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/* Pseudo Random Number Generator
Copyright (C) 2022 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <not-cancel.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/param.h>
#include <sys/random.h>
static void
arc4random_getrandom_failure (void)
{
__libc_fatal ("Fatal glibc error: cannot get entropy for arc4random\n");
}
void
__arc4random_buf (void *p, size_t n)
{
static int seen_initialized;
size_t l;
int fd;
if (n == 0)
return;
for (;;)
{
l = TEMP_FAILURE_RETRY (__getrandom_nocancel (p, n, 0));
if (l > 0)
{
if ((size_t) l == n)
return; /* Done reading, success. */
p = (uint8_t *) p + l;
n -= l;
continue; /* Interrupted by a signal; keep going. */
}
else if (l < 0 && errno == ENOSYS)
break; /* No syscall, so fallback to /dev/urandom. */
arc4random_getrandom_failure ();
}
if (atomic_load_relaxed (&seen_initialized) == 0)
{
/* Poll /dev/random as an approximation of RNG initialization. */
struct pollfd pfd = { .events = POLLIN };
pfd.fd = TEMP_FAILURE_RETRY (
__open64_nocancel ("/dev/random", O_RDONLY | O_CLOEXEC | O_NOCTTY));
if (pfd.fd < 0)
arc4random_getrandom_failure ();
if (TEMP_FAILURE_RETRY (__poll_infinity_nocancel (&pfd, 1)) < 0)
arc4random_getrandom_failure ();
if (__close_nocancel (pfd.fd) < 0)
arc4random_getrandom_failure ();
atomic_store_relaxed (&seen_initialized, 1);
}
fd = TEMP_FAILURE_RETRY (
__open64_nocancel ("/dev/urandom", O_RDONLY | O_CLOEXEC | O_NOCTTY));
if (fd < 0)
arc4random_getrandom_failure ();
for (;;)
{
l = TEMP_FAILURE_RETRY (__read_nocancel (fd, p, n));
if (l <= 0)
arc4random_getrandom_failure ();
if ((size_t) l == n)
break; /* Done reading, success. */
p = (uint8_t *) p + l;
n -= l;
}
if (__close_nocancel (fd) < 0)
arc4random_getrandom_failure ();
}
libc_hidden_def (__arc4random_buf)
weak_alias (__arc4random_buf, arc4random_buf)
uint32_t
__arc4random (void)
{
uint32_t r;
__arc4random_buf (&r, sizeof (r));
return r;
}
libc_hidden_def (__arc4random)
weak_alias (__arc4random, arc4random)
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