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/*
* SSH port forwarding.
*/
#include <stdio.h>
#include <stdlib.h>
#include "putty.h"
#include "ssh.h"
#ifndef FALSE
#define FALSE 0
#endif
#ifndef TRUE
#define TRUE 1
#endif
struct PortForwarding {
const struct plug_function_table *fn;
/* the above variable absolutely *must* be the first in this structure */
struct ssh_channel *c; /* channel structure held by ssh.c */
void *backhandle; /* instance of SSH backend itself */
/* Note that backhandle need not be filled in if c is non-NULL */
Socket s;
int throttled, throttle_override;
int ready;
/*
* `dynamic' does double duty. It's set to 0 for an ordinary
* forwarded port, and nonzero for SOCKS-style dynamic port
* forwarding; but the nonzero values are also a state machine
* tracking where the SOCKS exchange has got to.
*/
int dynamic;
/*
* `hostname' and `port' are the real hostname and port, once
* we know what we're connecting to.
*/
char *hostname;
int port;
/*
* `socksbuf' is the buffer we use to accumulate a SOCKS request.
*/
char *socksbuf;
int sockslen, sockssize;
/*
* When doing dynamic port forwarding, we can receive
* connection data before we are actually able to send it; so
* we may have to temporarily hold some in a dynamically
* allocated buffer here.
*/
void *buffer;
int buflen;
};
struct PortListener {
const struct plug_function_table *fn;
/* the above variable absolutely *must* be the first in this structure */
void *backhandle; /* instance of SSH backend itself */
Socket s;
/*
* `dynamic' is set to 0 for an ordinary forwarded port, and
* nonzero for SOCKS-style dynamic port forwarding.
*/
int dynamic;
/*
* `hostname' and `port' are the real hostname and port, for
* ordinary forwardings.
*/
char *hostname;
int port;
};
static struct PortForwarding *new_portfwd_state(void)
{
struct PortForwarding *pf = snew(struct PortForwarding);
pf->hostname = NULL;
pf->socksbuf = NULL;
pf->sockslen = pf->sockssize = 0;
pf->buffer = NULL;
return pf;
}
static void free_portfwd_state(struct PortForwarding *pf)
{
if (!pf)
return;
sfree(pf->hostname);
sfree(pf->socksbuf);
sfree(pf->buffer);
sfree(pf);
}
static struct PortListener *new_portlistener_state(void)
{
struct PortListener *pl = snew(struct PortListener);
pl->hostname = NULL;
return pl;
}
static void free_portlistener_state(struct PortListener *pl)
{
if (!pl)
return;
sfree(pl->hostname);
sfree(pl);
}
static void pfd_log(Plug plug, int type, SockAddr addr, int port,
const char *error_msg, int error_code)
{
/* we have to dump these since we have no interface to logging.c */
}
static void pfl_log(Plug plug, int type, SockAddr addr, int port,
const char *error_msg, int error_code)
{
/* we have to dump these since we have no interface to logging.c */
}
static void pfd_closing(Plug plug, const char *error_msg, int error_code,
int calling_back)
{
struct PortForwarding *pf = (struct PortForwarding *) plug;
if (error_msg) {
/*
* Socket error. Slam the connection instantly shut.
*/
if (pf->c) {
sshfwd_unclean_close(pf->c, error_msg);
} else {
/*
* We might not have an SSH channel, if a socket error
* occurred during SOCKS negotiation. If not, we must
* clean ourself up without sshfwd_unclean_close's call
* back to pfd_close.
*/
pfd_close(pf);
}
} else {
/*
* Ordinary EOF received on socket. Send an EOF on the SSH
* channel.
*/
if (pf->c)
sshfwd_write_eof(pf->c);
}
}
static void pfl_closing(Plug plug, const char *error_msg, int error_code,
int calling_back)
{
struct PortListener *pl = (struct PortListener *) plug;
pfl_terminate(pl);
}
static void wrap_send_port_open(void *channel, const char *hostname, int port,
Socket s)
{
char *peerinfo, *description;
peerinfo = sk_peer_info(s);
if (peerinfo) {
description = dupprintf("forwarding from %s", peerinfo);
sfree(peerinfo);
} else {
description = dupstr("forwarding");
}
ssh_send_port_open(channel, hostname, port, description);
sfree(description);
}
static void pfd_receive(Plug plug, int urgent, char *data, int len)
{
struct PortForwarding *pf = (struct PortForwarding *) plug;
if (pf->dynamic) {
while (len--) {
if (pf->sockslen >= pf->sockssize) {
pf->sockssize = pf->sockslen * 5 / 4 + 256;
pf->socksbuf = sresize(pf->socksbuf, pf->sockssize, char);
}
pf->socksbuf[pf->sockslen++] = *data++;
/*
* Now check what's in the buffer to see if it's a
* valid and complete message in the SOCKS exchange.
