1 /*
2 * Copyright (c) 2017 Thomas Pornin <pornin@bolet.org>
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining
5 * a copy of this software and associated documentation files (the
6 * "Software"), to deal in the Software without restriction, including
7 * without limitation the rights to use, copy, modify, merge, publish,
8 * distribute, sublicense, and/or sell copies of the Software, and to
9 * permit persons to whom the Software is furnished to do so, subject to
10 * the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
19 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
20 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
22 * SOFTWARE.
23 */
24
25 #include "inner.h"
26
27 #if BR_INT128 || BR_UMUL128
28
29 #if BR_INT128
30
31 #define MUL128(hi, lo, x, y) do { \
32 unsigned __int128 mul128tmp; \
33 mul128tmp = (unsigned __int128)(x) * (unsigned __int128)(y); \
34 (hi) = (uint64_t)(mul128tmp >> 64); \
35 (lo) = (uint64_t)mul128tmp; \
36 } while (0)
37
38 #elif BR_UMUL128
39
40 #include <intrin.h>
41
42 #define MUL128(hi, lo, x, y) do { \
43 (lo) = _umul128((x), (y), &(hi)); \
44 } while (0)
45
46 #endif
47
48 #define MASK42 ((uint64_t)0x000003FFFFFFFFFF)
49 #define MASK44 ((uint64_t)0x00000FFFFFFFFFFF)
50
51 /*
52 * The "accumulator" word is nominally a 130-bit value. We split it into
53 * words of 44 bits, each held in a 64-bit variable.
54 *
55 * If the current accumulator is a = a0 + a1*W + a2*W^2 (where W = 2^44)
56 * and r = r0 + r1*W + r2*W^2, then:
57 *
58 * a*r = (a0*r0)
59 * + (a0*r1 + a1*r0) * W
60 * + (a0*r2 + a1*r1 + a2*r0) * W^2
61 * + (a1*r2 + a2*r1) * W^3
62 * + (a2*r2) * W^4
63 *
64 * We want to reduce that value modulo p = 2^130-5, so W^3 = 20 mod p,
65 * and W^4 = 20*W mod p. Thus, if we define u1 = 20*r1 and u2 = 20*r2,
66 * then the equations above become:
67 *
68 * b0 = a0*r0 + a1*u2 + a2*u1
69 * b1 = a0*r1 + a1*r0 + a2*u2
70 * b2 = a0*r2 + a1*r1 + a2*r0
71 *
72 * In order to make u1 fit in 44 bits, we can change these equations
73 * into:
74 *
75 * b0 = a0*r0 + a1*u2 + a2*t1
76 * b1 = a0*r1 + a1*r0 + a2*t2
77 * b2 = a0*r2 + a1*r1 + a2*r0
78 *
79 * Where t1 is u1 truncated to 44 bits, and t2 is u2 added to the extra
80 * bits of u1. Note that since r is clamped down to a 124-bit value, the
81 * values u2 and t2 fit on 44 bits too.
82 *
83 * The bx values are larger than 44 bits, so we may split them into a
84 * lower half (cx, 44 bits) and an upper half (dx). The new values for
85 * the accumulator are then:
86 *
87 * e0 = c0 + 20*d2
88 * e1 = c1 + d0
89 * e2 = c2 + d1
90 *
91 * The equations allow for some room, i.e. the ax values may be larger
92 * than 44 bits. Similarly, the ex values will usually be larger than
93 * the ax. Thus, some sort of carry propagation must be done regularly,
94 * though not necessarily at each iteration. In particular, we do not
95 * need to compute the additions (for the bx values) over 128-bit
96 * quantities; we can stick to 64-bit computations.
97 *
98 *
99 * Since the 128-bit result of a 64x64 multiplication is actually
100 * represented over two 64-bit registers, it is cheaper to arrange for
101 * any split that happens between the "high" and "low" halves to be on
102 * that 64-bit boundary. This is done by left shifting the rx, ux and tx
103 * by 20 bits (since they all fit on 44 bits each, this shift is
104 * always possible).
