mdw@git.distorted.org.uk Git - catacomb/blob - rand/rand.c

   1 /* -*-c-*-
   2  *
   3  * Secure random number generator
   4  *
   5  * (c) 1998 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of Catacomb.
  11  *
  12  * Catacomb is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU Library General Public License as
  14  * published by the Free Software Foundation; either version 2 of the
  15  * License, or (at your option) any later version.
  16  *
  17  * Catacomb is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU Library General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Library General Public
  23  * License along with Catacomb; if not, write to the Free
  24  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  25  * MA 02111-1307, USA.
  26  */
  27
  28 /*----- Header files ------------------------------------------------------*/
  29
  30 #include "config.h"
  31
  32 #include <stdarg.h>
  33 #include <stdio.h>
  34 #include <string.h>
  35
  36 #include <mLib/bits.h>
  37 #include <mLib/sub.h>
  38
  39 #include "arena.h"
  40 #include "dispatch.h"
  41 #include "paranoia.h"
  42
  43 #define RAND__HACKS
  44 #include "rand.h"
  45
  46 #include "noise.h"
  47
  48 #include "twofish-counter.h"
  49 #include "sha256.h"
  50
  51 #define CIPHER_CTX twofish_counterctx
  52 #define CIPHER_INIT twofish_counterinit
  53 #define CIPHER_ENCRYPT twofish_counterencrypt
  54 #define CIPHER_IVSZ TWOFISH_BLKSZ
  55 #define CIPHER_KEYSZ TWOFISH_KEYSZ
  56
  57 #define HASH_CTX sha256_ctx
  58 #define HASH_INIT sha256_init
  59 #define HASH sha256_hash
  60 #define HASH_DONE sha256_done
  61 #define HASH_SZ SHA256_HASHSZ
  62
  63 /*----- Static variables --------------------------------------------------*/
  64
  65 static const grand_ops gops;
  66
  67 typedef struct rand__gctx {
  68   grand r;
  69   rand_pool p;
  70 } gctx;
  71
  72 gctx rand_global = {
  73   { &gops },
  74   { { 0 }, 0, 0, 0, 0,
  75     { 0 }, RAND_SECSZ, 0,
  76     { "Catacomb global random byte pool" },
  77     &noise_source }
  78 };
  79
  80 /*----- Macros ------------------------------------------------------------*/
  81
  82 #define RAND_RESOLVE(r)                                                 \
  83   do { if ((r) == RAND_GLOBAL) r = &rand_global.p; } while (0)
  84
  85 #define GENCHECK(r) do {                                                \
  86   unsigned gen = rand_generation();                                     \
  87   if (r->gen != gen) { r->gen = gen; rand_gate(r); }                    \
  88 } while (0)
  89
  90 static int quick(rand_pool *);
  91 #define QUICK(r) do {                                                   \
  92   quick(r);                                                             \
  93   if ((r)->s && (r)->s->timer) (r)->s->timer(r);                        \
  94 } while (0)
  95
  96 /*----- Main code ---------------------------------------------------------*/
  97
  98 /* --- @rand_init@ --- *
  99  *
 100  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 101  *
 102  * Returns:     ---
 103  *
 104  * Use:         Initializes a randomness pool.  The pool doesn't start out
 105  *              very random: that's your job to sort out.  A good suggestion
 106  *              would be to attach an appropriate noise source and call
 107  *              @rand_seed@.
 108  */
 109
 110 void rand_init(rand_pool *r)
 111 {
 112   RAND_RESOLVE(r);
 113   memset(r->pool, 0, sizeof(r->pool));
 114   memset(r->buf, 0, sizeof(r->buf));
 115   r->gen = rand_generation();
 116   r->i = 0;
 117   r->irot = 0;
 118   r->ibits = r->obits = 0;
 119   r->o = RAND_SECSZ;
 120   r->s = &noise_source;
 121   rand_key(r, 0, 0);
 122   rand_gate(r);
 123 }
 124
 125 /* --- @rand_noisesrc@ --- *
 126  *
 127  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 128  *              @const rand_source *s@ = pointer to source definition
 129  *
 130  * Returns:     ---
 131  *
 132  * Use:         Sets a noise source for a randomness pool.  When the pool's
 133  *              estimate of good random bits falls to zero, the @getnoise@
 134  *              function is called, passing the pool handle as an argument.
