summaryrefslogtreecommitdiff
path: root/networking/telnet.c (plain)
blob: f520fe1dda327f19b95da08fa6e7411fefd816ce
1/* vi: set sw=4 ts=4: */
2/*
3 * telnet implementation for busybox
4 *
5 * Author: Tomi Ollila <too@iki.fi>
6 * Copyright (C) 1994-2000 by Tomi Ollila
7 *
8 * Created: Thu Apr 7 13:29:41 1994 too
9 * Last modified: Fri Jun 9 14:34:24 2000 too
10 *
11 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
12 *
13 * HISTORY
14 * Revision 3.1 1994/04/17 11:31:54 too
15 * initial revision
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
18 * <jam@ltsp.org>
19 * Modified 2004/02/11 to add ability to pass the USER variable to remote host
20 * by Fernando Silveira <swrh@gmx.net>
21 *
22 */
23//config:config TELNET
24//config: bool "telnet"
25//config: default y
26//config: help
27//config: Telnet is an interface to the TELNET protocol, but is also commonly
28//config: used to test other simple protocols.
29//config:
30//config:config FEATURE_TELNET_TTYPE
31//config: bool "Pass TERM type to remote host"
32//config: default y
33//config: depends on TELNET
34//config: help
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.
38//config:
39//config:config FEATURE_TELNET_AUTOLOGIN
40//config: bool "Pass USER type to remote host"
41//config: default y
42//config: depends on TELNET
43//config: help
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.
48
49//applet:IF_TELNET(APPLET(telnet, BB_DIR_USR_BIN, BB_SUID_DROP))
50
51//kbuild:lib-$(CONFIG_TELNET) += telnet.o
52
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"
60//usage:
61//usage:#else
62//usage:#define telnet_trivial_usage
63//usage: "HOST [PORT]"
64//usage:#define telnet_full_usage "\n\n"
65//usage: "Connect to telnet server"
66//usage:#endif
67
68#include <arpa/telnet.h>
69#include <netinet/in.h>
70#include "libbb.h"
71#include "common_bufsiz.h"
72
73#ifdef __BIONIC__
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 */
86#endif
87
88#ifdef DOTRACE
89# define TRACE(x, y) do { if (x) printf y; } while (0)
90#else
91# define TRACE(x, y)
92#endif
93
94enum {
95 DATABUFSIZE = 128,
96 IACBUFSIZE = 128,
97
98 CHM_TRY = 0,
99 CHM_ON = 1,
100 CHM_OFF = 2,
101
102 UF_ECHO = 0x01,
103 UF_SGA = 0x02,
104
105 TS_NORMAL = 0,
106 TS_COPY = 1,
107 TS_IAC = 2,
108 TS_OPT = 3,
109 TS_SUB1 = 4,
110 TS_SUB2 = 5,
111 TS_CR = 6,
112};
113
114typedef unsigned char byte;
115
116enum { netfd = 3 };
117
118struct globals {
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 */
122 byte charmode;
123 byte telflags;
124 byte do_termios;
125#if ENABLE_FEATURE_TELNET_TTYPE
126 char *ttype;
127#endif
128#if ENABLE_FEATURE_TELNET_AUTOLOGIN
129 const char *autologin;
130#endif
131#if ENABLE_FEATURE_AUTOWIDTH
132 unsigned win_width, win_height;
133#endif
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;
140} FIX_ALIASING;
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); \
145} while (0)
146
147
148static void rawmode(void);
149static void cookmode(void);
150static void do_linemode(void);
151static void will_charmode(void);
152static void telopt(byte c);
153static void subneg(byte c);
154
155static void iac_flush(void)
156{
157 full_write(netfd, G.iacbuf, G.iaclen);
158 G.iaclen = 0;
159}
160
161static void doexit(int ev) NORETURN;
162static void doexit(int ev)
163{
164 cookmode();
165 exit(ev);
166}
167
168static void con_escape(void)
169{
170 char b;
171
172 if (bb_got_signal) /* came from line mode... go raw */
173 rawmode();
174
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");
180
181 if (read(STDIN_FILENO, &b, 1) <= 0)
182 doexit(EXIT_FAILURE);
183
184 switch (b) {
185 case 'l':
186 if (!bb_got_signal) {
187 do_linemode();
188 goto ret;
189 }
190 break;
191 case 'c':
192 if (bb_got_signal) {
193 will_charmode();
194 goto ret;
195 }
196 break;
197 case 'z':
198 cookmode();
199 kill(0, SIGTSTP);
200 rawmode();
201 break;
202 case 'e':
203 doexit(EXIT_SUCCESS);
204 }
205
206 full_write1_str("continuing...\r\n");
207
208 if (bb_got_signal)
209 cookmode();
210 ret:
211 bb_got_signal = 0;
212}
213
214static void handle_net_output(int len)
215{
216 byte outbuf[2 * DATABUFSIZE];
217 byte *dst = outbuf;
218 byte *src = (byte*)G.buf;
219 byte *end = src + len;
220
221 while (src < end) {
222 byte c = *src++;
223 if (c == 0x1d) {
224 con_escape();
225 return;
226 }
227 *dst = c;
228 if (c == IAC)
229 *++dst = c; /* IAC -> IAC IAC */
230 else
231 if (c == '\r' || c == '\n') {
232 /* Enter key sends '\r' in raw mode and '\n' in cooked one.
