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 #if CPUFAM_X86 || CPUFAM_AMD64
 165 extern int rand_quick_x86ish_rdrand(rand_pool */*r*/);
 166 #endif
 167
 168 static quick__functype *pick_quick(void)
 169 {
 170 #if CPUFAM_X86 || CPUFAM_AMD64
 171   DISPATCH_PICK_COND(rand_quick, rand_quick_x86ish_rdrand,
 172                      cpu_feature_p(CPUFEAT_X86_RDRAND));
 173 #endif
 174   DISPATCH_PICK_FALLBACK(rand_quick, trivial_quick);
 175 }
 176
 177 int rand_quick(rand_pool *r) { RAND_RESOLVE(r); return (quick(r)); }
 178
 179 /* --- @rand_seed@ --- *
 180  *
 181  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 182  *              @unsigned bits@ = number of bits to ensure
 183  *
 184  * Returns:     ---
 185  *
 186  * Use:         Ensures that there are at least @bits@ good bits of entropy
 187  *              in the pool.  It is recommended that you call this after
 188  *              initializing a new pool.  Requesting @bits > RAND_IBITS@ is
 189  *              doomed to failure (and is an error).
 190  */
 191
 192 void rand_seed(rand_pool *r, unsigned bits)
 193 {
 194   RAND_RESOLVE(r);
 195
 196   assert(((void)"bits pointlessly large in rand_seed", bits <= RAND_IBITS));
 197   assert(((void)"no noise source in rand_seed", r->s));
 198
 199   while (r->ibits < bits)
 200     r->s->getnoise(r);
 201   rand_gate(r);
 202 }
 203
 204 /* --- @rand_key@ --- *
 205  *
 206  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 207  *              @const void *k@ = pointer to key data
 208  *              @size_t sz@ = size of key data
 209  *
 210  * Returns:     ---
 211  *
 212  * Use:         Sets the secret key for a randomness pool.  The key is used
 213  *              when mixing in new random bits.
 214  */
 215
 216 void rand_key(rand_pool *r, const void *k, size_t sz)
 217 {
 218   HASH_CTX hc;
 219   octet h[HASH_SZ];
 220   static const char label[] = "Catacomb random pool key";
 221
 222   RAND_RESOLVE(r);
 223
 224   assert(HASH_SZ >= RAND_KEYSZ);
 225   HASH_INIT(&hc);
 226   HASH(&hc, label, sizeof(label));
 227   if (sz) HASH(&hc, k, sz);
 228   HASH_DONE(&hc, h);
 229   memcpy(r->k.k, h, RAND_KEYSZ);
 230 }
 231
 232 /* --- @rand_add@ --- *
 233  *
 234  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 235  *              @const void *p@ = pointer a buffer of data to add
 236  *              @size_t sz@ = size of the data buffer
 237  *              @unsigned goodbits@ = number of good bits estimated in buffer
 238  *
 239  * Returns:     ---
 240  *
 241  * Use:         Mixes the data in the buffer with the contents of the
 242  *              pool.  The estimate of the number of good bits is added to
 243  *              the pool's own count.  The mixing operation is not
 244  *              cryptographically strong.  However, data in the input pool
 245  *              isn't output directly, only through the one-way gating
 246  *              operation, so that shouldn't matter.
 247  */
 248
 249 void rand_add(rand_pool *r, const void *p, size_t sz, unsigned goodbits)
 250 {
 251   const octet *c = p;
 252   int i, rot;
 253
 254   STATIC_ASSERT(RAND_POOLSZ == 128, "Polynomial doesn't match pool size");
 255
 256   RAND_RESOLVE(r);
 257
 258   i = r->i; rot = r->irot;
 259
 260   while (sz) {
 261     octet o = *c++;
 262     r->pool[i] ^= (ROL8(o, rot) ^
 263                    r->pool[(i + 1) % RAND_POOLSZ] ^
 264                    r->pool[(i + 2) % RAND_POOLSZ] ^
 265                    r->pool[(i + 7) % RAND_POOLSZ]);
 266     rot = (rot + 5) & 7;
 267     i++; if (i >= RAND_POOLSZ) i -= RAND_POOLSZ;
 268     sz--;
 269   }
 270
 271   r->i = i;
 272   r->irot = rot;
 273   r->ibits += goodbits;
 274   if (r->ibits > RAND_IBITS)
 275     r->ibits = RAND_IBITS;
 276 }
 277
 278 /* --- @rand_goodbits@ --- *
 279  *
 280  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 281  *
 282  * Returns:     Estimate of the number of good bits remaining in the pool.
