busybox/networking/telnet.c

/* vi: set sw=4 ts=4: */
/*
 * telnet implementation for busybox
 *
 * Author: Tomi Ollila <too@iki.fi>
 * Copyright (C) 1994-2000 by Tomi Ollila
 *
 * Created: Thu Apr  7 13:29:41 1994 too
 * Last modified: Fri Jun  9 14:34:24 2000 too
 *
 * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
 *
 * HISTORY
 * Revision 3.1  1994/04/17  11:31:54  too
 * initial revision
 * Modified 2000/06/13 for inclusion into BusyBox by Erik Andersen <andersen@codepoet.org>
 * Modified 2001/05/07 to add ability to pass TTYPE to remote host by Jim McQuillan
 * <jam@ltsp.org>
 * Modified 2004/02/11 to add ability to pass the USER variable to remote host
 * by Fernando Silveira <swrh@gmx.net>
 *
 */

#include <arpa/telnet.h>
#include <netinet/in.h>
#include "libbb.h"

#ifdef DOTRACE
#define TRACE(x, y) do { if (x) printf y; } while (0)
#else
#define TRACE(x, y)
#endif

enum {
	DATABUFSIZE = 128,
	IACBUFSIZE  = 128,

	CHM_TRY = 0,
	CHM_ON = 1,
	CHM_OFF = 2,

	UF_ECHO = 0x01,
	UF_SGA = 0x02,

	TS_0 = 1,
	TS_IAC = 2,
	TS_OPT = 3,
	TS_SUB1 = 4,
	TS_SUB2 = 5,
};

typedef unsigned char byte;

enum { netfd = 3 };

struct globals {
	int	iaclen; /* could even use byte, but it's a loss on x86 */
	byte	telstate; /* telnet negotiation state from network input */
	byte	telwish;  /* DO, DONT, WILL, WONT */
	byte    charmode;
	byte    telflags;
	byte	do_termios;
#if ENABLE_FEATURE_TELNET_TTYPE
	char	*ttype;
#endif
#if ENABLE_FEATURE_TELNET_AUTOLOGIN
	const char *autologin;
#endif
#if ENABLE_FEATURE_AUTOWIDTH
	unsigned win_width, win_height;
#endif
	/* same buffer used both for network and console read/write */
	char    buf[DATABUFSIZE];
	/* buffer to handle telnet negotiations */
	char    iacbuf[IACBUFSIZE];
	struct termios termios_def;
	struct termios termios_raw;
};
#define G (*(struct globals*)&bb_common_bufsiz1)
#define INIT_G() do { \
	struct G_sizecheck { \
		char G_sizecheck[sizeof(G) > COMMON_BUFSIZE ? -1 : 1]; \
	}; \
} while (0)

/* Function prototypes */
static void rawmode(void);
static void cookmode(void);
static void do_linemode(void);
static void will_charmode(void);
static void telopt(byte c);
static int subneg(byte c);

static void iac_flush(void)
{
	write(netfd, G.iacbuf, G.iaclen);
	G.iaclen = 0;
}

#define write_str(fd, str) write(fd, str, sizeof(str) - 1)

static void doexit(int ev) NORETURN;
static void doexit(int ev)
{
	cookmode();
	exit(ev);
}

static void con_escape(void)
{
	char b;

	if (bb_got_signal) /* came from line mode... go raw */
		rawmode();

	write_str(1, "\r\nConsole escape. Commands are:\r\n\n"
			" l	go to line mode\r\n"
			" c	go to character mode\r\n"
			" z	suspend telnet\r\n"
			" e	exit telnet\r\n");

	if (read(STDIN_FILENO, &b, 1) <= 0)
		doexit(EXIT_FAILURE);

	switch (b) {
	case 'l':
		if (!bb_got_signal) {
			do_linemode();
			goto ret;
		}
		break;
	case 'c':
		if (bb_got_signal) {
			will_charmode();
			goto ret;
		}
		break;
	case 'z':
		cookmode();
		kill(0, SIGTSTP);
		rawmode();
		break;
	case 'e':
		doexit(EXIT_SUCCESS);
	}

	write_str(1, "continuing...\r\n");

	if (bb_got_signal)
		cookmode();
 ret:
	bb_got_signal = 0;

