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source: vbox/trunk/src/libs/openssl-3.1.7/crypto/bn/bn_rand.c@ 105945

Last change on this file since 105945 was 105945, checked in by vboxsync, 6 months ago

openssl-3.1.7: Applied and adjusted our OpenSSL changes to 3.1.7. bugref:10757
File size: 11.9 KB
Line 
1/*
2 * Copyright 1995-2024 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the Apache License 2.0 (the "License"). You may not use
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
8 */
9
10#include <stdio.h>
11#include <time.h>
12#include "internal/cryptlib.h"
13#include "crypto/rand.h"
14#include "bn_local.h"
15#include <openssl/rand.h>
16#include <openssl/sha.h>
17#include <openssl/evp.h>
18
19typedef enum bnrand_flag_e {
20 NORMAL, TESTING, PRIVATE
21} BNRAND_FLAG;
22
23static int bnrand(BNRAND_FLAG flag, BIGNUM *rnd, int bits, int top, int bottom,
24 unsigned int strength, BN_CTX *ctx)
25{
26 unsigned char *buf = NULL;
27 int b, ret = 0, bit, bytes, mask;
28 OSSL_LIB_CTX *libctx = ossl_bn_get_libctx(ctx);
29
30 if (bits == 0) {
31 if (top != BN_RAND_TOP_ANY || bottom != BN_RAND_BOTTOM_ANY)
32 goto toosmall;
33 BN_zero(rnd);
34 return 1;
35 }
36 if (bits < 0 || (bits == 1 && top > 0))
37 goto toosmall;
38
39 bytes = (bits + 7) / 8;
40 bit = (bits - 1) % 8;
41 mask = 0xff << (bit + 1);
42
43 buf = OPENSSL_malloc(bytes);
44 if (buf == NULL) {
45 ERR_raise(ERR_LIB_BN, ERR_R_MALLOC_FAILURE);
46 goto err;
47 }
48
49 /* make a random number and set the top and bottom bits */
50 b = flag == NORMAL ? RAND_bytes_ex(libctx, buf, bytes, strength)
51 : RAND_priv_bytes_ex(libctx, buf, bytes, strength);
52 if (b <= 0)
53 goto err;
54
55 if (flag == TESTING) {
56 /*
57 * generate patterns that are more likely to trigger BN library bugs
58 */
59 int i;
60 unsigned char c;
61
62 for (i = 0; i < bytes; i++) {
63 if (RAND_bytes_ex(libctx, &c, 1, strength) <= 0)
64 goto err;
65 if (c >= 128 && i > 0)
66 buf[i] = buf[i - 1];
67 else if (c < 42)
68 buf[i] = 0;
69 else if (c < 84)
70 buf[i] = 255;
71 }
72 }
73
74 if (top >= 0) {
75 if (top) {
76 if (bit == 0) {
77 buf[0] = 1;
78 buf[1] |= 0x80;
79 } else {
80 buf[0] |= (3 << (bit - 1));
81 }
82 } else {
83 buf[0] |= (1 << bit);
84 }
85 }
86 buf[0] &= ~mask;
87 if (bottom) /* set bottom bit if requested */
88 buf[bytes - 1] |= 1;
89 if (!BN_bin2bn(buf, bytes, rnd))
90 goto err;
91 ret = 1;
92 err:
93 OPENSSL_clear_free(buf, bytes);
94 bn_check_top(rnd);
95 return ret;
96
97toosmall:
98 ERR_raise(ERR_LIB_BN, BN_R_BITS_TOO_SMALL);
99 return 0;
100}
101
102int BN_rand_ex(BIGNUM *rnd, int bits, int top, int bottom,
103 unsigned int strength, BN_CTX *ctx)
104{
105 return bnrand(NORMAL, rnd, bits, top, bottom, strength, ctx);
106}
107#ifndef FIPS_MODULE
108int BN_rand(BIGNUM *rnd, int bits, int top, int bottom)
109{
110 return bnrand(NORMAL, rnd, bits, top, bottom, 0, NULL);
111}
112
113int BN_bntest_rand(BIGNUM *rnd, int bits, int top, int bottom)
114{
115 return bnrand(TESTING, rnd, bits, top, bottom, 0, NULL);
116}
117#endif
118
119int BN_priv_rand_ex(BIGNUM *rnd, int bits, int top, int bottom,
120 unsigned int strength, BN_CTX *ctx)
121{
122 return bnrand(PRIVATE, rnd, bits, top, bottom, strength, ctx);
123}
124
125#ifndef FIPS_MODULE
126int BN_priv_rand(BIGNUM *rnd, int bits, int top, int bottom)
127{
128 return bnrand(PRIVATE, rnd, bits, top, bottom, 0, NULL);
129}
130#endif
131
132/* random number r: 0 <= r < range */
133static int bnrand_range(BNRAND_FLAG flag, BIGNUM *r, const BIGNUM *range,
134 unsigned int strength, BN_CTX *ctx)
135{
136 int n;
137 int count = 100;
138
139 if (r == NULL) {
140 ERR_raise(ERR_LIB_BN, ERR_R_PASSED_NULL_PARAMETER);
141 return 0;
142 }
143
144 if (range->neg || BN_is_zero(range)) {
145 ERR_raise(ERR_LIB_BN, BN_R_INVALID_RANGE);
146 return 0;
147 }
148
149 n = BN_num_bits(range); /* n > 0 */
150
151 /* BN_is_bit_set(range, n - 1) always holds */
152
153 if (n == 1)
154 BN_zero(r);
155 else if (!BN_is_bit_set(range, n - 2) && !BN_is_bit_set(range, n - 3)) {
156 /*
157 * range = 100..._2, so 3*range (= 11..._2) is exactly one bit longer
158 * than range
159 */
160 do {
161 if (!bnrand(flag, r, n + 1, BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY,
162 strength, ctx))
163 return 0;
164
165 /*
166 * If r < 3*range, use r := r MOD range (which is either r, r -
167 * range, or r - 2*range). Otherwise, iterate once more. Since
168 * 3*range = 11..._2, each iteration succeeds with probability >=
169 * .75.
