/*
 * 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.
 */

#if 0
#ifndef lint
static const char sccsid[] = "@(#)state.c       8.5 (Berkeley) 5/30/95";
#endif
#endif
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <stdarg.h>
#include "telnetd.h"
#ifdef  AUTHENTICATION
#include <libtelnet/auth.h>
#endif
#ifdef  ENCRYPTION
#include <libtelnet/encrypt.h>
#endif

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[512], *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 " */

static void doclientstat(void);

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  /* ENCRYPTION */
                switch (state) {

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

                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  /* ENCRYPTION */
#ifdef  LINEMODE
                                /*
                                 * If we are operating in linemode,
                                 * convert to local end-of-line.
                                 */
                                if (linemode && (ncc > 0) && (('\n' == nc) ||
                                         ((0 == nc) && tty_iscrnl())) ) {
                                        netip++; ncc--;
                                        c = '\n';
                                } else
#endif
                                {
#ifdef  ENCRYPTION
                                        if (decrypt_input)
                                                (void)(*decrypt_input)(-1);
#endif  /* ENCRYPTION */
                                        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);
                        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, "panic state=%d", 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));
}

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

        /*
         * 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:
#if     defined(LINEMODE) && defined(KLUDGELINEMODE)
                        /*
                         * This telnetd implementation does not really
                         * support timing marks, it just uses them to
                         * support the kludge linemode stuff.  If we
                         * receive a will or wont TM in response to our
                         * do TM request that may have been sent to
                         * determine kludge linemode support, process
                         * it, otherwise TM should get a negative
                         * response back.
                         */
                        /*
                         * Handle the linemode kludge stuff.
                         * If we are not currently supporting any
                         * linemode at all, then we assume that this
                         * is the client telling us to use kludge
                         * linemode in response to our query.  Set the
                         * linemode type that is to be supported, note
                         * that the client wishes to use linemode, and
                         * eat the will TM as though it never arrived.
                         */
                        if (lmodetype < KLUDGE_LINEMODE) {
                                lmodetype = KLUDGE_LINEMODE;
                                clientstat(TELOPT_LINEMODE, WILL, 0);
                                send_wont(TELOPT_SGA, 1);
                        } else if (lmodetype == NO_AUTOKLUDGE) {
                                lmodetype = KLUDGE_OK;
                        }
#endif  /* defined(LINEMODE) && defined(KLUDGELINEMODE) */
                        /*
                         * 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  LINEMODE
                case TELOPT_LINEMODE:
# ifdef KLUDGELINEMODE
                        /*
                         * Note client's desire to use linemode.
                         */
                        lmodetype = REAL_LINEMODE;
# endif /* KLUDGELINEMODE */
                        func = doclientstat;
                        changeok++;
                        break;
#endif  /* LINEMODE */

#ifdef  AUTHENTICATION
                case TELOPT_AUTHENTICATION:
                        if (auth_level >= 0) {
                                func = auth_request;
                                changeok++;
                        }
                        break;
#endif

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

                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  LINEMODE
                case TELOPT_LINEMODE:
# ifdef KLUDGELINEMODE
                        /*
                         * Note client's desire to use linemode.
                         */
                        lmodetype = REAL_LINEMODE;
# endif /* KLUDGELINEMODE */
                        func = doclientstat;
                        break;
#endif  /* LINEMODE */

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

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

#ifdef  LINEMODE
                case TELOPT_LINEMODE:
# ifdef KLUDGELINEMODE
                        /*
                         * If real linemode is supported, then client is
                         * asking to turn linemode off.
                         */
                        if (lmodetype != REAL_LINEMODE)
                                break;
                        lmodetype = KLUDGE_LINEMODE;
# endif /* KLUDGELINEMODE */
                        clientstat(TELOPT_LINEMODE, WONT, 0);
                        break;
#endif  /* LINEMODE */

                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:
#if     defined(LINEMODE) && defined(KLUDGELINEMODE)
                        if (lmodetype < NO_AUTOKLUDGE) {
                                lmodetype = NO_LINEMODE;
                                clientstat(TELOPT_LINEMODE, WONT, 0);
                                send_will(TELOPT_SGA, 1);
                                send_will(TELOPT_ECHO, 1);
                        }
#endif  /* defined(LINEMODE) && defined(KLUDGELINEMODE) */
                        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));
}

#if     !defined(LINEMODE) || !defined(KLUDGELINEMODE)
/*
 * 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;
#endif

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:
#ifdef  LINEMODE
# ifdef KLUDGELINEMODE
                        if (lmodetype == NO_LINEMODE)
# else
                        if (his_state_is_wont(TELOPT_LINEMODE))
# endif
#endif
                        {
                                init_termbuf();
                                tty_setecho(1);
                                set_termbuf();
                        }
                        changeok++;
                        break;

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

                case TELOPT_SGA:
#if     defined(LINEMODE) && defined(KLUDGELINEMODE)
                        /*
                         * If kludge linemode is in use, then we must
                         * process an incoming do SGA for linemode
                         * purposes.
                         */
                        if (lmodetype == KLUDGE_LINEMODE) {
                                /*
                                 * Receipt of "do SGA" in kludge
                                 * linemode is the peer asking us to
                                 * turn off linemode.  Make note of
                                 * the request.
                                 */
                                clientstat(TELOPT_LINEMODE, WONT, 0);
                                /*
                                 * If linemode did not get turned off
                                 * then don't tell peer that we did.
                                 * Breaking here forces a wont SGA to
                                 * be returned.
                                 */
                                if (linemode)
                                        break;
                        }
#else
                        turn_on_sga = 0;
#endif  /* defined(LINEMODE) && defined(KLUDGELINEMODE) */
                        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);
                        (void)netflush();
                        cleanup(0);
                        /* NOT REACHED */
                        break;

