LXR 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
  64enum {
  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
  84typedef unsigned char byte;
  85
  86enum { netfd = 3 };
  87
  88struct 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
 119static void rawmode(void);
 120static void cookmode(void);
 121static void do_linemode(void);
 122static void will_charmode(void);
 123static void telopt(byte c);
 124static void subneg(byte c);
 125
 126static void iac_flush(void)
 127{
 128        full_write(netfd, G.iacbuf, G.iaclen);
 129        G.iaclen = 0;
 130}
 131
 132static void doexit(int ev) NORETURN;
 133static void doexit(int ev)
 134{
 135        cookmode();
 136        exit(ev);
 137}
 138
 139static 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
 185static 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
 218static 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
 309static void put_iac(int c)
 310{
 311        G.iacbuf[G.iaclen++] = c;
 312}
 313
 314static 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
 325static 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
 346static 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
 375static 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
 395static 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
 414static 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
 425static 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
 436static 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
 444static 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
 472static 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
 490static 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
 501static 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
 512static void to_naws(void)
 513{
 514        /* Tell server we will do NAWS */
 515        put_iac2(WILL, TELOPT_NAWS);
 516}
 517#endif
 518
 519static 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) */
 547static 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
 574static void rawmode(void)
 575{
 576        if (G.do_termios)
 577                tcsetattr(0, TCSADRAIN, &G.termios_raw);
 578}
 579
 580static void cookmode(void)
 581{
 582        if (G.do_termios)
 583                tcsetattr(0, TCSADRAIN, &G.termios_def);
 584}
 585
 586int telnet_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 587int 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}
 666