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 BUILD_BUG_ON(sizeof(G) > COMMON_BUFSIZE); \
118 static void rawmode(void);
119 static void cookmode(void);
120 static void do_linemode(void);
121 static void will_charmode(void);
122 static void telopt(byte c);
123 static void subneg(byte c);
125 static void iac_flush(void)
127 full_write(netfd, G.iacbuf, G.iaclen);
131 static void doexit(int ev) NORETURN;
132 static void doexit(int ev)
138 static void con_escape(void)
142 if (bb_got_signal) /* came from line mode... go raw */
145 full_write1_str("\r\nConsole escape. Commands are:\r\n\n"
146 " l go to line mode\r\n"
147 " c go to character mode\r\n"
148 " z suspend telnet\r\n"
149 " e exit telnet\r\n");
151 if (read(STDIN_FILENO, &b, 1) <= 0)
152 doexit(EXIT_FAILURE);
156 if (!bb_got_signal) {
173 doexit(EXIT_SUCCESS);
176 full_write1_str("continuing...\r\n");
184 static void handle_net_output(int len)
186 byte outbuf[2 * DATABUFSIZE];
188 byte *src = (byte*)G.buf;
189 byte *end = src + len;
199 *++dst = c; /* IAC -> IAC IAC */
201 if (c == '\r' || c == '\n') {
202 /* Enter key sends '\r' in raw mode and '\n' in cooked one.
204 * See RFC 1123 3.3.1 Telnet End-of-Line Convention.
205 * Using CR LF instead of other allowed possibilities
206 * like CR NUL - easier to talk to HTTP/SMTP servers.
208 *dst = '\r'; /* Enter -> CR LF */
213 if (dst - outbuf != 0)
214 full_write(netfd, outbuf, dst - outbuf);
217 static void handle_net_input(int len)
222 for (i = 0; i < len; i++) {
225 if (G.telstate == TS_NORMAL) { /* most typical state */
230 else if (c == '\r') {
234 /* No IACs were seen so far, no need to copy
235 * bytes within G.buf: */
239 switch (G.telstate) {
241 /* Prev char was CR. If cur one is NUL, ignore it.
242 * See RFC 1123 section 3.3.1 for discussion of telnet EOL handling.
244 G.telstate = TS_COPY;
247 /* else: fall through - need to handle CR IAC ... properly */
249 case TS_COPY: /* Prev char was ordinary */
250 /* Similar to NORMAL, but in TS_COPY we need to copy bytes */
259 case TS_IAC: /* Prev char was IAC */
260 if (c == IAC) { /* IAC IAC -> one IAC */
262 G.telstate = TS_COPY;
268 G.telstate = TS_SUB1;
277 /* DATA MARK must be added later */
279 G.telstate = TS_COPY;
283 case TS_OPT: /* Prev chars were IAC WILL/WONT/DO/DONT */
285 G.telstate = TS_COPY;
288 case TS_SUB1: /* Subnegotiation */
289 case TS_SUB2: /* Subnegotiation */
290 subneg(c); /* can change G.telstate */
295 if (G.telstate != TS_NORMAL) {
296 /* We had some IACs, or CR */
299 if (G.telstate == TS_COPY) /* we aren't in the middle of IAC */
300 G.telstate = TS_NORMAL;
305 full_write(STDOUT_FILENO, G.buf, len);
308 static void put_iac(int c)
310 G.iacbuf[G.iaclen++] = c;
313 static void put_iac2(byte wwdd, byte c)
315 if (G.iaclen + 3 > IACBUFSIZE)
323 #if ENABLE_FEATURE_TELNET_TTYPE
324 static void put_iac_subopt(byte c, char *str)
326 int len = strlen(str) + 6; // ( 2 + 1 + 1 + strlen + 2 )
328 if (G.iaclen + len > IACBUFSIZE)
344 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
345 static void put_iac_subopt_autologin(void)
347 int len = strlen(G.autologin) + 6; // (2 + 1 + 1 + strlen + 2)
348 const char *p = "USER";
350 if (G.iaclen + len > IACBUFSIZE)
355 put_iac(TELOPT_NEW_ENVIRON);
357 put_iac(NEW_ENV_VAR);
362 put_iac(NEW_ENV_VALUE);
373 #if ENABLE_FEATURE_AUTOWIDTH
374 static void put_iac_naws(byte c, int x, int y)
376 if (G.iaclen + 9 > IACBUFSIZE)
383 /* "... & 0xff" implicitly done below */
394 static void setConMode(void)
396 if (G.telflags & UF_ECHO) {
397 if (G.charmode == CHM_TRY) {
399 printf("\r\nEntering %s mode"
400 "\r\nEscape character is '^%c'.\r\n", "character", ']');
404 if (G.charmode != CHM_OFF) {
405 G.charmode = CHM_OFF;
406 printf("\r\nEntering %s mode"
407 "\r\nEscape character is '^%c'.\r\n", "line", 'C');
413 static void will_charmode(void)
415 G.charmode = CHM_TRY;
416 G.telflags |= (UF_ECHO | UF_SGA);
419 put_iac2(DO, TELOPT_ECHO);
