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Diffstat (limited to 'libc/pwd_grp/lckpwdf.c')
-rw-r--r--libc/pwd_grp/lckpwdf.c163
1 files changed, 163 insertions, 0 deletions
diff --git a/libc/pwd_grp/lckpwdf.c b/libc/pwd_grp/lckpwdf.c
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+++ b/libc/pwd_grp/lckpwdf.c
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+/* Handle locking of password file.
+ Copyright (C) 1996, 1998 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Library General Public License as
+ published by the Free Software Foundation; either version 2 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
+ Library General Public License for more details.
+
+ You should have received a copy of the GNU Library General Public
+ License along with the GNU C Library; see the file COPYING.LIB. If not,
+ write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ Boston, MA 02111-1307, USA. */
+
+#include <fcntl.h>
+#include <shadow.h>
+#include <signal.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/file.h>
+#include <paths.h>
+
+/* How long to wait for getting the lock before returning with an
+ error. */
+#define TIMEOUT 15 /* sec */
+
+/* File descriptor for lock file. */
+static int lock_fd = -1;
+
+/* Prototypes for local functions. */
+static void noop_handler __P ((int __sig));
+
+
+int
+lckpwdf ()
+{
+ int flags;
+ sigset_t saved_set; /* Saved set of caught signals. */
+ struct sigaction saved_act; /* Saved signal action. */
+ sigset_t new_set; /* New set of caught signals. */
+ struct sigaction new_act; /* New signal action. */
+ struct flock fl; /* Information struct for locking. */
+ int result;
+
+ if (lock_fd != -1)
+ /* Still locked by own process. */
+ return -1;
+
+ lock_fd = open (_PATH_PASSWD, O_WRONLY);
+ if (lock_fd == -1)
+ /* Cannot create lock file. */
+ return -1;
+
+ /* Make sure file gets correctly closed when process finished. */
+ flags = fcntl (lock_fd, F_GETFD, 0);
+ if (flags == -1) {
+ /* Cannot get file flags. */
+ close(lock_fd);
+ lock_fd = -1;
+ return -1;
+ }
+ flags |= FD_CLOEXEC; /* Close on exit. */
+ if (fcntl (lock_fd, F_SETFD, flags) < 0) {
+ /* Cannot set new flags. */
+ close(lock_fd);
+ lock_fd = -1;
+ return -1;
+ }
+
+ /* Now we have to get exclusive write access. Since multiple
+ process could try this we won't stop when it first fails.
+ Instead we set a timeout for the system call. Once the timer
+ expires it is likely that there are some problems which cannot be
+ resolved by waiting.
+
+ It is important that we don't change the signal state. We must
+ restore the old signal behaviour. */
+ memset (&new_act, '\0', sizeof (struct sigaction));
+ new_act.sa_handler = noop_handler;
+ sigfillset (&new_act.sa_mask);
+ new_act.sa_flags = 0ul;
+
+ /* Install new action handler for alarm and save old. */
+ if (sigaction (SIGALRM, &new_act, &saved_act) < 0) {
+ /* Cannot install signal handler. */
+ close(lock_fd);
+ lock_fd = -1;
+ return -1;
+ }
+
+ /* Now make sure the alarm signal is not blocked. */
+ sigemptyset (&new_set);
+ sigaddset (&new_set, SIGALRM);
+ if (sigprocmask (SIG_UNBLOCK, &new_set, &saved_set) < 0) {
+ sigaction (SIGALRM, &saved_act, NULL);
+ close(lock_fd);
+ lock_fd = -1;
+ return -1;
+ }
+
+ /* Start timer. If we cannot get the lock in the specified time we
+ get a signal. */
+ alarm (TIMEOUT);
+
+ /* Try to get the lock. */
+ memset (&fl, '\0', sizeof (struct flock));
+ fl.l_type = F_WRLCK;
+ fl.l_whence = SEEK_SET;
+ result = fcntl (lock_fd, F_SETLKW, &fl);
+
+ /* Clear alarm. */
+ alarm (0);
+
+ /* Restore old set of handled signals. We don't need to know
+ about the current one.*/
+ sigprocmask (SIG_SETMASK, &saved_set, NULL);
+
+ /* Restore old action handler for alarm. We don't need to know
+ about the current one. */
+ sigaction (SIGALRM, &saved_act, NULL);
+
+ if (result < 0) {
+ close(lock_fd);
+ lock_fd = -1;
+ return -1;
+ }
+
+ return 0;
+}
+
+
+int
+ulckpwdf ()
+{
+ int result;
+
+ if (lock_fd == -1) {
+ /* There is no lock set. */
+ result = -1;
+ }
+ else {
+ result = close (lock_fd);
+
+ /* Mark descriptor as unused. */
+ lock_fd = -1;
+ }
+
+ return result;
+}
+
+
+static void
+noop_handler (sig)
+ int sig;
+{
+ /* We simply return which makes the `fcntl' call return with an error. */
+}