diff --git a/src/random.cpp b/src/random.cpp index b49c49c10..436763f3a 100644 --- a/src/random.cpp +++ b/src/random.cpp @@ -1,800 +1,790 @@ // Copyright (c) 2009-2010 Satoshi Nakamoto // Copyright (c) 2009-2016 The Bitcoin Core developers // Distributed under the MIT software license, see the accompanying // file COPYING or http://www.opensource.org/licenses/mit-license.php. #include #ifdef WIN32 #include // for Windows API #include #endif #include #include #include // for LogPrintf() #include #include #include #include // for Mutex #include // for GetTime() #include #include #include #include #include #include #include #include #ifndef WIN32 #include #include #endif #ifdef HAVE_SYS_GETRANDOM #include #include #endif #if defined(HAVE_GETENTROPY) || \ (defined(HAVE_GETENTROPY_RAND) && defined(MAC_OSX)) #include #endif #if defined(HAVE_GETENTROPY_RAND) && defined(MAC_OSX) #include #endif #ifdef HAVE_SYSCTL_ARND #include #include // for ARRAYLEN #endif [[noreturn]] static void RandFailure() { LogPrintf("Failed to read randomness, aborting\n"); std::abort(); } static inline int64_t GetPerformanceCounter() noexcept { // Read the hardware time stamp counter when available. // See https://en.wikipedia.org/wiki/Time_Stamp_Counter for more information. #if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64)) return __rdtsc(); #elif !defined(_MSC_VER) && defined(__i386__) uint64_t r = 0; // Constrain the r variable to the eax:edx pair. __asm__ volatile("rdtsc" : "=A"(r)); return r; #elif !defined(_MSC_VER) && (defined(__x86_64__) || defined(__amd64__)) uint64_t r1 = 0, r2 = 0; // Constrain r1 to rax and r2 to rdx. __asm__ volatile("rdtsc" : "=a"(r1), "=d"(r2)); return (r2 << 32) | r1; #else // Fall back to using C++11 clock (usually microsecond or nanosecond // precision) return std::chrono::high_resolution_clock::now().time_since_epoch().count(); #endif } #ifdef HAVE_GETCPUID static bool g_rdrand_supported = false; static bool g_rdseed_supported = false; static constexpr uint32_t CPUID_F1_ECX_RDRAND = 0x40000000; static constexpr uint32_t CPUID_F7_EBX_RDSEED = 0x00040000; #ifdef bit_RDRND static_assert(CPUID_F1_ECX_RDRAND == bit_RDRND, "Unexpected value for bit_RDRND"); #endif #ifdef bit_RDSEED static_assert(CPUID_F7_EBX_RDSEED == bit_RDSEED, "Unexpected value for bit_RDSEED"); #endif static void InitHardwareRand() { uint32_t eax, ebx, ecx, edx; GetCPUID(1, 0, eax, ebx, ecx, edx); if (ecx & CPUID_F1_ECX_RDRAND) { g_rdrand_supported = true; } GetCPUID(7, 0, eax, ebx, ecx, edx); if (ebx & CPUID_F7_EBX_RDSEED) { g_rdseed_supported = true; } } static void ReportHardwareRand() { // This must be done in a separate function, as InitHardwareRand() may be // indirectly called from global constructors, before logging is // initialized. if (g_rdseed_supported) { LogPrintf("Using RdSeed as additional entropy source\n"); } if (g_rdrand_supported) { LogPrintf("Using RdRand as an additional entropy source\n"); } } /** * Read 64 bits of entropy using rdrand. * * Must only be called when RdRand is supported. */ static uint64_t GetRdRand() noexcept { // RdRand may very rarely fail. Invoke it up to 10 times in a loop to reduce // this risk. #ifdef __i386__ uint8_t ok; uint32_t r1, r2; for (int i = 0; i < 10; ++i) { // rdrand %eax __asm__ volatile(".byte 0x0f, 0xc7, 0xf0; setc %1" : "=a"(r1), "=q"(ok)::"cc"); if (ok) { break; } } for (int i = 0; i < 10; ++i) { // rdrand %eax __asm__ volatile(".byte 0x0f, 0xc7, 0xf0; setc %1" : "=a"(r2), "=q"(ok)::"cc"); if (ok) { break; } } return (uint64_t(r2) << 32) | r1; #elif defined(__x86_64__) || defined(__amd64__) uint8_t ok; uint64_t r1; for (int i = 0; i < 10; ++i) { // rdrand %rax __asm__ volatile(".byte 0x48, 