]>
Commit | Line | Data |
---|---|---|
21dcbebc | 1 | /* |
a28d06f3 | 2 | * Copyright 2014-2021 The OpenSSL Project Authors. All Rights Reserved. |
5a3d21c0 | 3 | * |
48f4ad77 | 4 | * Licensed under the Apache License 2.0 (the "License"). You may not use |
21dcbebc RS |
5 | * this file except in compliance with the License. You can obtain a copy |
6 | * in the file LICENSE in the source distribution or at | |
7 | * https://www.openssl.org/source/license.html | |
5a3d21c0 EK |
8 | */ |
9 | ||
ae4186b0 DMSP |
10 | #ifndef OSSL_INTERNAL_CONSTANT_TIME_H |
11 | # define OSSL_INTERNAL_CONSTANT_TIME_H | |
3a111aad | 12 | # pragma once |
5a3d21c0 | 13 | |
2688e7a0 | 14 | # include <stdlib.h> |
e0fa6324 | 15 | # include <string.h> |
80e0ecbf | 16 | # include <openssl/e_os2.h> /* For 'ossl_inline' */ |
5a3d21c0 | 17 | |
1d97c843 | 18 | /*- |
294d1e36 | 19 | * The boolean methods return a bitmask of all ones (0xff...f) for true |
5a3d21c0 EK |
20 | * and 0 for false. This is useful for choosing a value based on the result |
21 | * of a conditional in constant time. For example, | |
9018f3ce RS |
22 | * if (a < b) { |
23 | * c = a; | |
24 | * } else { | |
25 | * c = b; | |
26 | * } | |
5a3d21c0 | 27 | * can be written as |
9018f3ce RS |
28 | * unsigned int lt = constant_time_lt(a, b); |
29 | * c = constant_time_select(lt, a, b); | |
5a3d21c0 EK |
30 | */ |
31 | ||
b12169ee | 32 | /* Returns the given value with the MSB copied to all the other bits. */ |
80e0ecbf | 33 | static ossl_inline unsigned int constant_time_msb(unsigned int a); |
e0fa6324 MC |
34 | /* Convenience method for uint32_t. */ |
35 | static ossl_inline uint32_t constant_time_msb_32(uint32_t a); | |
9018f3ce RS |
36 | /* Convenience method for uint64_t. */ |
37 | static ossl_inline uint64_t constant_time_msb_64(uint64_t a); | |
5a3d21c0 | 38 | |
9018f3ce | 39 | /* Returns 0xff..f if a < b and 0 otherwise. */ |
80e0ecbf DSH |
40 | static ossl_inline unsigned int constant_time_lt(unsigned int a, |
41 | unsigned int b); | |
5a3d21c0 | 42 | /* Convenience method for getting an 8-bit mask. */ |
80e0ecbf DSH |
43 | static ossl_inline unsigned char constant_time_lt_8(unsigned int a, |
44 | unsigned int b); | |
9018f3ce RS |
45 | /* Convenience method for uint64_t. */ |
46 | static ossl_inline uint64_t constant_time_lt_64(uint64_t a, uint64_t b); | |
5a3d21c0 | 47 | |
9018f3ce | 48 | /* Returns 0xff..f if a >= b and 0 otherwise. */ |
80e0ecbf DSH |
49 | static ossl_inline unsigned int constant_time_ge(unsigned int a, |
50 | unsigned int b); | |
5a3d21c0 | 51 | /* Convenience method for getting an 8-bit mask. */ |
80e0ecbf DSH |
52 | static ossl_inline unsigned char constant_time_ge_8(unsigned int a, |
53 | unsigned int b); | |
5a3d21c0 | 54 | |
9018f3ce | 55 | /* Returns 0xff..f if a == 0 and 0 otherwise. */ |
80e0ecbf | 56 | static ossl_inline unsigned int constant_time_is_zero(unsigned int a); |
5a3d21c0 | 57 | /* Convenience method for getting an 8-bit mask. */ |
80e0ecbf | 58 | static ossl_inline unsigned char constant_time_is_zero_8(unsigned int a); |
e0fa6324 MC |
59 | /* Convenience method for getting a 32-bit mask. */ |
60 | static ossl_inline uint32_t constant_time_is_zero_32(uint32_t a); | |
5a3d21c0 | 61 | |
9018f3ce | 62 | /* Returns 0xff..f if a == b and 0 otherwise. */ |
80e0ecbf DSH |
