lib/libwrap/rfc931.c

   1 /*      $NetBSD: rfc931.c,v 1.7 2001/02/27 04:13:13 itojun Exp $        */
   2
   3  /*
   4   * rfc931() speaks a common subset of the RFC 931, AUTH, TAP, IDENT and RFC
   5   * 1413 protocols. It queries an RFC 931 etc. compatible daemon on a remote
   6   * host to look up the owner of a connection. The information should not be
   7   * used for authentication purposes. This routine intercepts alarm signals.
   8   *
   9   * Diagnostics are reported through syslog(3).
  10   *
  11   * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
  12   */
  13
  14 #include <sys/cdefs.h>
  15 #ifndef lint
  16 #if 0
  17 static char sccsid[] = "@(#) rfc931.c 1.10 95/01/02 16:11:34";
  18 #else
  19 __RCSID("$NetBSD: rfc931.c,v 1.7 2001/02/27 04:13:13 itojun Exp $");
  20 #endif
  21 #endif
  22
  23 /* System libraries. */
  24
  25 #include <stdio.h>
  26 #include <syslog.h>
  27 #include <sys/types.h>
  28 #include <sys/socket.h>
  29 #include <netinet/in.h>
  30 #include <stdlib.h>
  31 #include <unistd.h>
  32 #include <setjmp.h>
  33 #include <signal.h>
  34 #include <string.h>
  35
  36 /* Local stuff. */
  37
  38 #include "tcpd.h"
  39
  40 #define RFC931_PORT     113             /* Semi-well-known port */
  41 #define ANY_PORT        0               /* Any old port will do */
  42
  43 int     rfc931_timeout = RFC931_TIMEOUT;/* Global so it can be changed */
  44
  45 static jmp_buf timebuf;
  46
  47 static FILE *fsocket __P((int, int, int));
  48 static void timeout __P((int));
  49
  50 /* fsocket - open stdio stream on top of socket */
  51
  52 static FILE *fsocket(domain, type, protocol)
  53 int     domain;
  54 int     type;
  55 int     protocol;
  56 {
  57     int     s;
  58     FILE   *fp;
  59
  60     if ((s = socket(domain, type, protocol)) < 0) {
  61         tcpd_warn("socket: %m");
  62         return (0);
  63     } else {
  64         if ((fp = fdopen(s, "r+")) == 0) {
  65             tcpd_warn("fdopen: %m");
  66             close(s);
  67         }
  68         return (fp);
  69     }
  70 }
  71
  72 /* timeout - handle timeouts */
  73
  74 static void timeout(sig)
  75 int     sig;
  76 {
  77     longjmp(timebuf, sig);
  78 }
  79
  80 /* rfc931 - return remote user name, given socket structures */
  81
  82 void    rfc931(rmt_sin, our_sin, dest)
  83 struct sockaddr *rmt_sin;
  84 struct sockaddr *our_sin;
  85 char   *dest;
  86 {
  87     unsigned rmt_port;
  88     unsigned our_port;
  89     struct sockaddr_storage rmt_query_sin;
  90     struct sockaddr_storage our_query_sin;
  91     char    user[256];                  /* XXX */
  92     char    buffer[512];                /* XXX */
  93     char   *cp;
  94     char   *result = unknown;
  95     FILE   *fp;
  96     int salen;
  97     u_short *rmt_portp;
  98     u_short *our_portp;
  99
 100     /* address family must be the same */
 101     if (rmt_sin->sa_family != our_sin->sa_family) {
 102         strlcpy(dest, result, STRING_LENGTH);
 103         return;
 104     }
 105     switch (rmt_sin->sa_family) {
 106     case AF_INET:
 107         salen = sizeof(struct sockaddr_in);
 108         rmt_portp = &(((struct sockaddr_in *)rmt_sin)->sin_port);
 109         break;
 110 #ifdef INET6
 111     case AF_INET6:
 112         salen = sizeof(struct sockaddr_in6);
 113         rmt_portp = &(((struct sockaddr_in6 *)rmt_sin)->sin6_port);
 114         break;
 115 #endif
 116     default:
 117         strlcpy(dest, result, STRING_LENGTH);
 118         return;
 119     }
 120     switch (our_sin->sa_family) {
 121     case AF_INET:
 122         our_portp = &(((struct sockaddr_in *)our_sin)->sin_port);
 123         break;
 124 #ifdef INET6
 125     case AF_INET6:
 126         our_portp = &(((struct sockaddr_in6 *)our_sin)->sin6_port);
 127         break;
 128 #endif
 129     default:
 130         strlcpy(dest, result, STRING_LENGTH);
 131         return;
 132     }
 133
 134 #ifdef __GNUC__
 135     (void)&result; /* Avoid longjmp clobbering */
 136     (void)&fp;  /* XXX gcc */
 137 #endif
 138
 139     /*
 140      * Use one unbuffered stdio stream for writing to and for reading from
 141      * the RFC931 etc. server. This is done because of a bug in the SunOS
 142      * 4.1.x stdio library. The bug may live in other stdio implementations,
 143      * too. When we use a single, buffered, bidirectional stdio stream ("r+"
 144      * or "w+" mode) we read our own output. Such behaviour would make sense
 145      * with resources that support random-access operations, but not with
 146      * sockets.
