Merge upstream-master into master

Commit ecb2c02d994b3e21994f31a70ff911667c262f1f upstream

This nearly (but not quite) corresponds to V_8_3_P1; subsequent
cherry-picks will correct this.

Bug: 162492243
Change-Id: I3c079d86435b7c25aefff4538dc89a3002b1e25b

1 files changed, 761 insertions, 546 deletions

diff --git a/mux.c b/mux.c
index f3faaeec..fb31ad44 100644
--- a/mux.c
+++ b/mux.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: mux.c,v 1.50 2015/01/20 23:14:00 deraadt Exp $ */
+/* $OpenBSD: mux.c,v 1.82 2020/04/30 17:12:20 markus Exp $ */
 /*
  * Copyright (c) 2002-2008 Damien Miller <djm@openbsd.org>
  *
@@ -17,19 +17,6 @@
 
 /* ssh session multiplexing support */
 
-/*
- * TODO:
- *   - Better signalling from master to slave, especially passing of
- *      error messages
- *   - Better fall-back from mux slave error to new connection.
- *   - ExitOnForwardingFailure
- *   - Maybe extension mechanisms for multi-X11/multi-agent forwarding
- *   - Support ~^Z in mux slaves.
- *   - Inspect or control sessions in master.
- *   - If we ever support the "signal" channel request, send signals on
- *     sessions in master.
- */
-
 #include "includes.h"
 
 #include <sys/types.h>
@@ -70,15 +57,16 @@
 #include "pathnames.h"
 #include "misc.h"
 #include "match.h"
-#include "buffer.h"
+#include "sshbuf.h"
 #include "channels.h"
 #include "msg.h"
 #include "packet.h"
 #include "monitor_fdpass.h"
 #include "sshpty.h"
-#include "key.h"
+#include "sshkey.h"
 #include "readconf.h"
 #include "clientloop.h"
+#include "ssherr.h"
 
 /* from ssh.c */
 extern int tty_flag;
@@ -86,10 +74,8 @@ extern Options options;
 extern int stdin_null_flag;
 extern char *host;
 extern int subsystem_flag;
-extern Buffer command;
+extern struct sshbuf *command;
 extern volatile sig_atomic_t quit_pending;
-extern char *stdio_forward_host;
-extern int stdio_forward_port;
 
 /* Context for session open confirmation callback */
 struct mux_session_confirm_ctx {
@@ -97,7 +83,7 @@ struct mux_session_confirm_ctx {
 	u_int want_subsys;
 	u_int want_x_fwd;
 	u_int want_agent_fwd;
-	Buffer cmd;
+	struct sshbuf *cmd;
 	char *term;
 	struct termios tio;
 	char **env;
@@ -146,6 +132,7 @@ struct mux_master_state {
 #define MUX_C_CLOSE_FWD		0x10000007
 #define MUX_C_NEW_STDIO_FWD	0x10000008
 #define MUX_C_STOP_LISTENING	0x10000009
+#define MUX_C_PROXY		0x1000000f
 #define MUX_S_OK		0x80000001
 #define MUX_S_PERMISSION_DENIED	0x80000002
 #define MUX_S_FAILURE		0x80000003
@@ -154,88 +141,103 @@ struct mux_master_state {
 #define MUX_S_SESSION_OPENED	0x80000006
 #define MUX_S_REMOTE_PORT	0x80000007
 #define MUX_S_TTY_ALLOC_FAIL	0x80000008
+#define MUX_S_PROXY		0x8000000f
 
 /* type codes for MUX_C_OPEN_FWD and MUX_C_CLOSE_FWD */
 #define MUX_FWD_LOCAL   1
 #define MUX_FWD_REMOTE  2
 #define MUX_FWD_DYNAMIC 3
 
-static void mux_session_confirm(int, int, void *);
-static void mux_stdio_confirm(int, int, void *);
-
-static int process_mux_master_hello(u_int, Channel *, Buffer *, Buffer *);
-static int process_mux_new_session(u_int, Channel *, Buffer *, Buffer *);
-static int process_mux_alive_check(u_int, Channel *, Buffer *, Buffer *);
-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 void mux_session_confirm(struct ssh *, int, int, void *);
+static void mux_stdio_confirm(struct ssh *, int, int, void *);
+
+static int mux_master_process_hello(struct ssh *, u_int,
+	    Channel *, struct sshbuf *, struct sshbuf *);
+static int mux_master_process_new_session(struct ssh *, u_int,
+	    Channel *, struct sshbuf *, struct sshbuf *);
+static int mux_master_process_alive_check(struct ssh *, u_int,
+	    Channel *, struct sshbuf *, struct sshbuf *);
+static int mux_master_process_terminate(struct ssh *, u_int,
+	    Channel *, struct sshbuf *, struct sshbuf *);
+static int mux_master_process_open_fwd(struct ssh *, u_int,
+	    Channel *, struct sshbuf *, struct sshbuf *);
+static int mux_master_process_close_fwd(struct ssh *, u_int,
+	    Channel *, struct sshbuf *, struct sshbuf *);
+static int mux_master_process_stdio_fwd(struct ssh *, u_int,
+	    Channel *, struct sshbuf *, struct sshbuf *);
+static int mux_master_process_stop_listening(struct ssh *, u_int,
+	    Channel *, struct sshbuf *, struct sshbuf *);
+static int mux_master_process_proxy(struct ssh *, u_int,
+	    Channel *, struct sshbuf *, struct sshbuf *);
 
 static const struct {
 	u_int type;
-	int (*handler)(u_int, Channel *, Buffer *, Buffer *);
+	int (*handler)(struct ssh *, u_int, Channel *,
+	    struct sshbuf *, struct sshbuf *);
 } mux_master_handlers[] = {
-	{ MUX_MSG_HELLO, process_mux_master_hello },
-	{ MUX_C_NEW_SESSION, process_mux_new_session },
-	{ MUX_C_ALIVE_CHECK, process_mux_alive_check },
-	{ MUX_C_TERMINATE, process_mux_terminate },
-	{ 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 },
+	{ MUX_MSG_HELLO, mux_master_process_hello },
+	{ MUX_C_NEW_SESSION, mux_master_process_new_session },
+	{ MUX_C_ALIVE_CHECK, mux_master_process_alive_check },
+	{ MUX_C_TERMINATE, mux_master_process_terminate },
+	{ MUX_C_OPEN_FWD, mux_master_process_open_fwd },
+	{ MUX_C_CLOSE_FWD, mux_master_process_close_fwd },
+	{ MUX_C_NEW_STDIO_FWD, mux_master_process_stdio_fwd },
+	{ MUX_C_STOP_LISTENING, mux_master_process_stop_listening },
+	{ MUX_C_PROXY, mux_master_process_proxy },
 	{ 0, NULL }
 };
 
 /* Cleanup callback fired on closure of mux slave _session_ channel */
 /* ARGSUSED */
 static void
-mux_master_session_cleanup_cb(int cid, void *unused)
+mux_master_session_cleanup_cb(struct ssh *ssh, int cid, void *unused)
 {
-	Channel *cc, *c = channel_by_id(cid);
+	Channel *cc, *c = channel_by_id(ssh, cid);
 
 	debug3("%s: entering for channel %d", __func__, cid);
 	if (c == NULL)
 		fatal("%s: channel_by_id(%i) == NULL", __func__, cid);
 	if (c->ctl_chan != -1) {
-		if ((cc = channel_by_id(c->ctl_chan)) == NULL)
+		if ((cc = channel_by_id(ssh, c->ctl_chan)) == NULL)
 			fatal("%s: channel %d missing control channel %d",
 			    __func__, c->self, c->ctl_chan);
 		c->ctl_chan = -1;
-		cc->remote_id = -1;
-		chan_rcvd_oclose(cc);
+		cc->remote_id = 0;
+		cc->have_remote_id = 0;
+		chan_rcvd_oclose(ssh, cc);
 	}
-	channel_cancel_cleanup(c->self);
+	channel_cancel_cleanup(ssh, c->self);
 }
 
 /* Cleanup callback fired on closure of mux slave _control_ channel */
 /* ARGSUSED */
 static void
-mux_master_control_cleanup_cb(int cid, void *unused)
+mux_master_control_cleanup_cb(struct ssh *ssh, int cid, void *unused)
 {
-	Channel *sc, *c = channel_by_id(cid);
+	Channel *sc, *c = channel_by_id(ssh, cid);
 
 	debug3("%s: entering for channel %d", __func__, cid);
 	if (c == NULL)
 		fatal("%s: channel_by_id(%i) == NULL", __func__, cid);
-	if (c->remote_id != -1) {
-		if ((sc = channel_by_id(c->remote_id)) == NULL)
-			fatal("%s: channel %d missing session channel %d",
+	if (c->have_remote_id) {
+		if ((sc = channel_by_id(ssh, c->remote_id)) == NULL)
+			fatal("%s: channel %d missing session channel %u",
 			    __func__, c->self, c->remote_id);
-		c->remote_id = -1;
+		c->remote_id = 0;
+		c->have_remote_id = 0;
 		sc->ctl_chan = -1;
 		if (sc->type != SSH_CHANNEL_OPEN &&
 		    sc->type != SSH_CHANNEL_OPENING) {
 			debug2("%s: channel %d: not open", __func__, sc->self);
-			chan_mark_dead(sc);
+			chan_mark_dead(ssh, sc);
 		} else {
 			if (sc->istate == CHAN_INPUT_OPEN)
-				chan_read_failed(sc);
+				chan_read_failed(ssh, sc);
 			if (sc->ostate == CHAN_OUTPUT_OPEN)
-				chan_write_failed(sc);
+				chan_write_failed(ssh, sc);
 		}
 	}
-	channel_cancel_cleanup(c->self);
+	channel_cancel_cleanup(ssh, c->self);
 }
 
 /* Check mux client environment variables before passing them to mux master. */
@@ -249,7 +251,7 @@ env_permitted(char *env)
 		return 0;
 	ret = snprintf(name, sizeof(name), "%.*s", (int)(cp - env), env);
 	if (ret <= 0 || (size_t)ret >= sizeof(name)) {
-		error("env_permitted: name '%.100s...' too long", env);
+		error("%s: name '%.100s...' too long", __func__, env);
 		return 0;
 	}
 
@@ -263,10 +265,12 @@ env_permitted(char *env)
 /* Mux master protocol message handlers */
 
 static int
-process_mux_master_hello(u_int rid, Channel *c, Buffer *m, Buffer *r)
+mux_master_process_hello(struct ssh *ssh, u_int rid,
+    Channel *c, struct sshbuf *m, struct sshbuf *reply)
 {
 	u_int ver;
 	struct mux_master_state *state = (struct mux_master_state *)c->mux_ctx;
+	int r;
 
 	if (state == NULL)
 		fatal("%s: channel %d: c->mux_ctx == NULL", __func__, c->self);
@@ -274,63 +278,86 @@ process_mux_master_hello(u_int rid, Channel *c, Buffer *m, Buffer *r)
 		error("%s: HELLO received twice", __func__);
 		return -1;
 	}
-	if (buffer_get_int_ret(&ver, m) != 0) {
- malf:
-		error("%s: malformed message", __func__);
+	if ((r = sshbuf_get_u32(m, &ver)) != 0) {
+		error("%s: malformed message: %s", __func__, ssh_err(r));
 		return -1;
 	}
 	if (ver != SSHMUX_VER) {
-		error("Unsupported multiplexing protocol version %d "
-		    "(expected %d)", ver, SSHMUX_VER);
+		error("%s: unsupported multiplexing protocol version %u "
+		    "(expected %u)", __func__, ver, SSHMUX_VER);
 		return -1;
 	}
 	debug2("%s: channel %d slave version %u", __func__, c->self, ver);
 
 	/* No extensions are presently defined */
-	while (buffer_len(m) > 0) {
-		char *name = buffer_get_string_ret(m, NULL);
-		char *value = buffer_get_string_ret(m, NULL);
-
-		if (name == NULL || value == NULL) {
-			free(name);
-			free(value);
-			goto malf;
+	while (sshbuf_len(m) > 0) {
+		char *name = NULL;
+		size_t value_len = 0;
+
+		if ((r = sshbuf_get_cstring(m, &name, NULL)) != 0 ||
+		    (r = sshbuf_get_string_direct(m, NULL, &value_len)) != 0) {
+			error("%s: malformed extension: %s",
+			    __func__, ssh_err(r));
+			return -1;
 		}
-		debug2("Unrecognised slave extension \"%s\"", name);
+		debug2("%s: Unrecognised extension \"%s\" length %zu",
+		    __func__, name, value_len);
 		free(name);
-		free(value);
 	}
 	state->hello_rcvd = 1;
 	return 0;
 }
 
