state.c

linux下telnet服务端的源码实现

/*
 * 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.
 * 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.
 */

#ifndef lint
static char sccsid[] = "@(#)state.c	8.5 (Berkeley) 5/30/95";
#endif /* not lint */

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

/* Format lines for corresponing commands */
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
send_eof ()
{
  init_termbuf ();
  term_send_eof ();
  pty_output_byte (slctab[SLC_EOF].sptr ?
		   (unsigned char) *slctab[SLC_EOF].sptr : '\004');
}

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

static void
send_susp ()
{
#ifdef	SIGTSTP
  ptyflush ();			/* half-hearted */
#ifdef	TCSIG
  ioctl (pty, TCSIG, (char *) SIGTSTP);
#else /* TCSIG */
  pty_output_byte (slctab[SLC_SUSP].sptr ?
		   (unsigned char) *slctab[SLC_SUSP].sptr : '\032');
#endif /* TCSIG */
#endif /* SIGTSTP */
}

/*
 * Send quit to process on other side of pty.
 * If it is in raw mode, just write NULL;
 * otherwise, write quit char.
 */
static void
send_brk ()
{
  ptyflush ();			/* half-hearted */
#ifdef	TCSIG
  ioctl (pty, TCSIG, (char *) SIGQUIT);
#else /* TCSIG */
  init_termbuf ();
  pty_output_byte (slctab[SLC_ABORT].sptr ?
		   (unsigned char) *slctab[SLC_ABORT].sptr : '\034');
#endif /* TCSIG */
}

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

#if defined(HAVE_STREAMSPTY) && defined(TIOCSIGNAL)
  /* Streams PTY style ioctl to post a signal */
  {
    int sig = SIGINT;
    ioctl (pty, TIOCSIGNAL, &sig);
    ioctl (pty, I_FLUSH, FLUSHR);
  }
#else
#ifdef	TCSIG
  ioctl (pty, TCSIG, (char *) SIGINT);
#else /* TCSIG */
  init_termbuf ();
  pty_output_byte (slctab[SLC_IP].sptr ?
		   (unsigned char) *slctab[SLC_IP].sptr : '\177');
#endif /* TCSIG */
#endif
}

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

  while (net_input_level () > 0 & !pty_buffer_is_full () )
    {
      c = net_get_char (0);
#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;
	  /* 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 = net_get_char (1);
#ifdef	ENCRYPTION
	      if (decrypt_input)
		nc = (*decrypt_input) (nc & 0xff);
#endif /* ENCRYPTION */
	      /*
	       * If we are operating in linemode,
	       * convert to local end-of-line.
	       */
	      if (linemode
		  && net_input_level () > 0
		  && (('\n' == nc) || (!nc && tty_iscrnl ())))
		{
		  net_get_char (0); /* Remove from the buffer */
		  c = '\n';
		}
	      else
		{
#ifdef	ENCRYPTION
		  if (decrypt_input)
		    (*decrypt_input) (-1);
#endif /* ENCRYPTION */
		  state = TS_CR;
		}
	    }
	  pty_output_byte (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:
	      DEBUG (debug_options, 1,
		    printoption ("td: recv IAC", c));
	      send_intr ();
	      break;

	    case BREAK:
	      DEBUG (debug_options, 1,
		    printoption ("td: recv IAC", c));
	      send_brk ();
	      break;

	      /*
	       * Are You There?
	       */
	    case AYT:
	      DEBUG (debug_options, 1,
                     printoption ("td: recv IAC", c));
	      recv_ayt ();
	      break;

	      /*
	       * Abort Output
	       */
	    case AO:
	      {
                DEBUG (debug_options, 1,
		      printoption ("td: recv IAC", c));
		ptyflush ();	/* half-hearted */
		init_termbuf ();

		if (slctab[SLC_AO].sptr
		    && *slctab[SLC_AO].sptr != (cc_t) (_POSIX_VDISABLE))
		  pty_output_byte (*slctab[SLC_AO].sptr);

		netclear ();	/* clear buffer back */
		net_output_data ("%c%c", IAC, DM);
		set_neturg ();
		DEBUG(debug_options, 1,
		      printoption ("td: send IAC", DM));
		break;
	      }

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

                DEBUG(debug_options, 1,            
		      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))
		  pty_output_byte ((unsigned char)ch);
		break;
	      }

	      /*
	       * Check for urgent data...
	       */
	    case DM:
	      DEBUG(debug_options, 1,
		    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))
		send_eof ();
	      break;

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

	    case SUSP:
	      send_susp ();
	      break;

	    case ABORT:
	      send_brk ();
	      break;

	    case IAC:
	      pty_output_byte (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);
	}
    }
}				/* 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]++;
    }
  net_output_data (doopt, option);

  DEBUG(debug_options, 1, printoption ("td: send do", option));
}

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

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

  /*
   * process input from peer.
   */

  DEBUG(debug_options, 1, 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: