upstream: sshd: switch monitor to sshbuf API; lots of help & ok

djm@

OpenBSD-Commit-ID: d89bd02d33974fd35ca0b8940d88572227b34a48

3 files changed, 566 insertions, 421 deletions

diff --git a/monitor.c b/monitor.c
index 11f96b72d..bf83f3b56 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor.c,v 1.182 2018/07/09 21:35:50 markus Exp $ */
+/* $OpenBSD: monitor.c,v 1.183 2018/07/09 21:53:45 markus Exp $ */
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
  * Copyright 2002 Markus Friedl <markus@openbsd.org>
@@ -69,7 +69,7 @@
 #include "xmalloc.h"
 #include "ssh.h"
 #include "key.h"
-#include "buffer.h"
+#include "sshbuf.h"
 #include "hostfile.h"
 #include "auth.h"
 #include "cipher.h"
@@ -121,46 +121,46 @@ static struct sshbuf *child_state;
 
 /* Functions on the monitor that answer unprivileged requests */
 
-int mm_answer_moduli(int, Buffer *);
-int mm_answer_sign(int, Buffer *);
-int mm_answer_pwnamallow(int, Buffer *);
-int mm_answer_auth2_read_banner(int, Buffer *);
-int mm_answer_authserv(int, Buffer *);
-int mm_answer_authpassword(int, Buffer *);
-int mm_answer_bsdauthquery(int, Buffer *);
-int mm_answer_bsdauthrespond(int, Buffer *);
-int mm_answer_skeyquery(int, Buffer *);
-int mm_answer_skeyrespond(int, Buffer *);
-int mm_answer_keyallowed(int, Buffer *);
-int mm_answer_keyverify(int, Buffer *);
-int mm_answer_pty(int, Buffer *);
-int mm_answer_pty_cleanup(int, Buffer *);
-int mm_answer_term(int, Buffer *);
-int mm_answer_rsa_keyallowed(int, Buffer *);
-int mm_answer_rsa_challenge(int, Buffer *);
-int mm_answer_rsa_response(int, Buffer *);
-int mm_answer_sesskey(int, Buffer *);
-int mm_answer_sessid(int, Buffer *);
+int mm_answer_moduli(int, struct sshbuf *);
+int mm_answer_sign(int, struct sshbuf *);
+int mm_answer_pwnamallow(int, struct sshbuf *);
+int mm_answer_auth2_read_banner(int, struct sshbuf *);
+int mm_answer_authserv(int, struct sshbuf *);
+int mm_answer_authpassword(int, struct sshbuf *);
+int mm_answer_bsdauthquery(int, struct sshbuf *);
+int mm_answer_bsdauthrespond(int, struct sshbuf *);
+int mm_answer_skeyquery(int, struct sshbuf *);
+int mm_answer_skeyrespond(int, struct sshbuf *);
+int mm_answer_keyallowed(int, struct sshbuf *);
+int mm_answer_keyverify(int, struct sshbuf *);
+int mm_answer_pty(int, struct sshbuf *);
+int mm_answer_pty_cleanup(int, struct sshbuf *);
+int mm_answer_term(int, struct sshbuf *);
+int mm_answer_rsa_keyallowed(int, struct sshbuf *);
+int mm_answer_rsa_challenge(int, struct sshbuf *);
+int mm_answer_rsa_response(int, struct sshbuf *);
+int mm_answer_sesskey(int, struct sshbuf *);
+int mm_answer_sessid(int, struct sshbuf *);
 
 #ifdef USE_PAM
-int mm_answer_pam_start(int, Buffer *);
-int mm_answer_pam_account(int, Buffer *);
-int mm_answer_pam_init_ctx(int, Buffer *);
-int mm_answer_pam_query(int, Buffer *);
-int mm_answer_pam_respond(int, Buffer *);
-int mm_answer_pam_free_ctx(int, Buffer *);
+int mm_answer_pam_start(int, struct sshbuf *);
+int mm_answer_pam_account(int, struct sshbuf *);
+int mm_answer_pam_init_ctx(int, struct sshbuf *);
+int mm_answer_pam_query(int, struct sshbuf *);
+int mm_answer_pam_respond(int, struct sshbuf *);
+int mm_answer_pam_free_ctx(int, struct sshbuf *);
 #endif
 
 #ifdef GSSAPI
-int mm_answer_gss_setup_ctx(int, Buffer *);
-int mm_answer_gss_accept_ctx(int, Buffer *);
-int mm_answer_gss_userok(int, Buffer *);
-int mm_answer_gss_checkmic(int, Buffer *);
+int mm_answer_gss_setup_ctx(int, struct sshbuf *);
+int mm_answer_gss_accept_ctx(int, struct sshbuf *);
+int mm_answer_gss_userok(int, struct sshbuf *);
+int mm_answer_gss_checkmic(int, struct sshbuf *);
 #endif
 
 #ifdef SSH_AUDIT_EVENTS
-int mm_answer_audit_event(int, Buffer *);
-int mm_answer_audit_command(int, Buffer *);
+int mm_answer_audit_event(int, struct sshbuf *);
+int mm_answer_audit_command(int, struct sshbuf *);
 #endif
 
 static int monitor_read_log(struct monitor *);
@@ -169,7 +169,7 @@ static Authctxt *authctxt;
 
 /* local state for key verify */
 static u_char *key_blob = NULL;
-static u_int key_bloblen = 0;
+static size_t key_bloblen = 0;
 static int key_blobtype = MM_NOKEY;
 static struct sshauthopt *key_opts = NULL;
 static char *hostbased_cuser = NULL;
@@ -183,7 +183,7 @@ static pid_t monitor_child_pid;
 struct mon_table {
         enum monitor_reqtype type;
         int flags;
-        int (*f)(int, Buffer *);
+        int (*f)(int, struct sshbuf *);
 };
 
 #define MON_ISAUTH      0x0004  /* Required for Authentication */
@@ -426,18 +426,21 @@ monitor_child_postauth(struct monitor *pmonitor)
 static int
 monitor_read_log(struct monitor *pmonitor)
 {
-        Buffer logmsg;
+        struct sshbuf *logmsg;
         u_int len, level;
         char *msg;
+        u_char *p;
+        int r;
 
-        buffer_init(&logmsg);
+        if ((logmsg = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new", __func__);
 
         /* Read length */
-        buffer_append_space(&logmsg, 4);
-        if (atomicio(read, pmonitor->m_log_recvfd,
-            buffer_ptr(&logmsg), buffer_len(&logmsg)) != buffer_len(&logmsg)) {
+        if ((r = sshbuf_reserve(logmsg, 4, &p)) != 0)
+                fatal("%s: reserve: %s", __func__, ssh_err(r));
+        if (atomicio(read, pmonitor->m_log_recvfd, p, 4) != 4) {
                 if (errno == EPIPE) {
-                        buffer_free(&logmsg);
+                        sshbuf_free(logmsg);
                         debug("%s: child log fd closed", __func__);
                         close(pmonitor->m_log_recvfd);
                         pmonitor->m_log_recvfd = -1;
@@ -445,26 +448,28 @@ monitor_read_log(struct monitor *pmonitor)
                 }
                 fatal("%s: log fd read: %s", __func__, strerror(errno));
         }
-        len = buffer_get_int(&logmsg);
+        if ((r = sshbuf_get_u32(logmsg, &len)) != 0)
+                fatal("%s: get len: %s", __func__, ssh_err(r));
         if (len <= 4 || len > 8192)
                 fatal("%s: invalid log message length %u", __func__, len);
 
         /* Read severity, message */
-        buffer_clear(&logmsg);
-        buffer_append_space(&logmsg, len);
-        if (atomicio(read, pmonitor->m_log_recvfd,
-            buffer_ptr(&logmsg), buffer_len(&logmsg)) != buffer_len(&logmsg))
+        sshbuf_reset(logmsg);
+        if ((r = sshbuf_reserve(logmsg, len, &p)) != 0)
+                fatal("%s: reserve: %s", __func__, ssh_err(r));
+        if (atomicio(read, pmonitor->m_log_recvfd, p, len) != len)
                 fatal("%s: log fd read: %s", __func__, strerror(errno));
+        if ((r = sshbuf_get_u32(logmsg, &level)) != 0 ||
+            (r = sshbuf_get_cstring(logmsg, &msg, NULL)) != 0)
+                fatal("%s: decode: %s", __func__, ssh_err(r));
 
         /* Log it */
-        level = buffer_get_int(&logmsg);
-        msg = buffer_get_string(&logmsg, NULL);
         if (log_level_name(level) == NULL)
                 fatal("%s: invalid log level %u (corrupted message?)",
                     __func__, level);
         do_log2(level, "%s [preauth]", msg);
 
