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/*
 * 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.kafka.common.security;

import org.apache.kafka.common.config.SaslConfigs;
import org.apache.kafka.common.config.types.Password;
import org.apache.kafka.common.network.ListenerName;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.security.auth.login.AppConfigurationEntry;
import javax.security.auth.login.Configuration;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;

import static org.apache.kafka.common.security.JaasUtils.DISALLOWED_LOGIN_MODULES_CONFIG;
import static org.apache.kafka.common.security.JaasUtils.DISALLOWED_LOGIN_MODULES_DEFAULT;

public class JaasContext {

    private static final Logger LOG = LoggerFactory.getLogger(JaasContext.class);

    private static final String GLOBAL_CONTEXT_NAME_SERVER = "KafkaServer";
    private static final String GLOBAL_CONTEXT_NAME_CLIENT = "KafkaClient";

    /**
     * Returns an instance of this class.
     *
     * The context will contain the configuration specified by the JAAS configuration property
     * {@link SaslConfigs#SASL_JAAS_CONFIG} with prefix `listener.name.{listenerName}.{mechanism}.`
     * with listenerName and mechanism in lower case. The context `KafkaServer` will be returned
     * with a single login context entry loaded from the property.
     * 
     * If the property is not defined, the context will contain the default Configuration and
     * the context name will be one of:
     * 

     *   Lowercased listener name followed by a period and the string `KafkaServer`
     *   The string `KafkaServer`
     *  
     * If both are valid entries in the default JAAS configuration, the first option is chosen.
     * 
     *
     * @throws IllegalArgumentException if listenerName or mechanism is not defined.
     */
    public static JaasContext loadServerContext(ListenerName listenerName, String mechanism, Map configs) {
        if (listenerName == null)
            throw new IllegalArgumentException("listenerName should not be null for SERVER");
        if (mechanism == null)
            throw new IllegalArgumentException("mechanism should not be null for SERVER");
        String listenerContextName = listenerName.value().toLowerCase(Locale.ROOT) + "." + GLOBAL_CONTEXT_NAME_SERVER;
        Password dynamicJaasConfig = (Password) configs.get(mechanism.toLowerCase(Locale.ROOT) + "." + SaslConfigs.SASL_JAAS_CONFIG);
        if (dynamicJaasConfig == null && configs.get(SaslConfigs.SASL_JAAS_CONFIG) != null)
            LOG.warn("Server config {} should be prefixed with SASL mechanism name, ignoring config", SaslConfigs.SASL_JAAS_CONFIG);
        return load(Type.SERVER, listenerContextName, GLOBAL_CONTEXT_NAME_SERVER, dynamicJaasConfig);
    }

    /**
     * Returns an instance of this class.
     *
     * If JAAS configuration property @link SaslConfigs#SASL_JAAS_CONFIG} is specified,
     * the configuration object is created by parsing the property value. Otherwise, the default Configuration
     * is returned. The context name is always `KafkaClient`.
     *
     */
    public static JaasContext loadClientContext(Map configs) {
        Password dynamicJaasConfig = (Password) configs.get(SaslConfigs.SASL_JAAS_CONFIG);
        return load(JaasContext.Type.CLIENT, null, GLOBAL_CONTEXT_NAME_CLIENT, dynamicJaasConfig);
    }

    static JaasContext load(JaasContext.Type contextType, String listenerContextName,
                            String globalContextName, Password dynamicJaasConfig) {
        if (dynamicJaasConfig != null) {
            JaasConfig jaasConfig = new JaasConfig(globalContextName, dynamicJaasConfig.value());
            AppConfigurationEntry[] contextModules = jaasConfig.getAppConfigurationEntry(globalContextName);
            if (contextModules == null || contextModules.length == 0)
                throw new IllegalArgumentException("JAAS config property does not contain any login modules");
            else if (contextModules.length != 1)
                throw new IllegalArgumentException("JAAS config property contains " + contextModules.length + " login modules, should be 1 module");

            throwIfLoginModuleIsNotAllowed(contextModules[0]);
            return new JaasContext(globalContextName, contextType, jaasConfig, dynamicJaasConfig);
        } else
            return defaultContext(contextType, listenerContextName, globalContextName);
    }

