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)