-        buffer_free(&logmsg);
+        sshbuf_free(logmsg);
         free(msg);
 
         return 0;
@@ -474,8 +479,8 @@ int
 monitor_read(struct monitor *pmonitor, struct mon_table *ent,
     struct mon_table **pent)
 {
-        Buffer m;
-        int ret;
+        struct sshbuf *m;
+        int r, ret;
         u_char type;
         struct pollfd pfd[2];
 
@@ -502,10 +507,12 @@ monitor_read(struct monitor *pmonitor, struct mon_table *ent,
                         break;  /* Continues below */
         }
 
-        buffer_init(&m);
+        if ((m = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new", __func__);
 
-        mm_request_receive(pmonitor->m_sendfd, &m);
-        type = buffer_get_char(&m);
+        mm_request_receive(pmonitor->m_sendfd, m);
+        if ((r = sshbuf_get_u8(m, &type)) != 0)
+                fatal("%s: decode: %s", __func__, ssh_err(r));
 
         debug3("%s: checking request %d", __func__, type);
 
@@ -519,8 +526,8 @@ monitor_read(struct monitor *pmonitor, struct mon_table *ent,
                 if (!(ent->flags & MON_PERMIT))
                         fatal("%s: unpermitted request %d", __func__,
                             type);
-                ret = (*ent->f)(pmonitor->m_sendfd, &m);
-                buffer_free(&m);
+                ret = (*ent->f)(pmonitor->m_sendfd, m);
+                sshbuf_free(m);
 
                 /* The child may use this request only once, disable it */
                 if (ent->flags & MON_ONCE) {
@@ -570,14 +577,16 @@ monitor_reset_key_state(void)
 
 #ifdef WITH_OPENSSL
 int
-mm_answer_moduli(int sock, Buffer *m)
+mm_answer_moduli(int sock, struct sshbuf *m)
 {
         DH *dh;
-        int min, want, max;
+        int r;
+        u_int min, want, max;
 
-        min = buffer_get_int(m);
-        want = buffer_get_int(m);
-        max = buffer_get_int(m);
+        if ((r = sshbuf_get_u32(m, &min)) != 0 ||
+            (r = sshbuf_get_u32(m, &want)) != 0 ||
+            (r = sshbuf_get_u32(m, &max)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
         debug3("%s: got parameters: %d %d %d",
             __func__, min, want, max);
@@ -586,17 +595,19 @@ mm_answer_moduli(int sock, Buffer *m)
                 fatal("%s: bad parameters: %d %d %d",
                     __func__, min, want, max);
 
-        buffer_clear(m);
+        sshbuf_reset(m);
 
         dh = choose_dh(min, want, max);
         if (dh == NULL) {
-                buffer_put_char(m, 0);
+                if ((r = sshbuf_put_u8(m, 0)) != 0)
+                        fatal("%s: buffer error: %s", __func__, ssh_err(r));
                 return (0);
         } else {
                 /* Send first bignum */
-                buffer_put_char(m, 1);
-                buffer_put_bignum2(m, dh->p);
-                buffer_put_bignum2(m, dh->g);
+                if ((r = sshbuf_put_u8(m, 1)) != 0 ||
+                    (r = sshbuf_put_bignum2(m, dh->p)) != 0 ||
+                    (r = sshbuf_put_bignum2(m, dh->g)) != 0)
+                        fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
                 DH_free(dh);
         }
@@ -606,7 +617,7 @@ mm_answer_moduli(int sock, Buffer *m)
 #endif
 
 int
-mm_answer_sign(int sock, Buffer *m)
+mm_answer_sign(int sock, struct sshbuf *m)
 {
         struct ssh *ssh = active_state;         /* XXX */
         extern int auth_sock;                   /* XXX move to state struct? */
@@ -708,12 +719,12 @@ mm_answer_sign(int sock, Buffer *m)
 /* Retrieves the password entry and also checks if the user is permitted */
 
 int
-mm_answer_pwnamallow(int sock, Buffer *m)
+mm_answer_pwnamallow(int sock, struct sshbuf *m)
 {
         struct ssh *ssh = active_state; /* XXX */
         char *username;
         struct passwd *pwent;
-        int allowed = 0;
+        int r, allowed = 0;
         u_int i;
 
         debug3("%s", __func__);
@@ -721,7 +732,8 @@ mm_answer_pwnamallow(int sock, Buffer *m)
         if (authctxt->attempt++ != 0)
                 fatal("%s: multiple attempts for getpwnam", __func__);
 
-        username = buffer_get_string(m, NULL);
+        if ((r = sshbuf_get_cstring(m, &username, NULL)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
         pwent = getpwnamallow(username);
 
@@ -729,10 +741,11 @@ mm_answer_pwnamallow(int sock, Buffer *m)
         setproctitle("%s [priv]", pwent ? username : "unknown");
         free(username);
 
-        buffer_clear(m);
+        sshbuf_reset(m);
 
         if (pwent == NULL) {
-                buffer_put_char(m, 0);
+                if ((r = sshbuf_put_u8(m, 0)) != 0)
+                        fatal("%s: buffer error: %s", __func__, ssh_err(r));
                 authctxt->pw = fakepw();
                 goto out;
         }
@@ -741,31 +754,40 @@ mm_answer_pwnamallow(int sock, Buffer *m)
         authctxt->pw = pwent;
         authctxt->valid = 1;
 
-        buffer_put_char(m, 1);
-        buffer_put_string(m, pwent, sizeof(struct passwd));
-        buffer_put_cstring(m, pwent->pw_name);
-        buffer_put_cstring(m, "*");
+        /* XXX don't sent pwent to unpriv; send fake class/dir/shell too */
+        if ((r = sshbuf_put_u8(m, 1)) != 0 ||
+            (r = sshbuf_put_string(m, pwent, sizeof(*pwent))) != 0 ||
+            (r = sshbuf_put_cstring(m, pwent->pw_name)) != 0 ||
+            (r = sshbuf_put_cstring(m, "*")) != 0 ||
 #ifdef HAVE_STRUCT_PASSWD_PW_GECOS
-        buffer_put_cstring(m, pwent->pw_gecos);
+            (r = sshbuf_put_cstring(m, pwent->pw_gecos)) != 0 ||
 #endif
 #ifdef HAVE_STRUCT_PASSWD_PW_CLASS
-        buffer_put_cstring(m, pwent->pw_class);
+            (r = sshbuf_put_cstring(m, pwent->pw_class)) != 0 ||
 #endif
-        buffer_put_cstring(m, pwent->pw_dir);
-        buffer_put_cstring(m, pwent->pw_shell);
+            (r = sshbuf_put_cstring(m, pwent->pw_dir)) != 0 ||
+            (r = sshbuf_put_cstring(m, pwent->pw_shell)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
  out:
         ssh_packet_set_log_preamble(ssh, "%suser %s",
             authctxt->valid ? "authenticating" : "invalid ", authctxt->user);
-        buffer_put_string(m, &options, sizeof(options));
+        if ((r = sshbuf_put_string(m, &options, sizeof(options))) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
 #define M_CP_STROPT(x) do { \
-                if (options.x != NULL) \
-                        buffer_put_cstring(m, options.x); \
+                if (options.x != NULL) { \
+                        if ((r = sshbuf_put_cstring(m, options.x)) != 0) \
+                                fatal("%s: buffer error: %s", \
+                                    __func__, ssh_err(r)); \
+                } \
         } while (0)
 #define M_CP_STRARRAYOPT(x, nx) do { \
-                for (i = 0; i < options.nx; i++) \
-                        buffer_put_cstring(m, options.x[i]); \
+                for (i = 0; i < options.nx; i++) { \
+                        if ((r = sshbuf_put_cstring(m, options.x[i])) != 0) \
+                                fatal("%s: buffer error: %s", \
+                                    __func__, ssh_err(r)); \
+                } \
         } while (0)
         /* See comment in servconf.h */
         COPY_MATCH_STRING_OPTS();
@@ -797,13 +819,15 @@ mm_answer_pwnamallow(int sock, Buffer *m)
         return (0);
 }
 
-int mm_answer_auth2_read_banner(int sock, Buffer *m)
+int mm_answer_auth2_read_banner(int sock, struct sshbuf *m)
 {
         char *banner;
+        int r;
 
-        buffer_clear(m);
+        sshbuf_reset(m);
         banner = auth2_read_banner();
-        buffer_put_cstring(m, banner != NULL ? banner : "");
+        if ((r = sshbuf_put_cstring(m, banner != NULL ? banner : "")) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
         mm_request_send(sock, MONITOR_ANS_AUTH2_READ_BANNER, m);
         free(banner);
 
