/* GLIB - Library of useful routines for C programming

 * Copyright (C) 2011 Red Hat, Inc.

 *

 * glib-unix.c: UNIX specific API wrappers and convenience functions

 *

 * SPDX-License-Identifier: LGPL-2.1-or-later

 *

 * This 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.

 *

 * This 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 this library; if not, see <http://www.gnu.org/licenses/>.

 *

 * Authors: Colin Walters <walters@verbum.org>

 */

#include "config.h"

/* To make bionic export pipe2() */

#ifndef _GNU_SOURCE

#define _GNU_SOURCE 1

#endif

#include "glib-unix.h"

#include "gmain-internal.h"

#include <string.h>

#include <sys/types.h>

#include <pwd.h>

G_STATIC_ASSERT (sizeof (ssize_t) == GLIB_SIZEOF_SSIZE_T);

G_STATIC_ASSERT (G_ALIGNOF (gssize) == G_ALIGNOF (ssize_t));

G_STATIC_ASSERT (sizeof (GPid) == sizeof (pid_t));

G_STATIC_ASSERT (G_ALIGNOF (GPid) == G_ALIGNOF (pid_t));

/**

 * SECTION:gunix

 * @title: UNIX-specific utilities and integration

 * @short_description: pipes, signal handling

 * @include: glib-unix.h

 *

 * Most of GLib is intended to be portable; in contrast, this set of

 * functions is designed for programs which explicitly target UNIX,

 * or are using it to build higher level abstractions which would be

 * conditionally compiled if the platform matches %G_OS_UNIX.

 *

 * To use these functions, you must explicitly include the

 * "glib-unix.h" header.

 */

G_DEFINE_QUARK (g-unix-error-quark, g_unix_error)

static gboolean

g_unix_set_error_from_errno (GError **error,

                             gint     saved_errno)

{

  g_set_error_literal (error,

                       G_UNIX_ERROR,

                       0,

                       g_strerror (saved_errno));

  errno = saved_errno;

  return FALSE;

}

/**

 * g_unix_open_pipe:

 * @fds: (array fixed-size=2): Array of two integers

 * @flags: Bitfield of file descriptor flags, as for fcntl()

 * @error: a #GError

 *

 * Similar to the UNIX pipe() call, but on modern systems like Linux

 * uses the pipe2() system call, which atomically creates a pipe with

 * the configured flags. The only supported flag currently is

 * %FD_CLOEXEC. If for example you want to configure %O_NONBLOCK, that

 * must still be done separately with fcntl().

 *

 * This function does not take %O_CLOEXEC, it takes %FD_CLOEXEC as if

 * for fcntl(); these are different on Linux/glibc.

 *

 * Returns: %TRUE on success, %FALSE if not (and errno will be set).

 *

 * Since: 2.30

 */

gboolean

g_unix_open_pipe (int     *fds,

                  int      flags,

                  GError **error)

{

  int ecode;

  /* We only support FD_CLOEXEC */

  g_return_val_if_fail ((flags & (FD_CLOEXEC)) == flags, FALSE);

#ifdef HAVE_PIPE2

  {

    int pipe2_flags = 0;

    if (flags & FD_CLOEXEC)

      pipe2_flags |= O_CLOEXEC;

    /* Atomic */

    ecode = pipe2 (fds, pipe2_flags);

    if (ecode == -1 && errno != ENOSYS)

      return g_unix_set_error_from_errno (error, errno);

    else if (ecode == 0)

      return TRUE;

    /* Fall through on -ENOSYS, we must be running on an old kernel */

  }

#endif

  ecode = pipe (fds);

  if (ecode == -1)

    return g_unix_set_error_from_errno (error, errno);

  if (flags == 0)

    return TRUE;

  ecode = fcntl (fds[0], F_SETFD, flags);

  if (ecode == -1)

    {

      int saved_errno = errno;

      close (fds[0]);

      close (fds[1]);

      return g_unix_set_error_from_errno (error, saved_errno);

    }

  ecode = fcntl (fds[1], F_SETFD, flags);

  if (ecode == -1)

    {

      int saved_errno = errno;

      close (fds[0]);

      close (fds[1]);

      return g_unix_set_error_from_errno (error, saved_errno);

    }

  return TRUE;

}

/**

 * g_unix_set_fd_nonblocking:

 * @fd: A file descriptor

 * @nonblock: If %TRUE, set the descriptor to be non-blocking

 * @error: a #GError

 *

 * Control the non-blocking state of the given file descriptor,

 * according to @nonblock. On most systems this uses %O_NONBLOCK, but

 * on some older ones may use %O_NDELAY.

