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exechelp-posix.c
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/* exechelp.c - Fork and exec helpers for POSIX
* Copyright (C) 2004, 2007-2009, 2010 Free Software Foundation, Inc.
* Copyright (C) 2004, 2006-2012, 2014-2017 g10 Code GmbH
*
* This file is part of GnuPG.
*
* This file is free software; you can redistribute it and/or modify
* it under the terms of either
*
* - the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 3 of the License, or (at
* your option) any later version.
*
* or
*
* - the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* or both in parallel, as here.
*
* This file 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <https://www.gnu.org/licenses/>.
* SPDX-License-Identifier: (LGPL-3.0+ OR GPL-2.0+)
*/
#include <config.h>
#if defined(HAVE_W32_SYSTEM)
#error This code is only used on POSIX
#endif
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#ifdef HAVE_SIGNAL_H
# include <signal.h>
#endif
#include <unistd.h>
#include <fcntl.h>
#ifdef WITHOUT_NPTH /* Give the Makefile a chance to build without Pth. */
#undef HAVE_NPTH
#undef USE_NPTH
#endif
#ifdef HAVE_NPTH
#include <npth.h>
#endif
#include <sys/wait.h>
#ifdef HAVE_GETRLIMIT
#include <sys/time.h>
#include <sys/resource.h>
#endif /*HAVE_GETRLIMIT*/
#ifdef HAVE_STAT
# include <sys/stat.h>
#endif
#if __linux__
# include <sys/types.h>
# include <dirent.h>
#endif /*__linux__ */
#include "util.h"
#include "i18n.h"
#include "sysutils.h"
#include "exechelp.h"
/* Helper */
static inline gpg_error_t
my_error_from_syserror (void)
{
return gpg_err_make (default_errsource, gpg_err_code_from_syserror ());
}
/* Return the maximum number of currently allowed open file
descriptors. Only useful on POSIX systems but returns a value on
other systems too. */
int
get_max_fds (void)
{
int max_fds = -1;
#ifdef HAVE_GETRLIMIT
struct rlimit rl;
/* Under Linux we can figure out the highest used file descriptor by
* reading /proc/PID/fd. This is in the common cases much fast than
* for example doing 4096 close calls where almost all of them will
* fail. On a system with a limit of 4096 files and only 8 files
* open with the highest number being 10, we speedup close_all_fds
* from 125ms to 0.4ms including readdir.
*
* Another option would be to close the file descriptors as returned
* from reading that directory - however then we need to snapshot
* that list before starting to close them. */
#ifdef __linux__
{
DIR *dir = NULL;
struct dirent *dir_entry;
const char *s;
int x;
dir = opendir ("/proc/self/fd");
if (dir)
{
while ((dir_entry = readdir (dir)))
{
s = dir_entry->d_name;
if ( *s < '0' || *s > '9')
continue;
x = atoi (s);
if (x > max_fds)
max_fds = x;
}
closedir (dir);
}
if (max_fds != -1)
return max_fds + 1;
}
#endif /* __linux__ */
# ifdef RLIMIT_NOFILE
if (!getrlimit (RLIMIT_NOFILE, &rl))
max_fds = rl.rlim_max;
# endif
# ifdef RLIMIT_OFILE
if (max_fds == -1 && !getrlimit (RLIMIT_OFILE, &rl))
max_fds = rl.rlim_max;
# endif
#endif /*HAVE_GETRLIMIT*/
#ifdef _SC_OPEN_MAX
if (max_fds == -1)
{
long int scres = sysconf (_SC_OPEN_MAX);
if (scres >= 0)
max_fds = scres;
}
#endif
#ifdef _POSIX_OPEN_MAX
if (max_fds == -1)
max_fds = _POSIX_OPEN_MAX;
#endif
#ifdef OPEN_MAX
if (max_fds == -1)
max_fds = OPEN_MAX;
#endif
if (max_fds == -1)
max_fds = 256; /* Arbitrary limit. */
/* AIX returns INT32_MAX instead of a proper value. We assume that
this is always an error and use an arbitrary limit. */
#ifdef INT32_MAX
if (max_fds == INT32_MAX)
max_fds = 256;
#endif
return max_fds;
}
/* Close all file descriptors starting with descriptor FIRST. If
EXCEPT is not NULL, it is expected to be a list of file descriptors
which shall not be closed. This list shall be sorted in ascending
order with the end marked by -1. */
