aboutsummaryrefslogtreecommitdiffstats
path: root/crypto/salsa20_generic.c
blob: eac10c11685cd436472d9262347922b88165b50d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
/*
 * Salsa20: Salsa20 stream cipher algorithm
 *
 * Copyright (c) 2007 Tan Swee Heng <thesweeheng@gmail.com>
 *
 * Derived from:
 * - salsa20.c: Public domain C code by Daniel J. Bernstein <djb@cr.yp.to>
 *
 * Salsa20 is a stream cipher candidate in eSTREAM, the ECRYPT Stream
 * Cipher Project. It is designed by Daniel J. Bernstein <djb@cr.yp.to>.
 * 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");

Privacy Policy