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   */
  14
  15 #ifndef lint
  16 static char sccsid[] = "@(#) tcpd.c 1.10 96/02/11 17:01:32";
  17 #endif
  18
  19 /* System libraries. */
  20
  21 #include <sys/types.h>
  22 #include <sys/param.h>
  23 #include <sys/stat.h>
  24 #include <sys/socket.h>
  25 #include <netinet/in.h>
  26 #include <stdio.h>
  27 #include <syslog.h>
  28 #include <string.h>
  29 #include <unistd.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 int
  48 main(argc, argv)
  49 int     argc;
  50 char  **argv;
  51 {
  52     struct request_info request;
  53     char    path[MAXPATHNAMELEN];
  54
  55     /* Attempt to prevent the creation of world-writable files. */
  56
  57 #ifdef DAEMON_UMASK
  58     umask(DAEMON_UMASK);
  59 #endif
  60
  61     /*
  62      * If argv[0] is an absolute path name, ignore REAL_DAEMON_DIR, and strip
  63      * argv[0] to its basename.
  64      */
  65
  66     if (argv[0][0] == '/') {
  67         strcpy(path, argv[0]);
  68         argv[0] = strrchr(argv[0], '/') + 1;
  69     } else {
  70         sprintf(path, "%s/%s", REAL_DAEMON_DIR, argv[0]);
  71     }
  72
  73     /*
  74      * Open a channel to the syslog daemon. Older versions of openlog()
  75      * require only two arguments.
  76      */
  77
  78 #ifdef LOG_MAIL
  79     (void) openlog(argv[0], LOG_PID, FACILITY);
  80 #else
  81     (void) openlog(argv[0], LOG_PID);
  82 #endif
  83
  84     /*
  85      * Find out the endpoint addresses of this conversation. Host name
  86      * lookups and double checks will be done on demand.
  87      */
  88
  89     request_init(&request, RQ_DAEMON, argv[0], RQ_FILE, STDIN_FILENO, 0);
  90     fromhost(&request);
  91
  92     /*
  93      * Optionally look up and double check the remote host name. Sites
  94      * concerned with security may choose to refuse connections from hosts
  95      * that pretend to have someone elses host name.
  96      */
  97
  98 #ifdef PARANOID
  99     if (STR_EQ(eval_hostname(request.client), paranoid))
 100         refuse(&request);
 101 #endif
 102
 103     /*
 104      * The BSD rlogin and rsh daemons that came out after 4.3 BSD disallow
 105      * socket options at the IP level. They do so for a good reason.
 106      * Unfortunately, we cannot use this with SunOS 4.1.x because the
 107      * getsockopt() system call can panic the system.
 108      */
 109
 110 #ifdef KILL_IP_OPTIONS
 111     fix_options(&request);
 112 #endif
 113
 114     /*
 115      * Check whether this host can access the service in argv[0]. The
 116      * access-control code invokes optional shell commands as specified in
 117      * the access-control tables.
 118      */
 119
 120 #ifdef HOSTS_ACCESS
 121     if (!hosts_access(&request))
 122         refuse(&request);
 123 #endif
 124
 125     /* Report request and invoke the real daemon program. */
 126
 127 #ifdef INET6
 128     syslog(allow_severity, "connect from %s (%s)",
 129            eval_client(&request), eval_hostaddr(request.client));
 130 #else
 131     syslog(allow_severity, "connect from %s", eval_client(&request));
 132 #endif
 133     closelog();
 134     (void) execv(path, argv);
 135     syslog(LOG_ERR, "error: cannot execute %s: %m", path);
 136     clean_exit(&request);
 137     /* NOTREACHED */
 138 }