sudo/lib/util/locking.c

/*
 * Copyright (c) 1999-2005, 2007, 2009-2015
 *	Todd C. Miller <Todd.Miller@courtesan.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * Sponsored in part by the Defense Advanced Research Projects
 * Agency (DARPA) and Air Force Research Laboratory, Air Force
 * Materiel Command, USAF, under agreement number F39502-99-1-0512.
 */

#include <config.h>

#include <sys/types.h>
#ifdef HAVE_FLOCK
# include <sys/file.h>
#endif /* HAVE_FLOCK */
#ifdef STDC_HEADERS
# include <stdlib.h>
# include <stddef.h>
#else
# ifdef HAVE_STDLIB_H
#  include <stdlib.h>
# endif
#endif /* STDC_HEADERS */
#ifdef HAVE_STRING_H
# if defined(HAVE_MEMORY_H) && !defined(STDC_HEADERS)
#  include <memory.h>
# endif
# include <string.h>
#endif /* HAVE_STRING_H */
#ifdef HAVE_STRINGS_H
# include <strings.h>
#endif /* HAVE_STRING_H */
#if defined(HAVE_MALLOC_H) && !defined(STDC_HEADERS)
# include <malloc.h>
#endif /* HAVE_MALLOC_H && !STDC_HEADERS */
#include <ctype.h>
#ifdef HAVE_UNISTD_H
# include <unistd.h>
#endif /* HAVE_UNISTD_H */
#include <fcntl.h>
#ifdef HAVE_STDBOOL_H
# include <stdbool.h>
#else
# include "compat/stdbool.h"
#endif

#include "sudo_compat.h"
#include "sudo_util.h"
#include "sudo_debug.h"

/*
 * Lock/unlock a file.
 */
#ifdef HAVE_LOCKF
bool
sudo_lock_file_v1(int fd, int lockit)
{
    int op = 0;
    debug_decl(sudo_lock_file, SUDO_DEBUG_UTIL)

    switch (lockit) {
	case SUDO_LOCK:
	    op = F_LOCK;
	    break;
	case SUDO_TLOCK:
	    op = F_TLOCK;
	    break;
	case SUDO_UNLOCK:
	    op = F_ULOCK;
	    break;
    }
    debug_return_bool(lockf(fd, op, 0) == 0);
}
#elif defined(HAVE_FLOCK)
bool
sudo_lock_file_v1(int fd, int lockit)
{
    int op = 0;
    debug_decl(sudo_lock_file, SUDO_DEBUG_UTIL)

    switch (lockit) {
	case SUDO_LOCK:
	    op = LOCK_EX;
	    break;
	case SUDO_TLOCK:
	    op = LOCK_EX | LOCK_NB;
	    break;
	case SUDO_UNLOCK:
	    op = LOCK_UN;
	    break;
    }
    debug_return_bool(flock(fd, op) == 0);
}
#else
bool
sudo_lock_file_v1(int fd, int lockit)
{
#ifdef F_SETLK
    int func;
    struct flock lock;
    debug_decl(sudo_lock_file, SUDO_DEBUG_UTIL)

    lock.l_start = 0;
    lock.l_len = 0;
    lock.l_pid = getpid();
    lock.l_type = (lockit == SUDO_UNLOCK) ? F_UNLCK : F_WRLCK;
    lock.l_whence = SEEK_SET;
    func = (lockit == SUDO_LOCK) ? F_SETLKW : F_SETLK;

    debug_return_bool(fcntl(fd, func, &lock) == 0);
#else
    return true;
#endif
}
#endif