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putty/telnet.c

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35 KiB
C
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/*
* Telnet backend.
*/
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include "putty.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 && \
(telnet->opt_states[o_we_bin.index] == ACTIVE || (x) != CR))
static const 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
}
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 =
{ WILL, WONT, DO, DONT, TELOPT_NAWS, OPTINDEX_NAWS, REQUESTED };
static const struct Opt o_tspeed =
{ WILL, WONT, DO, DONT, TELOPT_TSPEED, OPTINDEX_TSPEED, REQUESTED };
static const struct Opt o_ttype =
{ WILL, WONT, DO, DONT, TELOPT_TTYPE, OPTINDEX_TTYPE, REQUESTED };
static const struct Opt o_oenv =
{ WILL, WONT, DO, DONT, TELOPT_OLD_ENVIRON, OPTINDEX_OENV, INACTIVE };
static const struct Opt o_nenv =
{ WILL, WONT, DO, DONT, TELOPT_NEW_ENVIRON, OPTINDEX_NENV, REQUESTED };
static const struct Opt o_echo =
{ DO, DONT, WILL, WONT, TELOPT_ECHO, OPTINDEX_ECHO, REQUESTED };
static const struct Opt o_we_sga =
{ WILL, WONT, DO, DONT, TELOPT_SGA, OPTINDEX_WE_SGA, REQUESTED };
static const struct Opt o_they_sga =
{ DO, DONT, WILL, WONT, TELOPT_SGA, OPTINDEX_THEY_SGA, REQUESTED };
static const struct Opt o_we_bin =
{ WILL, WONT, DO, DONT, TELOPT_BINARY, OPTINDEX_WE_BIN, INACTIVE };
static const struct Opt o_they_bin =
{ DO, DONT, WILL, WONT, TELOPT_BINARY, OPTINDEX_THEY_BIN, INACTIVE };
static const struct Opt *const opts[] = {
&o_naws, &o_tspeed, &o_ttype, &o_oenv, &o_nenv, &o_echo,
&o_we_sga, &o_they_sga, &o_we_bin, &o_they_bin, NULL
};
typedef struct Telnet Telnet;
struct Telnet {
Socket *s;
bool closed_on_socket_error;
Seat *seat;
LogContext *logctx;
Ldisc *ldisc;
int term_width, term_height;
int opt_states[NUM_OPTS];
bool echoing, editing;
bool activated;
size_t bufsize;
bool in_synch;
int sb_opt;
strbuf *sb_buf;
bool session_started;
enum {
TOP_LEVEL, SEENIAC, SEENWILL, SEENWONT, SEENDO, SEENDONT,
SEENSB, SUBNEGOT, SUBNEG_IAC, SEENCR
} state;
Conf *conf;
Pinger *pinger;
Plug plug;
Backend backend;
};
#define TELNET_MAX_BACKLOG 4096
#define SB_DELTA 1024
static void c_write(Telnet *telnet, const void *buf, size_t len)
{
size_t backlog = seat_stdout(telnet->seat, buf, len);
sk_set_frozen(telnet->s, backlog > TELNET_MAX_BACKLOG);
}
static void log_option(Telnet *telnet, const char *sender, int cmd, int option)
{
/*
* The strange-looking "<?""?>" below is there to avoid a
* trigraph - a double question mark followed by > maps to a
* closing brace character!
