1/*	$OpenBSD: arc4.c,v 1.3 2007/09/11 12:07:05 djm Exp $	*/
2/*
3 * Copyright (c) 2003 Markus Friedl <markus@openbsd.org>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18#include <sys/types.h>
19
20#include <crypto/arc4.h>
21
22#define RC4SWAP(x,y) \
23	do { \
24		u_int8_t t = ctx->state[x];  \
25		ctx->state[x] = ctx->state[y]; \
26		ctx->state[y] = t; \
27	} while(0)
28
29void
30rc4_keysetup(struct rc4_ctx *ctx, u_char *key, u_int32_t klen)
31{
32	u_int8_t x, y;
33	u_int32_t i;
34
35	x = y = 0;
36	for (i = 0; i < RC4STATE; i++)
37		ctx->state[i] = i;
38	for (i = 0; i < RC4STATE; i++) {
39		y = (key[x] + ctx->state[i] + y) & (RC4STATE - 1);
40		RC4SWAP(i, y);
41		x = (x + 1) % klen;
42	}
43	ctx->x = ctx->y = 0;
44}
45
46void
47rc4_crypt(struct rc4_ctx *ctx, u_char *src, u_char *dst,
48    u_int32_t len)
49{
50	u_int32_t i;
51
52	for (i = 0; i < len; i++) {
53		ctx->x = (ctx->x + 1) & (RC4STATE - 1);
54		ctx->y = (ctx->state[ctx->x] + ctx->y) & (RC4STATE - 1);
55		RC4SWAP(ctx->x, ctx->y);
56		dst[i] = src[i] ^ ctx->state[
57		   (ctx->state[ctx->x] + ctx->state[ctx->y]) & (RC4STATE - 1)];
58	}
59}
60
61void
62rc4_getbytes(struct rc4_ctx *ctx, u_char *dst, u_int32_t len)
63{
64	u_int32_t i;
65
66	for (i = 0; i < len; i++) {
67		ctx->x = (ctx->x + 1) & (RC4STATE - 1);
68		ctx->y = (ctx->state[ctx->x] + ctx->y) & (RC4STATE - 1);
69		RC4SWAP(ctx->x, ctx->y);
70		dst[i] = ctx->state[
71		   (ctx->state[ctx->x] + ctx->state[ctx->y]) & (RC4STATE - 1)];
72	}
73}
74
75void
76rc4_skip(struct rc4_ctx *ctx, u_int32_t len)
77{
78	for (; len > 0; len--) {
79		ctx->x = (ctx->x + 1) & (RC4STATE - 1);
80		ctx->y = (ctx->state[ctx->x] + ctx->y) & (RC4STATE - 1);
81		RC4SWAP(ctx->x, ctx->y);
82	}
83}
84