telnet.c

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    }
}

static void do_telnet_read(Telnet telnet, char *buf, int len)
{

    while (len--) {
	int c = (unsigned char) *buf++;

	switch (telnet->state) {
	  case TOP_LEVEL:
	  case SEENCR:
	    if (c == NUL && telnet->state == SEENCR)
		telnet->state = TOP_LEVEL;
	    else if (c == IAC)
		telnet->state = SEENIAC;
	    else {
		if (!telnet->in_synch)
		    c_write1(telnet, c);

#if 1
		/* I can't get the F***ing winsock to insert the urgent IAC
		 * into the right position! Even with SO_OOBINLINE it gives
		 * it to recv too soon. And of course the DM byte (that
		 * arrives in the same packet!) appears several K later!!
		 *
		 * Oh well, we do get the DM in the right place so I'll
		 * just stop hiding on the next 0xf2 and hope for the best.
		 */
		else if (c == DM)
		    telnet->in_synch = 0;
#endif
		if (c == CR && telnet->opt_states[o_they_bin.index] != ACTIVE)
		    telnet->state = SEENCR;
		else
		    telnet->state = TOP_LEVEL;
	    }
	    break;
	  case SEENIAC:
	    if (c == DO)
		telnet->state = SEENDO;
	    else if (c == DONT)
		telnet->state = SEENDONT;
	    else if (c == WILL)
		telnet->state = SEENWILL;
	    else if (c == WONT)
		telnet->state = SEENWONT;
	    else if (c == SB)
		telnet->state = SEENSB;
	    else if (c == DM) {
		telnet->in_synch = 0;
		telnet->state = TOP_LEVEL;
	    } else {
		/* ignore everything else; print it if it's IAC */
		if (c == IAC) {
		    c_write1(telnet, c);
		}
		telnet->state = TOP_LEVEL;
	    }
	    break;
	  case SEENWILL:
	    proc_rec_opt(telnet, WILL, c);
	    telnet->state = TOP_LEVEL;
	    break;
	  case SEENWONT:
	    proc_rec_opt(telnet, WONT, c);
	    telnet->state = TOP_LEVEL;
	    break;
	  case SEENDO:
	    proc_rec_opt(telnet, DO, c);
	    telnet->state = TOP_LEVEL;
	    break;
	  case SEENDONT:
	    proc_rec_opt(telnet, DONT, c);
	    telnet->state = TOP_LEVEL;
	    break;
	  case SEENSB:
	    telnet->sb_opt = c;
	    telnet->sb_len = 0;
	    telnet->state = SUBNEGOT;
	    break;
	  case SUBNEGOT:
	    if (c == IAC)
		telnet->state = SUBNEG_IAC;
	    else {
	      subneg_addchar:
		if (telnet->sb_len >= telnet->sb_size) {
		    telnet->sb_size += SB_DELTA;
		    telnet->sb_buf = sresize(telnet->sb_buf, telnet->sb_size,
					     unsigned char);
		}
		telnet->sb_buf[telnet->sb_len++] = c;
		telnet->state = SUBNEGOT;	/* in case we came here by goto */
	    }
	    break;
	  case SUBNEG_IAC:
	    if (c != SE)
		goto subneg_addchar;   /* yes, it's a hack, I know, but... */
	    else {
		process_subneg(telnet);
		telnet->state = TOP_LEVEL;
	    }
	    break;
	}
    }
}

static int telnet_closing(Plug plug, const char *error_msg, int error_code,
			  int calling_back)
{
    Telnet telnet = (Telnet) plug;

    if (telnet->s) {
        sk_close(telnet->s);
        telnet->s = NULL;
    }
    if (error_msg) {
	/* A socket error has occurred. */
	logevent(telnet->frontend, error_msg);
	connection_fatal(telnet->frontend, "%s", error_msg);
    }				       /* Otherwise, the remote side closed the connection normally. */
    return 0;
}

static int telnet_receive(Plug plug, int urgent, char *data, int len)
{
    Telnet telnet = (Telnet) plug;
    if (urgent)
	telnet->in_synch = TRUE;
    do_telnet_read(telnet, data, len);
    return 1;
}

static void telnet_sent(Plug plug, int bufsize)
{
    Telnet telnet = (Telnet) plug;
    telnet->bufsize = bufsize;
}

/*
 * Called to set up the Telnet connection.
 *
 * Returns an error message, or NULL on success.
 *
 * Also places the canonical host name into `realhost'. It must be
 * freed by the caller.
 */
static const char *telnet_init(void *frontend_handle, void **backend_handle,
			       Config *cfg,
			       char *host, int port, char **realhost,
			       int nodelay, int keepalive)
{
    static const struct plug_function_table fn_table = {
	telnet_closing,
	telnet_receive,
	telnet_sent
    };
    SockAddr addr;
    const char *err;
    Telnet telnet;

    telnet = snew(struct telnet_tag);
    telnet->fn = &fn_table;
    telnet->cfg = *cfg;		       /* STRUCTURE COPY */
    telnet->s = NULL;
    telnet->echoing = TRUE;
    telnet->editing = TRUE;
    telnet->activated = FALSE;
    telnet->sb_buf = NULL;
    telnet->sb_size = 0;
    telnet->frontend = frontend_handle;
    telnet->term_width = telnet->cfg.width;
    telnet->term_height = telnet->cfg.height;
    telnet->state = TOP_LEVEL;
    *backend_handle = telnet;

