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c08d0e64 MW |
1 | /* |
2 | * ChaCha20 256-bit cipher algorithm, RFC7539 | |
3 | * | |
4 | * Copyright (C) 2015 Martin Willi | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or modify | |
7 | * it under the terms of the GNU General Public License as published by | |
8 | * the Free Software Foundation; either version 2 of the License, or | |
9 | * (at your option) any later version. | |
10 | */ | |
11 | ||
12 | #include <crypto/algapi.h> | |
13 | #include <linux/crypto.h> | |
14 | #include <linux/kernel.h> | |
15 | #include <linux/module.h> | |
31d7247d | 16 | #include <crypto/chacha20.h> |
c08d0e64 | 17 | |
c08d0e64 MW |
18 | static inline u32 le32_to_cpuvp(const void *p) |
19 | { | |
20 | return le32_to_cpup(p); | |
21 | } | |
22 | ||
c08d0e64 MW |
23 | static void chacha20_docrypt(u32 *state, u8 *dst, const u8 *src, |
24 | unsigned int bytes) | |
25 | { | |
26 | u8 stream[CHACHA20_BLOCK_SIZE]; | |
27 | ||
28 | if (dst != src) | |
29 | memcpy(dst, src, bytes); | |
30 | ||
31 | while (bytes >= CHACHA20_BLOCK_SIZE) { | |
32 | chacha20_block(state, stream); | |
33 | crypto_xor(dst, stream, CHACHA20_BLOCK_SIZE); | |
34 | bytes -= CHACHA20_BLOCK_SIZE; | |
35 | dst += CHACHA20_BLOCK_SIZE; | |
36 | } | |
37 | if (bytes) { | |
38 | chacha20_block(state, stream); | |
39 | crypto_xor(dst, stream, bytes); | |
40 | } | |
41 | } | |
42 | ||
31d7247d | 43 | void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv) |
c08d0e64 MW |
44 | { |
45 | static const char constant[16] = "expand 32-byte k"; | |
46 | ||
47 | state[0] = le32_to_cpuvp(constant + 0); | |
48 | state[1] = le32_to_cpuvp(constant + 4); | |
49 | state[2] = le32_to_cpuvp(constant + 8); | |
50 | state[3] = le32_to_cpuvp(constant + 12); | |
51 | state[4] = ctx->key[0]; | |
52 | state[5] = ctx->key[1]; | |
53 | state[6] = ctx->key[2]; | |
54 | state[7] = ctx->key[3]; | |
55 | state[8] = ctx->key[4]; | |
56 | state[9] = ctx->key[5]; | |
57 | state[10] = ctx->key[6]; | |
58 | state[11] = ctx->key[7]; | |
59 | state[12] = le32_to_cpuvp(iv + 0); | |
60 | state[13] = le32_to_cpuvp(iv + 4); | |
61 | state[14] = le32_to_cpuvp(iv + 8); | |
62 | state[15] = le32_to_cpuvp(iv + 12); | |
63 | } | |
31d7247d | 64 | EXPORT_SYMBOL_GPL(crypto_chacha20_init); |
c08d0e64 | 65 | |
31d7247d | 66 | int crypto_chacha20_setkey(struct crypto_tfm *tfm, const u8 *key, |
c08d0e64 MW |
67 | unsigned int keysize) |
68 | { | |
69 | struct chacha20_ctx *ctx = crypto_tfm_ctx(tfm); | |
70 | int i; | |
71 | ||
72 | if (keysize != CHACHA20_KEY_SIZE) | |
73 | return -EINVAL; | |
74 | ||
75 | for (i = 0; i < ARRAY_SIZE(ctx->key); i++) | |
76 | ctx->key[i] = le32_to_cpuvp(key + i * sizeof(u32)); | |
77 | ||
78 | return 0; | |
79 | } | |
31d7247d | 80 | EXPORT_SYMBOL_GPL(crypto_chacha20_setkey); |
c08d0e64 | 81 | |
31d7247d | 82 | int crypto_chacha20_crypt(struct blkcipher_desc *desc, struct scatterlist *dst, |
c08d0e64 MW |
83 | struct scatterlist *src, unsigned int nbytes) |
84 | { | |
85 | struct blkcipher_walk walk; | |
86 | u32 state[16]; | |
87 | int err; | |
88 | ||
89 | blkcipher_walk_init(&walk, dst, src, nbytes); | |
90 | err = blkcipher_walk_virt_block(desc, &walk, CHACHA20_BLOCK_SIZE); | |
91 | ||
31d7247d | 92 | crypto_chacha20_init(state, crypto_blkcipher_ctx(desc->tfm), walk.iv); |
c08d0e64 MW |
93 | |
94 | while (walk.nbytes >= CHACHA20_BLOCK_SIZE) { | |
95 | chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr, | |
96 | rounddown(walk.nbytes, CHACHA20_BLOCK_SIZE)); | |
97 | err = blkcipher_walk_done(desc, &walk, | |
98 | walk.nbytes % CHACHA20_BLOCK_SIZE); | |
99 | } | |
100 | ||
101 | if (walk.nbytes) { | |
102 | chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr, | |
103 | walk.nbytes); | |
104 | err = blkcipher_walk_done(desc, &walk, 0); | |
105 | } | |
106 | ||
107 | return err; | |
108 | } | |
31d7247d | 109 | EXPORT_SYMBOL_GPL(crypto_chacha20_crypt); |
c08d0e64 MW |
110 | |
111 | static struct crypto_alg alg = { | |
112 | .cra_name = "chacha20", | |
113 | .cra_driver_name = "chacha20-generic", | |
114 | .cra_priority = 100, | |
115 | .cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER, | |
116 | .cra_blocksize = 1, | |
117 | .cra_type = &crypto_blkcipher_type, | |
118 | .cra_ctxsize = sizeof(struct chacha20_ctx), | |
119 | .cra_alignmask = sizeof(u32) - 1, | |
120 | .cra_module = THIS_MODULE, | |
121 | .cra_u = { | |
122 | .blkcipher = { | |
123 | .min_keysize = CHACHA20_KEY_SIZE, | |
124 | .max_keysize = CHACHA20_KEY_SIZE, | |
31d7247d | 125 | .ivsize = CHACHA20_IV_SIZE, |
c08d0e64 | 126 | .geniv = "seqiv", |
31d7247d MW |
127 | .setkey = crypto_chacha20_setkey, |
128 | .encrypt = crypto_chacha20_crypt, | |
129 | .decrypt = crypto_chacha20_crypt, | |
c08d0e64 MW |
130 | }, |
131 | }, | |
132 | }; | |
133 | ||
134 | static int __init chacha20_generic_mod_init(void) | |
135 | { | |
136 | return crypto_register_alg(&alg); | |
137 | } | |
138 | ||
139 | static void __exit chacha20_generic_mod_fini(void) | |
140 | { | |
141 | crypto_unregister_alg(&alg); | |
142 | } | |
143 | ||
144 | module_init(chacha20_generic_mod_init); | |
145 | module_exit(chacha20_generic_mod_fini); | |
146 | ||
147 | MODULE_LICENSE("GPL"); | |
148 | MODULE_AUTHOR("Martin Willi <martin@strongswan.org>"); | |
149 | MODULE_DESCRIPTION("chacha20 cipher algorithm"); | |
150 | MODULE_ALIAS_CRYPTO("chacha20"); | |
151 | MODULE_ALIAS_CRYPTO("chacha20-generic"); |