libexec/telnetd/state.c

   1 /*
   2  * Copyright (c) 1989, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  * @(#)state.c  8.5 (Berkeley) 5/30/95
  34  * $FreeBSD: src/libexec/telnetd/state.c,v 1.9.2.4 2002/04/13 11:07:12 markm Exp $
  35  * $DragonFly: src/libexec/telnetd/state.c,v 1.3 2006/01/12 13:43:10 corecode Exp $
  36  */
  37
  38 #include <stdarg.h>
  39 #include "telnetd.h"
  40
  41 static int envvarok(char *);
  42
  43 unsigned char   doopt[] = { IAC, DO, '%', 'c', 0 };
  44 unsigned char   dont[] = { IAC, DONT, '%', 'c', 0 };
  45 unsigned char   will[] = { IAC, WILL, '%', 'c', 0 };
  46 unsigned char   wont[] = { IAC, WONT, '%', 'c', 0 };
  47 int     not42 = 1;
  48
  49 /*
  50  * Buffer for sub-options, and macros
  51  * for suboptions buffer manipulations
  52  */
  53 unsigned char subbuffer[512], *subpointer= subbuffer, *subend= subbuffer;
  54
  55 #define SB_CLEAR()      subpointer = subbuffer
  56 #define SB_TERM()       { subend = subpointer; SB_CLEAR(); }
  57 #define SB_ACCUM(c)     if (subpointer < (subbuffer+sizeof subbuffer)) { \
  58                                 *subpointer++ = (c); \
  59                         }
  60 #define SB_GET()        ((*subpointer++)&0xff)
  61 #define SB_EOF()        (subpointer >= subend)
  62 #define SB_LEN()        (subend - subpointer)
  63
  64 #ifdef  ENV_HACK
  65 unsigned char *subsave;
  66 #define SB_SAVE()       subsave = subpointer;
  67 #define SB_RESTORE()    subpointer = subsave;
  68 #endif
  69
  70
  71 /*
  72  * State for recv fsm
  73  */
  74 #define TS_DATA         0       /* base state */
  75 #define TS_IAC          1       /* look for double IAC's */
  76 #define TS_CR           2       /* CR-LF ->'s CR */
  77 #define TS_SB           3       /* throw away begin's... */
  78 #define TS_SE           4       /* ...end's (suboption negotiation) */
  79 #define TS_WILL         5       /* will option negotiation */
  80 #define TS_WONT         6       /* wont " */
  81 #define TS_DO           7       /* do " */
  82 #define TS_DONT         8       /* dont " */
  83
  84 static void doclientstat(void);
  85
  86 void
  87 telrcv(void)
  88 {
  89         int c;
  90         static int state = TS_DATA;
  91
  92         while (ncc > 0) {
  93                 if ((&ptyobuf[BUFSIZ] - pfrontp) < 2)
  94                         break;
  95                 c = *netip++ & 0377, ncc--;
  96                 switch (state) {
  97
  98                 case TS_CR:
  99                         state = TS_DATA;
 100                         /* Strip off \n or \0 after a \r */
 101                         if ((c == 0) || (c == '\n')) {
 102                                 break;
 103                         }
 104                         /* FALL THROUGH */
 105
 106                 case TS_DATA:
 107                         if (c == IAC) {
 108                                 state = TS_IAC;
 109                                 break;
 110                         }
 111                         /*
 112                          * We now map \r\n ==> \r for pragmatic reasons.
 113                          * Many client implementations send \r\n when
 114                          * the user hits the CarriageReturn key.
 115                          *
 116                          * We USED to map \r\n ==> \n, since \r\n says
 117                          * that we want to be in column 1 of the next
 118                          * printable line, and \n is the standard
 119                          * unix way of saying that (\r is only good
 120                          * if CRMOD is set, which it normally is).
 121                          */
 122                         if ((c == '\r') && his_state_is_wont(TELOPT_BINARY)) {
 123                                 int nc = *netip;
 124 #ifdef  LINEMODE
 125                                 /*
 126                                  * If we are operating in linemode,
 127                                  * convert to local end-of-line.
 128                                  */
 129                                 if (linemode && (ncc > 0) && (('\n' == nc) ||
 130                                          ((0 == nc) && tty_iscrnl())) ) {
 131                                         netip++; ncc--;
 132                                         c = '\n';
 133                                 } else
 134 #endif
 135                                 {
 136                                         state = TS_CR;
 137                                 }
 138                         }
 139                         *pfrontp++ = c;
 140                         break;
 141
 142                 case TS_IAC:
 143 gotiac:                 switch (c) {
 144
 145                         /*
 146                          * Send the process on the pty side an
 147                          * interrupt.  Do this with a NULL or
 148                          * interrupt char; depending on the tty mode.
 149                          */
 150                         case IP:
 151                                 DIAG(TD_OPTIONS,
 152                                         printoption("td: recv IAC", c));
 153                                 interrupt();
 154                                 break;
 155
 156                         case BREAK:
 157                                 DIAG(TD_OPTIONS,
 158                                         printoption("td: recv IAC", c));
 159                                 sendbrk();
 160                                 break;
 161
 162                         /*
 163                          * Are You There?
 164                          */
 165                         case AYT:
 166                                 DIAG(TD_OPTIONS,
 167                                         printoption("td: recv IAC", c));
 168                                 recv_ayt();
 169                                 break;
 170
 171                         /*
 172                          * Abort Output
 173                          */
 174                         case AO:
 175                             {
 176                                 DIAG(TD_OPTIONS,
 177                                         printoption("td: recv IAC", c));
 178                                 ptyflush();     /* half-hearted */
 179                                 init_termbuf();
 180
 181                                 if (slctab[SLC_AO].sptr &&
 182                                     *slctab[SLC_AO].sptr != (cc_t)(_POSIX_VDISABLE)) {
 183                                     *pfrontp++ =
 184                                         (unsigned char)*slctab[SLC_AO].sptr;
 185                                 }
 186
 187                                 netclear();     /* clear buffer back */
 188                                 output_data("%c%c", IAC, DM);
 189                                 neturg = nfrontp-1; /* off by one XXX */
 190                                 DIAG(TD_OPTIONS,
 191                                         printoption("td: send IAC", DM));
 192                                 break;
 193                             }
 194
 195                         /*
 196                          * Erase Character and
 197                          * Erase Line
 198                          */
 199                         case EC:
 200                         case EL:
 201                             {
 202                                 cc_t ch;
 203
 204                                 DIAG(TD_OPTIONS,
 205                                         printoption("td: recv IAC", c));
 206                                 ptyflush();     /* half-hearted */
 207                                 init_termbuf();
 208                                 if (c == EC)
 209                                         ch = *slctab[SLC_EC].sptr;
 210                                 else
 211                                         ch = *slctab[SLC_EL].sptr;
 212                                 if (ch != (cc_t)(_POSIX_VDISABLE))
 213                                         *pfrontp++ = (unsigned char)ch;
 214                                 break;
 215                             }
 216
 217                         /*
 218                          * Check for urgent data...
