networking/telnet.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * telnet implementation for busybox
   4  *
   5  * Author: Tomi Ollila <too@iki.fi>
   6  * Copyright (C) 1994-2000 by Tomi Ollila
   7  *
   8  * Created: Thu Apr  7 13:29:41 1994 too
   9  * Last modified: Fri Jun  9 14:34:24 2000 too
  10  *
  11  * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
  12  *
  13  * HISTORY
  14  * Revision 3.1  1994/04/17  11:31:54  too
  15  * initial revision
  16  * Modified 2000/06/13 for inclusion into BusyBox by Erik Andersen <andersen@codepoet.org>
  17  * Modified 2001/05/07 to add ability to pass TTYPE to remote host by Jim McQuillan
  18  * <jam@ltsp.org>
  19  * Modified 2004/02/11 to add ability to pass the USER variable to remote host
  20  * by Fernando Silveira <swrh@gmx.net>
  21  *
  22  */
  23
  24 #include <termios.h>
  25 #include <unistd.h>
  26 #include <errno.h>
  27 #include <stdlib.h>
  28 #include <stdarg.h>
  29 #include <string.h>
  30 #include <signal.h>
  31 #include <arpa/telnet.h>
  32 #include <sys/types.h>
  33 #include <sys/socket.h>
  34 #include <netinet/in.h>
  35 #include "busybox.h"
  36
  37 #if 0
  38 enum { DOTRACE = 1 };
  39 #endif
  40
  41 #ifdef DOTRACE
  42 #include <arpa/inet.h> /* for inet_ntoa()... */
  43 #define TRACE(x, y) do { if (x) printf y; } while (0)
  44 #else
  45 #define TRACE(x, y)
  46 #endif
  47
  48 #define DATABUFSIZE  128
  49 #define IACBUFSIZE   128
  50
  51 enum {
  52         CHM_TRY = 0,
  53         CHM_ON = 1,
  54         CHM_OFF = 2,
  55
  56         UF_ECHO = 0x01,
  57         UF_SGA = 0x02,
  58
  59         TS_0 = 1,
  60         TS_IAC = 2,
  61         TS_OPT = 3,
  62         TS_SUB1 = 4,
  63         TS_SUB2 = 5,
  64 };
  65
  66 #define WriteCS(fd, str) write(fd, str, sizeof str -1)
  67
  68 typedef unsigned char byte;
  69
  70 /* use globals to reduce size ??? */ /* test this hypothesis later */
  71 static struct Globalvars {
  72         int             netfd; /* console fd:s are 0 and 1 (and 2) */
  73     /* same buffer used both for network and console read/write */
  74         char    buf[DATABUFSIZE]; /* allocating so static size is smaller */
  75         byte    telstate; /* telnet negotiation state from network input */
  76         byte    telwish;  /* DO, DONT, WILL, WONT */
  77         byte    charmode;
  78         byte    telflags;
  79         byte    gotsig;
  80         byte    do_termios;
  81         /* buffer to handle telnet negotiations */
  82         char    iacbuf[IACBUFSIZE];
  83         short   iaclen; /* could even use byte */
  84         struct termios termios_def;
  85         struct termios termios_raw;
  86 } G;
  87
  88 #define xUSE_GLOBALVAR_PTR /* xUSE... -> don't use :D (makes smaller code) */
  89
  90 #ifdef USE_GLOBALVAR_PTR
  91 struct Globalvars * Gptr;
  92 #define G (*Gptr)
  93 #endif
  94
  95 static inline void iacflush(void)
  96 {
  97         write(G.netfd, G.iacbuf, G.iaclen);
  98         G.iaclen = 0;
  99 }
 100
 101 /* Function prototypes */
 102 static void rawmode(void);
 103 static void cookmode(void);
 104 static void do_linemode(void);
 105 static void will_charmode(void);
 106 static void telopt(byte c);
 107 static int subneg(byte c);
 108
 109 /* Some globals */
 110 static int one = 1;
 111
 112 #ifdef CONFIG_FEATURE_TELNET_TTYPE
 113 static char *ttype;
 114 #endif
 115
 116 #ifdef CONFIG_FEATURE_TELNET_AUTOLOGIN
 117 static const char *autologin;
 118 #endif
 119
 120 #ifdef CONFIG_FEATURE_AUTOWIDTH
 121 static int win_width, win_height;
 122 #endif
 123
 124 static void doexit(int ev)
 125 {
 126         cookmode();
 127         exit(ev);
 128 }
 129
 130 static void conescape(void)
 131 {
 132         char b;
 133
