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   * $FreeBSD$
  12   */
  13
  14 #ifndef lint
  15 static char sccsid[] = "@(#) rfc931.c 1.10 95/01/02 16:11:34";
  16 #endif
  17
  18 /* System libraries. */
  19
  20 #include <stdio.h>
  21 #include <syslog.h>
  22 #include <sys/types.h>
  23 #include <sys/socket.h>
  24 #include <netinet/in.h>
  25 #include <setjmp.h>
  26 #include <signal.h>
  27 #include <string.h>
  28
  29 #ifndef SEEK_SET
  30 #define SEEK_SET 0
  31 #endif
  32
  33 /* Local stuff. */
  34
  35 #include "tcpd.h"
  36
  37 #define RFC931_PORT     113             /* Semi-well-known port */
  38 #define ANY_PORT        0               /* Any old port will do */
  39
  40 int     rfc931_timeout = RFC931_TIMEOUT;/* Global so it can be changed */
  41
  42 static jmp_buf timebuf;
  43
  44 /* fsocket - open stdio stream on top of socket */
  45
  46 static FILE *fsocket(domain, type, protocol)
  47 int     domain;
  48 int     type;
  49 int     protocol;
  50 {
  51     int     s;
  52     FILE   *fp;
  53
  54     if ((s = socket(domain, type, protocol)) < 0) {
  55         tcpd_warn("socket: %m");
  56         return (0);
  57     } else {
  58         if ((fp = fdopen(s, "r+")) == 0) {
  59             tcpd_warn("fdopen: %m");
  60             close(s);
  61         }
  62         return (fp);
  63     }
  64 }
  65
  66 /* timeout - handle timeouts */
  67
  68 static void timeout(sig)
  69 int     sig;
  70 {
  71     longjmp(timebuf, sig);
  72 }
  73
  74 /* rfc931 - return remote user name, given socket structures */
  75
  76 void    rfc931(rmt_sin, our_sin, dest)
  77 #ifdef INET6
  78 struct sockaddr *rmt_sin;
  79 struct sockaddr *our_sin;
  80 #else
  81 struct sockaddr_in *rmt_sin;
  82 struct sockaddr_in *our_sin;
  83 #endif
  84 char   *dest;
  85 {
  86     unsigned rmt_port;
  87     unsigned our_port;
  88 #ifdef INET6
  89     struct sockaddr_storage rmt_query_sin;
  90     struct sockaddr_storage our_query_sin;
  91     int alen;
  92 #else
  93     struct sockaddr_in rmt_query_sin;
  94     struct sockaddr_in our_query_sin;
  95 #endif
  96     char    user[256];                  /* XXX */
  97     char    buffer[512];                /* XXX */
  98     char   *cp;
  99     char   *result = unknown;
 100     FILE   *fp;
 101
 102 #ifdef INET6
 103     /* address family must be the same */
 104     if (rmt_sin->sa_family != our_sin->sa_family) {
 105         STRN_CPY(dest, result, STRING_LENGTH);
 106         return;
 107     }
 108     switch (our_sin->sa_family) {
 109     case AF_INET:
 110         alen = sizeof(struct sockaddr_in);
 111         break;
 112     case AF_INET6:
 113         alen = sizeof(struct sockaddr_in6);
 114         break;
 115     default:
 116         STRN_CPY(dest, result, STRING_LENGTH);
 117         return;
 118     }
 119 #endif
 120
 121     /*
 122      * If we use a single, buffered, bidirectional stdio stream ("r+" or
 123      * "w+" mode) we may read our own output. Such behaviour would make sense
 124      * with resources that support random-access operations, but not with
 125      * sockets. ANSI C suggests several functions which can be called when
 126      * you want to change IO direction, fseek seems the most portable.
 127      */
 128
 129 #ifdef INET6
 130     if ((fp = fsocket(our_sin->sa_family, SOCK_STREAM, 0)) != 0) {
 131 #else
 132     if ((fp = fsocket(AF_INET, SOCK_STREAM, 0)) != 0) {
 133 #endif
 134         /*
 135          * Set up a timer so we won't get stuck while waiting for the server.
