contrib/tcp_wrappers/eval.c

   1  /*
   2   * Routines for controlled evaluation of host names, user names, and so on.
   3   * They are, in fact, wrappers around the functions that are specific for
   4   * the sockets or TLI programming interfaces. The request_info and host_info
   5   * structures are used for result cacheing.
   6   *
   7   * These routines allows us to postpone expensive operations until their
   8   * results are really needed. Examples are hostname lookups and double
   9   * checks, or username lookups. Information that cannot be retrieved is
  10   * given the value "unknown" ("paranoid" in case of hostname problems).
  11   *
  12   * When ALWAYS_HOSTNAME is off, hostname lookup is done only when required by
  13   * tcpd paranoid mode, by access control patterns, or by %letter expansions.
  14   *
  15   * When ALWAYS_RFC931 mode is off, user lookup is done only when required by
  16   * access control patterns or %letter expansions.
  17   *
  18   * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
  19   */
  20
  21 /* System libraries. */
  22
  23 #include <stdio.h>
  24 #include <string.h>
  25
  26 /* Local stuff. */
  27
  28 #include "tcpd.h"
  29
  30  /*
  31   * When a string has the value STRING_UNKNOWN, it means: don't bother, I
  32   * tried to look up the data but it was unavailable for some reason. When a
  33   * host name has the value STRING_PARANOID it means there was a name/address
  34   * conflict.
  35   */
  36 char    unknown[] = STRING_UNKNOWN;
  37 char    paranoid[] = STRING_PARANOID;
  38
  39 /* eval_user - look up user name */
  40
  41 char   *eval_user(request)
  42 struct request_info *request;
  43 {
  44     if (request->user[0] == 0) {
  45         strcpy(request->user, unknown);
  46         if (request->sink == 0 && request->client->sin && request->server->sin)
  47             rfc931(request->client->sin, request->server->sin, request->user);
  48     }
  49     return (request->user);
  50 }
  51
  52 /* eval_hostaddr - look up printable address */
  53
  54 char   *eval_hostaddr(host)
  55 struct host_info *host;
  56 {
  57     if (host->addr[0] == 0) {
  58         strcpy(host->addr, unknown);
  59         if (host->request->hostaddr != 0)
  60             host->request->hostaddr(host);
  61     }
  62     return (host->addr);
  63 }
  64
  65 /* eval_hostname - look up host name */
  66
  67 char   *eval_hostname(host)
  68 struct host_info *host;
  69 {
  70     if (host->name[0] == 0) {
  71         strcpy(host->name, unknown);
  72         if (host->request->hostname != 0)
  73             host->request->hostname(host);
  74     }
  75     return (host->name);
  76 }
  77
  78 /* eval_hostinfo - return string with host name (preferred) or address */
  79
  80 char   *eval_hostinfo(host)
  81 struct host_info *host;
  82 {
  83     char   *hostname;
  84
  85 #ifndef ALWAYS_HOSTNAME                         /* no implicit host lookups */
  86     if (host->name[0] == 0)
  87         return (eval_hostaddr(host));
  88 #endif
  89     hostname = eval_hostname(host);
  90     if (HOSTNAME_KNOWN(hostname)) {
  91         return (host->name);
  92     } else {
  93         return (eval_hostaddr(host));
  94     }
  95 }
  96
  97 /* eval_client - return string with as much about the client as we know */
  98
  99 char   *eval_client(request)
 100 struct request_info *request;
 101 {
 102     static char both[2 * STRING_LENGTH];
 103     char   *hostinfo = eval_hostinfo(request->client);
 104
 105 #ifndef ALWAYS_RFC931                           /* no implicit user lookups */
 106     if (request->user[0] == 0)
 107         return (hostinfo);
 108 #endif
 109     if (STR_NE(eval_user(request), unknown)) {
 110         sprintf(both, "%s@%s", request->user, hostinfo);
 111         return (both);
 112     } else {
 113         return (hostinfo);
 114     }
 115 }
 116
 117 /* eval_server - return string with as much about the server as we know */
 118
 119 char   *eval_server(request)
 120 struct request_info *request;
 121 {
 122     static char both[2 * STRING_LENGTH];
 123     char   *host = eval_hostinfo(request->server);
 124     char   *daemon = eval_daemon(request);
 125
 126     if (STR_NE(host, unknown)) {
 127         sprintf(both, "%s@%s", daemon, host);
 128         return (both);
 129     } else {
 130         return (daemon);
 131     }
 132 }