/*
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. 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 "telnetd.h"

RCSID("$Id$");

unsigned char   doopt[] = { IAC, DO, '%', 'c', 0 };
unsigned char   dont[] = { IAC, DONT, '%', 'c', 0 };
unsigned char   will[] = { IAC, WILL, '%', 'c', 0 };
unsigned char   wont[] = { IAC, WONT, '%', 'c', 0 };
int     not42 = 1;

/*
 * Buffer for sub-options, and macros
 * for suboptions buffer manipulations
 */
unsigned char subbuffer[1024*64], *subpointer= subbuffer, *subend= subbuffer;

#define SB_CLEAR()      subpointer = subbuffer
#define SB_TERM()       { subend = subpointer; SB_CLEAR(); }
#define SB_ACCUM(c)     if (subpointer < (subbuffer+sizeof subbuffer)) { \
    *subpointer++ = (c); \
                             }
#define SB_GET()        ((*subpointer++)&0xff)
#define SB_EOF()        (subpointer >= subend)
#define SB_LEN()        (subend - subpointer)

#ifdef  ENV_HACK
unsigned char *subsave;
#define SB_SAVE()       subsave = subpointer;
#define SB_RESTORE()    subpointer = subsave;
#endif


/*
 * State for recv fsm
 */
#define TS_DATA         0       /* base state */
#define TS_IAC          1       /* look for double IAC's */
#define TS_CR           2       /* CR-LF ->'s CR */
#define TS_SB           3       /* throw away begin's... */
#define TS_SE           4       /* ...end's (suboption negotiation) */
#define TS_WILL         5       /* will option negotiation */
#define TS_WONT         6       /* wont -''- */
#define TS_DO           7       /* do -''- */
#define TS_DONT         8       /* dont -''- */

void
telrcv(void)
{
    int c;
    static int state = TS_DATA;

    while (ncc > 0) {
        if ((&ptyobuf[BUFSIZ] - pfrontp) < 2)
            break;
        c = *netip++ & 0377, ncc--;
#ifdef ENCRYPTION
        if (decrypt_input)
            c = (*decrypt_input)(c);
#endif
        switch (state) {

        case TS_CR:
            state = TS_DATA;
            /* Strip off \n or \0 after a \r */
            if ((c == 0) || (c == '\n')) {
                break;
            }
            /* FALL THROUGH */

        case TS_DATA:
            if (c == IAC) {
                state = TS_IAC;
                break;
            }
            /*
             * We now map \r\n ==> \r for pragmatic reasons.
             * Many client implementations send \r\n when
             * the user hits the CarriageReturn key.
             *
             * We USED to map \r\n ==> \n, since \r\n says
             * that we want to be in column 1 of the next
             * printable line, and \n is the standard
             * unix way of saying that (\r is only good
             * if CRMOD is set, which it normally is).
             */
            if ((c == '\r') && his_state_is_wont(TELOPT_BINARY)) {
                int nc = *netip;
#ifdef ENCRYPTION
                if (decrypt_input)
                    nc = (*decrypt_input)(nc & 0xff);
#endif
                {
#ifdef ENCRYPTION
                    if (decrypt_input)
                        (void)(*decrypt_input)(-1);
#endif
                    state = TS_CR;
                }
            }
            *pfrontp++ = c;
            break;

        case TS_IAC:
        gotiac:                 switch (c) {

            /*
             * Send the process on the pty side an
             * interrupt.  Do this with a NULL or
             * interrupt char; depending on the tty mode.
             */
        case IP:
            DIAG(TD_OPTIONS,
                 printoption("td: recv IAC", c));
            interrupt();
            break;

        case BREAK:
            DIAG(TD_OPTIONS,
                 printoption("td: recv IAC", c));
            sendbrk();
            break;

            /*
             * Are You There?
             */
        case AYT:
            DIAG(TD_OPTIONS,
                 printoption("td: recv IAC", c));
            recv_ayt();
            break;

            /*
             * Abort Output
             */
        case AO:
            {
                DIAG(TD_OPTIONS,
                     printoption("td: recv IAC", c));
                ptyflush();     /* half-hearted */
                init_termbuf();

                if (slctab[SLC_AO].sptr &&
                    *slctab[SLC_AO].sptr != (cc_t)(_POSIX_VDISABLE)) {
                    *pfrontp++ =
                        (unsigned char)*slctab[SLC_AO].sptr;
                }

                netclear();     /* clear buffer back */
                output_data ("%c%c", IAC, DM);
                neturg = nfrontp-1; /* off by one XXX */
                DIAG(TD_OPTIONS,
                     printoption("td: send IAC", DM));
                break;
            }

