granicus.if.org Git - imagemagick/blob - MagickCore/random.c

   1 /*
   2 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
   3 %                                                                             %
   4 %                                                                             %
   5 %                 RRRR    AAA   N   N  DDDD    OOO   M   M                    %
   6 %                 R   R  A   A  NN  N  D   D  O   O  MM MM                    %
   7 %                 RRRR   AAAAA  N N N  D   D  O   O  M M M                    %
   8 %                 R R    A   A  N  NN  D   D  O   O  M   M                    %
   9 %                 R  R   A   A  N   N  DDDD    OOO   M   M                    %
  10 %                                                                             %
  11 %                                                                             %
  12 %               MagickCore Methods to Generate Random Numbers                 %
  13 %                                                                             %
  14 %                             Software Design                                 %
  15 %                               John Cristy                                   %
  16 %                              December 2001                                  %
  17 %                                                                             %
  18 %                                                                             %
  19 %  Copyright 1999-2011 ImageMagick Studio LLC, a non-profit organization      %
  20 %  dedicated to making software imaging solutions freely available.           %
  21 %                                                                             %
  22 %  You may not use this file except in compliance with the License.  You may  %
  23 %  obtain a copy of the License at                                            %
  24 %                                                                             %
  25 %    http://www.imagemagick.org/script/license.php                            %
  26 %                                                                             %
  27 %  Unless required by applicable law or agreed to in writing, software        %
  28 %  distributed under the License is distributed on an "AS IS" BASIS,          %
  29 %  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.   %
  30 %  See the License for the specific language governing permissions and        %
  31 %  limitations under the License.                                             %
  32 %                                                                             %
  33 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  34 %
  35 %  The generation of random numbers is too important to be left to chance.
  36 %                               -- Tom Christiansen <tchrist@mox.perl.com>
  37 %
  38 %
  39 */
  40 \f
  41 /*
  42   Include declarations.
  43 */
  44 #if defined(__VMS)
  45 #include <time.h>
  46 #endif
  47 #if defined(__MINGW32__)
  48 #include <sys/time.h>
  49 #endif
  50 #include "MagickCore/studio.h"
  51 #include "MagickCore/exception.h"
  52 #include "MagickCore/exception-private.h"
  53 #include "MagickCore/memory_.h"
  54 #include "MagickCore/semaphore.h"
  55 #include "MagickCore/random_.h"
  56 #include "MagickCore/random-private.h"
  57 #include "MagickCore/resource_.h"
  58 #include "MagickCore/signature-private.h"
  59 #include "MagickCore/string_.h"
  60 #include "MagickCore/thread_.h"
  61 #include "MagickCore/thread-private.h"
  62 #include "MagickCore/utility.h"
  63 #include "MagickCore/utility-private.h"
  64 /*
  65   Define declarations.
  66 */
  67 #define PseudoRandomHash  SHA256Hash
  68 #define RandomEntropyLevel  9
  69 #define RandomFilename  "reservoir.xdm"
  70 #define RandomFiletype  "random"
  71 #define RandomProtocolMajorVersion  1
  72 #define RandomProtocolMinorVersion  0
  73 \f
  74 /*
  75   Typedef declarations.
  76 */
  77 struct _RandomInfo
  78 {
  79   SignatureInfo
  80     *signature_info;
  81
  82   StringInfo
  83     *nonce,
  84     *reservoir;
  85
  86   size_t
  87     i;
  88
  89   unsigned long
  90     seed[4];
  91
  92   double
  93     normalize;
  94
  95   unsigned short
  96     protocol_major,
  97     protocol_minor;
  98
  99   SemaphoreInfo
 100     *semaphore;
 101
 102   ssize_t
 103     timestamp;
 104
 105   size_t
 106     signature;
 107 };
