1 /* $NetBSD: utmp_update.c,v 1.14 2023/09/29 12:08:03 christos Exp $ */
2
3 /*-
4 * Copyright (c) 2002 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Christos Zoulas.
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 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31 #include <sys/cdefs.h>
32
33 __RCSID("$NetBSD: utmp_update.c,v 1.14 2023/09/29 12:08:03 christos Exp $");
34
35 #include <sys/types.h>
36 #include <sys/param.h>
37 #include <sys/stat.h>
38
39 #include <stdio.h>
40 #include <vis.h>
41 #include <err.h>
42 #include <fcntl.h>
43 #include <pwd.h>
44 #include <ctype.h>
45 #include <utmpx.h>
46 #include <stdlib.h>
47 #include <string.h>
48 #include <unistd.h>
49 #include <paths.h>
50 #include <stdarg.h>
51 #include <errno.h>
52 #include <syslog.h>
53
54 static __dead __printflike(2, 3) void
logerr(int e,const char * fmt,...)55 logerr(int e, const char *fmt, ...)
56 {
57 va_list sap, eap;
58 char *s = NULL;
59
60 if (e)
61 (void)asprintf(&s, "%s (%s)", fmt, strerror(e));
62 if (s)
63 fmt = s;
64
65 va_start(sap, fmt);
66 va_copy(eap, sap);
67 vsyslog(LOG_ERR, fmt, sap);
68 va_end(sap);
69 verrx(1, fmt, eap);
70 va_end(eap);
71 }
72
73 int
main(int argc,char * argv[])74 main(int argc, char *argv[])
75 {
76 struct utmpx *utx;
77 size_t len;
78 struct passwd *pwd;
79 struct stat st;
80 int fd;
81 int res;
82 uid_t euid, ruid;
83 char tty[MAXPATHLEN];
84 const char *p, *ep;
85
86 euid = geteuid();
87 ruid = getuid();
88
89 if (argc != 2) {
90 (void)fprintf(stderr, "Usage: %s <vis-utmpx-entry>\n",
91 getprogname());
92 return 1;
93 }
94
95 openlog(getprogname(), LOG_PID | LOG_NDELAY, LOG_AUTH);
96 if (seteuid(ruid) == -1)
97 logerr(errno, "Can't setuid %ld", (long)ruid);
98
99 len = strlen(argv[1]);
100
101 if (len > sizeof(*utx) * 4 + 1 || len < sizeof(*utx))
102 logerr(0, "Bad argument size %zu", len);
103
104 if ((utx = malloc(len+1)) == NULL)
105 logerr(errno, "Can't allocate %zu", len+1);
106
107 res = strunvis((char *)utx, argv[1]);
108 if (res != (int)sizeof(*utx))
109 logerr(0, "Decoding error %s %d != %zu", argv[1], res,
110 sizeof(*utx));
111
112 switch (utx->ut_type) {
113 case USER_PROCESS:
114 case DEAD_PROCESS:
115 break;
116 default:
117 logerr(0, "Invalid utmpx type %d", (int)utx->ut_type);
118 }
119
120 p = utx->ut_host;
121 ep = p + sizeof(utx->ut_host);
122 for (; p < ep && *p; p++)
123 if (!isprint((unsigned char)*p))
124 logerr(0, "Non-printable characters in hostname");
125
126 if (ruid != 0) {
127 if ((pwd = getpwuid(ruid)) == NULL)
128 logerr(0, "User %ld does not exist in password"
129 " database", (long)ruid);
130
131 if (strcmp(pwd->pw_name, utx->ut_name) != 0)
132 logerr(0, "Current user `%s' does not match "
133 "`%s' in utmpx entry", pwd->pw_name, utx->ut_name);
134 }
135
136 (void)snprintf(tty, sizeof(tty), "%s%s", _PATH_DEV, utx->ut_line);
137 fd = open(tty, O_RDONLY|O_NONBLOCK, 0);
138 if (fd != -1) {
139 if (fstat(fd, &st) == -1)
140 logerr(errno, "Cannot stat `%s'", tty);
141 if (ruid != 0 && st.st_uid != ruid)
142 logerr(0, "%s: Is not owned by you", tty);
143 if (!isatty(fd))
144 logerr(0, "%s: Not a tty device", tty);
145 (void)close(fd);
146 if (access(tty, W_OK|R_OK) == -1)
147 logerr(errno, "Can't access `%s'", tty);
148 } else {
149 struct utmpx utold, *utoldp;
150 pid_t ppid;
151
152 /*
153 * A daemon like ftpd that does not use a tty line?
154 * We only allow it to kill its own existing entries
155 */
156 if (utx->ut_type != DEAD_PROCESS)
157 logerr(errno, "Cannot open `%s'", tty);
158
159 (void)memcpy(utold.ut_line, utx->ut_line, sizeof(utx->ut_line));
160 if ((utoldp = getutxline(&utold)) == NULL)
161 logerr(0, "Cannot find existing entry for `%s'",
162 utx->ut_line);
163 if (utoldp->ut_pid != (ppid = getppid()))
164 logerr(0, "Cannot modify entry for `%s' "
165 "utmp pid %ld != parent %ld", tty,
166 (long)utoldp->ut_pid, (long)ppid);
167 }
168
169 if (seteuid(euid) == 1)
170 logerr(errno, "Can't setuid %ld", (long)euid);
171 if (pututxline(utx) == NULL)
172 logerr(errno, "Cannot update utmp entry");
173
174 return 0;
175 }
176