xref: /openbsd-src/libexec/mail.local/locking.c (revision da07b1a33098c80ae09a68169c20a6485e5f3453)

/*	$OpenBSD: locking.c,v 1.15 2020/05/27 03:12:06 millert Exp $	*/

/*
 * Copyright (c) 1996-1998 Theo de Raadt <deraadt@theos.com>
 * Copyright (c) 1996-1998 David Mazieres <dm@lcs.mit.edu>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the authors may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
 * THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <pwd.h>
#include <syslog.h>
#include <unistd.h>
#include <limits.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include "pathnames.h"
#include "mail.local.h"

static char lpath[PATH_MAX];

void
rellock(void)
{

	if (lpath[0])
		unlink(lpath);
}

int
getlock(const char *name, struct passwd *pw)
{
	struct stat sb;
	int lfd=-1;
	int tries = 0;

	(void)snprintf(lpath, sizeof lpath, "%s/%s.lock",
	    _PATH_MAILDIR, name);

	if (stat(_PATH_MAILDIR, &sb) != -1 &&
	    (sb.st_mode & S_IWOTH) == S_IWOTH) {
		mwarn("%s: will not deliver to world-writable spool",
		    _PATH_MAILDIR);
	} else {
		/*
		 * Only root can write the spool directory.
		 */
		while (1) {
			if ((lfd = open(lpath, O_CREAT|O_WRONLY|O_EXCL,
			    S_IRUSR|S_IWUSR)) != -1)
				break;
			if (tries > 9) {
				mwarn("%s: %s", lpath, strerror(errno));
				return(-1);
			}
			sleep(1U << tries);
			tries++;
		}
	}
	return(lfd);
}

void
mwarn(const char *fmt, ...)
{
	va_list ap;

	va_start(ap, fmt);
	vsyslog(LOG_ERR, fmt, ap);
	va_end(ap);
}

void
merr(int eval, const char *fmt, ...)
{
	va_list ap;

	va_start(ap, fmt);
	vsyslog(LOG_ERR, fmt, ap);
	va_end(ap);
	exit(eval);
}