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awilliam
GitHub Repository: awilliam/linux-vfio
 Path: blob/master/crypto/arc4.c
10814 views
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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 <[email protected]>

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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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	{

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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 <[email protected]>");

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