0x0f, 0xc7, 0xf0; setc %1" : "=a"(r1), "=q"(ok)::"cc"); if (ok) { break; } } return r1; #else #error "RdRand is only supported on x86 and x86_64" #endif } /** * Read 64 bits of entropy using rdseed. * * Must only be called when RdSeed is supported. */ static uint64_t GetRdSeed() noexcept { // RdSeed may fail when the HW RNG is overloaded. Loop indefinitely until // enough entropy is gathered, but pause after every failure. #ifdef __i386__ uint8_t ok; uint32_t r1, r2; do { // rdseed %eax __asm__ volatile(".byte 0x0f, 0xc7, 0xf8; setc %1" : "=a"(r1), "=q"(ok)::"cc"); if (ok) { break; } __asm__ volatile("pause"); } while (true); do { // rdseed %eax __asm__ volatile(".byte 0x0f, 0xc7, 0xf8; setc %1" : "=a"(r2), "=q"(ok)::"cc"); if (ok) { break; } __asm__ volatile("pause"); } while (true); return (uint64_t(r2) << 32) | r1; #elif defined(__x86_64__) || defined(__amd64__) uint8_t ok; uint64_t r1; do { // rdseed %rax __asm__ volatile(".byte 0x48, 0x0f, 0xc7, 0xf8; setc %1" : "=a"(r1), "=q"(ok)::"cc"); if (ok) { break; } __asm__ volatile("pause"); } while (true); return r1; #else #error "RdSeed is only supported on x86 and x86_64" #endif } #else /** * Access to other hardware random number generators could be added here later, * assuming it is sufficiently fast (in the order of a few hundred CPU cycles). * Slower sources should probably be invoked separately, and/or only from - * RandAddSeedSleep (which is called during idle background operation). + * RandAddPeriodic (which is called once a minute). */ static void InitHardwareRand() {} static void ReportHardwareRand() {} #endif /** * Add 64 bits of entropy gathered from hardware to hasher. Do nothing if not * supported. */ static void SeedHardwareFast(CSHA512 &hasher) noexcept { #if defined(__x86_64__) || defined(__amd64__) || defined(__i386__) if (g_rdrand_supported) { uint64_t out = GetRdRand(); hasher.Write((const uint8_t *)&out, sizeof(out)); return; } #endif } /** * Add 256 bits of entropy gathered from hardware to hasher. Do nothing if not * supported. */ static void SeedHardwareSlow(CSHA512 &hasher) noexcept { #if defined(__x86_64__) || defined(__amd64__) || defined(__i386__) // When we want 256 bits of entropy, prefer RdSeed over RdRand, as it's // guaranteed to produce independent randomness on every call. if (g_rdseed_supported) { for (int i = 0; i < 4; ++i) { uint64_t out = GetRdSeed(); hasher.Write((const uint8_t *)&out, sizeof(out)); } return; } // When falling back to RdRand, XOR the result of 1024 results. // This guarantees a reseeding occurs between each. if (g_rdrand_supported) { for (int i = 0; i < 4; ++i) { uint64_t out = 0; for (int j = 0; j < 1024; ++j) { out ^= GetRdRand(); } hasher.Write((const uint8_t *)&out, sizeof(out)); } return; } #endif } /** * Use repeated SHA512 to strengthen the randomness in seed32, and feed into * hasher. */ static void Strengthen(const uint8_t (&seed)[32], int microseconds, CSHA512 &hasher) noexcept { CSHA512 inner_hasher; inner_hasher.Write(seed, sizeof(seed)); // Hash loop uint8_t buffer[64]; int64_t stop = GetTimeMicros() + microseconds; do { for (int i = 0; i < 1000; ++i) { inner_hasher.Finalize(buffer); inner_hasher.Reset(); inner_hasher.Write(buffer, sizeof(buffer)); } // Benchmark operation and feed it into outer hasher. int64_t perf = GetPerformanceCounter(); hasher.Write((const uint8_t *)&perf, sizeof(perf)); } while (GetTimeMicros() < stop); // Produce output from inner state and feed it to outer hasher. inner_hasher.Finalize(buffer); hasher.Write(buffer, sizeof(buffer)); // Try to clean up. inner_hasher.Reset(); memory_cleanse(buffer, sizeof(buffer)); } #ifndef WIN32 /** * Fallback: get 32 bytes of system entropy from /dev/urandom. The most * compatible way to get cryptographic randomness on UNIX-ish platforms. */ static void GetDevURandom(uint8_t *ent32) { int f = open("/dev/urandom", O_RDONLY); if (f == -1) { RandFailure(); } int have = 0; do { ssize_t n = read(f, ent32 + have, NUM_OS_RANDOM_BYTES - have); if (n <= 0 || n + have > NUM_OS_RANDOM_BYTES) { close(f); RandFailure(); } have += n; } while (have < NUM_OS_RANDOM_BYTES); close(f); } #endif /** Get 32 bytes of system entropy. */ void GetOSRand(uint8_t *ent32) { #if defined(WIN32) HCRYPTPROV hProvider; int ret = CryptAcquireContextW(&hProvider, nullptr, nullptr, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT); if (!ret) { RandFailure(); } ret = CryptGenRandom(hProvider, NUM_OS_RANDOM_BYTES, ent32); if (!ret) { RandFailure(); } CryptReleaseContext(hProvider, 0); #elif defined(HAVE_SYS_GETRANDOM) /** * Linux. From the getrandom(2) man page: * "If the urandom source has been initialized, reads of up to 256 bytes * will always return as many bytes as requested and will not be interrupted * by signals." */ int rv = syscall(SYS_getrandom, ent32, NUM_OS_RANDOM_BYTES, 0); if (rv != NUM_OS_RANDOM_BYTES) { if (rv < 0 && errno == ENOSYS) { /* Fallback for kernel <3.17: the return value will be -1 and errno * ENOSYS if the syscall is not available, in that case fall back * to /dev/urandom. */ GetDevURandom(ent32); } else { RandFailure(); } } #elif defined(HAVE_GETENTROPY) && defined(__OpenBSD__) /** * On OpenBSD this can return up to 256 bytes of entropy, will return an * error if more are requested. * The call cannot return less than the requested number of bytes. * getentropy is explicitly limited to openbsd here, as a similar (but not * the same) function may exist on other platforms via glibc. */ if (getentropy(ent32, NUM_OS_RANDOM_BYTES) != 0) { RandFailure(); } #elif defined(HAVE_GETENTROPY_RAND) && defined(MAC_OSX) // We need a fallback for OSX < 10.12 if (&getentropy != nullptr) { if (getentropy(ent32, NUM_OS_RANDOM_BYTES) != 0) { RandFailure(); } } else { GetDevURandom(ent32); } #elif defined(HAVE_SYSCTL_ARND) /** * FreeBSD and similar. It is possible for the call to return less bytes * than requested, so need to read in a loop. */ static const int name[2] = {CTL_KERN, KERN_ARND}; int have = 0; do { size_t len = NUM_OS_RANDOM_BYTES - have; if (sysctl(name, ARRAYLEN(name), ent32 + have, &len, nullptr, 0) != 0) { RandFailure(); } have += len; } while (have < NUM_OS_RANDOM_BYTES); #else /** * Fall back to /dev/urandom if there is no specific method implemented to * get system entropy for this OS. */ GetDevURandom(ent32); #endif } void LockingCallbackOpenSSL(int mode, int i, const char *file, int line); namespace { class RNGState { Mutex m_mutex; /** * The RNG state consists of 256 bits of entropy, taken from the output of * one operation's SHA512 output, and fed as input to the next one. * Carrying 256 bits of entropy should be sufficient to guarantee * unpredictability as long as any entropy source was ever unpredictable * to an attacker. To protect against situations where an attacker might * observe the RNG's state, fresh entropy is always mixed when * GetStrongRandBytes is called. */ uint8_t m_state[32] GUARDED_BY(m_mutex) = {0}; uint64_t m_counter GUARDED_BY(m_mutex) = 0; bool m_strongly_seeded GUARDED_BY(m_mutex) = false; std::unique_ptr m_mutex_openssl; public: RNGState() noexcept { InitHardwareRand(); // Init OpenSSL library multithreading support m_mutex_openssl.reset(new Mutex[CRYPTO_num_locks()]); CRYPTO_set_locking_callback(LockingCallbackOpenSSL); // OpenSSL can optionally load a config file which lists optional // loadable modules and engines. We don't use them so we don't require // the config. However some of our libs may call functions which attempt // to load the config file, possibly resulting in an exit() or crash if // it is missing or corrupt. Explicitly tell OpenSSL not to try to load // the file. The result for our libs will be that the config appears to // have been loaded and there are no modules/engines available. OPENSSL_no_config(); } ~RNGState() { // Securely erase the memory used by the OpenSSL PRNG RAND_cleanup(); // Shutdown OpenSSL library multithreading support CRYPTO_set_locking_callback(nullptr); } /** * Extract up to 32 bytes of entropy from the RNG state, mixing in new * entropy from hasher. * * If this function has never been called with strong_seed = true, false is * returned. */ bool MixExtract(uint8_t *out, size_t num, CSHA512 &&hasher, bool strong_seed) noexcept { assert(num <= 32); uint8_t buf[64]; static_assert(sizeof(buf) == CSHA512::OUTPUT_SIZE, "Buffer needs to have hasher's output size"); bool ret; { LOCK(m_mutex); ret = (m_strongly_seeded |= strong_seed); // Write the current state of the RNG into the hasher hasher.Write(m_state, 32); // Write a new counter number into the state hasher.Write((const uint8_t *)&m_counter, sizeof(m_counter)); ++m_counter; // Finalize the hasher hasher.Finalize(buf); // Store the last 32 bytes of the hash output as new RNG state. memcpy(m_state, buf + 32, 32); } // If desired, copy (up to) the first 32 bytes of the hash output as // output. if (num) { assert(out != nullptr); memcpy(out, buf, num); } // Best effort cleanup of internal state hasher.Reset(); memory_cleanse(buf, 64); return ret; } Mutex &GetOpenSSLMutex(int i) { return m_mutex_openssl[i]; } }; RNGState &GetRNGState() noexcept { // This C++11 idiom relies on the guarantee that static variable are // initialized on first call, even when multiple parallel calls are // permitted. static std::vector> g_rng(1); return g_rng[0]; } } // namespace void LockingCallbackOpenSSL(int mode, int i, const char *file, int line) NO_THREAD_SAFETY_ANALYSIS { RNGState &rng = GetRNGState(); if (mode & CRYPTO_LOCK) { rng.GetOpenSSLMutex(i).lock(); } else { rng.GetOpenSSLMutex(i).unlock(); } } /** * A note on the use of noexcept in the seeding functions below: * - * None of the RNG code should ever throw any exception, with the sole exception - * of MilliSleep in SeedSleep, which can (and does) support interruptions which - * cause a boost::thread_interrupted to be thrown. - * - * This means that SeedSleep, and all functions that invoke it are throwing. - * However, we know that GetRandBytes() and GetStrongRandBytes() never trigger - * this sleeping logic, so they are noexcept. The same is true for all the - * GetRand*() functions that use GetRandBytes() indirectly. - * - * TODO: After moving away from interruptible boost-based thread management, - * everything can become noexcept here. + * None of the RNG code should ever throw any exception. */ static void SeedTimestamp(CSHA512 &hasher) noexcept { int64_t perfcounter = GetPerformanceCounter(); hasher.Write((const uint8_t *)&perfcounter, sizeof(perfcounter)); } static void SeedFast(CSHA512 &hasher) noexcept { uint8_t buffer[32]; // Stack pointer to indirectly commit to thread/callstack const uint8_t *ptr = buffer; hasher.Write((const uint8_t *)&ptr, sizeof(ptr)); // Hardware randomness is very fast when available; use it always. SeedHardwareFast(hasher); // High-precision timestamp SeedTimestamp(hasher); } static void SeedSlow(CSHA512 &hasher) noexcept { uint8_t buffer[32]; // Everything that the 'fast' seeder includes SeedFast(hasher); // OS randomness GetOSRand(buffer); hasher.Write(buffer, sizeof(buffer)); // OpenSSL RNG (for