/*
  Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001,
  2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012,
  2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021 Free Software
  Foundation, Inc.

  This file is part of GNU Inetutils.

  GNU Inetutils is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or (at
  your option) any later version.

  GNU Inetutils is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see `http://www.gnu.org/licenses/'. */

/*
 * 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 <config.h>

#include "telnetd.h"

/*
 * local variables
 */
static unsigned char *def_slcbuf = (unsigned char *) 0;
static int def_slclen = 0;
static int slcchange;		/* change to slc is requested */
static unsigned char *slcptr;	/* pointer into slc buffer */
static unsigned char slcbuf[NSLC * 6];	/* buffer for slc negotiation */

/*
 * send_slc
 *
 * Write out the current special characters to the client.
 */
void
send_slc (void)
{
  register int i;

  /*
   * Send out list of triplets of special characters
   * to client.  We only send info on the characters
   * that are currently supported, except that editing
   * characters without current support are conveyed
   * using SLC_DEFAULT, thus urging the client to make
   * a choice of his own.  This conforms to RFC 1184,
   * section 2.4, page 6.
   */
  for (i = 1; i <= NSLC; i++)
    {
      if ((slctab[i].current.flag & SLC_LEVELBITS) != SLC_NOSUPPORT)
	add_slc ((unsigned char) i, slctab[i].current.flag,
		 slctab[i].current.val);
      else
	{
	  /* Urge the client to choose sensible editing characters.  */
	  switch (i)
	    {
	    case SLC_EC:
	    case SLC_EL:
	    case SLC_EW:
	    case SLC_RP:
	    case SLC_LNEXT:
	      add_slc ((unsigned char) i,
		       (slctab[i].current.flag & ~SLC_LEVELBITS) | SLC_DEFAULT,
			0);
	      break;

	    default:
	      /* Be silent on other, unsupported characters.  */
	      break;
	    }
	}
    }

}				/* end of send_slc */

/*
 * default_slc
 *
 * Set pty special characters to all the defaults.
 */
void
default_slc (void)
{
  register int i;

  for (i = 1; i <= NSLC; i++)
    {
      slctab[i].current.val = slctab[i].defset.val;
      if (slctab[i].current.val == (cc_t) (_POSIX_VDISABLE))
	slctab[i].current.flag = SLC_NOSUPPORT;
      else
	slctab[i].current.flag = slctab[i].defset.flag;
      if (slctab[i].sptr)
	{
	  *(slctab[i].sptr) = slctab[i].defset.val;
	}
    }
  slcchange = 1;

}				/* end of default_slc */

/*
 * get_slc_defaults
 *
 * Initialize the slc mapping table.
 */
void
get_slc_defaults (void)
{
  register int i;

  init_termbuf ();

  for (i = 1; i <= NSLC; i++)
    {
      slctab[i].defset.flag =
	spcset (i, &slctab[i].defset.val, &slctab[i].sptr);
      slctab[i].current.flag = SLC_NOSUPPORT;
      slctab[i].current.val = 0;
    }

}				/* end of get_slc_defaults */

/*
 * add_slc
 *
 * Add an slc triplet to the slc buffer.
 */
void
add_slc (register char func, register char flag, register cc_t val)
{

  if ((*slcptr++ = (unsigned char) func) == 0xff)
    *slcptr++ = 0xff;

  if ((*slcptr++ = (unsigned char) flag) == 0xff)
    *slcptr++ = 0xff;

  if ((*slcptr++ = (unsigned char) val) == 0xff)
    *slcptr++ = 0xff;

}				/* end of add_slc */

/*
 * start_slc
 *
 * Get ready to process incoming slc's and respond to them.
 *
 * The parameter getit is non-zero if it is necessary to grab a copy
 * of the terminal control structures.
 */
void
start_slc (register int getit)
{

  slcchange = 0;
  if (getit)
    init_termbuf ();
  sprintf ((char *) slcbuf, "%c%c%c%c", IAC, SB, TELOPT_LINEMODE, LM_SLC);
  slcptr = slcbuf + 4;

}				/* end of start_slc */

/*
 * end_slc
 *
 * Finish up the slc negotiation.  If something to send, then send it.
 */
int
end_slc (register unsigned char **bufp)
{
  register int len;
  void netflush (void);

