openssh/openssh-7.8p1-gsskex.patch

diff -up openssh/auth2.c.gsskex openssh/auth2.c
--- openssh/auth2.c.gsskex	2018-08-22 11:47:33.260216045 +0200
+++ openssh/auth2.c	2018-08-22 11:47:33.307216424 +0200
@@ -74,6 +74,7 @@ extern Authmethod method_passwd;
 extern Authmethod method_kbdint;
 extern Authmethod method_hostbased;
 #ifdef GSSAPI
+extern Authmethod method_gsskeyex;
 extern Authmethod method_gssapi;
 #endif
 
@@ -81,6 +82,7 @@ Authmethod *authmethods[] = {
 	&method_none,
 	&method_pubkey,
 #ifdef GSSAPI
+	&method_gsskeyex,
 	&method_gssapi,
 #endif
 	&method_passwd,
diff -up openssh/auth2-gss.c.gsskex openssh/auth2-gss.c
--- openssh/auth2-gss.c.gsskex	2018-08-22 11:47:33.260216045 +0200
+++ openssh/auth2-gss.c	2018-08-22 13:00:48.722680124 +0200
@@ -31,6 +31,7 @@
 #include <sys/types.h>
 
 #include <stdarg.h>
+#include <string.h>
 
 #include "xmalloc.h"
 #include "sshkey.h"
@@ -54,6 +55,44 @@ static int input_gssapi_mic(int type, u_
 static int input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh);
 static int input_gssapi_errtok(int, u_int32_t, struct ssh *);
 
+/* 
+ * The 'gssapi_keyex' userauth mechanism.
+ */
+static int
+userauth_gsskeyex(struct ssh *ssh)
+{
+	Authctxt *authctxt = ssh->authctxt;
+	int authenticated = 0;
+	struct sshbuf *b = NULL;
+	gss_buffer_desc mic, gssbuf;
+	u_int len;
+
+	mic.value = packet_get_string(&len);
+	mic.length = len;
+
+	packet_check_eom();
+
+	if ((b = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new failed", __func__);
+
+	ssh_gssapi_buildmic(b, authctxt->user, authctxt->service,
+	    "gssapi-keyex");
+
+	gssbuf.value = sshbuf_mutable_ptr(b);
+	gssbuf.length = sshbuf_len(b);
+
+	/* gss_kex_context is NULL with privsep, so we can't check it here */
+	if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gss_kex_context, 
+	    &gssbuf, &mic))))
+		authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user,
+		    authctxt->pw));
+	
+	sshbuf_free(b);
+	free(mic.value);
+
+	return (authenticated);
+}
+
 /*
  * We only support those mechanisms that we know about (ie ones that we know
  * how to check local user kuserok and the like)
@@ -260,7 +296,8 @@ input_gssapi_exchange_complete(int type,
 	if ((r = sshpkt_get_end(ssh)) != 0)
 		fatal("%s: %s", __func__, ssh_err(r));
 
-	authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
+	authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user,
+	    authctxt->pw));
 
 	if ((!use_privsep || mm_is_monitor()) &&
 	    (displayname = ssh_gssapi_displayname()) != NULL)
@@ -313,7 +350,8 @@ input_gssapi_mic(int type, u_int32_t ple
 	gssbuf.length = sshbuf_len(b);
 
 	if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic))))
-		authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
+		authenticated = 
+		    PRIVSEP(ssh_gssapi_userok(authctxt->user, authctxt->pw));
 	else
 		logit("GSSAPI MIC check failed");
 
@@ -335,6 +373,12 @@ input_gssapi_mic(int type, u_int32_t ple
 	return 0;
 }
 
+Authmethod method_gsskeyex = {
+	"gssapi-keyex",
+	userauth_gsskeyex,
+	&options.gss_authentication
+};
+
 Authmethod method_gssapi = {
 	"gssapi-with-mic",
 	userauth_gssapi,
diff -up openssh/auth.c.gsskex openssh/auth.c
--- openssh/auth.c.gsskex	2018-08-22 11:47:33.274216158 +0200
+++ openssh/auth.c	2018-08-22 11:47:33.308216432 +0200
@@ -395,6 +395,7 @@ auth_root_allowed(struct ssh *ssh, const
 	case PERMIT_NO_PASSWD:
 		if (strcmp(method, "publickey") == 0 ||
 		    strcmp(method, "hostbased") == 0 ||
+		    strcmp(method, "gssapi-keyex") == 0 ||
 		    strcmp(method, "gssapi-with-mic") == 0)
 			return 1;
 		break;
diff -up openssh/clientloop.c.gsskex openssh/clientloop.c
--- openssh/clientloop.c.gsskex	2018-08-20 07:57:29.000000000 +0200
+++ openssh/clientloop.c	2018-08-22 11:47:33.309216441 +0200
@@ -112,6 +112,10 @@
 #include "ssherr.h"
 #include "hostfile.h"
 
+#ifdef GSSAPI
+#include "ssh-gss.h"
+#endif
+
 /* import options */
 extern Options options;
 
@@ -1357,9 +1361,18 @@ client_loop(struct ssh *ssh, int have_pt
 			break;
 
 		/* Do channel operations unless rekeying in progress. */
-		if (!ssh_packet_is_rekeying(ssh))
+		if (!ssh_packet_is_rekeying(ssh)) {
 			channel_after_select(ssh, readset, writeset);
 
+#ifdef GSSAPI
+			if (options.gss_renewal_rekey &&
+			    ssh_gssapi_credentials_updated(NULL)) {
+				debug("credentials updated - forcing rekey");
+				need_rekeying = 1;
+			}
+#endif
+		}
+
 		/* Buffer input from the connection.  */
 		client_process_net_input(readset);
 
diff -up openssh/configure.ac.gsskex openssh/configure.ac
--- openssh/configure.ac.gsskex	2018-08-22 11:47:33.296216335 +0200
+++ openssh/configure.ac	2018-08-22 11:47:33.309216441 +0200
@@ -673,6 +673,30 @@ main() { if (NSVersionOfRunTimeLibrary("
 	    [Use tunnel device compatibility to OpenBSD])
 	AC_DEFINE([SSH_TUN_PREPEND_AF], [1],
 	    [Prepend the address family to IP tunnel traffic])
+	AC_MSG_CHECKING(if we have the Security Authorization Session API)
+	AC_TRY_COMPILE([#include <Security/AuthSession.h>],
+		[SessionCreate(0, 0);],
+		[ac_cv_use_security_session_api="yes"
+		 AC_DEFINE(USE_SECURITY_SESSION_API, 1, 
+			[platform has the Security Authorization Session API])
+		 LIBS="$LIBS -framework Security"
+		 AC_MSG_RESULT(yes)],
+		[ac_cv_use_security_session_api="no"
+		 AC_MSG_RESULT(no)])
+	AC_MSG_CHECKING(if we have an in-memory credentials cache)
+	AC_TRY_COMPILE(
+		[#include <Kerberos/Kerberos.h>],
+		[cc_context_t c;
+		 (void) cc_initialize (&c, 0, NULL, NULL);],
+		[AC_DEFINE(USE_CCAPI, 1, 
+			[platform uses an in-memory credentials cache])
+		 LIBS="$LIBS -framework Security"
+		 AC_MSG_RESULT(yes)
+		 if test "x$ac_cv_use_security_session_api" = "xno"; then
+			AC_MSG_ERROR(*** Need a security framework to use the credentials cache API ***)
+		fi],
+		[AC_MSG_RESULT(no)]
+	)
 	m4_pattern_allow([AU_IPv])
 	AC_CHECK_DECL([AU_IPv4], [],
 	    AC_DEFINE([AU_IPv4], [0], [System only supports IPv4 audit records])
diff -up openssh/gss-genr.c.gsskex openssh/gss-genr.c
--- openssh/gss-genr.c.gsskex	2018-08-20 07:57:29.000000000 +0200
+++ openssh/gss-genr.c	2018-08-22 13:18:47.444383602 +0200
@@ -35,18 +35,177 @@
 #include <string.h>
 #include <signal.h>
 #include <unistd.h>
+#include <openssl/evp.h>
 
 #include "xmalloc.h"
 #include "ssherr.h"
 #include "sshbuf.h"
 #include "log.h"
 #include "ssh2.h"
+#include "cipher.h"
+#include "sshkey.h"
+#include "kex.h"
 
 #include "ssh-gss.h"
 
 extern u_char *session_id2;
 extern u_int session_id2_len;
 
+typedef struct {
+	char *encoded;
+	gss_OID oid;
+} ssh_gss_kex_mapping;
+
+/*
+ * XXX - It would be nice to find a more elegant way of handling the
+ * XXX   passing of the key exchange context to the userauth routines
+ */
+
+Gssctxt *gss_kex_context = NULL;
+
+static ssh_gss_kex_mapping *gss_enc2oid = NULL;
+
+int 
+ssh_gssapi_oid_table_ok() {
+	return (gss_enc2oid != NULL);
+}
+
+/*
+ * Return a list of the gss-group1-sha1 mechanisms supported by this program
+ *
+ * We test mechanisms to ensure that we can use them, to avoid starting
+ * a key exchange with a bad mechanism
+ */
+
+char *
+ssh_gssapi_client_mechanisms(const char *host, const char *client) {
+	gss_OID_set gss_supported;
+	OM_uint32 min_status;
+
+	if (GSS_ERROR(gss_indicate_mechs(&min_status, &gss_supported)))
+		return NULL;
+
+	return(ssh_gssapi_kex_mechs(gss_supported, ssh_gssapi_check_mechanism,
+	    host, client));
+}
+
+char *
+ssh_gssapi_kex_mechs(gss_OID_set gss_supported, ssh_gssapi_check_fn *check,
+    const char *host, const char *client) {
+	struct sshbuf *buf;
+	size_t i;
+	int oidpos, enclen, r;
+	char *mechs, *encoded;
+	u_char digest[EVP_MAX_MD_SIZE];
+	char deroid[2];
+	const EVP_MD *evp_md = EVP_md5();
+	EVP_MD_CTX md;
+
+	if (gss_enc2oid != NULL) {
+		for (i = 0; gss_enc2oid[i].encoded != NULL; i++)
+			free(gss_enc2oid[i].encoded);
+		free(gss_enc2oid);
+	}
+
+	gss_enc2oid = xmalloc(sizeof(ssh_gss_kex_mapping) *
+	    (gss_supported->count + 1));
+
+	if ((buf = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new failed", __func__);
+
+	oidpos = 0;
+	for (i = 0; i < gss_supported->count; i++) {
+		if (gss_supported->elements[i].length < 128 &&
+		    (*check)(NULL, &(gss_supported->elements[i]), host, client)) {
+
+			deroid[0] = SSH_GSS_OIDTYPE;
+			deroid[1] = gss_supported->elements[i].length;
+
+			EVP_DigestInit(&md, evp_md);
+			EVP_DigestUpdate(&md, deroid, 2);
+			EVP_DigestUpdate(&md,
+			    gss_supported->elements[i].elements,
+			    gss_supported->elements[i].length);
+			EVP_DigestFinal(&md, digest, NULL);
+
+			encoded = xmalloc(EVP_MD_size(evp_md) * 2);
+			enclen = __b64_ntop(digest, EVP_MD_size(evp_md),
+			    encoded, EVP_MD_size(evp_md) * 2);
+
+			if (oidpos != 0)
+				if ((r = sshbuf_put_u8(buf, ',')) != 0)
+					fatal("%s: buffer error: %s", __func__, ssh_err(r));
+
+			if ((r = sshbuf_put(buf, KEX_GSS_GEX_SHA1_ID,
+			    sizeof(KEX_GSS_GEX_SHA1_ID) - 1)) != 0 ||
+			    (r = sshbuf_put(buf, encoded, enclen)) != 0 ||
+			    (r = sshbuf_put_u8(buf, ',')) != 0 ||
+			    (r = sshbuf_put(buf, KEX_GSS_GRP1_SHA1_ID, 
+			    sizeof(KEX_GSS_GRP1_SHA1_ID) - 1)) != 0 ||
+			    (r = sshbuf_put(buf, encoded, enclen)) != 0 ||
+			    (r = sshbuf_put_u8(buf, ',')) != 0 ||
+			    (r = sshbuf_put(buf, KEX_GSS_GRP14_SHA1_ID,
+			    sizeof(KEX_GSS_GRP14_SHA1_ID) - 1)) != 0 ||
+			    (r = sshbuf_put(buf, encoded, enclen)) != 0)
+		 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+
+			gss_enc2oid[oidpos].oid = &(gss_supported->elements[i]);
+			gss_enc2oid[oidpos].encoded = encoded;
+			oidpos++;
+		}
+	}
+	gss_enc2oid[oidpos].oid = NULL;
+	gss_enc2oid[oidpos].encoded = NULL;
+
+	if ((r = sshbuf_put_u8(buf, '\0')) != 0)
+		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+
+	mechs = xmalloc(sshbuf_len(buf));
+	sshbuf_get(buf, mechs, sshbuf_len(buf));
+	sshbuf_free(buf);
+
+	if (strlen(mechs) == 0) {
+		free(mechs);
+		mechs = NULL;
+	}
+
+	return (mechs);
+}
+
+gss_OID
+ssh_gssapi_id_kex(Gssctxt *ctx, char *name, int kex_type) {
+	int i = 0;
+	
+	switch (kex_type) {
+	case KEX_GSS_GRP1_SHA1:
+		if (strlen(name) < sizeof(KEX_GSS_GRP1_SHA1_ID))
+			return GSS_C_NO_OID;
+		name += sizeof(KEX_GSS_GRP1_SHA1_ID) - 1;
+		break;
+	case KEX_GSS_GRP14_SHA1:
+		if (strlen(name) < sizeof(KEX_GSS_GRP14_SHA1_ID))
+			return GSS_C_NO_OID;
+		name += sizeof(KEX_GSS_GRP14_SHA1_ID) - 1;
+		break;
+	case KEX_GSS_GEX_SHA1:
+		if (strlen(name) < sizeof(KEX_GSS_GEX_SHA1_ID))
+			return GSS_C_NO_OID;
+		name += sizeof(KEX_GSS_GEX_SHA1_ID) - 1;
+		break;
+	default:
+		return GSS_C_NO_OID;
+	}
+
+	while (gss_enc2oid[i].encoded != NULL &&
+	    strcmp(name, gss_enc2oid[i].encoded) != 0)
+		i++;
+
+	if (gss_enc2oid[i].oid != NULL && ctx != NULL)
+		ssh_gssapi_set_oid(ctx, gss_enc2oid[i].oid);
+
+	return gss_enc2oid[i].oid;
+}
+
 /* sshbuf_get for gss_buffer_desc */
 int
 ssh_gssapi_get_buffer_desc(struct sshbuf *b, gss_buffer_desc *g)
@@ -218,7 +373,7 @@ ssh_gssapi_init_ctx(Gssctxt *ctx, int de
 	}
 
 	ctx->major = gss_init_sec_context(&ctx->minor,
-	    GSS_C_NO_CREDENTIAL, &ctx->context, ctx->name, ctx->oid,
+	    ctx->client_creds, &ctx->context, ctx->name, ctx->oid,
 	    GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG | deleg_flag,
 	    0, NULL, recv_tok, NULL, send_tok, flags, NULL);
 