105 */
106
107 static void
poly1305_inner_big(uint64_t * acc,uint64_t * r,const void * data,size_t len)108 poly1305_inner_big(uint64_t *acc, uint64_t *r, const void *data, size_t len)
109 {
110
111 #define MX(hi, lo, m0, m1, m2) do { \
112 uint64_t mxhi, mxlo; \
113 MUL128(mxhi, mxlo, a0, m0); \
114 (hi) = mxhi; \
115 (lo) = mxlo >> 20; \
116 MUL128(mxhi, mxlo, a1, m1); \
117 (hi) += mxhi; \
118 (lo) += mxlo >> 20; \
119 MUL128(mxhi, mxlo, a2, m2); \
120 (hi) += mxhi; \
121 (lo) += mxlo >> 20; \
122 } while (0)
123
124 const unsigned char *buf;
125 uint64_t a0, a1, a2;
126 uint64_t r0, r1, r2, t1, t2, u2;
127
128 r0 = r[0];
129 r1 = r[1];
130 r2 = r[2];
131 t1 = r[3];
132 t2 = r[4];
133 u2 = r[5];
134 a0 = acc[0];
135 a1 = acc[1];
136 a2 = acc[2];
137 buf = data;
138
139 while (len > 0) {
140 uint64_t v0, v1, v2;
141 uint64_t c0, c1, c2, d0, d1, d2;
142
143 v0 = br_dec64le(buf + 0);
144 v1 = br_dec64le(buf + 8);
145 v2 = v1 >> 24;
146 v1 = ((v0 >> 44) | (v1 << 20)) & MASK44;
147 v0 &= MASK44;
148 a0 += v0;
149 a1 += v1;
150 a2 += v2 + ((uint64_t)1 << 40);
151 MX(d0, c0, r0, u2, t1);
152 MX(d1, c1, r1, r0, t2);
153 MX(d2, c2, r2, r1, r0);
154 a0 = c0 + 20 * d2;
155 a1 = c1 + d0;
156 a2 = c2 + d1;
157
158 v0 = br_dec64le(buf + 16);
159 v1 = br_dec64le(buf + 24);
160 v2 = v1 >> 24;
161 v1 = ((v0 >> 44) | (v1 << 20)) & MASK44;
162 v0 &= MASK44;
163 a0 += v0;
164 a1 += v1;
165 a2 += v2 + ((uint64_t)1 << 40);
166 MX(d0, c0, r0, u2, t1);
167 MX(d1, c1, r1, r0, t2);
168 MX(d2, c2, r2, r1, r0);
169 a0 = c0 + 20 * d2;
170 a1 = c1 + d0;
171 a2 = c2 + d1;
172
173 v0 = br_dec64le(buf + 32);
174 v1 = br_dec64le(buf + 40);
175 v2 = v1 >> 24;
176 v1 = ((v0 >> 44) | (v1 << 20)) & MASK44;
177 v0 &= MASK44;
178 a0 += v0;
179 a1 += v1;
180 a2 += v2 + ((uint64_t)1 << 40);
181 MX(d0, c0, r0, u2, t1);
182 MX(d1, c1, r1, r0, t2);
183 MX(d2, c2, r2, r1, r0);
184 a0 = c0 + 20 * d2;
185 a1 = c1 + d0;
186 a2 = c2 + d1;
187
188 v0 = br_dec64le(buf + 48);
189 v1 = br_dec64le(buf + 56);
190 v2 = v1 >> 24;
191 v1 = ((v0 >> 44) | (v1 << 20)) & MASK44;
192 v0 &= MASK44;
193 a0 += v0;
194 a1 += v1;
195 a2 += v2 + ((uint64_t)1 << 40);
196 MX(d0, c0, r0, u2, t1);
197 MX(d1, c1, r1, r0, t2);
198 MX(d2, c2, r2, r1, r0);
199 a0 = c0 + 20 * d2;
200 a1 = c1 + d0;
201 a2 = c2 + d1;
202
203 a1 += a0 >> 44;
204 a0 &= MASK44;
205 a2 += a1 >> 44;
206 a1 &= MASK44;
207 a0 += 20 * (a2 >> 44);
208 a2 &= MASK44;
209
210 buf += 64;
211 len -= 64;
212 }
213 acc[0] = a0;
214 acc[1] = a1;
215 acc[2] = a2;
216
217 #undef MX
218 }
219
220 static void
poly1305_inner_small(uint64_t * acc,uint64_t * r,const void * data,size_t len)221 poly1305_inner_small(uint64_t *acc, uint64_t *r, const void *data, size_t len)
222 {
223 const unsigned char *buf;
224 uint64_t a0, a1, a2;
225 uint64_t r0, r1, r2, t1, t2, u2;
226
227 r0 = r[0];
228 r1 = r[1];
229 r2 = r[2];
230 t1 = r[3];
231 t2 = r[4];
232 u2 = r[5];
233 a0 = acc[0];
234 a1 = acc[1];
235 a2 = acc[2];
236 buf = data;
237
238 while (len > 0) {
239 uint64_t v0, v1, v2;
240 uint64_t c0, c1, c2, d0, d1, d2;
