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