xref: /openbmc/linux/crypto/chacha_generic.c (revision 0c6dfa75)
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 
15 static 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 
40 static 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 
48 static 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 
69 static 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 
118 static int __init chacha_generic_mod_init(void)
119 {
120 	return crypto_register_skciphers(algs, ARRAY_SIZE(algs));
121 }
122 
123 static void __exit chacha_generic_mod_fini(void)
124 {
125 	crypto_unregister_skciphers(algs, ARRAY_SIZE(algs));
126 }
127 
128 subsys_initcall(chacha_generic_mod_init);
129 module_exit(chacha_generic_mod_fini);
130 
131 MODULE_LICENSE("GPL");
132 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
133 MODULE_DESCRIPTION("ChaCha and XChaCha stream ciphers (generic)");
134 MODULE_ALIAS_CRYPTO("chacha20");
135 MODULE_ALIAS_CRYPTO("chacha20-generic");
136 MODULE_ALIAS_CRYPTO("xchacha20");
137 MODULE_ALIAS_CRYPTO("xchacha20-generic");
138 MODULE_ALIAS_CRYPTO("xchacha12");
139 MODULE_ALIAS_CRYPTO("xchacha12-generic");
140