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putty-source/contrib/cygtermd/telnet.c
Simon Tatham 5d718ef64b Whitespace rationalisation of entire code base. 
The number of people has been steadily increasing who read our source
code with an editor that thinks tab stops are 4 spaces apart, as
opposed to the traditional tty-derived 8 that the PuTTY code expects.

So I've been wondering for ages about just fixing it, and switching to
a spaces-only policy throughout the code. And I recently found out
about 'git blame -w', which should make this change not too disruptive
for the purposes of source-control archaeology; so perhaps now is the
time.

While I'm at it, I've also taken the opportunity to remove all the
trailing spaces from source lines (on the basis that git dislikes
them, and is the only thing that seems to have a strong opinion one
way or the other).
    
Apologies to anyone downstream of this code who has complicated patch
sets to rebase past this change. I don't intend it to be needed again.
2019-09-08 20:29:21 +01:00

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/*
* 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;
}
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