summaryrefslogtreecommitdiffstats
path: root/crypto/chacha_generic.c
blob: 35b583101f4f3dc5422968a4938194164bc6ad5e (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
/*
 * ChaCha and XChaCha stream ciphers, including ChaCha20 (RFC7539)
 *
 * Copyright (C) 2015 Martin Willi
 * Copyright (C) 2018 Google LLC
 *
 * 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 <asm/unaligned.h>
#include <crypto/algapi.h>
#include <crypto/chacha.h>
#include <crypto/internal/skcipher.h>
#include <linux/module.h>

static void chacha_docrypt(u32 *state, u8 *dst, const u8 *src,
			   unsigned int bytes, int nrounds)
{
	/* aligned to potentially speed up crypto_xor() */
	u8 stream[CHACHA_BLOCK_SIZE] __aligned(sizeof(long));

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

	while (bytes >= CHACHA_BLOCK_SIZE) {
		chacha_block(state, stream, nrounds);
		crypto_xor(dst, stream, CHACHA_BLOCK_SIZE);
		bytes -= CHACHA_BLOCK_SIZE;
		dst += CHACHA_BLOCK_SIZE;
	}
	if (bytes) {
		chacha_block(state, stream, nrounds);
		crypto_xor(dst, stream, bytes);
	}
}

static int chacha_stream_xor(struct skcipher_request *req,
			     struct chacha_ctx *ctx, u8 *iv)
{
	struct skcipher_walk walk;
	u32 state[16];
	int err;

	err = skcipher_walk_virt(&walk, req, false);

	crypto_chacha_init(state, ctx, iv);

	while (walk.nbytes > 0) {
		unsigned int nbytes = walk.nbytes;

		if (nbytes < walk.total)
			nbytes = round_down(nbytes, walk.stride);

		chacha_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
			       nbytes, ctx->nrounds);
		err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
	}

	return err;
}

void crypto_chacha_init(u32 *state, struct chacha_ctx *ctx, u8 *iv)
{
	state[0]  = 0x61707865; /* "expa" */
	state[1]  = 0x3320646e; /* "nd 3" */
	state[2]  = 0x79622d32; /* "2-by" */
	state[3]  = 0x6b206574; /* "te k" */
	state[4]  = ctx->key[0];
	state[5]  = ctx->key[1];
	state[6]  = ctx->key[2];
	state[7]  = ctx->key[3];
	state[8]  = ctx->key[4];
	state[9]  = ctx->key[5];
	state[10] = ctx->key[6];
	state[11] = ctx->key[7];
	state[12] = get_unaligned_le32(iv +  0);
	state[13] = get_unaligned_le32(iv +  4);
	state[14] = get_unaligned_le32(iv +  8);
	state[15] = get_unaligned_le32(iv + 12);
}
EXPORT_SYMBOL_GPL(crypto_chacha_init);

static int chacha_setkey(struct crypto_skcipher *tfm, const u8 *key,
			 unsigned int keysize, int nrounds)
{
	struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
	int i;

	if (keysize != CHACHA_KEY_SIZE)
		return -EINVAL;

	for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
		ctx->key[i] = get_unaligned_le32(key + i * sizeof(u32));

	ctx->nrounds = nrounds;
	return 0;
}

int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
			   unsigned int keysize)
{
	return chacha_setkey(tfm, key, keysize, 20);
}
EXPORT_SYMBOL_GPL(crypto_chacha20_setkey);

int crypto_chacha12_setkey(struct crypto_skcipher *tfm, const u8 *key,
			   unsigned int keysize)
{
	return chacha_setkey(tfm, key, keysize, 12);
}
EXPORT_SYMBOL_GPL(crypto_chacha12_setkey);

int crypto_chacha_crypt(struct skcipher_request *req)
{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);

	return chacha_stream_xor(req, ctx, req->iv);
}
EXPORT_SYMBOL_GPL(crypto_chacha_crypt);

int crypto_xchacha_crypt(struct skcipher_request *req)
{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
	struct chacha_ctx subctx;
	u32 state[16];
	u8 real_iv[16];