63 | static ossl_inline unsigned int constant_time_eq(unsigned int a, |
64 | unsigned int b); | |
5a3d21c0 | 65 | /* Convenience method for getting an 8-bit mask. */ |
80e0ecbf DSH |
66 | static ossl_inline unsigned char constant_time_eq_8(unsigned int a, |
67 | unsigned int b); | |
455b65df | 68 | /* Signed integers. */ |
80e0ecbf | 69 | static ossl_inline unsigned int constant_time_eq_int(int a, int b); |
455b65df | 70 | /* Convenience method for getting an 8-bit mask. */ |
80e0ecbf | 71 | static ossl_inline unsigned char constant_time_eq_int_8(int a, int b); |
455b65df | 72 | |
1d97c843 | 73 | /*- |
294d1e36 EK |
74 | * Returns (mask & a) | (~mask & b). |
75 | * | |
76 | * When |mask| is all 1s or all 0s (as returned by the methods above), | |
77 | * the select methods return either |a| (if |mask| is nonzero) or |b| | |
78 | * (if |mask| is zero). | |
79 | */ | |
80e0ecbf DSH |
80 | static ossl_inline unsigned int constant_time_select(unsigned int mask, |
81 | unsigned int a, | |
82 | unsigned int b); | |
294d1e36 | 83 | /* Convenience method for unsigned chars. */ |
80e0ecbf DSH |
84 | static ossl_inline unsigned char constant_time_select_8(unsigned char mask, |
85 | unsigned char a, | |
86 | unsigned char b); | |
e0fa6324 MC |
87 | |
88 | /* Convenience method for uint32_t. */ | |
89 | static ossl_inline uint32_t constant_time_select_32(uint32_t mask, uint32_t a, | |
90 | uint32_t b); | |
91 | ||
9018f3ce RS |
92 | /* Convenience method for uint64_t. */ |
93 | static ossl_inline uint64_t constant_time_select_64(uint64_t mask, uint64_t a, | |
94 | uint64_t b); | |
294d1e36 | 95 | /* Convenience method for signed integers. */ |
80e0ecbf DSH |
96 | static ossl_inline int constant_time_select_int(unsigned int mask, int a, |
97 | int b); | |
294d1e36 | 98 | |
9018f3ce | 99 | |
80e0ecbf | 100 | static ossl_inline unsigned int constant_time_msb(unsigned int a) |
0f113f3e MC |
101 | { |
102 | return 0 - (a >> (sizeof(a) * 8 - 1)); | |
103 | } | |
5a3d21c0 | 104 | |
e0fa6324 MC |
105 | |
106 | static ossl_inline uint32_t constant_time_msb_32(uint32_t a) | |
107 | { | |
108 | return 0 - (a >> 31); | |
109 | } | |
110 | ||
9018f3ce RS |
111 | static ossl_inline uint64_t constant_time_msb_64(uint64_t a) |
112 | { | |
113 | return 0 - (a >> 63); | |
114 | } | |
115 | ||
2688e7a0 MC |
116 | static ossl_inline size_t constant_time_msb_s(size_t a) |
117 | { | |
118 | return 0 - (a >> (sizeof(a) * 8 - 1)); | |
119 | } | |
120 | ||
80e0ecbf DSH |
121 | static ossl_inline unsigned int constant_time_lt(unsigned int a, |
122 | unsigned int b) | |
0f113f3e MC |
123 | { |
124 | return constant_time_msb(a ^ ((a ^ b) | ((a - b) ^ b))); | |
125 | } | |
5a3d21c0 | 126 | |
2688e7a0 MC |
127 | static ossl_inline size_t constant_time_lt_s(size_t a, size_t b) |
128 | { | |
129 | return constant_time_msb_s(a ^ ((a ^ b) | ((a - b) ^ b))); | |
130 | } | |
131 | ||
80e0ecbf DSH |
132 | static ossl_inline unsigned char constant_time_lt_8(unsigned int a, |
133 | unsigned int b) | |
0f113f3e | 134 | { |
26a7d938 | 135 | return (unsigned char)constant_time_lt(a, b); |
0f113f3e | 136 | } |
5a3d21c0 | 137 | |
9018f3ce RS |
138 | static ossl_inline uint64_t constant_time_lt_64(uint64_t a, uint64_t b) |
139 | { | |
140 | return constant_time_msb_64(a ^ ((a ^ b) | ((a - b) ^ b))); | |
141 | } | |
142 | ||
