/*
 * 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.ldap.authentication;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.ldap.NamingException;
import org.springframework.ldap.core.DirContextAdapter;
import org.springframework.ldap.core.DirContextOperations;
import org.springframework.ldap.core.DistinguishedName;
import org.springframework.ldap.core.support.BaseLdapPathContextSource;
import org.springframework.ldap.support.LdapUtils;
import org.springframework.security.authentication.BadCredentialsException;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.Authentication;
import org.springframework.security.ldap.ppolicy.PasswordPolicyControl;
import org.springframework.security.ldap.ppolicy.PasswordPolicyControlExtractor;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

import javax.naming.directory.Attributes;
import javax.naming.directory.DirContext;

/**
 * An authenticator which binds as a user.
 *
 * @author Luke Taylor
 *
 * @see AbstractLdapAuthenticator
 */
public class BindAuthenticator extends AbstractLdapAuthenticator {
	// ~ Static fields/initializers
	// =====================================================================================

	private static final Log logger = LogFactory.getLog(BindAuthenticator.class);

	// ~ Constructors
	// ===================================================================================================

	/**
	 * Create an initialized instance using the {@link BaseLdapPathContextSource}
	 * provided.
	 *
	 * @param contextSource the BaseLdapPathContextSource instance against which bind
	 * operations will be performed.
	 *
	 */
	public BindAuthenticator(BaseLdapPathContextSource contextSource) {
		super(contextSource);
	}

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

	public DirContextOperations authenticate(Authentication authentication) {
		DirContextOperations user = null;
		Assert.isInstanceOf(UsernamePasswordAuthenticationToken.class, authentication,
				"Can only process UsernamePasswordAuthenticationToken objects");

		String username = authentication.getName();
		String password = (String) authentication.getCredentials();

		if (!StringUtils.hasLength(password)) {
			logger.debug("Rejecting empty password for user " + username);
			throw new BadCredentialsException(messages.getMessage(
					"BindAuthenticator.emptyPassword", "Empty Password"));
		}

		// If DN patterns are configured, try authenticating with them directly
		for (String dn : getUserDns(username)) {
			user = bindWithDn(dn, username, password);

			if (user != null) {
				break;
			}
		}

		// Otherwise use the configured search object to find the user and authenticate
		// with the returned DN.
		if (user == null && getUserSearch() != null) {
			DirContextOperations userFromSearch = getUserSearch().searchForUser(username);
			user = bindWithDn(userFromSearch.getDn().toString(), username, password,
					userFromSearch.getAttributes());
		}

		if (user == null) {
			throw new BadCredentialsException(messages.getMessage(
					"BindAuthenticator.badCredentials", "Bad credentials"));
		}

		return user;
	}

	private DirContextOperations bindWithDn(String userDnStr, String username,
			String password) {
		return bindWithDn(userDnStr, username, password, null);
	}

	private DirContextOperations bindWithDn(String userDnStr, String username,
			String password, Attributes attrs) {
		BaseLdapPathContextSource ctxSource = (BaseLdapPathContextSource) getContextSource();
		DistinguishedName userDn = new DistinguishedName(userDnStr);
		DistinguishedName fullDn = new DistinguishedName(userDn);
		fullDn.prepend(ctxSource.getBaseLdapPath());

		logger.debug("Attempting to bind as " + fullDn);

		DirContext ctx = null;
		try {
			ctx = getContextSource().getContext(fullDn.toString(), password);
			// Check for password policy control
			PasswordPolicyControl ppolicy = PasswordPolicyControlExtractor
					.extractControl(ctx);

			logger.debug("Retrieving attributes...");
			if (attrs == null || attrs.size()==0) {
				attrs = ctx.getAttributes(userDn, getUserAttributes());
			}

			DirContextAdapter result = new DirContextAdapter(attrs, userDn,
					ctxSource.getBaseLdapPath());

			if (ppolicy != null) {
				result.setAttributeValue(ppolicy.getID(), ppolicy);
			}

			return result;
		}
		catch (NamingException e) {
			// This will be thrown if an invalid user name is used and the method may
			// be called multiple times to try different names, so we trap the exception
			// unless a subclass wishes to implement more specialized behaviour.
			if ((e instanceof org.springframework.ldap.AuthenticationException)
					|| (e instanceof org.springframework.ldap.OperationNotSupportedException)) {
				handleBindException(userDnStr, username, e);
			}
			else {
				throw e;
			}
		}
		catch (javax.naming.NamingException e) {
			throw LdapUtils.convertLdapException(e);
		}
		finally {
			LdapUtils.closeContext(ctx);
		}

		return null;
	}

	/**
	 * Allows subclasses to inspect the exception thrown by an attempt to bind with a
	 * particular DN. The default implementation just reports the failure to the debug
	 * logger.
	 */
	protected void handleBindException(String userDn, String username, Throwable cause) {
		if (logger.isDebugEnabled()) {
			logger.debug("Failed to bind as " + userDn + ": " + cause);
		}
	}
}