 283  */
 284
 285 unsigned rand_goodbits(rand_pool *r)
 286 {
 287   RAND_RESOLVE(r);
 288   return (r->ibits + r->obits);
 289 }
 290
 291 /* --- @rand_gate@ --- *
 292  *
 293  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 294  *
 295  * Returns:     ---
 296  *
 297  * Use:         Mixes up the entire state of the generator in a nonreversible
 298  *              way.
 299  */
 300
 301 void rand_gate(rand_pool *r)
 302 {
 303   octet h[HASH_SZ], g[4];
 304   HASH_CTX hc;
 305   CIPHER_CTX cc;
 306
 307   RAND_RESOLVE(r);
 308   QUICK(r);
 309
 310   /* --- Hash up all the data in the pool --- */
 311
 312   HASH_INIT(&hc);
 313   STORE32(g, r->gen); HASH(&hc, g, sizeof(g));
 314   HASH(&hc, r->k.k, RAND_KEYSZ);
 315   HASH(&hc, r->pool, RAND_POOLSZ);
 316   HASH(&hc, r->buf, RAND_BUFSZ);
 317   HASH_DONE(&hc, h);
 318   BURN(hc);
 319
 320   /* --- Now mangle all of the data based on the hash --- */
 321
 322   assert(CIPHER_KEYSZ <= HASH_SZ);
 323   CIPHER_INIT(&cc, h, CIPHER_KEYSZ, 0);
 324   CIPHER_ENCRYPT(&cc, r->pool, r->pool, RAND_POOLSZ);
 325   CIPHER_ENCRYPT(&cc, r->buf, r->buf, RAND_BUFSZ);
 326   BURN(cc);
 327
 328   /* --- Reset the various state variables --- */
 329
 330   r->o = RAND_SECSZ;
 331   r->obits += r->ibits;
 332   if (r->obits > RAND_OBITS) {
 333     r->ibits = r->obits - r->ibits;
 334     r->obits = RAND_OBITS;
 335   } else
 336     r->ibits = 0;
 337   QUICK(r);
 338 }
 339
 340 /* --- @rand_stretch@ --- *
 341  *
 342  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 343  *
 344  * Returns:     ---
 345  *
 346  * Use:         Stretches the contents of the output buffer by transforming
 347  *              it in a nonreversible way.  This doesn't add any entropy
 348  *              worth speaking about, but it works well enough when the
 349  *              caller doesn't care about that sort of thing.
 350  */
 351
 352 void rand_stretch(rand_pool *r)
 353 {
 354   octet h[HASH_SZ], g[4];
 355   HASH_CTX hc;
 356   CIPHER_CTX cc;
 357
 358   RAND_RESOLVE(r);
 359   QUICK(r);
 360
 361   /* --- Hash up all the data in the buffer --- */
 362
 363   HASH_INIT(&hc);
 364   STORE32(g, r->gen); HASH(&hc, g, sizeof(g));
 365   HASH(&hc, r->k.k, RAND_KEYSZ);
 366   HASH(&hc, r->pool, RAND_POOLSZ);
 367   HASH(&hc, r->buf, RAND_BUFSZ);
 368   HASH_DONE(&hc, h);
 369   BURN(hc);
 370
 371   /* --- Now mangle the buffer based on the hash --- */
 372
 373   assert(CIPHER_KEYSZ <= HASH_SZ);
 374   CIPHER_INIT(&cc, h, CIPHER_KEYSZ, 0);
 375   CIPHER_ENCRYPT(&cc, r->buf, r->buf, RAND_BUFSZ);
 376   BURN(cc);
 377
 378   /* --- Reset the various state variables --- */
 379
 380   r->o = RAND_SECSZ;
 381   QUICK(r);
 382 }
 383
 384 /* --- @rand_get@ --- *
 385  *
 386  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 387  *              @void *p@ = pointer to output buffer
 388  *              @size_t sz@ = size of output buffer
 389  *
 390  * Returns:     ---
 391  *
 392  * Use:         Gets random data from the pool.  The pool's contents can't be
 393  *              determined from the output of this function; nor can the
 394  *              output data be determined from a knowledge of the data input
 395  *              to the pool wihtout also having knowledge of the secret key.
