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 <asm/unaligned.h>
13 #include <crypto/algapi.h>
14 #include <crypto/chacha20.h>
15 #include <crypto/internal/skcipher.h>
16 #include <linux/module.h>
17
chacha20_docrypt(u32 * state,u8 * dst,const u8 * src,unsigned int bytes)18 static void chacha20_docrypt(u32 *state, u8 *dst, const u8 *src,
19 unsigned int bytes)
20 {
21 u32 stream[CHACHA20_BLOCK_WORDS];
22
23 if (dst != src)
24 memcpy(dst, src, bytes);
25
26 while (bytes >= CHACHA20_BLOCK_SIZE) {
27 chacha20_block(state, stream);
28 crypto_xor(dst, (const u8 *)stream, CHACHA20_BLOCK_SIZE);
29 bytes -= CHACHA20_BLOCK_SIZE;
30 dst += CHACHA20_BLOCK_SIZE;
31 }
32 if (bytes) {
33 chacha20_block(state, stream);
34 crypto_xor(dst, (const u8 *)stream, bytes);
35 }
36 }
37
crypto_chacha20_init(u32 * state,struct chacha20_ctx * ctx,u8 * iv)38 void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv)
39 {
40 state[0] = 0x61707865; /* "expa" */
41 state[1] = 0x3320646e; /* "nd 3" */
42 state[2] = 0x79622d32; /* "2-by" */
43 state[3] = 0x6b206574; /* "te k" */
44 state[4] = ctx->key[0];
45 state[5] = ctx->key[1];
46 state[6] = ctx->key[2];
47 state[7] = ctx->key[3];
48 state[8] = ctx->key[4];
49 state[9] = ctx->key[5];
50 state[10] = ctx->key[6];
51 state[11] = ctx->key[7];
52 state[12] = get_unaligned_le32(iv + 0);
53 state[13] = get_unaligned_le32(iv + 4);
54 state[14] = get_unaligned_le32(iv + 8);
55 state[15] = get_unaligned_le32(iv + 12);
56 }
57 EXPORT_SYMBOL_GPL(crypto_chacha20_init);
58
crypto_chacha20_setkey(struct crypto_skcipher * tfm,const u8 * key,unsigned int keysize)59 int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
60 unsigned int keysize)
61 {
62 struct chacha20_ctx *ctx = crypto_skcipher_ctx(tfm);
63 int i;
64
65 if (keysize != CHACHA20_KEY_SIZE)
66 return -EINVAL;
67
68 for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
69 ctx->key[i] = get_unaligned_le32(key + i * sizeof(u32));
70
71 return 0;
72 }
73 EXPORT_SYMBOL_GPL(crypto_chacha20_setkey);
74
crypto_chacha20_crypt(struct skcipher_request * req)75 int crypto_chacha20_crypt(struct skcipher_request *req)
76 {
77 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
78 struct chacha20_ctx *ctx = crypto_skcipher_ctx(tfm);
79 struct skcipher_walk walk;
80 u32 state[16];
81 int err;
82
83 err = skcipher_walk_virt(&walk, req, true);
84
85 crypto_chacha20_init(state, ctx, walk.iv);
86
87 while (walk.nbytes > 0) {
88 unsigned int nbytes = walk.nbytes;
89
90 if (nbytes < walk.total)
91 nbytes = round_down(nbytes, walk.stride);
92
93 chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
94 nbytes);
95 err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
96 }
97
98 return err;
99 }
100 EXPORT_SYMBOL_GPL(crypto_chacha20_crypt);
101
102 static struct skcipher_alg alg = {
103 .base.cra_name = "chacha20",
104 .base.cra_driver_name = "chacha20-generic",
105 .base.cra_priority = 100,
106 .base.cra_blocksize = 1,
107 .base.cra_ctxsize = sizeof(struct chacha20_ctx),
108 .base.cra_module = THIS_MODULE,
109
110 .min_keysize = CHACHA20_KEY_SIZE,
111 .max_keysize = CHACHA20_KEY_SIZE,
112 .ivsize = CHACHA20_IV_SIZE,
113 .chunksize = CHACHA20_BLOCK_SIZE,
114 .setkey = crypto_chacha20_setkey,
115 .encrypt = crypto_chacha20_crypt,
116 .decrypt = crypto_chacha20_crypt,
117 };
118
chacha20_generic_mod_init(void)119 static int __init chacha20_generic_mod_init(void)
120 {
121 return crypto_register_skcipher(&alg);
122 }
123
chacha20_generic_mod_fini(void)124 static void __exit chacha20_generic_mod_fini(void)
125 {
126 crypto_unregister_skcipher(&alg);
127 }
128
129 module_init(chacha20_generic_mod_init);
130 module_exit(chacha20_generic_mod_fini);
131
132 MODULE_LICENSE("GPL");
133 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
134 MODULE_DESCRIPTION("chacha20 cipher algorithm");
135 MODULE_ALIAS_CRYPTO("chacha20");
136 MODULE_ALIAS_CRYPTO("chacha20-generic");
137
