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108 lines
3.5 KiB
Python
108 lines
3.5 KiB
Python
"""
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This module holds an AES IGE class, if libssl is available on the system.
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"""
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import os
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import ctypes
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from ctypes.util import find_library
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lib = find_library('ssl')
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if not lib:
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AES = None
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else:
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""" <aes.h>
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# define AES_ENCRYPT 1
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# define AES_DECRYPT 0
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# define AES_MAXNR 14
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struct aes_key_st {
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# ifdef AES_LONG
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unsigned long rd_key[4 * (AES_MAXNR + 1)];
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# else
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unsigned int rd_key[4 * (AES_MAXNR + 1)];
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# endif
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int rounds;
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};
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typedef struct aes_key_st AES_KEY;
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int AES_set_encrypt_key(const unsigned char *userKey, const int bits,
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AES_KEY *key);
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int AES_set_decrypt_key(const unsigned char *userKey, const int bits,
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AES_KEY *key);
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void AES_ige_encrypt(const unsigned char *in, unsigned char *out,
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size_t length, const AES_KEY *key,
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unsigned char *ivec, const int enc);
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"""
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_libssl = ctypes.cdll.LoadLibrary(lib)
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AES_MAXNR = 14
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AES_ENCRYPT = ctypes.c_int(1)
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AES_DECRYPT = ctypes.c_int(0)
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class AES_KEY(ctypes.Structure):
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"""Helper class representing an AES key"""
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_fields_ = [
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('rd_key', ctypes.c_uint32 * (4*(AES_MAXNR + 1))),
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('rounds', ctypes.c_uint),
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]
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class AES:
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"""
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Class that servers as an interface to encrypt and decrypt
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text through the AES IGE mode, using the system's libssl.
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"""
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@staticmethod
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def decrypt_ige(cipher_text, key, iv):
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"""
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Decrypts the given text in 16-bytes blocks by using the
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given key and 32-bytes initialization vector.
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"""
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aeskey = AES_KEY()
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ckey = (ctypes.c_ubyte * len(key))(*key)
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cklen = ctypes.c_int(len(key)*8)
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cin = (ctypes.c_ubyte * len(cipher_text))(*cipher_text)
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ctlen = ctypes.c_size_t(len(cipher_text))
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cout = (ctypes.c_ubyte * len(cipher_text))()
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civ = (ctypes.c_ubyte * len(iv))(*iv)
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_libssl.AES_set_decrypt_key(ckey, cklen, ctypes.byref(aeskey))
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_libssl.AES_ige_encrypt(
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ctypes.byref(cin),
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ctypes.byref(cout),
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ctlen,
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ctypes.byref(aeskey),
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ctypes.byref(civ),
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AES_DECRYPT
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)
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return bytes(cout)
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@staticmethod
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def encrypt_ige(plain_text, key, iv):
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"""
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Encrypts the given text in 16-bytes blocks by using the
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given key and 32-bytes initialization vector.
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"""
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# Add random padding iff it's not evenly divisible by 16 already
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if len(plain_text) % 16 != 0:
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padding_count = 16 - len(plain_text) % 16
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plain_text += os.urandom(padding_count)
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aeskey = AES_KEY()
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ckey = (ctypes.c_ubyte * len(key))(*key)
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cklen = ctypes.c_int(len(key)*8)
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cin = (ctypes.c_ubyte * len(plain_text))(*plain_text)
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ctlen = ctypes.c_size_t(len(plain_text))
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cout = (ctypes.c_ubyte * len(plain_text))()
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civ = (ctypes.c_ubyte * len(iv))(*iv)
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_libssl.AES_set_encrypt_key(ckey, cklen, ctypes.byref(aeskey))
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_libssl.AES_ige_encrypt(
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ctypes.byref(cin),
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ctypes.byref(cout),
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ctlen,
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ctypes.byref(aeskey),
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ctypes.byref(civ),
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AES_ENCRYPT
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)
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return bytes(cout)
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