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(OPENSSL_RAND_SEED_OS)
 168 #   if !defined(DEVRANDOM)
 169 #    error "OS seeding requires DEVRANDOM to be configured"
 170 #   endif
 171 #   define OPENSSL_RAND_SEED_GETRANDOM
 172 #   define OPENSSL_RAND_SEED_DEVRANDOM
 173 #  endif
 174
 175 #  if defined(OPENSSL_RAND_SEED_LIBRANDOM)
 176 #   error "librandom not (yet) supported"
 177 #  endif
 178
 179 #  if (defined(__FreeBSD__) || defined(__NetBSD__)) && defined(KERN_ARND)
 180 /*
 181  * sysctl_random(): Use sysctl() to read a random number from the kernel
 182  * Returns the size on success, 0 on failure.
 183  */
 184 static size_t sysctl_random(char *buf, size_t buflen)
 185 {
 186     int mib[2];
 187     size_t done = 0;
 188     size_t len;
 189
 190     /*
 191      * On FreeBSD old implementations returned longs, newer versions support
 192      * variable sizes up to 256 byte. The code below would not work properly
 193      * when the sysctl returns long and we want to request something not a
 194      * multiple of longs, which should never be the case.
 195      */
 196     if (!ossl_assert(buflen % sizeof(long) == 0))
 197         return 0;
 198
 199     /*
 200      * On NetBSD before 4.0 KERN_ARND was an alias for KERN_URND, and only
 201      * filled in an int, leaving the rest uninitialized. Since NetBSD 4.0
 202      * it returns a variable number of bytes with the current version supporting
 203      * up to 256 bytes.
 204      * Just return an error on older NetBSD versions.
 205      */
 206 #if   defined(__NetBSD__) && __NetBSD_Version__ < 400000000
 207     return 0;
 208 #endif
 209
 210     mib[0] = CTL_KERN;
 211     mib[1] = KERN_ARND;
 212
 213     do {
 214         len = buflen;
 215         if (sysctl(mib, 2, buf, &len, NULL, 0) == -1)
 216             return done;
 217         done += len;
 218         buf += len;
 219         buflen -= len;
 220     } while (buflen > 0);
 221
 222     return done;
 223 }
 224 #  endif
 225
 226 /*
 227  * syscall_random(): Try to get random data using a system call
 228  * returns the number of bytes returned in buf, or <= 0 on error.
 229  */
 230 int syscall_random(void *buf, size_t buflen)
 231 {
 232     union {
 233         void *p;
 234         int (*f)(void *buffer, size_t length);
 235     } p_getentropy;
 236
 237     /*
 238      * Do runtime detection to find getentropy().
 239      *
 240      * We could cache the result of the lookup, but we normally don't
 241      * call this function often.
 242      *
 243      * Known OSs that should support this:
 244      * - Darwin since 16 (OSX 10.12, IOS 10.0).
 245      * - Solaris since 11.3
 246      * - OpenBSD since 5.6
 247      * - Linux since 3.17 with glibc 2.25
 248      * - FreeBSD since 12.0 (1200061)
 249      */
 250     p_getentropy.p = DSO_global_lookup("getentropy");
 251     if (p_getentropy.p != NULL)
 252         return p_getentropy.f(buf, buflen) == 0 ? buflen : 0;
 253
 254     /* Linux supports this since version 3.17 */
 255 #  if defined(__linux) && defined(SYS_getrandom)
 256     return (int)syscall(SYS_getrandom, buf, buflen, 0);
 257 #  endif
 258
 259 #  if (defined(__FreeBSD__) || defined(__NetBSD__)) && defined(KERN_ARND)
 260     return (int)sysctl_random(buf, buflen);
 261 #  endif
 262
 263     return -1;
 264 }
 265
 266 /*
 267  * Try the various seeding methods in turn, exit when successful.
 268  *
 269  * TODO(DRBG): If more than one entropy source is available, is it
 270  * preferable to stop as soon as enough entropy has been collected
 271  * (as favored by @rsalz) or should one rather be defensive and add
 272  * more entropy than requested and/or from different sources?