@@ -811,12 +835,15 @@ int mm_answer_auth2_read_banner(int sock, Buffer *m)
 }
 
 int
-mm_answer_authserv(int sock, Buffer *m)
+mm_answer_authserv(int sock, struct sshbuf *m)
 {
+        int r;
+
         monitor_permit_authentications(1);
 
-        authctxt->service = buffer_get_string(m, NULL);
-        authctxt->style = buffer_get_string(m, NULL);
+        if ((r = sshbuf_get_cstring(m, &authctxt->service, NULL)) != 0 ||
+            (r = sshbuf_get_cstring(m, &authctxt->style, NULL)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
         debug3("%s: service=%s, style=%s",
             __func__, authctxt->service, authctxt->style);
 
@@ -829,27 +856,30 @@ mm_answer_authserv(int sock, Buffer *m)
 }
 
 int
-mm_answer_authpassword(int sock, Buffer *m)
+mm_answer_authpassword(int sock, struct sshbuf *m)
 {
         struct ssh *ssh = active_state; /* XXX */
         static int call_count;
         char *passwd;
-        int authenticated;
-        u_int plen;
+        int r, authenticated;
+        size_t plen;
 
         if (!options.password_authentication)
                 fatal("%s: password authentication not enabled", __func__);
-        passwd = buffer_get_string(m, &plen);
+        if ((r = sshbuf_get_cstring(m, &passwd, &plen)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
         /* Only authenticate if the context is valid */
         authenticated = options.password_authentication &&
             auth_password(ssh, passwd);
-        explicit_bzero(passwd, strlen(passwd));
+        explicit_bzero(passwd, plen);
         free(passwd);
 
-        buffer_clear(m);
-        buffer_put_int(m, authenticated);
+        sshbuf_reset(m);
+        if ((r = sshbuf_put_u32(m, authenticated)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 #ifdef USE_PAM
-        buffer_put_int(m, sshpam_get_maxtries_reached());
+        if ((r = sshbuf_put_u32(m, sshpam_get_maxtries_reached())) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 #endif
 
         debug3("%s: sending result %d", __func__, authenticated);
@@ -867,23 +897,25 @@ mm_answer_authpassword(int sock, Buffer *m)
 
 #ifdef BSD_AUTH
 int
-mm_answer_bsdauthquery(int sock, Buffer *m)
+mm_answer_bsdauthquery(int sock, struct sshbuf *m)
 {
         char *name, *infotxt;
-        u_int numprompts;
-        u_int *echo_on;
+        u_int numprompts, *echo_on, success;
         char **prompts;
-        u_int success;
+        int r;
 
         if (!options.kbd_interactive_authentication)
                 fatal("%s: kbd-int authentication not enabled", __func__);
         success = bsdauth_query(authctxt, &name, &infotxt, &numprompts,
             &prompts, &echo_on) < 0 ? 0 : 1;
 
-        buffer_clear(m);
-        buffer_put_int(m, success);
-        if (success)
-                buffer_put_cstring(m, prompts[0]);
+        sshbuf_reset(m);
+        if ((r = sshbuf_put_u32(m, success)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        if (success) {
+                if ((r = sshbuf_put_cstring(m, prompts[0])) != 0)
+                        fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        }
 
         debug3("%s: sending challenge success: %u", __func__, success);
         mm_request_send(sock, MONITOR_ANS_BSDAUTHQUERY, m);
@@ -899,25 +931,27 @@ mm_answer_bsdauthquery(int sock, Buffer *m)
 }
 
 int
-mm_answer_bsdauthrespond(int sock, Buffer *m)
+mm_answer_bsdauthrespond(int sock, struct sshbuf *m)
 {
         char *response;
-        int authok;
+        int r, authok;
 
         if (!options.kbd_interactive_authentication)
                 fatal("%s: kbd-int authentication not enabled", __func__);
         if (authctxt->as == NULL)
                 fatal("%s: no bsd auth session", __func__);
 
-        response = buffer_get_string(m, NULL);
+        if ((r = sshbuf_get_cstring(m, &response, NULL)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
         authok = options.challenge_response_authentication &&
             auth_userresponse(authctxt->as, response, 0);
         authctxt->as = NULL;
         debug3("%s: <%s> = <%d>", __func__, response, authok);
         free(response);
 
-        buffer_clear(m);
-        buffer_put_int(m, authok);
+        sshbuf_reset(m);
+        if ((r = sshbuf_put_u32(m, authok)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
         debug3("%s: sending authenticated: %d", __func__, authok);
         mm_request_send(sock, MONITOR_ANS_BSDAUTHRESPOND, m);
@@ -1131,25 +1165,23 @@ mm_answer_pam_free_ctx(int sock, Buffer *m)
 #endif
 
 int
-mm_answer_keyallowed(int sock, Buffer *m)
+mm_answer_keyallowed(int sock, struct sshbuf *m)
 {
         struct ssh *ssh = active_state; /* XXX */
-        struct sshkey *key;
+        struct sshkey *key = NULL;
         char *cuser, *chost;
-        u_char *blob;
-        u_int bloblen, pubkey_auth_attempt;
+        u_int pubkey_auth_attempt;
         enum mm_keytype type = 0;
         int r, allowed = 0;
         struct sshauthopt *opts = NULL;
 
         debug3("%s entering", __func__);
-        type = buffer_get_int(m);
-        cuser = buffer_get_string(m, NULL);
-        chost = buffer_get_string(m, NULL);
-        blob = buffer_get_string(m, &bloblen);
-        pubkey_auth_attempt = buffer_get_int(m);
-
-        key = key_from_blob(blob, bloblen);
+        if ((r = sshbuf_get_u32(m, &type)) != 0 ||
+            (r = sshbuf_get_cstring(m, &cuser, NULL)) != 0 ||
+            (r = sshbuf_get_cstring(m, &chost, NULL)) != 0 ||
+            (r = sshkey_froms(m, &key)) != 0 ||
+            (r = sshbuf_get_u32(m, &pubkey_auth_attempt)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
         debug3("%s: key_from_blob: %p", __func__, key);
 
@@ -1199,15 +1231,14 @@ mm_answer_keyallowed(int sock, Buffer *m)
             allowed ? "allowed" : "not allowed");
 
         auth2_record_key(authctxt, 0, key);
-        sshkey_free(key);
 
         /* clear temporarily storage (used by verify) */
         monitor_reset_key_state();
 
         if (allowed) {
                 /* Save temporarily for comparison in verify */
-                key_blob = blob;
-                key_bloblen = bloblen;
+                if ((r = sshkey_to_blob(key, &key_blob, &key_bloblen)) != 0)
+                        fatal("%s: buffer error: %s", __func__, ssh_err(r));
                 key_blobtype = type;
                 key_opts = opts;
                 hostbased_cuser = cuser;
@@ -1215,13 +1246,14 @@ mm_answer_keyallowed(int sock, Buffer *m)
         } else {
                 /* Log failed attempt */
                 auth_log(authctxt, 0, 0, auth_method, NULL);
-                free(blob);
                 free(cuser);
                 free(chost);
         }
+        sshkey_free(key);
 
-        buffer_clear(m);
-        buffer_put_int(m, allowed);
+        sshbuf_reset(m);
+        if ((r = sshbuf_put_u32(m, allowed)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
         if (opts != NULL && (r = sshauthopt_serialise(opts, m, 1)) != 0)
                 fatal("%s: sshauthopt_serialise: %s", __func__, ssh_err(r));
         mm_request_send(sock, MONITOR_ANS_KEYALLOWED, m);
@@ -1235,34 +1267,41 @@ mm_answer_keyallowed(int sock, Buffer *m)
 static int
 monitor_valid_userblob(u_char *data, u_int datalen)
 {
-        Buffer b;
-        u_char *p;
+        struct sshbuf *b;
+        const u_char *p;
         char *userstyle, *cp;
-        u_int len;
-        int fail = 0;
+        size_t len;
+        u_char type;
+        int r, fail = 0;
 