 108 \f
 109 /*
 110   External declarations.
 111 */
 112 #if defined(__APPLE__) && !defined(TARGET_OS_IPHONE)
 113 #include <crt_externs.h>
 114 #define environ (*_NSGetEnviron())
 115 #endif
 116
 117 extern char
 118   **environ;
 119 \f
 120 /*
 121   Global declarations.
 122 */
 123 static SemaphoreInfo
 124   *random_semaphore = (SemaphoreInfo *) NULL;
 125
 126 static unsigned long
 127   random_seed = ~0UL;
 128
 129 static MagickBooleanType
 130   gather_true_random = MagickFalse;
 131 \f
 132 /*
 133   Forward declarations.
 134 */
 135 static StringInfo
 136   *GenerateEntropicChaos(RandomInfo *);
 137 \f
 138 /*
 139 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 140 %                                                                             %
 141 %                                                                             %
 142 %                                                                             %
 143 %   A c q u i r e R a n d o m I n f o                                         %
 144 %                                                                             %
 145 %                                                                             %
 146 %                                                                             %
 147 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 148 %
 149 %  AcquireRandomInfo() allocates the RandomInfo structure.
 150 %
 151 %  The format of the AcquireRandomInfo method is:
 152 %
 153 %      RandomInfo *AcquireRandomInfo(void)
 154 %
 155 */
 156
 157 static inline size_t MagickMin(const size_t x,const size_t y)
 158 {
 159   if (x < y)
 160     return(x);
 161   return(y);
 162 }
 163
 164 MagickExport RandomInfo *AcquireRandomInfo(void)
 165 {
 166   const StringInfo
 167     *digest;
 168
 169   RandomInfo
 170     *random_info;
 171
 172   StringInfo
 173     *entropy,
 174     *key,
 175     *nonce;
 176
 177   random_info=(RandomInfo *) AcquireMagickMemory(sizeof(*random_info));
 178   if (random_info == (RandomInfo *) NULL)
 179     ThrowFatalException(ResourceLimitFatalError,"MemoryAllocationFailed");
 180   (void) ResetMagickMemory(random_info,0,sizeof(*random_info));
 181   random_info->signature_info=AcquireSignatureInfo();
 182   random_info->nonce=AcquireStringInfo(2*GetSignatureDigestsize(
 183     random_info->signature_info));
 184   ResetStringInfo(random_info->nonce);
 185   random_info->reservoir=AcquireStringInfo(GetSignatureDigestsize(
 186     random_info->signature_info));
 187   ResetStringInfo(random_info->reservoir);
 188   random_info->normalize=1.0/(~0UL);
 189   random_info->semaphore=AllocateSemaphoreInfo();
 190   random_info->protocol_major=RandomProtocolMajorVersion;
 191   random_info->protocol_minor=RandomProtocolMinorVersion;
 192   random_info->timestamp=(ssize_t) time(0);
 193   random_info->signature=MagickSignature;
 194   /*
 195     Seed random nonce.
 196   */
 197   nonce=GenerateEntropicChaos(random_info);
 198   if (nonce == (StringInfo *) NULL)
 199     ThrowFatalException(ResourceLimitFatalError,"MemoryAllocationFailed");
 200   InitializeSignature(random_info->signature_info);
 201   UpdateSignature(random_info->signature_info,nonce);
 202   FinalizeSignature(random_info->signature_info);
 203   SetStringInfoLength(nonce,(GetSignatureDigestsize(
 204     random_info->signature_info)+1)/2);
 205   SetStringInfo(nonce,GetSignatureDigest(random_info->signature_info));
 206   SetStringInfo(random_info->nonce,nonce);
 207   nonce=DestroyStringInfo(nonce);
 208   /*
 209     Seed random reservoir with entropic data.
 210   */
 211   entropy=GenerateEntropicChaos(random_info);
 212   if (entropy == (StringInfo *) NULL)
 213     ThrowFatalException(ResourceLimitFatalError,"MemoryAllocationFailed");
 214   UpdateSignature(random_info->signature_info,entropy);
 215   FinalizeSignature(random_info->signature_info);
 216   SetStringInfo(random_info->reservoir,GetSignatureDigest(
 217     random_info->signature_info));
 218   entropy=DestroyStringInfo(entropy);
