[linux.git] / crypto / salsa20_generic.c

/*
 * Salsa20: Salsa20 stream cipher algorithm
 *
 * Copyright (c) 2007 Tan Swee Heng <[email protected]>
 *
 * Derived from:
 * - salsa20.c: Public domain C code by Daniel J. Bernstein <[email protected]>
 *
 * Salsa20 is a stream cipher candidate in eSTREAM, the ECRYPT Stream
 * Cipher Project. It is designed by Daniel J. Bernstein <[email protected]>.
 * More information about eSTREAM and Salsa20 can be found here:
 *   http://www.ecrypt.eu.org/stream/
 *   http://cr.yp.to/snuffle.html
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/crypto.h>
#include <linux/types.h>
#include <linux/bitops.h>
#include <crypto/algapi.h>
#include <asm/byteorder.h>

#define SALSA20_IV_SIZE        8U
#define SALSA20_MIN_KEY_SIZE  16U
#define SALSA20_MAX_KEY_SIZE  32U

/*
 * Start of code taken from D. J. Bernstein's reference implementation.
 * With some modifications and optimizations made to suit our needs.
 */

/*
salsa20-ref.c version 20051118
D. J. Bernstein
Public domain.
*/

#define U32TO8_LITTLE(p, v) \
	{ (p)[0] = (v >>  0) & 0xff; (p)[1] = (v >>  8) & 0xff; \
	  (p)[2] = (v >> 16) & 0xff; (p)[3] = (v >> 24) & 0xff; }
#define U8TO32_LITTLE(p)   \
	(((u32)((p)[0])      ) | ((u32)((p)[1]) <<  8) | \
	 ((u32)((p)[2]) << 16) | ((u32)((p)[3]) << 24)   )

struct salsa20_ctx
{
	u32 input[16];
};

static void salsa20_wordtobyte(u8 output[64], const u32 input[16])
{
	u32 x[16];
	int i;

	memcpy(x, input, sizeof(x));
	for (i = 20; i > 0; i -= 2) {
		x[ 4] ^= rol32((x[ 0] + x[12]),  7);
		x[ 8] ^= rol32((x[ 4] + x[ 0]),  9);
		x[12] ^= rol32((x[ 8] + x[ 4]), 13);
		x[ 0] ^= rol32((x[12] + x[ 8]), 18);
		x[ 9] ^= rol32((x[ 5] + x[ 1]),  7);
		x[13] ^= rol32((x[ 9] + x[ 5]),  9);
		x[ 1] ^= rol32((x[13] + x[ 9]), 13);
		x[ 5] ^= rol32((x[ 1] + x[13]), 18);
		x[14] ^= rol32((x[10] + x[ 6]),  7);
		x[ 2] ^= rol32((x[14] + x[10]),  9);
		x[ 6] ^= rol32((x[ 2] + x[14]), 13);
		x[10] ^= rol32((x[ 6] + x[ 2]), 18);
		x[ 3] ^= rol32((x[15] + x[11]),  7);
		x[ 7] ^= rol32((x[ 3] + x[15]),  9);
		x[11] ^= rol32((x[ 7] + x[ 3]), 13);
		x[15] ^= rol32((x[11] + x[ 7]), 18);
		x[ 1] ^= rol32((x[ 0] + x[ 3]),  7);
		x[ 2] ^= rol32((x[ 1] + x[ 0]),  9);
		x[ 3] ^= rol32((x[ 2] + x[ 1]), 13);
		x[ 0] ^= rol32((x[ 3] + x[ 2]), 18);
		x[ 6] ^= rol32((x[ 5] + x[ 4]),  7);
		x[ 7] ^= rol32((x[ 6] + x[ 5]),  9);
		x[ 4] ^= rol32((x[ 7] + x[ 6]), 13);
		x[ 5] ^= rol32((x[ 4] + x[ 7]), 18);
		x[11] ^= rol32((x[10] + x[ 9]),  7);
		x[ 8] ^= rol32((x[11] + x[10]),  9);
		x[ 9] ^= rol32((x[ 8] + x[11]), 13);
		x[10] ^= rol32((x[ 9] + x[ 8]), 18);
		x[12] ^= rol32((x[15] + x[14]),  7);
		x[13] ^= rol32((x[12] + x[15]),  9);
		x[14] ^= rol32((x[13] + x[12]), 13);
		x[15] ^= rol32((x[14] + x[13]), 18);
	}
	for (i = 0; i < 16; ++i)
		x[i] += input[i];
	for (i = 0; i < 16; ++i)
		U32TO8_LITTLE(output + 4 * i,x[i]);
}

