wpa_supplicant_node: wpa_supplicant_node: rc4.c Source File

00001 /*
00002  * RC4 stream cipher
00003  * Copyright (c) 2002-2005, Jouni Malinen <j@w1.fi>
00004  *
00005  * This program is free software; you can redistribute it and/or modify
00006  * it under the terms of the GNU General Public License version 2 as
00007  * published by the Free Software Foundation.
00008  *
00009  * Alternatively, this software may be distributed under the terms of BSD
00010  * license.
00011  *
00012  * See README and COPYING for more details.
00013  */
00014 
00015 #include "includes.h"
00016 
00017 #include "common.h"
00018 #include "crypto.h"
00019 
00020 #define S_SWAP(a,b) do { u8 t = S[a]; S[a] = S[b]; S[b] = t; } while(0)
00021 
00022 int rc4_skip(const u8 *key, size_t keylen, size_t skip,
00023              u8 *data, size_t data_len)
00024 {
00025         u32 i, j, k;
00026         u8 S[256], *pos;
00027         size_t kpos;
00028 
00029         /* Setup RC4 state */
00030         for (i = 0; i < 256; i++)
00031                 S[i] = i;
00032         j = 0;
00033         kpos = 0;
00034         for (i = 0; i < 256; i++) {
00035                 j = (j + S[i] + key[kpos]) & 0xff;
00036                 kpos++;
00037                 if (kpos >= keylen)
00038                         kpos = 0;
00039                 S_SWAP(i, j);
00040         }
00041 
00042         /* Skip the start of the stream */
00043         i = j = 0;
00044         for (k = 0; k < skip; k++) {
00045                 i = (i + 1) & 0xff;
00046                 j = (j + S[i]) & 0xff;
00047                 S_SWAP(i, j);
00048         }
00049 
00050         /* Apply RC4 to data */
00051         pos = data;
00052         for (k = 0; k < data_len; k++) {
00053                 i = (i + 1) & 0xff;
00054                 j = (j + S[i]) & 0xff;
00055                 S_SWAP(i, j);
00056                 *pos++ ^= S[(S[i] + S[j]) & 0xff];
00057         }
00058 
00059         return 0;
00060 }