/*
* Simple Telnet server code, adapted from PuTTY's own Telnet
* client code for use as a Cygwin local pty proxy.
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include "sel.h"
#include "telnet.h"
#include "malloc.h"
#include "pty.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 GA 249 /* you may reverse the line */
#define EL 248 /* erase the current line */
#define EC 247 /* erase the current character */
#define AYT 246 /* are you there */
#define AO 245 /* abort output--but let prog finish */
#define IP 244 /* interrupt process--permanently */
#define BREAK 243 /* break */
#define DM 242 /* data mark--for connect. cleaning */
#define NOP 241 /* nop */
#define EOR 239 /* end of record (transparent mode) */
#define ABORT 238 /* Abort process */
#define SUSP 237 /* Suspend process */
#define xEOF 236 /* End of file: EOF is already used... */
#define TELOPTS(X) \
X(BINARY, 0) /* 8-bit data path */ \
X(ECHO, 1) /* echo */ \
X(RCP, 2) /* prepare to reconnect */ \
X(SGA, 3) /* suppress go ahead */ \
X(NAMS, 4) /* approximate message size */ \
X(STATUS, 5) /* give status */ \
X(TM, 6) /* timing mark */ \
X(RCTE, 7) /* remote controlled transmission and echo */ \
X(NAOL, 8) /* negotiate about output line width */ \
X(NAOP, 9) /* negotiate about output page size */ \
X(NAOCRD, 10) /* negotiate about CR disposition */ \
X(NAOHTS, 11) /* negotiate about horizontal tabstops */ \
X(NAOHTD, 12) /* negotiate about horizontal tab disposition */ \
X(NAOFFD, 13) /* negotiate about formfeed disposition */ \
X(NAOVTS, 14) /* negotiate about vertical tab stops */ \
X(NAOVTD, 15) /* negotiate about vertical tab disposition */ \
X(NAOLFD, 16) /* negotiate about output LF disposition */ \
X(XASCII, 17) /* extended ascic character set */ \
X(LOGOUT, 18) /* force logout */ \
X(BM, 19) /* byte macro */ \
X(DET, 20) /* data entry terminal */ \
X(SUPDUP, 21) /* supdup protocol */ \
X(SUPDUPOUTPUT, 22) /* supdup output */ \
X(SNDLOC, 23) /* send location */ \
X(TTYPE, 24) /* terminal type */ \
X(EOR, 25) /* end or record */ \
X(TUID, 26) /* TACACS user identification */ \
X(OUTMRK, 27) /* output marking */ \
X(TTYLOC, 28) /* terminal location number */ \
X(3270REGIME, 29) /* 3270 regime */ \
X(X3PAD, 30) /* X.3 PAD */ \
X(NAWS, 31) /* window size */ \
X(TSPEED, 32) /* terminal speed */ \
X(LFLOW, 33) /* remote flow control */ \
X(LINEMODE, 34) /* Linemode option */ \
X(XDISPLOC, 35) /* X Display Location */ \
X(OLD_ENVIRON, 36) /* Old - Environment variables */ \
X(AUTHENTICATION, 37) /* Authenticate */ \
X(ENCRYPT, 38) /* Encryption option */ \
X(NEW_ENVIRON, 39) /* New - Environment variables */ \
X(TN3270E, 40) /* TN3270 enhancements */ \
X(XAUTH, 41) \
X(CHARSET, 42) /* Character set */ \
X(RSP, 43) /* Remote serial port */ \
X(COM_PORT_OPTION, 44) /* Com port control */ \
X(SLE, 45) /* Suppress local echo */ \
X(STARTTLS, 46) /* Start TLS */ \
X(KERMIT, 47) /* Automatic Kermit file transfer */ \
X(SEND_URL, 48) \
X(FORWARD_X, 49) \
X(PRAGMA_LOGON, 138) \