 136          */
 137
 138         if (setjmp(timebuf) == 0) {
 139             signal(SIGALRM, timeout);
 140             alarm(rfc931_timeout);
 141
 142             /*
 143              * Bind the local and remote ends of the query socket to the same
 144              * IP addresses as the connection under investigation. We go
 145              * through all this trouble because the local or remote system
 146              * might have more than one network address. The RFC931 etc.
 147              * client sends only port numbers; the server takes the IP
 148              * addresses from the query socket.
 149              */
 150
 151 #ifdef INET6
 152             memcpy(&our_query_sin, our_sin, alen);
 153             memcpy(&rmt_query_sin, rmt_sin, alen);
 154             switch (our_sin->sa_family) {
 155             case AF_INET:
 156                 ((struct sockaddr_in *)&our_query_sin)->sin_port = htons(ANY_PORT);
 157                 ((struct sockaddr_in *)&rmt_query_sin)->sin_port = htons(RFC931_PORT);
 158                 break;
 159             case AF_INET6:
 160                 ((struct sockaddr_in6 *)&our_query_sin)->sin6_port = htons(ANY_PORT);
 161                 ((struct sockaddr_in6 *)&rmt_query_sin)->sin6_port = htons(RFC931_PORT);
 162                 break;
 163             }
 164
 165             if (bind(fileno(fp), (struct sockaddr *) & our_query_sin,
 166                      alen) >= 0 &&
 167                 connect(fileno(fp), (struct sockaddr *) & rmt_query_sin,
 168                         alen) >= 0) {
 169 #else
 170             our_query_sin = *our_sin;
 171             our_query_sin.sin_port = htons(ANY_PORT);
 172             rmt_query_sin = *rmt_sin;
 173             rmt_query_sin.sin_port = htons(RFC931_PORT);
 174
 175             if (bind(fileno(fp), (struct sockaddr *) & our_query_sin,
 176                      sizeof(our_query_sin)) >= 0 &&
 177                 connect(fileno(fp), (struct sockaddr *) & rmt_query_sin,
 178                         sizeof(rmt_query_sin)) >= 0) {
 179 #endif
 180
 181                 /*
 182                  * Send query to server. Neglect the risk that a 13-byte
 183                  * write would have to be fragmented by the local system and
 184                  * cause trouble with buggy System V stdio libraries.
 185                  */
 186
 187                 fprintf(fp, "%u,%u\r\n",
 188 #ifdef INET6
 189                         ntohs(((struct sockaddr_in *)rmt_sin)->sin_port),
 190                         ntohs(((struct sockaddr_in *)our_sin)->sin_port));
 191 #else
 192                         ntohs(rmt_sin->sin_port),
 193                         ntohs(our_sin->sin_port));
 194 #endif
 195                 fflush(fp);
 196                 fseek(fp, 0, SEEK_SET);
 197
 198                 /*
 199                  * Read response from server. Use fgets()/sscanf() so we can
 200                  * work around System V stdio libraries that incorrectly
 201                  * assume EOF when a read from a socket returns less than
 202                  * requested.
 203                  */
 204
 205                 if (fgets(buffer, sizeof(buffer), fp) != 0
 206                     && ferror(fp) == 0 && feof(fp) == 0
 207                     && sscanf(buffer, "%u , %u : USERID :%*[^:]:%255s",
 208                               &rmt_port, &our_port, user) == 3
 209 #ifdef INET6
 210                     && ntohs(((struct sockaddr_in *)rmt_sin)->sin_port) == rmt_port
 211                     && ntohs(((struct sockaddr_in *)our_sin)->sin_port) == our_port) {
 212 #else
 213                     && ntohs(rmt_sin->sin_port) == rmt_port
 214                     && ntohs(our_sin->sin_port) == our_port) {
 215 #endif
 216
 217                     /*
 218                      * Strip trailing carriage return. It is part of the
 219                      * protocol, not part of the data.
 220                      */
 221
 222                     if (cp = strchr(user, '\r'))
 223                         *cp = 0;
 224                     result = user;
 225                 }
 226             }
 227             alarm(0);
 228         }
 229         fclose(fp);
 230     }
 231     STRN_CPY(dest, result, STRING_LENGTH);
 232 }