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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 PFwdPrivate {
const struct plug_function_table *fn;
/* the above variable absolutely *must* be the first in this structure */
void *c; /* (channel) data used 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 it also represents the state of the SOCKS
* exchange.
*/
int dynamic;
/*
* `hostname' and `port' are the real hostname and port, once
* we know what we're connecting to; they're unused for this
* purpose while conducting a local SOCKS exchange, which means
* we can also use them as a buffer and pointer for reading
* data from the SOCKS client.
*/
char hostname[256+8];
int port;
/*
* 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;
};
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 int pfd_closing(Plug plug, const char *error_msg, int error_code,
int calling_back)
{
struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;
/*
* We have no way to communicate down the forwarded connection,
* so if an error occurred on the socket, we just ignore it
* and treat it like a proper close.
*/
if (pr->c)
sshfwd_close(pr->c);
pfd_close(pr->s);
return 1;
}
static int pfd_receive(Plug plug, int urgent, char *data, int len)
{
struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;
if (pr->dynamic) {
while (len--) {
/*
* Throughout SOCKS negotiation, "hostname" is re-used as a
* random protocol buffer with "port" storing the length.
*/
if (pr->port >= lenof(pr->hostname)) {
/* Request too long. */
if ((pr->dynamic >> 12) == 4) {
/* Send back a SOCKS 4 error before closing. */
char data[8];
memset(data, 0, sizeof(data));
data[1] = 91; /* generic `request rejected' */
sk_write(pr->s, data, 8);
}
pfd_close(pr->s);
return 1;
}
pr->hostname[pr->port++] = *data++;
/*
* Now check what's in the buffer to see if it's a
* valid and complete message in the SOCKS exchange.
*/
if ((pr->dynamic == 1 || (pr->dynamic >> 12) == 4) &&
pr->hostname[0] == 4) {
/*
* SOCKS 4.
*/
if (pr->dynamic == 1)
pr->dynamic = 0x4000;
if (pr->port < 2) continue;/* don't have command code yet */
if (pr->hostname[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(pr->s, data, 8);
pfd_close(pr->s);
return 1;
}
if (pr->port <= 8) continue; /* haven't started user/hostname */
if (pr->hostname[pr->port-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 (pr->hostname[4] == 0 && pr->hostname[5] == 0 &&
pr->hostname[6] == 0 && pr->hostname[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 (pr->dynamic == 0x4000) {
pr->dynamic = 0x4001;
pr->port = 8; /* reset buffer to overwrite name */
continue;
}
pr->hostname[0] = 0; /* reply version code */
pr->hostname[1] = 90; /* request granted */
sk_write(pr->s, pr->hostname, 8);
len= pr->port - 8;
pr->port = GET_16BIT_MSB_FIRST(pr->hostname+2);
memmove(pr->hostname, pr->hostname + 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.
*/
pr->hostname[0] = 0; /* reply version code */
pr->hostname[1] = 90; /* request granted */
sk_write(pr->s, pr->hostname, 8);
pr->port = GET_16BIT_MSB_FIRST(pr->hostname+2);
sprintf(pr->hostname, "%d.%d.%d.%d",
(unsigned char)pr->hostname[4],
(unsigned char)pr->hostname[5],
(unsigned char)pr->hostname[6],
(unsigned char)pr->hostname[7]);
goto connect;
}
}
if ((pr->dynamic == 1 || (pr->dynamic >> 12) == 5) &&
pr->hostname[0] == 5) {
/*
* SOCKS 5.
*/
if (pr->dynamic == 1)
pr->dynamic = 0x5000;
if (pr->dynamic == 0x5000) {
int i, method;
char data[2];
/*
* We're receiving a set of method identifiers.