-        buffer_init(&b);
-        buffer_append(&b, data, datalen);
+        if ((b = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new", __func__);
+        if ((r = sshbuf_put(b, data, datalen)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
         if (datafellows & SSH_OLD_SESSIONID) {
-                p = buffer_ptr(&b);
-                len = buffer_len(&b);
+                p = sshbuf_ptr(b);
+                len = sshbuf_len(b);
                 if ((session_id2 == NULL) ||
                     (len < session_id2_len) ||
                     (timingsafe_bcmp(p, session_id2, session_id2_len) != 0))
                         fail++;
-                buffer_consume(&b, session_id2_len);
+                if ((r = sshbuf_consume(b, session_id2_len)) != 0)
+                        fatal("%s: buffer error: %s", __func__, ssh_err(r));
         } else {
-                p = buffer_get_string(&b, &len);
+                if ((r = sshbuf_get_string_direct(b, &p, &len)) != 0)
+                        fatal("%s: buffer error: %s", __func__, ssh_err(r));
                 if ((session_id2 == NULL) ||
                     (len != session_id2_len) ||
                     (timingsafe_bcmp(p, session_id2, session_id2_len) != 0))
                         fail++;
-                free(p);
         }
-        if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST)
+        if ((r = sshbuf_get_u8(b, &type)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        if (type != SSH2_MSG_USERAUTH_REQUEST)
                 fail++;
-        cp = buffer_get_cstring(&b, NULL);
+        if ((r = sshbuf_get_cstring(b, &cp, NULL)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
         xasprintf(&userstyle, "%s%s%s", authctxt->user,
             authctxt->style ? ":" : "",
             authctxt->style ? authctxt->style : "");
@@ -1273,18 +1312,22 @@ monitor_valid_userblob(u_char *data, u_int datalen)
         }
         free(userstyle);
         free(cp);
-        buffer_skip_string(&b);
-        cp = buffer_get_cstring(&b, NULL);
+        if ((r = sshbuf_skip_string(b)) != 0 || /* service */
+            (r = sshbuf_get_cstring(b, &cp, NULL)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
         if (strcmp("publickey", cp) != 0)
                 fail++;
         free(cp);
-        if (!buffer_get_char(&b))
+        if ((r = sshbuf_get_u8(b, &type)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        if (type == 0)
                 fail++;
-        buffer_skip_string(&b);
-        buffer_skip_string(&b);
-        if (buffer_len(&b) != 0)
+        if ((r = sshbuf_skip_string(b)) != 0 || /* pkalg */
+            (r = sshbuf_skip_string(b)) != 0)   /* pkblob */
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        if (sshbuf_len(b) != 0)
                 fail++;
-        buffer_free(&b);
+        sshbuf_free(b);
         return (fail == 0);
 }
 
@@ -1292,59 +1335,69 @@ static int
 monitor_valid_hostbasedblob(u_char *data, u_int datalen, char *cuser,
     char *chost)
 {
-        Buffer b;
-        char *p, *userstyle;
-        u_int len;
-        int fail = 0;
+        struct sshbuf *b;
+        const u_char *p;
+        char *cp, *userstyle;
+        size_t len;
+        int r, fail = 0;
+        u_char type;
 
-        buffer_init(&b);
-        buffer_append(&b, data, datalen);
+        if ((b = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new", __func__);
+        if ((r = sshbuf_put(b, data, datalen)) != 0 ||
+            (r = sshbuf_get_string_direct(b, &p, &len)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
-        p = buffer_get_string(&b, &len);
         if ((session_id2 == NULL) ||
             (len != session_id2_len) ||
             (timingsafe_bcmp(p, session_id2, session_id2_len) != 0))
                 fail++;
-        free(p);
 
-        if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST)
+        if ((r = sshbuf_get_u8(b, &type)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        if (type != SSH2_MSG_USERAUTH_REQUEST)
                 fail++;
-        p = buffer_get_cstring(&b, NULL);
+        if ((r = sshbuf_get_cstring(b, &cp, NULL)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
         xasprintf(&userstyle, "%s%s%s", authctxt->user,
             authctxt->style ? ":" : "",
             authctxt->style ? authctxt->style : "");
-        if (strcmp(userstyle, p) != 0) {
-                logit("wrong user name passed to monitor: expected %s != %.100s",
-                    userstyle, p);
+        if (strcmp(userstyle, cp) != 0) {
+                logit("wrong user name passed to monitor: "
+                    "expected %s != %.100s", userstyle, cp);
                 fail++;
         }
         free(userstyle);
-        free(p);
-        buffer_skip_string(&b); /* service */
-        p = buffer_get_cstring(&b, NULL);
-        if (strcmp(p, "hostbased") != 0)
+        free(cp);
+        if ((r = sshbuf_skip_string(b)) != 0 || /* service */
+            (r = sshbuf_get_cstring(b, &cp, NULL)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        if (strcmp(cp, "hostbased") != 0)
                 fail++;
-        free(p);
-        buffer_skip_string(&b); /* pkalg */
-        buffer_skip_string(&b); /* pkblob */
+        free(cp);
+        if ((r = sshbuf_skip_string(b)) != 0 || /* pkalg */
+            (r = sshbuf_skip_string(b)) != 0)   /* pkblob */
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
         /* verify client host, strip trailing dot if necessary */
-        p = buffer_get_string(&b, NULL);
-        if (((len = strlen(p)) > 0) && p[len - 1] == '.')
-                p[len - 1] = '\0';
-        if (strcmp(p, chost) != 0)
+        if ((r = sshbuf_get_cstring(b, &cp, NULL)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        if (((len = strlen(cp)) > 0) && cp[len - 1] == '.')
+                cp[len - 1] = '\0';
+        if (strcmp(cp, chost) != 0)
                 fail++;
-        free(p);
+        free(cp);
 
         /* verify client user */
-        p = buffer_get_string(&b, NULL);
-        if (strcmp(p, cuser) != 0)
+        if ((r = sshbuf_get_cstring(b, &cp, NULL)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        if (strcmp(cp, cuser) != 0)
                 fail++;
-        free(p);
+        free(cp);
 
-        if (buffer_len(&b) != 0)
+        if (sshbuf_len(b) != 0)
                 fail++;
-        buffer_free(&b);
+        sshbuf_free(b);
         return (fail == 0);
 }
 
@@ -1460,15 +1513,15 @@ mm_session_close(Session *s)
 }
 
 int
-mm_answer_pty(int sock, Buffer *m)
+mm_answer_pty(int sock, struct sshbuf *m)
 {
         extern struct monitor *pmonitor;
         Session *s;
-        int res, fd0;
+        int r, res, fd0;
 
         debug3("%s entering", __func__);
 
-        buffer_clear(m);
+        sshbuf_reset(m);
         s = session_new();
         if (s == NULL)
                 goto error;
@@ -1480,8 +1533,9 @@ mm_answer_pty(int sock, Buffer *m)
                 goto error;
         pty_setowner(authctxt->pw, s->tty);
 
-        buffer_put_int(m, 1);
-        buffer_put_cstring(m, s->tty);
+        if ((r = sshbuf_put_u32(m, 1)) != 0 ||
+            (r = sshbuf_put_cstring(m, s->tty)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
         /* We need to trick ttyslot */
         if (dup2(s->ttyfd, 0) == -1)
@@ -1493,8 +1547,9 @@ mm_answer_pty(int sock, Buffer *m)
         close(0);
 
         /* send messages generated by record_login */
-        buffer_put_string(m, buffer_ptr(loginmsg), buffer_len(loginmsg));
-        buffer_clear(loginmsg);
+        if ((r = sshbuf_put_stringb(m, loginmsg)) != 0)
+                fatal("%s: put login message: %s", __func__, ssh_err(r));
+        sshbuf_reset(loginmsg);
 
         mm_request_send(sock, MONITOR_ANS_PTY, m);
 
@@ -1521,29 +1576,32 @@ mm_answer_pty(int sock, Buffer *m)
  error:
         if (s != NULL)
                 mm_session_close(s);
-        buffer_put_int(m, 0);
+        if ((r = sshbuf_put_u32(m, 0)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
         mm_request_send(sock, MONITOR_ANS_PTY, m);
         return (0);
 }
 
 int
-mm_answer_pty_cleanup(int sock, Buffer *m)
+mm_answer_pty_cleanup(int sock, struct sshbuf *m)
 {
         Session *s;
         char *tty;
+        int r;
 
         debug3("%s entering", __func__);
 
-        tty = buffer_get_string(m, NULL);
+        if ((r = sshbuf_get_cstring(m, &tty, NULL)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
         if ((s = session_by_tty(tty)) != NULL)
                 mm_session_close(s);
-        buffer_clear(m);
+        sshbuf_reset(m);
         free(tty);
         return (0);
 }
 
 int
-mm_answer_term(int sock, Buffer *req)
+mm_answer_term(int sock, struct sshbuf *req)
 {
         struct ssh *ssh = active_state; /* XXX */
         extern struct monitor *pmonitor;
@@ -1732,24 +1790,27 @@ monitor_reinit(struct monitor *mon)
 
 #ifdef GSSAPI
 int
-mm_answer_gss_setup_ctx(int sock, Buffer *m)
+mm_answer_gss_setup_ctx(int sock, struct sshbuf *m)
 {
         gss_OID_desc goid;
         OM_uint32 major;
-        u_int len;
+        size_t len;
+        int r;
 
         if (!options.gss_authentication)
                 fatal("%s: GSSAPI authentication not enabled", __func__);
 