    /*
     * Try to find host.
     */
    {
	char *buf;
	buf = dupprintf("Looking up host \"%s\"", host);
	logevent(telnet->frontend, buf);
	sfree(buf);
    }
    addr = name_lookup(host, port, realhost, &telnet->cfg);
    if ((err = sk_addr_error(addr)) != NULL) {
	sk_addr_free(addr);
	return err;
    }

    if (port < 0)
	port = 23;		       /* default telnet port */

    /*
     * Open socket.
     */
    {
	char *buf, addrbuf[100];
	sk_getaddr(addr, addrbuf, 100);
	buf = dupprintf("Connecting to %s port %d", addrbuf, port);
	logevent(telnet->frontend, buf);
	sfree(buf);
    }
    telnet->s = new_connection(addr, *realhost, port, 0, 1,
			       nodelay, keepalive, (Plug) telnet, &telnet->cfg);
    if ((err = sk_socket_error(telnet->s)) != NULL)
	return err;

    /*
     * Initialise option states.
     */
    if (telnet->cfg.passive_telnet) {
	const struct Opt *const *o;

	for (o = opts; *o; o++)
	    telnet->opt_states[(*o)->index] = INACTIVE;
    } else {
	const struct Opt *const *o;

	for (o = opts; *o; o++) {
	    telnet->opt_states[(*o)->index] = (*o)->initial_state;
	    if (telnet->opt_states[(*o)->index] == REQUESTED)
		send_opt(telnet, (*o)->send, (*o)->option);
	}
	telnet->activated = TRUE;
    }

    /*
     * Set up SYNCH state.
     */
    telnet->in_synch = FALSE;

    /*
     * We can send special commands from the start.
     */
    update_specials_menu(telnet->frontend);

    return NULL;
}

static void telnet_free(void *handle)
{
    Telnet telnet = (Telnet) handle;

    sfree(telnet->sb_buf);
    if (telnet->s)
	sk_close(telnet->s);
    sfree(telnet);
}
/*
 * Reconfigure the Telnet backend. There's no immediate action
 * necessary, in this backend: we just save the fresh config for
 * any subsequent negotiations.
 */
static void telnet_reconfig(void *handle, Config *cfg)
{
    Telnet telnet = (Telnet) handle;
    telnet->cfg = *cfg;		       /* STRUCTURE COPY */
}

/*
 * Called to send data down the Telnet connection.
 */
static int telnet_send(void *handle, char *buf, int len)
{
    Telnet telnet = (Telnet) handle;
    unsigned char *p, *end;
    static const unsigned char iac[2] = { IAC, IAC };
    static const unsigned char cr[2] = { CR, NUL };
#if 0
    static const unsigned char nl[2] = { CR, LF };
#endif

    if (telnet->s == NULL)
	return 0;

    p = (unsigned char *)buf;
    end = (unsigned char *)(buf + len);
    while (p < end) {
	unsigned char *q = p;

	while (p < end && iswritable(*p))
	    p++;
	telnet->bufsize = sk_write(telnet->s, (char *)q, p - q);

	while (p < end && !iswritable(*p)) {
	    telnet->bufsize = 
		sk_write(telnet->s, (char *)(*p == IAC ? iac : cr), 2);
	    p++;
	}
    }

    return telnet->bufsize;
}

/*
 * Called to query the current socket sendability status.
 */
static int telnet_sendbuffer(void *handle)
{
    Telnet telnet = (Telnet) handle;
    return telnet->bufsize;
}

/*
 * Called to set the size of the window from Telnet's POV.
 */
static void telnet_size(void *handle, int width, int height)
{
    Telnet telnet = (Telnet) handle;
    unsigned char b[24];
    int n;
    char *logbuf;

    telnet->term_width = width;
    telnet->term_height = height;

    if (telnet->s == NULL || telnet->opt_states[o_naws.index] != ACTIVE)
	return;
    n = 0;
    b[n++] = IAC;
    b[n++] = SB;
    b[n++] = TELOPT_NAWS;
    b[n++] = telnet->term_width >> 8;
    if (b[n-1] == IAC) b[n++] = IAC;   /* duplicate any IAC byte occurs */
    b[n++] = telnet->term_width & 0xFF;
    if (b[n-1] == IAC) b[n++] = IAC;   /* duplicate any IAC byte occurs */
    b[n++] = telnet->term_height >> 8;
    if (b[n-1] == IAC) b[n++] = IAC;   /* duplicate any IAC byte occurs */
    b[n++] = telnet->term_height & 0xFF;
    if (b[n-1] == IAC) b[n++] = IAC;   /* duplicate any IAC byte occurs */
    b[n++] = IAC;
    b[n++] = SE;
    telnet->bufsize = sk_write(telnet->s, (char *)b, n);
    logbuf = dupprintf("client:\tSB NAWS %d,%d",
		       telnet->term_width, telnet->term_height);
    logevent(telnet->frontend, logbuf);
    sfree(logbuf);
}

