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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 | ||
24 | struct poly1305_ctx { | |
25 | /* key */ | |
26 | u32 r[5]; | |
27 | /* finalize key */ | |
28 | u32 s[4]; | |
29 | }; | |
30 | ||
31 | struct poly1305_desc_ctx { | |
32 | /* accumulator */ | |
33 | u32 h[5]; | |
34 | /* partial buffer */ | |
35 | u8 buf[POLY1305_BLOCK_SIZE]; | |
36 | /* bytes used in partial buffer */ | |
37 | unsigned int buflen; | |
38 | }; | |
39 | ||
40 | static inline u64 mlt(u64 a, u64 b) | |
41 | { | |
42 | return a * b; | |
43 | } | |
44 | ||
45 | static inline u32 sr(u64 v, u_char n) | |
46 | { | |
47 | return v >> n; | |
48 | } | |
49 | ||
50 | static inline u32 and(u32 v, u32 mask) | |
51 | { | |
52 | return v & mask; | |
53 | } | |
54 | ||
55 | static inline u32 le32_to_cpuvp(const void *p) | |
56 | { | |
57 | return le32_to_cpup(p); | |
58 | } | |
59 | ||
60 | static int poly1305_init(struct shash_desc *desc) | |
61 | { | |
62 | struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc); | |
63 | ||
64 | memset(dctx->h, 0, sizeof(dctx->h)); | |
65 | dctx->buflen = 0; | |
66 | ||
67 | return 0; | |
68 | } | |
69 | ||
70 | static int poly1305_setkey(struct crypto_shash *tfm, | |
71 | const u8 *key, unsigned int keylen) | |
72 | { | |
73 | struct poly1305_ctx *ctx = crypto_shash_ctx(tfm); | |
74 | ||
75 | if (keylen != POLY1305_KEY_SIZE) { | |
76 | crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN); | |
77 | return -EINVAL; | |
78 | } | |
79 | ||
80 | /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */ | |
81 | ctx->r[0] = (le32_to_cpuvp(key + 0) >> 0) & 0x3ffffff; | |
82 | ctx->r[1] = (le32_to_cpuvp(key + 3) >> 2) & 0x3ffff03; | |
83 | ctx->r[2] = (le32_to_cpuvp(key + 6) >> 4) & 0x3ffc0ff; | |
84 | ctx->r[3] = (le32_to_cpuvp(key + 9) >> 6) & 0x3f03fff; | |
85 | ctx->r[4] = (le32_to_cpuvp(key + 12) >> 8) & 0x00fffff; | |
86 | ||
87 | ctx->s[0] = le32_to_cpuvp(key + 16); | |
88 | ctx->s[1] = le32_to_cpuvp(key + 20); | |
89 | ctx->s[2] = le32_to_cpuvp(key + 24); | |
90 | ctx->s[3] = le32_to_cpuvp(key + 28); | |
91 | ||
92 | return 0; | |
93 | } | |
94 | ||
95 | static unsigned int poly1305_blocks(struct poly1305_desc_ctx *dctx, | |
96 | struct poly1305_ctx *ctx, const u8 *src, | |
97 | unsigned int srclen, u32 hibit) | |
98 | { | |
99 | u32 r0, r1, r2, r3, r4; | |
100 | u32 s1, s2, s3, s4; | |
101 | u32 h0, h1, h2, h3, h4; | |
102 | u64 d0, d1, d2, d3, d4; | |
103 | ||
104 | r0 = ctx->r[0]; | |
105 | r1 = ctx->r[1]; | |
106 | r2 = ctx->r[2]; | |
107 | r3 = ctx->r[3]; | |
108 | r4 = ctx->r[4]; | |
109 | ||
110 | s1 = r1 * 5; | |
111 | s2 = r2 * 5; | |
112 | s3 = r3 * 5; | |
113 | s4 = r4 * 5; | |
114 | ||
115 | h0 = dctx->h[0]; | |
116 | h1 = dctx->h[1]; | |
117 | h2 = dctx->h[2]; | |
118 | h3 = dctx->h[3]; | |
119 | h4 = dctx->h[4]; | |
120 | ||
121 | while (likely(srclen >= POLY1305_BLOCK_SIZE)) { | |
122 | ||
123 | /* h += m[i] */ | |
124 | h0 += (le32_to_cpuvp(src + 0) >> 0) & 0x3ffffff; | |
125 | h1 += (le32_to_cpuvp(src + 3) >> 2) & 0x3ffffff; | |