@@ -248,8 +403,42 @@ ssh_gssapi_import_name(Gssctxt *ctx, con
 }
 
 OM_uint32
+ssh_gssapi_client_identity(Gssctxt *ctx, const char *name)
+{
+	gss_buffer_desc gssbuf;
+	gss_name_t gssname;
+	OM_uint32 status;
+	gss_OID_set oidset;
+
+	gssbuf.value = (void *) name;
+	gssbuf.length = strlen(gssbuf.value);
+
+	gss_create_empty_oid_set(&status, &oidset);
+	gss_add_oid_set_member(&status, ctx->oid, &oidset);
+
+	ctx->major = gss_import_name(&ctx->minor, &gssbuf,
+	    GSS_C_NT_USER_NAME, &gssname);
+
+	if (!ctx->major)
+		ctx->major = gss_acquire_cred(&ctx->minor, 
+		    gssname, 0, oidset, GSS_C_INITIATE, 
+		    &ctx->client_creds, NULL, NULL);
+
+	gss_release_name(&status, &gssname);
+	gss_release_oid_set(&status, &oidset);
+
+	if (ctx->major)
+		ssh_gssapi_error(ctx);
+
+	return(ctx->major);
+}
+
+OM_uint32
 ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
 {
+	if (ctx == NULL) 
+		return -1;
+
 	if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context,
 	    GSS_C_QOP_DEFAULT, buffer, hash)))
 		ssh_gssapi_error(ctx);
@@ -257,6 +446,19 @@ ssh_gssapi_sign(Gssctxt *ctx, gss_buffer
 	return (ctx->major);
 }
 
+/* Priviledged when used by server */
+OM_uint32
+ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
+{
+	if (ctx == NULL)
+		return -1;
+
+	ctx->major = gss_verify_mic(&ctx->minor, ctx->context,
+	    gssbuf, gssmic, NULL);
+
+	return (ctx->major);
+}
+
 void
 ssh_gssapi_buildmic(struct sshbuf *b, const char *user, const char *service,
     const char *context)
@@ -273,11 +475,16 @@ ssh_gssapi_buildmic(struct sshbuf *b, co
 }
 
 int
-ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host)
+ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host, 
+    const char *client)
 {
 	gss_buffer_desc token = GSS_C_EMPTY_BUFFER;
 	OM_uint32 major, minor;
 	gss_OID_desc spnego_oid = {6, (void *)"\x2B\x06\x01\x05\x05\x02"};
+	Gssctxt *intctx = NULL;
+
+	if (ctx == NULL)
+		ctx = &intctx;
 
 	/* RFC 4462 says we MUST NOT do SPNEGO */
 	if (oid->length == spnego_oid.length && 
@@ -287,6 +494,10 @@ ssh_gssapi_check_mechanism(Gssctxt **ctx
 	ssh_gssapi_build_ctx(ctx);
 	ssh_gssapi_set_oid(*ctx, oid);
 	major = ssh_gssapi_import_name(*ctx, host);
+
+	if (!GSS_ERROR(major) && client)
+		major = ssh_gssapi_client_identity(*ctx, client);
+
 	if (!GSS_ERROR(major)) {
 		major = ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token, 
 		    NULL);
@@ -296,10 +507,66 @@ ssh_gssapi_check_mechanism(Gssctxt **ctx
 			    GSS_C_NO_BUFFER);
 	}
 
-	if (GSS_ERROR(major)) 
+	if (GSS_ERROR(major) || intctx != NULL) 
 		ssh_gssapi_delete_ctx(ctx);
 
 	return (!GSS_ERROR(major));
 }
 
+int
+ssh_gssapi_credentials_updated(Gssctxt *ctxt) {
+	static gss_name_t saved_name = GSS_C_NO_NAME;
+	static OM_uint32 saved_lifetime = 0;
+	static gss_OID saved_mech = GSS_C_NO_OID;
+	static gss_name_t name;
+	static OM_uint32 last_call = 0;
+	OM_uint32 lifetime, now, major, minor;
+	int equal;
+	
+	now = time(NULL);
+
+	if (ctxt) {
+		debug("Rekey has happened - updating saved versions");
+
+		if (saved_name != GSS_C_NO_NAME)
+			gss_release_name(&minor, &saved_name);
+
+		major = gss_inquire_cred(&minor, GSS_C_NO_CREDENTIAL,
+		    &saved_name, &saved_lifetime, NULL, NULL);
+
+		if (!GSS_ERROR(major)) {
+			saved_mech = ctxt->oid;
+		        saved_lifetime+= now;
+		} else {
+			/* Handle the error */
+		}
+		return 0;
+	}
+
+	if (now - last_call < 10)
+		return 0;
+
+	last_call = now;
+
+	if (saved_mech == GSS_C_NO_OID)
+		return 0;
+	
+	major = gss_inquire_cred(&minor, GSS_C_NO_CREDENTIAL, 
+	    &name, &lifetime, NULL, NULL);
+	if (major == GSS_S_CREDENTIALS_EXPIRED)
+		return 0;
+	else if (GSS_ERROR(major))
+		return 0;
+
+	major = gss_compare_name(&minor, saved_name, name, &equal);
+	gss_release_name(&minor, &name);
+	if (GSS_ERROR(major))
+		return 0;
+
+	if (equal && (saved_lifetime < lifetime + now - 10))
+		return 1;
+
+	return 0;
+}
+
 #endif /* GSSAPI */
diff -up openssh/gss-serv.c.gsskex openssh/gss-serv.c
--- openssh/gss-serv.c.gsskex	2018-08-20 07:57:29.000000000 +0200
+++ openssh/gss-serv.c	2018-08-22 11:47:33.310216448 +0200
@@ -44,17 +44,19 @@
 #include "session.h"
 #include "misc.h"
 #include "servconf.h"
+#include "uidswap.h"
 
 #include "ssh-gss.h"
+#include "monitor_wrap.h"
 
 extern ServerOptions options;
 
 static ssh_gssapi_client gssapi_client =
-    { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER,
-    GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL, NULL}};
+    { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER, GSS_C_NO_CREDENTIAL,
+    GSS_C_NO_NAME, NULL, {NULL, NULL, NULL, NULL}, 0, 0};
 
 ssh_gssapi_mech gssapi_null_mech =
-    { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL};
+    { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL, NULL};
 
 #ifdef KRB5
 extern ssh_gssapi_mech gssapi_kerberos_mech;
@@ -141,6 +143,28 @@ ssh_gssapi_server_ctx(Gssctxt **ctx, gss
 }
 
 /* Unprivileged */
+char *
+ssh_gssapi_server_mechanisms() {
+	if (supported_oids == NULL)
+		ssh_gssapi_prepare_supported_oids();
+	return (ssh_gssapi_kex_mechs(supported_oids,
+	    &ssh_gssapi_server_check_mech, NULL, NULL));
+}
+
+/* Unprivileged */
+int
+ssh_gssapi_server_check_mech(Gssctxt **dum, gss_OID oid, const char *data,
+    const char *dummy) {
+	Gssctxt *ctx = NULL;
+	int res;
+ 
+	res = !GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctx, oid)));
+	ssh_gssapi_delete_ctx(&ctx);
+
+	return (res);
+}
+
+/* Unprivileged */
 void
 ssh_gssapi_supported_oids(gss_OID_set *oidset)
 {
@@ -150,7 +174,9 @@ ssh_gssapi_supported_oids(gss_OID_set *o
 	gss_OID_set supported;
 
 	gss_create_empty_oid_set(&min_status, oidset);
-	gss_indicate_mechs(&min_status, &supported);
+
+	if (GSS_ERROR(gss_indicate_mechs(&min_status, &supported)))
+		return;
 
 	while (supported_mechs[i]->name != NULL) {
 		if (GSS_ERROR(gss_test_oid_set_member(&min_status,
@@ -276,8 +302,48 @@ OM_uint32
 ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
 {
 	int i = 0;
+	int equal = 0;
+	gss_name_t new_name = GSS_C_NO_NAME;
+	gss_buffer_desc ename = GSS_C_EMPTY_BUFFER;
+
+	if (options.gss_store_rekey && client->used && ctx->client_creds) {
+		if (client->mech->oid.length != ctx->oid->length ||
+		    (memcmp(client->mech->oid.elements,
+		     ctx->oid->elements, ctx->oid->length) !=0)) {
+			debug("Rekeyed credentials have different mechanism");
+			return GSS_S_COMPLETE;
+		}
+
+		if ((ctx->major = gss_inquire_cred_by_mech(&ctx->minor, 
+		    ctx->client_creds, ctx->oid, &new_name, 
+		    NULL, NULL, NULL))) {
+			ssh_gssapi_error(ctx);
+			return (ctx->major);
+		}
+
+		ctx->major = gss_compare_name(&ctx->minor, client->name, 
+		    new_name, &equal);
+
+		if (GSS_ERROR(ctx->major)) {
+			ssh_gssapi_error(ctx);
+			return (ctx->major);
+		}
+ 
+		if (!equal) {
+			debug("Rekeyed credentials have different name");
+			return GSS_S_COMPLETE;
+		}
+
+		debug("Marking rekeyed credentials for export");
 
-	gss_buffer_desc ename;
+		gss_release_name(&ctx->minor, &client->name);
+		gss_release_cred(&ctx->minor, &client->creds);
+		client->name = new_name;
+		client->creds = ctx->client_creds;
+        	ctx->client_creds = GSS_C_NO_CREDENTIAL;
+		client->updated = 1;
+		return GSS_S_COMPLETE;
+	}
 
 	client->mech = NULL;
 
@@ -292,6 +358,13 @@ ssh_gssapi_getclient(Gssctxt *ctx, ssh_g
 	if (client->mech == NULL)
 		return GSS_S_FAILURE;
 
+	if (ctx->client_creds &&
+	    (ctx->major = gss_inquire_cred_by_mech(&ctx->minor,
+	     ctx->client_creds, ctx->oid, &client->name, NULL, NULL, NULL))) {
+		ssh_gssapi_error(ctx);
+		return (ctx->major);
+	}
+
 	if ((ctx->major = gss_display_name(&ctx->minor, ctx->client,
 	    &client->displayname, NULL))) {
 		ssh_gssapi_error(ctx);
@@ -309,6 +382,8 @@ ssh_gssapi_getclient(Gssctxt *ctx, ssh_g
 		return (ctx->major);
 	}
 
+	gss_release_buffer(&ctx->minor, &ename);
+
 	/* We can't copy this structure, so we just move the pointer to it */
 	client->creds = ctx->client_creds;
 	ctx->client_creds = GSS_C_NO_CREDENTIAL;
@@ -319,11 +394,20 @@ ssh_gssapi_getclient(Gssctxt *ctx, ssh_g
 void
 ssh_gssapi_cleanup_creds(void)
 {
-	if (gssapi_client.store.filename != NULL) {
-		/* Unlink probably isn't sufficient */
-		debug("removing gssapi cred file\"%s\"",
-		    gssapi_client.store.filename);
-		unlink(gssapi_client.store.filename);
+	krb5_ccache ccache = NULL;
+	krb5_error_code problem;
+
+	if (gssapi_client.store.data != NULL) {
+		if ((problem = krb5_cc_resolve(gssapi_client.store.data, gssapi_client.store.envval, &ccache))) {
+			debug("%s: krb5_cc_resolve(): %.100s", __func__,
+				krb5_get_err_text(gssapi_client.store.data, problem));
+		} else if ((problem = krb5_cc_destroy(gssapi_client.store.data, ccache))) {
+			debug("%s: krb5_cc_resolve(): %.100s", __func__,
+				krb5_get_err_text(gssapi_client.store.data, problem));
+		} else {
+			krb5_free_context(gssapi_client.store.data);
+			gssapi_client.store.data = NULL;
+		}
 	}
 }
 
@@ -356,7 +440,7 @@ ssh_gssapi_do_child(char ***envp, u_int
 
 /* Privileged */
 int
-ssh_gssapi_userok(char *user)
+ssh_gssapi_userok(char *user, struct passwd *pw)
 {
 	OM_uint32 lmin;
 
@@ -366,9 +450,11 @@ ssh_gssapi_userok(char *user)
 		return 0;
 	}
 	if (gssapi_client.mech && gssapi_client.mech->userok)
-		if ((*gssapi_client.mech->userok)(&gssapi_client, user))
+		if ((*gssapi_client.mech->userok)(&gssapi_client, user)) {
+			gssapi_client.used = 1;
+			gssapi_client.store.owner = pw;
 			return 1;
-		else {
+		} else {
 			/* Destroy delegated credentials if userok fails */
 			gss_release_buffer(&lmin, &gssapi_client.displayname);
 			gss_release_buffer(&lmin, &gssapi_client.exportedname);
@@ -382,14 +468,89 @@ ssh_gssapi_userok(char *user)
 	return (0);
 }
 
-/* Privileged */
-OM_uint32
-ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
+/* These bits are only used for rekeying. The unpriviledged child is running 
+ * as the user, the monitor is root.
+ *
+ * In the child, we want to :
+ *    *) Ask the monitor to store our credentials into the store we specify
+ *    *) If it succeeds, maybe do a PAM update
+ */
+
+/* Stuff for PAM */
+
+#ifdef USE_PAM
+static int ssh_gssapi_simple_conv(int n, const struct pam_message **msg, 
+    struct pam_response **resp, void *data)
 {
-	ctx->major = gss_verify_mic(&ctx->minor, ctx->context,
-	    gssbuf, gssmic, NULL);
+	return (PAM_CONV_ERR);
+}
+#endif
 