 219   /*
 220     Seed pseudo random number generator.
 221   */
 222   if (random_seed == ~0UL)
 223     {
 224       key=GetRandomKey(random_info,sizeof(random_seed));
 225       (void) CopyMagickMemory(random_info->seed,GetStringInfoDatum(key),
 226         GetStringInfoLength(key));
 227       key=DestroyStringInfo(key);
 228     }
 229   else
 230     {
 231       SignatureInfo
 232         *signature_info;
 233
 234       signature_info=AcquireSignatureInfo();
 235       key=AcquireStringInfo(sizeof(random_seed));
 236       SetStringInfoDatum(key,(unsigned char *) &random_seed);
 237       UpdateSignature(signature_info,key);
 238       key=DestroyStringInfo(key);
 239       FinalizeSignature(signature_info);
 240       digest=GetSignatureDigest(signature_info);
 241       (void) CopyMagickMemory(random_info->seed,GetStringInfoDatum(digest),
 242         MagickMin(GetSignatureDigestsize(signature_info),
 243         sizeof(*random_info->seed)));
 244       signature_info=DestroySignatureInfo(signature_info);
 245     }
 246   random_info->seed[1]=0x50a7f451UL;
 247   random_info->seed[2]=0x5365417eUL;
 248   random_info->seed[3]=0xc3a4171aUL;
 249   return(random_info);
 250 }
 251 \f
 252 /*
 253 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 254 %                                                                             %
 255 %                                                                             %
 256 %                                                                             %
 257 +   D e s t r o y R a n d o m I n f o                                         %
 258 %                                                                             %
 259 %                                                                             %
 260 %                                                                             %
 261 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 262 %
 263 %  DestroyRandomInfo() deallocates memory associated with the random
 264 %  reservoir.
 265 %
 266 %  The format of the DestroyRandomInfo method is:
 267 %
 268 %      RandomInfo *DestroyRandomInfo(RandomInfo *random_info)
 269 %
 270 %  A description of each parameter follows:
 271 %
 272 %    o random_info: the random info.
 273 %
 274 */
 275 MagickExport RandomInfo *DestroyRandomInfo(RandomInfo *random_info)
 276 {
 277   (void) LogMagickEvent(TraceEvent,GetMagickModule(),"...");
 278   assert(random_info != (RandomInfo *) NULL);
 279   assert(random_info->signature == MagickSignature);
 280   LockSemaphoreInfo(random_info->semaphore);
 281   if (random_info->reservoir != (StringInfo *) NULL)
 282     random_info->reservoir=DestroyStringInfo(random_info->reservoir);
 283   if (random_info->nonce != (StringInfo *) NULL)
 284     random_info->nonce=DestroyStringInfo(random_info->nonce);
 285   if (random_info->signature_info != (SignatureInfo *) NULL)
 286     random_info->signature_info=DestroySignatureInfo(
 287       random_info->signature_info);
 288   (void) ResetMagickMemory(random_info->seed,0,sizeof(*random_info->seed));
 289   random_info->signature=(~MagickSignature);
 290   UnlockSemaphoreInfo(random_info->semaphore);
 291   DestroySemaphoreInfo(&random_info->semaphore);
 292   random_info=(RandomInfo *) RelinquishMagickMemory(random_info);
 293   return(random_info);
 294 }
 295 \f
 296 /*
 297 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 298 %                                                                             %
 299 %                                                                             %
 300 %                                                                             %
 301 +   G e n e r a t e E n t r o p i c C h a o s                                 %
 302 %                                                                             %
 303 %                                                                             %
 304 %                                                                             %
 305 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 306 %
 307 %  GenerateEntropicChaos() generate entropic chaos used to initialize the
 308 %  random reservoir.
 309 %
 310 %  The format of the GenerateEntropicChaos method is:
 311 %
 312 %      StringInfo *GenerateEntropicChaos(RandomInfo *random_info)
 313 %
 314 %  A description of each parameter follows:
 315 %
 316 %    o random_info: the random info.
