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   * $DragonFly: src/contrib/tcp_wrappers/rfc931.c,v 1.2 2003/06/17 04:24:06 dillon Exp $
  13   */
  14
  15 #ifndef lint
  16 static char sccsid[] = "@(#) rfc931.c 1.10 95/01/02 16:11:34";
  17 #endif
  18
  19 /* System libraries. */
  20
  21 #include <stdio.h>
  22 #include <syslog.h>
  23 #include <sys/types.h>
  24 #include <sys/socket.h>
  25 #include <netinet/in.h>
  26 #include <setjmp.h>
  27 #include <signal.h>
  28 #include <string.h>
  29
  30 #ifndef SEEK_SET
  31 #define SEEK_SET 0
  32 #endif
  33
  34 /* Local stuff. */
  35
  36 #include "tcpd.h"
  37
  38 #define RFC931_PORT     113             /* Semi-well-known port */
  39 #define ANY_PORT        0               /* Any old port will do */
  40
  41 int     rfc931_timeout = RFC931_TIMEOUT;/* Global so it can be changed */
  42
  43 static jmp_buf timebuf;
  44
  45 /* fsocket - open stdio stream on top of socket */
  46
  47 static FILE *fsocket(domain, type, protocol)
  48 int     domain;
  49 int     type;
  50 int     protocol;
  51 {
  52     int     s;
  53     FILE   *fp;
  54
  55     if ((s = socket(domain, type, protocol)) < 0) {
  56         tcpd_warn("socket: %m");
  57         return (0);
  58     } else {
  59         if ((fp = fdopen(s, "r+")) == 0) {
  60             tcpd_warn("fdopen: %m");
  61             close(s);
  62         }
  63         return (fp);
  64     }
  65 }
  66
  67 /* timeout - handle timeouts */
  68
  69 static void timeout(sig)
  70 int     sig;
  71 {
  72     longjmp(timebuf, sig);
  73 }
  74
  75 /* rfc931 - return remote user name, given socket structures */
  76
  77 void    rfc931(rmt_sin, our_sin, dest)
  78 #ifdef INET6
  79 struct sockaddr *rmt_sin;
  80 struct sockaddr *our_sin;
  81 #else
  82 struct sockaddr_in *rmt_sin;
  83 struct sockaddr_in *our_sin;
  84 #endif
  85 char   *dest;
  86 {
  87     unsigned rmt_port;
  88     unsigned our_port;
  89 #ifdef INET6
  90     struct sockaddr_storage rmt_query_sin;
  91     struct sockaddr_storage our_query_sin;
  92     int alen;
  93 #else
  94     struct sockaddr_in rmt_query_sin;
  95     struct sockaddr_in our_query_sin;
  96 #endif
  97     char    user[256];                  /* XXX */
  98     char    buffer[512];                /* XXX */
  99     char   *cp;
 100     char   *result = unknown;
 101     FILE   *fp;
 102
 103 #ifdef INET6
 104     /* address family must be the same */
 105     if (rmt_sin->sa_family != our_sin->sa_family) {
 106         STRN_CPY(dest, result, STRING_LENGTH);
 107         return;
 108     }
 109     switch (our_sin->sa_family) {
 110     case AF_INET:
 111         alen = sizeof(struct sockaddr_in);
 112         break;
 113     case AF_INET6:
 114         alen = sizeof(struct sockaddr_in6);
 115         break;
 116     default:
 117         STRN_CPY(dest, result, STRING_LENGTH);
 118         return;
 119     }
 120 #endif
 121
 122     /*
 123      * If we use a single, buffered, bidirectional stdio stream ("r+" or
 124      * "w+" mode) we may read our own output. Such behaviour would make sense
 125      * with resources that support random-access operations, but not with
 126      * sockets. ANSI C suggests several functions which can be called when
 127      * you want to change IO direction, fseek seems the most portable.
 128      */
 129
 130 #ifdef INET6
 131     if ((fp = fsocket(our_sin->sa_family, SOCK_STREAM, 0)) != 0) {
 132 #else
 133     if ((fp = fsocket(AF_INET, SOCK_STREAM, 0)) != 0) {
 134 #endif
 135         /*
 136          * Set up a timer so we won't get stuck while waiting for the server.