170 */
171 if (BN_cmp(r, range) >= 0) {
172 if (!BN_sub(r, r, range))
173 return 0;
174 if (BN_cmp(r, range) >= 0)
175 if (!BN_sub(r, r, range))
176 return 0;
177 }
178
179 if (!--count) {
180 ERR_raise(ERR_LIB_BN, BN_R_TOO_MANY_ITERATIONS);
181 return 0;
182 }
183
184 }
185 while (BN_cmp(r, range) >= 0);
186 } else {
187 do {
188 /* range = 11..._2 or range = 101..._2 */
189 if (!bnrand(flag, r, n, BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY,
190 strength, ctx))
191 return 0;
192
193 if (!--count) {
194 ERR_raise(ERR_LIB_BN, BN_R_TOO_MANY_ITERATIONS);
195 return 0;
196 }
197 }
198 while (BN_cmp(r, range) >= 0);
199 }
200
201 bn_check_top(r);
202 return 1;
203}
204
205int BN_rand_range_ex(BIGNUM *r, const BIGNUM *range, unsigned int strength,
206 BN_CTX *ctx)
207{
208 return bnrand_range(NORMAL, r, range, strength, ctx);
209}
210
211#ifndef FIPS_MODULE
212int BN_rand_range(BIGNUM *r, const BIGNUM *range)
213{
214 return bnrand_range(NORMAL, r, range, 0, NULL);
215}
216#endif
217
218int BN_priv_rand_range_ex(BIGNUM *r, const BIGNUM *range, unsigned int strength,
219 BN_CTX *ctx)
220{
221 return bnrand_range(PRIVATE, r, range, strength, ctx);
222}
223
224#ifndef FIPS_MODULE
225int BN_priv_rand_range(BIGNUM *r, const BIGNUM *range)
226{
227 return bnrand_range(PRIVATE, r, range, 0, NULL);
228}
229
230# ifndef OPENSSL_NO_DEPRECATED_3_0
231int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom)
232{
233 return BN_rand(rnd, bits, top, bottom);
234}
235
236int BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range)
237{
238 return BN_rand_range(r, range);
239}
240# endif
241#endif
242
243int ossl_bn_priv_rand_range_fixed_top(BIGNUM *r, const BIGNUM *range,
244 unsigned int strength, BN_CTX *ctx)
245{
246 int n;
247 int count = 100;
248
249 if (r == NULL) {
250 ERR_raise(ERR_LIB_BN, ERR_R_PASSED_NULL_PARAMETER);
251 return 0;
252 }
253
254 if (range->neg || BN_is_zero(range)) {
255 ERR_raise(ERR_LIB_BN, BN_R_INVALID_RANGE);
256 return 0;
257 }
258
259 n = BN_num_bits(range); /* n > 0 */
260
261 /* BN_is_bit_set(range, n - 1) always holds */
262
263 if (n == 1) {
264 BN_zero(r);
265 } else {
266 BN_set_flags(r, BN_FLG_CONSTTIME);
267 do {
268 if (!bnrand(PRIVATE, r, n + 1, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ANY,
269 strength, ctx))
270 return 0;
271
272 if (!--count) {
273 ERR_raise(ERR_LIB_BN, BN_R_TOO_MANY_ITERATIONS);
274 return 0;
275 }
276 ossl_bn_mask_bits_fixed_top(r, n);
277 }
278 while (BN_ucmp(r, range) >= 0);
279#ifdef BN_DEBUG
280 /* With BN_DEBUG on a fixed top number cannot be returned */
281 bn_correct_top(r);
282#endif
283 }
284
285 return 1;
286}
287
288/*
289 * ossl_bn_gen_dsa_nonce_fixed_top generates a random number 0 <= out < range.
290 * Unlike BN_rand_range, it also includes the contents of |priv| and |message|
291 * in the generation so that an RNG failure isn't fatal as long as |priv|
292 * remains secret. This is intended for use in DSA and ECDSA where an RNG
293 * weakness leads directly to private key exposure unless this function is
294 * used.