241 unsigned char tmp[16];
242
243 if (len < 16) {
244 memcpy(tmp, buf, len);
245 memset(tmp + len, 0, (sizeof tmp) - len);
246 buf = tmp;
247 len = 16;
248 }
249 v0 = br_dec64le(buf + 0);
250 v1 = br_dec64le(buf + 8);
251
252 v2 = v1 >> 24;
253 v1 = ((v0 >> 44) | (v1 << 20)) & MASK44;
254 v0 &= MASK44;
255
256 a0 += v0;
257 a1 += v1;
258 a2 += v2 + ((uint64_t)1 << 40);
259
260 #define MX(hi, lo, m0, m1, m2) do { \
261 uint64_t mxhi, mxlo; \
262 MUL128(mxhi, mxlo, a0, m0); \
263 (hi) = mxhi; \
264 (lo) = mxlo >> 20; \
265 MUL128(mxhi, mxlo, a1, m1); \
266 (hi) += mxhi; \
267 (lo) += mxlo >> 20; \
268 MUL128(mxhi, mxlo, a2, m2); \
269 (hi) += mxhi; \
270 (lo) += mxlo >> 20; \
271 } while (0)
272
273 MX(d0, c0, r0, u2, t1);
274 MX(d1, c1, r1, r0, t2);
275 MX(d2, c2, r2, r1, r0);
276
277 #undef MX
278
279 a0 = c0 + 20 * d2;
280 a1 = c1 + d0;
281 a2 = c2 + d1;
282
283 a1 += a0 >> 44;
284 a0 &= MASK44;
285 a2 += a1 >> 44;
286 a1 &= MASK44;
287 a0 += 20 * (a2 >> 44);
288 a2 &= MASK44;
289
290 buf += 16;
291 len -= 16;
292 }
293 acc[0] = a0;
294 acc[1] = a1;
295 acc[2] = a2;
296 }
297
298 static inline void
poly1305_inner(uint64_t * acc,uint64_t * r,const void * data,size_t len)299 poly1305_inner(uint64_t *acc, uint64_t *r, const void *data, size_t len)
300 {
301 if (len >= 64) {
302 size_t len2;
303
304 len2 = len & ~(size_t)63;
305 poly1305_inner_big(acc, r, data, len2);
306 data = (const unsigned char *)data + len2;
307 len -= len2;
308 }
309 if (len > 0) {
310 poly1305_inner_small(acc, r, data, len);
311 }
312 }
313
314 /* see bearssl_block.h */
315 void
br_poly1305_ctmulq_run(const void * key,const void * iv,void * data,size_t len,const void * aad,size_t aad_len,void * tag,br_chacha20_run ichacha,int encrypt)316 br_poly1305_ctmulq_run(const void *key, const void *iv,
317 void *data, size_t len, const void *aad, size_t aad_len,
318 void *tag, br_chacha20_run ichacha, int encrypt)
319 {
320 unsigned char pkey[32], foot[16];
321 uint64_t r[6], acc[3], r0, r1;
322 uint32_t v0, v1, v2, v3, v4;
323 uint64_t w0, w1, w2, w3;
324 uint32_t ctl;
325
326 /*
327 * Compute the MAC key. The 'r' value is the first 16 bytes of
328 * pkey[].
329 */
330 memset(pkey, 0, sizeof pkey);
331 ichacha(key, iv, 0, pkey, sizeof pkey);
332
333 /*
334 * If encrypting, ChaCha20 must run first, followed by Poly1305.
335 * When decrypting, the operations are reversed.
336 */
337 if (encrypt) {
338 ichacha(key, iv, 1, data, len);
339 }
340
341 /*
342 * Run Poly1305. We must process the AAD, then ciphertext, then
343 * the footer (with the lengths). Note that the AAD and ciphertext
344 * are meant to be padded with zeros up to the next multiple of 16,
345 * and the length of the footer is 16 bytes as well.
346 */
347
348 /*
349 * Apply the "clamping" on r.
350 */
351 pkey[ 3] &= 0x0F;
352 pkey[ 4] &= 0xFC;
353 pkey[ 7] &= 0x0F;
354 pkey[ 8] &= 0xFC;
355 pkey[11] &= 0x0F;
356 pkey[12] &= 0xFC;
357 pkey[15] &= 0x0F;
358
359 /*
360 * Decode the 'r' value into 44-bit words, left-shifted by 20 bits.
361 * Also compute the u1 and u2 values.