+/* Enqueue a "ok" response to the reply buffer */
+static void
+reply_ok(struct sshbuf *reply, u_int rid)
+{
+	int r;
+
+	if ((r = sshbuf_put_u32(reply, MUX_S_OK)) != 0 ||
+	    (r = sshbuf_put_u32(reply, rid)) != 0)
+		fatal("%s: reply: %s", __func__, ssh_err(r));
+}
+
+/* Enqueue an error response to the reply buffer */
+static void
+reply_error(struct sshbuf *reply, u_int type, u_int rid, const char *msg)
+{
+	int r;
+
+	if ((r = sshbuf_put_u32(reply, type)) != 0 ||
+	    (r = sshbuf_put_u32(reply, rid)) != 0 ||
+	    (r = sshbuf_put_cstring(reply, msg)) != 0)
+		fatal("%s: reply: %s", __func__, ssh_err(r));
+}
+
 static int
-process_mux_new_session(u_int rid, Channel *c, Buffer *m, Buffer *r)
+mux_master_process_new_session(struct ssh *ssh, u_int rid,
+    Channel *c, struct sshbuf *m, struct sshbuf *reply)
 {
 	Channel *nc;
 	struct mux_session_confirm_ctx *cctx;
-	char *reserved, *cmd, *cp;
-	u_int i, j, len, env_len, escape_char, window, packetmax;
-	int new_fd[3];
+	char *cmd, *cp;
+	u_int i, j, env_len, escape_char, window, packetmax;
+	int r, new_fd[3];
 
 	/* Reply for SSHMUX_COMMAND_OPEN */
 	cctx = xcalloc(1, sizeof(*cctx));
 	cctx->term = NULL;
 	cctx->rid = rid;
-	cmd = reserved = NULL;
+	cmd = NULL;
 	cctx->env = NULL;
 	env_len = 0;
-	if ((reserved = buffer_get_string_ret(m, NULL)) == NULL ||
-	    buffer_get_int_ret(&cctx->want_tty, m) != 0 ||
-	    buffer_get_int_ret(&cctx->want_x_fwd, m) != 0 ||
-	    buffer_get_int_ret(&cctx->want_agent_fwd, m) != 0 ||
-	    buffer_get_int_ret(&cctx->want_subsys, m) != 0 ||
-	    buffer_get_int_ret(&escape_char, m) != 0 ||
-	    (cctx->term = buffer_get_string_ret(m, &len)) == NULL ||
-	    (cmd = buffer_get_string_ret(m, &len)) == NULL) {
+	if ((r = sshbuf_skip_string(m)) != 0 || /* reserved */
+	    (r = sshbuf_get_u32(m, &cctx->want_tty)) != 0 ||
+	    (r = sshbuf_get_u32(m, &cctx->want_x_fwd)) != 0 ||
+	    (r = sshbuf_get_u32(m, &cctx->want_agent_fwd)) != 0 ||
+	    (r = sshbuf_get_u32(m, &cctx->want_subsys)) != 0 ||
+	    (r = sshbuf_get_u32(m, &escape_char)) != 0 ||
+	    (r = sshbuf_get_cstring(m, &cctx->term, NULL)) != 0 ||
+	    (r = sshbuf_get_cstring(m, &cmd, NULL)) != 0) {
  malf:
 		free(cmd);
-		free(reserved);
 		for (j = 0; j < env_len; j++)
 			free(cctx->env[j]);
 		free(cctx->env);
@@ -339,24 +366,22 @@ process_mux_new_session(u_int rid, Channel *c, Buffer *m, Buffer *r)
 		error("%s: malformed message", __func__);
 		return -1;
 	}
-	free(reserved);
-	reserved = NULL;
 
-	while (buffer_len(m) > 0) {
 #define MUX_MAX_ENV_VARS	4096
-		if ((cp = buffer_get_string_ret(m, &len)) == NULL)
+	while (sshbuf_len(m) > 0) {
+		if ((r = sshbuf_get_cstring(m, &cp, NULL)) != 0)
 			goto malf;
 		if (!env_permitted(cp)) {
 			free(cp);
 			continue;
 		}
-		cctx->env = xrealloc(cctx->env, env_len + 2,
+		cctx->env = xreallocarray(cctx->env, env_len + 2,
 		    sizeof(*cctx->env));
 		cctx->env[env_len++] = cp;
 		cctx->env[env_len] = NULL;
 		if (env_len > MUX_MAX_ENV_VARS) {
-			error(">%d environment variables received, ignoring "
-			    "additional", MUX_MAX_ENV_VARS);
+			error("%s: >%d environment variables received, "
+			    "ignoring additional", __func__, MUX_MAX_ENV_VARS);
 			break;
 		}
 	}
@@ -366,8 +391,10 @@ process_mux_new_session(u_int rid, Channel *c, Buffer *m, Buffer *r)
 	    cctx->want_tty, cctx->want_x_fwd, cctx->want_agent_fwd,
 	    cctx->want_subsys, cctx->term, cmd, env_len);
 
-	buffer_init(&cctx->cmd);
-	buffer_append(&cctx->cmd, cmd, strlen(cmd));
+	if ((cctx->cmd = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new", __func__);
+	if ((r = sshbuf_put(cctx->cmd, cmd, strlen(cmd))) != 0)
+		fatal("%s: sshbuf_put: %s", __func__, ssh_err(r));
 	free(cmd);
 	cmd = NULL;
 
@@ -382,13 +409,9 @@ process_mux_new_session(u_int rid, Channel *c, Buffer *m, Buffer *r)
 				free(cctx->env[j]);
 			free(cctx->env);
 			free(cctx->term);
-			buffer_free(&cctx->cmd);
+			sshbuf_free(cctx->cmd);
 			free(cctx);
-
-			/* prepare reply */
-			buffer_put_int(r, MUX_S_FAILURE);
-			buffer_put_int(r, rid);
-			buffer_put_cstring(r,
+			reply_error(reply, MUX_S_FAILURE, rid,
 			    "did not receive file descriptors");
 			return -1;
 		}
@@ -398,12 +421,10 @@ process_mux_new_session(u_int rid, Channel *c, Buffer *m, Buffer *r)
 	    new_fd[0], new_fd[1], new_fd[2]);
 
 	/* XXX support multiple child sessions in future */
-	if (c->remote_id != -1) {
+	if (c->have_remote_id) {
 		debug2("%s: session already open", __func__);
-		/* prepare reply */
-		buffer_put_int(r, MUX_S_FAILURE);
-		buffer_put_int(r, rid);
-		buffer_put_cstring(r, "Multiple sessions not supported");
+		reply_error(reply, MUX_S_FAILURE, rid,
+		    "Multiple sessions not supported");
  cleanup:
 		close(new_fd[0]);
 		close(new_fd[1]);
@@ -414,7 +435,7 @@ process_mux_new_session(u_int rid, Channel *c, Buffer *m, Buffer *r)
 				free(cctx->env[i]);
 			free(cctx->env);
 		}
-		buffer_free(&cctx->cmd);
+		sshbuf_free(cctx->cmd);
 		free(cctx);
 		return 0;
 	}
@@ -423,10 +444,8 @@ process_mux_new_session(u_int rid, Channel *c, Buffer *m, Buffer *r)
 	    options.control_master == SSHCTL_MASTER_AUTO_ASK) {
 		if (!ask_permission("Allow shared connection to %s? ", host)) {
 			debug2("%s: session refused by user", __func__);
-			/* prepare reply */
-			buffer_put_int(r, MUX_S_PERMISSION_DENIED);
-			buffer_put_int(r, rid);
-			buffer_put_cstring(r, "Permission denied");
+			reply_error(reply, MUX_S_PERMISSION_DENIED, rid,
+			    "Permission denied");
 			goto cleanup;
 		}
 	}
@@ -450,15 +469,16 @@ process_mux_new_session(u_int rid, Channel *c, Buffer *m, Buffer *r)
 		packetmax >>= 1;
 	}
 
-	nc = channel_new("session", SSH_CHANNEL_OPENING,
+	nc = channel_new(ssh, "session", SSH_CHANNEL_OPENING,
 	    new_fd[0], new_fd[1], new_fd[2], window, packetmax,
 	    CHAN_EXTENDED_WRITE, "client-session", /*nonblock*/0);
 
 	nc->ctl_chan = c->self;		/* link session -> control channel */
 	c->remote_id = nc->self; 	/* link control -> session channel */
+	c->have_remote_id = 1;
 
 	if (cctx->want_tty && escape_char != 0xffffffff) {
-		channel_register_filter(nc->self,
+		channel_register_filter(ssh, nc->self,
 		    client_simple_escape_filter, NULL,
 		    client_filter_cleanup,
 		    client_new_escape_filter_ctx((int)escape_char));
@@ -467,30 +487,36 @@ process_mux_new_session(u_int rid, Channel *c, Buffer *m, Buffer *r)
 	debug2("%s: channel_new: %d linked to control channel %d",
 	    __func__, nc->self, nc->ctl_chan);
 
-	channel_send_open(nc->self);
-	channel_register_open_confirm(nc->self, mux_session_confirm, cctx);
+	channel_send_open(ssh, nc->self);
+	channel_register_open_confirm(ssh, nc->self, mux_session_confirm, cctx);
 	c->mux_pause = 1; /* stop handling messages until open_confirm done */
-	channel_register_cleanup(nc->self, mux_master_session_cleanup_cb, 1);
+	channel_register_cleanup(ssh, nc->self,
+	    mux_master_session_cleanup_cb, 1);
 
 	/* reply is deferred, sent by mux_session_confirm */
 	return 0;
 }
 
 static int
-process_mux_alive_check(u_int rid, Channel *c, Buffer *m, Buffer *r)
+mux_master_process_alive_check(struct ssh *ssh, u_int rid,
+    Channel *c, struct sshbuf *m, struct sshbuf *reply)
 {
+	int r;
+
 	debug2("%s: channel %d: alive check", __func__, c->self);
 
 	/* prepare reply */
-	buffer_put_int(r, MUX_S_ALIVE);
-	buffer_put_int(r, rid);
-	buffer_put_int(r, (u_int)getpid());
+	if ((r = sshbuf_put_u32(reply, MUX_S_ALIVE)) != 0 ||
+	    (r = sshbuf_put_u32(reply, rid)) != 0 ||
+	    (r = sshbuf_put_u32(reply, (u_int)getpid())) != 0)
+		fatal("%s: reply: %s", __func__, ssh_err(r));
 
 	return 0;
 }
 
 static int
-process_mux_terminate(u_int rid, Channel *c, Buffer *m, Buffer *r)
+mux_master_process_terminate(struct ssh *ssh, u_int rid,
+    Channel *c, struct sshbuf *m, struct sshbuf *reply)
 {
 	debug2("%s: channel %d: terminate request", __func__, c->self);
 
@@ -499,16 +525,14 @@ process_mux_terminate(u_int rid, Channel *c, Buffer *m, Buffer *r)
 		if (!ask_permission("Terminate shared connection to %s? ",
 		    host)) {
 			debug2("%s: termination refused by user", __func__);
-			buffer_put_int(r, MUX_S_PERMISSION_DENIED);
-			buffer_put_int(r, rid);
-			buffer_put_cstring(r, "Permission denied");
+			reply_error(reply, MUX_S_PERMISSION_DENIED, rid,
+			    "Permission denied");
 			return 0;
 		}
 	}
 
 	quit_pending = 1;
-	buffer_put_int(r, MUX_S_OK);
-	buffer_put_int(r, rid);
+	reply_ok(reply, rid);
 	/* XXX exit happens too soon - message never makes it to client */
 	return 0;
 }
@@ -579,21 +603,26 @@ compare_forward(struct Forward *a, struct Forward *b)
 }
 
 static void
-mux_confirm_remote_forward(int type, u_int32_t seq, void *ctxt)
+mux_confirm_remote_forward(struct ssh *ssh, int type, u_int32_t seq, void *ctxt)
 {
 	struct mux_channel_confirm_ctx *fctx = ctxt;
 	char *failmsg = NULL;
 	struct Forward *rfwd;
 	Channel *c;
-	Buffer out;
+	struct sshbuf *out;
+	u_int port;
+	int r;
 