        /*
         * Erase Character and
         * Erase Line
         */
        case EC:
        case EL:
            {
                cc_t ch;

                DIAG(TD_OPTIONS,
                     printoption("td: recv IAC", c));
                ptyflush();     /* half-hearted */
                init_termbuf();
                if (c == EC)
                    ch = *slctab[SLC_EC].sptr;
                else
                    ch = *slctab[SLC_EL].sptr;
                if (ch != (cc_t)(_POSIX_VDISABLE))
                    *pfrontp++ = (unsigned char)ch;
                break;
            }

        /*
         * Check for urgent data...
         */
        case DM:
            DIAG(TD_OPTIONS,
                 printoption("td: recv IAC", c));
            SYNCHing = stilloob(net);
            settimer(gotDM);
            break;


            /*
             * Begin option subnegotiation...
             */
        case SB:
            state = TS_SB;
            SB_CLEAR();
            continue;

        case WILL:
            state = TS_WILL;
            continue;

        case WONT:
            state = TS_WONT;
            continue;

        case DO:
            state = TS_DO;
            continue;

        case DONT:
            state = TS_DONT;
            continue;
        case EOR:
            if (his_state_is_will(TELOPT_EOR))
                doeof();
            break;

            /*
             * Handle RFC 10xx Telnet linemode option additions
             * to command stream (EOF, SUSP, ABORT).
             */
        case xEOF:
            doeof();
            break;

        case SUSP:
            sendsusp();
            break;

        case ABORT:
            sendbrk();
            break;

        case IAC:
            *pfrontp++ = c;
            break;
        }
        state = TS_DATA;
        break;

        case TS_SB:
            if (c == IAC) {
                state = TS_SE;
            } else {
                SB_ACCUM(c);
            }
            break;

        case TS_SE:
            if (c != SE) {
                if (c != IAC) {
                    /*
                     * bad form of suboption negotiation.
                     * handle it in such a way as to avoid
                     * damage to local state.  Parse
                     * suboption buffer found so far,
                     * then treat remaining stream as
                     * another command sequence.
                     */

                    /* for DIAGNOSTICS */
                    SB_ACCUM(IAC);
                    SB_ACCUM(c);
                    subpointer -= 2;

                    SB_TERM();
                    suboption();
                    state = TS_IAC;
                    goto gotiac;
                }
                SB_ACCUM(c);
                state = TS_SB;
            } else {
                /* for DIAGNOSTICS */
                SB_ACCUM(IAC);
                SB_ACCUM(SE);
                subpointer -= 2;

                SB_TERM();
                suboption();    /* handle sub-option */
                state = TS_DATA;
            }
            break;

        case TS_WILL:
            willoption(c);
            state = TS_DATA;
            continue;

        case TS_WONT:
            wontoption(c);
            if (c==TELOPT_ENCRYPT && his_do_dont_is_changing(TELOPT_ENCRYPT) )
                dontoption(c);
            state = TS_DATA;
            continue;

        case TS_DO:
            dooption(c);
            state = TS_DATA;
            continue;

        case TS_DONT:
            dontoption(c);
            state = TS_DATA;
            continue;

        default:
            syslog(LOG_ERR, "telnetd: panic state=%d\n", state);
            printf("telnetd: panic state=%d\n", state);
            exit(1);
        }
    }
}  /* end of telrcv */

