contrib/tcp_wrappers/rfc931.c

   1  /*
   2   * rfc931() speaks a common subset of the RFC 931, AUTH, TAP, IDENT and RFC
   3   * 1413 protocols. It queries an RFC 931 etc. compatible daemon on a remote
   4   * host to look up the owner of a connection. The information should not be
   5   * used for authentication purposes. This routine intercepts alarm signals.
   6   *
   7   * Diagnostics are reported through syslog(3).
   8   *
   9   * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
  10   *
  11   * $FreeBSD: src/contrib/tcp_wrappers/rfc931.c,v 1.2.2.1 2000/07/18 16:41:11 dwmalone Exp $
  12   */
  13
  14 /* System libraries. */
  15
  16 #include <stdio.h>
  17 #include <syslog.h>
  18 #include <sys/types.h>
  19 #include <sys/socket.h>
  20 #include <netinet/in.h>
  21 #include <setjmp.h>
  22 #include <signal.h>
  23 #include <string.h>
  24 #include <unistd.h>
  25
  26 #ifndef SEEK_SET
  27 #define SEEK_SET 0
  28 #endif
  29
  30 /* Local stuff. */
  31
  32 #include "tcpd.h"
  33
  34 #define RFC931_PORT     113             /* Semi-well-known port */
  35 #define ANY_PORT        0               /* Any old port will do */
  36
  37 int     rfc931_timeout = RFC931_TIMEOUT;/* Global so it can be changed */
  38
  39 static jmp_buf timebuf;
  40
  41 /* fsocket - open stdio stream on top of socket */
  42
  43 static FILE *fsocket(domain, type, protocol)
  44 int     domain;
  45 int     type;
  46 int     protocol;
  47 {
  48     int     s;
  49     FILE   *fp;
  50
  51     if ((s = socket(domain, type, protocol)) < 0) {
  52         tcpd_warn("socket: %m");
  53         return (0);
  54     } else {
  55         if ((fp = fdopen(s, "r+")) == 0) {
  56             tcpd_warn("fdopen: %m");
  57             close(s);
  58         }
  59         return (fp);
  60     }
  61 }
  62
  63 /* timeout - handle timeouts */
  64
  65 static void timeout(sig)
  66 int     sig;
  67 {
  68     longjmp(timebuf, sig);
  69 }
  70
  71 /* rfc931 - return remote user name, given socket structures */
  72
  73 void    rfc931(rmt_sin, our_sin, dest)
  74 #ifdef INET6
  75 struct sockaddr *rmt_sin;
  76 struct sockaddr *our_sin;
  77 #else
  78 struct sockaddr_in *rmt_sin;
  79 struct sockaddr_in *our_sin;
  80 #endif
  81 char   *dest;
  82 {
  83     unsigned rmt_port;
  84     unsigned our_port;
  85 #ifdef INET6
  86     struct sockaddr_storage rmt_query_sin;
  87     struct sockaddr_storage our_query_sin;
  88     int alen;
  89 #else
  90     struct sockaddr_in rmt_query_sin;
  91     struct sockaddr_in our_query_sin;
  92 #endif
  93     char    user[256];                  /* XXX */
  94     char    buffer[512];                /* XXX */
  95     char   *cp;
  96     char   *result = unknown;
  97     FILE   *fp;
  98
  99 #ifdef INET6
 100     /* address family must be the same */
 101     if (rmt_sin->sa_family != our_sin->sa_family) {
 102         STRN_CPY(dest, result, STRING_LENGTH);
 103         return;
 104     }
 105     switch (our_sin->sa_family) {
 106     case AF_INET:
 107         alen = sizeof(struct sockaddr_in);
 108         break;
 109     case AF_INET6:
 110         alen = sizeof(struct sockaddr_in6);
 111         break;
 112     default:
 113         STRN_CPY(dest, result, STRING_LENGTH);
 114         return;
 115     }
 116 #endif
 117
 118     /*
 119      * If we use a single, buffered, bidirectional stdio stream ("r+" or
 120      * "w+" mode) we may read our own output. Such behaviour would make sense
 121      * with resources that support random-access operations, but not with
 122      * sockets. ANSI C suggests several functions which can be called when
 123      * you want to change IO direction, fseek seems the most portable.
