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/chacha.h>
12 #include <crypto/internal/skcipher.h>
13 #include <linux/module.h>
14
chacha_docrypt(u32 * state,u8 * dst,const u8 * src,unsigned int bytes,int nrounds)15 static void chacha_docrypt(u32 *state, u8 *dst, const u8 *src,
16 unsigned int bytes, int nrounds)
17 {
18 /* aligned to potentially speed up crypto_xor() */
19 u8 stream[CHACHA_BLOCK_SIZE] __aligned(sizeof(long));
20
21 while (bytes >= CHACHA_BLOCK_SIZE) {
22 chacha_block(state, stream, nrounds);
23 crypto_xor_cpy(dst, src, stream, CHACHA_BLOCK_SIZE);
24 bytes -= CHACHA_BLOCK_SIZE;
25 dst += CHACHA_BLOCK_SIZE;
26 src += CHACHA_BLOCK_SIZE;
27 }
28 if (bytes) {
29 chacha_block(state, stream, nrounds);
30 crypto_xor_cpy(dst, src, stream, bytes);
31 }
32 }
33
chacha_stream_xor(struct skcipher_request * req,const struct chacha_ctx * ctx,const u8 * iv)34 static int chacha_stream_xor(struct skcipher_request *req,
35 const struct chacha_ctx *ctx, const u8 *iv)
36 {
37 struct skcipher_walk walk;
38 u32 state[16];
39 int err;
40
41 err = skcipher_walk_virt(&walk, req, false);
42
43 crypto_chacha_init(state, ctx, iv);
44
45 while (walk.nbytes > 0) {
46 unsigned int nbytes = walk.nbytes;
47
48 if (nbytes < walk.total)
49 nbytes = round_down(nbytes, CHACHA_BLOCK_SIZE);
50
51 chacha_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
52 nbytes, ctx->nrounds);
53 err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
54 }
55
56 return err;
57 }
58
crypto_chacha_init(u32 * state,const struct chacha_ctx * ctx,const u8 * iv)59 void crypto_chacha_init(u32 *state, const struct chacha_ctx *ctx, const u8 *iv)
60 {
61 state[0] = 0x61707865; /* "expa" */
62 state[1] = 0x3320646e; /* "nd 3" */
63 state[2] = 0x79622d32; /* "2-by" */
64 state[3] = 0x6b206574; /* "te k" */
65 state[4] = ctx->key[0];
66 state[5] = ctx->key[1];
67 state[6] = ctx->key[2];
68 state[7] = ctx->key[3];
69 state[8] = ctx->key[4];
70 state[9] = ctx->key[5];
71 state[10] = ctx->key[6];
72 state[11] = ctx->key[7];
73 state[12] = get_unaligned_le32(iv + 0);
74 state[13] = get_unaligned_le32(iv + 4);
75 state[14] = get_unaligned_le32(iv + 8);
76 state[15] = get_unaligned_le32(iv + 12);
77 }
78 EXPORT_SYMBOL_GPL(crypto_chacha_init);
79
chacha_setkey(struct crypto_skcipher * tfm,const u8 * key,unsigned int keysize,int nrounds)80 static int chacha_setkey(struct crypto_skcipher *tfm, const u8 *key,
81 unsigned int keysize, int nrounds)
82 {
83 struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
84 int i;
85
86 if (keysize != CHACHA_KEY_SIZE)
87 return -EINVAL;
88
89 for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
90 ctx->key[i] = get_unaligned_le32(key + i * sizeof(u32));
91
92 ctx->nrounds = nrounds;
93 return 0;
94 }
95
crypto_chacha20_setkey(struct crypto_skcipher * tfm,const u8 * key,unsigned int keysize)96 int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
97 unsigned int keysize)
98 {
99 return chacha_setkey(tfm, key, keysize, 20);
100 }
101 EXPORT_SYMBOL_GPL(crypto_chacha20_setkey);
102
crypto_chacha12_setkey(struct crypto_skcipher * tfm,const u8 * key,unsigned int keysize)103 int crypto_chacha12_setkey(struct crypto_skcipher *tfm, const u8 *key,
104 unsigned int keysize)
105 {
106 return chacha_setkey(tfm, key, keysize, 12);
107 }
108 EXPORT_SYMBOL_GPL(crypto_chacha12_setkey);
109
crypto_chacha_crypt(struct skcipher_request * req)110 int crypto_chacha_crypt(struct skcipher_request *req)
