libexec/utmp_update/utmp_update.c

   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 }