 135  *              It is expected to increase the number of good bits by at
 136  *              least one, because it'll be called over and over again until
 137  *              there are enough bits to satisfy the caller.  The @timer@
 138  *              function is called frequently throughout the generator's
 139  *              operation.
 140  */
 141
 142 void rand_noisesrc(rand_pool *r, const rand_source *s)
 143 {
 144   RAND_RESOLVE(r);
 145   r->s = s;
 146 }
 147
 148 /* --- @rand_quick@ --- *
 149  *
 150  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 151  *
 152  * Returns:     Zero on success; @-1@ on failure.
 153  *
 154  * Use          Attempts to use some machine-specific `quick' source of
 155  *              entropy to top up @r@.  This may not do anything at all on
 156  *              many systems.
 157  */
 158
 159 CPU_DISPATCH(static, return, int, quick, (rand_pool *r), (r),
 160              pick_quick, trivial_quick);
 161
 162 static int trivial_quick(rand_pool *r) { return (-1); }
 163
 164 static quick__functype *pick_quick(void)
 165 {
 166   DISPATCH_PICK_FALLBACK(rand_quick, trivial_quick);
 167 }
 168
 169 int rand_quick(rand_pool *r) { RAND_RESOLVE(r); return (quick(r)); }
 170
 171 /* --- @rand_seed@ --- *
 172  *
 173  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 174  *              @unsigned bits@ = number of bits to ensure
 175  *
 176  * Returns:     ---
 177  *
 178  * Use:         Ensures that there are at least @bits@ good bits of entropy
 179  *              in the pool.  It is recommended that you call this after
 180  *              initializing a new pool.  Requesting @bits > RAND_IBITS@ is
 181  *              doomed to failure (and is an error).
 182  */
 183
 184 void rand_seed(rand_pool *r, unsigned bits)
 185 {
 186   RAND_RESOLVE(r);
 187
 188   assert(((void)"bits pointlessly large in rand_seed", bits <= RAND_IBITS));
 189   assert(((void)"no noise source in rand_seed", r->s));
 190
 191   while (r->ibits < bits)
 192     r->s->getnoise(r);
 193   rand_gate(r);
 194 }
 195
 196 /* --- @rand_key@ --- *
 197  *
 198  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 199  *              @const void *k@ = pointer to key data
 200  *              @size_t sz@ = size of key data
 201  *
 202  * Returns:     ---
 203  *
 204  * Use:         Sets the secret key for a randomness pool.  The key is used
 205  *              when mixing in new random bits.
 206  */
 207
 208 void rand_key(rand_pool *r, const void *k, size_t sz)
 209 {
 210   HASH_CTX hc;
 211   octet h[HASH_SZ];
 212   static const char label[] = "Catacomb random pool key";
 213
 214   RAND_RESOLVE(r);
 215
 216   assert(HASH_SZ >= RAND_KEYSZ);
 217   HASH_INIT(&hc);
 218   HASH(&hc, label, sizeof(label));
 219   if (sz) HASH(&hc, k, sz);
 220   HASH_DONE(&hc, h);
 221   memcpy(r->k.k, h, RAND_KEYSZ);
 222 }
 223
 224 /* --- @rand_add@ --- *
 225  *
 226  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 227  *              @const void *p@ = pointer a buffer of data to add
 228  *              @size_t sz@ = size of the data buffer
 229  *              @unsigned goodbits@ = number of good bits estimated in buffer
 230  *
 231  * Returns:     ---
 232  *
 233  * Use:         Mixes the data in the buffer with the contents of the
 234  *              pool.  The estimate of the number of good bits is added to
 235  *              the pool's own count.  The mixing operation is not
 236  *              cryptographically strong.  However, data in the input pool
 237  *              isn't output directly, only through the one-way gating
 238  *              operation, so that shouldn't matter.
 239  */
 240
 241 void rand_add(rand_pool *r, const void *p, size_t sz, unsigned goodbits)
 242 {
 243   const octet *c = p;
 244   int i, rot;
 245
 246 #if RAND_POOLSZ != 128
 247 #  error Polynomial in rand_add is out of date.  Fix it.
