| # Author: Trevor Perrin |
| # See the LICENSE file for legal information regarding use of this file. |
| |
| """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 bytearray(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 bytearray(plaintext) |