233 *
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.
237 */
238 *dst = '\r'; /* Enter -> CR LF */
239 *++dst = '\n';
240 }
241 dst++;
242 }
243 if (dst - outbuf != 0)
244 full_write(netfd, outbuf, dst - outbuf);
245}
246
247static void handle_net_input(int len)
248{
249 int i;
250 int cstart = 0;
251
252 for (i = 0; i < len; i++) {
253 byte c = G.buf[i];
254
255 if (G.telstate == TS_NORMAL) { /* most typical state */
256 if (c == IAC) {
257 cstart = i;
258 G.telstate = TS_IAC;
259 }
260 else if (c == '\r') {
261 cstart = i + 1;
262 G.telstate = TS_CR;
263 }
264 /* No IACs were seen so far, no need to copy
265 * bytes within G.buf: */
266 continue;
267 }
268
269 switch (G.telstate) {
270 case TS_CR:
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.
273 */
274 G.telstate = TS_COPY;
275 if (c == '\0')
276 break;
277 /* else: fall through - need to handle CR IAC ... properly */
278
279 case TS_COPY: /* Prev char was ordinary */
280 /* Similar to NORMAL, but in TS_COPY we need to copy bytes */
281 if (c == IAC)
282 G.telstate = TS_IAC;
283 else
284 G.buf[cstart++] = c;
285 if (c == '\r')
286 G.telstate = TS_CR;
287 break;
288
289 case TS_IAC: /* Prev char was IAC */
290 if (c == IAC) { /* IAC IAC -> one IAC */
291 G.buf[cstart++] = c;
292 G.telstate = TS_COPY;
293 break;
294 }
295 /* else */
296 switch (c) {
297 case SB:
298 G.telstate = TS_SUB1;
299 break;
300 case DO:
301 case DONT:
302 case WILL:
303 case WONT:
304 G.telwish = c;
305 G.telstate = TS_OPT;
306 break;
307 /* DATA MARK must be added later */
308 default:
309 G.telstate = TS_COPY;
310 }
311 break;
312
313 case TS_OPT: /* Prev chars were IAC WILL/WONT/DO/DONT */
314 telopt(c);
315 G.telstate = TS_COPY;
316 break;
317
318 case TS_SUB1: /* Subnegotiation */
319 case TS_SUB2: /* Subnegotiation */
320 subneg(c); /* can change G.telstate */
321 break;
322 }
323 }
324
325 if (G.telstate != TS_NORMAL) {
326 /* We had some IACs, or CR */
327 if (G.iaclen)
328 iac_flush();
329 if (G.telstate == TS_COPY) /* we aren't in the middle of IAC */
330 G.telstate = TS_NORMAL;
331 len = cstart;
332 }
333
334 if (len)
335 full_write(STDOUT_FILENO, G.buf, len);
336}
337
338static void put_iac(int c)
339{
340 G.iacbuf[G.iaclen++] = c;
341}
342
343static void put_iac2_merged(unsigned wwdd_and_c)
344{
345 if (G.iaclen + 3 > IACBUFSIZE)
346 iac_flush();
347
348 put_iac(IAC);
349 put_iac(wwdd_and_c >> 8);
350 put_iac(wwdd_and_c & 0xff);
351}
352#define put_iac2(wwdd,c) put_iac2_merged(((wwdd)<<8) + (c))
353
354#if ENABLE_FEATURE_TELNET_TTYPE
355static void put_iac_subopt(byte c, char *str)
356{
357 int len = strlen(str) + 6; // ( 2 + 1 + 1 + strlen + 2 )
358
359 if (G.iaclen + len > IACBUFSIZE)
360 iac_flush();
361
362 put_iac(IAC);
363 put_iac(SB);
364 put_iac(c);
365 put_iac(0);
366
367 while (*str)
368 put_iac(*str++);
369
370 put_iac(IAC);
371 put_iac(SE);
372}
373#endif
374
375#if ENABLE_FEATURE_TELNET_AUTOLOGIN
376static void put_iac_subopt_autologin(void)
377{
378 int len = strlen(G.autologin) + 6; // (2 + 1 + 1 + strlen + 2)
379 const char *p = "USER";
380
381 if (G.iaclen + len > IACBUFSIZE)
382 iac_flush();
383
384 put_iac(IAC);
385 put_iac(SB);
386 put_iac(TELOPT_NEW_ENVIRON);
387 put_iac(TELQUAL_IS);
