1 /* $NetBSD: utmp_update.c,v 1.13 2015/04/26 08:56:19 mlelstv 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 #include <sys/types.h> 34 #include <sys/param.h> 35 #include <sys/stat.h> 36 37 #include <stdio.h> 38 #include <vis.h> 39 #include <err.h> 40 #include <fcntl.h> 41 #include <pwd.h> 42 #include <utmpx.h> 43 #include <stdlib.h> 44 #include <string.h> 45 #include <unistd.h> 46 #include <paths.h> 47 #include <stdarg.h> 48 #include <errno.h> 49 #include <syslog.h> 50 51 static __dead2 __printflike(2, 3) void 52 logerr(int e, const char *fmt, ...) 53 { 54 va_list sap, eap; 55 char *s = NULL; 56 57 if (e) 58 (void)asprintf(&s, "%s (%s)", fmt, strerror(e)); 59 if (s) 60 fmt = s; 61 62 va_start(sap, fmt); 63 va_copy(eap, sap); 64 vsyslog(LOG_ERR, fmt, sap); 65 va_end(sap); 66 verrx(1, fmt, eap); 67 va_end(eap); 68 } 69 70 int 71 main(int argc, char *argv[]) 72 { 73 struct utmpx *utx; 74 size_t len; 75 struct passwd *pwd; 76 struct stat st; 77 int fd; 78 int res; 79 uid_t euid, ruid; 80 char tty[MAXPATHLEN]; 81 82 euid = geteuid(); 83 ruid = getuid(); 84 85 if (argc != 2) { 86 (void)fprintf(stderr, "Usage: %s <vis-utmpx-entry>\n", 87 getprogname()); 88 exit(1); 89 } 90 91 openlog(getprogname(), LOG_PID | LOG_NDELAY, LOG_AUTH); 92 if (seteuid(ruid) == -1) 93 logerr(errno, "Can't setuid %ld", (long)ruid); 94 95 len = strlen(argv[1]); 96 97 if (len > sizeof(*utx) * 4 + 1 || len < sizeof(*utx)) 98 logerr(0, "Bad argument size %zu", len); 99 100 if ((utx = malloc(len+1)) == NULL) 101 logerr(errno, "Can't allocate %zu", len+1); 102 103 res = strunvis((char *)utx, argv[1]); 104 if (res != (int)sizeof(*utx)) 105 logerr(0, "Decoding error %s %d != %zu", argv[1], res, 106 sizeof(*utx)); 107 108 switch (utx->ut_type) { 109 case USER_PROCESS: 110 case DEAD_PROCESS: 111 break; 112 default: 113 logerr(0, "Invalid utmpx type %hd", utx->ut_type); 114 } 115 116 if (ruid != 0) { 117 if ((pwd = getpwuid(ruid)) == NULL) 118 logerr(0, "User %ld does not exist in password" 119 " database", (long)ruid); 120 121 if (strcmp(pwd->pw_name, utx->ut_name) != 0) 122 logerr(0, "Current user `%s' does not match " 123 "`%s' in utmpx entry", pwd->pw_name, utx->ut_name); 124 } 125 126 (void)snprintf(tty, sizeof(tty), "%s%s", _PATH_DEV, utx->ut_line); 127 fd = open(tty, O_RDONLY|O_NONBLOCK, 0); 128 if (fd != -1) { 129 if (fstat(fd, &st) == -1) 130 logerr(errno, "Cannot stat `%s'", tty); 131 if (ruid != 0 && st.st_uid != ruid) 132 logerr(0, "%s: Is not owned by you", tty); 133 if (!isatty(fd)) 134 logerr(0, "%s: Not a tty device", tty); 135 (void)close(fd); 136 if (access(tty, W_OK|R_OK) == -1) 137 logerr(errno, "Can't access `%s'", tty); 138 } else { 139 struct utmpx utold, *utoldp; 140 pid_t ppid; 141 142 /* 143 * A daemon like ftpd that does not use a tty line? 144 * We only allow it to kill its own existing entries 145 */ 146 if (utx->ut_type != DEAD_PROCESS) 147 logerr(errno, "Cannot open `%s'", tty); 148 149 (void)memcpy(utold.ut_line, utx->ut_line, sizeof(utx->ut_line)); 150 if ((utoldp = getutxline(&utold)) == NULL) 151 logerr(0, "Cannot find existing entry for `%s'", 152 utx->ut_line); 153 if (utoldp->ut_pid != (ppid = getppid())) 154 logerr(0, "Cannot modify entry for `%s' " 155 "utmpx pid %ld != parent %ld", tty, 156 (long)utoldp->ut_pid, (long)ppid); 157 } 158 159 if (seteuid(euid) == 1) 160 logerr(errno, "Can't setuid %ld", (long)euid); 161 if (pututxline(utx) == NULL) 162 logerr(errno, "Cannot update utmpx entry"); 163 164 return 0; 165 } 166