}

static void handle_net_output(int len)
{
	/* here we could do smart tricks how to handle 0xFF:s in output
	 * stream like writing twice every sequence of FF:s (thus doing
	 * many write()s. But I think interactive telnet application does
	 * not need to be 100% 8-bit clean, so changing every 0xff:s to
	 * 0x7f:s
	 *
	 * 2002-mar-21, Przemyslaw Czerpak (druzus@polbox.com)
	 * I don't agree.
	 * first - I cannot use programs like sz/rz
	 * second - the 0x0D is sent as one character and if the next
	 *	char is 0x0A then it's eaten by a server side.
	 * third - why do you have to make 'many write()s'?
	 *	I don't understand.
	 * So I implemented it. It's really useful for me. I hope that
	 * other people will find it interesting too.
	 */

	int i, j;
	byte *p = (byte*)G.buf;
	byte outbuf[4*DATABUFSIZE];

	for (i = len, j = 0; i > 0; i--, p++) {
		if (*p == 0x1d) {
			con_escape();
			return;
		}
		outbuf[j++] = *p;
		if (*p == 0xff)
			outbuf[j++] = 0xff;
		else if (*p == 0x0d)
			outbuf[j++] = 0x00;
	}
	if (j > 0)
		write(netfd, outbuf, j);
}

static void handle_net_input(int len)
{
	int i;
	int cstart = 0;

	for (i = 0; i < len; i++) {
		byte c = G.buf[i];

		if (G.telstate == 0) { /* most of the time state == 0 */
			if (c == IAC) {
				cstart = i;
				G.telstate = TS_IAC;
			}
			continue;
		}
		switch (G.telstate) {
		case TS_0:
			if (c == IAC)
				G.telstate = TS_IAC;
			else
				G.buf[cstart++] = c;
			break;

		case TS_IAC:
			if (c == IAC) { /* IAC IAC -> 0xFF */
				G.buf[cstart++] = c;
				G.telstate = TS_0;
				break;
			}
			/* else */
			switch (c) {
			case SB:
				G.telstate = TS_SUB1;
				break;
			case DO:
			case DONT:
			case WILL:
			case WONT:
				G.telwish =  c;
				G.telstate = TS_OPT;
				break;
			default:
				G.telstate = TS_0;	/* DATA MARK must be added later */
			}
			break;
		case TS_OPT: /* WILL, WONT, DO, DONT */
			telopt(c);
			G.telstate = TS_0;
			break;
		case TS_SUB1: /* Subnegotiation */
		case TS_SUB2: /* Subnegotiation */
			if (subneg(c))
				G.telstate = TS_0;
			break;
		}
	}
	if (G.telstate) {
		if (G.iaclen)
			iac_flush();
		if (G.telstate == TS_0)
			G.telstate = 0;
		len = cstart;
	}

	if (len)
		write(STDOUT_FILENO, G.buf, len);
}

static void put_iac(int c)
{
	G.iacbuf[G.iaclen++] = c;
}

static void put_iac2(byte wwdd, byte c)
{
	if (G.iaclen + 3 > IACBUFSIZE)
		iac_flush();

	put_iac(IAC);
	put_iac(wwdd);
	put_iac(c);
}

#if ENABLE_FEATURE_TELNET_TTYPE
static void put_iac_subopt(byte c, char *str)
{
	int len = strlen(str) + 6;   // ( 2 + 1 + 1 + strlen + 2 )

	if (G.iaclen + len > IACBUFSIZE)
		iac_flush();

	put_iac(IAC);
	put_iac(SB);
	put_iac(c);
	put_iac(0);

	while (*str)
		put_iac(*str++);

	put_iac(IAC);
	put_iac(SE);
}
#endif

#if ENABLE_FEATURE_TELNET_AUTOLOGIN
static void put_iac_subopt_autologin(void)
{
	int len = strlen(G.autologin) + 6;	// (2 + 1 + 1 + strlen + 2)
	const char *user = "USER";

	if (G.iaclen + len > IACBUFSIZE)
		iac_flush();

	put_iac(IAC);
	put_iac(SB);
	put_iac(TELOPT_NEW_ENVIRON);
	put_iac(TELQUAL_IS);
	put_iac(NEW_ENV_VAR);

	while (*user)
		put_iac(*user++);

	put_iac(NEW_ENV_VALUE);

	while (*G.autologin)
		put_iac(*G.autologin++);

	put_iac(IAC);
	put_iac(SE);
}
#endif

#if ENABLE_FEATURE_AUTOWIDTH
static void put_iac_naws(byte c, int x, int y)
{
	if (G.iaclen + 9 > IACBUFSIZE)
		iac_flush();

	put_iac(IAC);
	put_iac(SB);
	put_iac(c);

	put_iac((x >> 8) & 0xff);
	put_iac(x & 0xff);
	put_iac((y >> 8) & 0xff);
	put_iac(y & 0xff);