now) RAND_bytes(buffer, sizeof(buffer)); hasher.Write(buffer, sizeof(buffer)); // High-precision timestamp. // // Note that we also commit to a timestamp in the Fast seeder, so we // indirectly commit to a benchmark of all the entropy gathering sources in // this function). SeedTimestamp(hasher); } /** Extract entropy from rng, strengthen it, and feed it into hasher. */ static void SeedStrengthen(CSHA512 &hasher, RNGState &rng, int microseconds) noexcept { // Generate 32 bytes of entropy from the RNG, and a copy of the entropy // already in hasher. uint8_t strengthen_seed[32]; rng.MixExtract(strengthen_seed, sizeof(strengthen_seed), CSHA512(hasher), false); // Strengthen the seed, and feed it into hasher. Strengthen(strengthen_seed, microseconds, hasher); } -static void SeedPeriodic(CSHA512 &hasher, RNGState &rng) { +static void SeedPeriodic(CSHA512 &hasher, RNGState &rng) noexcept { // Everything that the 'fast' seeder includes SeedFast(hasher); // High-precision timestamp SeedTimestamp(hasher); // Dynamic environment data (performance monitoring, ...) auto old_size = hasher.Size(); RandAddDynamicEnv(hasher); LogPrintf("Feeding %i bytes of dynamic environment data into RNG\n", hasher.Size() - old_size); // Strengthen for 10ms SeedStrengthen(hasher, rng, 10000); } static void SeedStartup(CSHA512 &hasher, RNGState &rng) noexcept { // Gather 256 bits of hardware randomness, if available SeedHardwareSlow(hasher); // Everything that the 'slow' seeder includes. SeedSlow(hasher); // Dynamic environment data (performance monitoring, ...) auto old_size = hasher.Size(); RandAddDynamicEnv(hasher); // Static environment data RandAddStaticEnv(hasher); LogPrintf("Feeding %i bytes of environment data into RNG\n", hasher.Size() - old_size); // Strengthen for 100ms SeedStrengthen(hasher, rng, 100000); } enum class RNGLevel { FAST, //!< Automatically called by GetRandBytes SLOW, //!< Automatically called by GetStrongRandBytes PERIODIC, //!< Called by RandAddPeriodic() }; static void ProcRand(uint8_t *out, int num, RNGLevel level) { // Make sure the RNG is initialized first (as all Seed* function possibly // need hwrand to be available). RNGState &rng = GetRNGState(); assert(num <= 32); CSHA512 hasher; switch (level) { case RNGLevel::FAST: SeedFast(hasher); break; case RNGLevel::SLOW: SeedSlow(hasher); break; case RNGLevel::PERIODIC: SeedPeriodic(hasher, rng); break; } // Combine with and update state if (!rng.MixExtract(out, num, std::move(hasher), false)) { // On the first invocation, also seed with SeedStartup(). CSHA512 startup_hasher; SeedStartup(startup_hasher, rng); rng.MixExtract(out, num, std::move(startup_hasher), true); } // For anything but the 'fast' level, feed the resulting RNG output (after // an additional hashing step) back into OpenSSL. if (level != RNGLevel::FAST) { uint8_t buf[64]; CSHA512().Write(out, num).Finalize(buf); RAND_add(buf, sizeof(buf), num); memory_cleanse(buf, 64); } } void GetRandBytes(uint8_t *buf, int num) noexcept { ProcRand(buf, num, RNGLevel::FAST); } void GetStrongRandBytes(uint8_t *buf, int num) noexcept { ProcRand(buf, num, RNGLevel::SLOW); } -void RandAddPeriodic() { +void RandAddPeriodic() noexcept { ProcRand(nullptr, 0, RNGLevel::PERIODIC); } bool g_mock_deterministic_tests{false}; uint64_t GetRand(uint64_t nMax) noexcept { return FastRandomContext(g_mock_deterministic_tests).randrange(nMax); } std::chrono::microseconds GetRandMicros(std::chrono::microseconds duration_max) noexcept { return std::chrono::microseconds{GetRand(duration_max.count())}; } int GetRandInt(int nMax) noexcept { return GetRand(nMax); } uint256 GetRandHash() noexcept { uint256 hash; GetRandBytes((uint8_t *)&hash, sizeof(hash)); return hash; } void