1 """OpenSSL/M2Crypto AES implementation."""
3 from cryptomath import *
8 def new(key, mode, IV):
9 return OpenSSL_AES(key, mode, IV)
11 class OpenSSL_AES(AES):
13 def __init__(self, key, mode, IV):
14 AES.__init__(self, key, mode, IV, "openssl")
18 def _createContext(self, encrypt):
19 context = m2.cipher_ctx_new()
21 cipherType = m2.aes_128_cbc()
23 cipherType = m2.aes_192_cbc()
25 cipherType = m2.aes_256_cbc()
26 m2.cipher_init(context, cipherType, self.key, self.IV, encrypt)
29 def encrypt(self, plaintext):
30 AES.encrypt(self, plaintext)
31 context = self._createContext(1)
32 ciphertext = m2.cipher_update(context, plaintext)
33 m2.cipher_ctx_free(context)
34 self.IV = ciphertext[-self.block_size:]
37 def decrypt(self, ciphertext):
38 AES.decrypt(self, ciphertext)
39 context = self._createContext(0)
40 #I think M2Crypto has a bug - it fails to decrypt and return the last block passed in.
41 #To work around this, we append sixteen zeros to the string, below:
42 plaintext = m2.cipher_update(context, ciphertext+('\0'*16))
44 #If this bug is ever fixed, then plaintext will end up having a garbage
45 #plaintext block on the end. That's okay - the below code will discard it.
46 plaintext = plaintext[:len(ciphertext)]
47 m2.cipher_ctx_free(context)
48 self.IV = ciphertext[-self.block_size:]