X(SSPI_LOGON, 139) \
X(PRAGMA_HEARTBEAT, 140) \
X(EXOPL, 255) /* extended-options-list */
#define telnet_enum(x,y) TELOPT_##x = y,
enum { TELOPTS(telnet_enum) dummy=0 };
#undef telnet_enum
#define TELQUAL_IS 0 /* option is... */
#define TELQUAL_SEND 1 /* send option */
#define TELQUAL_INFO 2 /* ENVIRON: informational version of IS */
#define BSD_VAR 1
#define BSD_VALUE 0
#define RFC_VAR 0
#define RFC_VALUE 1
#define CR 13
#define LF 10
#define NUL 0
#define iswritable(x) ( (x) != IAC && (x) != CR )
static char *telopt(int opt)
{
#define telnet_str(x,y) case TELOPT_##x: return #x;
switch (opt) {
TELOPTS(telnet_str)
default:
return "<unknown>";
}
#undef telnet_str
}
static void telnet_size(void *handle, int width, int height);
struct Opt {
int send; /* what we initially send */
int nsend; /* -ve send if requested to stop it */
int ack, nak; /* +ve and -ve acknowledgements */
int option; /* the option code */
int index; /* index into telnet->opt_states[] */
enum {
REQUESTED, ACTIVE, INACTIVE, REALLY_INACTIVE
} initial_state;
};
enum {
OPTINDEX_NAWS,
OPTINDEX_TSPEED,
OPTINDEX_TTYPE,
OPTINDEX_OENV,
OPTINDEX_NENV,
OPTINDEX_ECHO,
OPTINDEX_WE_SGA,
OPTINDEX_THEY_SGA,
OPTINDEX_WE_BIN,
OPTINDEX_THEY_BIN,
NUM_OPTS
};
static const struct Opt o_naws =
{ DO, DONT, WILL, WONT, TELOPT_NAWS, OPTINDEX_NAWS, REQUESTED };
static const struct Opt o_ttype =
{ DO, DONT, WILL, WONT, TELOPT_TTYPE, OPTINDEX_TTYPE, REQUESTED };
static const struct Opt o_oenv =
{ DO, DONT, WILL, WONT, TELOPT_OLD_ENVIRON, OPTINDEX_OENV, INACTIVE };
static const struct Opt o_nenv =
{ DO, DONT, WILL, WONT, TELOPT_NEW_ENVIRON, OPTINDEX_NENV, REQUESTED };
static const struct Opt o_echo =
{ WILL, WONT, DO, DONT, TELOPT_ECHO, OPTINDEX_ECHO, REQUESTED };
static const struct Opt o_they_sga =
{ DO, DONT, WILL, WONT, TELOPT_SGA, OPTINDEX_WE_SGA, REQUESTED };
static const struct Opt o_we_sga =
{ WILL, WONT, DO, DONT, TELOPT_SGA, OPTINDEX_THEY_SGA, REQUESTED };
static const struct Opt *const opts[] = {
&o_echo, &o_we_sga, &o_they_sga, &o_naws, &o_ttype, &o_oenv, &o_nenv, NULL
};
struct Telnet {
int opt_states[NUM_OPTS];
int sb_opt, sb_len;
unsigned char *sb_buf;
int sb_size;
enum {
TOP_LEVEL, SEENIAC, SEENWILL, SEENWONT, SEENDO, SEENDONT,
SEENSB, SUBNEGOT, SUBNEG_IAC, SEENCR
} state;
sel_wfd *net, *pty;
/*
* Options we must finish processing before launching the shell
*/
int old_environ_done, new_environ_done, ttype_done;
/*
* Ready to start shell?
*/
int shell_ok;
int envvarsize;
struct shell_data shdata;
};
#define TELNET_MAX_BACKLOG 4096
#define SB_DELTA 1024
static void send_opt(Telnet *telnet, int cmd, int option)
{
unsigned char b[3];
b[0] = IAC;
b[1] = cmd;
b[2] = option;
sel_write(telnet->net, b, 3);
}
static void deactivate_option(Telnet *telnet, const struct Opt *o)
{
if (telnet->opt_states[o->index] == REQUESTED ||
telnet->opt_states[o->index] == ACTIVE)
send_opt(telnet, o->nsend, o->option);
telnet->opt_states[o->index] = REALLY_INACTIVE;
}
/*
* Generate side effects of enabling or disabling an option.