*/
logeventf(telnet->logctx, "%s:\t%s %s", sender,
(cmd == WILL ? "WILL" : cmd == WONT ? "WONT" :
cmd == DO ? "DO" : cmd == DONT ? "DONT" : "<?""?>"),
telopt(option));
}
static void send_opt(Telnet *telnet, int cmd, int option)
{
unsigned char b[3];
b[0] = IAC;
b[1] = cmd;
b[2] = option;
telnet->bufsize = sk_write(telnet->s, b, 3);
log_option(telnet, "client", cmd, option);
}
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, bool enabled)
{
if (o->option == TELOPT_ECHO && o->send == DO)
telnet->echoing = !enabled;
else if (o->option == TELOPT_SGA && o->send == DO)
telnet->editing = !enabled;
if (telnet->ldisc) /* cause ldisc to notice the change */
ldisc_echoedit_update(telnet->ldisc);
/* Ensure we get the minimum options */
if (!telnet->activated) {
if (telnet->opt_states[o_echo.index] == INACTIVE) {
telnet->opt_states[o_echo.index] = REQUESTED;
send_opt(telnet, o_echo.send, o_echo.option);
}
if (telnet->opt_states[o_we_sga.index] == INACTIVE) {
telnet->opt_states[o_we_sga.index] = REQUESTED;
send_opt(telnet, o_we_sga.send, o_we_sga.option);
}
if (telnet->opt_states[o_they_sga.index] == INACTIVE) {
telnet->opt_states[o_they_sga.index] = REQUESTED;
send_opt(telnet, o_they_sga.send, o_they_sga.option);
}
telnet->activated = true;
}
}
static void activate_option(Telnet *telnet, const struct Opt *o)
{
if (o->send == WILL && o->option == TELOPT_NAWS)
backend_size(&telnet->backend,
telnet->term_width, telnet->term_height);
if (o->send == WILL &&
(o->option == TELOPT_NEW_ENVIRON ||
o->option == TELOPT_OLD_ENVIRON)) {
/*
* We may only have one kind of ENVIRON going at a time.
* This is a hack, but who cares.
*/
deactivate_option(telnet, o->option ==
TELOPT_NEW_ENVIRON ? &o_oenv : &o_nenv);
}
option_side_effects(telnet, o, true);
}
static void refused_option(Telnet *telnet, const struct Opt *o)
{
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;
}
option_side_effects(telnet, o, false);
}
static void proc_rec_opt(Telnet *telnet, int cmd, int option)
{
const struct Opt *const *o;
log_option(telnet, "server", cmd, option);
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, false);
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)
{
unsigned char *b, *p, *q;
int var, value, n, bsize;
char *e, *eval, *ekey, *user;
switch (telnet->sb_opt) {
case TELOPT_TSPEED:
if (telnet->sb_buf->len == 1 && telnet->sb_buf->u[0] == TELQUAL_SEND) {
char *termspeed = conf_get_str(telnet->conf, CONF_termspeed);
b = snewn(20 + strlen(termspeed), unsigned char);
b[0] = IAC;
b[1] = SB;
b[2] = TELOPT_TSPEED;
b[3] = TELQUAL_IS;
strcpy((char *)(b + 4), termspeed);
n = 4 + strlen(termspeed);
b[n] = IAC;
b[n + 1] = SE;
telnet->bufsize = sk_write(telnet->s, b, n + 2);
logevent(telnet->logctx, "server:\tSB TSPEED SEND");
logeventf(telnet->logctx, "client:\tSB TSPEED IS %s", termspeed);
sfree(b);
} else
logevent(telnet->logctx, "server:\tSB TSPEED <something weird>");
break;
case TELOPT_TTYPE:
if (telnet->sb_buf->len == 1 && telnet->sb_buf->u[0] == TELQUAL_SEND) {
char *termtype = conf_get_str(telnet->conf, CONF_termtype);
b = snewn(20 + strlen(termtype), unsigned char);
b[0] = IAC;
b[1] = SB;
b[2] = TELOPT_TTYPE;
b[3] = TELQUAL_IS;
for (n = 0; termtype[n]; n++)
b[n + 4] = (termtype[n] >= 'a' && termtype[n] <= 'z' ?
termtype[n] + 'A' - 'a' :
termtype[n]);
b[n + 4] = IAC;
b[n + 5] = SE;
telnet->bufsize = sk_write(telnet->s, b, n + 6);
b[n + 4] = 0;
logevent(telnet->logctx, "server:\tSB TTYPE SEND");
logeventf(telnet->logctx, "client:\tSB TTYPE IS %s", b + 4);
sfree(b);
} else
logevent(telnet->logctx, "server:\tSB TTYPE <something weird>\r\n");
break;
case TELOPT_OLD_ENVIRON:
case TELOPT_NEW_ENVIRON:
p = telnet->sb_buf->u;
q = p + telnet->sb_buf->len;
if (p < q && *p == TELQUAL_SEND) {
p++;
logeventf(telnet->logctx, "server:\tSB %s SEND",
telopt(telnet->sb_opt));
if (telnet->sb_opt == TELOPT_OLD_ENVIRON) {
if (conf_get_bool(telnet->conf, CONF_rfc_environ)) {
value = RFC_VALUE;
var = RFC_VAR;
} else {
value = BSD_VALUE;
var = BSD_VAR;
}
/*
* Try to guess the sense of VAR and VALUE.