FastRandomContext::RandomSeed() { uint256 seed = GetRandHash(); rng.SetKey(seed.begin(), 32); requires_seed = false; } uint256 FastRandomContext::rand256() noexcept { if (bytebuf_size < 32) { FillByteBuffer(); } uint256 ret; memcpy(ret.begin(), bytebuf + 64 - bytebuf_size, 32); bytebuf_size -= 32; return ret; } std::vector FastRandomContext::randbytes(size_t len) { if (requires_seed) { RandomSeed(); } std::vector ret(len); if (len > 0) { rng.Output(&ret[0], len); } return ret; } FastRandomContext::FastRandomContext(const uint256 &seed) noexcept : requires_seed(false), bytebuf_size(0), bitbuf_size(0) { rng.SetKey(seed.begin(), 32); } bool Random_SanityCheck() { uint64_t start = GetPerformanceCounter(); /** * This does not measure the quality of randomness, but it does test that * GetOSRand() overwrites all 32 bytes of the output given a maximum number * of tries. */ static const ssize_t MAX_TRIES = 1024; uint8_t data[NUM_OS_RANDOM_BYTES]; /* Tracks which bytes have been overwritten at least once */ bool overwritten[NUM_OS_RANDOM_BYTES] = {}; int num_overwritten; int tries = 0; /** * Loop until all bytes have been overwritten at least once, or max number * tries reached. */ do { memset(data, 0, NUM_OS_RANDOM_BYTES); GetOSRand(data); for (int x = 0; x < NUM_OS_RANDOM_BYTES; ++x) { overwritten[x] |= (data[x] != 0); } num_overwritten = 0; for (int x = 0; x < NUM_OS_RANDOM_BYTES; ++x) { if (overwritten[x]) { num_overwritten += 1; } } tries += 1; } while (num_overwritten < NUM_OS_RANDOM_BYTES && tries < MAX_TRIES); /* If this failed, bailed out after too many tries */ if (num_overwritten != NUM_OS_RANDOM_BYTES) { return false; } // Check that GetPerformanceCounter increases at least during a GetOSRand() // call + 1ms sleep. std::this_thread::sleep_for(std::chrono::milliseconds(1)); uint64_t stop = GetPerformanceCounter(); if (stop == start) { return false; } // We called GetPerformanceCounter. Use it as entropy. CSHA512 to_add; to_add.Write((const uint8_t *)&start, sizeof(start)); to_add.Write((const uint8_t *)&stop, sizeof(stop)); GetRNGState().MixExtract(nullptr, 0, std::move(to_add), false); return true; } FastRandomContext::FastRandomContext(bool fDeterministic) noexcept : requires_seed(!fDeterministic), bytebuf_size(0), bitbuf_size(0) { if (!fDeterministic) { return; } uint256 seed; rng.SetKey(seed.begin(), 32); } FastRandomContext &FastRandomContext:: operator=(FastRandomContext &&from) noexcept { requires_seed = from.requires_seed; rng = from.rng; std::copy(std::begin(from.bytebuf), std::end(from.bytebuf), std::begin(bytebuf)); bytebuf_size = from.bytebuf_size; bitbuf = from.bitbuf; bitbuf_size = from.bitbuf_size; from.requires_seed = true; from.bytebuf_size = 0; from.bitbuf_size = 0; return *this; } void RandomInit() { // Invoke RNG code to trigger initialization (if not already performed) ProcRand(nullptr, 0, RNGLevel::FAST); ReportHardwareRand(); } diff --git a/src/random.h b/src/random.h index f7d71846e..3dea3d072 100644 --- a/src/random.h +++ b/src/random.h @@ -1,261 +1,259 @@ // Copyright (c) 2009-2010 Satoshi Nakamoto // Copyright (c) 2009-2016 The Bitcoin Core developers // Distributed under the MIT software license, see the accompanying // file COPYING or http://www.opensource.org/licenses/mit-license.php. #ifndef BITCOIN_RANDOM_H #define BITCOIN_RANDOM_H #include #include #include #include // For std::chrono::microseconds #include #include /** * Overall design of the RNG and entropy sources. * * We maintain a single global 256-bit RNG state for all high-quality * randomness. The following (classes of) functions interact with that state by * mixing in new entropy, and optionally extracting random output from it: * * - The