/*      $NetBSD: telnetd.c,v 1.61 2025/12/13 05:40:16 andvar Exp $      */

/*
 * Copyright (C) 1997 and 1998 WIDE Project.
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the project nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * Copyright (c) 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#ifndef lint
__COPYRIGHT("@(#) Copyright (c) 1989, 1993\
 The Regents of the University of California.  All rights reserved.");
#if 0
static char sccsid[] = "@(#)telnetd.c   8.4 (Berkeley) 5/30/95";
#else
__RCSID("$NetBSD: telnetd.c,v 1.61 2025/12/13 05:40:16 andvar Exp $");
#endif
#endif /* not lint */

#include "telnetd.h"
#include "pathnames.h"

#include <arpa/inet.h>

#include <err.h>
#include <termcap.h>

#include <limits.h>

#ifdef KRB5
#define Authenticator   k5_Authenticator
#include <krb5.h>
#undef  Authenticator
#include <krb5/com_err.h>
#endif

#if     defined(AUTHENTICATION) || defined(ENCRYPTION)
#include <libtelnet/misc.h>
#endif

extern int require_hwpreauth;
#ifdef KRB5
extern krb5_context telnet_context;
#endif
int     registerd_host_only = 0;


/*
 * I/O data buffers,
 * pointers, and counters.
 */
char    ptyibuf[BUFSIZ], *ptyip = ptyibuf;
char    ptyibuf2[BUFSIZ];


int     hostinfo = 1;                   /* do we print login banner? */


static int debug = 0;
int keepalive = 1;
const char *gettyname = "default";
char *progname;

void usage(void) __dead;
int getterminaltype(char *, size_t);
int getent(char *, const char *);
static void doit(struct sockaddr *) __dead;
void _gettermname(void);
int terminaltypeok(char *);
char *getstr(const char *, char **);

/*
 * The string to pass to getopt().  We do it this way so
 * that only the actual options that we support will be
 * passed off to getopt().
 */
char valid_opts[] = {
        'd', ':', 'g', ':', 'h', 'k', 'n', 'S', ':', 'u', ':', 'U',
        '4', '6',
#ifdef  AUTHENTICATION
        'a', ':', 'X', ':',
#endif
#ifdef  ENCRYPTION
        'e', ':',
#endif
#ifdef DIAGNOSTICS
        'D', ':',
#endif
#ifdef  LINEMODE
        'l',
#endif
#ifdef  SECURELOGIN
        's',
#endif
#ifdef  KRB5
        'R', ':', 'H',
#endif
        '\0'
};

int family = AF_INET;
struct sockaddr_storage from;

int
main(int argc, char *argv[])
{
        static char Xline[] = NULL16STR;

        socklen_t fromlen;
        int on = 1;
        int ch;
#if     defined(IPPROTO_IP) && defined(IP_TOS)
        int tos = -1;
#endif

        line = Xline;

        pfrontp = pbackp = ptyobuf;
        netip = netibuf;
        nfrontp = nbackp = netobuf;
#ifdef  ENCRYPTION
        nclearto = 0;
#endif  /* ENCRYPTION */

        progname = *argv;


        while ((ch = getopt(argc, argv, valid_opts)) != -1) {
                switch (ch) {

#ifdef  AUTHENTICATION
                case 'a':
                        /*
                         * Check for required authentication level
                         */
                        if (strcmp(optarg, "debug") == 0) {
                                auth_debug_mode = 1;
                        } else if (strcasecmp(optarg, "none") == 0) {
                                auth_level = 0;
                        } else if (strcasecmp(optarg, "other") == 0) {
                                auth_level = AUTH_OTHER;
                        } else if (strcasecmp(optarg, "user") == 0) {
                                auth_level = AUTH_USER;
                        } else if (strcasecmp(optarg, "valid") == 0) {
                                auth_level = AUTH_VALID;
                        } else if (strcasecmp(optarg, "off") == 0) {
                                /*
                                 * This hack turns off authentication
                                 */
                                auth_level = -1;
                        } else {
                                fprintf(stderr,
                            "telnetd: unknown authorization level for -a\n");
                        }
                        break;
#endif  /* AUTHENTICATION */


                case 'd':
                        if (strcmp(optarg, "ebug") == 0) {
                                debug++;
                                break;
                        }
                        usage();
                        /* NOTREACHED */
                        break;

