/*
  Copyright (C) 1996-2025 Free Software Foundation, Inc.

  This file is part of GNU Inetutils.

  GNU Inetutils is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or (at
  your option) any later version.

  GNU Inetutils is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see `http://www.gnu.org/licenses/'. */

#include <sys/types.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <syslog.h>
#include <string.h>
#include <ctype.h>
#include <strings.h>
#ifdef HAVE_SYS_FILIO_H
# include <sys/filio.h>
#endif
#ifdef HAVE_SYS_TTY_H
# include <sys/tty.h>
#endif
#ifdef HAVE_SYS_PTYVAR_H
# include <sys/ptyvar.h>
#endif
#if defined HAVE_STROPTS_H && !defined HAVE_IOCTL
# include <stropts.h>
#endif
#include <sys/ioctl.h>

#include <arpa/telnet.h>

#include <libtelnet/auth.h>
#include <libtelnet/encrypt.h>

#include <termios.h>

#define obstack_chunk_alloc malloc
#define obstack_chunk_free free
#include <obstack.h>

#include "xalloc.h"

#ifndef HAVE_CC_T
typedef unsigned char cc_t;
#endif

typedef enum debug_mode
{
  debug_options,
  debug_report,
  debug_net_data,
  debug_pty_data,
  debug_auth,
  debug_encr,
  debug_max_mode
} debug_mode_t;

#define MAX_DEBUG_LEVEL 100

extern int debug_level[];

#define DEBUG(mode,level,c) if (debug_level[mode]>=level) c

struct telnetd_clocks
{
  int system;			/* what the current time is */
  int echotoggle;		/* last time user entered echo character */
  int modenegotiated;		/* last time operating mode negotiated */
  int didnetreceive;		/* last time we read data from network */
  int ttypesubopt;		/* ttype subopt is received */
  int tspeedsubopt;		/* tspeed subopt is received */
  int environsubopt;		/* environ subopt is received */
  int oenvironsubopt;		/* old environ subopt is received */
  int xdisplocsubopt;		/* xdisploc subopt is received */
  int baseline;			/* time started to do timed action */
  int gotDM;			/* when did we last see a data mark */
};
#define settimer(x)	(clocks.x = ++clocks.system)
#define sequenceIs(x,y)	(clocks.x < clocks.y)

/*
 * Structures of information for each special character function.
 */
typedef struct
{
  unsigned char flag;		/* the flags for this function */
  cc_t val;			/* the value of the special character */
} slcent, *Slcent;

typedef struct
{
  slcent defset;		/* the default settings */
  slcent current;		/* the current settings */
  cc_t *sptr;			/* a pointer to the char in */
  /* system data structures */
} slcfun, *Slcfun;

#ifdef HAVE_UNAME
   /* Prefix and suffix if the IM string can be generated from uname.  */
# define UNAME_IM_PREFIX "\r\n"
# define UNAME_IM_SUFFIX " (%l) (%t)\r\n\r\n"
#else /* ! HAVE_UNAME */
# define UNAME_IM_PREFIX "\r\n"
# define UNAME_IM_SUFFIX "\r\n"
#endif

/* ********************* */
/* State machine */
/*
 * We keep track of each side of the option negotiation.
 */

#define MY_STATE_WILL		0x01
#define MY_WANT_STATE_WILL	0x02
#define MY_STATE_DO		0x04
#define MY_WANT_STATE_DO	0x08

/*
 * Macros to check the current state of things
 */

#define my_state_is_do(opt)		(options[opt]&MY_STATE_DO)
#define my_state_is_will(opt)		(options[opt]&MY_STATE_WILL)
#define my_want_state_is_do(opt)	(options[opt]&MY_WANT_STATE_DO)
#define my_want_state_is_will(opt)	(options[opt]&MY_WANT_STATE_WILL)

#define my_state_is_dont(opt)		(!my_state_is_do(opt))
#define my_state_is_wont(opt)		(!my_state_is_will(opt))
#define my_want_state_is_dont(opt)	(!my_want_state_is_do(opt))
#define my_want_state_is_wont(opt)	(!my_want_state_is_will(opt))

