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 __GNUC__ && (CPUFAM_X86 || CPUFAM_AMD64)
 165 static int rdrand_quick(rand_pool *r)
 166 {
 167   unsigned long rr;
 168   unsigned char w;
 169   int i;
 170
 171   for (i = 0; i < 16; i++) {
 172     __asm__ ("rdrand %0; setc %1" : "=r" (rr), "=g" (w) : : "cc");
 173     if (w) {
 174       rand_add(r, &rr, sizeof(rr), 8*sizeof(rr));
 175       return (0);
 176     }
 177   }
 178   return (-1);
 179 }
 180 #endif
 181
 182 static quick__functype *pick_quick(void)
 183 {
 184 #if __GNUC__ && (CPUFAM_X86 || CPUFAM_AMD64)
 185   DISPATCH_PICK_COND(rand_quick, rdrand_quick,
 186                      cpu_feature_p(CPUFEAT_X86_RDRAND));
 187 #endif
 188   DISPATCH_PICK_FALLBACK(rand_quick, trivial_quick);
 189 }
 190
 191 int rand_quick(rand_pool *r) { RAND_RESOLVE(r); return (quick(r)); }
 192
 193 /* --- @rand_seed@ --- *
 194  *
 195  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 196  *              @unsigned bits@ = number of bits to ensure
 197  *
 198  * Returns:     ---
 199  *
 200  * Use:         Ensures that there are at least @bits@ good bits of entropy
 201  *              in the pool.  It is recommended that you call this after
 202  *              initializing a new pool.  Requesting @bits > RAND_IBITS@ is
 203  *              doomed to failure (and is an error).
 204  */
 205
 206 void rand_seed(rand_pool *r, unsigned bits)
 207 {
 208   RAND_RESOLVE(r);
 209
 210   assert(((void)"bits pointlessly large in rand_seed", bits <= RAND_IBITS));
 211   assert(((void)"no noise source in rand_seed", r->s));
 212
 213   while (r->ibits < bits)
 214     r->s->getnoise(r);
 215   rand_gate(r);
 216 }
 217
 218 /* --- @rand_key@ --- *
 219  *
 220  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 221  *              @const void *k@ = pointer to key data
 222  *              @size_t sz@ = size of key data
 223  *
 224  * Returns:     ---
 225  *
 226  * Use:         Sets the secret key for a randomness pool.  The key is used
 227  *              when mixing in new random bits.
 228  */
 229
 230 void rand_key(rand_pool *r, const void *k, size_t sz)
 231 {
 232   HASH_CTX hc;
 233   octet h[HASH_SZ];
 234   static const char label[] = "Catacomb random pool key";
 235
 236   RAND_RESOLVE(r);
 237
 238   assert(HASH_SZ >= RAND_KEYSZ);
 239   HASH_INIT(&hc);
 240   HASH(&hc, label, sizeof(label));
 241   if (sz) HASH(&hc, k, sz);
 242   HASH_DONE(&hc, h);
 243   memcpy(r->k.k, h, RAND_KEYSZ);
 244 }
 245
 246 /* --- @rand_add@ --- *
 247  *
 248  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 249  *              @const void *p@ = pointer a buffer of data to add
 250  *              @size_t sz@ = size of the data buffer
 251  *              @unsigned goodbits@ = number of good bits estimated in buffer
 252  *
 253  * Returns:     ---
 254  *
 255  * Use:         Mixes the data in the buffer with the contents of the
 256  *              pool.  The estimate of the number of good bits is added to
 257  *              the pool's own count.  The mixing operation is not
 258  *              cryptographically strong.  However, data in the input pool
 259  *              isn't output directly, only through the one-way gating
 260  *              operation, so that shouldn't matter.
 261  */
 262
 263 void rand_add(rand_pool *r, const void *p, size_t sz, unsigned goodbits)
 264 {
 265   const octet *c = p;
 266   int i, rot;
 267
 268 #if RAND_POOLSZ != 128
 269 #  error Polynomial in rand_add is out of date.  Fix it.