	put_iac(IAC);
	put_iac(SE);
}
#endif

static char const escapecharis[] ALIGN1 = "\r\nEscape character is ";

static void setConMode(void)
{
	if (G.telflags & UF_ECHO) {
		if (G.charmode == CHM_TRY) {
			G.charmode = CHM_ON;
			printf("\r\nEntering character mode%s'^]'.\r\n", escapecharis);
			rawmode();
		}
	} else {
		if (G.charmode != CHM_OFF) {
			G.charmode = CHM_OFF;
			printf("\r\nEntering line mode%s'^C'.\r\n", escapecharis);
			cookmode();
		}
	}
}

static void will_charmode(void)
{
	G.charmode = CHM_TRY;
	G.telflags |= (UF_ECHO | UF_SGA);
	setConMode();

	put_iac2(DO, TELOPT_ECHO);
	put_iac2(DO, TELOPT_SGA);
	iac_flush();
}

static void do_linemode(void)
{
	G.charmode = CHM_TRY;
	G.telflags &= ~(UF_ECHO | UF_SGA);
	setConMode();

	put_iac2(DONT, TELOPT_ECHO);
	put_iac2(DONT, TELOPT_SGA);
	iac_flush();
}

static void to_notsup(char c)
{
	if (G.telwish == WILL)
		put_iac2(DONT, c);
	else if (G.telwish == DO)
		put_iac2(WONT, c);
}

static void to_echo(void)
{
	/* if server requests ECHO, don't agree */
	if (G.telwish == DO) {
		put_iac2(WONT, TELOPT_ECHO);
		return;
	}
	if (G.telwish == DONT)
		return;

	if (G.telflags & UF_ECHO) {
		if (G.telwish == WILL)
			return;
	} else if (G.telwish == WONT)
		return;

	if (G.charmode != CHM_OFF)
		G.telflags ^= UF_ECHO;

	if (G.telflags & UF_ECHO)
		put_iac2(DO, TELOPT_ECHO);
	else
		put_iac2(DONT, TELOPT_ECHO);

	setConMode();
	write_str(1, "\r\n");  /* sudden modec */
}

static void to_sga(void)
{
	/* daemon always sends will/wont, client do/dont */

	if (G.telflags & UF_SGA) {
		if (G.telwish == WILL)
			return;
	} else if (G.telwish == WONT)
		return;

	G.telflags ^= UF_SGA; /* toggle */
	if (G.telflags & UF_SGA)
		put_iac2(DO, TELOPT_SGA);
	else
		put_iac2(DONT, TELOPT_SGA);
}

#if ENABLE_FEATURE_TELNET_TTYPE
static void to_ttype(void)
{
	/* Tell server we will (or won't) do TTYPE */

	if (G.ttype)
		put_iac2(WILL, TELOPT_TTYPE);
	else
		put_iac2(WONT, TELOPT_TTYPE);
}
#endif

#if ENABLE_FEATURE_TELNET_AUTOLOGIN
static void to_new_environ(void)
{
	/* Tell server we will (or will not) do AUTOLOGIN */

	if (G.autologin)
		put_iac2(WILL, TELOPT_NEW_ENVIRON);
	else
		put_iac2(WONT, TELOPT_NEW_ENVIRON);
}
#endif

#if ENABLE_FEATURE_AUTOWIDTH
static void to_naws(void)
{
	/* Tell server we will do NAWS */
	put_iac2(WILL, TELOPT_NAWS);
}
#endif

static void telopt(byte c)
{
	switch (c) {
	case TELOPT_ECHO:
		to_echo(); break;
	case TELOPT_SGA:
		to_sga(); break;
#if ENABLE_FEATURE_TELNET_TTYPE
	case TELOPT_TTYPE:
		to_ttype(); break;
#endif
#if ENABLE_FEATURE_TELNET_AUTOLOGIN
	case TELOPT_NEW_ENVIRON:
		to_new_environ(); break;
#endif
#if ENABLE_FEATURE_AUTOWIDTH
	case TELOPT_NAWS:
		to_naws();
		put_iac_naws(c, G.win_width, G.win_height);
		break;
#endif
	default:
		to_notsup(c);
		break;
	}
}