 219                          */
 220                         case DM:
 221                                 DIAG(TD_OPTIONS,
 222                                         printoption("td: recv IAC", c));
 223                                 SYNCHing = stilloob(net);
 224                                 settimer(gotDM);
 225                                 break;
 226
 227
 228                         /*
 229                          * Begin option subnegotiation...
 230                          */
 231                         case SB:
 232                                 state = TS_SB;
 233                                 SB_CLEAR();
 234                                 continue;
 235
 236                         case WILL:
 237                                 state = TS_WILL;
 238                                 continue;
 239
 240                         case WONT:
 241                                 state = TS_WONT;
 242                                 continue;
 243
 244                         case DO:
 245                                 state = TS_DO;
 246                                 continue;
 247
 248                         case DONT:
 249                                 state = TS_DONT;
 250                                 continue;
 251                         case EOR:
 252                                 if (his_state_is_will(TELOPT_EOR))
 253                                         doeof();
 254                                 break;
 255
 256                         /*
 257                          * Handle RFC 10xx Telnet linemode option additions
 258                          * to command stream (EOF, SUSP, ABORT).
 259                          */
 260                         case xEOF:
 261                                 doeof();
 262                                 break;
 263
 264                         case SUSP:
 265                                 sendsusp();
 266                                 break;
 267
 268                         case ABORT:
 269                                 sendbrk();
 270                                 break;
 271
 272                         case IAC:
 273                                 *pfrontp++ = c;
 274                                 break;
 275                         }
 276                         state = TS_DATA;
 277                         break;
 278
 279                 case TS_SB:
 280                         if (c == IAC) {
 281                                 state = TS_SE;
 282                         } else {
 283                                 SB_ACCUM(c);
 284                         }
 285                         break;
 286
 287                 case TS_SE:
 288                         if (c != SE) {
 289                                 if (c != IAC) {
 290                                         /*
 291                                          * bad form of suboption negotiation.
 292                                          * handle it in such a way as to avoid
 293                                          * damage to local state.  Parse
 294                                          * suboption buffer found so far,
 295                                          * then treat remaining stream as
 296                                          * another command sequence.
 297                                          */
 298
 299                                         /* for DIAGNOSTICS */
 300                                         SB_ACCUM(IAC);
 301                                         SB_ACCUM(c);
 302                                         subpointer -= 2;
 303
 304                                         SB_TERM();
 305                                         suboption();
 306                                         state = TS_IAC;
 307                                         goto gotiac;
 308                                 }
 309                                 SB_ACCUM(c);
 310                                 state = TS_SB;
 311                         } else {
 312                                 /* for DIAGNOSTICS */
 313                                 SB_ACCUM(IAC);
 314                                 SB_ACCUM(SE);
 315                                 subpointer -= 2;
 316
 317                                 SB_TERM();
 318                                 suboption();    /* handle sub-option */
 319                                 state = TS_DATA;
 320                         }
 321                         break;
 322
 323                 case TS_WILL:
 324                         willoption(c);
 325                         state = TS_DATA;
 326                         continue;
 327
 328                 case TS_WONT:
 329                         wontoption(c);
 330                         state = TS_DATA;
 331                         continue;
 332
 333                 case TS_DO:
 334                         dooption(c);
 335                         state = TS_DATA;
 336                         continue;
 337
 338                 case TS_DONT:
 339                         dontoption(c);
 340                         state = TS_DATA;
 341                         continue;
 342
 343                 default:
 344                         syslog(LOG_ERR, "panic state=%d", state);
 345                         printf("telnetd: panic state=%d\n", state);
 346                         exit(1);
 347                 }
 348         }
 349 }  /* end of telrcv */
 350
 351 /*
 352  * The will/wont/do/dont state machines are based on Dave Borman's
 353  * Telnet option processing state machine.
 354  *
 355  * These correspond to the following states:
 356  *      my_state = the last negotiated state
 357  *      want_state = what I want the state to go to
 358  *      want_resp = how many requests I have sent
 359  * All state defaults are negative, and resp defaults to 0.
 360  *
 361  * When initiating a request to change state to new_state:
 362  *
 363  * if ((want_resp == 0 && new_state == my_state) || want_state == new_state) {
 364  *      do nothing;
 365  * } else {
 366  *      want_state = new_state;
 367  *      send new_state;
 368  *      want_resp++;
 369  * }
 370  *
 371  * When receiving new_state:
 372  *
 373  * if (want_resp) {
 374  *      want_resp--;
 375  *      if (want_resp && (new_state == my_state))
 376  *              want_resp--;
 377  * }
 378  * if ((want_resp == 0) && (new_state != want_state)) {
 379  *      if (ok_to_switch_to new_state)
 380  *              want_state = new_state;
 381  *      else
 382  *              want_resp++;
 383  *      send want_state;
 384  * }
 385  * my_state = new_state;
 386  *
 387  * Note that new_state is implied in these functions by the function itself.
 388  * will and do imply positive new_state, wont and dont imply negative.
 389  *
 390  * Finally, there is one catch.  If we send a negative response to a
 391  * positive request, my_state will be the positive while want_state will
 392  * remain negative.  my_state will revert to negative when the negative
 393  * acknowlegment arrives from the peer.  Thus, my_state generally tells
 394  * us not only the last negotiated state, but also tells us what the peer
 395  * wants to be doing as well.  It is important to understand this difference
 396  * as we may wish to be processing data streams based on our desired state
 397  * (want_state) or based on what the peer thinks the state is (my_state).
 398  *
 399  * This all works fine because if the peer sends a positive request, the data
 400  * that we receive prior to negative acknowlegment will probably be affected
 401  * by the positive state, and we can process it as such (if we can; if we
 402  * can't then it really doesn't matter).  If it is that important, then the
 403  * peer probably should be buffering until this option state negotiation
 404  * is complete.
 405  *
 406  */
 407 void
 408 send_do(int option, int init)
 409 {
 410         if (init) {
 411                 if ((do_dont_resp[option] == 0 && his_state_is_will(option)) ||
 412                     his_want_state_is_will(option))
 413                         return;
 414                 /*
 415                  * Special case for TELOPT_TM:  We send a DO, but pretend
 416                  * that we sent a DONT, so that we can send more DOs if
 417                  * we want to.