-	if ((c = channel_by_id(fctx->cid)) == NULL) {
+	if ((c = channel_by_id(ssh, fctx->cid)) == NULL) {
 		/* no channel for reply */
 		error("%s: unknown channel", __func__);
 		return;
 	}
-	buffer_init(&out);
-	if (fctx->fid >= options.num_remote_forwards) {
+	if ((out = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new", __func__);
+	if (fctx->fid >= options.num_remote_forwards ||
+	    (options.remote_forwards[fctx->fid].connect_path == NULL &&
+	    options.remote_forwards[fctx->fid].connect_host == NULL)) {
 		xasprintf(&failmsg, "unknown forwarding id %d", fctx->fid);
 		goto fail;
 	}
@@ -604,60 +633,83 @@ mux_confirm_remote_forward(int type, u_int32_t seq, void *ctxt)
 	    rfwd->connect_host, rfwd->connect_port);
 	if (type == SSH2_MSG_REQUEST_SUCCESS) {
 		if (rfwd->listen_port == 0) {
-			rfwd->allocated_port = packet_get_int();
-			logit("Allocated port %u for mux remote forward"
+			if ((r = sshpkt_get_u32(ssh, &port)) != 0)
+				fatal("%s: packet error: %s",
+				    __func__, ssh_err(r));
+			if (port > 65535) {
+				fatal("Invalid allocated port %u for "
+				    "mux remote forward to %s:%d", port,
+				    rfwd->connect_host, rfwd->connect_port);
+			}
+			rfwd->allocated_port = (int)port;
+			debug("Allocated port %u for mux remote forward"
 			    " to %s:%d", rfwd->allocated_port,
 			    rfwd->connect_host, rfwd->connect_port);
-			buffer_put_int(&out, MUX_S_REMOTE_PORT);
-			buffer_put_int(&out, fctx->rid);
-			buffer_put_int(&out, rfwd->allocated_port);
-			channel_update_permitted_opens(rfwd->handle,
+			if ((r = sshbuf_put_u32(out,
+			    MUX_S_REMOTE_PORT)) != 0 ||
+			    (r = sshbuf_put_u32(out, fctx->rid)) != 0 ||
+			    (r = sshbuf_put_u32(out,
+			    rfwd->allocated_port)) != 0)
+				fatal("%s: reply: %s", __func__, ssh_err(r));
+			channel_update_permission(ssh, rfwd->handle,
 			   rfwd->allocated_port);
 		} else {
-			buffer_put_int(&out, MUX_S_OK);
-			buffer_put_int(&out, fctx->rid);
+			reply_ok(out, fctx->rid);
 		}
 		goto out;
 	} else {
 		if (rfwd->listen_port == 0)
-			channel_update_permitted_opens(rfwd->handle, -1);
+			channel_update_permission(ssh, rfwd->handle, -1);
 		if (rfwd->listen_path != NULL)
 			xasprintf(&failmsg, "remote port forwarding failed for "
 			    "listen path %s", rfwd->listen_path);
 		else
 			xasprintf(&failmsg, "remote port forwarding failed for "
 			    "listen port %d", rfwd->listen_port);
+
+                debug2("%s: clearing registered forwarding for listen %d, "
+		    "connect %s:%d", __func__, rfwd->listen_port,
+		    rfwd->connect_path ? rfwd->connect_path :
+		    rfwd->connect_host, rfwd->connect_port);
+
+		free(rfwd->listen_host);
+		free(rfwd->listen_path);
+		free(rfwd->connect_host);
+		free(rfwd->connect_path);
+		memset(rfwd, 0, sizeof(*rfwd));
 	}
  fail:
 	error("%s: %s", __func__, failmsg);
-	buffer_put_int(&out, MUX_S_FAILURE);
-	buffer_put_int(&out, fctx->rid);
-	buffer_put_cstring(&out, failmsg);
+	reply_error(out, MUX_S_FAILURE, fctx->rid, failmsg);
 	free(failmsg);
  out:
-	buffer_put_string(&c->output, buffer_ptr(&out), buffer_len(&out));
-	buffer_free(&out);
+	if ((r = sshbuf_put_stringb(c->output, out)) != 0)
+		fatal("%s: sshbuf_put_stringb: %s", __func__, ssh_err(r));
+	sshbuf_free(out);
 	if (c->mux_pause <= 0)
 		fatal("%s: mux_pause %d", __func__, c->mux_pause);
 	c->mux_pause = 0; /* start processing messages again */
 }
 
 static int
-process_mux_open_fwd(u_int rid, Channel *c, Buffer *m, Buffer *r)
+mux_master_process_open_fwd(struct ssh *ssh, u_int rid,
+    Channel *c, struct sshbuf *m, struct sshbuf *reply)
 {
 	struct Forward fwd;
 	char *fwd_desc = NULL;
 	char *listen_addr, *connect_addr;
 	u_int ftype;
 	u_int lport, cport;
-	int i, ret = 0, freefwd = 1;
+	int r, i, ret = 0, freefwd = 1;
+
+	memset(&fwd, 0, sizeof(fwd));
 
 	/* XXX - lport/cport check redundant */
-	if (buffer_get_int_ret(&ftype, m) != 0 ||
-	    (listen_addr = buffer_get_string_ret(m, NULL)) == NULL ||
-	    buffer_get_int_ret(&lport, m) != 0 ||
-	    (connect_addr = buffer_get_string_ret(m, NULL)) == NULL ||
-	    buffer_get_int_ret(&cport, m) != 0 ||
+	if ((r = sshbuf_get_u32(m, &ftype)) != 0 ||
+	    (r = sshbuf_get_cstring(m, &listen_addr, NULL)) != 0 ||
+	    (r = sshbuf_get_u32(m, &lport)) != 0 ||
+	    (r = sshbuf_get_cstring(m, &connect_addr, NULL)) != 0 ||
+	    (r = sshbuf_get_u32(m, &cport)) != 0 ||
 	    (lport != (u_int)PORT_STREAMLOCAL && lport > 65535) ||
 	    (cport != (u_int)PORT_STREAMLOCAL && cport > 65535)) {
 		error("%s: malformed message", __func__);
@@ -694,9 +746,8 @@ process_mux_open_fwd(u_int rid, Channel *c, Buffer *m, Buffer *r)
  invalid:
 		free(listen_addr);
 		free(connect_addr);
-		buffer_put_int(r, MUX_S_FAILURE);
-		buffer_put_int(r, rid);
-		buffer_put_cstring(r, "Invalid forwarding request");
+		reply_error(reply, MUX_S_FAILURE, rid,
+		    "Invalid forwarding request");
 		return 0;
 	}
 	if (ftype == MUX_FWD_DYNAMIC && fwd.listen_path) {
@@ -709,13 +760,16 @@ process_mux_open_fwd(u_int rid, Channel *c, Buffer *m, Buffer *r)
 		    fwd.listen_port);
 		goto invalid;
 	}
-	if ((fwd.connect_port != PORT_STREAMLOCAL && fwd.connect_port >= 65536)
-	    || (ftype != MUX_FWD_DYNAMIC && ftype != MUX_FWD_REMOTE && fwd.connect_port == 0)) {
+	if ((fwd.connect_port != PORT_STREAMLOCAL &&
+	    fwd.connect_port >= 65536) ||
+	    (ftype != MUX_FWD_DYNAMIC && ftype != MUX_FWD_REMOTE &&
+	    fwd.connect_port == 0)) {
 		logit("%s: invalid connect port %u", __func__,
 		    fwd.connect_port);
 		goto invalid;
 	}
-	if (ftype != MUX_FWD_DYNAMIC && fwd.connect_host == NULL && fwd.connect_path == NULL) {
+	if (ftype != MUX_FWD_DYNAMIC && fwd.connect_host == NULL &&
+	    fwd.connect_path == NULL) {
 		logit("%s: missing connect host", __func__);
 		goto invalid;
 	}
@@ -730,26 +784,25 @@ process_mux_open_fwd(u_int rid, Channel *c, Buffer *m, Buffer *r)
  exists:
 				debug2("%s: found existing forwarding",
 				    __func__);
-				buffer_put_int(r, MUX_S_OK);
-				buffer_put_int(r, rid);
+				reply_ok(reply, rid);
 				goto out;
 			}
 		}
 		break;
 	case MUX_FWD_REMOTE:
 		for (i = 0; i < options.num_remote_forwards; i++) {
-			if (compare_forward(&fwd,
-			    options.remote_forwards + i)) {
-				if (fwd.listen_port != 0)
-					goto exists;
-				debug2("%s: found allocated port",
-				    __func__);
-				buffer_put_int(r, MUX_S_REMOTE_PORT);
-				buffer_put_int(r, rid);
-				buffer_put_int(r,
-				    options.remote_forwards[i].allocated_port);
-				goto out;
-			}
+			if (!compare_forward(&fwd, options.remote_forwards + i))
+				continue;
+			if (fwd.listen_port != 0)
+				goto exists;
+			debug2("%s: found allocated port", __func__);
+			if ((r = sshbuf_put_u32(reply,
+			    MUX_S_REMOTE_PORT)) != 0 ||
+			    (r = sshbuf_put_u32(reply, rid)) != 0 ||
+			    (r = sshbuf_put_u32(reply,
+			    options.remote_forwards[i].allocated_port)) != 0)
+				fatal("%s: reply: %s", __func__, ssh_err(r));
+			goto out;
 		}
 		break;
 	}
@@ -758,21 +811,19 @@ process_mux_open_fwd(u_int rid, Channel *c, Buffer *m, Buffer *r)
 	    options.control_master == SSHCTL_MASTER_AUTO_ASK) {
 		if (!ask_permission("Open %s on %s?", fwd_desc, host)) {
 			debug2("%s: forwarding refused by user", __func__);
-			buffer_put_int(r, MUX_S_PERMISSION_DENIED);
-			buffer_put_int(r, rid);
-			buffer_put_cstring(r, "Permission denied");
+			reply_error(reply, MUX_S_PERMISSION_DENIED, rid,
+			    "Permission denied");
 			goto out;
 		}
 	}
 
 	if (ftype == MUX_FWD_LOCAL || ftype == MUX_FWD_DYNAMIC) {
-		if (!channel_setup_local_fwd_listener(&fwd,
+		if (!channel_setup_local_fwd_listener(ssh, &fwd,
 		    &options.fwd_opts)) {
  fail:
-			logit("slave-requested %s failed", fwd_desc);
-			buffer_put_int(r, MUX_S_FAILURE);
-			buffer_put_int(r, rid);
-			buffer_put_cstring(r, "Port forwarding failed");
+			logit("%s: requested %s failed", __func__, fwd_desc);
+			reply_error(reply, MUX_S_FAILURE, rid,
+			    "Port forwarding failed");
 			goto out;
 		}
 		add_local_forward(&options, &fwd);
@@ -780,7 +831,7 @@ process_mux_open_fwd(u_int rid, Channel *c, Buffer *m, Buffer *r)
 	} else {
 		struct mux_channel_confirm_ctx *fctx;
 
-		fwd.handle = channel_request_remote_forwarding(&fwd);
+		fwd.handle = channel_request_remote_forwarding(ssh, &fwd);
 		if (fwd.handle < 0)
 			goto fail;
 		add_remote_forward(&options, &fwd);
@@ -795,8 +846,7 @@ process_mux_open_fwd(u_int rid, Channel *c, Buffer *m, Buffer *r)
 		/* delayed reply in mux_confirm_remote_forward */
 		goto out;
 	}
-	buffer_put_int(r, MUX_S_OK);
-	buffer_put_int(r, rid);
+	reply_ok(reply, rid);
  out:
 	free(fwd_desc);
 	if (freefwd) {
@@ -809,21 +859,24 @@ process_mux_open_fwd(u_int rid, Channel *c, Buffer *m, Buffer *r)
 }
 
 static int
-process_mux_close_fwd(u_int rid, Channel *c, Buffer *m, Buffer *r)
+mux_master_process_close_fwd(struct ssh *ssh, u_int rid,
+    Channel *c, struct sshbuf *m, struct sshbuf *reply)
 {
 	struct Forward fwd, *found_fwd;
 	char *fwd_desc = NULL;
 	const char *error_reason = NULL;
 	char *listen_addr = NULL, *connect_addr = NULL;
 	u_int ftype;
-	int i, ret = 0;
+	int r, i, ret = 0;
 	u_int lport, cport;
 
-	if (buffer_get_int_ret(&ftype, m) != 0 ||
-	    (listen_addr = buffer_get_string_ret(m, NULL)) == NULL ||
-	    buffer_get_int_ret(&lport, m) != 0 ||
-	    (connect_addr = buffer_get_string_ret(m, NULL)) == NULL ||
-	    buffer_get_int_ret(&cport, m) != 0 ||
+	memset(&fwd, 0, sizeof(fwd));
+
+	if ((r = sshbuf_get_u32(m, &ftype)) != 0 ||
+	    (r = sshbuf_get_cstring(m, &listen_addr, NULL)) != 0 ||
+	    (r = sshbuf_get_u32(m, &lport)) != 0 ||
+	    (r = sshbuf_get_cstring(m, &connect_addr, NULL)) != 0 ||
+	    (r = sshbuf_get_u32(m, &cport)) != 0 ||
 	    (lport != (u_int)PORT_STREAMLOCAL && lport > 65535) ||
 	    (cport != (u_int)PORT_STREAMLOCAL && cport > 65535)) {
 		error("%s: malformed message", __func__);
@@ -888,19 +941,19 @@ process_mux_close_fwd(u_int rid, Channel *c, Buffer *m, Buffer *r)
 		 * However, for dynamic allocated listen ports we need
 		 * to use the actual listen port.
 		 */
-		if (channel_request_rforward_cancel(found_fwd) == -1)
+		if (channel_request_rforward_cancel(ssh, found_fwd) == -1)
 			error_reason = "port not in permitted opens";
 	} else {	/* local and dynamic forwards */
 		/* Ditto */
-		if (channel_cancel_lport_listener(&fwd, fwd.connect_port,
+		if (channel_cancel_lport_listener(ssh, &fwd, fwd.connect_port,
 		    &options.fwd_opts) == -1)
 			error_reason = "port not found";
 	}
 
