release/src/router/busybox/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 GPLv2 or later, see file LICENSE in this source tree.
  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 //usage:#if ENABLE_FEATURE_TELNET_AUTOLOGIN
  25 //usage:#define telnet_trivial_usage
  26 //usage:       "[-a] [-l USER] HOST [PORT]"
  27 //usage:#define telnet_full_usage "\n\n"
  28 //usage:       "Connect to telnet server\n"
  29 //usage:     "\n        -a      Automatic login with $USER variable"
  30 //usage:     "\n        -l USER Automatic login as USER"
  31 //usage:
  32 //usage:#else
  33 //usage:#define telnet_trivial_usage
  34 //usage:       "HOST [PORT]"
  35 //usage:#define telnet_full_usage "\n\n"
  36 //usage:       "Connect to telnet server"
  37 //usage:#endif
  38
  39 #include <arpa/telnet.h>
  40 #include <netinet/in.h>
  41 #include "libbb.h"
  42
  43 #ifdef __BIONIC__
  44 /* should be in arpa/telnet.h */
  45 # define IAC         255  /* interpret as command: */
  46 # define DONT        254  /* you are not to use option */
  47 # define DO          253  /* please, you use option */
  48 # define WONT        252  /* I won't use option */
  49 # define WILL        251  /* I will use option */
  50 # define SB          250  /* interpret as subnegotiation */
  51 # define SE          240  /* end sub negotiation */
  52 # define TELOPT_ECHO   1  /* echo */
  53 # define TELOPT_SGA    3  /* suppress go ahead */
  54 # define TELOPT_TTYPE 24  /* terminal type */
  55 # define TELOPT_NAWS  31  /* window size */
  56 #endif
  57
  58 #ifdef DOTRACE
  59 # define TRACE(x, y) do { if (x) printf y; } while (0)
  60 #else
  61 # define TRACE(x, y)
  62 #endif
  63
  64 enum {
  65         DATABUFSIZE = 128,
  66         IACBUFSIZE  = 128,
  67
  68         CHM_TRY = 0,
  69         CHM_ON = 1,
  70         CHM_OFF = 2,
  71
  72         UF_ECHO = 0x01,
  73         UF_SGA = 0x02,
  74
  75         TS_NORMAL = 0,
  76         TS_COPY = 1,
  77         TS_IAC = 2,
  78         TS_OPT = 3,
  79         TS_SUB1 = 4,
  80         TS_SUB2 = 5,
  81         TS_CR = 6,
  82 };
  83
  84 typedef unsigned char byte;
  85
  86 enum { netfd = 3 };
  87
  88 struct globals {
  89         int     iaclen; /* could even use byte, but it's a loss on x86 */
  90         byte    telstate; /* telnet negotiation state from network input */
  91         byte    telwish;  /* DO, DONT, WILL, WONT */
  92         byte    charmode;
  93         byte    telflags;
  94         byte    do_termios;
  95 #if ENABLE_FEATURE_TELNET_TTYPE
  96         char    *ttype;
  97 #endif
  98 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
  99         const char *autologin;
 100 #endif
 101 #if ENABLE_FEATURE_AUTOWIDTH
 102         unsigned win_width, win_height;
 103 #endif
 104         /* same buffer used both for network and console read/write */
 105         char    buf[DATABUFSIZE];
 106         /* buffer to handle telnet negotiations */
 107         char    iacbuf[IACBUFSIZE];
 108         struct termios termios_def;
 109         struct termios termios_raw;
 110 } FIX_ALIASING;
 111 #define G (*(struct globals*)&bb_common_bufsiz1)
 112 #define INIT_G() do { \
 113         struct G_sizecheck { \
 114                 char G_sizecheck[sizeof(G) > COMMON_BUFSIZE ? -1 : 1]; \
 115         }; \
 116 } while (0)
 117
 118
 119 static void rawmode(void);
 120 static void cookmode(void);
 121 static void do_linemode(void);
 122 static void will_charmode(void);
 123 static void telopt(byte c);
 124 static void subneg(byte c);
 125
 126 static void iac_flush(void)
 127 {
 128         write(netfd, G.iacbuf, G.iaclen);
 129         G.iaclen = 0;
 130 }
 131
 132 #define write_str(fd, str) write(fd, str, sizeof(str) - 1)
 133
 134 static void doexit(int ev) NORETURN;
 135 static void doexit(int ev)
 136 {
 137         cookmode();