/* subnegotiation -- ignore all (except TTYPE,NAWS) */
static int subneg(byte c)
{
	switch (G.telstate) {
	case TS_SUB1:
		if (c == IAC)
			G.telstate = TS_SUB2;
#if ENABLE_FEATURE_TELNET_TTYPE
		else
		if (c == TELOPT_TTYPE)
			put_iac_subopt(TELOPT_TTYPE, G.ttype);
#endif
#if ENABLE_FEATURE_TELNET_AUTOLOGIN
		else
		if (c == TELOPT_NEW_ENVIRON)
			put_iac_subopt_autologin();
#endif
		break;
	case TS_SUB2:
		if (c == SE)
			return TRUE;
		G.telstate = TS_SUB1;
		/* break; */
	}
	return FALSE;
}

static void rawmode(void)
{
	if (G.do_termios)
		tcsetattr(0, TCSADRAIN, &G.termios_raw);
}

static void cookmode(void)
{
	if (G.do_termios)
		tcsetattr(0, TCSADRAIN, &G.termios_def);
}

/* poll gives smaller (-70 bytes) code */
#define USE_POLL 1

int telnet_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int telnet_main(int argc UNUSED_PARAM, char **argv)
{
	char *host;
	int port;
	int len;
#ifdef USE_POLL
	struct pollfd ufds[2];
#else
	fd_set readfds;
	int maxfd;
#endif

	INIT_G();

#if ENABLE_FEATURE_AUTOWIDTH
	get_terminal_width_height(0, &G.win_width, &G.win_height);
#endif

#if ENABLE_FEATURE_TELNET_TTYPE
	G.ttype = getenv("TERM");
#endif

	if (tcgetattr(0, &G.termios_def) >= 0) {
		G.do_termios = 1;
		G.termios_raw = G.termios_def;
		cfmakeraw(&G.termios_raw);
	}

#if ENABLE_FEATURE_TELNET_AUTOLOGIN
	if (1 & getopt32(argv, "al:", &G.autologin))
		G.autologin = getenv("USER");
	argv += optind;
#else
	argv++;
#endif
	if (!*argv)
		bb_show_usage();
	host = *argv++;
	port = bb_lookup_port(*argv ? *argv++ : "telnet", "tcp", 23);
	if (*argv) /* extra params?? */
		bb_show_usage();

	xmove_fd(create_and_connect_stream_or_die(host, port), netfd);

	setsockopt(netfd, SOL_SOCKET, SO_KEEPALIVE, &const_int_1, sizeof(const_int_1));

	signal(SIGINT, record_signo);

#ifdef USE_POLL
	ufds[0].fd = 0; ufds[1].fd = netfd;
	ufds[0].events = ufds[1].events = POLLIN;
#else
	FD_ZERO(&readfds);
	FD_SET(STDIN_FILENO, &readfds);
	FD_SET(netfd, &readfds);
	maxfd = netfd + 1;
#endif

	while (1) {
#ifndef USE_POLL
		fd_set rfds = readfds;

		switch (select(maxfd, &rfds, NULL, NULL, NULL))
#else
		switch (poll(ufds, 2, -1))
#endif
		{
		case 0:
			/* timeout */
		case -1:
			/* error, ignore and/or log something, bay go to loop */
			if (bb_got_signal)
				con_escape();
			else
				sleep(1);
			break;
		default:

#ifdef USE_POLL
			if (ufds[0].revents)
#else
			if (FD_ISSET(STDIN_FILENO, &rfds))
#endif
			{
				len = safe_read(STDIN_FILENO, G.buf, DATABUFSIZE);
				if (len <= 0)
					doexit(EXIT_SUCCESS);
				TRACE(0, ("Read con: %d\n", len));
				handle_net_output(len);
			}