 418                  */
 419                 if (option == TELOPT_TM)
 420                         set_his_want_state_wont(option);
 421                 else
 422                         set_his_want_state_will(option);
 423                 do_dont_resp[option]++;
 424         }
 425         output_data((const char *)doopt, option);
 426
 427         DIAG(TD_OPTIONS, printoption("td: send do", option));
 428 }
 429
 430 void
 431 willoption(int option)
 432 {
 433         int changeok = 0;
 434         void (*func)(void) = 0;
 435
 436         /*
 437          * process input from peer.
 438          */
 439
 440         DIAG(TD_OPTIONS, printoption("td: recv will", option));
 441
 442         if (do_dont_resp[option]) {
 443                 do_dont_resp[option]--;
 444                 if (do_dont_resp[option] && his_state_is_will(option))
 445                         do_dont_resp[option]--;
 446         }
 447         if (do_dont_resp[option] == 0) {
 448             if (his_want_state_is_wont(option)) {
 449                 switch (option) {
 450
 451                 case TELOPT_BINARY:
 452                         init_termbuf();
 453                         tty_binaryin(1);
 454                         set_termbuf();
 455                         changeok++;
 456                         break;
 457
 458                 case TELOPT_ECHO:
 459                         /*
 460                          * See comments below for more info.
 461                          */
 462                         not42 = 0;      /* looks like a 4.2 system */
 463                         break;
 464
 465                 case TELOPT_TM:
 466 #if     defined(LINEMODE) && defined(KLUDGELINEMODE)
 467                         /*
 468                          * This telnetd implementation does not really
 469                          * support timing marks, it just uses them to
 470                          * support the kludge linemode stuff.  If we
 471                          * receive a will or wont TM in response to our
 472                          * do TM request that may have been sent to
 473                          * determine kludge linemode support, process
 474                          * it, otherwise TM should get a negative
 475                          * response back.
 476                          */
 477                         /*
 478                          * Handle the linemode kludge stuff.
 479                          * If we are not currently supporting any
 480                          * linemode at all, then we assume that this
 481                          * is the client telling us to use kludge
 482                          * linemode in response to our query.  Set the
 483                          * linemode type that is to be supported, note
 484                          * that the client wishes to use linemode, and
 485                          * eat the will TM as though it never arrived.
 486                          */
 487                         if (lmodetype < KLUDGE_LINEMODE) {
 488                                 lmodetype = KLUDGE_LINEMODE;
 489                                 clientstat(TELOPT_LINEMODE, WILL, 0);
 490                                 send_wont(TELOPT_SGA, 1);
 491                         } else if (lmodetype == NO_AUTOKLUDGE) {
 492                                 lmodetype = KLUDGE_OK;
 493                         }
 494 #endif  /* defined(LINEMODE) && defined(KLUDGELINEMODE) */
 495                         /*
 496                          * We never respond to a WILL TM, and
 497                          * we leave the state WONT.
 498                          */
 499                         return;
 500
 501                 case TELOPT_LFLOW:
 502                         /*
 503                          * If we are going to support flow control
 504                          * option, then don't worry peer that we can't
 505                          * change the flow control characters.
 506                          */
 507                         slctab[SLC_XON].defset.flag &= ~SLC_LEVELBITS;
 508                         slctab[SLC_XON].defset.flag |= SLC_DEFAULT;
 509                         slctab[SLC_XOFF].defset.flag &= ~SLC_LEVELBITS;
 510                         slctab[SLC_XOFF].defset.flag |= SLC_DEFAULT;
 511                 case TELOPT_TTYPE:
 512                 case TELOPT_SGA:
 513                 case TELOPT_NAWS:
 514                 case TELOPT_TSPEED:
 515                 case TELOPT_XDISPLOC:
 516                 case TELOPT_NEW_ENVIRON:
 517                 case TELOPT_OLD_ENVIRON:
 518                         changeok++;
 519                         break;
 520
 521 #ifdef  LINEMODE
 522                 case TELOPT_LINEMODE:
 523 # ifdef KLUDGELINEMODE
 524                         /*
 525                          * Note client's desire to use linemode.
 526                          */
 527                         lmodetype = REAL_LINEMODE;
 528 # endif /* KLUDGELINEMODE */
 529                         func = doclientstat;
 530                         changeok++;
 531                         break;
 532 #endif  /* LINEMODE */
 533
 534
 535
 536                 default:
 537                         break;
 538                 }
 539                 if (changeok) {
 540                         set_his_want_state_will(option);
 541                         send_do(option, 0);
 542                 } else {
 543                         do_dont_resp[option]++;
 544                         send_dont(option, 0);
 545                 }
 546             } else {
 547                 /*
 548                  * Option processing that should happen when
 549                  * we receive conformation of a change in
 550                  * state that we had requested.
 551                  */
 552                 switch (option) {
 553                 case TELOPT_ECHO:
 554                         not42 = 0;      /* looks like a 4.2 system */
 555                         /*
 556                          * Egads, he responded "WILL ECHO".  Turn
 557                          * it off right now!
 558                          */
 559                         send_dont(option, 1);
 560                         /*
 561                          * "WILL ECHO".  Kludge upon kludge!
 562                          * A 4.2 client is now echoing user input at
 563                          * the tty.  This is probably undesireable and
 564                          * it should be stopped.  The client will
 565                          * respond WONT TM to the DO TM that we send to
 566                          * check for kludge linemode.  When the WONT TM
 567                          * arrives, linemode will be turned off and a
 568                          * change propogated to the pty.  This change
 569                          * will cause us to process the new pty state
 570                          * in localstat(), which will notice that
 571                          * linemode is off and send a WILL ECHO
 572                          * so that we are properly in character mode and
 573                          * all is well.
 574                          */
 575                         break;
 576 #ifdef  LINEMODE
 577                 case TELOPT_LINEMODE:
 578 # ifdef KLUDGELINEMODE
 579                         /*
 580                          * Note client's desire to use linemode.
 581                          */
 582                         lmodetype = REAL_LINEMODE;
 583 # endif /* KLUDGELINEMODE */
 584                         func = doclientstat;
 585                         break;
 586 #endif  /* LINEMODE */
 587
 588
 589                 case TELOPT_LFLOW:
 590                         func = flowstat;
 591                         break;
 592                 }
 593             }
 594         }
 595         set_his_state_will(option);
 596         if (func)
 597                 (*func)();
 598 }  /* end of willoption */
 599
 600 void
 601 send_dont(int option, int init)
 602 {
 603         if (init) {
 604                 if ((do_dont_resp[option] == 0 && his_state_is_wont(option)) ||
 605                     his_want_state_is_wont(option))
 606                         return;
 607                 set_his_want_state_wont(option);
 608                 do_dont_resp[option]++;
 609         }
 610         output_data((const char *)dont, option);
 611
 612         DIAG(TD_OPTIONS, printoption("td: send dont", option));
 613 }
 614
 615 void
 616 wontoption(int option)
 617 {
 618         /*
 619          * Process client input.
