| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: dsarand.c,v 1.4 2004/04/08 01:36:15 mdw Exp $ |
| 4 | * |
| 5 | * Random number generator for DSA |
| 6 | * |
| 7 | * (c) 1999 Straylight/Edgeware |
| 8 | */ |
| 9 | |
| 10 | /*----- Licensing notice --------------------------------------------------* |
| 11 | * |
| 12 | * This file is part of Catacomb. |
| 13 | * |
| 14 | * Catacomb is free software; you can redistribute it and/or modify |
| 15 | * it under the terms of the GNU Library General Public License as |
| 16 | * published by the Free Software Foundation; either version 2 of the |
| 17 | * License, or (at your option) any later version. |
| 18 | * |
| 19 | * Catacomb is distributed in the hope that it will be useful, |
| 20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 22 | * GNU Library General Public License for more details. |
| 23 | * |
| 24 | * You should have received a copy of the GNU Library General Public |
| 25 | * License along with Catacomb; if not, write to the Free |
| 26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
| 27 | * MA 02111-1307, USA. |
| 28 | */ |
| 29 | |
| 30 | /*----- Header files ------------------------------------------------------*/ |
| 31 | |
| 32 | #include <stdarg.h> |
| 33 | #include <string.h> |
| 34 | |
| 35 | #include <mLib/alloc.h> |
| 36 | #include <mLib/bits.h> |
| 37 | #include <mLib/sub.h> |
| 38 | |
| 39 | #include "dsarand.h" |
| 40 | #include "grand.h" |
| 41 | #include "sha.h" |
| 42 | |
| 43 | /*----- Main code ---------------------------------------------------------*/ |
| 44 | |
| 45 | /* --- @STEP@ --- * |
| 46 | * |
| 47 | * Arguments: @dsarand *d@ = pointer to context |
| 48 | * |
| 49 | * Use: Increments the buffer by one, interpreting it as a big-endian |
| 50 | * integer. Carries outside the integer are discarded. |
| 51 | */ |
| 52 | |
| 53 | #define STEP(d) do { \ |
| 54 | dsarand *_d = (d); \ |
| 55 | octet *_p = _d->p; \ |
| 56 | octet *_q = _p + _d->sz; \ |
| 57 | unsigned _c = 1; \ |
| 58 | while (_c && _q > _p) { \ |
| 59 | _c += *--_q; \ |
| 60 | *_q = U8(_c); \ |
| 61 | _c >>= 8; \ |
| 62 | } \ |
| 63 | } while (0) |
| 64 | |
| 65 | /* --- @dsarand_init@ --- * |
| 66 | * |
| 67 | * Arguments: @dsarand *d@ = pointer to context |
| 68 | * @const void *p@ = pointer to seed buffer |
| 69 | * @size_t sz@ = size of the buffer |
| 70 | * |
| 71 | * Returns: --- |
| 72 | * |
| 73 | * Use: Initializes a DSA random number generator. |
| 74 | */ |
| 75 | |
| 76 | void dsarand_init(dsarand *d, const void *p, size_t sz) |
| 77 | { |
| 78 | d->p = xmalloc(sz); |
| 79 | d->sz = sz; |
| 80 | d->passes = 1; |
| 81 | if (p) |
| 82 | memcpy(d->p, p, sz); |
| 83 | } |
| 84 | |
| 85 | /* --- @dsarand_reseed@ --- * |
| 86 | * |
| 87 | * Arguments: @dsarand *d@ = pointer to context |
| 88 | * @const void *p@ = pointer to seed buffer |
| 89 | * @size_t sz@ = size of the buffer |
| 90 | * |
| 91 | * Returns: --- |
| 92 | * |
| 93 | * Use: Initializes a DSA random number generator. |
| 94 | */ |
| 95 | |
| 96 | void dsarand_reseed(dsarand *d, const void *p, size_t sz) |
| 97 | { |
| 98 | xfree(d->p); |
| 99 | d->p = xmalloc(sz); |
| 100 | d->sz = sz; |
| 101 | d->passes = 1; |
| 102 | if (p) |
| 103 | memcpy(d->p, p, sz); |
| 104 | } |
