upstream: client: switch mux to sshbuf API; with & ok djm@

OpenBSD-Commit-ID: 5948fb98d704f9c4e075b92edda64e0290b5feb2

1 files changed, 507 insertions, 414 deletions

diff --git a/mux.c b/mux.c
index 474d610a3..95d74b62e 100644
--- a/mux.c
+++ b/mux.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: mux.c,v 1.72 2018/07/09 21:03:30 markus Exp $ */
+/* $OpenBSD: mux.c,v 1.73 2018/07/09 21:18:10 markus Exp $ */
 /*
  * Copyright (c) 2002-2008 Damien Miller <djm@openbsd.org>
  *
@@ -70,7 +70,7 @@
 #include "pathnames.h"
 #include "misc.h"
 #include "match.h"
-#include "buffer.h"
+#include "sshbuf.h"
 #include "channels.h"
 #include "msg.h"
 #include "packet.h"
@@ -96,7 +96,7 @@ 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;
@@ -279,10 +279,11 @@ env_permitted(char *env)
 
 static int
 process_mux_master_hello(struct ssh *ssh, u_int rid,
-    Channel *c, Buffer *m, Buffer *r)
+    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);
@@ -290,9 +291,8 @@ process_mux_master_hello(struct ssh *ssh, u_int rid,
                 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) {
@@ -303,51 +303,72 @@ process_mux_master_hello(struct ssh *ssh, u_int rid,
         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);
+        while (sshbuf_len(m) > 0) {
+                char *name = NULL;
 
-                if (name == NULL || value == NULL) {
-                        free(name);
-                        free(value);
-                        goto malf;
+                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));
+                        return -1;
                 }
                 debug2("Unrecognised slave extension \"%s\"", name);
                 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(struct ssh *ssh, u_int rid,
-    Channel *c, Buffer *m, Buffer *r)
+    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);
@@ -356,12 +377,10 @@ process_mux_new_session(struct ssh *ssh, u_int rid,
                 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);
@@ -383,8 +402,10 @@ process_mux_new_session(struct ssh *ssh, u_int rid,
             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;
 
@@ -399,13 +420,9 @@ process_mux_new_session(struct ssh *ssh, u_int rid,
                                 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;
                 }
@@ -417,10 +434,8 @@ process_mux_new_session(struct ssh *ssh, u_int rid,
         /* XXX support multiple child sessions in future */
         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]);
@@ -431,7 +446,7 @@ process_mux_new_session(struct ssh *ssh, u_int rid,
                                 free(cctx->env[i]);
                         free(cctx->env);
                 }
-                buffer_free(&cctx->cmd);
+                sshbuf_free(cctx->cmd);
                 free(cctx);
                 return 0;
         }
@@ -440,10 +455,8 @@ process_mux_new_session(struct ssh *ssh, u_int rid,
             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;
                 }
         }
@@ -497,21 +510,24 @@ process_mux_new_session(struct ssh *ssh, u_int rid,
 
 static int
 process_mux_alive_check(struct ssh *ssh, u_int rid,
-    Channel *c, Buffer *m, Buffer *r)
+    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(struct ssh *ssh, u_int rid,
-    Channel *c, Buffer *m, Buffer *r)
+    Channel *c, struct sshbuf *m, struct sshbuf *reply)
 {
         debug2("%s: channel %d: terminate request", __func__, c->self);
 
@@ -520,16 +536,14 @@ process_mux_terminate(struct ssh *ssh, u_int rid,
                 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;
 }
@@ -606,14 +620,16 @@ mux_confirm_remote_forward(struct ssh *ssh, int type, u_int32_t seq, void *ctxt)
         char *failmsg = NULL;
         struct Forward *rfwd;
         Channel *c;
-        Buffer out;
+        struct sshbuf *out;
+        int r;
 