 137          */
 138
 139         if (setjmp(timebuf) == 0) {
 140             signal(SIGALRM, timeout);
 141             alarm(rfc931_timeout);
 142
 143             /*
 144              * Bind the local and remote ends of the query socket to the same
 145              * IP addresses as the connection under investigation. We go
 146              * through all this trouble because the local or remote system
 147              * might have more than one network address. The RFC931 etc.
 148              * client sends only port numbers; the server takes the IP
 149              * addresses from the query socket.
 150              */
 151
 152 #ifdef INET6
 153             memcpy(&our_query_sin, our_sin, alen);
 154             memcpy(&rmt_query_sin, rmt_sin, alen);
 155             switch (our_sin->sa_family) {
 156             case AF_INET:
 157                 ((struct sockaddr_in *)&our_query_sin)->sin_port = htons(ANY_PORT);
 158                 ((struct sockaddr_in *)&rmt_query_sin)->sin_port = htons(RFC931_PORT);
 159                 break;
 160             case AF_INET6:
 161                 ((struct sockaddr_in6 *)&our_query_sin)->sin6_port = htons(ANY_PORT);
 162                 ((struct sockaddr_in6 *)&rmt_query_sin)->sin6_port = htons(RFC931_PORT);
 163                 break;
 164             }
 165
 166             if (bind(fileno(fp), (struct sockaddr *) & our_query_sin,
 167                      alen) >= 0 &&
 168                 connect(fileno(fp), (struct sockaddr *) & rmt_query_sin,
 169                         alen) >= 0) {
 170 #else
 171             our_query_sin = *our_sin;
 172             our_query_sin.sin_port = htons(ANY_PORT);
 173             rmt_query_sin = *rmt_sin;
 174             rmt_query_sin.sin_port = htons(RFC931_PORT);
 175
 176             if (bind(fileno(fp), (struct sockaddr *) & our_query_sin,
 177                      sizeof(our_query_sin)) >= 0 &&
 178                 connect(fileno(fp), (struct sockaddr *) & rmt_query_sin,
 179                         sizeof(rmt_query_sin)) >= 0) {
 180 #endif
 181
 182                 /*
 183                  * Send query to server. Neglect the risk that a 13-byte
 184                  * write would have to be fragmented by the local system and
 185                  * cause trouble with buggy System V stdio libraries.
 186                  */
 187
 188                 fprintf(fp, "%u,%u\r\n",
 189 #ifdef INET6
 190                         ntohs(((struct sockaddr_in *)rmt_sin)->sin_port),
 191                         ntohs(((struct sockaddr_in *)our_sin)->sin_port));
 192 #else
 193                         ntohs(rmt_sin->sin_port),
 194                         ntohs(our_sin->sin_port));
 195 #endif
 196                 fflush(fp);
 197                 fseek(fp, 0, SEEK_SET);
 198
 199                 /*
 200                  * Read response from server. Use fgets()/sscanf() so we can
 201                  * work around System V stdio libraries that incorrectly
 202                  * assume EOF when a read from a socket returns less than
 203                  * requested.
 204                  */
 205
 206                 if (fgets(buffer, sizeof(buffer), fp) != 0
 207                     && ferror(fp) == 0 && feof(fp) == 0
 208                     && sscanf(buffer, "%u , %u : USERID :%*[^:]:%255s",
 209                               &rmt_port, &our_port, user) == 3
 210 #ifdef INET6
 211                     && ntohs(((struct sockaddr_in *)rmt_sin)->sin_port) == rmt_port
 212                     && ntohs(((struct sockaddr_in *)our_sin)->sin_port) == our_port) {
 213 #else
 214                     && ntohs(rmt_sin->sin_port) == rmt_port
 215                     && ntohs(our_sin->sin_port) == our_port) {
 216 #endif
 217
 218                     /*
 219                      * Strip trailing carriage return. It is part of the
 220                      * protocol, not part of the data.
 221                      */
 222
 223                     if (cp = strchr(user, '\r'))
 224                         *cp = 0;
 225                     result = user;
 226                 }
 227             }
 228             alarm(0);
 229         }
 230         fclose(fp);
 231     }
 232     STRN_CPY(dest, result, STRING_LENGTH);
 233 }