*/
if ((pf->dynamic == 1 || (pf->dynamic >> 12) == 4) &&
pf->socksbuf[0] == 4) {
/*
* SOCKS 4.
*/
if (pf->dynamic == 1)
pf->dynamic = 0x4000;
if (pf->sockslen < 2)
continue; /* don't have command code yet */
if (pf->socksbuf[1] != 1) {
/* Not CONNECT. */
/* Send back a SOCKS 4 error before closing. */
char data[8];
memset(data, 0, sizeof(data));
data[1] = 91; /* generic `request rejected' */
sk_write(pf->s, data, 8);
pfd_close(pf);
return;
}
if (pf->sockslen <= 8)
continue; /* haven't started user/hostname */
if (pf->socksbuf[pf->sockslen-1] != 0)
continue; /* haven't _finished_ user/hostname */
/*
* Now we have a full SOCKS 4 request. Check it to
* see if it's a SOCKS 4A request.
*/
if (pf->socksbuf[4] == 0 && pf->socksbuf[5] == 0 &&
pf->socksbuf[6] == 0 && pf->socksbuf[7] != 0) {
/*
* It's SOCKS 4A. So if we haven't yet
* collected the host name, we should continue
* waiting for data in order to do so; if we
* have, we can go ahead.
*/
int len;
if (pf->dynamic == 0x4000) {
pf->dynamic = 0x4001;
pf->sockslen = 8; /* reset buffer to overwrite name */
continue;
}
pf->socksbuf[0] = 0; /* reply version code */
pf->socksbuf[1] = 90; /* request granted */
sk_write(pf->s, pf->socksbuf, 8);
len = pf->sockslen - 8;
pf->port = GET_16BIT_MSB_FIRST(pf->socksbuf+2);
pf->hostname = snewn(len+1, char);
pf->hostname[len] = '\0';
memcpy(pf->hostname, pf->socksbuf + 8, len);
goto connect;
} else {
/*
* It's SOCKS 4, which means we should format
* the IP address into the hostname string and
* then just go.
*/
pf->socksbuf[0] = 0; /* reply version code */
pf->socksbuf[1] = 90; /* request granted */
sk_write(pf->s, pf->socksbuf, 8);
pf->port = GET_16BIT_MSB_FIRST(pf->socksbuf+2);
pf->hostname = dupprintf("%d.%d.%d.%d",
(unsigned char)pf->socksbuf[4],
(unsigned char)pf->socksbuf[5],
(unsigned char)pf->socksbuf[6],
(unsigned char)pf->socksbuf[7]);
goto connect;
}
}
if ((pf->dynamic == 1 || (pf->dynamic >> 12) == 5) &&
pf->socksbuf[0] == 5) {
/*
* SOCKS 5.
*/
if (pf->dynamic == 1)
pf->dynamic = 0x5000;
if (pf->dynamic == 0x5000) {
int i, method;
char data[2];
/*
* We're receiving a set of method identifiers.
*/
if (pf->sockslen < 2)
continue; /* no method count yet */
if (pf->sockslen < 2 + (unsigned char)pf->socksbuf[1])
continue; /* no methods yet */
method = 0xFF; /* invalid */
for (i = 0; i < (unsigned char)pf->socksbuf[1]; i++)
if (pf->socksbuf[2+i] == 0) {
method = 0;/* no auth */
break;
}
data[0] = 5;
data[1] = method;
sk_write(pf->s, data, 2);
pf->dynamic = 0x5001;
pf->sockslen = 0; /* re-empty the buffer */
continue;
}
if (pf->dynamic == 0x5001) {
/*
* We're receiving a SOCKS request.
*/
unsigned char reply[10]; /* SOCKS5 atyp=1 reply */
int atype, alen = 0;
/*
* Pre-fill reply packet.
* In all cases, we set BND.{HOST,ADDR} to 0.0.0.0:0
* (atyp=1) in the reply; if we succeed, we don't know
* the right answers, and if we fail, they should be
* ignored.