/*
 * Send Telnet special codes.
 */
static void telnet_special(void *handle, Telnet_Special code)
{
    Telnet telnet = (Telnet) handle;
    unsigned char b[2];

    if (telnet->s == NULL)
	return;

    b[0] = IAC;
    switch (code) {
      case TS_AYT:
	b[1] = AYT;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_BRK:
	b[1] = BREAK;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_EC:
	b[1] = EC;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_EL:
	b[1] = EL;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_GA:
	b[1] = GA;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_NOP:
	b[1] = NOP;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_ABORT:
	b[1] = ABORT;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_AO:
	b[1] = AO;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_IP:
	b[1] = IP;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_SUSP:
	b[1] = SUSP;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_EOR:
	b[1] = EOR;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_EOF:
	b[1] = xEOF;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_EOL:
	/* In BINARY mode, CR-LF becomes just CR -
	 * and without the NUL suffix too. */
	if (telnet->opt_states[o_we_bin.index] == ACTIVE)
	    telnet->bufsize = sk_write(telnet->s, "\r", 1);
	else
	    telnet->bufsize = sk_write(telnet->s, "\r\n", 2);
	break;
      case TS_SYNCH:
	b[1] = DM;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 1);
	telnet->bufsize = sk_write_oob(telnet->s, (char *)(b + 1), 1);
	break;
      case TS_RECHO:
	if (telnet->opt_states[o_echo.index] == INACTIVE ||
	    telnet->opt_states[o_echo.index] == REALLY_INACTIVE) {
	    telnet->opt_states[o_echo.index] = REQUESTED;
	    send_opt(telnet, o_echo.send, o_echo.option);
	}
	break;
      case TS_LECHO:
	if (telnet->opt_states[o_echo.index] == ACTIVE) {
	    telnet->opt_states[o_echo.index] = REQUESTED;
	    send_opt(telnet, o_echo.nsend, o_echo.option);
	}
	break;
      case TS_PING:
	if (telnet->opt_states[o_they_sga.index] == ACTIVE) {
	    b[1] = NOP;
	    telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	}
	break;
      default:
	break;	/* never heard of it */
    }
}

static const struct telnet_special *telnet_get_specials(void *handle)
{
    static const struct telnet_special specials[] = {
	{"Are You There", TS_AYT},
	{"Break", TS_BRK},
	{"Synch", TS_SYNCH},
	{"Erase Character", TS_EC},
	{"Erase Line", TS_EL},
	{"Go Ahead", TS_GA},
	{"No Operation", TS_NOP},
	{NULL, TS_SEP},
	{"Abort Process", TS_ABORT},
	{"Abort Output", TS_AO},
	{"Interrupt Process", TS_IP},
	{"Suspend Process", TS_SUSP},
	{NULL, TS_SEP},
	{"End Of Record", TS_EOR},
	{"End Of File", TS_EOF},
	{NULL, TS_EXITMENU}
    };
    return specials;
}

static Socket telnet_socket(void *handle)
{
    Telnet telnet = (Telnet) handle;
    return telnet->s;
}

static int telnet_sendok(void *handle)
{
    /* Telnet telnet = (Telnet) handle; */
    return 1;
}

static void telnet_unthrottle(void *handle, int backlog)
{
    Telnet telnet = (Telnet) handle;
    sk_set_frozen(telnet->s, backlog > TELNET_MAX_BACKLOG);
}

static int telnet_ldisc(void *handle, int option)
{
    Telnet telnet = (Telnet) handle;
    if (option == LD_ECHO)
	return telnet->echoing;
    if (option == LD_EDIT)
	return telnet->editing;
    return FALSE;
}

static void telnet_provide_ldisc(void *handle, void *ldisc)
{
    Telnet telnet = (Telnet) handle;
    telnet->ldisc = ldisc;
}

static void telnet_provide_logctx(void *handle, void *logctx)
{
    /* This is a stub. */
}

static int telnet_exitcode(void *handle)
{
    Telnet telnet = (Telnet) handle;
    if (telnet->s != NULL)
        return -1;                     /* still connected */
    else
        /* Telnet doesn't transmit exit codes back to the client */
        return 0;
}

Backend telnet_backend = {
    telnet_init,
    telnet_free,
    telnet_reconfig,
    telnet_send,
    telnet_sendbuffer,
    telnet_size,
    telnet_special,
    telnet_get_specials,
    telnet_socket,
    telnet_exitcode,
    telnet_sendok,
    telnet_ldisc,
    telnet_provide_ldisc,
    telnet_provide_logctx,
    telnet_unthrottle,
    23
};