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 #include <arpa/telnet.h>
  25 #include <netinet/in.h>
  26 #include "libbb.h"
  27
  28 #ifdef DOTRACE
  29 #define TRACE(x, y) do { if (x) printf y; } while (0)
  30 #else
  31 #define TRACE(x, y)
  32 #endif
  33
  34 enum {
  35         DATABUFSIZE = 128,
  36         IACBUFSIZE  = 128,
  37
  38         CHM_TRY = 0,
  39         CHM_ON = 1,
  40         CHM_OFF = 2,
  41
  42         UF_ECHO = 0x01,
  43         UF_SGA = 0x02,
  44
  45         TS_NORMAL = 0,
  46         TS_COPY = 1,
  47         TS_IAC = 2,
  48         TS_OPT = 3,
  49         TS_SUB1 = 4,
  50         TS_SUB2 = 5,
  51         TS_CR = 6,
  52 };
  53
  54 typedef unsigned char byte;
  55
  56 enum { netfd = 3 };
  57
  58 struct globals {
  59         int     iaclen; /* could even use byte, but it's a loss on x86 */
  60         byte    telstate; /* telnet negotiation state from network input */
  61         byte    telwish;  /* DO, DONT, WILL, WONT */
  62         byte    charmode;
  63         byte    telflags;
  64         byte    do_termios;
  65 #if ENABLE_FEATURE_TELNET_TTYPE
  66         char    *ttype;
  67 #endif
  68 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
  69         const char *autologin;
  70 #endif
  71 #if ENABLE_FEATURE_AUTOWIDTH
  72         unsigned win_width, win_height;
  73 #endif
  74         /* same buffer used both for network and console read/write */
  75         char    buf[DATABUFSIZE];
  76         /* buffer to handle telnet negotiations */
  77         char    iacbuf[IACBUFSIZE];
  78         struct termios termios_def;
  79         struct termios termios_raw;
  80 } FIX_ALIASING;
  81 #define G (*(struct globals*)&bb_common_bufsiz1)
  82 #define INIT_G() do { \
  83         struct G_sizecheck { \
  84                 char G_sizecheck[sizeof(G) > COMMON_BUFSIZE ? -1 : 1]; \
  85         }; \
  86 } while (0)
  87
  88
  89 static void rawmode(void);
  90 static void cookmode(void);
  91 static void do_linemode(void);
  92 static void will_charmode(void);
  93 static void telopt(byte c);
  94 static void subneg(byte c);
  95
  96 static void iac_flush(void)
  97 {
  98         write(netfd, G.iacbuf, G.iaclen);
  99         G.iaclen = 0;
 100 }
 101
 102 #define write_str(fd, str) write(fd, str, sizeof(str) - 1)
 103
 104 static void doexit(int ev) NORETURN;
 105 static void doexit(int ev)
 106 {
 107         cookmode();
 108         exit(ev);
 109 }
 110
 111 static void con_escape(void)
 112 {
 113         char b;
 114
 115         if (bb_got_signal) /* came from line mode... go raw */
 116                 rawmode();
 117
 118         write_str(1, "\r\nConsole escape. Commands are:\r\n\n"
 119                         " l     go to line mode\r\n"
 120                         " c     go to character mode\r\n"
 121                         " z     suspend telnet\r\n"
 122                         " e     exit telnet\r\n");
 123
 124         if (read(STDIN_FILENO, &b, 1) <= 0)
 125                 doexit(EXIT_FAILURE);
 126
 127         switch (b) {
 128         case 'l':
 129                 if (!bb_got_signal) {
 130                         do_linemode();
 131                         goto ret;
 132                 }
 133                 break;
 134         case 'c':
 135                 if (bb_got_signal) {
 136                         will_charmode();
 137                         goto ret;
 138                 }
 139                 break;
 140         case 'z':
 141                 cookmode();
 142                 kill(0, SIGTSTP);
 143                 rawmode();
 144                 break;
 145         case 'e':
 146                 doexit(EXIT_SUCCESS);
 147         }
 148
 149         write_str(1, "continuing...\r\n");
 150
 151         if (bb_got_signal)
 152                 cookmode();
 153  ret:
 154         bb_got_signal = 0;
 155 }
 156
 157 static void handle_net_output(int len)
 158 {
 159         /* here we could do smart tricks how to handle 0xFF:s in output
 160          * stream like writing twice every sequence of FF:s (thus doing
 161          * many write()s. But I think interactive telnet application does
 162          * not need to be 100% 8-bit clean, so changing every 0xff:s to
 163          * 0x7f:s
 164          *
 165          * 2002-mar-21, Przemyslaw Czerpak (druzus@polbox.com)
 166          * I don't agree.