 134         if (G.gotsig)   /* came from line  mode... go raw */
 135                 rawmode();
 136
 137         WriteCS(1, "\r\nConsole escape. Commands are:\r\n\n"
 138                         " l     go to line mode\r\n"
 139                         " c     go to character mode\r\n"
 140                         " z     suspend telnet\r\n"
 141                         " e     exit telnet\r\n");
 142
 143         if (read(0, &b, 1) <= 0)
 144                 doexit(1);
 145
 146         switch (b)
 147         {
 148         case 'l':
 149                 if (!G.gotsig)
 150                 {
 151                         do_linemode();
 152                         goto rrturn;
 153                 }
 154                 break;
 155         case 'c':
 156                 if (G.gotsig)
 157                 {
 158                         will_charmode();
 159                         goto rrturn;
 160                 }
 161                 break;
 162         case 'z':
 163                 cookmode();
 164                 kill(0, SIGTSTP);
 165                 rawmode();
 166                 break;
 167         case 'e':
 168                 doexit(0);
 169         }
 170
 171         WriteCS(1, "continuing...\r\n");
 172
 173         if (G.gotsig)
 174                 cookmode();
 175
 176  rrturn:
 177         G.gotsig = 0;
 178
 179 }
 180 static void handlenetoutput(int len)
 181 {
 182         /*      here we could do smart tricks how to handle 0xFF:s in output
 183          *      stream  like writing twice every sequence of FF:s (thus doing
 184          *      many write()s. But I think interactive telnet application does
 185          *      not need to be 100% 8-bit clean, so changing every 0xff:s to
 186          *      0x7f:s
 187          *
 188          *      2002-mar-21, Przemyslaw Czerpak (druzus@polbox.com)
 189          *      I don't agree.
 190          *      first - I cannot use programs like sz/rz
 191          *      second - the 0x0D is sent as one character and if the next
 192          *               char is 0x0A then it's eaten by a server side.
 193          *      third - whay doy you have to make 'many write()s'?
 194          *              I don't understand.
 195          *      So I implemented it. It's realy useful for me. I hope that
 196          *      others people will find it interesting to.
 197          */
 198
 199         int i, j;
 200         byte * p = (byte*)G.buf;
 201         byte outbuf[4*DATABUFSIZE];
 202
 203         for (i = len, j = 0; i > 0; i--, p++)
 204         {
 205                 if (*p == 0x1d)
 206                 {
 207                         conescape();
 208                         return;
 209                 }
 210                 outbuf[j++] = *p;
 211                 if (*p == 0xff)
 212                     outbuf[j++] = 0xff;
 213                 else if (*p == 0x0d)
 214                     outbuf[j++] = 0x00;
 215         }
 216         if (j > 0 )
 217             write(G.netfd, outbuf, j);
 218 }
 219
 220
 221 static void handlenetinput(int len)
 222 {
 223         int i;
 224         int cstart = 0;
 225
 226         for (i = 0; i < len; i++)
 227         {
 228                 byte c = G.buf[i];
 229
 230                 if (G.telstate == 0) /* most of the time state == 0 */
 231                 {
 232                         if (c == IAC)
 233                         {
 234                                 cstart = i;
 235                                 G.telstate = TS_IAC;
 236                         }
 237                 }
 238                 else
 239                         switch (G.telstate)
 240                          {
 241                          case TS_0:
 242                                  if (c == IAC)