111 {
112 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
113 struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
114
115 return chacha_stream_xor(req, ctx, req->iv);
116 }
117 EXPORT_SYMBOL_GPL(crypto_chacha_crypt);
118
crypto_xchacha_crypt(struct skcipher_request * req)119 int crypto_xchacha_crypt(struct skcipher_request *req)
120 {
121 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
122 struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
123 struct chacha_ctx subctx;
124 u32 state[16];
125 u8 real_iv[16];
126
127 /* Compute the subkey given the original key and first 128 nonce bits */
128 crypto_chacha_init(state, ctx, req->iv);
129 hchacha_block(state, subctx.key, ctx->nrounds);
130 subctx.nrounds = ctx->nrounds;
131
132 /* Build the real IV */
133 memcpy(&real_iv[0], req->iv + 24, 8); /* stream position */
134 memcpy(&real_iv[8], req->iv + 16, 8); /* remaining 64 nonce bits */
135
136 /* Generate the stream and XOR it with the data */
137 return chacha_stream_xor(req, &subctx, real_iv);
138 }
139 EXPORT_SYMBOL_GPL(crypto_xchacha_crypt);
140
141 static struct skcipher_alg algs[] = {
142 {
143 .base.cra_name = "chacha20",
144 .base.cra_driver_name = "chacha20-generic",
145 .base.cra_priority = 100,
146 .base.cra_blocksize = 1,
147 .base.cra_ctxsize = sizeof(struct chacha_ctx),
148 .base.cra_module = THIS_MODULE,
149
150 .min_keysize = CHACHA_KEY_SIZE,
151 .max_keysize = CHACHA_KEY_SIZE,
152 .ivsize = CHACHA_IV_SIZE,
153 .chunksize = CHACHA_BLOCK_SIZE,
154 .setkey = crypto_chacha20_setkey,
155 .encrypt = crypto_chacha_crypt,
156 .decrypt = crypto_chacha_crypt,
157 }, {
158 .base.cra_name = "xchacha20",
159 .base.cra_driver_name = "xchacha20-generic",
160 .base.cra_priority = 100,
161 .base.cra_blocksize = 1,
162 .base.cra_ctxsize = sizeof(struct chacha_ctx),
163 .base.cra_module = THIS_MODULE,
164
165 .min_keysize = CHACHA_KEY_SIZE,
166 .max_keysize = CHACHA_KEY_SIZE,
167 .ivsize = XCHACHA_IV_SIZE,
168 .chunksize = CHACHA_BLOCK_SIZE,
169 .setkey = crypto_chacha20_setkey,
170 .encrypt = crypto_xchacha_crypt,
171 .decrypt = crypto_xchacha_crypt,
172 }, {
173 .base.cra_name = "xchacha12",
174 .base.cra_driver_name = "xchacha12-generic",
175 .base.cra_priority = 100,
176 .base.cra_blocksize = 1,
177 .base.cra_ctxsize = sizeof(struct chacha_ctx),
178 .base.cra_module = THIS_MODULE,
179
180 .min_keysize = CHACHA_KEY_SIZE,
181 .max_keysize = CHACHA_KEY_SIZE,
182 .ivsize = XCHACHA_IV_SIZE,
183 .chunksize = CHACHA_BLOCK_SIZE,
184 .setkey = crypto_chacha12_setkey,
185 .encrypt = crypto_xchacha_crypt,
186 .decrypt = crypto_xchacha_crypt,
187 }
188 };
189
chacha_generic_mod_init(void)190 static int __init chacha_generic_mod_init(void)
191 {
192 return crypto_register_skciphers(algs, ARRAY_SIZE(algs));
193 }
194
chacha_generic_mod_fini(void)195 static void __exit chacha_generic_mod_fini(void)
196 {
197 crypto_unregister_skciphers(algs, ARRAY_SIZE(algs));
198 }
199
200 subsys_initcall(chacha_generic_mod_init);
201 module_exit(chacha_generic_mod_fini);
202
203 MODULE_LICENSE("GPL");
204 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
205 MODULE_DESCRIPTION("ChaCha and XChaCha stream ciphers (generic)");
206 MODULE_ALIAS_CRYPTO("chacha20");
207 MODULE_ALIAS_CRYPTO("chacha20-generic");
208 MODULE_ALIAS_CRYPTO("xchacha20");
209 MODULE_ALIAS_CRYPTO("xchacha20-generic");
210 MODULE_ALIAS_CRYPTO("xchacha12");
211 MODULE_ALIAS_CRYPTO("xchacha12-generic");
212
