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f979e014 MW |
1 | /* |
2 | * Poly1305 authenticator algorithm, RFC7539 | |
3 | * | |
4 | * Copyright (C) 2015 Martin Willi | |
5 | * | |
6 | * Based on public domain code by Andrew Moon and Daniel J. Bernstein. | |
7 | * | |
8 | * This program is free software; you can redistribute it and/or modify | |
9 | * it under the terms of the GNU General Public License as published by | |
10 | * the Free Software Foundation; either version 2 of the License, or | |
11 | * (at your option) any later version. | |
12 | */ | |
13 | ||
14 | #include <crypto/algapi.h> | |
15 | #include <crypto/internal/hash.h> | |
16 | #include <linux/crypto.h> | |
17 | #include <linux/kernel.h> | |
18 | #include <linux/module.h> | |
19 | ||
20 | #define POLY1305_BLOCK_SIZE 16 | |
21 | #define POLY1305_KEY_SIZE 32 | |
22 | #define POLY1305_DIGEST_SIZE 16 | |
23 | ||
c2b7b20a | 24 | struct poly1305_desc_ctx { |
f979e014 MW |
25 | /* key */ |
26 | u32 r[5]; | |
27 | /* finalize key */ | |
28 | u32 s[4]; | |
f979e014 MW |
29 | /* accumulator */ |
30 | u32 h[5]; | |
31 | /* partial buffer */ | |
32 | u8 buf[POLY1305_BLOCK_SIZE]; | |
33 | /* bytes used in partial buffer */ | |
34 | unsigned int buflen; | |
c2b7b20a MW |
35 | /* r key has been set */ |
36 | bool rset; | |
37 | /* s key has been set */ | |
38 | bool sset; | |
f979e014 MW |
39 | }; |
40 | ||
41 | static inline u64 mlt(u64 a, u64 b) | |
42 | { | |
43 | return a * b; | |
44 | } | |
45 | ||
46 | static inline u32 sr(u64 v, u_char n) | |
47 | { | |
48 | return v >> n; | |
49 | } | |
50 | ||
51 | static inline u32 and(u32 v, u32 mask) | |
52 | { | |
53 | return v & mask; | |
54 | } | |
55 | ||
56 | static inline u32 le32_to_cpuvp(const void *p) | |
57 | { | |
58 | return le32_to_cpup(p); | |
59 | } | |
60 | ||
61 | static int poly1305_init(struct shash_desc *desc) | |
62 | { | |
63 | struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc); | |
64 | ||
65 | memset(dctx->h, 0, sizeof(dctx->h)); | |
66 | dctx->buflen = 0; | |
c2b7b20a MW |
67 | dctx->rset = false; |
68 | dctx->sset = false; | |
f979e014 MW |
69 | |
70 | return 0; | |
71 | } | |
72 | ||
73 | static int poly1305_setkey(struct crypto_shash *tfm, | |
74 | const u8 *key, unsigned int keylen) | |
75 | { | |
c2b7b20a MW |
76 | /* Poly1305 requires a unique key for each tag, which implies that |
77 | * we can't set it on the tfm that gets accessed by multiple users | |
78 | * simultaneously. Instead we expect the key as the first 32 bytes in | |
79 | * the update() call. */ | |
80 | return -ENOTSUPP; | |
81 | } | |
f979e014 | 82 | |
c2b7b20a MW |
83 | static void poly1305_setrkey(struct poly1305_desc_ctx *dctx, const u8 *key) |
84 | { | |
