utmp_update.tproj/utmp_update.c

   1 /*      $NetBSD: utmp_update.c,v 1.6 2003/02/26 18:16:50 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  * 3. All advertising materials mentioning features or use of this software
  19  *    must display the following acknowledgement:
  20  *        This product includes software developed by the NetBSD
  21  *        Foundation, Inc. and its contributors.
  22  * 4. Neither the name of The NetBSD Foundation nor the names of its
  23  *    contributors may be used to endorse or promote products derived
  24  *    from this software without specific prior written permission.
  25  *
  26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  36  * POSSIBILITY OF SUCH DAMAGE.
  37  */
  38 #include <sys/cdefs.h>
  39
  40 __RCSID("$NetBSD: utmp_update.c,v 1.6 2003/02/26 18:16:50 christos Exp $");
  41
  42 #include <sys/types.h>
  43 #include <sys/param.h>
  44 #include <sys/stat.h>
  45
  46 #include <stdio.h>
  47 #include <vis.h>
  48 #include <err.h>
  49 #include <fcntl.h>
  50 #include <pwd.h>
  51 #include <utmpx.h>
  52 #include <stdlib.h>
  53 #include <string.h>
  54 #include <unistd.h>
  55 #include <paths.h>
  56
  57 int main(int, char *[]);
  58
  59 int
  60 main(int argc, char *argv[])
  61 {
  62         struct utmpx *utx;
  63         size_t len;
  64         struct passwd *pwd;
  65         struct stat st;
  66         int fd;
  67         uid_t euid, ruid;
  68         char tty[MAXPATHLEN];
  69
  70         euid = geteuid();
  71         ruid = getuid();
  72         if (seteuid(ruid) == -1)
  73                 err(1, "seteuid");
  74
  75         if (argc != 2) {
  76                 (void)fprintf(stderr, "Usage: %s <vis-utmpx-entry>\n",
  77                         getprogname());
  78                 exit(1);
  79         }
  80
  81         len = strlen(argv[1]);
  82
  83         // arg string can't be greater the 4x the size of struct utmpx
  84         // nor less that the size of struct utmpx
  85         if (len > sizeof(*utx) * 4 || len < sizeof(*utx))
  86                 errx(1, "Bad argument");
  87
  88         // need an extra byte because strunvis will null terminate
  89         if ((utx = malloc(len + 1)) == NULL)
  90                 err(1, NULL);
  91
  92         if (strunvis((char *)utx, argv[1]) != sizeof(*utx))
  93                 errx(1, "Decoding error");
  94
  95         switch (utx->ut_type) {
  96         case USER_PROCESS:
  97         case DEAD_PROCESS:
  98                 break;
  99         default:
 100                 errx(1, "Invalid utmpx type %d", (int)utx->ut_type);
 101         }
 102
 103         if (ruid != 0) {
 104                 if ((pwd = getpwuid(ruid)) == NULL)
 105                         errx(1, "User %lu does not exist in password database",
 106                             (long)ruid);
 107
 108                 if (strcmp(pwd->pw_name, utx->ut_user) != 0)
 109                         errx(1, "Current user `%s' does not match "
 110                             "`%s' in utmpx entry", pwd->pw_name, utx->ut_user);
 111         }
 112
 113         (void)snprintf(tty, sizeof(tty), "%s%s", _PATH_DEV, utx->ut_line);
 114         fd = open(tty, O_RDONLY, 0);
 115         if (fd != -1) {
 116                 if (fstat(fd, &st) == -1)
 117                         err(1, "Cannot stat `%s'", tty);
 118                 if (ruid != 0 && st.st_uid != ruid)
 119                         errx(1, "%s: Is not owned by you", tty);
 120                 if (!isatty(fd))
 121                         errx(1, "%s: Not a tty device", tty);
 122                 (void)close(fd);
 123                 if (access(tty, W_OK|R_OK) == -1)
 124                         err(1, "%s", tty);
 125         } else {
 126                 struct utmpx utold, *utoldp;
 127                 /*
 128                  * A daemon like ftpd that does not use a tty line?
 129                  * We only allow it to kill its own existing entries
 130                  */
 131                 if (utx->ut_type != DEAD_PROCESS)
 132                         err(1, "Cannot open `%s'", tty);
 133
 134                 (void)memcpy(utold.ut_line, utx->ut_line, sizeof(utx->ut_line));
 135                 if ((utoldp = getutxline(&utold)) == NULL)
 136                         err(1, "Cannot find existing entry for `%s'",
 137                             utx->ut_line);
 138                 if (utoldp->ut_pid != getppid())
 139                         err(1, "Cannot modify entry for `%s'", tty);
 140         }
 141
 142         (void)seteuid(euid);
 143         if (pututxline(utx) == NULL)
 144                 err(1, "Cannot update utmp entry");
 145
 146         return 0;
 147 }