/*
    * Copyright 2013–2021 Michael Osipov
    *
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    *     http://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package net.sf.michaelo.tomcat.authenticator;
  
  import java.io.IOException;
  import java.security.Principal;
  import java.security.PrivilegedActionException;
  import java.security.PrivilegedExceptionAction;
  
  import javax.security.auth.Subject;
  import javax.security.auth.login.LoginContext;
  import javax.security.auth.login.LoginException;
  import javax.servlet.http.HttpServletResponse;
  
  import org.apache.catalina.GSSRealm;
  import org.apache.catalina.connector.Request;
  import org.ietf.jgss.GSSCredential;
  import org.ietf.jgss.GSSException;
  import org.ietf.jgss.GSSManager;
  import org.ietf.jgss.GSSName;
  
  /**
   * A Windows Identity Authenticator which uses GSS-API to retrieve to currently logged in user.
   *
   * This authenticator requires a realm which implements the {@link GSSRealm} interface.
   */
  public class CurrentWindowsIdentityAuthenticator extends GSSAuthenticatorBase {
  
  	protected static final String CURRENT_WINDOWS_IDENTITY_METHOD = "CURRENT_WINDOWS_IDENTITY";
  	protected static final String CURRENT_WINDOWS_IDENTITY_AUTH_SCHEME = "CWI";
  
  	@Override
  	protected boolean doAuthenticate(Request request, HttpServletResponse response)
  			throws IOException {
  
  		if (checkForCachedAuthentication(request, response, true)) {
  			return true;
  		}
  
  		LoginContext lc = null;
  
  		try {
  			try {
  				lc = new LoginContext(getLoginEntryName());
  				lc.login();
  			} catch (LoginException e) {
  				logger.error(sm.getString("cwiAuthenticator.obtainFailed"), e);
  
  				sendUnauthorized(request, response, CURRENT_WINDOWS_IDENTITY_AUTH_SCHEME,
  						"cwiAuthenticator.obtainFailed");
  				return false;
  			}
  
  			final GSSManager manager = GSSManager.getInstance();
  			final PrivilegedExceptionAction<GSSCredential> action = new PrivilegedExceptionAction<GSSCredential>() {
  				@Override
  				public GSSCredential run() throws GSSException {
  					return manager.createCredential(null, GSSCredential.INDEFINITE_LIFETIME,
  							KRB5_MECHANISM, GSSCredential.INITIATE_ONLY);
  				}
  			};
  
  			GSSCredential gssCredential = null;
  
  			try {
  				gssCredential = Subject.doAs(lc.getSubject(), action);
  			} catch (PrivilegedActionException e) {
  				logger.error(sm.getString("cwiAuthenticator.obtainFailed"), e.getException());
  
  				sendUnauthorized(request, response, CURRENT_WINDOWS_IDENTITY_AUTH_SCHEME,
  						"cwiAuthenticator.obtainFailed");
  				return false;
  			}
  
  			try {
  				GSSRealm realm = (GSSRealm) context.getRealm();
  				GSSName gssName = gssCredential.getName();
  
  				Principal principal = realm.authenticate(gssName,
  						isStoreDelegatedCredential() ? gssCredential : null);
  
  				if (principal != null) {
  					register(request, response, principal, getAuthMethod(), principal.getName(),
  							null);
  					return true;
  				} else {
 					sendUnauthorized(request, response, CURRENT_WINDOWS_IDENTITY_AUTH_SCHEME,
 							"gssAuthenticatorBase.userNotFound", gssName);
 					return false;
 				}
 			} catch (GSSException e) {
 				logger.error(sm.getString("gssAuthenticatorBase.inquireNameFailed"), e);
 
 				sendInternalServerError(request, response, "gssAuthenticatorBase.inquireNameFailed");
 				return false;
 			}
 		} finally {
 			if (lc != null) {
 				try {
 					lc.logout();
 				} catch (LoginException e) {
 					; // Ignore
 				}
 			}
 		}
 	}
 
 	@Override
 	protected String getAuthMethod() {
 		return CURRENT_WINDOWS_IDENTITY_METHOD;
 	}
 
 }