-	return (ctx->major);
+void
+ssh_gssapi_rekey_creds() {
+	int ok;
+	int ret;
+#ifdef USE_PAM
+	pam_handle_t *pamh = NULL;
+	struct pam_conv pamconv = {ssh_gssapi_simple_conv, NULL};
+	char *envstr;
+#endif
+
+	if (gssapi_client.store.envval == NULL &&
+	    gssapi_client.store.envvar == NULL)
+		return;
+ 
+	ok = PRIVSEP(ssh_gssapi_update_creds(&gssapi_client.store));
+
+	if (!ok)
+		return;
+
+	debug("Rekeyed credentials stored successfully");
+
+	/* Actually managing to play with the ssh pam stack from here will
+	 * be next to impossible. In any case, we may want different options
+	 * for rekeying. So, use our own :)
+	 */
+#ifdef USE_PAM	
+	if (!use_privsep) {
+		debug("Not even going to try and do PAM with privsep disabled");
+		return;
+	}
+
+	ret = pam_start("sshd-rekey", gssapi_client.store.owner->pw_name,
+ 	    &pamconv, &pamh);
+	if (ret)
+		return;
+
+	xasprintf(&envstr, "%s=%s", gssapi_client.store.envvar, 
+	    gssapi_client.store.envval);
+
+	ret = pam_putenv(pamh, envstr);
+	if (!ret)
+		pam_setcred(pamh, PAM_REINITIALIZE_CRED);
+	pam_end(pamh, PAM_SUCCESS);
+#endif
+}
+
+int 
+ssh_gssapi_update_creds(ssh_gssapi_ccache *store) {
+	int ok = 0;
+
+	/* Check we've got credentials to store */
+	if (!gssapi_client.updated)
+		return 0;
+
+	gssapi_client.updated = 0;
+
+	temporarily_use_uid(gssapi_client.store.owner);
+	if (gssapi_client.mech && gssapi_client.mech->updatecreds)
+		ok = (*gssapi_client.mech->updatecreds)(store, &gssapi_client);
+	else
+		debug("No update function for this mechanism");
+
+	restore_uid();
+
+	return ok;
 }
 
 /* Privileged */
diff -up openssh/gss-serv-krb5.c.gsskex openssh/gss-serv-krb5.c
--- openssh/gss-serv-krb5.c.gsskex	2018-08-20 07:57:29.000000000 +0200
+++ openssh/gss-serv-krb5.c	2018-08-22 11:47:33.311216457 +0200
@@ -120,7 +120,7 @@ ssh_gssapi_krb5_storecreds(ssh_gssapi_cl
 	krb5_error_code problem;
 	krb5_principal princ;
 	OM_uint32 maj_status, min_status;
-	int len;
+	const char *new_ccname, *new_cctype;
 	const char *errmsg;
 
 	if (client->creds == NULL) {
@@ -180,11 +180,23 @@ ssh_gssapi_krb5_storecreds(ssh_gssapi_cl
 		return;
 	}
 
-	client->store.filename = xstrdup(krb5_cc_get_name(krb_context, ccache));
+	new_cctype = krb5_cc_get_type(krb_context, ccache);
+	new_ccname = krb5_cc_get_name(krb_context, ccache);
+
 	client->store.envvar = "KRB5CCNAME";
-	len = strlen(client->store.filename) + 6;
-	client->store.envval = xmalloc(len);
-	snprintf(client->store.envval, len, "FILE:%s", client->store.filename);
+#ifdef USE_CCAPI
+	xasprintf(&client->store.envval, "API:%s", new_ccname);
+#else
+	if (new_ccname[0] == ':')
+		new_ccname++;
+	xasprintf(&client->store.envval, "%s:%s", new_cctype, new_ccname);
+	if (strcmp(new_cctype, "DIR") == 0) {
+		char *p;
+		p = strrchr(client->store.envval, '/');
+		if (p)
+			*p = '\0';
+	}
+#endif
 
 #ifdef USE_PAM
 	if (options.use_pam)
@@ -193,9 +205,76 @@ ssh_gssapi_krb5_storecreds(ssh_gssapi_cl
 
 	krb5_cc_close(krb_context, ccache);
 
+	client->store.data = krb_context;
+
 	return;
 }
 
+int
+ssh_gssapi_krb5_updatecreds(ssh_gssapi_ccache *store, 
+    ssh_gssapi_client *client)
+{
+	krb5_ccache ccache = NULL;
+	krb5_principal principal = NULL;
+	char *name = NULL;
+	krb5_error_code problem;
+	OM_uint32 maj_status, min_status;
+
+   	if ((problem = krb5_cc_resolve(krb_context, store->envval, &ccache))) {
+                logit("krb5_cc_resolve(): %.100s",
+                    krb5_get_err_text(krb_context, problem));
+                return 0;
+       	}
+	
+	/* Find out who the principal in this cache is */
+	if ((problem = krb5_cc_get_principal(krb_context, ccache, 
+	    &principal))) {
+		logit("krb5_cc_get_principal(): %.100s",
+		    krb5_get_err_text(krb_context, problem));
+		krb5_cc_close(krb_context, ccache);
+		return 0;
+	}
+
+	if ((problem = krb5_unparse_name(krb_context, principal, &name))) {
+		logit("krb5_unparse_name(): %.100s",
+		    krb5_get_err_text(krb_context, problem));
+		krb5_free_principal(krb_context, principal);
+		krb5_cc_close(krb_context, ccache);
+		return 0;
+	}
+
+
+	if (strcmp(name,client->exportedname.value)!=0) {
+		debug("Name in local credentials cache differs. Not storing");
+		krb5_free_principal(krb_context, principal);
+		krb5_cc_close(krb_context, ccache);
+		krb5_free_unparsed_name(krb_context, name);
+		return 0;
+	}
+	krb5_free_unparsed_name(krb_context, name);
+
+	/* Name matches, so lets get on with it! */
+
+	if ((problem = krb5_cc_initialize(krb_context, ccache, principal))) {
+		logit("krb5_cc_initialize(): %.100s",
+		    krb5_get_err_text(krb_context, problem));
+		krb5_free_principal(krb_context, principal);
+		krb5_cc_close(krb_context, ccache);
+		return 0;
+	}
+
+	krb5_free_principal(krb_context, principal);
+
+	if ((maj_status = gss_krb5_copy_ccache(&min_status, client->creds,
+	    ccache))) {
+		logit("gss_krb5_copy_ccache() failed. Sorry!");
+		krb5_cc_close(krb_context, ccache);
+		return 0;
+	}
+
+	return 1;
+}
+
 ssh_gssapi_mech gssapi_kerberos_mech = {
 	"toWM5Slw5Ew8Mqkay+al2g==",
 	"Kerberos",
@@ -203,7 +282,8 @@ ssh_gssapi_mech gssapi_kerberos_mech = {
 	NULL,
 	&ssh_gssapi_krb5_userok,
 	NULL,
-	&ssh_gssapi_krb5_storecreds
+	&ssh_gssapi_krb5_storecreds,
+	&ssh_gssapi_krb5_updatecreds
 };
 
 #endif /* KRB5 */
diff -up openssh/kex.c.gsskex openssh/kex.c
--- openssh/kex.c.gsskex	2018-08-20 07:57:29.000000000 +0200
+++ openssh/kex.c	2018-08-22 11:47:33.311216457 +0200
@@ -54,6 +54,10 @@
 #include "sshbuf.h"
 #include "digest.h"
 
+#ifdef GSSAPI
+#include "ssh-gss.h"
+#endif
+
 /* prototype */
 static int kex_choose_conf(struct ssh *);
 static int kex_input_newkeys(int, u_int32_t, struct ssh *);
@@ -103,6 +107,11 @@ static const struct kexalg kexalgs[] = {
 	{ KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
 	{ KEX_CURVE25519_SHA256_OLD, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
 #endif /* HAVE_EVP_SHA256 || !WITH_OPENSSL */
+#ifdef GSSAPI
+	{ KEX_GSS_GEX_SHA1_ID, KEX_GSS_GEX_SHA1, 0, SSH_DIGEST_SHA1 },
+	{ KEX_GSS_GRP1_SHA1_ID, KEX_GSS_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
+	{ KEX_GSS_GRP14_SHA1_ID, KEX_GSS_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },
+#endif
 	{ NULL, -1, -1, -1},
 };
 