| 105 | |
| 106 | /* --- @dsarand_destroy@ --- * |
| 107 | * |
| 108 | * Arguments: @dsarand *d@ = pointer to context |
| 109 | * |
| 110 | * Returns: --- |
| 111 | * |
| 112 | * Use: Disposes of a DSA random number generation context. |
| 113 | */ |
| 114 | |
| 115 | void dsarand_destroy(dsarand *d) |
| 116 | { |
| 117 | xfree(d->p); |
| 118 | } |
| 119 | |
| 120 | /* --- @dsarand_fill@ --- * |
| 121 | * |
| 122 | * Arguments: @dsarand *d@ = pointer to context |
| 123 | * @void *p@ = pointer to output buffer |
| 124 | * @size_t sz@ = size of output buffer |
| 125 | * |
| 126 | * Returns: --- |
| 127 | * |
| 128 | * Use: Fills an output buffer with pseudorandom data. |
| 129 | * |
| 130 | * Let %$p$% be the numerical value of the input buffer, and let |
| 131 | * %$b$% be the number of bytes required. Let |
| 132 | * %$z = \lceil b / 20 \rceil$% be the number of SHA outputs |
| 133 | * required. Then the output of pass %$n$% is |
| 134 | * |
| 135 | * %$P_n = \sum_{0 \le i < z} 2^{160i} SHA(p + nz + i)$% |
| 136 | * %${} \bmod 2^{8b}$% |
| 137 | * |
| 138 | * and the actual result in the output buffer is the XOR of all |
| 139 | * of the output passes. |
| 140 | * |
| 141 | * The DSA procedure for choosing @q@ involves two passes with |
| 142 | * %$z = 1$%; the procedure for choosing @p@ involves one pass |
| 143 | * with larger %$z$%. This generalization of the DSA generation |
| 144 | * procedure is my own invention but it seems relatively sound. |
| 145 | */ |
| 146 | |
| 147 | void dsarand_fill(dsarand *d, void *p, size_t sz) |
| 148 | { |
| 149 | octet *q = p; |
| 150 | unsigned n = d->passes; |
| 151 | |
| 152 | /* --- Write out the first pass --- * |
| 153 | * |
| 154 | * This can write directly to the output buffer, so it's done differently |
| 155 | * from the latter passes. |
| 156 | */ |
| 157 | |
| 158 | { |
| 159 | size_t o = sz; |
| 160 | |
| 161 | while (o) { |
| 162 | sha_ctx h; |
| 163 | |
| 164 | /* --- Hash the input buffer --- */ |
| 165 | |
| 166 | sha_init(&h); |
| 167 | sha_hash(&h, d->p, d->sz); |
| 168 | |
| 169 | /* --- If enough space, extract the hash output directly --- */ |
| 170 | |
| 171 | if (o >= SHA_HASHSZ) { |
| 172 | o -= SHA_HASHSZ; |
| 173 | sha_done(&h, q + o); |
| 174 | } |
| 175 | |
| 176 | /* --- Otherwise take the hash result out of line and copy it --- */ |
| 177 | |
| 178 | else { |
| 179 | octet hash[SHA_HASHSZ]; |
| 180 | sha_done(&h, hash); |
| 181 | memcpy(q, hash + (SHA_HASHSZ - o), o); |
| 182 | o = 0; |
| 183 | } |
| 184 | |
| 185 | /* --- Step the input buffer --- */ |
| 186 | |
| 187 | STEP(d); |
| 188 | } |
| 189 | |
| 190 | /* --- Another pass has been done --- */ |
| 191 | |
| 192 | n--; |
| 193 | } |
| 194 | |
| 195 | /* --- Write out subsequent passes --- * |
| 196 | * |
| 197 | * The hash output has to be done offline, so this is slightly easier. |
| 198 | */ |
| 199 | |
| 200 | while (n) { |
| 201 | size_t o = sz; |
| 202 | |
| 203 | while (o) { |
| 204 | sha_ctx h; |
| 205 | octet hash[SHA_HASHSZ]; |
| 206 | size_t n; |
| 207 | octet *pp, *qq; |
| 208 | |
| 209 | /* --- Hash the input buffer --- */ |
| 210 | |
| 211 | sha_init(&h); |
| 212 | sha_hash(&h, d->p, d->sz); |
| 213 | sha_done(&h, hash); |
| 214 | |
| 215 | /* --- Work out how much output is wanted --- */ |
