auth2-gss.c - platform/external/openssh - Gitiles

 /* $OpenBSD: auth2-gss.c,v 1.29 2018/07/31 03:10:27 djm Exp $ */

 /*
  * Copyright (c) 2001-2003 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 <sys/types.h>

 #include <stdarg.h>

 #include "xmalloc.h"
 #include "sshkey.h"
 #include "hostfile.h"
 #include "auth.h"
 #include "ssh2.h"
 #include "log.h"
 #include "dispatch.h"
 #include "sshbuf.h"
 #include "ssherr.h"
 #include "misc.h"
 #include "servconf.h"
 #include "packet.h"
 #include "ssh-gss.h"
 #include "monitor_wrap.h"

 extern ServerOptions options;

 static int input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh);
 static int input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh);
 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 *);

 /*
  * We only support those mechanisms that we know about (ie ones that we know
  * how to check local user kuserok and the like)
  */
 static int
 userauth_gssapi(struct ssh *ssh)
 {
 	Authctxt *authctxt = ssh->authctxt;
 	gss_OID_desc goid = {0, NULL};
 	Gssctxt *ctxt = NULL;
 	int r, present;
 	u_int mechs;
 	OM_uint32 ms;
 	size_t len;
 	u_char *doid = NULL;

 	if ((r = sshpkt_get_u32(ssh, &mechs)) != 0)
 		fatal("%s: %s", __func__, ssh_err(r));

 	if (mechs == 0) {
 		debug("Mechanism negotiation is not supported");
 		return (0);
 	}

 	do {
 		mechs--;

 		free(doid);

 		present = 0;
 		if ((r = sshpkt_get_string(ssh, &doid, &len)) != 0)
 			fatal("%s: %s", __func__, ssh_err(r));

 		if (len > 2 && doid[0] == SSH_GSS_OIDTYPE &&
 		    doid[1] == len - 2) {
 			goid.elements = doid + 2;
 			goid.length   = len - 2;
 			ssh_gssapi_test_oid_supported(&ms, &goid, &present);
 		} else {
 			logit("Badly formed OID received");
 		}
 	} while (mechs > 0 && !present);

 	if (!present) {
 		free(doid);
 		authctxt->server_caused_failure = 1;
 		return (0);
 	}

 	if (!authctxt->valid || authctxt->user == NULL) {
 		debug2("%s: disabled because of invalid user", __func__);
 		free(doid);
 		return (0);
 	}

 	if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) {
 		if (ctxt != NULL)
 			ssh_gssapi_delete_ctx(&ctxt);
 		free(doid);
 		authctxt->server_caused_failure = 1;
 		return (0);
 	}

 	authctxt->methoddata = (void *)ctxt;

 	/* Return the OID that we received */
 	if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_GSSAPI_RESPONSE)) != 0 ||
 	    (r = sshpkt_put_string(ssh, doid, len)) != 0 ||
 	    (r = sshpkt_send(ssh)) != 0)
 		fatal("%s: %s", __func__, ssh_err(r));

 	free(doid);

 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
 	authctxt->postponed = 1;

 	return (0);
 }

 static int
 input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh)
 {
 	Authctxt *authctxt = ssh->authctxt;
 	Gssctxt *gssctxt;
 	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 	gss_buffer_desc recv_tok;
 	OM_uint32 maj_status, min_status, flags;
 	u_char *p;
 	size_t len;
 	int r;

 	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 		fatal("No authentication or GSSAPI context");

 	gssctxt = authctxt->methoddata;
 	if ((r = sshpkt_get_string(ssh, &p, &len)) != 0 ||
 	    (r = sshpkt_get_end(ssh)) != 0)
 		fatal("%s: %s", __func__, ssh_err(r));

 	recv_tok.value = p;
 	recv_tok.length = len;
 	maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
 	    &send_tok, &flags));

 	free(p);

 	if (GSS_ERROR(maj_status)) {
 		if (send_tok.length != 0) {
 			if ((r = sshpkt_start(ssh,
 			    SSH2_MSG_USERAUTH_GSSAPI_ERRTOK)) != 0 ||
 			    (r = sshpkt_put_string(ssh, send_tok.value,
 			    send_tok.length)) != 0 ||
 			    (r = sshpkt_send(ssh)) != 0)
 				fatal("%s: %s", __func__, ssh_err(r));
 		}
 		authctxt->postponed = 0;
 		ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 		userauth_finish(ssh, 0, "gssapi-with-mic", NULL);
 	} else {
 		if (send_tok.length != 0) {
 			if ((r = sshpkt_start(ssh,
 			    SSH2_MSG_USERAUTH_GSSAPI_TOKEN)) != 0 ||
 			    (r = sshpkt_put_string(ssh, send_tok.value,
 			    send_tok.length)) != 0 ||
 			    (r = sshpkt_send(ssh)) != 0)
 				fatal("%s: %s", __func__, ssh_err(r));
 		}
 		if (maj_status == GSS_S_COMPLETE) {
 			ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 			if (flags & GSS_C_INTEG_FLAG)
 				ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC,
 				    &input_gssapi_mic);
 			else
 				ssh_dispatch_set(ssh,
 				    SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE,
 				    &input_gssapi_exchange_complete);
 		}
 	}