 138         exit(ev);
 139 }
 140
 141 static void con_escape(void)
 142 {
 143         char b;
 144
 145         if (bb_got_signal) /* came from line mode... go raw */
 146                 rawmode();
 147
 148         write_str(1, "\r\nConsole escape. Commands are:\r\n\n"
 149                         " l     go to line mode\r\n"
 150                         " c     go to character mode\r\n"
 151                         " z     suspend telnet\r\n"
 152                         " e     exit telnet\r\n");
 153
 154         if (read(STDIN_FILENO, &b, 1) <= 0)
 155                 doexit(EXIT_FAILURE);
 156
 157         switch (b) {
 158         case 'l':
 159                 if (!bb_got_signal) {
 160                         do_linemode();
 161                         goto ret;
 162                 }
 163                 break;
 164         case 'c':
 165                 if (bb_got_signal) {
 166                         will_charmode();
 167                         goto ret;
 168                 }
 169                 break;
 170         case 'z':
 171                 cookmode();
 172                 kill(0, SIGTSTP);
 173                 rawmode();
 174                 break;
 175         case 'e':
 176                 doexit(EXIT_SUCCESS);
 177         }
 178
 179         write_str(1, "continuing...\r\n");
 180
 181         if (bb_got_signal)
 182                 cookmode();
 183  ret:
 184         bb_got_signal = 0;
 185 }
 186
 187 static void handle_net_output(int len)
 188 {
 189         byte outbuf[2 * DATABUFSIZE];
 190         byte *dst = outbuf;
 191         byte *src = (byte*)G.buf;
 192         byte *end = src + len;
 193
 194         while (src < end) {
 195                 byte c = *src++;
 196                 if (c == 0x1d) {
 197                         con_escape();
 198                         return;
 199                 }
 200                 *dst = c;
 201                 if (c == IAC)
 202                         *++dst = c; /* IAC -> IAC IAC */
 203                 else
 204                 if (c == '\r' || c == '\n') {
 205                         /* Enter key sends '\r' in raw mode and '\n' in cooked one.
 206                          *
 207                          * See RFC 1123 3.3.1 Telnet End-of-Line Convention.
 208                          * Using CR LF instead of other allowed possibilities
 209                          * like CR NUL - easier to talk to HTTP/SMTP servers.
 210                          */
 211                         *dst = '\r'; /* Enter -> CR LF */
 212                         *++dst = '\n';
 213                 }
 214                 dst++;
 215         }
 216         if (dst - outbuf != 0)
 217                 full_write(netfd, outbuf, dst - outbuf);
 218 }
 219
 220 static void handle_net_input(int len)
 221 {
 222         int i;
 223         int cstart = 0;
 224
 225         for (i = 0; i < len; i++) {
 226                 byte c = G.buf[i];
 227
 228                 if (G.telstate == TS_NORMAL) { /* most typical state */
 229                         if (c == IAC) {
 230                                 cstart = i;
 231                                 G.telstate = TS_IAC;
 232                         }
 233                         else if (c == '\r') {
 234                                 cstart = i + 1;
 235                                 G.telstate = TS_CR;
 236                         }
 237                         /* No IACs were seen so far, no need to copy
 238                          * bytes within G.buf: */
 239                         continue;
 240                 }
 241
 242                 switch (G.telstate) {
 243                 case TS_CR:
 244                         /* Prev char was CR. If cur one is NUL, ignore it.
 245                          * See RFC 1123 section 3.3.1 for discussion of telnet EOL handling.
