rbutil/ipodpatcher/arc4.c

/*
 * arc4.c
 * Release $Name: MATRIXSSL_1_8_3_OPEN $
 *
 * ARC4 stream cipher implementation
 */
/*
 * Copyright (c) PeerSec Networks, 2002-2007. All Rights Reserved.
 * The latest version of this code is available at http://www.matrixssl.org
 *
 * This software is open source; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This General Public License does NOT permit incorporating this software 
 * into proprietary programs.  If you are unable to comply with the GPL, a 
 * commercial license for this software may be purchased from PeerSec Networks
 * at http://www.peersec.com
 * 
 * This program is distributed in WITHOUT ANY WARRANTY; without even the 
 * implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 
 * See the GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 * http://www.gnu.org/copyleft/gpl.html
 */
/******************************************************************************/

#include "arc4.h"

/*
    Some accounts, such as O'Reilly's Secure Programming Cookbook say that no 
    more than 2^30 bytes should be processed without rekeying, so we 
    enforce that limit here.  FYI, this is equal to 1GB of data transferred.
*/
#define ARC4_MAX_BYTES 0x40000000

/******************************************************************************/
/*
    SSL_RSA_WITH_RC4_* cipher callbacks
 */
void matrixArc4Init(struct rc4_key_t *ctx, unsigned char *key, int32_t keylen)
{
    unsigned char    index1, index2, tmp, *state;
    int16_t            counter;

    ctx->byteCount = 0;
    state = &ctx->state[0];

    for (counter = 0; counter < 256; counter++) {
        state[counter] = (unsigned char)counter;
    }
    ctx->x = 0;
    ctx->y = 0;
    index1 = 0;
    index2 = 0;

    for (counter = 0; counter < 256; counter++) {
        index2 = (key[index1] + state[counter] + index2) & 0xff;

        tmp = state[counter];
        state[counter] = state[index2];
        state[index2] = tmp;

        index1 = (index1 + 1) % keylen;
    }
}

int32_t matrixArc4(struct rc4_key_t *ctx, unsigned char *in,
                   unsigned char *out, int32_t len)
{
    unsigned char    x, y, *state, xorIndex, tmp;
    int   counter;     /* NOTE BY DAVE CHAPMAN: This was a short in
			  the original code, which caused a segfault
			  when attempting to process data > 32767
			  bytes. */

    ctx->byteCount += len;
    if (ctx->byteCount > ARC4_MAX_BYTES) {
        return -1;
    }

    x = ctx->x;
    y = ctx->y;
    state = &ctx->state[0];
    for (counter = 0; counter < len; counter++) {
        x = (x + 1) & 0xff;
        y = (state[x] + y) & 0xff;

        tmp = state[x];
        state[x] = state[y];
        state[y] = tmp;

        xorIndex = (state[x] + state[y]) & 0xff;

        tmp = in[counter];
        tmp ^= state[xorIndex];
        out[counter] = tmp;
    }
    ctx->x = x;
    ctx->y = y;
    return len;
}

/*****************************************************************************/