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 1999-2012 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       if ((random_seed << 1) > random_seed)
 238         random_seed<<=1;
 239       else
 240         random_seed>>=1;
 241       UpdateSignature(signature_info,key);
 242       key=DestroyStringInfo(key);
 243       FinalizeSignature(signature_info);
 244       digest=GetSignatureDigest(signature_info);
 245       (void) CopyMagickMemory(random_info->seed,GetStringInfoDatum(digest),
 246         MagickMin(GetSignatureDigestsize(signature_info),
 247         sizeof(*random_info->seed)));
 248       signature_info=DestroySignatureInfo(signature_info);
 249     }
 250   random_info->seed[1]=0x50a7f451UL;
 251   random_info->seed[2]=0x5365417eUL;
 252   random_info->seed[3]=0xc3a4171aUL;
 253   return(random_info);
 254 }
 255 \f
 256 /*
 257 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 258 %                                                                             %
 259 %                                                                             %
 260 %                                                                             %
 261 +   D e s t r o y R a n d o m I n f o                                         %
 262 %                                                                             %
 263 %                                                                             %
 264 %                                                                             %
 265 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 266 %
 267 %  DestroyRandomInfo() deallocates memory associated with the random
 268 %  reservoir.
 269 %
 270 %  The format of the DestroyRandomInfo method is:
 271 %
 272 %      RandomInfo *DestroyRandomInfo(RandomInfo *random_info)
 273 %
 274 %  A description of each parameter follows:
 275 %
 276 %    o random_info: the random info.
 277 %
 278 */
 279 MagickExport RandomInfo *DestroyRandomInfo(RandomInfo *random_info)
 280 {
 281   (void) LogMagickEvent(TraceEvent,GetMagickModule(),"...");
 282   assert(random_info != (RandomInfo *) NULL);
 283   assert(random_info->signature == MagickSignature);
 284   LockSemaphoreInfo(random_info->semaphore);
 285   if (random_info->reservoir != (StringInfo *) NULL)
 286     random_info->reservoir=DestroyStringInfo(random_info->reservoir);
 287   if (random_info->nonce != (StringInfo *) NULL)
 288     random_info->nonce=DestroyStringInfo(random_info->nonce);
 289   if (random_info->signature_info != (SignatureInfo *) NULL)
 290     random_info->signature_info=DestroySignatureInfo(
 291       random_info->signature_info);
 292   (void) ResetMagickMemory(random_info->seed,0,sizeof(*random_info->seed));
 293   random_info->signature=(~MagickSignature);
 294   UnlockSemaphoreInfo(random_info->semaphore);
 295   DestroySemaphoreInfo(&random_info->semaphore);
 296   random_info=(RandomInfo *) RelinquishMagickMemory(random_info);
 297   return(random_info);
 298 }
 299 \f
 300 /*
 301 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 302 %                                                                             %
 303 %                                                                             %
 304 %                                                                             %
 305 +   G e n e r a t e E n t r o p i c C h a o s                                 %
 306 %                                                                             %
 307 %                                                                             %
 308 %                                                                             %
 309 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 310 %
 311 %  GenerateEntropicChaos() generate entropic chaos used to initialize the
 312 %  random reservoir.
 313 %
 314 %  The format of the GenerateEntropicChaos method is:
 315 %
 316 %      StringInfo *GenerateEntropicChaos(RandomInfo *random_info)
 317 %
 318 %  A description of each parameter follows:
 319 %
 320 %    o random_info: the random info.
 321 %
 322 */
 323
 324 #if !defined(MAGICKCORE_WINDOWS_SUPPORT)
 325 static ssize_t ReadRandom(int file,unsigned char *source,size_t length)
 326 {
 327   register unsigned char
 328     *q;
 329
 330   ssize_t
 331     offset,
 332     count;
 333
 334   offset=0;
 335   for (q=source; length != 0; length-=count)
 336   {
 337     count=(ssize_t) read(file,q,length);
 338     if (count <= 0)
 339       {
 340         count=0;
 341         if (errno == EINTR)
 342           continue;
 343         return(-1);
 344       }
 345     q+=count;
 346     offset+=count;
 347   }
 348   return(offset);
 349 }
 350 #endif
 351
 352 static StringInfo *GenerateEntropicChaos(RandomInfo *random_info)
 353 {
 354 #define MaxEntropyExtent  64
 355
 356   MagickThreadType
 357     tid;
 358
 359   StringInfo
 360     *chaos,
 361     *entropy;
 362
 363   size_t
 364     nanoseconds,
 365     seconds;
 366
 367   ssize_t
 368     pid;