static const char sigma[16] = "expand 32-byte k";
static const char tau[16] = "expand 16-byte k";

static void salsa20_keysetup(struct salsa20_ctx *ctx, const u8 *k, u32 kbytes)
{
	const char *constants;

	ctx->input[1] = U8TO32_LITTLE(k + 0);
	ctx->input[2] = U8TO32_LITTLE(k + 4);
	ctx->input[3] = U8TO32_LITTLE(k + 8);
	ctx->input[4] = U8TO32_LITTLE(k + 12);
	if (kbytes == 32) { /* recommended */
		k += 16;
		constants = sigma;
	} else { /* kbytes == 16 */
		constants = tau;
	}
	ctx->input[11] = U8TO32_LITTLE(k + 0);
	ctx->input[12] = U8TO32_LITTLE(k + 4);
	ctx->input[13] = U8TO32_LITTLE(k + 8);
	ctx->input[14] = U8TO32_LITTLE(k + 12);
	ctx->input[0] = U8TO32_LITTLE(constants + 0);
	ctx->input[5] = U8TO32_LITTLE(constants + 4);
	ctx->input[10] = U8TO32_LITTLE(constants + 8);
	ctx->input[15] = U8TO32_LITTLE(constants + 12);
}

static void salsa20_ivsetup(struct salsa20_ctx *ctx, const u8 *iv)
{
	ctx->input[6] = U8TO32_LITTLE(iv + 0);
	ctx->input[7] = U8TO32_LITTLE(iv + 4);
	ctx->input[8] = 0;
	ctx->input[9] = 0;
}

static void salsa20_encrypt_bytes(struct salsa20_ctx *ctx, u8 *dst,
				  const u8 *src, unsigned int bytes)
{
	u8 buf[64];

	if (dst != src)
		memcpy(dst, src, bytes);

	while (bytes) {
		salsa20_wordtobyte(buf, ctx->input);

		ctx->input[8]++;
		if (!ctx->input[8])
			ctx->input[9]++;

		if (bytes <= 64) {
			crypto_xor(dst, buf, bytes);
			return;
		}

		crypto_xor(dst, buf, 64);
		bytes -= 64;
		dst += 64;
	}
}

/*
 * End of code taken from D. J. Bernstein's reference implementation.
 */

static int setkey(struct crypto_tfm *tfm, const u8 *key,
		  unsigned int keysize)
{
	struct salsa20_ctx *ctx = crypto_tfm_ctx(tfm);
	salsa20_keysetup(ctx, key, keysize);
	return 0;
}

static int encrypt(struct blkcipher_desc *desc,
		   struct scatterlist *dst, struct scatterlist *src,
		   unsigned int nbytes)
{
	struct blkcipher_walk walk;
	struct crypto_blkcipher *tfm = desc->tfm;
	struct salsa20_ctx *ctx = crypto_blkcipher_ctx(tfm);
	int err;

	blkcipher_walk_init(&walk, dst, src, nbytes);
	err = blkcipher_walk_virt_block(desc, &walk, 64);

	salsa20_ivsetup(ctx, walk.iv);

	if (likely(walk.nbytes == nbytes))
	{
		salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
				      walk.src.virt.addr, nbytes);
		return blkcipher_walk_done(desc, &walk, 0);
	}

	while (walk.nbytes >= 64) {
		salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
				      walk.src.virt.addr,
				      walk.nbytes - (walk.nbytes % 64));
		err = blkcipher_walk_done(desc, &walk, walk.nbytes % 64);
	}

	if (walk.nbytes) {
		salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
				      walk.src.virt.addr, walk.nbytes);
		err = blkcipher_walk_done(desc, &walk, 0);
	}