  /*
   * If a change has occured, store the new terminal control
   * structures back to the terminal driver.
   */
  if (slcchange)
    {
      set_termbuf ();
    }

  /*
   * If the pty state has not yet been fully processed and there is a
   * deferred slc request from the client, then do not send any
   * sort of slc negotiation now.  We will respond to the client's
   * request very soon.
   */
  if (def_slcbuf && (terminit () == 0))
    {
      return (0);
    }

  if (slcptr > (slcbuf + 4))
    {
      if (bufp)
	{
	  *bufp = &slcbuf[4];
	  return (slcptr - slcbuf - 4);
	}
      else
	{
	  sprintf ((char *) slcptr, "%c%c", IAC, SE);
	  slcptr += 2;
	  len = slcptr - slcbuf;
	  net_output_datalen (slcbuf, len);
	  netflush ();		/* force it out immediately */
	  DEBUG (debug_options, 1, printsub ('>', slcbuf + 2, len - 2));
	}
    }
  return (0);

}				/* end of end_slc */

/*
 * process_slc
 *
 * Figure out what to do about the client's slc
 */
void
process_slc (register unsigned char func, register unsigned char flag,
	     register cc_t val)
{
  register int hislevel, mylevel, ack;

  /*
   * Ensure that we know something about this function
   */
  if (func > NSLC)
    {
      add_slc (func, SLC_NOSUPPORT, 0);
      return;
    }

  /*
   * Process the special case requests of 0 SLC_DEFAULT 0
   * and 0 SLC_VARIABLE 0.  Be a little forgiving here, don't
   * worry about whether the value is actually 0 or not.
   */
  if (func == 0)
    {
      if ((flag = flag & SLC_LEVELBITS) == SLC_DEFAULT)
	{
	  default_slc ();
	  send_slc ();
	}
      else if (flag == SLC_VARIABLE)
	{
	  send_slc ();
	}
      return;
    }

  /*
   * Appears to be a function that we know something about.  So
   * get on with it and see what we know.
   */

  hislevel = flag & SLC_LEVELBITS;
  mylevel = slctab[func].current.flag & SLC_LEVELBITS;
  ack = flag & SLC_ACK;
  /*
   * ignore the command if:
   * the function value and level are the same as what we already have;
   * or the level is the same and the ack bit is set
   */
  if (hislevel == mylevel && (val == slctab[func].current.val || ack))
    {
      return;
    }
  else if (ack)
    {
      /*
       * If we get here, we got an ack, but the levels don't match.
       * This shouldn't happen.  If it does, it is probably because
       * we have sent two requests to set a variable without getting
       * a response between them, and this is the first response.
       * So, ignore it, and wait for the next response.
       */
      return;
    }
  else
    {
      change_slc (func, flag, val);
    }

}				/* end of process_slc */

/*
 * change_slc
 *
 * Process a request to change one of our special characters.
 * Compare client's request with what we are capable of supporting.
 */
void
change_slc (register char func_c, register char flag, register cc_t val)
{
  register int func = func_c;
  register int hislevel, mylevel;

  hislevel = flag & SLC_LEVELBITS;
  mylevel = slctab[func].defset.flag & SLC_LEVELBITS;
  /*
   * If client is setting a function to NOSUPPORT
   * or DEFAULT, then we can easily and directly
   * accomodate the request.
   */
  if (hislevel == SLC_NOSUPPORT)
    {
      slctab[func].current.flag = flag;
      slctab[func].current.val = (cc_t) _POSIX_VDISABLE;
      flag |= SLC_ACK;
      add_slc (func, flag, val);
      return;
    }
  if (hislevel == SLC_DEFAULT)
    {
      /*
       * Special case here.  If client tells us to use
       * the default on a function we don't support, then
       * return NOSUPPORT instead of what we may have as a
       * default level of DEFAULT.
       */
      if (mylevel == SLC_DEFAULT)
	{
	  slctab[func].current.flag = SLC_NOSUPPORT;
	}
      else
	{
	  slctab[func].current.flag = slctab[func].defset.flag;
	}
      slctab[func].current.val = slctab[func].defset.val;
      add_slc (func, slctab[func].current.flag, slctab[func].current.val);
      return;
    }