 369
 370   /*
 371     Initialize random reservoir.
 372   */
 373   entropy=AcquireStringInfo(0);
 374   LockSemaphoreInfo(random_info->semaphore);
 375   chaos=AcquireStringInfo(sizeof(unsigned char *));
 376   SetStringInfoDatum(chaos,(unsigned char *) &entropy);
 377   ConcatenateStringInfo(entropy,chaos);
 378   SetStringInfoDatum(chaos,(unsigned char *) entropy);
 379   ConcatenateStringInfo(entropy,chaos);
 380   pid=(ssize_t) getpid();
 381   SetStringInfoLength(chaos,sizeof(pid));
 382   SetStringInfoDatum(chaos,(unsigned char *) &pid);
 383   ConcatenateStringInfo(entropy,chaos);
 384   tid=GetMagickThreadId();
 385   SetStringInfoLength(chaos,sizeof(tid));
 386   SetStringInfoDatum(chaos,(unsigned char *) &tid);
 387   ConcatenateStringInfo(entropy,chaos);
 388 #if defined(MAGICKCORE_HAVE_GETRUSAGE) && defined(RUSAGE_SELF)
 389   {
 390     struct rusage
 391       usage;
 392
 393     if (getrusage(RUSAGE_SELF,&usage) == 0)
 394       {
 395         SetStringInfoLength(chaos,sizeof(usage));
 396         SetStringInfoDatum(chaos,(unsigned char *) &usage);
 397       }
 398   }
 399 #endif
 400   seconds=time((time_t *) 0);
 401   nanoseconds=0;
 402 #if defined(MAGICKCORE_HAVE_GETTIMEOFDAY)
 403   {
 404     struct timeval
 405       timer;
 406
 407     if (gettimeofday(&timer,(struct timezone *) NULL) == 0)
 408       {
 409         seconds=timer.tv_sec;
 410         nanoseconds=1000UL*timer.tv_usec;
 411       }
 412   }
 413 #endif
 414 #if defined(MAGICKCORE_HAVE_CLOCK_GETTIME) && defined(CLOCK_REALTIME_HR)
 415   {
 416     struct timespec
 417       timer;
 418
 419     if (clock_gettime(CLOCK_REALTIME_HR,&timer) == 0)
 420       {
 421         seconds=timer.tv_sec;
 422         nanoseconds=timer.tv_nsec;
 423       }
 424   }
 425 #endif
 426   SetStringInfoLength(chaos,sizeof(seconds));
 427   SetStringInfoDatum(chaos,(unsigned char *) &seconds);
 428   ConcatenateStringInfo(entropy,chaos);
 429   SetStringInfoLength(chaos,sizeof(nanoseconds));
 430   SetStringInfoDatum(chaos,(unsigned char *) &nanoseconds);
 431   ConcatenateStringInfo(entropy,chaos);
 432   nanoseconds=0;
 433 #if defined(MAGICKCORE_HAVE_CLOCK)
 434   nanoseconds=clock();
 435 #endif
 436 #if defined(MAGICKCORE_HAVE_TIMES)
 437   {
 438     struct tms
 439       timer;
 440
 441     (void) times(&timer);
 442     nanoseconds=timer.tms_utime+timer.tms_stime;
 443   }
 444 #endif
 445   SetStringInfoLength(chaos,sizeof(nanoseconds));
 446   SetStringInfoDatum(chaos,(unsigned char *) &nanoseconds);
 447   ConcatenateStringInfo(entropy,chaos);
 448 #if defined(MAGICKCORE_HAVE_MKSTEMP)
 449   {
 450     char
 451       *filename;
 452
 453     int
 454       file;
 455
 456     filename=ConstantString("magickXXXXXX");
 457     file=mkstemp(filename);
 458 #if defined(__OS2__)
 459     setmode(file,O_BINARY);
 460 #endif
 461     if (file != -1)
 462       (void) close(file);
 463     (void) remove_utf8(filename);
 464     SetStringInfoLength(chaos,strlen(filename));
 465     SetStringInfoDatum(chaos,(unsigned char *) filename);
 466     ConcatenateStringInfo(entropy,chaos);
 467     filename=DestroyString(filename);
 468   }
 469 #endif
 470 #if defined(MAGICKCORE_WINDOWS_SUPPORT)
 471   {
 472     double
 473       seconds;
 474
 475     LARGE_INTEGER
 476       nanoseconds;
 477
 478     MagickBooleanType
 479       status;