*/
static void option_side_effects(Telnet *telnet, const struct Opt *o, int enabled)
{
}
static void activate_option(Telnet *telnet, const struct Opt *o)
{
if (o->option == TELOPT_NEW_ENVIRON ||
o->option == TELOPT_OLD_ENVIRON ||
o->option == TELOPT_TTYPE) {
char buf[6];
buf[0] = IAC;
buf[1] = SB;
buf[2] = o->option;
buf[3] = TELQUAL_SEND;
buf[4] = IAC;
buf[5] = SE;
sel_write(telnet->net, buf, 6);
}
option_side_effects(telnet, o, 1);
}
static void done_option(Telnet *telnet, int option)
{
if (option == TELOPT_OLD_ENVIRON)
telnet->old_environ_done = 1;
else if (option == TELOPT_NEW_ENVIRON)
telnet->new_environ_done = 1;
else if (option == TELOPT_TTYPE)
telnet->ttype_done = 1;
if (telnet->old_environ_done && telnet->new_environ_done &&
telnet->ttype_done) {
telnet->shell_ok = 1;
}
}
static void refused_option(Telnet *telnet, const struct Opt *o)
{
done_option(telnet, o->option);
if (o->send == WILL && o->option == TELOPT_NEW_ENVIRON &&
telnet->opt_states[o_oenv.index] == INACTIVE) {
send_opt(telnet, WILL, TELOPT_OLD_ENVIRON);
telnet->opt_states[o_oenv.index] = REQUESTED;
telnet->old_environ_done = 0;
}
option_side_effects(telnet, o, 0);
}
static void proc_rec_opt(Telnet *telnet, int cmd, int option)
{
const struct Opt *const *o;
for (o = opts; *o; o++) {
if ((*o)->option == option && (*o)->ack == cmd) {
switch (telnet->opt_states[(*o)->index]) {
case REQUESTED:
telnet->opt_states[(*o)->index] = ACTIVE;
activate_option(telnet, *o);
break;
case ACTIVE:
break;
case INACTIVE:
telnet->opt_states[(*o)->index] = ACTIVE;
send_opt(telnet, (*o)->send, option);
activate_option(telnet, *o);
break;
case REALLY_INACTIVE:
send_opt(telnet, (*o)->nsend, option);
break;
}
return;
} else if ((*o)->option == option && (*o)->nak == cmd) {
switch (telnet->opt_states[(*o)->index]) {
case REQUESTED:
telnet->opt_states[(*o)->index] = INACTIVE;
refused_option(telnet, *o);
break;
case ACTIVE:
telnet->opt_states[(*o)->index] = INACTIVE;
send_opt(telnet, (*o)->nsend, option);
option_side_effects(telnet, *o, 0);
break;
case INACTIVE:
case REALLY_INACTIVE:
break;
}
return;
}
}
/*
* If we reach here, the option was one we weren't prepared to
* cope with. If the request was positive (WILL or DO), we send
* a negative ack to indicate refusal. If the request was
* negative (WONT / DONT), we must do nothing.
*/
if (cmd == WILL || cmd == DO)
send_opt(telnet, (cmd == WILL ? DONT : WONT), option);
}
static void process_subneg(Telnet *telnet)
{
int var, value, n;
switch (telnet->sb_opt) {
case TELOPT_OLD_ENVIRON:
case TELOPT_NEW_ENVIRON:
if (telnet->sb_buf[0] == TELQUAL_IS) {
if (telnet->sb_opt == TELOPT_NEW_ENVIRON) {
var = RFC_VAR;
value = RFC_VALUE;
} else {
if (telnet->sb_len > 1 && !(telnet->sb_buf[0] &~ 1)) {
var = telnet->sb_buf[0];
value = BSD_VAR ^ BSD_VALUE ^ var;
} else {
var = BSD_VAR;
value = BSD_VALUE;
}
}
}
n = 1;
while (n < telnet->sb_len && telnet->sb_buf[n] == var) {
int varpos, varlen, valpos, vallen;
char *result;
varpos = ++n;
while (n < telnet->sb_len && telnet->sb_buf[n] != value)
n++;
if (n == telnet->sb_len)
break;
varlen = n - varpos;
valpos = ++n;
while (n < telnet->sb_len && telnet->sb_buf[n] != var)
n++;
vallen = n - valpos;
result = snewn(varlen + vallen + 2, char);
sprintf(result, "%.*s=%.*s",
varlen, telnet->sb_buf+varpos,
vallen, telnet->sb_buf+valpos);
if (telnet->shdata.nenvvars >= telnet->envvarsize) {
telnet->envvarsize = telnet->shdata.nenvvars * 3 / 2 + 16;
telnet->shdata.envvars = sresize(telnet->shdata.envvars,
telnet->envvarsize, char *);
}
telnet->shdata.envvars[telnet->shdata.nenvvars++] = result;
}
done_option(telnet, telnet->sb_opt);
break;
case TELOPT_TTYPE:
if (telnet->sb_len >= 1 && telnet->sb_buf[0] == TELQUAL_IS) {
telnet->shdata.termtype = snewn(5 + telnet->sb_len, char);
strcpy(telnet->shdata.termtype, "TERM=");
for (n = 0; n < telnet->sb_len-1; n++) {
char c = telnet->sb_buf[n+1];
if (c >= 'A' && c <= 'Z')
c = c + 'a' - 'A';
telnet->shdata.termtype[n+5] = c;
}
telnet->shdata.termtype[telnet->sb_len+5-1] = '\0';
}
done_option(telnet, telnet->sb_opt);
break;
case TELOPT_NAWS:
if (telnet->sb_len == 4) {
int w, h;
w = (unsigned char)telnet->sb_buf[0];
w = (w << 8) | (unsigned char)telnet->sb_buf[1];
h = (unsigned char)telnet->sb_buf[2];
h = (h << 8) | (unsigned char)telnet->sb_buf[3];
pty_resize(w, h);
}
break;
}
}
void telnet_from_net(Telnet *telnet, char *buf, int len)
{
while (len--) {
int c = (unsigned char) *buf++;
switch (telnet->state) {
case TOP_LEVEL:
case SEENCR:
/*
* PuTTY sends Telnet's new line sequence (CR LF on
* the wire) in response to the return key. We must
* therefore treat that as equivalent to CR NUL, and
* send CR to the pty.
