- djm@cvs.openbsd.org 2011/04/17 22:42:42

[PROTOCOL.mux clientloop.c clientloop.h mux.c ssh.1 ssh.c]
     allow graceful shutdown of multiplexing: request that a mux server
     removes its listener socket and refuse future multiplexing requests;
     ok markus@

ChangeLog

@@ -55,6 +55,11 @@
    - djm@cvs.openbsd.org 2011/04/13 04:09:37
      [ssh-keygen.1]
      mention valid -b sizes for ECDSA keys; bz#1862
+   - djm@cvs.openbsd.org 2011/04/17 22:42:42
+     [PROTOCOL.mux clientloop.c clientloop.h mux.c ssh.1 ssh.c]
+     allow graceful shutdown of multiplexing: request that a mux server
+     removes its listener socket and refuse future multiplexing requests;
+     ok markus@
 
 20110221
  - (dtucker) [contrib/cygwin/ssh-host-config] From Corinna: revamp of the

PROTOCOL.mux

@@ -149,10 +149,21 @@ The client then sends its standard input and output file descriptors
 
 The contents of "reserved" are currently ignored.
 
-A server may reply with a MUX_S_SESSION_OPEED, a MUX_S_PERMISSION_DENIED
+A server may reply with a MUX_S_SESSION_OPENED, a MUX_S_PERMISSION_DENIED
 or a MUX_S_FAILURE.
 
-8. Status messages
+8. Requesting shutdown of mux listener
+
+A client may request the master to stop accepting new multiplexing requests
+and remove its listener socket.
+
+	uint32	MUX_C_STOP_LISTENING
+	uint32	request id
+
+A server may reply with a MUX_S_OK, a MUX_S_PERMISSION_DENIED or a
+MUX_S_FAILURE.
+
+9. Status messages
 
 The MUX_S_OK message is empty:
 
@@ -178,6 +189,7 @@ The MUX_S_PERMISSION_DENIED and MUX_S_FAILURE include a reason:
 #define MUX_C_OPEN_FWD		0x10000006
 #define MUX_C_CLOSE_FWD		0x10000007
 #define MUX_C_NEW_STDIO_FWD	0x10000008
+#define MUX_C_STOP_LISTENING	0x10000009
 #define MUX_S_OK		0x80000001
 #define MUX_S_PERMISSION_DENIED	0x80000002
 #define MUX_S_FAILURE		0x80000003
@@ -192,7 +204,6 @@ The MUX_S_PERMISSION_DENIED and MUX_S_FAILURE include a reason:
 
 XXX TODO
 XXX extended status (e.g. report open channels / forwards)
-XXX graceful close (delete listening socket, but keep existing sessions active)
 XXX lock (maybe)
 XXX watch in/out traffic (pre/post crypto)
 XXX inject packet (what about replies)
@@ -200,4 +211,4 @@ XXX server->client error/warning notifications
 XXX port0 rfwd (need custom response message)
 XXX send signals via mux
 
-$OpenBSD: PROTOCOL.mux,v 1.4 2011/01/31 21:42:15 djm Exp $
+$OpenBSD: PROTOCOL.mux,v 1.5 2011/04/17 22:42:41 djm Exp $

clientloop.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: clientloop.c,v 1.231 2011/01/16 12:05:59 djm Exp $ */
+/* $OpenBSD: clientloop.c,v 1.232 2011/04/17 22:42:41 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -265,10 +265,10 @@ static void
 set_control_persist_exit_time(void)
 {
 	if (muxserver_sock == -1 || !options.control_persist
-	    || options.control_persist_timeout == 0)
+	    || options.control_persist_timeout == 0) {
 		/* not using a ControlPersist timeout */
 		control_persist_exit_time = 0;
-	else if (channel_still_open()) {
+	} else if (channel_still_open()) {
 		/* some client connections are still open */
 		if (control_persist_exit_time > 0)
 			debug2("%s: cancel scheduled exit", __func__);
@@ -1419,14 +1419,17 @@ client_loop(int have_pty, int escape_char_arg, int ssh2_chan_id)
 
 	if (compat20) {
 		session_ident = ssh2_chan_id;
-		if (escape_char_arg != SSH_ESCAPECHAR_NONE)
+		if (session_ident != -1) {
-			channel_register_filter(session_ident,
+			if (escape_char_arg != SSH_ESCAPECHAR_NONE) {
-			    client_simple_escape_filter, NULL,
+				channel_register_filter(session_ident,
-			    client_filter_cleanup,
+				    client_simple_escape_filter, NULL,
-			    client_new_escape_filter_ctx(escape_char_arg));
+				    client_filter_cleanup,
-		if (session_ident != -1)
+				    client_new_escape_filter_ctx(
+				    escape_char_arg));
+			}
 			channel_register_cleanup(session_ident,
 			    client_channel_closed, 0);
+		}
 	} else {
 		/* Check if we should immediately send eof on stdin. */
 		client_check_initial_eof_on_stdin();
@@ -2122,6 +2125,19 @@ client_init_dispatch(void)
 		client_init_dispatch_15();
 }
 
