/* * RC4 stream cipher * Copyright (c) 2002-2005, Jouni Malinen <jkmaline@cc.hut.fi> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. * * Alternatively, this software may be distributed under the terms of BSD * license. * * See README and COPYING for more details. */#include "includes.h"#include "common.h"#include "rc4.h"#define S_SWAP(a,b) do { u8 t = S[a]; S[a] = S[b]; S[b] = t; } while(0)/** * rc4 - XOR RC4 stream to given data with skip-stream-start * @key: RC4 key * @keylen: RC4 key length * @skip: number of bytes to skip from the beginning of the RC4 stream * @data: data to be XOR'ed with RC4 stream * @data_len: buf length * * Generate RC4 pseudo random stream for the given key, skip beginning of the * stream, and XOR the end result with the data buffer to perform RC4 * encryption/decryption. */void rc4_skip(const u8 *key, size_t keylen, size_t skip,	      u8 *data, size_t data_len){	u32 i, j, k;	u8 S[256], *pos;	size_t kpos;	/* Setup RC4 state */	for (i = 0; i < 256; i++)		S[i] = i;	j = 0;	kpos = 0;	for (i = 0; i < 256; i++) {		j = (j + S[i] + key[kpos]) & 0xff;		kpos++;		if (kpos >= keylen)			kpos = 0;		S_SWAP(i, j);	}	/* Skip the start of the stream */	i = j = 0;	for (k = 0; k < skip; k++) {		i = (i + 1) & 0xff;		j = (j + S[i]) & 0xff;		S_SWAP(i, j);	}	/* Apply RC4 to data */	pos = data;	for (k = 0; k < data_len; k++) {		i = (i + 1) & 0xff;		j = (j + S[i]) & 0xff;		S_SWAP(i, j);		*pos++ ^= S[(S[i] + S[j]) & 0xff];	}}/** * rc4 - XOR RC4 stream to given data * @buf: data to be XOR'ed with RC4 stream * @len: buf length * @key: RC4 key * @key_len: RC4 key length * * Generate RC4 pseudo random stream for the given key and XOR this with the * data buffer to perform RC4 encryption/decryption. */void rc4(u8 *buf, size_t len, const u8 *key, size_t key_len){	rc4_skip(key, key_len, 0, buf, len);}