crypto/rand/rand_unix.c

   1 /*
   2  * Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the OpenSSL license (the "License").  You may not use
   5  * this file except in compliance with the License.  You can obtain a copy
   6  * in the file LICENSE in the source distribution or at
   7  * https://www.openssl.org/source/license.html
   8  */
   9
  10 #define _GNU_SOURCE
  11 #include "e_os.h"
  12 #include <stdio.h>
  13 #include "internal/cryptlib.h"
  14 #include <openssl/rand.h>
  15 #include "rand_lcl.h"
  16 #include "internal/rand_int.h"
  17 #include <stdio.h>
  18 #include "internal/dso.h"
  19 #if defined(__linux)
  20 # include <sys/syscall.h>
  21 #endif
  22 #if defined(__FreeBSD__)
  23 # include <sys/types.h>
  24 # include <sys/sysctl.h>
  25 # include <sys/param.h>
  26 #endif
  27 #if defined(__OpenBSD__) || defined(__NetBSD__)
  28 # include <sys/param.h>
  29 #endif
  30 #ifdef OPENSSL_SYS_UNIX
  31 # include <sys/types.h>
  32 # include <unistd.h>
  33 # include <sys/time.h>
  34
  35 static uint64_t get_time_stamp(void);
  36 static uint64_t get_timer_bits(void);
  37
  38 /* Macro to convert two thirty two bit values into a sixty four bit one */
  39 # define TWO32TO64(a, b) ((((uint64_t)(a)) << 32) + (b))
  40
  41 /*
  42  * Check for the existence and support of POSIX timers.  The standard
  43  * says that the _POSIX_TIMERS macro will have a positive value if they
  44  * are available.
  45  *
  46  * However, we want an additional constraint: that the timer support does
  47  * not require an extra library dependency.  Early versions of glibc
  48  * require -lrt to be specified on the link line to access the timers,
  49  * so this needs to be checked for.
  50  *
  51  * It is worse because some libraries define __GLIBC__ but don't
  52  * support the version testing macro (e.g. uClibc).  This means
  53  * an extra check is needed.
  54  *
  55  * The final condition is:
  56  *      "have posix timers and either not glibc or glibc without -lrt"
  57  *
  58  * The nested #if sequences are required to avoid using a parameterised
  59  * macro that might be undefined.
  60  */
  61 # undef OSSL_POSIX_TIMER_OKAY
  62 # if defined(_POSIX_TIMERS) && _POSIX_TIMERS > 0
  63 #  if defined(__GLIBC__)
  64 #   if defined(__GLIBC_PREREQ)
  65 #    if __GLIBC_PREREQ(2, 17)
  66 #     define OSSL_POSIX_TIMER_OKAY
  67 #    endif
  68 #   endif
  69 #  else
  70 #   define OSSL_POSIX_TIMER_OKAY
  71 #  endif
  72 # endif
  73 #endif
  74
  75 int syscall_random(void *buf, size_t buflen);
  76
  77 #if (defined(OPENSSL_SYS_VXWORKS) || defined(OPENSSL_SYS_UEFI)) && \
  78         !defined(OPENSSL_RAND_SEED_NONE)
  79 # error "UEFI and VXWorks only support seeding NONE"
  80 #endif
  81
  82 #if !(defined(OPENSSL_SYS_WINDOWS) || defined(OPENSSL_SYS_WIN32) \
  83     || defined(OPENSSL_SYS_VMS) || defined(OPENSSL_SYS_VXWORKS) \
  84     || defined(OPENSSL_SYS_UEFI))
  85
  86 # if defined(OPENSSL_SYS_VOS)
  87
  88 #  ifndef OPENSSL_RAND_SEED_OS
  89 #   error "Unsupported seeding method configured; must be os"
  90 #  endif
  91
  92 #  if defined(OPENSSL_SYS_VOS_HPPA) && defined(OPENSSL_SYS_VOS_IA32)
  93 #   error "Unsupported HP-PA and IA32 at the same time."