d7d1bdcb TM |
143 | #ifdef BN_ULONG |
144 | static ossl_inline BN_ULONG constant_time_msb_bn(BN_ULONG a) | |
145 | { | |
146 | return 0 - (a >> (sizeof(a) * 8 - 1)); | |
147 | } | |
148 | ||
149 | static ossl_inline BN_ULONG constant_time_lt_bn(BN_ULONG a, BN_ULONG b) | |
150 | { | |
151 | return constant_time_msb_bn(a ^ ((a ^ b) | ((a - b) ^ b))); | |
152 | } | |
153 | #endif | |
154 | ||
80e0ecbf DSH |
155 | static ossl_inline unsigned int constant_time_ge(unsigned int a, |
156 | unsigned int b) | |
0f113f3e MC |
157 | { |
158 | return ~constant_time_lt(a, b); | |
159 | } | |
5a3d21c0 | 160 | |
2688e7a0 MC |
161 | static ossl_inline size_t constant_time_ge_s(size_t a, size_t b) |
162 | { | |
163 | return ~constant_time_lt_s(a, b); | |
164 | } | |
165 | ||
80e0ecbf DSH |
166 | static ossl_inline unsigned char constant_time_ge_8(unsigned int a, |
167 | unsigned int b) | |
0f113f3e | 168 | { |
26a7d938 | 169 | return (unsigned char)constant_time_ge(a, b); |
0f113f3e | 170 | } |
5a3d21c0 | 171 | |
2688e7a0 MC |
172 | static ossl_inline unsigned char constant_time_ge_8_s(size_t a, size_t b) |
173 | { | |
26a7d938 | 174 | return (unsigned char)constant_time_ge_s(a, b); |
2688e7a0 MC |
175 | } |
176 | ||
80e0ecbf | 177 | static ossl_inline unsigned int constant_time_is_zero(unsigned int a) |
0f113f3e MC |
178 | { |
179 | return constant_time_msb(~a & (a - 1)); | |
180 | } | |
5a3d21c0 | 181 | |
2688e7a0 MC |
182 | static ossl_inline size_t constant_time_is_zero_s(size_t a) |
183 | { | |
184 | return constant_time_msb_s(~a & (a - 1)); | |
185 | } | |
186 | ||
80e0ecbf | 187 | static ossl_inline unsigned char constant_time_is_zero_8(unsigned int a) |
0f113f3e | 188 | { |
26a7d938 | 189 | return (unsigned char)constant_time_is_zero(a); |
0f113f3e | 190 | } |
5a3d21c0 | 191 | |
e0fa6324 MC |
192 | static ossl_inline uint32_t constant_time_is_zero_32(uint32_t a) |
193 | { | |
194 | return constant_time_msb_32(~a & (a - 1)); | |
195 | } | |
196 | ||
ceaa6b31 AI |
197 | static ossl_inline uint64_t constant_time_is_zero_64(uint64_t a) |
198 | { | |
199 | return constant_time_msb_64(~a & (a - 1)); | |
200 | } | |
201 | ||
80e0ecbf DSH |
202 | static ossl_inline unsigned int constant_time_eq(unsigned int a, |
203 | unsigned int b) | |
0f113f3e MC |
204 | { |
205 | return constant_time_is_zero(a ^ b); | |
206 | } | |
5a3d21c0 | 207 | |
2688e7a0 MC |
208 | static ossl_inline size_t constant_time_eq_s(size_t a, size_t b) |
209 | { | |
210 | return constant_time_is_zero_s(a ^ b); | |
211 | } | |
212 | ||
80e0ecbf DSH |
213 | static ossl_inline unsigned char constant_time_eq_8(unsigned int a, |
214 | unsigned int b) | |
0f113f3e | 215 | { |
26a7d938 | 216 | return (unsigned char)constant_time_eq(a, b); |
0f113f3e | 217 | } |
5a3d21c0 | 218 | |
2688e7a0 MC |
219 | static ossl_inline unsigned char constant_time_eq_8_s(size_t a, size_t b) |
220 | { | |
26a7d938 | 221 | return (unsigned char)constant_time_eq_s(a, b); |
2688e7a0 MC |
222 | } |
223 | ||
80e0ecbf | 224 | static ossl_inline unsigned int constant_time_eq_int(int a, int b) |
0f113f3e MC |
225 | { |
226 | return constant_time_eq((unsigned)(a), (unsigned)(b)); | |
227 | } | |
455b65df | 228 | |
80e0ecbf | 229 | static ossl_inline unsigned char constant_time_eq_int_8(int a, int b) |
0f113f3e MC |
230 | { |
