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