-        goid.elements = buffer_get_string(m, &len);
+        if ((r = sshbuf_get_string(m, &goid.elements, &len)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
         goid.length = len;
 
         major = ssh_gssapi_server_ctx(&gsscontext, &goid);
 
         free(goid.elements);
 
-        buffer_clear(m);
-        buffer_put_int(m, major);
+        sshbuf_reset(m);
+        if ((r = sshbuf_put_u32(m, major)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
         mm_request_send(sock, MONITOR_ANS_GSSSETUP, m);
 
@@ -1760,26 +1821,27 @@ mm_answer_gss_setup_ctx(int sock, Buffer *m)
 }
 
 int
-mm_answer_gss_accept_ctx(int sock, Buffer *m)
+mm_answer_gss_accept_ctx(int sock, struct sshbuf *m)
 {
         gss_buffer_desc in;
         gss_buffer_desc out = GSS_C_EMPTY_BUFFER;
         OM_uint32 major, minor;
         OM_uint32 flags = 0; /* GSI needs this */
-        u_int len;
+        int r;
 
         if (!options.gss_authentication)
                 fatal("%s: GSSAPI authentication not enabled", __func__);
 
-        in.value = buffer_get_string(m, &len);
-        in.length = len;
+        if ((r = sshbuf_get_string(m, &in.value, &in.length)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
         major = ssh_gssapi_accept_ctx(gsscontext, &in, &out, &flags);
         free(in.value);
 
-        buffer_clear(m);
-        buffer_put_int(m, major);
-        buffer_put_string(m, out.value, out.length);
-        buffer_put_int(m, flags);
+        sshbuf_reset(m);
+        if ((r = sshbuf_put_u32(m, major)) != 0 ||
+            (r = sshbuf_put_string(m, out.value, out.length)) != 0 ||
+            (r = sshbuf_put_u32(m, flags)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
         mm_request_send(sock, MONITOR_ANS_GSSSTEP, m);
 
         gss_release_buffer(&minor, &out);
@@ -1793,27 +1855,26 @@ mm_answer_gss_accept_ctx(int sock, Buffer *m)
 }
 
 int
-mm_answer_gss_checkmic(int sock, Buffer *m)
+mm_answer_gss_checkmic(int sock, struct sshbuf *m)
 {
         gss_buffer_desc gssbuf, mic;
         OM_uint32 ret;
-        u_int len;
 
         if (!options.gss_authentication)
                 fatal("%s: GSSAPI authentication not enabled", __func__);
 
-        gssbuf.value = buffer_get_string(m, &len);
-        gssbuf.length = len;
-        mic.value = buffer_get_string(m, &len);
-        mic.length = len;
+        if ((r = sshbuf_get_string(m, &gssbuf.value, &gssbuf.length)) != 0 ||
+            (r = sshbuf_get_string(m, &mic.value, &mic.length)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
         ret = ssh_gssapi_checkmic(gsscontext, &gssbuf, &mic);
 
         free(gssbuf.value);
         free(mic.value);
 
-        buffer_clear(m);
-        buffer_put_int(m, ret);
+        sshbuf_reset(m);
+        if ((r = sshbuf_put_u32(m, ret)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
         mm_request_send(sock, MONITOR_ANS_GSSCHECKMIC, m);
 
@@ -1824,7 +1885,7 @@ mm_answer_gss_checkmic(int sock, Buffer *m)
 }
 
 int
-mm_answer_gss_userok(int sock, Buffer *m)
+mm_answer_gss_userok(int sock, struct sshbuf *m)
 {
         int authenticated;
         const char *displayname;
@@ -1834,8 +1895,9 @@ mm_answer_gss_userok(int sock, Buffer *m)
 
         authenticated = authctxt->valid && ssh_gssapi_userok(authctxt->user);
 
-        buffer_clear(m);
-        buffer_put_int(m, authenticated);
+        sshbuf_reset(m);
+        if ((r = sshbuf_put_u32(m, authenticated)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
         debug3("%s: sending result %d", __func__, authenticated);
         mm_request_send(sock, MONITOR_ANS_GSSUSEROK, m);
diff --git a/monitor.h b/monitor.h
index d68f67458..0c7635000 100644
--- a/monitor.h
+++ b/monitor.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor.h,v 1.20 2016/09/28 16:33:07 djm Exp $ */
+/* $OpenBSD: monitor.h,v 1.21 2018/07/09 21:53:45 markus Exp $ */
 
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
@@ -87,8 +87,8 @@ struct mon_table;
 int monitor_read(struct monitor*, struct mon_table *, struct mon_table **);
 
 /* Prototypes for request sending and receiving */
-void mm_request_send(int, enum monitor_reqtype, Buffer *);
-void mm_request_receive(int, Buffer *);
-void mm_request_receive_expect(int, enum monitor_reqtype, Buffer *);
+void mm_request_send(int, enum monitor_reqtype, struct sshbuf *);
+void mm_request_receive(int, struct sshbuf *);
+void mm_request_receive_expect(int, enum monitor_reqtype, struct sshbuf *);
 
 #endif /* _MONITOR_H_ */
diff --git a/monitor_wrap.c b/monitor_wrap.c
index 6bf041093..cf38b230b 100644
--- a/monitor_wrap.c
+++ b/monitor_wrap.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor_wrap.c,v 1.102 2018/07/09 21:26:02 markus Exp $ */
+/* $OpenBSD: monitor_wrap.c,v 1.103 2018/07/09 21:53:45 markus Exp $ */
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
  * Copyright 2002 Markus Friedl <markus@openbsd.org>
@@ -50,7 +50,7 @@
 #ifdef WITH_OPENSSL
 #include "dh.h"
 #endif
-#include "buffer.h"
+#include "sshbuf.h"
 #include "key.h"
 #include "cipher.h"
 #include "kex.h"
@@ -93,27 +93,28 @@ extern ServerOptions options;
 void
 mm_log_handler(LogLevel level, const char *msg, void *ctx)
 {
-        Buffer log_msg;
+        struct sshbuf *log_msg;
         struct monitor *mon = (struct monitor *)ctx;
+        int r;
+        size_t len;
 
         if (mon->m_log_sendfd == -1)
                 fatal("%s: no log channel", __func__);
 
-        buffer_init(&log_msg);
-        /*
-         * Placeholder for packet length. Will be filled in with the actual
-         * packet length once the packet has been constucted. This saves
-         * fragile math.
-         */
-        buffer_put_int(&log_msg, 0);
+        if ((log_msg = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new failed", __func__);
 
-        buffer_put_int(&log_msg, level);
-        buffer_put_cstring(&log_msg, msg);
-        put_u32(buffer_ptr(&log_msg), buffer_len(&log_msg) - 4);
-        if (atomicio(vwrite, mon->m_log_sendfd, buffer_ptr(&log_msg),
-            buffer_len(&log_msg)) != buffer_len(&log_msg))
+        if ((r = sshbuf_put_u32(log_msg, 0)) != 0 || /* length; filled below */
+            (r = sshbuf_put_u32(log_msg, level)) != 0 ||
+            (r = sshbuf_put_cstring(log_msg, msg)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        if ((len = sshbuf_len(log_msg)) < 4 || len > 0xffffffff)
+                fatal("%s: bad length %zu", __func__, len);
+        POKE_U32(sshbuf_mutable_ptr(log_msg), len - 4);
+        if (atomicio(vwrite, mon->m_log_sendfd,
+            sshbuf_mutable_ptr(log_msg), len) != len)
                 fatal("%s: write: %s", __func__, strerror(errno));
-        buffer_free(&log_msg);
+        sshbuf_free(log_msg);
 }
 
 int
@@ -127,26 +128,29 @@ mm_is_monitor(void)
 }
 
 void
-mm_request_send(int sock, enum monitor_reqtype type, Buffer *m)
+mm_request_send(int sock, enum monitor_reqtype type, struct sshbuf *m)
 {
-        u_int mlen = buffer_len(m);
+        size_t mlen = sshbuf_len(m);
         u_char buf[5];
 
         debug3("%s entering: type %d", __func__, type);
 
-        put_u32(buf, mlen + 1);
+        if (mlen >= 0xffffffff)
+                fatal("%s: bad length %zu", __func__, mlen);
+        POKE_U32(buf, mlen + 1);
         buf[4] = (u_char) type;         /* 1st byte of payload is mesg-type */
         if (atomicio(vwrite, sock, buf, sizeof(buf)) != sizeof(buf))
                 fatal("%s: write: %s", __func__, strerror(errno));
-        if (atomicio(vwrite, sock, buffer_ptr(m), mlen) != mlen)
+        if (atomicio(vwrite, sock, sshbuf_mutable_ptr(m), mlen) != mlen)
                 fatal("%s: write: %s", __func__, strerror(errno));
 }
 
 void
-mm_request_receive(int sock, Buffer *m)
+mm_request_receive(int sock, struct sshbuf *m)
 {
-        u_char buf[4];
+        u_char buf[4], *p = NULL;
         u_int msg_len;
+        int r;
 
         debug3("%s entering", __func__);
 