*/
memset(reply, 0, lenof(reply));
reply[0] = 5; /* VER */
reply[3] = 1; /* ATYP = 1 (IPv4, 0.0.0.0:0) */
if (pf->sockslen < 6) continue;
atype = (unsigned char)pf->socksbuf[3];
if (atype == 1) /* IPv4 address */
alen = 4;
if (atype == 4) /* IPv6 address */
alen = 16;
if (atype == 3) /* domain name has leading length */
alen = 1 + (unsigned char)pf->socksbuf[4];
if (pf->sockslen < 6 + alen) continue;
if (pf->socksbuf[1] != 1 || pf->socksbuf[2] != 0) {
/* Not CONNECT or reserved field nonzero - error */
reply[1] = 1; /* generic failure */
sk_write(pf->s, (char *) reply, lenof(reply));
pfd_close(pf);
return;
}
/*
* Now we have a viable connect request. Switch
* on atype.
*/
pf->port = GET_16BIT_MSB_FIRST(pf->socksbuf+4+alen);
if (atype == 1) {
/* REP=0 (success) already */
sk_write(pf->s, (char *) reply, lenof(reply));
pf->hostname = dupprintf("%d.%d.%d.%d",
(unsigned char)pf->socksbuf[4],
(unsigned char)pf->socksbuf[5],
(unsigned char)pf->socksbuf[6],
(unsigned char)pf->socksbuf[7]);
goto connect;
} else if (atype == 3) {
/* REP=0 (success) already */
sk_write(pf->s, (char *) reply, lenof(reply));
pf->hostname = snewn(alen, char);
pf->hostname[alen-1] = '\0';
memcpy(pf->hostname, pf->socksbuf + 5, alen-1);
goto connect;
} else {
/*
* Unknown address type. (FIXME: support IPv6!)
*/
reply[1] = 8; /* atype not supported */
sk_write(pf->s, (char *) reply, lenof(reply));
pfd_close(pf);
return;
}
}
}
/*
* If we get here without either having done `continue'
* or `goto connect', it must be because there is no
* sensible interpretation of what's in our buffer. So
* close the connection rudely.
*/
pfd_close(pf);
break;
}
return;
/*
* We come here when we're ready to make an actual
* connection.
*/
connect:
sfree(pf->socksbuf);
pf->socksbuf = NULL;
/*
* Freeze the socket until the SSH server confirms the
* connection.
*/
sk_set_frozen(pf->s, 1);
pf->c = new_sock_channel(pf->backhandle, pf);
if (pf->c == NULL) {
pfd_close(pf);
return;
} else {
/* asks to forward to the specified host/port for this */
wrap_send_port_open(pf->c, pf->hostname, pf->port, pf->s);
}
pf->dynamic = 0;
/*
* If there's any data remaining in our current buffer,
* save it to be sent on pfd_confirm().
*/
if (len > 0) {
pf->buffer = snewn(len, char);
memcpy(pf->buffer, data, len);
pf->buflen = len;
}
}
if (pf->ready) {
if (sshfwd_write(pf->c, data, len) > 0) {
pf->throttled = 1;
sk_set_frozen(pf->s, 1);
}
}
}
static void pfd_sent(Plug plug, int bufsize)
{
struct PortForwarding *pf = (struct PortForwarding *) plug;
if (pf->c)
sshfwd_unthrottle(pf->c, bufsize);
}
/*
* Called when receiving a PORT OPEN from the server to make a
* connection to a destination host.
*
* On success, returns NULL and fills in *pf_ret. On error, returns a
* dynamically allocated error message string.
*/
char *pfd_connect(struct PortForwarding **pf_ret, char *hostname,int port,
void *c, Conf *conf, int addressfamily)
{
static const struct plug_function_table fn_table = {
pfd_log,
pfd_closing,
pfd_receive,
pfd_sent,
NULL
};
SockAddr addr;
const char *err;
char *dummy_realhost;
struct PortForwarding *pf;
/*
* Try to find host.
*/
addr = name_lookup(hostname, port, &dummy_realhost, conf, addressfamily,
NULL, NULL);
if ((err = sk_addr_error(addr)) != NULL) {
char *err_ret = dupstr(err);
sk_addr_free(addr);
sfree(dummy_realhost);
return err_ret;
}
/*
* Open socket.