#ifdef USE_POLL
			if (ufds[1].revents)
#else
			if (FD_ISSET(netfd, &rfds))
#endif
			{
				len = safe_read(netfd, G.buf, DATABUFSIZE);
				if (len <= 0) {
					write_str(1, "Connection closed by foreign host\r\n");
					doexit(EXIT_FAILURE);
				}
				TRACE(0, ("Read netfd (%d): %d\n", netfd, len));
				handle_net_input(len);
			}
		}
	} /* while (1) */
}
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 the GPL v2 or later, see the file LICENSE in this tarball.
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
24	#include <arpa/telnet.h>
25	#include <netinet/in.h>
26	#include "libbb.h"
27
28	#ifdef DOTRACE
29	#define TRACE(x, y) do { if (x) printf y; } while (0)
30	#else
31	#define TRACE(x, y)
32	#endif
33
34	enum {
35	DATABUFSIZE = 128,
36	IACBUFSIZE = 128,
37
38	CHM_TRY = 0,
39	CHM_ON = 1,
40	CHM_OFF = 2,
41
42	UF_ECHO = 0x01,
43	UF_SGA = 0x02,
44
45	TS_0 = 1,
46	TS_IAC = 2,
47	TS_OPT = 3,
48	TS_SUB1 = 4,
49	TS_SUB2 = 5,
50	};
51
52	typedef unsigned char byte;
53
54	enum { netfd = 3 };
55
56	struct globals {
57	int iaclen; /* could even use byte, but it's a loss on x86 */
58	byte telstate; /* telnet negotiation state from network input */
59	byte telwish; /* DO, DONT, WILL, WONT */
60	byte charmode;
61	byte telflags;
62	byte do_termios;
63	#if ENABLE_FEATURE_TELNET_TTYPE
64	char *ttype;
65	#endif
66	#if ENABLE_FEATURE_TELNET_AUTOLOGIN
67	const char *autologin;
68	#endif
69	#if ENABLE_FEATURE_AUTOWIDTH
70	unsigned win_width, win_height;
71	#endif
72	/* same buffer used both for network and console read/write */
73	char buf[DATABUFSIZE];
74	/* buffer to handle telnet negotiations */
75	char iacbuf[IACBUFSIZE];
76	struct termios termios_def;
77	struct termios termios_raw;
78	};
79	#define G ((struct globals)&bb_common_bufsiz1)
80	#define INIT_G() do { \
81	struct G_sizecheck { \
82	char G_sizecheck[sizeof(G) > COMMON_BUFSIZE ? -1 : 1]; \
83	}; \
84	} while (0)
85
86	/* Function prototypes */
87	static void rawmode(void);
88	static void cookmode(void);
89	static void do_linemode(void);
90	static void will_charmode(void);
91	static void telopt(byte c);
92	static int subneg(byte c);
93
94	static void iac_flush(void)
95	{
96	write(netfd, G.iacbuf, G.iaclen);
97	G.iaclen = 0;
98	}
99
100	#define write_str(fd, str) write(fd, str, sizeof(str) - 1)
101
102	static void doexit(int ev) NORETURN;
103	static void doexit(int ev)
104	{
105	cookmode();
106	exit(ev);
107	}
108
109	static void con_escape(void)
110	{
111	char b;
112
113	if (bb_got_signal) /* came from line mode... go raw */
114	rawmode();
115
116	write_str(1, "\r\nConsole escape. Commands are:\r\n\n"
117	" l go to line mode\r\n"
118	" c go to character mode\r\n"
119	" z suspend telnet\r\n"
120	" e exit telnet\r\n");
121
122	if (read(STDIN_FILENO, &b, 1) <= 0)
123	doexit(EXIT_FAILURE);
124
125	switch (b) {
126	case 'l':
127	if (!bb_got_signal) {
128	do_linemode();
129	goto ret;
130	}
131	break;
132	case 'c':
133	if (bb_got_signal) {
134	will_charmode();
135	goto ret;
136	}
137	break;
138	case 'z':
139	cookmode();
140	kill(0, SIGTSTP);
141	rawmode();
142	break;
143	case 'e':
144	doexit(EXIT_SUCCESS);
145	}
146
147	write_str(1, "continuing...\r\n");
148
149	if (bb_got_signal)
150	cookmode();
151	ret:
152	bb_got_signal = 0;
153
154	}
155
156	static void handle_net_output(int len)
157	{
158	/* here we could do smart tricks how to handle 0xFF:s in output
159	* stream like writing twice every sequence of FF:s (thus doing