 270 #endif
 271
 272   RAND_RESOLVE(r);
 273
 274   i = r->i; rot = r->irot;
 275
 276   while (sz) {
 277     octet o = *c++;
 278     r->pool[i] ^= (ROL8(o, rot) ^
 279                    r->pool[(i + 1) % RAND_POOLSZ] ^
 280                    r->pool[(i + 2) % RAND_POOLSZ] ^
 281                    r->pool[(i + 7) % RAND_POOLSZ]);
 282     rot = (rot + 5) & 7;
 283     i++; if (i >= RAND_POOLSZ) i -= RAND_POOLSZ;
 284     sz--;
 285   }
 286
 287   r->i = i;
 288   r->irot = rot;
 289   r->ibits += goodbits;
 290   if (r->ibits > RAND_IBITS)
 291     r->ibits = RAND_IBITS;
 292 }
 293
 294 /* --- @rand_goodbits@ --- *
 295  *
 296  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 297  *
 298  * Returns:     Estimate of the number of good bits remaining in the pool.
 299  */
 300
 301 unsigned rand_goodbits(rand_pool *r)
 302 {
 303   RAND_RESOLVE(r);
 304   return (r->ibits + r->obits);
 305 }
 306
 307 /* --- @rand_gate@ --- *
 308  *
 309  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 310  *
 311  * Returns:     ---
 312  *
 313  * Use:         Mixes up the entire state of the generator in a nonreversible
 314  *              way.
 315  */
 316
 317 void rand_gate(rand_pool *r)
 318 {
 319   octet h[HASH_SZ], g[4];
 320   HASH_CTX hc;
 321   CIPHER_CTX cc;
 322
 323   RAND_RESOLVE(r);
 324   QUICK(r);
 325
 326   /* --- Hash up all the data in the pool --- */
 327
 328   HASH_INIT(&hc);
 329   STORE32(g, r->gen); HASH(&hc, g, sizeof(g));
 330   HASH(&hc, r->pool, RAND_POOLSZ);
 331   HASH(&hc, r->buf, RAND_BUFSZ);
 332   HASH_DONE(&hc, h);
 333   BURN(hc);
 334
 335   /* --- Now mangle all of the data based on the hash --- */
 336
 337   assert(CIPHER_KEYSZ <= HASH_SZ);
 338   CIPHER_INIT(&cc, h, CIPHER_KEYSZ, 0);
 339   CIPHER_ENCRYPT(&cc, r->pool, r->pool, RAND_POOLSZ);
 340   CIPHER_ENCRYPT(&cc, r->buf, r->buf, RAND_BUFSZ);
 341   BURN(cc);
 342
 343   /* --- Reset the various state variables --- */
 344
 345   r->o = RAND_SECSZ;
 346   r->obits += r->ibits;
 347   if (r->obits > RAND_OBITS) {
 348     r->ibits = r->obits - r->ibits;
 349     r->obits = RAND_OBITS;
 350   } else
 351     r->ibits = 0;
 352   QUICK(r);
 353 }
 354
 355 /* --- @rand_stretch@ --- *
 356  *
 357  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 358  *
 359  * Returns:     ---
 360  *
 361  * Use:         Stretches the contents of the output buffer by transforming
 362  *              it in a nonreversible way.  This doesn't add any entropy
 363  *              worth speaking about, but it works well enough when the
 364  *              caller doesn't care about that sort of thing.
 365  */
 366
 367 void rand_stretch(rand_pool *r)
 368 {
 369   octet h[HASH_SZ], g[4];
 370   HASH_CTX hc;
 371   CIPHER_CTX cc;
 372
 373   RAND_RESOLVE(r);
 374   QUICK(r);
 375
 376   /* --- Hash up all the data in the buffer --- */
 377
 378   HASH_INIT(&hc);
 379   STORE32(g, r->gen); HASH(&hc, g, sizeof(g));
 380   HASH(&hc, r->pool, RAND_POOLSZ);
 381   HASH(&hc, r->buf, RAND_BUFSZ);
 382   HASH_DONE(&hc, h);
 383   BURN(hc);
 384
 385   /* --- Now mangle the buffer based on the hash --- */
 386
 387   assert(CIPHER_KEYSZ <= HASH_SZ);
 388   CIPHER_INIT(&cc, h, CIPHER_KEYSZ, 0);
 389   CIPHER_ENCRYPT(&cc, r->buf, r->buf, RAND_BUFSZ);
 390   BURN(cc);
 391
 392   /* --- Reset the various state variables --- */
 393
 394   r->o = RAND_SECSZ;
 395   QUICK(r);
 396 }
 397
 398 /* --- @rand_get@ --- *
 399  *
 400  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 401  *              @void *p@ = pointer to output buffer
 402  *              @size_t sz@ = size of output buffer
 403  *
 404  * Returns:     ---
 405  *
 406  * Use:         Gets random data from the pool.  The pool's contents can't be
 407  *              determined from the output of this function; nor can the
 408  *              output data be determined from a knowledge of the data input
 409  *              to the pool wihtout also having knowledge of the secret key.