362 */
363 r0 = br_dec64le(pkey + 0);
364 r1 = br_dec64le(pkey + 8);
365 r[0] = r0 << 20;
366 r[1] = ((r0 >> 24) | (r1 << 40)) & ~(uint64_t)0xFFFFF;
367 r[2] = (r1 >> 4) & ~(uint64_t)0xFFFFF;
368 r1 = 20 * (r[1] >> 20);
369 r[3] = r1 << 20;
370 r[5] = 20 * r[2];
371 r[4] = (r[5] + (r1 >> 24)) & ~(uint64_t)0xFFFFF;
372
373 /*
374 * Accumulator is 0.
375 */
376 acc[0] = 0;
377 acc[1] = 0;
378 acc[2] = 0;
379
380 /*
381 * Process the additional authenticated data, ciphertext, and
382 * footer in due order.
383 */
384 br_enc64le(foot, (uint64_t)aad_len);
385 br_enc64le(foot + 8, (uint64_t)len);
386 poly1305_inner(acc, r, aad, aad_len);
387 poly1305_inner(acc, r, data, len);
388 poly1305_inner_small(acc, r, foot, sizeof foot);
389
390 /*
391 * Finalise modular reduction. At that point, the value consists
392 * in three 44-bit values (the lowest one might be slightly above
393 * 2^44). Two loops shall be sufficient.
394 */
395 acc[1] += (acc[0] >> 44);
396 acc[0] &= MASK44;
397 acc[2] += (acc[1] >> 44);
398 acc[1] &= MASK44;
399 acc[0] += 5 * (acc[2] >> 42);
400 acc[2] &= MASK42;
401 acc[1] += (acc[0] >> 44);
402 acc[0] &= MASK44;
403 acc[2] += (acc[1] >> 44);
404 acc[1] &= MASK44;
405 acc[0] += 5 * (acc[2] >> 42);
406 acc[2] &= MASK42;
407
408 /*
409 * The value may still fall in the 2^130-5..2^130-1 range, in
410 * which case we must reduce it again. The code below selects,
411 * in constant-time, between 'acc' and 'acc-p'. We encode the
412 * value over four 32-bit integers to finish the operation.
413 */
414 v0 = (uint32_t)acc[0];
415 v1 = (uint32_t)(acc[0] >> 32) | ((uint32_t)acc[1] << 12);
416 v2 = (uint32_t)(acc[1] >> 20) | ((uint32_t)acc[2] << 24);
417 v3 = (uint32_t)(acc[2] >> 8);
418 v4 = (uint32_t)(acc[2] >> 40);
419
420 ctl = GT(v0, 0xFFFFFFFA);
421 ctl &= EQ(v1, 0xFFFFFFFF);
422 ctl &= EQ(v2, 0xFFFFFFFF);
423 ctl &= EQ(v3, 0xFFFFFFFF);
424 ctl &= EQ(v4, 0x00000003);
425 v0 = MUX(ctl, v0 + 5, v0);
426 v1 = MUX(ctl, 0, v1);
427 v2 = MUX(ctl, 0, v2);
428 v3 = MUX(ctl, 0, v3);
429
430 /*
431 * Add the "s" value. This is done modulo 2^128. Don't forget
432 * carry propagation...
433 */
434 w0 = (uint64_t)v0 + (uint64_t)br_dec32le(pkey + 16);
435 w1 = (uint64_t)v1 + (uint64_t)br_dec32le(pkey + 20) + (w0 >> 32);
436 w2 = (uint64_t)v2 + (uint64_t)br_dec32le(pkey + 24) + (w1 >> 32);
437 w3 = (uint64_t)v3 + (uint64_t)br_dec32le(pkey + 28) + (w2 >> 32);
438 v0 = (uint32_t)w0;
439 v1 = (uint32_t)w1;
440 v2 = (uint32_t)w2;
441 v3 = (uint32_t)w3;
442
443 /*
444 * Encode the tag.
445 */
446 br_enc32le((unsigned char *)tag + 0, v0);
447 br_enc32le((unsigned char *)tag + 4, v1);
448 br_enc32le((unsigned char *)tag + 8, v2);
449 br_enc32le((unsigned char *)tag + 12, v3);
450
451 /*
452 * If decrypting, then ChaCha20 runs _after_ Poly1305.
453 */
454 if (!encrypt) {
455 ichacha(key, iv, 1, data, len);
456 }
457 }
458
459 /* see bearssl_block.h */
460 br_poly1305_run
br_poly1305_ctmulq_get(void)461 br_poly1305_ctmulq_get(void)
462 {
463 return &br_poly1305_ctmulq_run;
464 }
465
466 #else
467
468 /* see bearssl_block.h */
469 br_poly1305_run
br_poly1305_ctmulq_get(void)470 br_poly1305_ctmulq_get(void)
471 {
472 return 0;
473 }
474
475 #endif
476