 396  *              The good bits counter is decremented, although no special
 397  *              action is taken if it reaches zero.
 398  */
 399
 400 void rand_get(rand_pool *r, void *p, size_t sz)
 401 {
 402   octet *o = p;
 403
 404   RAND_RESOLVE(r);
 405   GENCHECK(r);
 406   QUICK(r);
 407
 408   if (!sz)
 409     return;
 410   for (;;) {
 411     if (r->o + sz <= RAND_BUFSZ) {
 412       memcpy(o, r->buf + r->o, sz);
 413       r->o += sz;
 414       break;
 415     } else {
 416       size_t chunk = RAND_BUFSZ - r->o;
 417       if (chunk) {
 418         memcpy(o, r->buf + r->o, chunk);
 419         sz -= chunk;
 420         o += chunk;
 421       }
 422       rand_stretch(r);
 423     }
 424   }
 425
 426   if (r->obits > sz * 8)
 427     r->obits -= sz * 8;
 428   else
 429     r->obits = 0;
 430 }
 431
 432 /* --- @rand_getgood@ --- *
 433  *
 434  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 435  *              @void *p@ = pointer to output buffer
 436  *              @size_t sz@ = size of output buffer
 437  *
 438  * Returns:     ---
 439  *
 440  * Use:         Gets random data from the pool, ensuring that there are
 441  *              enough good bits.  This interface isn't recommended: it makes
 442  *              the generator slow, and doesn't provide much more security
 443  *              than @rand_get@, assuming you've previously done a
 444  *              @rand_seed@.
 445  */
 446
 447 void rand_getgood(rand_pool *r, void *p, size_t sz)
 448 {
 449   octet *o = p;
 450
 451   RAND_RESOLVE(r);
 452
 453   if (!sz)
 454     return;
 455   if (!r->s || !r->s->getnoise) {
 456     rand_get(r, p, sz);
 457     return;
 458   }
 459   GENCHECK(r);
 460   QUICK(r);
 461
 462   while (sz) {
 463     size_t chunk = sz;
 464
 465     if (chunk * 8 > r->obits) {
 466       if (chunk * 8 > r->ibits + r->obits)
 467         do r->s->getnoise(r); while (r->ibits + r->obits < 256);
 468       rand_gate(r);
 469       if (chunk * 8 > r->obits)
 470         chunk = r->obits / 8;
 471     }
 472
 473     if (chunk + r->o > RAND_BUFSZ)
 474       chunk = RAND_BUFSZ - r->o;
 475
 476     memcpy(o, r->buf + r->o, chunk);
 477     r->o += chunk;
 478     r->obits -= chunk * 8;
 479     o += chunk;
 480     sz -= chunk;
 481   }
 482 }
 483
 484 /*----- Generic random number generator interface -------------------------*/
 485
 486 static void gdestroy(grand *r)
 487 {
 488   gctx *g = (gctx *)r;
 489   if (g != &rand_global) {
 490     BURN(*g);
 491     S_DESTROY(g);
 492   }
 493 }
 494
 495 static int gmisc(grand *r, unsigned op, ...)
