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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 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 <termios.h>
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <signal.h>
#include <arpa/telnet.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include "busybox.h"
#if 0
static const int DOTRACE = 1;
#endif
#ifdef DOTRACE
#include <arpa/inet.h> /* for inet_ntoa()... */
#define TRACE(x, y) do { if (x) printf y; } while (0)
#else
#define TRACE(x, y)
#endif
#if 0
#define USE_POLL
#include <sys/poll.h>
#else
#include <sys/time.h>
#endif
#define DATABUFSIZE 128
#define IACBUFSIZE 128
static const int CHM_TRY = 0;
static const int CHM_ON = 1;
static const int CHM_OFF = 2;
static const int UF_ECHO = 0x01;
static const int UF_SGA = 0x02;
enum {
TS_0 = 1,
TS_IAC = 2,
TS_OPT = 3,
TS_SUB1 = 4,
TS_SUB2 = 5,
};
#define WriteCS(fd, str) write(fd, str, sizeof str -1)
typedef unsigned char byte;
/* use globals to reduce size ??? */ /* test this hypothesis later */
static struct Globalvars {
int netfd; /* console fd:s are 0 and 1 (and 2) */
/* same buffer used both for network and console read/write */
char buf[DATABUFSIZE]; /* allocating so static size is smaller */
byte telstate; /* telnet negotiation state from network input */
byte telwish; /* DO, DONT, WILL, WONT */
byte charmode;
byte telflags;
byte gotsig;
byte do_termios;
/* buffer to handle telnet negotiations */
char iacbuf[IACBUFSIZE];
short iaclen; /* could even use byte */
struct termios termios_def;
struct termios termios_raw;
} G;
#define xUSE_GLOBALVAR_PTR /* xUSE... -> don't use :D (makes smaller code) */
#ifdef USE_GLOBALVAR_PTR
struct Globalvars * Gptr;
#define G (*Gptr)
#endif
static inline void iacflush(void)
{
write(G.netfd, G.iacbuf, G.iaclen);
G.iaclen = 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);
/* Some globals */
static int one = 1;
#ifdef CONFIG_FEATURE_TELNET_TTYPE
static char *ttype;
#endif
#ifdef CONFIG_FEATURE_TELNET_AUTOLOGIN
static const char *autologin;
#endif
#ifdef CONFIG_FEATURE_AUTOWIDTH
static int win_width, win_height;
#endif
static void doexit(int ev)
{
cookmode();
exit(ev);
}
static void conescape(void)
{
char b;
if (G.gotsig) /* came from line mode... go raw */
rawmode();
WriteCS(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(0, &b, 1) <= 0)
doexit(1);
switch (b)
{
case 'l':
if (!G.gotsig)
{
do_linemode();
goto rrturn;
}
break;
case 'c':
if (G.gotsig)
{
will_charmode();
goto rrturn;
}
break;
case 'z':
cookmode();
kill(0, SIGTSTP);
rawmode();
break;
case 'e':
doexit(0);
}
WriteCS(1, "continuing...\r\n");
if (G.gotsig)
cookmode();
rrturn:
G.gotsig = 0;
}
static void handlenetoutput(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 - whay doy you have to make 'many write()s'?
* I don't understand.
* So I implemented it. It's realy useful for me. I hope that
* others people will find it interesting to.