160	* many write()s. But I think interactive telnet application does
161	* not need to be 100% 8-bit clean, so changing every 0xff:s to
162	* 0x7f:s
163	*
164	* 2002-mar-21, Przemyslaw Czerpak (druzus@polbox.com)
165	* I don't agree.
166	* first - I cannot use programs like sz/rz
167	* second - the 0x0D is sent as one character and if the next
168	* char is 0x0A then it's eaten by a server side.
169	* third - why do you have to make 'many write()s'?
170	* I don't understand.
171	* So I implemented it. It's really useful for me. I hope that
172	* other people will find it interesting too.
173	*/
174
175	int i, j;
176	byte p = (byte)G.buf;
177	byte outbuf[4*DATABUFSIZE];
178
179	for (i = len, j = 0; i > 0; i--, p++) {
180	if (*p == 0x1d) {
181	con_escape();
182	return;
183	}
184	outbuf[j++] = *p;
185	if (*p == 0xff)
186	outbuf[j++] = 0xff;
187	else if (*p == 0x0d)
188	outbuf[j++] = 0x00;
189	}
190	if (j > 0)
191	write(netfd, outbuf, j);
192	}
193
194	static void handle_net_input(int len)
195	{
196	int i;
197	int cstart = 0;
198
199	for (i = 0; i < len; i++) {
200	byte c = G.buf[i];
201
202	if (G.telstate == 0) { /* most of the time state == 0 */
203	if (c == IAC) {
204	cstart = i;
205	G.telstate = TS_IAC;
206	}
207	continue;
208	}
209	switch (G.telstate) {
210	case TS_0:
211	if (c == IAC)
212	G.telstate = TS_IAC;
213	else
214	G.buf[cstart++] = c;
215	break;
216
217	case TS_IAC:
218	if (c == IAC) { /* IAC IAC -> 0xFF */
219	G.buf[cstart++] = c;
220	G.telstate = TS_0;
221	break;
222	}
223	/* else */
224	switch (c) {
225	case SB:
226	G.telstate = TS_SUB1;
227	break;
228	case DO:
229	case DONT:
230	case WILL:
231	case WONT:
232	G.telwish = c;
233	G.telstate = TS_OPT;
234	break;
235	default:
236	G.telstate = TS_0; /* DATA MARK must be added later */
237	}
238	break;
239	case TS_OPT: /* WILL, WONT, DO, DONT */
240	telopt(c);
241	G.telstate = TS_0;
242	break;
243	case TS_SUB1: /* Subnegotiation */
244	case TS_SUB2: /* Subnegotiation */
245	if (subneg(c))
246	G.telstate = TS_0;
247	break;
248	}
249	}
250	if (G.telstate) {
251	if (G.iaclen)
252	iac_flush();
253	if (G.telstate == TS_0)
254	G.telstate = 0;
255	len = cstart;
256	}
257
258	if (len)
259	write(STDOUT_FILENO, G.buf, len);
260	}
261
262	static void put_iac(int c)
263	{
264	G.iacbuf[G.iaclen++] = c;
265	}
266
267	static void put_iac2(byte wwdd, byte c)
268	{
269	if (G.iaclen + 3 > IACBUFSIZE)
270	iac_flush();
271
272	put_iac(IAC);
273	put_iac(wwdd);
274	put_iac(c);
275	}
276
277	#if ENABLE_FEATURE_TELNET_TTYPE
278	static void put_iac_subopt(byte c, char *str)
279	{
280	int len = strlen(str) + 6; // ( 2 + 1 + 1 + strlen + 2 )
281
282	if (G.iaclen + len > IACBUFSIZE)
283	iac_flush();
284
285	put_iac(IAC);
286	put_iac(SB);
287	put_iac(c);
288	put_iac(0);
289
290	while (*str)
291	put_iac(*str++);
292
293	put_iac(IAC);
294	put_iac(SE);
295	}
296	#endif
297
298	#if ENABLE_FEATURE_TELNET_AUTOLOGIN
299	static void put_iac_subopt_autologin(void)
300	{
301	int len = strlen(G.autologin) + 6; // (2 + 1 + 1 + strlen + 2)
302	const char *user = "USER";
303
304	if (G.iaclen + len > IACBUFSIZE)
305	iac_flush();
306
307	put_iac(IAC);
308	put_iac(SB);
309	put_iac(TELOPT_NEW_ENVIRON);
310	put_iac(TELQUAL_IS);
311	put_iac(NEW_ENV_VAR);
312
313	while (*user)
314	put_iac(*user++);
315
316	put_iac(NEW_ENV_VALUE);
317
318	while (*G.autologin)
319	put_iac(*G.autologin++);
320
321	put_iac(IAC);
322	put_iac(SE);
323	}
324	#endif
325
326	#if ENABLE_FEATURE_AUTOWIDTH
