/*

 * Copyright (c) 2006, 2013, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package com.sun.net.httpserver;

import java.nio.charset.Charset;

import java.util.Base64;

import java.util.Objects;

import static java.nio.charset.StandardCharsets.UTF_8;

/**

 * BasicAuthenticator provides an implementation of HTTP Basic

 * authentication. It is an abstract class and must be extended

 * to provide an implementation of {@link #checkCredentials(String,String)}

 * which is called to verify each incoming request.

 */

public abstract class BasicAuthenticator extends Authenticator {

    protected final String realm;

    protected final Charset charset;

    private final boolean isUTF8;

    /**

     * Creates a BasicAuthenticator for the given HTTP realm.

     * The Basic authentication credentials (username and password) are decoded

     * using the platform's {@link Charset#defaultCharset() default character set}.

     *

     * @param realm The HTTP Basic authentication realm

     * @throws NullPointerException if realm is {@code null}

     * @throws IllegalArgumentException if realm is an empty string

     */

    public BasicAuthenticator (String realm) {

        this(realm, Charset.defaultCharset());

    }

    /**

     * Creates a BasicAuthenticator for the given HTTP realm and using the

     * given {@link Charset} to decode the Basic authentication credentials

     * (username and password).

     *

     * @apiNote {@code UTF-8} is the recommended charset because its usage is

     * communicated to the client, and therefore more likely to be used also

     * by the client.

     *

     * @param realm The HTTP Basic authentication realm

     * @param charset The Charset to decode incoming credentials from the client

     * @throws NullPointerException if realm or charset are {@code null}

     * @throws IllegalArgumentException if realm is an empty string

     */

    public BasicAuthenticator (String realm, Charset charset) {

        Objects.requireNonNull(charset);

        if (realm.isEmpty()) // implicit NPE check

            throw new IllegalArgumentException("realm must not be empty");

        this.realm = realm;

        this.charset = charset;

        this.isUTF8 = charset.equals(UTF_8);

    }

    /**

     * returns the realm this BasicAuthenticator was created with

     * @return the authenticator's realm string.

     */

    public String getRealm () {

        return realm;

    }

    public Result authenticate (HttpExchange t)

    {

        Headers rmap = t.getRequestHeaders();

        /*

         * look for auth token

         */

        String auth = rmap.getFirst ("Authorization");

        if (auth == null) {

            Headers map = t.getResponseHeaders();

            var authString = "Basic realm=" + "\"" + realm + "\"" +

                (isUTF8 ? " charset=\"UTF-8\"" : "");

            map.set ("WWW-Authenticate", authString);

            return new Authenticator.Retry (401);

        }

        int sp = auth.indexOf (' ');

        if (sp == -1 || !auth.substring(0, sp).equals ("Basic")) {

            return new Authenticator.Failure (401);

        }

        byte[] b = Base64.getDecoder().decode(auth.substring(sp+1));

        String userpass = new String (b, charset);

        int colon = userpass.indexOf (':');

        String uname = userpass.substring (0, colon);

        String pass = userpass.substring (colon+1);

        if (checkCredentials (uname, pass)) {

            return new Authenticator.Success (

                new HttpPrincipal (

                    uname, realm

                )

            );

        } else {

            /* reject the request again with 401 */

            Headers map = t.getResponseHeaders();

            map.set ("WWW-Authenticate", "Basic realm=" + "\""+realm+"\"");

            return new Authenticator.Failure(401);

        }

    }

    /**

     * called for each incoming request to verify the

     * given name and password in the context of this

     * Authenticator's realm. Any caching of credentials

     * must be done by the implementation of this method

     * @param username the username from the request

     * @param password the password from the request

     * @return <code>true</code> if the credentials are valid,

     *    <code>false</code> otherwise.

     */

    public abstract boolean checkCredentials (String username, String password);

}