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         /* here we could do smart tricks how to handle 0xFF:s in output
 190          * stream like writing twice every sequence of FF:s (thus doing
 191          * many write()s. But I think interactive telnet application does
 192          * not need to be 100% 8-bit clean, so changing every 0xff:s to
 193          * 0x7f:s
 194          *
 195          * 2002-mar-21, Przemyslaw Czerpak (druzus@polbox.com)
 196          * I don't agree.
 197          * first - I cannot use programs like sz/rz
 198          * second - the 0x0D is sent as one character and if the next
 199          *      char is 0x0A then it's eaten by a server side.
 200          * third - why do you have to make 'many write()s'?
 201          *      I don't understand.
 202          * So I implemented it. It's really useful for me. I hope that
 203          * other people will find it interesting too.
 204          */
 205         byte outbuf[2 * DATABUFSIZE];
 206         byte *p = (byte*)G.buf;
 207         int j = 0;
 208
 209         for (; len > 0; len--, p++) {
 210                 byte c = *p;
 211                 if (c == 0x1d) {
 212                         con_escape();
 213                         return;
 214                 }
 215                 outbuf[j++] = c;
 216                 if (c == IAC)
 217                         outbuf[j++] = c; /* IAC -> IAC IAC */
 218                 else if (c == '\r')
 219                         outbuf[j++] = '\0'; /* CR -> CR NUL */
 220         }
 221         if (j > 0)
 222                 full_write(netfd, outbuf, j);
 223 }
 224
 225 static void handle_net_input(int len)
 226 {
 227         int i;
 228         int cstart = 0;
 229
 230         for (i = 0; i < len; i++) {
 231                 byte c = G.buf[i];
 232
 233                 if (G.telstate == TS_NORMAL) { /* most typical state */
 234                         if (c == IAC) {
 235                                 cstart = i;
 236                                 G.telstate = TS_IAC;
 237                         }
 238                         else if (c == '\r') {
 239                                 cstart = i + 1;
 240                                 G.telstate = TS_CR;
 241                         }
 242                         /* No IACs were seen so far, no need to copy
 243                          * bytes within G.buf: */
 244                         continue;
 245                 }
 246
 247                 switch (G.telstate) {
 248                 case TS_CR:
 249                         /* Prev char was CR. If cur one is NUL, ignore it.
 250                          * See RFC 1123 section 3.3.1 for discussion of telnet EOL handling.
 251                          */
 252                         G.telstate = TS_COPY;
 253                         if (c == '\0')
 254                                 break;
 255                         /* else: fall through - need to handle CR IAC ... properly */
 256
 257                 case TS_COPY: /* Prev char was ordinary */
 258                         /* Similar to NORMAL, but in TS_COPY we need to copy bytes */
 259                         if (c == IAC)
 260                                 G.telstate = TS_IAC;
 261                         else
 262                                 G.buf[cstart++] = c;
 263                         if (c == '\r')
 264                                 G.telstate = TS_CR;
 265                         break;
 266
 267                 case TS_IAC: /* Prev char was IAC */
 268                         if (c == IAC) { /* IAC IAC -> one IAC */
 269                                 G.buf[cstart++] = c;
 270                                 G.telstate = TS_COPY;
 271                                 break;
 272                         }
 273                         /* else */
 274                         switch (c) {
 275                         case SB:
 276                                 G.telstate = TS_SUB1;
 277                                 break;