#ifdef DIAGNOSTICS
                case 'D':
                        /*
                         * Check for desired diagnostics capabilities.
                         */
                        if (!strcmp(optarg, "report")) {
                                diagnostic |= TD_REPORT|TD_OPTIONS;
                        } else if (!strcmp(optarg, "exercise")) {
                                diagnostic |= TD_EXERCISE;
                        } else if (!strcmp(optarg, "netdata")) {
                                diagnostic |= TD_NETDATA;
                        } else if (!strcmp(optarg, "ptydata")) {
                                diagnostic |= TD_PTYDATA;
                        } else if (!strcmp(optarg, "options")) {
                                diagnostic |= TD_OPTIONS;
                        } else {
                                usage();
                                /* NOT REACHED */
                        }
                        break;
#endif /* DIAGNOSTICS */

#ifdef  ENCRYPTION
                case 'e':
                        if (strcmp(optarg, "debug") == 0) {
                                EncryptDebug(1);
                                break;
                        }
                        usage();
                        /* NOTREACHED */
                        break;
#endif  /* ENCRYPTION */

                case 'g':
                        gettyname = optarg;
                        break;

                case 'h':
                        hostinfo = 0;
                        break;

#ifdef  KRB5
                case 'H':
                    {
                        require_hwpreauth = 1;
                        break;
                    }
#endif  /* KRB5 */


#ifdef  LINEMODE
                case 'l':
                        alwayslinemode = 1;
                        break;
#endif  /* LINEMODE */

                case 'k':
#if     defined(LINEMODE) && defined(KLUDGELINEMODE)
                        lmodetype = NO_AUTOKLUDGE;
#else
                        /* ignore -k option if built without kludge linemode */
#endif  /* defined(LINEMODE) && defined(KLUDGELINEMODE) */
                        break;

                case 'n':
                        keepalive = 0;
                        break;


#ifdef  KRB5
                case 'R':
                    {
                        krb5_error_code retval;

                        if (telnet_context == 0) {
                                retval = krb5_init_context(&telnet_context);
                                if (retval) {
                                        com_err("telnetd", retval,
                                            "while initializing krb5");
                                        exit(1);
                                }
                        }
                        krb5_set_default_realm(telnet_context, optarg);
                        break;
                    }
#endif  /* KRB5 */

#ifdef  SECURELOGIN
                case 's':
                        /* Secure login required */
                        require_secure_login = 1;
                        break;
#endif  /* SECURELOGIN */
                case 'S':
                        fprintf(stderr, "%s%s\n", "TOS option unavailable; ",
                                                "-S flag not supported\n");
                        break;

                case 'u':
                        fprintf(stderr, "telnetd: -u option unneeded\n");
                        break;

                case 'U':
                        registerd_host_only = 1;
                        break;

#ifdef  AUTHENTICATION
                case 'X':
                        /*
                         * Check for invalid authentication types
                         */
                        auth_disable_name(optarg);
                        break;
#endif  /* AUTHENTICATION */

                case '4':
                        family = AF_INET;
                        break;

                case '6':
                        family = AF_INET6;
                        break;

                default:
                        fprintf(stderr, "telnetd: %c: unknown option\n", ch);
                        /* FALLTHROUGH */
                case '?':
                        usage();
                        /* NOTREACHED */
                }
        }

        argc -= optind;
        argv += optind;

        if (debug) {
            int s, ns, error;
            socklen_t foo;
            const char *service = "telnet";
            struct addrinfo hints, *res;

            if (argc > 1) {
                usage();
                /* NOT REACHED */
            } else if (argc == 1)
                service = *argv;

            memset(&hints, 0, sizeof(hints));
            hints.ai_flags = AI_PASSIVE;
            hints.ai_family = family;
            hints.ai_socktype = SOCK_STREAM;
            hints.ai_protocol = 0;
            error = getaddrinfo(NULL, service, &hints, &res);

            if (error) {
                fprintf(stderr, "tcp/%s: %s\n", service, gai_strerror(error));
                exit(1);
            }