  94 #  endif
  95 #  if !defined(OPENSSL_SYS_VOS_HPPA) && !defined(OPENSSL_SYS_VOS_IA32)
  96 #   error "Must have one of HP-PA or IA32"
  97 #  endif
  98
  99 /*
 100  * The following algorithm repeatedly samples the real-time clock (RTC) to
 101  * generate a sequence of unpredictable data.  The algorithm relies upon the
 102  * uneven execution speed of the code (due to factors such as cache misses,
 103  * interrupts, bus activity, and scheduling) and upon the rather large
 104  * relative difference between the speed of the clock and the rate at which
 105  * it can be read.  If it is ported to an environment where execution speed
 106  * is more constant or where the RTC ticks at a much slower rate, or the
 107  * clock can be read with fewer instructions, it is likely that the results
 108  * would be far more predictable.  This should only be used for legacy
 109  * platforms.
 110  *
 111  * As a precaution, we assume only 2 bits of entropy per byte.
 112  */
 113 size_t rand_pool_acquire_entropy(RAND_POOL *pool)
 114 {
 115     short int code;
 116     int i, k;
 117     size_t bytes_needed;
 118     struct timespec ts;
 119     unsigned char v;
 120 #  ifdef OPENSSL_SYS_VOS_HPPA
 121     long duration;
 122     extern void s$sleep(long *_duration, short int *_code);
 123 #  else
 124     long long duration;
 125     extern void s$sleep2(long long *_duration, short int *_code);
 126 #  endif
 127
 128     bytes_needed = rand_pool_bytes_needed(pool, 4 /*entropy_factor*/);
 129
 130     for (i = 0; i < bytes_needed; i++) {
 131         /*
 132          * burn some cpu; hope for interrupts, cache collisions, bus
 133          * interference, etc.
 134          */
 135         for (k = 0; k < 99; k++)
 136             ts.tv_nsec = random();
 137
 138 #  ifdef OPENSSL_SYS_VOS_HPPA
 139         /* sleep for 1/1024 of a second (976 us).  */
 140         duration = 1;
 141         s$sleep(&duration, &code);
 142 #  else
 143         /* sleep for 1/65536 of a second (15 us).  */
 144         duration = 1;
 145         s$sleep2(&duration, &code);
 146 #  endif
 147
 148         /* Get wall clock time, take 8 bits. */
 149         clock_gettime(CLOCK_REALTIME, &ts);
 150         v = (unsigned char)(ts.tv_nsec & 0xFF);
 151         rand_pool_add(pool, arg, &v, sizeof(v) , 2);
 152     }
 153     return rand_pool_entropy_available(pool);
 154 }
 155
 156 # else
 157
 158 #  if defined(OPENSSL_RAND_SEED_EGD) && \
 159         (defined(OPENSSL_NO_EGD) || !defined(DEVRANDOM_EGD))
 160 #   error "Seeding uses EGD but EGD is turned off or no device given"
 161 #  endif
 162
 163 #  if defined(OPENSSL_RAND_SEED_DEVRANDOM) && !defined(DEVRANDOM)
 164 #   error "Seeding uses urandom but DEVRANDOM is not configured"
 165 #  endif
 166
 167 #  if defined(__GLIBC__) && defined(__GLIBC_PREREQ)
 168 #   if __GLIBC_PREREQ(2, 25)
 169 #    define OPENSSL_HAVE_GETRANDOM
 170 #   endif
 171 #  endif
 172
 173 #  if (defined(__FreeBSD__) && __FreeBSD_version >= 1200061)
 174 #   define OPENSSL_HAVE_GETRANDOM
 175 #  endif
 176
 177 #  if defined(OPENSSL_HAVE_GETRANDOM)
 178 #   include <sys/random.h>
 179 #  endif
 180
 181 #  if defined(OPENSSL_RAND_SEED_OS)
 182 #   if !defined(DEVRANDOM)
 183 #    error "OS seeding requires DEVRANDOM to be configured"
 184 #   endif
 185 #   define OPENSSL_RAND_SEED_GETRANDOM
 186 #   define OPENSSL_RAND_SEED_DEVRANDOM
 187 #  endif
 188
 189 #  if defined(OPENSSL_RAND_SEED_LIBRANDOM)
 190 #   error "librandom not (yet) supported"
 191 #  endif
 192
 193 #  if (defined(__FreeBSD__) || defined(__NetBSD__)) && defined(KERN_ARND)
 194 /*
 195  * sysctl_random(): Use sysctl() to read a random number from the kernel
 196  * Returns the size on success, 0 on failure.