 620          */
 621
 622         DIAG(TD_OPTIONS, printoption("td: recv wont", option));
 623
 624         if (do_dont_resp[option]) {
 625                 do_dont_resp[option]--;
 626                 if (do_dont_resp[option] && his_state_is_wont(option))
 627                         do_dont_resp[option]--;
 628         }
 629         if (do_dont_resp[option] == 0) {
 630             if (his_want_state_is_will(option)) {
 631                 /* it is always ok to change to negative state */
 632                 switch (option) {
 633                 case TELOPT_ECHO:
 634                         not42 = 1; /* doesn't seem to be a 4.2 system */
 635                         break;
 636
 637                 case TELOPT_BINARY:
 638                         init_termbuf();
 639                         tty_binaryin(0);
 640                         set_termbuf();
 641                         break;
 642
 643 #ifdef  LINEMODE
 644                 case TELOPT_LINEMODE:
 645 # ifdef KLUDGELINEMODE
 646                         /*
 647                          * If real linemode is supported, then client is
 648                          * asking to turn linemode off.
 649                          */
 650                         if (lmodetype != REAL_LINEMODE)
 651                                 break;
 652                         lmodetype = KLUDGE_LINEMODE;
 653 # endif /* KLUDGELINEMODE */
 654                         clientstat(TELOPT_LINEMODE, WONT, 0);
 655                         break;
 656 #endif  /* LINEMODE */
 657
 658                 case TELOPT_TM:
 659                         /*
 660                          * If we get a WONT TM, and had sent a DO TM,
 661                          * don't respond with a DONT TM, just leave it
 662                          * as is.  Short circut the state machine to
 663                          * achive this.
 664                          */
 665                         set_his_want_state_wont(TELOPT_TM);
 666                         return;
 667
 668                 case TELOPT_LFLOW:
 669                         /*
 670                          * If we are not going to support flow control
 671                          * option, then let peer know that we can't
 672                          * change the flow control characters.
 673                          */
 674                         slctab[SLC_XON].defset.flag &= ~SLC_LEVELBITS;
 675                         slctab[SLC_XON].defset.flag |= SLC_CANTCHANGE;
 676                         slctab[SLC_XOFF].defset.flag &= ~SLC_LEVELBITS;
 677                         slctab[SLC_XOFF].defset.flag |= SLC_CANTCHANGE;
 678                         break;
 679
 680
 681                 /*
 682                  * For options that we might spin waiting for
 683                  * sub-negotiation, if the client turns off the
 684                  * option rather than responding to the request,
 685                  * we have to treat it here as if we got a response
 686                  * to the sub-negotiation, (by updating the timers)
 687                  * so that we'll break out of the loop.
 688                  */
 689                 case TELOPT_TTYPE:
 690                         settimer(ttypesubopt);
 691                         break;
 692
 693                 case TELOPT_TSPEED:
 694                         settimer(tspeedsubopt);
 695                         break;
 696
 697                 case TELOPT_XDISPLOC:
 698                         settimer(xdisplocsubopt);
 699                         break;
 700
 701                 case TELOPT_OLD_ENVIRON:
 702                         settimer(oenvironsubopt);
 703                         break;
 704
 705                 case TELOPT_NEW_ENVIRON:
 706                         settimer(environsubopt);
 707                         break;
 708
 709                 default:
 710                         break;
 711                 }
 712                 set_his_want_state_wont(option);
 713                 if (his_state_is_will(option))
 714                         send_dont(option, 0);
 715             } else {
 716                 switch (option) {
 717                 case TELOPT_TM:
 718 #if     defined(LINEMODE) && defined(KLUDGELINEMODE)
 719                         if (lmodetype < NO_AUTOKLUDGE) {
 720                                 lmodetype = NO_LINEMODE;
 721                                 clientstat(TELOPT_LINEMODE, WONT, 0);
 722                                 send_will(TELOPT_SGA, 1);
 723                                 send_will(TELOPT_ECHO, 1);
 724                         }
 725 #endif  /* defined(LINEMODE) && defined(KLUDGELINEMODE) */
 726                         break;
 727
 728                 default:
 729                         break;
 730                 }
 731             }
 732         }
 733         set_his_state_wont(option);
 734
 735 }  /* end of wontoption */
 736
 737 void
 738 send_will(int option, int init)
 739 {
 740         if (init) {
 741                 if ((will_wont_resp[option] == 0 && my_state_is_will(option))||
 742                     my_want_state_is_will(option))
 743                         return;
 744                 set_my_want_state_will(option);
 745                 will_wont_resp[option]++;
 746         }
 747         output_data((const char *)will, option);
 748
 749         DIAG(TD_OPTIONS, printoption("td: send will", option));
 750 }
 751
 752 #if     !defined(LINEMODE) || !defined(KLUDGELINEMODE)
 753 /*
 754  * When we get a DONT SGA, we will try once to turn it
 755  * back on.  If the other side responds DONT SGA, we
 756  * leave it at that.  This is so that when we talk to
 757  * clients that understand KLUDGELINEMODE but not LINEMODE,
 758  * we'll keep them in char-at-a-time mode.
 759  */
 760 int turn_on_sga = 0;
 761 #endif
 762
 763 void
 764 dooption(int option)
 765 {
 766         int changeok = 0;
 767
 768         /*
 769          * Process client input.
 770          */
 771
 772         DIAG(TD_OPTIONS, printoption("td: recv do", option));
 773
 774         if (will_wont_resp[option]) {
 775                 will_wont_resp[option]--;
 776                 if (will_wont_resp[option] && my_state_is_will(option))
 777                         will_wont_resp[option]--;
 778         }
 779         if ((will_wont_resp[option] == 0) && (my_want_state_is_wont(option))) {
 780                 switch (option) {
 781                 case TELOPT_ECHO:
 782 #ifdef  LINEMODE
 783 # ifdef KLUDGELINEMODE
 784                         if (lmodetype == NO_LINEMODE)
 785 # else
 786                         if (his_state_is_wont(TELOPT_LINEMODE))
 787 # endif
 788 #endif
 789                         {
 790                                 init_termbuf();
 791                                 tty_setecho(1);
 792                                 set_termbuf();
 793                         }
 794                         changeok++;
 795                         break;
 796
 797                 case TELOPT_BINARY:
 798                         init_termbuf();
 799                         tty_binaryout(1);
 800                         set_termbuf();
 801                         changeok++;
 802                         break;
 803
 804                 case TELOPT_SGA:
 805 #if     defined(LINEMODE) && defined(KLUDGELINEMODE)
 806                         /*
 807                          * If kludge linemode is in use, then we must
 808                          * process an incoming do SGA for linemode
 809                          * purposes.