 317 %
 318 */
 319
 320 #if !defined(MAGICKCORE_WINDOWS_SUPPORT)
 321 static ssize_t ReadRandom(int file,unsigned char *source,size_t length)
 322 {
 323   register unsigned char
 324     *q;
 325
 326   ssize_t
 327     offset,
 328     count;
 329
 330   offset=0;
 331   for (q=source; length != 0; length-=count)
 332   {
 333     count=(ssize_t) read(file,q,length);
 334     if (count <= 0)
 335       {
 336         count=0;
 337         if (errno == EINTR)
 338           continue;
 339         return(-1);
 340       }
 341     q+=count;
 342     offset+=count;
 343   }
 344   return(offset);
 345 }
 346 #endif
 347
 348 static StringInfo *GenerateEntropicChaos(RandomInfo *random_info)
 349 {
 350 #define MaxEntropyExtent  64
 351
 352   MagickThreadType
 353     tid;
 354
 355   StringInfo
 356     *chaos,
 357     *entropy;
 358
 359   size_t
 360     nanoseconds,
 361     seconds;
 362
 363   ssize_t
 364     pid;
 365
 366   /*
 367     Initialize random reservoir.
 368   */
 369   entropy=AcquireStringInfo(0);
 370   LockSemaphoreInfo(random_info->semaphore);
 371   chaos=AcquireStringInfo(sizeof(unsigned char *));
 372   SetStringInfoDatum(chaos,(unsigned char *) &entropy);
 373   ConcatenateStringInfo(entropy,chaos);
 374   SetStringInfoDatum(chaos,(unsigned char *) entropy);
 375   ConcatenateStringInfo(entropy,chaos);
 376   pid=(ssize_t) getpid();
 377   SetStringInfoLength(chaos,sizeof(pid));
 378   SetStringInfoDatum(chaos,(unsigned char *) &pid);
 379   ConcatenateStringInfo(entropy,chaos);
 380   tid=GetMagickThreadId();
 381   SetStringInfoLength(chaos,sizeof(tid));
 382   SetStringInfoDatum(chaos,(unsigned char *) &tid);
 383   ConcatenateStringInfo(entropy,chaos);
 384 #if defined(MAGICKCORE_HAVE_GETRUSAGE) && defined(RUSAGE_SELF)
 385   {
 386     struct rusage
 387       usage;
 388
 389     if (getrusage(RUSAGE_SELF,&usage) == 0)
 390       {
 391         SetStringInfoLength(chaos,sizeof(usage));
 392         SetStringInfoDatum(chaos,(unsigned char *) &usage);
 393       }
 394   }
 395 #endif
 396   seconds=time((time_t *) 0);
 397   nanoseconds=0;
 398 #if defined(MAGICKCORE_HAVE_GETTIMEOFDAY)
 399   {
 400     struct timeval
 401       timer;
 402
 403     if (gettimeofday(&timer,(struct timezone *) NULL) == 0)
 404       {
 405         seconds=timer.tv_sec;
 406         nanoseconds=1000UL*timer.tv_usec;
 407       }
 408   }
 409 #endif
 410 #if defined(MAGICKCORE_HAVE_CLOCK_GETTIME) && defined(CLOCK_REALTIME_HR)
 411   {
 412     struct timespec
 413       timer;
 414
 415     if (clock_gettime(CLOCK_REALTIME_HR,&timer) == 0)
 416       {
 417         seconds=timer.tv_sec;
 418         nanoseconds=timer.tv_nsec;
 419       }
 420   }
 421 #endif
 422   SetStringInfoLength(chaos,sizeof(seconds));
 423   SetStringInfoDatum(chaos,(unsigned char *) &seconds);
 424   ConcatenateStringInfo(entropy,chaos);
 425   SetStringInfoLength(chaos,sizeof(nanoseconds));
 426   SetStringInfoDatum(chaos,(unsigned char *) &nanoseconds);
 427   ConcatenateStringInfo(entropy,chaos);
 428   nanoseconds=0;
 429 #if defined(MAGICKCORE_HAVE_CLOCK)
 430   nanoseconds=clock();
 431 #endif
 432 #if defined(MAGICKCORE_HAVE_TIMES)
 433   {
 434     struct tms
 435       timer;
 436
 437     (void) times(&timer);
