1 /* vi: set sw=4 ts=4: */
3 * telnet implementation for busybox
5 * Author: Tomi Ollila <too@iki.fi>
6 * Copyright (C) 1994-2000 by Tomi Ollila
8 * Created: Thu Apr 7 13:29:41 1994 too
9 * Last modified: Fri Jun 9 14:34:24 2000 too
11 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
14 * Revision 3.1 1994/04/17 11:31:54 too
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
19 * Modified 2004/02/11 to add ability to pass the USER variable to remote host
20 * by Fernando Silveira <swrh@gmx.net>
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"
33 //usage:#define telnet_trivial_usage
34 //usage: "HOST [PORT]"
35 //usage:#define telnet_full_usage "\n\n"
36 //usage: "Connect to telnet server"
39 #include <arpa/telnet.h>
40 #include <netinet/in.h>
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 */
59 # define TRACE(x, y) do { if (x) printf y; } while (0)
84 typedef unsigned char byte;
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 */
95 #if ENABLE_FEATURE_TELNET_TTYPE
98 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
99 const char *autologin;
101 #if ENABLE_FEATURE_AUTOWIDTH
102 unsigned win_width, win_height;
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;
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]; \
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);
126 static void iac_flush(void)
128 write(netfd, G.iacbuf, G.iaclen);
132 #define write_str(fd, str) write(fd, str, sizeof(str) - 1)
134 static void doexit(int ev) NORETURN;
135 static void doexit(int ev)
141 static void con_escape(void)
145 if (bb_got_signal) /* came from line mode... go raw */
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");
154 if (read(STDIN_FILENO, &b, 1) <= 0)
155 doexit(EXIT_FAILURE);
159 if (!bb_got_signal) {
176 doexit(EXIT_SUCCESS);
179 write_str(1, "continuing...\r\n");
187 static void handle_net_output(int len)
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
195 * 2002-mar-21, Przemyslaw Czerpak (druzus@polbox.com)
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.
205 byte outbuf[2 * DATABUFSIZE];
206 byte *p = (byte*)G.buf;
209 for (; len > 0; len--, p++) {
217 outbuf[j++] = c; /* IAC -> IAC IAC */
219 outbuf[j++] = '\0'; /* CR -> CR NUL */
222 full_write(netfd, outbuf, j);
225 static void handle_net_input(int len)
230 for (i = 0; i < len; i++) {
233 if (G.telstate == TS_NORMAL) { /* most typical state */
238 else if (c == '\r') {
242 /* No IACs were seen so far, no need to copy
243 * bytes within G.buf: */
247 switch (G.telstate) {
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.
252 G.telstate = TS_COPY;
255 /* else: fall through - need to handle CR IAC ... properly */
257 case TS_COPY: /* Prev char was ordinary */
258 /* Similar to NORMAL, but in TS_COPY we need to copy bytes */
267 case TS_IAC: /* Prev char was IAC */
268 if (c == IAC) { /* IAC IAC -> one IAC */
270 G.telstate = TS_COPY;
276 G.telstate = TS_SUB1;
285 /* DATA MARK must be added later */
287 G.telstate = TS_COPY;
291 case TS_OPT: /* Prev chars were IAC WILL/WONT/DO/DONT */
293 G.telstate = TS_COPY;
296 case TS_SUB1: /* Subnegotiation */
297 case TS_SUB2: /* Subnegotiation */
298 subneg(c); /* can change G.telstate */
303 if (G.telstate != TS_NORMAL) {
304 /* We had some IACs, or CR */
307 if (G.telstate == TS_COPY) /* we aren't in the middle of IAC */
308 G.telstate = TS_NORMAL;
313 full_write(STDOUT_FILENO, G.buf, len);
316 static void put_iac(int c)
318 G.iacbuf[G.iaclen++] = c;
321 static void put_iac2(byte wwdd, byte c)
323 if (G.iaclen + 3 > IACBUFSIZE)
331 #if ENABLE_FEATURE_TELNET_TTYPE
332 static void put_iac_subopt(byte c, char *str)
334 int len = strlen(str) + 6; // ( 2 + 1 + 1 + strlen + 2 )
336 if (G.iaclen + len > IACBUFSIZE)
352 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
353 static void put_iac_subopt_autologin(void)
355 int len = strlen(G.autologin) + 6; // (2 + 1 + 1 + strlen + 2)
356 const char *p = "USER";
358 if (G.iaclen + len > IACBUFSIZE)
363 put_iac(TELOPT_NEW_ENVIRON);
365 put_iac(NEW_ENV_VAR);
370 put_iac(NEW_ENV_VALUE);
381 #if ENABLE_FEATURE_AUTOWIDTH
382 static void put_iac_naws(byte c, int x, int y)
384 if (G.iaclen + 9 > IACBUFSIZE)
391 put_iac((x >> 8) & 0xff);
393 put_iac((y >> 8) & 0xff);
401 static char const escapecharis[] ALIGN1 = "\r\nEscape character is ";
403 static void setConMode(void)