	/* Compute the subkey given the original key and first 128 nonce bits */
	crypto_chacha_init(state, ctx, req->iv);
	hchacha_block(state, subctx.key, ctx->nrounds);
	subctx.nrounds = ctx->nrounds;

	/* Build the real IV */
	memcpy(&real_iv[0], req->iv + 24, 8); /* stream position */
	memcpy(&real_iv[8], req->iv + 16, 8); /* remaining 64 nonce bits */

	/* Generate the stream and XOR it with the data */
	return chacha_stream_xor(req, &subctx, real_iv);
}
EXPORT_SYMBOL_GPL(crypto_xchacha_crypt);

static struct skcipher_alg algs[] = {
	{
		.base.cra_name		= "chacha20",
		.base.cra_driver_name	= "chacha20-generic",
		.base.cra_priority	= 100,
		.base.cra_blocksize	= 1,
		.base.cra_ctxsize	= sizeof(struct chacha_ctx),
		.base.cra_module	= THIS_MODULE,

		.min_keysize		= CHACHA_KEY_SIZE,
		.max_keysize		= CHACHA_KEY_SIZE,
		.ivsize			= CHACHA_IV_SIZE,
		.chunksize		= CHACHA_BLOCK_SIZE,
		.setkey			= crypto_chacha20_setkey,
		.encrypt		= crypto_chacha_crypt,
		.decrypt		= crypto_chacha_crypt,
	}, {
		.base.cra_name		= "xchacha20",
		.base.cra_driver_name	= "xchacha20-generic",
		.base.cra_priority	= 100,
		.base.cra_blocksize	= 1,
		.base.cra_ctxsize	= sizeof(struct chacha_ctx),
		.base.cra_module	= THIS_MODULE,

		.min_keysize		= CHACHA_KEY_SIZE,
		.max_keysize		= CHACHA_KEY_SIZE,
		.ivsize			= XCHACHA_IV_SIZE,
		.chunksize		= CHACHA_BLOCK_SIZE,
		.setkey			= crypto_chacha20_setkey,
		.encrypt		= crypto_xchacha_crypt,
		.decrypt		= crypto_xchacha_crypt,
	}, {
		.base.cra_name		= "xchacha12",
		.base.cra_driver_name	= "xchacha12-generic",
		.base.cra_priority	= 100,
		.base.cra_blocksize	= 1,
		.base.cra_ctxsize	= sizeof(struct chacha_ctx),
		.base.cra_module	= THIS_MODULE,

		.min_keysize		= CHACHA_KEY_SIZE,
		.max_keysize		= CHACHA_KEY_SIZE,
		.ivsize			= XCHACHA_IV_SIZE,
		.chunksize		= CHACHA_BLOCK_SIZE,
		.setkey			= crypto_chacha12_setkey,
		.encrypt		= crypto_xchacha_crypt,
		.decrypt		= crypto_xchacha_crypt,
	}
};

static int __init chacha_generic_mod_init(void)
{
	return crypto_register_skciphers(algs, ARRAY_SIZE(algs));
}

static void __exit chacha_generic_mod_fini(void)
{
	crypto_unregister_skciphers(algs, ARRAY_SIZE(algs));
}

module_init(chacha_generic_mod_init);
module_exit(chacha_generic_mod_fini);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
MODULE_DESCRIPTION("ChaCha and XChaCha stream ciphers (generic)");
MODULE_ALIAS_CRYPTO("chacha20");
MODULE_ALIAS_CRYPTO("chacha20-generic");
MODULE_ALIAS_CRYPTO("xchacha20");
MODULE_ALIAS_CRYPTO("xchacha20-generic");
MODULE_ALIAS_CRYPTO("xchacha12");
MODULE_ALIAS_CRYPTO("xchacha12-generic");