104 lines
2.0 KiB
C
104 lines
2.0 KiB
C
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/*
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* Cryptographic API
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*
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* ARC4 Cipher Algorithm
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*
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* Jon Oberheide <jon@oberheide.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/crypto.h>
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#define ARC4_MIN_KEY_SIZE 1
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#define ARC4_MAX_KEY_SIZE 256
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#define ARC4_BLOCK_SIZE 1
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struct arc4_ctx {
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u8 S[256];
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u8 x, y;
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};
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static int arc4_set_key(struct crypto_tfm *tfm, const u8 *in_key,
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unsigned int key_len)
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{
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struct arc4_ctx *ctx = crypto_tfm_ctx(tfm);
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int i, j = 0, k = 0;
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ctx->x = 1;
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ctx->y = 0;
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for (i = 0; i < 256; i++)
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ctx->S[i] = i;
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for (i = 0; i < 256; i++) {
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u8 a = ctx->S[i];
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j = (j + in_key[k] + a) & 0xff;
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ctx->S[i] = ctx->S[j];
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ctx->S[j] = a;
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if (++k >= key_len)
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k = 0;
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}
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return 0;
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}
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static void arc4_crypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
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{
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struct arc4_ctx *ctx = crypto_tfm_ctx(tfm);
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u8 *const S = ctx->S;
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u8 x = ctx->x;
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u8 y = ctx->y;
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u8 a, b;
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a = S[x];
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y = (y + a) & 0xff;
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b = S[y];
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S[x] = b;
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S[y] = a;
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x = (x + 1) & 0xff;
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*out++ = *in ^ S[(a + b) & 0xff];
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ctx->x = x;
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ctx->y = y;
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}
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static struct crypto_alg arc4_alg = {
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.cra_name = "arc4",
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.cra_flags = CRYPTO_ALG_TYPE_CIPHER,
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.cra_blocksize = ARC4_BLOCK_SIZE,
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.cra_ctxsize = sizeof(struct arc4_ctx),
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.cra_module = THIS_MODULE,
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.cra_list = LIST_HEAD_INIT(arc4_alg.cra_list),
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.cra_u = { .cipher = {
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.cia_min_keysize = ARC4_MIN_KEY_SIZE,
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.cia_max_keysize = ARC4_MAX_KEY_SIZE,
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.cia_setkey = arc4_set_key,
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.cia_encrypt = arc4_crypt,
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.cia_decrypt = arc4_crypt } }
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};
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static int __init arc4_init(void)
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{
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return crypto_register_alg(&arc4_alg);
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}
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static void __exit arc4_exit(void)
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{
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crypto_unregister_alg(&arc4_alg);
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}
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module_init(arc4_init);
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module_exit(arc4_exit);
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("ARC4 Cipher Algorithm");
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MODULE_AUTHOR("Jon Oberheide <jon@oberheide.org>");
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