You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
 
 
 
 
 
 

293 lines
8.1 KiB

// 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 "random.h"
#include "crypto/sha512.h"
#include "support/cleanse.h"
#ifdef WIN32
#include "compat.h" // for Windows API
#include <wincrypt.h>
#endif
#include "util.h" // for LogPrint()
#include "utilstrencodings.h" // for GetTime()
#include <stdlib.h>
#include <limits>
#ifndef WIN32
#include <sys/time.h>
#endif
#ifdef HAVE_SYS_GETRANDOM
#include <sys/syscall.h>
#include <linux/random.h>
#endif
#ifdef HAVE_GETENTROPY
#include <unistd.h>
#endif
#ifdef HAVE_SYSCTL_ARND
#include <sys/sysctl.h>
#endif
#include <openssl/err.h>
#include <openssl/rand.h>
static void RandFailure()
{
LogPrintf("Failed to read randomness, aborting\n");
abort();
}
static inline int64_t GetPerformanceCounter()
{
int64_t nCounter = 0;
#ifdef WIN32
QueryPerformanceCounter((LARGE_INTEGER*)&nCounter);
#else
timeval t;
gettimeofday(&t, NULL);
nCounter = (int64_t)(t.tv_sec * 1000000 + t.tv_usec);
#endif
return nCounter;
}
void RandAddSeed()
{
// Seed with CPU performance counter
int64_t nCounter = GetPerformanceCounter();
RAND_add(&nCounter, sizeof(nCounter), 1.5);
memory_cleanse((void*)&nCounter, sizeof(nCounter));
}
static void RandAddSeedPerfmon()
{
RandAddSeed();
#ifdef WIN32
// Don't need this on Linux, OpenSSL automatically uses /dev/urandom
// Seed with the entire set of perfmon data
// This can take up to 2 seconds, so only do it every 10 minutes
static int64_t nLastPerfmon;
if (GetTime() < nLastPerfmon + 10 * 60)
return;
nLastPerfmon = GetTime();
std::vector<unsigned char> vData(250000, 0);
long ret = 0;
unsigned long nSize = 0;
const size_t nMaxSize = 10000000; // Bail out at more than 10MB of performance data
while (true) {
nSize = vData.size();
ret = RegQueryValueExA(HKEY_PERFORMANCE_DATA, "Global", NULL, NULL, vData.data(), &nSize);
if (ret != ERROR_MORE_DATA || vData.size() >= nMaxSize)
break;
vData.resize(std::max((vData.size() * 3) / 2, nMaxSize)); // Grow size of buffer exponentially
}
RegCloseKey(HKEY_PERFORMANCE_DATA);
if (ret == ERROR_SUCCESS) {
RAND_add(vData.data(), nSize, nSize / 100.0);
memory_cleanse(vData.data(), nSize);
LogPrint(BCLog::RAND, "%s: %lu bytes\n", __func__, nSize);
} else {
static bool warned = false; // Warn only once
if (!warned) {
LogPrintf("%s: Warning: RegQueryValueExA(HKEY_PERFORMANCE_DATA) failed with code %i\n", __func__, ret);
warned = true;
}
}
#endif
}
#ifndef WIN32
/** Fallback: get 32 bytes of system entropy from /dev/urandom. The most
* compatible way to get cryptographic randomness on UNIX-ish platforms.
*/
void GetDevURandom(unsigned char *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) {
RandFailure();
}
have += n;
} while (have < NUM_OS_RANDOM_BYTES);
close(f);
}
#endif
/** Get 32 bytes of system entropy. */
void GetOSRand(unsigned char *ent32)
{
#if defined(WIN32)
HCRYPTPROV hProvider;
int ret = CryptAcquireContextW(&hProvider, NULL, NULL, 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)
/* 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.
*/
if (getentropy(ent32, NUM_OS_RANDOM_BYTES) != 0) {
RandFailure();
}
#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, NULL, 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 GetRandBytes(unsigned char* buf, int num)
{
if (RAND_bytes(buf, num) != 1) {
RandFailure();
}
}
void GetStrongRandBytes(unsigned char* out, int num)
{
assert(num <= 32);
CSHA512 hasher;
unsigned char buf[64];
// First source: OpenSSL's RNG
RandAddSeedPerfmon();
GetRandBytes(buf, 32);
hasher.Write(buf, 32);
// Second source: OS RNG
GetOSRand(buf);
hasher.Write(buf, 32);
// Produce output
hasher.Finalize(buf);
memcpy(out, buf, num);
memory_cleanse(buf, 64);
}
uint64_t GetRand(uint64_t nMax)
{
if (nMax == 0)
return 0;
// The range of the random source must be a multiple of the modulus
// to give every possible output value an equal possibility
uint64_t nRange = (std::numeric_limits<uint64_t>::max() / nMax) * nMax;
uint64_t nRand = 0;
do {
GetRandBytes((unsigned char*)&nRand, sizeof(nRand));
} while (nRand >= nRange);
return (nRand % nMax);
}
int GetRandInt(int nMax)
{
return GetRand(nMax);
}
uint256 GetRandHash()
{
uint256 hash;
GetRandBytes((unsigned char*)&hash, sizeof(hash));
return hash;
}
void FastRandomContext::RandomSeed()
{
uint256 seed = GetRandHash();
rng.SetKey(seed.begin(), 32);
requires_seed = false;
}
FastRandomContext::FastRandomContext(const uint256& seed) : requires_seed(false), bytebuf_size(0), bitbuf_size(0)
{
rng.SetKey(seed.begin(), 32);
}
bool Random_SanityCheck()
{
/* 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.
*/
static const ssize_t MAX_TRIES = 1024;
uint8_t data[NUM_OS_RANDOM_BYTES];
bool overwritten[NUM_OS_RANDOM_BYTES] = {}; /* Tracks which bytes have been overwritten at least once */
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);
return (num_overwritten == NUM_OS_RANDOM_BYTES); /* If this failed, bailed out after too many tries */
}
FastRandomContext::FastRandomContext(bool fDeterministic) : requires_seed(!fDeterministic), bytebuf_size(0), bitbuf_size(0)
{
if (!fDeterministic) {
return;
}
uint256 seed;
rng.SetKey(seed.begin(), 32);
}