@@ -155,24 +159,27 @@ mm_request_receive(int sock, Buffer *m)
                         cleanup_exit(255);
                 fatal("%s: read: %s", __func__, strerror(errno));
         }
-        msg_len = get_u32(buf);
+        msg_len = PEEK_U32(buf);
         if (msg_len > 256 * 1024)
                 fatal("%s: read: bad msg_len %d", __func__, msg_len);
-        buffer_clear(m);
-        buffer_append_space(m, msg_len);
-        if (atomicio(read, sock, buffer_ptr(m), msg_len) != msg_len)
+        sshbuf_reset(m);
+        if ((r = sshbuf_reserve(m, msg_len, &p)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        if (atomicio(read, sock, p, msg_len) != msg_len)
                 fatal("%s: read: %s", __func__, strerror(errno));
 }
 
 void
-mm_request_receive_expect(int sock, enum monitor_reqtype type, Buffer *m)
+mm_request_receive_expect(int sock, enum monitor_reqtype type, struct sshbuf *m)
 {
         u_char rtype;
+        int r;
 
         debug3("%s entering: type %d", __func__, type);
 
         mm_request_receive(sock, m);
-        rtype = buffer_get_char(m);
+        if ((r = sshbuf_get_u8(m, &rtype)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
         if (rtype != type)
                 fatal("%s: read: rtype %d != type %d", __func__,
                     rtype, type);
@@ -183,20 +190,24 @@ DH *
 mm_choose_dh(int min, int nbits, int max)
 {
         BIGNUM *p, *g;
-        int success = 0;
-        Buffer m;
+        int r;
+        u_char success = 0;
+        struct sshbuf *m;
 
-        buffer_init(&m);
-        buffer_put_int(&m, min);
-        buffer_put_int(&m, nbits);
-        buffer_put_int(&m, max);
+        if ((m = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new failed", __func__);
+        if ((r = sshbuf_put_u32(m, min)) != 0 ||
+            (r = sshbuf_put_u32(m, nbits)) != 0 ||
+            (r = sshbuf_put_u32(m, max)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
-        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_MODULI, &m);
+        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_MODULI, m);
 
         debug3("%s: waiting for MONITOR_ANS_MODULI", __func__);
-        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_MODULI, &m);
+        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_MODULI, m);
 
-        success = buffer_get_char(&m);
+        if ((r = sshbuf_get_u8(m, &success)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
         if (success == 0)
                 fatal("%s: MONITOR_ANS_MODULI failed", __func__);
 
@@ -204,11 +215,12 @@ mm_choose_dh(int min, int nbits, int max)
                 fatal("%s: BN_new failed", __func__);
         if ((g = BN_new()) == NULL)
                 fatal("%s: BN_new failed", __func__);
-        buffer_get_bignum2(&m, p);
-        buffer_get_bignum2(&m, g);
+        if ((r = sshbuf_get_bignum2(m, p)) != 0 ||
+            (r = sshbuf_get_bignum2(m, g)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
-        debug3("%s: remaining %d", __func__, buffer_len(&m));
-        buffer_free(&m);
+        debug3("%s: remaining %zu", __func__, sshbuf_len(m));
+        sshbuf_free(m);
 
         return (dh_new_group(g, p));
 }
@@ -219,21 +231,30 @@ mm_key_sign(struct sshkey *key, u_char **sigp, u_int *lenp,
     const u_char *data, u_int datalen, const char *hostkey_alg)
 {
         struct kex *kex = *pmonitor->m_pkex;
-        Buffer m;
+        struct sshbuf *m;
+        size_t xxxlen;
+        u_int ndx = kex->host_key_index(key, 0, active_state);
+        int r;
 
         debug3("%s entering", __func__);
 
-        buffer_init(&m);
-        buffer_put_int(&m, kex->host_key_index(key, 0, active_state));
-        buffer_put_string(&m, data, datalen);
-        buffer_put_cstring(&m, hostkey_alg);
+        if ((m = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new failed", __func__);
+        if ((r = sshbuf_put_u32(m, ndx)) != 0 ||
+            (r = sshbuf_put_string(m, data, datalen)) != 0 ||
+            (r = sshbuf_put_cstring(m, hostkey_alg)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
-        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_SIGN, &m);
+        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_SIGN, m);
 
         debug3("%s: waiting for MONITOR_ANS_SIGN", __func__);
-        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_SIGN, &m);
-        *sigp  = buffer_get_string(&m, lenp);
-        buffer_free(&m);
+        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_SIGN, m);
+        if ((r = sshbuf_get_string(m, sigp, &xxxlen)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        if (xxxlen > 0xffffffff)
+                fatal("%s: bad length %zu", __func__, xxxlen);
+        *lenp = xxxlen; /* XXX fix API: size_t vs u_int */
+        sshbuf_free(m);
 
         return (0);
 }
@@ -242,54 +263,80 @@ struct passwd *
 mm_getpwnamallow(const char *username)
 {
         struct ssh *ssh = active_state;         /* XXX */
-        Buffer m;
+        struct sshbuf *m;
         struct passwd *pw;
-        u_int len, i;
+        size_t len;
+        u_int i;
         ServerOptions *newopts;
+        int r;
+        u_char ok;
+        const u_char *p;
 
         debug3("%s entering", __func__);
 
-        buffer_init(&m);
-        buffer_put_cstring(&m, username);
+        if ((m = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new failed", __func__);
+        if ((r = sshbuf_put_cstring(m, username)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
-        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_PWNAM, &m);
+        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_PWNAM, m);
 
         debug3("%s: waiting for MONITOR_ANS_PWNAM", __func__);
-        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_PWNAM, &m);
+        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_PWNAM, m);
 
-        if (buffer_get_char(&m) == 0) {
+        if ((r = sshbuf_get_u8(m, &ok)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        if (ok == 0) {
                 pw = NULL;
                 goto out;
         }
-        pw = buffer_get_string(&m, &len);
-        if (len != sizeof(struct passwd))
+
+        /* XXX don't like passing struct passwd like this */
+        pw = xcalloc(sizeof(*pw), 1);
+        if ((r = sshbuf_get_string_direct(m, &p, &len)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        if (len != sizeof(*pw))
                 fatal("%s: struct passwd size mismatch", __func__);
-        pw->pw_name = buffer_get_string(&m, NULL);
-        pw->pw_passwd = buffer_get_string(&m, NULL);
+        memcpy(pw, p, sizeof(*pw));
+
+        if ((r = sshbuf_get_cstring(m, &pw->pw_name, NULL)) != 0 ||
+            (r = sshbuf_get_cstring(m, &pw->pw_passwd, NULL)) != 0 ||
 #ifdef HAVE_STRUCT_PASSWD_PW_GECOS
-        pw->pw_gecos = buffer_get_string(&m, NULL);
+            (r = sshbuf_get_cstring(m, &pw->pw_gecos, NULL)) != 0 ||
 #endif
 #ifdef HAVE_STRUCT_PASSWD_PW_CLASS
-        pw->pw_class = buffer_get_string(&m, NULL);
+            (r = sshbuf_get_cstring(m, &pw->pw_class, NULL)) != 0 ||
 #endif
-        pw->pw_dir = buffer_get_string(&m, NULL);
-        pw->pw_shell = buffer_get_string(&m, NULL);
+            (r = sshbuf_get_cstring(m, &pw->pw_dir, NULL)) != 0 ||
+            (r = sshbuf_get_cstring(m, &pw->pw_shell, NULL)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
 out:
         /* copy options block as a Match directive may have changed some */
-        newopts = buffer_get_string(&m, &len);
+        if ((r = sshbuf_get_string_direct(m, &p, &len)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
         if (len != sizeof(*newopts))
                 fatal("%s: option block size mismatch", __func__);
+        newopts = xcalloc(sizeof(*newopts), 1);
+        memcpy(newopts, p, sizeof(*newopts));
 
