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
33#include <sys/types.h>
34#include <sys/file.h>
35#include <dirent.h>
36#include <errno.h>
37#include <paths.h>
38#include <signal.h>
39#include <stdio.h>
40#include <stdlib.h>
41#include <string.h>
42#include <unistd.h>
43#include "libutil.h"
44
45#define MAXTRIES 5
46
47#define LOCKTMP "LCKTMP..%d"
48#define LOCKFMT "LCK..%s"
49
50#define GORET(level, val) { err = errno; uuerr = (val); \
51			    goto __CONCAT(ret, level); }
52
53/* Forward declarations */
54static int put_pid (int fd, pid_t pid);
55static pid_t get_pid (int fd,int *err);
56
57/*
58 * uucp style locking routines
59 */
60
61int
62uu_lock(const char *tty_name)
63{
64	int fd, tmpfd, i;
65	pid_t pid, pid_old;
66	char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN],
67	     lcktmpname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
68	int err, uuerr;
69
70	pid = getpid();
71	(void)snprintf(lcktmpname, sizeof(lcktmpname), _PATH_UUCPLOCK LOCKTMP,
72			pid);
73	(void)snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT,
74			tty_name);
75	if ((tmpfd = open(lcktmpname, O_CREAT | O_TRUNC | O_WRONLY | O_CLOEXEC,
76	    0664)) < 0)
77		GORET(0, UU_LOCK_CREAT_ERR);
78
79	for (i = 0; i < MAXTRIES; i++) {
80		if (link (lcktmpname, lckname) < 0) {
81			if (errno != EEXIST)
82				GORET(1, UU_LOCK_LINK_ERR);
83			/*
84			 * file is already locked
85			 * check to see if the process holding the lock
86			 * still exists
87			 */
88			if ((fd = open(lckname, O_RDONLY | O_CLOEXEC)) < 0)
89				GORET(1, UU_LOCK_OPEN_ERR);
90
91			if ((pid_old = get_pid (fd, &err)) == -1)
92				GORET(2, UU_LOCK_READ_ERR);
93
94			close(fd);
95
96			if (kill(pid_old, 0) == 0 || errno != ESRCH)
97				GORET(1, UU_LOCK_INUSE);
98			/*
99			 * The process that locked the file isn't running, so
100			 * we'll lock it ourselves
101			 */
102			(void)unlink(lckname);
103		} else {
104			if (!put_pid (tmpfd, pid))
105				GORET(3, UU_LOCK_WRITE_ERR);
106			break;
107		}
108	}
109	GORET(1, (i >= MAXTRIES) ? UU_LOCK_TRY_ERR : UU_LOCK_OK);
110
111ret3:
112	(void)unlink(lckname);
113	goto ret1;
114ret2:
115	(void)close(fd);
116ret1:
117	(void)close(tmpfd);
118	(void)unlink(lcktmpname);
119ret0:
120	errno = err;
121	return uuerr;
122}
123
124int
125uu_lock_txfr(const char *tty_name, pid_t pid)
126{
127	int fd, err;
128	char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
129
130	snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, tty_name);
131
132	if ((fd = open(lckname, O_RDWR | O_CLOEXEC)) < 0)
133		return UU_LOCK_OWNER_ERR;
134	if (get_pid(fd, &err) != getpid())
135		err = UU_LOCK_OWNER_ERR;
136	else {
137        	lseek(fd, (off_t)0, SEEK_SET);
138		err = put_pid(fd, pid) ? 0 : UU_LOCK_WRITE_ERR;
139	}
140	close(fd);
141
142	return err;
143}
144
145int
146uu_unlock(const char *tty_name)
147{
148	char tbuf[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
149
150	(void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, tty_name);
151	return unlink(tbuf);
152}
153
154const char *
155uu_lockerr(int uu_lockresult)
156{
157	static char errbuf[128];
158	const char *fmt;
159
160	switch (uu_lockresult) {
161		case UU_LOCK_INUSE:
162			return "device in use";
163		case UU_LOCK_OK:
164			return "";
165		case UU_LOCK_OPEN_ERR:
166			fmt = "open error: %s";
167			break;
168		case UU_LOCK_READ_ERR:
169			fmt = "read error: %s";
170			break;
171		case UU_LOCK_CREAT_ERR:
172			fmt = "creat error: %s";
173			break;
174		case UU_LOCK_WRITE_ERR:
175			fmt = "write error: %s";
176			break;
177		case UU_LOCK_LINK_ERR:
178			fmt = "link error: %s";
179			break;
180		case UU_LOCK_TRY_ERR:
181			fmt = "too many tries: %s";
182			break;
183		case UU_LOCK_OWNER_ERR:
184			fmt = "not locking process: %s";
185			break;
186		default:
187			fmt = "undefined error: %s";
188			break;
189	}
190
191	(void)snprintf(errbuf, sizeof(errbuf), fmt, strerror(errno));
192	return errbuf;
193}
194
195static int
196put_pid(int fd, pid_t pid)
197{
198	char buf[32];
199	int len;
200
201	len = sprintf (buf, "%10d\n", (int)pid);
202	return write (fd, buf, (size_t)len) == len;
203}
204
205static pid_t
206get_pid(int fd, int *err)
207{
208	int bytes_read;
209	char buf[32];
210	pid_t pid;
211
212	bytes_read = read (fd, buf, sizeof (buf) - 1);
213	if (bytes_read > 0) {
214		buf[bytes_read] = '\0';
215		pid = (pid_t)strtol (buf, (char **) NULL, 10);
216	} else {
217		pid = -1;
218		*err = bytes_read ? errno : EINVAL;
219	}
220	return pid;
221}
222
223/* end of uucplock.c */
224