diff options
Diffstat (limited to 'src/random.cpp')
| -rw-r--r-- | src/random.cpp | 38 |
1 files changed, 30 insertions, 8 deletions
diff --git a/src/random.cpp b/src/random.cpp index 6187f16290..805d7d3872 100644 --- a/src/random.cpp +++ b/src/random.cpp @@ -16,6 +16,8 @@ #include <stdlib.h> #include <limits> +#include <chrono> +#include <thread> #ifndef WIN32 #include <sys/time.h> @@ -43,15 +45,22 @@ static void RandFailure() static inline int64_t GetPerformanceCounter() { - int64_t nCounter = 0; -#ifdef WIN32 - QueryPerformanceCounter((LARGE_INTEGER*)&nCounter); + // 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; + __asm__ volatile ("rdtsc" : "=A"(r)); // Constrain the r variable to the eax:edx pair. + return r; +#elif !defined(_MSC_VER) && (defined(__x86_64__) || defined(__amd64__)) + uint64_t r1 = 0, r2 = 0; + __asm__ volatile ("rdtsc" : "=a"(r1), "=d"(r2)); // Constrain r1 to rax and r2 to rdx. + return (r2 << 32) | r1; #else - timeval t; - gettimeofday(&t, NULL); - nCounter = (int64_t)(t.tv_sec * 1000000 + t.tv_usec); + // Fall back to using C++11 clock (usually microsecond or nanosecond precision) + return std::chrono::high_resolution_clock::now().time_since_epoch().count(); #endif - return nCounter; } void RandAddSeed() @@ -254,6 +263,8 @@ FastRandomContext::FastRandomContext(const uint256& seed) : requires_seed(false) bool Random_SanityCheck() { + uint64_t start = GetPerformanceCounter(); + /* This does not measure the quality of randomness, but it does test that * OSRandom() overwrites all 32 bytes of the output given a maximum * number of tries. @@ -280,7 +291,18 @@ bool Random_SanityCheck() tries += 1; } while (num_overwritten < NUM_OS_RANDOM_BYTES && tries < MAX_TRIES); - return (num_overwritten == NUM_OS_RANDOM_BYTES); /* If this failed, bailed out after too many tries */ + if (num_overwritten != NUM_OS_RANDOM_BYTES) return false; /* If this failed, bailed out after too many tries */ + + // 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. + RAND_add((const unsigned char*)&start, sizeof(start), 1); + RAND_add((const unsigned char*)&stop, sizeof(stop), 1); + + return true; } FastRandomContext::FastRandomContext(bool fDeterministic) : requires_seed(!fDeterministic), bytebuf_size(0), bitbuf_size(0) |