@@ -136,6 +145,12 @@ kex_alg_by_name(const char *name)
 	for (k = kexalgs; k->name != NULL; k++) {
 		if (strcmp(k->name, name) == 0)
 			return k;
+#ifdef GSSAPI
+		if (strncmp(name, "gss-", 4) == 0) {
+			if (strncmp(k->name, name, strlen(k->name)) == 0)
+				return k;
+		}
+#endif
 	}
 	return NULL;
 }
diff -up openssh/kexgssc.c.gsskex openssh/kexgssc.c
--- openssh/kexgssc.c.gsskex	2018-08-22 11:47:33.311216457 +0200
+++ openssh/kexgssc.c	2018-08-22 11:47:33.311216457 +0200
@@ -0,0 +1,338 @@
+/*
+ * Copyright (c) 2001-2009 Simon Wilkinson. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "includes.h"
+
+#ifdef GSSAPI
+
+#include "includes.h"
+
+#include <openssl/crypto.h>
+#include <openssl/bn.h>
+
+#include <string.h>
+
+#include "xmalloc.h"
+#include "sshbuf.h"
+#include "ssh2.h"
+#include "sshkey.h"
+#include "cipher.h"
+#include "kex.h"
+#include "log.h"
+#include "packet.h"
+#include "dh.h"
+#include "digest.h"
+
+#include "ssh-gss.h"
+
+int
+kexgss_client(struct ssh *ssh) {
+	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
+	gss_buffer_desc recv_tok, gssbuf, msg_tok, *token_ptr;
+	Gssctxt *ctxt;
+	OM_uint32 maj_status, min_status, ret_flags;
+	u_int klen, kout, slen = 0, strlen;
+	DH *dh; 
+	BIGNUM *dh_server_pub = NULL;
+	BIGNUM *shared_secret = NULL;
+	BIGNUM *p = NULL;
+	BIGNUM *g = NULL;	
+	u_char *kbuf;
+	u_char *serverhostkey = NULL;
+	u_char *empty = "";
+	char *msg;
+	char *lang;
+	int type = 0;
+	int first = 1;
+	int nbits = 0, min = DH_GRP_MIN, max = DH_GRP_MAX;
+	u_char hash[SSH_DIGEST_MAX_LENGTH];
+	size_t hashlen;
+
+	/* Initialise our GSSAPI world */	
+	ssh_gssapi_build_ctx(&ctxt);
+	if (ssh_gssapi_id_kex(ctxt, ssh->kex->name, ssh->kex->kex_type) 
+	    == GSS_C_NO_OID)
+		fatal("Couldn't identify host exchange");
+
+	if (ssh_gssapi_import_name(ctxt, ssh->kex->gss_host))
+		fatal("Couldn't import hostname");
+
+	if (ssh->kex->gss_client && 
+	    ssh_gssapi_client_identity(ctxt, ssh->kex->gss_client))
+		fatal("Couldn't acquire client credentials");
+
+	switch (ssh->kex->kex_type) {
+	case KEX_GSS_GRP1_SHA1:
+		dh = dh_new_group1();
+		break;
+	case KEX_GSS_GRP14_SHA1:
+		dh = dh_new_group14();
+		break;
+	case KEX_GSS_GEX_SHA1:
+		debug("Doing group exchange\n");
+		nbits = dh_estimate(ssh->kex->we_need * 8);
+		packet_start(SSH2_MSG_KEXGSS_GROUPREQ);
+		packet_put_int(min);
+		packet_put_int(nbits);
+		packet_put_int(max);
+
+		packet_send();
+
+		packet_read_expect(SSH2_MSG_KEXGSS_GROUP);
+
+		if ((p = BN_new()) == NULL)
+			fatal("BN_new() failed");
+		packet_get_bignum2(p);
+		if ((g = BN_new()) == NULL)
+			fatal("BN_new() failed");
+		packet_get_bignum2(g);
+		packet_check_eom();
+
+		if (BN_num_bits(p) < min || BN_num_bits(p) > max)
+			fatal("GSSGRP_GEX group out of range: %d !< %d !< %d",
+			    min, BN_num_bits(p), max);
+
+		dh = dh_new_group(g, p);
+		break;
+	default:
+		fatal("%s: Unexpected KEX type %d", __func__, ssh->kex->kex_type);
+	}
+	
+	/* Step 1 - e is dh->pub_key */
+	dh_gen_key(dh, ssh->kex->we_need * 8);
+
+	/* This is f, we initialise it now to make life easier */
+	dh_server_pub = BN_new();
+	if (dh_server_pub == NULL)
+		fatal("dh_server_pub == NULL");
+
+	token_ptr = GSS_C_NO_BUFFER;
+			 
+	do {
+		debug("Calling gss_init_sec_context");
+		
+		maj_status = ssh_gssapi_init_ctx(ctxt,
+		    ssh->kex->gss_deleg_creds, token_ptr, &send_tok,
+		    &ret_flags);
+
+		if (GSS_ERROR(maj_status)) {
+			if (send_tok.length != 0) {
+				packet_start(SSH2_MSG_KEXGSS_CONTINUE);
+				packet_put_string(send_tok.value,
+				    send_tok.length);
+			}
+			fatal("gss_init_context failed");
+		}
+
+		/* If we've got an old receive buffer get rid of it */
+		if (token_ptr != GSS_C_NO_BUFFER)
+			free(recv_tok.value);
+
+		if (maj_status == GSS_S_COMPLETE) {
+			/* If mutual state flag is not true, kex fails */
+			if (!(ret_flags & GSS_C_MUTUAL_FLAG))
+				fatal("Mutual authentication failed");
+
+			/* If integ avail flag is not true kex fails */
+			if (!(ret_flags & GSS_C_INTEG_FLAG))
+				fatal("Integrity check failed");
+		}
+
+		/* 
+		 * If we have data to send, then the last message that we
+		 * received cannot have been a 'complete'. 
+		 */
+		if (send_tok.length != 0) {
+			if (first) {
+				packet_start(SSH2_MSG_KEXGSS_INIT);
+				packet_put_string(send_tok.value,
+				    send_tok.length);
+				packet_put_bignum2(dh->pub_key);
+				first = 0;
+			} else {
+				packet_start(SSH2_MSG_KEXGSS_CONTINUE);
+				packet_put_string(send_tok.value,
+				    send_tok.length);
+			}
+			packet_send();
+			gss_release_buffer(&min_status, &send_tok);
+
+			/* If we've sent them data, they should reply */
+			do {	
+				type = packet_read();
+				if (type == SSH2_MSG_KEXGSS_HOSTKEY) {
+					debug("Received KEXGSS_HOSTKEY");
+					if (serverhostkey)
+						fatal("Server host key received more than once");
+					serverhostkey = 
+					    packet_get_string(&slen);
+				}
+			} while (type == SSH2_MSG_KEXGSS_HOSTKEY);
+
+			switch (type) {
+			case SSH2_MSG_KEXGSS_CONTINUE:
+				debug("Received GSSAPI_CONTINUE");
+				if (maj_status == GSS_S_COMPLETE) 
+					fatal("GSSAPI Continue received from server when complete");
+				recv_tok.value = packet_get_string(&strlen);
+				recv_tok.length = strlen; 
+				break;
+			case SSH2_MSG_KEXGSS_COMPLETE:
+				debug("Received GSSAPI_COMPLETE");
+				packet_get_bignum2(dh_server_pub);
+				msg_tok.value =  packet_get_string(&strlen);
+				msg_tok.length = strlen; 
+
+				/* Is there a token included? */
+				if (packet_get_char()) {
+					recv_tok.value=
+					    packet_get_string(&strlen);
+					recv_tok.length = strlen;
+					/* If we're already complete - protocol error */
+					if (maj_status == GSS_S_COMPLETE)
+						packet_disconnect("Protocol error: received token when complete");
+					} else {
+						/* No token included */
+						if (maj_status != GSS_S_COMPLETE)
+							packet_disconnect("Protocol error: did not receive final token");
+				}
+				break;
+			case SSH2_MSG_KEXGSS_ERROR:
+				debug("Received Error");
+				maj_status = packet_get_int();
+				min_status = packet_get_int();
+				msg = packet_get_string(NULL);
+				lang = packet_get_string(NULL);
+				fatal("GSSAPI Error: \n%.400s",msg);
+			default:
+				packet_disconnect("Protocol error: didn't expect packet type %d",
+		    		type);
+			}
+			token_ptr = &recv_tok;
+		} else {
+			/* No data, and not complete */
+			if (maj_status != GSS_S_COMPLETE)
+				fatal("Not complete, and no token output");
+		}
+	} while (maj_status & GSS_S_CONTINUE_NEEDED);
+
+	/* 
+	 * We _must_ have received a COMPLETE message in reply from the 
+	 * server, which will have set dh_server_pub and msg_tok 
+	 */
+
+	if (type != SSH2_MSG_KEXGSS_COMPLETE)
+		fatal("Didn't receive a SSH2_MSG_KEXGSS_COMPLETE when I expected it");
+
+	/* Check f in range [1, p-1] */
+	if (!dh_pub_is_valid(dh, dh_server_pub))
+		packet_disconnect("bad server public DH value");
+
+	/* compute K=f^x mod p */
+	klen = DH_size(dh);
+	kbuf = xmalloc(klen);
+	kout = DH_compute_key(kbuf, dh_server_pub, dh);
+	if ((int)kout < 0)
+		fatal("DH_compute_key: failed");
+
+	shared_secret = BN_new();
+	if (shared_secret == NULL)
+		fatal("kexgss_client: BN_new failed");
+
+	if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
+		fatal("kexdh_client: BN_bin2bn failed");
+
+	memset(kbuf, 0, klen);
+	free(kbuf);
+
+	hashlen = sizeof(hash);
+	switch (ssh->kex->kex_type) {
+	case KEX_GSS_GRP1_SHA1:
+	case KEX_GSS_GRP14_SHA1:
+		kex_dh_hash(ssh->kex->hash_alg, ssh->kex->client_version_string, 
+		    ssh->kex->server_version_string,
+		    sshbuf_ptr(ssh->kex->my), sshbuf_len(ssh->kex->my),
+		    sshbuf_ptr(ssh->kex->peer), sshbuf_len(ssh->kex->peer),
+		    (serverhostkey ? serverhostkey : empty), slen,
+		    dh->pub_key,	/* e */
+		    dh_server_pub,	/* f */
+		    shared_secret,	/* K */
+		    hash, &hashlen
+		);
+		break;
+	case KEX_GSS_GEX_SHA1:
+		kexgex_hash(
+		    ssh->kex->hash_alg,
+		    ssh->kex->client_version_string,
+		    ssh->kex->server_version_string,
+		    sshbuf_ptr(ssh->kex->my), sshbuf_len(ssh->kex->my),
+		    sshbuf_ptr(ssh->kex->peer), sshbuf_len(ssh->kex->peer),
+		    (serverhostkey ? serverhostkey : empty), slen,
+ 		    min, nbits, max,
+		    dh->p, dh->g,
+		    dh->pub_key,
+		    dh_server_pub,
+		    shared_secret,
+		    hash, &hashlen
+		);
+		break;
+	default:
+		fatal("%s: Unexpected KEX type %d", __func__, ssh->kex->kex_type);
+	}
+
+	gssbuf.value = hash;
+	gssbuf.length = hashlen;
+
+	/* Verify that the hash matches the MIC we just got. */
+	if (GSS_ERROR(ssh_gssapi_checkmic(ctxt, &gssbuf, &msg_tok)))
+		packet_disconnect("Hash's MIC didn't verify");
+
+	free(msg_tok.value);
+
+	DH_free(dh);
+	if (serverhostkey)
+		free(serverhostkey);
+	BN_clear_free(dh_server_pub);
+
+	/* save session id */
+	if (ssh->kex->session_id == NULL) {
+		ssh->kex->session_id_len = hashlen;
+		ssh->kex->session_id = xmalloc(ssh->kex->session_id_len);
+		memcpy(ssh->kex->session_id, hash, ssh->kex->session_id_len);
+	}
+
+	if (ssh->kex->gss_deleg_creds)
+		ssh_gssapi_credentials_updated(ctxt);
+
+	if (gss_kex_context == NULL)
+		gss_kex_context = ctxt;
+	else
+		ssh_gssapi_delete_ctx(&ctxt);
+
+	kex_derive_keys_bn(ssh, hash, hashlen, shared_secret);
+	BN_clear_free(shared_secret);
+	return kex_send_newkeys(ssh);
+}
+
+#endif /* GSSAPI */
diff -up openssh/kexgsss.c.gsskex openssh/kexgsss.c
--- openssh/kexgsss.c.gsskex	2018-08-22 11:47:33.311216457 +0200
+++ openssh/kexgsss.c	2018-08-22 11:47:33.311216457 +0200
@@ -0,0 +1,297 @@
+/*
+ * Copyright (c) 2001-2009 Simon Wilkinson. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "includes.h"
+
+#ifdef GSSAPI
+
+#include <string.h>
+
+#include <openssl/crypto.h>
+#include <openssl/bn.h>
+
+#include "xmalloc.h"
+#include "sshbuf.h"
+#include "ssh2.h"
+#include "sshkey.h"
+#include "cipher.h"
+#include "kex.h"
+#include "log.h"
+#include "packet.h"
+#include "dh.h"
+#include "ssh-gss.h"
+#include "monitor_wrap.h"
+#include "misc.h"      /* servconf.h needs misc.h for struct ForwardOptions */
+#include "servconf.h"
+#include "ssh-gss.h"
+#include "digest.h"
+
+extern ServerOptions options;
+
+int
+kexgss_server(struct ssh *ssh)
+{
+	OM_uint32 maj_status, min_status;
+	
+	/* 
+	 * Some GSSAPI implementations use the input value of ret_flags (an
+ 	 * output variable) as a means of triggering mechanism specific 
+ 	 * features. Initializing it to zero avoids inadvertently 
+ 	 * activating this non-standard behaviour.
+	 */
+
+	OM_uint32 ret_flags = 0;
+	gss_buffer_desc gssbuf, recv_tok, msg_tok;
+	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
+	Gssctxt *ctxt = NULL;
+	u_int slen, klen, kout;
+	u_char *kbuf;
+	DH *dh;
+	int min = -1, max = -1, nbits = -1;
+	int cmin = -1, cmax = -1; /* client proposal */
+	BIGNUM *shared_secret = NULL;
+	BIGNUM *dh_client_pub = NULL;
+	int type = 0;
+	gss_OID oid;
+	char *mechs;
+	u_char hash[SSH_DIGEST_MAX_LENGTH];
+	size_t hashlen;
+
+	/* Initialise GSSAPI */
+
+	/* If we're rekeying, privsep means that some of the private structures
+	 * in the GSSAPI code are no longer available. This kludges them back
+	 * into life
+	 */
+	if (!ssh_gssapi_oid_table_ok()) 
+		if ((mechs = ssh_gssapi_server_mechanisms()))
+			free(mechs);
+
+	debug2("%s: Identifying %s", __func__, ssh->kex->name);
+	oid = ssh_gssapi_id_kex(NULL, ssh->kex->name, ssh->kex->kex_type);
+	if (oid == GSS_C_NO_OID)
+	   fatal("Unknown gssapi mechanism");
+
+	debug2("%s: Acquiring credentials", __func__);
+
+	if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, oid))))
+		fatal("Unable to acquire credentials for the server");
+
+	switch (ssh->kex->kex_type) {
+	case KEX_GSS_GRP1_SHA1:
+		dh = dh_new_group1();
+		break;
+	case KEX_GSS_GRP14_SHA1:
+		dh = dh_new_group14();
+		break;
+	case KEX_GSS_GEX_SHA1:
+		debug("Doing group exchange");
+		packet_read_expect(SSH2_MSG_KEXGSS_GROUPREQ);
+		/* store client proposal to provide valid signature */
+		cmin = packet_get_int();
+		nbits = packet_get_int();
+		cmax = packet_get_int();
+		min = MAX(DH_GRP_MIN, cmin);
+		max = MIN(DH_GRP_MAX, cmax);
+		packet_check_eom();
+		if (max < min || nbits < min || max < nbits)
+			fatal("GSS_GEX, bad parameters: %d !< %d !< %d",
+			    min, nbits, max);
+		dh = PRIVSEP(choose_dh(min, nbits, max));
+		if (dh == NULL)
+			packet_disconnect("Protocol error: no matching group found");
+
+		packet_start(SSH2_MSG_KEXGSS_GROUP);
+		packet_put_bignum2(dh->p);
+		packet_put_bignum2(dh->g);
+		packet_send();
+
+		packet_write_wait();
+		break;
+	default:
+		fatal("%s: Unexpected KEX type %d", __func__, ssh->kex->kex_type);
+	}
+
+	dh_gen_key(dh, ssh->kex->we_need * 8);
+
+	do {
+		debug("Wait SSH2_MSG_GSSAPI_INIT");
+		type = packet_read();
+		switch(type) {
+		case SSH2_MSG_KEXGSS_INIT:
+			if (dh_client_pub != NULL) 
+				fatal("Received KEXGSS_INIT after initialising");
+			recv_tok.value = packet_get_string(&slen);
+			recv_tok.length = slen; 
+
+			if ((dh_client_pub = BN_new()) == NULL)
+				fatal("dh_client_pub == NULL");
+
+			packet_get_bignum2(dh_client_pub);
+
+			/* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */
+			break;
+		case SSH2_MSG_KEXGSS_CONTINUE:
+			recv_tok.value = packet_get_string(&slen);
+			recv_tok.length = slen; 
+			break;
+		default:
+			packet_disconnect(
+			    "Protocol error: didn't expect packet type %d",
+			    type);
+		}
+
+		maj_status = PRIVSEP(ssh_gssapi_accept_ctx(ctxt, &recv_tok, 
+		    &send_tok, &ret_flags));
+
+		free(recv_tok.value);
+
+		if (maj_status != GSS_S_COMPLETE && send_tok.length == 0)
+			fatal("Zero length token output when incomplete");
+
+		if (dh_client_pub == NULL)
+			fatal("No client public key");
+		
+		if (maj_status & GSS_S_CONTINUE_NEEDED) {
+			debug("Sending GSSAPI_CONTINUE");
+			packet_start(SSH2_MSG_KEXGSS_CONTINUE);
+			packet_put_string(send_tok.value, send_tok.length);
+			packet_send();
+			gss_release_buffer(&min_status, &send_tok);
+		}
+	} while (maj_status & GSS_S_CONTINUE_NEEDED);
+
+	if (GSS_ERROR(maj_status)) {
+		if (send_tok.length > 0) {
+			packet_start(SSH2_MSG_KEXGSS_CONTINUE);
+			packet_put_string(send_tok.value, send_tok.length);
+			packet_send();
+		}
+		fatal("accept_ctx died");
+	}
+
+	if (!(ret_flags & GSS_C_MUTUAL_FLAG))
+		fatal("Mutual Authentication flag wasn't set");
+
+	if (!(ret_flags & GSS_C_INTEG_FLAG))
+		fatal("Integrity flag wasn't set");
+	
+	if (!dh_pub_is_valid(dh, dh_client_pub))
+		packet_disconnect("bad client public DH value");
+
+	klen = DH_size(dh);
+	kbuf = xmalloc(klen); 
+	kout = DH_compute_key(kbuf, dh_client_pub, dh);
+	if ((int)kout < 0)
+		fatal("DH_compute_key: failed");
+
+	shared_secret = BN_new();
+	if (shared_secret == NULL)
+		fatal("kexgss_server: BN_new failed");
+
+	if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
+		fatal("kexgss_server: BN_bin2bn failed");
+
+	memset(kbuf, 0, klen);
+	free(kbuf);
+
+	hashlen = sizeof(hash);
+	switch (ssh->kex->kex_type) {
+	case KEX_GSS_GRP1_SHA1:
+	case KEX_GSS_GRP14_SHA1:
+		kex_dh_hash(ssh->kex->hash_alg,
+		    ssh->kex->client_version_string, ssh->kex->server_version_string,
+		    sshbuf_ptr(ssh->kex->peer), sshbuf_len(ssh->kex->peer),
+		    sshbuf_ptr(ssh->kex->my), sshbuf_len(ssh->kex->my),
+		    NULL, 0, /* Change this if we start sending host keys */
+		    dh_client_pub, dh->pub_key, shared_secret,
+		    hash, &hashlen
+		);
+		break;
+	case KEX_GSS_GEX_SHA1:
+		kexgex_hash(
+		    ssh->kex->hash_alg,
+		    ssh->kex->client_version_string, ssh->kex->server_version_string,
+		    sshbuf_ptr(ssh->kex->peer), sshbuf_len(ssh->kex->peer),
+		    sshbuf_ptr(ssh->kex->my), sshbuf_len(ssh->kex->my),
+		    NULL, 0,
+		    cmin, nbits, cmax,
+		    dh->p, dh->g,
+		    dh_client_pub,
+		    dh->pub_key,
+		    shared_secret,
+		    hash, &hashlen
+		);
+		break;
+	default:
+		fatal("%s: Unexpected KEX type %d", __func__, ssh->kex->kex_type);
+	}
+
+	BN_clear_free(dh_client_pub);
+
+	if (ssh->kex->session_id == NULL) {
+		ssh->kex->session_id_len = hashlen;
+		ssh->kex->session_id = xmalloc(ssh->kex->session_id_len);
+		memcpy(ssh->kex->session_id, hash, ssh->kex->session_id_len);
+	}
+
+	gssbuf.value = hash;
+	gssbuf.length = hashlen;
+
+	if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt,&gssbuf,&msg_tok))))
+		fatal("Couldn't get MIC");
+
+	packet_start(SSH2_MSG_KEXGSS_COMPLETE);
+	packet_put_bignum2(dh->pub_key);
+	packet_put_string(msg_tok.value,msg_tok.length);
+
+	if (send_tok.length != 0) {
+		packet_put_char(1); /* true */
+		packet_put_string(send_tok.value, send_tok.length);
+	} else {
+		packet_put_char(0); /* false */
+	}
+	packet_send();
+
+	gss_release_buffer(&min_status, &send_tok);
+	gss_release_buffer(&min_status, &msg_tok);
+
+	if (gss_kex_context == NULL)
+		gss_kex_context = ctxt;
+	else 
+		ssh_gssapi_delete_ctx(&ctxt);
+
+	DH_free(dh);
+
+	kex_derive_keys_bn(ssh, hash, hashlen, shared_secret);
+	BN_clear_free(shared_secret);
+	kex_send_newkeys(ssh);
+
+	/* If this was a rekey, then save out any delegated credentials we
+	 * just exchanged.  */
+	if (options.gss_store_rekey)
+		ssh_gssapi_rekey_creds();
+	return 0;
+}
+#endif /* GSSAPI */
diff -up openssh/kex.h.gsskex openssh/kex.h
--- openssh/kex.h.gsskex	2018-08-20 07:57:29.000000000 +0200
+++ openssh/kex.h	2018-08-22 11:47:33.311216457 +0200
@@ -100,6 +100,11 @@ enum kex_exchange {
 	KEX_DH_GEX_SHA256,
 	KEX_ECDH_SHA2,
 	KEX_C25519_SHA256,
+#ifdef GSSAPI
+	KEX_GSS_GRP1_SHA1,
+	KEX_GSS_GRP14_SHA1,
+	KEX_GSS_GEX_SHA1,
+#endif
 	KEX_MAX
 };
 
