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-rw-r--r--REORG.TODO/shadow/lckpwdf.c176
1 files changed, 176 insertions, 0 deletions
diff --git a/REORG.TODO/shadow/lckpwdf.c b/REORG.TODO/shadow/lckpwdf.c
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index 0000000000..15602efb68
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+++ b/REORG.TODO/shadow/lckpwdf.c
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+/* Handle locking of password file.
+   Copyright (C) 1996-2017 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 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.
+
+   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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <fcntl.h>
+#include <libc-lock.h>
+#include <shadow.h>
+#include <signal.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/file.h>
+#include <sigsetops.h>
+
+#include <kernel-features.h>
+
+
+/* Name of the lock file.  */
+#define PWD_LOCKFILE "/etc/.pwd.lock"
+
+/* 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;
+
+/* Prevent problems in multithreaded program by using mutex.  */
+__libc_lock_define_initialized (static, lock)
+
+
+/* Prototypes for local functions.  */
+static void noop_handler (int __sig);
+
+
+/* We cannot simply return in error cases.  We have to close the file
+   and perhaps restore the signal handler.  */
+#define RETURN_CLOSE_FD(code)						      \
+  do {									      \
+    if ((code) < 0 && lock_fd >= 0)					      \
+      {									      \
+	__close (lock_fd);						      \
+	lock_fd = -1;							      \
+      }									      \
+    __libc_lock_unlock (lock);						      \
+    return (code);							      \
+  } while (0)
+
+#define RETURN_RESTORE_HANDLER(code)					      \
+  do {									      \
+    /* Restore old action handler for alarm.  We don't need to know	      \
+       about the current one.  */					      \
+    __sigaction (SIGALRM, &saved_act, NULL);				      \
+    RETURN_CLOSE_FD (code);						      \
+  } while (0)
+
+#define RETURN_CLEAR_ALARM(code)					      \
+  do {									      \
+    /* 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);			      \
+    RETURN_RESTORE_HANDLER (code);					      \
+  } while (0)
+
+
+int
+__lckpwdf (void)
+{
+  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;
+
+  /* Prevent problems caused by multiple threads.  */
+  __libc_lock_lock (lock);
+
+  int oflags = O_WRONLY | O_CREAT | O_CLOEXEC;
+  lock_fd = __open (PWD_LOCKFILE, oflags, 0600);
+  if (lock_fd == -1)
+    /* Cannot create lock file.  */
+    RETURN_CLOSE_FD (-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.  */
+    RETURN_CLOSE_FD (-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)
+    RETURN_RESTORE_HANDLER (-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);
+
+  RETURN_CLEAR_ALARM (result);
+}
+weak_alias (__lckpwdf, lckpwdf)
+
+
+int
+__ulckpwdf (void)
+{
+  int result;
+
+  if (lock_fd == -1)
+    /* There is no lock set.  */
+    result = -1;
+  else
+    {
+      /* Prevent problems caused by multiple threads.  */
+      __libc_lock_lock (lock);
+
+      result = __close (lock_fd);
+
+      /* Mark descriptor as unused.  */
+      lock_fd = -1;
+
+      /* Clear mutex.  */
+      __libc_lock_unlock (lock);
+    }
+
+  return result;
+}
+weak_alias (__ulckpwdf, ulckpwdf)
+
+
+static void
+noop_handler (int sig)
+{
+  /* We simply return which makes the `fcntl' call return with an error.  */
+}