1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22#include <linux/init.h>
23#include <linux/module.h>
24#include <linux/errno.h>
25#include <linux/crypto.h>
26#include <linux/types.h>
27#include <crypto/algapi.h>
28#include <asm/byteorder.h>
29
30#define SALSA20_IV_SIZE 8U
31#define SALSA20_MIN_KEY_SIZE 16U
32#define SALSA20_MAX_KEY_SIZE 32U
33
34
35
36
37
38
39
40
41
42
43
44
45#define ROTATE(v,n) (((v) << (n)) | ((v) >> (32 - (n))))
46#define XOR(v,w) ((v) ^ (w))
47#define PLUS(v,w) (((v) + (w)))
48#define PLUSONE(v) (PLUS((v),1))
49#define U32TO8_LITTLE(p, v) \
50 { (p)[0] = (v >> 0) & 0xff; (p)[1] = (v >> 8) & 0xff; \
51 (p)[2] = (v >> 16) & 0xff; (p)[3] = (v >> 24) & 0xff; }
52#define U8TO32_LITTLE(p) \
53 (((u32)((p)[0]) ) | ((u32)((p)[1]) << 8) | \
54 ((u32)((p)[2]) << 16) | ((u32)((p)[3]) << 24) )
55
56struct salsa20_ctx
57{
58 u32 input[16];
59};
60
61static void salsa20_wordtobyte(u8 output[64], const u32 input[16])
62{
63 u32 x[16];
64 int i;
65
66 memcpy(x, input, sizeof(x));
67 for (i = 20; i > 0; i -= 2) {
68 x[ 4] = XOR(x[ 4],ROTATE(PLUS(x[ 0],x[12]), 7));
69 x[ 8] = XOR(x[ 8],ROTATE(PLUS(x[ 4],x[ 0]), 9));
70 x[12] = XOR(x[12],ROTATE(PLUS(x[ 8],x[ 4]),13));
71 x[ 0] = XOR(x[ 0],ROTATE(PLUS(x[12],x[ 8]),18));
72 x[ 9] = XOR(x[ 9],ROTATE(PLUS(x[ 5],x[ 1]), 7));
73 x[13] = XOR(x[13],ROTATE(PLUS(x[ 9],x[ 5]), 9));
74 x[ 1] = XOR(x[ 1],ROTATE(PLUS(x[13],x[ 9]),13));
75 x[ 5] = XOR(x[ 5],ROTATE(PLUS(x[ 1],x[13]),18));
76 x[14] = XOR(x[14],ROTATE(PLUS(x[10],x[ 6]), 7));
77 x[ 2] = XOR(x[ 2],ROTATE(PLUS(x[14],x[10]), 9));
78 x[ 6] = XOR(x[ 6],ROTATE(PLUS(x[ 2],x[14]),13));
79 x[10] = XOR(x[10],ROTATE(PLUS(x[ 6],x[ 2]),18));
80 x[ 3] = XOR(x[ 3],ROTATE(PLUS(x[15],x[11]), 7));
81 x[ 7] = XOR(x[ 7],ROTATE(PLUS(x[ 3],x[15]), 9));
82 x[11] = XOR(x[11],ROTATE(PLUS(x[ 7],x[ 3]),13));
83 x[15] = XOR(x[15],ROTATE(PLUS(x[11],x[ 7]),18));
84 x[ 1] = XOR(x[ 1],ROTATE(PLUS(x[ 0],x[ 3]), 7));
85 x[ 2] = XOR(x[ 2],ROTATE(PLUS(x[ 1],x[ 0]), 9));
86 x[ 3] = XOR(x[ 3],ROTATE(PLUS(x[ 2],x[ 1]),13));
87 x[ 0] = XOR(x[ 0],ROTATE(PLUS(x[ 3],x[ 2]),18));
88 x[ 6] = XOR(x[ 6],ROTATE(PLUS(x[ 5],x[ 4]), 7));
89 x[ 7] = XOR(x[ 7],ROTATE(PLUS(x[ 6],x[ 5]), 9));
90 x[ 4] = XOR(x[ 4],ROTATE(PLUS(x[ 7],x[ 6]),13));
91 x[ 5] = XOR(x[ 5],ROTATE(PLUS(x[ 4],x[ 7]),18));
92 x[11] = XOR(x[11],ROTATE(PLUS(x[10],x[ 9]), 7));
93 x[ 8] = XOR(x[ 8],ROTATE(PLUS(x[11],x[10]), 9));
94 x[ 9] = XOR(x[ 9],ROTATE(PLUS(x[ 8],x[11]),13));
95 x[10] = XOR(x[10],ROTATE(PLUS(x[ 9],x[ 8]),18));
96 x[12] = XOR(x[12],ROTATE(PLUS(x[15],x[14]), 7));
97 x[13] = XOR(x[13],ROTATE(PLUS(x[12],x[15]), 9));
98 x[14] = XOR(x[14],ROTATE(PLUS(x[13],x[12]),13));
99 x[15] = XOR(x[15],ROTATE(PLUS(x[14],x[13]),18));
100 }
101 for (i = 0; i < 16; ++i)
102 x[i] = PLUS(x[i],input[i]);
103 for (i = 0; i < 16; ++i)
104 U32TO8_LITTLE(output + 4 * i,x[i]);
105}
106
107static const char sigma[16] = "expand 32-byte k";
108static const char tau[16] = "expand 16-byte k";
109
110static void salsa20_keysetup(struct salsa20_ctx *ctx, const u8 *k, u32 kbytes)
111{
112 const char *constants;
113
114 ctx->input[1] = U8TO32_LITTLE(k + 0);
115 ctx->input[2] = U8TO32_LITTLE(k + 4);
116 ctx->input[3] = U8TO32_LITTLE(k + 8);
117 ctx->input[4] = U8TO32_LITTLE(k + 12);
118 if (kbytes == 32) {
119 k += 16;
120 constants = sigma;
121 } else {
122 constants = tau;
123 }
124 ctx->input[11] = U8TO32_LITTLE(k + 0);