*/
if (pr->port < 2) continue;/* no method count yet */
if (pr->port < 2 + (unsigned char)pr->hostname[1])
continue; /* no methods yet */
method = 0xFF; /* invalid */
for (i = 0; i < (unsigned char)pr->hostname[1]; i++)
if (pr->hostname[2+i] == 0) {
method = 0;/* no auth */
break;
}
data[0] = 5;
data[1] = method;
sk_write(pr->s, data, 2);
pr->dynamic = 0x5001;
pr->port = 0; /* re-empty the buffer */
continue;
}
if (pr->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 (pr->port < 6) continue;
atype = (unsigned char)pr->hostname[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)pr->hostname[4];
if (pr->port < 6 + alen) continue;
if (pr->hostname[1] != 1 || pr->hostname[2] != 0) {
/* Not CONNECT or reserved field nonzero - error */
reply[1] = 1; /* generic failure */
sk_write(pr->s, (char *) reply, lenof(reply));
pfd_close(pr->s);
return 1;
}
/*
* Now we have a viable connect request. Switch
* on atype.
*/
pr->port = GET_16BIT_MSB_FIRST(pr->hostname+4+alen);
if (atype == 1) {
/* REP=0 (success) already */
sk_write(pr->s, (char *) reply, lenof(reply));
sprintf(pr->hostname, "%d.%d.%d.%d",
(unsigned char)pr->hostname[4],
(unsigned char)pr->hostname[5],
(unsigned char)pr->hostname[6],
(unsigned char)pr->hostname[7]);
goto connect;
} else if (atype == 3) {
/* REP=0 (success) already */
sk_write(pr->s, (char *) reply, lenof(reply));
memmove(pr->hostname, pr->hostname + 5, alen-1);
pr->hostname[alen-1] = '\0';
goto connect;
} else {
/*
* Unknown address type. (FIXME: support IPv6!)
*/
reply[1] = 8; /* atype not supported */
sk_write(pr->s, (char *) reply, lenof(reply));
pfd_close(pr->s);
return 1;
}
}
}
/*
* 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(pr->s);
return 1;
}
return 1;
/*
* We come here when we're ready to make an actual
* connection.
*/
connect:
/*
* Freeze the socket until the SSH server confirms the
* connection.
*/
sk_set_frozen(pr->s, 1);
pr->c = new_sock_channel(pr->backhandle, pr->s);
if (pr->c == NULL) {
pfd_close(pr->s);
return 1;
} else {
/* asks to forward to the specified host/port for this */
ssh_send_port_open(pr->c, pr->hostname, pr->port, "forwarding");
}
pr->dynamic = 0;
/*
* If there's any data remaining in our current buffer,
* save it to be sent on pfd_confirm().
*/
if (len > 0) {
pr->buffer = snewn(len, char);
memcpy(pr->buffer, data, len);
pr->buflen = len;
}
}
if (pr->ready) {
if (sshfwd_write(pr->c, data, len) > 0) {
pr->throttled = 1;
sk_set_frozen(pr->s, 1);
}
}
return 1;
}
static void pfd_sent(Plug plug, int bufsize)
{
struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;
if (pr->c)
sshfwd_unthrottle(pr->c, bufsize);
}
/*
* Called when receiving a PORT OPEN from the server
*/
const char *pfd_newconnect(Socket *s, char *hostname, int port,
void *c, const Config *cfg, 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 PFwdPrivate *pr;
/*
* Try to find host.
*/
addr = name_lookup(hostname, port, &dummy_realhost, cfg, addressfamily);
if ((err = sk_addr_error(addr)) != NULL) {
sk_addr_free(addr);
return err;
}
/*
* Open socket.
