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22#include <asm/unaligned.h>
23#include <crypto/internal/skcipher.h>
24#include <crypto/salsa20.h>
25#include <linux/module.h>
26
27static void salsa20_block(u32 *state, __le32 *stream)
28{
29 u32 x[16];
30 int i;
31
32 memcpy(x, state, sizeof(x));
33
34 for (i = 0; i < 20; i += 2) {
35 x[ 4] ^= rol32((x[ 0] + x[12]), 7);
36 x[ 8] ^= rol32((x[ 4] + x[ 0]), 9);
37 x[12] ^= rol32((x[ 8] + x[ 4]), 13);
38 x[ 0] ^= rol32((x[12] + x[ 8]), 18);
39 x[ 9] ^= rol32((x[ 5] + x[ 1]), 7);
40 x[13] ^= rol32((x[ 9] + x[ 5]), 9);
41 x[ 1] ^= rol32((x[13] + x[ 9]), 13);
42 x[ 5] ^= rol32((x[ 1] + x[13]), 18);
43 x[14] ^= rol32((x[10] + x[ 6]), 7);
44 x[ 2] ^= rol32((x[14] + x[10]), 9);
45 x[ 6] ^= rol32((x[ 2] + x[14]), 13);
46 x[10] ^= rol32((x[ 6] + x[ 2]), 18);
47 x[ 3] ^= rol32((x[15] + x[11]), 7);
48 x[ 7] ^= rol32((x[ 3] + x[15]), 9);
49 x[11] ^= rol32((x[ 7] + x[ 3]), 13);
50 x[15] ^= rol32((x[11] + x[ 7]), 18);
51 x[ 1] ^= rol32((x[ 0] + x[ 3]), 7);
52 x[ 2] ^= rol32((x[ 1] + x[ 0]), 9);
53 x[ 3] ^= rol32((x[ 2] + x[ 1]), 13);
54 x[ 0] ^= rol32((x[ 3] + x[ 2]), 18);
55 x[ 6] ^= rol32((x[ 5] + x[ 4]), 7);
56 x[ 7] ^= rol32((x[ 6] + x[ 5]), 9);
57 x[ 4] ^= rol32((x[ 7] + x[ 6]), 13);
58 x[ 5] ^= rol32((x[ 4] + x[ 7]), 18);
59 x[11] ^= rol32((x[10] + x[ 9]), 7);
60 x[ 8] ^= rol32((x[11] + x[10]), 9);
61 x[ 9] ^= rol32((x[ 8] + x[11]), 13);
62 x[10] ^= rol32((x[ 9] + x[ 8]), 18);
63 x[12] ^= rol32((x[15] + x[14]), 7);
64 x[13] ^= rol32((x[12] + x[15]), 9);
65 x[14] ^= rol32((x[13] + x[12]), 13);
66 x[15] ^= rol32((x[14] + x[13]), 18);
67 }
68
69 for (i = 0; i < 16; i++)
70 stream[i] = cpu_to_le32(x[i] + state[i]);
71
72 if (++state[8] == 0)
73 state[9]++;
74}
75
76static void salsa20_docrypt(u32 *state, u8 *dst, const u8 *src,
77 unsigned int bytes)
78{
79 __le32 stream[SALSA20_BLOCK_SIZE / sizeof(__le32)];
80
81 if (dst != src)
82 memcpy(dst, src, bytes);
83
84 while (bytes >= SALSA20_BLOCK_SIZE) {
85 salsa20_block(state, stream);
86 crypto_xor(dst, (const u8 *)stream, SALSA20_BLOCK_SIZE);
87 bytes -= SALSA20_BLOCK_SIZE;
88 dst += SALSA20_BLOCK_SIZE;
89 }
90 if (bytes) {
91 salsa20_block(state, stream);
92 crypto_xor(dst, (const u8 *)stream, bytes);
93 }
94}
95
96void crypto_salsa20_init(u32 *state, const struct salsa20_ctx *ctx,
97 const u8 *iv)
98{
99 memcpy(state, ctx->initial_state, sizeof(ctx->initial_state));
100 state[6] = get_unaligned_le32(iv + 0);
101 state[7] = get_unaligned_le32(iv + 4);
102}
103EXPORT_SYMBOL_GPL(crypto_salsa20_init);
104
105int crypto_salsa20_setkey(struct crypto_skcipher *tfm, const u8 *key,
106 unsigned int keysize)
107{
108 static const char sigma[16] = "expand 32-byte k";
109 static const char tau[16] = "expand 16-byte k";
110 struct salsa20_ctx *ctx = crypto_skcipher_ctx(tfm);
111 const char *constants;
