contrib/tcp_wrappers/tcpd.c

   1  /*
   2   * General front end for stream and datagram IP services. This program logs
   3   * the remote host name and then invokes the real daemon. For example,
   4   * install as /usr/etc/{tftpd,fingerd,telnetd,ftpd,rlogind,rshd,rexecd},
   5   * after saving the real daemons in the directory specified with the
   6   * REAL_DAEMON_DIR macro. This arrangement requires that the network daemons
   7   * are started by inetd or something similar. Connections and diagnostics
   8   * are logged through syslog(3).
   9   *
  10   * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
  11   *
  12   * $FreeBSD: src/contrib/tcp_wrappers/tcpd.c,v 1.2 2000/02/03 10:26:59 shin Exp $
  13   * $DragonFly: src/contrib/tcp_wrappers/tcpd.c,v 1.2 2003/06/17 04:24:06 dillon Exp $
  14   */
  15
  16 #ifndef lint
  17 static char sccsid[] = "@(#) tcpd.c 1.10 96/02/11 17:01:32";
  18 #endif
  19
  20 /* System libraries. */
  21
  22 #include <sys/types.h>
  23 #include <sys/param.h>
  24 #include <sys/stat.h>
  25 #include <sys/socket.h>
  26 #include <netinet/in.h>
  27 #include <stdio.h>
  28 #include <syslog.h>
  29 #include <string.h>
  30
  31 #ifndef MAXPATHNAMELEN
  32 #define MAXPATHNAMELEN  BUFSIZ
  33 #endif
  34
  35 #ifndef STDIN_FILENO
  36 #define STDIN_FILENO    0
  37 #endif
  38
  39 /* Local stuff. */
  40
  41 #include "patchlevel.h"
  42 #include "tcpd.h"
  43
  44 int     allow_severity = SEVERITY;      /* run-time adjustable */
  45 int     deny_severity = LOG_WARNING;    /* ditto */
  46
  47 main(argc, argv)
  48 int     argc;
  49 char  **argv;
  50 {
  51     struct request_info request;
  52     char    path[MAXPATHNAMELEN];
  53
  54     /* Attempt to prevent the creation of world-writable files. */
  55
  56 #ifdef DAEMON_UMASK
  57     umask(DAEMON_UMASK);
  58 #endif
  59
  60     /*
  61      * If argv[0] is an absolute path name, ignore REAL_DAEMON_DIR, and strip
  62      * argv[0] to its basename.
  63      */
  64
  65     if (argv[0][0] == '/') {
  66         strcpy(path, argv[0]);
  67         argv[0] = strrchr(argv[0], '/') + 1;
  68     } else {
  69         sprintf(path, "%s/%s", REAL_DAEMON_DIR, argv[0]);
  70     }
  71
  72     /*
  73      * Open a channel to the syslog daemon. Older versions of openlog()
  74      * require only two arguments.
  75      */
  76
  77 #ifdef LOG_MAIL
  78     (void) openlog(argv[0], LOG_PID, FACILITY);
  79 #else
  80     (void) openlog(argv[0], LOG_PID);
  81 #endif
  82
  83     /*
  84      * Find out the endpoint addresses of this conversation. Host name
  85      * lookups and double checks will be done on demand.
  86      */
  87
  88     request_init(&request, RQ_DAEMON, argv[0], RQ_FILE, STDIN_FILENO, 0);
  89     fromhost(&request);
  90
  91     /*
  92      * Optionally look up and double check the remote host name. Sites
  93      * concerned with security may choose to refuse connections from hosts
  94      * that pretend to have someone elses host name.
  95      */
  96
  97 #ifdef PARANOID
  98     if (STR_EQ(eval_hostname(request.client), paranoid))
  99         refuse(&request);
 100 #endif
 101
 102     /*
 103      * The BSD rlogin and rsh daemons that came out after 4.3 BSD disallow
 104      * socket options at the IP level. They do so for a good reason.
 105      * Unfortunately, we cannot use this with SunOS 4.1.x because the
 106      * getsockopt() system call can panic the system.
 107      */
 108
 109 #ifdef KILL_IP_OPTIONS
 110     fix_options(&request);
 111 #endif
 112
 113     /*
 114      * Check whether this host can access the service in argv[0]. The
 115      * access-control code invokes optional shell commands as specified in
 116      * the access-control tables.
 117      */
 118
 119 #ifdef HOSTS_ACCESS
 120     if (!hosts_access(&request))
 121         refuse(&request);
 122 #endif
 123
 124     /* Report request and invoke the real daemon program. */
 125
 126 #ifdef INET6
 127     syslog(allow_severity, "connect from %s (%s)",
 128            eval_client(&request), eval_hostaddr(request.client));
 129 #else
 130     syslog(allow_severity, "connect from %s", eval_client(&request));
 131 #endif
 132     closelog();
 133     (void) execv(path, argv);
 134     syslog(LOG_ERR, "error: cannot execute %s: %m", path);
 135     clean_exit(&request);
 136     /* NOTREACHED */
 137 }