1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1988, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 *    may be used to endorse or promote products derived from this software
17 *    without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32#include <sys/cdefs.h>
33__FBSDID("$FreeBSD$");
34__SCCSID("@(#)uucplock.c	8.1 (Berkeley) 6/6/93");
35
36#include <sys/types.h>
37#include <sys/file.h>
38#include <dirent.h>
39#include <errno.h>
40#include <paths.h>
41#include <signal.h>
42#include <stdio.h>
43#include <stdlib.h>
44#include <string.h>
45#include <unistd.h>
46#include "libutil.h"
47
48#define MAXTRIES 5
49
50#define LOCKTMP "LCKTMP..%d"
51#define LOCKFMT "LCK..%s"
52
53#define GORET(level, val) { err = errno; uuerr = (val); \
54			    goto __CONCAT(ret, level); }
55
56/* Forward declarations */
57static int put_pid (int fd, pid_t pid);
58static pid_t get_pid (int fd,int *err);
59
60/*
61 * uucp style locking routines
62 */
63
64int
65uu_lock(const char *tty_name)
66{
67	int fd, tmpfd, i;
68	pid_t pid, pid_old;
69	char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN],
70	     lcktmpname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
71	int err, uuerr;
72
73	pid = getpid();
74	(void)snprintf(lcktmpname, sizeof(lcktmpname), _PATH_UUCPLOCK LOCKTMP,
75			pid);
76	(void)snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT,
77			tty_name);
78	if ((tmpfd = open(lcktmpname, O_CREAT | O_TRUNC | O_WRONLY | O_CLOEXEC,
79	    0664)) < 0)
80		GORET(0, UU_LOCK_CREAT_ERR);
81
82	for (i = 0; i < MAXTRIES; i++) {
83		if (link (lcktmpname, lckname) < 0) {
84			if (errno != EEXIST)
85				GORET(1, UU_LOCK_LINK_ERR);
86			/*
87			 * file is already locked
88			 * check to see if the process holding the lock
89			 * still exists
90			 */
91			if ((fd = open(lckname, O_RDONLY | O_CLOEXEC)) < 0)
92				GORET(1, UU_LOCK_OPEN_ERR);
93
94			if ((pid_old = get_pid (fd, &err)) == -1)
95				GORET(2, UU_LOCK_READ_ERR);
96
97			close(fd);
98
99			if (kill(pid_old, 0) == 0 || errno != ESRCH)
100				GORET(1, UU_LOCK_INUSE);
101			/*
102			 * The process that locked the file isn't running, so
103			 * we'll lock it ourselves
104			 */
105			(void)unlink(lckname);
106		} else {
107			if (!put_pid (tmpfd, pid))
108				GORET(3, UU_LOCK_WRITE_ERR);
109			break;
110		}
111	}
112	GORET(1, (i >= MAXTRIES) ? UU_LOCK_TRY_ERR : UU_LOCK_OK);
113
114ret3:
115	(void)unlink(lckname);
116	goto ret1;
117ret2:
118	(void)close(fd);
119ret1:
120	(void)close(tmpfd);
121	(void)unlink(lcktmpname);
122ret0:
123	errno = err;
124	return uuerr;
125}
126
127int
128uu_lock_txfr(const char *tty_name, pid_t pid)
129{
130	int fd, err;
131	char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
132
133	snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, tty_name);
134
135	if ((fd = open(lckname, O_RDWR | O_CLOEXEC)) < 0)
136		return UU_LOCK_OWNER_ERR;
137	if (get_pid(fd, &err) != getpid())
138		err = UU_LOCK_OWNER_ERR;
139	else {
140        	lseek(fd, (off_t)0, SEEK_SET);
141		err = put_pid(fd, pid) ? 0 : UU_LOCK_WRITE_ERR;
142	}
143	close(fd);
144
145	return err;
146}
147
148int
149uu_unlock(const char *tty_name)
150{
151	char tbuf[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
152
153	(void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, tty_name);
154	return unlink(tbuf);
155}
156
157const char *
158uu_lockerr(int uu_lockresult)
159{
160	static char errbuf[128];
161	const char *fmt;
162
163	switch (uu_lockresult) {
164		case UU_LOCK_INUSE:
165			return "device in use";
166		case UU_LOCK_OK:
167			return "";
168		case UU_LOCK_OPEN_ERR:
169			fmt = "open error: %s";
170			break;
171		case UU_LOCK_READ_ERR:
172			fmt = "read error: %s";
173			break;
174		case UU_LOCK_CREAT_ERR:
175			fmt = "creat error: %s";
176			break;
177		case UU_LOCK_WRITE_ERR:
178			fmt = "write error: %s";
179			break;
180		case UU_LOCK_LINK_ERR:
181			fmt = "link error: %s";
182			break;
183		case UU_LOCK_TRY_ERR:
184			fmt = "too many tries: %s";
185			break;
186		case UU_LOCK_OWNER_ERR:
187			fmt = "not locking process: %s";
188			break;
189		default:
190			fmt = "undefined error: %s";
191			break;
192	}
193
194	(void)snprintf(errbuf, sizeof(errbuf), fmt, strerror(errno));
195	return errbuf;
196}
197
198static int
199put_pid(int fd, pid_t pid)
200{
201	char buf[32];
202	int len;
203
204	len = sprintf (buf, "%10d\n", (int)pid);
205	return write (fd, buf, (size_t)len) == len;
206}
207
208static pid_t
209get_pid(int fd, int *err)
210{
211	int bytes_read;
212	char buf[32];
213	pid_t pid;
214
215	bytes_read = read (fd, buf, sizeof (buf) - 1);
216	if (bytes_read > 0) {
217		buf[bytes_read] = '\0';
218		pid = (pid_t)strtol (buf, (char **) NULL, 10);
219	} else {
220		pid = -1;
221		*err = bytes_read ? errno : EINVAL;
222	}
223	return pid;
224}
225
226/* end of uucplock.c */
227