            s = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
            if (s < 0) {
                perror("telnetd: socket");
                exit(1);
            }
            (void) setsockopt(s, SOL_SOCKET, SO_REUSEADDR,
                                (char *)&on, sizeof(on));
            if (bind(s, res->ai_addr, res->ai_addrlen) < 0) {
                perror("bind");
                exit(1);
            }
            if (listen(s, 1) < 0) {
                perror("listen");
                exit(1);
            }
            foo = res->ai_addrlen;
            ns = accept(s, res->ai_addr, &foo);
            if (ns < 0) {
                perror("accept");
                exit(1);
            }
            (void) dup2(ns, 0);
            (void) close(ns);
            (void) close(s);
            freeaddrinfo(res);
        } else if (argc > 0) {
                usage();
                /* NOT REACHED */
        }

        openlog("telnetd", LOG_PID, LOG_DAEMON);
        fromlen = sizeof (from);
        if (getpeername(0, (struct sockaddr *)&from, &fromlen) < 0) {
                fprintf(stderr, "%s: ", progname);
                perror("getpeername");
                _exit(1);
        }
        if (keepalive &&
            setsockopt(0, SOL_SOCKET, SO_KEEPALIVE,
                        (char *)&on, sizeof (on)) < 0) {
                syslog(LOG_WARNING, "setsockopt (SO_KEEPALIVE): %m");
        }

#if     defined(IPPROTO_IP) && defined(IP_TOS)
        if (((struct sockaddr *)&from)->sa_family == AF_INET) {
                if (tos < 0)
                        tos = 020;      /* Low Delay bit */
                if (tos
                   && (setsockopt(0, IPPROTO_IP, IP_TOS,
                                  (char *)&tos, sizeof(tos)) < 0)
                   && (errno != ENOPROTOOPT) )
                        syslog(LOG_WARNING, "setsockopt (IP_TOS): %m");
        }
#endif  /* defined(IPPROTO_IP) && defined(IP_TOS) */

        net = 0;
        doit((struct sockaddr *)&from);
        /* NOTREACHED */
#ifdef __GNUC__
        exit(0);
#endif
}  /* end of main */

void
usage(void)
{
        fprintf(stderr, "Usage: telnetd");
#ifdef  AUTHENTICATION
        fprintf(stderr, " [-a (debug|other|user|valid|off|none)]\n\t");
#endif
        fprintf(stderr, " [-debug]");
#ifdef DIAGNOSTICS
        fprintf(stderr, " [-D (options|report|exercise|netdata|ptydata)]\n\t");
#endif
#ifdef  ENCRYPTION
        fprintf(stderr, " [-edebug]");
#endif
        fprintf(stderr, " [-h]");
#if     defined(LINEMODE) && defined(KLUDGELINEMODE)
        fprintf(stderr, " [-k]");
#endif
#ifdef LINEMODE
        fprintf(stderr, " [-l]");
#endif
        fprintf(stderr, " [-n]");
        fprintf(stderr, "\n\t");
#ifdef  SECURELOGIN
        fprintf(stderr, " [-s]");
#endif
#ifdef  AUTHENTICATION
        fprintf(stderr, " [-X auth-type]");
#endif
        fprintf(stderr, " [-u utmp_hostname_length] [-U]");
        fprintf(stderr, " [port]\n");
        exit(1);
}

/*
 * getterminaltype
 *
 *      Ask the other end to send along its terminal type and speed.
 * Output is the variable terminaltype filled in.
 */
static unsigned char ttytype_sbbuf[] = {
        IAC, SB, TELOPT_TTYPE, TELQUAL_SEND, IAC, SE
};

int
getterminaltype(char *name, size_t l)
{
    int retval = -1;

    settimer(baseline);
#ifdef AUTHENTICATION
    /*
     * Handle the Authentication option before we do anything else.
     */
    if (auth_level >= 0) {
        send_do(TELOPT_AUTHENTICATION, 1);
        while (his_will_wont_is_changing(TELOPT_AUTHENTICATION))
            ttloop();
        if (his_state_is_will(TELOPT_AUTHENTICATION)) {
            retval = auth_wait(name, l);
        }
    }
#endif