 278                         case DO:
 279                         case DONT:
 280                         case WILL:
 281                         case WONT:
 282                                 G.telwish = c;
 283                                 G.telstate = TS_OPT;
 284                                 break;
 285                         /* DATA MARK must be added later */
 286                         default:
 287                                 G.telstate = TS_COPY;
 288                         }
 289                         break;
 290
 291                 case TS_OPT: /* Prev chars were IAC WILL/WONT/DO/DONT */
 292                         telopt(c);
 293                         G.telstate = TS_COPY;
 294                         break;
 295
 296                 case TS_SUB1: /* Subnegotiation */
 297                 case TS_SUB2: /* Subnegotiation */
 298                         subneg(c); /* can change G.telstate */
 299                         break;
 300                 }
 301         }
 302
 303         if (G.telstate != TS_NORMAL) {
 304                 /* We had some IACs, or CR */
 305                 if (G.iaclen)
 306                         iac_flush();
 307                 if (G.telstate == TS_COPY) /* we aren't in the middle of IAC */
 308                         G.telstate = TS_NORMAL;
 309                 len = cstart;
 310         }
 311
 312         if (len)
 313                 full_write(STDOUT_FILENO, G.buf, len);
 314 }
 315
 316 static void put_iac(int c)
 317 {
 318         G.iacbuf[G.iaclen++] = c;
 319 }
 320
 321 static void put_iac2(byte wwdd, byte c)
 322 {
 323         if (G.iaclen + 3 > IACBUFSIZE)
 324                 iac_flush();
 325
 326         put_iac(IAC);
 327         put_iac(wwdd);
 328         put_iac(c);
 329 }
 330
 331 #if ENABLE_FEATURE_TELNET_TTYPE
 332 static void put_iac_subopt(byte c, char *str)
 333 {
 334         int len = strlen(str) + 6;   // ( 2 + 1 + 1 + strlen + 2 )
 335
 336         if (G.iaclen + len > IACBUFSIZE)
 337                 iac_flush();
 338
 339         put_iac(IAC);
 340         put_iac(SB);
 341         put_iac(c);
 342         put_iac(0);
 343
 344         while (*str)
 345                 put_iac(*str++);
 346
 347         put_iac(IAC);
 348         put_iac(SE);
 349 }
 350 #endif
 351
 352 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
 353 static void put_iac_subopt_autologin(void)
 354 {
 355         int len = strlen(G.autologin) + 6;      // (2 + 1 + 1 + strlen + 2)
 356         const char *p = "USER";
 357
 358         if (G.iaclen + len > IACBUFSIZE)
 359                 iac_flush();
 360
 361         put_iac(IAC);
 362         put_iac(SB);
 363         put_iac(TELOPT_NEW_ENVIRON);
 364         put_iac(TELQUAL_IS);
 365         put_iac(NEW_ENV_VAR);
 366
 367         while (*p)
 368                 put_iac(*p++);
 369
 370         put_iac(NEW_ENV_VALUE);
 371
 372         p = G.autologin;
 373         while (*p)
 374                 put_iac(*p++);
 375
 376         put_iac(IAC);
 377         put_iac(SE);
 378 }
 379 #endif
 380
 381 #if ENABLE_FEATURE_AUTOWIDTH
 382 static void put_iac_naws(byte c, int x, int y)
 383 {
 384         if (G.iaclen + 9 > IACBUFSIZE)
 385                 iac_flush();
 386
 387         put_iac(IAC);
 388         put_iac(SB);
 389         put_iac(c);
 390
 391         put_iac((x >> 8) & 0xff);
 392         put_iac(x & 0xff);
 393         put_iac((y >> 8) & 0xff);
 394         put_iac(y & 0xff);
 395
 396         put_iac(IAC);
 397         put_iac(SE);
 398 }
 399 #endif
 400
 401 static char const escapecharis[] ALIGN1 = "\r\nEscape character is ";
 402
 403 static void setConMode(void)
 404 {
 405         if (G.telflags & UF_ECHO) {
 406                 if (G.charmode == CHM_TRY) {
 407                         G.charmode = CHM_ON;
 408                         printf("\r\nEntering character mode%s'^]'.\r\n", escapecharis);
 409                         rawmode();
 410                 }
 411         } else {
