busybox/networking/telnet.c

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/* 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 GPLv2 or later, see file LICENSE in this source tree.
*
* 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>
*
*/
//config:config TELNET
//config: bool "telnet (8.7 kb)"
//config: default y
//config: help
//config: Telnet is an interface to the TELNET protocol, but is also commonly
//config: used to test other simple protocols.
//config:
//config:config FEATURE_TELNET_TTYPE
//config: bool "Pass TERM type to remote host"
//config: default y
//config: depends on TELNET
//config: help
//config: Setting this option will forward the TERM environment variable to the
//config: remote host you are connecting to. This is useful to make sure that
//config: things like ANSI colors and other control sequences behave.
//config:
//config:config FEATURE_TELNET_AUTOLOGIN
//config: bool "Pass USER type to remote host"
//config: default y
//config: depends on TELNET
//config: help
//config: Setting this option will forward the USER environment variable to the
//config: remote host you are connecting to. This is useful when you need to
//config: log into a machine without telling the username (autologin). This
//config: option enables `-a' and `-l USER' arguments.
//config:
//config:config FEATURE_TELNET_WIDTH
//config: bool "Enable window size autodetection"
//config: default y
//config: depends on TELNET
//applet:IF_TELNET(APPLET(telnet, BB_DIR_USR_BIN, BB_SUID_DROP))
//kbuild:lib-$(CONFIG_TELNET) += telnet.o
//usage:#if ENABLE_FEATURE_TELNET_AUTOLOGIN
//usage:#define telnet_trivial_usage
//usage: "[-a] [-l USER] HOST [PORT]"
//usage:#define telnet_full_usage "\n\n"
//usage: "Connect to telnet server\n"
//usage: "\n -a Automatic login with $USER variable"
//usage: "\n -l USER Automatic login as USER"
//usage:
//usage:#else
//usage:#define telnet_trivial_usage
//usage: "HOST [PORT]"
//usage:#define telnet_full_usage "\n\n"
//usage: "Connect to telnet server"
//usage:#endif
#include <arpa/telnet.h>
#include <netinet/in.h>
#include "libbb.h"
#include "common_bufsiz.h"
#ifdef __BIONIC__
/* should be in arpa/telnet.h */
# define IAC 255 /* interpret as command: */
# define DONT 254 /* you are not to use option */
# define DO 253 /* please, you use option */
# define WONT 252 /* I won't use option */
# define WILL 251 /* I will use option */
# define SB 250 /* interpret as subnegotiation */
# define SE 240 /* end sub negotiation */
# define TELOPT_ECHO 1 /* echo */
# define TELOPT_SGA 3 /* suppress go ahead */
# define TELOPT_TTYPE 24 /* terminal type */
# define TELOPT_NAWS 31 /* window size */
#endif
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#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_NORMAL = 0,
TS_COPY = 1,
TS_IAC = 2,
TS_OPT = 3,
TS_SUB1 = 4,
TS_SUB2 = 5,
TS_CR = 6,
};
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_TELNET_WIDTH
unsigned win_width, win_height;
#endif
/* same buffer used both for network and console read/write */
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char buf[DATABUFSIZE];
/* buffer to handle telnet negotiations */
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char iacbuf[IACBUFSIZE];
struct termios termios_def;
struct termios termios_raw;
} FIX_ALIASING;
#define G (*(struct globals*)bb_common_bufsiz1)
#define INIT_G() do { \
setup_common_bufsiz(); \
BUILD_BUG_ON(sizeof(G) > COMMON_BUFSIZE); \
} while (0)
static void rawmode(void);
static void cookmode(void);
static void do_linemode(void);
static void will_charmode(void);
static void telopt(byte c);
static void subneg(byte c);
static void iac_flush(void)
{
full_write(netfd, G.iacbuf, G.iaclen);
G.iaclen = 0;
}
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static void doexit(int ev) NORETURN;
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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();
full_write1_str("\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);
}
full_write1_str("continuing...\r\n");
if (bb_got_signal)
cookmode();
ret:
bb_got_signal = 0;
}
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static void handle_net_output(int len)
{
byte outbuf[2 * DATABUFSIZE];
byte *dst = outbuf;
byte *src = (byte*)G.buf;
byte *end = src + len;
while (src < end) {
byte c = *src++;
if (c == 0x1d) {
con_escape();
return;
}
*dst = c;
if (c == IAC)
*++dst = c; /* IAC -> IAC IAC */
else
if (c == '\r' || c == '\n') {
/* Enter key sends '\r' in raw mode and '\n' in cooked one.
*
* See RFC 1123 3.3.1 Telnet End-of-Line Convention.
* Using CR LF instead of other allowed possibilities
* like CR NUL - easier to talk to HTTP/SMTP servers.
