f797d7f4d87e88e86832ae438651d18dde68..91c5283a659f70767620826ef81ae4fd7e1b33a2 100644 (file)
--- a/ctypescrypto/cipher.py
+++ b/ctypescrypto/cipher.py
@@ -101,6 +101,10 @@ class Cipher:
 
                """
                self._clean_ctx()
+               # Check key and iv length
+               if key is None:
+                       raise ValueError("No key specified")
+
                key_ptr = c_char_p(key)
                iv_ptr = c_char_p(iv)
                self.ctx = libcrypto.EVP_CIPHER_CTX_new()
@@ -111,6 +115,19 @@ class Cipher:
                        enc = 1
                else: 
                        enc = 0
+               if not iv is None and len(iv) != cipher_type.iv_length():
+                       raise ValueError("Invalid IV length for this algorithm")
+                       
+               if len(key) != cipher_type.key_length():
+                       if (cipher_type.flags() & 8) != 0:
+                               # Variable key length cipher.
+                               result = libcrypto.EVP_CipherInit_ex(self.ctx,cipher_type.cipher,None,None,None,c_int(enc))
+                               result=libcrypto.EVP_CIPHER_CTX_set_key_length(self.ctx,len(key))
+                               if result == 0:
+                                       self._clean_ctx()
+                                       raise CipherError("Unable to set key length")
+                       else:
+                               raise ValueError("Invalid key length for this algorithm")
                result = libcrypto.EVP_CipherInit_ex(self.ctx, cipher_type.cipher, None, key_ptr, iv_ptr, c_int(enc))
                if result == 0:
                        self._clean_ctx()

diff --git a/tests/testcipher.py b/tests/testcipher.py
index ae74d412dd44c2befb829ef885c6457750502003..de426cba665f50d988009b7c08f375c065301222 100644 (file)
--- a/tests/testcipher.py
+++ b/tests/testcipher.py
@@ -64,8 +64,28 @@ class TestEncryptDecrypt(unittest.TestCase):
                enc=c.update(data)+c.finish()
                # See if padding is added by default
                self.assertEqual(len(enc),len(data))
-               d=cipher.new("AES-256-OFB",decryptkey)
+               d=cipher.new("AES-256-OFB",decryptkey,encrypt=False)
                dec=d.update(enc)+d.finish()
                self.assertEqual(data,dec)
+       def test_wrong_keylength(self):
+               data="sdfsdfxxx"
+               key="abcdabcd"
+               with self.assertRaises(ValueError):
+                       c=cipher.new("AES-128-OFB",key)
+       def test_wrong_ivlength(self):
+               key="abcdabcdabcdabcd"
+               iv="xxxxx"
+               with self.assertRaises(ValueError):
+                       c=cipher.new("AES-128-OFB",key,iv=iv)
+       def test_variable_keylength(self):
+               encryptkey="abcdefabcdef"
+               data="asdfsdfsdfsdfsdfsdfsdfsdf"
+               iv="abcdefgh"
+               c=cipher.new("bf-ofb",encryptkey,iv=iv)
+               ciphertext=c.update(data)+c.finish()
+               decryptkey=encryptkey[0:5]+encryptkey[5:]
+               d=cipher.new("bf-ofb",decryptkey,iv=iv)
+               deciph=d.update(ciphertext)+d.finish()
+               self.assertEqual(deciph,data)
 if __name__ == '__main__':
        unittest.main()