/*
 * Copyright 2002-2015 the original author or authors.
 *
 * 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 org.springframework.security.messaging.web.csrf;

import java.util.Map;

import org.springframework.messaging.Message;
import org.springframework.messaging.MessageChannel;
import org.springframework.messaging.simp.SimpMessageHeaderAccessor;
import org.springframework.messaging.simp.SimpMessageType;
import org.springframework.messaging.support.ChannelInterceptorAdapter;
import org.springframework.security.messaging.util.matcher.MessageMatcher;
import org.springframework.security.messaging.util.matcher.SimpMessageTypeMatcher;
import org.springframework.security.web.csrf.CsrfToken;
import org.springframework.security.web.csrf.InvalidCsrfTokenException;
import org.springframework.security.web.csrf.MissingCsrfTokenException;

/**
 * {@link ChannelInterceptorAdapter} that validates that a valid CSRF is included in the
 * header of any {@link SimpMessageType#CONNECT} message. The expected {@link CsrfToken}
 * is populated by CsrfTokenHandshakeInterceptor.
 *
 * @author Rob Winch
 * @since 4.0
 */
public final class CsrfChannelInterceptor extends ChannelInterceptorAdapter {
	private final MessageMatcher<Object> matcher = new SimpMessageTypeMatcher(
			SimpMessageType.CONNECT);

	@Override
	public Message<?> preSend(Message<?> message, MessageChannel channel) {
		if (!matcher.matches(message)) {
			return message;
		}

		Map<String, Object> sessionAttributes = SimpMessageHeaderAccessor
				.getSessionAttributes(message.getHeaders());
		CsrfToken expectedToken = sessionAttributes == null ? null
				: (CsrfToken) sessionAttributes.get(CsrfToken.class.getName());

		if (expectedToken == null) {
			throw new MissingCsrfTokenException(null);
		}

		String actualTokenValue = SimpMessageHeaderAccessor.wrap(message)
				.getFirstNativeHeader(expectedToken.getHeaderName());

		boolean csrfCheckPassed = expectedToken.getToken().equals(actualTokenValue);
		if (csrfCheckPassed) {
			return message;
		}
		throw new InvalidCsrfTokenException(expectedToken, actualTokenValue);
	}
}
