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>
23 //config:config TELNET
24 //config: bool "telnet"
27 //config: Telnet is an interface to the TELNET protocol, but is also commonly
28 //config: used to test other simple protocols.
30 //config:config FEATURE_TELNET_TTYPE
31 //config: bool "Pass TERM type to remote host"
33 //config: depends on TELNET
35 //config: Setting this option will forward the TERM environment variable to the
36 //config: remote host you are connecting to. This is useful to make sure that
37 //config: things like ANSI colors and other control sequences behave.
39 //config:config FEATURE_TELNET_AUTOLOGIN
40 //config: bool "Pass USER type to remote host"
42 //config: depends on TELNET
44 //config: Setting this option will forward the USER environment variable to the
45 //config: remote host you are connecting to. This is useful when you need to
46 //config: log into a machine without telling the username (autologin). This
47 //config: option enables `-a' and `-l USER' arguments.
49 //applet:IF_TELNET(APPLET(telnet, BB_DIR_USR_BIN, BB_SUID_DROP))
51 //kbuild:lib-$(CONFIG_TELNET) += telnet.o
53 //usage:#if ENABLE_FEATURE_TELNET_AUTOLOGIN
54 //usage:#define telnet_trivial_usage
55 //usage: "[-a] [-l USER] HOST [PORT]"
56 //usage:#define telnet_full_usage "\n\n"
57 //usage: "Connect to telnet server\n"
58 //usage: "\n -a Automatic login with $USER variable"
59 //usage: "\n -l USER Automatic login as USER"
62 //usage:#define telnet_trivial_usage
63 //usage: "HOST [PORT]"
64 //usage:#define telnet_full_usage "\n\n"
65 //usage: "Connect to telnet server"
68 #include <arpa/telnet.h>
69 #include <netinet/in.h>
71 #include "common_bufsiz.h"
74 /* should be in arpa/telnet.h */
75 # define IAC 255 /* interpret as command: */
76 # define DONT 254 /* you are not to use option */
77 # define DO 253 /* please, you use option */
78 # define WONT 252 /* I won't use option */
79 # define WILL 251 /* I will use option */
80 # define SB 250 /* interpret as subnegotiation */
81 # define SE 240 /* end sub negotiation */
82 # define TELOPT_ECHO 1 /* echo */
83 # define TELOPT_SGA 3 /* suppress go ahead */
84 # define TELOPT_TTYPE 24 /* terminal type */
85 # define TELOPT_NAWS 31 /* window size */
89 # define TRACE(x, y) do { if (x) printf y; } while (0)
114 typedef unsigned char byte;
119 int iaclen; /* could even use byte, but it's a loss on x86 */
120 byte telstate; /* telnet negotiation state from network input */
121 byte telwish; /* DO, DONT, WILL, WONT */
125 #if ENABLE_FEATURE_TELNET_TTYPE
128 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
129 const char *autologin;
131 #if ENABLE_FEATURE_AUTOWIDTH
132 unsigned win_width, win_height;
134 /* same buffer used both for network and console read/write */
135 char buf[DATABUFSIZE];
136 /* buffer to handle telnet negotiations */
137 char iacbuf[IACBUFSIZE];
138 struct termios termios_def;
139 struct termios termios_raw;
141 #define G (*(struct globals*)bb_common_bufsiz1)
142 #define INIT_G() do { \
143 setup_common_bufsiz(); \
144 BUILD_BUG_ON(sizeof(G) > COMMON_BUFSIZE); \
148 static void rawmode(void);
149 static void cookmode(void);
150 static void do_linemode(void);
151 static void will_charmode(void);
152 static void telopt(byte c);
153 static void subneg(byte c);
155 static void iac_flush(void)
157 full_write(netfd, G.iacbuf, G.iaclen);
161 static void doexit(int ev) NORETURN;
162 static void doexit(int ev)
168 static void con_escape(void)
172 if (bb_got_signal) /* came from line mode... go raw */
175 full_write1_str("\r\nConsole escape. Commands are:\r\n\n"
176 " l go to line mode\r\n"
177 " c go to character mode\r\n"
178 " z suspend telnet\r\n"
179 " e exit telnet\r\n");
181 if (read(STDIN_FILENO, &b, 1) <= 0)
182 doexit(EXIT_FAILURE);
186 if (!bb_got_signal) {
203 doexit(EXIT_SUCCESS);
206 full_write1_str("continuing...\r\n");
214 static void handle_net_output(int len)
216 byte outbuf[2 * DATABUFSIZE];
218 byte *src = (byte*)G.buf;
219 byte *end = src + len;
229 *++dst = c; /* IAC -> IAC IAC */
231 if (c == '\r' || c == '\n') {
232 /* Enter key sends '\r' in raw mode and '\n' in cooked one.