/*
 * The will/wont/do/dont state machines are based on Dave Borman's
 * Telnet option processing state machine.
 *
 * These correspond to the following states:
 *      my_state = the last negotiated state
 *      want_state = what I want the state to go to
 *      want_resp = how many requests I have sent
 * All state defaults are negative, and resp defaults to 0.
 *
 * When initiating a request to change state to new_state:
 *
 * if ((want_resp == 0 && new_state == my_state) || want_state == new_state) {
 *      do nothing;
 * } else {
 *      want_state = new_state;
 *      send new_state;
 *      want_resp++;
 * }
 *
 * When receiving new_state:
 *
 * if (want_resp) {
 *      want_resp--;
 *      if (want_resp && (new_state == my_state))
 *              want_resp--;
 * }
 * if ((want_resp == 0) && (new_state != want_state)) {
 *      if (ok_to_switch_to new_state)
 *              want_state = new_state;
 *      else
 *              want_resp++;
 *      send want_state;
 * }
 * my_state = new_state;
 *
 * Note that new_state is implied in these functions by the function itself.
 * will and do imply positive new_state, wont and dont imply negative.
 *
 * Finally, there is one catch.  If we send a negative response to a
 * positive request, my_state will be the positive while want_state will
 * remain negative.  my_state will revert to negative when the negative
 * acknowlegment arrives from the peer.  Thus, my_state generally tells
 * us not only the last negotiated state, but also tells us what the peer
 * wants to be doing as well.  It is important to understand this difference
 * as we may wish to be processing data streams based on our desired state
 * (want_state) or based on what the peer thinks the state is (my_state).
 *
 * This all works fine because if the peer sends a positive request, the data
 * that we receive prior to negative acknowlegment will probably be affected
 * by the positive state, and we can process it as such (if we can; if we
 * can't then it really doesn't matter).  If it is that important, then the
 * peer probably should be buffering until this option state negotiation
 * is complete.
 *
 */
void
send_do(int option, int init)
{
    if (init) {
        if ((do_dont_resp[option] == 0 && his_state_is_will(option)) ||
            his_want_state_is_will(option))
            return;
        /*
         * Special case for TELOPT_TM:  We send a DO, but pretend
         * that we sent a DONT, so that we can send more DOs if
         * we want to.
         */
        if (option == TELOPT_TM)
            set_his_want_state_wont(option);
        else
            set_his_want_state_will(option);
        do_dont_resp[option]++;
    }
    output_data((const char *)doopt, option);

    DIAG(TD_OPTIONS, printoption("td: send do", option));
}

#ifdef  AUTHENTICATION
extern void auth_request(void);
#endif
#ifdef  ENCRYPTION
extern void encrypt_send_support(void);
#endif

void
willoption(int option)
{
    int changeok = 0;
    void (*func)(void) = NULL;

    /*
     * process input from peer.
     */

    DIAG(TD_OPTIONS, printoption("td: recv will", option));

    if (do_dont_resp[option]) {
        do_dont_resp[option]--;
        if (do_dont_resp[option] && his_state_is_will(option))
            do_dont_resp[option]--;
    }
    if (do_dont_resp[option] == 0) {
        if (his_want_state_is_wont(option)) {
            switch (option) {

            case TELOPT_BINARY:
                init_termbuf();
                tty_binaryin(1);
                set_termbuf();
                changeok++;
                break;

            case TELOPT_ECHO:
                /*
                 * See comments below for more info.
                 */
                not42 = 0;      /* looks like a 4.2 system */
                break;

            case TELOPT_TM:
                /*
                 * We never respond to a WILL TM, and
                 * we leave the state WONT.
                 */
                return;

            case TELOPT_LFLOW:
                /*
                 * If we are going to support flow control
                 * option, then don't worry peer that we can't
                 * change the flow control characters.
                 */
                slctab[SLC_XON].defset.flag &= ~SLC_LEVELBITS;
                slctab[SLC_XON].defset.flag |= SLC_DEFAULT;
                slctab[SLC_XOFF].defset.flag &= ~SLC_LEVELBITS;
                slctab[SLC_XOFF].defset.flag |= SLC_DEFAULT;
            case TELOPT_TTYPE:
            case TELOPT_SGA:
            case TELOPT_NAWS:
            case TELOPT_TSPEED:
            case TELOPT_XDISPLOC:
            case TELOPT_NEW_ENVIRON:
            case TELOPT_OLD_ENVIRON:
                changeok++;
                break;


#ifdef  AUTHENTICATION
            case TELOPT_AUTHENTICATION:
                func = auth_request;
                changeok++;
                break;
#endif

#ifdef  ENCRYPTION
            case TELOPT_ENCRYPT:
                func = encrypt_send_support;
                changeok++;
                break;
#endif

            default:
                break;
            }
            if (changeok) {
                set_his_want_state_will(option);
                send_do(option, 0);
            } else {
                do_dont_resp[option]++;
                send_dont(option, 0);
            }
        } else {
            /*
             * Option processing that should happen when
             * we receive conformation of a change in
             * state that we had requested.
             */
            switch (option) {
            case TELOPT_ECHO:
                not42 = 0;      /* looks like a 4.2 system */
                /*
                 * Egads, he responded "WILL ECHO".  Turn
                 * it off right now!
                 */
                send_dont(option, 1);
                /*
                 * "WILL ECHO".  Kludge upon kludge!
                 * A 4.2 client is now echoing user input at
                 * the tty.  This is probably undesireable and
                 * it should be stopped.  The client will
                 * respond WONT TM to the DO TM that we send to
                 * check for kludge linemode.  When the WONT TM
                 * arrives, linemode will be turned off and a
                 * change propogated to the pty.  This change
                 * will cause us to process the new pty state
                 * in localstat(), which will notice that
                 * linemode is off and send a WILL ECHO
                 * so that we are properly in character mode and
                 * all is well.
                 */
                break;

