Home | History | Annotate | Line # | Download | only in write 
      1 /* $NetBSD: term_chk.c,v 1.8 2009/04/14 07:59:17 lukem Exp $ */
      2 
      3 /*
      4  * Copyright (c) 1989, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This code is derived from software contributed to Berkeley by
      8  * Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. Neither the name of the University nor the names of its contributors
     19  *    may be used to endorse or promote products derived from this software
     20  *    without specific prior written permission.
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     32  * SUCH DAMAGE.
     33  */
     34 
     35 #include <sys/cdefs.h>
     36 #ifndef lint
     37 __RCSID("$NetBSD: term_chk.c,v 1.8 2009/04/14 07:59:17 lukem Exp $");
     38 #endif
     39 
     40 #include <sys/types.h>
     41 #include <sys/param.h>
     42 #include <sys/stat.h>
     43 #include <time.h>
     44 #include <stdio.h>
     45 #include <errno.h>
     46 #include <unistd.h>
     47 #include <paths.h>
     48 #include <fcntl.h>
     49 #include <string.h>
     50 #include <err.h>
     51 
     52 #include "term_chk.h"
     53 
     54 /*
     55  * term_chk - check that a terminal exists, and get the message bit
     56  *     and the access time
     57  */
     58 int
     59 term_chk(uid_t uid, const char *tty, int *msgsokP, time_t *atimeP, int ismytty,
     60     gid_t saved_egid)
     61 {
     62 	char path[MAXPATHLEN];
     63 	struct stat s;
     64 	int i, fd, serrno;
     65 
     66 	if (strstr(tty, "../") != NULL) {
     67 		errno = EINVAL;
     68 		return -1;
     69 	}
     70 	i = snprintf(path, sizeof path, _PATH_DEV "%s", tty);
     71 	if (i < 0 || i >= (int)sizeof(path)) {
     72 		errno = ENOMEM;
     73 		return -1;
     74 	}
     75 
     76 	(void)setegid(saved_egid);
     77 	fd = open(path, O_WRONLY, 0);
     78 	serrno = errno;
     79 	(void)setegid(getgid());
     80 	errno = serrno;
     81 
     82 	if (fd == -1)
     83 		return(-1);
     84 	if (fstat(fd, &s) == -1)
     85 		goto error;
     86 	if (!isatty(fd))
     87 		goto error;
     88 	if (s.st_uid != uid && uid != 0) {
     89 		errno = EPERM;
     90 		goto error;
     91 	}
     92 	if (msgsokP)
     93 		*msgsokP = (s.st_mode & S_IWGRP) != 0;	/* group write bit */
     94 	if (atimeP)
     95 		*atimeP = s.st_atime;
     96 	if (ismytty)
     97 		(void)close(fd);
     98 	return ismytty ? 0 : fd;
     99 error:
    100 	if (fd != -1) {
    101 		serrno = errno;
    102 		(void)close(fd);
    103 		errno = serrno;
    104 	}
    105 	return -1;
    106 }
    107 
    108 char *
    109 check_sender(time_t *atime, uid_t myuid, gid_t saved_egid)
    110 {
    111 	int myttyfd;
    112 	int msgsok;
    113 	char *mytty;
    114 
    115 	/* check that sender has write enabled */
    116 	if (isatty(fileno(stdin)))
    117 		myttyfd = fileno(stdin);
    118 	else if (isatty(fileno(stdout)))
    119 		myttyfd = fileno(stdout);
    120 	else if (isatty(fileno(stderr)))
    121 		myttyfd = fileno(stderr);
    122 	else if (atime == NULL)
    123 		return NULL;
    124 	else
    125 		errx(1, "Cannot find your tty");
    126 	if ((mytty = ttyname(myttyfd)) == NULL)
    127 		err(1, "Cannot find the name of your tty");
    128 	if (strncmp(mytty, _PATH_DEV, sizeof(_PATH_DEV) - 1) == 0)
    129 		mytty += sizeof(_PATH_DEV) - 1;
    130 	if (term_chk(myuid, mytty, &msgsok, atime, 1, saved_egid) == -1)
    131 		err(1, "%s%s", _PATH_DEV, mytty);
    132 	if (!msgsok) {
    133 		warnx(
    134 		    "You have write permission turned off; no reply possible");
    135 	}
    136 	return mytty;
    137 }
    138