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12#include <crypto/algapi.h>
13#include <linux/crypto.h>
14#include <linux/kernel.h>
15#include <linux/module.h>
16
17#define CHACHA20_NONCE_SIZE 16
18#define CHACHA20_KEY_SIZE 32
19#define CHACHA20_BLOCK_SIZE 64
20
21struct chacha20_ctx {
22 u32 key[8];
23};
24
25static inline u32 rotl32(u32 v, u8 n)
26{
27 return (v << n) | (v >> (sizeof(v) * 8 - n));
28}
29
30static inline u32 le32_to_cpuvp(const void *p)
31{
32 return le32_to_cpup(p);
33}
34
35static void chacha20_block(u32 *state, void *stream)
36{
37 u32 x[16], *out = stream;
38 int i;
39
40 for (i = 0; i < ARRAY_SIZE(x); i++)
41 x[i] = state[i];
42
43 for (i = 0; i < 20; i += 2) {
44 x[0] += x[4]; x[12] = rotl32(x[12] ^ x[0], 16);
45 x[1] += x[5]; x[13] = rotl32(x[13] ^ x[1], 16);
46 x[2] += x[6]; x[14] = rotl32(x[14] ^ x[2], 16);
47 x[3] += x[7]; x[15] = rotl32(x[15] ^ x[3], 16);
48
49 x[8] += x[12]; x[4] = rotl32(x[4] ^ x[8], 12);
50 x[9] += x[13]; x[5] = rotl32(x[5] ^ x[9], 12);
51 x[10] += x[14]; x[6] = rotl32(x[6] ^ x[10], 12);
52 x[11] += x[15]; x[7] = rotl32(x[7] ^ x[11], 12);
53
54 x[0] += x[4]; x[12] = rotl32(x[12] ^ x[0], 8);
55 x[1] += x[5]; x[13] = rotl32(x[13] ^ x[1], 8);
56 x[2] += x[6]; x[14] = rotl32(x[14] ^ x[2], 8);
57 x[3] += x[7]; x[15] = rotl32(x[15] ^ x[3], 8);
58
59 x[8] += x[12]; x[4] = rotl32(x[4] ^ x[8], 7);
60 x[9] += x[13]; x[5] = rotl32(x[5] ^ x[9], 7);
61 x[10] += x[14]; x[6] = rotl32(x[6] ^ x[10], 7);
62 x[11] += x[15]; x[7] = rotl32(x[7] ^ x[11], 7);
63
64 x[0] += x[5]; x[15] = rotl32(x[15] ^ x[0], 16);
65 x[1] += x[6]; x[12] = rotl32(x[12] ^ x[1], 16);
66 x[2] += x[7]; x[13] = rotl32(x[13] ^ x[2], 16);
67 x[3] += x[4]; x[14] = rotl32(x[14] ^ x[3], 16);
68
69 x[10] += x[15]; x[5] = rotl32(x[5] ^ x[10], 12);
70 x[11] += x[12]; x[6] = rotl32(x[6] ^ x[11], 12);
71 x[8] += x[13]; x[7] = rotl32(x[7] ^ x[8], 12);
72 x[9] += x[14]; x[4] = rotl32(x[4] ^ x[9], 12);
73
74 x[0] += x[5]; x[15] = rotl32(x[15] ^ x[0], 8);
75 x[1] += x[6]; x[12] = rotl32(x[12] ^ x[1], 8);
76 x[2] += x[7]; x[13] = rotl32(x[13] ^ x[2], 8);
77 x[3] += x[4]; x[14] = rotl32(x[14] ^ x[3], 8);
78
79 x[10] += x[15]; x[5] = rotl32(x[5] ^ x[10], 7);
80 x[11] += x[12]; x[6] = rotl32(x[6] ^ x[11], 7);
81 x[8] += x[13]; x[7] = rotl32(x[7] ^ x[8], 7);
82 x[9] += x[14]; x[4] = rotl32(x[4] ^ x[9], 7);
83 }
84
85 for (i = 0; i < ARRAY_SIZE(x); i++)
86 out[i] = cpu_to_le32(x[i] + state[i]);
87
88 state[12]++;
89}
90
91static void chacha20_docrypt(u32 *state, u8 *dst, const u8 *src,
92 unsigned int bytes)
93{
94 u8 stream[CHACHA20_BLOCK_SIZE];
95
96 if (dst != src)
97 memcpy(dst, src, bytes);
98
99 while (bytes >= CHACHA20_BLOCK_SIZE) {
100 chacha20_block(state, stream);
101 crypto_xor(dst, stream, CHACHA20_BLOCK_SIZE);
102 bytes -= CHACHA20_BLOCK_SIZE;
103 dst += CHACHA20_BLOCK_SIZE;
104 }
105 if (bytes) {
106 chacha20_block(state, stream);
107 crypto_xor(dst, stream, bytes);
108 }
109}
110
111static void chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv)
112{