*/
int i, j;
byte * p = (byte*)G.buf;
byte outbuf[4*DATABUFSIZE];
for (i = len, j = 0; i > 0; i--, p++)
{
if (*p == 0x1d)
{
conescape();
return;
}
outbuf[j++] = *p;
if (*p == 0xff)
outbuf[j++] = 0xff;
else if (*p == 0x0d)
outbuf[j++] = 0x00;
}
if (j > 0 )
write(G.netfd, outbuf, j);
}
static void handlenetinput(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;
}
}
else
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) iacflush();
if (G.telstate == TS_0) G.telstate = 0;
len = cstart;
}
if (len)
write(1, G.buf, len);
}
/* ******************************* */
static inline void putiac(int c)
{
G.iacbuf[G.iaclen++] = c;
}
static void putiac2(byte wwdd, byte c)
{
if (G.iaclen + 3 > IACBUFSIZE)
iacflush();
putiac(IAC);
putiac(wwdd);
putiac(c);
}
#if 0
static void putiac1(byte c)
{
if (G.iaclen + 2 > IACBUFSIZE)
iacflush();
putiac(IAC);
putiac(c);
}
#endif
#ifdef CONFIG_FEATURE_TELNET_TTYPE
static void putiac_subopt(byte c, char *str)
{
int len = strlen(str) + 6; // ( 2 + 1 + 1 + strlen + 2 )
if (G.iaclen + len > IACBUFSIZE)
iacflush();
putiac(IAC);
putiac(SB);
putiac(c);
putiac(0);
while(*str)
putiac(*str++);
putiac(IAC);
putiac(SE);
}
#endif
#ifdef CONFIG_FEATURE_TELNET_AUTOLOGIN
static void putiac_subopt_autologin(void)
{
int len = strlen(autologin) + 6; // (2 + 1 + 1 + strlen + 2)
char *user = "USER";
if (G.iaclen + len > IACBUFSIZE)
iacflush();
putiac(IAC);
putiac(SB);
putiac(TELOPT_NEW_ENVIRON);
putiac(TELQUAL_IS);
putiac(NEW_ENV_VAR);
while(*user)
putiac(*user++);
putiac(NEW_ENV_VALUE);
while(*autologin)
putiac(*autologin++);
putiac(IAC);
putiac(SE);
}
#endif
#ifdef CONFIG_FEATURE_AUTOWIDTH
static void putiac_naws(byte c, int x, int y)
{
if (G.iaclen + 9 > IACBUFSIZE)
iacflush();
putiac(IAC);
putiac(SB);
putiac(c);
putiac((x >> 8) & 0xff);
putiac(x & 0xff);
putiac((y >> 8) & 0xff);
putiac(y & 0xff);
putiac(IAC);
putiac(SE);
}
#endif
/* void putiacstring (subneg strings) */
/* ******************************* */
static char const escapecharis[] = "\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();
putiac2(DO, TELOPT_ECHO);
putiac2(DO, TELOPT_SGA);
iacflush();
}
static void do_linemode(void)
{
G.charmode = CHM_TRY;
G.telflags &= ~(UF_ECHO | UF_SGA);
setConMode();
putiac2(DONT, TELOPT_ECHO);
putiac2(DONT, TELOPT_SGA);
iacflush();
}
/* ******************************* */
static inline void to_notsup(char c)
{
if (G.telwish == WILL) putiac2(DONT, c);
else if (G.telwish == DO) putiac2(WONT, c);
}
static inline void to_echo(void)
{
/* if server requests ECHO, don't agree */
if (G.telwish == DO) { putiac2(WONT, TELOPT_ECHO); return; }
else 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)
putiac2(DO, TELOPT_ECHO);
else
putiac2(DONT, TELOPT_ECHO);
setConMode();
WriteCS(1, "\r\n"); /* sudden modec */
}
static inline 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;
if ((G.telflags ^= UF_SGA) & UF_SGA) /* toggle */
putiac2(DO, TELOPT_SGA);
else
putiac2(DONT, TELOPT_SGA);
return;
}
#ifdef CONFIG_FEATURE_TELNET_TTYPE
static inline void to_ttype(void)
{
/* Tell server we will (or won't) do TTYPE */
if(ttype)
putiac2(WILL, TELOPT_TTYPE);
else
putiac2(WONT, TELOPT_TTYPE);
return;
}
#endif
#ifdef CONFIG_FEATURE_TELNET_AUTOLOGIN
static inline void to_new_environ(void)
{
