src/random.cpp

   1 // Copyright (c) 2009-2010 Satoshi Nakamoto
   2 // Copyright (c) 2009-2016 The Bitcoin Core developers
   3 // Distributed under the MIT software license, see the accompanying
   4 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   5
   6 #include "random.h"
   7
   8 #include "crypto/sha512.h"
   9 #include "support/cleanse.h"
  10 #ifdef WIN32
  11 #include "compat.h" // for Windows API
  12 #include <wincrypt.h>
  13 #endif
  14 #include "util.h"             // for LogPrint()
  15 #include "utilstrencodings.h" // for GetTime()
  16
  17 #include <stdlib.h>
  18 #include <limits>
  19 #include <chrono>
  20 #include <thread>
  21
  22 #ifndef WIN32
  23 #include <sys/time.h>
  24 #endif
  25
  26 #ifdef HAVE_SYS_GETRANDOM
  27 #include <sys/syscall.h>
  28 #include <linux/random.h>
  29 #endif
  30 #ifdef HAVE_GETENTROPY
  31 #include <unistd.h>
  32 #endif
  33 #ifdef HAVE_SYSCTL_ARND
  34 #include <sys/sysctl.h>
  35 #endif
  36
  37 #include <mutex>
  38
  39 #include <openssl/err.h>
  40 #include <openssl/rand.h>
  41
  42 static void RandFailure()
  43 {
  44     LogPrintf("Failed to read randomness, aborting\n");
  45     abort();
  46 }
  47
  48 static inline int64_t GetPerformanceCounter()
  49 {
  50     // Read the hardware time stamp counter when available.
  51     // See https://en.wikipedia.org/wiki/Time_Stamp_Counter for more information.
  52 #if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
  53     return __rdtsc();
  54 #elif !defined(_MSC_VER) && defined(__i386__)
  55     uint64_t r = 0;
  56     __asm__ volatile ("rdtsc" : "=A"(r)); // Constrain the r variable to the eax:edx pair.
  57     return r;
  58 #elif !defined(_MSC_VER) && (defined(__x86_64__) || defined(__amd64__))
  59     uint64_t r1 = 0, r2 = 0;
  60     __asm__ volatile ("rdtsc" : "=a"(r1), "=d"(r2)); // Constrain r1 to rax and r2 to rdx.
  61     return (r2 << 32) | r1;
  62 #else
  63     // Fall back to using C++11 clock (usually microsecond or nanosecond precision)
  64     return std::chrono::high_resolution_clock::now().time_since_epoch().count();
  65 #endif
  66 }
  67
  68
  69 #if defined(__x86_64__) || defined(__amd64__) || defined(__i386__)
  70 static std::atomic<bool> hwrand_initialized{false};
  71 static bool rdrand_supported = false;
  72 static constexpr uint32_t CPUID_F1_ECX_RDRAND = 0x40000000;
  73 static void RDRandInit()
  74 {
  75     //! When calling cpuid function #1, ecx register will have this set if RDRAND is available.
  76     // Avoid clobbering ebx, as that is used for PIC on x86.
  77     uint32_t eax, tmp, ecx, edx;
  78     __asm__ ("mov %%ebx, %1; cpuid; mov %1, %%ebx": "=a"(eax), "=g"(tmp), "=c"(ecx), "=d"(edx) : "a"(1));
  79     if (ecx & CPUID_F1_ECX_RDRAND) {
  80         LogPrintf("Using RdRand as entropy source\n");
  81         rdrand_supported = true;
  82     }
  83     hwrand_initialized.store(true);
  84 }
  85 #else
  86 static void RDRandInit() {}
  87 #endif
  88
  89 static bool GetHWRand(unsigned char* ent32) {
  90 #if defined(__x86_64__) || defined(__amd64__) || defined(__i386__)
  91     assert(hwrand_initialized.load(std::memory_order_relaxed));
  92     if (rdrand_supported) {
  93         uint8_t ok;
  94         // Not all assemblers support the rdrand instruction, write it in hex.
