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cryb-to/lib/cipher/cryb_rc4.c
2017-04-06 19:51:46 +02:00

124 lines
3.4 KiB
C

/*-
* Copyright (c) 2015-2016 Dag-Erling Smørgrav
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "cryb/impl.h"
#include <stdint.h>
#include <string.h>
#include <cryb/assert.h>
#include <cryb/bitwise.h>
#include <cryb/endian.h>
#include <cryb/memset_s.h>
#include <cryb/rc4.h>
void
rc4_init(rc4_ctx *ctx, cipher_mode mode CRYB_UNUSED,
const uint8_t *key, size_t keylen)
{
unsigned int i, j;
uint8_t t;
assert(mode == CIPHER_MODE_ENCRYPT || mode == CIPHER_MODE_DECRYPT);
assert(keylen > 0);
memset(ctx, 0, sizeof *ctx);
for (i = 0; i < 256; ++i)
ctx->s[i] = i;
for (i = j = 0; i < 256; ++i) {
j = (j + ctx->s[i] + key[i % keylen]) % 256;
t = ctx->s[i];
ctx->s[i] = ctx->s[j];
ctx->s[j] = t;
}
}
size_t
rc4_keystream(rc4_ctx *ctx, uint8_t *ks, size_t len)
{
unsigned int i;
uint8_t t;
for (i = 0; i < len; ++i) {
ctx->i = ctx->i + 1;
ctx->j = ctx->j + ctx->s[ctx->i];
t = ctx->s[ctx->i];
ctx->s[ctx->i] = ctx->s[ctx->j];
ctx->s[ctx->j] = t;
t = ctx->s[ctx->i] + ctx->s[ctx->j];
*ks++ = ctx->s[t];
}
return (len);
}
size_t
rc4_encrypt(rc4_ctx *ctx, const void *vpt, uint8_t *ct, size_t len)
{
const uint8_t *pt = vpt;
unsigned int i;
uint8_t t, k;
for (i = 0; i < len; ++i) {
ctx->i = ctx->i + 1;
ctx->j = ctx->j + ctx->s[ctx->i];
t = ctx->s[ctx->i];
ctx->s[ctx->i] = ctx->s[ctx->j];
ctx->s[ctx->j] = t;
t = ctx->s[ctx->i] + ctx->s[ctx->j];
k = ctx->s[t];
*ct++ = *pt++ ^ k;
}
return (len);
}
size_t
rc4_decrypt(rc4_ctx *ctx, const uint8_t *ct, void *vpt, size_t len)
{
return (rc4_encrypt(ctx, ct, vpt, len));
}
void
rc4_finish(rc4_ctx *ctx)
{
memset_s(ctx, 0, sizeof *ctx, sizeof *ctx);
}
cipher_algorithm rc4_cipher = {
.name = "rc4",
.contextlen = sizeof(rc4_ctx),
.blocklen = 1,
.keylen = 0,
.init = (cipher_init_func)rc4_init,
.keystream = (cipher_keystream_func)rc4_keystream,
.encrypt = (cipher_encrypt_func)rc4_encrypt,
.decrypt = (cipher_decrypt_func)rc4_decrypt,
.finish = (cipher_finish_func)rc4_finish,
};