libexec/utmp_update/utmp_update.c

   1 /*      $NetBSD: utmp_update.c,v 1.8 2008/04/28 20:23:04 martin 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
  48 int
  49 main(int argc, char *argv[])
  50 {
  51         struct utmpx *utx;
  52         size_t len;
  53         struct passwd *pwd;
  54         struct stat st;
  55         int fd;
  56         int res;
  57         uid_t euid, ruid;
  58         char tty[MAXPATHLEN];
  59
  60         euid = geteuid();
  61         ruid = getuid();
  62         if (seteuid(ruid) == -1)
  63                 err(1, "seteuid");
  64
  65         if (argc != 2) {
  66                 (void)fprintf(stderr, "Usage: %s <vis-utmpx-entry>\n",
  67                         getprogname());
  68                 exit(1);
  69         }
  70
  71         len = strlen(argv[1]);
  72
  73         if (len > sizeof(*utx) * 4 + 1 || len < sizeof(*utx))
  74                 errx(1, "Bad argument");
  75
  76         if ((utx = malloc(len)) == NULL)
  77                 err(1, NULL);
  78
  79         res = strunvis((char *)utx, argv[1]);
  80         if (res != (int)sizeof(*utx))
  81                 errx(1, "Decoding error %s %d != %zu", argv[1], res, sizeof(*utx));
  82
  83         switch (utx->ut_type) {
  84         case USER_PROCESS:
  85         case DEAD_PROCESS:
  86                 break;
  87         default:
  88                 errx(1, "Invalid utmpx type %d", (int)utx->ut_type);
  89         }
  90
  91         if (ruid != 0) {
  92                 if ((pwd = getpwuid(ruid)) == NULL)
  93                         errx(1, "User %lu does not exist in password database",
  94                             (long)ruid);
  95
  96                 if (strcmp(pwd->pw_name, utx->ut_name) != 0)
  97                         errx(1, "Current user `%s' does not match "
  98                             "`%s' in utmpx entry", pwd->pw_name, utx->ut_name);
  99         }
 100
 101         (void)snprintf(tty, sizeof(tty), "%s%s", _PATH_DEV, utx->ut_line);
 102         fd = open(tty, O_RDONLY|O_NONBLOCK, 0);
 103         if (fd != -1) {
 104                 if (fstat(fd, &st) == -1)
 105                         err(1, "Cannot stat `%s'", tty);
 106                 if (ruid != 0 && st.st_uid != ruid)
 107                         errx(1, "%s: Is not owned by you", tty);
 108                 if (!isatty(fd))
 109                         errx(1, "%s: Not a tty device", tty);
 110                 (void)close(fd);
 111                 if (access(tty, W_OK|R_OK) == -1)
 112                         err(1, "%s", tty);
 113         } else {
 114                 struct utmpx utold, *utoldp;
 115                 /*
 116                  * A daemon like ftpd that does not use a tty line?
 117                  * We only allow it to kill its own existing entries
 118                  */
 119                 if (utx->ut_type != DEAD_PROCESS)
 120                         err(1, "Cannot open `%s'", tty);
 121
 122                 (void)memcpy(utold.ut_line, utx->ut_line, sizeof(utx->ut_line));
 123                 if ((utoldp = getutxline(&utold)) == NULL)
 124                         err(1, "Cannot find existing entry for `%s'",
 125                             utx->ut_line);
 126                 if (utoldp->ut_pid != getppid())
 127                         err(1, "Cannot modify entry for `%s'", tty);
 128         }
 129
 130         (void)seteuid(euid);
 131         if (pututxline(utx) == NULL)
 132                 err(1, "Cannot update utmp entry");
 133
 134         return 0;
 135 }