         if ((c = channel_by_id(ssh, fctx->cid)) == NULL) {
                 /* no channel for reply */
                 error("%s: unknown channel", __func__);
                 return;
         }
-        buffer_init(&out);
+        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)) {
@@ -631,14 +647,16 @@ mux_confirm_remote_forward(struct ssh *ssh, int type, u_int32_t seq, void *ctxt)
                         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);
+                        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 {
@@ -664,13 +682,12 @@ mux_confirm_remote_forward(struct ssh *ssh, int type, u_int32_t seq, void *ctxt)
         }
  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 */
@@ -678,23 +695,23 @@ mux_confirm_remote_forward(struct ssh *ssh, int type, u_int32_t seq, void *ctxt)
 
 static int
 process_mux_open_fwd(struct ssh *ssh, u_int rid,
-    Channel *c, Buffer *m, Buffer *r)
+    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__);
@@ -731,9 +748,8 @@ process_mux_open_fwd(struct ssh *ssh, u_int rid,
  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) {
@@ -770,26 +786,25 @@ process_mux_open_fwd(struct ssh *ssh, u_int rid,
  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;
         }
@@ -798,9 +813,8 @@ process_mux_open_fwd(struct ssh *ssh, u_int rid,
             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;
                 }
         }
@@ -810,9 +824,8 @@ process_mux_open_fwd(struct ssh *ssh, u_int rid,
                     &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");
+                        reply_error(reply, MUX_S_FAILURE, rid,
+                            "Port forwarding failed");
                         goto out;
                 }
                 add_local_forward(&options, &fwd);
@@ -835,8 +848,7 @@ process_mux_open_fwd(struct ssh *ssh, u_int rid,
                 /* 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) {
@@ -850,23 +862,23 @@ process_mux_open_fwd(struct ssh *ssh, u_int rid,
 
 static int
 process_mux_close_fwd(struct ssh *ssh, u_int rid,
-    Channel *c, Buffer *m, Buffer *r)
+    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;
 
         memset(&fwd, 0, sizeof(fwd));
 
-        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__);
@@ -940,10 +952,10 @@ process_mux_close_fwd(struct ssh *ssh, u_int rid,
                         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);
@@ -951,10 +963,6 @@ process_mux_close_fwd(struct ssh *ssh, u_int rid,
                 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);
@@ -966,24 +974,21 @@ process_mux_close_fwd(struct ssh *ssh, u_int rid,
 
 static int
 process_mux_stdio_fwd(struct ssh *ssh, u_int rid,
-    Channel *c, Buffer *m, Buffer *r)
+    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);
@@ -998,9 +1003,7 @@ process_mux_stdio_fwd(struct ssh *ssh, u_int rid,
                         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;
                 }
@@ -1012,10 +1015,8 @@ process_mux_stdio_fwd(struct ssh *ssh, u_int rid,
         /* XXX support multiple child sessions in future */
         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]);
@@ -1028,10 +1029,8 @@ process_mux_stdio_fwd(struct ssh *ssh, u_int rid,
                 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;
                 }
         }
@@ -1069,7 +1068,8 @@ 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__);
@@ -1078,28 +1078,29 @@ mux_stdio_confirm(struct ssh *ssh, int id, int success, void *arg)
         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);
@@ -1110,7 +1111,7 @@ mux_stdio_confirm(struct ssh *ssh, int id, int success, void *arg)
 
 static int
 process_mux_stop_listening(struct ssh *ssh, u_int rid,
-    Channel *c, Buffer *m, Buffer *r)
+    Channel *c, struct sshbuf *m, struct sshbuf *reply)
 {
         debug("%s: channel %d: stop listening", __func__, c->self);
 
@@ -1119,9 +1120,8 @@ process_mux_stop_listening(struct ssh *ssh, u_int rid,
                 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;
                 }
         }
@@ -1135,22 +1135,22 @@ process_mux_stop_listening(struct ssh *ssh, u_int rid,
                 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
 process_mux_proxy(struct ssh *ssh, u_int rid,
-    Channel *c, Buffer *m, Buffer *r)
+    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;
-        buffer_put_int(r, MUX_S_PROXY);
-        buffer_put_int(r, rid);
+        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;
 }
@@ -1160,10 +1160,12 @@ static int
 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) {
@@ -1173,32 +1175,29 @@ mux_master_read_cb(struct ssh *ssh, Channel *c)
                     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;
@@ -1208,40 +1207,40 @@ mux_master_read_cb(struct ssh *ssh, 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(ssh, rid,
-                            c, &in, &out);
+                            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(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);
@@ -1251,20 +1250,22 @@ mux_exit_message(struct ssh *ssh, Channel *c, int exitval)
                     __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(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);
 