 	gss_release_buffer(&min_status, &send_tok);
 	return 0;
 }

 static int
 input_gssapi_errtok(int type, u_int32_t plen, struct ssh *ssh)
 {
 	Authctxt *authctxt = ssh->authctxt;
 	Gssctxt *gssctxt;
 	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 	gss_buffer_desc recv_tok;
 	OM_uint32 maj_status;
 	int r;
 	u_char *p;
 	size_t len;

 	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 		fatal("No authentication or GSSAPI context");

 	gssctxt = authctxt->methoddata;
 	if ((r = sshpkt_get_string(ssh, &p, &len)) != 0 ||
 	    (r = sshpkt_get_end(ssh)) != 0)
 		fatal("%s: %s", __func__, ssh_err(r));
 	recv_tok.value = p;
 	recv_tok.length = len;

 	/* Push the error token into GSSAPI to see what it says */
 	maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
 	    &send_tok, NULL));

 	free(recv_tok.value);

 	/* We can't return anything to the client, even if we wanted to */
 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);

 	/* The client will have already moved on to the next auth */

 	gss_release_buffer(&maj_status, &send_tok);
 	return 0;
 }

 /*
  * This is called when the client thinks we've completed authentication.
  * It should only be enabled in the dispatch handler by the function above,
  * which only enables it once the GSSAPI exchange is complete.
  */

 static int
 input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh)
 {
 	Authctxt *authctxt = ssh->authctxt;
 	int r, authenticated;
 	const char *displayname;

 	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 		fatal("No authentication or GSSAPI context");

 	/*
 	 * We don't need to check the status, because we're only enabled in
 	 * the dispatcher once the exchange is complete
 	 */

 	if ((r = sshpkt_get_end(ssh)) != 0)
 		fatal("%s: %s", __func__, ssh_err(r));

 	authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));

 	if ((!use_privsep || mm_is_monitor()) &&
 	    (displayname = ssh_gssapi_displayname()) != NULL)
 		auth2_record_info(authctxt, "%s", displayname);

 	authctxt->postponed = 0;
 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 	userauth_finish(ssh, authenticated, "gssapi-with-mic", NULL);
 	return 0;
 }

 static int
 input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh)
 {
 	Authctxt *authctxt = ssh->authctxt;
 	Gssctxt *gssctxt;
 	int r, authenticated = 0;
 	struct sshbuf *b;
 	gss_buffer_desc mic, gssbuf;
 	const char *displayname;
 	u_char *p;
 	size_t len;

 	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 		fatal("No authentication or GSSAPI context");

 	gssctxt = authctxt->methoddata;

 	if ((r = sshpkt_get_string(ssh, &p, &len)) != 0)
 		fatal("%s: %s", __func__, ssh_err(r));
 	if ((b = sshbuf_new()) == NULL)
 		fatal("%s: sshbuf_new failed", __func__);
 	mic.value = p;
 	mic.length = len;
 	ssh_gssapi_buildmic(b, authctxt->user, authctxt->service,
 	    "gssapi-with-mic");

 	if ((gssbuf.value = sshbuf_mutable_ptr(b)) == NULL)
 		fatal("%s: sshbuf_mutable_ptr failed", __func__);
 	gssbuf.length = sshbuf_len(b);

 	if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic))))
 		authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
 	else
 		logit("GSSAPI MIC check failed");

 	sshbuf_free(b);
 	free(mic.value);

 	if ((!use_privsep || mm_is_monitor()) &&
 	    (displayname = ssh_gssapi_displayname()) != NULL)
 		auth2_record_info(authctxt, "%s", displayname);

 	authctxt->postponed = 0;
 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 	userauth_finish(ssh, authenticated, "gssapi-with-mic", NULL);
 	return 0;
 }

 Authmethod method_gssapi = {
 	"gssapi-with-mic",
 	userauth_gssapi,
 	&options.gss_authentication
 };

