1 /* $OpenBSD: uucplock.c,v 1.21 2019/07/03 03:24:04 deraadt Exp $ */ 2 /* 3 * Copyright (c) 1988, 1993 4 * The Regents of the University of California. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. Neither the name of the University nor the names of its contributors 15 * may be used to endorse or promote products derived from this software 16 * without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 * 30 * 31 */ 32 33 #include <sys/types.h> 34 #include <dirent.h> 35 #include <errno.h> 36 #include <fcntl.h> 37 #include <unistd.h> 38 #include <signal.h> 39 #include <stdio.h> 40 #include <stdlib.h> 41 #include <paths.h> 42 #include <string.h> 43 #include "util.h" 44 45 #define MAXTRIES 5 46 47 #define LOCKTMP "LCKTMP..%ld" 48 #define LOCKFMT "LCK..%s" 49 50 #define GORET(level, val) { err = errno; uuerr = (val); \ 51 goto __CONCAT(ret, level); } 52 53 /* Forward declarations */ 54 static int put_pid(int fd, pid_t pid); 55 static pid_t get_pid(int fd,int *err); 56 57 /* 58 * uucp style locking routines 59 */ 60 int 61 uu_lock(const char *ttyname) 62 { 63 char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN], 64 lcktmpname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN]; 65 int fd, tmpfd, i, err, uuerr; 66 pid_t pid, pid_old; 67 68 pid = getpid(); 69 (void)snprintf(lcktmpname, sizeof(lcktmpname), _PATH_UUCPLOCK LOCKTMP, 70 (long)pid); 71 (void)snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, 72 ttyname); 73 tmpfd = open(lcktmpname, O_CREAT|O_TRUNC|O_WRONLY|O_CLOEXEC, 0664); 74 if (tmpfd == -1) 75 GORET(0, UU_LOCK_CREAT_ERR); 76 77 for (i = 0; i < MAXTRIES; i++) { 78 if (link(lcktmpname, lckname) == -1) { 79 if (errno != EEXIST) 80 GORET(1, UU_LOCK_LINK_ERR); 81 /* 82 * file is already locked 83 * check to see if the process holding the lock 84 * still exists 85 */ 86 if ((fd = open(lckname, O_RDONLY | O_CLOEXEC)) == -1) 87 GORET(1, UU_LOCK_OPEN_ERR); 88 89 if ((pid_old = get_pid(fd, &err)) == -1) 90 GORET(2, UU_LOCK_READ_ERR); 91 92 close(fd); 93 94 if (kill(pid_old, 0) == 0 || errno != ESRCH) 95 GORET(1, UU_LOCK_INUSE); 96 /* 97 * The process that locked the file isn't running, so 98 * we'll lock it ourselves 99 */ 100 (void)unlink(lckname); 101 } else { 102 if (!put_pid(tmpfd, pid)) 103 GORET(3, UU_LOCK_WRITE_ERR); 104 break; 105 } 106 } 107 GORET(1, (i >= MAXTRIES) ? UU_LOCK_TRY_ERR : UU_LOCK_OK); 108 109 ret3: 110 (void)unlink(lckname); 111 goto ret1; 112 ret2: 113 (void)close(fd); 114 ret1: 115 (void)close(tmpfd); 116 (void)unlink(lcktmpname); 117 ret0: 118 errno = err; 119 return uuerr; 120 } 121 122 int 123 uu_lock_txfr(const char *ttyname, pid_t pid) 124 { 125 char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN]; 126 int fd, err, ret; 127 128 snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, ttyname); 129 130 if ((fd = open(lckname, O_RDWR | O_CLOEXEC)) == -1) 131 return UU_LOCK_OWNER_ERR; 132 if (get_pid(fd, &err) != getpid()) 133 ret = UU_LOCK_OWNER_ERR; 134 else { 135 lseek(fd, 0, SEEK_SET); 136 ret = put_pid(fd, pid) ? UU_LOCK_OK : UU_LOCK_WRITE_ERR; 137 } 138 139 close(fd); 140 return ret; 141 } 142 143 int 144 uu_unlock(const char *ttyname) 145 { 146 char tbuf[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN]; 147 148 (void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, ttyname); 149 return unlink(tbuf); 150 } 151 152 const char * 153 uu_lockerr(int uu_lockresult) 154 { 155 static char errbuf[128]; 156 const char *err; 157 158 switch (uu_lockresult) { 159 case UU_LOCK_INUSE: 160 return "device in use"; 161 case UU_LOCK_OK: 162 return ""; 163 case UU_LOCK_OPEN_ERR: 164 err = "open error"; 165 break; 166 case UU_LOCK_READ_ERR: 167 err = "read error"; 168 break; 169 case UU_LOCK_CREAT_ERR: 170 err = "creat error"; 171 break; 172 case UU_LOCK_WRITE_ERR: 173 err = "write error"; 174 break; 175 case UU_LOCK_LINK_ERR: 176 err = "link error"; 177 break; 178 case UU_LOCK_TRY_ERR: 179 err = "too many tries"; 180 break; 181 case UU_LOCK_OWNER_ERR: 182 err = "not locking process"; 183 break; 184 default: 185 err = "undefined error"; 186 break; 187 } 188 189 (void)snprintf(errbuf, sizeof(errbuf), "%s: %s", err, strerror(errno)); 190 return errbuf; 191 } 192 193 static int 194 put_pid(int fd, pid_t pid) 195 { 196 char buf[32]; 197 int len; 198 199 len = snprintf(buf, sizeof buf, "%10ld\n", (long)pid); 200 if (len < 0 || len >= sizeof buf) 201 return 0; 202 203 if (write(fd, buf, len) != len) 204 return 0; 205 206 /* We don't mind too much if ftruncate() fails - see get_pid */ 207 ftruncate(fd, (off_t)len); 208 return 1; 209 } 210 211 static pid_t 212 get_pid(int fd, int *err) 213 { 214 ssize_t bytes_read; 215 char buf[32]; 216 pid_t pid; 217 218 bytes_read = read(fd, buf, sizeof (buf) - 1); 219 if (bytes_read > 0) { 220 buf[bytes_read] = '\0'; 221 pid = (pid_t)strtoul(buf, (char **) NULL, 10); 222 } else { 223 pid = -1; 224 *err = bytes_read ? errno : EINVAL; 225 } 226 return pid; 227 } 228