#ifdef  ENCRYPTION
                case TELOPT_ENCRYPT:
                        changeok++;
                        break;
#endif  /* ENCRYPTION */
                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 */
#ifdef  LINEMODE
# ifdef KLUDGELINEMODE
                        if ((lmodetype != REAL_LINEMODE) &&
                            (lmodetype != KLUDGE_LINEMODE))
# else
                        if (his_state_is_wont(TELOPT_LINEMODE))
# endif
#endif
                        {
                                init_termbuf();
                                tty_setecho(0);
                                set_termbuf();
                        }
                        break;

                case TELOPT_SGA:
#if     defined(LINEMODE) && defined(KLUDGELINEMODE)
                        /*
                         * If kludge linemode is in use, then we
                         * must process an incoming do SGA for
                         * linemode purposes.
                         */
                        if ((lmodetype == KLUDGE_LINEMODE) ||
                            (lmodetype == KLUDGE_OK)) {
                                /*
                                 * The client is asking us to turn
                                 * linemode on.
                                 */
                                lmodetype = KLUDGE_LINEMODE;
                                clientstat(TELOPT_LINEMODE, WILL, 0);
                                /*
                                 * If we did not turn line mode on,
                                 * then what do we say?  Will SGA?
                                 * This violates design of telnet.
                                 * Gross.  Very Gross.
                                 */
                        }
                        break;
#else
                        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;
#endif  /* defined(LINEMODE) && defined(KLUDGELINEMODE) */

                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! */
        static char terminalname[41];

        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 */
        }

        terminaltype = terminalname;

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

            c = SB_GET();
            if (isupper(c)) {
                c = tolower(c);
            }
            *terminaltype++ = c;    /* accumulate name */
        }
        *terminaltype = 0;
        terminaltype = terminalname;
        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 */

#ifdef  LINEMODE
    case TELOPT_LINEMODE: {
        int request;

        if (his_state_is_wont(TELOPT_LINEMODE)) /* Ignore if option disabled */
                break;
        /*
         * Process linemode suboptions.
         */
        if (SB_EOF())
            break;              /* garbage was sent */
        request = SB_GET();     /* get will/wont */

        if (SB_EOF())
            break;              /* another garbage check */

        if (request == LM_SLC) {  /* SLC is not preceeded by WILL or WONT */
                /*
                 * Process suboption buffer of slc's
                 */
                start_slc(1);
                do_opt_slc(subpointer, subend - subpointer);
                (void) end_slc(0);
                break;
        } else if (request == LM_MODE) {
                if (SB_EOF())
                    return;
                useeditmode = SB_GET();  /* get mode flag */
                clientstat(LM_MODE, 0, 0);
                break;
        }

        if (SB_EOF())
            break;
        switch (SB_GET()) {  /* what suboption? */
        case LM_FORWARDMASK:
                /*
                 * According to spec, only server can send request for
                 * forwardmask, and client can only return a positive response.
                 * So don't worry about it.
                 */

        default:
                break;
        }
        break;
    }  /* end of case TELOPT_LINEMODE */
#endif
    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';
        (void)setenv("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();
                                /* FALLTHROUGH */
                        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)
                                (void)setenv(varp, valp, 1);
                        else
                                unsetenv(varp);
                        cp = varp = (char *)subpointer;
                        valp = 0;
                        break;

                case ENV_ESC:
                        if (SB_EOF())
                                break;
                        c = SB_GET();
                        /* FALLTHROUGH */
                default:
                        *cp++ = c;
                        break;
                }
        }
        *cp = '\0';
        if (valp)
                (void)setenv(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:
                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.
                 */
                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  /* ENCRYPTION */

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

}  /* end of suboption */

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

#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 (i == IAC)
                                ADD(IAC);
                }
                if (his_want_state_is_will(i)) {
                        ADD(DO);
                        ADD_DATA(i);
                        if (i == IAC)
                                ADD(IAC);
                }
        }

        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);
                }
        }

#ifdef  LINEMODE
        if (his_want_state_is_will(TELOPT_LINEMODE)) {
                unsigned char *cp, *cpe;
                int len;

                ADD(SB);
                ADD(TELOPT_LINEMODE);
                ADD(LM_MODE);
                ADD_DATA(editmode);
                ADD(SE);

                ADD(SB);
                ADD(TELOPT_LINEMODE);
                ADD(LM_SLC);
                start_slc(0);
                send_slc();
                len = end_slc(&cp);
                for (cpe = cp + len; cp < cpe; cp++)
                        ADD_DATA(*cp);
                ADD(SE);
        }
#endif  /* LINEMODE */

        ADD(IAC);
        ADD(SE);

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

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

/*
 * This function appends data to nfrontp and advances nfrontp.
 * Returns the number of characters written altogether (the
 * buffer may have been flushed in the process).
 */

int
output_data(const char *format, ...)
{
        va_list args;
        int len;
        char *buf;

        va_start(args, format);
        if ((len = vasprintf(&buf, format, args)) == -1) {
                va_end(args);
                return -1;
        }
        output_datalen(buf, len);
        va_end(args);
        free(buf);
        return (len);
}

void
output_datalen(const char *buf, int len)
{
        int remaining, copied;
        
        remaining = BUFSIZ - (nfrontp - netobuf);
        while (len > 0) {
                /* Free up enough space if the room is too low*/
                if ((len > BUFSIZ ? BUFSIZ : len) > remaining) {
                        netflush();
                        remaining = BUFSIZ - (nfrontp - netobuf);
                }

                /* Copy out as much as will fit */
                copied = remaining > len ? len : remaining;
                memmove(nfrontp, buf, copied);
                nfrontp += copied;
                len -= copied;
                remaining -= copied;
                buf += copied;
        }
        return;
}