 #endif /* GSSAPI */
	/* $OpenBSD: auth2-gss.c,v 1.29 2018/07/31 03:10:27 djm Exp $ */

	/*
	* Copyright (c) 2001-2003 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 <sys/types.h>

	#include <stdarg.h>

	#include "xmalloc.h"
	#include "sshkey.h"
	#include "hostfile.h"
	#include "auth.h"
	#include "ssh2.h"
	#include "log.h"
	#include "dispatch.h"
	#include "sshbuf.h"
	#include "ssherr.h"
	#include "misc.h"
	#include "servconf.h"
	#include "packet.h"
	#include "ssh-gss.h"
	#include "monitor_wrap.h"

	extern ServerOptions options;

	static int input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh);
	static int input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh);
	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 *);

	/*
	* We only support those mechanisms that we know about (ie ones that we know
	* how to check local user kuserok and the like)
	*/
	static int
	userauth_gssapi(struct ssh *ssh)
	{
	Authctxt *authctxt = ssh->authctxt;
	gss_OID_desc goid = {0, NULL};
	Gssctxt *ctxt = NULL;
	int r, present;
	u_int mechs;
	OM_uint32 ms;
	size_t len;
	u_char *doid = NULL;

	if ((r = sshpkt_get_u32(ssh, &mechs)) != 0)
	fatal("%s: %s", __func__, ssh_err(r));

	if (mechs == 0) {
	debug("Mechanism negotiation is not supported");
	return (0);
	}

	do {
	mechs--;

	free(doid);

	present = 0;
	if ((r = sshpkt_get_string(ssh, &doid, &len)) != 0)
	fatal("%s: %s", __func__, ssh_err(r));

	if (len > 2 && doid[0] == SSH_GSS_OIDTYPE &&
	doid[1] == len - 2) {
	goid.elements = doid + 2;
	goid.length = len - 2;
	ssh_gssapi_test_oid_supported(&ms, &goid, &present);
	} else {
	logit("Badly formed OID received");
	}
	} while (mechs > 0 && !present);

	if (!present) {
	free(doid);
	authctxt->server_caused_failure = 1;
	return (0);
	}

	if (!authctxt->valid \|\| authctxt->user == NULL) {
	debug2("%s: disabled because of invalid user", __func__);
	free(doid);
	return (0);
	}

	if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) {
	if (ctxt != NULL)
	ssh_gssapi_delete_ctx(&ctxt);
	free(doid);
	authctxt->server_caused_failure = 1;
	return (0);
	}

	authctxt->methoddata = (void *)ctxt;

	/* Return the OID that we received */
	if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_GSSAPI_RESPONSE)) != 0 \|\|
	(r = sshpkt_put_string(ssh, doid, len)) != 0 \|\|
	(r = sshpkt_send(ssh)) != 0)
	fatal("%s: %s", __func__, ssh_err(r));

	free(doid);

	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
	authctxt->postponed = 1;

	return (0);
	}

	static int
	input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh)
	{
	Authctxt *authctxt = ssh->authctxt;
	Gssctxt *gssctxt;
	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
	gss_buffer_desc recv_tok;
	OM_uint32 maj_status, min_status, flags;
	u_char *p;
	size_t len;
	int r;

	if (authctxt == NULL \|\| (authctxt->methoddata == NULL && !use_privsep))
	fatal("No authentication or GSSAPI context");

	gssctxt = authctxt->methoddata;
	if ((r = sshpkt_get_string(ssh, &p, &len)) != 0 \|\|
	(r = sshpkt_get_end(ssh)) != 0)
	fatal("%s: %s", __func__, ssh_err(r));

	recv_tok.value = p;
	recv_tok.length = len;
	maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
	&send_tok, &flags));

	free(p);

	if (GSS_ERROR(maj_status)) {
	if (send_tok.length != 0) {
	if ((r = sshpkt_start(ssh,
	SSH2_MSG_USERAUTH_GSSAPI_ERRTOK)) != 0 \|\|
	(r = sshpkt_put_string(ssh, send_tok.value,
	send_tok.length)) != 0 \|\|
	(r = sshpkt_send(ssh)) != 0)
	fatal("%s: %s", __func__, ssh_err(r));
	}
	authctxt->postponed = 0;
	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
	userauth_finish(ssh, 0, "gssapi-with-mic", NULL);
	} else {
	if (send_tok.length != 0) {
	if ((r = sshpkt_start(ssh,
	SSH2_MSG_USERAUTH_GSSAPI_TOKEN)) != 0 \|\|
	(r = sshpkt_put_string(ssh, send_tok.value,
	send_tok.length)) != 0 \|\|
	(r = sshpkt_send(ssh)) != 0)
	fatal("%s: %s", __func__, ssh_err(r));
	}
	if (maj_status == GSS_S_COMPLETE) {
	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
	if (flags & GSS_C_INTEG_FLAG)
	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC,
	&input_gssapi_mic);
	else
	ssh_dispatch_set(ssh,
	SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE,
	&input_gssapi_exchange_complete);
	}
	}

