[331] | 1 | /*
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| 2 | * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
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| 3 | *
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| 4 | * Licensed under the OpenSSL license (the "License"). You may not use
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| 5 | * this file except in compliance with the License. You can obtain a copy
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| 6 | * in the file LICENSE in the source distribution or at
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| 7 | * https://www.openssl.org/source/license.html
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| 8 | */
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| 9 |
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| 10 | #include <stdio.h>
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| 11 | #include <time.h>
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| 12 | #include "internal/cryptlib.h"
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| 13 | #include "bn_lcl.h"
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| 14 | #include <openssl/rand.h>
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| 15 | #include <openssl/sha.h>
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| 16 |
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| 17 | static int bnrand(int pseudorand, BIGNUM *rnd, int bits, int top, int bottom)
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| 18 | {
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| 19 | unsigned char *buf = NULL;
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| 20 | int ret = 0, bit, bytes, mask;
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| 21 | time_t tim;
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| 22 |
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| 23 | if (bits == 0) {
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| 24 | if (top != BN_RAND_TOP_ANY || bottom != BN_RAND_BOTTOM_ANY)
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| 25 | goto toosmall;
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| 26 | BN_zero(rnd);
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| 27 | return 1;
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| 28 | }
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| 29 | if (bits < 0 || (bits == 1 && top > 0))
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| 30 | goto toosmall;
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| 31 |
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| 32 | bytes = (bits + 7) / 8;
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| 33 | bit = (bits - 1) % 8;
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| 34 | mask = 0xff << (bit + 1);
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| 35 |
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| 36 | buf = OPENSSL_malloc(bytes);
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| 37 | if (buf == NULL) {
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| 38 | BNerr(BN_F_BNRAND, ERR_R_MALLOC_FAILURE);
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| 39 | goto err;
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| 40 | }
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| 41 |
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| 42 | /* make a random number and set the top and bottom bits */
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| 43 | time(&tim);
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| 44 | RAND_add(&tim, sizeof(tim), 0.0);
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| 45 |
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| 46 | if (RAND_bytes(buf, bytes) <= 0)
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| 47 | goto err;
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| 48 |
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| 49 | if (pseudorand == 2) {
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| 50 | /*
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| 51 | * generate patterns that are more likely to trigger BN library bugs
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| 52 | */
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| 53 | int i;
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| 54 | unsigned char c;
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| 55 |
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| 56 | for (i = 0; i < bytes; i++) {
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| 57 | if (RAND_bytes(&c, 1) <= 0)
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| 58 | goto err;
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| 59 | if (c >= 128 && i > 0)
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| 60 | buf[i] = buf[i - 1];
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| 61 | else if (c < 42)
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| 62 | buf[i] = 0;
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| 63 | else if (c < 84)
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| 64 | buf[i] = 255;
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| 65 | }
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| 66 | }
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| 67 |
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| 68 | if (top >= 0) {
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| 69 | if (top) {
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| 70 | if (bit == 0) {
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| 71 | buf[0] = 1;
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| 72 | buf[1] |= 0x80;
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| 73 | } else {
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| 74 | buf[0] |= (3 << (bit - 1));
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| 75 | }
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| 76 | } else {
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| 77 | buf[0] |= (1 << bit);
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| 78 | }
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| 79 | }
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| 80 | buf[0] &= ~mask;
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| 81 | if (bottom) /* set bottom bit if requested */
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| 82 | buf[bytes - 1] |= 1;
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| 83 | if (!BN_bin2bn(buf, bytes, rnd))
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| 84 | goto err;
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| 85 | ret = 1;
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| 86 | err:
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| 87 | OPENSSL_clear_free(buf, bytes);
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| 88 | bn_check_top(rnd);
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| 89 | return (ret);
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| 90 |
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| 91 | toosmall:
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| 92 | BNerr(BN_F_BNRAND, BN_R_BITS_TOO_SMALL);
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| 93 | return 0;
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| 94 | }
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| 95 |
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| 96 | int BN_rand(BIGNUM *rnd, int bits, int top, int bottom)
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| 97 | {
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| 98 | return bnrand(0, rnd, bits, top, bottom);
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| 99 | }
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| 100 |