@@ -148,6 +153,12 @@ struct kex {
 	u_int	flags;
 	int	hash_alg;
 	int	ec_nid;
+#ifdef GSSAPI
+	int	gss_deleg_creds;
+	int	gss_trust_dns;
+	char    *gss_host;
+	char	*gss_client;
+#endif
 	char	*client_version_string;
 	char	*server_version_string;
 	char	*failed_choice;
@@ -197,6 +208,10 @@ int	 kexecdh_client(struct ssh *);
 int	 kexecdh_server(struct ssh *);
 int	 kexc25519_client(struct ssh *);
 int	 kexc25519_server(struct ssh *);
+#ifdef GSSAPI
+int	 kexgss_client(struct ssh *);
+int	 kexgss_server(struct ssh *);
+#endif
 
 int	 kex_dh_hash(int, const char *, const char *,
     const u_char *, size_t, const u_char *, size_t, const u_char *, size_t,
diff -up openssh/Makefile.in.gsskex openssh/Makefile.in
--- openssh/Makefile.in.gsskex	2018-08-22 11:47:33.312216465 +0200
+++ openssh/Makefile.in	2018-08-22 13:19:54.955928277 +0200
@@ -100,6 +100,7 @@ LIBSSH_OBJS=${LIBOPENSSH_OBJS} \
 	readpass.o ttymodes.o xmalloc.o addrmatch.o \
 	atomicio.o dispatch.o mac.o uuencode.o misc.o utf8.o \
 	monitor_fdpass.o rijndael.o ssh-dss.o ssh-ecdsa.o ssh-rsa.o dh.o \
+	kexgssc.o \
 	msg.o progressmeter.o dns.o entropy.o gss-genr.o umac.o umac128.o \
 	ssh-pkcs11.o smult_curve25519_ref.o \
 	poly1305.o chacha.o cipher-chachapoly.o \
@@ -121,7 +122,7 @@ SSHDOBJS=sshd.o auth-rhosts.o auth-passw
 	auth-bsdauth.o auth2-hostbased.o auth2-kbdint.o \
 	auth2-none.o auth2-passwd.o auth2-pubkey.o \
 	monitor.o monitor_wrap.o auth-krb5.o \
-	auth2-gss.o gss-serv.o gss-serv-krb5.o \
+	auth2-gss.o gss-serv.o gss-serv-krb5.o kexgsss.o \
 	loginrec.o auth-pam.o auth-shadow.o auth-sia.o md5crypt.o \
 	sftp-server.o sftp-common.o \
 	sandbox-null.o sandbox-rlimit.o sandbox-systrace.o sandbox-darwin.o \
diff -up openssh/monitor.c.gsskex openssh/monitor.c
--- openssh/monitor.c.gsskex	2018-08-22 11:47:33.263216069 +0200
+++ openssh/monitor.c	2018-08-22 13:22:19.589095240 +0200
@@ -146,6 +146,8 @@ int mm_answer_gss_setup_ctx(int, struct
 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 *);
+int mm_answer_gss_sign(int, struct sshbuf *);
+int mm_answer_gss_updatecreds(int, struct sshbuf *);
 #endif
 
 #ifdef SSH_AUDIT_EVENTS
@@ -219,11 +221,18 @@ struct mon_table mon_dispatch_proto20[]
     {MONITOR_REQ_GSSSTEP, 0, mm_answer_gss_accept_ctx},
     {MONITOR_REQ_GSSUSEROK, MON_ONCE|MON_AUTHDECIDE, mm_answer_gss_userok},
     {MONITOR_REQ_GSSCHECKMIC, MON_ONCE, mm_answer_gss_checkmic},
+    {MONITOR_REQ_GSSSIGN, MON_ONCE, mm_answer_gss_sign},
 #endif
     {0, 0, NULL}
 };
 
 struct mon_table mon_dispatch_postauth20[] = {
+#ifdef GSSAPI
+    {MONITOR_REQ_GSSSETUP, 0, mm_answer_gss_setup_ctx},
+    {MONITOR_REQ_GSSSTEP, 0, mm_answer_gss_accept_ctx},
+    {MONITOR_REQ_GSSSIGN, 0, mm_answer_gss_sign},
+    {MONITOR_REQ_GSSUPCREDS, 0, mm_answer_gss_updatecreds},
+#endif
 #ifdef WITH_OPENSSL
     {MONITOR_REQ_MODULI, 0, mm_answer_moduli},
 #endif
@@ -293,6 +302,10 @@ monitor_child_preauth(Authctxt *_authctx
 	/* Permit requests for moduli and signatures */
 	monitor_permit(mon_dispatch, MONITOR_REQ_MODULI, 1);
 	monitor_permit(mon_dispatch, MONITOR_REQ_SIGN, 1);
+#ifdef GSSAPI
+	/* and for the GSSAPI key exchange */
+	monitor_permit(mon_dispatch, MONITOR_REQ_GSSSETUP, 1);
+#endif
 
 	/* The first few requests do not require asynchronous access */
 	while (!authenticated) {
@@ -405,6 +418,10 @@ monitor_child_postauth(struct monitor *p
 	monitor_permit(mon_dispatch, MONITOR_REQ_MODULI, 1);
 	monitor_permit(mon_dispatch, MONITOR_REQ_SIGN, 1);
 	monitor_permit(mon_dispatch, MONITOR_REQ_TERM, 1);
+#ifdef GSSAPI
+	/* and for the GSSAPI key exchange */
+	monitor_permit(mon_dispatch, MONITOR_REQ_GSSSETUP, 1);
+#endif		
 
 	if (auth_opts->permit_pty_flag) {
 		monitor_permit(mon_dispatch, MONITOR_REQ_PTY, 1);
@@ -1695,6 +1712,13 @@ monitor_apply_keystate(struct monitor *p
 # endif
 #endif /* WITH_OPENSSL */
 		kex->kex[KEX_C25519_SHA256] = kexc25519_server;
+#ifdef GSSAPI
+	if (options.gss_keyex) {
+		kex->kex[KEX_GSS_GRP1_SHA1] = kexgss_server;
+		kex->kex[KEX_GSS_GRP14_SHA1] = kexgss_server;
+		kex->kex[KEX_GSS_GEX_SHA1] = kexgss_server;
+	}
+#endif
 		kex->load_host_public_key=&get_hostkey_public_by_type;
 		kex->load_host_private_key=&get_hostkey_private_by_type;
 		kex->host_key_index=&get_hostkey_index;
@@ -1785,7 +1809,7 @@ mm_answer_gss_setup_ctx(int sock, struct
 	u_char *p;
 	int r;
 
-	if (!options.gss_authentication)
+	if (!options.gss_authentication && !options.gss_keyex)
 		fatal("%s: GSSAPI authentication not enabled", __func__);
 
 	if ((r = sshbuf_get_string(m, &p, &len)) != 0)
@@ -1818,7 +1842,7 @@ mm_answer_gss_accept_ctx(int sock, struc
 	OM_uint32 flags = 0; /* GSI needs this */
 	int r;
 
-	if (!options.gss_authentication)
+	if (!options.gss_authentication && !options.gss_keyex)
 		fatal("%s: GSSAPI authentication not enabled", __func__);
 
 	if ((r = ssh_gssapi_get_buffer_desc(m, &in)) != 0)
@@ -1839,6 +1863,7 @@ mm_answer_gss_accept_ctx(int sock, struc
 		monitor_permit(mon_dispatch, MONITOR_REQ_GSSSTEP, 0);
 		monitor_permit(mon_dispatch, MONITOR_REQ_GSSUSEROK, 1);
 		monitor_permit(mon_dispatch, MONITOR_REQ_GSSCHECKMIC, 1);
+		monitor_permit(mon_dispatch, MONITOR_REQ_GSSSIGN, 1);
 	}
 	return (0);
 }
@@ -1850,7 +1875,7 @@ mm_answer_gss_checkmic(int sock, struct
 	OM_uint32 ret;
 	int r;
 
-	if (!options.gss_authentication)
+	if (!options.gss_authentication && !options.gss_keyex)
 		fatal("%s: GSSAPI authentication not enabled", __func__);
 
 	if ((r = ssh_gssapi_get_buffer_desc(m, &gssbuf)) != 0 ||
@@ -1880,10 +1905,11 @@ mm_answer_gss_userok(int sock, struct ss
 	int r, authenticated;
 	const char *displayname;
 
-	if (!options.gss_authentication)
+	if (!options.gss_authentication && !options.gss_keyex)
 		fatal("%s: GSSAPI authentication not enabled", __func__);
 
-	authenticated = authctxt->valid && ssh_gssapi_userok(authctxt->user);
+	authenticated = authctxt->valid &&
+	    ssh_gssapi_userok(authctxt->user, authctxt->pw);
 
 	sshbuf_reset(m);
 	if ((r = sshbuf_put_u32(m, authenticated)) != 0)
@@ -1900,5 +1926,74 @@ mm_answer_gss_userok(int sock, struct ss
 	/* Monitor loop will terminate if authenticated */
 	return (authenticated);
 }
+
+int 
+mm_answer_gss_sign(int socket, struct sshbuf *m)
+{
+	gss_buffer_desc data;
+	gss_buffer_desc hash = GSS_C_EMPTY_BUFFER;
+	OM_uint32 major, minor;
+	int r;
+
+	if (!options.gss_authentication && !options.gss_keyex)
+		fatal("In GSSAPI monitor when GSSAPI is disabled");
+
+	if ((r = sshbuf_get_string(m, (u_char **)&data.value, &data.length)) != 0)
+		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+	if (data.length != 20) 
+		fatal("%s: data length incorrect: %d", __func__, 
+		    (int) data.length);
+
+	/* Save the session ID on the first time around */
+	if (session_id2_len == 0) {
+		session_id2_len = data.length;
+		session_id2 = xmalloc(session_id2_len);
+		memcpy(session_id2, data.value, session_id2_len);
+	}
+	major = ssh_gssapi_sign(gsscontext, &data, &hash);
+
+	free(data.value);
+
+	sshbuf_reset(m);
+	if ((r = sshbuf_put_u32(m, major)) != 0 ||
+	    (r = sshbuf_put_string(m, hash.value, hash.length)) != 0)
+		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+
+	mm_request_send(socket, MONITOR_ANS_GSSSIGN, m);
+
+	gss_release_buffer(&minor, &hash);
+
+	/* Turn on getpwnam permissions */
+	monitor_permit(mon_dispatch, MONITOR_REQ_PWNAM, 1);
+	
+	/* And credential updating, for when rekeying */
+	monitor_permit(mon_dispatch, MONITOR_REQ_GSSUPCREDS, 1);
+
+	return (0);
+}
+
+int
+mm_answer_gss_updatecreds(int socket, struct sshbuf *m) {
+	ssh_gssapi_ccache store;
+	int ok, r;
+
+	if ((r = sshbuf_get_cstring(m, &store.envvar, NULL)) != 0 ||
+	    (r = sshbuf_get_cstring(m, &store.envval, NULL)) != 0)
+		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+
+	ok = ssh_gssapi_update_creds(&store);
+
+	free(store.envvar);
+	free(store.envval);
+
+	sshbuf_reset(m);
+	if ((r = sshbuf_put_u32(m, ok)) != 0)
+		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+
+	mm_request_send(socket, MONITOR_ANS_GSSUPCREDS, m);
+
+	return(0);
+}
+
 #endif /* GSSAPI */
 
diff -up openssh/monitor.h.gsskex openssh/monitor.h
--- openssh/monitor.h.gsskex	2018-08-22 11:47:33.263216069 +0200
+++ openssh/monitor.h	2018-08-22 11:47:33.313216473 +0200
@@ -58,6 +58,8 @@ enum monitor_reqtype {
 #ifdef WITH_SELINUX
 	MONITOR_REQ_AUTHROLE = 80,
 #endif
+	MONITOR_REQ_GSSSIGN = 82, MONITOR_ANS_GSSSIGN = 83,
+	MONITOR_REQ_GSSUPCREDS = 84, MONITOR_ANS_GSSUPCREDS = 85,
 