125 ctx->input[12] = U8TO32_LITTLE(k + 4);
126 ctx->input[13] = U8TO32_LITTLE(k + 8);
127 ctx->input[14] = U8TO32_LITTLE(k + 12);
128 ctx->input[0] = U8TO32_LITTLE(constants + 0);
129 ctx->input[5] = U8TO32_LITTLE(constants + 4);
130 ctx->input[10] = U8TO32_LITTLE(constants + 8);
131 ctx->input[15] = U8TO32_LITTLE(constants + 12);
132}
133
134static void salsa20_ivsetup(struct salsa20_ctx *ctx, const u8 *iv)
135{
136 ctx->input[6] = U8TO32_LITTLE(iv + 0);
137 ctx->input[7] = U8TO32_LITTLE(iv + 4);
138 ctx->input[8] = 0;
139 ctx->input[9] = 0;
140}
141
142static void salsa20_encrypt_bytes(struct salsa20_ctx *ctx, u8 *dst,
143 const u8 *src, unsigned int bytes)
144{
145 u8 buf[64];
146
147 if (dst != src)
148 memcpy(dst, src, bytes);
149
150 while (bytes) {
151 salsa20_wordtobyte(buf, ctx->input);
152
153 ctx->input[8] = PLUSONE(ctx->input[8]);
154 if (!ctx->input[8])
155 ctx->input[9] = PLUSONE(ctx->input[9]);
156
157 if (bytes <= 64) {
158 crypto_xor(dst, buf, bytes);
159 return;
160 }
161
162 crypto_xor(dst, buf, 64);
163 bytes -= 64;
164 dst += 64;
165 }
166}
167
168
169
170
171
172static int setkey(struct crypto_tfm *tfm, const u8 *key,
173 unsigned int keysize)
174{
175 struct salsa20_ctx *ctx = crypto_tfm_ctx(tfm);
176 salsa20_keysetup(ctx, key, keysize);
177 return 0;
178}
179
180static int encrypt(struct blkcipher_desc *desc,
181 struct scatterlist *dst, struct scatterlist *src,
182 unsigned int nbytes)
183{
184 struct blkcipher_walk walk;
185 struct crypto_blkcipher *tfm = desc->tfm;
186 struct salsa20_ctx *ctx = crypto_blkcipher_ctx(tfm);
187 int err;
188
189 blkcipher_walk_init(&walk, dst, src, nbytes);
190 err = blkcipher_walk_virt_block(desc, &walk, 64);
191
192 salsa20_ivsetup(ctx, walk.iv);
193
194 if (likely(walk.nbytes == nbytes))
195 {
196 salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
197 walk.src.virt.addr, nbytes);
198 return blkcipher_walk_done(desc, &walk, 0);
199 }
200
201 while (walk.nbytes >= 64) {
202 salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
203 walk.src.virt.addr,
204 walk.nbytes - (walk.nbytes % 64));
205 err = blkcipher_walk_done(desc, &walk, walk.nbytes % 64);
206 }
207
208 if (walk.nbytes) {
209 salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
210 walk.src.virt.addr, walk.nbytes);
211 err = blkcipher_walk_done(desc, &walk, 0);
212 }
213
214 return err;
215}
216
217static struct crypto_alg alg = {
218 .cra_name = "salsa20",
219 .cra_driver_name = "salsa20-generic",
220 .cra_priority = 100,
221 .cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER,
222 .cra_type = &crypto_blkcipher_type,
223 .cra_blocksize = 1,
224 .cra_ctxsize = sizeof(struct salsa20_ctx),
225 .cra_alignmask = 3,
226 .cra_module = THIS_MODULE,
227 .cra_list = LIST_HEAD_INIT(alg.cra_list),
228 .cra_u = {
229 .blkcipher = {
230 .setkey = setkey,
231 .encrypt = encrypt,
232 .decrypt = encrypt,
233 .min_keysize = SALSA20_MIN_KEY_SIZE,
234 .max_keysize = SALSA20_MAX_KEY_SIZE,
235 .ivsize = SALSA20_IV_SIZE,
236 }
237 }
238};
239
240static int __init salsa20_generic_mod_init(void)
241{
242 return crypto_register_alg(&alg);
243}
244
245static void __exit salsa20_generic_mod_fini(void)
246{
247 crypto_unregister_alg(&alg);
248}
249
250module_init(salsa20_generic_mod_init);
251module_exit(salsa20_generic_mod_fini);
252
253MODULE_LICENSE("GPL");
254MODULE_DESCRIPTION ("Salsa20 stream cipher algorithm");
255MODULE_ALIAS("salsa20");
256