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| 101 | int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom)
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| 102 | {
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| 103 | return bnrand(1, rnd, bits, top, bottom);
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| 104 | }
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| 105 |
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| 106 | int BN_bntest_rand(BIGNUM *rnd, int bits, int top, int bottom)
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| 107 | {
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| 108 | return bnrand(2, rnd, bits, top, bottom);
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| 109 | }
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| 110 |
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| 111 | /* random number r: 0 <= r < range */
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| 112 | static int bn_rand_range(int pseudo, BIGNUM *r, const BIGNUM *range)
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| 113 | {
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| 114 | int (*bn_rand) (BIGNUM *, int, int, int) =
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| 115 | pseudo ? BN_pseudo_rand : BN_rand;
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| 116 | int n;
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| 117 | int count = 100;
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| 118 |
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| 119 | if (range->neg || BN_is_zero(range)) {
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| 120 | BNerr(BN_F_BN_RAND_RANGE, BN_R_INVALID_RANGE);
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| 121 | return 0;
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| 122 | }
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| 123 |
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| 124 | n = BN_num_bits(range); /* n > 0 */
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| 125 |
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| 126 | /* BN_is_bit_set(range, n - 1) always holds */
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| 127 |
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| 128 | if (n == 1)
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| 129 | BN_zero(r);
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| 130 | else if (!BN_is_bit_set(range, n - 2) && !BN_is_bit_set(range, n - 3)) {
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| 131 | /*
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| 132 | * range = 100..._2, so 3*range (= 11..._2) is exactly one bit longer
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| 133 | * than range
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| 134 | */
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| 135 | do {
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| 136 | if (!bn_rand(r, n + 1, BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY))
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| 137 | return 0;
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| 138 | /*
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| 139 | * If r < 3*range, use r := r MOD range (which is either r, r -
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| 140 | * range, or r - 2*range). Otherwise, iterate once more. Since
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| 141 | * 3*range = 11..._2, each iteration succeeds with probability >=
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| 142 | * .75.
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| 143 | */
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| 144 | if (BN_cmp(r, range) >= 0) {
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| 145 | if (!BN_sub(r, r, range))
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| 146 | return 0;
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| 147 | if (BN_cmp(r, range) >= 0)
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| 148 | if (!BN_sub(r, r, range))
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| 149 | return 0;
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| 150 | }
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| 151 |
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| 152 | if (!--count) {
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| 153 | BNerr(BN_F_BN_RAND_RANGE, BN_R_TOO_MANY_ITERATIONS);
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| 154 | return 0;
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| 155 | }
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| 156 |
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| 157 | }
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| 158 | while (BN_cmp(r, range) >= 0);
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| 159 | } else {
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| 160 | do {
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| 161 | /* range = 11..._2 or range = 101..._2 */
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| 162 | if (!bn_rand(r, n, BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY))
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| 163 | return 0;
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| 164 |
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| 165 | if (!--count) {
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| 166 | BNerr(BN_F_BN_RAND_RANGE, BN_R_TOO_MANY_ITERATIONS);
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| 167 | return 0;
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| 168 | }
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| 169 | }
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| 170 | while (BN_cmp(r, range) >= 0);
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| 171 | }
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| 172 |
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| 173 | bn_check_top(r);
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| 174 | return 1;
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| 175 | }
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| 176 |
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| 177 | int BN_rand_range(BIGNUM *r, const BIGNUM *range)
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| 178 | {
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| 179 | return bn_rand_range(0, r, range);
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| 180 | }
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| 181 |
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| 182 | int BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range)
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| 183 | {
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| 184 | return bn_rand_range(1, r, range);
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| 185 | }
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| 186 |
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| 187 | /*
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| 188 | * BN_generate_dsa_nonce generates a random number 0 <= out < range. Unlike
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| 189 | * BN_rand_range, it also includes the contents of |priv| and |message| in
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| 190 | * the generation so that an RNG failure isn't fatal as long as |priv|
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| 191 | * remains secret. This is intended for use in DSA and ECDSA where an RNG
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| 192 | * weakness leads directly to private key exposure unless this function is
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| 193 | * used.