 197  */
 198 static size_t sysctl_random(char *buf, size_t buflen)
 199 {
 200     int mib[2];
 201     size_t done = 0;
 202     size_t len;
 203
 204     /*
 205      * On FreeBSD old implementations returned longs, newer versions support
 206      * variable sizes up to 256 byte. The code below would not work properly
 207      * when the sysctl returns long and we want to request something not a
 208      * multiple of longs, which should never be the case.
 209      */
 210     if (!ossl_assert(buflen % sizeof(long) == 0))
 211         return 0;
 212
 213     /*
 214      * On NetBSD before 4.0 KERN_ARND was an alias for KERN_URND, and only
 215      * filled in an int, leaving the rest uninitialized. Since NetBSD 4.0
 216      * it returns a variable number of bytes with the current version supporting
 217      * up to 256 bytes.
 218      * Just return an error on older NetBSD versions.
 219      */
 220 #if   defined(__NetBSD__) && __NetBSD_Version__ < 400000000
 221     return 0;
 222 #endif
 223
 224     mib[0] = CTL_KERN;
 225     mib[1] = KERN_ARND;
 226
 227     do {
 228         len = buflen;
 229         if (sysctl(mib, 2, buf, &len, NULL, 0) == -1)
 230             return done;
 231         done += len;
 232         buf += len;
 233         buflen -= len;
 234     } while (buflen > 0);
 235
 236     return done;
 237 }
 238 #  endif
 239
 240 /*
 241  * syscall_random(): Try to get random data using a system call
 242  * returns the number of bytes returned in buf, or <= 0 on error.
 243  */
 244 int syscall_random(void *buf, size_t buflen)
 245 {
 246     union {
 247         void *p;
 248         int (*f)(void *buffer, size_t length);
 249     } p_getentropy;
 250
 251     /*
 252      * Do runtime detection to find getentropy().
 253      *
 254      * We could cache the result of the lookup, but we normally don't
 255      * call this function often.
 256      *
 257      * Known OSs that should support this:
 258      * - Darwin since 16 (OSX 10.12, IOS 10.0).
 259      * - Solaris since 11.3
 260      * - OpenBSD since 5.6
 261      * - Linux since 3.17 with glibc 2.25
 262      * - FreeBSD since 12.0 (1200061)
 263      */
 264     p_getentropy.p = DSO_global_lookup("getentropy");
 265     if (p_getentropy.p != NULL)
 266         return p_getentropy.f(buf, buflen);
 267
 268 #  if defined(OPENSSL_HAVE_GETRANDOM)
 269     return (int)getrandom(buf, buflen, 0);
 270 #  endif
 271
 272     /* Linux supports this since version 3.17 */
 273 #  if defined(__linux) && defined(SYS_getrandom)
 274     return (int)syscall(SYS_getrandom, buf, buflen, 0);
 275 #  endif
 276
 277 #  if (defined(__FreeBSD__) || defined(__NetBSD__)) && defined(KERN_ARND)
 278     return (int)sysctl_random(buf, buflen);
 279 #  endif
 280
 281     return -1;
 282 }
 283
 284 /*
 285  * Try the various seeding methods in turn, exit when successful.
 286  *
 287  * TODO(DRBG): If more than one entropy source is available, is it
 288  * preferable to stop as soon as enough entropy has been collected
 289  * (as favored by @rsalz) or should one rather be defensive and add
 290  * more entropy than requested and/or from different sources?
 291  *
 292  * Currently, the user can select multiple entropy sources in the
 293  * configure step, yet in practice only the first available source
 294  * will be used. A more flexible solution has been requested, but
 295  * currently it is not clear how this can be achieved without
 296  * overengineering the problem. There are many parameters which
 297  * could be taken into account when selecting the order and amount
 298  * of input from the different entropy sources (trust, quality,
 299  * possibility of blocking).