	return err;
}

static struct crypto_alg alg = {
	.cra_name           =   "salsa20",
	.cra_driver_name    =   "salsa20-generic",
	.cra_priority       =   100,
	.cra_flags          =   CRYPTO_ALG_TYPE_BLKCIPHER,
	.cra_type           =   &crypto_blkcipher_type,
	.cra_blocksize      =   1,
	.cra_ctxsize        =   sizeof(struct salsa20_ctx),
	.cra_alignmask      =	3,
	.cra_module         =   THIS_MODULE,
	.cra_list           =   LIST_HEAD_INIT(alg.cra_list),
	.cra_u              =   {
		.blkcipher = {
			.setkey         =   setkey,
			.encrypt        =   encrypt,
			.decrypt        =   encrypt,
			.min_keysize    =   SALSA20_MIN_KEY_SIZE,
			.max_keysize    =   SALSA20_MAX_KEY_SIZE,
			.ivsize         =   SALSA20_IV_SIZE,
		}
	}
};

static int __init salsa20_generic_mod_init(void)
{
	return crypto_register_alg(&alg);
}

static void __exit salsa20_generic_mod_fini(void)
{
	crypto_unregister_alg(&alg);
}

module_init(salsa20_generic_mod_init);
module_exit(salsa20_generic_mod_fini);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION ("Salsa20 stream cipher algorithm");
MODULE_ALIAS("salsa20");
Commit	Line	Data
2407d608 TSH	1	/*
	2	* Salsa20: Salsa20 stream cipher algorithm
	3	*
	4	* Copyright (c) 2007 Tan Swee Heng <[email protected]>
	5	*
	6	* Derived from:
	7	* - salsa20.c: Public domain C code by Daniel J. Bernstein <[email protected]>
	8	*
	9	* Salsa20 is a stream cipher candidate in eSTREAM, the ECRYPT Stream
	10	* Cipher Project. It is designed by Daniel J. Bernstein <[email protected]>.
	11	* More information about eSTREAM and Salsa20 can be found here:
	12	* http://www.ecrypt.eu.org/stream/
	13	* http://cr.yp.to/snuffle.html
	14	*
	15	* This program is free software; you can redistribute it and/or modify it
	16	* under the terms of the GNU General Public License as published by the Free
	17	* Software Foundation; either version 2 of the License, or (at your option)
	18	* any later version.
	19	*
	20	*/
	21
	22	#include <linux/init.h>
	23	#include <linux/module.h>
	24	#include <linux/errno.h>
	25	#include <linux/crypto.h>
	26	#include <linux/types.h>
f0d1ec3a	27	#include <linux/bitops.h>
2407d608 TSH	28	#include <crypto/algapi.h>
	29	#include <asm/byteorder.h>
	30
	31	#define SALSA20_IV_SIZE 8U
	32	#define SALSA20_MIN_KEY_SIZE 16U
	33	#define SALSA20_MAX_KEY_SIZE 32U
	34
	35	/*
	36	* Start of code taken from D. J. Bernstein's reference implementation.
	37	* With some modifications and optimizations made to suit our needs.
	38	*/
	39
	40	/*
	41	salsa20-ref.c version 20051118
	42	D. J. Bernstein
	43	Public domain.
	44	*/
	45
2407d608 TSH	46	#define U32TO8_LITTLE(p, v) \
	47	{ (p)[0] = (v >> 0) & 0xff; (p)[1] = (v >> 8) & 0xff; \
	48	(p)[2] = (v >> 16) & 0xff; (p)[3] = (v >> 24) & 0xff; }
	49	#define U8TO32_LITTLE(p) \
	50	(((u32)((p)[0]) ) \| ((u32)((p)[1]) << 8) \| \
	51	((u32)((p)[2]) << 16) \| ((u32)((p)[3]) << 24) )
	52
	53	struct salsa20_ctx
	54	{
	55	u32 input[16];
	56	};
	57
	58	static void salsa20_wordtobyte(u8 output[64], const u32 input[16])
