source: MondoRescue/branches/2.2.9/mindi-busybox/networking/telnet.c@ 2887

/* vi: set sw=4 ts=4: */
/*
 * telnet implementation for busybox
 *
 * Author: Tomi Ollila <too@iki.fi>
 * Copyright (C) 1994-2000 by Tomi Ollila
 *
 * Created: Thu Apr  7 13:29:41 1994 too
 * Last modified: Fri Jun  9 14:34:24 2000 too
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 *
 * HISTORY
 * Revision 3.1  1994/04/17  11:31:54  too
 * initial revision
 * Modified 2000/06/13 for inclusion into BusyBox by Erik Andersen <andersen@codepoet.org>
 * Modified 2001/05/07 to add ability to pass TTYPE to remote host by Jim McQuillan
 * <jam@ltsp.org>
 * Modified 2004/02/11 to add ability to pass the USER variable to remote host
 * by Fernando Silveira <swrh@gmx.net>
 *
 */

#include <arpa/telnet.h>
#include <netinet/in.h>
#include "libbb.h"

#ifdef DOTRACE
#define TRACE(x, y) do { if (x) printf y; } while (0)
#else
#define TRACE(x, y)
#endif

enum {
    DATABUFSIZE = 128,
    IACBUFSIZE  = 128,

    CHM_TRY = 0,
    CHM_ON = 1,
    CHM_OFF = 2,

    UF_ECHO = 0x01,
    UF_SGA = 0x02,

    TS_NORMAL = 0,
    TS_COPY = 1,
    TS_IAC = 2,
    TS_OPT = 3,
    TS_SUB1 = 4,
    TS_SUB2 = 5,
    TS_CR = 6,
};

typedef unsigned char byte;

enum { netfd = 3 };

struct globals {
    int iaclen; /* could even use byte, but it's a loss on x86 */
    byte    telstate; /* telnet negotiation state from network input */
    byte    telwish;  /* DO, DONT, WILL, WONT */
    byte    charmode;
    byte    telflags;
    byte    do_termios;
#if ENABLE_FEATURE_TELNET_TTYPE
    char    *ttype;
#endif
#if ENABLE_FEATURE_TELNET_AUTOLOGIN
    const char *autologin;
#endif
#if ENABLE_FEATURE_AUTOWIDTH
    unsigned win_width, win_height;
#endif
    /* same buffer used both for network and console read/write */
    char    buf[DATABUFSIZE];
    /* buffer to handle telnet negotiations */
    char    iacbuf[IACBUFSIZE];
    struct termios termios_def;
    struct termios termios_raw;
} FIX_ALIASING;
#define G (*(struct globals*)&bb_common_bufsiz1)
#define INIT_G() do { \
    struct G_sizecheck { \
        char G_sizecheck[sizeof(G) > COMMON_BUFSIZE ? -1 : 1]; \
    }; \
} while (0)


static void rawmode(void);
static void cookmode(void);
static void do_linemode(void);
static void will_charmode(void);
static void telopt(byte c);
static void subneg(byte c);

static void iac_flush(void)
{
    write(netfd, G.iacbuf, G.iaclen);
    G.iaclen = 0;
}

#define write_str(fd, str) write(fd, str, sizeof(str) - 1)

static void doexit(int ev) NORETURN;
static void doexit(int ev)
{
    cookmode();
    exit(ev);
}

static void con_escape(void)
{
    char b;

    if (bb_got_signal) /* came from line mode... go raw */
        rawmode();

    write_str(1, "\r\nConsole escape. Commands are:\r\n\n"
            " l go to line mode\r\n"
            " c go to character mode\r\n"
            " z suspend telnet\r\n"
            " e exit telnet\r\n");

    if (read(STDIN_FILENO, &b, 1) <= 0)
        doexit(EXIT_FAILURE);

    switch (b) {
    case 'l':
        if (!bb_got_signal) {
            do_linemode();
            goto ret;
        }
        break;
    case 'c':
        if (bb_got_signal) {
            will_charmode();
            goto ret;
        }
        break;
    case 'z':
        cookmode();
        kill(0, SIGTSTP);
        rawmode();
        break;
    case 'e':
        doexit(EXIT_SUCCESS);
    }

    write_str(1, "continuing...\r\n");