 410  *              The good bits counter is decremented, although no special
 411  *              action is taken if it reaches zero.
 412  */
 413
 414 void rand_get(rand_pool *r, void *p, size_t sz)
 415 {
 416   octet *o = p;
 417
 418   RAND_RESOLVE(r);
 419   GENCHECK(r);
 420   QUICK(r);
 421
 422   if (!sz)
 423     return;
 424   for (;;) {
 425     if (r->o + sz <= RAND_BUFSZ) {
 426       memcpy(o, r->buf + r->o, sz);
 427       r->o += sz;
 428       break;
 429     } else {
 430       size_t chunk = RAND_BUFSZ - r->o;
 431       if (chunk) {
 432         memcpy(o, r->buf + r->o, chunk);
 433         sz -= chunk;
 434         o += chunk;
 435       }
 436       rand_stretch(r);
 437     }
 438   }
 439
 440   if (r->obits > sz * 8)
 441     r->obits -= sz * 8;
 442   else
 443     r->obits = 0;
 444 }
 445
 446 /* --- @rand_getgood@ --- *
 447  *
 448  * Arguments:   @rand_pool *r@ = pointer to a randomness pool
 449  *              @void *p@ = pointer to output buffer
 450  *              @size_t sz@ = size of output buffer
 451  *
 452  * Returns:     ---
 453  *
 454  * Use:         Gets random data from the pool, ensuring that there are
 455  *              enough good bits.  This interface isn't recommended: it makes
 456  *              the generator slow, and doesn't provide much more security
 457  *              than @rand_get@, assuming you've previously done a
 458  *              @rand_seed@.
 459  */
 460
 461 void rand_getgood(rand_pool *r, void *p, size_t sz)
 462 {
 463   octet *o = p;
 464
 465   RAND_RESOLVE(r);
 466
 467   if (!sz)
 468     return;
 469   if (!r->s || !r->s->getnoise) {
 470     rand_get(r, p, sz);
 471     return;
 472   }
 473   GENCHECK(r);
 474   QUICK(r);
 475
 476   while (sz) {
 477     size_t chunk = sz;
 478
 479     if (chunk * 8 > r->obits) {
 480       if (chunk * 8 > r->ibits + r->obits)
 481         do r->s->getnoise(r); while (r->ibits + r->obits < 256);
 482       rand_gate(r);
 483       if (chunk * 8 > r->obits)
 484         chunk = r->obits / 8;
 485     }
 486
 487     if (chunk + r->o > RAND_BUFSZ)
 488       chunk = RAND_BUFSZ - r->o;
 489
 490     memcpy(o, r->buf + r->o, chunk);
 491     r->o += chunk;
 492     r->obits -= chunk * 8;
 493     o += chunk;
 494     sz -= chunk;
 495   }
 496 }
 497
 498 /*----- Generic random number generator interface -------------------------*/
 499
 500 static void gdestroy(grand *r)
 501 {
 502   gctx *g = (gctx *)r;
 503   if (g != &rand_global) {
 504     BURN(*g);
 505     S_DESTROY(g);
 506   }
 507 }
 508
 509 static int gmisc(grand *r, unsigned op, ...)
