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
term_chk(uid_t uid,const char * tty,int * msgsokP,time_t * atimeP,int ismytty,gid_t saved_egid)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 *
check_sender(time_t * atime,uid_t myuid,gid_t saved_egid)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