/*
 * Copyright 2004, 2005, 2006 Acegi Technology Pty Limited
 *
 * 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.web.authentication.www;

import java.io.IOException;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.security.authentication.AnonymousAuthenticationToken;
import org.springframework.security.authentication.AuthenticationDetailsSource;
import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.authentication.BadCredentialsException;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.AuthenticationException;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.security.crypto.codec.Base64;
import org.springframework.security.web.AuthenticationEntryPoint;
import org.springframework.security.web.authentication.NullRememberMeServices;
import org.springframework.security.web.authentication.RememberMeServices;
import org.springframework.security.web.authentication.WebAuthenticationDetailsSource;
import org.springframework.util.Assert;
import org.springframework.web.filter.OncePerRequestFilter;

/**
 * Processes a HTTP request's BASIC authorization headers, putting the result into the
 * <code>SecurityContextHolder</code>.
 *
 * <p>
 * For a detailed background on what this filter is designed to process, refer to
 * <a href="http://www.faqs.org/rfcs/rfc1945.html">RFC 1945, Section 11.1</a>. Any realm
 * name presented in the HTTP request is ignored.
 *
 * <p>
 * In summary, this filter is responsible for processing any request that has a HTTP
 * request header of <code>Authorization</code> with an authentication scheme of
 * <code>Basic</code> and a Base64-encoded <code>username:password</code> token. For
 * example, to authenticate user "Aladdin" with password "open sesame" the following
 * header would be presented:
 *
 * <pre>
 *
 * Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==
 * </pre>
 *
 * <p>
 * This filter can be used to provide BASIC authentication services to both remoting
 * protocol clients (such as Hessian and SOAP) as well as standard user agents (such as
 * Internet Explorer and Netscape).
 * <p>
 * If authentication is successful, the resulting {@link Authentication} object will be
 * placed into the <code>SecurityContextHolder</code>.
 *
 * <p>
 * If authentication fails and <code>ignoreFailure</code> is <code>false</code> (the
 * default), an {@link AuthenticationEntryPoint} implementation is called (unless the
 * <tt>ignoreFailure</tt> property is set to <tt>true</tt>). Usually this should be
 * {@link BasicAuthenticationEntryPoint}, which will prompt the user to authenticate again
 * via BASIC authentication.
 *
 * <p>
 * Basic authentication is an attractive protocol because it is simple and widely
 * deployed. However, it still transmits a password in clear text and as such is
 * undesirable in many situations. Digest authentication is also provided by Spring
 * Security and should be used instead of Basic authentication wherever possible. See
 * {@link org.springframework.security.web.authentication.www.DigestAuthenticationFilter}.
 * <p>
 * Note that if a {@link RememberMeServices} is set, this filter will automatically send
 * back remember-me details to the client. Therefore, subsequent requests will not need to
 * present a BASIC authentication header as they will be authenticated using the
 * remember-me mechanism.
 *
 * @author Ben Alex
 */
public class BasicAuthenticationFilter extends OncePerRequestFilter {

	// ~ Instance fields
	// ================================================================================================

	private AuthenticationDetailsSource<HttpServletRequest, ?> authenticationDetailsSource = new WebAuthenticationDetailsSource();
	private AuthenticationEntryPoint authenticationEntryPoint;
	private AuthenticationManager authenticationManager;
	private RememberMeServices rememberMeServices = new NullRememberMeServices();
	private boolean ignoreFailure = false;
	private String credentialsCharset = "UTF-8";

	/**
	 * Creates an instance which will authenticate against the supplied
	 * {@code AuthenticationManager} and which will ignore failed authentication attempts,
	 * allowing the request to proceed down the filter chain.
	 *
	 * @param authenticationManager the bean to submit authentication requests to
	 */
	public BasicAuthenticationFilter(AuthenticationManager authenticationManager) {
		Assert.notNull(authenticationManager, "authenticationManager cannot be null");
		this.authenticationManager = authenticationManager;
		this.ignoreFailure = true;
	}

	/**
	 * Creates an instance which will authenticate against the supplied
	 * {@code AuthenticationManager} and use the supplied {@code AuthenticationEntryPoint}
	 * to handle authentication failures.
	 *
	 * @param authenticationManager the bean to submit authentication requests to
	 * @param authenticationEntryPoint will be invoked when authentication fails.
	 * Typically an instance of {@link BasicAuthenticationEntryPoint}.
	 */
	public BasicAuthenticationFilter(AuthenticationManager authenticationManager,
			AuthenticationEntryPoint authenticationEntryPoint) {
		Assert.notNull(authenticationManager, "authenticationManager cannot be null");
		Assert.notNull(authenticationEntryPoint,
				"authenticationEntryPoint cannot be null");
		this.authenticationManager = authenticationManager;
		this.authenticationEntryPoint = authenticationEntryPoint;
	}

	// ~ Methods
	// ========================================================================================================

	@Override
	public void afterPropertiesSet() {
		Assert.notNull(this.authenticationManager,
				"An AuthenticationManager is required");

		if (!isIgnoreFailure()) {
			Assert.notNull(this.authenticationEntryPoint,
					"An AuthenticationEntryPoint is required");
		}
	}

	@Override
	protected void doFilterInternal(HttpServletRequest request,
			HttpServletResponse response, FilterChain chain)
					throws IOException, ServletException {
		final boolean debug = this.logger.isDebugEnabled();