| 216 | |
| 217 | n = SHA_HASHSZ; |
| 218 | if (n > o) |
| 219 | n = o; |
| 220 | o -= n; |
| 221 | |
| 222 | /* --- XOR the data out --- */ |
| 223 | |
| 224 | for (pp = hash + (SHA_HASHSZ - n), qq = q + o; |
| 225 | pp < hash + SHA_HASHSZ; pp++, qq++) |
| 226 | *qq ^= *pp; |
| 227 | |
| 228 | /* --- Step the input buffer --- */ |
| 229 | |
| 230 | STEP(d); |
| 231 | } |
| 232 | |
| 233 | /* --- Another pass is done --- */ |
| 234 | |
| 235 | n--; |
| 236 | } |
| 237 | } |
| 238 | |
| 239 | /*----- Generic pseudorandom-number generator interface -------------------*/ |
| 240 | |
| 241 | static const grand_ops gops; |
| 242 | |
| 243 | typedef struct gctx { |
| 244 | grand r; |
| 245 | dsarand d; |
| 246 | } gctx; |
| 247 | |
| 248 | static void gdestroy(grand *r) |
| 249 | { |
| 250 | gctx *g = (gctx *)r; |
| 251 | dsarand_destroy(&g->d); |
| 252 | DESTROY(g); |
| 253 | } |
| 254 | |
| 255 | static int gmisc(grand *r, unsigned op, ...) |
| 256 | { |
| 257 | gctx *g = (gctx *)r; |
| 258 | va_list ap; |
| 259 | int rc = 0; |
| 260 | va_start(ap, op); |
| 261 | |
| 262 | switch (op) { |
| 263 | case GRAND_CHECK: |
| 264 | switch (va_arg(ap, unsigned)) { |
| 265 | case GRAND_CHECK: |
| 266 | case GRAND_SEEDBLOCK: |
| 267 | case GRAND_SEEDRAND: |
| 268 | case DSARAND_PASSES: |
| 269 | case DSARAND_SEEDSZ: |
| 270 | case DSARAND_GETSEED: |
| 271 | rc = 1; |
| 272 | break; |
| 273 | default: |
| 274 | rc = 0; |
| 275 | break; |
| 276 | } |
| 277 | break; |
| 278 | case GRAND_SEEDBLOCK: { |
| 279 | const void *p = va_arg(ap, const void *); |
| 280 | size_t sz = va_arg(ap, size_t); |
| 281 | dsarand_reseed(&g->d, p, sz); |
| 282 | } break; |
| 283 | case GRAND_SEEDRAND: { |
| 284 | grand *rr = va_arg(ap, grand *); |
| 285 | rr->ops->fill(rr, g->d.p, g->d.sz); |
| 286 | } break; |
| 287 | case DSARAND_PASSES: |
| 288 | g->d.passes = va_arg(ap, unsigned); |
| 289 | break; |
| 290 | case DSARAND_SEEDSZ: |
| 291 | rc = g->d.sz; |
| 292 | break; |
| 293 | case DSARAND_GETSEED: |
| 294 | memcpy(va_arg(ap, void *), g->d.p, g->d.sz); |
| 295 | break; |
| 296 | default: |
| 297 | GRAND_BADOP; |
| 298 | break; |
| 299 | } |
| 300 | |
| 301 | va_end(ap); |
| 302 | return (rc); |
| 303 | } |
| 304 | |
| 305 | static void gfill(grand *r, void *p, size_t sz) |
| 306 | { |
| 307 | gctx *g = (gctx *)r; |
| 308 | dsarand_fill(&g->d, p, sz); |
| 309 | } |
| 310 | |
| 311 | static const grand_ops gops = { |
| 312 | "dsarand", |
| 313 | 0, 0, |
| 314 | gmisc, gdestroy, |
| 315 | grand_word, grand_byte, grand_word, grand_range, gfill |
| 316 | }; |
| 317 | |
| 318 | /* --- @dsarand_create@ --- * |
| 319 | * |
| 320 | * Arguments: @const void *p@ = pointer to seed buffer |
| 321 | * @size_t sz@ = size of seed buffer |
| 322 | * |
| 323 | * Returns: Pointer to a generic generator. |
| 324 | * |
| 325 | * Use: Constructs a generic generator interface over a Catacomb |
| 326 | * entropy pool generator. |
| 327 | */ |
| 328 | |
| 329 | grand *dsarand_create(const void *p, size_t sz) |
| 330 | { |
| 331 | gctx *g = CREATE(gctx); |
| 332 | g->r.ops = &gops; |
| 333 | dsarand_init(&g->d, p, sz); |
| 334 | return (&g->r); |
| 335 | } |
| 336 | |
| 337 | /*----- That's all, folks -------------------------------------------------*/ |