GetRand*() class of functions, as well as construction of * FastRandomContext objects, perform 'fast' seeding, consisting of mixing in: * - A stack pointer (indirectly committing to calling thread and call stack) * - A high-precision timestamp (rdtsc when available, c++ * high_resolution_clock otherwise) * - 64 bits from the hardware RNG (rdrand) when available. * These entropy sources are very fast, and only designed to protect against * situations where a VM state restore/copy results in multiple systems with the * same randomness. FastRandomContext on the other hand does not protect against * this once created, but is even faster (and acceptable to use inside tight * loops). * * - The GetStrongRand*() class of function perform 'slow' seeding, including * everything that fast seeding includes, but additionally: * - OS entropy (/dev/urandom, getrandom(), ...). The application will * terminate if this entropy source fails. * - Bytes from OpenSSL's RNG (which itself may be seeded from various * sources) * - Another high-precision timestamp (indirectly committing to a benchmark of * all the previous sources). These entropy sources are slower, but designed to * make sure the RNG state contains fresh data that is unpredictable to * attackers. * - * - RandAddSeedSleep() seeds everything that fast seeding includes, but + * - RandAddPeriodic() seeds everything that fast seeding includes, but * additionally: - * - A high-precision timestamp before and after sleeping 1ms. - * - (On Windows) Once every 10 minutes, performance monitoring data from the - * OS. - * - Once every minute, strengthen the entropy for 10 ms using repeated - * SHA512. - * These just exploit the fact the system is idle to improve the quality - * of the RNG slightly. + * - A high-precision timestamp + * - Dynamic environment data (performance monitoring, ...) + * - Strengthen the entropy for 10 ms using repeated SHA512. + * This is run once every minute. * * On first use of the RNG (regardless of what function is called first), all * entropy sources used in the 'slow' seeder are included, but also: * - 256 bits from the hardware RNG (rdseed or rdrand) when available. - * - (On Windows) Performance monitoring data from the OS. + * - Dynamic environment data (performance monitoring, ...) + * - Static environment data * - Strengthen the entropy for 100 ms using repeated SHA512. * * When mixing in new entropy, H = SHA512(entropy || old_rng_state) is computed, * and (up to) the first 32 bytes of H are produced as output, while the last 32 * bytes become the new RNG state. */ /** * Generate random data via the internal PRNG. * * These functions are designed to be fast (sub microsecond), but do not * necessarily meaningfully add entropy to the PRNG state. * * Thread-safe. */ void GetRandBytes(uint8_t *buf, int num) noexcept; uint64_t GetRand(uint64_t nMax) noexcept; std::chrono::microseconds GetRandMicros(std::chrono::microseconds duration_max) noexcept; int GetRandInt(int nMax) noexcept; uint256 GetRandHash() noexcept; /** * Gather entropy from various sources, feed it into the internal PRNG, and * generate random data using it. * * This function will cause failure whenever the OS RNG fails. * * Thread-safe. */ void GetStrongRandBytes(uint8_t *buf, int num) noexcept; /** * Gather entropy from various expensive sources, and feed them to the PRNG * state. * * Thread-safe. */ -void RandAddPeriodic(); +void RandAddPeriodic() noexcept; /** * Fast randomness source. This is seeded once with secure random data, but * is completely deterministic and does not gather more entropy after that. * * This class is not thread-safe. */ class FastRandomContext { private: bool requires_seed; ChaCha20 