| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id$ |
| 4 | * |
| 5 | * Random number generator for DSA |
| 6 | * |
| 7 | * (c) 1999 Straylight/Edgeware |
| 8 | * (c) 2000 Mark Wooding |
| 9 | */ |
| 10 | |
| 11 | /*----- Licensing notice --------------------------------------------------* |
| 12 | * |
| 13 | * Copyright (c) 2000 Mark Wooding |
| 14 | * All rights reserved. |
| 15 | * |
| 16 | * Redistribution and use in source and binary forms, with or without |
| 17 | * modification, are permitted provided that the following conditions are |
| 18 | * met: |
| 19 | * |
| 20 | * 1. Redistributions of source code must retain the above copyright |
| 21 | * notice, this list of conditions and the following disclaimer. |
| 22 | * |
| 23 | * 2, Redistributions in binary form must reproduce the above copyright |
| 24 | * notice, this list of conditions and the following disclaimer in the |
| 25 | * documentation and/or other materials provided with the distribution. |
| 26 | * |
| 27 | * 3. The name of the authors may not be used to endorse or promote |
| 28 | * products derived from this software without specific prior written |
| 29 | * permission. |
| 30 | * |
| 31 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED |
| 32 | * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF |
| 33 | * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN |
| 34 | * NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, |
| 35 | * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES |
| 36 | * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR |
| 37 | * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| 38 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, |
| 39 | * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN |
| 40 | * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| 41 | * POSSIBILITY OF SUCH DAMAGE. |
| 42 | * |
| 43 | * Instead of accepting the above terms, you may redistribute and/or modify |
| 44 | * this software under the terms of either the GNU General Public License, |
| 45 | * or the GNU Library General Public License, published by the Free |
| 46 | * Software Foundation; either version 2 of the License, or (at your |
| 47 | * option) any later version. |
| 48 | */ |
| 49 | |
| 50 | /*----- Revision history --------------------------------------------------* |
| 51 | * |
| 52 | * $Log: dsarand.c,v $ |
| 53 | * Revision 1.2 2000/07/02 15:21:20 mdw |
| 54 | * Fix licence text. |
| 55 | * |
| 56 | * Revision 1.1 2000/05/21 11:28:30 mdw |
| 57 | * Initial check-in. |
| 58 | * |
| 59 | * --- Past lives (Catacomb) --- * |
| 60 | * |
| 61 | * Revision 1.1 1999/12/22 15:53:12 mdw |
| 62 | * Random number generator for finding DSA parameters. |
| 63 | * |
| 64 | */ |
| 65 | |
| 66 | /*----- Header files ------------------------------------------------------*/ |
| 67 | |
| 68 | #include <stdio.h> |
| 69 | #include <stdlib.h> |
| 70 | #include <string.h> |
| 71 | |
| 72 | #include "bits.h" |
| 73 | #include "dsarand.h" |
| 74 | #include "sha.h" |
| 75 | |
| 76 | /*----- Main code ---------------------------------------------------------*/ |
| 77 | |
| 78 | /* --- @STEP@ --- * |
| 79 | * |
| 80 | * Arguments: @dsarand *d@ = pointer to context |
| 81 | * |
| 82 | * Use: Increments the buffer by one, interpreting it as a big-endian |
| 83 | * integer. Carries outside the integer are discarded. |
| 84 | */ |
| 85 | |
| 86 | #define STEP(d) do { \ |
| 87 | dsarand *_d = (d); \ |
| 88 | octet *_p = _d->p; \ |
| 89 | octet *_q = _p + _d->sz; \ |
| 90 | unsigned _c = 1; \ |
| 91 | while (_c && _q > _p) { \ |
| 92 | _c += *--_q; \ |
| 93 | *_q = U8(_c); \ |
| 94 | _c >>= 8; \ |
| 95 | } \ |
| 96 | } while (0) |
| 97 | |
| 98 | /* --- @dsarand_init@ --- * |
| 99 | * |
| 100 | * Arguments: @dsarand *d@ = pointer to context |
| 101 | * @const void *p@ = pointer to seed buffer |
| 102 | * @size_t sz@ = size of the buffer |
| 103 | * |
| 104 | * Returns: --- |
| 105 | * |
| 106 | * Use: Initializes a DSA random number generator. |
| 107 | */ |
| 108 | |
| 109 | void dsarand_init(dsarand *d, const void *p, size_t sz) |
| 110 | { |
| 111 | if ((d->p = malloc(sz)) == 0) { |
| 112 | fputs("Out of memory in dsarand_init!\n", stderr); |
| 113 | exit(EXIT_FAILURE); |
| 114 | } |
| 115 | d->sz = sz; |
| 116 | d->passes = 1; |
| 117 | if (p) |
| 118 | memcpy(d->p, p, sz); |
| 119 | } |
| 120 | |
| 121 | /* --- @dsarand_reseed@ --- * |
| 122 | * |
| 123 | * Arguments: @dsarand *d@ = pointer to context |