 438     nanoseconds=timer.tms_utime+timer.tms_stime;
 439   }
 440 #endif
 441   SetStringInfoLength(chaos,sizeof(nanoseconds));
 442   SetStringInfoDatum(chaos,(unsigned char *) &nanoseconds);
 443   ConcatenateStringInfo(entropy,chaos);
 444 #if defined(MAGICKCORE_HAVE_MKSTEMP)
 445   {
 446     char
 447       *filename;
 448
 449     int
 450       file;
 451
 452     filename=ConstantString("magickXXXXXX");
 453     file=mkstemp(filename);
 454 #if defined(__OS2__)
 455     setmode(file,O_BINARY);
 456 #endif
 457     if (file != -1)
 458       (void) close(file);
 459     (void) remove_utf8(filename);
 460     SetStringInfoLength(chaos,strlen(filename));
 461     SetStringInfoDatum(chaos,(unsigned char *) filename);
 462     ConcatenateStringInfo(entropy,chaos);
 463     filename=DestroyString(filename);
 464   }
 465 #endif
 466 #if defined(MAGICKCORE_WINDOWS_SUPPORT)
 467   {
 468     double
 469       seconds;
 470
 471     LARGE_INTEGER
 472       nanoseconds;
 473
 474     MagickBooleanType
 475       status;
 476
 477     /*
 478       Not crytographically strong but better than nothing.
 479     */
 480     seconds=NTElapsedTime()+NTUserTime();
 481     SetStringInfoLength(chaos,sizeof(seconds));
 482     SetStringInfoDatum(chaos,(unsigned char *) &seconds);
 483     ConcatenateStringInfo(entropy,chaos);
 484     if (QueryPerformanceCounter(&nanoseconds) != 0)
 485       {
 486         SetStringInfoLength(chaos,sizeof(nanoseconds));
 487         SetStringInfoDatum(chaos,(unsigned char *) &nanoseconds);
 488         ConcatenateStringInfo(entropy,chaos);
 489       }
 490     /*
 491       Our best hope for true entropy.
 492     */
 493     SetStringInfoLength(chaos,MaxEntropyExtent);
 494     status=NTGatherRandomData(MaxEntropyExtent,GetStringInfoDatum(chaos));
 495     ConcatenateStringInfo(entropy,chaos);
 496   }
 497 #else
 498   {
 499     char
 500       *filename;
 501
 502     int
 503       file;
 504
 505     ssize_t
 506       count;
 507
 508     StringInfo
 509       *device;
 510
 511     /*
 512       Not crytographically strong but better than nothing.
 513     */
 514     if (environ != (char **) NULL)
 515       {
 516         register ssize_t
 517           i;
 518
 519         /*
 520           Squeeze some entropy from the sometimes unpredicatble environment.
 521         */
 522         for (i=0; environ[i] != (char *) NULL; i++)
 523         {
 524           SetStringInfoLength(chaos,strlen(environ[i]));
 525           SetStringInfoDatum(chaos,(unsigned char *) environ[i]);
 526           ConcatenateStringInfo(entropy,chaos);
 527         }
 528       }
 529     filename=AcquireString("/dev/urandom");
 530     device=StringToStringInfo(filename);
 531     device=DestroyStringInfo(device);
 532     file=open_utf8(filename,O_RDONLY | O_BINARY,0);
 533     filename=DestroyString(filename);
 534     if (file != -1)
 535       {
 536         SetStringInfoLength(chaos,MaxEntropyExtent);
 537         count=ReadRandom(file,GetStringInfoDatum(chaos),MaxEntropyExtent);
 538         (void) close(file);
 539         SetStringInfoLength(chaos,(size_t) count);
 540         ConcatenateStringInfo(entropy,chaos);
 541       }
 542     if (gather_true_random != MagickFalse)
