001/*
002 * Copyright (C) 2022-2023 The Prometheus jmx_exporter Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package io.prometheus.jmx.common.http.authenticator;
018
019import com.sun.net.httpserver.BasicAuthenticator;
020import io.prometheus.jmx.common.util.Precondition;
021import java.math.BigInteger;
022import java.nio.charset.StandardCharsets;
023import java.security.GeneralSecurityException;
024import java.security.MessageDigest;
025import java.security.NoSuchAlgorithmException;
026import java.util.Collections;
027import java.util.HashSet;
028import java.util.LinkedList;
029import java.util.Set;
030
031/** Class to implement a username / salted message digest password BasicAuthenticator */
032public class MessageDigestAuthenticator extends BasicAuthenticator {
033
034    private static final int MAXIMUM_INVALID_CACHE_KEY_ENTRIES = 16;
035
036    private final String username;
037    private final String passwordHash;
038    private final String algorithm;
039    private final String salt;
040    private final Set<CacheKey> validCacheKeys;
041    private final LinkedList<CacheKey> invalidCacheKeys;
042
043    /**
044     * Constructor
045     *
046     * @param realm realm
047     * @param username username
048     * @param passwordHash passwordHash
049     * @param algorithm algorithm
050     * @param salt salt
051     * @throws NoSuchAlgorithmException NoSuchAlgorithmException
052     */
053    public MessageDigestAuthenticator(
054            String realm, String username, String passwordHash, String algorithm, String salt)
055            throws GeneralSecurityException {
056        super(realm);
057
058        Precondition.notNullOrEmpty(username);
059        Precondition.notNullOrEmpty(passwordHash);
060        Precondition.notNullOrEmpty(algorithm);
061        Precondition.notNullOrEmpty(salt);
062
063        MessageDigest.getInstance(algorithm);
064
065        this.username = username;
066        this.passwordHash = passwordHash.toLowerCase().replace(":", "");
067        this.algorithm = algorithm;
068        this.salt = salt;
069        this.validCacheKeys = Collections.synchronizedSet(new HashSet<>());
070        this.invalidCacheKeys = new LinkedList<>();
071    }
072
073    /**
074     * called for each incoming request to verify the given name and password in the context of this
075     * Authenticator's realm. Any caching of credentials must be done by the implementation of this
076     * method
077     *
078     * @param username the username from the request
079     * @param password the password from the request
080     * @return <code>true</code> if the credentials are valid, <code>false</code> otherwise.
081     */
082    @Override
083    public boolean checkCredentials(String username, String password) {
084        if (username == null || password == null) {
085            return false;
086        }
087
088        CacheKey cacheKey = new CacheKey(username, password);
089        if (validCacheKeys.contains(cacheKey)) {
090            return true;
091        } else {
092            synchronized (invalidCacheKeys) {
093                if (invalidCacheKeys.contains(cacheKey)) {
094                    return false;
095                }
096            }
097        }
098
099        boolean isValid =
100                this.username.equals(username)
101                        && this.passwordHash.equals(
102                                generatePasswordHash(algorithm, salt, password));
103
104        if (isValid) {
105            validCacheKeys.add(cacheKey);
106        } else {
107            synchronized (invalidCacheKeys) {
108                invalidCacheKeys.add(cacheKey);
109                if (invalidCacheKeys.size() > MAXIMUM_INVALID_CACHE_KEY_ENTRIES) {
110                    invalidCacheKeys.removeFirst();
111                }
112            }
113        }
114
115        return isValid;
116    }
117
118    /**
119     * Method to generate a hash based on the configured message digest algorithm
120     *
121     * @param algorithm algorithm
122     * @param salt salt
123     * @param password password
124     * @return the hash
125     */
126    private static String generatePasswordHash(String algorithm, String salt, String password) {
127        try {
128            MessageDigest digest = MessageDigest.getInstance(algorithm);
129            byte[] hash = digest.digest((salt + ":" + password).getBytes(StandardCharsets.UTF_8));
130            BigInteger number = new BigInteger(1, hash);
131            return number.toString(16).toLowerCase();
132        } catch (GeneralSecurityException e) {
133            throw new RuntimeException(e);
134        }
135    }
136}