234 * See RFC 1123 3.3.1 Telnet End-of-Line Convention.
235 * Using CR LF instead of other allowed possibilities
236 * like CR NUL - easier to talk to HTTP/SMTP servers.
238 *dst = '\r'; /* Enter -> CR LF */
243 if (dst - outbuf != 0)
244 full_write(netfd, outbuf, dst - outbuf);
247 static void handle_net_input(int len)
252 for (i = 0; i < len; i++) {
255 if (G.telstate == TS_NORMAL) { /* most typical state */
260 else if (c == '\r') {
264 /* No IACs were seen so far, no need to copy
265 * bytes within G.buf: */
269 switch (G.telstate) {
271 /* Prev char was CR. If cur one is NUL, ignore it.
272 * See RFC 1123 section 3.3.1 for discussion of telnet EOL handling.
274 G.telstate = TS_COPY;
277 /* else: fall through - need to handle CR IAC ... properly */
279 case TS_COPY: /* Prev char was ordinary */
280 /* Similar to NORMAL, but in TS_COPY we need to copy bytes */
289 case TS_IAC: /* Prev char was IAC */
290 if (c == IAC) { /* IAC IAC -> one IAC */
292 G.telstate = TS_COPY;
298 G.telstate = TS_SUB1;
307 /* DATA MARK must be added later */
309 G.telstate = TS_COPY;
313 case TS_OPT: /* Prev chars were IAC WILL/WONT/DO/DONT */
315 G.telstate = TS_COPY;
318 case TS_SUB1: /* Subnegotiation */
319 case TS_SUB2: /* Subnegotiation */
320 subneg(c); /* can change G.telstate */
325 if (G.telstate != TS_NORMAL) {
326 /* We had some IACs, or CR */
329 if (G.telstate == TS_COPY) /* we aren't in the middle of IAC */
330 G.telstate = TS_NORMAL;
335 full_write(STDOUT_FILENO, G.buf, len);
338 static void put_iac(int c)
340 G.iacbuf[G.iaclen++] = c;
343 static void put_iac2_merged(unsigned wwdd_and_c)
345 if (G.iaclen + 3 > IACBUFSIZE)
349 put_iac(wwdd_and_c >> 8);
350 put_iac(wwdd_and_c & 0xff);
352 #define put_iac2(wwdd,c) put_iac2_merged(((wwdd)<<8) + (c))
354 #if ENABLE_FEATURE_TELNET_TTYPE
355 static void put_iac_subopt(byte c, char *str)
357 int len = strlen(str) + 6; // ( 2 + 1 + 1 + strlen + 2 )
359 if (G.iaclen + len > IACBUFSIZE)
375 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
376 static void put_iac_subopt_autologin(void)
378 int len = strlen(G.autologin) + 6; // (2 + 1 + 1 + strlen + 2)
379 const char *p = "USER";
381 if (G.iaclen + len > IACBUFSIZE)
386 put_iac(TELOPT_NEW_ENVIRON);
388 put_iac(NEW_ENV_VAR);
393 put_iac(NEW_ENV_VALUE);
404 #if ENABLE_FEATURE_AUTOWIDTH
405 static void put_iac_naws(byte c, int x, int y)
407 if (G.iaclen + 9 > IACBUFSIZE)
414 /* "... & 0xff" implicitly done below */
425 static void setConMode(void)
427 if (G.telflags & UF_ECHO) {
428 if (G.charmode == CHM_TRY) {
430 printf("\r\nEntering %s mode"
431 "\r\nEscape character is '^%c'.\r\n", "character", ']');
435 if (G.charmode != CHM_OFF) {
436 G.charmode = CHM_OFF;
437 printf("\r\nEntering %s mode"
438 "\r\nEscape character is '^%c'.\r\n", "line", 'C');
444 static void will_charmode(void)
446 G.charmode = CHM_TRY;
447 G.telflags |= (UF_ECHO | UF_SGA);
450 put_iac2(DO, TELOPT_ECHO);
451 put_iac2(DO, TELOPT_SGA);
455 static void do_linemode(void)
457 G.charmode = CHM_TRY;
458 G.telflags &= ~(UF_ECHO | UF_SGA);
461 put_iac2(DONT, TELOPT_ECHO);
462 put_iac2(DONT, TELOPT_SGA);
466 static void to_notsup(char c)
468 if (G.telwish == WILL)
470 else if (G.telwish == DO)
474 static void to_echo(void)
476 /* if server requests ECHO, don't agree */
477 if (G.telwish == DO) {
478 put_iac2(WONT, TELOPT_ECHO);
481 if (G.telwish == DONT)
484 if (G.telflags & UF_ECHO) {
485 if (G.telwish == WILL)