327	static void put_iac_naws(byte c, int x, int y)
328	{
329	if (G.iaclen + 9 > IACBUFSIZE)
330	iac_flush();
331
332	put_iac(IAC);
333	put_iac(SB);
334	put_iac(c);
335
336	put_iac((x >> 8) & 0xff);
337	put_iac(x & 0xff);
338	put_iac((y >> 8) & 0xff);
339	put_iac(y & 0xff);
340
341	put_iac(IAC);
342	put_iac(SE);
343	}
344	#endif
345
346	static char const escapecharis[] ALIGN1 = "\r\nEscape character is ";
347
348	static void setConMode(void)
349	{
350	if (G.telflags & UF_ECHO) {
351	if (G.charmode == CHM_TRY) {
352	G.charmode = CHM_ON;
353	printf("\r\nEntering character mode%s'^]'.\r\n", escapecharis);
354	rawmode();
355	}
356	} else {
357	if (G.charmode != CHM_OFF) {
358	G.charmode = CHM_OFF;
359	printf("\r\nEntering line mode%s'^C'.\r\n", escapecharis);
360	cookmode();
361	}
362	}
363	}
364
365	static void will_charmode(void)
366	{
367	G.charmode = CHM_TRY;
368	G.telflags \|= (UF_ECHO \| UF_SGA);
369	setConMode();
370
371	put_iac2(DO, TELOPT_ECHO);
372	put_iac2(DO, TELOPT_SGA);
373	iac_flush();
374	}
375
376	static void do_linemode(void)
377	{
378	G.charmode = CHM_TRY;
379	G.telflags &= ~(UF_ECHO \| UF_SGA);
380	setConMode();
381
382	put_iac2(DONT, TELOPT_ECHO);
383	put_iac2(DONT, TELOPT_SGA);
384	iac_flush();
385	}
386
387	static void to_notsup(char c)
388	{
389	if (G.telwish == WILL)
390	put_iac2(DONT, c);
391	else if (G.telwish == DO)
392	put_iac2(WONT, c);
393	}
394
395	static void to_echo(void)
396	{
397	/* if server requests ECHO, don't agree */
398	if (G.telwish == DO) {
399	put_iac2(WONT, TELOPT_ECHO);
400	return;
401	}
402	if (G.telwish == DONT)
403	return;
404
405	if (G.telflags & UF_ECHO) {
406	if (G.telwish == WILL)
407	return;
408	} else if (G.telwish == WONT)
409	return;
410
411	if (G.charmode != CHM_OFF)
412	G.telflags ^= UF_ECHO;
413
414	if (G.telflags & UF_ECHO)
415	put_iac2(DO, TELOPT_ECHO);
416	else
417	put_iac2(DONT, TELOPT_ECHO);
418
419	setConMode();
420	write_str(1, "\r\n"); /* sudden modec */
421	}
422
423	static void to_sga(void)
424	{
425	/* daemon always sends will/wont, client do/dont */
426
427	if (G.telflags & UF_SGA) {
428	if (G.telwish == WILL)
429	return;
430	} else if (G.telwish == WONT)
431	return;
432
433	G.telflags ^= UF_SGA; /* toggle */
434	if (G.telflags & UF_SGA)
435	put_iac2(DO, TELOPT_SGA);
436	else
437	put_iac2(DONT, TELOPT_SGA);
438	}
439
440	#if ENABLE_FEATURE_TELNET_TTYPE
441	static void to_ttype(void)
442	{
443	/* Tell server we will (or won't) do TTYPE */
444
445	if (G.ttype)
446	put_iac2(WILL, TELOPT_TTYPE);
447	else
448	put_iac2(WONT, TELOPT_TTYPE);
449	}
450	#endif
451
452	#if ENABLE_FEATURE_TELNET_AUTOLOGIN
453	static void to_new_environ(void)
454	{
455	/* Tell server we will (or will not) do AUTOLOGIN */
456
457	if (G.autologin)
458	put_iac2(WILL, TELOPT_NEW_ENVIRON);
459	else
460	put_iac2(WONT, TELOPT_NEW_ENVIRON);
461	}
462	#endif
463
464	#if ENABLE_FEATURE_AUTOWIDTH
465	static void to_naws(void)
466	{
467	/* Tell server we will do NAWS */
468	put_iac2(WILL, TELOPT_NAWS);
469	}
470	#endif
471
472	static void telopt(byte c)
473	{
474	switch (c) {
475	case TELOPT_ECHO:
476	to_echo(); break;
477	case TELOPT_SGA:
478	to_sga(); break;
479	#if ENABLE_FEATURE_TELNET_TTYPE
480	case TELOPT_TTYPE:
481	to_ttype(); break;
482	#endif
483	#if ENABLE_FEATURE_TELNET_AUTOLOGIN
484	case TELOPT_NEW_ENVIRON:
485	to_new_environ(); break;
486	#endif
487	#if ENABLE_FEATURE_AUTOWIDTH
488	case TELOPT_NAWS:
489	to_naws();
490	put_iac_naws(c, G.win_width, G.win_height);