rng; uint8_t bytebuf[64]; int bytebuf_size; uint64_t bitbuf; int bitbuf_size; void RandomSeed(); void FillByteBuffer() { if (requires_seed) { RandomSeed(); } rng.Output(bytebuf, sizeof(bytebuf)); bytebuf_size = sizeof(bytebuf); } void FillBitBuffer() { bitbuf = rand64(); bitbuf_size = 64; } public: explicit FastRandomContext(bool fDeterministic = false) noexcept; /** Initialize with explicit seed (only for testing) */ explicit FastRandomContext(const uint256 &seed) noexcept; // Do not permit copying a FastRandomContext (move it, or create a new one // to get reseeded). FastRandomContext(const FastRandomContext &) = delete; FastRandomContext(FastRandomContext &&) = delete; FastRandomContext &operator=(const FastRandomContext &) = delete; /** * Move a FastRandomContext. If the original one is used again, it will be * reseeded. */ FastRandomContext &operator=(FastRandomContext &&from) noexcept; /** Generate a random 64-bit integer. */ uint64_t rand64() noexcept { if (bytebuf_size < 8) { FillByteBuffer(); } uint64_t ret = ReadLE64(bytebuf + 64 - bytebuf_size); bytebuf_size -= 8; return ret; } /** Generate a random (bits)-bit integer. */ uint64_t randbits(int bits) noexcept { if (bits == 0) { return 0; } else if (bits > 32) { return rand64() >> (64 - bits); } else { if (bitbuf_size < bits) { FillBitBuffer(); } uint64_t ret = bitbuf & (~uint64_t(0) >> (64 - bits)); bitbuf >>= bits; bitbuf_size -= bits; return ret; } } /** Generate a random integer in the range [0..range). */ uint64_t randrange(uint64_t range) noexcept { --range; int bits = CountBits(range); while (true) { uint64_t ret = randbits(bits); if (ret <= range) { return ret; } } } /** Generate random bytes. */ std::vector randbytes(size_t len); /** Generate a random 32-bit integer. */ uint32_t rand32() noexcept { return randbits(32); } /** generate a random uint256. */ uint256 rand256() noexcept; /** Generate a random boolean. */ bool randbool() noexcept { return randbits(1); } // Compatibility with the C++11 UniformRandomBitGenerator concept typedef uint64_t result_type; static constexpr uint64_t min() { return 0; } static constexpr uint64_t max() { return std::numeric_limits::max(); } inline uint64_t operator()() noexcept { return rand64(); } }; /** * More efficient than using std::shuffle on a FastRandomContext. * * This is more efficient as std::shuffle will consume entropy in groups of * 64 bits at the time and throw away most. * * This also works around a bug in libstdc++ std::shuffle that may cause * type::operator=(type&&) to be invoked on itself, which the library's * debug mode detects and panics on. This is a known issue, see * https://stackoverflow.com/questions/22915325/avoiding-self-assignment-in-stdshuffle */ template void Shuffle(I first, I last, R &&rng) { while (first != last) { size_t j = rng.randrange(last - first); if (j) { using std::swap; swap(*first, *(first + j)); } ++first; } } /** * Number of random bytes returned by GetOSRand. * When changing this constant make sure to change all call sites, and make * sure that the underlying OS APIs for all platforms support the number. * (many cap out at 256 bytes). */ static const ssize_t NUM_OS_RANDOM_BYTES = 32; /** * Get 32 bytes of system entropy. Do not use this in application code: use * GetStrongRandBytes instead. */ void GetOSRand(uint8_t *ent32); /** * Check that OS randomness is available and returning the requested number of * bytes. */ bool Random_SanityCheck(); /** * Initialize global RNG state and log any CPU features that are used. * * Calling this function is optional. RNG state will be initialized when first * needed if it is not called. */ void RandomInit(); #endif // BITCOIN_RANDOM_H