*/
while (p < q) {
if (*p == RFC_VAR) {
value = RFC_VALUE;
var = RFC_VAR;
} else if (*p == BSD_VAR) {
value = BSD_VALUE;
var = BSD_VAR;
}
p++;
}
} else {
/*
* With NEW_ENVIRON, the sense of VAR and VALUE
* isn't in doubt.
*/
value = RFC_VALUE;
var = RFC_VAR;
}
bsize = 20;
for (eval = conf_get_str_strs(telnet->conf, CONF_environmt,
NULL, &ekey);
eval != NULL;
eval = conf_get_str_strs(telnet->conf, CONF_environmt,
ekey, &ekey))
bsize += strlen(ekey) + strlen(eval) + 2;
user = get_remote_username(telnet->conf);
if (user)
bsize += 6 + strlen(user);
b = snewn(bsize, unsigned char);
b[0] = IAC;
b[1] = SB;
b[2] = telnet->sb_opt;
b[3] = TELQUAL_IS;
n = 4;
for (eval = conf_get_str_strs(telnet->conf, CONF_environmt,
NULL, &ekey);
eval != NULL;
eval = conf_get_str_strs(telnet->conf, CONF_environmt,
ekey, &ekey)) {
b[n++] = var;
for (e = ekey; *e; e++)
b[n++] = *e;
b[n++] = value;
for (e = eval; *e; e++)
b[n++] = *e;
}
if (user) {
b[n++] = var;
b[n++] = 'U';
b[n++] = 'S';
b[n++] = 'E';
b[n++] = 'R';
b[n++] = value;
for (e = user; *e; e++)
b[n++] = *e;
}
b[n++] = IAC;
b[n++] = SE;
telnet->bufsize = sk_write(telnet->s, b, n);
if (n == 6) {
logeventf(telnet->logctx, "client:\tSB %s IS <nothing>",
telopt(telnet->sb_opt));
} else {
logeventf(telnet->logctx, "client:\tSB %s IS:",
telopt(telnet->sb_opt));
for (eval = conf_get_str_strs(telnet->conf, CONF_environmt,
NULL, &ekey);
eval != NULL;
eval = conf_get_str_strs(telnet->conf, CONF_environmt,
ekey, &ekey)) {
logeventf(telnet->logctx, "\t%s=%s", ekey, eval);
}
if (user)
logeventf(telnet->logctx, "\tUSER=%s", user);
}
sfree(b);
sfree(user);
}
break;
}
}
static void do_telnet_read(Telnet *telnet, const char *buf, size_t len)
{
strbuf *outbuf = strbuf_new_nm();
while (len--) {
int c = (unsigned char) *buf++;
switch (telnet->state) {
case TOP_LEVEL:
case SEENCR:
if (c == NUL && telnet->state == SEENCR)
telnet->state = TOP_LEVEL;
else if (c == IAC)
telnet->state = SEENIAC;
else {
if (!telnet->in_synch)
put_byte(outbuf, c);
#if 1
/* I can't get the F***ing winsock to insert the urgent IAC
* into the right position! Even with SO_OOBINLINE it gives
* it to recv too soon. And of course the DM byte (that
* arrives in the same packet!) appears several K later!!
*
* Oh well, we do get the DM in the right place so I'll
* just stop hiding on the next 0xf2 and hope for the best.
*/
else if (c == DM)
telnet->in_synch = false;
#endif
if (c == CR && telnet->opt_states[o_they_bin.index] != ACTIVE)
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->in_synch = false;
telnet->state = TOP_LEVEL;
} else {
/* ignore everything else; print it if it's IAC */
if (c == IAC) {
put_byte(outbuf, c);
}
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;
strbuf_clear(telnet->sb_buf);
telnet->state = SUBNEGOT;
break;
case SUBNEGOT:
if (c == IAC)
telnet->state = SUBNEG_IAC;
else {
subneg_addchar:
put_byte(telnet->sb_buf, 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;
}
if (outbuf->len >= 4096) {
c_write(telnet, outbuf->u, outbuf->len);
strbuf_clear(outbuf);
}
}
if (outbuf->len)
c_write(telnet, outbuf->u, outbuf->len);
strbuf_free(outbuf);
}
static void telnet_log(Plug *plug, PlugLogType type, SockAddr *addr, int port,
const char *error_msg, int error_code)
{
Telnet *telnet = container_of(plug, Telnet, plug);
backend_socket_log(telnet->seat, telnet->logctx, type, addr, port,
error_msg, error_code, telnet->conf,
telnet->session_started);
}
static void telnet_closing(Plug *plug, const char *error_msg, int error_code,
bool calling_back)
{
Telnet *telnet = container_of(plug, Telnet, plug);
/*
* We don't implement independent EOF in each direction for Telnet
* connections; as soon as we get word that the remote side has
* sent us EOF, we wind up the whole connection.