487 } else if (G.telwish == WONT)
490 if (G.charmode != CHM_OFF)
491 G.telflags ^= UF_ECHO;
493 if (G.telflags & UF_ECHO)
494 put_iac2(DO, TELOPT_ECHO);
496 put_iac2(DONT, TELOPT_ECHO);
499 full_write1_str("\r\n"); /* sudden modec */
502 static void to_sga(void)
504 /* daemon always sends will/wont, client do/dont */
506 if (G.telflags & UF_SGA) {
507 if (G.telwish == WILL)
509 } else if (G.telwish == WONT)
512 G.telflags ^= UF_SGA; /* toggle */
513 if (G.telflags & UF_SGA)
514 put_iac2(DO, TELOPT_SGA);
516 put_iac2(DONT, TELOPT_SGA);
519 #if ENABLE_FEATURE_TELNET_TTYPE
520 static void to_ttype(void)
522 /* Tell server we will (or won't) do TTYPE */
524 put_iac2(WILL, TELOPT_TTYPE);
526 put_iac2(WONT, TELOPT_TTYPE);
530 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
531 static void to_new_environ(void)
533 /* Tell server we will (or will not) do AUTOLOGIN */
535 put_iac2(WILL, TELOPT_NEW_ENVIRON);
537 put_iac2(WONT, TELOPT_NEW_ENVIRON);
541 #if ENABLE_FEATURE_AUTOWIDTH
542 static void to_naws(void)
544 /* Tell server we will do NAWS */
545 put_iac2(WILL, TELOPT_NAWS);
549 static void telopt(byte c)
556 #if ENABLE_FEATURE_TELNET_TTYPE
560 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
561 case TELOPT_NEW_ENVIRON:
562 to_new_environ(); break;
564 #if ENABLE_FEATURE_AUTOWIDTH
567 put_iac_naws(c, G.win_width, G.win_height);
576 /* subnegotiation -- ignore all (except TTYPE,NAWS) */
577 static void subneg(byte c)
579 switch (G.telstate) {
582 G.telstate = TS_SUB2;
583 #if ENABLE_FEATURE_TELNET_TTYPE
585 if (c == TELOPT_TTYPE && G.ttype)
586 put_iac_subopt(TELOPT_TTYPE, G.ttype);
588 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
590 if (c == TELOPT_NEW_ENVIRON && G.autologin)
591 put_iac_subopt_autologin();
596 G.telstate = TS_COPY;
599 G.telstate = TS_SUB1;
604 static void rawmode(void)
607 tcsetattr(0, TCSADRAIN, &G.termios_raw);
610 static void cookmode(void)
613 tcsetattr(0, TCSADRAIN, &G.termios_def);
616 int telnet_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
617 int telnet_main(int argc UNUSED_PARAM, char **argv)
622 struct pollfd ufds[2];
626 #if ENABLE_FEATURE_AUTOWIDTH
627 get_terminal_width_height(0, &G.win_width, &G.win_height);
630 #if ENABLE_FEATURE_TELNET_TTYPE
631 G.ttype = getenv("TERM");
634 if (tcgetattr(0, &G.termios_def) >= 0) {
636 G.termios_raw = G.termios_def;
637 cfmakeraw(&G.termios_raw);
640 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
641 if (1 & getopt32(argv, "al:", &G.autologin))
642 G.autologin = getenv("USER");
650 port = bb_lookup_port(*argv ? *argv++ : "telnet", "tcp", 23);
651 if (*argv) /* extra params?? */
654 xmove_fd(create_and_connect_stream_or_die(host, port), netfd);
656 setsockopt_keepalive(netfd);
658 signal(SIGINT, record_signo);
660 ufds[0].fd = STDIN_FILENO;
661 ufds[0].events = POLLIN;
663 ufds[1].events = POLLIN;
666 if (poll(ufds, 2, -1) < 0) {
667 /* error, ignore and/or log something, bay go to loop */
675 // FIXME: reads can block. Need full bidirectional buffering.
677 if (ufds[0].revents) {
678 len = safe_read(STDIN_FILENO, G.buf, DATABUFSIZE);
680 doexit(EXIT_SUCCESS);
681 TRACE(0, ("Read con: %d\n", len));
682 handle_net_output(len);
685 if (ufds[1].revents) {
686 len = safe_read(netfd, G.buf, DATABUFSIZE);
688 full_write1_str("Connection closed by foreign host\r\n");
689 doexit(EXIT_FAILURE);
691 TRACE(0, ("Read netfd (%d): %d\n", netfd, len));
692 handle_net_input(len);