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| 194 | */
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| 195 | int BN_generate_dsa_nonce(BIGNUM *out, const BIGNUM *range,
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| 196 | const BIGNUM *priv, const unsigned char *message,
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| 197 | size_t message_len, BN_CTX *ctx)
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| 198 | {
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| 199 | SHA512_CTX sha;
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| 200 | /*
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| 201 | * We use 512 bits of random data per iteration to ensure that we have at
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| 202 | * least |range| bits of randomness.
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| 203 | */
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| 204 | unsigned char random_bytes[64];
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| 205 | unsigned char digest[SHA512_DIGEST_LENGTH];
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| 206 | unsigned done, todo;
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| 207 | /* We generate |range|+8 bytes of random output. */
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| 208 | const unsigned num_k_bytes = BN_num_bytes(range) + 8;
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| 209 | unsigned char private_bytes[96];
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| 210 | unsigned char *k_bytes;
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| 211 | int ret = 0;
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| 212 |
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| 213 | k_bytes = OPENSSL_malloc(num_k_bytes);
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| 214 | if (k_bytes == NULL)
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| 215 | goto err;
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| 216 |
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| 217 | /* We copy |priv| into a local buffer to avoid exposing its length. */
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| 218 | todo = sizeof(priv->d[0]) * priv->top;
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| 219 | if (todo > sizeof(private_bytes)) {
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| 220 | /*
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| 221 | * No reasonable DSA or ECDSA key should have a private key this
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| 222 | * large and we don't handle this case in order to avoid leaking the
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| 223 | * length of the private key.
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| 224 | */
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| 225 | BNerr(BN_F_BN_GENERATE_DSA_NONCE, BN_R_PRIVATE_KEY_TOO_LARGE);
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| 226 | goto err;
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| 227 | }
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| 228 | memcpy(private_bytes, priv->d, todo);
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| 229 | memset(private_bytes + todo, 0, sizeof(private_bytes) - todo);
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| 230 |
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| 231 | for (done = 0; done < num_k_bytes;) {
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| 232 | if (RAND_bytes(random_bytes, sizeof(random_bytes)) != 1)
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| 233 | goto err;
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| 234 | SHA512_Init(&sha);
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| 235 | SHA512_Update(&sha, &done, sizeof(done));
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| 236 | SHA512_Update(&sha, private_bytes, sizeof(private_bytes));
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| 237 | SHA512_Update(&sha, message, message_len);
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| 238 | SHA512_Update(&sha, random_bytes, sizeof(random_bytes));
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| 239 | SHA512_Final(digest, &sha);
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| 240 |
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| 241 | todo = num_k_bytes - done;
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| 242 | if (todo > SHA512_DIGEST_LENGTH)
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| 243 | todo = SHA512_DIGEST_LENGTH;
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| 244 | memcpy(k_bytes + done, digest, todo);
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| 245 | done += todo;
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| 246 | }
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| 247 |
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| 248 | if (!BN_bin2bn(k_bytes, num_k_bytes, out))
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| 249 | goto err;
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| 250 | if (BN_mod(out, out, range, ctx) != 1)
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| 251 | goto err;
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| 252 | ret = 1;
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| 253 |
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| 254 | err:
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| 255 | OPENSSL_free(k_bytes);
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| 256 | OPENSSL_cleanse(private_bytes, sizeof(private_bytes));
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| 257 | return ret;
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| 258 | }
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