 300  */
 301 size_t rand_pool_acquire_entropy(RAND_POOL *pool)
 302 {
 303 #  ifdef OPENSSL_RAND_SEED_NONE
 304     return rand_pool_entropy_available(pool);
 305 #  else
 306     size_t bytes_needed;
 307     size_t entropy_available = 0;
 308     unsigned char *buffer;
 309
 310 #   ifdef OPENSSL_RAND_SEED_GETRANDOM
 311     bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
 312     buffer = rand_pool_add_begin(pool, bytes_needed);
 313     if (buffer != NULL) {
 314         size_t bytes = 0;
 315
 316         if (syscall_random(buffer, bytes_needed) == (int)bytes_needed)
 317             bytes = bytes_needed;
 318
 319         rand_pool_add_end(pool, bytes, 8 * bytes);
 320         entropy_available = rand_pool_entropy_available(pool);
 321     }
 322     if (entropy_available > 0)
 323         return entropy_available;
 324 #   endif
 325
 326 #   if defined(OPENSSL_RAND_SEED_LIBRANDOM)
 327     {
 328         /* Not yet implemented. */
 329     }
 330 #   endif
 331
 332 #   ifdef OPENSSL_RAND_SEED_DEVRANDOM
 333     bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
 334     if (bytes_needed > 0) {
 335         static const char *paths[] = { DEVRANDOM, NULL };
 336         FILE *fp;
 337         int i;
 338
 339         for (i = 0; paths[i] != NULL; i++) {
 340             if ((fp = fopen(paths[i], "rb")) == NULL)
 341                 continue;
 342             setbuf(fp, NULL);
 343             buffer = rand_pool_add_begin(pool, bytes_needed);
 344             if (buffer != NULL) {
 345                 size_t bytes = 0;
 346                 if (fread(buffer, 1, bytes_needed, fp) == bytes_needed)
 347                     bytes = bytes_needed;
 348
 349                 rand_pool_add_end(pool, bytes, 8 * bytes);
 350                 entropy_available = rand_pool_entropy_available(pool);
 351             }
 352             fclose(fp);
 353             if (entropy_available > 0)
 354                 return entropy_available;
 355
 356             bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
 357         }
 358     }
 359 #   endif
 360
 361 #   ifdef OPENSSL_RAND_SEED_RDTSC
 362     entropy_available = rand_acquire_entropy_from_tsc(pool);
 363     if (entropy_available > 0)
 364         return entropy_available;
 365 #   endif
 366
 367 #   ifdef OPENSSL_RAND_SEED_RDCPU
 368     entropy_available = rand_acquire_entropy_from_cpu(pool);
 369     if (entropy_available > 0)
 370         return entropy_available;
 371 #   endif
 372
 373 #   ifdef OPENSSL_RAND_SEED_EGD
 374     bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
 375     if (bytes_needed > 0) {
 376         static const char *paths[] = { DEVRANDOM_EGD, NULL };
 377         int i;
 378
 379         for (i = 0; paths[i] != NULL; i++) {
 380             buffer = rand_pool_add_begin(pool, bytes_needed);
 381             if (buffer != NULL) {
 382                 size_t bytes = 0;
 383                 int num = RAND_query_egd_bytes(paths[i],
 384                                                buffer, (int)bytes_needed);
 385                 if (num == (int)bytes_needed)
 386                     bytes = bytes_needed;
 387
 388                 rand_pool_add_end(pool, bytes, 8 * bytes);
 389                 entropy_available = rand_pool_entropy_available(pool);
 390             }
 391             if (entropy_available > 0)
 392                 return entropy_available;
 393         }
 394     }
 395 #   endif
 396
 397     return rand_pool_entropy_available(pool);
 398 #  endif
 399 }
 400 # endif
 401 #endif
 402
 403 #ifdef OPENSSL_SYS_UNIX
 404 int rand_pool_add_nonce_data(RAND_POOL *pool)
 405 {
 406     struct {
 407         pid_t pid;
 408         CRYPTO_THREAD_ID tid;
 409         uint64_t time;
 410     } data = { 0 };
 411
 412     /*
 413      * Add process id, thread id, and a high resolution timestamp to
 414      * ensure that the nonce is unique whith high probability for
 415      * different process instances.