 246                          */
 247                         G.telstate = TS_COPY;
 248                         if (c == '\0')
 249                                 break;
 250                         /* else: fall through - need to handle CR IAC ... properly */
 251
 252                 case TS_COPY: /* Prev char was ordinary */
 253                         /* Similar to NORMAL, but in TS_COPY we need to copy bytes */
 254                         if (c == IAC)
 255                                 G.telstate = TS_IAC;
 256                         else
 257                                 G.buf[cstart++] = c;
 258                         if (c == '\r')
 259                                 G.telstate = TS_CR;
 260                         break;
 261
 262                 case TS_IAC: /* Prev char was IAC */
 263                         if (c == IAC) { /* IAC IAC -> one IAC */
 264                                 G.buf[cstart++] = c;
 265                                 G.telstate = TS_COPY;
 266                                 break;
 267                         }
 268                         /* else */
 269                         switch (c) {
 270                         case SB:
 271                                 G.telstate = TS_SUB1;
 272                                 break;
 273                         case DO:
 274                         case DONT:
 275                         case WILL:
 276                         case WONT:
 277                                 G.telwish = c;
 278                                 G.telstate = TS_OPT;
 279                                 break;
 280                         /* DATA MARK must be added later */
 281                         default:
 282                                 G.telstate = TS_COPY;
 283                         }
 284                         break;
 285
 286                 case TS_OPT: /* Prev chars were IAC WILL/WONT/DO/DONT */
 287                         telopt(c);
 288                         G.telstate = TS_COPY;
 289                         break;
 290
 291                 case TS_SUB1: /* Subnegotiation */
 292                 case TS_SUB2: /* Subnegotiation */
 293                         subneg(c); /* can change G.telstate */
 294                         break;
 295                 }
 296         }
 297
 298         if (G.telstate != TS_NORMAL) {
 299                 /* We had some IACs, or CR */
 300                 if (G.iaclen)
 301                         iac_flush();
 302                 if (G.telstate == TS_COPY) /* we aren't in the middle of IAC */
 303                         G.telstate = TS_NORMAL;
 304                 len = cstart;
 305         }
 306
 307         if (len)
 308                 full_write(STDOUT_FILENO, G.buf, len);
 309 }
 310
 311 static void put_iac(int c)
 312 {
 313         G.iacbuf[G.iaclen++] = c;
 314 }
 315
 316 static void put_iac2(byte wwdd, byte c)
 317 {
 318         if (G.iaclen + 3 > IACBUFSIZE)
 319                 iac_flush();
 320
 321         put_iac(IAC);
 322         put_iac(wwdd);
 323         put_iac(c);
 324 }
 325
 326 #if ENABLE_FEATURE_TELNET_TTYPE
 327 static void put_iac_subopt(byte c, char *str)
 328 {
 329         int len = strlen(str) + 6;   // ( 2 + 1 + 1 + strlen + 2 )
 330
 331         if (G.iaclen + len > IACBUFSIZE)
 332                 iac_flush();
 333
 334         put_iac(IAC);
 335         put_iac(SB);
 336         put_iac(c);
 337         put_iac(0);
 338
 339         while (*str)
 340                 put_iac(*str++);
 341
 342         put_iac(IAC);
 343         put_iac(SE);
 344 }
 345 #endif
 346
 347 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
 348 static void put_iac_subopt_autologin(void)
 349 {
 350         int len = strlen(G.autologin) + 6;      // (2 + 1 + 1 + strlen + 2)
 351         const char *p = "USER";
 352
 353         if (G.iaclen + len > IACBUFSIZE)
 354                 iac_flush();
 355
 356         put_iac(IAC);
 357         put_iac(SB);
 358         put_iac(TELOPT_NEW_ENVIRON);
 359         put_iac(TELQUAL_IS);
 360         put_iac(NEW_ENV_VAR);
 361
 362         while (*p)
 363                 put_iac(*p++);
 364
 365         put_iac(NEW_ENV_VALUE);
 366
 367         p = G.autologin;
 368         while (*p)
 369                 put_iac(*p++);
 370
 371         put_iac(IAC);
 372         put_iac(SE);
 373 }
 374 #endif
 375
 376 #if ENABLE_FEATURE_AUTOWIDTH
 377 static void put_iac_naws(byte c, int x, int y)
 378 {
 379         if (G.iaclen + 9 > IACBUFSIZE)
 380                 iac_flush();