 810                          */
 811                         if (lmodetype == KLUDGE_LINEMODE) {
 812                                 /*
 813                                  * Receipt of "do SGA" in kludge
 814                                  * linemode is the peer asking us to
 815                                  * turn off linemode.  Make note of
 816                                  * the request.
 817                                  */
 818                                 clientstat(TELOPT_LINEMODE, WONT, 0);
 819                                 /*
 820                                  * If linemode did not get turned off
 821                                  * then don't tell peer that we did.
 822                                  * Breaking here forces a wont SGA to
 823                                  * be returned.
 824                                  */
 825                                 if (linemode)
 826                                         break;
 827                         }
 828 #else
 829                         turn_on_sga = 0;
 830 #endif  /* defined(LINEMODE) && defined(KLUDGELINEMODE) */
 831                         changeok++;
 832                         break;
 833
 834                 case TELOPT_STATUS:
 835                         changeok++;
 836                         break;
 837
 838                 case TELOPT_TM:
 839                         /*
 840                          * Special case for TM.  We send a WILL, but
 841                          * pretend we sent a WONT.
 842                          */
 843                         send_will(option, 0);
 844                         set_my_want_state_wont(option);
 845                         set_my_state_wont(option);
 846                         return;
 847
 848                 case TELOPT_LOGOUT:
 849                         /*
 850                          * When we get a LOGOUT option, respond
 851                          * with a WILL LOGOUT, make sure that
 852                          * it gets written out to the network,
 853                          * and then just go away...
 854                          */
 855                         set_my_want_state_will(TELOPT_LOGOUT);
 856                         send_will(TELOPT_LOGOUT, 0);
 857                         set_my_state_will(TELOPT_LOGOUT);
 858                         (void)netflush();
 859                         cleanup(0);
 860                         /* NOT REACHED */
 861                         break;
 862
 863                 case TELOPT_LINEMODE:
 864                 case TELOPT_TTYPE:
 865                 case TELOPT_NAWS:
 866                 case TELOPT_TSPEED:
 867                 case TELOPT_LFLOW:
 868                 case TELOPT_XDISPLOC:
 869 #ifdef  TELOPT_ENVIRON
 870                 case TELOPT_NEW_ENVIRON:
 871 #endif
 872                 case TELOPT_OLD_ENVIRON:
 873                 default:
 874                         break;
 875                 }
 876                 if (changeok) {
 877                         set_my_want_state_will(option);
 878                         send_will(option, 0);
 879                 } else {
 880                         will_wont_resp[option]++;
 881                         send_wont(option, 0);
 882                 }
 883         }
 884         set_my_state_will(option);
 885
 886 }  /* end of dooption */
 887
 888 void
 889 send_wont(int option, int init)
 890 {
 891         if (init) {
 892                 if ((will_wont_resp[option] == 0 && my_state_is_wont(option)) ||
 893                     my_want_state_is_wont(option))
 894                         return;
 895                 set_my_want_state_wont(option);
 896                 will_wont_resp[option]++;
 897         }
 898         output_data((const char *)wont, option);
 899
 900         DIAG(TD_OPTIONS, printoption("td: send wont", option));
 901 }
 902
 903 void
 904 dontoption(int option)
 905 {
 906         /*
 907          * Process client input.
 908          */
 909
 910
 911         DIAG(TD_OPTIONS, printoption("td: recv dont", option));
 912
 913         if (will_wont_resp[option]) {
 914                 will_wont_resp[option]--;
 915                 if (will_wont_resp[option] && my_state_is_wont(option))
 916                         will_wont_resp[option]--;
 917         }
 918         if ((will_wont_resp[option] == 0) && (my_want_state_is_will(option))) {
 919                 switch (option) {
 920                 case TELOPT_BINARY:
 921                         init_termbuf();
 922                         tty_binaryout(0);
 923                         set_termbuf();
 924                         break;
 925
 926                 case TELOPT_ECHO:       /* we should stop echoing */
 927 #ifdef  LINEMODE
 928 # ifdef KLUDGELINEMODE
 929                         if ((lmodetype != REAL_LINEMODE) &&
 930                             (lmodetype != KLUDGE_LINEMODE))
 931 # else
 932                         if (his_state_is_wont(TELOPT_LINEMODE))
 933 # endif
 934 #endif
 935                         {
 936                                 init_termbuf();
 937                                 tty_setecho(0);
 938                                 set_termbuf();
 939                         }
 940                         break;
 941
 942                 case TELOPT_SGA:
 943 #if     defined(LINEMODE) && defined(KLUDGELINEMODE)
 944                         /*
 945                          * If kludge linemode is in use, then we
 946                          * must process an incoming do SGA for
 947                          * linemode purposes.
 948                          */
 949                         if ((lmodetype == KLUDGE_LINEMODE) ||
 950                             (lmodetype == KLUDGE_OK)) {
 951                                 /*
 952                                  * The client is asking us to turn
 953                                  * linemode on.
 954                                  */
 955                                 lmodetype = KLUDGE_LINEMODE;
 956                                 clientstat(TELOPT_LINEMODE, WILL, 0);
 957                                 /*
 958                                  * If we did not turn line mode on,
 959                                  * then what do we say?  Will SGA?
 960                                  * This violates design of telnet.
 961                                  * Gross.  Very Gross.