f979e014 | 85 | /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */ |
c2b7b20a MW |
86 | dctx->r[0] = (le32_to_cpuvp(key + 0) >> 0) & 0x3ffffff; |
87 | dctx->r[1] = (le32_to_cpuvp(key + 3) >> 2) & 0x3ffff03; | |
88 | dctx->r[2] = (le32_to_cpuvp(key + 6) >> 4) & 0x3ffc0ff; | |
89 | dctx->r[3] = (le32_to_cpuvp(key + 9) >> 6) & 0x3f03fff; | |
90 | dctx->r[4] = (le32_to_cpuvp(key + 12) >> 8) & 0x00fffff; | |
91 | } | |
f979e014 | 92 | |
c2b7b20a MW |
93 | static void poly1305_setskey(struct poly1305_desc_ctx *dctx, const u8 *key) |
94 | { | |
95 | dctx->s[0] = le32_to_cpuvp(key + 0); | |
96 | dctx->s[1] = le32_to_cpuvp(key + 4); | |
97 | dctx->s[2] = le32_to_cpuvp(key + 8); | |
98 | dctx->s[3] = le32_to_cpuvp(key + 12); | |
f979e014 MW |
99 | } |
100 | ||
101 | static unsigned int poly1305_blocks(struct poly1305_desc_ctx *dctx, | |
c2b7b20a MW |
102 | const u8 *src, unsigned int srclen, |
103 | u32 hibit) | |
f979e014 MW |
104 | { |
105 | u32 r0, r1, r2, r3, r4; | |
106 | u32 s1, s2, s3, s4; | |
107 | u32 h0, h1, h2, h3, h4; | |
108 | u64 d0, d1, d2, d3, d4; | |
109 | ||
c2b7b20a MW |
110 | if (unlikely(!dctx->sset)) { |
111 | if (!dctx->rset && srclen >= POLY1305_BLOCK_SIZE) { | |
112 | poly1305_setrkey(dctx, src); | |
113 | src += POLY1305_BLOCK_SIZE; | |
114 | srclen -= POLY1305_BLOCK_SIZE; | |
115 | dctx->rset = true; | |
116 | } | |
117 | if (srclen >= POLY1305_BLOCK_SIZE) { | |
118 | poly1305_setskey(dctx, src); | |
119 | src += POLY1305_BLOCK_SIZE; | |
120 | srclen -= POLY1305_BLOCK_SIZE; | |
121 | dctx->sset = true; | |
122 | } | |
123 | } | |
124 | ||
125 | r0 = dctx->r[0]; | |
126 | r1 = dctx->r[1]; | |
127 | r2 = dctx->r[2]; | |
128 | r3 = dctx->r[3]; | |
129 | r4 = dctx->r[4]; | |
f979e014 MW |
130 | |
131 | s1 = r1 * 5; | |
132 | s2 = r2 * 5; | |
133 | s3 = r3 * 5; | |
134 | s4 = r4 * 5; | |
135 | ||
136 | h0 = dctx->h[0]; | |
137 | h1 = dctx->h[1]; | |
138 | h2 = dctx->h[2]; | |
139 | h3 = dctx->h[3]; | |
140 | h4 = dctx->h[4]; | |
141 | ||
142 | while (likely(srclen >= POLY1305_BLOCK_SIZE)) { | |
143 | ||
144 | /* h += m[i] */ | |
145 | h0 += (le32_to_cpuvp(src + 0) >> 0) & 0x3ffffff; | |
146 | h1 += (le32_to_cpuvp(src + 3) >> 2) & 0x3ffffff; | |
147 | h2 += (le32_to_cpuvp(src + 6) >> 4) & 0x3ffffff; | |
148 | h3 += (le32_to_cpuvp(src + 9) >> 6) & 0x3ffffff; | |
149 | h4 += (le32_to_cpuvp(src + 12) >> 8) | hibit; | |
150 | ||
151 | /* h *= r */ | |
152 | d0 = mlt(h0, r0) + mlt(h1, s4) + mlt(h2, s3) + | |
153 | mlt(h3, s2) + mlt(h4, s1); | |
154 | d1 = mlt(h0, r1) + mlt(h1, r0) + mlt(h2, s4) + | |
155 | mlt(h3, s3) + mlt(h4, s2); | |
156 | d2 = mlt(h0, r2) + mlt(h1, r1) + mlt(h2, r0) + | |
157 | mlt(h3, s4) + mlt(h4, s3); | |
158 | d3 = mlt(h0, r3) + mlt(h1, r2) + mlt(h2, r1) + | |
159 | mlt(h3, r0) + mlt(h4, s4); | |