420 put_iac2(DO, TELOPT_SGA);
424 static void do_linemode(void)
426 G.charmode = CHM_TRY;
427 G.telflags &= ~(UF_ECHO | UF_SGA);
430 put_iac2(DONT, TELOPT_ECHO);
431 put_iac2(DONT, TELOPT_SGA);
435 static void to_notsup(char c)
437 if (G.telwish == WILL)
439 else if (G.telwish == DO)
443 static void to_echo(void)
445 /* if server requests ECHO, don't agree */
446 if (G.telwish == DO) {
447 put_iac2(WONT, TELOPT_ECHO);
450 if (G.telwish == DONT)
453 if (G.telflags & UF_ECHO) {
454 if (G.telwish == WILL)
456 } else if (G.telwish == WONT)
459 if (G.charmode != CHM_OFF)
460 G.telflags ^= UF_ECHO;
462 if (G.telflags & UF_ECHO)
463 put_iac2(DO, TELOPT_ECHO);
465 put_iac2(DONT, TELOPT_ECHO);
468 full_write1_str("\r\n"); /* sudden modec */
471 static void to_sga(void)
473 /* daemon always sends will/wont, client do/dont */
475 if (G.telflags & UF_SGA) {
476 if (G.telwish == WILL)
478 } else if (G.telwish == WONT)
481 G.telflags ^= UF_SGA; /* toggle */
482 if (G.telflags & UF_SGA)
483 put_iac2(DO, TELOPT_SGA);
485 put_iac2(DONT, TELOPT_SGA);
488 #if ENABLE_FEATURE_TELNET_TTYPE
489 static void to_ttype(void)
491 /* Tell server we will (or won't) do TTYPE */
493 put_iac2(WILL, TELOPT_TTYPE);
495 put_iac2(WONT, TELOPT_TTYPE);
499 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
500 static void to_new_environ(void)
502 /* Tell server we will (or will not) do AUTOLOGIN */
504 put_iac2(WILL, TELOPT_NEW_ENVIRON);
506 put_iac2(WONT, TELOPT_NEW_ENVIRON);
510 #if ENABLE_FEATURE_AUTOWIDTH
511 static void to_naws(void)
513 /* Tell server we will do NAWS */
514 put_iac2(WILL, TELOPT_NAWS);
518 static void telopt(byte c)
525 #if ENABLE_FEATURE_TELNET_TTYPE
529 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
530 case TELOPT_NEW_ENVIRON:
531 to_new_environ(); break;
533 #if ENABLE_FEATURE_AUTOWIDTH
536 put_iac_naws(c, G.win_width, G.win_height);
545 /* subnegotiation -- ignore all (except TTYPE,NAWS) */
546 static void subneg(byte c)
548 switch (G.telstate) {
551 G.telstate = TS_SUB2;
552 #if ENABLE_FEATURE_TELNET_TTYPE
554 if (c == TELOPT_TTYPE && G.ttype)
555 put_iac_subopt(TELOPT_TTYPE, G.ttype);
557 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
559 if (c == TELOPT_NEW_ENVIRON && G.autologin)
560 put_iac_subopt_autologin();
565 G.telstate = TS_COPY;
568 G.telstate = TS_SUB1;
573 static void rawmode(void)
576 tcsetattr(0, TCSADRAIN, &G.termios_raw);
579 static void cookmode(void)
582 tcsetattr(0, TCSADRAIN, &G.termios_def);
585 int telnet_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
586 int telnet_main(int argc UNUSED_PARAM, char **argv)
591 struct pollfd ufds[2];
595 #if ENABLE_FEATURE_AUTOWIDTH
596 get_terminal_width_height(0, &G.win_width, &G.win_height);
599 #if ENABLE_FEATURE_TELNET_TTYPE
600 G.ttype = getenv("TERM");
603 if (tcgetattr(0, &G.termios_def) >= 0) {
605 G.termios_raw = G.termios_def;
606 cfmakeraw(&G.termios_raw);
609 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
610 if (1 & getopt32(argv, "al:", &G.autologin))
611 G.autologin = getenv("USER");
619 port = bb_lookup_port(*argv ? *argv++ : "telnet", "tcp", 23);
620 if (*argv) /* extra params?? */
623 xmove_fd(create_and_connect_stream_or_die(host, port), netfd);
625 setsockopt_keepalive(netfd);
627 signal(SIGINT, record_signo);
629 ufds[0].fd = STDIN_FILENO;
630 ufds[0].events = POLLIN;
632 ufds[1].events = POLLIN;
635 if (poll(ufds, 2, -1) < 0) {
636 /* error, ignore and/or log something, bay go to loop */
644 // FIXME: reads can block. Need full bidirectional buffering.
646 if (ufds[0].revents) {
647 len = safe_read(STDIN_FILENO, G.buf, DATABUFSIZE);
649 doexit(EXIT_SUCCESS);
650 TRACE(0, ("Read con: %d\n", len));
651 handle_net_output(len);
654 if (ufds[1].revents) {
655 len = safe_read(netfd, G.buf, DATABUFSIZE);
657 full_write1_str("Connection closed by foreign host\r\n");
658 doexit(EXIT_FAILURE);
660 TRACE(0, ("Read netfd (%d): %d\n", netfd, len));
661 handle_net_input(len);