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>
42 #include "common_bufsiz.h"
45 /* should be in arpa/telnet.h */
46 # define IAC 255 /* interpret as command: */
47 # define DONT 254 /* you are not to use option */
48 # define DO 253 /* please, you use option */
49 # define WONT 252 /* I won't use option */
50 # define WILL 251 /* I will use option */
51 # define SB 250 /* interpret as subnegotiation */
52 # define SE 240 /* end sub negotiation */
53 # define TELOPT_ECHO 1 /* echo */
54 # define TELOPT_SGA 3 /* suppress go ahead */
55 # define TELOPT_TTYPE 24 /* terminal type */
56 # define TELOPT_NAWS 31 /* window size */
60 # define TRACE(x, y) do { if (x) printf y; } while (0)
85 typedef unsigned char byte;
90 int iaclen; /* could even use byte, but it's a loss on x86 */
91 byte telstate; /* telnet negotiation state from network input */
92 byte telwish; /* DO, DONT, WILL, WONT */
96 #if ENABLE_FEATURE_TELNET_TTYPE
99 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
100 const char *autologin;
102 #if ENABLE_FEATURE_AUTOWIDTH
103 unsigned win_width, win_height;
105 /* same buffer used both for network and console read/write */
106 char buf[DATABUFSIZE];
107 /* buffer to handle telnet negotiations */
108 char iacbuf[IACBUFSIZE];
109 struct termios termios_def;
110 struct termios termios_raw;
112 #define G (*(struct globals*)bb_common_bufsiz1)
113 #define INIT_G() do { \
114 setup_common_bufsiz(); \
115 BUILD_BUG_ON(sizeof(G) > COMMON_BUFSIZE); \
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 full_write(netfd, G.iacbuf, G.iaclen);
132 static void doexit(int ev) NORETURN;
133 static void doexit(int ev)
139 static void con_escape(void)
143 if (bb_got_signal) /* came from line mode... go raw */
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");
152 if (read(STDIN_FILENO, &b, 1) <= 0)
153 doexit(EXIT_FAILURE);
157 if (!bb_got_signal) {
174 doexit(EXIT_SUCCESS);
177 full_write1_str("continuing...\r\n");
185 static void handle_net_output(int len)
187 byte outbuf[2 * DATABUFSIZE];
189 byte *src = (byte*)G.buf;
190 byte *end = src + len;
200 *++dst = c; /* IAC -> IAC IAC */
202 if (c == '\r' || c == '\n') {
203 /* Enter key sends '\r' in raw mode and '\n' in cooked one.
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.
209 *dst = '\r'; /* Enter -> CR LF */
214 if (dst - outbuf != 0)
215 full_write(netfd, outbuf, dst - outbuf);
218 static void handle_net_input(int len)
223 for (i = 0; i < len; i++) {
226 if (G.telstate == TS_NORMAL) { /* most typical state */
231 else if (c == '\r') {
235 /* No IACs were seen so far, no need to copy
236 * bytes within G.buf: */
240 switch (G.telstate) {
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.
245 G.telstate = TS_COPY;
248 /* else: fall through - need to handle CR IAC ... properly */
250 case TS_COPY: /* Prev char was ordinary */
251 /* Similar to NORMAL, but in TS_COPY we need to copy bytes */
260 case TS_IAC: /* Prev char was IAC */
261 if (c == IAC) { /* IAC IAC -> one IAC */
263 G.telstate = TS_COPY;
269 G.telstate = TS_SUB1;
278 /* DATA MARK must be added later */
280 G.telstate = TS_COPY;
284 case TS_OPT: /* Prev chars were IAC WILL/WONT/DO/DONT */
286 G.telstate = TS_COPY;
289 case TS_SUB1: /* Subnegotiation */
290 case TS_SUB2: /* Subnegotiation */
291 subneg(c); /* can change G.telstate */
296 if (G.telstate != TS_NORMAL) {
297 /* We had some IACs, or CR */
300 if (G.telstate == TS_COPY) /* we aren't in the middle of IAC */
301 G.telstate = TS_NORMAL;
306 full_write(STDOUT_FILENO, G.buf, len);
309 static void put_iac(int c)
311 G.iacbuf[G.iaclen++] = c;
314 static void put_iac2_merged(unsigned wwdd_and_c)
316 if (G.iaclen + 3 > IACBUFSIZE)
320 put_iac(wwdd_and_c >> 8);
321 put_iac(wwdd_and_c & 0xff);
323 #define put_iac2(wwdd,c) put_iac2_merged(((wwdd)<<8) + (c))
325 #if ENABLE_FEATURE_TELNET_TTYPE
326 static void put_iac_subopt(byte c, char *str)
328 int len = strlen(str) + 6; // ( 2 + 1 + 1 + strlen + 2 )
330 if (G.iaclen + len > IACBUFSIZE)
346 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
347 static void put_iac_subopt_autologin(void)
349 int len = strlen(G.autologin) + 6; // (2 + 1 + 1 + strlen + 2)
350 const char *p = "USER";
352 if (G.iaclen + len > IACBUFSIZE)
357 put_iac(TELOPT_NEW_ENVIRON);
359 put_iac(NEW_ENV_VAR);
364 put_iac(NEW_ENV_VALUE);
375 #if ENABLE_FEATURE_AUTOWIDTH
376 static void put_iac_naws(byte c, int x, int y)
378 if (G.iaclen + 9 > IACBUFSIZE)
