support remote port forwarding with a zero listen port (-R0:...) to

dyamically allocate a listen port at runtime (this is actually
specified in rfc4254); bz#1003 ok markus@

9 files changed, 83 insertions, 29 deletions

diff --git a/usr.bin/ssh/canohost.c b/usr.bin/ssh/canohost.c
index 1d4696ddb24..0b37e7a5db1 100644
--- a/usr.bin/ssh/canohost.c
+++ b/usr.bin/ssh/canohost.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: canohost.c,v 1.63 2008/06/12 00:03:49 dtucker Exp $ */
+/* $OpenBSD: canohost.c,v 1.64 2009/02/12 03:00:56 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -300,7 +300,7 @@ get_remote_name_or_ip(u_int utmp_len, int use_dns)
 
 /* Returns the local/remote port for the socket. */
 
-static int
+int
 get_sock_port(int sock, int local)
 {
 	struct sockaddr_storage from;
diff --git a/usr.bin/ssh/canohost.h b/usr.bin/ssh/canohost.h
index acc77c00e34..cdd7b46826c 100644
--- a/usr.bin/ssh/canohost.h
+++ b/usr.bin/ssh/canohost.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: canohost.h,v 1.9 2006/03/25 22:22:42 djm Exp $ */
+/* $OpenBSD: canohost.h,v 1.10 2009/02/12 03:00:56 djm Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -23,3 +23,5 @@ char		*get_local_name(int);
 
 int		 get_remote_port(void);
 int		 get_local_port(void);
+int		 get_sock_port(int, int);
+
diff --git a/usr.bin/ssh/channels.c b/usr.bin/ssh/channels.c
index 1791f478c8b..b1dc7b9fde5 100644
--- a/usr.bin/ssh/channels.c
+++ b/usr.bin/ssh/channels.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: channels.c,v 1.294 2009/01/22 09:49:57 djm Exp $ */
+/* $OpenBSD: channels.c,v 1.295 2009/02/12 03:00:56 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -2438,7 +2438,8 @@ channel_set_af(int af)
 }
 
 static int
-channel_setup_fwd_listener(int type, const char *listen_addr, u_short listen_port,
+channel_setup_fwd_listener(int type, const char *listen_addr,
+    u_short listen_port, int *allocated_listen_port,
     const char *host_to_connect, u_short port_to_connect, int gateway_ports)
 {
 	Channel *c;
@@ -2446,6 +2447,7 @@ channel_setup_fwd_listener(int type, const char *listen_addr, u_short listen_por
 	struct addrinfo hints, *ai, *aitop;
 	const char *host, *addr;
 	char ntop[NI_MAXHOST], strport[NI_MAXSERV];
+	in_port_t *lport_p;
 
 	host = (type == SSH_CHANNEL_RPORT_LISTENER) ?
 	    listen_addr : host_to_connect;
@@ -2514,10 +2516,29 @@ channel_setup_fwd_listener(int type, const char *listen_addr, u_short listen_por
 		}
 		return 0;
 	}
-
+	if (allocated_listen_port != NULL)
+		*allocated_listen_port = 0;
 	for (ai = aitop; ai; ai = ai->ai_next) {
-		if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
+		switch (ai->ai_family) {
+		case AF_INET:
+			lport_p = &((struct sockaddr_in *)ai->ai_addr)->
+			    sin_port;
+			break;
+		case AF_INET6:
+			lport_p = &((struct sockaddr_in6 *)ai->ai_addr)->
+			    sin6_port;
+			break;
+		default:
 			continue;
+		}
+		/*
+		 * If allocating a port for -R forwards, then use the
+		 * same port for all address families.
+		 */
+		if (type == SSH_CHANNEL_RPORT_LISTENER && listen_port == 0 &&
+		    allocated_listen_port != NULL && *allocated_listen_port > 0)
+			*lport_p = htons(*allocated_listen_port);
+
 		if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop, sizeof(ntop),
 		    strport, sizeof(strport), NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
 			error("channel_setup_fwd_listener: getnameinfo failed");
@@ -2533,7 +2554,8 @@ channel_setup_fwd_listener(int type, const char *listen_addr, u_short listen_por
 
 		channel_set_reuseaddr(sock);
 
-		debug("Local forwarding listening on %s port %s.", ntop, strport);
+		debug("Local forwarding listening on %s port %s.",
+		    ntop, strport);
 