112
113 if (keysize != SALSA20_MIN_KEY_SIZE &&
114 keysize != SALSA20_MAX_KEY_SIZE)
115 return -EINVAL;
116
117 ctx->initial_state[1] = get_unaligned_le32(key + 0);
118 ctx->initial_state[2] = get_unaligned_le32(key + 4);
119 ctx->initial_state[3] = get_unaligned_le32(key + 8);
120 ctx->initial_state[4] = get_unaligned_le32(key + 12);
121 if (keysize == 32) {
122 key += 16;
123 constants = sigma;
124 } else {
125 constants = tau;
126 }
127 ctx->initial_state[11] = get_unaligned_le32(key + 0);
128 ctx->initial_state[12] = get_unaligned_le32(key + 4);
129 ctx->initial_state[13] = get_unaligned_le32(key + 8);
130 ctx->initial_state[14] = get_unaligned_le32(key + 12);
131 ctx->initial_state[0] = get_unaligned_le32(constants + 0);
132 ctx->initial_state[5] = get_unaligned_le32(constants + 4);
133 ctx->initial_state[10] = get_unaligned_le32(constants + 8);
134 ctx->initial_state[15] = get_unaligned_le32(constants + 12);
135
136
137 ctx->initial_state[6] = 0;
138 ctx->initial_state[7] = 0;
139
140
141 ctx->initial_state[8] = 0;
142 ctx->initial_state[9] = 0;
143
144 return 0;
145}
146EXPORT_SYMBOL_GPL(crypto_salsa20_setkey);
147
148static int salsa20_crypt(struct skcipher_request *req)
149{
150 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
151 const struct salsa20_ctx *ctx = crypto_skcipher_ctx(tfm);
152 struct skcipher_walk walk;
153 u32 state[16];
154 int err;
155
156 err = skcipher_walk_virt(&walk, req, true);
157
158 crypto_salsa20_init(state, ctx, walk.iv);
159
160 while (walk.nbytes > 0) {
161 unsigned int nbytes = walk.nbytes;
162
163 if (nbytes < walk.total)
164 nbytes = round_down(nbytes, walk.stride);
165
166 salsa20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
167 nbytes);
168 err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
169 }
170
171 return err;
172}
173
174static struct skcipher_alg alg = {
175 .base.cra_name = "salsa20",
176 .base.cra_driver_name = "salsa20-generic",
177 .base.cra_priority = 100,
178 .base.cra_blocksize = 1,
179 .base.cra_ctxsize = sizeof(struct salsa20_ctx),
180 .base.cra_module = THIS_MODULE,
181
182 .min_keysize = SALSA20_MIN_KEY_SIZE,
183 .max_keysize = SALSA20_MAX_KEY_SIZE,
184 .ivsize = SALSA20_IV_SIZE,
185 .chunksize = SALSA20_BLOCK_SIZE,
186 .setkey = crypto_salsa20_setkey,
187 .encrypt = salsa20_crypt,
188 .decrypt = salsa20_crypt,
189};
190
191static int __init salsa20_generic_mod_init(void)
192{
193 return crypto_register_skcipher(&alg);
194}
195
196static void __exit salsa20_generic_mod_fini(void)
197{
198 crypto_unregister_skcipher(&alg);
199}
200
201module_init(salsa20_generic_mod_init);
202module_exit(salsa20_generic_mod_fini);
203
204MODULE_LICENSE("GPL");
205MODULE_DESCRIPTION ("Salsa20 stream cipher algorithm");
206MODULE_ALIAS_CRYPTO("salsa20");
207MODULE_ALIAS_CRYPTO("salsa20-generic");
208