*/
if (telnet->s) {
sk_close(telnet->s);
telnet->s = NULL;
if (error_msg)
telnet->closed_on_socket_error = true;
seat_notify_remote_exit(telnet->seat);
}
if (error_msg) {
logevent(telnet->logctx, error_msg);
seat_connection_fatal(telnet->seat, "%s", error_msg);
}
/* Otherwise, the remote side closed the connection normally. */
}
static void telnet_receive(
Plug *plug, int urgent, const char *data, size_t len)
{
Telnet *telnet = container_of(plug, Telnet, plug);
if (urgent)
telnet->in_synch = true;
telnet->session_started = true;
do_telnet_read(telnet, data, len);
}
static void telnet_sent(Plug *plug, size_t bufsize)
{
Telnet *telnet = container_of(plug, Telnet, plug);
telnet->bufsize = bufsize;
}
static const PlugVtable Telnet_plugvt = {
.log = telnet_log,
.closing = telnet_closing,
.receive = telnet_receive,
.sent = telnet_sent,
};
/*
* Called to set up the Telnet connection.
*
* Returns an error message, or NULL on success.
*
* Also places the canonical host name into `realhost'. It must be
* freed by the caller.
*/
static char *telnet_init(const BackendVtable *vt, Seat *seat,
Backend **backend_handle, LogContext *logctx,
Conf *conf, const char *host, int port,
char **realhost, bool nodelay, bool keepalive)
{
SockAddr *addr;
const char *err;
Telnet *telnet;
char *loghost;
int addressfamily;
/* No local authentication phase in this protocol */
seat_set_trust_status(seat, false);
telnet = snew(Telnet);
telnet->plug.vt = &Telnet_plugvt;
telnet->backend.vt = vt;
telnet->conf = conf_copy(conf);
telnet->s = NULL;
telnet->closed_on_socket_error = false;
telnet->echoing = true;
telnet->editing = true;
telnet->activated = false;
telnet->sb_buf = strbuf_new();
telnet->seat = seat;
telnet->logctx = logctx;
telnet->term_width = conf_get_int(telnet->conf, CONF_width);
telnet->term_height = conf_get_int(telnet->conf, CONF_height);
telnet->state = TOP_LEVEL;
telnet->ldisc = NULL;
telnet->pinger = NULL;
telnet->session_started = true;
*backend_handle = &telnet->backend;
/*
* Try to find host.
*/
addressfamily = conf_get_int(telnet->conf, CONF_addressfamily);
addr = name_lookup(host, port, realhost, telnet->conf, addressfamily,
telnet->logctx, "Telnet connection");
if ((err = sk_addr_error(addr)) != NULL) {
sk_addr_free(addr);
return dupstr(err);
}
if (port < 0)
port = 23; /* default telnet port */
/*
* Open socket.
*/
telnet->s = new_connection(addr, *realhost, port, false, true, nodelay,
keepalive, &telnet->plug, telnet->conf);
if ((err = sk_socket_error(telnet->s)) != NULL)
return dupstr(err);
telnet->pinger = pinger_new(telnet->conf, &telnet->backend);
/*
* Initialise option states.
*/
if (conf_get_bool(telnet->conf, CONF_passive_telnet)) {
const struct Opt *const *o;
for (o = opts; *o; o++)
telnet->opt_states[(*o)->index] = INACTIVE;
} else {
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->activated = true;
}
/*
* Set up SYNCH state.
*/
telnet->in_synch = false;
/*
* We can send special commands from the start.
*/
seat_update_specials_menu(telnet->seat);
/*
* loghost overrides realhost, if specified.
