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 /* aligned to potentially speed up crypto_xor() */
22 u8 stream[CHACHA20_BLOCK_SIZE] __aligned(sizeof(long));
23
24 if (dst != src)
25 memcpy(dst, src, bytes);
26
27 while (bytes >= CHACHA20_BLOCK_SIZE) {
28 chacha20_block(state, stream);
29 crypto_xor(dst, stream, CHACHA20_BLOCK_SIZE);
30 bytes -= CHACHA20_BLOCK_SIZE;
31 dst += CHACHA20_BLOCK_SIZE;
32 }
33 if (bytes) {
34 chacha20_block(state, stream);
35 crypto_xor(dst, stream, bytes);
36 }
37 }
38
crypto_chacha20_init(u32 * state,struct chacha20_ctx * ctx,u8 * iv)39 void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv)
40 {
41 state[0] = 0x61707865; /* "expa" */
42 state[1] = 0x3320646e; /* "nd 3" */
43 state[2] = 0x79622d32; /* "2-by" */
44 state[3] = 0x6b206574; /* "te k" */
45 state[4] = ctx->key[0];
46 state[5] = ctx->key[1];
47 state[6] = ctx->key[2];
48 state[7] = ctx->key[3];
49 state[8] = ctx->key[4];
50 state[9] = ctx->key[5];
51 state[10] = ctx->key[6];
52 state[11] = ctx->key[7];
53 state[12] = get_unaligned_le32(iv + 0);
54 state[13] = get_unaligned_le32(iv + 4);
55 state[14] = get_unaligned_le32(iv + 8);
56 state[15] = get_unaligned_le32(iv + 12);
57 }
58 EXPORT_SYMBOL_GPL(crypto_chacha20_init);
59
crypto_chacha20_setkey(struct crypto_skcipher * tfm,const u8 * key,unsigned int keysize)60 int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
61 unsigned int keysize)
62 {
63 struct chacha20_ctx *ctx = crypto_skcipher_ctx(tfm);
64 int i;
65
66 if (keysize != CHACHA20_KEY_SIZE)
67 return -EINVAL;
68
69 for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
70 ctx->key[i] = get_unaligned_le32(key + i * sizeof(u32));
71
72 return 0;
73 }
74 EXPORT_SYMBOL_GPL(crypto_chacha20_setkey);
75
crypto_chacha20_crypt(struct skcipher_request * req)76 int crypto_chacha20_crypt(struct skcipher_request *req)
77 {
78 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
79 struct chacha20_ctx *ctx = crypto_skcipher_ctx(tfm);
80 struct skcipher_walk walk;
81 u32 state[16];
82 int err;
83
84 err = skcipher_walk_virt(&walk, req, true);
85
86 crypto_chacha20_init(state, ctx, walk.iv);
87
88 while (walk.nbytes > 0) {
89 unsigned int nbytes = walk.nbytes;
90
91 if (nbytes < walk.total)
92 nbytes = round_down(nbytes, walk.stride);
93
94 chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
95 nbytes);
96 err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
97 }
98
99 return err;
100 }
101 EXPORT_SYMBOL_GPL(crypto_chacha20_crypt);
102
103 static struct skcipher_alg alg = {
104 .base.cra_name = "chacha20",
105 .base.cra_driver_name = "chacha20-generic",
106 .base.cra_priority = 100,
107 .base.cra_blocksize = 1,
108 .base.cra_ctxsize = sizeof(struct chacha20_ctx),
109 .base.cra_module = THIS_MODULE,
110
111 .min_keysize = CHACHA20_KEY_SIZE,
112 .max_keysize = CHACHA20_KEY_SIZE,
113 .ivsize = CHACHA20_IV_SIZE,
114 .chunksize = CHACHA20_BLOCK_SIZE,
115 .setkey = crypto_chacha20_setkey,
116 .encrypt = crypto_chacha20_crypt,
117 .decrypt = crypto_chacha20_crypt,
118 };
119
chacha20_generic_mod_init(void)120 static int __init chacha20_generic_mod_init(void)
121 {
122 return crypto_register_skcipher(&alg);
123 }
124
chacha20_generic_mod_fini(void)125 static void __exit chacha20_generic_mod_fini(void)
126 {
127 crypto_unregister_skcipher(&alg);
128 }
129
130 module_init(chacha20_generic_mod_init);
131 module_exit(chacha20_generic_mod_fini);
132
133 MODULE_LICENSE("GPL");
134 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
135 MODULE_DESCRIPTION("chacha20 cipher algorithm");
136 MODULE_ALIAS_CRYPTO("chacha20");
137 MODULE_ALIAS_CRYPTO("chacha20-generic");
138