  95 #ifdef __i386__
  96         for (int iter = 0; iter < 4; ++iter) {
  97             uint32_t r1, r2;
  98             __asm__ volatile (".byte 0x0f, 0xc7, 0xf0;" // rdrand %eax
  99                               ".byte 0x0f, 0xc7, 0xf2;" // rdrand %edx
 100                               "setc %2" :
 101                               "=a"(r1), "=d"(r2), "=q"(ok) :: "cc");
 102             if (!ok) return false;
 103             WriteLE32(ent32 + 8 * iter, r1);
 104             WriteLE32(ent32 + 8 * iter + 4, r2);
 105         }
 106 #else
 107         uint64_t r1, r2, r3, r4;
 108         __asm__ volatile (".byte 0x48, 0x0f, 0xc7, 0xf0, " // rdrand %rax
 109                                 "0x48, 0x0f, 0xc7, 0xf3, " // rdrand %rbx
 110                                 "0x48, 0x0f, 0xc7, 0xf1, " // rdrand %rcx
 111                                 "0x48, 0x0f, 0xc7, 0xf2; " // rdrand %rdx
 112                           "setc %4" :
 113                           "=a"(r1), "=b"(r2), "=c"(r3), "=d"(r4), "=q"(ok) :: "cc");
 114         if (!ok) return false;
 115         WriteLE64(ent32, r1);
 116         WriteLE64(ent32 + 8, r2);
 117         WriteLE64(ent32 + 16, r3);
 118         WriteLE64(ent32 + 24, r4);
 119 #endif
 120         return true;
 121     }
 122 #endif
 123     return false;
 124 }
 125
 126 void RandAddSeed()
 127 {
 128     // Seed with CPU performance counter
 129     int64_t nCounter = GetPerformanceCounter();
 130     RAND_add(&nCounter, sizeof(nCounter), 1.5);
 131     memory_cleanse((void*)&nCounter, sizeof(nCounter));
 132 }
 133
 134 static void RandAddSeedPerfmon()
 135 {
 136     RandAddSeed();
 137
 138 #ifdef WIN32
 139     // Don't need this on Linux, OpenSSL automatically uses /dev/urandom
 140     // Seed with the entire set of perfmon data
 141
 142     // This can take up to 2 seconds, so only do it every 10 minutes
 143     static int64_t nLastPerfmon;
 144     if (GetTime() < nLastPerfmon + 10 * 60)
 145         return;
 146     nLastPerfmon = GetTime();
 147
 148     std::vector<unsigned char> vData(250000, 0);
 149     long ret = 0;
 150     unsigned long nSize = 0;
 151     const size_t nMaxSize = 10000000; // Bail out at more than 10MB of performance data
 152     while (true) {
 153         nSize = vData.size();
 154         ret = RegQueryValueExA(HKEY_PERFORMANCE_DATA, "Global", NULL, NULL, vData.data(), &nSize);
 155         if (ret != ERROR_MORE_DATA || vData.size() >= nMaxSize)
 156             break;
 157         vData.resize(std::max((vData.size() * 3) / 2, nMaxSize)); // Grow size of buffer exponentially
 158     }
 159     RegCloseKey(HKEY_PERFORMANCE_DATA);
 160     if (ret == ERROR_SUCCESS) {
 161         RAND_add(vData.data(), nSize, nSize / 100.0);
 162         memory_cleanse(vData.data(), nSize);
 163         LogPrint(BCLog::RAND, "%s: %lu bytes\n", __func__, nSize);
 164     } else {
 165         static bool warned = false; // Warn only once
 166         if (!warned) {
 167             LogPrintf("%s: Warning: RegQueryValueExA(HKEY_PERFORMANCE_DATA) failed with code %i\n", __func__, ret);
 168             warned = true;
 169         }
 170     }
 171 #endif
 172 }
 173
 174 #ifndef WIN32
 175 /** Fallback: get 32 bytes of system entropy from /dev/urandom. The most
 176  * compatible way to get cryptographic randomness on UNIX-ish platforms.
 177  */
 178 void GetDevURandom(unsigned char *ent32)
 179 {
 180     int f = open("/dev/urandom", O_RDONLY);
 181     if (f == -1) {
 182         RandFailure();
 183     }
 184     int have = 0;
 185     do {
 186         ssize_t n = read(f, ent32 + have, NUM_OS_RANDOM_BYTES - have);
 187         if (n <= 0 || n + have > NUM_OS_RANDOM_BYTES) {
 188             RandFailure();
 189         }
 190         have += n;
 191     } while (have < NUM_OS_RANDOM_BYTES);
 192     close(f);
 193 }
 194 #endif
 195
 196 /** Get 32 bytes of system entropy. */
 197 void GetOSRand(unsigned char *ent32)
 198 {
 199 #if defined(WIN32)
 200     HCRYPTPROV hProvider;
 201     int ret = CryptAcquireContextW(&hProvider, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
 202     if (!ret) {
 203         RandFailure();
 204     }
 205     ret = CryptGenRandom(hProvider, NUM_OS_RANDOM_BYTES, ent32);
 206     if (!ret) {
 207         RandFailure();
 208     }
 209     CryptReleaseContext(hProvider, 0);
 210 #elif defined(HAVE_SYS_GETRANDOM)
 211     /* Linux. From the getrandom(2) man page:
 212      * "If the urandom source has been initialized, reads of up to 256 bytes
 213      * will always return as many bytes as requested and will not be
 214      * interrupted by signals."
