1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * ChaCha and XChaCha stream ciphers, including ChaCha20 (RFC7539)
4 *
5 * Copyright (C) 2015 Martin Willi
6 * Copyright (C) 2018 Google LLC
7 */
8
9#include <asm/unaligned.h>
10#include <crypto/algapi.h>
11#include <crypto/internal/chacha.h>
12#include <crypto/internal/skcipher.h>
13#include <linux/module.h>
14
15static int chacha_stream_xor(struct skcipher_request *req,
16			     const struct chacha_ctx *ctx, const u8 *iv)
17{
18	struct skcipher_walk walk;
19	u32 state[16];
20	int err;
21
22	err = skcipher_walk_virt(&walk, req, false);
23
24	chacha_init_generic(state, ctx->key, iv);
25
26	while (walk.nbytes > 0) {
27		unsigned int nbytes = walk.nbytes;
28
29		if (nbytes < walk.total)
30			nbytes = round_down(nbytes, CHACHA_BLOCK_SIZE);
31
32		chacha_crypt_generic(state, walk.dst.virt.addr,
33				     walk.src.virt.addr, nbytes, ctx->nrounds);
34		err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
35	}
36
37	return err;
38}
39
40static int crypto_chacha_crypt(struct skcipher_request *req)
41{
42	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
43	struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
44
45	return chacha_stream_xor(req, ctx, req->iv);
46}
47
48static int crypto_xchacha_crypt(struct skcipher_request *req)
49{
50	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
51	struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
52	struct chacha_ctx subctx;
53	u32 state[16];
54	u8 real_iv[16];
55
56	/* Compute the subkey given the original key and first 128 nonce bits */
57	chacha_init_generic(state, ctx->key, req->iv);
58	hchacha_block_generic(state, subctx.key, ctx->nrounds);
59	subctx.nrounds = ctx->nrounds;
60
61	/* Build the real IV */
62	memcpy(&real_iv[0], req->iv + 24, 8); /* stream position */
63	memcpy(&real_iv[8], req->iv + 16, 8); /* remaining 64 nonce bits */
64
65	/* Generate the stream and XOR it with the data */
66	return chacha_stream_xor(req, &subctx, real_iv);
67}
68
69static struct skcipher_alg algs[] = {
70	{
71		.base.cra_name		= "chacha20",
72		.base.cra_driver_name	= "chacha20-generic",
73		.base.cra_priority	= 100,
74		.base.cra_blocksize	= 1,
75		.base.cra_ctxsize	= sizeof(struct chacha_ctx),
76		.base.cra_module	= THIS_MODULE,
77
78		.min_keysize		= CHACHA_KEY_SIZE,
79		.max_keysize		= CHACHA_KEY_SIZE,
80		.ivsize			= CHACHA_IV_SIZE,
81		.chunksize		= CHACHA_BLOCK_SIZE,
82		.setkey			= chacha20_setkey,
83		.encrypt		= crypto_chacha_crypt,
84		.decrypt		= crypto_chacha_crypt,
85	}, {
86		.base.cra_name		= "xchacha20",
87		.base.cra_driver_name	= "xchacha20-generic",
88		.base.cra_priority	= 100,
89		.base.cra_blocksize	= 1,
90		.base.cra_ctxsize	= sizeof(struct chacha_ctx),
91		.base.cra_module	= THIS_MODULE,
92
93		.min_keysize		= CHACHA_KEY_SIZE,
94		.max_keysize		= CHACHA_KEY_SIZE,
95		.ivsize			= XCHACHA_IV_SIZE,
96		.chunksize		= CHACHA_BLOCK_SIZE,
97		.setkey			= chacha20_setkey,
98		.encrypt		= crypto_xchacha_crypt,
99		.decrypt		= crypto_xchacha_crypt,
100	}, {
101		.base.cra_name		= "xchacha12",
102		.base.cra_driver_name	= "xchacha12-generic",
103		.base.cra_priority	= 100,
104		.base.cra_blocksize	= 1,
105		.base.cra_ctxsize	= sizeof(struct chacha_ctx),
106		.base.cra_module	= THIS_MODULE,
107
108		.min_keysize		= CHACHA_KEY_SIZE,
109		.max_keysize		= CHACHA_KEY_SIZE,
110		.ivsize			= XCHACHA_IV_SIZE,
111		.chunksize		= CHACHA_BLOCK_SIZE,
112		.setkey			= chacha12_setkey,
113		.encrypt		= crypto_xchacha_crypt,
114		.decrypt		= crypto_xchacha_crypt,
115	}
116};
117
118static int __init chacha_generic_mod_init(void)
119{
120	return crypto_register_skciphers(algs, ARRAY_SIZE(algs));
121}
122
123static void __exit chacha_generic_mod_fini(void)
124{
125	crypto_unregister_skciphers(algs, ARRAY_SIZE(algs));
126}
127
128subsys_initcall(chacha_generic_mod_init);
129module_exit(chacha_generic_mod_fini);
130
131MODULE_LICENSE("GPL");
132MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
133MODULE_DESCRIPTION("ChaCha and XChaCha stream ciphers (generic)");
134MODULE_ALIAS_CRYPTO("chacha20");
135MODULE_ALIAS_CRYPTO("chacha20-generic");
136MODULE_ALIAS_CRYPTO("xchacha20");
137MODULE_ALIAS_CRYPTO("xchacha20-generic");
138MODULE_ALIAS_CRYPTO("xchacha12");
139MODULE_ALIAS_CRYPTO("xchacha12-generic");
140