 167          * first - I cannot use programs like sz/rz
 168          * second - the 0x0D is sent as one character and if the next
 169          *      char is 0x0A then it's eaten by a server side.
 170          * third - why do you have to make 'many write()s'?
 171          *      I don't understand.
 172          * So I implemented it. It's really useful for me. I hope that
 173          * other people will find it interesting too.
 174          */
 175         byte outbuf[2 * DATABUFSIZE];
 176         byte *p = (byte*)G.buf;
 177         int j = 0;
 178
 179         for (; len > 0; len--, p++) {
 180                 byte c = *p;
 181                 if (c == 0x1d) {
 182                         con_escape();
 183                         return;
 184                 }
 185                 outbuf[j++] = c;
 186                 if (c == IAC)
 187                         outbuf[j++] = c; /* IAC -> IAC IAC */
 188                 else if (c == '\r')
 189                         outbuf[j++] = '\0'; /* CR -> CR NUL */
 190         }
 191         if (j > 0)
 192                 full_write(netfd, outbuf, j);
 193 }
 194
 195 static void handle_net_input(int len)
 196 {
 197         int i;
 198         int cstart = 0;
 199
 200         for (i = 0; i < len; i++) {
 201                 byte c = G.buf[i];
 202
 203                 if (G.telstate == TS_NORMAL) { /* most typical state */
 204                         if (c == IAC) {
 205                                 cstart = i;
 206                                 G.telstate = TS_IAC;
 207                         }
 208                         else if (c == '\r') {
 209                                 cstart = i + 1;
 210                                 G.telstate = TS_CR;
 211                         }
 212                         /* No IACs were seen so far, no need to copy
 213                          * bytes within G.buf: */
 214                         continue;
 215                 }
 216
 217                 switch (G.telstate) {
 218                 case TS_CR:
 219                         /* Prev char was CR. If cur one is NUL, ignore it.
 220                          * See RFC 1123 section 3.3.1 for discussion of telnet EOL handling.
 221                          */
 222                         G.telstate = TS_COPY;
 223                         if (c == '\0')
 224                                 break;
 225                         /* else: fall through - need to handle CR IAC ... properly */
 226
 227                 case TS_COPY: /* Prev char was ordinary */
 228                         /* Similar to NORMAL, but in TS_COPY we need to copy bytes */
 229                         if (c == IAC)
 230                                 G.telstate = TS_IAC;
 231                         else
 232                                 G.buf[cstart++] = c;
 233                         if (c == '\r')
 234                                 G.telstate = TS_CR;
 235                         break;
 236
 237                 case TS_IAC: /* Prev char was IAC */
 238                         if (c == IAC) { /* IAC IAC -> one IAC */
 239                                 G.buf[cstart++] = c;
 240                                 G.telstate = TS_COPY;
 241                                 break;
 242                         }
 243                         /* else */
 244                         switch (c) {
 245                         case SB:
 246                                 G.telstate = TS_SUB1;
 247                                 break;
 248                         case DO:
 249                         case DONT:
 250                         case WILL:
 251                         case WONT:
 252                                 G.telwish = c;
 253                                 G.telstate = TS_OPT;
 254                                 break;
 255                         /* DATA MARK must be added later */
 256                         default:
 257                                 G.telstate = TS_COPY;
 258                         }
 259                         break;
 260
 261                 case TS_OPT: /* Prev chars were IAC WILL/WONT/DO/DONT */
 262                         telopt(c);
 263                         G.telstate = TS_COPY;
 264                         break;
 265
 266                 case TS_SUB1: /* Subnegotiation */
 267                 case TS_SUB2: /* Subnegotiation */
 268                         subneg(c); /* can change G.telstate */
 269                         break;
 270                 }
 271         }
 272
 273         if (G.telstate != TS_NORMAL) {
 274                 /* We had some IACs, or CR */
 275                 if (G.iaclen)
 276                         iac_flush();
 277                 if (G.telstate == TS_COPY) /* we aren't in the middle of IAC */
 278                         G.telstate = TS_NORMAL;
 279                 len = cstart;
 280         }
 281
 282         if (len)
 283                 full_write(STDOUT_FILENO, G.buf, len);
 284 }
 285
 286 static void put_iac(int c)
 287 {
 288         G.iacbuf[G.iaclen++] = c;
 289 }
 290
 291 static void put_iac2(byte wwdd, byte c)
 292 {
 293         if (G.iaclen + 3 > IACBUFSIZE)
 294                 iac_flush();
 295
 296         put_iac(IAC);
 297         put_iac(wwdd);
 298         put_iac(c);
 299 }
 300
 301 #if ENABLE_FEATURE_TELNET_TTYPE
 302 static void put_iac_subopt(byte c, char *str)
 303 {
 304         int len = strlen(str) + 6;   // ( 2 + 1 + 1 + strlen + 2 )
 305
 306         if (G.iaclen + len > IACBUFSIZE)
 307                 iac_flush();
 308
 309         put_iac(IAC);
 310         put_iac(SB);
 311         put_iac(c);
 312         put_iac(0);
 313
 314         while (*str)
 315                 put_iac(*str++);
 316
 317         put_iac(IAC);
 318         put_iac(SE);
 319 }
 320 #endif
 321
 322 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
 323 static void put_iac_subopt_autologin(void)
 324 {
 325         int len = strlen(G.autologin) + 6;      // (2 + 1 + 1 + strlen + 2)
 326         const char *p = "USER";
 327
 328         if (G.iaclen + len > IACBUFSIZE)
 329                 iac_flush();
 330
 331         put_iac(IAC);
 332         put_iac(SB);
 333         put_iac(TELOPT_NEW_ENVIRON);
 334         put_iac(TELQUAL_IS);
 335         put_iac(NEW_ENV_VAR);
 336
 337         while (*p)
 338                 put_iac(*p++);
 339
 340         put_iac(NEW_ENV_VALUE);
 341
 342         p = G.autologin;
 343         while (*p)
 344                 put_iac(*p++);
 345
 346         put_iac(IAC);
 347         put_iac(SE);
 348 }
 349 #endif
 350
 351 #if ENABLE_FEATURE_AUTOWIDTH
 352 static void put_iac_naws(byte c, int x, int y)
 353 {
 354         if (G.iaclen + 9 > IACBUFSIZE)
 355                 iac_flush();
 356
 357         put_iac(IAC);
 358         put_iac(SB);
 359         put_iac(c);
 360
 361         put_iac((x >> 8) & 0xff);
 362         put_iac(x & 0xff);
 363         put_iac((y >> 8) & 0xff);
 364         put_iac(y & 0xff);
 365
 366         put_iac(IAC);
 367         put_iac(SE);
 368 }
 369 #endif
 370
 371 static char const escapecharis[] ALIGN1 = "\r\nEscape character is ";
 372
 373 static void setConMode(void)
 374 {
 375         if (G.telflags & UF_ECHO) {
 376                 if (G.charmode == CHM_TRY) {
 377                         G.charmode = CHM_ON;
 378                         printf("\r\nEntering character mode%s'^]'.\r\n", escapecharis);
 379                         rawmode();
 380                 }
 381         } else {
 382                 if (G.charmode != CHM_OFF) {
 383                         G.charmode = CHM_OFF;
 384                         printf("\r\nEntering line mode%s'^C'.\r\n", escapecharis);
 385                         cookmode();
 386                 }
 387         }
 388 }
 389
 390 static void will_charmode(void)
 391 {
 392         G.charmode = CHM_TRY;