 510 {
 511   gctx *g = (gctx *)r;
 512   va_list ap;
 513   int rc = 0;
 514   va_start(ap, op);
 515
 516   switch (op) {
 517     case GRAND_CHECK:
 518       switch (va_arg(ap, unsigned)) {
 519         case GRAND_CHECK:
 520         case GRAND_SEEDINT:
 521         case GRAND_SEEDUINT32:
 522         case GRAND_SEEDBLOCK:
 523         case GRAND_SEEDRAND:
 524         case RAND_GATE:
 525         case RAND_STRETCH:
 526         case RAND_KEY:
 527         case RAND_NOISESRC:
 528         case RAND_SEED:
 529         case RAND_TIMER:
 530         case RAND_GOODBITS:
 531         case RAND_ADD:
 532           rc = 1;
 533           break;
 534         default:
 535           rc = 0;
 536           break;
 537       }
 538       break;
 539     case GRAND_SEEDINT: {
 540       unsigned u = va_arg(ap, unsigned);
 541       rand_add(&g->p, &u, sizeof(u), sizeof(u));
 542     } break;
 543     case GRAND_SEEDUINT32: {
 544       uint32 i = va_arg(ap, uint32);
 545       rand_add(&g->p, &i, sizeof(i), 4);
 546     } break;
 547     case GRAND_SEEDBLOCK: {
 548       const void *p = va_arg(ap, const void *);
 549       size_t sz = va_arg(ap, size_t);
 550       rand_add(&g->p, p, sz, sz);
 551     } break;
 552     case GRAND_SEEDRAND: {
 553       grand *rr = va_arg(ap, grand *);
 554       octet buf[16];
 555       rr->ops->fill(rr, buf, sizeof(buf));
 556       rand_add(&g->p, buf, sizeof(buf), 8);
 557     } break;
 558     case RAND_GATE:
 559       rand_gate(&g->p);
 560       break;
 561     case RAND_STRETCH:
 562       rand_stretch(&g->p);
 563       break;
 564     case RAND_KEY: {
 565       const void *k = va_arg(ap, const void *);
 566       size_t sz = va_arg(ap, size_t);
 567       rand_key(&g->p, k, sz);
 568     } break;
 569     case RAND_NOISESRC:
 570       rand_noisesrc(&g->p, va_arg(ap, const rand_source *));
 571       break;
 572     case RAND_SEED:
 573       rand_seed(&g->p, va_arg(ap, unsigned));
 574       break;
 575     case RAND_TIMER:
 576       QUICK(&g->p);
 577       break;
 578     case RAND_GOODBITS:
 579       rc = rand_goodbits(&g->p);
 580       break;
 581     case RAND_ADD: {
 582       const void *p = va_arg(ap, const void *);
 583       size_t sz = va_arg(ap, size_t);
 584       unsigned goodbits = va_arg(ap, unsigned);
 585       rand_add(&g->p, p, sz, goodbits);
 586     } break;
 587     default:
 588       GRAND_BADOP;
 589       break;
 590   }
 591
 592   va_end(ap);
 593   return (rc);
 594 }
 595
 596 static octet gbyte(grand *r)
 597 {
 598   gctx *g = (gctx *)r;
 599   octet o;
 600   rand_getgood(&g->p, &o, 1);
 601   return (o);
 602 }
 603
 604 static uint32 gword(grand *r)
 605 {
 606   gctx *g = (gctx *)r;
 607   octet b[4];
 608   rand_getgood(&g->p, &b, sizeof(b));
 609   return (LOAD32(b));
 610 }
 611
 612 static void gfill(grand *r, void *p, size_t sz)
 613 {
 614   gctx *g = (gctx *)r;
 615   rand_get(&g->p, p, sz);
 616 }
 617
 618 static const grand_ops gops = {
 619   "rand",
 620   GRAND_CRYPTO, 0,
 621   gmisc, gdestroy,
 622   gword, gbyte, gword, grand_defaultrange, gfill
 623 };
 624
 625 /* --- @rand_create@ --- *
 626  *
 627  * Arguments:   ---
 628  *
 629  * Returns:     Pointer to a generic generator.
 630  *
 631  * Use:         Constructs a generic generator interface over a Catacomb
 632  *              entropy pool generator.
 633  */
 634
 635 grand *rand_create(void)
 636 {
 637   gctx *g = S_CREATE(gctx);
 638   g->r.ops = &gops;
 639   rand_init(&g->p);
 640   return (&g->r);
 641 }
 642
 643 /*----- That's all, folks -------------------------------------------------*/