#define set_my_state_do(opt)		(options[opt] |= MY_STATE_DO)
#define set_my_state_will(opt)		(options[opt] |= MY_STATE_WILL)
#define set_my_want_state_do(opt)	(options[opt] |= MY_WANT_STATE_DO)
#define set_my_want_state_will(opt)	(options[opt] |= MY_WANT_STATE_WILL)

#define set_my_state_dont(opt)		(options[opt] &= ~MY_STATE_DO)
#define set_my_state_wont(opt)		(options[opt] &= ~MY_STATE_WILL)
#define set_my_want_state_dont(opt)	(options[opt] &= ~MY_WANT_STATE_DO)
#define set_my_want_state_wont(opt)	(options[opt] &= ~MY_WANT_STATE_WILL)

/*
 * Tricky code here.  What we want to know is if the MY_STATE_WILL
 * and MY_WANT_STATE_WILL bits have the same value.  Since the two
 * bits are adjacent, a little arithmetic will show that by adding
 * in the lower bit, the upper bit will be set if the two bits were
 * different, and clear if they were the same.
 */
#define my_will_wont_is_changing(opt) \
			((options[opt]+MY_STATE_WILL) & MY_WANT_STATE_WILL)

#define my_do_dont_is_changing(opt) \
			((options[opt]+MY_STATE_DO) & MY_WANT_STATE_DO)

/*
 * Make everything symmetrical
 */

#define HIS_STATE_WILL			MY_STATE_DO
#define HIS_WANT_STATE_WILL		MY_WANT_STATE_DO
#define HIS_STATE_DO			MY_STATE_WILL
#define HIS_WANT_STATE_DO		MY_WANT_STATE_WILL

#define his_state_is_do			my_state_is_will
#define his_state_is_will		my_state_is_do
#define his_want_state_is_do		my_want_state_is_will
#define his_want_state_is_will		my_want_state_is_do

#define his_state_is_dont		my_state_is_wont
#define his_state_is_wont		my_state_is_dont
#define his_want_state_is_dont		my_want_state_is_wont
#define his_want_state_is_wont		my_want_state_is_dont

#define set_his_state_do		set_my_state_will
#define set_his_state_will		set_my_state_do
#define set_his_want_state_do		set_my_want_state_will
#define set_his_want_state_will		set_my_want_state_do

#define set_his_state_dont		set_my_state_wont
#define set_his_state_wont		set_my_state_dont
#define set_his_want_state_dont		set_my_want_state_wont
#define set_his_want_state_wont		set_my_want_state_dont

#define his_will_wont_is_changing	my_do_dont_is_changing
#define his_do_dont_is_changing		my_will_wont_is_changing

/* ******* */

void fatal (int f, char *msg);

/*
 * Linemode support states, in decreasing order of importance
 */
#define REAL_LINEMODE	0x04
#define KLUDGE_OK	0x03
#define NO_AUTOKLUDGE	0x02
#define KLUDGE_LINEMODE	0x01
#define NO_LINEMODE	0x00

#include <arpa/telnet.h>

#define NETSLOP 64

#define ttloop(c) while (c) io_drain ()

/* External variables */
extern char options[256];
extern char do_dont_resp[256];
extern char will_wont_resp[256];
extern int linemode;		/* linemode on/off */
extern int uselinemode;		/* what linemode to use (on/off) */
extern int editmode;		/* edit modes in use */
extern int useeditmode;		/* edit modes to use */
extern int alwayslinemode;	/* command line option */
extern int lmodetype;		/* Client support for linemode */
extern int flowmode;		/* current flow control state */
extern int restartany;		/* restart output on any character state */
extern int diagnostic;		/* telnet diagnostic capabilities */
#if defined AUTHENTICATION
extern int auth_level;
extern int autologin;
#endif

extern slcfun slctab[NSLC + 1];	/* slc mapping table */

extern char *terminaltype;
extern char *remote_hostname;
extern char *local_hostname;
extern char *login_invocation;
extern char *user_name;

