91 lines
3.3 KiB
C
91 lines
3.3 KiB
C
/*
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* rc4.c
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*
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* Copyright (c) 1996-2000 Whistle Communications, Inc.
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* All rights reserved.
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*
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* Subject to the following obligations and disclaimer of warranty, use and
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* redistribution of this software, in source or object code forms, with or
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* without modifications are expressly permitted by Whistle Communications;
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* provided, however, that:
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* 1. Any and all reproductions of the source or object code must include the
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* copyright notice above and the following disclaimer of warranties; and
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* 2. No rights are granted, in any manner or form, to use Whistle
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* Communications, Inc. trademarks, including the mark "WHISTLE
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* COMMUNICATIONS" on advertising, endorsements, or otherwise except as
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* such appears in the above copyright notice or in the software.
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*
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* THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
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* TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
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* REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
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* INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
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* WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
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* REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
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* SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
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* IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
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* RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
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* WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
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* PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
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* OF SUCH DAMAGE.
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*/
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#include "rc4.h"
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static __inline void swap_bytes(uint8_t *a, uint8_t *b) {
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uint8_t temp;
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temp = *a;
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*a = *b;
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*b = temp;
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}
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/*
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* Initialize an RC4 state buffer using the supplied key,
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* which can have arbitrary length.
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*/
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void rc4_init(struct rc4_state *const state, const uint8_t *key, int keylen) {
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uint8_t j;
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int i;
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/* Initialize state with identity permutation */
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for (i = 0; i < 256; i++) state->perm[i] = (uint8_t)i;
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state->index1 = 0;
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state->index2 = 0;
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/* Randomize the permutation using key data */
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for (j = i = 0; i < 256; i++) {
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j += state->perm[i] + key[i % keylen];
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swap_bytes(&state->perm[i], &state->perm[j]);
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}
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}
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/*
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* Encrypt some data using the supplied RC4 state buffer.
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* The input and output buffers may be the same buffer.
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* Since RC4 is a stream cypher, this function is used
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* for both encryption and decryption.
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*/
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void rc4_crypt(struct rc4_state *const state, const uint8_t *inbuf,
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uint8_t *outbuf, int buflen) {
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int i;
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uint8_t j;
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for (i = 0; i < buflen; i++) {
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/* Update modification indicies */
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state->index1++;
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state->index2 += state->perm[state->index1];
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/* Modify permutation */
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swap_bytes(&state->perm[state->index1], &state->perm[state->index2]);
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/* Encrypt/decrypt next byte */
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j = state->perm[state->index1] + state->perm[state->index2];
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outbuf[i] = inbuf[i] ^ state->perm[j];
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}
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}
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