 496 {
 497   gctx *g = (gctx *)r;
 498   va_list ap;
 499   int rc = 0;
 500   va_start(ap, op);
 501
 502   switch (op) {
 503     case GRAND_CHECK:
 504       switch (va_arg(ap, unsigned)) {
 505         case GRAND_CHECK:
 506         case GRAND_SEEDINT:
 507         case GRAND_SEEDUINT32:
 508         case GRAND_SEEDBLOCK:
 509         case GRAND_SEEDRAND:
 510         case RAND_GATE:
 511         case RAND_STRETCH:
 512         case RAND_KEY:
 513         case RAND_NOISESRC:
 514         case RAND_SEED:
 515         case RAND_TIMER:
 516         case RAND_GOODBITS:
 517         case RAND_ADD:
 518           rc = 1;
 519           break;
 520         default:
 521           rc = 0;
 522           break;
 523       }
 524       break;
 525     case GRAND_SEEDINT: {
 526       unsigned u = va_arg(ap, unsigned);
 527       rand_add(&g->p, &u, sizeof(u), sizeof(u));
 528     } break;
 529     case GRAND_SEEDUINT32: {
 530       uint32 i = va_arg(ap, uint32);
 531       rand_add(&g->p, &i, sizeof(i), 4);
 532     } break;
 533     case GRAND_SEEDBLOCK: {
 534       const void *p = va_arg(ap, const void *);
 535       size_t sz = va_arg(ap, size_t);
 536       rand_add(&g->p, p, sz, sz);
 537     } break;
 538     case GRAND_SEEDRAND: {
 539       grand *rr = va_arg(ap, grand *);
 540       octet buf[16];
 541       rr->ops->fill(rr, buf, sizeof(buf));
 542       rand_add(&g->p, buf, sizeof(buf), 8);
 543     } break;
 544     case RAND_GATE:
 545       rand_gate(&g->p);
 546       break;
 547     case RAND_STRETCH:
 548       rand_stretch(&g->p);
 549       break;
 550     case RAND_KEY: {
 551       const void *k = va_arg(ap, const void *);
 552       size_t sz = va_arg(ap, size_t);
 553       rand_key(&g->p, k, sz);
 554     } break;
 555     case RAND_NOISESRC:
 556       rand_noisesrc(&g->p, va_arg(ap, const rand_source *));
 557       break;
 558     case RAND_SEED:
 559       rand_seed(&g->p, va_arg(ap, unsigned));
 560       break;
 561     case RAND_TIMER:
 562       QUICK(&g->p);
 563       break;
 564     case RAND_GOODBITS:
 565       rc = rand_goodbits(&g->p);
 566       break;
 567     case RAND_ADD: {
 568       const void *p = va_arg(ap, const void *);
 569       size_t sz = va_arg(ap, size_t);
 570       unsigned goodbits = va_arg(ap, unsigned);
 571       rand_add(&g->p, p, sz, goodbits);
 572     } break;
 573     default:
 574       GRAND_BADOP;
 575       break;
 576   }
 577
 578   va_end(ap);
 579   return (rc);
 580 }
 581
 582 static octet gbyte(grand *r)
 583 {
 584   gctx *g = (gctx *)r;
 585   octet o;
 586   rand_getgood(&g->p, &o, 1);
 587   return (o);
 588 }
 589
 590 static uint32 gword(grand *r)
 591 {
 592   gctx *g = (gctx *)r;
 593   octet b[4];
 594   rand_getgood(&g->p, &b, sizeof(b));
 595   return (LOAD32(b));
 596 }
 597
 598 static void gfill(grand *r, void *p, size_t sz)
 599 {
 600   gctx *g = (gctx *)r;
 601   rand_get(&g->p, p, sz);
 602 }
 603
 604 static const grand_ops gops = {
 605   "rand",
 606   GRAND_CRYPTO, 0,
 607   gmisc, gdestroy,
 608   gword, gbyte, gword, grand_defaultrange, gfill
 609 };
 610
 611 /* --- @rand_create@ --- *
 612  *
 613  * Arguments:   ---
 614  *
 615  * Returns:     Pointer to a generic generator.
 616  *
 617  * Use:         Constructs a generic generator interface over a Catacomb
 618  *              entropy pool generator.
 619  */
 620
 621 grand *rand_create(void)
 622 {
 623   gctx *g = S_CREATE(gctx);
 624   g->r.ops = &gops;
 625   rand_init(&g->p);
 626   return (&g->r);
 627 }
 628
 629 /*----- That's all, folks -------------------------------------------------*/