#ifdef  AUTHENTICATION
            case TELOPT_AUTHENTICATION:
                func = auth_request;
                break;
#endif

#ifdef  ENCRYPTION
            case TELOPT_ENCRYPT:
                func = encrypt_send_support;
                break;
#endif

            case TELOPT_LFLOW:
                func = flowstat;
                break;
            }
        }
    }
    set_his_state_will(option);
    if (func)
        (*func)();
}  /* end of willoption */

void
send_dont(int option, int init)
{
    if (init) {
        if ((do_dont_resp[option] == 0 && his_state_is_wont(option)) ||
            his_want_state_is_wont(option))
            return;
        set_his_want_state_wont(option);
        do_dont_resp[option]++;
    }
    output_data((const char *)dont, option);

    DIAG(TD_OPTIONS, printoption("td: send dont", option));
}

void
wontoption(int option)
{
    /*
     * Process client input.
         */

    DIAG(TD_OPTIONS, printoption("td: recv wont", option));

    if (do_dont_resp[option]) {
        do_dont_resp[option]--;
        if (do_dont_resp[option] && his_state_is_wont(option))
            do_dont_resp[option]--;
    }
    if (do_dont_resp[option] == 0) {
        if (his_want_state_is_will(option)) {
            /* it is always ok to change to negative state */
            switch (option) {
            case TELOPT_ECHO:
                not42 = 1; /* doesn't seem to be a 4.2 system */
                break;

            case TELOPT_BINARY:
                init_termbuf();
                tty_binaryin(0);
                set_termbuf();
                break;

            case TELOPT_TM:
                /*
                 * If we get a WONT TM, and had sent a DO TM,
                 * don't respond with a DONT TM, just leave it
                 * as is.  Short circut the state machine to
                 * achive this.
                 */
                set_his_want_state_wont(TELOPT_TM);
                return;

            case TELOPT_LFLOW:
                /*
                 * If we are not going to support flow control
                 * option, then let peer know that we can't
                 * change the flow control characters.
                 */
                slctab[SLC_XON].defset.flag &= ~SLC_LEVELBITS;
                slctab[SLC_XON].defset.flag |= SLC_CANTCHANGE;
                slctab[SLC_XOFF].defset.flag &= ~SLC_LEVELBITS;
                slctab[SLC_XOFF].defset.flag |= SLC_CANTCHANGE;
                break;

#ifdef AUTHENTICATION
            case TELOPT_AUTHENTICATION:
                auth_finished(0, AUTH_REJECT);
                break;
#endif

                /*
                 * For options that we might spin waiting for
                 * sub-negotiation, if the client turns off the
                 * option rather than responding to the request,
                 * we have to treat it here as if we got a response
                 * to the sub-negotiation, (by updating the timers)
                 * so that we'll break out of the loop.
                 */
            case TELOPT_TTYPE:
                settimer(ttypesubopt);
                break;

            case TELOPT_TSPEED:
                settimer(tspeedsubopt);
                break;

            case TELOPT_XDISPLOC:
                settimer(xdisplocsubopt);
                break;

            case TELOPT_OLD_ENVIRON:
                settimer(oenvironsubopt);
                break;

            case TELOPT_NEW_ENVIRON:
                settimer(environsubopt);
                break;

            default:
                break;
            }
            set_his_want_state_wont(option);
            if (his_state_is_will(option))
                send_dont(option, 0);
        } else {
            switch (option) {
            case TELOPT_TM:
                break;

#ifdef AUTHENTICATION
            case TELOPT_AUTHENTICATION:
                auth_finished(0, AUTH_REJECT);
                break;
#endif
            default:
                break;
            }
        }
    }
    set_his_state_wont(option);

}  /* end of wontoption */

void
send_will(int option, int init)
{
    if (init) {
        if ((will_wont_resp[option] == 0 && my_state_is_will(option))||
            my_want_state_is_will(option))
            return;
        set_my_want_state_will(option);
        will_wont_resp[option]++;
    }
    output_data ((const char *)will, option);