 *

 * Returns: %TRUE if successful

 *

 * Since: 2.30

 */

gboolean

g_unix_set_fd_nonblocking (gint       fd,

                           gboolean   nonblock,

                           GError   **error)

{

#ifdef F_GETFL

  glong fcntl_flags;

  fcntl_flags = fcntl (fd, F_GETFL);

  if (fcntl_flags == -1)

    return g_unix_set_error_from_errno (error, errno);

  if (nonblock)

    {

#ifdef O_NONBLOCK

      fcntl_flags |= O_NONBLOCK;

#else

      fcntl_flags |= O_NDELAY;

#endif

    }

  else

    {

#ifdef O_NONBLOCK

      fcntl_flags &= ~O_NONBLOCK;

#else

      fcntl_flags &= ~O_NDELAY;

#endif

    }

  if (fcntl (fd, F_SETFL, fcntl_flags) == -1)

    return g_unix_set_error_from_errno (error, errno);

  return TRUE;

#else

  return g_unix_set_error_from_errno (error, EINVAL);

#endif

}

/**

 * g_unix_signal_source_new:

 * @signum: A signal number

 *

 * Create a #GSource that will be dispatched upon delivery of the UNIX

 * signal @signum.  In GLib versions before 2.36, only `SIGHUP`, `SIGINT`,

 * `SIGTERM` can be monitored.  In GLib 2.36, `SIGUSR1` and `SIGUSR2`

 * were added. In GLib 2.54, `SIGWINCH` was added.

 *

 * Note that unlike the UNIX default, all sources which have created a

 * watch will be dispatched, regardless of which underlying thread

 * invoked g_unix_signal_source_new().

 *

 * For example, an effective use of this function is to handle `SIGTERM`

 * cleanly; flushing any outstanding files, and then calling

 * g_main_loop_quit().  It is not safe to do any of this from a regular

 * UNIX signal handler; such a handler may be invoked while malloc() or

 * another library function is running, causing reentrancy issues if the

 * handler attempts to use those functions.  None of the GLib/GObject

 * API is safe against this kind of reentrancy.

 *

 * The interaction of this source when combined with native UNIX

 * functions like sigprocmask() is not defined.

 *

 * The source will not initially be associated with any #GMainContext

 * and must be added to one with g_source_attach() before it will be

 * executed.

 *

 * Returns: A newly created #GSource

 *

 * Since: 2.30

 */

GSource *

g_unix_signal_source_new (int signum)

{

  g_return_val_if_fail (signum == SIGHUP || signum == SIGINT || signum == SIGTERM ||

                        signum == SIGUSR1 || signum == SIGUSR2 || signum == SIGWINCH,

                        NULL);

  return _g_main_create_unix_signal_watch (signum);

}

/**

 * g_unix_signal_add_full: (rename-to g_unix_signal_add)

 * @priority: the priority of the signal source. Typically this will be in

 *            the range between %G_PRIORITY_DEFAULT and %G_PRIORITY_HIGH.

 * @signum: Signal number

 * @handler: Callback

 * @user_data: Data for @handler

 * @notify: #GDestroyNotify for @handler

 *

 * A convenience function for g_unix_signal_source_new(), which

 * attaches to the default #GMainContext.  You can remove the watch

 * using g_source_remove().

 *

 * Returns: An ID (greater than 0) for the event source

 *

 * Since: 2.30

 */

guint

g_unix_signal_add_full (int            priority,

                        int            signum,

                        GSourceFunc    handler,

                        gpointer       user_data,

                        GDestroyNotify notify)

{

  guint id;

  GSource *source;

  source = g_unix_signal_source_new (signum);

  if (priority != G_PRIORITY_DEFAULT)

    g_source_set_priority (source, priority);

  g_source_set_callback (source, handler, user_data, notify);

  id = g_source_attach (source, NULL);

  g_source_unref (source);

  return id;

}

/**

 * g_unix_signal_add:

 * @signum: Signal number

 * @handler: Callback

 * @user_data: Data for @handler

 *

 * A convenience function for g_unix_signal_source_new(), which

 * attaches to the default #GMainContext.  You can remove the watch

 * using g_source_remove().