    private static void throwIfLoginModuleIsNotAllowed(AppConfigurationEntry appConfigurationEntry) {
        Set disallowedLoginModuleList = Arrays.stream(
                System.getProperty(DISALLOWED_LOGIN_MODULES_CONFIG, DISALLOWED_LOGIN_MODULES_DEFAULT).split(","))
                .map(String::trim)
                .collect(Collectors.toSet());
        String loginModuleName = appConfigurationEntry.getLoginModuleName().trim();
        if (disallowedLoginModuleList.contains(loginModuleName)) {
            throw new IllegalArgumentException(loginModuleName + " is not allowed. Update System property '"
                    + DISALLOWED_LOGIN_MODULES_CONFIG + "' to allow " + loginModuleName);
        }
    }

    private static JaasContext defaultContext(JaasContext.Type contextType, String listenerContextName,
                                              String globalContextName) {
        String jaasConfigFile = System.getProperty(JaasUtils.JAVA_LOGIN_CONFIG_PARAM);
        if (jaasConfigFile == null) {
            if (contextType == Type.CLIENT) {
                LOG.debug("System property '" + JaasUtils.JAVA_LOGIN_CONFIG_PARAM + "' and Kafka SASL property '" +
                        SaslConfigs.SASL_JAAS_CONFIG + "' are not set, using default JAAS configuration.");
            } else {
                LOG.debug("System property '" + JaasUtils.JAVA_LOGIN_CONFIG_PARAM + "' is not set, using default JAAS " +
                        "configuration.");
            }
        }

        Configuration jaasConfig = Configuration.getConfiguration();

        AppConfigurationEntry[] configEntries = null;
        String contextName = globalContextName;

        if (listenerContextName != null) {
            configEntries = jaasConfig.getAppConfigurationEntry(listenerContextName);
            if (configEntries != null)
                contextName = listenerContextName;
        }

        if (configEntries == null)
            configEntries = jaasConfig.getAppConfigurationEntry(globalContextName);

        if (configEntries == null) {
            String listenerNameText = listenerContextName == null ? "" : " or '" + listenerContextName + "'";
            String errorMessage = "Could not find a '" + globalContextName + "'" + listenerNameText + " entry in the JAAS " +
                    "configuration. System property '" + JaasUtils.JAVA_LOGIN_CONFIG_PARAM + "' is " +
                    (jaasConfigFile == null ? "not set" : jaasConfigFile);
            throw new IllegalArgumentException(errorMessage);
        }

        for (AppConfigurationEntry appConfigurationEntry : configEntries) {
            throwIfLoginModuleIsNotAllowed(appConfigurationEntry);
        }
        return new JaasContext(contextName, contextType, jaasConfig, null);
    }

    /**
     * The type of the SASL login context, it should be SERVER for the broker and CLIENT for the clients (consumer, producer,
     * etc.). This is used to validate behaviour (e.g. some functionality is only available in the broker or clients).
     */
    public enum Type { CLIENT, SERVER }

    private final String name;
    private final Type type;
    private final Configuration configuration;
    private final List configurationEntries;
    private final Password dynamicJaasConfig;

    public JaasContext(String name, Type type, Configuration configuration, Password dynamicJaasConfig) {
        this.name = name;
        this.type = type;
        this.configuration = configuration;
        AppConfigurationEntry[] entries = configuration.getAppConfigurationEntry(name);
        if (entries == null)
            throw new IllegalArgumentException("Could not find a '" + name + "' entry in this JAAS configuration.");
        this.configurationEntries = Collections.unmodifiableList(new ArrayList<>(Arrays.asList(entries)));
        this.dynamicJaasConfig = dynamicJaasConfig;
    }

    public String name() {
        return name;
    }

    public Type type() {
        return type;
    }

    public Configuration configuration() {
        return configuration;
    }

    public List configurationEntries() {
        return configurationEntries;
    }

    public Password dynamicJaasConfig() {
        return dynamicJaasConfig;
    }

    /**
     * Returns the configuration option for key from this context.
     * If login module name is specified, return option value only from that module.
     */
    public static String configEntryOption(List configurationEntries, String key, String loginModuleName) {
        for (AppConfigurationEntry entry : configurationEntries) {
            if (loginModuleName != null && !loginModuleName.equals(entry.getLoginModuleName()))
                continue;
            Object val = entry.getOptions().get(key);
            if (val != null)
                return (String) val;
        }
        return null;
    }

}