126 | h2 += (le32_to_cpuvp(src + 6) >> 4) & 0x3ffffff; | |
127 | h3 += (le32_to_cpuvp(src + 9) >> 6) & 0x3ffffff; | |
128 | h4 += (le32_to_cpuvp(src + 12) >> 8) | hibit; | |
129 | ||
130 | /* h *= r */ | |
131 | d0 = mlt(h0, r0) + mlt(h1, s4) + mlt(h2, s3) + | |
132 | mlt(h3, s2) + mlt(h4, s1); | |
133 | d1 = mlt(h0, r1) + mlt(h1, r0) + mlt(h2, s4) + | |
134 | mlt(h3, s3) + mlt(h4, s2); | |
135 | d2 = mlt(h0, r2) + mlt(h1, r1) + mlt(h2, r0) + | |
136 | mlt(h3, s4) + mlt(h4, s3); | |
137 | d3 = mlt(h0, r3) + mlt(h1, r2) + mlt(h2, r1) + | |
138 | mlt(h3, r0) + mlt(h4, s4); | |
139 | d4 = mlt(h0, r4) + mlt(h1, r3) + mlt(h2, r2) + | |
140 | mlt(h3, r1) + mlt(h4, r0); | |
141 | ||
142 | /* (partial) h %= p */ | |
143 | d1 += sr(d0, 26); h0 = and(d0, 0x3ffffff); | |
144 | d2 += sr(d1, 26); h1 = and(d1, 0x3ffffff); | |
145 | d3 += sr(d2, 26); h2 = and(d2, 0x3ffffff); | |
146 | d4 += sr(d3, 26); h3 = and(d3, 0x3ffffff); | |
147 | h0 += sr(d4, 26) * 5; h4 = and(d4, 0x3ffffff); | |
148 | h1 += h0 >> 26; h0 = h0 & 0x3ffffff; | |
149 | ||
150 | src += POLY1305_BLOCK_SIZE; | |
151 | srclen -= POLY1305_BLOCK_SIZE; | |
152 | } | |
153 | ||
154 | dctx->h[0] = h0; | |
155 | dctx->h[1] = h1; | |
156 | dctx->h[2] = h2; | |
157 | dctx->h[3] = h3; | |
158 | dctx->h[4] = h4; | |
159 | ||
160 | return srclen; | |
161 | } | |
162 | ||
163 | static int poly1305_update(struct shash_desc *desc, | |
164 | const u8 *src, unsigned int srclen) | |
165 | { | |
166 | struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc); | |
167 | struct poly1305_ctx *ctx = crypto_shash_ctx(desc->tfm); | |
168 | unsigned int bytes; | |
169 | ||
170 | if (unlikely(dctx->buflen)) { | |
171 | bytes = min(srclen, POLY1305_BLOCK_SIZE - dctx->buflen); | |
172 | memcpy(dctx->buf + dctx->buflen, src, bytes); | |
173 | src += bytes; | |
174 | srclen -= bytes; | |
175 | dctx->buflen += bytes; | |
176 | ||
177 | if (dctx->buflen == POLY1305_BLOCK_SIZE) { | |
178 | poly1305_blocks(dctx, ctx, dctx->buf, | |
179 | POLY1305_BLOCK_SIZE, 1 << 24); | |
180 | dctx->buflen = 0; | |
181 | } | |
182 | } | |
183 | ||
184 | if (likely(srclen >= POLY1305_BLOCK_SIZE)) { | |
185 | bytes = poly1305_blocks(dctx, ctx, src, srclen, 1 << 24); | |
186 | src += srclen - bytes; | |
187 | srclen = bytes; | |
188 | } | |
189 | ||
190 | if (unlikely(srclen)) { | |
191 | dctx->buflen = srclen; | |
192 | memcpy(dctx->buf, src, srclen); | |
193 | } | |
194 | ||
195 | return 0; | |
196 | } | |
197 | ||
198 | static int poly1305_final(struct shash_desc *desc, u8 *dst) | |
199 | { | |
200 | struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc); | |
201 | struct poly1305_ctx *ctx = crypto_shash_ctx(desc->tfm); | |
202 | __le32 *mac = (__le32 *)dst; | |
203 | u32 h0, h1, h2, h3, h4; | |
204 | u32 g0, g1, g2, g3, g4; | |
205 | u32 mask; | |
206 | u64 f = 0; | |
207 | ||
208 | if (unlikely(dctx->buflen)) { | |
209 | dctx->buf[dctx->buflen++] = 1; | |
210 | memset(dctx->buf + dctx->buflen, 0, | |
211 | POLY1305_BLOCK_SIZE - dctx->buflen); | |