113 static const char constant[16] = "expand 32-byte k";
114
115 state[0] = le32_to_cpuvp(constant + 0);
116 state[1] = le32_to_cpuvp(constant + 4);
117 state[2] = le32_to_cpuvp(constant + 8);
118 state[3] = le32_to_cpuvp(constant + 12);
119 state[4] = ctx->key[0];
120 state[5] = ctx->key[1];
121 state[6] = ctx->key[2];
122 state[7] = ctx->key[3];
123 state[8] = ctx->key[4];
124 state[9] = ctx->key[5];
125 state[10] = ctx->key[6];
126 state[11] = ctx->key[7];
127 state[12] = le32_to_cpuvp(iv + 0);
128 state[13] = le32_to_cpuvp(iv + 4);
129 state[14] = le32_to_cpuvp(iv + 8);
130 state[15] = le32_to_cpuvp(iv + 12);
131}
132
133static int chacha20_setkey(struct crypto_tfm *tfm, const u8 *key,
134 unsigned int keysize)
135{
136 struct chacha20_ctx *ctx = crypto_tfm_ctx(tfm);
137 int i;
138
139 if (keysize != CHACHA20_KEY_SIZE)
140 return -EINVAL;
141
142 for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
143 ctx->key[i] = le32_to_cpuvp(key + i * sizeof(u32));
144
145 return 0;
146}
147
148static int chacha20_crypt(struct blkcipher_desc *desc, struct scatterlist *dst,
149 struct scatterlist *src, unsigned int nbytes)
150{
151 struct blkcipher_walk walk;
152 u32 state[16];
153 int err;
154
155 blkcipher_walk_init(&walk, dst, src, nbytes);
156 err = blkcipher_walk_virt_block(desc, &walk, CHACHA20_BLOCK_SIZE);
157
158 chacha20_init(state, crypto_blkcipher_ctx(desc->tfm), walk.iv);
159
160 while (walk.nbytes >= CHACHA20_BLOCK_SIZE) {
161 chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
162 rounddown(walk.nbytes, CHACHA20_BLOCK_SIZE));
163 err = blkcipher_walk_done(desc, &walk,
164 walk.nbytes % CHACHA20_BLOCK_SIZE);
165 }
166
167 if (walk.nbytes) {
168 chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
169 walk.nbytes);
170 err = blkcipher_walk_done(desc, &walk, 0);
171 }
172
173 return err;
174}
175
176static struct crypto_alg alg = {
177 .cra_name = "chacha20",
178 .cra_driver_name = "chacha20-generic",
179 .cra_priority = 100,
180 .cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER,
181 .cra_blocksize = 1,
182 .cra_type = &crypto_blkcipher_type,
183 .cra_ctxsize = sizeof(struct chacha20_ctx),
184 .cra_alignmask = sizeof(u32) - 1,
185 .cra_module = THIS_MODULE,
186 .cra_u = {
187 .blkcipher = {
188 .min_keysize = CHACHA20_KEY_SIZE,
189 .max_keysize = CHACHA20_KEY_SIZE,
190 .ivsize = CHACHA20_NONCE_SIZE,
191 .geniv = "seqiv",
192 .setkey = chacha20_setkey,
193 .encrypt = chacha20_crypt,
194 .decrypt = chacha20_crypt,
195 },
196 },
197};
198
199static int __init chacha20_generic_mod_init(void)
200{
201 return crypto_register_alg(&alg);
202}
203
204static void __exit chacha20_generic_mod_fini(void)
205{
206 crypto_unregister_alg(&alg);
207}
208
209module_init(chacha20_generic_mod_init);
210module_exit(chacha20_generic_mod_fini);
211
212MODULE_LICENSE("GPL");
213MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
214MODULE_DESCRIPTION("chacha20 cipher algorithm");
215MODULE_ALIAS_CRYPTO("chacha20");
216MODULE_ALIAS_CRYPTO("chacha20-generic");
217
