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/* Copyright (C) 2000-2021 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 <fcntl.h>
#include <paths.h>
#include <unistd.h>
#include <hurd.h>
#include <hurd/fd.h>
#include <set-hooks.h>
/* Try to get a machine dependent instruction which will make the
program crash. This is used in case everything else fails. */
#include <abort-instr.h>
#ifndef ABORT_INSTRUCTION
/* No such instruction is available. */
# define ABORT_INSTRUCTION
#endif
static void
check_one_fd (int fd, int mode)
{
struct hurd_fd *d;
d = _hurd_fd_get (fd);
if (d == NULL)
{
/* This descriptor hasn't been opened. We try to allocate the
descriptor and open /dev/null on it so that the SUID program
we are about to start does not accidentally use this
descriptor. */
d = _hurd_alloc_fd (NULL, fd);
if (d != NULL)
{
mach_port_t port;
port = __file_name_lookup (_PATH_DEVNULL, mode, 0);
if (port)
{
/* Since /dev/null isn't supposed to be a terminal, we
avoid any ctty magic. */
d->port.port = port;
d->flags = 0;
__spin_unlock (&d->port.lock);
return;
}
}
/* We cannot even give an error message here since it would run
into the same problems. */
while (1)
/* Try for ever and ever. */
ABORT_INSTRUCTION;
}
}
static void
check_standard_fds (void)
{
/* Check all three standard file descriptors. */
check_one_fd (STDIN_FILENO, O_RDONLY);
check_one_fd (STDOUT_FILENO, O_RDWR);
check_one_fd (STDERR_FILENO, O_RDWR);
}
static void attribute_used_retain
init_standard_fds (void)
{
/* Now that we have FDs, make sure that, if this is a SUID program,
FDs 0, 1 and 2 are allocated. If necessary we'll set them up
ourselves. If that's not possible we stop the program. */
if (__builtin_expect (__libc_enable_secure, 0))
check_standard_fds ();
}
SET_RELHOOK (_hurd_fd_subinit, init_standard_fds);
#ifndef SHARED
void
__libc_check_standard_fds (void)
{
/* We don't check the standard file descriptors here. They will be
checked when we initialize the file descriptor table, as part of
the _hurd_fd_subinit hook.
This function is only present to make sure that this module gets
linked in when part of the static libc. */
}
#endif
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