    DIAG(TD_OPTIONS, printoption("td: send will", option));
}

/*
 * When we get a DONT SGA, we will try once to turn it
 * back on.  If the other side responds DONT SGA, we
 * leave it at that.  This is so that when we talk to
 * clients that understand KLUDGELINEMODE but not LINEMODE,
 * we'll keep them in char-at-a-time mode.
 */
int turn_on_sga = 0;

void
dooption(int option)
{
    int changeok = 0;

    /*
     * Process client input.
     */

    DIAG(TD_OPTIONS, printoption("td: recv do", option));

    if (will_wont_resp[option]) {
        will_wont_resp[option]--;
        if (will_wont_resp[option] && my_state_is_will(option))
            will_wont_resp[option]--;
    }
    if ((will_wont_resp[option] == 0) && (my_want_state_is_wont(option))) {
        switch (option) {
        case TELOPT_ECHO:
            {
                init_termbuf();
                tty_setecho(1);
                set_termbuf();
            }
        changeok++;
        break;

        case TELOPT_BINARY:
            init_termbuf();
            tty_binaryout(1);
            set_termbuf();
            changeok++;
            break;

        case TELOPT_SGA:
            turn_on_sga = 0;
            changeok++;
            break;

        case TELOPT_STATUS:
            changeok++;
            break;

        case TELOPT_TM:
            /*
             * Special case for TM.  We send a WILL, but
             * pretend we sent a WONT.
             */
            send_will(option, 0);
            set_my_want_state_wont(option);
            set_my_state_wont(option);
            return;

        case TELOPT_LOGOUT:
            /*
             * When we get a LOGOUT option, respond
             * with a WILL LOGOUT, make sure that
             * it gets written out to the network,
             * and then just go away...
             */
            set_my_want_state_will(TELOPT_LOGOUT);
            send_will(TELOPT_LOGOUT, 0);
            set_my_state_will(TELOPT_LOGOUT);
            netflush();
            cleanup(0);
            /* NOT REACHED */
            break;

#ifdef ENCRYPTION
        case TELOPT_ENCRYPT:
            changeok++;
            break;
#endif
        case TELOPT_LINEMODE:
        case TELOPT_TTYPE:
        case TELOPT_NAWS:
        case TELOPT_TSPEED:
        case TELOPT_LFLOW:
        case TELOPT_XDISPLOC:
#ifdef  TELOPT_ENVIRON
        case TELOPT_NEW_ENVIRON:
#endif
        case TELOPT_OLD_ENVIRON:
        default:
            break;
        }
        if (changeok) {
            set_my_want_state_will(option);
            send_will(option, 0);
        } else {
            will_wont_resp[option]++;
            send_wont(option, 0);
        }
    }
    set_my_state_will(option);

}  /* end of dooption */

void
send_wont(int option, int init)
{
    if (init) {
        if ((will_wont_resp[option] == 0 && my_state_is_wont(option)) ||
            my_want_state_is_wont(option))
            return;
        set_my_want_state_wont(option);
        will_wont_resp[option]++;
    }
    output_data ((const char *)wont, option);

    DIAG(TD_OPTIONS, printoption("td: send wont", option));
}

void
dontoption(int option)
{
    /*
     * Process client input.
         */


    DIAG(TD_OPTIONS, printoption("td: recv dont", option));

    if (will_wont_resp[option]) {
        will_wont_resp[option]--;
        if (will_wont_resp[option] && my_state_is_wont(option))
            will_wont_resp[option]--;
    }
    if ((will_wont_resp[option] == 0) && (my_want_state_is_will(option))) {
        switch (option) {
        case TELOPT_BINARY:
            init_termbuf();
            tty_binaryout(0);
            set_termbuf();
            break;

        case TELOPT_ECHO:       /* we should stop echoing */
            {
                init_termbuf();
                tty_setecho(0);
                set_termbuf();
            }
        break;

        case TELOPT_SGA:
            set_my_want_state_wont(option);
            if (my_state_is_will(option))
                send_wont(option, 0);
            set_my_state_wont(option);
            if (turn_on_sga ^= 1)
                send_will(option, 1);
            return;

        default:
            break;
        }

        set_my_want_state_wont(option);
        if (my_state_is_will(option))
            send_wont(option, 0);
    }
    set_my_state_wont(option);