		String header = request.getHeader("Authorization");

		if (header == null || !header.toLowerCase().startsWith("basic ")) {
			chain.doFilter(request, response);
			return;
		}

		try {
			String[] tokens = extractAndDecodeHeader(header, request);
			assert tokens.length == 2;

			String username = tokens[0];

			if (debug) {
				this.logger
						.debug("Basic Authentication Authorization header found for user '"
								+ username + "'");
			}

			if (authenticationIsRequired(username)) {
				UsernamePasswordAuthenticationToken authRequest = new UsernamePasswordAuthenticationToken(
						username, tokens[1]);
				authRequest.setDetails(
						this.authenticationDetailsSource.buildDetails(request));
				Authentication authResult = this.authenticationManager
						.authenticate(authRequest);

				if (debug) {
					this.logger.debug("Authentication success: " + authResult);
				}

				SecurityContextHolder.getContext().setAuthentication(authResult);

				this.rememberMeServices.loginSuccess(request, response, authResult);

				onSuccessfulAuthentication(request, response, authResult);
			}

		}
		catch (AuthenticationException failed) {
			SecurityContextHolder.clearContext();

			if (debug) {
				this.logger.debug("Authentication request for failed: " + failed);
			}

			this.rememberMeServices.loginFail(request, response);

			onUnsuccessfulAuthentication(request, response, failed);

			if (this.ignoreFailure) {
				chain.doFilter(request, response);
			}
			else {
				this.authenticationEntryPoint.commence(request, response, failed);
			}

			return;
		}

		chain.doFilter(request, response);
	}

	/**
	 * Decodes the header into a username and password.
	 *
	 * @throws BadCredentialsException if the Basic header is not present or is not valid
	 * Base64
	 */
	private String[] extractAndDecodeHeader(String header, HttpServletRequest request)
			throws IOException {

		byte[] base64Token = header.substring(6).getBytes("UTF-8");
		byte[] decoded;
		try {
			decoded = Base64.decode(base64Token);
		}
		catch (IllegalArgumentException e) {
			throw new BadCredentialsException(
					"Failed to decode basic authentication token");
		}

		String token = new String(decoded, getCredentialsCharset(request));

		int delim = token.indexOf(":");

		if (delim == -1) {
			throw new BadCredentialsException("Invalid basic authentication token");
		}
		return new String[] { token.substring(0, delim), token.substring(delim + 1) };
	}

	private boolean authenticationIsRequired(String username) {
		// Only reauthenticate if username doesn't match SecurityContextHolder and user
		// isn't authenticated
		// (see SEC-53)
		Authentication existingAuth = SecurityContextHolder.getContext()
				.getAuthentication();

		if (existingAuth == null || !existingAuth.isAuthenticated()) {
			return true;
		}

		// Limit username comparison to providers which use usernames (ie
		// UsernamePasswordAuthenticationToken)
		// (see SEC-348)

		if (existingAuth instanceof UsernamePasswordAuthenticationToken
				&& !existingAuth.getName().equals(username)) {
			return true;
		}

		// Handle unusual condition where an AnonymousAuthenticationToken is already
		// present
		// This shouldn't happen very often, as BasicProcessingFitler is meant to be
		// earlier in the filter
		// chain than AnonymousAuthenticationFilter. Nevertheless, presence of both an
		// AnonymousAuthenticationToken
		// together with a BASIC authentication request header should indicate
		// reauthentication using the
		// BASIC protocol is desirable. This behaviour is also consistent with that
		// provided by form and digest,
		// both of which force re-authentication if the respective header is detected (and
		// in doing so replace
		// any existing AnonymousAuthenticationToken). See SEC-610.
		if (existingAuth instanceof AnonymousAuthenticationToken) {
			return true;
		}

		return false;
	}

	protected void onSuccessfulAuthentication(HttpServletRequest request,
			HttpServletResponse response, Authentication authResult) throws IOException {
	}

	protected void onUnsuccessfulAuthentication(HttpServletRequest request,
			HttpServletResponse response, AuthenticationException failed)
					throws IOException {
	}

	protected AuthenticationEntryPoint getAuthenticationEntryPoint() {
		return this.authenticationEntryPoint;
	}

	protected AuthenticationManager getAuthenticationManager() {
		return this.authenticationManager;
	}

	protected boolean isIgnoreFailure() {
		return this.ignoreFailure;
	}

	public void setAuthenticationDetailsSource(
			AuthenticationDetailsSource<HttpServletRequest, ?> authenticationDetailsSource) {
		Assert.notNull(authenticationDetailsSource,
				"AuthenticationDetailsSource required");
		this.authenticationDetailsSource = authenticationDetailsSource;
	}

	public void setRememberMeServices(RememberMeServices rememberMeServices) {
		Assert.notNull(rememberMeServices, "rememberMeServices cannot be null");
		this.rememberMeServices = rememberMeServices;
	}

	public void setCredentialsCharset(String credentialsCharset) {
		Assert.hasText(credentialsCharset, "credentialsCharset cannot be null or empty");
		this.credentialsCharset = credentialsCharset;
	}

	protected String getCredentialsCharset(HttpServletRequest httpRequest) {
		return this.credentialsCharset;
	}
}