    if (bb_got_signal)
        cookmode();
 ret:
    bb_got_signal = 0;
}

static void handle_net_output(int len)
{
    /* here we could do smart tricks how to handle 0xFF:s in output
     * stream like writing twice every sequence of FF:s (thus doing
     * many write()s. But I think interactive telnet application does
     * not need to be 100% 8-bit clean, so changing every 0xff:s to
     * 0x7f:s
     *
     * 2002-mar-21, Przemyslaw Czerpak (druzus@polbox.com)
     * I don't agree.
     * first - I cannot use programs like sz/rz
     * second - the 0x0D is sent as one character and if the next
     *  char is 0x0A then it's eaten by a server side.
     * third - why do you have to make 'many write()s'?
     *  I don't understand.
     * So I implemented it. It's really useful for me. I hope that
     * other people will find it interesting too.
     */
    byte outbuf[2 * DATABUFSIZE];
    byte *p = (byte*)G.buf;
    int j = 0;

    for (; len > 0; len--, p++) {
        byte c = *p;
        if (c == 0x1d) {
            con_escape();
            return;
        }
        outbuf[j++] = c;
        if (c == IAC)
            outbuf[j++] = c; /* IAC -> IAC IAC */
        else if (c == '\r')
            outbuf[j++] = '\0'; /* CR -> CR NUL */
    }
    if (j > 0)
        full_write(netfd, outbuf, j);
}

static void handle_net_input(int len)
{
    int i;
    int cstart = 0;

    for (i = 0; i < len; i++) {
        byte c = G.buf[i];

        if (G.telstate == TS_NORMAL) { /* most typical state */
            if (c == IAC) {
                cstart = i;
                G.telstate = TS_IAC;
            }
            else if (c == '\r') {
                cstart = i + 1;
                G.telstate = TS_CR;
            }
            /* No IACs were seen so far, no need to copy
             * bytes within G.buf: */
            continue;
        }

        switch (G.telstate) {
        case TS_CR:
            /* Prev char was CR. If cur one is NUL, ignore it.
             * See RFC 1123 section 3.3.1 for discussion of telnet EOL handling.
             */
            G.telstate = TS_COPY;
            if (c == '\0')
                break;
            /* else: fall through - need to handle CR IAC ... properly */

        case TS_COPY: /* Prev char was ordinary */
            /* Similar to NORMAL, but in TS_COPY we need to copy bytes */
            if (c == IAC)
                G.telstate = TS_IAC;
            else
                G.buf[cstart++] = c;
            if (c == '\r')
                G.telstate = TS_CR;
            break;

        case TS_IAC: /* Prev char was IAC */
            if (c == IAC) { /* IAC IAC -> one IAC */
                G.buf[cstart++] = c;
                G.telstate = TS_COPY;
                break;
            }
            /* else */
            switch (c) {
            case SB:
                G.telstate = TS_SUB1;
                break;
            case DO:
            case DONT:
            case WILL:
            case WONT:
                G.telwish = c;
                G.telstate = TS_OPT;
                break;
            /* DATA MARK must be added later */
            default:
                G.telstate = TS_COPY;
            }
            break;

        case TS_OPT: /* Prev chars were IAC WILL/WONT/DO/DONT */
            telopt(c);
            G.telstate = TS_COPY;
            break;

        case TS_SUB1: /* Subnegotiation */
        case TS_SUB2: /* Subnegotiation */
            subneg(c); /* can change G.telstate */
            break;
        }
    }

    if (G.telstate != TS_NORMAL) {
        /* We had some IACs, or CR */
        if (G.iaclen)
            iac_flush();
        if (G.telstate == TS_COPY) /* we aren't in the middle of IAC */
            G.telstate = TS_NORMAL;
        len = cstart;
    }

    if (len)
        full_write(STDOUT_FILENO, G.buf, len);
}

static void put_iac(int c)
{
    G.iacbuf[G.iaclen++] = c;
}

static void put_iac2(byte wwdd, byte c)
{
    if (G.iaclen + 3 > IACBUFSIZE)
        iac_flush();

    put_iac(IAC);
    put_iac(wwdd);
    put_iac(c);
}

#if ENABLE_FEATURE_TELNET_TTYPE
static void put_iac_subopt(byte c, char *str)
{
    int len = strlen(str) + 6;   // ( 2 + 1 + 1 + strlen + 2 )

    if (G.iaclen + len > IACBUFSIZE)
        iac_flush();

    put_iac(IAC);
    put_iac(SB);
    put_iac(c);
    put_iac(0);

    while (*str)
        put_iac(*str++);