*/
pf = *pf_ret = new_portfwd_state();
pf->fn = &fn_table;
pf->throttled = pf->throttle_override = 0;
pf->ready = 1;
pf->c = c;
pf->backhandle = NULL; /* we shouldn't need this */
pf->dynamic = 0;
pf->s = new_connection(addr, dummy_realhost, port,
0, 1, 0, 0, (Plug) pf, conf);
sfree(dummy_realhost);
if ((err = sk_socket_error(pf->s)) != NULL) {
char *err_ret = dupstr(err);
sk_close(pf->s);
free_portfwd_state(pf);
*pf_ret = NULL;
return err_ret;
}
return NULL;
}
/*
called when someone connects to the local port
*/
static int pfl_accepting(Plug p, accept_fn_t constructor, accept_ctx_t ctx)
{
static const struct plug_function_table fn_table = {
pfd_log,
pfd_closing,
pfd_receive,
pfd_sent,
NULL
};
struct PortForwarding *pf;
struct PortListener *pl;
Socket s;
const char *err;
pl = (struct PortListener *)p;
pf = new_portfwd_state();
pf->fn = &fn_table;
pf->c = NULL;
pf->backhandle = pl->backhandle;
pf->s = s = constructor(ctx, (Plug) pf);
if ((err = sk_socket_error(s)) != NULL) {
free_portfwd_state(pf);
return err != NULL;
}
pf->throttled = pf->throttle_override = 0;
pf->ready = 0;
if (pl->dynamic) {
pf->dynamic = 1;
pf->port = 0; /* "hostname" buffer is so far empty */
sk_set_frozen(s, 0); /* we want to receive SOCKS _now_! */
} else {
pf->dynamic = 0;
pf->hostname = dupstr(pl->hostname);
pf->port = pl->port;
pf->c = new_sock_channel(pl->backhandle, pf);
if (pf->c == NULL) {
free_portfwd_state(pf);
return 1;
} else {
/* asks to forward to the specified host/port for this */
wrap_send_port_open(pf->c, pf->hostname, pf->port, s);
}
}
return 0;
}
/*
* Add a new port-forwarding listener from srcaddr:port -> desthost:destport.
*
* On success, returns NULL and fills in *pl_ret. On error, returns a
* dynamically allocated error message string.
*/
char *pfl_listen(char *desthost, int destport, char *srcaddr,
int port, void *backhandle, Conf *conf,
struct PortListener **pl_ret, int address_family)
{
static const struct plug_function_table fn_table = {
pfl_log,
pfl_closing,
NULL, /* recv */
NULL, /* send */
pfl_accepting
};
const char *err;
struct PortListener *pl;
/*
* Open socket.
*/
pl = *pl_ret = new_portlistener_state();
pl->fn = &fn_table;
if (desthost) {
pl->hostname = dupstr(desthost);
pl->port = destport;
pl->dynamic = 0;
} else
pl->dynamic = 1;
pl->backhandle = backhandle;
pl->s = new_listener(srcaddr, port, (Plug) pl,
!conf_get_int(conf, CONF_lport_acceptall),
conf, address_family);
if ((err = sk_socket_error(pl->s)) != NULL) {
char *err_ret = dupstr(err);
sk_close(pl->s);
free_portlistener_state(pl);
*pl_ret = NULL;
return err_ret;
}
return NULL;
}
void pfd_close(struct PortForwarding *pf)
{
if (!pf)
return;
sk_close(pf->s);
free_portfwd_state(pf);
}
/*
* Terminate a listener.
*/
void pfl_terminate(struct PortListener *pl)
{
if (!pl)
return;
sk_close(pl->s);
free_portlistener_state(pl);
}
void pfd_unthrottle(struct PortForwarding *pf)
{
if (!pf)
return;
pf->throttled = 0;
sk_set_frozen(pf->s, pf->throttled || pf->throttle_override);
}
void pfd_override_throttle(struct PortForwarding *pf, int enable)
{
if (!pf)
return;
pf->throttle_override = enable;
sk_set_frozen(pf->s, pf->throttled || pf->throttle_override);
}
/*
* Called to send data down the raw connection.
*/
int pfd_send(struct PortForwarding *pf, char *data, int len)
{
if (pf == NULL)
return 0;
return sk_write(pf->s, data, len);
}
void pfd_send_eof(struct PortForwarding *pf)
{
sk_write_eof(pf->s);
}
void pfd_confirm(struct PortForwarding *pf)
{
if (pf == NULL)
return;
pf->ready = 1;
sk_set_frozen(pf->s, 0);
sk_write(pf->s, NULL, 0);
if (pf->buffer) {
sshfwd_write(pf->c, pf->buffer, pf->buflen);
sfree(pf->buffer);
pf->buffer = NULL;
}
}