-	if (error_reason == NULL) {
-		buffer_put_int(r, MUX_S_OK);
-		buffer_put_int(r, rid);
-
+	if (error_reason != NULL)
+		reply_error(reply, MUX_S_FAILURE, rid, error_reason);
+	else {
+		reply_ok(reply, rid);
 		free(found_fwd->listen_host);
 		free(found_fwd->listen_path);
 		free(found_fwd->connect_host);
@@ -908,10 +961,6 @@ process_mux_close_fwd(u_int rid, Channel *c, Buffer *m, Buffer *r)
 		found_fwd->listen_host = found_fwd->connect_host = NULL;
 		found_fwd->listen_path = found_fwd->connect_path = NULL;
 		found_fwd->listen_port = found_fwd->connect_port = 0;
-	} else {
-		buffer_put_int(r, MUX_S_FAILURE);
-		buffer_put_int(r, rid);
-		buffer_put_cstring(r, error_reason);
 	}
  out:
 	free(fwd_desc);
@@ -922,24 +971,22 @@ process_mux_close_fwd(u_int rid, Channel *c, Buffer *m, Buffer *r)
 }
 
 static int
-process_mux_stdio_fwd(u_int rid, Channel *c, Buffer *m, Buffer *r)
+mux_master_process_stdio_fwd(struct ssh *ssh, u_int rid,
+    Channel *c, struct sshbuf *m, struct sshbuf *reply)
 {
 	Channel *nc;
-	char *reserved, *chost;
+	char *chost = NULL;
 	u_int cport, i, j;
-	int new_fd[2];
+	int r, new_fd[2];
 	struct mux_stdio_confirm_ctx *cctx;
 
-	chost = reserved = NULL;
-	if ((reserved = buffer_get_string_ret(m, NULL)) == NULL ||
-	   (chost = buffer_get_string_ret(m, NULL)) == NULL ||
-	    buffer_get_int_ret(&cport, m) != 0) {
-		free(reserved);
+	if ((r = sshbuf_skip_string(m)) != 0 || /* reserved */
+	    (r = sshbuf_get_cstring(m, &chost, NULL)) != 0 ||
+	    (r = sshbuf_get_u32(m, &cport)) != 0) {
 		free(chost);
 		error("%s: malformed message", __func__);
 		return -1;
 	}
-	free(reserved);
 
 	debug2("%s: channel %d: request stdio fwd to %s:%u",
 	    __func__, c->self, chost, cport);
@@ -954,9 +1001,7 @@ process_mux_stdio_fwd(u_int rid, Channel *c, Buffer *m, Buffer *r)
 			free(chost);
 
 			/* prepare reply */
-			buffer_put_int(r, MUX_S_FAILURE);
-			buffer_put_int(r, rid);
-			buffer_put_cstring(r,
+			reply_error(reply, MUX_S_FAILURE, rid,
 			    "did not receive file descriptors");
 			return -1;
 		}
@@ -966,12 +1011,10 @@ process_mux_stdio_fwd(u_int rid, Channel *c, Buffer *m, Buffer *r)
 	    new_fd[0], new_fd[1]);
 
 	/* XXX support multiple child sessions in future */
-	if (c->remote_id != -1) {
+	if (c->have_remote_id) {
 		debug2("%s: session already open", __func__);
-		/* prepare reply */
-		buffer_put_int(r, MUX_S_FAILURE);
-		buffer_put_int(r, rid);
-		buffer_put_cstring(r, "Multiple sessions not supported");
+		reply_error(reply, MUX_S_FAILURE, rid,
+		    "Multiple sessions not supported");
  cleanup:
 		close(new_fd[0]);
 		close(new_fd[1]);
@@ -984,10 +1027,8 @@ process_mux_stdio_fwd(u_int rid, Channel *c, Buffer *m, Buffer *r)
 		if (!ask_permission("Allow forward to %s:%u? ",
 		    chost, cport)) {
 			debug2("%s: stdio fwd refused by user", __func__);
-			/* prepare reply */
-			buffer_put_int(r, MUX_S_PERMISSION_DENIED);
-			buffer_put_int(r, rid);
-			buffer_put_cstring(r, "Permission denied");
+			reply_error(reply, MUX_S_PERMISSION_DENIED, rid,
+			    "Permission denied");
 			goto cleanup;
 		}
 	}
@@ -998,19 +1039,22 @@ process_mux_stdio_fwd(u_int rid, Channel *c, Buffer *m, Buffer *r)
 	if (!isatty(new_fd[1]))
 		set_nonblock(new_fd[1]);
 
-	nc = channel_connect_stdio_fwd(chost, cport, new_fd[0], new_fd[1]);
+	nc = channel_connect_stdio_fwd(ssh, chost, cport, new_fd[0], new_fd[1]);
+	free(chost);
 
 	nc->ctl_chan = c->self;		/* link session -> control channel */
 	c->remote_id = nc->self; 	/* link control -> session channel */
+	c->have_remote_id = 1;
 
 	debug2("%s: channel_new: %d linked to control channel %d",
 	    __func__, nc->self, nc->ctl_chan);
 
-	channel_register_cleanup(nc->self, mux_master_session_cleanup_cb, 1);
+	channel_register_cleanup(ssh, nc->self,
+	    mux_master_session_cleanup_cb, 1);
 
 	cctx = xcalloc(1, sizeof(*cctx));
 	cctx->rid = rid;
-	channel_register_open_confirm(nc->self, mux_stdio_confirm, cctx);
+	channel_register_open_confirm(ssh, nc->self, mux_stdio_confirm, cctx);
 	c->mux_pause = 1; /* stop handling messages until open_confirm done */
 
 	/* reply is deferred, sent by mux_session_confirm */
@@ -1019,41 +1063,43 @@ process_mux_stdio_fwd(u_int rid, Channel *c, Buffer *m, Buffer *r)
 
 /* Callback on open confirmation in mux master for a mux stdio fwd session. */
 static void
-mux_stdio_confirm(int id, int success, void *arg)
+mux_stdio_confirm(struct ssh *ssh, int id, int success, void *arg)
 {
 	struct mux_stdio_confirm_ctx *cctx = arg;
 	Channel *c, *cc;
-	Buffer reply;
+	struct sshbuf *reply;
+	int r;
 
 	if (cctx == NULL)
 		fatal("%s: cctx == NULL", __func__);
-	if ((c = channel_by_id(id)) == NULL)
+	if ((c = channel_by_id(ssh, id)) == NULL)
 		fatal("%s: no channel for id %d", __func__, id);
-	if ((cc = channel_by_id(c->ctl_chan)) == NULL)
+	if ((cc = channel_by_id(ssh, c->ctl_chan)) == NULL)
 		fatal("%s: channel %d lacks control channel %d", __func__,
 		    id, c->ctl_chan);
+	if ((reply = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new", __func__);
 
 	if (!success) {
 		debug3("%s: sending failure reply", __func__);
+		reply_error(reply, MUX_S_FAILURE, cctx->rid,
+		    "Session open refused by peer");
 		/* prepare reply */
-		buffer_init(&reply);
-		buffer_put_int(&reply, MUX_S_FAILURE);
-		buffer_put_int(&reply, cctx->rid);
-		buffer_put_cstring(&reply, "Session open refused by peer");
 		goto done;
 	}
 
 	debug3("%s: sending success reply", __func__);
 	/* prepare reply */
-	buffer_init(&reply);
-	buffer_put_int(&reply, MUX_S_SESSION_OPENED);
-	buffer_put_int(&reply, cctx->rid);
-	buffer_put_int(&reply, c->self);
+	if ((r = sshbuf_put_u32(reply, MUX_S_SESSION_OPENED)) != 0 ||
+	    (r = sshbuf_put_u32(reply, cctx->rid)) != 0 ||
+	    (r = sshbuf_put_u32(reply, c->self)) != 0)
+		fatal("%s: reply: %s", __func__, ssh_err(r));
 
  done:
 	/* Send reply */
-	buffer_put_string(&cc->output, buffer_ptr(&reply), buffer_len(&reply));
-	buffer_free(&reply);
+	if ((r = sshbuf_put_stringb(cc->output, reply)) != 0)
+		fatal("%s: sshbuf_put_stringb: %s", __func__, ssh_err(r));
+	sshbuf_free(reply);
 
 	if (cc->mux_pause <= 0)
 		fatal("%s: mux_pause %d", __func__, cc->mux_pause);
@@ -1063,7 +1109,8 @@ mux_stdio_confirm(int id, int success, void *arg)
 }
 
 static int
-process_mux_stop_listening(u_int rid, Channel *c, Buffer *m, Buffer *r)
+mux_master_process_stop_listening(struct ssh *ssh, u_int rid,
+    Channel *c, struct sshbuf *m, struct sshbuf *reply)
 {
 	debug("%s: channel %d: stop listening", __func__, c->self);
 
@@ -1072,15 +1119,14 @@ process_mux_stop_listening(u_int rid, Channel *c, Buffer *m, Buffer *r)
 		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");
+			reply_error(reply, MUX_S_PERMISSION_DENIED, rid,
+			    "Permission denied");
 			return 0;
 		}
 	}
 
 	if (mux_listener_channel != NULL) {
-		channel_free(mux_listener_channel);
+		channel_free(ssh, mux_listener_channel);
 		client_stop_mux();
 		free(options.control_path);
 		options.control_path = NULL;
@@ -1088,57 +1134,69 @@ process_mux_stop_listening(u_int rid, Channel *c, Buffer *m, Buffer *r)
 		muxserver_sock = -1;
 	}
 
-	/* prepare reply */
-	buffer_put_int(r, MUX_S_OK);
-	buffer_put_int(r, rid);
+	reply_ok(reply, rid);
+	return 0;
+}
+
+static int
+mux_master_process_proxy(struct ssh *ssh, u_int rid,
+    Channel *c, struct sshbuf *m, struct sshbuf *reply)
+{
+	int r;
+
+	debug("%s: channel %d: proxy request", __func__, c->self);
+
+	c->mux_rcb = channel_proxy_downstream;
+	if ((r = sshbuf_put_u32(reply, MUX_S_PROXY)) != 0 ||
+	    (r = sshbuf_put_u32(reply, rid)) != 0)
+		fatal("%s: reply: %s", __func__, ssh_err(r));
 
 	return 0;
 }
 
 /* Channel callbacks fired on read/write from mux slave fd */
 static int
-mux_master_read_cb(Channel *c)
+mux_master_read_cb(struct ssh *ssh, Channel *c)
 {
 	struct mux_master_state *state = (struct mux_master_state *)c->mux_ctx;
-	Buffer in, out;
-	const u_char *ptr;
-	u_int type, rid, have, i;
-	int ret = -1;
+	struct sshbuf *in = NULL, *out = NULL;
+	u_int type, rid, i;
+	int r, ret = -1;
+
+	if ((out = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new", __func__);
 
 	/* Setup ctx and  */
 	if (c->mux_ctx == NULL) {
 		state = xcalloc(1, sizeof(*state));
 		c->mux_ctx = state;
-		channel_register_cleanup(c->self,
+		channel_register_cleanup(ssh, c->self,
 		    mux_master_control_cleanup_cb, 0);
 
 		/* Send hello */
-		buffer_init(&out);
-		buffer_put_int(&out, MUX_MSG_HELLO);
-		buffer_put_int(&out, SSHMUX_VER);
+		if ((r = sshbuf_put_u32(out, MUX_MSG_HELLO)) != 0 ||
+		    (r = sshbuf_put_u32(out, SSHMUX_VER)) != 0)
+			fatal("%s: reply: %s", __func__, ssh_err(r));
 		/* no extensions */
-		buffer_put_string(&c->output, buffer_ptr(&out),
-		    buffer_len(&out));
-		buffer_free(&out);
+		if ((r = sshbuf_put_stringb(c->output, out)) != 0)
+			fatal("%s: sshbuf_put_stringb: %s",
+			    __func__, ssh_err(r));
 		debug3("%s: channel %d: hello sent", __func__, c->self);
-		return 0;
+		ret = 0;
+		goto out;
 	}
 
-	buffer_init(&in);
-	buffer_init(&out);
-
 	/* Channel code ensures that we receive whole packets */
-	if ((ptr = buffer_get_string_ptr_ret(&c->input, &have)) == NULL) {
+	if ((r = sshbuf_froms(c->input, &in)) != 0) {
  malf:
 		error("%s: malformed message", __func__);
 		goto out;
 	}
-	buffer_append(&in, ptr, have);
 