*/
*dst = '\r'; /* Enter -> CR LF */
*++dst = '\n';
}
dst++;
}
if (dst - outbuf != 0)
full_write(netfd, outbuf, dst - outbuf);
}
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 == TS_NORMAL) { /* most typical state */
if (c == IAC) {
cstart = i;
G.telstate = TS_IAC;
}
else if (c == '\r') {
cstart = i + 1;
G.telstate = TS_CR;
}
/* No IACs were seen so far, no need to copy
* bytes within G.buf: */
continue;
}
switch (G.telstate) {
case TS_CR:
/* Prev char was CR. If cur one is NUL, ignore it.
* See RFC 1123 section 3.3.1 for discussion of telnet EOL handling.
*/
G.telstate = TS_COPY;
if (c == '\0')
break;
/* else: fall through - need to handle CR IAC ... properly */
case TS_COPY: /* Prev char was ordinary */
/* Similar to NORMAL, but in TS_COPY we need to copy bytes */
if (c == IAC)
G.telstate = TS_IAC;
else
G.buf[cstart++] = c;
if (c == '\r')
G.telstate = TS_CR;
break;
case TS_IAC: /* Prev char was IAC */
if (c == IAC) { /* IAC IAC -> one IAC */
G.buf[cstart++] = c;
G.telstate = TS_COPY;
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;
/* DATA MARK must be added later */
default:
G.telstate = TS_COPY;
}
break;
case TS_OPT: /* Prev chars were IAC WILL/WONT/DO/DONT */
telopt(c);
G.telstate = TS_COPY;
break;
case TS_SUB1: /* Subnegotiation */
case TS_SUB2: /* Subnegotiation */
subneg(c); /* can change G.telstate */
break;
}
}
if (G.telstate != TS_NORMAL) {
/* We had some IACs, or CR */
if (G.iaclen)
iac_flush();
if (G.telstate == TS_COPY) /* we aren't in the middle of IAC */
G.telstate = TS_NORMAL;
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len = cstart;
}
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if (len)
full_write(STDOUT_FILENO, G.buf, len);
}
static void put_iac(int c)
{
G.iacbuf[G.iaclen++] = c;
}
static void put_iac2_merged(unsigned wwdd_and_c)
{
if (G.iaclen + 3 > IACBUFSIZE)
iac_flush();
put_iac(IAC);
put_iac(wwdd_and_c >> 8);
put_iac(wwdd_and_c & 0xff);
}
#define put_iac2(wwdd,c) put_iac2_merged(((wwdd)<<8) + (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 *p = "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 (*p)
put_iac(*p++);
put_iac(NEW_ENV_VALUE);
p = G.autologin;
while (*p)
put_iac(*p++);
put_iac(IAC);
put_iac(SE);
}
#endif
#if ENABLE_FEATURE_TELNET_WIDTH
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);
/* "... & 0xff" implicitly done below */
put_iac(x >> 8);
put_iac(x);
put_iac(y >> 8);
put_iac(y);
put_iac(IAC);
put_iac(SE);
}
#endif
static void setConMode(void)
{
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if (G.telflags & UF_ECHO) {
if (G.charmode == CHM_TRY) {
G.charmode = CHM_ON;
printf("\r\nEntering %s mode"
"\r\nEscape character is '^%c'.\r\n", "character", ']');
rawmode();
}
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} else {
if (G.charmode != CHM_OFF) {
G.charmode = CHM_OFF;
printf("\r\nEntering %s mode"
"\r\nEscape character is '^%c'.\r\n", "line", 'C');
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();
full_write1_str("\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_TELNET_WIDTH
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_TELNET_WIDTH
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 void 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 && G.ttype)
put_iac_subopt(TELOPT_TTYPE, G.ttype);
#endif
#if ENABLE_FEATURE_TELNET_AUTOLOGIN
else
if (c == TELOPT_NEW_ENVIRON && G.autologin)
put_iac_subopt_autologin();
#endif
break;
case TS_SUB2:
if (c == SE) {
G.telstate = TS_COPY;
return;
}
G.telstate = TS_SUB1;
break;
}
}
static void rawmode(void)
{
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if (G.do_termios)
tcsetattr(0, TCSADRAIN, &G.termios_raw);
}
static void cookmode(void)
{
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if (G.do_termios)
tcsetattr(0, TCSADRAIN, &G.termios_def);
}
int telnet_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int telnet_main(int argc UNUSED_PARAM, char **argv)
{
char *host;
int port;
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int len;
struct pollfd ufds[2];
INIT_G();
#if ENABLE_FEATURE_TELNET_WIDTH
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_keepalive(netfd);
signal(SIGINT, record_signo);
ufds[0].fd = STDIN_FILENO;
ufds[0].events = POLLIN;
ufds[1].fd = netfd;
ufds[1].events = POLLIN;
while (1) {
if (poll(ufds, 2, -1) < 0) {
/* error, ignore and/or log something, bay go to loop */
if (bb_got_signal)
con_escape();
else
sleep(1);
continue;
}
// FIXME: reads can block. Need full bidirectional buffering.
if (ufds[0].revents) {
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);
}
if (ufds[1].revents) {
len = safe_read(netfd, G.buf, DATABUFSIZE);
if (len <= 0) {
full_write1_str("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) */
}