diff options
Diffstat (limited to 'libc/pwd_grp/lckpwdf.c')
| -rw-r--r-- | libc/pwd_grp/lckpwdf.c | 163 |
1 files changed, 163 insertions, 0 deletions
diff --git a/libc/pwd_grp/lckpwdf.c b/libc/pwd_grp/lckpwdf.c new file mode 100644 index 000000000..2f55ff65a --- /dev/null +++ b/libc/pwd_grp/lckpwdf.c @@ -0,0 +1,163 @@ +/* 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. */ +} |