-	if (buffer_get_int_ret(&type, &in) != 0)
+	if ((r = sshbuf_get_u32(in, &type)) != 0)
 		goto malf;
-	debug3("%s: channel %d packet type 0x%08x len %u",
-	    __func__, c->self, type, buffer_len(&in));
+	debug3("%s: channel %d packet type 0x%08x len %zu",
+	    __func__, c->self, type, sshbuf_len(in));
 
 	if (type == MUX_MSG_HELLO)
 		rid = 0;
@@ -1148,81 +1206,85 @@ mux_master_read_cb(Channel *c)
 			    "received 0x%08x", __func__, MUX_MSG_HELLO, type);
 			goto out;
 		}
-		if (buffer_get_int_ret(&rid, &in) != 0)
+		if ((r = sshbuf_get_u32(in, &rid)) != 0)
 			goto malf;
 	}
 
 	for (i = 0; mux_master_handlers[i].handler != NULL; i++) {
 		if (type == mux_master_handlers[i].type) {
-			ret = mux_master_handlers[i].handler(rid, c, &in, &out);
+			ret = mux_master_handlers[i].handler(ssh, rid,
+			    c, in, out);
 			break;
 		}
 	}
 	if (mux_master_handlers[i].handler == NULL) {
 		error("%s: unsupported mux message 0x%08x", __func__, type);
-		buffer_put_int(&out, MUX_S_FAILURE);
-		buffer_put_int(&out, rid);
-		buffer_put_cstring(&out, "unsupported request");
+		reply_error(out, MUX_S_FAILURE, rid, "unsupported request");
 		ret = 0;
 	}
 	/* Enqueue reply packet */
-	if (buffer_len(&out) != 0) {
-		buffer_put_string(&c->output, buffer_ptr(&out),
-		    buffer_len(&out));
+	if (sshbuf_len(out) != 0) {
+		if ((r = sshbuf_put_stringb(c->output, out)) != 0)
+			fatal("%s: sshbuf_put_stringb: %s",
+			    __func__, ssh_err(r));
 	}
  out:
-	buffer_free(&in);
-	buffer_free(&out);
+	sshbuf_free(in);
+	sshbuf_free(out);
 	return ret;
 }
 
 void
-mux_exit_message(Channel *c, int exitval)
+mux_exit_message(struct ssh *ssh, Channel *c, int exitval)
 {
-	Buffer m;
+	struct sshbuf *m;
 	Channel *mux_chan;
+	int r;
 
 	debug3("%s: channel %d: exit message, exitval %d", __func__, c->self,
 	    exitval);
 
-	if ((mux_chan = channel_by_id(c->ctl_chan)) == NULL)
+	if ((mux_chan = channel_by_id(ssh, c->ctl_chan)) == NULL)
 		fatal("%s: channel %d missing mux channel %d",
 		    __func__, c->self, c->ctl_chan);
 
 	/* Append exit message packet to control socket output queue */
-	buffer_init(&m);
-	buffer_put_int(&m, MUX_S_EXIT_MESSAGE);
-	buffer_put_int(&m, c->self);
-	buffer_put_int(&m, exitval);
-
-	buffer_put_string(&mux_chan->output, buffer_ptr(&m), buffer_len(&m));
-	buffer_free(&m);
+	if ((m = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new", __func__);
+	if ((r = sshbuf_put_u32(m, MUX_S_EXIT_MESSAGE)) != 0 ||
+	    (r = sshbuf_put_u32(m, c->self)) != 0 ||
+	    (r = sshbuf_put_u32(m, exitval)) != 0 ||
+	    (r = sshbuf_put_stringb(mux_chan->output, m)) != 0)
+		fatal("%s: reply: %s", __func__, ssh_err(r));
+	sshbuf_free(m);
 }
 
 void
-mux_tty_alloc_failed(Channel *c)
+mux_tty_alloc_failed(struct ssh *ssh, Channel *c)
 {
-	Buffer m;
+	struct sshbuf *m;
 	Channel *mux_chan;
+	int r;
 
 	debug3("%s: channel %d: TTY alloc failed", __func__, c->self);
 
-	if ((mux_chan = channel_by_id(c->ctl_chan)) == NULL)
+	if ((mux_chan = channel_by_id(ssh, c->ctl_chan)) == NULL)
 		fatal("%s: channel %d missing mux channel %d",
 		    __func__, c->self, c->ctl_chan);
 
 	/* Append exit message packet to control socket output queue */
-	buffer_init(&m);
-	buffer_put_int(&m, MUX_S_TTY_ALLOC_FAIL);
-	buffer_put_int(&m, c->self);
-
-	buffer_put_string(&mux_chan->output, buffer_ptr(&m), buffer_len(&m));
-	buffer_free(&m);
+	if ((m = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new", __func__);
+	if ((r = sshbuf_put_u32(m, MUX_S_TTY_ALLOC_FAIL)) != 0 ||
+	    (r = sshbuf_put_u32(m, c->self)) != 0 ||
+	    (r = sshbuf_put_stringb(mux_chan->output, m)) != 0)
+		fatal("%s: reply: %s", __func__, ssh_err(r));
+	sshbuf_free(m);
 }
 
 /* Prepare a mux master to listen on a Unix domain socket. */
 void
-muxserver_listen(void)
+muxserver_listen(struct ssh *ssh)
 {
 	mode_t old_umask;
 	char *orig_control_path = options.control_path;
@@ -1280,7 +1342,7 @@ muxserver_listen(void)
 	/* Now atomically "move" the mux socket into position */
 	if (link(options.control_path, orig_control_path) != 0) {
 		if (errno != EEXIST) {
-			fatal("%s: link mux listener %s => %s: %s", __func__, 
+			fatal("%s: link mux listener %s => %s: %s", __func__,
 			    options.control_path, orig_control_path,
 			    strerror(errno));
 		}
@@ -1295,7 +1357,7 @@ muxserver_listen(void)
 
 	set_nonblock(muxserver_sock);
 
-	mux_listener_channel = channel_new("mux listener",
+	mux_listener_channel = channel_new(ssh, "mux listener",
 	    SSH_CHANNEL_MUX_LISTENER, muxserver_sock, muxserver_sock, -1,
 	    CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT,
 	    0, options.control_path, 1);
@@ -1306,29 +1368,28 @@ muxserver_listen(void)
 
 /* Callback on open confirmation in mux master for a mux client session. */
 static void
-mux_session_confirm(int id, int success, void *arg)
+mux_session_confirm(struct ssh *ssh, int id, int success, void *arg)
 {
 	struct mux_session_confirm_ctx *cctx = arg;
 	const char *display;
 	Channel *c, *cc;
-	int i;
-	Buffer reply;
+	int i, r;
+	struct sshbuf *reply;
 
 	if (cctx == NULL)
 		fatal("%s: cctx == NULL", __func__);
-	if ((c = channel_by_id(id)) == NULL)
+	if ((c = channel_by_id(ssh, id)) == NULL)
 		fatal("%s: no channel for id %d", __func__, id);
-	if ((cc = channel_by_id(c->ctl_chan)) == NULL)
+	if ((cc = channel_by_id(ssh, c->ctl_chan)) == NULL)
 		fatal("%s: channel %d lacks control channel %d", __func__,
 		    id, c->ctl_chan);
+	if ((reply = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new", __func__);
 
 	if (!success) {
 		debug3("%s: sending failure reply", __func__);
-		/* prepare reply */
-		buffer_init(&reply);
-		buffer_put_int(&reply, MUX_S_FAILURE);
-		buffer_put_int(&reply, cctx->rid);
-		buffer_put_cstring(&reply, "Session open refused by peer");
+		reply_error(reply, MUX_S_FAILURE, cctx->rid,
+		    "Session open refused by peer");
 		goto done;
 	}
 
@@ -1337,44 +1398,48 @@ mux_session_confirm(int id, int success, void *arg)
 		char *proto, *data;
 
 		/* Get reasonable local authentication information. */
-		client_x11_get_proto(display, options.xauth_location,
+		if (client_x11_get_proto(ssh, display, options.xauth_location,
 		    options.forward_x11_trusted, options.forward_x11_timeout,
-		    &proto, &data);
-		/* Request forwarding with authentication spoofing. */
-		debug("Requesting X11 forwarding with authentication "
-		    "spoofing.");
-		x11_request_forwarding_with_spoofing(id, display, proto,
-		    data, 1);
-		client_expect_confirm(id, "X11 forwarding", CONFIRM_WARN);
-		/* XXX exit_on_forward_failure */
+		    &proto, &data) == 0) {
+			/* Request forwarding with authentication spoofing. */
+			debug("Requesting X11 forwarding with authentication "
+			    "spoofing.");
+			x11_request_forwarding_with_spoofing(ssh, id,
+			    display, proto, data, 1);
+			/* XXX exit_on_forward_failure */
+			client_expect_confirm(ssh, id, "X11 forwarding",
+			    CONFIRM_WARN);
+		}
 	}
 
 	if (cctx->want_agent_fwd && options.forward_agent) {
 		debug("Requesting authentication agent forwarding.");
-		channel_request_start(id, "auth-agent-req@openssh.com", 0);
-		packet_send();
+		channel_request_start(ssh, id, "auth-agent-req@openssh.com", 0);
+		if ((r = sshpkt_send(ssh)) != 0)
+			fatal("%s: packet error: %s", __func__, ssh_err(r));
 	}
 
-	client_session2_setup(id, cctx->want_tty, cctx->want_subsys,
-	    cctx->term, &cctx->tio, c->rfd, &cctx->cmd, cctx->env);
+	client_session2_setup(ssh, id, cctx->want_tty, cctx->want_subsys,
+	    cctx->term, &cctx->tio, c->rfd, cctx->cmd, cctx->env);
 
 	debug3("%s: sending success reply", __func__);
 	/* prepare reply */
-	buffer_init(&reply);
-	buffer_put_int(&reply, MUX_S_SESSION_OPENED);
-	buffer_put_int(&reply, cctx->rid);
-	buffer_put_int(&reply, c->self);
+	if ((r = sshbuf_put_u32(reply, MUX_S_SESSION_OPENED)) != 0 ||
+	    (r = sshbuf_put_u32(reply, cctx->rid)) != 0 ||
+	    (r = sshbuf_put_u32(reply, c->self)) != 0)
+		fatal("%s: reply: %s", __func__, ssh_err(r));
 
  done:
 	/* Send reply */
-	buffer_put_string(&cc->output, buffer_ptr(&reply), buffer_len(&reply));
-	buffer_free(&reply);
+	if ((r = sshbuf_put_stringb(cc->output, reply)) != 0)
+		fatal("%s: sshbuf_put_stringb: %s", __func__, ssh_err(r));
+	sshbuf_free(reply);
 
 	if (cc->mux_pause <= 0)
 		fatal("%s: mux_pause %d", __func__, cc->mux_pause);
 	cc->mux_pause = 0; /* start processing messages again */
 	c->open_confirm_ctx = NULL;
-	buffer_free(&cctx->cmd);
+	sshbuf_free(cctx->cmd);
 	free(cctx->term);
 	if (cctx->env != NULL) {
 		for (i = 0; cctx->env[i] != NULL; i++)
@@ -1409,23 +1474,25 @@ control_client_sigrelay(int signo)
 }
 
 static int
-mux_client_read(int fd, Buffer *b, u_int need)
+mux_client_read(int fd, struct sshbuf *b, size_t need)
 {
-	u_int have;
+	size_t have;
 	ssize_t len;
 	u_char *p;
 	struct pollfd pfd;
+	int r;
 
 	pfd.fd = fd;
 	pfd.events = POLLIN;
-	p = buffer_append_space(b, need);
+	if ((r = sshbuf_reserve(b, need, &p)) != 0)
+		fatal("%s: reserve: %s", __func__, ssh_err(r));
 	for (have = 0; have < need; ) {
 		if (muxclient_terminate) {
 			errno = EINTR;
 			return -1;
 		}
 		len = read(fd, p + have, need - have);
-		if (len < 0) {
+		if (len == -1) {
 			switch (errno) {
 #if defined(EWOULDBLOCK) && (EWOULDBLOCK != EAGAIN)
 			case EWOULDBLOCK:
@@ -1443,36 +1510,38 @@ mux_client_read(int fd, Buffer *b, u_int need)
 			errno = EPIPE;
 			return -1;
 		}
-		have += (u_int)len;
+		have += (size_t)len;
 	}
 	return 0;
 }
 
 static int
-mux_client_write_packet(int fd, Buffer *m)
+mux_client_write_packet(int fd, struct sshbuf *m)
 {
-	Buffer queue;
+	struct sshbuf *queue;
 	u_int have, need;
-	int oerrno, len;
-	u_char *ptr;
+	int r, oerrno, len;
+	const u_char *ptr;
 	struct pollfd pfd;
 
 	pfd.fd = fd;
 	pfd.events = POLLOUT;
-	buffer_init(&queue);
-	buffer_put_string(&queue, buffer_ptr(m), buffer_len(m));
+	if ((queue = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new", __func__);
+	if ((r = sshbuf_put_stringb(queue, m)) != 0)
+		fatal("%s: sshbuf_put_stringb: %s", __func__, ssh_err(r));
 