/* Tell server we will (or will not) do AUTOLOGIN */
if (autologin)
putiac2(WILL, TELOPT_NEW_ENVIRON);
else
putiac2(WONT, TELOPT_NEW_ENVIRON);
return;
}
#endif
#ifdef CONFIG_FEATURE_AUTOWIDTH
static inline void to_naws(void)
{
/* Tell server we will do NAWS */
putiac2(WILL, TELOPT_NAWS);
return;
}
#endif
static void telopt(byte c)
{
switch (c)
{
case TELOPT_ECHO: to_echo(); break;
case TELOPT_SGA: to_sga(); break;
#ifdef CONFIG_FEATURE_TELNET_TTYPE
case TELOPT_TTYPE: to_ttype();break;
#endif
#ifdef CONFIG_FEATURE_TELNET_AUTOLOGIN
case TELOPT_NEW_ENVIRON: to_new_environ(); break;
#endif
#ifdef CONFIG_FEATURE_AUTOWIDTH
case TELOPT_NAWS: to_naws();
putiac_naws(c, win_width, 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;
#ifdef CONFIG_FEATURE_TELNET_TTYPE
else
if (c == TELOPT_TTYPE)
putiac_subopt(TELOPT_TTYPE,ttype);
#endif
#ifdef CONFIG_FEATURE_TELNET_AUTOLOGIN
else
if (c == TELOPT_NEW_ENVIRON)
putiac_subopt_autologin();
#endif
break;
case TS_SUB2:
if (c == SE)
return TRUE;
G.telstate = TS_SUB1;
/* break; */
}
return FALSE;
}
/* ******************************* */
static void fgotsig(int sig)
{
G.gotsig = sig;
}
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);
}
extern int telnet_main(int argc, char** argv)
{
int len;
struct sockaddr_in s_in;
#ifdef USE_POLL
struct pollfd ufds[2];
#else
fd_set readfds;
int maxfd;
#endif
#ifdef CONFIG_FEATURE_AUTOWIDTH
get_terminal_width_height(0, &win_width, &win_height);
#endif
#ifdef CONFIG_FEATURE_TELNET_TTYPE
ttype = getenv("TERM");
#endif
memset(&G, 0, sizeof G);
if (tcgetattr(0, &G.termios_def) >= 0) {
G.do_termios = 1;
G.termios_raw = G.termios_def;
cfmakeraw(&G.termios_raw);
}
if (argc < 2)
bb_show_usage();
#ifdef CONFIG_FEATURE_TELNET_AUTOLOGIN
if (1 & bb_getopt_ulflags(argc, argv, "al:", &autologin))
autologin = getenv("USER");
if (optind < argc) {
bb_lookup_host(&s_in, argv[optind++]);
s_in.sin_port = bb_lookup_port((optind < argc) ? argv[optind++] :
"telnet", "tcp", 23);
if (optind < argc)
bb_show_usage();
} else
bb_show_usage();
#else
bb_lookup_host(&s_in, argv[1]);
s_in.sin_port = bb_lookup_port((argc == 3) ? argv[2] : "telnet", "tcp", 23);
#endif
G.netfd = xconnect(&s_in);
setsockopt(G.netfd, SOL_SOCKET, SO_KEEPALIVE, &one, sizeof one);
signal(SIGINT, fgotsig);
#ifdef USE_POLL
ufds[0].fd = 0; ufds[1].fd = G.netfd;
ufds[0].events = ufds[1].events = POLLIN;
#else
FD_ZERO(&readfds);
FD_SET(0, &readfds);
FD_SET(G.netfd, &readfds);
maxfd = G.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 (G.gotsig)
conescape();
else
sleep(1);
break;
default:
#ifdef USE_POLL
if (ufds[0].revents) /* well, should check POLLIN, but ... */
#else
if (FD_ISSET(0, &rfds))
#endif
{
len = read(0, G.buf, DATABUFSIZE);
if (len <= 0)
doexit(0);
TRACE(0, ("Read con: %d\n", len));
handlenetoutput(len);
}
#ifdef USE_POLL
if (ufds[1].revents) /* well, should check POLLIN, but ... */
#else
if (FD_ISSET(G.netfd, &rfds))
#endif
{
len = read(G.netfd, G.buf, DATABUFSIZE);
if (len <= 0)
{
WriteCS(1, "Connection closed by foreign host.\r\n");
doexit(1);
}
TRACE(0, ("Read netfd (%d): %d\n", G.netfd, len));
handlenetinput(len);
}
}
}
}
/*
Local Variables:
c-file-style: "linux"
c-basic-offset: 4
tab-width: 4
End:
*/
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