 215      */
 216     int rv = syscall(SYS_getrandom, ent32, NUM_OS_RANDOM_BYTES, 0);
 217     if (rv != NUM_OS_RANDOM_BYTES) {
 218         if (rv < 0 && errno == ENOSYS) {
 219             /* Fallback for kernel <3.17: the return value will be -1 and errno
 220              * ENOSYS if the syscall is not available, in that case fall back
 221              * to /dev/urandom.
 222              */
 223             GetDevURandom(ent32);
 224         } else {
 225             RandFailure();
 226         }
 227     }
 228 #elif defined(HAVE_GETENTROPY)
 229     /* On OpenBSD this can return up to 256 bytes of entropy, will return an
 230      * error if more are requested.
 231      * The call cannot return less than the requested number of bytes.
 232      */
 233     if (getentropy(ent32, NUM_OS_RANDOM_BYTES) != 0) {
 234         RandFailure();
 235     }
 236 #elif defined(HAVE_SYSCTL_ARND)
 237     /* FreeBSD and similar. It is possible for the call to return less
 238      * bytes than requested, so need to read in a loop.
 239      */
 240     static const int name[2] = {CTL_KERN, KERN_ARND};
 241     int have = 0;
 242     do {
 243         size_t len = NUM_OS_RANDOM_BYTES - have;
 244         if (sysctl(name, ARRAYLEN(name), ent32 + have, &len, NULL, 0) != 0) {
 245             RandFailure();
 246         }
 247         have += len;
 248     } while (have < NUM_OS_RANDOM_BYTES);
 249 #else
 250     /* Fall back to /dev/urandom if there is no specific method implemented to
 251      * get system entropy for this OS.
 252      */
 253     GetDevURandom(ent32);
 254 #endif
 255 }
 256
 257 void GetRandBytes(unsigned char* buf, int num)
 258 {
 259     if (RAND_bytes(buf, num) != 1) {
 260         RandFailure();
 261     }
 262 }
 263
 264 static void AddDataToRng(void* data, size_t len);
 265
 266 void RandAddSeedSleep()
 267 {
 268     int64_t nPerfCounter1 = GetPerformanceCounter();
 269     std::this_thread::sleep_for(std::chrono::milliseconds(1));
 270     int64_t nPerfCounter2 = GetPerformanceCounter();
 271
 272     // Combine with and update state
 273     AddDataToRng(&nPerfCounter1, sizeof(nPerfCounter1));
 274     AddDataToRng(&nPerfCounter2, sizeof(nPerfCounter2));
 275
 276     memory_cleanse(&nPerfCounter1, sizeof(nPerfCounter1));
 277     memory_cleanse(&nPerfCounter2, sizeof(nPerfCounter2));
 278 }
 279
 280
 281 static std::mutex cs_rng_state;
 282 static unsigned char rng_state[32] = {0};
 283 static uint64_t rng_counter = 0;
 284
 285 static void AddDataToRng(void* data, size_t len) {
 286     CSHA512 hasher;
 287     hasher.Write((const unsigned char*)&len, sizeof(len));
 288     hasher.Write((const unsigned char*)data, len);
 289     unsigned char buf[64];
 290     {
 291         std::unique_lock<std::mutex> lock(cs_rng_state);
 292         hasher.Write(rng_state, sizeof(rng_state));
 293         hasher.Write((const unsigned char*)&rng_counter, sizeof(rng_counter));
 294         ++rng_counter;
 295         hasher.Finalize(buf);
 296         memcpy(rng_state, buf + 32, 32);
 297     }
 298     memory_cleanse(buf, 64);
 299 }
 300
 301 void GetStrongRandBytes(unsigned char* out, int num)
 302 {
 303     assert(num <= 32);
 304     CSHA512 hasher;
 305     unsigned char buf[64];
 306
 307     // First source: OpenSSL's RNG
 308     RandAddSeedPerfmon();
 309     GetRandBytes(buf, 32);
 310     hasher.Write(buf, 32);
 311
 312     // Second source: OS RNG
 313     GetOSRand(buf);
 314     hasher.Write(buf, 32);
 315
 316     // Third source: HW RNG, if available.