+void
+client_stop_mux(void)
+{
+	if (options.control_path != NULL && muxserver_sock != -1)
+		unlink(options.control_path);
+	/*
+	 * If we are in persist mode, signal that we should close when all
+	 * active channels are closed.
+	 */
+	if (options.control_persist)
+		session_closed = 1;
+}
+
 /* client specific fatal cleanup */
 void
 cleanup_exit(int i)

clientloop.h

@@ -1,4 +1,4 @@
-/* $OpenBSD: clientloop.h,v 1.25 2010/06/25 23:15:36 djm Exp $ */
+/* $OpenBSD: clientloop.h,v 1.26 2011/04/17 22:42:41 djm Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -45,6 +45,7 @@ void	 client_global_request_reply_fwd(int, u_int32_t, void *);
 void	 client_session2_setup(int, int, int, const char *, struct termios *,
 	    int, Buffer *, char **);
 int	 client_request_tun_fwd(int, int, int);
+void	 client_stop_mux(void);
 
 /* Escape filter for protocol 2 sessions */
 void	*client_new_escape_filter_ctx(int);
@@ -64,6 +65,7 @@ void	 client_register_global_confirm(global_confirm_cb *, void *);
 #define SSHMUX_COMMAND_TERMINATE	3	/* Ask master to exit */
 #define SSHMUX_COMMAND_STDIO_FWD	4	/* Open stdio fwd (ssh -W) */
 #define SSHMUX_COMMAND_FORWARD		5	/* Forward only, no command */
+#define SSHMUX_COMMAND_STOP		6	/* Disable mux but not conn */
 
 void	muxserver_listen(void);
 void	muxclient(const char *);

mux.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: mux.c,v 1.24 2011/01/13 21:54:53 djm Exp $ */
+/* $OpenBSD: mux.c,v 1.25 2011/04/17 22:42:41 djm Exp $ */
 /*
  * Copyright (c) 2002-2008 Damien Miller <djm@openbsd.org>
  *
@@ -146,6 +146,7 @@ struct mux_master_state {
 #define MUX_C_OPEN_FWD		0x10000006
 #define MUX_C_CLOSE_FWD		0x10000007
 #define MUX_C_NEW_STDIO_FWD	0x10000008
+#define MUX_C_STOP_LISTENING	0x10000009
 #define MUX_S_OK		0x80000001
 #define MUX_S_PERMISSION_DENIED	0x80000002
 #define MUX_S_FAILURE		0x80000003
@@ -168,6 +169,7 @@ static int process_mux_terminate(u_int, Channel *, Buffer *, Buffer *);
 static int process_mux_open_fwd(u_int, Channel *, Buffer *, Buffer *);
 static int process_mux_close_fwd(u_int, Channel *, Buffer *, Buffer *);
 static int process_mux_stdio_fwd(u_int, Channel *, Buffer *, Buffer *);
+static int process_mux_stop_listening(u_int, Channel *, Buffer *, Buffer *);
 
 static const struct {
 	u_int type;
@@ -180,6 +182,7 @@ static const struct {
 	{ MUX_C_OPEN_FWD, process_mux_open_fwd },
 	{ MUX_C_CLOSE_FWD, process_mux_close_fwd },
 	{ MUX_C_NEW_STDIO_FWD, process_mux_stdio_fwd },
+	{ MUX_C_STOP_LISTENING, process_mux_stop_listening },
 	{ 0, NULL }
 };
 
@@ -915,6 +918,39 @@ process_mux_stdio_fwd(u_int rid, Channel *c, Buffer *m, Buffer *r)
 	return 0;
 }
 