 243                                          G.telstate = TS_IAC;
 244                                  else
 245                                          G.buf[cstart++] = c;
 246                                  break;
 247
 248                          case TS_IAC:
 249                                  if (c == IAC) /* IAC IAC -> 0xFF */
 250                                  {
 251                                          G.buf[cstart++] = c;
 252                                          G.telstate = TS_0;
 253                                          break;
 254                                  }
 255                                  /* else */
 256                                  switch (c)
 257                                  {
 258                                  case SB:
 259                                          G.telstate = TS_SUB1;
 260                                          break;
 261                                  case DO:
 262                                  case DONT:
 263                                  case WILL:
 264                                  case WONT:
 265                                          G.telwish =  c;
 266                                          G.telstate = TS_OPT;
 267                                          break;
 268                                  default:
 269                                          G.telstate = TS_0;     /* DATA MARK must be added later */
 270                                  }
 271                                  break;
 272                          case TS_OPT: /* WILL, WONT, DO, DONT */
 273                                  telopt(c);
 274                                  G.telstate = TS_0;
 275                                  break;
 276                          case TS_SUB1: /* Subnegotiation */
 277                          case TS_SUB2: /* Subnegotiation */
 278                                  if (subneg(c))
 279                                          G.telstate = TS_0;
 280                                  break;
 281                          }
 282         }
 283         if (G.telstate)
 284         {
 285                 if (G.iaclen)                   iacflush();
 286                 if (G.telstate == TS_0) G.telstate = 0;
 287
 288                 len = cstart;
 289         }
 290
 291         if (len)
 292                 write(1, G.buf, len);
 293 }
 294
 295
 296 /* ******************************* */
 297
 298 static inline void putiac(int c)
 299 {
 300         G.iacbuf[G.iaclen++] = c;
 301 }
 302
 303
 304 static void putiac2(byte wwdd, byte c)
 305 {
 306         if (G.iaclen + 3 > IACBUFSIZE)
 307                 iacflush();
 308
 309         putiac(IAC);
 310         putiac(wwdd);
 311         putiac(c);
 312 }
 313
 314 #if 0
 315 static void putiac1(byte c)
 316 {
 317         if (G.iaclen + 2 > IACBUFSIZE)
 318                 iacflush();
 319
 320         putiac(IAC);
 321         putiac(c);
 322 }
 323 #endif
 324
 325 #ifdef CONFIG_FEATURE_TELNET_TTYPE
 326 static void putiac_subopt(byte c, char *str)
 327 {
 328         int     len = strlen(str) + 6;   // ( 2 + 1 + 1 + strlen + 2 )
 329
 330         if (G.iaclen + len > IACBUFSIZE)
 331                 iacflush();
 332
 333         putiac(IAC);
 334         putiac(SB);
 335         putiac(c);
 336         putiac(0);
 337
 338         while(*str)
 339                 putiac(*str++);
 340
 341         putiac(IAC);
 342         putiac(SE);
 343 }
 344 #endif
 345
 346 #ifdef CONFIG_FEATURE_TELNET_AUTOLOGIN
 347 static void putiac_subopt_autologin(void)
 348 {
 349         int len = strlen(autologin) + 6;        // (2 + 1 + 1 + strlen + 2)
 350         char *user = "USER";
 351
 352         if (G.iaclen + len > IACBUFSIZE)
 353                 iacflush();