}  /* end of dontoption */

#ifdef  ENV_HACK
int env_ovar = -1;
int env_ovalue = -1;
#else   /* ENV_HACK */
# define env_ovar OLD_ENV_VAR
# define env_ovalue OLD_ENV_VALUE
#endif  /* ENV_HACK */

/*
 * suboption()
 *
 *      Look at the sub-option buffer, and try to be helpful to the other
 * side.
 *
 *      Currently we recognize:
 *
 *      Terminal type is
 *      Linemode
 *      Window size
 *      Terminal speed
 */
void
suboption(void)
{
    int subchar;

    DIAG(TD_OPTIONS, {netflush(); printsub('<', subpointer, SB_LEN()+2);});

    subchar = SB_GET();
    switch (subchar) {
    case TELOPT_TSPEED: {
        int xspeed, rspeed;

        if (his_state_is_wont(TELOPT_TSPEED))   /* Ignore if option disabled */
            break;

        settimer(tspeedsubopt);

        if (SB_EOF() || SB_GET() != TELQUAL_IS)
            return;

        xspeed = atoi((char *)subpointer);

        while (SB_GET() != ',' && !SB_EOF());
        if (SB_EOF())
            return;

        rspeed = atoi((char *)subpointer);
        clientstat(TELOPT_TSPEED, xspeed, rspeed);

        break;

    }  /* end of case TELOPT_TSPEED */

    case TELOPT_TTYPE: {                /* Yaaaay! */
        char *p;

        if (his_state_is_wont(TELOPT_TTYPE))    /* Ignore if option disabled */
            break;
        settimer(ttypesubopt);

        if (SB_EOF() || SB_GET() != TELQUAL_IS) {
            return;             /* ??? XXX but, this is the most robust */
        }

        p = terminaltype;

        while ((p < (terminaltype + sizeof terminaltype-1)) &&
               !SB_EOF()) {
            int c;

            c = SB_GET();
            if (isupper(c)) {
                c = tolower(c);
            }
            *p++ = c;    /* accumulate name */
        }
        *p = 0;
        break;
    }  /* end of case TELOPT_TTYPE */

    case TELOPT_NAWS: {
        int xwinsize, ywinsize;

        if (his_state_is_wont(TELOPT_NAWS))     /* Ignore if option disabled */
            break;

        if (SB_EOF())
            return;
        xwinsize = SB_GET() << 8;
        if (SB_EOF())
            return;
        xwinsize |= SB_GET();
        if (SB_EOF())
            return;
        ywinsize = SB_GET() << 8;
        if (SB_EOF())
            return;
        ywinsize |= SB_GET();
        clientstat(TELOPT_NAWS, xwinsize, ywinsize);

        break;

    }  /* end of case TELOPT_NAWS */

    case TELOPT_STATUS: {
        int mode;

        if (SB_EOF())
            break;
        mode = SB_GET();
        switch (mode) {
        case TELQUAL_SEND:
            if (my_state_is_will(TELOPT_STATUS))
                send_status();
            break;

        case TELQUAL_IS:
            break;

        default:
            break;
        }
        break;
    }  /* end of case TELOPT_STATUS */

    case TELOPT_XDISPLOC: {
        if (SB_EOF() || SB_GET() != TELQUAL_IS)
            return;
        settimer(xdisplocsubopt);
        subpointer[SB_LEN()] = '\0';
        esetenv("DISPLAY", (char *)subpointer, 1);
        break;
    }  /* end of case TELOPT_XDISPLOC */

#ifdef  TELOPT_NEW_ENVIRON
    case TELOPT_NEW_ENVIRON:
#endif
    case TELOPT_OLD_ENVIRON: {
        int c;
        char *cp, *varp, *valp;

        if (SB_EOF())
            return;
        c = SB_GET();
        if (c == TELQUAL_IS) {
            if (subchar == TELOPT_OLD_ENVIRON)
                settimer(oenvironsubopt);
            else
                settimer(environsubopt);
        } else if (c != TELQUAL_INFO) {
            return;
        }

#ifdef  TELOPT_NEW_ENVIRON
        if (subchar == TELOPT_NEW_ENVIRON) {
            while (!SB_EOF()) {
                c = SB_GET();
                if ((c == NEW_ENV_VAR) || (c == ENV_USERVAR))
                    break;
            }
        } else
#endif
            {
#ifdef  ENV_HACK
                /*
                 * We only want to do this if we haven't already decided
                 * whether or not the other side has its VALUE and VAR
                 * reversed.
                 */
                if (env_ovar < 0) {
                    int last = -1;              /* invalid value */
                    int empty = 0;
                    int got_var = 0, got_value = 0, got_uservar = 0;