385 /* "... & 0xff" implicitly done below */
396 static void setConMode(void)
398 if (G.telflags & UF_ECHO) {
399 if (G.charmode == CHM_TRY) {
401 printf("\r\nEntering %s mode"
402 "\r\nEscape character is '^%c'.\r\n", "character", ']');
406 if (G.charmode != CHM_OFF) {
407 G.charmode = CHM_OFF;
408 printf("\r\nEntering %s mode"
409 "\r\nEscape character is '^%c'.\r\n", "line", 'C');
415 static void will_charmode(void)
417 G.charmode = CHM_TRY;
418 G.telflags |= (UF_ECHO | UF_SGA);
421 put_iac2(DO, TELOPT_ECHO);
422 put_iac2(DO, TELOPT_SGA);
426 static void do_linemode(void)
428 G.charmode = CHM_TRY;
429 G.telflags &= ~(UF_ECHO | UF_SGA);
432 put_iac2(DONT, TELOPT_ECHO);
433 put_iac2(DONT, TELOPT_SGA);
437 static void to_notsup(char c)
439 if (G.telwish == WILL)
441 else if (G.telwish == DO)
445 static void to_echo(void)
447 /* if server requests ECHO, don't agree */
448 if (G.telwish == DO) {
449 put_iac2(WONT, TELOPT_ECHO);
452 if (G.telwish == DONT)
455 if (G.telflags & UF_ECHO) {
456 if (G.telwish == WILL)
458 } else if (G.telwish == WONT)
461 if (G.charmode != CHM_OFF)
462 G.telflags ^= UF_ECHO;
464 if (G.telflags & UF_ECHO)
465 put_iac2(DO, TELOPT_ECHO);
467 put_iac2(DONT, TELOPT_ECHO);
470 full_write1_str("\r\n"); /* sudden modec */
473 static void to_sga(void)
475 /* daemon always sends will/wont, client do/dont */
477 if (G.telflags & UF_SGA) {
478 if (G.telwish == WILL)
480 } else if (G.telwish == WONT)
483 G.telflags ^= UF_SGA; /* toggle */
484 if (G.telflags & UF_SGA)
485 put_iac2(DO, TELOPT_SGA);
487 put_iac2(DONT, TELOPT_SGA);
490 #if ENABLE_FEATURE_TELNET_TTYPE
491 static void to_ttype(void)
493 /* Tell server we will (or won't) do TTYPE */
495 put_iac2(WILL, TELOPT_TTYPE);
497 put_iac2(WONT, TELOPT_TTYPE);
501 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
502 static void to_new_environ(void)
504 /* Tell server we will (or will not) do AUTOLOGIN */
506 put_iac2(WILL, TELOPT_NEW_ENVIRON);
508 put_iac2(WONT, TELOPT_NEW_ENVIRON);
512 #if ENABLE_FEATURE_AUTOWIDTH
513 static void to_naws(void)
515 /* Tell server we will do NAWS */
516 put_iac2(WILL, TELOPT_NAWS);
520 static void telopt(byte c)
527 #if ENABLE_FEATURE_TELNET_TTYPE
531 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
532 case TELOPT_NEW_ENVIRON:
533 to_new_environ(); break;
535 #if ENABLE_FEATURE_AUTOWIDTH
538 put_iac_naws(c, G.win_width, G.win_height);
547 /* subnegotiation -- ignore all (except TTYPE,NAWS) */
548 static void subneg(byte c)
550 switch (G.telstate) {
553 G.telstate = TS_SUB2;
554 #if ENABLE_FEATURE_TELNET_TTYPE
556 if (c == TELOPT_TTYPE && G.ttype)
557 put_iac_subopt(TELOPT_TTYPE, G.ttype);
559 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
561 if (c == TELOPT_NEW_ENVIRON && G.autologin)
562 put_iac_subopt_autologin();
567 G.telstate = TS_COPY;
570 G.telstate = TS_SUB1;
575 static void rawmode(void)
578 tcsetattr(0, TCSADRAIN, &G.termios_raw);
581 static void cookmode(void)
584 tcsetattr(0, TCSADRAIN, &G.termios_def);
587 int telnet_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
588 int telnet_main(int argc UNUSED_PARAM, char **argv)
593 struct pollfd ufds[2];
597 #if ENABLE_FEATURE_AUTOWIDTH
598 get_terminal_width_height(0, &G.win_width, &G.win_height);
601 #if ENABLE_FEATURE_TELNET_TTYPE
602 G.ttype = getenv("TERM");
605 if (tcgetattr(0, &G.termios_def) >= 0) {
607 G.termios_raw = G.termios_def;
608 cfmakeraw(&G.termios_raw);
611 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
612 if (1 & getopt32(argv, "al:", &G.autologin))
613 G.autologin = getenv("USER");
621 port = bb_lookup_port(*argv ? *argv++ : "telnet", "tcp", 23);
622 if (*argv) /* extra params?? */
625 xmove_fd(create_and_connect_stream_or_die(host, port), netfd);
627 setsockopt_keepalive(netfd);
629 signal(SIGINT, record_signo);
631 ufds[0].fd = STDIN_FILENO;
632 ufds[0].events = POLLIN;
634 ufds[1].events = POLLIN;
637 if (poll(ufds, 2, -1) < 0) {
638 /* error, ignore and/or log something, bay go to loop */
646 // FIXME: reads can block. Need full bidirectional buffering.
648 if (ufds[0].revents) {
649 len = safe_read(STDIN_FILENO, G.buf, DATABUFSIZE);
651 doexit(EXIT_SUCCESS);
652 TRACE(0, ("Read con: %d\n", len));
653 handle_net_output(len);
656 if (ufds[1].revents) {
657 len = safe_read(netfd, G.buf, DATABUFSIZE);
659 full_write1_str("Connection closed by foreign host\r\n");
660 doexit(EXIT_FAILURE);
662 TRACE(0, ("Read netfd (%d): %d\n", netfd, len));
663 handle_net_input(len);