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 54static __dead __printflike(2, 3) void 55logerr(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 73int 74main(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