                    /*
                     * The other side might have its VALUE and VAR values
                     * reversed.  To be interoperable, we need to determine
                     * which way it is.  If the first recognized character
                     * is a VAR or VALUE, then that will tell us what
                     * type of client it is.  If the fist recognized
                     * character is a USERVAR, then we continue scanning
                     * the suboption looking for two consecutive
                     * VAR or VALUE fields.  We should not get two
                     * consecutive VALUE fields, so finding two
                     * consecutive VALUE or VAR fields will tell us
                     * what the client is.
                     */
                    SB_SAVE();
                    while (!SB_EOF()) {
                        c = SB_GET();
                        switch(c) {
                        case OLD_ENV_VAR:
                            if (last < 0 || last == OLD_ENV_VAR
                                || (empty && (last == OLD_ENV_VALUE)))
                                goto env_ovar_ok;
                            got_var++;
                            last = OLD_ENV_VAR;
                            break;
                        case OLD_ENV_VALUE:
                            if (last < 0 || last == OLD_ENV_VALUE
                                || (empty && (last == OLD_ENV_VAR)))
                                goto env_ovar_wrong;
                            got_value++;
                            last = OLD_ENV_VALUE;
                            break;
                        case ENV_USERVAR:
                            /* count strings of USERVAR as one */
                            if (last != ENV_USERVAR)
                                got_uservar++;
                            if (empty) {
                                if (last == OLD_ENV_VALUE)
                                    goto env_ovar_ok;
                                if (last == OLD_ENV_VAR)
                                    goto env_ovar_wrong;
                            }
                            last = ENV_USERVAR;
                            break;
                        case ENV_ESC:
                            if (!SB_EOF())
                                c = SB_GET();
                            /* FALL THROUGH */
                        default:
                            empty = 0;
                            continue;
                        }
                        empty = 1;
                    }
                    if (empty) {
                        if (last == OLD_ENV_VALUE)
                            goto env_ovar_ok;
                        if (last == OLD_ENV_VAR)
                            goto env_ovar_wrong;
                    }
                    /*
                     * Ok, the first thing was a USERVAR, and there
                     * are not two consecutive VAR or VALUE commands,
                     * and none of the VAR or VALUE commands are empty.
                     * If the client has sent us a well-formed option,
                     * then the number of VALUEs received should always
                     * be less than or equal to the number of VARs and
                     * USERVARs received.
                     *
                     * If we got exactly as many VALUEs as VARs and
                     * USERVARs, the client has the same definitions.
                     *
                     * If we got exactly as many VARs as VALUEs and
                     * USERVARS, the client has reversed definitions.
                     */
                    if (got_uservar + got_var == got_value) {
                    env_ovar_ok:
                        env_ovar = OLD_ENV_VAR;
                        env_ovalue = OLD_ENV_VALUE;
                    } else if (got_uservar + got_value == got_var) {
                    env_ovar_wrong:
                        env_ovar = OLD_ENV_VALUE;
                        env_ovalue = OLD_ENV_VAR;
                        DIAG(TD_OPTIONS, {
                            output_data("ENVIRON VALUE and VAR are reversed!\r\n");
                        });

                    }
                }
                SB_RESTORE();
#endif

                while (!SB_EOF()) {
                    c = SB_GET();
                    if ((c == env_ovar) || (c == ENV_USERVAR))
                        break;
                }
            }

        if (SB_EOF())
            return;

        cp = varp = (char *)subpointer;
        valp = 0;

        while (!SB_EOF()) {
            c = SB_GET();
            if (subchar == TELOPT_OLD_ENVIRON) {
                if (c == env_ovar)
                    c = NEW_ENV_VAR;
                else if (c == env_ovalue)
                    c = NEW_ENV_VALUE;
            }
            switch (c) {

            case NEW_ENV_VALUE:
                *cp = '\0';
                cp = valp = (char *)subpointer;
                break;

            case NEW_ENV_VAR:
            case ENV_USERVAR:
                *cp = '\0';
                if (valp)
                    esetenv(varp, valp, 1);
                else
                    unsetenv(varp);
                cp = varp = (char *)subpointer;
                valp = 0;
                break;

