Package tlslite :: Package utils :: Module openssl_aes
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Source Code for Module tlslite.utils.openssl_aes

 1  # Author: Trevor Perrin 
 2  # See the LICENSE file for legal information regarding use of this file. 
 3   
 4  """OpenSSL/M2Crypto AES implementation.""" 
 5   
 6  from .cryptomath import * 
 7  from .aes import * 
 8   
 9  if 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