/*

   Derby - Class org.apache.derby.impl.jdbc.authentication.BasicAuthenticationServiceImpl

   Licensed to the Apache Software Foundation (ASF) under one or more
   contributor license agreements.  See the NOTICE file distributed with
   this work for additional information regarding copyright ownership.
   The ASF licenses this file to you 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.apache.derby.impl.jdbc.authentication;

import org.apache.derby.iapi.sql.dictionary.PasswordHasher;
import org.apache.derby.iapi.reference.Attribute;
import org.apache.derby.iapi.reference.SQLState;
import org.apache.derby.authentication.UserAuthenticator;
import org.apache.derby.iapi.services.property.PropertyUtil;
import org.apache.derby.iapi.services.monitor.Monitor;
import org.apache.derby.iapi.store.access.TransactionController;
import org.apache.derby.iapi.error.StandardException;
import org.apache.derby.iapi.util.StringUtil;
import org.apache.derby.impl.jdbc.Util;

import java.util.Properties;
// security imports - for SHA-1 digest
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.sql.SQLException;

/**
 * This authentication service is the basic Derby user authentication
 * level support.
 *
 * It is activated upon setting derby.authentication.provider database
 * or system property to 'BUILTIN'.
 * <p>
 * It instantiates and calls the basic User authentication scheme at runtime.
 * <p>
 * In 2.0, users can now be defined as database properties.
 * If derby.database.propertiesOnly is set to true, then in this
 * case, only users defined as database properties for the current database
 * will be considered.
 *
 */
public final class BasicAuthenticationServiceImpl
	extends AuthenticationServiceBase implements UserAuthenticator {

	//
	// ModuleControl implementation (overriden)
	//

	/**
	 *  Check if we should activate this authentication service.
	 */
	public boolean canSupport(Properties properties) {

		if (!requireAuthentication(properties))
			return false;

		//
		// We check 2 System/Database properties:
		//
		//
		// - if derby.authentication.provider is set to 'BUILTIN'.
		//
		// and in that case we are the authentication service that should
		// be run.
		//

		String authenticationProvider = PropertyUtil.getPropertyFromSet(
					properties,
					org.apache.derby.iapi.reference.Property.AUTHENTICATION_PROVIDER_PARAMETER);

		if ( (authenticationProvider != null) &&
			 (authenticationProvider.length() != 0) &&
			 (!(StringUtil.SQLEqualsIgnoreCase(authenticationProvider,
				  org.apache.derby.iapi.reference.Property.AUTHENTICATION_PROVIDER_BUILTIN))))
			return false;
		else
			return true;	// Yep, we're on!
	}

	/**
	 * @see org.apache.derby.iapi.services.monitor.ModuleControl#boot
	 * @exception StandardException upon failure to load/boot the expected
	 * authentication service.
	 */
	public void boot(boolean create, Properties properties)
	  throws StandardException {

		// We need authentication
		// setAuthentication(true);

		// we call the super in case there is anything to get initialized.
		super.boot(create, properties);

		// Initialize the MessageDigest class engine here
		// (we don't need to do that ideally, but there is some
		// overhead the first time it is instantiated.
		// SHA-1 is expected in jdk 1.1x and jdk1.2
		// This is a standard name: check,
		// http://java.sun.com/products/jdk/1.{1,2}
		//					/docs/guide/security/CryptoSpec.html#AppA 
		try {
			MessageDigest digestAlgorithm = MessageDigest.getInstance("SHA-1");
			digestAlgorithm.reset();

		} catch (NoSuchAlgorithmException nsae) {
			throw Monitor.exceptionStartingModule(nsae);
		}

		// Set ourselves as being ready and loading the proper
		// authentication scheme for this service
		//
		this.setAuthenticationService(this);
	}

	/*
	** UserAuthenticator methods.
	*/

	/**
	 * Authenticate the passed-in user's credentials.
	 *
	 * @param userName		The user's name used to connect to JBMS system
	 * @param userPassword	The user's password used to connect to JBMS system
	 * @param databaseName	The database which the user wants to connect to.
	 * @param info			Additional jdbc connection info.
	 */
	public boolean	authenticateUser(String userName,
								 String userPassword,
								 String databaseName,
								 Properties info
									)
            throws SQLException
	{
        // Client security mechanism if any specified
        // Note: Right now it is only used to handle clients authenticating
        // via DRDA SECMEC_USRSSBPWD mechanism
        String clientSecurityMechanism = null;
        // Client security mechanism (if any) short representation
        // Default value is none.
        int secMec = 0;

		// let's check if the user has been defined as a valid user of the
		// JBMS system.
		// We expect to find and match a System property corresponding to the
		// credentials passed-in.
		//
		if (userName == null)
			// We don't tolerate 'guest' user for now.
			return false;

