state.c

里面包含了telnet的客户端和服务器端

/*
 * Copyright (c) 1989 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.
 */

/*
 * From: @(#)state.c	5.10 (Berkeley) 3/22/91
 */
char state_rcsid[] = 
  "$Id: state.c,v 1.12 1999/12/12 19:41:44 dholland Exp $";

#include "telnetd.h"

int not42 = 1;

static int envvarok(char *varp);

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

/*
 * 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)-1)) { \
				*subpointer++ = (c); \
			}
#define	SB_GET()	((*subpointer++)&0xff)
#define	SB_EOF()	(subpointer >= subend)
#define	SB_LEN()	(subend - subpointer)



/*
 * 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) {
    register int c;
    static int state = TS_DATA;

    while (ncc > 0) {
	if ((&ptyobuf[BUFSIZ] - pfrontp) < 2) break;
	c = *netip++ & 0377;
	ncc--;

#if defined(ENCRYPT)
	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)) {
#if defined(ENCRYPT)
		 int nc = *netip;
		 if (decrypt_input) {
		     nc = (*decrypt_input)(nc & 0xff);
		 }
#endif
#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
		 {
#if defined(ENCRYPT)
		     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 */
		      *nfrontp++ = (char)IAC;
		      *nfrontp++ = (char)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, "telnetd: panic state=%d\n", state);
	     printf("telnetd: panic state=%d\n", state);
	     exit(1);
	}
    }
}

/*
 * 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]++;
    }
    netoprintf((char *)doopt, option);
    
    DIAG(TD_OPTIONS, printoption("td: send do", option));
}

#ifdef	AUTHENTICATE
extern void auth_request();
#endif

#ifdef	LINEMODE
static void doclientstat(void);
#endif

#ifdef	ENCRYPT
extern void encrypt_send_support();
#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.