 273  *
 274  * Currently, the user can select multiple entropy sources in the
 275  * configure step, yet in practice only the first available source
 276  * will be used. A more flexible solution has been requested, but
 277  * currently it is not clear how this can be achieved without
 278  * overengineering the problem. There are many parameters which
 279  * could be taken into account when selecting the order and amount
 280  * of input from the different entropy sources (trust, quality,
 281  * possibility of blocking).
 282  */
 283 size_t rand_pool_acquire_entropy(RAND_POOL *pool)
 284 {
 285 #  ifdef OPENSSL_RAND_SEED_NONE
 286     return rand_pool_entropy_available(pool);
 287 #  else
 288     size_t bytes_needed;
 289     size_t entropy_available = 0;
 290     unsigned char *buffer;
 291
 292 #   ifdef OPENSSL_RAND_SEED_GETRANDOM
 293     bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
 294     buffer = rand_pool_add_begin(pool, bytes_needed);
 295     if (buffer != NULL) {
 296         size_t bytes = 0;
 297
 298         if (syscall_random(buffer, bytes_needed) == (int)bytes_needed)
 299             bytes = bytes_needed;
 300
 301         rand_pool_add_end(pool, bytes, 8 * bytes);
 302         entropy_available = rand_pool_entropy_available(pool);
 303     }
 304     if (entropy_available > 0)
 305         return entropy_available;
 306 #   endif
 307
 308 #   if defined(OPENSSL_RAND_SEED_LIBRANDOM)
 309     {
 310         /* Not yet implemented. */
 311     }
 312 #   endif
 313
 314 #   ifdef OPENSSL_RAND_SEED_DEVRANDOM
 315     bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
 316     if (bytes_needed > 0) {
 317         static const char *paths[] = { DEVRANDOM, NULL };
 318         FILE *fp;
 319         int i;
 320
 321         for (i = 0; paths[i] != NULL; i++) {
 322             if ((fp = fopen(paths[i], "rb")) == NULL)
 323                 continue;
 324             setbuf(fp, NULL);
 325             buffer = rand_pool_add_begin(pool, bytes_needed);
 326             if (buffer != NULL) {
 327                 size_t bytes = 0;
 328                 if (fread(buffer, 1, bytes_needed, fp) == bytes_needed)
 329                     bytes = bytes_needed;
 330
 331                 rand_pool_add_end(pool, bytes, 8 * bytes);
 332                 entropy_available = rand_pool_entropy_available(pool);
 333             }
 334             fclose(fp);
 335             if (entropy_available > 0)
 336                 return entropy_available;
 337
 338             bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
 339         }
 340     }
 341 #   endif
 342
 343 #   ifdef OPENSSL_RAND_SEED_RDTSC
 344     entropy_available = rand_acquire_entropy_from_tsc(pool);
 345     if (entropy_available > 0)
 346         return entropy_available;
 347 #   endif
 348
 349 #   ifdef OPENSSL_RAND_SEED_RDCPU
 350     entropy_available = rand_acquire_entropy_from_cpu(pool);
 351     if (entropy_available > 0)
 352         return entropy_available;
 353 #   endif
 354
 355 #   ifdef OPENSSL_RAND_SEED_EGD
 356     bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
 357     if (bytes_needed > 0) {
 358         static const char *paths[] = { DEVRANDOM_EGD, NULL };
 359         int i;
 360
 361         for (i = 0; paths[i] != NULL; i++) {
 362             buffer = rand_pool_add_begin(pool, bytes_needed);
 363             if (buffer != NULL) {
 364                 size_t bytes = 0;
 365                 int num = RAND_query_egd_bytes(paths[i],
 366                                                buffer, (int)bytes_needed);
 367                 if (num == (int)bytes_needed)
 368                     bytes = bytes_needed;
 369
 370                 rand_pool_add_end(pool, bytes, 8 * bytes);
 371                 entropy_available = rand_pool_entropy_available(pool);
 372             }
 373             if (entropy_available > 0)
 374                 return entropy_available;
 375         }
 376     }
 377 #   endif
 378
 379     return rand_pool_entropy_available(pool);
 380 #  endif
 381 }
 382 # endif
 383 #endif
 384
 385 #ifdef OPENSSL_SYS_UNIX
 386 int rand_pool_add_nonce_data(RAND_POOL *pool)
 387 {
 388     struct {
 389         pid_t pid;
 390         CRYPTO_THREAD_ID tid;
 391         uint64_t time;
 392     } data = { 0 };
 393
 394     /*
 395      * Add process id, thread id, and a high resolution timestamp to
 396      * ensure that the nonce is unique whith high probability for
 397      * different process instances.