 		/* Bind the socket to the address. */
 		if (bind(sock, ai->ai_addr, ai->ai_addrlen) < 0) {
@@ -2548,6 +2570,19 @@ channel_setup_fwd_listener(int type, const char *listen_addr, u_short listen_por
 			close(sock);
 			continue;
 		}
+
+		/*
+		 * listen_port == 0 requests a dynamically allocated port -
+		 * record what we got.
+		 */
+		if (type == SSH_CHANNEL_RPORT_LISTENER && listen_port == 0 &&
+		    allocated_listen_port != NULL &&
+		    *allocated_listen_port == 0) {
+			*allocated_listen_port = get_sock_port(sock, 1);
+			debug("Allocated listen port %d",
+			    *allocated_listen_port);
+		}
+
 		/* Allocate a channel number for the socket. */
 		c = channel_new("port listener", type, sock, sock, -1,
 		    CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT,
@@ -2590,17 +2625,18 @@ channel_setup_local_fwd_listener(const char *listen_host, u_short listen_port,
     const char *host_to_connect, u_short port_to_connect, int gateway_ports)
 {
 	return channel_setup_fwd_listener(SSH_CHANNEL_PORT_LISTENER,
-	    listen_host, listen_port, host_to_connect, port_to_connect,
+	    listen_host, listen_port, NULL, host_to_connect, port_to_connect,
 	    gateway_ports);
 }
 
 /* protocol v2 remote port fwd, used by sshd */
 int
 channel_setup_remote_fwd_listener(const char *listen_address,
-    u_short listen_port, int gateway_ports)
+    u_short listen_port, int *allocated_listen_port, int gateway_ports)
 {
 	return channel_setup_fwd_listener(SSH_CHANNEL_RPORT_LISTENER,
-	    listen_address, listen_port, NULL, 0, gateway_ports);
+	    listen_address, listen_port, allocated_listen_port,
+	    NULL, 0, gateway_ports);
 }
 
 /*
diff --git a/usr.bin/ssh/channels.h b/usr.bin/ssh/channels.h
index 185b477b014..10b0c075a94 100644
--- a/usr.bin/ssh/channels.h
+++ b/usr.bin/ssh/channels.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: channels.h,v 1.97 2009/01/22 09:46:01 djm Exp $ */
+/* $OpenBSD: channels.h,v 1.98 2009/02/12 03:00:56 djm Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -244,7 +244,7 @@ int	 channel_request_remote_forwarding(const char *, u_short,
 int	 channel_setup_local_fwd_listener(const char *, u_short,
 	     const char *, u_short, int);
 void	 channel_request_rforward_cancel(const char *host, u_short port);
-int	 channel_setup_remote_fwd_listener(const char *, u_short, int);
+int	 channel_setup_remote_fwd_listener(const char *, u_short, int *, int);
 int	 channel_cancel_rport_listener(const char *, u_short);
 
 /* x11 forwarding */
diff --git a/usr.bin/ssh/clientloop.c b/usr.bin/ssh/clientloop.c
index eeaba5274f5..23b2dea58bb 100644
--- a/usr.bin/ssh/clientloop.c
+++ b/usr.bin/ssh/clientloop.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: clientloop.c,v 1.208 2009/01/22 10:02:34 djm Exp $ */
+/* $OpenBSD: clientloop.c,v 1.209 2009/02/12 03:00:56 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -840,7 +840,7 @@ process_cmdline(void)
 		}
 		channel_request_rforward_cancel(cancel_host, cancel_port);
 	} else {
-		if (!parse_forward(&fwd, s, dynamic ? 1 : 0)) {
+		if (!parse_forward(&fwd, s, dynamic, remote)) {
 			logit("Bad forwarding specification.");
 			goto out;
 		}
diff --git a/usr.bin/ssh/readconf.c b/usr.bin/ssh/readconf.c
index 963709e729f..9aee3ecc6c8 100644
--- a/usr.bin/ssh/readconf.c
+++ b/usr.bin/ssh/readconf.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: readconf.c,v 1.175 2009/01/22 10:02:34 djm Exp $ */
+/* $OpenBSD: readconf.c,v 1.176 2009/02/12 03:00:56 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -730,7 +730,8 @@ parse_int:
 		}
 
 		if (parse_forward(&fwd, fwdarg,
-		    opcode == oDynamicForward ? 1 : 0) == 0)
+		    opcode == oDynamicForward ? 1 : 0,
+		    opcode == oRemoteForward ? 1 : 0) == 0)
 			fatal("%.200s line %d: Bad forwarding specification.",
 			    filename, linenum);
 
@@ -1215,7 +1216,7 @@ fill_default_options(Options * options)
  * returns number of arguments parsed or zero on error
  */
 int
-parse_forward(Forward *fwd, const char *fwdspec, int dynamicfwd)
+parse_forward(Forward *fwd, const char *fwdspec, int dynamicfwd, int remotefwd)
 {
 	int i;
 	char *p, *cp, *fwdarg[4];
@@ -1278,12 +1279,16 @@ parse_forward(Forward *fwd, const char *fwdspec, int dynamicfwd)
 			goto fail_free;
 	}
 