#ifdef  ENCRYPTION
    send_will(TELOPT_ENCRYPT, 1);
#endif  /* ENCRYPTION */
    send_do(TELOPT_TTYPE, 1);
    send_do(TELOPT_TSPEED, 1);
    send_do(TELOPT_XDISPLOC, 1);
    send_do(TELOPT_NEW_ENVIRON, 1);
    send_do(TELOPT_OLD_ENVIRON, 1);
    while (
#ifdef  ENCRYPTION
           his_do_dont_is_changing(TELOPT_ENCRYPT) ||
#endif  /* ENCRYPTION */
           his_will_wont_is_changing(TELOPT_TTYPE) ||
           his_will_wont_is_changing(TELOPT_TSPEED) ||
           his_will_wont_is_changing(TELOPT_XDISPLOC) ||
           his_will_wont_is_changing(TELOPT_NEW_ENVIRON) ||
           his_will_wont_is_changing(TELOPT_OLD_ENVIRON)) {
        ttloop();
    }
    if (his_state_is_will(TELOPT_TSPEED)) {
        static unsigned char sb[] =
                        { IAC, SB, TELOPT_TSPEED, TELQUAL_SEND, IAC, SE };

        output_datalen((const char *)sb, sizeof sb);
        DIAG(TD_OPTIONS, printsub('>', sb + 2, sizeof sb - 2););
    }
#ifdef  ENCRYPTION
    /*
     * Wait for the negotiation of what type of encryption we can
     * send with.  If autoencrypt is not set, this will just return.
     */
    if (his_state_is_will(TELOPT_ENCRYPT)) {
        encrypt_wait();
    }
#endif  /* ENCRYPTION */
    if (his_state_is_will(TELOPT_XDISPLOC)) {
        static unsigned char sb[] =
                        { IAC, SB, TELOPT_XDISPLOC, TELQUAL_SEND, IAC, SE };

        output_datalen((const char *)sb, sizeof sb);
        DIAG(TD_OPTIONS, printsub('>', sb + 2, sizeof sb - 2););
    }
    if (his_state_is_will(TELOPT_NEW_ENVIRON)) {
        static unsigned char sb[] =
                        { IAC, SB, TELOPT_NEW_ENVIRON, TELQUAL_SEND, IAC, SE };

        output_datalen((const char *)sb, sizeof sb);
        DIAG(TD_OPTIONS, printsub('>', sb + 2, sizeof sb - 2););
    }
    else if (his_state_is_will(TELOPT_OLD_ENVIRON)) {
        static unsigned char sb[] =
                        { IAC, SB, TELOPT_OLD_ENVIRON, TELQUAL_SEND, IAC, SE };

        output_datalen((const char *)sb, sizeof sb);
        DIAG(TD_OPTIONS, printsub('>', sb + 2, sizeof sb - 2););
    }
    if (his_state_is_will(TELOPT_TTYPE)) {

        output_datalen((const char *)ttytype_sbbuf, sizeof ttytype_sbbuf);
        DIAG(TD_OPTIONS, printsub('>', ttytype_sbbuf + 2,
                                        sizeof ttytype_sbbuf - 2););
    }
    if (his_state_is_will(TELOPT_TSPEED)) {
        while (sequenceIs(tspeedsubopt, baseline))
            ttloop();
    }
    if (his_state_is_will(TELOPT_XDISPLOC)) {
        while (sequenceIs(xdisplocsubopt, baseline))
            ttloop();
    }
    if (his_state_is_will(TELOPT_NEW_ENVIRON)) {
        while (sequenceIs(environsubopt, baseline))
            ttloop();
    }
    if (his_state_is_will(TELOPT_OLD_ENVIRON)) {
        while (sequenceIs(oenvironsubopt, baseline))
            ttloop();
    }
    if (his_state_is_will(TELOPT_TTYPE)) {
        char first[256], last[256];

        while (sequenceIs(ttypesubopt, baseline))
            ttloop();