    put_iac(IAC);
    put_iac(SE);
}
#endif

#if ENABLE_FEATURE_TELNET_AUTOLOGIN
static void put_iac_subopt_autologin(void)
{
    int len = strlen(G.autologin) + 6;  // (2 + 1 + 1 + strlen + 2)
    const char *p = "USER";

    if (G.iaclen + len > IACBUFSIZE)
        iac_flush();

    put_iac(IAC);
    put_iac(SB);
    put_iac(TELOPT_NEW_ENVIRON);
    put_iac(TELQUAL_IS);
    put_iac(NEW_ENV_VAR);

    while (*p)
        put_iac(*p++);

    put_iac(NEW_ENV_VALUE);

    p = G.autologin;
    while (*p)
        put_iac(*p++);

    put_iac(IAC);
    put_iac(SE);
}
#endif

#if ENABLE_FEATURE_AUTOWIDTH
static void put_iac_naws(byte c, int x, int y)
{
    if (G.iaclen + 9 > IACBUFSIZE)
        iac_flush();

    put_iac(IAC);
    put_iac(SB);
    put_iac(c);

    put_iac((x >> 8) & 0xff);
    put_iac(x & 0xff);
    put_iac((y >> 8) & 0xff);
    put_iac(y & 0xff);

    put_iac(IAC);
    put_iac(SE);
}
#endif

static char const escapecharis[] ALIGN1 = "\r\nEscape character is ";

static void setConMode(void)
{
    if (G.telflags & UF_ECHO) {
        if (G.charmode == CHM_TRY) {
            G.charmode = CHM_ON;
            printf("\r\nEntering character mode%s'^]'.\r\n", escapecharis);
            rawmode();
        }
    } else {
        if (G.charmode != CHM_OFF) {
            G.charmode = CHM_OFF;
            printf("\r\nEntering line mode%s'^C'.\r\n", escapecharis);
            cookmode();
        }
    }
}

static void will_charmode(void)
{
    G.charmode = CHM_TRY;
    G.telflags |= (UF_ECHO | UF_SGA);
    setConMode();

    put_iac2(DO, TELOPT_ECHO);
    put_iac2(DO, TELOPT_SGA);
    iac_flush();
}

static void do_linemode(void)
{
    G.charmode = CHM_TRY;
    G.telflags &= ~(UF_ECHO | UF_SGA);
    setConMode();

    put_iac2(DONT, TELOPT_ECHO);
    put_iac2(DONT, TELOPT_SGA);
    iac_flush();
}

static void to_notsup(char c)
{
    if (G.telwish == WILL)
        put_iac2(DONT, c);
    else if (G.telwish == DO)
        put_iac2(WONT, c);
}

static void to_echo(void)
{
    /* if server requests ECHO, don't agree */
    if (G.telwish == DO) {
        put_iac2(WONT, TELOPT_ECHO);
        return;
    }
    if (G.telwish == DONT)
        return;

    if (G.telflags & UF_ECHO) {
        if (G.telwish == WILL)
            return;
    } else if (G.telwish == WONT)
        return;

    if (G.charmode != CHM_OFF)
        G.telflags ^= UF_ECHO;

    if (G.telflags & UF_ECHO)
        put_iac2(DO, TELOPT_ECHO);
    else
        put_iac2(DONT, TELOPT_ECHO);

    setConMode();
    full_write1_str("\r\n");  /* sudden modec */
}

static void to_sga(void)
{
    /* daemon always sends will/wont, client do/dont */

    if (G.telflags & UF_SGA) {
        if (G.telwish == WILL)
            return;
    } else if (G.telwish == WONT)
        return;

    G.telflags ^= UF_SGA; /* toggle */
    if (G.telflags & UF_SGA)
        put_iac2(DO, TELOPT_SGA);
    else
        put_iac2(DONT, TELOPT_SGA);
}

#if ENABLE_FEATURE_TELNET_TTYPE
static void to_ttype(void)
{
    /* Tell server we will (or won't) do TTYPE */
    if (G.ttype)
        put_iac2(WILL, TELOPT_TTYPE);
    else
        put_iac2(WONT, TELOPT_TTYPE);
}
#endif

#if ENABLE_FEATURE_TELNET_AUTOLOGIN
static void to_new_environ(void)
{
    /* Tell server we will (or will not) do AUTOLOGIN */
    if (G.autologin)
        put_iac2(WILL, TELOPT_NEW_ENVIRON);
    else
        put_iac2(WONT, TELOPT_NEW_ENVIRON);
}
#endif

