1 /* crypto/bn/bn_rand.c */ 2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) 3 * All rights reserved. 4 * 5 * This package is an SSL implementation written 6 * by Eric Young (eay@cryptsoft.com). 7 * The implementation was written so as to conform with Netscapes SSL. 8 * 9 * This library is free for commercial and non-commercial use as long as 10 * the following conditions are aheared to. The following conditions 11 * apply to all code found in this distribution, be it the RC4, RSA, 12 * lhash, DES, etc., code; not just the SSL code. The SSL documentation 13 * included with this distribution is covered by the same copyright terms 14 * except that the holder is Tim Hudson (tjh@cryptsoft.com). 15 * 16 * Copyright remains Eric Young's, and as such any Copyright notices in 17 * the code are not to be removed. 18 * If this package is used in a product, Eric Young should be given attribution 19 * as the author of the parts of the library used. 20 * This can be in the form of a textual message at program startup or 21 * in documentation (online or textual) provided with the package. 22 * 23 * Redistribution and use in source and binary forms, with or without 24 * modification, are permitted provided that the following conditions 25 * are met: 26 * 1. Redistributions of source code must retain the copyright 27 * notice, this list of conditions and the following disclaimer. 28 * 2. Redistributions in binary form must reproduce the above copyright 29 * notice, this list of conditions and the following disclaimer in the 30 * documentation and/or other materials provided with the distribution. 31 * 3. All advertising materials mentioning features or use of this software 32 * must display the following acknowledgement: 33 * "This product includes cryptographic software written by 34 * Eric Young (eay@cryptsoft.com)" 35 * The word 'cryptographic' can be left out if the rouines from the library 36 * being used are not cryptographic related :-). 37 * 4. If you include any Windows specific code (or a derivative thereof) from 38 * the apps directory (application code) you must include an acknowledgement: 39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" 40 * 41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND 42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 44 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 51 * SUCH DAMAGE. 52 * 53 * The licence and distribution terms for any publically available version or 54 * derivative of this code cannot be changed. i.e. this code cannot simply be 55 * copied and put under another distribution licence 56 * [including the GNU Public Licence.] 57 */ 58 59 #include <stdio.h> 60 #include <time.h> 61 #include "cryptlib.h" 62 #include "bn_lcl.h" 63 #include <openssl/rand.h> 64 65 static int bnrand(int pseudorand, BIGNUM *rnd, int bits, int top, int bottom) 66 { 67 unsigned char *buf=NULL; 68 int ret=0,bit,bytes,mask; 69 time_t tim; 70 71 if (bits == 0) 72 { 73 BN_zero(rnd); 74 return 1; 75 } 76 77 bytes=(bits+7)/8; 78 bit=(bits-1)%8; 79 mask=0xff<<(bit+1); 80 81 buf=(unsigned char *)OPENSSL_malloc(bytes); 82 if (buf == NULL) 83 { 84 BNerr(BN_F_BN_RAND,ERR_R_MALLOC_FAILURE); 85 goto err; 86 } 87 88 /* make a random number and set the top and bottom bits */ 89 time(&tim); 90 RAND_add(&tim,sizeof(tim),0); 91 92 if (pseudorand) 93 { 94 if (RAND_pseudo_bytes(buf, bytes) == -1) 95 goto err; 96 } 97 else 98 { 99 if (RAND_bytes(buf, bytes) <= 0) 100 goto err; 101 } 102 103 #if 1 104 if (pseudorand == 2) 105 { 106 /* generate patterns that are more likely to trigger BN 107 library bugs */ 108 int i; 109 unsigned char c; 110 111 for (i = 0; i < bytes; i++) 112 { 113 RAND_pseudo_bytes(&c, 1); 114 if (c >= 128 && i > 0) 115 buf[i] = buf[i-1]; 116 else if (c < 42) 117 buf[i] = 0; 118 else if (c < 84) 119 buf[i] = 255; 120 } 121 } 122 #endif 123 124 if (top != -1) 125 { 126 if (top) 127 { 128 if (bit == 0) 129 { 130 buf[0]=1; 131 buf[1]|=0x80; 132 } 133 else 134 { 135 buf[0]|=(3<<(bit-1)); 136 } 137 } 138 else 139 { 140 buf[0]|=(1<<bit); 141 } 142 } 143 buf[0] &= ~mask; 144 if (bottom) /* set bottom bit if requested */ 145 buf[bytes-1]|=1; 146 if (!BN_bin2bn(buf,bytes,rnd)) goto err; 147 ret=1; 148 err: 149 if (buf != NULL) 150 { 151 memset(buf,0,bytes); 152 OPENSSL_free(buf); 153 } 154 return(ret); 155 } 156 157 int BN_rand(BIGNUM *rnd, int bits, int top, int bottom) 158 { 159 return bnrand(0, rnd, bits, top, bottom); 160 } 161 162 int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom) 163 { 164 return bnrand(1, rnd, bits, top, bottom); 165 } 166 167 #if 1 168 int BN_bntest_rand(BIGNUM *rnd, int bits, int top, int bottom) 169 { 170 return bnrand(2, rnd, bits, top, bottom); 171 } 172 #endif 173 174 /* random number r: 0 <= r < range */ 175 int BN_rand_range(BIGNUM *r, BIGNUM *range) 176 { 177 int n; 178 179 if (range->neg || BN_is_zero(range)) 180 { 181 BNerr(BN_F_BN_RAND_RANGE, BN_R_INVALID_RANGE); 182 return 0; 183 } 184 185 n = BN_num_bits(range); /* n > 0 */ 186 187 if (n == 1) 188 { 189 if (!BN_zero(r)) return 0; 190 } 191 else if (BN_is_bit_set(range, n - 2)) 192 { 193 do 194 { 195 /* range = 11..._2, so each iteration succeeds with probability >= .75 */ 196 if (!BN_rand(r, n, -1, 0)) return 0; 197 } 198 while (BN_cmp(r, range) >= 0); 199 } 200 else 201 { 202 /* range = 10..._2, 203 * so 3*range (= 11..._2) is exactly one bit longer than range */ 204 do 205 { 206 if (!BN_rand(r, n + 1, -1, 0)) return 0; 207 /* If r < 3*range, use r := r MOD range 208 * (which is either r, r - range, or r - 2*range). 209 * Otherwise, iterate once more. 210 * Since 3*range = 11..._2, each iteration succeeds with 211 * probability >= .75. */ 212 if (BN_cmp(r ,range) >= 0) 213 { 214 if (!BN_sub(r, r, range)) return 0; 215 if (BN_cmp(r, range) >= 0) 216 if (!BN_sub(r, r, range)) return 0; 217 } 218 } 219 while (BN_cmp(r, range) >= 0); 220 } 221 222 return 1; 223 } 224