 317     if (GetHWRand(buf)) {
 318         hasher.Write(buf, 32);
 319     }
 320
 321     // Combine with and update state
 322     {
 323         std::unique_lock<std::mutex> lock(cs_rng_state);
 324         hasher.Write(rng_state, sizeof(rng_state));
 325         hasher.Write((const unsigned char*)&rng_counter, sizeof(rng_counter));
 326         ++rng_counter;
 327         hasher.Finalize(buf);
 328         memcpy(rng_state, buf + 32, 32);
 329     }
 330
 331     // Produce output
 332     memcpy(out, buf, num);
 333     memory_cleanse(buf, 64);
 334 }
 335
 336 uint64_t GetRand(uint64_t nMax)
 337 {
 338     if (nMax == 0)
 339         return 0;
 340
 341     // The range of the random source must be a multiple of the modulus
 342     // to give every possible output value an equal possibility
 343     uint64_t nRange = (std::numeric_limits<uint64_t>::max() / nMax) * nMax;
 344     uint64_t nRand = 0;
 345     do {
 346         GetRandBytes((unsigned char*)&nRand, sizeof(nRand));
 347     } while (nRand >= nRange);
 348     return (nRand % nMax);
 349 }
 350
 351 int GetRandInt(int nMax)
 352 {
 353     return GetRand(nMax);
 354 }
 355
 356 uint256 GetRandHash()
 357 {
 358     uint256 hash;
 359     GetRandBytes((unsigned char*)&hash, sizeof(hash));
 360     return hash;
 361 }
 362
 363 void FastRandomContext::RandomSeed()
 364 {
 365     uint256 seed = GetRandHash();
 366     rng.SetKey(seed.begin(), 32);
 367     requires_seed = false;
 368 }
 369
 370 FastRandomContext::FastRandomContext(const uint256& seed) : requires_seed(false), bytebuf_size(0), bitbuf_size(0)
 371 {
 372     rng.SetKey(seed.begin(), 32);
 373 }
 374
 375 bool Random_SanityCheck()
 376 {
 377     uint64_t start = GetPerformanceCounter();
 378
 379     /* This does not measure the quality of randomness, but it does test that
 380      * OSRandom() overwrites all 32 bytes of the output given a maximum
 381      * number of tries.
 382      */
 383     static const ssize_t MAX_TRIES = 1024;
 384     uint8_t data[NUM_OS_RANDOM_BYTES];
 385     bool overwritten[NUM_OS_RANDOM_BYTES] = {}; /* Tracks which bytes have been overwritten at least once */
 386     int num_overwritten;
 387     int tries = 0;
 388     /* Loop until all bytes have been overwritten at least once, or max number tries reached */
 389     do {
 390         memset(data, 0, NUM_OS_RANDOM_BYTES);
 391         GetOSRand(data);
 392         for (int x=0; x < NUM_OS_RANDOM_BYTES; ++x) {
 393             overwritten[x] |= (data[x] != 0);
 394         }
 395
 396         num_overwritten = 0;
 397         for (int x=0; x < NUM_OS_RANDOM_BYTES; ++x) {
 398             if (overwritten[x]) {
 399                 num_overwritten += 1;
 400             }
 401         }
 402
 403         tries += 1;
 404     } while (num_overwritten < NUM_OS_RANDOM_BYTES && tries < MAX_TRIES);
 405     if (num_overwritten != NUM_OS_RANDOM_BYTES) return false; /* If this failed, bailed out after too many tries */
 406
 407     // Check that GetPerformanceCounter increases at least during a GetOSRand() call + 1ms sleep.
 408     std::this_thread::sleep_for(std::chrono::milliseconds(1));
 409     uint64_t stop = GetPerformanceCounter();
 410     if (stop == start) return false;
 411
 412     // We called GetPerformanceCounter. Use it as entropy.
 413     RAND_add((const unsigned char*)&start, sizeof(start), 1);
 414     RAND_add((const unsigned char*)&stop, sizeof(stop), 1);
 415
 416     return true;
 417 }
 418
 419 FastRandomContext::FastRandomContext(bool fDeterministic) : requires_seed(!fDeterministic), bytebuf_size(0), bitbuf_size(0)
 420 {
 421     if (!fDeterministic) {
 422         return;
 423     }
 424     uint256 seed;
 425     rng.SetKey(seed.begin(), 32);
 426 }
 427
 428 void RandomInit()
 429 {
 430     RDRandInit();
 431 }