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Merge #10322: Use hardware timestamps in RNG seeding

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2c0a6f1 Use sanity check timestamps as entropy (Pieter Wuille)
33f853d Test that GetPerformanceCounter() increments (Pieter Wuille)
f544094 Use hardware timestamps in RNG seeding (Pieter Wuille)

Tree-SHA512: ea96ff56d425b5dc693b4dd35c8aa64ba20a01b9bd7d2d65298ece623f434e8cfa190f9c0f9b76df8aa496547bfa64533eb751edec8401d09bd5ee3478928a59
This commit is contained in:
Pieter Wuille 2017-05-09 10:10:23 -07:00
commit bc64b5aa0f
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GPG key ID: A636E97631F767E0
1 changed files with 30 additions and 8 deletions
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38
src/random.cpp
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@ -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)