/gdata/tlslite/utils/OpenSSL_TripleDES.py

 1"""OpenSSL/M2Crypto 3DES implementation."""
 2
 3from cryptomath import *
 4from TripleDES import *
 5
 6if m2cryptoLoaded:
 7
 8    def new(key, mode, IV):
 9        return OpenSSL_TripleDES(key, mode, IV)
10
11    class OpenSSL_TripleDES(TripleDES):
12
13        def __init__(self, key, mode, IV):
14            TripleDES.__init__(self, key, mode, IV, "openssl")
15            self.key = key
16            self.IV = IV
17
18        def _createContext(self, encrypt):
19            context = m2.cipher_ctx_new()
20            cipherType = m2.des_ede3_cbc()
21            m2.cipher_init(context, cipherType, self.key, self.IV, encrypt)
22            return context
23
24        def encrypt(self, plaintext):
25            TripleDES.encrypt(self, plaintext)
26            context = self._createContext(1)
27            ciphertext = m2.cipher_update(context, plaintext)
28            m2.cipher_ctx_free(context)
29            self.IV = ciphertext[-self.block_size:]
30            return ciphertext
31
32        def decrypt(self, ciphertext):
33            TripleDES.decrypt(self, ciphertext)
34            context = self._createContext(0)
35            #I think M2Crypto has a bug - it fails to decrypt and return the last block passed in.
36            #To work around this, we append sixteen zeros to the string, below:
37            plaintext = m2.cipher_update(context, ciphertext+('\0'*16))
38
39            #If this bug is ever fixed, then plaintext will end up having a garbage
40            #plaintext block on the end.  That's okay - the below code will ignore it.
41            plaintext = plaintext[:len(ciphertext)]
42            m2.cipher_ctx_free(context)
43            self.IV = ciphertext[-self.block_size:]
44            return plaintext