-	if (fwd->listen_port <= 0)
+	if (fwd->listen_port < 0 || (!remotefwd && fwd->listen_port == 0))
 		goto fail_free;
 
 	if (fwd->connect_host != NULL &&
 	    strlen(fwd->connect_host) >= NI_MAXHOST)
 		goto fail_free;
+	if (fwd->listen_host != NULL &&
+	    strlen(fwd->listen_host) >= NI_MAXHOST)
+		goto fail_free;
+
 
 	return (i);
 
diff --git a/usr.bin/ssh/readconf.h b/usr.bin/ssh/readconf.h
index d94d65890d2..8fb3a852816 100644
--- a/usr.bin/ssh/readconf.h
+++ b/usr.bin/ssh/readconf.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: readconf.h,v 1.77 2009/01/22 10:02:34 djm Exp $ */
+/* $OpenBSD: readconf.h,v 1.78 2009/02/12 03:00:56 djm Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -134,7 +134,7 @@ typedef struct {
 void     initialize_options(Options *);
 void     fill_default_options(Options *);
 int	 read_config_file(const char *, const char *, Options *, int);
-int	 parse_forward(Forward *, const char *, int);
+int	 parse_forward(Forward *, const char *, int, int);
 
 int
 process_config_line(Options *, const char *, char *, const char *, int, int *);
diff --git a/usr.bin/ssh/serverloop.c b/usr.bin/ssh/serverloop.c
index 86ee4ae31d4..999e5be8a49 100644
--- a/usr.bin/ssh/serverloop.c
+++ b/usr.bin/ssh/serverloop.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: serverloop.c,v 1.155 2009/01/22 10:02:34 djm Exp $ */
+/* $OpenBSD: serverloop.c,v 1.156 2009/02/12 03:00:56 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1058,7 +1058,7 @@ server_input_global_request(int type, u_int32_t seq, void *ctxt)
 {
 	char *rtype;
 	int want_reply;
-	int success = 0;
+	int success = 0, allocated_listen_port = 0;
 
 	rtype = packet_get_string(NULL);
 	want_reply = packet_get_char();
@@ -1081,13 +1081,15 @@ server_input_global_request(int type, u_int32_t seq, void *ctxt)
 		/* check permissions */
 		if (!options.allow_tcp_forwarding ||
 		    no_port_forwarding_flag ||
-		    (listen_port < IPPORT_RESERVED && pw->pw_uid != 0)) {
+		    (listen_port != 0 && listen_port < IPPORT_RESERVED &&
+		    pw->pw_uid != 0)) {
 			success = 0;
 			packet_send_debug("Server has disabled port forwarding.");
 		} else {
 			/* Start listening on the port */
 			success = channel_setup_remote_fwd_listener(
-			    listen_address, listen_port, options.gateway_ports);
+			    listen_address, listen_port,
+			    &allocated_listen_port, options.gateway_ports);
 		}
 		xfree(listen_address);
 	} else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
@@ -1109,6 +1111,8 @@ server_input_global_request(int type, u_int32_t seq, void *ctxt)
 	if (want_reply) {
 		packet_start(success ?
 		    SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
+		if (success && allocated_listen_port > 0)
+			packet_put_int(allocated_listen_port);
 		packet_send();
 		packet_write_wait();
 	}
diff --git a/usr.bin/ssh/ssh.c b/usr.bin/ssh/ssh.c
index 912ff5e54dd..49cdfed145a 100644
--- a/usr.bin/ssh/ssh.c
+++ b/usr.bin/ssh/ssh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.c,v 1.323 2009/01/22 10:02:34 djm Exp $ */
+/* $OpenBSD: ssh.c,v 1.324 2009/02/12 03:00:56 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -440,7 +440,7 @@ main(int ac, char **av)
 			break;
 
 		case 'L':
-			if (parse_forward(&fwd, optarg, 0))
+			if (parse_forward(&fwd, optarg, 0, 0))
 				add_local_forward(&options, &fwd);
 			else {
 				fprintf(stderr,
@@ -451,7 +451,7 @@ main(int ac, char **av)
 			break;
 
 		case 'R':
-			if (parse_forward(&fwd, optarg, 0)) {
+			if (parse_forward(&fwd, optarg, 0, 1)) {
 				add_remote_forward(&options, &fwd);
 			} else {
 				fprintf(stderr,
@@ -462,7 +462,7 @@ main(int ac, char **av)
 			break;
 
 		case 'D':
-			if (parse_forward(&fwd, optarg, 1)) {
+			if (parse_forward(&fwd, optarg, 1, 0)) {
 				add_local_forward(&options, &fwd);
 			} else {
 				fprintf(stderr,
@@ -818,9 +818,16 @@ ssh_confirm_remote_forward(int type, u_int32_t seq, void *ctxt)
 {
 	Forward *rfwd = (Forward *)ctxt;
 
+	/* XXX verbose() on failure? */
 	debug("remote forward %s for: listen %d, connect %s:%d",
 	    type == SSH2_MSG_REQUEST_SUCCESS ? "success" : "failure",
 	    rfwd->listen_port, rfwd->connect_host, rfwd->connect_port);
+	if (type == SSH2_MSG_REQUEST_SUCCESS && rfwd->listen_port == 0) {
+		logit("Allocated port %u for remote forward to %s:%d",
+			packet_get_int(),
+			rfwd->connect_host, rfwd->connect_port);
+	}
+	
 	if (type == SSH2_MSG_REQUEST_FAILURE) {
 		if (options.exit_on_forward_failure)
 			fatal("Error: remote port forwarding failed for "