            case ENV_ESC:
                if (SB_EOF())
                    break;
                c = SB_GET();
                /* FALL THROUGH */
            default:
                *cp++ = c;
                break;
            }
        }
        *cp = '\0';
        if (valp)
            esetenv(varp, valp, 1);
        else
            unsetenv(varp);
        break;
    }  /* end of case TELOPT_NEW_ENVIRON */
#ifdef AUTHENTICATION
    case TELOPT_AUTHENTICATION:
        if (SB_EOF())
            break;
        switch(SB_GET()) {
        case TELQUAL_SEND:
        case TELQUAL_REPLY:
            /*
             * These are sent by us and cannot be sent by
             * the client.
             */
            break;
        case TELQUAL_IS:
            auth_is(subpointer, SB_LEN());
            break;
        case TELQUAL_NAME:
            auth_name(subpointer, SB_LEN());
            break;
        }
        break;
#endif
#ifdef ENCRYPTION
    case TELOPT_ENCRYPT:
        if (SB_EOF())
            break;
        switch(SB_GET()) {
        case ENCRYPT_SUPPORT:
            encrypt_support(subpointer, SB_LEN());
            break;
        case ENCRYPT_IS:
            encrypt_is(subpointer, SB_LEN());
            break;
        case ENCRYPT_REPLY:
            encrypt_reply(subpointer, SB_LEN());
            break;
        case ENCRYPT_START:
            encrypt_start(subpointer, SB_LEN());
            break;
        case ENCRYPT_END:
            if (require_encryption)
                fatal(net, "Output encryption is not possible to turn off");
            encrypt_end();
            break;
        case ENCRYPT_REQSTART:
            encrypt_request_start(subpointer, SB_LEN());
            break;
        case ENCRYPT_REQEND:
            /*
             * We can always send an REQEND so that we cannot
             * get stuck encrypting.  We should only get this
             * if we have been able to get in the correct mode
             * anyhow.
             */
            if (require_encryption)
                fatal(net, "Input encryption is not possible to turn off");
            encrypt_request_end();
            break;
        case ENCRYPT_ENC_KEYID:
            encrypt_enc_keyid(subpointer, SB_LEN());
            break;
        case ENCRYPT_DEC_KEYID:
            encrypt_dec_keyid(subpointer, SB_LEN());
            break;
        default:
            break;
        }
        break;
#endif

    default:
        break;
    }  /* end of switch */

}  /* end of suboption */

void
doclientstat(void)
{
    clientstat(TELOPT_LINEMODE, WILL, 0);
}

#undef ADD
#define ADD(c)   *ncp++ = c
#define ADD_DATA(c) { *ncp++ = c; if (c == SE || c == IAC) *ncp++ = c; }

void
send_status(void)
{
    unsigned char statusbuf[256];
    unsigned char *ncp;
    unsigned char i;

    ncp = statusbuf;

    netflush(); /* get rid of anything waiting to go out */

    ADD(IAC);
    ADD(SB);
    ADD(TELOPT_STATUS);
    ADD(TELQUAL_IS);

    /*
     * We check the want_state rather than the current state,
     * because if we received a DO/WILL for an option that we
     * don't support, and the other side didn't send a DONT/WONT
     * in response to our WONT/DONT, then the "state" will be
     * WILL/DO, and the "want_state" will be WONT/DONT.  We
     * need to go by the latter.
     */
    for (i = 0; i < (unsigned char)NTELOPTS; i++) {
        if (my_want_state_is_will(i)) {
            ADD(WILL);
            ADD_DATA(i);
        }
        if (his_want_state_is_will(i)) {
            ADD(DO);
            ADD_DATA(i);
        }
    }

    if (his_want_state_is_will(TELOPT_LFLOW)) {
        ADD(SB);
        ADD(TELOPT_LFLOW);
        if (flowmode) {
            ADD(LFLOW_ON);
        } else {
            ADD(LFLOW_OFF);
        }
        ADD(SE);

        if (restartany >= 0) {
            ADD(SB);
            ADD(TELOPT_LFLOW);
            if (restartany) {
                ADD(LFLOW_RESTART_ANY);
            } else {
                ADD(LFLOW_RESTART_XON);
            }
            ADD(SE);
        }
    }


    ADD(IAC);
    ADD(SE);

    writenet(statusbuf, ncp - statusbuf);
    netflush(); /* Send it on its way */

    DIAG(TD_OPTIONS,
         {printsub('>', statusbuf, ncp - statusbuf); netflush();});
}