*/
if ((c == NUL || c == '\n') && telnet->state == SEENCR)
telnet->state = TOP_LEVEL;
else if (c == IAC)
telnet->state = SEENIAC;
else {
char cc = c;
sel_write(telnet->pty, &cc, 1);
if (c == CR)
telnet->state = SEENCR;
else
telnet->state = TOP_LEVEL;
}
break;
case SEENIAC:
if (c == DO)
telnet->state = SEENDO;
else if (c == DONT)
telnet->state = SEENDONT;
else if (c == WILL)
telnet->state = SEENWILL;
else if (c == WONT)
telnet->state = SEENWONT;
else if (c == SB)
telnet->state = SEENSB;
else if (c == DM)
telnet->state = TOP_LEVEL;
else {
/* ignore everything else; print it if it's IAC */
if (c == IAC) {
char cc = c;
sel_write(telnet->pty, &cc, 1);
}
telnet->state = TOP_LEVEL;
}
break;
case SEENWILL:
proc_rec_opt(telnet, WILL, c);
telnet->state = TOP_LEVEL;
break;
case SEENWONT:
proc_rec_opt(telnet, WONT, c);
telnet->state = TOP_LEVEL;
break;
case SEENDO:
proc_rec_opt(telnet, DO, c);
telnet->state = TOP_LEVEL;
break;
case SEENDONT:
proc_rec_opt(telnet, DONT, c);
telnet->state = TOP_LEVEL;
break;
case SEENSB:
telnet->sb_opt = c;
telnet->sb_len = 0;
telnet->state = SUBNEGOT;
break;
case SUBNEGOT:
if (c == IAC)
telnet->state = SUBNEG_IAC;
else {
subneg_addchar:
if (telnet->sb_len >= telnet->sb_size) {
telnet->sb_size += SB_DELTA;
telnet->sb_buf = sresize(telnet->sb_buf, telnet->sb_size,
unsigned char);
}
telnet->sb_buf[telnet->sb_len++] = c;
telnet->state = SUBNEGOT; /* in case we came here by goto */
}
break;
case SUBNEG_IAC:
if (c != SE)
goto subneg_addchar; /* yes, it's a hack, I know, but... */
else {
process_subneg(telnet);
telnet->state = TOP_LEVEL;
}
break;
}
}
}
Telnet *telnet_new(sel_wfd *net, sel_wfd *pty)
{
Telnet *telnet;
telnet = snew(Telnet);
telnet->sb_buf = NULL;
telnet->sb_size = 0;
telnet->state = TOP_LEVEL;
telnet->net = net;
telnet->pty = pty;
telnet->shdata.envvars = NULL;
telnet->shdata.nenvvars = telnet->envvarsize = 0;
telnet->shdata.termtype = NULL;
/*
* Initialise option states.
*/
{
const struct Opt *const *o;
for (o = opts; *o; o++) {
telnet->opt_states[(*o)->index] = (*o)->initial_state;
if (telnet->opt_states[(*o)->index] == REQUESTED)
send_opt(telnet, (*o)->send, (*o)->option);
}
}
telnet->old_environ_done = 1; /* initially don't want to bother */
telnet->new_environ_done = 0;
telnet->ttype_done = 0;
telnet->shell_ok = 0;
return telnet;
}
void telnet_free(Telnet *telnet)
{
sfree(telnet->sb_buf);
sfree(telnet);
}
void telnet_from_pty(Telnet *telnet, char *buf, int len)
{
unsigned char *p, *end;
static const unsigned char iac[2] = { IAC, IAC };
static const unsigned char cr[2] = { CR, NUL };
#if 0
static const unsigned char nl[2] = { CR, LF };
#endif
p = (unsigned char *)buf;
end = (unsigned char *)(buf + len);
while (p < end) {
unsigned char *q = p;
while (p < end && iswritable(*p))
p++;
sel_write(telnet->net, q, p - q);
while (p < end && !iswritable(*p)) {
sel_write(telnet->net, *p == IAC ? iac : cr, 2);
p++;
}
}
}
int telnet_shell_ok(Telnet *telnet, struct shell_data *shdata)
{
if (telnet->shell_ok)
*shdata = telnet->shdata; /* structure copy */
return telnet->shell_ok;
}