 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 static void will_charmode(void)
 421 {
 422         G.charmode = CHM_TRY;
 423         G.telflags |= (UF_ECHO | UF_SGA);
 424         setConMode();
 425
 426         put_iac2(DO, TELOPT_ECHO);
 427         put_iac2(DO, TELOPT_SGA);
 428         iac_flush();
 429 }
 430
 431 static void do_linemode(void)
 432 {
 433         G.charmode = CHM_TRY;
 434         G.telflags &= ~(UF_ECHO | UF_SGA);
 435         setConMode();
 436
 437         put_iac2(DONT, TELOPT_ECHO);
 438         put_iac2(DONT, TELOPT_SGA);
 439         iac_flush();
 440 }
 441
 442 static void to_notsup(char c)
 443 {
 444         if (G.telwish == WILL)
 445                 put_iac2(DONT, c);
 446         else if (G.telwish == DO)
 447                 put_iac2(WONT, c);
 448 }
 449
 450 static void to_echo(void)
 451 {
 452         /* if server requests ECHO, don't agree */
 453         if (G.telwish == DO) {
 454                 put_iac2(WONT, TELOPT_ECHO);
 455                 return;
 456         }
 457         if (G.telwish == DONT)
 458                 return;
 459
 460         if (G.telflags & UF_ECHO) {
 461                 if (G.telwish == WILL)
 462                         return;
 463         } else if (G.telwish == WONT)
 464                 return;
 465
 466         if (G.charmode != CHM_OFF)
 467                 G.telflags ^= UF_ECHO;
 468
 469         if (G.telflags & UF_ECHO)
 470                 put_iac2(DO, TELOPT_ECHO);
 471         else
 472                 put_iac2(DONT, TELOPT_ECHO);
 473
 474         setConMode();
 475         full_write1_str("\r\n");  /* sudden modec */
 476 }
 477
 478 static void to_sga(void)
 479 {
 480         /* daemon always sends will/wont, client do/dont */
 481
 482         if (G.telflags & UF_SGA) {
 483                 if (G.telwish == WILL)
 484                         return;
 485         } else if (G.telwish == WONT)
 486                 return;
 487
 488         G.telflags ^= UF_SGA; /* toggle */
 489         if (G.telflags & UF_SGA)
 490                 put_iac2(DO, TELOPT_SGA);
 491         else
 492                 put_iac2(DONT, TELOPT_SGA);
 493 }
 494
 495 #if ENABLE_FEATURE_TELNET_TTYPE
 496 static void to_ttype(void)
 497 {
 498         /* Tell server we will (or won't) do TTYPE */
 499         if (G.ttype)
 500                 put_iac2(WILL, TELOPT_TTYPE);
 501         else
 502                 put_iac2(WONT, TELOPT_TTYPE);
 503 }
 504 #endif
 505
 506 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
 507 static void to_new_environ(void)
 508 {
 509         /* Tell server we will (or will not) do AUTOLOGIN */
 510         if (G.autologin)
 511                 put_iac2(WILL, TELOPT_NEW_ENVIRON);
 512         else
 513                 put_iac2(WONT, TELOPT_NEW_ENVIRON);
 514 }
 515 #endif
 516
 517 #if ENABLE_FEATURE_AUTOWIDTH
 518 static void to_naws(void)
 519 {
 520         /* Tell server we will do NAWS */
 521         put_iac2(WILL, TELOPT_NAWS);
 522 }
 523 #endif
 524
 525 static void telopt(byte c)
 526 {
 527         switch (c) {
 528         case TELOPT_ECHO:
 529                 to_echo(); break;
 530         case TELOPT_SGA:
 531                 to_sga(); break;
 532 #if ENABLE_FEATURE_TELNET_TTYPE
 533         case TELOPT_TTYPE:
 534                 to_ttype(); break;
 535 #endif
 536 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
 537         case TELOPT_NEW_ENVIRON:
 538                 to_new_environ(); break;
 539 #endif
 540 #if ENABLE_FEATURE_AUTOWIDTH
 541         case TELOPT_NAWS:
 542                 to_naws();
 543                 put_iac_naws(c, G.win_width, G.win_height);
 544                 break;
 545 #endif
 546         default:
 547                 to_notsup(c);
 548                 break;
 549         }
 550 }
 551
 552 /* subnegotiation -- ignore all (except TTYPE,NAWS) */
 553 static void subneg(byte c)
 554 {
 555         switch (G.telstate) {
 556         case TS_SUB1:
 557                 if (c == IAC)