        /*
         * If the other side has already disabled the option, then
         * we have to just go with what we (might) have already gotten.
         */
        if (his_state_is_will(TELOPT_TTYPE) && !terminaltypeok(terminaltype)) {
            (void) strlcpy(first, terminaltype, sizeof(first));
            for(;;) {
                /*
                 * Save the unknown name, and request the next name.
                 */
                (void) strlcpy(last, terminaltype, sizeof(last));
                _gettermname();
                if (terminaltypeok(terminaltype))
                    break;
                if ((strncmp(last, terminaltype, sizeof(last)) == 0) ||
                    his_state_is_wont(TELOPT_TTYPE)) {
                    /*
                     * We've hit the end.  If this is the same as
                     * the first name, just go with it.
                     */
                    if (strncmp(first, terminaltype, sizeof(first)) == 0)
                        break;
                    /*
                     * Get the terminal name one more time, so that
                     * RFC1091 compliant telnets will cycle back to
                     * the start of the list.
                     */
                     _gettermname();
                    if (strncmp(first, terminaltype, sizeof(first)) != 0) {
                        (void) strlcpy(terminaltype, first, sizeof(terminaltype));
                    }
                    break;
                }
            }
        }
    }
    return(retval);
}  /* end of getterminaltype */

void
_gettermname(void)
{
    /*
     * If the client turned off the option,
     * we can't send another request, so we
     * just return.
     */
    if (his_state_is_wont(TELOPT_TTYPE))
        return;
    settimer(baseline);
    output_datalen((const char *)ttytype_sbbuf, sizeof ttytype_sbbuf);
    DIAG(TD_OPTIONS, printsub('>', ttytype_sbbuf + 2,
                                        sizeof ttytype_sbbuf - 2););
    while (sequenceIs(ttypesubopt, baseline))
        ttloop();
}

int
terminaltypeok(char *s)
{
    char buf[1024];

    /*
     * tgetent() will return 1 if the type is known, and
     * 0 if it is not known.  If it returns -1, it couldn't
     * open the database.  But if we can't open the database,
     * it won't help to say we failed, because we won't be
     * able to verify anything else.  So, we treat -1 like 1.
     */
    if (tgetent(buf, s) == 0)
        return(0);
    return(1);
}

char *hostname;
char host_name[MAXHOSTNAMELEN + 1];
char remote_host_name[MAXHOSTNAMELEN + 1];

static void telnet(int, int) __dead;

/*
 * Get a pty, scan input lines.
 */
static void
doit(struct sockaddr *who)
{
        char *host;
        int error;
        int level;
        int ptynum;
        int flags;
        char user_name[256];

        /*
         * Initialize the slc mapping table.
         */
        get_slc_defaults();

        /*
         * Find an available pty to use.
         */
        pty = getpty(&ptynum);
        if (pty < 0)
                fatal(net, "All network ports in use");

        flags = registerd_host_only ? NI_NAMEREQD : 0;

        /* get name of connected client */
        error = getnameinfo(who, who->sa_len, remote_host_name,
            sizeof(remote_host_name), NULL, 0, flags);

        if (error) {
                fatal(net, "Couldn't resolve your address into a host name.\r\n\
         Please contact your net administrator");
#ifdef __GNUC__
                host = NULL;    /* XXX gcc */
#endif
        }

        remote_host_name[sizeof(remote_host_name)-1] = 0;
        host = remote_host_name;

        (void)gethostname(host_name, sizeof(host_name));
        host_name[sizeof(host_name) - 1] = '\0';
        hostname = host_name;

#if     defined(AUTHENTICATION) || defined(ENCRYPTION)
        auth_encrypt_init(hostname, host, "TELNETD", 1);
#endif

        init_env();
        /*
         * get terminal type.
         */
        *user_name = 0;
        level = getterminaltype(user_name, sizeof(user_name));
        setenv("TERM", terminaltype[0] ? terminaltype : "network", 1);

        /*
         * Start up the login process on the slave side of the terminal
         */
        startslave(host, level, user_name);

        telnet(net, pty);  /* begin server processing */
        /*NOTREACHED*/
}  /* end of doit */


/*
 * Main loop.  Select from pty and network, and
 * hand data to telnet receiver finite state machine.
 */
static void
telnet(int f, int p)
{
        int on = 1;
#define TABBUFSIZ       512
        char    defent[TABBUFSIZ];
        char    defstrs[TABBUFSIZ];
#undef  TABBUFSIZ
        char *HE, *HN, *IF, *ptyibuf2ptr;
        const char *IM;
        struct pollfd set[2];