*/
pr = snew(struct PFwdPrivate);
pr->buffer = NULL;
pr->fn = &fn_table;
pr->throttled = pr->throttle_override = 0;
pr->ready = 1;
pr->c = c;
pr->backhandle = NULL; /* we shouldn't need this */
pr->dynamic = 0;
pr->s = *s = new_connection(addr, dummy_realhost, port,
0, 1, 0, 0, (Plug) pr, cfg);
if ((err = sk_socket_error(*s)) != NULL) {
sfree(pr);
return err;
}
sk_set_private_ptr(*s, pr);
return NULL;
}
/*
called when someone connects to the local port
*/
static int pfd_accepting(Plug p, OSSocket sock)
{
static const struct plug_function_table fn_table = {
pfd_log,
pfd_closing,
pfd_receive,
pfd_sent,
NULL
};
struct PFwdPrivate *pr, *org;
Socket s;
const char *err;
org = (struct PFwdPrivate *)p;
pr = snew(struct PFwdPrivate);
pr->buffer = NULL;
pr->fn = &fn_table;
pr->c = NULL;
pr->backhandle = org->backhandle;
pr->s = s = sk_register(sock, (Plug) pr);
if ((err = sk_socket_error(s)) != NULL) {
sfree(pr);
return err != NULL;
}
sk_set_private_ptr(s, pr);
pr->throttled = pr->throttle_override = 0;
pr->ready = 0;
if (org->dynamic) {
pr->dynamic = 1;
pr->port = 0; /* "hostname" buffer is so far empty */
sk_set_frozen(s, 0); /* we want to receive SOCKS _now_! */
} else {
pr->dynamic = 0;
strcpy(pr->hostname, org->hostname);
pr->port = org->port;
pr->c = new_sock_channel(org->backhandle, s);
if (pr->c == NULL) {
sfree(pr);
return 1;
} else {
/* asks to forward to the specified host/port for this */
ssh_send_port_open(pr->c, pr->hostname, pr->port, "forwarding");
}
}
return 0;
}
/* Add a new forwarding from port -> desthost:destport
sets up a listener on the local machine on (srcaddr:)port
*/
const char *pfd_addforward(char *desthost, int destport, char *srcaddr,
int port, void *backhandle, const Config *cfg,
void **sockdata, int address_family)
{
static const struct plug_function_table fn_table = {
pfd_log,
pfd_closing,
pfd_receive, /* should not happen... */
pfd_sent, /* also should not happen */
pfd_accepting
};
const char *err;
struct PFwdPrivate *pr;
Socket s;
/*
* Open socket.
*/
pr = snew(struct PFwdPrivate);
pr->buffer = NULL;
pr->fn = &fn_table;
pr->c = NULL;
if (desthost) {
strcpy(pr->hostname, desthost);
pr->port = destport;
pr->dynamic = 0;
} else
pr->dynamic = 1;
pr->throttled = pr->throttle_override = 0;
pr->ready = 0;
pr->backhandle = backhandle;
pr->s = s = new_listener(srcaddr, port, (Plug) pr,
!cfg->lport_acceptall, cfg, address_family);
if ((err = sk_socket_error(s)) != NULL) {
sfree(pr);
return err;
}
sk_set_private_ptr(s, pr);
*sockdata = (void *)s;
return NULL;
}
void pfd_close(Socket s)
{
struct PFwdPrivate *pr;
if (!s)
return;
pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
sfree(pr->buffer);
sfree(pr);
sk_close(s);
}
/*
* Terminate a listener.
*/
void pfd_terminate(void *sv)
{
pfd_close((Socket)sv);
}
void pfd_unthrottle(Socket s)
{
struct PFwdPrivate *pr;
if (!s)
return;
pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
pr->throttled = 0;
sk_set_frozen(s, pr->throttled || pr->throttle_override);
}
void pfd_override_throttle(Socket s, int enable)
{
struct PFwdPrivate *pr;
if (!s)
return;
pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
pr->throttle_override = enable;
sk_set_frozen(s, pr->throttled || pr->throttle_override);
}
/*
* Called to send data down the raw connection.
*/
int pfd_send(Socket s, char *data, int len)
{
if (s == NULL)
return 0;
return sk_write(s, data, len);
}
void pfd_confirm(Socket s)
{
struct PFwdPrivate *pr;
if (s == NULL)
return;
pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
pr->ready = 1;
sk_set_frozen(s, 0);
sk_write(s, NULL, 0);
if (pr->buffer) {
sshfwd_write(pr->c, pr->buffer, pr->buflen);
sfree(pr->buffer);
pr->buffer = NULL;
}
}
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