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/* $OpenBSD: uucplock.c,v 1.21 2019/07/03 03:24:04 deraadt Exp $ */
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/*
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* Copyright (c) 1988, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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*
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*/
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#include <sys/types.h>
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#include <dirent.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <signal.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <paths.h>
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#include <string.h>
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#include "util.h"
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#define MAXTRIES 5
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#define LOCKTMP "LCKTMP..%ld"
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#define LOCKFMT "LCK..%s"
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#define GORET(level, val) { err = errno; uuerr = (val); \
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goto __CONCAT(ret, level); }
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/* Forward declarations */
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static int put_pid(int fd, pid_t pid);
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static pid_t get_pid(int fd,int *err);
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/*
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* uucp style locking routines
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*/
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int
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uu_lock(const char *ttyname)
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{
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char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN],
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lcktmpname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
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int fd, tmpfd, i, err, uuerr;
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pid_t pid, pid_old;
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pid = getpid();
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(void)snprintf(lcktmpname, sizeof(lcktmpname), _PATH_UUCPLOCK LOCKTMP,
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(long)pid);
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(void)snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT,
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ttyname);
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tmpfd = open(lcktmpname, O_CREAT|O_TRUNC|O_WRONLY|O_CLOEXEC, 0664);
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if (tmpfd == -1)
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GORET(0, UU_LOCK_CREAT_ERR);
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for (i = 0; i < MAXTRIES; i++) {
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if (link(lcktmpname, lckname) == -1) {
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if (errno != EEXIST)
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GORET(1, UU_LOCK_LINK_ERR);
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/*
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* file is already locked
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* check to see if the process holding the lock
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* still exists
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*/
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if ((fd = open(lckname, O_RDONLY | O_CLOEXEC)) == -1)
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GORET(1, UU_LOCK_OPEN_ERR);
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if ((pid_old = get_pid(fd, &err)) == -1)
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GORET(2, UU_LOCK_READ_ERR);
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close(fd);
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if (kill(pid_old, 0) == 0 || errno != ESRCH)
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GORET(1, UU_LOCK_INUSE);
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/*
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* The process that locked the file isn't running, so
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* we'll lock it ourselves
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*/
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(void)unlink(lckname);
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} else {
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if (!put_pid(tmpfd, pid))
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GORET(3, UU_LOCK_WRITE_ERR);
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break;
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}
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}
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GORET(1, (i >= MAXTRIES) ? UU_LOCK_TRY_ERR : UU_LOCK_OK);
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ret3:
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(void)unlink(lckname);
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goto ret1;
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ret2:
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(void)close(fd);
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ret1:
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(void)close(tmpfd);
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(void)unlink(lcktmpname);
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ret0:
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errno = err;
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return uuerr;
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}
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int
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uu_lock_txfr(const char *ttyname, pid_t pid)
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{
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char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
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int fd, err, ret;
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snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, ttyname);
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if ((fd = open(lckname, O_RDWR | O_CLOEXEC)) == -1)
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return UU_LOCK_OWNER_ERR;
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if (get_pid(fd, &err) != getpid())
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ret = UU_LOCK_OWNER_ERR;
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else {
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lseek(fd, 0, SEEK_SET);
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ret = put_pid(fd, pid) ? UU_LOCK_OK : UU_LOCK_WRITE_ERR;
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}
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close(fd);
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return ret;
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}
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int
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uu_unlock(const char *ttyname)
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{
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char tbuf[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
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(void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, ttyname);
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return unlink(tbuf);
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}
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const char *
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uu_lockerr(int uu_lockresult)
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{
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static char errbuf[128];
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const char *err;
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switch (uu_lockresult) {
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case UU_LOCK_INUSE:
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return "device in use";
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case UU_LOCK_OK:
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return "";
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case UU_LOCK_OPEN_ERR:
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err = "open error";
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break;
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case UU_LOCK_READ_ERR:
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err = "read error";
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break;
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case UU_LOCK_CREAT_ERR:
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err = "creat error";
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break;
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case UU_LOCK_WRITE_ERR:
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err = "write error";
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break;
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case UU_LOCK_LINK_ERR:
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err = "link error";
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break;
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case UU_LOCK_TRY_ERR:
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err = "too many tries";
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break;
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case UU_LOCK_OWNER_ERR:
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err = "not locking process";
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break;
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default:
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err = "undefined error";
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break;
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}
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(void)snprintf(errbuf, sizeof(errbuf), "%s: %s", err, strerror(errno));
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return errbuf;
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}
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static int
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put_pid(int fd, pid_t pid)
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{
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char buf[32];
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int len;
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len = snprintf(buf, sizeof buf, "%10ld\n", (long)pid);
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if (len < 0 || len >= sizeof buf)
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return 0;
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if (write(fd, buf, len) != len)
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return 0;
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/* We don't mind too much if ftruncate() fails - see get_pid */
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ftruncate(fd, (off_t)len);
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return 1;
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}
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static pid_t
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get_pid(int fd, int *err)
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{
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ssize_t bytes_read;
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char buf[32];
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pid_t pid;
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bytes_read = read(fd, buf, sizeof (buf) - 1);
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if (bytes_read > 0) {
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buf[bytes_read] = '\0';
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pid = (pid_t)strtoul(buf, (char **) NULL, 10);
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} else {
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pid = -1;
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*err = bytes_read ? errno : EINVAL;
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}
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return pid;
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}
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