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