 248 #endif
 249
 250   RAND_RESOLVE(r);
 251
 252   i = r->i; rot = r->irot;
 253
 254   while (sz) {
 255     octet o = *c++;
 256     r->pool[i] ^= (ROL8(o, rot) ^
 257                    r->pool[(i + 1) % RAND_POOLSZ] ^
 258                    r->pool[(i + 2) % RAND_POOLSZ] ^
 259                    r->pool[(i + 7) % RAND_POOLSZ]);
 260     rot = (rot + 5) & 7;
 261     i++; if (i >= RAND_POOLSZ) i -= RAND_POOLSZ;
 262     sz--;
 263   }
 264
 265   r->i = i;
 266   r->irot = rot;
 267   r->ibits += goodbits;
 268   if (r->ibits > RAND_IBITS)
 269     r->ibits = RAND_IBITS;
 270 }
 271
 272 /* --- @rand_goodbits@ --- *
 273  *
 274  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 275  *
 276  * Returns:     Estimate of the number of good bits remaining in the pool.
 277  */
 278
 279 unsigned rand_goodbits(rand_pool *r)
 280 {
 281   RAND_RESOLVE(r);
 282   return (r->ibits + r->obits);
 283 }
 284
 285 /* --- @rand_gate@ --- *
 286  *
 287  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 288  *
 289  * Returns:     ---
 290  *
 291  * Use:         Mixes up the entire state of the generator in a nonreversible
 292  *              way.
 293  */
 294
 295 void rand_gate(rand_pool *r)
 296 {
 297   octet h[HASH_SZ], g[4];
 298   HASH_CTX hc;
 299   CIPHER_CTX cc;
 300
 301   RAND_RESOLVE(r);
 302   QUICK(r);
 303
 304   /* --- Hash up all the data in the pool --- */
 305
 306   HASH_INIT(&hc);
 307   STORE32(g, r->gen); HASH(&hc, g, sizeof(g));
 308   HASH(&hc, r->pool, RAND_POOLSZ);
 309   HASH(&hc, r->buf, RAND_BUFSZ);
 310   HASH_DONE(&hc, h);
 311   BURN(hc);
 312
 313   /* --- Now mangle all of the data based on the hash --- */
 314
 315   assert(CIPHER_KEYSZ <= HASH_SZ);
 316   CIPHER_INIT(&cc, h, CIPHER_KEYSZ, 0);
 317   CIPHER_ENCRYPT(&cc, r->pool, r->pool, RAND_POOLSZ);
 318   CIPHER_ENCRYPT(&cc, r->buf, r->buf, RAND_BUFSZ);
 319   BURN(cc);
 320
 321   /* --- Reset the various state variables --- */
 322
 323   r->o = RAND_SECSZ;
 324   r->obits += r->ibits;
 325   if (r->obits > RAND_OBITS) {
 326     r->ibits = r->obits - r->ibits;
 327     r->obits = RAND_OBITS;
 328   } else
 329     r->ibits = 0;
 330   QUICK(r);
 331 }
 332
 333 /* --- @rand_stretch@ --- *
 334  *
 335  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 336  *
 337  * Returns:     ---
 338  *
 339  * Use:         Stretches the contents of the output buffer by transforming
 340  *              it in a nonreversible way.  This doesn't add any entropy
 341  *              worth speaking about, but it works well enough when the
 342  *              caller doesn't care about that sort of thing.
 343  */
 344
 345 void rand_stretch(rand_pool *r)
 346 {
 347   octet h[HASH_SZ], g[4];
 348   HASH_CTX hc;
 349   CIPHER_CTX cc;
 350
 351   RAND_RESOLVE(r);
 352   QUICK(r);
 353
 354   /* --- Hash up all the data in the buffer --- */
 355
 356   HASH_INIT(&hc);
 357   STORE32(g, r->gen); HASH(&hc, g, sizeof(g));
 358   HASH(&hc, r->pool, RAND_POOLSZ);
 359   HASH(&hc, r->buf, RAND_BUFSZ);
 360   HASH_DONE(&hc, h);
 361   BURN(hc);
 362
 363   /* --- Now mangle the buffer based on the hash --- */
 364
 365   assert(CIPHER_KEYSZ <= HASH_SZ);
 366   CIPHER_INIT(&cc, h, CIPHER_KEYSZ, 0);
 367   CIPHER_ENCRYPT(&cc, r->buf, r->buf, RAND_BUFSZ);
 368   BURN(cc);
 369
 370   /* --- Reset the various state variables --- */
 371
 372   r->o = RAND_SECSZ;
 373   QUICK(r);
 374 }
 375
 376 /* --- @rand_get@ --- *
 377  *
 378  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 379  *              @void *p@ = pointer to output buffer
 380  *              @size_t sz@ = size of output buffer
 381  *
 382  * Returns:     ---
 383  *
 384  * Use:         Gets random data from the pool.  The pool's contents can't be
 385  *              determined from the output of this function; nor can the
 386  *              output data be determined from a knowledge of the data input
 387  *              to the pool wihtout also having knowledge of the secret key.