 962                                  */
 963                         }
 964                         break;
 965 #else
 966                         set_my_want_state_wont(option);
 967                         if (my_state_is_will(option))
 968                                 send_wont(option, 0);
 969                         set_my_state_wont(option);
 970                         if (turn_on_sga ^= 1)
 971                                 send_will(option, 1);
 972                         return;
 973 #endif  /* defined(LINEMODE) && defined(KLUDGELINEMODE) */
 974
 975                 default:
 976                         break;
 977                 }
 978
 979                 set_my_want_state_wont(option);
 980                 if (my_state_is_will(option))
 981                         send_wont(option, 0);
 982         }
 983         set_my_state_wont(option);
 984
 985 }  /* end of dontoption */
 986
 987 #ifdef  ENV_HACK
 988 int env_ovar = -1;
 989 int env_ovalue = -1;
 990 #else   /* ENV_HACK */
 991 # define env_ovar OLD_ENV_VAR
 992 # define env_ovalue OLD_ENV_VALUE
 993 #endif  /* ENV_HACK */
 994
 995 /* envvarok(char*) */
 996 /* check that variable is safe to pass to login or shell */
 997 static int
 998 envvarok(char *varp)
 999 {
1000
1001         if (strcmp(varp, "TERMCAP") &&  /* to prevent a security hole */
1002             strcmp(varp, "TERMINFO") && /* with tgetent */
1003             strcmp(varp, "TERMPATH") &&
1004             strcmp(varp, "HOME") &&     /* to prevent the tegetent bug  */
1005             strncmp(varp, "LD_", strlen("LD_")) &&      /* most systems */
1006             strncmp(varp, "_RLD_", strlen("_RLD_")) &&  /* IRIX */
1007             strcmp(varp, "LIBPATH") &&                  /* AIX */
1008             strcmp(varp, "ENV") &&
1009             strcmp(varp, "BASH_ENV") &&
1010             strcmp(varp, "IFS") &&
1011             strncmp(varp, "KRB5", strlen("KRB5")) &&    /* Krb5 */
1012             /*
1013              * The above case is a catch-all for now.  Here are some of
1014              * the specific ones we must avoid passing, at least until
1015              * we can prove it can be done safely.  Keep this list
1016              * around un case someone wants to remove the catch-all.
1017              */
1018             strcmp(varp, "KRB5_CONFIG") &&              /* Krb5 */
1019             strcmp(varp, "KRB5CCNAME") &&               /* Krb5 */
1020             strcmp(varp, "KRB5_KTNAME") &&              /* Krb5 */
1021             strcmp(varp, "KRBTKFILE") &&                /* Krb4 */
1022             strcmp(varp, "KRB_CONF") &&                 /* CNS 4 */
1023             strcmp(varp, "KRB_REALMS") &&               /* CNS 4 */
1024             strcmp(varp, "RESOLV_HOST_CONF"))           /* Linux */
1025                 return (1);
1026         else {
1027                 syslog(LOG_INFO, "Rejected the attempt to modify the "
1028                     "environment variable \"%s\"", varp);
1029                 return (0);
1030         }
1031 }
1032
1033 /*
1034  * suboption()
1035  *
1036  *      Look at the sub-option buffer, and try to be helpful to the other
1037  * side.
1038  *
1039  *      Currently we recognize:
1040  *
1041  *      Terminal type is
1042  *      Linemode
1043  *      Window size
1044  *      Terminal speed
1045  */
1046 void
1047 suboption(void)
1048 {
1049     int subchar;
1050
1051     DIAG(TD_OPTIONS, {netflush(); printsub('<', subpointer, SB_LEN()+2);});
1052
1053     subchar = SB_GET();
1054     switch (subchar) {
1055     case TELOPT_TSPEED: {
1056         int xspeed, rspeed;
1057
1058         if (his_state_is_wont(TELOPT_TSPEED))   /* Ignore if option disabled */
1059                 break;
1060
1061         settimer(tspeedsubopt);
1062
1063         if (SB_EOF() || SB_GET() != TELQUAL_IS)
1064                 return;
1065
1066         xspeed = atoi((char *)subpointer);
1067
1068         while (SB_GET() != ',' && !SB_EOF());
1069         if (SB_EOF())
1070                 return;
1071
1072         rspeed = atoi((char *)subpointer);
1073         clientstat(TELOPT_TSPEED, xspeed, rspeed);
1074
1075         break;
1076
1077     }  /* end of case TELOPT_TSPEED */
1078
1079     case TELOPT_TTYPE: {                /* Yaaaay! */
1080         static char terminalname[41];
1081
1082         if (his_state_is_wont(TELOPT_TTYPE))    /* Ignore if option disabled */
1083                 break;
1084         settimer(ttypesubopt);
1085
1086         if (SB_EOF() || SB_GET() != TELQUAL_IS) {
1087             return;             /* ??? XXX but, this is the most robust */
1088         }
1089
1090         terminaltype = terminalname;
1091
1092         while ((terminaltype < (terminalname + sizeof terminalname-1)) &&
1093                                                                     !SB_EOF()) {
1094             int c;
1095
1096             c = SB_GET();
1097             if (isupper(c)) {
1098                 c = tolower(c);
1099             }
1100             *terminaltype++ = c;    /* accumulate name */
1101         }
1102         *terminaltype = 0;
1103         terminaltype = terminalname;
1104         break;
1105     }  /* end of case TELOPT_TTYPE */
1106
1107     case TELOPT_NAWS: {
1108         int xwinsize, ywinsize;
1109
1110         if (his_state_is_wont(TELOPT_NAWS))     /* Ignore if option disabled */
1111                 break;
1112
1113         if (SB_EOF())
1114                 return;
1115         xwinsize = SB_GET() << 8;
1116         if (SB_EOF())
1117                 return;
1118         xwinsize |= SB_GET();
1119         if (SB_EOF())
1120                 return;
1121         ywinsize = SB_GET() << 8;
1122         if (SB_EOF())
1123                 return;
1124         ywinsize |= SB_GET();
1125         clientstat(TELOPT_NAWS, xwinsize, ywinsize);
1126
1127         break;
1128
1129     }  /* end of case TELOPT_NAWS */
1130
1131 #ifdef  LINEMODE
1132     case TELOPT_LINEMODE: {
1133         int request;
1134
1135         if (his_state_is_wont(TELOPT_LINEMODE)) /* Ignore if option disabled */
1136                 break;
1137         /*
1138          * Process linemode suboptions.
1139          */
1140         if (SB_EOF())
1141             break;              /* garbage was sent */
1142         request = SB_GET();     /* get will/wont */
1143
1144         if (SB_EOF())
1145             break;              /* another garbage check */
1146
1147         if (request == LM_SLC) {  /* SLC is not preceeded by WILL or WONT */
1148                 /*
1149                  * Process suboption buffer of slc's
1150                  */
1151                 start_slc(1);
1152                 do_opt_slc(subpointer, subend - subpointer);
1153                 (void) end_slc(0);
1154                 break;
1155         } else if (request == LM_MODE) {
1156                 if (SB_EOF())
1157                     return;
1158                 useeditmode = SB_GET();  /* get mode flag */
1159                 clientstat(LM_MODE, 0, 0);
1160                 break;
1161         }
1162
1163         if (SB_EOF())
1164             break;
1165         switch (SB_GET()) {  /* what suboption? */
1166         case LM_FORWARDMASK:
1167                 /*
1168                  * According to spec, only server can send request for
1169                  * forwardmask, and client can only return a positive response.
1170                  * So don't worry about it.