 *

 * Returns: An ID (greater than 0) for the event source

 *

 * Since: 2.30

 */

guint

g_unix_signal_add (int         signum,

                   GSourceFunc handler,

                   gpointer    user_data)

{

  return g_unix_signal_add_full (G_PRIORITY_DEFAULT, signum, handler, user_data, NULL);

}

typedef struct

{

  GSource source;

  gint     fd;

  gpointer tag;

} GUnixFDSource;

static gboolean

g_unix_fd_source_dispatch (GSource     *source,

                           GSourceFunc  callback,

                           gpointer     user_data)

{

  GUnixFDSource *fd_source = (GUnixFDSource *) source;

  GUnixFDSourceFunc func = (GUnixFDSourceFunc) callback;

  if (!callback)

    {

      g_warning ("GUnixFDSource dispatched without callback. "

                 "You must call g_source_set_callback().");

      return FALSE;

    }

  return (* func) (fd_source->fd, g_source_query_unix_fd (source, fd_source->tag), user_data);

}

GSourceFuncs g_unix_fd_source_funcs = {

  NULL, NULL, g_unix_fd_source_dispatch, NULL, NULL, NULL

};

/**

 * g_unix_fd_source_new:

 * @fd: a file descriptor

 * @condition: IO conditions to watch for on @fd

 *

 * Creates a #GSource to watch for a particular IO condition on a file

 * descriptor.

 *

 * The source will never close the fd -- you must do it yourself.

 *

 * Returns: the newly created #GSource

 *

 * Since: 2.36

 **/

GSource *

g_unix_fd_source_new (gint         fd,

                      GIOCondition condition)

{

  GUnixFDSource *fd_source;

  GSource *source;

  source = g_source_new (&g_unix_fd_source_funcs, sizeof (GUnixFDSource));

  fd_source = (GUnixFDSource *) source;

  fd_source->fd = fd;

  fd_source->tag = g_source_add_unix_fd (source, fd, condition);

  return source;

}

/**

 * g_unix_fd_add_full:

 * @priority: the priority of the source

 * @fd: a file descriptor

 * @condition: IO conditions to watch for on @fd

 * @function: a #GUnixFDSourceFunc

 * @user_data: data to pass to @function

 * @notify: function to call when the idle is removed, or %NULL

 *

 * Sets a function to be called when the IO condition, as specified by

 * @condition becomes true for @fd.

 *

 * This is the same as g_unix_fd_add(), except that it allows you to

 * specify a non-default priority and a provide a #GDestroyNotify for

 * @user_data.

 *

 * Returns: the ID (greater than 0) of the event source

 *

 * Since: 2.36

 **/

guint

g_unix_fd_add_full (gint              priority,

                    gint              fd,

                    GIOCondition      condition,

                    GUnixFDSourceFunc function,

                    gpointer          user_data,

                    GDestroyNotify    notify)

{

  GSource *source;

  guint id;

  g_return_val_if_fail (function != NULL, 0);

  source = g_unix_fd_source_new (fd, condition);

  if (priority != G_PRIORITY_DEFAULT)

    g_source_set_priority (source, priority);

  g_source_set_callback (source, (GSourceFunc) function, user_data, notify);

  id = g_source_attach (source, NULL);

  g_source_unref (source);

  return id;

}

/**

 * g_unix_fd_add:

 * @fd: a file descriptor

 * @condition: IO conditions to watch for on @fd

 * @function: a #GUnixFDSourceFunc

 * @user_data: data to pass to @function

 *

 * Sets a function to be called when the IO condition, as specified by

 * @condition becomes true for @fd.

 *

 * @function will be called when the specified IO condition becomes

 * %TRUE.  The function is expected to clear whatever event caused the

 * IO condition to become true and return %TRUE in order to be notified

 * when it happens again.  If @function returns %FALSE then the watch

 * will be cancelled.