 388  *              The good bits counter is decremented, although no special
 389  *              action is taken if it reaches zero.
 390  */
 391
 392 void rand_get(rand_pool *r, void *p, size_t sz)
 393 {
 394   octet *o = p;
 395
 396   RAND_RESOLVE(r);
 397   GENCHECK(r);
 398   QUICK(r);
 399
 400   if (!sz)
 401     return;
 402   for (;;) {
 403     if (r->o + sz <= RAND_BUFSZ) {
 404       memcpy(o, r->buf + r->o, sz);
 405       r->o += sz;
 406       break;
 407     } else {
 408       size_t chunk = RAND_BUFSZ - r->o;
 409       if (chunk) {
 410         memcpy(o, r->buf + r->o, chunk);
 411         sz -= chunk;
 412         o += chunk;
 413       }
 414       rand_stretch(r);
 415     }
 416   }
 417
 418   if (r->obits > sz * 8)
 419     r->obits -= sz * 8;
 420   else
 421     r->obits = 0;
 422 }
 423
 424 /* --- @rand_getgood@ --- *
 425  *
 426  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 427  *              @void *p@ = pointer to output buffer
 428  *              @size_t sz@ = size of output buffer
 429  *
 430  * Returns:     ---
 431  *
 432  * Use:         Gets random data from the pool, ensuring that there are
 433  *              enough good bits.  This interface isn't recommended: it makes
 434  *              the generator slow, and doesn't provide much more security
 435  *              than @rand_get@, assuming you've previously done a
 436  *              @rand_seed@.
 437  */
 438
 439 void rand_getgood(rand_pool *r, void *p, size_t sz)
 440 {
 441   octet *o = p;
 442
 443   RAND_RESOLVE(r);
 444
 445   if (!sz)
 446     return;
 447   if (!r->s || !r->s->getnoise) {
 448     rand_get(r, p, sz);
 449     return;
 450   }
 451   GENCHECK(r);
 452   QUICK(r);
 453
 454   while (sz) {
 455     size_t chunk = sz;
 456
 457     if (chunk * 8 > r->obits) {
 458       if (chunk * 8 > r->ibits + r->obits)
 459         do r->s->getnoise(r); while (r->ibits + r->obits < 256);
 460       rand_gate(r);
 461       if (chunk * 8 > r->obits)
 462         chunk = r->obits / 8;
 463     }
 464
 465     if (chunk + r->o > RAND_BUFSZ)
 466       chunk = RAND_BUFSZ - r->o;
 467
 468     memcpy(o, r->buf + r->o, chunk);
 469     r->o += chunk;
 470     r->obits -= chunk * 8;
 471     o += chunk;
 472     sz -= chunk;
 473   }
 474 }
 475
 476 /*----- Generic random number generator interface -------------------------*/
 477
 478 static void gdestroy(grand *r)
 479 {
 480   gctx *g = (gctx *)r;
 481   if (g != &rand_global) {
 482     BURN(*g);
 483     S_DESTROY(g);
 484   }
 485 }
 486
 487 static int gmisc(grand *r, unsigned op, ...)
