state.c

经典的unix下telnetd代码

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

#include "telnetd.h"
#include <syslog.h>

/* RCSID("$KTH: state.c,v 1.14 2000/10/02 05:06:02 assar Exp $"); */

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[2048], *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)) {
#ifdef ENCRYPTION
		int nc = *netip;

		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", 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) = 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:
		/*