160 | d4 = mlt(h0, r4) + mlt(h1, r3) + mlt(h2, r2) + | |
161 | mlt(h3, r1) + mlt(h4, r0); | |
162 | ||
163 | /* (partial) h %= p */ | |
164 | d1 += sr(d0, 26); h0 = and(d0, 0x3ffffff); | |
165 | d2 += sr(d1, 26); h1 = and(d1, 0x3ffffff); | |
166 | d3 += sr(d2, 26); h2 = and(d2, 0x3ffffff); | |
167 | d4 += sr(d3, 26); h3 = and(d3, 0x3ffffff); | |
168 | h0 += sr(d4, 26) * 5; h4 = and(d4, 0x3ffffff); | |
169 | h1 += h0 >> 26; h0 = h0 & 0x3ffffff; | |
170 | ||
171 | src += POLY1305_BLOCK_SIZE; | |
172 | srclen -= POLY1305_BLOCK_SIZE; | |
173 | } | |
174 | ||
175 | dctx->h[0] = h0; | |
176 | dctx->h[1] = h1; | |
177 | dctx->h[2] = h2; | |
178 | dctx->h[3] = h3; | |
179 | dctx->h[4] = h4; | |
180 | ||
181 | return srclen; | |
182 | } | |
183 | ||
184 | static int poly1305_update(struct shash_desc *desc, | |
185 | const u8 *src, unsigned int srclen) | |
186 | { | |
187 | struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc); | |
f979e014 MW |
188 | unsigned int bytes; |
189 | ||
190 | if (unlikely(dctx->buflen)) { | |
191 | bytes = min(srclen, POLY1305_BLOCK_SIZE - dctx->buflen); | |
192 | memcpy(dctx->buf + dctx->buflen, src, bytes); | |
193 | src += bytes; | |
194 | srclen -= bytes; | |
195 | dctx->buflen += bytes; | |
196 | ||
197 | if (dctx->buflen == POLY1305_BLOCK_SIZE) { | |
c2b7b20a | 198 | poly1305_blocks(dctx, dctx->buf, |
f979e014 MW |
199 | POLY1305_BLOCK_SIZE, 1 << 24); |
200 | dctx->buflen = 0; | |
201 | } | |
202 | } | |
203 | ||
204 | if (likely(srclen >= POLY1305_BLOCK_SIZE)) { | |
c2b7b20a | 205 | bytes = poly1305_blocks(dctx, src, srclen, 1 << 24); |
f979e014 MW |
206 | src += srclen - bytes; |
207 | srclen = bytes; | |
208 | } | |
209 | ||
210 | if (unlikely(srclen)) { | |
211 | dctx->buflen = srclen; | |
212 | memcpy(dctx->buf, src, srclen); | |
213 | } | |
214 | ||
215 | return 0; | |
216 | } | |
217 | ||
218 | static int poly1305_final(struct shash_desc *desc, u8 *dst) | |
219 | { | |
220 | struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc); | |
f979e014 MW |
221 | __le32 *mac = (__le32 *)dst; |
222 | u32 h0, h1, h2, h3, h4; | |
223 | u32 g0, g1, g2, g3, g4; | |
224 | u32 mask; | |
225 | u64 f = 0; | |
226 | ||
c2b7b20a MW |
227 | if (unlikely(!dctx->sset)) |
228 | return -ENOKEY; | |
229 | ||
f979e014 MW |
230 | if (unlikely(dctx->buflen)) { |
231 | dctx->buf[dctx->buflen++] = 1; | |
232 | memset(dctx->buf + dctx->buflen, 0, | |
233 | POLY1305_BLOCK_SIZE - dctx->buflen); | |
c2b7b20a | 234 | poly1305_blocks(dctx, dctx->buf, POLY1305_BLOCK_SIZE, 0); |
f979e014 MW |
235 | } |
236 | ||
237 | /* fully carry h */ | |
238 | h0 = dctx->h[0]; | |
239 | h1 = dctx->h[1]; | |
240 | h2 = dctx->h[2]; | |
241 | h3 = dctx->h[3]; | |
242 | h4 = dctx->h[4]; | |
243 | ||
244 | h2 += (h1 >> 26); h1 = h1 & 0x3ffffff; | |
