/*
 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

 /*
  * rfc931() speaks a common subset of the RFC 931, AUTH, TAP, IDENT and RFC
  * 1413 protocols. It queries an RFC 931 etc. compatible daemon on a remote
  * host to look up the owner of a connection. The information should not be
  * used for authentication purposes. This routine intercepts alarm signals.
  *
  * Diagnostics are reported through syslog(3).
  *
  * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
  */

/* System libraries. */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <syslog.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <setjmp.h>
#include <signal.h>
#include <string.h>

/* Local stuff. */

#include "tcpd.h"

#define RFC931_PORT     113             /* Semi-well-known port */
#define ANY_PORT        0               /* Any old port will do */

int     rfc931_timeout = RFC931_TIMEOUT;/* Global so it can be changed */

static jmp_buf timebuf;

/* fsocket - open stdio stream on top of socket */

static FILE *fsocket(domain, type, protocol)
int     domain;
int     type;
int     protocol;
{
    int     s;
    FILE   *fp;

    if ((s = socket(domain, type, protocol)) < 0) {
        tcpd_warn("socket: %m");
        return (0);
    } else {
        if ((fp = fdopen(s, "r+")) == 0) {
            tcpd_warn("fdopen: %m");
            close(s);
        }
        return (fp);
    }
}

/* timeout - handle timeouts */

static void timeout(sig)
int     sig;
{
    longjmp(timebuf, sig);
}

/* rfc931 - return remote user name, given socket structures */

void    rfc931(rmt_sin, our_sin, dest)
struct sockaddr_gen *rmt_sin;
struct sockaddr_gen *our_sin;
char   *dest;
{
    unsigned rmt_port;
    unsigned our_port;
    struct sockaddr_gen rmt_query_sin;
    struct sockaddr_gen our_query_sin;
    char    user[256];                  /* XXX */
    char    buffer[512];                /* XXX */
    char   *cp;
    char   *volatile result = unknown;
    FILE   *fp;
    volatile unsigned saved_timeout = 0;
    struct sigaction nact, oact;

    /*
     * Use one unbuffered stdio stream for writing to and for reading from
     * the RFC931 etc. server. This is done because of a bug in the SunOS
     * 4.1.x stdio library. The bug may live in other stdio implementations,
     * too. When we use a single, buffered, bidirectional stdio stream ("r+"
     * or "w+" mode) we read our own output. Such behaviour would make sense
     * with resources that support random-access operations, but not with
     * sockets.
     */

    if ((fp = fsocket(SGFAM(rmt_sin), SOCK_STREAM, 0)) != 0) {
        setbuf(fp, NULL);

        /*
         * Set up a timer so we won't get stuck while waiting for the server.
         */

        if (setjmp(timebuf) == 0) {
            /*
             * save the pending time in case the caller has armed an alarm.
             */

            saved_timeout = alarm(0);

            /*
             * It's guaranteed to enter this 'if' condition on the direct
             * invocation of setjmp and hence no additional checks while
             * restoring the signal handler.
             * Now, get the old handler and set the new one
             */
            nact.sa_handler = timeout;
            nact.sa_flags = 0;
            (void) sigemptyset(&nact.sa_mask);
            (void) sigaction(SIGALRM, &nact, &oact);
            alarm(rfc931_timeout);

            /*
             * Bind the local and remote ends of the query socket to the same
             * IP addresses as the connection under investigation. We go
             * through all this trouble because the local or remote system
             * might have more than one network address. The RFC931 etc.
             * client sends only port numbers; the server takes the IP
             * addresses from the query socket.
             */

            our_query_sin = *our_sin;
            SGPORT(&our_query_sin) = htons(ANY_PORT);
            rmt_query_sin = *rmt_sin;
            SGPORT(&rmt_query_sin) = htons(RFC931_PORT);

            if (bind(fileno(fp), (struct sockaddr *) &our_query_sin,
                     SGSOCKADDRSZ(&our_query_sin)) >= 0 &&
                connect(fileno(fp), (struct sockaddr *) &rmt_query_sin,
                        SGSOCKADDRSZ(&rmt_query_sin)) >= 0) {

                /*
                 * Send query to server. Neglect the risk that a 13-byte
                 * write would have to be fragmented by the local system and
                 * cause trouble with buggy System V stdio libraries.
                 */

                fprintf(fp, "%u,%u\r\n",
                        ntohs(SGPORT(rmt_sin)),
                        ntohs(SGPORT(our_sin)));
                fflush(fp);

                /*
                 * Read response from server. Use fgets()/sscanf() so we can
                 * work around System V stdio libraries that incorrectly
                 * assume EOF when a read from a socket returns less than
                 * requested.
                 */

                if (fgets(buffer, sizeof(buffer), fp) != 0
                    && ferror(fp) == 0 && feof(fp) == 0
                    && sscanf(buffer, "%u , %u : USERID :%*[^:]:%255s",
                              &rmt_port, &our_port, user) == 3
                    && ntohs(SGPORT(rmt_sin)) == rmt_port
                    && ntohs(SGPORT(our_sin)) == our_port) {

                    /*
                     * Strip trailing carriage return. It is part of the
                     * protocol, not part of the data.
                     */

                    if (cp = strchr(user, '\r'))
                        *cp = 0;
                    result = user;
                }
            }
            alarm(0);
        }
        /* Restore the old handler */
        (void) sigaction(SIGALRM, &oact, NULL);
        if (saved_timeout > 0)
                alarm(saved_timeout);
        fclose(fp);
    }
    STRN_CPY(dest, result, STRING_LENGTH);
}