/* * SSH port forwarding. */ #include #include #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 int 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); } return 1; } static int pfl_closing(Plug plug, const char *error_msg, int error_code, int calling_back) { struct PortListener *pl = (struct PortListener *) plug; pfl_terminate(pl); return 1; } static int 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 1; } 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 1; } /* * 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 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(pf); return 1; } return 1; /* * 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 1; } else { /* asks to forward to the specified host/port for this */ ssh_send_port_open(pf->c, pf->hostname, pf->port, "forwarding"); } 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); } } return 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); 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 */ ssh_send_port_open(pf->c, pf->hostname, pf->port, "forwarding"); } } 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; } }