sys/crypto/rc4/rc4.c

   1
   2 /*
   3  * rc4.c
   4  *
   5  * Copyright (c) 1996-2000 Whistle Communications, Inc.
   6  * All rights reserved.
   7  *
   8  * Subject to the following obligations and disclaimer of warranty, use and
   9  * redistribution of this software, in source or object code forms, with or
  10  * without modifications are expressly permitted by Whistle Communications;
  11  * provided, however, that:
  12  * 1. Any and all reproductions of the source or object code must include the
  13  *    copyright notice above and the following disclaimer of warranties; and
  14  * 2. No rights are granted, in any manner or form, to use Whistle
  15  *    Communications, Inc. trademarks, including the mark "WHISTLE
  16  *    COMMUNICATIONS" on advertising, endorsements, or otherwise except as
  17  *    such appears in the above copyright notice or in the software.
  18  *
  19  * THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
  20  * TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
  21  * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
  22  * INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
  23  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
  24  * WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
  25  * REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
  26  * SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
  27  * IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
  28  * RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
  29  * WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
  30  * PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
  31  * SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY
  32  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  33  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  34  * THIS SOFTWARE, EVEN IF WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
  35  * OF SUCH DAMAGE.
  36  *
  37  * $FreeBSD: src/sys/crypto/rc4/rc4.c,v 1.2.2.1 2000/04/18 04:48:31 archie Exp $
  38  * $DragonFly: src/sys/crypto/rc4/rc4.c,v 1.2 2003/06/17 04:28:20 dillon Exp $
  39  */
  40
  41 #include <sys/types.h>
  42 #include <crypto/rc4/rc4.h>
  43
  44 static __inline void
  45 swap_bytes(u_char *a, u_char *b)
  46 {
  47         u_char temp;
  48
  49         temp = *a;
  50         *a = *b;
  51         *b = temp;
  52 }
  53
  54 /*
  55  * Initialize an RC4 state buffer using the supplied key,
  56  * which can have arbitrary length.
  57  */
  58 void
  59 rc4_init(struct rc4_state *const state, const u_char *key, int keylen)
  60 {
  61         u_char j;
  62         int i;
  63
  64         /* Initialize state with identity permutation */
  65         for (i = 0; i < 256; i++)
  66                 state->perm[i] = (u_char)i;
  67         state->index1 = 0;
  68         state->index2 = 0;
  69
  70         /* Randomize the permutation using key data */
  71         for (j = i = 0; i < 256; i++) {
  72                 j += state->perm[i] + key[i % keylen];
  73                 swap_bytes(&state->perm[i], &state->perm[j]);
  74         }
  75 }
  76
  77 /*
  78  * Encrypt some data using the supplied RC4 state buffer.
  79  * The input and output buffers may be the same buffer.
  80  * Since RC4 is a stream cypher, this function is used
  81  * for both encryption and decryption.
  82  */
  83 void
  84 rc4_crypt(struct rc4_state *const state,
  85         const u_char *inbuf, u_char *outbuf, int buflen)
  86 {
  87         int i;
  88         u_char j;
  89
  90         for (i = 0; i < buflen; i++) {
  91
  92                 /* Update modification indicies */
  93                 state->index1++;
  94                 state->index2 += state->perm[state->index1];
  95
  96                 /* Modify permutation */
  97                 swap_bytes(&state->perm[state->index1],
  98                     &state->perm[state->index2]);
  99
 100                 /* Encrypt/decrypt next byte */
 101                 j = state->perm[state->index1] + state->perm[state->index2];
 102                 outbuf[i] = inbuf[i] ^ state->perm[j];
 103         }
 104 }
 105