		String definedUserPassword = null, passedUserPassword = null;

        // If a security mechanism is specified as part of the connection
        // properties, it indicates that we've to account as far as how the
        // password is presented to us - in the case of SECMEC_USRSSBPWD
        // (only expected one at the moment), the password is a substitute
        // one which has already been hashed differently than what we store
        // at the database level (for instance) - this will influence how we
        // assess the substitute password to be legitimate for Derby's
        // BUILTIN authentication scheme/provider.
        if ((clientSecurityMechanism =
                info.getProperty(Attribute.DRDA_SECMEC)) != null)
        {
            secMec = Integer.parseInt(clientSecurityMechanism);
        }

		//
		// Check if user has been defined at the database or/and
		// system level. The user (administrator) can configure it the
		// way he/she wants (as well as forcing users properties to
		// be retrieved at the datbase level only).
		//
        String userNameProperty =
          org.apache.derby.iapi.reference.Property.USER_PROPERTY_PREFIX.concat(
                        userName);

		// check if user defined at the database level
		definedUserPassword = getDatabaseProperty(userNameProperty);

        if (definedUserPassword != null)
        {
            if (secMec != SECMEC_USRSSBPWD)
            {
                // hash passed-in password
                try {
                    passedUserPassword = hashPasswordUsingStoredAlgorithm(
                            userName, userPassword, definedUserPassword);
                } catch (StandardException se) {
                    // The UserAuthenticator interface does not allow us to
                    // throw a StandardException, so convert to SQLException.
                    throw Util.generateCsSQLException(se);
                }
            }
            else
            {
                // Dealing with a client SECMEC - password checking is
                // slightly different and we need to generate a
                // password substitute to compare with the substitute
                // generated one from the client.
                definedUserPassword = substitutePassword(userName,
                                                         definedUserPassword,
                                                         info, true);
                // As SecMec is SECMEC_USRSSBPWD, expected passed-in password
                // to be HexString'ified already
                passedUserPassword = userPassword;
            }
        }
        else
        {
            // DERBY-5539: Generate a hashed token even if the user is not
            // defined at the database level (that is, the user is defined at
            // the system level or does not exist at all). If we don't do that,
            // authentication failures would take less time for non-existing
            // users than they would for existing users, since generating the
            // hashed token is a relatively expensive operation. Attackers
            // could use this to determine if a user exists. By generating the
            // hashed token also for non-existing users, authentication
            // failures will take the same time for existing and non-existing
            // users, and it will be more difficult for attackers to tell the
            // difference.
            try {
                Properties props = getDatabaseProperties();
                if (props != null) {
                    hashUsingDefaultAlgorithm(
                            userName, userPassword, props);
                }
            } catch (StandardException se) {
                throw Util.generateCsSQLException(se);
            }

            // check if user defined at the system level
            definedUserPassword = getSystemProperty(userNameProperty);
            passedUserPassword = userPassword;

            if ((definedUserPassword != null) &&
                (secMec == SECMEC_USRSSBPWD))
            {
                // Dealing with a client SECMEC - see above comments
                definedUserPassword = substitutePassword(userName,
                                                         definedUserPassword,
                                                         info, false);
            }
        }

        // Check if the passwords match.
		// NOTE: We do not look at the passed-in database name value as
		// we rely on the authorization service that was put in
		// in 2.0 . (if a database name was passed-in)
        boolean passwordsMatch =
                (definedUserPassword != null) &&
                definedUserPassword.equals(passedUserPassword);

        // Provide extra information on mismatch if strong password
        // substitution is used, since the problem may be that the stored
        // password was stored using the configurable hash authentication
        // scheme which is incompatible with strong password substitution.
        if (!passwordsMatch && secMec == SECMEC_USRSSBPWD) {
            throw Util.generateCsSQLException(
                    SQLState.NET_CONNECT_SECMEC_INCOMPATIBLE_SCHEME);
        }

        return passwordsMatch;
	}

    /**
     * Hash a password using the same algorithm as we used to generate the
     * stored password token.
     *
     * @param user the user whose password to hash
     * @param password the plaintext password
     * @param storedPassword the password token that's stored in the database
     * @return a digest of the password created the same way as the stored
     *         password
     * @throws StandardException if the password cannot be hashed with the
     *         requested algorithm
     */
    private String hashPasswordUsingStoredAlgorithm(
                String user, String password, String storedPassword)
            throws StandardException
    {
        if (storedPassword.startsWith( PasswordHasher.ID_PATTERN_SHA1_SCHEME )) {
            return hashPasswordSHA1Scheme(password);
        }
        else
        {
            PasswordHasher  hasher = new PasswordHasher( storedPassword );

            return hasher.hashAndEncode( user, password );
        }
    }
}