 543       {
 544         /*
 545           Our best hope for true entropy.
 546         */
 547         filename=AcquireString("/dev/random");
 548         device=StringToStringInfo(filename);
 549         device=DestroyStringInfo(device);
 550         file=open_utf8(filename,O_RDONLY | O_BINARY,0);
 551         filename=DestroyString(filename);
 552         if (file == -1)
 553           {
 554             filename=AcquireString("/dev/srandom");
 555             device=StringToStringInfo(filename);
 556             device=DestroyStringInfo(device);
 557             file=open_utf8(filename,O_RDONLY | O_BINARY,0);
 558           }
 559         if (file != -1)
 560           {
 561             SetStringInfoLength(chaos,MaxEntropyExtent);
 562             count=ReadRandom(file,GetStringInfoDatum(chaos),MaxEntropyExtent);
 563             (void) close(file);
 564             SetStringInfoLength(chaos,(size_t) count);
 565             ConcatenateStringInfo(entropy,chaos);
 566           }
 567       }
 568   }
 569 #endif
 570   chaos=DestroyStringInfo(chaos);
 571   UnlockSemaphoreInfo(random_info->semaphore);
 572   return(entropy);
 573 }
 574 \f
 575 /*
 576 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 577 %                                                                             %
 578 %                                                                             %
 579 %                                                                             %
 580 %   G e t P s e u d o R a n d o m V a l u e                                   %
 581 %                                                                             %
 582 %                                                                             %
 583 %                                                                             %
 584 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 585 %
 586 %  GetPseudoRandomValue() return a non-negative double-precision floating-point
 587 %  value uniformly distributed over the interval [0.0, 1.0) with a 2 to the
 588 %  128th-1 period.
 589 %
 590 %  The format of the GetPseudoRandomValue method is:
 591 %
 592 %      double GetPseudoRandomValue(RandomInfo *randon_info)
 593 %
 594 %  A description of each parameter follows:
 595 %
 596 %    o random_info: the random info.
 597 %
 598 */
 599 MagickExport double GetPseudoRandomValue(RandomInfo *random_info)
 600 {
 601   register unsigned long
 602     *seed;
 603
 604   unsigned long
 605     alpha;
 606
 607   seed=random_info->seed;
 608   do
 609   {
 610     alpha=(unsigned long) (seed[1] ^ (seed[1] << 11));
 611     seed[1]=seed[2];
 612     seed[2]=seed[3];
 613     seed[3]=seed[0];
 614     seed[0]=(seed[0] ^ (seed[0] >> 19)) ^ (alpha ^ (alpha >> 8));
 615   } while (seed[0] == ~0UL);
 616   return(random_info->normalize*seed[0]);
 617 }
 618 \f
 619 /*
 620 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 621 %                                                                             %
 622 %                                                                             %
 623 %                                                                             %
 624 %   G e t R a n d o m K e y                                                   %
 625 %                                                                             %
 626 %                                                                             %
 627 %                                                                             %
 628 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 629 %
 630 %  GetRandomKey() gets a random key from the reservoir.
 631 %
 632 %  The format of the GetRandomKey method is:
 633 %
 634 %      StringInfo *GetRandomKey(RandomInfo *random_info,const size_t length)
 635 %
 636 %  A description of each parameter follows:
 637 %
 638 %    o random_info: the random info.
 639 %
 640 %    o length: the key length.