*/
loghost = conf_get_str(telnet->conf, CONF_loghost);
if (*loghost) {
char *colon;
sfree(*realhost);
*realhost = dupstr(loghost);
colon = host_strrchr(*realhost, ':');
if (colon)
*colon++ = '\0';
}
return NULL;
}
static void telnet_free(Backend *be)
{
Telnet *telnet = container_of(be, Telnet, backend);
strbuf_free(telnet->sb_buf);
if (telnet->s)
sk_close(telnet->s);
if (telnet->pinger)
pinger_free(telnet->pinger);
conf_free(telnet->conf);
sfree(telnet);
}
/*
* Reconfigure the Telnet backend. There's no immediate action
* necessary, in this backend: we just save the fresh config for
* any subsequent negotiations.
*/
static void telnet_reconfig(Backend *be, Conf *conf)
{
Telnet *telnet = container_of(be, Telnet, backend);
pinger_reconfig(telnet->pinger, telnet->conf, conf);
conf_free(telnet->conf);
telnet->conf = conf_copy(conf);
}
/*
* Called to send data down the Telnet connection.
*/
static size_t telnet_send(Backend *be, const char *buf, size_t len)
{
Telnet *telnet = container_of(be, Telnet, backend);
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
if (telnet->s == NULL)
return 0;
p = (unsigned char *)buf;
end = (unsigned char *)(buf + len);
while (p < end) {
unsigned char *q = p;
while (p < end && iswritable(*p))
p++;
telnet->bufsize = sk_write(telnet->s, q, p - q);
while (p < end && !iswritable(*p)) {
telnet->bufsize =
sk_write(telnet->s, *p == IAC ? iac : cr, 2);
p++;
}
}
return telnet->bufsize;
}
/*
* Called to query the current socket sendability status.
*/
static size_t telnet_sendbuffer(Backend *be)
{
Telnet *telnet = container_of(be, Telnet, backend);
return telnet->bufsize;
}
/*
* Called to set the size of the window from Telnet's POV.
*/
static void telnet_size(Backend *be, int width, int height)
{
Telnet *telnet = container_of(be, Telnet, backend);
unsigned char b[24];
int n;
telnet->term_width = width;
telnet->term_height = height;
if (telnet->s == NULL || telnet->opt_states[o_naws.index] != ACTIVE)
return;
n = 0;
b[n++] = IAC;
b[n++] = SB;
b[n++] = TELOPT_NAWS;
b[n++] = telnet->term_width >> 8;
if (b[n-1] == IAC) b[n++] = IAC; /* duplicate any IAC byte occurs */
b[n++] = telnet->term_width & 0xFF;
if (b[n-1] == IAC) b[n++] = IAC; /* duplicate any IAC byte occurs */
b[n++] = telnet->term_height >> 8;
if (b[n-1] == IAC) b[n++] = IAC; /* duplicate any IAC byte occurs */
b[n++] = telnet->term_height & 0xFF;
if (b[n-1] == IAC) b[n++] = IAC; /* duplicate any IAC byte occurs */
b[n++] = IAC;
b[n++] = SE;
telnet->bufsize = sk_write(telnet->s, b, n);
logeventf(telnet->logctx, "client:\tSB NAWS %d,%d",
telnet->term_width, telnet->term_height);
}
/*
* Send Telnet special codes.