491	break;
492	#endif
493	default:
494	to_notsup(c);
495	break;
496	}
497	}
498
499	/* subnegotiation -- ignore all (except TTYPE,NAWS) */
500	static int subneg(byte c)
501	{
502	switch (G.telstate) {
503	case TS_SUB1:
504	if (c == IAC)
505	G.telstate = TS_SUB2;
506	#if ENABLE_FEATURE_TELNET_TTYPE
507	else
508	if (c == TELOPT_TTYPE)
509	put_iac_subopt(TELOPT_TTYPE, G.ttype);
510	#endif
511	#if ENABLE_FEATURE_TELNET_AUTOLOGIN
512	else
513	if (c == TELOPT_NEW_ENVIRON)
514	put_iac_subopt_autologin();
515	#endif
516	break;
517	case TS_SUB2:
518	if (c == SE)
519	return TRUE;
520	G.telstate = TS_SUB1;
521	/* break; */
522	}
523	return FALSE;
524	}
525
526	static void rawmode(void)
527	{
528	if (G.do_termios)
529	tcsetattr(0, TCSADRAIN, &G.termios_raw);
530	}
531
532	static void cookmode(void)
533	{
534	if (G.do_termios)
535	tcsetattr(0, TCSADRAIN, &G.termios_def);
536	}
537
538	/* poll gives smaller (-70 bytes) code */
539	#define USE_POLL 1
540
541	int telnet_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
542	int telnet_main(int argc UNUSED_PARAM, char **argv)
543	{
544	char *host;
545	int port;
546	int len;
547	#ifdef USE_POLL
548	struct pollfd ufds[2];
549	#else
550	fd_set readfds;
551	int maxfd;
552	#endif
553
554	INIT_G();
555
556	#if ENABLE_FEATURE_AUTOWIDTH
557	get_terminal_width_height(0, &G.win_width, &G.win_height);
558	#endif
559
560	#if ENABLE_FEATURE_TELNET_TTYPE
561	G.ttype = getenv("TERM");
562	#endif
563
564	if (tcgetattr(0, &G.termios_def) >= 0) {
565	G.do_termios = 1;
566	G.termios_raw = G.termios_def;
567	cfmakeraw(&G.termios_raw);
568	}
569
570	#if ENABLE_FEATURE_TELNET_AUTOLOGIN
571	if (1 & getopt32(argv, "al:", &G.autologin))
572	G.autologin = getenv("USER");
573	argv += optind;
574	#else
575	argv++;
576	#endif
577	if (!*argv)
578	bb_show_usage();
579	host = *argv++;
580	port = bb_lookup_port(argv ? argv++ : "telnet", "tcp", 23);
581	if (argv) / extra params?? */
582	bb_show_usage();
583
584	xmove_fd(create_and_connect_stream_or_die(host, port), netfd);
585
586	setsockopt(netfd, SOL_SOCKET, SO_KEEPALIVE, &const_int_1, sizeof(const_int_1));
587
588	signal(SIGINT, record_signo);
589
590	#ifdef USE_POLL
591	ufds[0].fd = 0; ufds[1].fd = netfd;
592	ufds[0].events = ufds[1].events = POLLIN;
593	#else
594	FD_ZERO(&readfds);
595	FD_SET(STDIN_FILENO, &readfds);
596	FD_SET(netfd, &readfds);
597	maxfd = netfd + 1;
598	#endif
599
600	while (1) {
601	#ifndef USE_POLL
602	fd_set rfds = readfds;
603
604	switch (select(maxfd, &rfds, NULL, NULL, NULL))
605	#else
606	switch (poll(ufds, 2, -1))
607	#endif
608	{
609	case 0:
610	/* timeout */
611	case -1:
612	/* error, ignore and/or log something, bay go to loop */
613	if (bb_got_signal)
614	con_escape();
615	else
616	sleep(1);
617	break;
618	default:
619
620	#ifdef USE_POLL
621	if (ufds[0].revents)
622	#else
623	if (FD_ISSET(STDIN_FILENO, &rfds))
624	#endif
625	{
626	len = safe_read(STDIN_FILENO, G.buf, DATABUFSIZE);
627	if (len <= 0)
628	doexit(EXIT_SUCCESS);
629	TRACE(0, ("Read con: %d\n", len));
630	handle_net_output(len);
631	}
632
633	#ifdef USE_POLL
634	if (ufds[1].revents)
635	#else
636	if (FD_ISSET(netfd, &rfds))
637	#endif
638	{
639	len = safe_read(netfd, G.buf, DATABUFSIZE);
640	if (len <= 0) {
641	write_str(1, "Connection closed by foreign host\r\n");
642	doexit(EXIT_FAILURE);
643	}
644	TRACE(0, ("Read netfd (%d): %d\n", netfd, len));
645	handle_net_input(len);
646	}
647	}
648	} /* while (1) */
649	}