	gss_release_buffer(&min_status, &send_tok);
	return 0;
	}

	static int
	input_gssapi_errtok(int type, u_int32_t plen, struct ssh *ssh)
	{
	Authctxt *authctxt = ssh->authctxt;
	Gssctxt *gssctxt;
	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
	gss_buffer_desc recv_tok;
	OM_uint32 maj_status;
	int r;
	u_char *p;
	size_t len;

	if (authctxt == NULL \|\| (authctxt->methoddata == NULL && !use_privsep))
	fatal("No authentication or GSSAPI context");

	gssctxt = authctxt->methoddata;
	if ((r = sshpkt_get_string(ssh, &p, &len)) != 0 \|\|
	(r = sshpkt_get_end(ssh)) != 0)
	fatal("%s: %s", __func__, ssh_err(r));
	recv_tok.value = p;
	recv_tok.length = len;

	/* Push the error token into GSSAPI to see what it says */
	maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
	&send_tok, NULL));

	free(recv_tok.value);

	/* We can't return anything to the client, even if we wanted to */
	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);

	/* The client will have already moved on to the next auth */

	gss_release_buffer(&maj_status, &send_tok);
	return 0;
	}

	/*
	* This is called when the client thinks we've completed authentication.
	* It should only be enabled in the dispatch handler by the function above,
	* which only enables it once the GSSAPI exchange is complete.
	*/

	static int
	input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh)
	{
	Authctxt *authctxt = ssh->authctxt;
	int r, authenticated;
	const char *displayname;

	if (authctxt == NULL \|\| (authctxt->methoddata == NULL && !use_privsep))
	fatal("No authentication or GSSAPI context");

	/*
	* We don't need to check the status, because we're only enabled in
	* the dispatcher once the exchange is complete
	*/

	if ((r = sshpkt_get_end(ssh)) != 0)
	fatal("%s: %s", __func__, ssh_err(r));

	authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));

	if ((!use_privsep \|\| mm_is_monitor()) &&
	(displayname = ssh_gssapi_displayname()) != NULL)
	auth2_record_info(authctxt, "%s", displayname);

	authctxt->postponed = 0;
	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
	userauth_finish(ssh, authenticated, "gssapi-with-mic", NULL);
	return 0;
	}

	static int
	input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh)
	{
	Authctxt *authctxt = ssh->authctxt;
	Gssctxt *gssctxt;
	int r, authenticated = 0;
	struct sshbuf *b;
	gss_buffer_desc mic, gssbuf;
	const char *displayname;
	u_char *p;
	size_t len;

	if (authctxt == NULL \|\| (authctxt->methoddata == NULL && !use_privsep))
	fatal("No authentication or GSSAPI context");

	gssctxt = authctxt->methoddata;

	if ((r = sshpkt_get_string(ssh, &p, &len)) != 0)
	fatal("%s: %s", __func__, ssh_err(r));
	if ((b = sshbuf_new()) == NULL)
	fatal("%s: sshbuf_new failed", __func__);
	mic.value = p;
	mic.length = len;
	ssh_gssapi_buildmic(b, authctxt->user, authctxt->service,
	"gssapi-with-mic");

	if ((gssbuf.value = sshbuf_mutable_ptr(b)) == NULL)
	fatal("%s: sshbuf_mutable_ptr failed", __func__);
	gssbuf.length = sshbuf_len(b);

	if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic))))
	authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
	else
	logit("GSSAPI MIC check failed");

	sshbuf_free(b);
	free(mic.value);

	if ((!use_privsep \|\| mm_is_monitor()) &&
	(displayname = ssh_gssapi_displayname()) != NULL)
	auth2_record_info(authctxt, "%s", displayname);

	authctxt->postponed = 0;
	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
	userauth_finish(ssh, authenticated, "gssapi-with-mic", NULL);
	return 0;
	}

	Authmethod method_gssapi = {
	"gssapi-with-mic",
	userauth_gssapi,
	&options.gss_authentication
	};

	#endif /* GSSAPI */