void
close_all_fds (int first, const int *except)
{
int max_fd = get_max_fds ();
int fd, i, except_start;
if (except)
{
except_start = 0;
for (fd=first; fd < max_fd; fd++)
{
for (i=except_start; except[i] != -1; i++)
{
if (except[i] == fd)
{
/* If we found the descriptor in the exception list
we can start the next compare run at the next
index because the exception list is ordered. */
except_start = i + 1;
break;
}
}
if (except[i] == -1)
close (fd);
}
}
else
{
for (fd=first; fd < max_fd; fd++)
close (fd);
}
gpg_err_set_errno (0);
}
/* Returns an array with all currently open file descriptors. The end
of the array is marked by -1. The caller needs to release this
array using the *standard free* and not with xfree. This allow the
use of this function right at startup even before libgcrypt has
been initialized. Returns NULL on error and sets ERRNO
accordingly. */
int *
get_all_open_fds (void)
{
int *array;
size_t narray;
int fd, max_fd, idx;
#ifndef HAVE_STAT
array = calloc (1, sizeof *array);
if (array)
array[0] = -1;
#else /*HAVE_STAT*/
struct stat statbuf;
max_fd = get_max_fds ();
narray = 32; /* If you change this change also t-exechelp.c. */
array = calloc (narray, sizeof *array);
if (!array)
return NULL;
/* Note: The list we return is ordered. */
for (idx=0, fd=0; fd < max_fd; fd++)
if (!(fstat (fd, &statbuf) == -1 && errno == EBADF))
{
if (idx+1 >= narray)
{
int *tmp;
narray += (narray < 256)? 32:256;
tmp = realloc (array, narray * sizeof *array);
if (!tmp)
{
free (array);
return NULL;
}
array = tmp;
}
array[idx++] = fd;
}
array[idx] = -1;
#endif /*HAVE_STAT*/
return array;
}
static gpg_error_t
do_create_pipe (int filedes[2])
{
gpg_error_t err = 0;
if (pipe (filedes) == -1)
{
err = my_error_from_syserror ();
filedes[0] = filedes[1] = -1;
}
return err;
}
static gpg_error_t
create_pipe_and_estream (gnupg_fd_t *r_fd, estream_t *r_fp,
int outbound, int nonblock)
{
gpg_error_t err;
int filedes[2];
if (pipe (filedes) == -1)
{
err = my_error_from_syserror ();
log_error (_("error creating a pipe: %s\n"), gpg_strerror (err));
*r_fd = -1;
*r_fp = NULL;
return err;
}
if (!outbound)
{
*r_fd = filedes[1];
*r_fp = es_fdopen (filedes[0], nonblock? "r,nonblock" : "r");
}
else
{
*r_fd = filedes[0];
*r_fp = es_fdopen (filedes[1], nonblock? "w,nonblock" : "w");
}
if (!*r_fp)
{
err = my_error_from_syserror ();
log_error (_("error creating a stream for a pipe: %s\n"),
gpg_strerror (err));
close (filedes[0]);
close (filedes[1]);
*r_fd = -1;
return err;
}
return 0;
}
/* Portable function to create a pipe. Under Windows the write end is
inheritable. Pipe is created and the read end is stored at R_FD.
An estream is created for the write end and stored at R_FP. */
gpg_error_t
gnupg_create_inbound_pipe (gnupg_fd_t *r_fd, estream_t *r_fp, int nonblock)
{
if (!r_fd || !r_fp)
gpg_error (GPG_ERR_INV_ARG);
return create_pipe_and_estream (r_fd, r_fp, 0, nonblock);
}
/* Portable function to create a pipe. Under Windows the read end is
inheritable. Pipe is created and the write end is stored at R_FD.
An estream is created for the write end and stored at R_FP. */
gpg_error_t
gnupg_create_outbound_pipe (gnupg_fd_t *r_fd, estream_t *r_fp, int nonblock)
{
if (!r_fd || !r_fp)
gpg_error (GPG_ERR_INV_ARG);
return create_pipe_and_estream (r_fd, r_fp, 1, nonblock);
}
/* Portable function to create a pipe. FLAGS=GNUPG_PIPE_INBOUND for
ihneritable write-end for Windows, GNUPG_PIPE_OUTBOUND for
inheritable read-end for Windows, GNUPG_PIPE_BOTH to specify
both ends may be inheritable. */
gpg_error_t
gnupg_create_pipe (int filedes[2], int flags)
{
(void)flags;
return do_create_pipe (filedes);
}
/* Close the end of a pipe. */
void
gnupg_close_pipe (int fd)
{
if (fd != -1)
close (fd);
}

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