405 if (G.telflags & UF_ECHO) {
406 if (G.charmode == CHM_TRY) {
408 printf("\r\nEntering character mode%s'^]'.\r\n", escapecharis);
412 if (G.charmode != CHM_OFF) {
413 G.charmode = CHM_OFF;
414 printf("\r\nEntering line mode%s'^C'.\r\n", escapecharis);
420 static void will_charmode(void)
422 G.charmode = CHM_TRY;
423 G.telflags |= (UF_ECHO | UF_SGA);
426 put_iac2(DO, TELOPT_ECHO);
427 put_iac2(DO, TELOPT_SGA);
431 static void do_linemode(void)
433 G.charmode = CHM_TRY;
434 G.telflags &= ~(UF_ECHO | UF_SGA);
437 put_iac2(DONT, TELOPT_ECHO);
438 put_iac2(DONT, TELOPT_SGA);
442 static void to_notsup(char c)
444 if (G.telwish == WILL)
446 else if (G.telwish == DO)
450 static void to_echo(void)
452 /* if server requests ECHO, don't agree */
453 if (G.telwish == DO) {
454 put_iac2(WONT, TELOPT_ECHO);
457 if (G.telwish == DONT)
460 if (G.telflags & UF_ECHO) {
461 if (G.telwish == WILL)
463 } else if (G.telwish == WONT)
466 if (G.charmode != CHM_OFF)
467 G.telflags ^= UF_ECHO;
469 if (G.telflags & UF_ECHO)
470 put_iac2(DO, TELOPT_ECHO);
472 put_iac2(DONT, TELOPT_ECHO);
475 full_write1_str("\r\n"); /* sudden modec */
478 static void to_sga(void)
480 /* daemon always sends will/wont, client do/dont */
482 if (G.telflags & UF_SGA) {
483 if (G.telwish == WILL)
485 } else if (G.telwish == WONT)
488 G.telflags ^= UF_SGA; /* toggle */
489 if (G.telflags & UF_SGA)
490 put_iac2(DO, TELOPT_SGA);
492 put_iac2(DONT, TELOPT_SGA);
495 #if ENABLE_FEATURE_TELNET_TTYPE
496 static void to_ttype(void)
498 /* Tell server we will (or won't) do TTYPE */
500 put_iac2(WILL, TELOPT_TTYPE);
502 put_iac2(WONT, TELOPT_TTYPE);
506 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
507 static void to_new_environ(void)
509 /* Tell server we will (or will not) do AUTOLOGIN */
511 put_iac2(WILL, TELOPT_NEW_ENVIRON);
513 put_iac2(WONT, TELOPT_NEW_ENVIRON);
517 #if ENABLE_FEATURE_AUTOWIDTH
518 static void to_naws(void)
520 /* Tell server we will do NAWS */
521 put_iac2(WILL, TELOPT_NAWS);
525 static void telopt(byte c)
532 #if ENABLE_FEATURE_TELNET_TTYPE
536 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
537 case TELOPT_NEW_ENVIRON:
538 to_new_environ(); break;
540 #if ENABLE_FEATURE_AUTOWIDTH
543 put_iac_naws(c, G.win_width, G.win_height);
552 /* subnegotiation -- ignore all (except TTYPE,NAWS) */
553 static void subneg(byte c)
555 switch (G.telstate) {
558 G.telstate = TS_SUB2;
559 #if ENABLE_FEATURE_TELNET_TTYPE
561 if (c == TELOPT_TTYPE && G.ttype)
562 put_iac_subopt(TELOPT_TTYPE, G.ttype);
564 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
566 if (c == TELOPT_NEW_ENVIRON && G.autologin)
567 put_iac_subopt_autologin();
572 G.telstate = TS_COPY;
575 G.telstate = TS_SUB1;
580 static void rawmode(void)
583 tcsetattr(0, TCSADRAIN, &G.termios_raw);
586 static void cookmode(void)
589 tcsetattr(0, TCSADRAIN, &G.termios_def);
592 int telnet_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
593 int telnet_main(int argc UNUSED_PARAM, char **argv)
598 struct pollfd ufds[2];
602 #if ENABLE_FEATURE_AUTOWIDTH
603 get_terminal_width_height(0, &G.win_width, &G.win_height);
606 #if ENABLE_FEATURE_TELNET_TTYPE
607 G.ttype = getenv("TERM");
610 if (tcgetattr(0, &G.termios_def) >= 0) {
612 G.termios_raw = G.termios_def;
613 cfmakeraw(&G.termios_raw);
616 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
617 if (1 & getopt32(argv, "al:", &G.autologin))
618 G.autologin = getenv("USER");
626 port = bb_lookup_port(*argv ? *argv++ : "telnet", "tcp", 23);
627 if (*argv) /* extra params?? */
630 xmove_fd(create_and_connect_stream_or_die(host, port), netfd);
632 setsockopt(netfd, SOL_SOCKET, SO_KEEPALIVE, &const_int_1, sizeof(const_int_1));
634 signal(SIGINT, record_signo);
636 ufds[0].fd = STDIN_FILENO;
637 ufds[0].events = POLLIN;
639 ufds[1].events = POLLIN;
642 if (poll(ufds, 2, -1) < 0) {
643 /* error, ignore and/or log something, bay go to loop */
651 // FIXME: reads can block. Need full bidirectional buffering.
653 if (ufds[0].revents) {
654 len = safe_read(STDIN_FILENO, G.buf, DATABUFSIZE);
656 doexit(EXIT_SUCCESS);
657 TRACE(0, ("Read con: %d\n", len));
658 handle_net_output(len);
661 if (ufds[1].revents) {
662 len = safe_read(netfd, G.buf, DATABUFSIZE);
664 full_write1_str("Connection closed by foreign host\r\n");
665 doexit(EXIT_FAILURE);
667 TRACE(0, ("Read netfd (%d): %d\n", netfd, len));
668 handle_net_input(len);