summaryrefslogtreecommitdiffstats
path: root/crypto/chacha_generic.c
blob: 8beea79ab1178298f0c72ad1df8a40a1febae2ec (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
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * ChaCha and XChaCha stream ciphers, including ChaCha20 (RFC7539)
 *
 * Copyright (C) 2015 Martin Willi
 * Copyright (C) 2018 Google LLC
 */

#include <asm/unaligned.h>
#include <crypto/algapi.h>
#include <crypto/internal/chacha.h>
#include <crypto/internal/skcipher.h>
#include <linux/module.h>

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

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

	chacha_init_generic(state, ctx->key, iv);

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

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

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

	return err;
}

static 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);
}

static 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 */
	chacha_init_generic(state, ctx->key, req->iv);
	hchacha_block_generic(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);
}

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			= 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			= 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			= 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));
}

subsys_initcall(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");