 393         G.telflags |= (UF_ECHO | UF_SGA);
 394         setConMode();
 395
 396         put_iac2(DO, TELOPT_ECHO);
 397         put_iac2(DO, TELOPT_SGA);
 398         iac_flush();
 399 }
 400
 401 static void do_linemode(void)
 402 {
 403         G.charmode = CHM_TRY;
 404         G.telflags &= ~(UF_ECHO | UF_SGA);
 405         setConMode();
 406
 407         put_iac2(DONT, TELOPT_ECHO);
 408         put_iac2(DONT, TELOPT_SGA);
 409         iac_flush();
 410 }
 411
 412 static void to_notsup(char c)
 413 {
 414         if (G.telwish == WILL)
 415                 put_iac2(DONT, c);
 416         else if (G.telwish == DO)
 417                 put_iac2(WONT, c);
 418 }
 419
 420 static void to_echo(void)
 421 {
 422         /* if server requests ECHO, don't agree */
 423         if (G.telwish == DO) {
 424                 put_iac2(WONT, TELOPT_ECHO);
 425                 return;
 426         }
 427         if (G.telwish == DONT)
 428                 return;
 429
 430         if (G.telflags & UF_ECHO) {
 431                 if (G.telwish == WILL)
 432                         return;
 433         } else if (G.telwish == WONT)
 434                 return;
 435
 436         if (G.charmode != CHM_OFF)
 437                 G.telflags ^= UF_ECHO;
 438
 439         if (G.telflags & UF_ECHO)
 440                 put_iac2(DO, TELOPT_ECHO);
 441         else
 442                 put_iac2(DONT, TELOPT_ECHO);
 443
 444         setConMode();
 445         full_write1_str("\r\n");  /* sudden modec */
 446 }
 447
 448 static void to_sga(void)
 449 {
 450         /* daemon always sends will/wont, client do/dont */
 451
 452         if (G.telflags & UF_SGA) {
 453                 if (G.telwish == WILL)
 454                         return;
 455         } else if (G.telwish == WONT)
 456                 return;
 457
 458         G.telflags ^= UF_SGA; /* toggle */
 459         if (G.telflags & UF_SGA)
 460                 put_iac2(DO, TELOPT_SGA);
 461         else
 462                 put_iac2(DONT, TELOPT_SGA);
 463 }
 464
 465 #if ENABLE_FEATURE_TELNET_TTYPE
 466 static void to_ttype(void)
 467 {
 468         /* Tell server we will (or won't) do TTYPE */
 469         if (G.ttype)
 470                 put_iac2(WILL, TELOPT_TTYPE);
 471         else
 472                 put_iac2(WONT, TELOPT_TTYPE);
 473 }
 474 #endif
 475
 476 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
 477 static void to_new_environ(void)
 478 {
 479         /* Tell server we will (or will not) do AUTOLOGIN */
 480         if (G.autologin)
 481                 put_iac2(WILL, TELOPT_NEW_ENVIRON);
 482         else
 483                 put_iac2(WONT, TELOPT_NEW_ENVIRON);
 484 }
 485 #endif
 486
 487 #if ENABLE_FEATURE_AUTOWIDTH
 488 static void to_naws(void)
 489 {
 490         /* Tell server we will do NAWS */
 491         put_iac2(WILL, TELOPT_NAWS);
 492 }
 493 #endif
 494
 495 static void telopt(byte c)
 496 {
 497         switch (c) {
 498         case TELOPT_ECHO:
 499                 to_echo(); break;
 500         case TELOPT_SGA:
 501                 to_sga(); break;
 502 #if ENABLE_FEATURE_TELNET_TTYPE
 503         case TELOPT_TTYPE:
 504                 to_ttype(); break;
 505 #endif
 506 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
 507         case TELOPT_NEW_ENVIRON:
 508                 to_new_environ(); break;
 509 #endif
 510 #if ENABLE_FEATURE_AUTOWIDTH
 511         case TELOPT_NAWS:
 512                 to_naws();
 513                 put_iac_naws(c, G.win_width, G.win_height);
 514                 break;
 515 #endif
 516         default:
 517                 to_notsup(c);
 518                 break;
 519         }
 520 }
 521
 522 /* subnegotiation -- ignore all (except TTYPE,NAWS) */
 523 static void subneg(byte c)
 524 {
 525         switch (G.telstate) {
 526         case TS_SUB1:
 527                 if (c == IAC)
 528                         G.telstate = TS_SUB2;
 529 #if ENABLE_FEATURE_TELNET_TTYPE