#if ENABLE_FEATURE_AUTOWIDTH
static void to_naws(void)
{
    /* Tell server we will do NAWS */
    put_iac2(WILL, TELOPT_NAWS);
}
#endif

static void telopt(byte c)
{
    switch (c) {
    case TELOPT_ECHO:
        to_echo(); break;
    case TELOPT_SGA:
        to_sga(); break;
#if ENABLE_FEATURE_TELNET_TTYPE
    case TELOPT_TTYPE:
        to_ttype(); break;
#endif
#if ENABLE_FEATURE_TELNET_AUTOLOGIN
    case TELOPT_NEW_ENVIRON:
        to_new_environ(); break;
#endif
#if ENABLE_FEATURE_AUTOWIDTH
    case TELOPT_NAWS:
        to_naws();
        put_iac_naws(c, G.win_width, G.win_height);
        break;
#endif
    default:
        to_notsup(c);
        break;
    }
}

/* subnegotiation -- ignore all (except TTYPE,NAWS) */
static void subneg(byte c)
{
    switch (G.telstate) {
    case TS_SUB1:
        if (c == IAC)
            G.telstate = TS_SUB2;
#if ENABLE_FEATURE_TELNET_TTYPE
        else
        if (c == TELOPT_TTYPE && G.ttype)
            put_iac_subopt(TELOPT_TTYPE, G.ttype);
#endif
#if ENABLE_FEATURE_TELNET_AUTOLOGIN
        else
        if (c == TELOPT_NEW_ENVIRON && G.autologin)
            put_iac_subopt_autologin();
#endif
        break;
    case TS_SUB2:
        if (c == SE) {
            G.telstate = TS_COPY;
            return;
        }
        G.telstate = TS_SUB1;
        break;
    }
}

static void rawmode(void)
{
    if (G.do_termios)
        tcsetattr(0, TCSADRAIN, &G.termios_raw);
}

static void cookmode(void)
{
    if (G.do_termios)
        tcsetattr(0, TCSADRAIN, &G.termios_def);
}

int telnet_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int telnet_main(int argc UNUSED_PARAM, char **argv)
{
    char *host;
    int port;
    int len;
    struct pollfd ufds[2];

    INIT_G();

#if ENABLE_FEATURE_AUTOWIDTH
    get_terminal_width_height(0, &G.win_width, &G.win_height);
#endif

#if ENABLE_FEATURE_TELNET_TTYPE
    G.ttype = getenv("TERM");
#endif

    if (tcgetattr(0, &G.termios_def) >= 0) {
        G.do_termios = 1;
        G.termios_raw = G.termios_def;
        cfmakeraw(&G.termios_raw);
    }

#if ENABLE_FEATURE_TELNET_AUTOLOGIN
    if (1 & getopt32(argv, "al:", &G.autologin))
        G.autologin = getenv("USER");
    argv += optind;
#else
    argv++;
#endif
    if (!*argv)
        bb_show_usage();
    host = *argv++;
    port = bb_lookup_port(*argv ? *argv++ : "telnet", "tcp", 23);
    if (*argv) /* extra params?? */
        bb_show_usage();

    xmove_fd(create_and_connect_stream_or_die(host, port), netfd);

    setsockopt(netfd, SOL_SOCKET, SO_KEEPALIVE, &const_int_1, sizeof(const_int_1));

    signal(SIGINT, record_signo);

    ufds[0].fd = STDIN_FILENO;
    ufds[0].events = POLLIN;
    ufds[1].fd = netfd;
    ufds[1].events = POLLIN;

    while (1) {
        if (poll(ufds, 2, -1) < 0) {
            /* error, ignore and/or log something, bay go to loop */
            if (bb_got_signal)
                con_escape();
            else
                sleep(1);
            continue;
        }

// FIXME: reads can block. Need full bidirectional buffering.

        if (ufds[0].revents) {
            len = safe_read(STDIN_FILENO, G.buf, DATABUFSIZE);
            if (len <= 0)
                doexit(EXIT_SUCCESS);
            TRACE(0, ("Read con: %d\n", len));
            handle_net_output(len);
        }

        if (ufds[1].revents) {
            len = safe_read(netfd, G.buf, DATABUFSIZE);
            if (len <= 0) {
                full_write1_str("Connection closed by foreign host\r\n");
                doexit(EXIT_FAILURE);
            }
            TRACE(0, ("Read netfd (%d): %d\n", netfd, len));
            handle_net_input(len);
        }
    } /* while (1) */
}