	59	{
	60	u32 x[16];
	61	int i;
	62
	63	memcpy(x, input, sizeof(x));
	64	for (i = 20; i > 0; i -= 2) {
f0d1ec3a HH	65	x[ 4] ^= rol32((x[ 0] + x[12]), 7);
	66	x[ 8] ^= rol32((x[ 4] + x[ 0]), 9);
	67	x[12] ^= rol32((x[ 8] + x[ 4]), 13);
	68	x[ 0] ^= rol32((x[12] + x[ 8]), 18);
	69	x[ 9] ^= rol32((x[ 5] + x[ 1]), 7);
	70	x[13] ^= rol32((x[ 9] + x[ 5]), 9);
	71	x[ 1] ^= rol32((x[13] + x[ 9]), 13);
	72	x[ 5] ^= rol32((x[ 1] + x[13]), 18);
	73	x[14] ^= rol32((x[10] + x[ 6]), 7);
	74	x[ 2] ^= rol32((x[14] + x[10]), 9);
	75	x[ 6] ^= rol32((x[ 2] + x[14]), 13);
	76	x[10] ^= rol32((x[ 6] + x[ 2]), 18);
	77	x[ 3] ^= rol32((x[15] + x[11]), 7);
	78	x[ 7] ^= rol32((x[ 3] + x[15]), 9);
	79	x[11] ^= rol32((x[ 7] + x[ 3]), 13);
	80	x[15] ^= rol32((x[11] + x[ 7]), 18);
	81	x[ 1] ^= rol32((x[ 0] + x[ 3]), 7);
	82	x[ 2] ^= rol32((x[ 1] + x[ 0]), 9);
	83	x[ 3] ^= rol32((x[ 2] + x[ 1]), 13);
	84	x[ 0] ^= rol32((x[ 3] + x[ 2]), 18);
	85	x[ 6] ^= rol32((x[ 5] + x[ 4]), 7);
	86	x[ 7] ^= rol32((x[ 6] + x[ 5]), 9);
	87	x[ 4] ^= rol32((x[ 7] + x[ 6]), 13);
	88	x[ 5] ^= rol32((x[ 4] + x[ 7]), 18);
	89	x[11] ^= rol32((x[10] + x[ 9]), 7);
	90	x[ 8] ^= rol32((x[11] + x[10]), 9);
	91	x[ 9] ^= rol32((x[ 8] + x[11]), 13);
	92	x[10] ^= rol32((x[ 9] + x[ 8]), 18);
	93	x[12] ^= rol32((x[15] + x[14]), 7);
	94	x[13] ^= rol32((x[12] + x[15]), 9);
	95	x[14] ^= rol32((x[13] + x[12]), 13);
	96	x[15] ^= rol32((x[14] + x[13]), 18);
2407d608 TSH	97	}
2407d608 TSH	98	for (i = 0; i < 16; ++i)
f0d1ec3a	99	x[i] += input[i];
2407d608 TSH	100	for (i = 0; i < 16; ++i)
	101	U32TO8_LITTLE(output + 4 * i,x[i]);
	102	}
	103
	104	static const char sigma[16] = "expand 32-byte k";
	105	static const char tau[16] = "expand 16-byte k";
	106
	107	static void salsa20_keysetup(struct salsa20_ctx ctx, const u8 k, u32 kbytes)
	108	{
	109	const char *constants;
	110
	111	ctx->input[1] = U8TO32_LITTLE(k + 0);
	112	ctx->input[2] = U8TO32_LITTLE(k + 4);
	113	ctx->input[3] = U8TO32_LITTLE(k + 8);
	114	ctx->input[4] = U8TO32_LITTLE(k + 12);
	115	if (kbytes == 32) { /* recommended */
	116	k += 16;
	117	constants = sigma;
	118	} else { /* kbytes == 16 */
	119	constants = tau;
	120	}
	121	ctx->input[11] = U8TO32_LITTLE(k + 0);
	122	ctx->input[12] = U8TO32_LITTLE(k + 4);
	123	ctx->input[13] = U8TO32_LITTLE(k + 8);
	124	ctx->input[14] = U8TO32_LITTLE(k + 12);
	125	ctx->input[0] = U8TO32_LITTLE(constants + 0);
	126	ctx->input[5] = U8TO32_LITTLE(constants + 4);
	127	ctx->input[10] = U8TO32_LITTLE(constants + 8);
	128	ctx->input[15] = U8TO32_LITTLE(constants + 12);
	129	}
	130
	131	static void salsa20_ivsetup(struct salsa20_ctx ctx, const u8 iv)
	132	{
	133	ctx->input[6] = U8TO32_LITTLE(iv + 0);
	134	ctx->input[7] = U8TO32_LITTLE(iv + 4);
	135	ctx->input[8] = 0;
	136	ctx->input[9] = 0;
	137	}
	138
	139	static void salsa20_encrypt_bytes(struct salsa20_ctx ctx, u8 dst,
	140	const u8 *src, unsigned int bytes)
	141	{
	142	u8 buf[64];
2407d608 TSH	143
	144	if (dst != src)
	145	memcpy(dst, src, bytes);
	146
	147	while (bytes) {