 124      */
 125
 126 #ifdef INET6
 127     if ((fp = fsocket(our_sin->sa_family, SOCK_STREAM, 0)) != 0) {
 128 #else
 129     if ((fp = fsocket(AF_INET, SOCK_STREAM, 0)) != 0) {
 130 #endif
 131         /*
 132          * Set up a timer so we won't get stuck while waiting for the server.
 133          */
 134
 135         if (setjmp(timebuf) == 0) {
 136             signal(SIGALRM, timeout);
 137             alarm(rfc931_timeout);
 138
 139             /*
 140              * Bind the local and remote ends of the query socket to the same
 141              * IP addresses as the connection under investigation. We go
 142              * through all this trouble because the local or remote system
 143              * might have more than one network address. The RFC931 etc.
 144              * client sends only port numbers; the server takes the IP
 145              * addresses from the query socket.
 146              */
 147
 148 #ifdef INET6
 149             memcpy(&our_query_sin, our_sin, alen);
 150             memcpy(&rmt_query_sin, rmt_sin, alen);
 151             switch (our_sin->sa_family) {
 152             case AF_INET:
 153                 ((struct sockaddr_in *)&our_query_sin)->sin_port = htons(ANY_PORT);
 154                 ((struct sockaddr_in *)&rmt_query_sin)->sin_port = htons(RFC931_PORT);
 155                 break;
 156             case AF_INET6:
 157                 ((struct sockaddr_in6 *)&our_query_sin)->sin6_port = htons(ANY_PORT);
 158                 ((struct sockaddr_in6 *)&rmt_query_sin)->sin6_port = htons(RFC931_PORT);
 159                 break;
 160             }
 161
 162             if (bind(fileno(fp), (struct sockaddr *) & our_query_sin,
 163                      alen) >= 0 &&
 164                 connect(fileno(fp), (struct sockaddr *) & rmt_query_sin,
 165                         alen) >= 0) {
 166 #else
 167             our_query_sin = *our_sin;
 168             our_query_sin.sin_port = htons(ANY_PORT);
 169             rmt_query_sin = *rmt_sin;
 170             rmt_query_sin.sin_port = htons(RFC931_PORT);
 171
 172             if (bind(fileno(fp), (struct sockaddr *) & our_query_sin,
 173                      sizeof(our_query_sin)) >= 0 &&
 174                 connect(fileno(fp), (struct sockaddr *) & rmt_query_sin,
 175                         sizeof(rmt_query_sin)) >= 0) {
 176 #endif
 177
 178                 /*
 179                  * Send query to server. Neglect the risk that a 13-byte
 180                  * write would have to be fragmented by the local system and
 181                  * cause trouble with buggy System V stdio libraries.
 182                  */
 183
 184                 fprintf(fp, "%u,%u\r\n",
 185 #ifdef INET6
 186                         ntohs(((struct sockaddr_in *)rmt_sin)->sin_port),
 187                         ntohs(((struct sockaddr_in *)our_sin)->sin_port));
 188 #else
 189                         ntohs(rmt_sin->sin_port),
 190                         ntohs(our_sin->sin_port));
 191 #endif
 192                 fflush(fp);
 193                 fseek(fp, 0, SEEK_SET);
 194
 195                 /*
 196                  * Read response from server. Use fgets()/sscanf() so we can
 197                  * work around System V stdio libraries that incorrectly
 198                  * assume EOF when a read from a socket returns less than
 199                  * requested.
 200                  */
 201
 202                 if (fgets(buffer, sizeof(buffer), fp) != 0
 203                     && ferror(fp) == 0 && feof(fp) == 0
 204                     && sscanf(buffer, "%u , %u : USERID :%*[^:]:%255s",
 205                               &rmt_port, &our_port, user) == 3
 206 #ifdef INET6
 207                     && ntohs(((struct sockaddr_in *)rmt_sin)->sin_port) == rmt_port
 208                     && ntohs(((struct sockaddr_in *)our_sin)->sin_port) == our_port) {
 209 #else
 210                     && ntohs(rmt_sin->sin_port) == rmt_port
 211                     && ntohs(our_sin->sin_port) == our_port) {
 212 #endif
 213
 214                     /*
 215                      * Strip trailing carriage return. It is part of the
 216                      * protocol, not part of the data.
 217                      */
 218
 219                     if ((cp = strchr(user, '\r')) != NULL)
 220                         *cp = 0;
 221                     result = user;
 222                 }
 223             }
 224             alarm(0);
 225         }
 226         fclose(fp);
 227     }
 228     STRN_CPY(dest, result, STRING_LENGTH);
 229 }