1171                  */
1172
1173         default:
1174                 break;
1175         }
1176         break;
1177     }  /* end of case TELOPT_LINEMODE */
1178 #endif
1179     case TELOPT_STATUS: {
1180         int mode;
1181
1182         if (SB_EOF())
1183             break;
1184         mode = SB_GET();
1185         switch (mode) {
1186         case TELQUAL_SEND:
1187             if (my_state_is_will(TELOPT_STATUS))
1188                 send_status();
1189             break;
1190
1191         case TELQUAL_IS:
1192             break;
1193
1194         default:
1195             break;
1196         }
1197         break;
1198     }  /* end of case TELOPT_STATUS */
1199
1200     case TELOPT_XDISPLOC: {
1201         if (SB_EOF() || SB_GET() != TELQUAL_IS)
1202                 return;
1203         settimer(xdisplocsubopt);
1204         subpointer[SB_LEN()] = '\0';
1205         if (setenv("DISPLAY", (char *)subpointer, 1) == -1)
1206                 syslog(LOG_ERR, "setenv: cannot set DISPLAY=%s: %m", (char *)subpointer);
1207         break;
1208     }  /* end of case TELOPT_XDISPLOC */
1209
1210 #ifdef  TELOPT_NEW_ENVIRON
1211     case TELOPT_NEW_ENVIRON:
1212 #endif
1213     case TELOPT_OLD_ENVIRON: {
1214         int c;
1215         char *cp, *varp, *valp;
1216
1217         if (SB_EOF())
1218                 return;
1219         c = SB_GET();
1220         if (c == TELQUAL_IS) {
1221                 if (subchar == TELOPT_OLD_ENVIRON)
1222                         settimer(oenvironsubopt);
1223                 else
1224                         settimer(environsubopt);
1225         } else if (c != TELQUAL_INFO) {
1226                 return;
1227         }
1228
1229 #ifdef  TELOPT_NEW_ENVIRON
1230         if (subchar == TELOPT_NEW_ENVIRON) {
1231             while (!SB_EOF()) {
1232                 c = SB_GET();
1233                 if ((c == NEW_ENV_VAR) || (c == ENV_USERVAR))
1234                         break;
1235             }
1236         } else
1237 #endif
1238         {
1239 #ifdef  ENV_HACK
1240             /*
1241              * We only want to do this if we haven't already decided
1242              * whether or not the other side has its VALUE and VAR
1243              * reversed.
1244              */
1245             if (env_ovar < 0) {
1246                 int last = -1;          /* invalid value */
1247                 int empty = 0;
1248                 int got_var = 0, got_value = 0, got_uservar = 0;
1249
1250                 /*
1251                  * The other side might have its VALUE and VAR values
1252                  * reversed.  To be interoperable, we need to determine
1253                  * which way it is.  If the first recognized character
1254                  * is a VAR or VALUE, then that will tell us what
1255                  * type of client it is.  If the fist recognized
1256                  * character is a USERVAR, then we continue scanning
1257                  * the suboption looking for two consecutive
1258                  * VAR or VALUE fields.  We should not get two
1259                  * consecutive VALUE fields, so finding two
1260                  * consecutive VALUE or VAR fields will tell us
1261                  * what the client is.
1262                  */
1263                 SB_SAVE();
1264                 while (!SB_EOF()) {
1265                         c = SB_GET();
1266                         switch(c) {
1267                         case OLD_ENV_VAR:
1268                                 if (last < 0 || last == OLD_ENV_VAR
1269                                     || (empty && (last == OLD_ENV_VALUE)))
1270                                         goto env_ovar_ok;
1271                                 got_var++;
1272                                 last = OLD_ENV_VAR;
1273                                 break;
1274                         case OLD_ENV_VALUE:
1275                                 if (last < 0 || last == OLD_ENV_VALUE
1276                                     || (empty && (last == OLD_ENV_VAR)))
1277                                         goto env_ovar_wrong;
1278                                 got_value++;
1279                                 last = OLD_ENV_VALUE;
1280                                 break;
1281                         case ENV_USERVAR:
1282                                 /* count strings of USERVAR as one */
1283                                 if (last != ENV_USERVAR)
1284                                         got_uservar++;
1285                                 if (empty) {
1286                                         if (last == OLD_ENV_VALUE)
1287                                                 goto env_ovar_ok;
1288                                         if (last == OLD_ENV_VAR)
1289                                                 goto env_ovar_wrong;
1290                                 }
1291                                 last = ENV_USERVAR;
1292                                 break;
1293                         case ENV_ESC:
1294                                 if (!SB_EOF())
1295                                         c = SB_GET();
1296                                 /* FALL THROUGH */
1297                         default:
1298                                 empty = 0;
1299                                 continue;
1300                         }
1301                         empty = 1;
1302                 }
1303                 if (empty) {
1304                         if (last == OLD_ENV_VALUE)
1305                                 goto env_ovar_ok;
1306                         if (last == OLD_ENV_VAR)
1307                                 goto env_ovar_wrong;
1308                 }
1309                 /*
1310                  * Ok, the first thing was a USERVAR, and there
1311                  * are not two consecutive VAR or VALUE commands,
1312                  * and none of the VAR or VALUE commands are empty.
1313                  * If the client has sent us a well-formed option,
1314                  * then the number of VALUEs received should always
1315                  * be less than or equal to the number of VARs and
1316                  * USERVARs received.
1317                  *
1318                  * If we got exactly as many VALUEs as VARs and
1319                  * USERVARs, the client has the same definitions.
1320                  *
1321                  * If we got exactly as many VARs as VALUEs and
1322                  * USERVARS, the client has reversed definitions.