 	MONITOR_REQ_PAM_START = 100,
 	MONITOR_REQ_PAM_ACCOUNT = 102, MONITOR_ANS_PAM_ACCOUNT = 103,
diff -up openssh/monitor_wrap.c.gsskex openssh/monitor_wrap.c
--- openssh/monitor_wrap.c.gsskex	2018-08-22 11:47:33.313216473 +0200
+++ openssh/monitor_wrap.c	2018-08-22 13:27:38.665669643 +0200
@@ -1004,7 +1004,7 @@ mm_ssh_gssapi_checkmic(Gssctxt *ctx, gss
 }
 
 int
-mm_ssh_gssapi_userok(char *user)
+mm_ssh_gssapi_userok(char *user, struct passwd *pw)
 {
 	struct sshbuf *m;
 	int r, authenticated = 0;
@@ -1023,4 +1023,52 @@ mm_ssh_gssapi_userok(char *user)
 	debug3("%s: user %sauthenticated",__func__, authenticated ? "" : "not ");
 	return (authenticated);
 }
+
+OM_uint32
+mm_ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_desc *data, gss_buffer_desc *hash)
+{
+	struct sshbuf *m;
+	OM_uint32 major;
+	int r;
+
+	if ((m = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new failed", __func__);
+	if ((r = sshbuf_put_string(m, data->value, data->length)) != 0)
+		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+
+	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSSIGN, m);
+	mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_GSSSIGN, m);
+
+	if ((r = sshbuf_get_u32(m, &major)) != 0 ||
+	    (r = sshbuf_get_string(m, (u_char **)&hash->value, &hash->length)) != 0)
+		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+
+	sshbuf_free(m);
+
+	return(major);
+}
+
+int
+mm_ssh_gssapi_update_creds(ssh_gssapi_ccache *store)
+{
+	struct sshbuf *m;
+	int ok, r;
+
+	if ((m = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new failed", __func__);
+
+	if ((r = sshbuf_put_cstring(m, store->envvar ? store->envvar : "")) != 0 ||
+	    (r = sshbuf_put_cstring(m, store->envval ? store->envval : "")) != 0)
+		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+
+	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSUPCREDS, m);
+	mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_GSSUPCREDS, m);
+
+	if ((r = sshbuf_get_u32(m, &ok)) != 0)
+		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+
+	sshbuf_free(m);
+
+	return (ok);
+}
 #endif /* GSSAPI */
diff -up openssh/monitor_wrap.h.gsskex openssh/monitor_wrap.h
--- openssh/monitor_wrap.h.gsskex	2018-08-22 11:47:33.263216069 +0200
+++ openssh/monitor_wrap.h	2018-08-22 11:47:33.313216473 +0200
@@ -63,8 +63,10 @@ int mm_sshkey_verify(const struct sshkey
 OM_uint32 mm_ssh_gssapi_server_ctx(Gssctxt **, gss_OID);
 OM_uint32 mm_ssh_gssapi_accept_ctx(Gssctxt *,
    gss_buffer_desc *, gss_buffer_desc *, OM_uint32 *);
-int mm_ssh_gssapi_userok(char *user);
+int mm_ssh_gssapi_userok(char *user, struct passwd *);
 OM_uint32 mm_ssh_gssapi_checkmic(Gssctxt *, gss_buffer_t, gss_buffer_t);
+OM_uint32 mm_ssh_gssapi_sign(Gssctxt *, gss_buffer_t, gss_buffer_t);
+int mm_ssh_gssapi_update_creds(ssh_gssapi_ccache *);
 #endif
 
 #ifdef USE_PAM
diff -up openssh/readconf.c.gsskex openssh/readconf.c
--- openssh/readconf.c.gsskex	2018-08-20 07:57:29.000000000 +0200
+++ openssh/readconf.c	2018-08-22 13:28:17.487982869 +0200
@@ -161,6 +161,8 @@ typedef enum {
 	oClearAllForwardings, oNoHostAuthenticationForLocalhost,
 	oEnableSSHKeysign, oRekeyLimit, oVerifyHostKeyDNS, oConnectTimeout,
 	oAddressFamily, oGssAuthentication, oGssDelegateCreds,
+	oGssTrustDns, oGssKeyEx, oGssClientIdentity, oGssRenewalRekey,
+	oGssServerIdentity, 
 	oServerAliveInterval, oServerAliveCountMax, oIdentitiesOnly,
 	oSendEnv, oSetEnv, oControlPath, oControlMaster, oControlPersist,
 	oHashKnownHosts,
@@ -201,10 +203,19 @@ static struct {
 	/* Sometimes-unsupported options */
 #if defined(GSSAPI)
 	{ "gssapiauthentication", oGssAuthentication },
+	{ "gssapikeyexchange", oGssKeyEx },
 	{ "gssapidelegatecredentials", oGssDelegateCreds },
+	{ "gssapitrustdns", oGssTrustDns },
+	{ "gssapiclientidentity", oGssClientIdentity },
+	{ "gssapiserveridentity", oGssServerIdentity },
+	{ "gssapirenewalforcesrekey", oGssRenewalRekey },
 # else
 	{ "gssapiauthentication", oUnsupported },
+	{ "gssapikeyexchange", oUnsupported },
 	{ "gssapidelegatecredentials", oUnsupported },
+	{ "gssapitrustdns", oUnsupported },
+	{ "gssapiclientidentity", oUnsupported },
+	{ "gssapirenewalforcesrekey", oUnsupported },
 #endif
 #ifdef ENABLE_PKCS11
 	{ "smartcarddevice", oPKCS11Provider },
@@ -973,10 +984,30 @@ parse_time:
 		intptr = &options->gss_authentication;
 		goto parse_flag;
 
+	case oGssKeyEx:
+		intptr = &options->gss_keyex;
+		goto parse_flag;
+
 	case oGssDelegateCreds:
 		intptr = &options->gss_deleg_creds;
 		goto parse_flag;
 
+	case oGssTrustDns:
+		intptr = &options->gss_trust_dns;
+		goto parse_flag;
+
+	case oGssClientIdentity:
+		charptr = &options->gss_client_identity;
+		goto parse_string;
+
+	case oGssServerIdentity:
+		charptr = &options->gss_server_identity;
+		goto parse_string;
+
+	case oGssRenewalRekey:
+		intptr = &options->gss_renewal_rekey;
+		goto parse_flag;
+
 	case oBatchMode:
 		intptr = &options->batch_mode;
 		goto parse_flag;
@@ -1817,7 +1848,12 @@ initialize_options(Options * options)
 	options->pubkey_authentication = -1;
 	options->challenge_response_authentication = -1;
 	options->gss_authentication = -1;
+	options->gss_keyex = -1;
 	options->gss_deleg_creds = -1;
+	options->gss_trust_dns = -1;
+	options->gss_renewal_rekey = -1;
+	options->gss_client_identity = NULL;
+	options->gss_server_identity = NULL;
 	options->password_authentication = -1;
 	options->kbd_interactive_authentication = -1;
 	options->kbd_interactive_devices = NULL;
@@ -1962,8 +1998,14 @@ fill_default_options(Options * options)
 		options->challenge_response_authentication = 1;
 	if (options->gss_authentication == -1)
 		options->gss_authentication = 0;
+	if (options->gss_keyex == -1)
+		options->gss_keyex = 0;
 	if (options->gss_deleg_creds == -1)
 		options->gss_deleg_creds = 0;
+	if (options->gss_trust_dns == -1)
+		options->gss_trust_dns = 0;
+	if (options->gss_renewal_rekey == -1)
+		options->gss_renewal_rekey = 0;
 	if (options->password_authentication == -1)
 		options->password_authentication = 1;
 	if (options->kbd_interactive_authentication == -1)
diff -up openssh/readconf.h.gsskex openssh/readconf.h
--- openssh/readconf.h.gsskex	2018-08-20 07:57:29.000000000 +0200
+++ openssh/readconf.h	2018-08-22 11:47:33.314216481 +0200
@@ -40,7 +40,12 @@ typedef struct {
 	int     challenge_response_authentication;
 					/* Try S/Key or TIS, authentication. */
 	int     gss_authentication;	/* Try GSS authentication */
+	int     gss_keyex;		/* Try GSS key exchange */
 	int     gss_deleg_creds;	/* Delegate GSS credentials */
+	int	gss_trust_dns;		/* Trust DNS for GSS canonicalization */
+	int	gss_renewal_rekey;	/* Credential renewal forces rekey */
+	char    *gss_client_identity;   /* Principal to initiate GSSAPI with */
+	char    *gss_server_identity;   /* GSSAPI target principal */
 	int     password_authentication;	/* Try password
 						 * authentication. */
 	int     kbd_interactive_authentication; /* Try keyboard-interactive auth. */
diff -up openssh/regress/cert-hostkey.sh.gsskex openssh/regress/cert-hostkey.sh
--- openssh/regress/cert-hostkey.sh.gsskex	2018-08-20 07:57:29.000000000 +0200
+++ openssh/regress/cert-hostkey.sh	2018-08-22 11:47:33.314216481 +0200
@@ -66,7 +66,7 @@ touch $OBJ/host_revoked_plain
 touch $OBJ/host_revoked_cert
 cat $OBJ/host_ca_key.pub $OBJ/host_ca_key2.pub > $OBJ/host_revoked_ca
 
-PLAIN_TYPES=`$SSH -Q key-plain | sed 's/^ssh-dss/ssh-dsa/g;s/^ssh-//'`
+PLAIN_TYPES=`$SSH -Q key-plain | grep -v null | sed 's/^ssh-dss/ssh-dsa/g;s/^ssh-//'`
 
 if echo "$PLAIN_TYPES" | grep '^rsa$' >/dev/null 2>&1 ; then
 	PLAIN_TYPES="$PLAIN_TYPES rsa-sha2-256 rsa-sha2-512"
diff -up openssh/regress/cert-userkey.sh.gsskex openssh/regress/cert-userkey.sh
--- openssh/regress/cert-userkey.sh.gsskex	2018-08-20 07:57:29.000000000 +0200
+++ openssh/regress/cert-userkey.sh	2018-08-22 11:47:33.314216481 +0200
@@ -7,7 +7,7 @@ rm -f $OBJ/authorized_keys_$USER $OBJ/us
 cp $OBJ/sshd_proxy $OBJ/sshd_proxy_bak
 cp $OBJ/ssh_proxy $OBJ/ssh_proxy_bak
 
-PLAIN_TYPES=`$SSH -Q key-plain | sed 's/^ssh-dss/ssh-dsa/;s/^ssh-//'`
+PLAIN_TYPES=`$SSH -Q key-plain | grep -v null | sed 's/^ssh-dss/ssh-dsa/;s/^ssh-//'`
 EXTRA_TYPES=""
 
 if echo "$PLAIN_TYPES" | grep '^rsa$' >/dev/null 2>&1 ; then
diff -up openssh/regress/kextype.sh.gsskex openssh/regress/kextype.sh
--- openssh/regress/kextype.sh.gsskex	2018-08-20 07:57:29.000000000 +0200
+++ openssh/regress/kextype.sh	2018-08-22 11:47:33.315216489 +0200
@@ -14,6 +14,9 @@ echo "KexAlgorithms=$KEXOPT" >> $OBJ/ssh
 
 tries="1 2 3 4"
 for k in `${SSH} -Q kex`; do
+	if [ $k = "gss-gex-sha1-" -o $k = "gss-group1-sha1-" -o $k = "gss-group14-sha1-" ]; then
+		continue
+	fi
 	verbose "kex $k"
 	for i in $tries; do
 		${SSH} -F $OBJ/ssh_proxy -o KexAlgorithms=$k x true
diff -up openssh/regress/rekey.sh.gsskex openssh/regress/rekey.sh
--- openssh/regress/rekey.sh.gsskex	2018-08-20 07:57:29.000000000 +0200
+++ openssh/regress/rekey.sh	2018-08-22 11:47:33.315216489 +0200
@@ -38,6 +38,9 @@ increase_datafile_size 300
 
 opts=""
 for i in `${SSH} -Q kex`; do
+	if [ $i = "gss-gex-sha1-" -o $i = "gss-group1-sha1-" -o $i = "gss-group14-sha1-" ]; then
+		continue
+	fi
 	opts="$opts KexAlgorithms=$i"
 done
 for i in `${SSH} -Q cipher`; do
@@ -56,6 +59,9 @@ done
 if ${SSH} -Q cipher-auth | grep '^.*$' >/dev/null 2>&1 ; then
   for c in `${SSH} -Q cipher-auth`; do
     for kex in `${SSH} -Q kex`; do
+	if [ $kex = "gss-gex-sha1-" -o $kex = "gss-group1-sha1-" -o $kex = "gss-group14-sha1-" ]; then
+		continue
+	fi
 	verbose "client rekey $c $kex"
 	ssh_data_rekeying "KexAlgorithms=$kex" -oRekeyLimit=256k -oCiphers=$c
     done
diff -up openssh/servconf.c.gsskex openssh/servconf.c
--- openssh/servconf.c.gsskex	2018-08-22 11:47:33.296216335 +0200
+++ openssh/servconf.c	2018-08-22 13:28:41.905179879 +0200
@@ -124,8 +124,10 @@ initialize_server_options(ServerOptions
 	options->kerberos_ticket_cleanup = -1;
 	options->kerberos_get_afs_token = -1;
 	options->gss_authentication=-1;
+	options->gss_keyex = -1;
 	options->gss_cleanup_creds = -1;
 	options->gss_strict_acceptor = -1;
+	options->gss_store_rekey = -1;
 	options->password_authentication = -1;
 	options->kbd_interactive_authentication = -1;
 	options->challenge_response_authentication = -1;
@@ -334,10 +336,14 @@ fill_default_server_options(ServerOption
 		options->kerberos_get_afs_token = 0;
 	if (options->gss_authentication == -1)
 		options->gss_authentication = 0;
+	if (options->gss_keyex == -1)
+		options->gss_keyex = 0;
 	if (options->gss_cleanup_creds == -1)
 		options->gss_cleanup_creds = 1;
 	if (options->gss_strict_acceptor == -1)
 		options->gss_strict_acceptor = 1;
+	if (options->gss_store_rekey == -1)
+		options->gss_store_rekey = 0;
 	if (options->password_authentication == -1)
 		options->password_authentication = 1;
 	if (options->kbd_interactive_authentication == -1)
@@ -484,7 +490,7 @@ typedef enum {
 	sHostKeyAlgorithms,
 	sClientAliveInterval, sClientAliveCountMax, sAuthorizedKeysFile,
 	sGssAuthentication, sGssCleanupCreds, sGssStrictAcceptor,
-	sAcceptEnv, sSetEnv, sPermitTunnel,
+	sGssKeyEx, sGssStoreRekey, sAcceptEnv, sSetEnv, sPermitTunnel,
 	sMatch, sPermitOpen, sPermitListen, sForceCommand, sChrootDirectory,
 	sUsePrivilegeSeparation, sAllowAgentForwarding,
 	sHostCertificate,
@@ -559,11 +565,17 @@ static struct {
 	{ "gssapiauthentication", sGssAuthentication, SSHCFG_ALL },
 	{ "gssapicleanupcredentials", sGssCleanupCreds, SSHCFG_GLOBAL },
 	{ "gssapistrictacceptorcheck", sGssStrictAcceptor, SSHCFG_GLOBAL },
+	{ "gssapikeyexchange", sGssKeyEx, SSHCFG_GLOBAL },
+	{ "gssapistorecredentialsonrekey", sGssStoreRekey, SSHCFG_GLOBAL },
 #else
 	{ "gssapiauthentication", sUnsupported, SSHCFG_ALL },
 	{ "gssapicleanupcredentials", sUnsupported, SSHCFG_GLOBAL },
 	{ "gssapistrictacceptorcheck", sUnsupported, SSHCFG_GLOBAL },
+	{ "gssapikeyexchange", sUnsupported, SSHCFG_GLOBAL },
+	{ "gssapistorecredentialsonrekey", sUnsupported, SSHCFG_GLOBAL },
 #endif
+	{ "gssusesessionccache", sUnsupported, SSHCFG_GLOBAL },
+	{ "gssapiusesessioncredcache", sUnsupported, SSHCFG_GLOBAL },
 	{ "passwordauthentication", sPasswordAuthentication, SSHCFG_ALL },
 	{ "kbdinteractiveauthentication", sKbdInteractiveAuthentication, SSHCFG_ALL },
 	{ "challengeresponseauthentication", sChallengeResponseAuthentication, SSHCFG_GLOBAL },
@@ -1463,6 +1475,10 @@ process_server_config_line(ServerOptions
 		intptr = &options->gss_authentication;
 		goto parse_flag;
 
