/*      $OpenBSD: uucplock.c,v 1.22 2025/08/25 14:59:13 claudio 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 || (size_t)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;
}