 354
 355         putiac(IAC);
 356         putiac(SB);
 357         putiac(TELOPT_NEW_ENVIRON);
 358         putiac(TELQUAL_IS);
 359         putiac(NEW_ENV_VAR);
 360
 361         while(*user)
 362                 putiac(*user++);
 363
 364         putiac(NEW_ENV_VALUE);
 365
 366         while(*autologin)
 367                 putiac(*autologin++);
 368
 369         putiac(IAC);
 370         putiac(SE);
 371 }
 372 #endif
 373
 374 #ifdef CONFIG_FEATURE_AUTOWIDTH
 375 static void putiac_naws(byte c, int x, int y)
 376 {
 377         if (G.iaclen + 9 > IACBUFSIZE)
 378                 iacflush();
 379
 380         putiac(IAC);
 381         putiac(SB);
 382         putiac(c);
 383
 384         putiac((x >> 8) & 0xff);
 385         putiac(x & 0xff);
 386         putiac((y >> 8) & 0xff);
 387         putiac(y & 0xff);
 388
 389         putiac(IAC);
 390         putiac(SE);
 391 }
 392 #endif
 393
 394 /* void putiacstring (subneg strings) */
 395
 396 /* ******************************* */
 397
 398 static char const escapecharis[] = "\r\nEscape character is ";
 399
 400 static void setConMode(void)
 401 {
 402         if (G.telflags & UF_ECHO)
 403         {
 404                 if (G.charmode == CHM_TRY) {
 405                         G.charmode = CHM_ON;
 406                         printf("\r\nEntering character mode%s'^]'.\r\n", escapecharis);
 407                         rawmode();
 408                 }
 409         }
 410         else
 411         {
 412                 if (G.charmode != CHM_OFF) {
 413                         G.charmode = CHM_OFF;
 414                         printf("\r\nEntering line mode%s'^C'.\r\n", escapecharis);
 415                         cookmode();
 416                 }
 417         }
 418 }
 419
 420 /* ******************************* */
 421
 422 static void will_charmode(void)
 423 {
 424         G.charmode = CHM_TRY;
 425         G.telflags |= (UF_ECHO | UF_SGA);
 426         setConMode();
 427
 428         putiac2(DO, TELOPT_ECHO);
 429         putiac2(DO, TELOPT_SGA);
 430         iacflush();
 431 }
 432
 433 static void do_linemode(void)
 434 {
 435         G.charmode = CHM_TRY;
 436         G.telflags &= ~(UF_ECHO | UF_SGA);
 437         setConMode();
 438
 439         putiac2(DONT, TELOPT_ECHO);
 440         putiac2(DONT, TELOPT_SGA);
 441         iacflush();
 442 }
 443
 444 /* ******************************* */
 445
 446 static inline void to_notsup(char c)
 447 {
 448         if      (G.telwish == WILL)     putiac2(DONT, c);
 449         else if (G.telwish == DO)       putiac2(WONT, c);
 450 }
 451
 452 static inline void to_echo(void)
 453 {
 454         /* if server requests ECHO, don't agree */
 455         if      (G.telwish == DO) {     putiac2(WONT, TELOPT_ECHO);     return; }
 456         else if (G.telwish == DONT)     return;
 457
 458         if (G.telflags & UF_ECHO)
 459         {
 460                 if (G.telwish == WILL)
 461                         return;
 462         }
 463         else
 464                 if (G.telwish == WONT)
 465                         return;
 466
 467         if (G.charmode != CHM_OFF)
 468                 G.telflags ^= UF_ECHO;
 469
 470         if (G.telflags & UF_ECHO)
 471                 putiac2(DO, TELOPT_ECHO);
 472         else
 473                 putiac2(DONT, TELOPT_ECHO);
 474
 475         setConMode();
 476         WriteCS(1, "\r\n");  /* sudden modec */
 477 }
 478
 479 static inline void to_sga(void)
 480 {
 481         /* daemon always sends will/wont, client do/dont */
 482
 483         if (G.telflags & UF_SGA)
 484         {
 485                 if (G.telwish == WILL)
 486                         return;
 487         }
 488         else
 489                 if (G.telwish == WONT)
