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#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <sys/stat.h>
#include <unistd.h>
#ifdef HAVE_GETENTROPY
#ifndef DO_NOT_USE_GET_ENTROPY
static int ensure_pool_initialized_getentropy()
{
char tmp;
return getentropy(&tmp, sizeof(tmp));
}
#endif
#endif
// Poll /dev/random to wait for randomness. This is a proxy for the /dev/urandom
// pool being initialized.
static int ensure_pool_initialized_poll()
{
struct pollfd pfd;
int dev_random = open("/dev/random", O_RDONLY);
if (dev_random == -1)
return -1;
pfd.fd = dev_random;
pfd.events = POLLIN;
pfd.revents = 0;
while (1) {
int ret = poll(&pfd, 1, -1);
if (ret < 0 && (errno == EAGAIN || errno == EINTR))
continue;
if (ret != 1) {
close(dev_random);
errno = EIO;
return -1;
}
break;
}
return close(dev_random);
}
// Returns 0 on success, non-zero on failure.
int ensure_pool_initialized()
{
#ifdef HAVE_GETENTROPY
#ifndef DO_NOT_USE_GET_ENTROPY
if (ensure_pool_initialized_getentropy() == 0)
return 0;
#endif
#endif
return ensure_pool_initialized_poll();
}
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