-	need = buffer_len(&queue);
-	ptr = buffer_ptr(&queue);
+	need = sshbuf_len(queue);
+	ptr = sshbuf_ptr(queue);
 
 	for (have = 0; have < need; ) {
 		if (muxclient_terminate) {
-			buffer_free(&queue);
+			sshbuf_free(queue);
 			errno = EINTR;
 			return -1;
 		}
 		len = write(fd, ptr + have, need - have);
-		if (len < 0) {
+		if (len == -1) {
 			switch (errno) {
 #if defined(EWOULDBLOCK) && (EWOULDBLOCK != EAGAIN)
 			case EWOULDBLOCK:
@@ -1484,132 +1553,160 @@ mux_client_write_packet(int fd, Buffer *m)
 				continue;
 			default:
 				oerrno = errno;
-				buffer_free(&queue);
+				sshbuf_free(queue);
 				errno = oerrno;
 				return -1;
 			}
 		}
 		if (len == 0) {
-			buffer_free(&queue);
+			sshbuf_free(queue);
 			errno = EPIPE;
 			return -1;
 		}
 		have += (u_int)len;
 	}
-	buffer_free(&queue);
+	sshbuf_free(queue);
 	return 0;
 }
 
 static int
-mux_client_read_packet(int fd, Buffer *m)
+mux_client_read_packet(int fd, struct sshbuf *m)
 {
-	Buffer queue;
-	u_int need, have;
+	struct sshbuf *queue;
+	size_t need, have;
 	const u_char *ptr;
-	int oerrno;
+	int r, oerrno;
 
-	buffer_init(&queue);
-	if (mux_client_read(fd, &queue, 4) != 0) {
+	if ((queue = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new", __func__);
+	if (mux_client_read(fd, queue, 4) != 0) {
 		if ((oerrno = errno) == EPIPE)
 			debug3("%s: read header failed: %s", __func__,
 			    strerror(errno));
-		buffer_free(&queue);
+		sshbuf_free(queue);
 		errno = oerrno;
 		return -1;
 	}
-	need = get_u32(buffer_ptr(&queue));
-	if (mux_client_read(fd, &queue, need) != 0) {
+	need = PEEK_U32(sshbuf_ptr(queue));
+	if (mux_client_read(fd, queue, need) != 0) {
 		oerrno = errno;
 		debug3("%s: read body failed: %s", __func__, strerror(errno));
-		buffer_free(&queue);
+		sshbuf_free(queue);
 		errno = oerrno;
 		return -1;
 	}
-	ptr = buffer_get_string_ptr(&queue, &have);
-	buffer_append(m, ptr, have);
-	buffer_free(&queue);
+	if ((r = sshbuf_get_string_direct(queue, &ptr, &have)) != 0 ||
+	    (r = sshbuf_put(m, ptr, have)) != 0)
+		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+	sshbuf_free(queue);
 	return 0;
 }
 
 static int
 mux_client_hello_exchange(int fd)
 {
-	Buffer m;
+	struct sshbuf *m;
 	u_int type, ver;
+	int r, ret = -1;
 
-	buffer_init(&m);
-	buffer_put_int(&m, MUX_MSG_HELLO);
-	buffer_put_int(&m, SSHMUX_VER);
+	if ((m = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new", __func__);
+	if ((r = sshbuf_put_u32(m, MUX_MSG_HELLO)) != 0 ||
+	    (r = sshbuf_put_u32(m, SSHMUX_VER)) != 0)
+		fatal("%s: hello: %s", __func__, ssh_err(r));
 	/* no extensions */
 
-	if (mux_client_write_packet(fd, &m) != 0)
-		fatal("%s: write packet: %s", __func__, strerror(errno));
+	if (mux_client_write_packet(fd, m) != 0) {
+		debug("%s: write packet: %s", __func__, strerror(errno));
+		goto out;
+	}
 
-	buffer_clear(&m);
+	sshbuf_reset(m);
 
 	/* Read their HELLO */
-	if (mux_client_read_packet(fd, &m) != 0) {
-		buffer_free(&m);
-		return -1;
+	if (mux_client_read_packet(fd, m) != 0) {
+		debug("%s: read packet failed", __func__);
+		goto out;
 	}
 
-	type = buffer_get_int(&m);
-	if (type != MUX_MSG_HELLO)
-		fatal("%s: expected HELLO (%u) received %u",
+	if ((r = sshbuf_get_u32(m, &type)) != 0)
+		fatal("%s: decode type: %s", __func__, ssh_err(r));
+	if (type != MUX_MSG_HELLO) {
+		error("%s: expected HELLO (%u) received %u",
 		    __func__, MUX_MSG_HELLO, type);
-	ver = buffer_get_int(&m);
-	if (ver != SSHMUX_VER)
-		fatal("Unsupported multiplexing protocol version %d "
+		goto out;
+	}
+	if ((r = sshbuf_get_u32(m, &ver)) != 0)
+		fatal("%s: decode version: %s", __func__, ssh_err(r));
+	if (ver != SSHMUX_VER) {
+		error("Unsupported multiplexing protocol version %d "
 		    "(expected %d)", ver, SSHMUX_VER);
+		goto out;
+	}
 	debug2("%s: master version %u", __func__, ver);
 	/* No extensions are presently defined */
-	while (buffer_len(&m) > 0) {
-		char *name = buffer_get_string(&m, NULL);
-		char *value = buffer_get_string(&m, NULL);
+	while (sshbuf_len(m) > 0) {
+		char *name = NULL;
 
+		if ((r = sshbuf_get_cstring(m, &name, NULL)) != 0 ||
+		    (r = sshbuf_skip_string(m)) != 0) { /* value */
+			error("%s: malformed extension: %s",
+			    __func__, ssh_err(r));
+			goto out;
+		}
 		debug2("Unrecognised master extension \"%s\"", name);
 		free(name);
-		free(value);
 	}
-	buffer_free(&m);
-	return 0;
+	/* success */
+	ret = 0;
+ out:
+	sshbuf_free(m);
+	return ret;
 }
 
 static u_int
 mux_client_request_alive(int fd)
 {
-	Buffer m;
+	struct sshbuf *m;
 	char *e;
 	u_int pid, type, rid;
+	int r;
 
 	debug3("%s: entering", __func__);
 
-	buffer_init(&m);
-	buffer_put_int(&m, MUX_C_ALIVE_CHECK);
-	buffer_put_int(&m, muxclient_request_id);
+	if ((m = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new", __func__);
+	if ((r = sshbuf_put_u32(m, MUX_C_ALIVE_CHECK)) != 0 ||
+	    (r = sshbuf_put_u32(m, muxclient_request_id)) != 0)
+		fatal("%s: request: %s", __func__, ssh_err(r));
 
-	if (mux_client_write_packet(fd, &m) != 0)
+	if (mux_client_write_packet(fd, m) != 0)
 		fatal("%s: write packet: %s", __func__, strerror(errno));
 
-	buffer_clear(&m);
+	sshbuf_reset(m);
 
 	/* Read their reply */
-	if (mux_client_read_packet(fd, &m) != 0) {
-		buffer_free(&m);
+	if (mux_client_read_packet(fd, m) != 0) {
+		sshbuf_free(m);
 		return 0;
 	}
 
-	type = buffer_get_int(&m);
+	if ((r = sshbuf_get_u32(m, &type)) != 0)
+		fatal("%s: decode type: %s", __func__, ssh_err(r));
 	if (type != MUX_S_ALIVE) {
-		e = buffer_get_string(&m, NULL);
+		if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0)
+			fatal("%s: decode error: %s", __func__, ssh_err(r));
 		fatal("%s: master returned error: %s", __func__, e);
 	}
 
-	if ((rid = buffer_get_int(&m)) != muxclient_request_id)
+	if ((r = sshbuf_get_u32(m, &rid)) != 0)
+		fatal("%s: decode remote ID: %s", __func__, ssh_err(r));
+	if (rid != muxclient_request_id)
 		fatal("%s: out of sequence reply: my id %u theirs %u",
 		    __func__, muxclient_request_id, rid);
-	pid = buffer_get_int(&m);
-	buffer_free(&m);
+	if ((r = sshbuf_get_u32(m, &pid)) != 0)
+		fatal("%s: decode PID: %s", __func__, ssh_err(r));
+	sshbuf_free(m);
 
 	debug3("%s: done pid = %u", __func__, pid);
 
@@ -1621,129 +1718,152 @@ mux_client_request_alive(int fd)
 static void
 mux_client_request_terminate(int fd)
 {
-	Buffer m;
+	struct sshbuf *m;
 	char *e;
 	u_int type, rid;
+	int r;
 
 	debug3("%s: entering", __func__);
 
-	buffer_init(&m);
-	buffer_put_int(&m, MUX_C_TERMINATE);
-	buffer_put_int(&m, muxclient_request_id);
+	if ((m = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new", __func__);
+	if ((r = sshbuf_put_u32(m, MUX_C_TERMINATE)) != 0 ||
+	    (r = sshbuf_put_u32(m, muxclient_request_id)) != 0)
+		fatal("%s: request: %s", __func__, ssh_err(r));
 
-	if (mux_client_write_packet(fd, &m) != 0)
+	if (mux_client_write_packet(fd, m) != 0)
 		fatal("%s: write packet: %s", __func__, strerror(errno));
 
-	buffer_clear(&m);
+	sshbuf_reset(m);
 
 	/* Read their reply */
-	if (mux_client_read_packet(fd, &m) != 0) {
+	if (mux_client_read_packet(fd, m) != 0) {
 		/* Remote end exited already */
 		if (errno == EPIPE) {
-			buffer_free(&m);
+			sshbuf_free(m);
 			return;
 		}
 		fatal("%s: read from master failed: %s",
 		    __func__, strerror(errno));
 	}
 
-	type = buffer_get_int(&m);
-	if ((rid = buffer_get_int(&m)) != muxclient_request_id)
+	if ((r = sshbuf_get_u32(m, &type)) != 0 ||
+	    (r = sshbuf_get_u32(m, &rid)) != 0)
+		fatal("%s: decode: %s", __func__, ssh_err(r));
+	if (rid != 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);
+		if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0)
+			fatal("%s: decode error: %s", __func__, ssh_err(r));
 		fatal("Master refused termination request: %s", e);
 	case MUX_S_FAILURE:
-		e = buffer_get_string(&m, NULL);
+		if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0)
+			fatal("%s: decode error: %s", __func__, ssh_err(r));
 		fatal("%s: termination request failed: %s", __func__, e);
 	default:
 		fatal("%s: unexpected response from master 0x%08x",
 		    __func__, type);
 	}
-	buffer_free(&m);
+	sshbuf_free(m);
 	muxclient_request_id++;
 }
 
 static int
 mux_client_forward(int fd, int cancel_flag, u_int ftype, struct Forward *fwd)
 {
-	Buffer m;
+	struct sshbuf *m;
 	char *e, *fwd_desc;
+	const char *lhost, *chost;
 	u_int type, rid;
+	int r;
 
 	fwd_desc = format_forward(ftype, fwd);
 	debug("Requesting %s %s",
 	    cancel_flag ? "cancellation of" : "forwarding of", fwd_desc);
 	free(fwd_desc);
 
-	buffer_init(&m);
-	buffer_put_int(&m, cancel_flag ? MUX_C_CLOSE_FWD : MUX_C_OPEN_FWD);
-	buffer_put_int(&m, muxclient_request_id);
-	buffer_put_int(&m, ftype);
-	if (fwd->listen_path != NULL) {
-		buffer_put_cstring(&m, fwd->listen_path);
-	} else {
-		buffer_put_cstring(&m,
-		    fwd->listen_host == NULL ? "" :
-		    (*fwd->listen_host == '\0' ? "*" : fwd->listen_host));
-	}
-	buffer_put_int(&m, fwd->listen_port);
-	if (fwd->connect_path != NULL) {
-		buffer_put_cstring(&m, fwd->connect_path);
-	} else {
-		buffer_put_cstring(&m,
-		    fwd->connect_host == NULL ? "" : fwd->connect_host);
-	}
-	buffer_put_int(&m, fwd->connect_port);
+	type = cancel_flag ? MUX_C_CLOSE_FWD : MUX_C_OPEN_FWD;
+	if (fwd->listen_path != NULL)
+		lhost = fwd->listen_path;
+	else if (fwd->listen_host == NULL)
+		lhost = "";
+	else if (*fwd->listen_host == '\0')
+		lhost = "*";
+	else
+		lhost = fwd->listen_host;
 
