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
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