  /*
   * Client wants us to change to a new value or he
   * is telling us that he can't change to our value.
   * Some of the slc's we support and can change,
   * some we do support but can't change,
   * and others we don't support at all.
   * If we can change it then we have a pointer to
   * the place to put the new value, so change it,
   * otherwise, continue the negotiation.
   */
  if (slctab[func].sptr)
    {
      /*
       * We can change this one.
       */
      slctab[func].current.val = val;
      *(slctab[func].sptr) = val;
      slctab[func].current.flag = flag;
      flag |= SLC_ACK;
      slcchange = 1;
      add_slc (func, flag, val);
    }
  else
    {
      /*
       * It is not possible for us to support this
       * request as he asks.
       *
       * If our level is DEFAULT, then just ack whatever was
       * sent.
       *
       * If he can't change and we can't change,
       * then degenerate to NOSUPPORT.
       *
       * Otherwise we send our level back to him, (CANTCHANGE
       * or NOSUPPORT) and if CANTCHANGE, send
       * our value as well.
       */
      if (mylevel == SLC_DEFAULT)
	{
	  slctab[func].current.flag = flag;
	  slctab[func].current.val = val;
	  flag |= SLC_ACK;
	}
      else if (hislevel == SLC_CANTCHANGE && mylevel == SLC_CANTCHANGE)
	{
	  flag &= ~SLC_LEVELBITS;
	  flag |= SLC_NOSUPPORT;
	  slctab[func].current.flag = flag;
	}
      else
	{
	  flag &= ~SLC_LEVELBITS;
	  flag |= mylevel;
	  slctab[func].current.flag = flag;
	  if (mylevel == SLC_CANTCHANGE)
	    {
	      slctab[func].current.val = slctab[func].defset.val;
	      val = slctab[func].current.val;
	    }
	}
      add_slc (func, flag, val);
    }

}				/* end of change_slc */

/*
 * check_slc
 *
 * Check the special characters in use and notify the client if any have
 * changed.  Only those characters that are capable of being changed are
 * likely to have changed.  If a local change occurs, kick the support level
 * and flags up to the defaults.
 */
void
check_slc (void)
{
  register int i;

  for (i = 1; i <= NSLC; i++)
    {
      if (i == SLC_EOF && term_change_eof ())
	continue;
      if (slctab[i].sptr && (*(slctab[i].sptr) != slctab[i].current.val))
	{
	  slctab[i].current.val = *(slctab[i].sptr);
	  if (*(slctab[i].sptr) == (cc_t) _POSIX_VDISABLE)
	    slctab[i].current.flag = SLC_NOSUPPORT;
	  else
	    slctab[i].current.flag = slctab[i].defset.flag;
	  add_slc ((unsigned char) i, slctab[i].current.flag,
		   slctab[i].current.val);
	}
    }
}				/* check_slc */

/*
 * do_opt_slc
 *
 * Process an slc option buffer.  Defer processing of incoming slc's
 * until after the terminal state has been processed.  Save the first slc
 * request that comes along, but discard all others.
 *
 * ptr points to the beginning of the buffer, len is the length.
 */
void
do_opt_slc (register unsigned char *ptr, register int len)
{
  register unsigned char func, flag;
  cc_t val;
  register unsigned char *end = ptr + len;

  if (terminit ())
    {				/* go ahead */
      while (ptr < end)
	{
	  func = *ptr++;
	  if (ptr >= end)
	    break;
	  flag = *ptr++;
	  if (ptr >= end)
	    break;
	  val = (cc_t) * ptr++;

	  process_slc (func, flag, val);

	}
    }
  else
    {
      /*
       * save this slc buffer if it is the first, otherwise dump
       * it.
       */
      if (def_slcbuf == (unsigned char *) 0)
	{
	  def_slclen = len;
	  def_slcbuf = (unsigned char *) malloc ((unsigned) len);
	  if (def_slcbuf == (unsigned char *) 0)
	    return;		/* too bad */
	  memmove (def_slcbuf, ptr, len);
	}
    }

}				/* end of do_opt_slc */

/*
 * deferslc
 *
 * Do slc stuff that was deferred.
 */
void
deferslc (void)
{
  if (def_slcbuf)
    {
      start_slc (1);
      do_opt_slc (def_slcbuf, def_slclen);
      end_slc (0);
      free (def_slcbuf);
      def_slcbuf = (unsigned char *) 0;
      def_slclen = 0;
    }

}				/* end of deferslc */