        /*
         * Do some tests where it is desirable to wait for a response.
         * Rather than doing them slowly, one at a time, do them all
         * at once.
         */
        if (my_state_is_wont(TELOPT_SGA))
                send_will(TELOPT_SGA, 1);
        /*
         * Is the client side a 4.2 (NOT 4.3) system?  We need to know this
         * because 4.2 clients are unable to deal with TCP urgent data.
         *
         * To find out, we send out a "DO ECHO".  If the remote system
         * answers "WILL ECHO" it is probably a 4.2 client, and we note
         * that fact ("WILL ECHO" ==> that the client will echo what
         * WE, the server, sends it; it does NOT mean that the client will
         * echo the terminal input).
         */
        send_do(TELOPT_ECHO, 1);

#ifdef  LINEMODE
        if (his_state_is_wont(TELOPT_LINEMODE)) {
                /* Query the peer for linemode support by trying to negotiate
                 * the linemode option.
                 */
                linemode = 0;
                editmode = 0;
                send_do(TELOPT_LINEMODE, 1);  /* send do linemode */
        }
#endif  /* LINEMODE */

        /*
         * Send along a couple of other options that we wish to negotiate.
         */
        send_do(TELOPT_NAWS, 1);
        send_will(TELOPT_STATUS, 1);
        flowmode = 1;           /* default flow control state */
        restartany = -1;        /* uninitialized... */
        send_do(TELOPT_LFLOW, 1);

        /*
         * Spin, waiting for a response from the DO ECHO.  However,
         * some REALLY DUMB telnets out there might not respond
         * to the DO ECHO.  So, we spin looking for NAWS, (most dumb
         * telnets so far seem to respond with WONT for a DO that
         * they don't understand...) because by the time we get the
         * response, it will already have processed the DO ECHO.
         * Kludge upon kludge.
         */
        while (his_will_wont_is_changing(TELOPT_NAWS))
                ttloop();

        /*
         * But...
         * The client might have sent a WILL NAWS as part of its
         * startup code; if so, we'll be here before we get the
         * response to the DO ECHO.  We'll make the assumption
         * that any implementation that understands about NAWS
         * is a modern enough implementation that it will respond
         * to our DO ECHO request; hence we'll do another spin
         * waiting for the ECHO option to settle down, which is
         * what we wanted to do in the first place...
         */
        if (his_want_state_is_will(TELOPT_ECHO) &&
            his_state_is_will(TELOPT_NAWS)) {
                while (his_will_wont_is_changing(TELOPT_ECHO))
                        ttloop();
        }
        /*
         * On the off chance that the telnet client is broken and does not
         * respond to the DO ECHO we sent, (after all, we did send the
         * DO NAWS negotiation after the DO ECHO, and we won't get here
         * until a response to the DO NAWS comes back) simulate the
         * receipt of a will echo.  This will also send a WONT ECHO
         * to the client, since we assume that the client failed to
         * respond because it believes that it is already in DO ECHO
         * mode, which we do not want.
         */
        if (his_want_state_is_will(TELOPT_ECHO)) {
                DIAG(TD_OPTIONS,
                        {output_data("td: simulating recv\r\n");});
                willoption(TELOPT_ECHO);
        }

        /*
         * Finally, to clean things up, we turn on our echo.  This
         * will break stupid 4.2 telnets out of local terminal echo.
         */

        if (my_state_is_wont(TELOPT_ECHO))
                send_will(TELOPT_ECHO, 1);

        /*
         * Turn on packet mode
         */
        (void) ioctl(p, TIOCPKT, (char *)&on);

#if     defined(LINEMODE) && defined(KLUDGELINEMODE)
        /*
         * Continuing line mode support.  If client does not support
         * real linemode, attempt to negotiate kludge linemode by sending
         * the do timing mark sequence.
         */
        if (lmodetype < REAL_LINEMODE)
                send_do(TELOPT_TM, 1);
#endif  /* defined(LINEMODE) && defined(KLUDGELINEMODE) */

        /*
         * Call telrcv() once to pick up anything received during
         * terminal type negotiation, 4.2/4.3 determination, and
         * linemode negotiation.
         */
        telrcv();

        (void) ioctl(f, FIONBIO, (char *)&on);
        (void) ioctl(p, FIONBIO, (char *)&on);

        (void) setsockopt(f, SOL_SOCKET, SO_OOBINLINE, (char *)&on, sizeof on);