 480
 481     /*
 482       Not crytographically strong but better than nothing.
 483     */
 484     seconds=NTElapsedTime()+NTUserTime();
 485     SetStringInfoLength(chaos,sizeof(seconds));
 486     SetStringInfoDatum(chaos,(unsigned char *) &seconds);
 487     ConcatenateStringInfo(entropy,chaos);
 488     if (QueryPerformanceCounter(&nanoseconds) != 0)
 489       {
 490         SetStringInfoLength(chaos,sizeof(nanoseconds));
 491         SetStringInfoDatum(chaos,(unsigned char *) &nanoseconds);
 492         ConcatenateStringInfo(entropy,chaos);
 493       }
 494     /*
 495       Our best hope for true entropy.
 496     */
 497     SetStringInfoLength(chaos,MaxEntropyExtent);
 498     status=NTGatherRandomData(MaxEntropyExtent,GetStringInfoDatum(chaos));
 499     (void) status;
 500     ConcatenateStringInfo(entropy,chaos);
 501   }
 502 #else
 503   {
 504     char
 505       *filename;
 506
 507     int
 508       file;
 509
 510     ssize_t
 511       count;
 512
 513     StringInfo
 514       *device;
 515
 516     /*
 517       Not crytographically strong but better than nothing.
 518     */
 519     if (environ != (char **) NULL)
 520       {
 521         register ssize_t
 522           i;
 523
 524         /*
 525           Squeeze some entropy from the sometimes unpredicatble environment.
 526         */
 527         for (i=0; environ[i] != (char *) NULL; i++)
 528         {
 529           SetStringInfoLength(chaos,strlen(environ[i]));
 530           SetStringInfoDatum(chaos,(unsigned char *) environ[i]);
 531           ConcatenateStringInfo(entropy,chaos);
 532         }
 533       }
 534     filename=AcquireString("/dev/urandom");
 535     device=StringToStringInfo(filename);
 536     device=DestroyStringInfo(device);
 537     file=open_utf8(filename,O_RDONLY | O_BINARY,0);
 538     filename=DestroyString(filename);
 539     if (file != -1)
 540       {
 541         SetStringInfoLength(chaos,MaxEntropyExtent);
 542         count=ReadRandom(file,GetStringInfoDatum(chaos),MaxEntropyExtent);
 543         (void) close(file);
 544         SetStringInfoLength(chaos,(size_t) count);
 545         ConcatenateStringInfo(entropy,chaos);
 546       }
 547     if (gather_true_random != MagickFalse)
 548       {
 549         /*
 550           Our best hope for true entropy.
 551         */
 552         filename=AcquireString("/dev/random");
 553         device=StringToStringInfo(filename);
 554         device=DestroyStringInfo(device);
 555         file=open_utf8(filename,O_RDONLY | O_BINARY,0);
 556         filename=DestroyString(filename);
 557         if (file == -1)
 558           {
 559             filename=AcquireString("/dev/srandom");
 560             device=StringToStringInfo(filename);
 561             device=DestroyStringInfo(device);
 562             file=open_utf8(filename,O_RDONLY | O_BINARY,0);
 563           }
 564         if (file != -1)
 565           {
 566             SetStringInfoLength(chaos,MaxEntropyExtent);
 567             count=ReadRandom(file,GetStringInfoDatum(chaos),MaxEntropyExtent);
 568             (void) close(file);
 569             SetStringInfoLength(chaos,(size_t) count);
 570             ConcatenateStringInfo(entropy,chaos);
 571           }
 572       }
 573   }
 574 #endif
 575   chaos=DestroyStringInfo(chaos);
 576   UnlockSemaphoreInfo(random_info->semaphore);
 577   return(entropy);
 578 }
 579 \f
 580 /*
 581 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 582 %                                                                             %
 583 %                                                                             %
 584 %                                                                             %
 585 %   G e t P s e u d o R a n d o m V a l u e                                   %
 586 %                                                                             %
 587 %                                                                             %
 588 %                                                                             %
 589 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 590 %
 591 %  GetPseudoRandomValue() return a non-negative double-precision floating-point
 592 %  value uniformly distributed over the interval [0.0, 1.0) with a 2 to the
 593 %  128th-1 period.
 594 %
 595 %  The format of the GetPseudoRandomValue method is:
 596 %
 597 %      double GetPseudoRandomValue(RandomInfo *randon_info)
 598 %
 599 %  A description of each parameter follows:
 600 %
 601 %    o random_info: the random info.
