text: /* $OpenBSD: auth2-gss.c,v 1.21 2014/02/26 20:28:44 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 "key.h"
  #include "hostfile.h"
  #include "auth.h"
  #include "ssh2.h"
  #include "log.h"
  #include "dispatch.h"
  #include "buffer.h"
  #include "misc.h"
  #include "servconf.h"
  #include "packet.h"
  #include "ssh-gss.h"
  #include "monitor_wrap.h"
  
  extern ServerOptions options;
  
  static void input_gssapi_token(int type, u_int32_t plen, void *ctxt);
  static void input_gssapi_mic(int type, u_int32_t plen, void *ctxt);
  static void input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt);
  static void input_gssapi_errtok(int, u_int32_t, void *);
  
  /*
   * 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(Authctxt *authctxt)
  {
  	gss_OID_desc goid = {0, NULL};
  	Gssctxt *ctxt = NULL;
  	int mechs;
  	int present;
  	OM_uint32 ms;
  	u_int len;
  	u_char *doid = NULL;
  
  	if (!authctxt->valid || authctxt->user == NULL)
  		return (0);
  
  	mechs = packet_get_int();
  	if (mechs == 0) {
  		debug("Mechanism negotiation is not supported");
  		return (0);
  	}
  
  	do {
  		mechs--;
  
  		free(doid);
  
  		present = 0;
  		doid = packet_get_string(&len);
  
  		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 (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;
  
  	packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE);
  
  	/* Return the OID that we received */
  	packet_put_string(doid, len);
  
  	packet_send();
  	free(doid);
  
  	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
  	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
  	authctxt->postponed = 1;
  
  	return (0);
  }
  
  static void
  input_gssapi_token(int type, u_int32_t plen, void *ctxt)
  {
  	Authctxt *authctxt = ctxt;
  	Gssctxt *gssctxt;
  	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
  	gss_buffer_desc recv_tok;
  	OM_uint32 maj_status, min_status, flags;
  	u_int len;
  
  	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
  		fatal("No authentication or GSSAPI context");
  
  	gssctxt = authctxt->methoddata;
  	recv_tok.value = packet_get_string(&len);
  	recv_tok.length = len; /* u_int vs. size_t */
  
  	packet_check_eom();
  
  	maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
  	    &send_tok, &flags));
  
  	free(recv_tok.value);
  
  	if (GSS_ERROR(maj_status)) {
  		if (send_tok.length != 0) {
  			packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK);
  			packet_put_string(send_tok.value, send_tok.length);
  			packet_send();
  		}
  		authctxt->postponed = 0;
  		dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
  		userauth_finish(authctxt, 0, "gssapi-with-mic", NULL);
  	} else {
  		if (send_tok.length != 0) {
  			packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN);
  			packet_put_string(send_tok.value, send_tok.length);
  			packet_send();
  		}
  		if (maj_status == GSS_S_COMPLETE) {
  			dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
  			if (flags & GSS_C_INTEG_FLAG)
  				dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC,
  				    &input_gssapi_mic);
  			else
  				dispatch_set(
  				    SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE,
  				    &input_gssapi_exchange_complete);
  		}
  	}
  
  	gss_release_buffer(&min_status, &send_tok);
  }
  
  static void
  input_gssapi_errtok(int type, u_int32_t plen, void *ctxt)
  {
  	Authctxt *authctxt = ctxt;
  	Gssctxt *gssctxt;
  	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
  	gss_buffer_desc recv_tok;
  	OM_uint32 maj_status;
  	u_int len;
  
  	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
  		fatal("No authentication or GSSAPI context");
  
  	gssctxt = authctxt->methoddata;
  	recv_tok.value = packet_get_string(&len);
  	recv_tok.length = len;
  
  	packet_check_eom();
  
  	/* 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 */
  	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
  	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
  
  	/* The client will have already moved on to the next auth */
  
  	gss_release_buffer(&maj_status, &send_tok);
  }
  
  /*
   * 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 void
  input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt)
  {
  	Authctxt *authctxt = ctxt;
  	int authenticated;
  
  	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
  	 */
  
  	packet_check_eom();
  
  	authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
  
  	authctxt->postponed = 0;
  	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
  	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
  	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
  	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
  	userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL);
  }
  
  static void
  input_gssapi_mic(int type, u_int32_t plen, void *ctxt)
  {
  	Authctxt *authctxt = ctxt;
  	Gssctxt *gssctxt;
  	int authenticated = 0;
  	Buffer b;
  	gss_buffer_desc mic, gssbuf;
  	u_int len;
  
  	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
  		fatal("No authentication or GSSAPI context");
  
  	gssctxt = authctxt->methoddata;
  
  	mic.value = packet_get_string(&len);
  	mic.length = len;
  
  	ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service,
  	    "gssapi-with-mic");
  
  	gssbuf.value = buffer_ptr(&b);
  	gssbuf.length = buffer_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");
  
  	buffer_free(&b);
  	free(mic.value);
  
  	authctxt->postponed = 0;
  	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
  	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
  	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
  	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
  	userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL);
  }
  
  Authmethod method_gssapi = {
  	"gssapi-with-mic",
  	userauth_gssapi,
  	&options.gss_authentication
  };
  
  #endif /* GSSAPI */
  