 641 %
 642 */
 643 MagickExport StringInfo *GetRandomKey(RandomInfo *random_info,
 644   const size_t length)
 645 {
 646   StringInfo
 647     *key;
 648
 649   assert(random_info != (RandomInfo *) NULL);
 650   key=AcquireStringInfo(length);
 651   SetRandomKey(random_info,length,GetStringInfoDatum(key));
 652   return(key);
 653 }
 654 \f
 655 /*
 656 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 657 %                                                                             %
 658 %                                                                             %
 659 %                                                                             %
 660 %   G e t R a n d o m V a l u e                                               %
 661 %                                                                             %
 662 %                                                                             %
 663 %                                                                             %
 664 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 665 %
 666 %  GetRandomValue() return a non-negative double-precision floating-point
 667 %  value uniformly distributed over the interval [0.0, 1.0) with a 2 to the
 668 %  128th-1 period (not cryptographically strong).
 669 %
 670 %  The format of the GetRandomValue method is:
 671 %
 672 %      double GetRandomValue(void)
 673 %
 674 */
 675 MagickExport double GetRandomValue(RandomInfo *random_info)
 676 {
 677   unsigned long
 678     key,
 679     range;
 680
 681   range=(~0UL);
 682   do
 683   {
 684     SetRandomKey(random_info,sizeof(key),(unsigned char *) &key);
 685   } while (key == range);
 686   return((double) key/range);
 687 }
 688 \f
 689 /*
 690 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 691 %                                                                             %
 692 %                                                                             %
 693 %                                                                             %
 694 +   R a n d o m C o m p o n e n t G e n e s i s                               %
 695 %                                                                             %
 696 %                                                                             %
 697 %                                                                             %
 698 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 699 %
 700 %  RandomComponentGenesis() instantiates the random component.
 701 %
 702 %  The format of the RandomComponentGenesis method is:
 703 %
 704 %      MagickBooleanType RandomComponentGenesis(void)
 705 %
 706 */
 707 MagickPrivate MagickBooleanType RandomComponentGenesis(void)
 708 {
 709   AcquireSemaphoreInfo(&random_semaphore);
 710   return(MagickTrue);
 711 }
 712 \f
 713 /*
 714 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 715 %                                                                             %
 716 %                                                                             %
 717 %                                                                             %
 718 +   R a n d o m C o m p o n e n t T e r m i n u s                             %
 719 %                                                                             %
 720 %                                                                             %
 721 %                                                                             %
 722 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 723 %
 724 %  RandomComponentTerminus() destroys the random component.
 725 %
 726 %  The format of the RandomComponentTerminus method is:
 727 %
 728 %      RandomComponentTerminus(void)
 729 %
 730 */
 731 MagickPrivate void RandomComponentTerminus(void)
 732 {
 733   if (random_semaphore == (SemaphoreInfo *) NULL)
 734     AcquireSemaphoreInfo(&random_semaphore);
 735   DestroySemaphoreInfo(&random_semaphore);
 736 }
 737 \f
 738 /*
 739 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 740 %                                                                             %
 741 %                                                                             %
 742 %                                                                             %
 743 %   S e e d P s e u d o R a n d o m G e n e r a t o r                         %
 744 %                                                                             %
 745 %                                                                             %
 746 %                                                                             %
 747 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 748 %
 749 %  SeedPseudoRandomGenerator() initializes the pseudo-random number generator
 750 %  with a random seed.
 751 %
 752 %  The format of the SeedPseudoRandomGenerator method is:
 753 %
 754 %      void SeedPseudoRandomGenerator(const unsigned long seed)
 755 %
 756 %  A description of each parameter follows:
 757 %
 758 %    o seed: the seed.
 759 %
 760 */
 761 MagickExport void SeedPseudoRandomGenerator(const unsigned long seed)
 762 {
 763   random_seed=seed;
 764 }
 765 \f
 766 /*
 767 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 768 %                                                                             %
 769 %                                                                             %
 770 %                                                                             %
 771 %   S e t R a n d o m K e y                                                   %
 772 %                                                                             %
 773 %                                                                             %
 774 %                                                                             %
 775 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 776 %
 777 %  SetRandomKey() sets a random key from the reservoir.