        (void) signal(SIGTSTP, SIG_IGN);
        /*
         * Ignoring SIGTTOU keeps the kernel from blocking us
         * in ttioctl() in /sys/tty.c.
         */
        (void) signal(SIGTTOU, SIG_IGN);

        (void) signal(SIGCHLD, cleanup);


        {
                int t;
                t = open(_PATH_TTY, O_RDWR);
                if (t >= 0) {
                        (void) ioctl(t, TIOCNOTTY, (char *)0);
                        (void) close(t);
                }
        }


        /*
         * Show banner that getty never gave.
         *
         * We put the banner in the pty input buffer.  This way, it
         * gets carriage return null processing, etc., just like all
         * other pty --> client data.
         */

        if (getent(defent, gettyname) == 1) {
                char *cp=defstrs;

                HE = getstr("he", &cp);
                HN = getstr("hn", &cp);
                IM = getstr("im", &cp);
                IF = getstr("if", &cp);
                if (HN && *HN)
                        (void)strlcpy(host_name, HN, sizeof(host_name));
                if (IM == 0)
                        IM = "";
        } else {
                IM = DEFAULT_IM;
                HE = 0;
                IF = NULL;
        }
        edithost(HE, host_name);
        ptyibuf2ptr = ptyibuf2;
        if (hostinfo) {
                if (IF) {
                        char buf[_POSIX2_LINE_MAX];
                        FILE *fd;

                        if ((fd = fopen(IF, "r")) != NULL) {
                                while (fgets(buf, sizeof(buf) - 1, fd) != NULL)
                                        ptyibuf2ptr = putf(buf, ptyibuf2ptr);
                                fclose(fd);
                        }
                }
                if (*IM)
                        ptyibuf2ptr = putf(IM, ptyibuf2ptr);
        }

        if (pcc)
                strncpy(ptyibuf2ptr, ptyip, pcc+1);
        ptyip = ptyibuf2;
        pcc = strlen(ptyip);
#ifdef  LINEMODE
        /*
         * Last check to make sure all our states are correct.
         */
        init_termbuf();
        localstat();
#endif  /* LINEMODE */

        DIAG(TD_REPORT,
                {output_data("td: Entering processing loop\r\n");});


        set[0].fd = f;
        set[1].fd = p;
        for (;;) {
                int c;

                if (ncc < 0 && pcc < 0)
                        break;

                /*
                 * Never look for input if there's still
                 * stuff in the corresponding output buffer
                 */
                set[0].events = 0;
                set[1].events = 0;
                if (nfrontp - nbackp || pcc > 0)
                        set[0].events |= POLLOUT;
                else
                        set[1].events |= POLLIN;
                if (pfrontp - pbackp || ncc > 0)
                        set[1].events |= POLLOUT;
                else
                        set[0].events |= POLLIN;
                if (!SYNCHing)
                        set[0].events |= POLLPRI;

                if ((c = poll(set, 2, INFTIM)) < 1) {
                        if (c == -1) {
                                if (errno == EINTR) {
                                        continue;
                                }
                        }
                        sleep(5);
                        continue;
                }

                /*
                 * Any urgent data?
                 */
                if (set[0].revents & POLLPRI) {
                    SYNCHing = 1;
                }

                /*
                 * Something to read from the network...
                 */
                if (set[0].revents & POLLIN) {
                    ncc = read(f, netibuf, sizeof (netibuf));
                    if (ncc < 0 && errno == EWOULDBLOCK)
                        ncc = 0;
                    else {
                        if (ncc <= 0) {
                            break;
                        }
                        netip = netibuf;
                    }
                    DIAG((TD_REPORT | TD_NETDATA),
                            {output_data("td: netread %d chars\r\n", ncc);});
                    DIAG(TD_NETDATA, printdata("nd", netip, ncc));
                }