 490                         return;
 491
 492         if ((G.telflags ^= UF_SGA) & UF_SGA) /* toggle */
 493                 putiac2(DO, TELOPT_SGA);
 494         else
 495                 putiac2(DONT, TELOPT_SGA);
 496
 497         return;
 498 }
 499
 500 #ifdef CONFIG_FEATURE_TELNET_TTYPE
 501 static inline void to_ttype(void)
 502 {
 503         /* Tell server we will (or won't) do TTYPE */
 504
 505         if(ttype)
 506                 putiac2(WILL, TELOPT_TTYPE);
 507         else
 508                 putiac2(WONT, TELOPT_TTYPE);
 509
 510         return;
 511 }
 512 #endif
 513
 514 #ifdef CONFIG_FEATURE_TELNET_AUTOLOGIN
 515 static inline void to_new_environ(void)
 516 {
 517         /* Tell server we will (or will not) do AUTOLOGIN */
 518
 519         if (autologin)
 520                 putiac2(WILL, TELOPT_NEW_ENVIRON);
 521         else
 522                 putiac2(WONT, TELOPT_NEW_ENVIRON);
 523
 524         return;
 525 }
 526 #endif
 527
 528 #ifdef CONFIG_FEATURE_AUTOWIDTH
 529 static inline void to_naws(void)
 530 {
 531         /* Tell server we will do NAWS */
 532         putiac2(WILL, TELOPT_NAWS);
 533         return;
 534 }
 535 #endif
 536
 537 static void telopt(byte c)
 538 {
 539         switch (c)
 540         {
 541                 case TELOPT_ECHO:               to_echo();      break;
 542                 case TELOPT_SGA:                to_sga();       break;
 543 #ifdef CONFIG_FEATURE_TELNET_TTYPE
 544                 case TELOPT_TTYPE:              to_ttype();break;
 545 #endif
 546 #ifdef CONFIG_FEATURE_TELNET_AUTOLOGIN
 547                 case TELOPT_NEW_ENVIRON:        to_new_environ();       break;
 548 #endif
 549 #ifdef CONFIG_FEATURE_AUTOWIDTH
 550                 case TELOPT_NAWS:               to_naws();
 551                                                                 putiac_naws(c, win_width, win_height);
 552                                                                 break;
 553 #endif
 554                 default:                                to_notsup(c);
 555                                                                 break;
 556         }
 557 }
 558
 559
 560 /* ******************************* */
 561
 562 /* subnegotiation -- ignore all (except TTYPE,NAWS) */
 563
 564 static int subneg(byte c)
 565 {
 566         switch (G.telstate)
 567         {
 568         case TS_SUB1:
 569                 if (c == IAC)
 570                         G.telstate = TS_SUB2;
 571 #ifdef CONFIG_FEATURE_TELNET_TTYPE
 572                 else
 573                 if (c == TELOPT_TTYPE)
 574                         putiac_subopt(TELOPT_TTYPE,ttype);
 575 #endif
 576 #ifdef CONFIG_FEATURE_TELNET_AUTOLOGIN
 577                 else
 578                 if (c == TELOPT_NEW_ENVIRON)
 579                         putiac_subopt_autologin();
 580 #endif
 581                 break;
 582         case TS_SUB2:
 583                 if (c == SE)
 584                         return TRUE;
 585                 G.telstate = TS_SUB1;
 586                 /* break; */
 587         }
 588         return FALSE;
 589 }
 590
 591 /* ******************************* */
 592
 593 static void fgotsig(int sig)
 594 {
 595         G.gotsig = sig;
 596 }
 597
 598
 599 static void rawmode(void)
 600 {
 601         if (G.do_termios) tcsetattr(0, TCSADRAIN, &G.termios_raw);
 602 }
 603
 604 static void cookmode(void)
 605 {
 606         if (G.do_termios) tcsetattr(0, TCSADRAIN, &G.termios_def);
 607 }
 608
 609 int telnet_main(int argc, char** argv)
 610 {
 611         int len;
 612         struct sockaddr_in s_in;
 613 #ifdef USE_POLL
 614         struct pollfd ufds[2];
 615 #else
 616         fd_set readfds;
 617         int maxfd;
 618 #endif
 619
 620 #ifdef CONFIG_FEATURE_AUTOWIDTH