-	if (mux_client_write_packet(fd, &m) != 0)
+	if (fwd->connect_path != NULL)
+		chost = fwd->connect_path;
+	else if (fwd->connect_host == NULL)
+		chost = "";
+	else
+		chost = fwd->connect_host;
+
+	if ((m = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new", __func__);
+	if ((r = sshbuf_put_u32(m, type)) != 0 ||
+	    (r = sshbuf_put_u32(m, muxclient_request_id)) != 0 ||
+	    (r = sshbuf_put_u32(m, ftype)) != 0 ||
+	    (r = sshbuf_put_cstring(m, lhost)) != 0 ||
+	    (r = sshbuf_put_u32(m, fwd->listen_port)) != 0 ||
+	    (r = sshbuf_put_cstring(m, chost)) != 0 ||
+	    (r = sshbuf_put_u32(m, fwd->connect_port)) != 0)
+		fatal("%s: request: %s", __func__, ssh_err(r));
+
+	if (mux_client_write_packet(fd, m) != 0)
 		fatal("%s: write packet: %s", __func__, strerror(errno));
 
-	buffer_clear(&m);
+	sshbuf_reset(m);
 
 	/* Read their reply */
-	if (mux_client_read_packet(fd, &m) != 0) {
-		buffer_free(&m);
+	if (mux_client_read_packet(fd, m) != 0) {
+		sshbuf_free(m);
 		return -1;
 	}
 
-	type = buffer_get_int(&m);
-	if ((rid = buffer_get_int(&m)) != muxclient_request_id)
+	if ((r = sshbuf_get_u32(m, &type)) != 0 ||
+	    (r = sshbuf_get_u32(m, &rid)) != 0)
+		fatal("%s: decode: %s", __func__, ssh_err(r));
+	if (rid != 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_REMOTE_PORT:
 		if (cancel_flag)
 			fatal("%s: got MUX_S_REMOTE_PORT for cancel", __func__);
-		fwd->allocated_port = buffer_get_int(&m);
-		logit("Allocated port %u for remote forward to %s:%d",
+		if ((r = sshbuf_get_u32(m, &fwd->allocated_port)) != 0)
+			fatal("%s: decode port: %s", __func__, ssh_err(r));
+		verbose("Allocated port %u for remote forward to %s:%d",
 		    fwd->allocated_port,
 		    fwd->connect_host ? fwd->connect_host : "",
 		    fwd->connect_port);
 		if (muxclient_command == SSHMUX_COMMAND_FORWARD)
-			fprintf(stdout, "%u\n", fwd->allocated_port);
+			fprintf(stdout, "%i\n", fwd->allocated_port);
 		break;
 	case MUX_S_PERMISSION_DENIED:
-		e = buffer_get_string(&m, NULL);
-		buffer_free(&m);
+		if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0)
+			fatal("%s: decode error: %s", __func__, ssh_err(r));
+		sshbuf_free(m);
 		error("Master refused forwarding request: %s", e);
 		return -1;
 	case MUX_S_FAILURE:
-		e = buffer_get_string(&m, NULL);
-		buffer_free(&m);
+		if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0)
+			fatal("%s: decode error: %s", __func__, ssh_err(r));
+		sshbuf_free(m);
 		error("%s: forwarding request failed: %s", __func__, e);
 		return -1;
 	default:
 		fatal("%s: unexpected response from master 0x%08x",
 		    __func__, type);
 	}
-	buffer_free(&m);
+	sshbuf_free(m);
 
 	muxclient_request_id++;
 	return 0;
@@ -1777,11 +1897,12 @@ mux_client_forwards(int fd, int cancel_flag)
 static int
 mux_client_request_session(int fd)
 {
-	Buffer m;
-	char *e, *term;
-	u_int i, rid, sid, esid, exitval, type, exitval_seen;
+	struct sshbuf *m;
+	char *e;
+	const char *term;
+	u_int echar, rid, sid, esid, exitval, type, exitval_seen;
 	extern char **environ;
-	int devnull, rawmode;
+	int r, i, devnull, rawmode;
 
 	debug3("%s: entering", __func__);
 
@@ -1790,7 +1911,7 @@ mux_client_request_session(int fd)
 		return -1;
 	}
 
-	signal(SIGPIPE, SIG_IGN);
+	ssh_signal(SIGPIPE, SIG_IGN);
 
 	if (stdin_null_flag) {
 		if ((devnull = open(_PATH_DEVNULL, O_RDONLY)) == -1)
@@ -1801,31 +1922,41 @@ mux_client_request_session(int fd)
 			close(devnull);
 	}
 
-	term = getenv("TERM");
-
-	buffer_init(&m);
-	buffer_put_int(&m, MUX_C_NEW_SESSION);
-	buffer_put_int(&m, muxclient_request_id);
-	buffer_put_cstring(&m, ""); /* reserved */
-	buffer_put_int(&m, tty_flag);
-	buffer_put_int(&m, options.forward_x11);
-	buffer_put_int(&m, options.forward_agent);
-	buffer_put_int(&m, subsystem_flag);
-	buffer_put_int(&m, options.escape_char == SSH_ESCAPECHAR_NONE ?
-	    0xffffffff : (u_int)options.escape_char);
-	buffer_put_cstring(&m, term == NULL ? "" : term);
-	buffer_put_string(&m, buffer_ptr(&command), buffer_len(&command));
-
+	if ((term = getenv("TERM")) == NULL)
+		term = "";
+	echar = 0xffffffff;
+	if (options.escape_char != SSH_ESCAPECHAR_NONE)
+	    echar = (u_int)options.escape_char;
+
+	if ((m = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new", __func__);
+	if ((r = sshbuf_put_u32(m, MUX_C_NEW_SESSION)) != 0 ||
+	    (r = sshbuf_put_u32(m, muxclient_request_id)) != 0 ||
+	    (r = sshbuf_put_string(m, NULL, 0)) != 0 || /* reserved */
+	    (r = sshbuf_put_u32(m, tty_flag)) != 0 ||
+	    (r = sshbuf_put_u32(m, options.forward_x11)) != 0 ||
+	    (r = sshbuf_put_u32(m, options.forward_agent)) != 0 ||
+	    (r = sshbuf_put_u32(m, subsystem_flag)) != 0 ||
+	    (r = sshbuf_put_u32(m, echar)) != 0 ||
+	    (r = sshbuf_put_cstring(m, term)) != 0 ||
+	    (r = sshbuf_put_stringb(m, command)) != 0)
+		fatal("%s: request: %s", __func__, ssh_err(r));
+
+	/* Pass environment */
 	if (options.num_send_env > 0 && environ != NULL) {
-		/* Pass environment */
 		for (i = 0; environ[i] != NULL; i++) {
-			if (env_permitted(environ[i])) {
-				buffer_put_cstring(&m, environ[i]);
-			}
+			if (!env_permitted(environ[i]))
+				continue;
+			if ((r = sshbuf_put_cstring(m, environ[i])) != 0)
+				fatal("%s: request: %s", __func__, ssh_err(r));
 		}
 	}
+	for (i = 0; i < options.num_setenv; i++) {
+		if ((r = sshbuf_put_cstring(m, options.setenv[i])) != 0)
+			fatal("%s: request: %s", __func__, ssh_err(r));
+	}
 
-	if (mux_client_write_packet(fd, &m) != 0)
+	if (mux_client_write_packet(fd, m) != 0)
 		fatal("%s: write packet: %s", __func__, strerror(errno));
 
 	/* Send the stdio file descriptors */
@@ -1837,45 +1968,55 @@ mux_client_request_session(int fd)
 	debug3("%s: session request sent", __func__);
 
 	/* Read their reply */
-	buffer_clear(&m);
-	if (mux_client_read_packet(fd, &m) != 0) {
+	sshbuf_reset(m);
+	if (mux_client_read_packet(fd, m) != 0) {
 		error("%s: read from master failed: %s",
 		    __func__, strerror(errno));
-		buffer_free(&m);
+		sshbuf_free(m);
 		return -1;
 	}
 
-	type = buffer_get_int(&m);
-	if ((rid = buffer_get_int(&m)) != muxclient_request_id)
+	if ((r = sshbuf_get_u32(m, &type)) != 0 ||
+	    (r = sshbuf_get_u32(m, &rid)) != 0)
+		fatal("%s: decode: %s", __func__, ssh_err(r));
+	if (rid != muxclient_request_id)
 		fatal("%s: out of sequence reply: my id %u theirs %u",
 		    __func__, muxclient_request_id, rid);
+
 	switch (type) {
 	case MUX_S_SESSION_OPENED:
-		sid = buffer_get_int(&m);
+		if ((r = sshbuf_get_u32(m, &sid)) != 0)
+			fatal("%s: decode ID: %s", __func__, ssh_err(r));
 		debug("%s: master session id: %u", __func__, sid);
 		break;
 	case MUX_S_PERMISSION_DENIED:
-		e = buffer_get_string(&m, NULL);
-		buffer_free(&m);
+		if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0)
+			fatal("%s: decode error: %s", __func__, ssh_err(r));
 		error("Master refused session request: %s", e);
+		sshbuf_free(m);
 		return -1;
 	case MUX_S_FAILURE:
-		e = buffer_get_string(&m, NULL);
-		buffer_free(&m);
+		if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0)
+			fatal("%s: decode error: %s", __func__, ssh_err(r));
 		error("%s: session request failed: %s", __func__, e);
+		sshbuf_free(m);
 		return -1;
 	default:
-		buffer_free(&m);
+		sshbuf_free(m);
 		error("%s: unexpected response from master 0x%08x",
 		    __func__, type);
 		return -1;
 	}
 	muxclient_request_id++;
 
-	signal(SIGHUP, control_client_sighandler);
-	signal(SIGINT, control_client_sighandler);
-	signal(SIGTERM, control_client_sighandler);
-	signal(SIGWINCH, control_client_sigrelay);
+	if (pledge("stdio proc tty", NULL) == -1)
+		fatal("%s pledge(): %s", __func__, strerror(errno));
+	platform_pledge_mux();
+
+	ssh_signal(SIGHUP, control_client_sighandler);
+	ssh_signal(SIGINT, control_client_sighandler);
+	ssh_signal(SIGTERM, control_client_sighandler);
+	ssh_signal(SIGWINCH, control_client_sigrelay);
 
 	rawmode = tty_flag;
 	if (tty_flag)
@@ -1889,13 +2030,17 @@ mux_client_request_session(int fd)
 	 * terminate early too (possibly losing data).
 	 */
 	for (exitval = 255, exitval_seen = 0;;) {
-		buffer_clear(&m);
-		if (mux_client_read_packet(fd, &m) != 0)
+		sshbuf_reset(m);
+		if (mux_client_read_packet(fd, m) != 0)
 			break;
-		type = buffer_get_int(&m);
+		if ((r = sshbuf_get_u32(m, &type)) != 0)
+			fatal("%s: decode type: %s", __func__, ssh_err(r));
 		switch (type) {
 		case MUX_S_TTY_ALLOC_FAIL:
-			if ((esid = buffer_get_int(&m)) != sid)
+			if ((r = sshbuf_get_u32(m, &esid)) != 0)
+				fatal("%s: decode ID: %s",
+				    __func__, ssh_err(r));
+			if (esid != sid)
 				fatal("%s: tty alloc fail on unknown session: "
 				    "my id %u theirs %u",
 				    __func__, sid, esid);
@@ -1904,17 +2049,24 @@ mux_client_request_session(int fd)
 			rawmode = 0;
 			continue;
 		case MUX_S_EXIT_MESSAGE:
-			if ((esid = buffer_get_int(&m)) != sid)
+			if ((r = sshbuf_get_u32(m, &esid)) != 0)
+				fatal("%s: decode ID: %s",
+				    __func__, ssh_err(r));
+			if (esid != sid)
 				fatal("%s: exit on unknown session: "
 				    "my id %u theirs %u",
 				    __func__, sid, esid);
 			if (exitval_seen)
 				fatal("%s: exitval sent twice", __func__);
-			exitval = buffer_get_int(&m);
+			if ((r = sshbuf_get_u32(m, &exitval)) != 0)
+				fatal("%s: decode exit value: %s",
+				    __func__, ssh_err(r));
 			exitval_seen = 1;
 			continue;
 		default:
-			e = buffer_get_string(&m, NULL);
+			if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0)
+				fatal("%s: decode error: %s",
+				    __func__, ssh_err(r));
 			fatal("%s: master returned error: %s", __func__, e);
 		}
 	}
@@ -1924,7 +2076,7 @@ mux_client_request_session(int fd)
 		leave_raw_mode(options.request_tty == REQUEST_TTY_FORCE);
 