 398      */
 399     data.pid = getpid();
 400     data.tid = CRYPTO_THREAD_get_current_id();
 401     data.time = get_time_stamp();
 402
 403     return rand_pool_add(pool, (unsigned char *)&data, sizeof(data), 0);
 404 }
 405
 406 int rand_pool_add_additional_data(RAND_POOL *pool)
 407 {
 408     struct {
 409         CRYPTO_THREAD_ID tid;
 410         uint64_t time;
 411     } data = { 0 };
 412
 413     /*
 414      * Add some noise from the thread id and a high resolution timer.
 415      * The thread id adds a little randomness if the drbg is accessed
 416      * concurrently (which is the case for the <master> drbg).
 417      */
 418     data.tid = CRYPTO_THREAD_get_current_id();
 419     data.time = get_timer_bits();
 420
 421     return rand_pool_add(pool, (unsigned char *)&data, sizeof(data), 0);
 422 }
 423
 424
 425
 426 /*
 427  * Get the current time with the highest possible resolution
 428  *
 429  * The time stamp is added to the nonce, so it is optimized for not repeating.
 430  * The current time is ideal for this purpose, provided the computer's clock
 431  * is synchronized.
 432  */
 433 static uint64_t get_time_stamp(void)
 434 {
 435 # if defined(OSSL_POSIX_TIMER_OKAY)
 436     {
 437         struct timespec ts;
 438
 439         if (clock_gettime(CLOCK_REALTIME, &ts) == 0)
 440             return TWO32TO64(ts.tv_sec, ts.tv_nsec);
 441     }
 442 # endif
 443 # if defined(__unix__) \
 444      || (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200112L)
 445     {
 446         struct timeval tv;
 447
 448         if (gettimeofday(&tv, NULL) == 0)
 449             return TWO32TO64(tv.tv_sec, tv.tv_usec);
 450     }
 451 # endif
 452     return time(NULL);
 453 }
 454
 455 /*
 456  * Get an arbitrary timer value of the highest possible resolution
 457  *
 458  * The timer value is added as random noise to the additional data,
 459  * which is not considered a trusted entropy sourec, so any result
 460  * is acceptable.
 461  */
 462 static uint64_t get_timer_bits(void)
 463 {
 464     uint64_t res = OPENSSL_rdtsc();
 465
 466     if (res != 0)
 467         return res;
 468
 469 # if defined(__sun) || defined(__hpux)
 470     return gethrtime();
 471 # elif defined(_AIX)
 472     {
 473         timebasestruct_t t;
 474
 475         read_wall_time(&t, TIMEBASE_SZ);
 476         return TWO32TO64(t.tb_high, t.tb_low);
 477     }
 478 # elif defined(OSSL_POSIX_TIMER_OKAY)
 479     {
 480         struct timespec ts;
 481
 482 #  ifdef CLOCK_BOOTTIME
 483 #   define CLOCK_TYPE CLOCK_BOOTTIME
 484 #  elif defined(_POSIX_MONOTONIC_CLOCK)
 485 #   define CLOCK_TYPE CLOCK_MONOTONIC
 486 #  else
 487 #   define CLOCK_TYPE CLOCK_REALTIME
 488 #  endif
 489
 490         if (clock_gettime(CLOCK_TYPE, &ts) == 0)
 491             return TWO32TO64(ts.tv_sec, ts.tv_nsec);
 492     }
 493 # endif
 494 # if defined(__unix__) \
 495      || (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200112L)
 496     {
 497         struct timeval tv;
 498
 499         if (gettimeofday(&tv, NULL) == 0)
 500             return TWO32TO64(tv.tv_sec, tv.tv_usec);
 501     }
 502 # endif
 503     return time(NULL);
 504 }
 505 #endif