 #define M_CP_STROPT(x) do { \
-                if (newopts->x != NULL) \
-                        newopts->x = buffer_get_string(&m, NULL); \
+                if (newopts->x != NULL) { \
+                        if ((r = sshbuf_get_cstring(m, \
+                            &newopts->x, NULL)) != 0) \
+                                fatal("%s: buffer error: %s", \
+                                    __func__, ssh_err(r)); \
+                } \
         } while (0)
 #define M_CP_STRARRAYOPT(x, nx) do { \
                 newopts->x = newopts->nx == 0 ? \
                     NULL : xcalloc(newopts->nx, sizeof(*newopts->x)); \
-                for (i = 0; i < newopts->nx; i++) \
-                        newopts->x[i] = buffer_get_string(&m, NULL); \
+                for (i = 0; i < newopts->nx; i++) { \
+                        if ((r = sshbuf_get_cstring(m, \
+                            &newopts->x[i], NULL)) != 0) \
+                                fatal("%s: buffer error: %s", \
+                                    __func__, ssh_err(r)); \
+                } \
         } while (0)
         /* See comment in servconf.h */
         COPY_MATCH_STRING_OPTS();
@@ -301,7 +348,7 @@ out:
         process_permitopen(ssh, &options);
         free(newopts);
 
-        buffer_free(&m);
+        sshbuf_free(m);
 
         return (pw);
 }
@@ -309,19 +356,22 @@ out:
 char *
 mm_auth2_read_banner(void)
 {
-        Buffer m;
+        struct sshbuf *m;
         char *banner;
+        int r;
 
         debug3("%s entering", __func__);
 
-        buffer_init(&m);
-        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_AUTH2_READ_BANNER, &m);
-        buffer_clear(&m);
+        if ((m = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new failed", __func__);
+        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_AUTH2_READ_BANNER, m);
+        sshbuf_reset(m);
 
         mm_request_receive_expect(pmonitor->m_recvfd,
-            MONITOR_ANS_AUTH2_READ_BANNER, &m);
-        banner = buffer_get_string(&m, NULL);
-        buffer_free(&m);
+            MONITOR_ANS_AUTH2_READ_BANNER, m);
+        if ((r = sshbuf_get_cstring(m, &banner, NULL)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        sshbuf_free(m);
 
         /* treat empty banner as missing banner */
         if (strlen(banner) == 0) {
@@ -336,41 +386,50 @@ mm_auth2_read_banner(void)
 void
 mm_inform_authserv(char *service, char *style)
 {
-        Buffer m;
+        struct sshbuf *m;
+        int r;
 
         debug3("%s entering", __func__);
 
-        buffer_init(&m);
-        buffer_put_cstring(&m, service);
-        buffer_put_cstring(&m, style ? style : "");
+        if ((m = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new failed", __func__);
+        if ((r = sshbuf_put_cstring(m, service)) != 0 ||
+            (r = sshbuf_put_cstring(m, style ? style : "")) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
-        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_AUTHSERV, &m);
+        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_AUTHSERV, m);
 
-        buffer_free(&m);
+        sshbuf_free(m);
 }
 
 /* Do the password authentication */
 int
 mm_auth_password(struct ssh *ssh, char *password)
 {
-        Buffer m;
-        int authenticated = 0;
+        struct sshbuf *m;
+        int r, maxtries = 0, authenticated = 0;
 
         debug3("%s entering", __func__);
 
-        buffer_init(&m);
-        buffer_put_cstring(&m, password);
-        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_AUTHPASSWORD, &m);
+        if ((m = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new failed", __func__);
+        if ((r = sshbuf_put_cstring(m, password)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_AUTHPASSWORD, m);
 
         debug3("%s: waiting for MONITOR_ANS_AUTHPASSWORD", __func__);
-        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_AUTHPASSWORD, &m);
+        mm_request_receive_expect(pmonitor->m_recvfd,
+            MONITOR_ANS_AUTHPASSWORD, m);
 
-        authenticated = buffer_get_int(&m);
+        if ((r = sshbuf_get_u32(m, &authenticated)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 #ifdef USE_PAM
-        sshpam_set_maxtries_reached(buffer_get_int(&m));
+        if ((r = sshbuf_get_u32(m, &maxtries)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        sshpam_set_maxtries_reached(maxtries);
 #endif
 
-        buffer_free(&m);
+        sshbuf_free(m);
 
         debug3("%s: user %sauthenticated",
             __func__, authenticated ? "" : "not ");
@@ -396,9 +455,7 @@ int
 mm_key_allowed(enum mm_keytype type, const char *user, const char *host,
     struct sshkey *key, int pubkey_auth_attempt, struct sshauthopt **authoptp)
 {
-        Buffer m;
-        u_char *blob;
-        u_int len;
+        struct sshbuf *m;
         int r, allowed = 0;
         struct sshauthopt *opts = NULL;
 
@@ -407,31 +464,29 @@ mm_key_allowed(enum mm_keytype type, const char *user, const char *host,
         if (authoptp != NULL)
                 *authoptp = NULL;
 
-        /* Convert the key to a blob and the pass it over */
-        if (!key_to_blob(key, &blob, &len))
-                return 0;
-
-        buffer_init(&m);
-        buffer_put_int(&m, type);
-        buffer_put_cstring(&m, user ? user : "");
-        buffer_put_cstring(&m, host ? host : "");
-        buffer_put_string(&m, blob, len);
-        buffer_put_int(&m, pubkey_auth_attempt);
-        free(blob);
+        if ((m = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new failed", __func__);
+        if ((r = sshbuf_put_u32(m, type)) != 0 ||
+            (r = sshbuf_put_cstring(m, user ? user : "")) != 0 ||
+            (r = sshbuf_put_cstring(m, host ? host : "")) != 0 ||
+            (r = sshkey_puts(key, m)) != 0 ||
+            (r = sshbuf_put_u32(m, pubkey_auth_attempt)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
-        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_KEYALLOWED, &m);
+        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_KEYALLOWED, m);
 
         debug3("%s: waiting for MONITOR_ANS_KEYALLOWED", __func__);
         mm_request_receive_expect(pmonitor->m_recvfd,
-            MONITOR_ANS_KEYALLOWED, &m);
+            MONITOR_ANS_KEYALLOWED, m);
 
-        allowed = buffer_get_int(&m);
+        if ((r = sshbuf_get_u32(m, &allowed)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
         if (allowed && type == MM_USERKEY) {
-                if ((r = sshauthopt_deserialise(&m, &opts)) != 0)
+                if ((r = sshauthopt_deserialise(m, &opts)) != 0)
                         fatal("%s: sshauthopt_deserialise: %s",
                             __func__, ssh_err(r));
         }
-        buffer_free(&m);
+        sshbuf_free(m);
 
         if (authoptp != NULL) {
                 *authoptp = opts;
@@ -452,32 +507,31 @@ int
 mm_sshkey_verify(const struct sshkey *key, const u_char *sig, size_t siglen,
     const u_char *data, size_t datalen, const char *sigalg, u_int compat)
 {
-        Buffer m;
-        u_char *blob;
-        u_int len;
+        struct sshbuf *m;
         u_int encoded_ret = 0;
+        int r;
 
         debug3("%s entering", __func__);
 
-        /* Convert the key to a blob and the pass it over */
-        if (!key_to_blob(key, &blob, &len))
-                return (0);
 
-        buffer_init(&m);
-        buffer_put_string(&m, blob, len);
-        buffer_put_string(&m, sig, siglen);
-        buffer_put_string(&m, data, datalen);
-        buffer_put_cstring(&m, sigalg == NULL ? "" : sigalg);
-        free(blob);
+        if ((m = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new failed", __func__);
+        if ((r = sshkey_puts(key, m)) != 0 ||
+            (r = sshbuf_put_string(m, sig, siglen)) != 0 ||
+            (r = sshbuf_put_string(m, data, datalen)) != 0 ||
+            (r = sshbuf_put_cstring(m, sigalg == NULL ? "" : sigalg)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
-        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_KEYVERIFY, &m);
+        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_KEYVERIFY, m);
 
         debug3("%s: waiting for MONITOR_ANS_KEYVERIFY", __func__);
-        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_KEYVERIFY, &m);
+        mm_request_receive_expect(pmonitor->m_recvfd,
+            MONITOR_ANS_KEYVERIFY, m);
 
-        encoded_ret = buffer_get_int(&m);
+        if ((r = sshbuf_get_u32(m, &encoded_ret)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
-        buffer_free(&m);
+        sshbuf_free(m);
 
         if (encoded_ret != 0)
                 return SSH_ERR_SIGNATURE_INVALID;
@@ -504,7 +558,7 @@ mm_send_keystate(struct monitor *monitor)
 int
 mm_pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, size_t namebuflen)
 {
-        Buffer m;
+        struct sshbuf *m;
         char *p, *msg;
         int success = 0, tmp1 = -1, tmp2 = -1, r;
 
@@ -521,21 +575,24 @@ mm_pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, size_t namebuflen)
         close(tmp1);
         close(tmp2);
 