 778 %
 779 %  The format of the SetRandomKey method is:
 780 %
 781 %      void SetRandomKey(RandomInfo *random_info,const size_t length,
 782 %        unsigned char *key)
 783 %
 784 %  A description of each parameter follows:
 785 %
 786 %    o random_info: the random info.
 787 %
 788 %    o length: the key length.
 789 %
 790 %    o key: the key.
 791 %
 792 */
 793
 794 static inline void IncrementRandomNonce(StringInfo *nonce)
 795 {
 796   register ssize_t
 797     i;
 798
 799   unsigned char
 800     *datum;
 801
 802   datum=GetStringInfoDatum(nonce);
 803   for (i=(ssize_t) (GetStringInfoLength(nonce)-1); i != 0; i--)
 804   {
 805     datum[i]++;
 806     if (datum[i] != 0)
 807       return;
 808   }
 809   ThrowFatalException(RandomFatalError,"SequenceWrapError");
 810 }
 811
 812 MagickExport void SetRandomKey(RandomInfo *random_info,const size_t length,
 813   unsigned char *key)
 814 {
 815   register size_t
 816     i;
 817
 818   register unsigned char
 819     *p;
 820
 821   SignatureInfo
 822     *signature_info;
 823
 824   unsigned char
 825     *datum;
 826
 827   assert(random_info != (RandomInfo *) NULL);
 828   if (length == 0)
 829     return;
 830   LockSemaphoreInfo(random_info->semaphore);
 831   signature_info=random_info->signature_info;
 832   datum=GetStringInfoDatum(random_info->reservoir);
 833   i=length;
 834   for (p=key; (i != 0) && (random_info->i != 0); i--)
 835   {
 836     *p++=datum[random_info->i];
 837     random_info->i++;
 838     if (random_info->i == GetSignatureDigestsize(signature_info))
 839       random_info->i=0;
 840   }
 841   while (i >= GetSignatureDigestsize(signature_info))
 842   {
 843     InitializeSignature(signature_info);
 844     UpdateSignature(signature_info,random_info->nonce);
 845     FinalizeSignature(signature_info);
 846     IncrementRandomNonce(random_info->nonce);
 847     (void) CopyMagickMemory(p,GetStringInfoDatum(GetSignatureDigest(
 848       signature_info)),GetSignatureDigestsize(signature_info));
 849     p+=GetSignatureDigestsize(signature_info);
 850     i-=GetSignatureDigestsize(signature_info);
 851   }
 852   if (i != 0)
 853     {
 854       InitializeSignature(signature_info);
 855       UpdateSignature(signature_info,random_info->nonce);
 856       FinalizeSignature(signature_info);
 857       IncrementRandomNonce(random_info->nonce);
 858       SetStringInfo(random_info->reservoir,GetSignatureDigest(signature_info));
 859       random_info->i=i;
 860       datum=GetStringInfoDatum(random_info->reservoir);
 861       while (i-- != 0)
 862         p[i]=datum[i];
 863     }
 864   UnlockSemaphoreInfo(random_info->semaphore);
 865 }
 866 \f
 867 /*
 868 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 869 %                                                                             %
 870 %                                                                             %
 871 %                                                                             %
 872 %   S e t R a n d o m T r u e R a n d o m                                     %
 873 %                                                                             %
 874 %                                                                             %
 875 %                                                                             %
 876 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 877 %
 878 %  SetRandomTrueRandom() declares your intentions to use true random numbers.
 879 %  True random numbers are encouraged but may not always be practical because
 880 %  your application may block while entropy is gathered from your environment.
 881 %
 882 %  The format of the SetRandomTrueRandom method is:
 883 %
 884 %      void SetRandomTrueRandom(const MagickBooleanType true_random)
 885 %
 886 %  A description of each parameter follows:
 887 %
 888 %    o true_random: declare your intentions to use true-random number.
 889 %
 890 */
 891 MagickExport void SetRandomTrueRandom(const MagickBooleanType true_random)
 892 {
 893   gather_true_random=true_random;
 894 }