+	case sGssKeyEx:
+		intptr = &options->gss_keyex;
+		goto parse_flag;
+
 	case sGssCleanupCreds:
 		intptr = &options->gss_cleanup_creds;
 		goto parse_flag;
@@ -1471,6 +1487,10 @@ process_server_config_line(ServerOptions
 		intptr = &options->gss_strict_acceptor;
 		goto parse_flag;
 
+	case sGssStoreRekey:
+		intptr = &options->gss_store_rekey;
+		goto parse_flag;
+
 	case sPasswordAuthentication:
 		intptr = &options->password_authentication;
 		goto parse_flag;
@@ -2560,6 +2580,9 @@ dump_config(ServerOptions *o)
 #ifdef GSSAPI
 	dump_cfg_fmtint(sGssAuthentication, o->gss_authentication);
 	dump_cfg_fmtint(sGssCleanupCreds, o->gss_cleanup_creds);
+	dump_cfg_fmtint(sGssKeyEx, o->gss_keyex);
+	dump_cfg_fmtint(sGssStrictAcceptor, o->gss_strict_acceptor);
+	dump_cfg_fmtint(sGssStoreRekey, o->gss_store_rekey);
 #endif
 	dump_cfg_fmtint(sPasswordAuthentication, o->password_authentication);
 	dump_cfg_fmtint(sKbdInteractiveAuthentication,
diff -up openssh/servconf.h.gsskex openssh/servconf.h
--- openssh/servconf.h.gsskex	2018-08-22 11:47:33.296216335 +0200
+++ openssh/servconf.h	2018-08-22 11:47:33.316216497 +0200
@@ -124,8 +124,10 @@ typedef struct {
 	int     kerberos_get_afs_token;		/* If true, try to get AFS token if
 						 * authenticated with Kerberos. */
 	int     gss_authentication;	/* If true, permit GSSAPI authentication */
+	int     gss_keyex;		/* If true, permit GSSAPI key exchange */
 	int     gss_cleanup_creds;	/* If true, destroy cred cache on logout */
 	int     gss_strict_acceptor;	/* If true, restrict the GSSAPI acceptor name */
+	int 	gss_store_rekey;
 	int     password_authentication;	/* If true, permit password
 						 * authentication. */
 	int     kbd_interactive_authentication;	/* If true, permit */
diff -up openssh/ssh_config.5.gsskex openssh/ssh_config.5
--- openssh/ssh_config.5.gsskex	2018-08-20 07:57:29.000000000 +0200
+++ openssh/ssh_config.5	2018-08-22 11:47:33.316216497 +0200
@@ -718,10 +718,40 @@ The default is
 Specifies whether user authentication based on GSSAPI is allowed.
 The default is
 .Cm no .
+.It Cm GSSAPIClientIdentity
+If set, specifies the GSSAPI client identity that ssh should use when 
+connecting to the server. The default is unset, which means that the default 
+identity will be used.
 .It Cm GSSAPIDelegateCredentials
 Forward (delegate) credentials to the server.
 The default is
 .Cm no .
+.It Cm GSSAPIKeyExchange
+Specifies whether key exchange based on GSSAPI may be used. When using
+GSSAPI key exchange the server need not have a host key.
+The default is
+.Dq no .
+.It Cm GSSAPIRenewalForcesRekey
+If set to 
+.Dq yes
+then renewal of the client's GSSAPI credentials will force the rekeying of the
+ssh connection. With a compatible server, this can delegate the renewed 
+credentials to a session on the server.
+The default is
+.Dq no .
+.It Cm GSSAPIServerIdentity
+If set, specifies the GSSAPI server identity that ssh should expect when 
+connecting to the server. The default is unset, which means that the
+expected GSSAPI server identity will be determined from the target
+hostname.
+.It Cm GSSAPITrustDns
+Set to 
+.Dq yes to indicate that the DNS is trusted to securely canonicalize
+the name of the host being connected to. If 
+.Dq no, the hostname entered on the
+command line will be passed untouched to the GSSAPI library.
+The default is
+.Dq no .
 .It Cm HashKnownHosts
 Indicates that
 .Xr ssh 1
diff -up openssh/ssh_config.gsskex openssh/ssh_config
--- openssh/ssh_config.gsskex	2018-08-22 11:47:33.289216279 +0200
+++ openssh/ssh_config	2018-08-22 11:47:33.316216497 +0200
@@ -24,6 +24,8 @@
 #   HostbasedAuthentication no
 #   GSSAPIAuthentication no
 #   GSSAPIDelegateCredentials no
+#   GSSAPIKeyExchange no
+#   GSSAPITrustDNS no
 #   BatchMode no
 #   CheckHostIP yes
 #   AddressFamily any
diff -up openssh/sshconnect2.c.gsskex openssh/sshconnect2.c
--- openssh/sshconnect2.c.gsskex	2018-08-20 07:57:29.000000000 +0200
+++ openssh/sshconnect2.c	2018-08-22 13:33:01.674275795 +0200
@@ -82,6 +82,124 @@ extern char *client_version_string;
 extern char *server_version_string;
 extern Options options;
 
+/* XXX from auth.h -- refactoring move these useful functions away of client context*/
+
+/*
+ * Returns the remote DNS hostname as a string. The returned string must not
+ * be freed. NB. this will usually trigger a DNS query the first time it is
+ * called.
+ * This function does additional checks on the hostname to mitigate some
+ * attacks on legacy rhosts-style authentication.
+ * XXX is RhostsRSAAuthentication vulnerable to these?
+ * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?)
+ */
+
+static char *
+remote_hostname(struct ssh *ssh)
+{
+	struct sockaddr_storage from;
+	socklen_t fromlen;
+	struct addrinfo hints, *ai, *aitop;
+	char name[NI_MAXHOST], ntop2[NI_MAXHOST];
+	const char *ntop = ssh_remote_ipaddr(ssh);
+
+	/* Get IP address of client. */
+	fromlen = sizeof(from);
+	memset(&from, 0, sizeof(from));
+	if (getpeername(ssh_packet_get_connection_in(ssh),
+	    (struct sockaddr *)&from, &fromlen) < 0) {
+		debug("getpeername failed: %.100s", strerror(errno));
+		return strdup(ntop);
+	}
+
+	ipv64_normalise_mapped(&from, &fromlen);
+	if (from.ss_family == AF_INET6)
+		fromlen = sizeof(struct sockaddr_in6);
+
+	debug3("Trying to reverse map address %.100s.", ntop);
+	/* Map the IP address to a host name. */
+	if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
+	    NULL, 0, NI_NAMEREQD) != 0) {
+		/* Host name not found.  Use ip address. */
+		return strdup(ntop);
+	}
+
+	/*
+	 * if reverse lookup result looks like a numeric hostname,
+	 * someone is trying to trick us by PTR record like following:
+	 *	1.1.1.10.in-addr.arpa.	IN PTR	2.3.4.5
+	 */
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_socktype = SOCK_DGRAM;	/*dummy*/
+	hints.ai_flags = AI_NUMERICHOST;
+	if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
+		logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
+		    name, ntop);
+		freeaddrinfo(ai);
+		return strdup(ntop);
+	}
+
+	/* Names are stored in lowercase. */
+	lowercase(name);
+
+	/*
+	 * Map it back to an IP address and check that the given
+	 * address actually is an address of this host.  This is
+	 * necessary because anyone with access to a name server can
+	 * define arbitrary names for an IP address. Mapping from
+	 * name to IP address can be trusted better (but can still be
+	 * fooled if the intruder has access to the name server of
+	 * the domain).
+	 */
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_family = from.ss_family;
+	hints.ai_socktype = SOCK_STREAM;
+	if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
+		logit("reverse mapping checking getaddrinfo for %.700s "
+		    "[%s] failed.", name, ntop);
+		return strdup(ntop);
+	}
+	/* Look for the address from the list of addresses. */
+	for (ai = aitop; ai; ai = ai->ai_next) {
+		if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
+		    sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
+		    (strcmp(ntop, ntop2) == 0))
+				break;
+	}
+	freeaddrinfo(aitop);
+	/* If we reached the end of the list, the address was not there. */
+	if (ai == NULL) {
+		/* Address not found for the host name. */
+		logit("Address %.100s maps to %.600s, but this does not "
+		    "map back to the address.", ntop, name);
+		return strdup(ntop);
+	}
+	return strdup(name);
+}
+
+/*
+ * Return the canonical name of the host in the other side of the current
+ * connection.  The host name is cached, so it is efficient to call this
+ * several times.
+ */
+
+const char *
+get_canonical_hostname(struct ssh *ssh, int use_dns)
+{
+	static char *dnsname;
+
+	if (!use_dns)
+		return ssh_remote_ipaddr(ssh);
+	else if (dnsname != NULL)
+		return dnsname;
+	else {
+		dnsname = remote_hostname(ssh);
+		return dnsname;
+	}
+}
+
+
+
 /*
  * SSH2 key exchange
  */
@@ -162,9 +280,34 @@ ssh_kex2(char *host, struct sockaddr *ho
 	struct kex *kex;
 	int r;
 
+#ifdef GSSAPI
+	char *orig = NULL, *gss = NULL;
+	char *gss_host = NULL;
+#endif
+
 	xxx_host = host;
 	xxx_hostaddr = hostaddr;
 
+#ifdef GSSAPI
+	if (options.gss_keyex) {
+		/* Add the GSSAPI mechanisms currently supported on this 
+		 * client to the key exchange algorithm proposal */
+		orig = options.kex_algorithms;
+
+		if (options.gss_trust_dns)
+			gss_host = (char *)get_canonical_hostname(active_state, 1);
+		else
+			gss_host = host;
+
+		gss = ssh_gssapi_client_mechanisms(gss_host, options.gss_client_identity);
+		if (gss) {
+			debug("Offering GSSAPI proposal: %s", gss);
+			xasprintf(&options.kex_algorithms,
+			    "%s,%s", gss, orig);
+		}
+	}
+#endif
+
 	if ((s = kex_names_cat(options.kex_algorithms, "ext-info-c")) == NULL)
 		fatal("%s: kex_names_cat", __func__);
 	myproposal[PROPOSAL_KEX_ALGS] = compat_kex_proposal(s);
@@ -194,6 +337,17 @@ ssh_kex2(char *host, struct sockaddr *ho
 		    order_hostkeyalgs(host, hostaddr, port));
 	}
 
+#ifdef GSSAPI
+	/* If we've got GSSAPI algorithms, then we also support the
+	 * 'null' hostkey, as a last resort */
+	if (options.gss_keyex && gss) {
+		orig = myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS];
+		xasprintf(&myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS],
+		    "%s,null", orig);
+		free(gss);
+	}
+#endif
+
 	if (options.rekey_limit || options.rekey_interval)
 		packet_set_rekey_limits(options.rekey_limit,
 		    options.rekey_interval);
@@ -214,11 +368,31 @@ ssh_kex2(char *host, struct sockaddr *ho
 	kex->kex[KEX_ECDH_SHA2] = kexecdh_client;
 # endif
 #endif
+#ifdef GSSAPI
+	if (options.gss_keyex) {
+		kex->kex[KEX_GSS_GRP1_SHA1] = kexgss_client;
+		kex->kex[KEX_GSS_GRP14_SHA1] = kexgss_client;
+		kex->kex[KEX_GSS_GEX_SHA1] = kexgss_client;
+	}
+#endif
 	kex->kex[KEX_C25519_SHA256] = kexc25519_client;
 	kex->client_version_string=client_version_string;
 	kex->server_version_string=server_version_string;
 	kex->verify_host_key=&verify_host_key_callback;
 
+#ifdef GSSAPI
+	if (options.gss_keyex) {
+		kex->gss_deleg_creds = options.gss_deleg_creds;
+		kex->gss_trust_dns = options.gss_trust_dns;
+		kex->gss_client = options.gss_client_identity;
+		if (options.gss_server_identity) {
+			kex->gss_host = options.gss_server_identity;
+		} else {
+			kex->gss_host = gss_host;
+        }
+	}
+#endif
+
 	ssh_dispatch_run_fatal(active_state, DISPATCH_BLOCK, &kex->done);
 
 	/* remove ext-info from the KEX proposals for rekeying */
@@ -314,6 +488,7 @@ int	input_gssapi_token(int type, u_int32
 int	input_gssapi_hash(int type, u_int32_t, struct ssh *);
 int	input_gssapi_error(int, u_int32_t, struct ssh *);
 int	input_gssapi_errtok(int, u_int32_t, struct ssh *);
+int	userauth_gsskeyex(Authctxt *authctxt);
 #endif
 
 void	userauth(Authctxt *, char *);
@@ -330,6 +505,11 @@ static char *authmethods_get(void);
 
 Authmethod authmethods[] = {
 #ifdef GSSAPI
+	{"gssapi-keyex",
+		userauth_gsskeyex,
+		NULL,
+		&options.gss_authentication,
+		NULL},
 	{"gssapi-with-mic",
 		userauth_gssapi,
 		NULL,
@@ -657,19 +837,31 @@ userauth_gssapi(Authctxt *authctxt)
 	static u_int mech = 0;
 	OM_uint32 min;
 	int r, ok = 0;
+	const char *gss_host;
+
+	if (options.gss_server_identity)
+		gss_host = options.gss_server_identity;
+	else if (options.gss_trust_dns)
+		gss_host = get_canonical_hostname(active_state, 1);
+	else
+		gss_host = authctxt->host;
 
 	/* Try one GSSAPI method at a time, rather than sending them all at
 	 * once. */
 
 	if (gss_supported == NULL)
-		gss_indicate_mechs(&min, &gss_supported);
+		if (GSS_ERROR(gss_indicate_mechs(&min, &gss_supported))) {
+			gss_supported = NULL;
+			return 0;
+		}
 