 530                 else
 531                 if (c == TELOPT_TTYPE && G.ttype)
 532                         put_iac_subopt(TELOPT_TTYPE, G.ttype);
 533 #endif
 534 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
 535                 else
 536                 if (c == TELOPT_NEW_ENVIRON && G.autologin)
 537                         put_iac_subopt_autologin();
 538 #endif
 539                 break;
 540         case TS_SUB2:
 541                 if (c == SE) {
 542                         G.telstate = TS_COPY;
 543                         return;
 544                 }
 545                 G.telstate = TS_SUB1;
 546                 break;
 547         }
 548 }
 549
 550 static void rawmode(void)
 551 {
 552         if (G.do_termios)
 553                 tcsetattr(0, TCSADRAIN, &G.termios_raw);
 554 }
 555
 556 static void cookmode(void)
 557 {
 558         if (G.do_termios)
 559                 tcsetattr(0, TCSADRAIN, &G.termios_def);
 560 }
 561
 562 int telnet_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 563 int telnet_main(int argc UNUSED_PARAM, char **argv)
 564 {
 565         char *host;
 566         int port;
 567         int len;
 568         struct pollfd ufds[2];
 569
 570         INIT_G();
 571
 572 #if ENABLE_FEATURE_AUTOWIDTH
 573         get_terminal_width_height(0, &G.win_width, &G.win_height);
 574 #endif
 575
 576 #if ENABLE_FEATURE_TELNET_TTYPE
 577         G.ttype = getenv("TERM");
 578 #endif
 579
 580         if (tcgetattr(0, &G.termios_def) >= 0) {
 581                 G.do_termios = 1;
 582                 G.termios_raw = G.termios_def;
 583                 cfmakeraw(&G.termios_raw);
 584         }
 585
 586 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
 587         if (1 & getopt32(argv, "al:", &G.autologin))
 588                 G.autologin = getenv("USER");
 589         argv += optind;
 590 #else
 591         argv++;
 592 #endif
 593         if (!*argv)
 594                 bb_show_usage();
 595         host = *argv++;
 596         port = bb_lookup_port(*argv ? *argv++ : "telnet", "tcp", 23);
 597         if (*argv) /* extra params?? */
 598                 bb_show_usage();
 599
 600         xmove_fd(create_and_connect_stream_or_die(host, port), netfd);
 601
 602         setsockopt(netfd, SOL_SOCKET, SO_KEEPALIVE, &const_int_1, sizeof(const_int_1));
 603
 604         signal(SIGINT, record_signo);
 605
 606         ufds[0].fd = STDIN_FILENO;
 607         ufds[0].events = POLLIN;
 608         ufds[1].fd = netfd;
 609         ufds[1].events = POLLIN;
 610
 611         while (1) {
 612                 if (poll(ufds, 2, -1) < 0) {
 613                         /* error, ignore and/or log something, bay go to loop */
 614                         if (bb_got_signal)
 615                                 con_escape();
 616                         else
 617                                 sleep(1);
 618                         continue;
 619                 }
 620
 621 // FIXME: reads can block. Need full bidirectional buffering.
 622
 623                 if (ufds[0].revents) {
 624                         len = safe_read(STDIN_FILENO, G.buf, DATABUFSIZE);
 625                         if (len <= 0)
 626                                 doexit(EXIT_SUCCESS);
 627                         TRACE(0, ("Read con: %d\n", len));
 628                         handle_net_output(len);
 629                 }
 630
 631                 if (ufds[1].revents) {
 632                         len = safe_read(netfd, G.buf, DATABUFSIZE);
 633                         if (len <= 0) {
 634                                 full_write1_str("Connection closed by foreign host\r\n");
 635                                 doexit(EXIT_FAILURE);
 636                         }
 637                         TRACE(0, ("Read netfd (%d): %d\n", netfd, len));
 638                         handle_net_input(len);
 639                 }
 640         } /* while (1) */
 641 }