view common/linuxlockfile.c @ 1306:845048d4a69f

(issue159) Use user specific appdata directory for nss list with simple rights. Using the ProgramData folder with resticted access rights failed in case the process was not elevated.
author Andre Heinecke <andre.heinecke@intevation.de>
date Mon, 13 Oct 2014 12:31:37 +0200
parents 7ea3a4c0e2ae
children 8362e30f7b55
line wrap: on
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/* Copyright (C) 2014 by Bundesamt für Sicherheit in der Informationstechnik
 * Software engineering by Intevation GmbH
 *
 * This file is Free Software under the GNU GPL (v>=2)
 * and comes with ABSOLUTELY NO WARRANTY!
 * See LICENSE.txt for details.
 */

#ifndef WIN32

#include <fcntl.h>
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>

#include "logging.h"

int
open_lockfile(char *path)
{
  int fd;
  char pidstr[20];
  size_t pidstrlen;
  struct flock lk;
  fd = open(path, O_RDWR | O_CREAT, 0600);
  if (fd != -1)
    {
      /* Get an exclusive lock on the whole file. */
      lk.l_type = F_WRLCK;
      lk.l_whence = SEEK_SET;
      lk.l_start = 0;
      lk.l_len = 0;
      if (fcntl(fd, F_SETLK, &lk) != -1)
        {
          /* FIXME (issue139): For extra security we should check if there is
             already a pid in the file.  If so we should check in
             /proc/$PID if there is still a process of the same name
             as ours running... */
          ftruncate(fd, 0);
          pidstrlen = (size_t)snprintf(pidstr, sizeof(pidstr), "%d", getpid());
          write(fd, pidstr, pidstrlen);
        }
      else
        {
          /* Lock can not be acquired.  Bail out... */
          close(fd);
          DEBUGPRINTF("Could not get an exclusive lock on %s.\n", path);
          return -1;
        }
    }
  else
    {
      DEBUGPRINTF("Failed to open lock file: %s.\n", path);
    }
  return fd;
}

void
close_lockfile(int fd)
{
  struct flock lk;

  /* Delete the PID from file. */
  /* We do this instead of trying to unlink the file. */
  ftruncate(fd, 0);

  /* Remove lock from the file. */
  lk.l_type = F_UNLCK;
  lk.l_whence = SEEK_SET;
  lk.l_start = 0;
  lk.l_len = 0;
  if (fcntl(fd, F_SETLK, &lk) == -1)
    {
      /* Lock can not be removed */
      DEBUGPRINTF("Could not remove lock from pid file.\n");
    }
  close(fd);
}

#endif /* Not WIN32 */

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