 416      */
 417     data.pid = getpid();
 418     data.tid = CRYPTO_THREAD_get_current_id();
 419     data.time = get_time_stamp();
 420
 421     return rand_pool_add(pool, (unsigned char *)&data, sizeof(data), 0);
 422 }
 423
 424 int rand_pool_add_additional_data(RAND_POOL *pool)
 425 {
 426     struct {
 427         CRYPTO_THREAD_ID tid;
 428         uint64_t time;
 429     } data = { 0 };
 430
 431     /*
 432      * Add some noise from the thread id and a high resolution timer.
 433      * The thread id adds a little randomness if the drbg is accessed
 434      * concurrently (which is the case for the <master> drbg).
 435      */
 436     data.tid = CRYPTO_THREAD_get_current_id();
 437     data.time = get_timer_bits();
 438
 439     return rand_pool_add(pool, (unsigned char *)&data, sizeof(data), 0);
 440 }
 441
 442
 443
 444 /*
 445  * Get the current time with the highest possible resolution
 446  *
 447  * The time stamp is added to the nonce, so it is optimized for not repeating.
 448  * The current time is ideal for this purpose, provided the computer's clock
 449  * is synchronized.
 450  */
 451 static uint64_t get_time_stamp(void)
 452 {
 453 # if defined(OSSL_POSIX_TIMER_OKAY)
 454     {
 455         struct timespec ts;
 456
 457         if (clock_gettime(CLOCK_REALTIME, &ts) == 0)
 458             return TWO32TO64(ts.tv_sec, ts.tv_nsec);
 459     }
 460 # endif
 461 # if defined(__unix__) \
 462      || (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200112L)
 463     {
 464         struct timeval tv;
 465
 466         if (gettimeofday(&tv, NULL) == 0)
 467             return TWO32TO64(tv.tv_sec, tv.tv_usec);
 468     }
 469 # endif
 470     return time(NULL);
 471 }
 472
 473 /*
 474  * Get an arbitrary timer value of the highest possible resolution
 475  *
 476  * The timer value is added as random noise to the additional data,
 477  * which is not considered a trusted entropy sourec, so any result
 478  * is acceptable.
 479  */
 480 static uint64_t get_timer_bits(void)
 481 {
 482     uint64_t res = OPENSSL_rdtsc();
 483
 484     if (res != 0)
 485         return res;
 486
 487 # if defined(__sun) || defined(__hpux)
 488     return gethrtime();
 489 # elif defined(_AIX)
 490     {
 491         timebasestruct_t t;
 492
 493         read_wall_time(&t, TIMEBASE_SZ);
 494         return TWO32TO64(t.tb_high, t.tb_low);
 495     }
 496 # elif defined(OSSL_POSIX_TIMER_OKAY)
 497     {
 498         struct timespec ts;
 499
 500 #  ifdef CLOCK_BOOTTIME
 501 #   define CLOCK_TYPE CLOCK_BOOTTIME
 502 #  elif defined(_POSIX_MONOTONIC_CLOCK)
 503 #   define CLOCK_TYPE CLOCK_MONOTONIC
 504 #  else
 505 #   define CLOCK_TYPE CLOCK_REALTIME
 506 #  endif
 507
 508         if (clock_gettime(CLOCK_TYPE, &ts) == 0)
 509             return TWO32TO64(ts.tv_sec, ts.tv_nsec);
 510     }
 511 # endif
 512 # if defined(__unix__) \
 513      || (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200112L)
 514     {
 515         struct timeval tv;
 516
 517         if (gettimeofday(&tv, NULL) == 0)
 518             return TWO32TO64(tv.tv_sec, tv.tv_usec);
 519     }
 520 # endif
 521     return time(NULL);
 522 }
 523 #endif