295 */
296int ossl_bn_gen_dsa_nonce_fixed_top(BIGNUM *out, const BIGNUM *range,
297 const BIGNUM *priv,
298 const unsigned char *message,
299 size_t message_len, BN_CTX *ctx)
300{
301 EVP_MD_CTX *mdctx = EVP_MD_CTX_new();
302 /*
303 * We use 512 bits of random data per iteration to ensure that we have at
304 * least |range| bits of randomness.
305 */
306 unsigned char random_bytes[64];
307 unsigned char digest[SHA512_DIGEST_LENGTH];
308 unsigned done, todo;
309 /* We generate |range|+1 bytes of random output. */
310 const unsigned num_k_bytes = BN_num_bytes(range) + 1;
311 unsigned char private_bytes[96];
312 unsigned char *k_bytes = NULL;
313 const int max_n = 64; /* Pr(failure to generate) < 2^max_n */
314 int n;
315 int ret = 0;
316 EVP_MD *md = NULL;
317 OSSL_LIB_CTX *libctx = ossl_bn_get_libctx(ctx);
318
319 if (mdctx == NULL)
320 goto end;
321
322 k_bytes = OPENSSL_malloc(num_k_bytes);
323 if (k_bytes == NULL)
324 goto end;
325 /* Ensure top byte is set to avoid non-constant time in bin2bn */
326 k_bytes[0] = 0xff;
327
328 /* We copy |priv| into a local buffer to avoid exposing its length. */
329 if (BN_bn2binpad(priv, private_bytes, sizeof(private_bytes)) < 0) {
330 /*
331 * No reasonable DSA or ECDSA key should have a private key this
332 * large and we don't handle this case in order to avoid leaking the
333 * length of the private key.
334 */
335 ERR_raise(ERR_LIB_BN, BN_R_PRIVATE_KEY_TOO_LARGE);
336 goto end;
337 }
338
339 md = EVP_MD_fetch(libctx, "SHA512", NULL);
340 if (md == NULL) {
341 ERR_raise(ERR_LIB_BN, BN_R_NO_SUITABLE_DIGEST);
342 goto end;
343 }
344 for (n = 0; n < max_n; n++) {
345 unsigned char i = 0;
346
347 for (done = 1; done < num_k_bytes;) {
348 if (RAND_priv_bytes_ex(libctx, random_bytes, sizeof(random_bytes),
349 0) <= 0)
350 goto end;
351
352 if (!EVP_DigestInit_ex(mdctx, md, NULL)
353 || !EVP_DigestUpdate(mdctx, &i, sizeof(i))
354 || !EVP_DigestUpdate(mdctx, private_bytes,
355 sizeof(private_bytes))
356 || !EVP_DigestUpdate(mdctx, message, message_len)
357 || !EVP_DigestUpdate(mdctx, random_bytes,
358 sizeof(random_bytes))
359 || !EVP_DigestFinal_ex(mdctx, digest, NULL))
360 goto end;
361
362 todo = num_k_bytes - done;
363 if (todo > SHA512_DIGEST_LENGTH)
364 todo = SHA512_DIGEST_LENGTH;
365 memcpy(k_bytes + done, digest, todo);
366 done += todo;
367 ++i;
368 }
369
370 if (!BN_bin2bn(k_bytes, num_k_bytes, out))
371 goto end;
372
373 /* Clear out the top bits and rejection filter into range */
374 BN_set_flags(out, BN_FLG_CONSTTIME);
375 ossl_bn_mask_bits_fixed_top(out, BN_num_bits(range));
376
377 if (BN_ucmp(out, range) < 0) {
378 ret = 1;
379#ifdef BN_DEBUG
380 /* With BN_DEBUG on a fixed top number cannot be returned */
381 bn_correct_top(out);
382#endif
383 goto end;
384 }
385 }
386 /* Failed to generate anything */
387 ERR_raise(ERR_LIB_BN, ERR_R_INTERNAL_ERROR);
388
389 end:
390 EVP_MD_CTX_free(mdctx);
391 EVP_MD_free(md);
392 OPENSSL_clear_free(k_bytes, num_k_bytes);
393 OPENSSL_cleanse(digest, sizeof(digest));
394 OPENSSL_cleanse(random_bytes, sizeof(random_bytes));
395 OPENSSL_cleanse(private_bytes, sizeof(private_bytes));
396 return ret;
397}
398
399int BN_generate_dsa_nonce(BIGNUM *out, const BIGNUM *range,
400 const BIGNUM *priv, const unsigned char *message,
401 size_t message_len, BN_CTX *ctx)
402{
403 int ret;
404
405 ret = ossl_bn_gen_dsa_nonce_fixed_top(out, range, priv, message,
406 message_len, ctx);
407 /*
408 * This call makes the BN_generate_dsa_nonce non-const-time, thus we
409 * do not use it internally. But fixed_top BNs currently cannot be returned
410 * from public API calls.
411 */
412 bn_correct_top(out);
413 return ret;
414}
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