extern int pty, net;
extern int SYNCHing;		/* we are in TELNET SYNCH mode */
extern struct telnetd_clocks clocks;
extern char line[];

extern char *xstrdup (const char *);
extern int argcv_get (const char *command, const char *delim,
		      int *argc, char ***argv);

void io_setup (void);
int net_has_data (void);
int net_get_char (int peek);
void set_neturg (void);
int net_output_data (const char *format, ...);
int net_output_datalen (const void *buf, size_t l);
int net_buffer_level (void);
void io_drain (void);

int stilloob (int s);
void ptyflush (void);
char *nextitem (char *current, const char *endp);
void netclear (void);
void netflush (void);

int pty_buffer_is_full (void);
void pty_output_byte (int c);
void pty_output_datalen (const void *data, size_t len);
int pty_buffer_level (void);

/* Debugging functions */
extern void printoption (char *, int);
extern void printdata (char *, char *, int);
extern void printsub (int, unsigned char *, int);
extern void debug_output_datalen (const char *data, size_t len);
extern void debug_output_data (const char *fmt, ...);

/* TTY functions */
extern void init_termbuf (void);
extern void set_termbuf (void);
extern int spcset (int func, cc_t * valp, cc_t ** valpp);
extern void term_send_eof (void);
extern int term_change_eof (void);

extern void tty_binaryin (int);
extern void tty_binaryout (int);
extern int tty_flowmode (void);
extern int tty_restartany (void);
extern int tty_isbinaryin (void);
extern int tty_isbinaryout (void);
extern int tty_iscrnl (void);
extern int tty_isecho (void);
extern int tty_isediting (void);
extern int tty_islitecho (void);
extern int tty_isnewmap (void);
extern int tty_israw (void);
extern int tty_issofttab (void);
extern int tty_istrapsig (void);
extern int tty_linemode (void);
extern void tty_rspeed (int);
extern void tty_setecho (int);
extern void tty_setedit (int);
extern void tty_setlinemode (int);
extern void tty_setlitecho (int);
extern void tty_setsig (int);
extern void tty_setsofttab (int);
extern void tty_tspeed (int);

extern char *expand_line (const char *fmt);

/*  FIXME */
extern void _termstat (void);
extern void add_slc (char func, char flag, cc_t val);
extern void check_slc (void);
extern void change_slc (char func, char flag, cc_t val);

extern void cleanup (int);
extern void clientstat (int, int, int);
extern void copy_termbuf (void);
extern void deferslc (void);
extern void defer_terminit (void);
extern void do_opt_slc (unsigned char *, int);
extern void dooption (int);
extern void dontoption (int);
extern void edithost (char *, char *);
extern void fatal (int, char *);
extern void fatalperror (int, char *);
extern void get_slc_defaults (void);
extern void localstat (void);
extern void flowstat (void);
extern void netclear (void);

extern void send_do (int, int);
extern void send_dont (int, int);
extern void send_slc (void);
extern void send_status (void);
extern void send_will (int, int);
extern void send_wont (int, int);
extern void set_termbuf (void);
extern void start_login (char *, int, char *);
extern void start_slc (int);
extern void start_slave (char *, int, char *);

extern void suboption (void);
extern void telrcv (void);

extern int end_slc (unsigned char **);
extern int spcset (int, cc_t *, cc_t **);
extern int stilloob (int);
extern int terminit (void);
extern int termstat (void);
extern void willoption (int);
extern void wontoption (int);

#ifdef	ENCRYPTION
extern void (*encrypt_output) (unsigned char *, int);
extern int (*decrypt_input) (int);
#endif /* ENCRYPTION */

extern int startslave (char *host, int autologin, char *autoname);
extern int getterminaltype (char *user_name, size_t len);
extern int net_input_level (void);
extern int net_output_level (void);
extern int net_read (void);
extern int net_buffer_is_full (void);
extern void net_output_byte (int c);
extern int pty_input_level (void);
extern int pty_read (void);
extern int pty_output_level (void);
extern int pty_get_char (int peek);
extern int pty_input_putback (const char *str, size_t len);

extern int terminaltypeok (char *s);