 488 {
 489   gctx *g = (gctx *)r;
 490   va_list ap;
 491   int rc = 0;
 492   va_start(ap, op);
 493
 494   switch (op) {
 495     case GRAND_CHECK:
 496       switch (va_arg(ap, unsigned)) {
 497         case GRAND_CHECK:
 498         case GRAND_SEEDINT:
 499         case GRAND_SEEDUINT32:
 500         case GRAND_SEEDBLOCK:
 501         case GRAND_SEEDRAND:
 502         case RAND_GATE:
 503         case RAND_STRETCH:
 504         case RAND_KEY:
 505         case RAND_NOISESRC:
 506         case RAND_SEED:
 507         case RAND_TIMER:
 508         case RAND_GOODBITS:
 509         case RAND_ADD:
 510           rc = 1;
 511           break;
 512         default:
 513           rc = 0;
 514           break;
 515       }
 516       break;
 517     case GRAND_SEEDINT: {
 518       unsigned u = va_arg(ap, unsigned);
 519       rand_add(&g->p, &u, sizeof(u), sizeof(u));
 520     } break;
 521     case GRAND_SEEDUINT32: {
 522       uint32 i = va_arg(ap, uint32);
 523       rand_add(&g->p, &i, sizeof(i), 4);
 524     } break;
 525     case GRAND_SEEDBLOCK: {
 526       const void *p = va_arg(ap, const void *);
 527       size_t sz = va_arg(ap, size_t);
 528       rand_add(&g->p, p, sz, sz);
 529     } break;
 530     case GRAND_SEEDRAND: {
 531       grand *rr = va_arg(ap, grand *);
 532       octet buf[16];
 533       rr->ops->fill(rr, buf, sizeof(buf));
 534       rand_add(&g->p, buf, sizeof(buf), 8);
 535     } break;
 536     case RAND_GATE:
 537       rand_gate(&g->p);
 538       break;
 539     case RAND_STRETCH:
 540       rand_stretch(&g->p);
 541       break;
 542     case RAND_KEY: {
 543       const void *k = va_arg(ap, const void *);
 544       size_t sz = va_arg(ap, size_t);
 545       rand_key(&g->p, k, sz);
 546     } break;
 547     case RAND_NOISESRC:
 548       rand_noisesrc(&g->p, va_arg(ap, const rand_source *));
 549       break;
 550     case RAND_SEED:
 551       rand_seed(&g->p, va_arg(ap, unsigned));
 552       break;
 553     case RAND_TIMER:
 554       QUICK(&g->p);
 555       break;
 556     case RAND_GOODBITS:
 557       rc = rand_goodbits(&g->p);
 558       break;
 559     case RAND_ADD: {
 560       const void *p = va_arg(ap, const void *);
 561       size_t sz = va_arg(ap, size_t);
 562       unsigned goodbits = va_arg(ap, unsigned);
 563       rand_add(&g->p, p, sz, goodbits);
 564     } break;
 565     default:
 566       GRAND_BADOP;
 567       break;
 568   }
 569
 570   va_end(ap);
 571   return (rc);
 572 }
 573
 574 static octet gbyte(grand *r)
 575 {
 576   gctx *g = (gctx *)r;
 577   octet o;
 578   rand_getgood(&g->p, &o, 1);
 579   return (o);
 580 }
 581
 582 static uint32 gword(grand *r)
 583 {
 584   gctx *g = (gctx *)r;
 585   octet b[4];
 586   rand_getgood(&g->p, &b, sizeof(b));
 587   return (LOAD32(b));
 588 }
 589
 590 static void gfill(grand *r, void *p, size_t sz)
 591 {
 592   gctx *g = (gctx *)r;
 593   rand_get(&g->p, p, sz);
 594 }
 595
 596 static const grand_ops gops = {
 597   "rand",
 598   GRAND_CRYPTO, 0,
 599   gmisc, gdestroy,
 600   gword, gbyte, gword, grand_defaultrange, gfill
 601 };
 602
 603 /* --- @rand_create@ --- *
 604  *
 605  * Arguments:   ---
 606  *
 607  * Returns:     Pointer to a generic generator.
 608  *
 609  * Use:         Constructs a generic generator interface over a Catacomb
 610  *              entropy pool generator.
 611  */
 612
 613 grand *rand_create(void)
 614 {
 615   gctx *g = S_CREATE(gctx);
 616   g->r.ops = &gops;
 617   rand_init(&g->p);
 618   return (&g->r);
 619 }
 620
 621 /*----- That's all, folks -------------------------------------------------*/