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