*/
static void telnet_special(Backend *be, SessionSpecialCode code, int arg)
{
Telnet *telnet = container_of(be, Telnet, backend);
unsigned char b[2];
if (telnet->s == NULL)
return;
b[0] = IAC;
switch (code) {
case SS_AYT:
b[1] = AYT;
telnet->bufsize = sk_write(telnet->s, b, 2);
break;
case SS_BRK:
b[1] = BREAK;
telnet->bufsize = sk_write(telnet->s, b, 2);
break;
case SS_EC:
b[1] = EC;
telnet->bufsize = sk_write(telnet->s, b, 2);
break;
case SS_EL:
b[1] = EL;
telnet->bufsize = sk_write(telnet->s, b, 2);
break;
case SS_GA:
b[1] = GA;
telnet->bufsize = sk_write(telnet->s, b, 2);
break;
case SS_NOP:
b[1] = NOP;
telnet->bufsize = sk_write(telnet->s, b, 2);
break;
case SS_ABORT:
b[1] = ABORT;
telnet->bufsize = sk_write(telnet->s, b, 2);
break;
case SS_AO:
b[1] = AO;
telnet->bufsize = sk_write(telnet->s, b, 2);
break;
case SS_IP:
b[1] = IP;
telnet->bufsize = sk_write(telnet->s, b, 2);
break;
case SS_SUSP:
b[1] = SUSP;
telnet->bufsize = sk_write(telnet->s, b, 2);
break;
case SS_EOR:
b[1] = EOR;
telnet->bufsize = sk_write(telnet->s, b, 2);
break;
case SS_EOF:
b[1] = xEOF;
telnet->bufsize = sk_write(telnet->s, b, 2);
break;
case SS_EOL:
/* In BINARY mode, CR-LF becomes just CR -
* and without the NUL suffix too. */
if (telnet->opt_states[o_we_bin.index] == ACTIVE)
telnet->bufsize = sk_write(telnet->s, "\r", 1);
else
telnet->bufsize = sk_write(telnet->s, "\r\n", 2);
break;
case SS_SYNCH:
b[1] = DM;
telnet->bufsize = sk_write(telnet->s, b, 1);
telnet->bufsize = sk_write_oob(telnet->s, b + 1, 1);
break;
case SS_PING:
if (telnet->opt_states[o_they_sga.index] == ACTIVE) {
b[1] = NOP;
telnet->bufsize = sk_write(telnet->s, b, 2);
}
break;
default:
break; /* never heard of it */
}
}
static const SessionSpecial *telnet_get_specials(Backend *be)
{
static const SessionSpecial specials[] = {
{"Are You There", SS_AYT},
{"Break", SS_BRK},
{"Synch", SS_SYNCH},
{"Erase Character", SS_EC},
{"Erase Line", SS_EL},
{"Go Ahead", SS_GA},
{"No Operation", SS_NOP},
{NULL, SS_SEP},
{"Abort Process", SS_ABORT},
{"Abort Output", SS_AO},
{"Interrupt Process", SS_IP},
{"Suspend Process", SS_SUSP},
{NULL, SS_SEP},
{"End Of Record", SS_EOR},
{"End Of File", SS_EOF},
{NULL, SS_EXITMENU}
};
return specials;
}
static bool telnet_connected(Backend *be)
{
Telnet *telnet = container_of(be, Telnet, backend);
return telnet->s != NULL;
}
static bool telnet_sendok(Backend *be)
{
/* Telnet *telnet = container_of(be, Telnet, backend); */
return true;
}
static void telnet_unthrottle(Backend *be, size_t backlog)
{
Telnet *telnet = container_of(be, Telnet, backend);
sk_set_frozen(telnet->s, backlog > TELNET_MAX_BACKLOG);
}
static bool telnet_ldisc(Backend *be, int option)
{
Telnet *telnet = container_of(be, Telnet, backend);
if (option == LD_ECHO)
return telnet->echoing;
if (option == LD_EDIT)
return telnet->editing;
return false;
}
static void telnet_provide_ldisc(Backend *be, Ldisc *ldisc)
{
Telnet *telnet = container_of(be, Telnet, backend);
telnet->ldisc = ldisc;
}
static int telnet_exitcode(Backend *be)
{
Telnet *telnet = container_of(be, Telnet, backend);
if (telnet->s != NULL)
return -1; /* still connected */
else if (telnet->closed_on_socket_error)
return INT_MAX; /* a socket error counts as an unclean exit */
else
/* Telnet doesn't transmit exit codes back to the client */
return 0;
}
/*
* cfg_info for Telnet does nothing at all.
*/
static int telnet_cfg_info(Backend *be)
{
return 0;
}
const BackendVtable telnet_backend = {
.init = telnet_init,
.free = telnet_free,
.reconfig = telnet_reconfig,
.send = telnet_send,
.sendbuffer = telnet_sendbuffer,
.size = telnet_size,
.special = telnet_special,
.get_specials = telnet_get_specials,
.connected = telnet_connected,
.exitcode = telnet_exitcode,
.sendok = telnet_sendok,
.ldisc_option_state = telnet_ldisc,
.provide_ldisc = telnet_provide_ldisc,
.unthrottle = telnet_unthrottle,
.cfg_info = telnet_cfg_info,
.id = "telnet",
.displayname = "Telnet",
.protocol = PROT_TELNET,
.default_port = 23,
};
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