	148	salsa20_wordtobyte(buf, ctx->input);
	149
f0d1ec3a	150	ctx->input[8]++;
2407d608	151	if (!ctx->input[8])
f0d1ec3a	152	ctx->input[9]++;
2407d608 TSH	153
2407d608 TSH	154	if (bytes <= 64) {
eb6f13eb	155	crypto_xor(dst, buf, bytes);
2407d608 TSH	156	return;
	157	}
	158
eb6f13eb	159	crypto_xor(dst, buf, 64);
2407d608 TSH	160	bytes -= 64;
	161	dst += 64;
	162	}
	163	}
	164
	165	/*
	166	* End of code taken from D. J. Bernstein's reference implementation.
	167	*/
	168
	169	static int setkey(struct crypto_tfm tfm, const u8 key,
	170	unsigned int keysize)
	171	{
	172	struct salsa20_ctx *ctx = crypto_tfm_ctx(tfm);
	173	salsa20_keysetup(ctx, key, keysize);
	174	return 0;
	175	}
	176
	177	static int encrypt(struct blkcipher_desc *desc,
	178	struct scatterlist dst, struct scatterlist src,
	179	unsigned int nbytes)
	180	{
	181	struct blkcipher_walk walk;
	182	struct crypto_blkcipher *tfm = desc->tfm;
	183	struct salsa20_ctx *ctx = crypto_blkcipher_ctx(tfm);
	184	int err;
	185
	186	blkcipher_walk_init(&walk, dst, src, nbytes);
eb6f13eb	187	err = blkcipher_walk_virt_block(desc, &walk, 64);
2407d608 TSH	188
2407d608 TSH	189	salsa20_ivsetup(ctx, walk.iv);
2407d608	190
eb6f13eb TSH	191	if (likely(walk.nbytes == nbytes))
	192	{
	193	salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
	194	walk.src.virt.addr, nbytes);
	195	return blkcipher_walk_done(desc, &walk, 0);
	196	}
	197
	198	while (walk.nbytes >= 64) {
	199	salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
	200	walk.src.virt.addr,
	201	walk.nbytes - (walk.nbytes % 64));
	202	err = blkcipher_walk_done(desc, &walk, walk.nbytes % 64);
	203	}
	204
	205	if (walk.nbytes) {
	206	salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
	207	walk.src.virt.addr, walk.nbytes);
	208	err = blkcipher_walk_done(desc, &walk, 0);
	209	}
	210
2407d608 TSH	211	return err;
	212	}
	213
	214	static struct crypto_alg alg = {
	215	.cra_name = "salsa20",
	216	.cra_driver_name = "salsa20-generic",
	217	.cra_priority = 100,
	218	.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER,
	219	.cra_type = &crypto_blkcipher_type,
	220	.cra_blocksize = 1,
	221	.cra_ctxsize = sizeof(struct salsa20_ctx),
	222	.cra_alignmask = 3,
	223	.cra_module = THIS_MODULE,
	224	.cra_list = LIST_HEAD_INIT(alg.cra_list),
	225	.cra_u = {
	226	.blkcipher = {
	227	.setkey = setkey,
	228	.encrypt = encrypt,
	229	.decrypt = encrypt,
	230	.min_keysize = SALSA20_MIN_KEY_SIZE,
	231	.max_keysize = SALSA20_MAX_KEY_SIZE,
	232	.ivsize = SALSA20_IV_SIZE,
	233	}
	234	}
	235	};
	236
3af5b90b	237	static int __init salsa20_generic_mod_init(void)
2407d608 TSH	238	{
	239	return crypto_register_alg(&alg);
	240	}
	241
3af5b90b	242	static void __exit salsa20_generic_mod_fini(void)
2407d608 TSH	243	{
	244	crypto_unregister_alg(&alg);
	245	}
	246
3af5b90b KB	247	module_init(salsa20_generic_mod_init);
3af5b90b KB	248	module_exit(salsa20_generic_mod_fini);
2407d608 TSH	249
	250	MODULE_LICENSE("GPL");
	251	MODULE_DESCRIPTION ("Salsa20 stream cipher algorithm");
	252	MODULE_ALIAS("salsa20");