 381
 382         put_iac(IAC);
 383         put_iac(SB);
 384         put_iac(c);
 385
 386         put_iac((x >> 8) & 0xff);
 387         put_iac(x & 0xff);
 388         put_iac((y >> 8) & 0xff);
 389         put_iac(y & 0xff);
 390
 391         put_iac(IAC);
 392         put_iac(SE);
 393 }
 394 #endif
 395
 396 static void setConMode(void)
 397 {
 398         if (G.telflags & UF_ECHO) {
 399                 if (G.charmode == CHM_TRY) {
 400                         G.charmode = CHM_ON;
 401                         printf("\r\nEntering %s mode"
 402                                 "\r\nEscape character is '^%c'.\r\n", "character", ']');
 403                         rawmode();
 404                 }
 405         } else {
 406                 if (G.charmode != CHM_OFF) {
 407                         G.charmode = CHM_OFF;
 408                         printf("\r\nEntering %s mode"
 409                                 "\r\nEscape character is '^%c'.\r\n", "line", 'C');
 410                         cookmode();
 411                 }
 412         }
 413 }
 414
 415 static void will_charmode(void)
 416 {
 417         G.charmode = CHM_TRY;
 418         G.telflags |= (UF_ECHO | UF_SGA);
 419         setConMode();
 420
 421         put_iac2(DO, TELOPT_ECHO);
 422         put_iac2(DO, TELOPT_SGA);
 423         iac_flush();
 424 }
 425
 426 static void do_linemode(void)
 427 {
 428         G.charmode = CHM_TRY;
 429         G.telflags &= ~(UF_ECHO | UF_SGA);
 430         setConMode();
 431
 432         put_iac2(DONT, TELOPT_ECHO);
 433         put_iac2(DONT, TELOPT_SGA);
 434         iac_flush();
 435 }
 436
 437 static void to_notsup(char c)
 438 {
 439         if (G.telwish == WILL)
 440                 put_iac2(DONT, c);
 441         else if (G.telwish == DO)
 442                 put_iac2(WONT, c);
 443 }
 444
 445 static void to_echo(void)
 446 {
 447         /* if server requests ECHO, don't agree */
 448         if (G.telwish == DO) {
 449                 put_iac2(WONT, TELOPT_ECHO);
 450                 return;
 451         }
 452         if (G.telwish == DONT)
 453                 return;
 454
 455         if (G.telflags & UF_ECHO) {
 456                 if (G.telwish == WILL)
 457                         return;
 458         } else if (G.telwish == WONT)
 459                 return;
 460
 461         if (G.charmode != CHM_OFF)
 462                 G.telflags ^= UF_ECHO;
 463
 464         if (G.telflags & UF_ECHO)
 465                 put_iac2(DO, TELOPT_ECHO);
 466         else
 467                 put_iac2(DONT, TELOPT_ECHO);
 468
 469         setConMode();
 470         full_write1_str("\r\n");  /* sudden modec */
 471 }
 472
 473 static void to_sga(void)
 474 {
 475         /* daemon always sends will/wont, client do/dont */
 476
 477         if (G.telflags & UF_SGA) {
 478                 if (G.telwish == WILL)
 479                         return;
 480         } else if (G.telwish == WONT)
 481                 return;
 482
 483         G.telflags ^= UF_SGA; /* toggle */
 484         if (G.telflags & UF_SGA)
 485                 put_iac2(DO, TELOPT_SGA);
 486         else
 487                 put_iac2(DONT, TELOPT_SGA);
 488 }
 489
 490 #if ENABLE_FEATURE_TELNET_TTYPE
 491 static void to_ttype(void)
 492 {
 493         /* Tell server we will (or won't) do TTYPE */
 494         if (G.ttype)
 495                 put_iac2(WILL, TELOPT_TTYPE);
 496         else
 497                 put_iac2(WONT, TELOPT_TTYPE);
 498 }
 499 #endif
 500
 501 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
 502 static void to_new_environ(void)
 503 {
 504         /* Tell server we will (or will not) do AUTOLOGIN */
 505         if (G.autologin)
 506                 put_iac2(WILL, TELOPT_NEW_ENVIRON);
 507         else
 508                 put_iac2(WONT, TELOPT_NEW_ENVIRON);
 509 }
 510 #endif
 511
 512 #if ENABLE_FEATURE_AUTOWIDTH
 513 static void to_naws(void)
 514 {
 515         /* Tell server we will do NAWS */
 516         put_iac2(WILL, TELOPT_NAWS);
 517 }
 518 #endif
 519
 520 static void telopt(byte c)
 521 {
 522         switch (c) {
 523         case TELOPT_ECHO:
 524                 to_echo(); break;
 525         case TELOPT_SGA:
 526                 to_sga(); break;
 527 #if ENABLE_FEATURE_TELNET_TTYPE
 528         case TELOPT_TTYPE:
 529                 to_ttype(); break;
 530 #endif
 531 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
 532         case TELOPT_NEW_ENVIRON:
 533                 to_new_environ(); break;
 534 #endif