1323                  */
1324                 if (got_uservar + got_var == got_value) {
1325             env_ovar_ok:
1326                         env_ovar = OLD_ENV_VAR;
1327                         env_ovalue = OLD_ENV_VALUE;
1328                 } else if (got_uservar + got_value == got_var) {
1329             env_ovar_wrong:
1330                         env_ovar = OLD_ENV_VALUE;
1331                         env_ovalue = OLD_ENV_VAR;
1332                         DIAG(TD_OPTIONS,
1333                             output_data("ENVIRON VALUE and VAR are reversed!\r\n"));
1334
1335                 }
1336             }
1337             SB_RESTORE();
1338 #endif
1339
1340             while (!SB_EOF()) {
1341                 c = SB_GET();
1342                 if ((c == env_ovar) || (c == ENV_USERVAR))
1343                         break;
1344             }
1345         }
1346
1347         if (SB_EOF())
1348                 return;
1349
1350         cp = varp = (char *)subpointer;
1351         valp = 0;
1352
1353         while (!SB_EOF()) {
1354                 c = SB_GET();
1355                 if (subchar == TELOPT_OLD_ENVIRON) {
1356                         if (c == env_ovar)
1357                                 c = NEW_ENV_VAR;
1358                         else if (c == env_ovalue)
1359                                 c = NEW_ENV_VALUE;
1360                 }
1361                 switch (c) {
1362
1363                 case NEW_ENV_VALUE:
1364                         *cp = '\0';
1365                         cp = valp = (char *)subpointer;
1366                         break;
1367
1368                 case NEW_ENV_VAR:
1369                 case ENV_USERVAR:
1370                         *cp = '\0';
1371                         if (envvarok(varp)) {
1372                                 if (valp) {
1373                                         if (setenv(varp, valp, 1) == -1)
1374                                                 syslog(LOG_ERR, "setenv: cannot set %s=%s: %m", varp, valp);
1375                                 }
1376                                 else
1377                                         unsetenv(varp);
1378                         }
1379                         cp = varp = (char *)subpointer;
1380                         valp = 0;
1381                         break;
1382
1383                 case ENV_ESC:
1384                         if (SB_EOF())
1385                                 break;
1386                         c = SB_GET();
1387                         /* FALL THROUGH */
1388                 default:
1389                         *cp++ = c;
1390                         break;
1391                 }
1392         }
1393         *cp = '\0';
1394         if (envvarok(varp)) {
1395                 if (valp) {
1396                         if (setenv(varp, valp, 1) == -1)
1397                                 syslog(LOG_ERR, "setenv: cannot set %s=%s: %m", varp, valp);
1398                 }
1399                 else
1400                         unsetenv(varp);
1401         }
1402         break;
1403     }  /* end of case TELOPT_NEW_ENVIRON */
1404
1405     default:
1406         break;
1407     }  /* end of switch */
1408
1409 }  /* end of suboption */
1410
1411 static void
1412 doclientstat(void)
1413 {
1414         clientstat(TELOPT_LINEMODE, WILL, 0);
1415 }
1416
1417 #define ADD(c)   *ncp++ = c
1418 #define ADD_DATA(c) { *ncp++ = c; if (c == SE || c == IAC) *ncp++ = c; }
1419 void
1420 send_status(void)
1421 {
1422         unsigned char statusbuf[256];
1423         unsigned char *ncp;
1424         unsigned char i;
1425
1426         ncp = statusbuf;
1427
1428         netflush();     /* get rid of anything waiting to go out */
1429
1430         ADD(IAC);
1431         ADD(SB);
1432         ADD(TELOPT_STATUS);
1433         ADD(TELQUAL_IS);
1434
1435         /*
1436          * We check the want_state rather than the current state,
1437          * because if we received a DO/WILL for an option that we
1438          * don't support, and the other side didn't send a DONT/WONT
1439          * in response to our WONT/DONT, then the "state" will be
1440          * WILL/DO, and the "want_state" will be WONT/DONT.  We
1441          * need to go by the latter.
1442          */
1443         for (i = 0; i < (unsigned char)NTELOPTS; i++) {
1444                 if (my_want_state_is_will(i)) {
1445                         ADD(WILL);
1446                         ADD_DATA(i);
1447                         if (i == IAC)
1448                                 ADD(IAC);
1449                 }
1450                 if (his_want_state_is_will(i)) {
1451                         ADD(DO);
1452                         ADD_DATA(i);
1453                         if (i == IAC)
1454                                 ADD(IAC);
1455                 }
1456         }
1457
1458         if (his_want_state_is_will(TELOPT_LFLOW)) {
1459                 ADD(SB);
1460                 ADD(TELOPT_LFLOW);
1461                 if (flowmode) {
1462                         ADD(LFLOW_ON);
1463                 } else {
1464                         ADD(LFLOW_OFF);
1465                 }
1466                 ADD(SE);
1467
1468                 if (restartany >= 0) {
1469                         ADD(SB);
1470                         ADD(TELOPT_LFLOW);
1471                         if (restartany) {
1472                                 ADD(LFLOW_RESTART_ANY);
1473                         } else {
1474                                 ADD(LFLOW_RESTART_XON);
1475                         }
1476                         ADD(SE);
1477                 }
1478         }
1479
1480 #ifdef  LINEMODE
1481         if (his_want_state_is_will(TELOPT_LINEMODE)) {
1482                 unsigned char *cp, *cpe;
1483                 int len;
1484
1485                 ADD(SB);
1486                 ADD(TELOPT_LINEMODE);
1487                 ADD(LM_MODE);
1488                 ADD_DATA(editmode);
1489                 ADD(SE);
1490
1491                 ADD(SB);
1492                 ADD(TELOPT_LINEMODE);
1493                 ADD(LM_SLC);
1494                 start_slc(0);
1495                 send_slc();
1496                 len = end_slc(&cp);
1497                 for (cpe = cp + len; cp < cpe; cp++)
1498                         ADD_DATA(*cp);
1499                 ADD(SE);
1500         }
1501 #endif  /* LINEMODE */
1502
1503         ADD(IAC);
1504         ADD(SE);
1505
1506         output_datalen(statusbuf, ncp - statusbuf);
1507         netflush();     /* Send it on its way */
1508
1509         DIAG(TD_OPTIONS,
1510                 {printsub('>', statusbuf, ncp - statusbuf); netflush();});
1511 }
1512
1513 /*
1514  * This function appends data to nfrontp and advances nfrontp.
1515  * Returns the number of characters written altogether (the
1516  * buffer may have been flushed in the process).
1517  */
1518
1519 int
1520 output_data(const char *format, ...)
1521 {
1522         va_list args;
1523         int len;
1524         char *buf;
1525
1526         va_start(args, format);
1527         if ((len = vasprintf(&buf, format, args)) == -1)
1528                 return -1;
1529         output_datalen(buf, len);
1530         va_end(args);
1531         free(buf);
1532         return (len);
1533 }
1534
1535 void
1536 output_datalen(const char *buf, int len)
1537 {
1538         int remaining, copied;
1539
1540         remaining = BUFSIZ - (nfrontp - netobuf);
1541         while (len > 0) {
1542                 /* Free up enough space if the room is too low*/
1543                 if ((len > BUFSIZ ? BUFSIZ : len) > remaining) {
1544                         netflush();
1545                         remaining = BUFSIZ - (nfrontp - netobuf);
1546                 }
1547
1548                 /* Copy out as much as will fit */
1549                 copied = remaining > len ? len : remaining;
1550                 memmove(nfrontp, buf, copied);
1551                 nfrontp += copied;
1552                 len -= copied;
1553                 remaining -= copied;
1554                 buf += copied;
1555         }
1556         return;
1557 }