 602 %
 603 */
 604 MagickExport double GetPseudoRandomValue(RandomInfo *random_info)
 605 {
 606   register unsigned long
 607     *seed;
 608
 609   unsigned long
 610     alpha;
 611
 612   seed=random_info->seed;
 613   do
 614   {
 615     alpha=(unsigned long) (seed[1] ^ (seed[1] << 11));
 616     seed[1]=seed[2];
 617     seed[2]=seed[3];
 618     seed[3]=seed[0];
 619     seed[0]=(seed[0] ^ (seed[0] >> 19)) ^ (alpha ^ (alpha >> 8));
 620   } while (seed[0] == ~0UL);
 621   return(random_info->normalize*seed[0]);
 622 }
 623 \f
 624 /*
 625 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 626 %                                                                             %
 627 %                                                                             %
 628 %                                                                             %
 629 %   G e t R a n d o m K e y                                                   %
 630 %                                                                             %
 631 %                                                                             %
 632 %                                                                             %
 633 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 634 %
 635 %  GetRandomKey() gets a random key from the reservoir.
 636 %
 637 %  The format of the GetRandomKey method is:
 638 %
 639 %      StringInfo *GetRandomKey(RandomInfo *random_info,const size_t length)
 640 %
 641 %  A description of each parameter follows:
 642 %
 643 %    o random_info: the random info.
 644 %
 645 %    o length: the key length.
 646 %
 647 */
 648 MagickExport StringInfo *GetRandomKey(RandomInfo *random_info,
 649   const size_t length)
 650 {
 651   StringInfo
 652     *key;
 653
 654   assert(random_info != (RandomInfo *) NULL);
 655   key=AcquireStringInfo(length);
 656   SetRandomKey(random_info,length,GetStringInfoDatum(key));
 657   return(key);
 658 }
 659 \f
 660 /*
 661 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 662 %                                                                             %
 663 %                                                                             %
 664 %                                                                             %
 665 %   G e t R a n d o m V a l u e                                               %
 666 %                                                                             %
 667 %                                                                             %
 668 %                                                                             %
 669 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 670 %
 671 %  GetRandomValue() return a non-negative double-precision floating-point
 672 %  value uniformly distributed over the interval [0.0, 1.0) with a 2 to the
 673 %  128th-1 period (not cryptographically strong).
 674 %
 675 %  The format of the GetRandomValue method is:
 676 %
 677 %      double GetRandomValue(void)
 678 %
 679 */
 680 MagickExport double GetRandomValue(RandomInfo *random_info)
 681 {
 682   unsigned long
 683     key,
 684     range;
 685
 686   range=(~0UL);
 687   do
 688   {
 689     SetRandomKey(random_info,sizeof(key),(unsigned char *) &key);
 690   } while (key == range);
 691   return((double) key/range);
 692 }
 693 \f
 694 /*
 695 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 696 %                                                                             %
 697 %                                                                             %
 698 %                                                                             %
 699 +   R a n d o m C o m p o n e n t G e n e s i s                               %
 700 %                                                                             %
 701 %                                                                             %
 702 %                                                                             %
 703 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 704 %
 705 %  RandomComponentGenesis() instantiates the random component.
 706 %
 707 %  The format of the RandomComponentGenesis method is:
 708 %
 709 %      MagickBooleanType RandomComponentGenesis(void)
 710 %
 711 */
 712 MagickPrivate MagickBooleanType RandomComponentGenesis(void)
 713 {
 714   AcquireSemaphoreInfo(&random_semaphore);
 715   return(MagickTrue);
 716 }
 717 \f
 718 /*
 719 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 720 %                                                                             %
 721 %                                                                             %
 722 %                                                                             %
 723 +   R a n d o m C o m p o n e n t T e r m i n u s                             %
 724 %                                                                             %
 725 %                                                                             %
 726 %                                                                             %
 727 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 728 %
 729 %  RandomComponentTerminus() destroys the random component.
 730 %
 731 %  The format of the RandomComponentTerminus method is:
 732 %
 733 %      RandomComponentTerminus(void)
 734 %
 735 */
 736 MagickPrivate void RandomComponentTerminus(void)
 737 {
 738   if (random_semaphore == (SemaphoreInfo *) NULL)
 739     AcquireSemaphoreInfo(&random_semaphore);
 740   DestroySemaphoreInfo(&random_semaphore);
 741 }
 742 \f
 743 /*
 744 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 745 %                                                                             %
 746 %                                                                             %
 747 %                                                                             %
 748 %   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                         %
 749 %                                                                             %
 750 %                                                                             %
 751 %                                                                             %
 752 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 753 %
 754 %  SeedPseudoRandomGenerator() initializes the pseudo-random number generator
 755 %  with a random seed.
 756 %
 757 %  The format of the SeedPseudoRandomGenerator method is:
 758 %
 759 %      void SeedPseudoRandomGenerator(const unsigned long seed)
 760 %
 761 %  A description of each parameter follows:
 762 %
 763 %    o seed: the seed.