245 | h3 += (h2 >> 26); h2 = h2 & 0x3ffffff; | |
246 | h4 += (h3 >> 26); h3 = h3 & 0x3ffffff; | |
247 | h0 += (h4 >> 26) * 5; h4 = h4 & 0x3ffffff; | |
248 | h1 += (h0 >> 26); h0 = h0 & 0x3ffffff; | |
249 | ||
250 | /* compute h + -p */ | |
251 | g0 = h0 + 5; | |
252 | g1 = h1 + (g0 >> 26); g0 &= 0x3ffffff; | |
253 | g2 = h2 + (g1 >> 26); g1 &= 0x3ffffff; | |
254 | g3 = h3 + (g2 >> 26); g2 &= 0x3ffffff; | |
255 | g4 = h4 + (g3 >> 26) - (1 << 26); g3 &= 0x3ffffff; | |
256 | ||
257 | /* select h if h < p, or h + -p if h >= p */ | |
258 | mask = (g4 >> ((sizeof(u32) * 8) - 1)) - 1; | |
259 | g0 &= mask; | |
260 | g1 &= mask; | |
261 | g2 &= mask; | |
262 | g3 &= mask; | |
263 | g4 &= mask; | |
264 | mask = ~mask; | |
265 | h0 = (h0 & mask) | g0; | |
266 | h1 = (h1 & mask) | g1; | |
267 | h2 = (h2 & mask) | g2; | |
268 | h3 = (h3 & mask) | g3; | |
269 | h4 = (h4 & mask) | g4; | |
270 | ||
271 | /* h = h % (2^128) */ | |
272 | h0 = (h0 >> 0) | (h1 << 26); | |
273 | h1 = (h1 >> 6) | (h2 << 20); | |
274 | h2 = (h2 >> 12) | (h3 << 14); | |
275 | h3 = (h3 >> 18) | (h4 << 8); | |
276 | ||
277 | /* mac = (h + s) % (2^128) */ | |
c2b7b20a MW |
278 | f = (f >> 32) + h0 + dctx->s[0]; mac[0] = cpu_to_le32(f); |
279 | f = (f >> 32) + h1 + dctx->s[1]; mac[1] = cpu_to_le32(f); | |
280 | f = (f >> 32) + h2 + dctx->s[2]; mac[2] = cpu_to_le32(f); | |
281 | f = (f >> 32) + h3 + dctx->s[3]; mac[3] = cpu_to_le32(f); | |
f979e014 MW |
282 | |
283 | return 0; | |
284 | } | |
285 | ||
286 | static struct shash_alg poly1305_alg = { | |
287 | .digestsize = POLY1305_DIGEST_SIZE, | |
288 | .init = poly1305_init, | |
289 | .update = poly1305_update, | |
290 | .final = poly1305_final, | |
291 | .setkey = poly1305_setkey, | |
292 | .descsize = sizeof(struct poly1305_desc_ctx), | |
293 | .base = { | |
294 | .cra_name = "poly1305", | |
295 | .cra_driver_name = "poly1305-generic", | |
296 | .cra_priority = 100, | |
297 | .cra_flags = CRYPTO_ALG_TYPE_SHASH, | |
298 | .cra_alignmask = sizeof(u32) - 1, | |
299 | .cra_blocksize = POLY1305_BLOCK_SIZE, | |
f979e014 MW |
300 | .cra_module = THIS_MODULE, |
301 | }, | |
302 | }; | |
303 | ||
304 | static int __init poly1305_mod_init(void) | |
305 | { | |
306 | return crypto_register_shash(&poly1305_alg); | |
307 | } | |
308 | ||
309 | static void __exit poly1305_mod_exit(void) | |
310 | { | |
311 | crypto_unregister_shash(&poly1305_alg); | |
312 | } | |
313 | ||
314 | module_init(poly1305_mod_init); | |
315 | module_exit(poly1305_mod_exit); | |
316 | ||
317 | MODULE_LICENSE("GPL"); | |
318 | MODULE_AUTHOR("Martin Willi <martin@strongswan.org>"); | |
319 | MODULE_DESCRIPTION("Poly1305 authenticator"); | |
320 | MODULE_ALIAS_CRYPTO("poly1305"); | |
321 | MODULE_ALIAS_CRYPTO("poly1305-generic"); |