1# Author: Trevor Perrin 2# See the LICENSE file for legal information regarding use of this file. 3 4"""OpenSSL/M2Crypto 3DES implementation.""" 5 6from .cryptomath import * 7from .tripledes import * 8 9if m2cryptoLoaded: 10 11 def new(key, mode, IV): 12 return OpenSSL_TripleDES(key, mode, IV) 13 14 class OpenSSL_TripleDES(TripleDES): 15 16 def __init__(self, key, mode, IV): 17 TripleDES.__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 cipherType = m2.des_ede3_cbc() 24 m2.cipher_init(context, cipherType, self.key, self.IV, encrypt) 25 return context 26 27 def encrypt(self, plaintext): 28 TripleDES.encrypt(self, plaintext) 29 context = self._createContext(1) 30 ciphertext = m2.cipher_update(context, plaintext) 31 m2.cipher_ctx_free(context) 32 self.IV = ciphertext[-self.block_size:] 33 return bytearray(ciphertext) 34 35 def decrypt(self, ciphertext): 36 TripleDES.decrypt(self, ciphertext) 37 context = self._createContext(0) 38 #I think M2Crypto has a bug - it fails to decrypt and return the last block passed in. 39 #To work around this, we append sixteen zeros to the string, below: 40 plaintext = m2.cipher_update(context, ciphertext+('\0'*16)) 41 42 #If this bug is ever fixed, then plaintext will end up having a garbage 43 #plaintext block on the end. That's okay - the below code will ignore it. 44 plaintext = plaintext[:len(ciphertext)] 45 m2.cipher_ctx_free(context) 46 self.IV = ciphertext[-self.block_size:] 47 return bytearray(plaintext)