212 | poly1305_blocks(dctx, ctx, dctx->buf, POLY1305_BLOCK_SIZE, 0); | |
213 | } | |
214 | ||
215 | /* fully carry h */ | |
216 | h0 = dctx->h[0]; | |
217 | h1 = dctx->h[1]; | |
218 | h2 = dctx->h[2]; | |
219 | h3 = dctx->h[3]; | |
220 | h4 = dctx->h[4]; | |
221 | ||
222 | h2 += (h1 >> 26); h1 = h1 & 0x3ffffff; | |
223 | h3 += (h2 >> 26); h2 = h2 & 0x3ffffff; | |
224 | h4 += (h3 >> 26); h3 = h3 & 0x3ffffff; | |
225 | h0 += (h4 >> 26) * 5; h4 = h4 & 0x3ffffff; | |
226 | h1 += (h0 >> 26); h0 = h0 & 0x3ffffff; | |
227 | ||
228 | /* compute h + -p */ | |
229 | g0 = h0 + 5; | |
230 | g1 = h1 + (g0 >> 26); g0 &= 0x3ffffff; | |
231 | g2 = h2 + (g1 >> 26); g1 &= 0x3ffffff; | |
232 | g3 = h3 + (g2 >> 26); g2 &= 0x3ffffff; | |
233 | g4 = h4 + (g3 >> 26) - (1 << 26); g3 &= 0x3ffffff; | |
234 | ||
235 | /* select h if h < p, or h + -p if h >= p */ | |
236 | mask = (g4 >> ((sizeof(u32) * 8) - 1)) - 1; | |
237 | g0 &= mask; | |
238 | g1 &= mask; | |
239 | g2 &= mask; | |
240 | g3 &= mask; | |
241 | g4 &= mask; | |
242 | mask = ~mask; | |
243 | h0 = (h0 & mask) | g0; | |
244 | h1 = (h1 & mask) | g1; | |
245 | h2 = (h2 & mask) | g2; | |
246 | h3 = (h3 & mask) | g3; | |
247 | h4 = (h4 & mask) | g4; | |
248 | ||
249 | /* h = h % (2^128) */ | |
250 | h0 = (h0 >> 0) | (h1 << 26); | |
251 | h1 = (h1 >> 6) | (h2 << 20); | |
252 | h2 = (h2 >> 12) | (h3 << 14); | |
253 | h3 = (h3 >> 18) | (h4 << 8); | |
254 | ||
255 | /* mac = (h + s) % (2^128) */ | |
256 | f = (f >> 32) + h0 + ctx->s[0]; mac[0] = cpu_to_le32(f); | |
257 | f = (f >> 32) + h1 + ctx->s[1]; mac[1] = cpu_to_le32(f); | |
258 | f = (f >> 32) + h2 + ctx->s[2]; mac[2] = cpu_to_le32(f); | |
259 | f = (f >> 32) + h3 + ctx->s[3]; mac[3] = cpu_to_le32(f); | |
260 | ||
261 | return 0; | |
262 | } | |
263 | ||
264 | static struct shash_alg poly1305_alg = { | |
265 | .digestsize = POLY1305_DIGEST_SIZE, | |
266 | .init = poly1305_init, | |
267 | .update = poly1305_update, | |
268 | .final = poly1305_final, | |
269 | .setkey = poly1305_setkey, | |
270 | .descsize = sizeof(struct poly1305_desc_ctx), | |
271 | .base = { | |
272 | .cra_name = "poly1305", | |
273 | .cra_driver_name = "poly1305-generic", | |
274 | .cra_priority = 100, | |
275 | .cra_flags = CRYPTO_ALG_TYPE_SHASH, | |
276 | .cra_alignmask = sizeof(u32) - 1, | |
277 | .cra_blocksize = POLY1305_BLOCK_SIZE, | |
278 | .cra_ctxsize = sizeof(struct poly1305_ctx), | |
279 | .cra_module = THIS_MODULE, | |
280 | }, | |
281 | }; | |
282 | ||
283 | static int __init poly1305_mod_init(void) | |
284 | { | |
285 | return crypto_register_shash(&poly1305_alg); | |
286 | } | |
287 | ||
288 | static void __exit poly1305_mod_exit(void) | |
289 | { | |
290 | crypto_unregister_shash(&poly1305_alg); | |
291 | } | |
292 | ||
293 | module_init(poly1305_mod_init); | |
294 | module_exit(poly1305_mod_exit); | |
295 | ||
296 | MODULE_LICENSE("GPL"); | |
297 | MODULE_AUTHOR("Martin Willi <martin@strongswan.org>"); | |
298 | MODULE_DESCRIPTION("Poly1305 authenticator"); | |
299 | MODULE_ALIAS_CRYPTO("poly1305"); | |
300 | MODULE_ALIAS_CRYPTO("poly1305-generic"); |