 	/* Check to see if the mechanism is usable before we offer it */
 	while (mech < gss_supported->count && !ok) {
 		/* My DER encoding requires length<128 */
 		if (gss_supported->elements[mech].length < 128 &&
 		    ssh_gssapi_check_mechanism(&gssctxt,
-		    &gss_supported->elements[mech], authctxt->host)) {
+		    &gss_supported->elements[mech], gss_host, 
+                    options.gss_client_identity)) {
 			ok = 1; /* Mechanism works */
 		} else {
 			mech++;
@@ -906,6 +1098,51 @@ input_gssapi_error(int type, u_int32_t p
 	free(lang);
 	return r;
 }
+
+int
+userauth_gsskeyex(Authctxt *authctxt)
+{
+	struct sshbuf *b = NULL;
+	gss_buffer_desc gssbuf;
+	gss_buffer_desc mic = GSS_C_EMPTY_BUFFER;
+	OM_uint32 ms;
+
+	static int attempt = 0;
+	if (attempt++ >= 1)
+		return (0);
+
+	if (gss_kex_context == NULL) {
+		debug("No valid Key exchange context"); 
+		return (0);
+	}
+
+	if ((b = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new failed", __func__);
+
+	ssh_gssapi_buildmic(b, authctxt->server_user, authctxt->service,
+	    "gssapi-keyex");
+
+	gssbuf.value = sshbuf_mutable_ptr(b);
+	gssbuf.length = sshbuf_len(b);
+
+	if (GSS_ERROR(ssh_gssapi_sign(gss_kex_context, &gssbuf, &mic))) {
+		sshbuf_free(b);
+		return (0);
+	}
+
+	packet_start(SSH2_MSG_USERAUTH_REQUEST);
+	packet_put_cstring(authctxt->server_user);
+	packet_put_cstring(authctxt->service);
+	packet_put_cstring(authctxt->method->name);
+	packet_put_string(mic.value, mic.length);
+	packet_send();
+
+	sshbuf_free(b);
+	gss_release_buffer(&ms, &mic);
+
+	return (1);
+}
+
 #endif /* GSSAPI */
 
 int
diff -up openssh/sshd.c.gsskex openssh/sshd.c
--- openssh/sshd.c.gsskex	2018-08-22 11:47:33.299216360 +0200
+++ openssh/sshd.c	2018-08-22 13:34:28.455975954 +0200
@@ -537,8 +537,7 @@ privsep_preauth_child(void)
 
 #ifdef GSSAPI
 	/* Cache supported mechanism OIDs for later use */
-	if (options.gss_authentication)
-		ssh_gssapi_prepare_supported_oids();
+	ssh_gssapi_prepare_supported_oids();
 #endif
 
 	reseed_prngs();
@@ -887,8 +887,9 @@ notify_hostkeys(struct ssh *ssh)
 	}
 	debug3("%s: sent %u hostkeys", __func__, nkeys);
 	if (nkeys == 0)
-		fatal("%s: no hostkeys", __func__);
-	packet_send();
+		debug3("%s: no hostkeys", __func__);
+	else
+		packet_send();
 	sshbuf_free(buf);
 }
 
@@ -1841,7 +1842,8 @@ main(int ac, char **av)
 		free(fp);
 	}
 	accumulate_host_timing_secret(cfg, NULL);
-	if (!sensitive_data.have_ssh2_key) {
+	/* The GSSAPI key exchange can run without a host key */
+	if (!sensitive_data.have_ssh2_key && !options.gss_keyex) {
 		logit("sshd: no hostkeys available -- exiting.");
 		exit(1);
 	}
@@ -2321,6 +2323,48 @@ do_ssh2_kex(void)
 	myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = compat_pkalg_proposal(
 	    list_hostkey_types());
 
+#ifdef GSSAPI
+	{
+	char *orig;
+	char *gss = NULL;
+	char *newstr = NULL;
+	orig = myproposal[PROPOSAL_KEX_ALGS];
+
+	/* 
+	 * If we don't have a host key, then there's no point advertising
+	 * the other key exchange algorithms
+	 */
+
+	if (strlen(myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS]) == 0)
+		orig = NULL;
+
+	if (options.gss_keyex)
+		gss = ssh_gssapi_server_mechanisms();
+	else
+		gss = NULL;
+
+	if (gss && orig)
+		xasprintf(&newstr, "%s,%s", gss, orig);
+	else if (gss)
+		newstr = gss;
+	else if (orig)
+		newstr = orig;
+
+	/* 
+	 * If we've got GSSAPI mechanisms, then we've got the 'null' host
+	 * key alg, but we can't tell people about it unless its the only
+  	 * host key algorithm we support
+	 */
+	if (gss && (strlen(myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS])) == 0)
+		myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = "null";
+
+	if (newstr)
+		myproposal[PROPOSAL_KEX_ALGS] = newstr;
+	else
+		fatal("No supported key exchange algorithms");
+	}
+#endif
+
 	/* start key exchange */
 	if ((r = kex_setup(active_state, myproposal)) != 0)
 		fatal("kex_setup: %s", ssh_err(r));
@@ -2338,6 +2382,13 @@ do_ssh2_kex(void)
 # endif
 #endif
 	kex->kex[KEX_C25519_SHA256] = kexc25519_server;
+#ifdef GSSAPI
+	if (options.gss_keyex) {
+		kex->kex[KEX_GSS_GRP1_SHA1] = kexgss_server;
+		kex->kex[KEX_GSS_GRP14_SHA1] = kexgss_server;
+		kex->kex[KEX_GSS_GEX_SHA1] = kexgss_server;
+	}
+#endif
 	kex->server = 1;
 	kex->client_version_string=client_version_string;
 	kex->server_version_string=server_version_string;
diff -up openssh/sshd_config.5.gsskex openssh/sshd_config.5
--- openssh/sshd_config.5.gsskex	2018-08-22 11:47:33.297216344 +0200
+++ openssh/sshd_config.5	2018-08-22 13:35:05.531275099 +0200
@@ -642,6 +642,11 @@ Specifies whether to automatically destr
 on logout.
 The default is
 .Cm yes .
+.It Cm GSSAPIKeyExchange
+Specifies whether key exchange based on GSSAPI is allowed. GSSAPI key exchange
+doesn't rely on ssh keys to verify host identity.
+The default is
+.Dq no .
 .It Cm GSSAPIStrictAcceptorCheck
 Determines whether to be strict about the identity of the GSSAPI acceptor
 a client authenticates against.
@@ -656,6 +661,11 @@ machine's default store.
 This facility is provided to assist with operation on multi homed machines.
 The default is
 .Cm yes .
+.It Cm GSSAPIStoreCredentialsOnRekey
+Controls whether the user's GSSAPI credentials should be updated following a 
+successful connection rekeying. This option can be used to accepted renewed 
+or updated credentials from a compatible client. The default is
+.Dq no .
 .It Cm HostbasedAcceptedKeyTypes
 Specifies the key types that will be accepted for hostbased authentication
 as a list of comma-separated patterns.
diff -up openssh/sshd_config.gsskex openssh/sshd_config
--- openssh/sshd_config.gsskex	2018-08-22 11:47:33.299216360 +0200
+++ openssh/sshd_config	2018-08-22 11:47:33.318216513 +0200
@@ -85,6 +85,8 @@ ChallengeResponseAuthentication no
 # GSSAPI options
 GSSAPIAuthentication yes
 GSSAPICleanupCredentials no
+#GSSAPIStrictAcceptorCheck yes
+#GSSAPIKeyExchange no
 
 # Set this to 'yes' to enable PAM authentication, account processing,
 # and session processing. If this is enabled, PAM authentication will
diff -up openssh/ssh-gss.h.gsskex openssh/ssh-gss.h
--- openssh/ssh-gss.h.gsskex	2018-08-20 07:57:29.000000000 +0200
+++ openssh/ssh-gss.h	2018-08-22 13:36:44.773075793 +0200
@@ -1,6 +1,6 @@
 /* $OpenBSD: ssh-gss.h,v 1.14 2018/07/10 09:13:30 djm Exp $ */
 /*
- * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved.
+ * Copyright (c) 2001-2009 Simon Wilkinson. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -61,10 +61,22 @@
 
 #define SSH_GSS_OIDTYPE 0x06
 
+#define SSH2_MSG_KEXGSS_INIT                            30
+#define SSH2_MSG_KEXGSS_CONTINUE                        31
+#define SSH2_MSG_KEXGSS_COMPLETE                        32
+#define SSH2_MSG_KEXGSS_HOSTKEY                         33
+#define SSH2_MSG_KEXGSS_ERROR                           34
+#define SSH2_MSG_KEXGSS_GROUPREQ			40
+#define SSH2_MSG_KEXGSS_GROUP				41
+#define KEX_GSS_GRP1_SHA1_ID				"gss-group1-sha1-"
+#define KEX_GSS_GRP14_SHA1_ID				"gss-group14-sha1-"
+#define KEX_GSS_GEX_SHA1_ID				"gss-gex-sha1-"
+
 typedef struct {
 	char *filename;
 	char *envvar;
 	char *envval;
+	struct passwd *owner;
 	void *data;
 } ssh_gssapi_ccache;
 
@@ -72,8 +84,11 @@ typedef struct {
 	gss_buffer_desc displayname;
 	gss_buffer_desc exportedname;
 	gss_cred_id_t creds;
+	gss_name_t name;
 	struct ssh_gssapi_mech_struct *mech;
 	ssh_gssapi_ccache store;
+	int used;
+	int updated;
 } ssh_gssapi_client;
 
 typedef struct ssh_gssapi_mech_struct {
@@ -84,6 +99,7 @@ typedef struct ssh_gssapi_mech_struct {
 	int (*userok) (ssh_gssapi_client *, char *);
 	int (*localname) (ssh_gssapi_client *, char **);
 	void (*storecreds) (ssh_gssapi_client *);
+	int (*updatecreds) (ssh_gssapi_ccache *, ssh_gssapi_client *);
 } ssh_gssapi_mech;
 
 typedef struct {
@@ -94,10 +110,11 @@ typedef struct {
 	gss_OID		oid; /* client */
 	gss_cred_id_t	creds; /* server */
 	gss_name_t	client; /* server */
-	gss_cred_id_t	client_creds; /* server */
+	gss_cred_id_t	client_creds; /* both */
 } Gssctxt;
 
 extern ssh_gssapi_mech *supported_mechs[];
+extern Gssctxt *gss_kex_context;
 
 int  ssh_gssapi_check_oid(Gssctxt *, void *, size_t);
 void ssh_gssapi_set_oid_data(Gssctxt *, void *, size_t);
@@ -123,17 +140,33 @@ void ssh_gssapi_delete_ctx(Gssctxt **);
 OM_uint32 ssh_gssapi_sign(Gssctxt *, gss_buffer_t, gss_buffer_t);
 void ssh_gssapi_buildmic(struct sshbuf *, const char *,
     const char *, const char *);
-int ssh_gssapi_check_mechanism(Gssctxt **, gss_OID, const char *);
+int ssh_gssapi_check_mechanism(Gssctxt **, gss_OID, const char *, const char *);
+OM_uint32 ssh_gssapi_client_identity(Gssctxt *, const char *);
+int ssh_gssapi_credentials_updated(Gssctxt *);
 
 /* In the server */
+typedef int ssh_gssapi_check_fn(Gssctxt **, gss_OID, const char *, 
+    const char *);
+char *ssh_gssapi_client_mechanisms(const char *, const char *);
+char *ssh_gssapi_kex_mechs(gss_OID_set, ssh_gssapi_check_fn *, const char *,
+    const char *);
+gss_OID ssh_gssapi_id_kex(Gssctxt *, char *, int);
+int ssh_gssapi_server_check_mech(Gssctxt **,gss_OID, const char *, 
+    const char *);
 OM_uint32 ssh_gssapi_server_ctx(Gssctxt **, gss_OID);
-int ssh_gssapi_userok(char *name);
+int ssh_gssapi_userok(char *name, struct passwd *);
 OM_uint32 ssh_gssapi_checkmic(Gssctxt *, gss_buffer_t, gss_buffer_t);
 void ssh_gssapi_do_child(char ***, u_int *);
 void ssh_gssapi_cleanup_creds(void);
 void ssh_gssapi_storecreds(void);
 const char *ssh_gssapi_displayname(void);
 
+char *ssh_gssapi_server_mechanisms(void);
+int ssh_gssapi_oid_table_ok();
+
+int ssh_gssapi_update_creds(ssh_gssapi_ccache *store);
+
+void ssh_gssapi_rekey_creds(void);
 #endif /* GSSAPI */
 
 #endif /* _SSH_GSS_H */
diff -up openssh/sshkey.c.gsskex openssh/sshkey.c
--- openssh/sshkey.c.gsskex	2018-08-22 11:47:33.319216521 +0200
+++ openssh/sshkey.c	2018-08-22 13:37:18.979351804 +0200
@@ -140,6 +140,7 @@ static const struct keytype keytypes[] =
 #  endif /* OPENSSL_HAS_NISTP521 */
 # endif /* OPENSSL_HAS_ECC */
 #endif /* WITH_OPENSSL */
+	{ "null", "null", NULL, KEY_NULL, 0, 0, 1 },
 	{ NULL, NULL, NULL, -1, -1, 0, 0 }
 };
 
diff -up openssh/sshkey.h.gsskex openssh/sshkey.h
--- openssh/sshkey.h.gsskex	2018-08-20 07:57:29.000000000 +0200
+++ openssh/sshkey.h	2018-08-22 11:47:33.320216529 +0200
@@ -63,6 +63,7 @@ enum sshkey_types {
 	KEY_ED25519_CERT,
 	KEY_XMSS,
 	KEY_XMSS_CERT,
+	KEY_NULL,
 	KEY_UNSPEC
 };

--- openssh/sshconnect2.c.orig  2017-01-04 19:47:10.000000000 +0100
+++ openssh/sshconnect2.c       2017-01-05 04:13:08.977425272 +0100
@@ -344,7 +344,6 @@
 		orig = myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS];
 		xasprintf(&myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS],
 		    "%s,null", orig);
-		free(gss);
 	}
 #endif
 
@@ -398,6 +397,16 @@
 	/* remove ext-info from the KEX proposals for rekeying */
 	myproposal[PROPOSAL_KEX_ALGS] =
 	    compat_kex_proposal(options.kex_algorithms);
+#ifdef GSSAPI
+	/* repair myproposal after it was crumpled by the */
+	/* ext-info removal above */
+	if (gss) {
+		orig = myproposal[PROPOSAL_KEX_ALGS];
+		xasprintf(&myproposal[PROPOSAL_KEX_ALGS],
+		    "%s,%s", gss, orig);
+		free(gss);
+	}
+#endif
 	if ((r = kex_prop2buf(kex->my, myproposal)) != 0)
 		fatal("kex_prop2buf: %s", ssh_err(r));