186 lines
5.4 KiB
C
186 lines
5.4 KiB
C
/* Handle locking of password file.
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Copyright (C) 1996, 1998 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
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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 Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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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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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If not,
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write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#include <fcntl.h>
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#include <bits/libc-lock.h>
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#include <shadow.h>
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#include <signal.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/file.h>
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/* Name of the lock file. */
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#define PWD_LOCKFILE "/etc/.pwd.lock"
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/* How long to wait for getting the lock before returning with an
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error. */
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#define TIMEOUT 15 /* sec */
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/* File descriptor for lock file. */
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static int lock_fd = -1;
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/* Prevent problems in multithreaded program by using mutex. */
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__libc_lock_define_initialized (static, lock)
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/* Prototypes for local functions. */
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static void noop_handler __P ((int __sig));
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/* We cannot simply return in error cases. We have to close the file
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and perhaps restore the signal handler. */
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#define RETURN_CLOSE_FD(code) \
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do { \
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if ((code) < 0 && lock_fd >= 0) \
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{ \
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__close (lock_fd); \
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lock_fd = -1; \
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} \
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__libc_lock_unlock (lock); \
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return (code); \
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} while (0)
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#define RETURN_RESTORE_HANDLER(code) \
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do { \
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/* Restore old action handler for alarm. We don't need to know \
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about the current one. */ \
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__sigaction (SIGALRM, &saved_act, NULL); \
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RETURN_CLOSE_FD (code); \
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} while (0)
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#define RETURN_CLEAR_ALARM(code) \
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do { \
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/* Clear alarm. */ \
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alarm (0); \
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/* Restore old set of handled signals. We don't need to know \
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about the current one.*/ \
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__sigprocmask (SIG_SETMASK, &saved_set, NULL); \
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RETURN_RESTORE_HANDLER (code); \
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} while (0)
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int
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__lckpwdf ()
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{
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int flags;
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sigset_t saved_set; /* Saved set of caught signals. */
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struct sigaction saved_act; /* Saved signal action. */
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sigset_t new_set; /* New set of caught signals. */
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struct sigaction new_act; /* New signal action. */
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struct flock fl; /* Information struct for locking. */
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int result;
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if (lock_fd != -1)
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/* Still locked by own process. */
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return -1;
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/* Prevent problems caused by multiple threads. */
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__libc_lock_lock (lock);
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lock_fd = __open (PWD_LOCKFILE, O_WRONLY | O_CREAT, 0600);
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if (lock_fd == -1)
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/* Cannot create lock file. */
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RETURN_CLOSE_FD (-1);
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/* Make sure file gets correctly closed when process finished. */
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flags = __fcntl (lock_fd, F_GETFD, 0);
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if (flags == -1)
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/* Cannot get file flags. */
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RETURN_CLOSE_FD (-1);
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flags |= FD_CLOEXEC; /* Close on exit. */
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if (__fcntl (lock_fd, F_SETFD, flags) < 0)
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/* Cannot set new flags. */
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RETURN_CLOSE_FD (-1);
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/* Now we have to get exclusive write access. Since multiple
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process could try this we won't stop when it first fails.
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Instead we set a timeout for the system call. Once the timer
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expires it is likely that there are some problems which cannot be
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resolved by waiting.
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It is important that we don't change the signal state. We must
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restore the old signal behaviour. */
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memset (&new_act, '\0', sizeof (struct sigaction));
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new_act.sa_handler = noop_handler;
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sigfillset (&new_act.sa_mask);
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new_act.sa_flags = 0ul;
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/* Install new action handler for alarm and save old. */
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if (__sigaction (SIGALRM, &new_act, &saved_act) < 0)
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/* Cannot install signal handler. */
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RETURN_CLOSE_FD (-1);
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/* Now make sure the alarm signal is not blocked. */
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sigemptyset (&new_set);
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sigaddset (&new_set, SIGALRM);
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if (__sigprocmask (SIG_UNBLOCK, &new_set, &saved_set) < 0)
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RETURN_RESTORE_HANDLER (-1);
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/* Start timer. If we cannot get the lock in the specified time we
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get a signal. */
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alarm (TIMEOUT);
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/* Try to get the lock. */
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memset (&fl, '\0', sizeof (struct flock));
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fl.l_type = F_WRLCK;
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fl.l_whence = SEEK_SET;
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result = __fcntl (lock_fd, F_SETLKW, &fl);
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RETURN_CLEAR_ALARM (result);
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}
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weak_alias (__lckpwdf, lckpwdf)
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int
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__ulckpwdf ()
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{
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int result;
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if (lock_fd == -1)
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/* There is no lock set. */
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result = -1;
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else
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{
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/* Prevent problems caused by multiple threads. */
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__libc_lock_lock (lock);
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result = __close (lock_fd);
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/* Mark descriptor as unused. */
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lock_fd = -1;
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/* Clear mutex. */
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__libc_lock_unlock (lock);
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}
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return result;
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}
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weak_alias (__ulckpwdf, ulckpwdf)
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static void
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noop_handler (sig)
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int sig;
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{
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/* We simply return which makes the `fcntl' call return with an error. */
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}
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