+static int
+process_mux_stop_listening(u_int rid, Channel *c, Buffer *m, Buffer *r)
+{
+	debug("%s: channel %d: stop listening", __func__, c->self);
+
+	if (options.control_master == SSHCTL_MASTER_ASK ||
+	    options.control_master == SSHCTL_MASTER_AUTO_ASK) {
+		if (!ask_permission("Disable further multiplexing on shared "
+		    "connection to %s? ", host)) {
+			debug2("%s: stop listen refused by user", __func__);
+			buffer_put_int(r, MUX_S_PERMISSION_DENIED);
+			buffer_put_int(r, rid);
+			buffer_put_cstring(r, "Permission denied");
+			return 0;
+		}
+	}
+
+	if (mux_listener_channel != NULL) {
+		channel_free(mux_listener_channel);
+		client_stop_mux();
+		xfree(options.control_path);
+		options.control_path = NULL;
+		mux_listener_channel = NULL;
+		muxserver_sock = -1;
+	}
+
+	/* prepare reply */
+	buffer_put_int(r, MUX_S_OK);
+	buffer_put_int(r, rid);
+
+	return 0;
+}
+
 /* Channel callbacks fired on read/write from mux slave fd */
 static int
 mux_master_read_cb(Channel *c)
@@ -1813,6 +1849,50 @@ mux_client_request_stdio_fwd(int fd)
 	fatal("%s: master returned unexpected message %u", __func__, type);
 }
 
+static void
+mux_client_request_stop_listening(int fd)
+{
+	Buffer m;
+	char *e;
+	u_int type, rid;
+
+	debug3("%s: entering", __func__);
+
+	buffer_init(&m);
+	buffer_put_int(&m, MUX_C_STOP_LISTENING);
+	buffer_put_int(&m, muxclient_request_id);
+
+	if (mux_client_write_packet(fd, &m) != 0)
+		fatal("%s: write packet: %s", __func__, strerror(errno));
+
+	buffer_clear(&m);
+
+	/* Read their reply */
+	if (mux_client_read_packet(fd, &m) != 0)
+		fatal("%s: read from master failed: %s",
+		    __func__, strerror(errno));
+
+	type = buffer_get_int(&m);
+	if ((rid = buffer_get_int(&m)) != muxclient_request_id)
+		fatal("%s: out of sequence reply: my id %u theirs %u",
+		    __func__, muxclient_request_id, rid);
+	switch (type) {
+	case MUX_S_OK:
+		break;
+	case MUX_S_PERMISSION_DENIED:
+		e = buffer_get_string(&m, NULL);
+		fatal("Master refused stop listening request: %s", e);
+	case MUX_S_FAILURE:
+		e = buffer_get_string(&m, NULL);
+		fatal("%s: stop listening request failed: %s", __func__, e);
+	default:
+		fatal("%s: unexpected response from master 0x%08x",
+		    __func__, type);
+	}
+	buffer_free(&m);
+	muxclient_request_id++;
+}
+
 /* Multiplex client main loop. */
 void
 muxclient(const char *path)
@@ -1906,6 +1986,10 @@ muxclient(const char *path)
 	case SSHMUX_COMMAND_STDIO_FWD:
 		mux_client_request_stdio_fwd(sock);
 		exit(0);
+	case SSHMUX_COMMAND_STOP:
+		mux_client_request_stop_listening(sock);
+		fprintf(stderr, "Stop listening request sent.\r\n");
+		exit(0);
 	default:
 		fatal("unrecognised muxclient_command %d", muxclient_command);
 	}

ssh.1

@@ -33,8 +33,8 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.\" $OpenBSD: ssh.1,v 1.316 2010/11/18 15:01:00 jmc Exp $
+.\" $OpenBSD: ssh.1,v 1.317 2011/04/17 22:42:41 djm Exp $
-.Dd $Mdocdate: November 18 2010 $
+.Dd $Mdocdate: April 17 2011 $
 .Dt SSH 1
 .Os
 .Sh NAME
@@ -395,6 +395,8 @@ Valid commands are:
 (request forwardings without command execution) and
 .Dq exit
 (request the master to exit).
+.Dq stop
+(request the master to stop accepting further multiplexing requests).
 .It Fl o Ar option
 Can be used to give options in the format used in the configuration file.
 This is useful for specifying options for which there is no separate

ssh.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.c,v 1.356 2011/01/06 22:23:53 djm Exp $ */
+/* $OpenBSD: ssh.c,v 1.357 2011/04/17 22:42:42 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -345,6 +345,8 @@ main(int ac, char **av)
 				muxclient_command = SSHMUX_COMMAND_FORWARD;
 			else if (strcmp(optarg, "exit") == 0)
 				muxclient_command = SSHMUX_COMMAND_TERMINATE;
+			else if (strcmp(optarg, "stop") == 0)
+				muxclient_command = SSHMUX_COMMAND_STOP;
 			else
 				fatal("Invalid multiplex command.");
 			break;