@@ -1273,12 +1274,13 @@ mux_tty_alloc_failed(struct ssh *ssh, Channel *c)
                     __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. */
@@ -1372,8 +1374,8 @@ 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__);
@@ -1382,14 +1384,13 @@ mux_session_confirm(struct ssh *ssh, int id, int success, void *arg)
         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;
         }
 
@@ -1419,25 +1420,26 @@ mux_session_confirm(struct ssh *ssh, int id, int success, void *arg)
         }
 
         client_session2_setup(ssh, id, cctx->want_tty, cctx->want_subsys,
-            cctx->term, &cctx->tio, c->rfd, &cctx->cmd, cctx->env);
+            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++)
@@ -1472,16 +1474,18 @@ 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;
@@ -1506,31 +1510,33 @@ 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;
                 }
@@ -1547,85 +1553,91 @@ 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 ret = -1;
+        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) {
+        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) {
+        if (mux_client_read_packet(fd, m) != 0) {
                 debug("%s: read packet failed", __func__);
                 goto out;
         }
 
-        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_MSG_HELLO) {
                 error("%s: expected HELLO (%u) received %u",
                     __func__, MUX_MSG_HELLO, type);
                 goto out;
         }
-        ver = buffer_get_int(&m);
+        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);
@@ -1633,56 +1645,68 @@ mux_client_hello_exchange(int fd)
         }
         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);
         }
         /* success */
         ret = 0;
  out:
-        buffer_free(&m);
+        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);
 
@@ -1694,107 +1718,128 @@ 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);
+                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 : "",
@@ -1803,20 +1848,22 @@ mux_client_forward(int fd, int cancel_flag, u_int ftype, struct Forward *fwd)
                         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;
@@ -1850,11 +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 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 i, devnull, rawmode;
+        int r, i, devnull, rawmode;
 
         debug3("%s: entering", __func__);
 
@@ -1874,33 +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) {
                 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++)
-                buffer_put_cstring(&m, options.setenv[i]);
+        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 */
@@ -1912,35 +1968,40 @@ 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);
-                debug("%s: master session id: %u", __func__, sid);
+                if ((r = sshbuf_get_u32(m, &sid)) != 0)
+                        fatal("%s: decode ID: %s", __func__, ssh_err(r));
                 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;
@@ -1968,13 +2029,17 @@ 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);
@@ -1983,17 +2048,24 @@ 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);
                 }
         }
@@ -2020,32 +2092,38 @@ mux_client_request_session(int fd)
 static int
 mux_client_proxy(int fd)
 {
-        Buffer m;
+        struct sshbuf *m;
         char *e;
         u_int type, rid;
-
-        buffer_init(&m);
-        buffer_put_int(&m, MUX_C_PROXY);
-        buffer_put_int(&m, muxclient_request_id);
-        if (mux_client_write_packet(fd, &m) != 0)
+        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));
 
-        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 ||
+            (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) {
-                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)
-                fatal("%s: out of sequence reply: my id %u theirs %u",
-                    __func__, muxclient_request_id, rid);
-        buffer_free(&m);
+        sshbuf_free(m);
 
         debug3("%s: done", __func__);
         muxclient_request_id++;
@@ -2055,10 +2133,10 @@ mux_client_proxy(int fd)
 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__);
 
@@ -2078,14 +2156,16 @@ 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, options.stdio_forward_host);
-        buffer_put_int(&m, options.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 */
@@ -2100,34 +2180,39 @@ mux_client_request_stdio_fwd(int fd)
         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;
@@ -2142,8 +2227,8 @@ mux_client_request_stdio_fwd(int fd)
         /*
          * 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;
@@ -2156,44 +2241,52 @@ 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++;
 }