 558                         G.telstate = TS_SUB2;
 559 #if ENABLE_FEATURE_TELNET_TTYPE
 560                 else
 561                 if (c == TELOPT_TTYPE && G.ttype)
 562                         put_iac_subopt(TELOPT_TTYPE, G.ttype);
 563 #endif
 564 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
 565                 else
 566                 if (c == TELOPT_NEW_ENVIRON && G.autologin)
 567                         put_iac_subopt_autologin();
 568 #endif
 569                 break;
 570         case TS_SUB2:
 571                 if (c == SE) {
 572                         G.telstate = TS_COPY;
 573                         return;
 574                 }
 575                 G.telstate = TS_SUB1;
 576                 break;
 577         }
 578 }
 579
 580 static void rawmode(void)
 581 {
 582         if (G.do_termios)
 583                 tcsetattr(0, TCSADRAIN, &G.termios_raw);
 584 }
 585
 586 static void cookmode(void)
 587 {
 588         if (G.do_termios)
 589                 tcsetattr(0, TCSADRAIN, &G.termios_def);
 590 }
 591
 592 int telnet_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 593 int telnet_main(int argc UNUSED_PARAM, char **argv)
 594 {
 595         char *host;
 596         int port;
 597         int len;
 598         struct pollfd ufds[2];
 599
 600         INIT_G();
 601
 602 #if ENABLE_FEATURE_AUTOWIDTH
 603         get_terminal_width_height(0, &G.win_width, &G.win_height);
 604 #endif
 605
 606 #if ENABLE_FEATURE_TELNET_TTYPE
 607         G.ttype = getenv("TERM");
 608 #endif
 609
 610         if (tcgetattr(0, &G.termios_def) >= 0) {
 611                 G.do_termios = 1;
 612                 G.termios_raw = G.termios_def;
 613                 cfmakeraw(&G.termios_raw);
 614         }
 615
 616 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
 617         if (1 & getopt32(argv, "al:", &G.autologin))
 618                 G.autologin = getenv("USER");
 619         argv += optind;
 620 #else
 621         argv++;
 622 #endif
 623         if (!*argv)
 624                 bb_show_usage();
 625         host = *argv++;
 626         port = bb_lookup_port(*argv ? *argv++ : "telnet", "tcp", 23);
 627         if (*argv) /* extra params?? */
 628                 bb_show_usage();
 629
 630         xmove_fd(create_and_connect_stream_or_die(host, port), netfd);
 631
 632         setsockopt(netfd, SOL_SOCKET, SO_KEEPALIVE, &const_int_1, sizeof(const_int_1));
 633
 634         signal(SIGINT, record_signo);
 635
 636         ufds[0].fd = STDIN_FILENO;
 637         ufds[0].events = POLLIN;
 638         ufds[1].fd = netfd;
 639         ufds[1].events = POLLIN;
 640
 641         while (1) {
 642                 if (poll(ufds, 2, -1) < 0) {
 643                         /* error, ignore and/or log something, bay go to loop */
 644                         if (bb_got_signal)
 645                                 con_escape();
 646                         else
 647                                 sleep(1);
 648                         continue;
 649                 }
 650
 651 // FIXME: reads can block. Need full bidirectional buffering.
 652
 653                 if (ufds[0].revents) {
 654                         len = safe_read(STDIN_FILENO, G.buf, DATABUFSIZE);
 655                         if (len <= 0)
 656                                 doexit(EXIT_SUCCESS);
 657                         TRACE(0, ("Read con: %d\n", len));
 658                         handle_net_output(len);
 659                 }
 660
 661                 if (ufds[1].revents) {
 662                         len = safe_read(netfd, G.buf, DATABUFSIZE);
 663                         if (len <= 0) {
 664                                 full_write1_str("Connection closed by foreign host\r\n");
 665                                 doexit(EXIT_FAILURE);
 666                         }
 667                         TRACE(0, ("Read netfd (%d): %d\n", netfd, len));
 668                         handle_net_input(len);
 669                 }
 670         } /* while (1) */
 671 }