-        buffer_init(&m);
-        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_PTY, &m);
+        if ((m = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new failed", __func__);
+        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_PTY, m);
 
         debug3("%s: waiting for MONITOR_ANS_PTY", __func__);
-        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_PTY, &m);
+        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_PTY, m);
 
-        success = buffer_get_int(&m);
+        if ((r = sshbuf_get_u32(m, &success)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
         if (success == 0) {
                 debug3("%s: pty alloc failed", __func__);
-                buffer_free(&m);
+                sshbuf_free(m);
                 return (0);
         }
-        p = buffer_get_string(&m, NULL);
-        msg = buffer_get_string(&m, NULL);
-        buffer_free(&m);
+        if ((r = sshbuf_get_cstring(m, &p, NULL)) != 0 ||
+            (r = sshbuf_get_cstring(m, &msg, NULL)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        sshbuf_free(m);
 
         strlcpy(namebuf, p, namebuflen); /* Possible truncation */
         free(p);
@@ -555,14 +612,17 @@ mm_pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, size_t namebuflen)
 void
 mm_session_pty_cleanup2(Session *s)
 {
-        Buffer m;
+        struct sshbuf *m;
+        int r;
 
         if (s->ttyfd == -1)
                 return;
-        buffer_init(&m);
-        buffer_put_cstring(&m, s->tty);
-        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_PTYCLEANUP, &m);
-        buffer_free(&m);
+        if ((m = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new failed", __func__);
+        if ((r = sshbuf_put_cstring(m, s->tty)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_PTYCLEANUP, m);
+        sshbuf_free(m);
 
         /* closed dup'ed master */
         if (s->ptymaster != -1 && close(s->ptymaster) < 0)
@@ -710,11 +770,12 @@ mm_sshpam_free_ctx(void *ctxtp)
 void
 mm_terminate(void)
 {
-        Buffer m;
+        struct sshbuf *m;
 
-        buffer_init(&m);
-        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_TERM, &m);
-        buffer_free(&m);
+        if ((m = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new failed", __func__);
+        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_TERM, m);
+        sshbuf_free(m);
 }
 
 static void
@@ -733,27 +794,31 @@ int
 mm_bsdauth_query(void *ctx, char **name, char **infotxt,
    u_int *numprompts, char ***prompts, u_int **echo_on)
 {
-        Buffer m;
+        struct sshbuf *m;
         u_int success;
         char *challenge;
+        int r;
 
         debug3("%s: entering", __func__);
 
-        buffer_init(&m);
-        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_BSDAUTHQUERY, &m);
+        if ((m = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new failed", __func__);
+        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_BSDAUTHQUERY, m);
 
-        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_BSDAUTHQUERY,
-            &m);
-        success = buffer_get_int(&m);
+        mm_request_receive_expect(pmonitor->m_recvfd,
+            MONITOR_ANS_BSDAUTHQUERY, m);
+        if ((r = sshbuf_get_u32(m, &success)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
         if (success == 0) {
                 debug3("%s: no challenge", __func__);
-                buffer_free(&m);
+                sshbuf_free(m);
                 return (-1);
         }
 
         /* Get the challenge, and format the response */
-        challenge  = buffer_get_string(&m, NULL);
-        buffer_free(&m);
+        if ((r = sshbuf_get_cstring(m, &challenge, NULL)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        sshbuf_free(m);
 
         mm_chall_setup(name, infotxt, numprompts, prompts, echo_on);
         (*prompts)[0] = challenge;
@@ -766,22 +831,25 @@ mm_bsdauth_query(void *ctx, char **name, char **infotxt,
 int
 mm_bsdauth_respond(void *ctx, u_int numresponses, char **responses)
 {
-        Buffer m;
-        int authok;
+        struct sshbuf *m;
+        int r, authok;
 
         debug3("%s: entering", __func__);
         if (numresponses != 1)
                 return (-1);
 
-        buffer_init(&m);
-        buffer_put_cstring(&m, responses[0]);
-        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_BSDAUTHRESPOND, &m);
+        if ((m = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new failed", __func__);
+        if ((r = sshbuf_put_cstring(m, responses[0])) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_BSDAUTHRESPOND, m);
 
         mm_request_receive_expect(pmonitor->m_recvfd,
-            MONITOR_ANS_BSDAUTHRESPOND, &m);
+            MONITOR_ANS_BSDAUTHRESPOND, m);
 
-        authok = buffer_get_int(&m);
-        buffer_free(&m);
+        if ((r = sshbuf_get_u32(m, &authok)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        sshbuf_free(m);
 
         return ((authok == 0) ? -1 : 0);
 }
@@ -881,45 +949,55 @@ mm_audit_run_command(const char *command)
 OM_uint32
 mm_ssh_gssapi_server_ctx(Gssctxt **ctx, gss_OID goid)
 {
-        Buffer m;
+        struct sshbuf *m;
         OM_uint32 major;
+        int r;
 
         /* Client doesn't get to see the context */
         *ctx = NULL;
 
-        buffer_init(&m);
-        buffer_put_string(&m, goid->elements, goid->length);
+        if ((m = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new failed", __func__);
+        if ((r = sshbuf_put_string(m, goid->elements, goid->length)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
-        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSSETUP, &m);
-        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_GSSSETUP, &m);
+        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSSETUP, m);
+        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_GSSSETUP, m);
 
-        major = buffer_get_int(&m);
+        if ((r = sshbuf_get_u32(m, &major)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
-        buffer_free(&m);
+        sshbuf_free(m);
         return (major);
 }
 
 OM_uint32
 mm_ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *in,
-    gss_buffer_desc *out, OM_uint32 *flags)
+    gss_buffer_desc *out, OM_uint32 *flagsp)
 {
-        Buffer m;
+        struct sshbuf *m;
         OM_uint32 major;
-        u_int len;
+        u_int flags;
+        int r;
 
-        buffer_init(&m);
-        buffer_put_string(&m, in->value, in->length);
+        if ((m = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new failed", __func__);
+        if ((r = sshbuf_put_string(m, in->value, in->length)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
-        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSSTEP, &m);
-        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_GSSSTEP, &m);
+        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSSTEP, m);
+        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_GSSSTEP, m);
 
-        major = buffer_get_int(&m);
-        out->value = buffer_get_string(&m, &len);
-        out->length = len;
-        if (flags)
-                *flags = buffer_get_int(&m);
+        if ((r = sshbuf_get_u32(m, &major)) != 0 ||
+            (r = sshbuf_get_string(m, &out->value, &out->length)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        if (flagsp != NULL) {
+                if ((r = sshbuf_get_u32(m, &flags)) != 0)
+                        fatal("%s: buffer error: %s", __func__, ssh_err(r));
+                *flagsp = flags;
+        }
 
-        buffer_free(&m);
+        sshbuf_free(m);
 
         return (major);
 }
@@ -927,39 +1005,44 @@ mm_ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *in,
 OM_uint32
 mm_ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
 {
-        Buffer m;
+        struct sshbuf *m;
         OM_uint32 major;
+        int r;
 
-        buffer_init(&m);
-        buffer_put_string(&m, gssbuf->value, gssbuf->length);
-        buffer_put_string(&m, gssmic->value, gssmic->length);
+        if ((m = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new failed", __func__);
+        if ((r = sshbuf_put_string(m, gssbuf->value, gssbuf->length)) != 0 ||
+            (r = sshbuf_put_string(m, gssmic->value, gssmic->length)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
-        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSCHECKMIC, &m);
-        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_GSSCHECKMIC,
-            &m);
+        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSCHECKMIC, m);
+        mm_request_receive_expect(pmonitor->m_recvfd,
+            MONITOR_ANS_GSSCHECKMIC, m);
 
-        major = buffer_get_int(&m);
-        buffer_free(&m);
+        if ((r = sshbuf_get_u32(m, &major)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        sshbuf_free(m);
         return(major);
 }
 
 int
 mm_ssh_gssapi_userok(char *user)
 {
-        Buffer m;
-        int authenticated = 0;
+        struct sshbuf *m;
+        int r, authenticated = 0;
 
-        buffer_init(&m);
+        if ((m = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new failed", __func__);
 
-        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSUSEROK, &m);
-        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_GSSUSEROK,
-                                  &m);
+        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSUSEROK, m);
+        mm_request_receive_expect(pmonitor->m_recvfd,
+            MONITOR_ANS_GSSUSEROK, m);
 
-        authenticated = buffer_get_int(&m);
+        if ((r = sshbuf_get_u32(m, &authenticated)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
-        buffer_free(&m);
+        sshbuf_free(m);
         debug3("%s: user %sauthenticated",__func__, authenticated ? "" : "not ");
         return (authenticated);
 }
 #endif /* GSSAPI */
-