 147      */
 148
 149     if ((fp = fsocket(rmt_sin->sa_family, SOCK_STREAM, 0)) != 0) {
 150         setbuf(fp, (char *) 0);
 151
 152         /*
 153          * Set up a timer so we won't get stuck while waiting for the server.
 154          */
 155
 156         if (setjmp(timebuf) == 0) {
 157             signal(SIGALRM, timeout);
 158             alarm(rfc931_timeout);
 159
 160             /*
 161              * Bind the local and remote ends of the query socket to the same
 162              * IP addresses as the connection under investigation. We go
 163              * through all this trouble because the local or remote system
 164              * might have more than one network address. The RFC931 etc.
 165              * client sends only port numbers; the server takes the IP
 166              * addresses from the query socket.
 167              */
 168
 169             memcpy(&our_query_sin, our_sin, salen);
 170             switch (our_query_sin.ss_family) {
 171             case AF_INET:
 172                 ((struct sockaddr_in *)&our_query_sin)->sin_port =
 173                         htons(ANY_PORT);
 174                 break;
 175 #ifdef INET6
 176             case AF_INET6:
 177                 ((struct sockaddr_in6 *)&our_query_sin)->sin6_port =
 178                         htons(ANY_PORT);
 179                 break;
 180 #endif
 181             }
 182             memcpy(&rmt_query_sin, rmt_sin, salen);
 183             switch (rmt_query_sin.ss_family) {
 184             case AF_INET:
 185                 ((struct sockaddr_in *)&rmt_query_sin)->sin_port =
 186                         htons(RFC931_PORT);
 187                 break;
 188 #ifdef INET6
 189             case AF_INET6:
 190                 ((struct sockaddr_in6 *)&rmt_query_sin)->sin6_port =
 191                         htons(RFC931_PORT);
 192                 break;
 193 #endif
 194             }
 195
 196             if (bind(fileno(fp), (struct sockaddr *) & our_query_sin,
 197                      salen) >= 0 &&
 198                 connect(fileno(fp), (struct sockaddr *) & rmt_query_sin,
 199                         salen) >= 0) {
 200
 201                 /*
 202                  * Send query to server. Neglect the risk that a 13-byte
 203                  * write would have to be fragmented by the local system and
 204                  * cause trouble with buggy System V stdio libraries.
 205                  */
 206
 207                 fprintf(fp, "%u,%u\r\n",
 208                         ntohs(*rmt_portp),
 209                         ntohs(*our_portp));
 210                 fflush(fp);
 211
 212                 /*
 213                  * Read response from server. Use fgets()/sscanf() so we can
 214                  * work around System V stdio libraries that incorrectly
 215                  * assume EOF when a read from a socket returns less than
 216                  * requested.
 217                  */
 218
 219                 if (fgets(buffer, sizeof(buffer), fp) != 0
 220                     && ferror(fp) == 0 && feof(fp) == 0
 221                     && sscanf(buffer, "%u , %u : USERID :%*[^:]:%255s",
 222                               &rmt_port, &our_port, user) == 3
 223                     && ntohs(*rmt_portp) == rmt_port
 224                     && ntohs(*our_portp) == our_port) {
 225
 226                     /*
 227                      * Strip trailing carriage return. It is part of the
 228                      * protocol, not part of the data.
 229                      */
 230
 231                     if ((cp = strchr(user, '\r')) != NULL)
 232                         *cp = '\0';
 233                     result = user;
 234                 }
 235             }
 236             alarm(0);
 237         }
 238         fclose(fp);
 239     }
 240     strlcpy(dest, result, STRING_LENGTH);
 241 }