231 | return constant_time_eq_8((unsigned)(a), (unsigned)(b)); | |
232 | } | |
455b65df | 233 | |
04edd688 BE |
234 | /* |
235 | * Returns the value unmodified, but avoids optimizations. | |
236 | * The barriers prevent the compiler from narrowing down the | |
237 | * possible value range of the mask and ~mask in the select | |
238 | * statements, which avoids the recognition of the select | |
239 | * and turning it into a conditional load or branch. | |
240 | */ | |
241 | static ossl_inline unsigned int value_barrier(unsigned int a) | |
242 | { | |
243 | #if !defined(OPENSSL_NO_ASM) && defined(__GNUC__) | |
244 | unsigned int r; | |
245 | __asm__("" : "=r"(r) : "0"(a)); | |
246 | #else | |
247 | volatile unsigned int r = a; | |
248 | #endif | |
249 | return r; | |
250 | } | |
251 | ||
252 | /* Convenience method for uint32_t. */ | |
253 | static ossl_inline uint32_t value_barrier_32(uint32_t a) | |
254 | { | |
255 | #if !defined(OPENSSL_NO_ASM) && defined(__GNUC__) | |
256 | uint32_t r; | |
257 | __asm__("" : "=r"(r) : "0"(a)); | |
258 | #else | |
259 | volatile uint32_t r = a; | |
260 | #endif | |
261 | return r; | |
262 | } | |
263 | ||
264 | /* Convenience method for uint64_t. */ | |
265 | static ossl_inline uint64_t value_barrier_64(uint64_t a) | |
266 | { | |
267 | #if !defined(OPENSSL_NO_ASM) && defined(__GNUC__) | |
268 | uint64_t r; | |
269 | __asm__("" : "=r"(r) : "0"(a)); | |
270 | #else | |
271 | volatile uint64_t r = a; | |
272 | #endif | |
273 | return r; | |
274 | } | |
275 | ||
276 | /* Convenience method for size_t. */ | |
277 | static ossl_inline size_t value_barrier_s(size_t a) | |
278 | { | |
279 | #if !defined(OPENSSL_NO_ASM) && defined(__GNUC__) | |
280 | size_t r; | |
281 | __asm__("" : "=r"(r) : "0"(a)); | |
282 | #else | |
283 | volatile size_t r = a; | |
284 | #endif | |
285 | return r; | |
286 | } | |
287 | ||
80e0ecbf DSH |
288 | static ossl_inline unsigned int constant_time_select(unsigned int mask, |
289 | unsigned int a, | |
290 | unsigned int b) | |
0f113f3e | 291 | { |
04edd688 | 292 | return (value_barrier(mask) & a) | (value_barrier(~mask) & b); |
0f113f3e | 293 | } |
294d1e36 | 294 | |
2688e7a0 MC |
295 | static ossl_inline size_t constant_time_select_s(size_t mask, |
296 | size_t a, | |
297 | size_t b) | |
298 | { | |
04edd688 | 299 | return (value_barrier_s(mask) & a) | (value_barrier_s(~mask) & b); |
2688e7a0 MC |
300 | } |
301 | ||
80e0ecbf DSH |
302 | static ossl_inline unsigned char constant_time_select_8(unsigned char mask, |
303 | unsigned char a, | |
304 | unsigned char b) | |
0f113f3e | 305 | { |
26a7d938 | 306 | return (unsigned char)constant_time_select(mask, a, b); |
0f113f3e | 307 | } |
294d1e36 | 308 | |
80e0ecbf DSH |
309 | static ossl_inline int constant_time_select_int(unsigned int mask, int a, |
310 | int b) | |
0f113f3e | 311 | { |
26a7d938 | 312 | return (int)constant_time_select(mask, (unsigned)(a), (unsigned)(b)); |
0f113f3e | 313 | } |
294d1e36 | 314 | |
2688e7a0 MC |
315 | static ossl_inline int constant_time_select_int_s(size_t mask, int a, int b) |
316 | { | |
26a7d938 K |
317 | return (int)constant_time_select((unsigned)mask, (unsigned)(a), |
318 | (unsigned)(b)); | |
2688e7a0 MC |
319 | } |
320 | ||
e0fa6324 MC |
321 | static ossl_inline uint32_t constant_time_select_32(uint32_t mask, uint32_t a, |
