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"""OpenSSL/M2Crypto AES implementation."""
from cryptomath import *
from AES import *
if m2cryptoLoaded:
def new(key, mode, IV):
return OpenSSL_AES(key, mode, IV)
class OpenSSL_AES(AES):
def __init__(self, key, mode, IV):
AES.__init__(self, key, mode, IV, "openssl")
self.key = key
self.IV = IV
def _createContext(self, encrypt):
context = m2.cipher_ctx_new()
if len(self.key)==16:
cipherType = m2.aes_128_cbc()
if len(self.key)==24:
cipherType = m2.aes_192_cbc()
if len(self.key)==32:
cipherType = m2.aes_256_cbc()
m2.cipher_init(context, cipherType, self.key, self.IV, encrypt)
return context
def encrypt(self, plaintext):
AES.encrypt(self, plaintext)
context = self._createContext(1)
ciphertext = m2.cipher_update(context, plaintext)
m2.cipher_ctx_free(context)
self.IV = ciphertext[-self.block_size:]
return ciphertext
def decrypt(self, ciphertext):
AES.decrypt(self, ciphertext)
context = self._createContext(0)
#I think M2Crypto has a bug - it fails to decrypt and return the last block passed in.
#To work around this, we append sixteen zeros to the string, below:
plaintext = m2.cipher_update(context, ciphertext+('\0'*16))
#If this bug is ever fixed, then plaintext will end up having a garbage
#plaintext block on the end. That's okay - the below code will discard it.
plaintext = plaintext[:len(ciphertext)]
m2.cipher_ctx_free(context)
self.IV = ciphertext[-self.block_size:]
return plaintext
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