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