322 | uint32_t b) | |
323 | { | |
04edd688 | 324 | return (value_barrier_32(mask) & a) | (value_barrier_32(~mask) & b); |
e0fa6324 MC |
325 | } |
326 | ||
9018f3ce RS |
327 | static ossl_inline uint64_t constant_time_select_64(uint64_t mask, uint64_t a, |
328 | uint64_t b) | |
329 | { | |
04edd688 | 330 | return (value_barrier_64(mask) & a) | (value_barrier_64(~mask) & b); |
9018f3ce RS |
331 | } |
332 | ||
e0fa6324 MC |
333 | /* |
334 | * mask must be 0xFFFFFFFF or 0x00000000. | |
335 | * | |
336 | * if (mask) { | |
337 | * uint32_t tmp = *a; | |
338 | * | |
339 | * *a = *b; | |
340 | * *b = tmp; | |
341 | * } | |
342 | */ | |
343 | static ossl_inline void constant_time_cond_swap_32(uint32_t mask, uint32_t *a, | |
344 | uint32_t *b) | |
345 | { | |
346 | uint32_t xor = *a ^ *b; | |
347 | ||
348 | xor &= mask; | |
349 | *a ^= xor; | |
350 | *b ^= xor; | |
351 | } | |
352 | ||
353 | /* | |
354 | * mask must be 0xFFFFFFFF or 0x00000000. | |
355 | * | |
356 | * if (mask) { | |
357 | * uint64_t tmp = *a; | |
358 | * | |
359 | * *a = *b; | |
360 | * *b = tmp; | |
361 | * } | |
362 | */ | |
363 | static ossl_inline void constant_time_cond_swap_64(uint64_t mask, uint64_t *a, | |
364 | uint64_t *b) | |
365 | { | |
366 | uint64_t xor = *a ^ *b; | |
367 | ||
368 | xor &= mask; | |
369 | *a ^= xor; | |
370 | *b ^= xor; | |
371 | } | |
372 | ||
677c4a01 PS |
373 | /* |
374 | * mask must be 0xFF or 0x00. | |
375 | * "constant time" is per len. | |
376 | * | |
377 | * if (mask) { | |
378 | * unsigned char tmp[len]; | |
379 | * | |
380 | * memcpy(tmp, a, len); | |
381 | * memcpy(a, b); | |
382 | * memcpy(b, tmp); | |
383 | * } | |
384 | */ | |
385 | static ossl_inline void constant_time_cond_swap_buff(unsigned char mask, | |
386 | unsigned char *a, | |
387 | unsigned char *b, | |
388 | size_t len) | |
389 | { | |
390 | size_t i; | |
391 | unsigned char tmp; | |
392 | ||
393 | for (i = 0; i < len; i++) { | |
394 | tmp = a[i] ^ b[i]; | |
395 | tmp &= mask; | |
396 | a[i] ^= tmp; | |
397 | b[i] ^= tmp; | |
398 | } | |
399 | } | |
400 | ||
e0fa6324 MC |
401 | /* |
402 | * table is a two dimensional array of bytes. Each row has rowsize elements. | |
403 | * Copies row number idx into out. rowsize and numrows are not considered | |
404 | * private. | |
405 | */ | |
406 | static ossl_inline void constant_time_lookup(void *out, | |
407 | const void *table, | |
408 | size_t rowsize, | |
409 | size_t numrows, | |
410 | size_t idx) | |
411 | { | |
412 | size_t i, j; | |
413 | const unsigned char *tablec = (const unsigned char *)table; | |
414 | unsigned char *outc = (unsigned char *)out; | |
415 | unsigned char mask; | |
416 | ||
417 | memset(out, 0, rowsize); | |
418 | ||
419 | /* Note idx may underflow - but that is well defined */ | |
420 | for (i = 0; i < numrows; i++, idx--) { | |
421 | mask = (unsigned char)constant_time_is_zero_s(idx); | |
422 | for (j = 0; j < rowsize; j++) | |
423 | *(outc + j) |= constant_time_select_8(mask, *(tablec++), 0); | |
424 | } | |
425 | } | |
426 | ||
f658a3b6 AP |
427 | /* |
428 | * Expected usage pattern is to unconditionally set error and then | |
429 | * wipe it if there was no actual error. |clear| is 1 or 0. | |
430 | */ | |
431 | void err_clear_last_constant_time(int clear); | |
432 | ||
ae4186b0 | 433 | #endif /* OSSL_INTERNAL_CONSTANT_TIME_H */ |