                /*
                 * Something to read from the pty...
                 */
                if (set[1].revents & POLLIN) {
                        pcc = read(p, ptyibuf, BUFSIZ);
                        /*
                         * On some systems, if we try to read something
                         * off the master side before the slave side is
                         * opened, we get EIO.
                         */
                        if (pcc < 0 && (errno == EWOULDBLOCK ||
                                        errno == EAGAIN ||
                                        errno == EIO)) {
                                pcc = 0;
                        } else {
                                if (pcc <= 0)
                                        break;
#ifdef  LINEMODE
                                /*
                                 * If ioctl from pty, pass it through net
                                 */
                                if (ptyibuf[0] & TIOCPKT_IOCTL) {
                                        copy_termbuf(ptyibuf+1, pcc-1);
                                        localstat();
                                        pcc = 1;
                                }
#endif  /* LINEMODE */
                                if (ptyibuf[0] & TIOCPKT_FLUSHWRITE) {
                                        netclear();     /* clear buffer back */
                                        /*
                                         * There are client telnets on some
                                         * operating systems get screwed up
                                         * royally if we send them urgent
                                         * mode data.
                                         */
                                        output_data("%c%c", IAC, DM);
                                        neturg = nfrontp - 1; /* off by one XXX */
                                        DIAG(TD_OPTIONS,
                                            printoption("td: send IAC", DM));
                                }
                                if (his_state_is_will(TELOPT_LFLOW) &&
                                    (ptyibuf[0] &
                                     (TIOCPKT_NOSTOP|TIOCPKT_DOSTOP))) {
                                        int newflow =
                                            ptyibuf[0] & TIOCPKT_DOSTOP ? 1 : 0;
                                        if (newflow != flowmode) {
                                                flowmode = newflow;
                                                (void) output_data(
                                                        "%c%c%c%c%c%c",
                                                        IAC, SB, TELOPT_LFLOW,
                                                        flowmode ? LFLOW_ON
                                                                 : LFLOW_OFF,
                                                        IAC, SE);
                                                DIAG(TD_OPTIONS, printsub('>',
                                                    (unsigned char *)nfrontp - 4,
                                                    4););
                                        }
                                }
                                pcc--;
                                ptyip = ptyibuf+1;
                        }
                }

                while (pcc > 0) {
                        if ((&netobuf[BUFSIZ] - nfrontp) < 2)
                                break;
                        c = *ptyip++ & 0377, pcc--;
                        if (c == IAC)
                                output_data("%c", c);
                        output_data("%c", c);
                        if ((c == '\r') && (my_state_is_wont(TELOPT_BINARY))) {
                                if (pcc > 0 && ((*ptyip & 0377) == '\n')) {
                                        output_data("%c", *ptyip++ & 0377);
                                        pcc--;
                                } else
                                        output_datalen("\0", 1);
                        }
                }

                if ((set[0].revents & POLLOUT) && (nfrontp - nbackp) > 0)
                        netflush();
                if (ncc > 0)
                        telrcv();
                if ((set[1].revents & POLLOUT) && (pfrontp - pbackp) > 0)
                        ptyflush();
        }
        cleanup(0);
}  /* end of telnet */

/*
 * Send interrupt to process on other side of pty.
 * If it is in raw mode, just write NULL;
 * otherwise, write intr char.
 */
void
interrupt(void)
{
        ptyflush();     /* half-hearted */

        (void) ioctl(pty, TIOCSIG, (char *)SIGINT);
}

/*
 * Send quit to process on other side of pty.
 * If it is in raw mode, just write NULL;
 * otherwise, write quit char.
 */
void
sendbrk(void)
{
        ptyflush();     /* half-hearted */
        (void) ioctl(pty, TIOCSIG, (char *)SIGQUIT);
}

void
sendsusp(void)
{
        ptyflush();     /* half-hearted */
        (void) ioctl(pty, TIOCSIG, (char *)SIGTSTP);
}

/*
 * When we get an AYT, if ^T is enabled, use that.  Otherwise,
 * just send back "[Yes]".
 */
void
recv_ayt(void)
{
        if (slctab[SLC_AYT].sptr && *slctab[SLC_AYT].sptr != _POSIX_VDISABLE) {
                (void) ioctl(pty, TIOCSIG, (char *)SIGINFO);
                return;
        }
        (void) output_data("\r\n[Yes]\r\n");
}

void
doeof(void)
{
        init_termbuf();

#if     defined(LINEMODE) && (VEOF == VMIN)
        if (!tty_isediting()) {
                extern char oldeofc;
                *pfrontp++ = oldeofc;
                return;
        }
#endif
        *pfrontp++ = slctab[SLC_EOF].sptr ?
                        (unsigned char)*slctab[SLC_EOF].sptr : '\004';
}