1/*
2 *  An implementation of the ARCFOUR algorithm
3 *
4 *  Based on XySSL: Copyright (C) 2006-2008  Christophe Devine
5 *
6 *  Copyright (C) 2009  Paul Bakker <polarssl_maintainer at polarssl dot org>
7 *
8 *  All rights reserved.
9 *
10 *  Redistribution and use in source and binary forms, with or without
11 *  modification, are permitted provided that the following conditions
12 *  are met:
13 *
14 *    * Redistributions of source code must retain the above copyright
15 *      notice, this list of conditions and the following disclaimer.
16 *    * Redistributions in binary form must reproduce the above copyright
17 *      notice, this list of conditions and the following disclaimer in the
18 *      documentation and/or other materials provided with the distribution.
19 *    * Neither the names of PolarSSL or XySSL nor the names of its contributors
20 *      may be used to endorse or promote products derived from this software
21 *      without specific prior written permission.
22 *
23 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
24 *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
25 *  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
26 *  FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
27 *  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
28 *  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
29 *  TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
30 *  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
31 *  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
32 *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
33 *  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
34 */
35/*
36 *  The ARCFOUR algorithm was publicly disclosed on 94/09.
37 *
38 *  http://groups.google.com/group/sci.crypt/msg/10a300c9d21afca0
39 */
40
41#include "netif/ppp/ppp_opts.h"
42#if PPP_SUPPORT && LWIP_INCLUDED_POLARSSL_ARC4
43
44#include "netif/ppp/polarssl/arc4.h"
45/*
46 * ARC4 key schedule
47 */
48void arc4_setup( arc4_context *ctx, unsigned char *key, int keylen )
49{
50    int i, j, k, a;
51    unsigned char *m;
52
53    ctx->x = 0;
54    ctx->y = 0;
55    m = ctx->m;
56
57    for( i = 0; i < 256; i++ )
58        m[i] = (unsigned char) i;
59
60    j = k = 0;
61
62    for( i = 0; i < 256; i++, k++ )
63    {
64        if( k >= keylen ) k = 0;
65
66        a = m[i];
67        j = ( j + a + key[k] ) & 0xFF;
68        m[i] = m[j];
69        m[j] = (unsigned char) a;
70    }
71}
72
73/*
74 * ARC4 cipher function
75 */
76void arc4_crypt( arc4_context *ctx, unsigned char *buf, int buflen )
77{
78    int i, x, y, a, b;
79    unsigned char *m;
80
81    x = ctx->x;
82    y = ctx->y;
83    m = ctx->m;
84
85    for( i = 0; i < buflen; i++ )
86    {
87        x = ( x + 1 ) & 0xFF; a = m[x];
88        y = ( y + a ) & 0xFF; b = m[y];
89
90        m[x] = (unsigned char) b;
91        m[y] = (unsigned char) a;
92
93        buf[i] = (unsigned char)
94            ( buf[i] ^ m[(unsigned char)( a + b )] );
95    }
96
97    ctx->x = x;
98    ctx->y = y;
99}
100
101#endif /* PPP_SUPPORT && LWIP_INCLUDED_POLARSSL_DES */
102