 764 %
 765 */
 766 MagickExport void SeedPseudoRandomGenerator(const unsigned long seed)
 767 {
 768   random_seed=seed;
 769 }
 770 \f
 771 /*
 772 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 773 %                                                                             %
 774 %                                                                             %
 775 %                                                                             %
 776 %   S e t R a n d o m K e y                                                   %
 777 %                                                                             %
 778 %                                                                             %
 779 %                                                                             %
 780 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 781 %
 782 %  SetRandomKey() sets a random key from the reservoir.
 783 %
 784 %  The format of the SetRandomKey method is:
 785 %
 786 %      void SetRandomKey(RandomInfo *random_info,const size_t length,
 787 %        unsigned char *key)
 788 %
 789 %  A description of each parameter follows:
 790 %
 791 %    o random_info: the random info.
 792 %
 793 %    o length: the key length.
 794 %
 795 %    o key: the key.
 796 %
 797 */
 798
 799 static inline void IncrementRandomNonce(StringInfo *nonce)
 800 {
 801   register ssize_t
 802     i;
 803
 804   unsigned char
 805     *datum;
 806
 807   datum=GetStringInfoDatum(nonce);
 808   for (i=(ssize_t) (GetStringInfoLength(nonce)-1); i != 0; i--)
 809   {
 810     datum[i]++;
 811     if (datum[i] != 0)
 812       return;
 813   }
 814   ThrowFatalException(RandomFatalError,"SequenceWrapError");
 815 }
 816
 817 MagickExport void SetRandomKey(RandomInfo *random_info,const size_t length,
 818   unsigned char *key)
 819 {
 820   register size_t
 821     i;
 822
 823   register unsigned char
 824     *p;
 825
 826   SignatureInfo
 827     *signature_info;
 828
 829   unsigned char
 830     *datum;
 831
 832   assert(random_info != (RandomInfo *) NULL);
 833   if (length == 0)
 834     return;
 835   LockSemaphoreInfo(random_info->semaphore);
 836   signature_info=random_info->signature_info;
 837   datum=GetStringInfoDatum(random_info->reservoir);
 838   i=length;
 839   for (p=key; (i != 0) && (random_info->i != 0); i--)
 840   {
 841     *p++=datum[random_info->i];
 842     random_info->i++;
 843     if (random_info->i == GetSignatureDigestsize(signature_info))
 844       random_info->i=0;
 845   }
 846   while (i >= GetSignatureDigestsize(signature_info))
 847   {
 848     InitializeSignature(signature_info);
 849     UpdateSignature(signature_info,random_info->nonce);
 850     FinalizeSignature(signature_info);
 851     IncrementRandomNonce(random_info->nonce);
 852     (void) CopyMagickMemory(p,GetStringInfoDatum(GetSignatureDigest(
 853       signature_info)),GetSignatureDigestsize(signature_info));
 854     p+=GetSignatureDigestsize(signature_info);
 855     i-=GetSignatureDigestsize(signature_info);
 856   }
 857   if (i != 0)
 858     {
 859       InitializeSignature(signature_info);
 860       UpdateSignature(signature_info,random_info->nonce);
 861       FinalizeSignature(signature_info);
 862       IncrementRandomNonce(random_info->nonce);
 863       SetStringInfo(random_info->reservoir,GetSignatureDigest(signature_info));
 864       random_info->i=i;
 865       datum=GetStringInfoDatum(random_info->reservoir);
 866       while (i-- != 0)
 867         p[i]=datum[i];
 868     }
 869   UnlockSemaphoreInfo(random_info->semaphore);
 870 }
 871 \f
 872 /*
 873 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 874 %                                                                             %
 875 %                                                                             %
 876 %                                                                             %
 877 %   S e t R a n d o m T r u e R a n d o m                                     %
 878 %                                                                             %
 879 %                                                                             %
 880 %                                                                             %
 881 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 882 %
 883 %  SetRandomTrueRandom() declares your intentions to use true random numbers.
 884 %  True random numbers are encouraged but may not always be practical because
 885 %  your application may block while entropy is gathered from your environment.
 886 %
 887 %  The format of the SetRandomTrueRandom method is:
 888 %
 889 %      void SetRandomTrueRandom(const MagickBooleanType true_random)
 890 %
 891 %  A description of each parameter follows:
 892 %
 893 %    o true_random: declare your intentions to use true-random number.
 894 %
 895 */
 896 MagickExport void SetRandomTrueRandom(const MagickBooleanType true_random)
 897 {
 898   gather_true_random=true_random;
 899 }