 *

 * The return value of this function can be passed to g_source_remove()

 * to cancel the watch at any time that it exists.

 *

 * The source will never close the fd -- you must do it yourself.

 *

 * Returns: the ID (greater than 0) of the event source

 *

 * Since: 2.36

 **/

guint

g_unix_fd_add (gint              fd,

               GIOCondition      condition,

               GUnixFDSourceFunc function,

               gpointer          user_data)

{

  return g_unix_fd_add_full (G_PRIORITY_DEFAULT, fd, condition, function, user_data, NULL);

}

/**

 * g_unix_get_passwd_entry:

 * @user_name: the username to get the passwd file entry for

 * @error: return location for a #GError, or %NULL

 *

 * Get the `passwd` file entry for the given @user_name using `getpwnam_r()`.

 * This can fail if the given @user_name doesn’t exist.

 *

 * The returned `struct passwd` has been allocated using g_malloc() and should

 * be freed using g_free(). The strings referenced by the returned struct are

 * included in the same allocation, so are valid until the `struct passwd` is

 * freed.

 *

 * This function is safe to call from multiple threads concurrently.

 *

 * You will need to include `pwd.h` to get the definition of `struct passwd`.

 *

 * Returns: (transfer full): passwd entry, or %NULL on error; free the returned

 *    value with g_free()

 * Since: 2.64

 */

struct passwd *

g_unix_get_passwd_entry (const gchar  *user_name,

                         GError      **error)

{

  struct passwd *passwd_file_entry;

  struct

    {

      struct passwd pwd;

      char string_buffer[];

    } *buffer = NULL;

  gsize string_buffer_size = 0;

  GError *local_error = NULL;

  g_return_val_if_fail (user_name != NULL, NULL);

  g_return_val_if_fail (error == NULL || *error == NULL, NULL);

#ifdef _SC_GETPW_R_SIZE_MAX

    {

      /* Get the recommended buffer size */

      glong string_buffer_size_long = sysconf (_SC_GETPW_R_SIZE_MAX);

      if (string_buffer_size_long > 0)

        string_buffer_size = string_buffer_size_long;

    }

#endif /* _SC_GETPW_R_SIZE_MAX */

  /* Default starting size. */

  if (string_buffer_size == 0)

    string_buffer_size = 64;

  do

    {

      int retval;

      g_free (buffer);

      /* Allocate space for the `struct passwd`, and then a buffer for all its

       * strings (whose size is @string_buffer_size, which increases in this

       * loop until it’s big enough). Add 6 extra bytes to work around a bug in

       * macOS < 10.3. See #156446.

       */

      buffer = g_malloc0 (sizeof (*buffer) + string_buffer_size + 6);

      retval = getpwnam_r (user_name, &buffer->pwd, buffer->string_buffer,

                           string_buffer_size, &passwd_file_entry);

      /* Bail out if: the lookup was successful, or if the user id can't be

       * found (should be pretty rare case actually), or if the buffer should be

       * big enough and yet lookups are still not successful.

       */

      if (passwd_file_entry != NULL)

        {

          /* Success. */

          break;

        }

      else if (retval == 0 ||

          retval == ENOENT || retval == ESRCH ||

          retval == EBADF || retval == EPERM)

        {

          /* Username not found. */

          g_unix_set_error_from_errno (&local_error, retval);

          break;

        }

      else if (retval == ERANGE)

        {

          /* Can’t allocate enough string buffer space. */

          if (string_buffer_size > 32 * 1024)

            {

              g_unix_set_error_from_errno (&local_error, retval);

              break;

            }

          string_buffer_size *= 2;

          continue;

        }

      else

        {

          g_unix_set_error_from_errno (&local_error, retval);

          break;

        }

    }

  while (passwd_file_entry == NULL);

  g_assert (passwd_file_entry == NULL ||

            (gpointer) passwd_file_entry == (gpointer) buffer);

  /* Success or error. */

  if (local_error != NULL)

    {

      g_clear_pointer (&buffer, g_free);

      g_propagate_error (error, g_steal_pointer (&local_error));

    }

  return (struct passwd *) g_steal_pointer (&buffer);

}