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 */
57 static int put_pid (int fd, pid_t pid);
58 static pid_t get_pid (int fd,int *err);
59
60 /*
61 * uucp style locking routines
62 */
63
64 int
uu_lock(const char * tty_name)65 uu_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
114 ret3:
115 (void)unlink(lckname);
116 goto ret1;
117 ret2:
118 (void)close(fd);
119 ret1:
120 (void)close(tmpfd);
121 (void)unlink(lcktmpname);
122 ret0:
123 errno = err;
124 return uuerr;
125 }
126
127 int
uu_lock_txfr(const char * tty_name,pid_t pid)128 uu_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
148 int
uu_unlock(const char * tty_name)149 uu_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
157 const char *
uu_lockerr(int uu_lockresult)158 uu_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
198 static int
put_pid(int fd,pid_t pid)199 put_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
208 static pid_t
get_pid(int fd,int * err)209 get_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