 621         get_terminal_width_height(0, &win_width, &win_height);
 622 #endif
 623
 624 #ifdef CONFIG_FEATURE_TELNET_TTYPE
 625     ttype = getenv("TERM");
 626 #endif
 627
 628         memset(&G, 0, sizeof G);
 629
 630         if (tcgetattr(0, &G.termios_def) >= 0) {
 631                 G.do_termios = 1;
 632
 633                 G.termios_raw = G.termios_def;
 634                 cfmakeraw(&G.termios_raw);
 635         }
 636
 637         if (argc < 2)
 638                 bb_show_usage();
 639
 640 #ifdef CONFIG_FEATURE_TELNET_AUTOLOGIN
 641         if (1 & bb_getopt_ulflags(argc, argv, "al:", &autologin))
 642                 autologin = getenv("USER");
 643
 644         if (optind < argc) {
 645                 bb_lookup_host(&s_in, argv[optind++]);
 646                 s_in.sin_port = bb_lookup_port((optind < argc) ? argv[optind++] :
 647                                 "telnet", "tcp", 23);
 648                 if (optind < argc)
 649                         bb_show_usage();
 650         } else
 651                 bb_show_usage();
 652 #else
 653         bb_lookup_host(&s_in, argv[1]);
 654         s_in.sin_port = bb_lookup_port((argc == 3) ? argv[2] : "telnet", "tcp", 23);
 655 #endif
 656
 657         G.netfd = xconnect(&s_in);
 658
 659         setsockopt(G.netfd, SOL_SOCKET, SO_KEEPALIVE, &one, sizeof one);
 660
 661         signal(SIGINT, fgotsig);
 662
 663 #ifdef USE_POLL
 664         ufds[0].fd = 0; ufds[1].fd = G.netfd;
 665         ufds[0].events = ufds[1].events = POLLIN;
 666 #else
 667         FD_ZERO(&readfds);
 668         FD_SET(0, &readfds);
 669         FD_SET(G.netfd, &readfds);
 670         maxfd = G.netfd + 1;
 671 #endif
 672
 673         while (1)
 674         {
 675 #ifndef USE_POLL
 676                 fd_set rfds = readfds;
 677
 678                 switch (select(maxfd, &rfds, NULL, NULL, NULL))
 679 #else
 680                 switch (poll(ufds, 2, -1))
 681 #endif
 682                 {
 683                 case 0:
 684                         /* timeout */
 685                 case -1:
 686                         /* error, ignore and/or log something, bay go to loop */
 687                         if (G.gotsig)
 688                                 conescape();
 689                         else
 690                                 sleep(1);
 691                         break;
 692                 default:
 693
 694 #ifdef USE_POLL
 695                         if (ufds[0].revents) /* well, should check POLLIN, but ... */
 696 #else
 697                         if (FD_ISSET(0, &rfds))
 698 #endif
 699                         {
 700                                 len = read(0, G.buf, DATABUFSIZE);
 701
 702                                 if (len <= 0)
 703                                         doexit(0);
 704
 705                                 TRACE(0, ("Read con: %d\n", len));
 706
 707                                 handlenetoutput(len);
 708                         }
 709
 710 #ifdef USE_POLL
 711                         if (ufds[1].revents) /* well, should check POLLIN, but ... */
 712 #else
 713                         if (FD_ISSET(G.netfd, &rfds))
 714 #endif
 715                         {
 716                                 len = read(G.netfd, G.buf, DATABUFSIZE);
 717
 718                                 if (len <= 0)
 719                                 {
 720                                         WriteCS(1, "Connection closed by foreign host.\r\n");
 721                                         doexit(1);
 722                                 }
 723                                 TRACE(0, ("Read netfd (%d): %d\n", G.netfd, len));
 724
 725                                 handlenetinput(len);
 726                         }
 727                 }
 728         }
 729 }