1# Author: Trevor Perrin 2# See the LICENSE file for legal information regarding use of this file. 3 4"""OpenSSL/M2Crypto AES implementation.""" 5 6from .cryptomath import * 7from .aes import * 8 9if m2cryptoLoaded: 10 11 def new(key, mode, IV): 12 return OpenSSL_AES(key, mode, IV) 13 14 class OpenSSL_AES(AES): 15 16 def __init__(self, key, mode, IV): 17 AES.__init__(self, key, mode, IV, "openssl") 18 self.key = key 19 self.IV = IV 20 21 def _createContext(self, encrypt): 22 context = m2.cipher_ctx_new() 23 if len(self.key)==16: 24 cipherType = m2.aes_128_cbc() 25 if len(self.key)==24: 26 cipherType = m2.aes_192_cbc() 27 if len(self.key)==32: 28 cipherType = m2.aes_256_cbc() 29 m2.cipher_init(context, cipherType, self.key, self.IV, encrypt) 30 return context 31 32 def encrypt(self, plaintext): 33 AES.encrypt(self, plaintext) 34 context = self._createContext(1) 35 ciphertext = m2.cipher_update(context, plaintext) 36 m2.cipher_ctx_free(context) 37 self.IV = ciphertext[-self.block_size:] 38 return bytearray(ciphertext) 39 40 def decrypt(self, ciphertext): 41 AES.decrypt(self, ciphertext) 42 context = self._createContext(0) 43 #I think M2Crypto has a bug - it fails to decrypt and return the last block passed in. 44 #To work around this, we append sixteen zeros to the string, below: 45 plaintext = m2.cipher_update(context, ciphertext+('\0'*16)) 46 47 #If this bug is ever fixed, then plaintext will end up having a garbage 48 #plaintext block on the end. That's okay - the below code will discard it. 49 plaintext = plaintext[:len(ciphertext)] 50 m2.cipher_ctx_free(context) 51 self.IV = ciphertext[-self.block_size:] 52 return bytearray(plaintext) 53