388 put_iac(NEW_ENV_VAR);
389
390 while (*p)
391 put_iac(*p++);
392
393 put_iac(NEW_ENV_VALUE);
394
395 p = G.autologin;
396 while (*p)
397 put_iac(*p++);
398
399 put_iac(IAC);
400 put_iac(SE);
401}
402#endif
403
404#if ENABLE_FEATURE_AUTOWIDTH
405static void put_iac_naws(byte c, int x, int y)
406{
407 if (G.iaclen + 9 > IACBUFSIZE)
408 iac_flush();
409
410 put_iac(IAC);
411 put_iac(SB);
412 put_iac(c);
413
414 /* "... & 0xff" implicitly done below */
415 put_iac(x >> 8);
416 put_iac(x);
417 put_iac(y >> 8);
418 put_iac(y);
419
420 put_iac(IAC);
421 put_iac(SE);
422}
423#endif
424
425static void setConMode(void)
426{
427 if (G.telflags & UF_ECHO) {
428 if (G.charmode == CHM_TRY) {
429 G.charmode = CHM_ON;
430 printf("\r\nEntering %s mode"
431 "\r\nEscape character is '^%c'.\r\n", "character", ']');
432 rawmode();
433 }
434 } else {
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');
439 cookmode();
440 }
441 }
442}
443
444static void will_charmode(void)
445{
446 G.charmode = CHM_TRY;
447 G.telflags |= (UF_ECHO | UF_SGA);
448 setConMode();
449
450 put_iac2(DO, TELOPT_ECHO);
451 put_iac2(DO, TELOPT_SGA);
452 iac_flush();
453}
454
455static void do_linemode(void)
456{
457 G.charmode = CHM_TRY;
458 G.telflags &= ~(UF_ECHO | UF_SGA);
459 setConMode();
460
461 put_iac2(DONT, TELOPT_ECHO);
462 put_iac2(DONT, TELOPT_SGA);
463 iac_flush();
464}
465
466static void to_notsup(char c)
467{
468 if (G.telwish == WILL)
469 put_iac2(DONT, c);
470 else if (G.telwish == DO)
471 put_iac2(WONT, c);
472}
473
474static void to_echo(void)
475{
476 /* if server requests ECHO, don't agree */
477 if (G.telwish == DO) {
478 put_iac2(WONT, TELOPT_ECHO);
479 return;
480 }
481 if (G.telwish == DONT)
482 return;
483
484 if (G.telflags & UF_ECHO) {
485 if (G.telwish == WILL)
486 return;
487 } else if (G.telwish == WONT)
488 return;
489
490 if (G.charmode != CHM_OFF)
491 G.telflags ^= UF_ECHO;
492
493 if (G.telflags & UF_ECHO)
494 put_iac2(DO, TELOPT_ECHO);
495 else
496 put_iac2(DONT, TELOPT_ECHO);
497
498 setConMode();
499 full_write1_str("\r\n"); /* sudden modec */
500}
501
502static void to_sga(void)
503{
504 /* daemon always sends will/wont, client do/dont */
505
506 if (G.telflags & UF_SGA) {
507 if (G.telwish == WILL)
508 return;
509 } else if (G.telwish == WONT)
510 return;
511
512 G.telflags ^= UF_SGA; /* toggle */
513 if (G.telflags & UF_SGA)
514 put_iac2(DO, TELOPT_SGA);
515 else
516 put_iac2(DONT, TELOPT_SGA);
517}
518
519#if ENABLE_FEATURE_TELNET_TTYPE
520static void to_ttype(void)
521{
522 /* Tell server we will (or won't) do TTYPE */
523 if (G.ttype)
524 put_iac2(WILL, TELOPT_TTYPE);
525 else
526 put_iac2(WONT, TELOPT_TTYPE);
527}
528#endif
529
530#if ENABLE_FEATURE_TELNET_AUTOLOGIN
531static void to_new_environ(void)
532{
533 /* Tell server we will (or will not) do AUTOLOGIN */
534 if (G.autologin)
535 put_iac2(WILL, TELOPT_NEW_ENVIRON);
536 else
537 put_iac2(WONT, TELOPT_NEW_ENVIRON);
538}
539#endif
540
541#if ENABLE_FEATURE_AUTOWIDTH
542static void to_naws(void)
543{
544 /* Tell server we will do NAWS */
545 put_iac2(WILL, TELOPT_NAWS);
546}
547#endif
548
549static void telopt(byte c)
550{
551 switch (c) {
552 case TELOPT_ECHO:
553 to_echo(); break;
554 case TELOPT_SGA:
555 to_sga(); break;
556#if ENABLE_FEATURE_TELNET_TTYPE
557 case TELOPT_TTYPE:
558 to_ttype(); break;
559#endif
560#if ENABLE_FEATURE_TELNET_AUTOLOGIN
561 case TELOPT_NEW_ENVIRON:
562 to_new_environ(); break;
563#endif
564#if ENABLE_FEATURE_AUTOWIDTH
565 case TELOPT_NAWS:
566 to_naws();
567 put_iac_naws(c, G.win_width, G.win_height);
568 break;
569#endif
570 default:
571 to_notsup(c);
572 break;
573 }
574}
575
576/* subnegotiation -- ignore all (except TTYPE,NAWS) */
577static void subneg(byte c)
578{
579 switch (G.telstate) {
580 case TS_SUB1:
581 if (c == IAC)
582 G.telstate = TS_SUB2;
583#if ENABLE_FEATURE_TELNET_TTYPE
584 else
585 if (c == TELOPT_TTYPE && G.ttype)
586 put_iac_subopt(TELOPT_TTYPE, G.ttype);
587#endif
588#if ENABLE_FEATURE_TELNET_AUTOLOGIN
589 else
590 if (c == TELOPT_NEW_ENVIRON && G.autologin)
591 put_iac_subopt_autologin();
592#endif
593 break;
594 case TS_SUB2:
595 if (c == SE) {
596 G.telstate = TS_COPY;
597 return;
598 }
599 G.telstate = TS_SUB1;
600 break;
601 }
602}
603
604static void rawmode(void)
605{
606 if (G.do_termios)
607 tcsetattr(0, TCSADRAIN, &G.termios_raw);
608}
609
610static void cookmode(void)
611{
612 if (G.do_termios)
613 tcsetattr(0, TCSADRAIN, &G.termios_def);
614}
615
616int telnet_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
617int telnet_main(int argc UNUSED_PARAM, char **argv)
618{
619 char *host;
620 int port;
621 int len;
622 struct pollfd ufds[2];
623
624 INIT_G();
625
626#if ENABLE_FEATURE_AUTOWIDTH
627 get_terminal_width_height(0, &G.win_width, &G.win_height);
628#endif
629
630#if ENABLE_FEATURE_TELNET_TTYPE
631 G.ttype = getenv("TERM");
632#endif
633
634 if (tcgetattr(0, &G.termios_def) >= 0) {
635 G.do_termios = 1;
636 G.termios_raw = G.termios_def;
637 cfmakeraw(&G.termios_raw);
638 }
639
640#if ENABLE_FEATURE_TELNET_AUTOLOGIN
641 if (1 & getopt32(argv, "al:", &G.autologin))
642 G.autologin = getenv("USER");
643 argv += optind;
644#else
645 argv++;
646#endif
647 if (!*argv)
648 bb_show_usage();
649 host = *argv++;
650 port = bb_lookup_port(*argv ? *argv++ : "telnet", "tcp", 23);
651 if (*argv) /* extra params?? */
652 bb_show_usage();
653
654 xmove_fd(create_and_connect_stream_or_die(host, port), netfd);
655
656 setsockopt_keepalive(netfd);
657
658 signal(SIGINT, record_signo);
659
660 ufds[0].fd = STDIN_FILENO;
661 ufds[0].events = POLLIN;
662 ufds[1].fd = netfd;
663 ufds[1].events = POLLIN;
664
665 while (1) {
666 if (poll(ufds, 2, -1) < 0) {
667 /* error, ignore and/or log something, bay go to loop */
668 if (bb_got_signal)
669 con_escape();
670 else
671 sleep(1);
672 continue;
673 }
674
675// FIXME: reads can block. Need full bidirectional buffering.
676
677 if (ufds[0].revents) {
678 len = safe_read(STDIN_FILENO, G.buf, DATABUFSIZE);
679 if (len <= 0)
680 doexit(EXIT_SUCCESS);
681 TRACE(0, ("Read con: %d\n", len));
682 handle_net_output(len);
683 }
684
685 if (ufds[1].revents) {
686 len = safe_read(netfd, G.buf, DATABUFSIZE);
687 if (len <= 0) {
688 full_write1_str("Connection closed by foreign host\r\n");
689 doexit(EXIT_FAILURE);
690 }
691 TRACE(0, ("Read netfd (%d): %d\n", netfd, len));
692 handle_net_input(len);
693 }
694 } /* while (1) */
695}
696
generated by cgit at 2024-05-15 07:43:14 (GMT)