 535 #if ENABLE_FEATURE_AUTOWIDTH
 536         case TELOPT_NAWS:
 537                 to_naws();
 538                 put_iac_naws(c, G.win_width, G.win_height);
 539                 break;
 540 #endif
 541         default:
 542                 to_notsup(c);
 543                 break;
 544         }
 545 }
 546
 547 /* subnegotiation -- ignore all (except TTYPE,NAWS) */
 548 static void subneg(byte c)
 549 {
 550         switch (G.telstate) {
 551         case TS_SUB1:
 552                 if (c == IAC)
 553                         G.telstate = TS_SUB2;
 554 #if ENABLE_FEATURE_TELNET_TTYPE
 555                 else
 556                 if (c == TELOPT_TTYPE && G.ttype)
 557                         put_iac_subopt(TELOPT_TTYPE, G.ttype);
 558 #endif
 559 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
 560                 else
 561                 if (c == TELOPT_NEW_ENVIRON && G.autologin)
 562                         put_iac_subopt_autologin();
 563 #endif
 564                 break;
 565         case TS_SUB2:
 566                 if (c == SE) {
 567                         G.telstate = TS_COPY;
 568                         return;
 569                 }
 570                 G.telstate = TS_SUB1;
 571                 break;
 572         }
 573 }
 574
 575 static void rawmode(void)
 576 {
 577         if (G.do_termios)
 578                 tcsetattr(0, TCSADRAIN, &G.termios_raw);
 579 }
 580
 581 static void cookmode(void)
 582 {
 583         if (G.do_termios)
 584                 tcsetattr(0, TCSADRAIN, &G.termios_def);
 585 }
 586
 587 int telnet_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 588 int telnet_main(int argc UNUSED_PARAM, char **argv)
 589 {
 590         char *host;
 591         int port;
 592         int len;
 593         struct pollfd ufds[2];
 594
 595         INIT_G();
 596
 597 #if ENABLE_FEATURE_AUTOWIDTH
 598         get_terminal_width_height(0, &G.win_width, &G.win_height);
 599 #endif
 600
 601 #if ENABLE_FEATURE_TELNET_TTYPE
 602         G.ttype = getenv("TERM");
 603 #endif
 604
 605         if (tcgetattr(0, &G.termios_def) >= 0) {
 606                 G.do_termios = 1;
 607                 G.termios_raw = G.termios_def;
 608                 cfmakeraw(&G.termios_raw);
 609         }
 610
 611 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
 612         if (1 & getopt32(argv, "al:", &G.autologin))
 613                 G.autologin = getenv("USER");
 614         argv += optind;
 615 #else
 616         argv++;
 617 #endif
 618         if (!*argv)
 619                 bb_show_usage();
 620         host = *argv++;
 621         port = bb_lookup_port(*argv ? *argv++ : "telnet", "tcp", 23);
 622         if (*argv) /* extra params?? */
 623                 bb_show_usage();
 624
 625         xmove_fd(create_and_connect_stream_or_die(host, port), netfd);
 626
 627         setsockopt(netfd, SOL_SOCKET, SO_KEEPALIVE, &const_int_1, sizeof(const_int_1));
 628
 629         signal(SIGINT, record_signo);
 630
 631         ufds[0].fd = STDIN_FILENO;
 632         ufds[0].events = POLLIN;
 633         ufds[1].fd = netfd;
 634         ufds[1].events = POLLIN;
 635
 636         while (1) {
 637                 if (poll(ufds, 2, -1) < 0) {
 638                         /* error, ignore and/or log something, bay go to loop */
 639                         if (bb_got_signal)
 640                                 con_escape();
 641                         else
 642                                 sleep(1);
 643                         continue;
 644                 }
 645
 646 // FIXME: reads can block. Need full bidirectional buffering.
 647
 648                 if (ufds[0].revents) {
 649                         len = safe_read(STDIN_FILENO, G.buf, DATABUFSIZE);
 650                         if (len <= 0)
 651                                 doexit(EXIT_SUCCESS);
 652                         TRACE(0, ("Read con: %d\n", len));
 653                         handle_net_output(len);
 654                 }
 655
 656                 if (ufds[1].revents) {
 657                         len = safe_read(netfd, G.buf, DATABUFSIZE);
 658                         if (len <= 0) {
 659                                 full_write1_str("Connection closed by foreign host\r\n");
 660                                 doexit(EXIT_FAILURE);
 661                         }
 662                         TRACE(0, ("Read netfd (%d): %d\n", netfd, len));
 663                         handle_net_input(len);
 664                 }
 665         } /* while (1) */
 666 }