| 124 | * @const void *p@ = pointer to seed buffer |
| 125 | * @size_t sz@ = size of the buffer |
| 126 | * |
| 127 | * Returns: --- |
| 128 | * |
| 129 | * Use: Initializes a DSA random number generator. |
| 130 | */ |
| 131 | |
| 132 | void dsarand_reseed(dsarand *d, const void *p, size_t sz) |
| 133 | { |
| 134 | free(d->p); |
| 135 | if ((d->p = malloc(sz)) != 0) { |
| 136 | fputs("Out of memory in dsarand_init!\n", stderr); |
| 137 | exit(EXIT_FAILURE); |
| 138 | } |
| 139 | d->sz = sz; |
| 140 | d->passes = 1; |
| 141 | if (p) |
| 142 | memcpy(d->p, p, sz); |
| 143 | } |
| 144 | |
| 145 | /* --- @dsarand_destroy@ --- * |
| 146 | * |
| 147 | * Arguments: @dsarand *d@ = pointer to context |
| 148 | * |
| 149 | * Returns: --- |
| 150 | * |
| 151 | * Use: Disposes of a DSA random number generation context. |
| 152 | */ |
| 153 | |
| 154 | void dsarand_destroy(dsarand *d) |
| 155 | { |
| 156 | free(d->p); |
| 157 | } |
| 158 | |
| 159 | /* --- @dsarand_fill@ --- * |
| 160 | * |
| 161 | * Arguments: @dsarand *d@ = pointer to context |
| 162 | * @void *p@ = pointer to output buffer |
| 163 | * @size_t sz@ = size of output buffer |
| 164 | * |
| 165 | * Returns: --- |
| 166 | * |
| 167 | * Use: Fills an output buffer with pseudorandom data. |
| 168 | * |
| 169 | * Let %$p$% be the numerical value of the input buffer, and let |
| 170 | * %$b$% be the number of bytes required. Let |
| 171 | * %$z = \lceil b / 20 \rceil$% be the number of SHA outputs |
| 172 | * required. Then the output of pass %$n$% is |
| 173 | * |
| 174 | * %$P_n = \sum_{0 \le i < z} 2^{160i} SHA(p + nz + i)$% |
| 175 | * %${} \bmod 2^{8b}$% |
| 176 | * |
| 177 | * and the actual result in the output buffer is the XOR of all |
| 178 | * of the output passes. |
| 179 | * |
| 180 | * The DSA procedure for choosing @q@ involves two passes with |
| 181 | * %$z = 1$%; the procedure for choosing @p@ involves one pass |
| 182 | * with larger %$z$%. This generalization of the DSA generation |
| 183 | * procedure is my own invention but it seems relatively sound. |
| 184 | */ |
| 185 | |
| 186 | void dsarand_fill(dsarand *d, void *p, size_t sz) |
| 187 | { |
| 188 | octet *q = p; |
| 189 | unsigned n = d->passes; |
| 190 | |
| 191 | /* --- Write out the first pass --- * |
| 192 | * |
| 193 | * This can write directly to the output buffer, so it's done differently |
| 194 | * from the latter passes. |
| 195 | */ |
| 196 | |
| 197 | { |
| 198 | size_t o = sz; |
| 199 | |
| 200 | while (o) { |
| 201 | sha_ctx h; |
| 202 | |
| 203 | /* --- Hash the input buffer --- */ |
| 204 | |
| 205 | sha_init(&h); |
| 206 | sha_hash(&h, d->p, d->sz); |
| 207 | |
| 208 | /* --- If enough space, extract the hash output directly --- */ |
| 209 | |
| 210 | if (o >= SHA_HASHSZ) { |
| 211 | o -= SHA_HASHSZ; |
| 212 | sha_done(&h, q + o); |
| 213 | } |
| 214 | |
| 215 | /* --- Otherwise take the hash result out of line and copy it --- */ |
| 216 | |
| 217 | else { |
| 218 | octet hash[SHA_HASHSZ]; |
| 219 | sha_done(&h, hash); |
| 220 | memcpy(q, hash + (SHA_HASHSZ - o), o); |
| 221 | o = 0; |
| 222 | } |
| 223 | |
| 224 | /* --- Step the input buffer --- */ |
| 225 | |
| 226 | STEP(d); |
| 227 | } |
| 228 | |
| 229 | /* --- Another pass has been done --- */ |
| 230 | |
| 231 | n--; |
| 232 | } |
| 233 | |
| 234 | /* --- Write out subsequent passes --- * |
| 235 | * |
| 236 | * The hash output has to be done offline, so this is slightly easier. |
| 237 | */ |
| 238 | |
| 239 | while (n) { |
| 240 | size_t o = sz; |
| 241 | |
| 242 | while (o) { |
| 243 | sha_ctx h; |
| 244 | octet hash[SHA_HASHSZ]; |
| 245 | size_t n; |
| 246 | octet *pp, *qq; |
| 247 | |
| 248 | /* --- Hash the input buffer --- */ |
| 249 | |
| 250 | sha_init(&h); |
| 251 | sha_hash(&h, d->p, d->sz); |
| 252 | sha_done(&h, hash); |
| 253 | |
| 254 | /* --- Work out how much output is wanted --- */ |
| 255 | |
| 256 | n = SHA_HASHSZ; |
| 257 | if (n > o) |
| 258 | n = o; |
| 259 | o -= n; |
| 260 | |
| 261 | /* --- XOR the data out --- */ |
| 262 | |
| 263 | for (pp = hash + (SHA_HASHSZ - n), qq = q + o; |
| 264 | pp < hash + SHA_HASHSZ; pp++, qq++) |
| 265 | *qq ^= *pp; |
| 266 | |
| 267 | /* --- Step the input buffer --- */ |
| 268 | |
| 269 | STEP(d); |
| 270 | } |
| 271 | |
| 272 | /* --- Another pass is done --- */ |
| 273 | |
| 274 | n--; |
| 275 | } |
| 276 | } |
| 277 | |
| 278 | /*----- That's all, folks -------------------------------------------------*/ |