 	if (muxclient_terminate) {
-		debug2("Exiting on signal %d", muxclient_terminate);
+		debug2("Exiting on signal: %s", strsignal(muxclient_terminate));
 		exitval = 255;
 	} else if (!exitval_seen) {
 		debug2("Control master terminated unexpectedly");
@@ -1939,12 +2091,53 @@ mux_client_request_session(int fd)
 }
 
 static int
+mux_client_proxy(int fd)
+{
+	struct sshbuf *m;
+	char *e;
+	u_int type, rid;
+	int r;
+
+	if ((m = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new", __func__);
+	if ((r = sshbuf_put_u32(m, MUX_C_PROXY)) != 0 ||
+	    (r = sshbuf_put_u32(m, muxclient_request_id)) != 0)
+		fatal("%s: request: %s", __func__, ssh_err(r));
+	if (mux_client_write_packet(fd, m) != 0)
+		fatal("%s: write packet: %s", __func__, strerror(errno));
+
+	sshbuf_reset(m);
+
+	/* Read their reply */
+	if (mux_client_read_packet(fd, m) != 0) {
+		sshbuf_free(m);
+		return 0;
+	}
+	if ((r = sshbuf_get_u32(m, &type)) != 0 ||
+	    (r = sshbuf_get_u32(m, &rid)) != 0)
+		fatal("%s: decode: %s", __func__, ssh_err(r));
+	if (rid != muxclient_request_id)
+		fatal("%s: out of sequence reply: my id %u theirs %u",
+		    __func__, muxclient_request_id, rid);
+	if (type != MUX_S_PROXY) {
+		if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0)
+			fatal("%s: decode error: %s", __func__, ssh_err(r));
+		fatal("%s: master returned error: %s", __func__, e);
+	}
+	sshbuf_free(m);
+
+	debug3("%s: done", __func__);
+	muxclient_request_id++;
+	return 0;
+}
+
+static int
 mux_client_request_stdio_fwd(int fd)
 {
-	Buffer m;
+	struct sshbuf *m;
 	char *e;
 	u_int type, rid, sid;
-	int devnull;
+	int r, devnull;
 
 	debug3("%s: entering", __func__);
 
@@ -1953,7 +2146,7 @@ mux_client_request_stdio_fwd(int fd)
 		return -1;
 	}
 
-	signal(SIGPIPE, SIG_IGN);
+	ssh_signal(SIGPIPE, SIG_IGN);
 
 	if (stdin_null_flag) {
 		if ((devnull = open(_PATH_DEVNULL, O_RDONLY)) == -1)
@@ -1964,14 +2157,16 @@ mux_client_request_stdio_fwd(int fd)
 			close(devnull);
 	}
 
-	buffer_init(&m);
-	buffer_put_int(&m, MUX_C_NEW_STDIO_FWD);
-	buffer_put_int(&m, muxclient_request_id);
-	buffer_put_cstring(&m, ""); /* reserved */
-	buffer_put_cstring(&m, stdio_forward_host);
-	buffer_put_int(&m, stdio_forward_port);
+	if ((m = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new", __func__);
+	if ((r = sshbuf_put_u32(m, MUX_C_NEW_STDIO_FWD)) != 0 ||
+	    (r = sshbuf_put_u32(m, muxclient_request_id)) != 0 ||
+	    (r = sshbuf_put_string(m, NULL, 0)) != 0 || /* reserved */
+	    (r = sshbuf_put_cstring(m, options.stdio_forward_host)) != 0 ||
+	    (r = sshbuf_put_u32(m, options.stdio_forward_port)) != 0)
+		fatal("%s: request: %s", __func__, ssh_err(r));
 
-	if (mux_client_write_packet(fd, &m) != 0)
+	if (mux_client_write_packet(fd, m) != 0)
 		fatal("%s: write packet: %s", __func__, strerror(errno));
 
 	/* Send the stdio file descriptors */
@@ -1979,53 +2174,62 @@ mux_client_request_stdio_fwd(int fd)
 	    mm_send_fd(fd, STDOUT_FILENO) == -1)
 		fatal("%s: send fds failed", __func__);
 
+	if (pledge("stdio proc tty", NULL) == -1)
+		fatal("%s pledge(): %s", __func__, strerror(errno));
+	platform_pledge_mux();
+
 	debug3("%s: stdio forward request sent", __func__);
 
 	/* Read their reply */
-	buffer_clear(&m);
+	sshbuf_reset(m);
 
-	if (mux_client_read_packet(fd, &m) != 0) {
+	if (mux_client_read_packet(fd, m) != 0) {
 		error("%s: read from master failed: %s",
 		    __func__, strerror(errno));
-		buffer_free(&m);
+		sshbuf_free(m);
 		return -1;
 	}
 
-	type = buffer_get_int(&m);
-	if ((rid = buffer_get_int(&m)) != muxclient_request_id)
+	if ((r = sshbuf_get_u32(m, &type)) != 0 ||
+	    (r = sshbuf_get_u32(m, &rid)) != 0)
+		fatal("%s: decode: %s", __func__, ssh_err(r));
+	if (rid != muxclient_request_id)
 		fatal("%s: out of sequence reply: my id %u theirs %u",
 		    __func__, muxclient_request_id, rid);
 	switch (type) {
 	case MUX_S_SESSION_OPENED:
-		sid = buffer_get_int(&m);
+		if ((r = sshbuf_get_u32(m, &sid)) != 0)
+			fatal("%s: decode ID: %s", __func__, ssh_err(r));
 		debug("%s: master session id: %u", __func__, sid);
 		break;
 	case MUX_S_PERMISSION_DENIED:
-		e = buffer_get_string(&m, NULL);
-		buffer_free(&m);
+		if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0)
+			fatal("%s: decode error: %s", __func__, ssh_err(r));
+		sshbuf_free(m);
 		fatal("Master refused stdio forwarding request: %s", e);
 	case MUX_S_FAILURE:
-		e = buffer_get_string(&m, NULL);
-		buffer_free(&m);
+		if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0)
+			fatal("%s: decode error: %s", __func__, ssh_err(r));
+		sshbuf_free(m);
 		fatal("Stdio forwarding request failed: %s", e);
 	default:
-		buffer_free(&m);
+		sshbuf_free(m);
 		error("%s: unexpected response from master 0x%08x",
 		    __func__, type);
 		return -1;
 	}
 	muxclient_request_id++;
 
-	signal(SIGHUP, control_client_sighandler);
-	signal(SIGINT, control_client_sighandler);
-	signal(SIGTERM, control_client_sighandler);
-	signal(SIGWINCH, control_client_sigrelay);
+	ssh_signal(SIGHUP, control_client_sighandler);
+	ssh_signal(SIGINT, control_client_sighandler);
+	ssh_signal(SIGTERM, control_client_sighandler);
+	ssh_signal(SIGWINCH, control_client_sigrelay);
 
 	/*
 	 * Stick around until the controlee closes the client_fd.
 	 */
-	buffer_clear(&m);
-	if (mux_client_read_packet(fd, &m) != 0) {
+	sshbuf_reset(m);
+	if (mux_client_read_packet(fd, m) != 0) {
 		if (errno == EPIPE ||
 		    (errno == EINTR && muxclient_terminate != 0))
 			return 0;
@@ -2038,58 +2242,65 @@ mux_client_request_stdio_fwd(int fd)
 static void
 mux_client_request_stop_listening(int fd)
 {
-	Buffer m;
+	struct sshbuf *m;
 	char *e;
 	u_int type, rid;
+	int r;
 
 	debug3("%s: entering", __func__);
 
-	buffer_init(&m);
-	buffer_put_int(&m, MUX_C_STOP_LISTENING);
-	buffer_put_int(&m, muxclient_request_id);
+	if ((m = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new", __func__);
+	if ((r = sshbuf_put_u32(m, MUX_C_STOP_LISTENING)) != 0 ||
+	    (r = sshbuf_put_u32(m, muxclient_request_id)) != 0)
+		fatal("%s: request: %s", __func__, ssh_err(r));
 
-	if (mux_client_write_packet(fd, &m) != 0)
+	if (mux_client_write_packet(fd, m) != 0)
 		fatal("%s: write packet: %s", __func__, strerror(errno));
 
-	buffer_clear(&m);
+	sshbuf_reset(m);
 
 	/* Read their reply */
-	if (mux_client_read_packet(fd, &m) != 0)
+	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)
+	if ((r = sshbuf_get_u32(m, &type)) != 0 ||
+	    (r = sshbuf_get_u32(m, &rid)) != 0)
+		fatal("%s: decode: %s", __func__, ssh_err(r));
+	if (rid != 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);
+		if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0)
+			fatal("%s: decode error: %s", __func__, ssh_err(r));
 		fatal("Master refused stop listening request: %s", e);
 	case MUX_S_FAILURE:
-		e = buffer_get_string(&m, NULL);
+		if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0)
+			fatal("%s: decode error: %s", __func__, ssh_err(r));
 		fatal("%s: stop listening request failed: %s", __func__, e);
 	default:
 		fatal("%s: unexpected response from master 0x%08x",
 		    __func__, type);
 	}
-	buffer_free(&m);
+	sshbuf_free(m);
 	muxclient_request_id++;
 }
 
 /* Multiplex client main loop. */
-void
+int
 muxclient(const char *path)
 {
 	struct sockaddr_un addr;
-	socklen_t sun_len;
 	int sock;
 	u_int pid;
 
 	if (muxclient_command == 0) {
-		if (stdio_forward_host != NULL)
+		if (options.stdio_forward_host != NULL)
 			muxclient_command = SSHMUX_COMMAND_STDIO_FWD;
 		else
 			muxclient_command = SSHMUX_COMMAND_OPEN;
@@ -2103,22 +2314,21 @@ muxclient(const char *path)
 	case SSHCTL_MASTER_NO:
 		break;
 	default:
-		return;
+		return -1;
 	}
 
 	memset(&addr, '\0', sizeof(addr));
 	addr.sun_family = AF_UNIX;
-	sun_len = offsetof(struct sockaddr_un, sun_path) +
-	    strlen(path) + 1;
 
 	if (strlcpy(addr.sun_path, path,
 	    sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
-		fatal("ControlPath too long");
+		fatal("ControlPath too long ('%s' >= %u bytes)", path,
+		     (unsigned int)sizeof(addr.sun_path));
 
-	if ((sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
+	if ((sock = socket(PF_UNIX, SOCK_STREAM, 0)) == -1)
 		fatal("%s socket(): %s", __func__, strerror(errno));
 
-	if (connect(sock, (struct sockaddr *)&addr, sun_len) == -1) {
+	if (connect(sock, (struct sockaddr *)&addr, sizeof(addr)) == -1) {
 		switch (muxclient_command) {
 		case SSHMUX_COMMAND_OPEN:
 		case SSHMUX_COMMAND_STDIO_FWD:
@@ -2138,25 +2348,26 @@ muxclient(const char *path)
 			    strerror(errno));
 		}
 		close(sock);
-		return;
+		return -1;
 	}
 	set_nonblock(sock);
 
 	if (mux_client_hello_exchange(sock) != 0) {
 		error("%s: master hello exchange failed", __func__);
 		close(sock);
-		return;
+		return -1;
 	}
 
 	switch (muxclient_command) {
 	case SSHMUX_COMMAND_ALIVE_CHECK:
 		if ((pid = mux_client_request_alive(sock)) == 0)
 			fatal("%s: master alive check failed", __func__);
-		fprintf(stderr, "Master running (pid=%d)\r\n", pid);
+		fprintf(stderr, "Master running (pid=%u)\r\n", pid);
 		exit(0);
 	case SSHMUX_COMMAND_TERMINATE:
 		mux_client_request_terminate(sock);
-		fprintf(stderr, "Exit request sent.\r\n");
+		if (options.log_level != SYSLOG_LEVEL_QUIET)
+			fprintf(stderr, "Exit request sent.\r\n");
 		exit(0);
 	case SSHMUX_COMMAND_FORWARD:
 		if (mux_client_forwards(sock, 0) != 0)
@@ -2165,22 +2376,26 @@ muxclient(const char *path)
 	case SSHMUX_COMMAND_OPEN:
 		if (mux_client_forwards(sock, 0) != 0) {
 			error("%s: master forward request failed", __func__);
-			return;
+			return -1;
 		}
 		mux_client_request_session(sock);
-		return;
+		return -1;
 	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");
+		if (options.log_level != SYSLOG_LEVEL_QUIET)
+			fprintf(stderr, "Stop listening request sent.\r\n");
 		exit(0);
 	case SSHMUX_COMMAND_CANCEL_FWD:
 		if (mux_client_forwards(sock, 1) != 0)
 			error("%s: master cancel forward request failed",
 			    __func__);
 		exit(0);
+	case SSHMUX_COMMAND_PROXY:
+		mux_client_proxy(sock);
+		return (sock);
 	default:
 		fatal("unrecognised muxclient_command %d", muxclient_command);
 	}