/*
 * 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.catalina.realm;

import java.io.File;
import java.io.IOException;
import java.security.Principal;
import java.util.HashSet;
import java.util.Map;
import java.util.Map.Entry;

import javax.security.auth.Subject;
import javax.security.auth.callback.Callback;
import javax.security.auth.callback.CallbackHandler;
import javax.security.auth.callback.NameCallback;
import javax.security.auth.callback.PasswordCallback;
import javax.security.auth.callback.TextInputCallback;
import javax.security.auth.callback.UnsupportedCallbackException;
import javax.security.auth.login.FailedLoginException;
import javax.security.auth.login.LoginException;
import javax.security.auth.spi.LoginModule;
import javax.servlet.http.HttpServletRequest;

import org.apache.catalina.CredentialHandler;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.apache.tomcat.util.IntrospectionUtils;
import org.apache.tomcat.util.digester.Digester;

/**
 * <p>
 * Implementation of the JAAS <strong>LoginModule</strong> interface, primarily for use in testing
 * <code>JAASRealm</code>. It utilizes an XML-format data file of username/password/role information identical to that
 * supported by <code>org.apache.catalina.realm.MemoryRealm</code>.
 * </p>
 * <p>
 * This class recognizes the following string-valued options, which are specified in the configuration file and passed
 * to {@link #initialize(Subject, CallbackHandler, Map, Map)} in the <code>options</code> argument:
 * </p>
 * <ul>
 * <li><strong>pathname</strong> - Relative (to the pathname specified by the "catalina.base" system property) or
 * absolute pathname to the XML file containing our user information, in the format supported by {@link MemoryRealm}.
 * The default value matches the MemoryRealm default.</li>
 * <li><strong>credentialHandlerClassName</strong> - The fully qualified class name of the CredentialHandler to use. If
 * not specified, {@link MessageDigestCredentialHandler} will be used.</li>
 * <li>Any additional options will be used to identify and call setters on the {@link CredentialHandler}. For example,
 * <code>algorithm=SHA256</code> would result in a call to {@link MessageDigestCredentialHandler#setAlgorithm(String)}
 * with a parameter of <code>"SHA256"</code></li>
 * </ul>
 * <p>
 * <strong>IMPLEMENTATION NOTE</strong> - This class implements <code>Realm</code> only to satisfy the calling
 * requirements of the <code>GenericPrincipal</code> constructor. It does not actually perform the functionality
 * required of a <code>Realm</code> implementation.
 * </p>
 */
public class JAASMemoryLoginModule extends MemoryRealm implements LoginModule {
    // We need to extend MemoryRealm to avoid class cast

    private static final Log log = LogFactory.getLog(JAASMemoryLoginModule.class);

    // ----------------------------------------------------- Instance Variables


    /**
     * The callback handler responsible for answering our requests.
     */
    protected CallbackHandler callbackHandler = null;


    /**
     * Has our own <code>commit()</code> returned successfully?
     */
    protected boolean committed = false;


    /**
     * The configuration information for this <code>LoginModule</code>.
     */
    protected Map<String,?> options = null;


    /**
     * The absolute or relative pathname to the XML configuration file.
     */
    protected String pathname = "conf/tomcat-users.xml";


    /**
     * The <code>Principal</code> identified by our validation, or <code>null</code> if validation failed.
     */
    protected Principal principal = null;


    /**
     * The <code>Principal</code> for the roles.
     */
    protected HashSet<Principal> roles = null;


    /**
     * The state information that is shared with other configured <code>LoginModule</code> instances.
     */
    protected Map<String,?> sharedState = null;


    /**
     * The subject for which we are performing authentication.
     */
    protected Subject subject = null;


    // --------------------------------------------------------- Public Methods

    /**
     * Constructs a new JAASMemoryLoginModule.
     */
    public JAASMemoryLoginModule() {
        if (log.isTraceEnabled()) {
            log.trace("MEMORY LOGIN MODULE");
        }
    }


    @Override
    public boolean abort() throws LoginException {

        // If our authentication was not successful, just return false
        if (principal == null) {
            return false;
        }

        // Clean up if overall authentication failed
        if (committed) {
            logout();
        } else {
            principal = null;
        }
        if (log.isTraceEnabled()) {
            log.trace("Abort");
        }
        return true;
    }


    @Override
    public boolean commit() throws LoginException {
        if (log.isTraceEnabled()) {
            log.trace("commit " + principal);
        }

        // If authentication was not successful, just return false
        if (principal == null) {
            return false;
        }

        // Add our Principal to the Subject if needed
        if (!subject.getPrincipals().contains(principal)) {
            subject.getPrincipals().add(principal);
            // Add the roles as additional subjects as per the contract with the
            // JAASRealm
            if (principal instanceof GenericPrincipal) {
                this.roles = new HashSet<>();
                String[] roles = ((GenericPrincipal) principal).getRoles();
                for (String role : roles) {
                    GenericPrincipal roleGp = new GenericPrincipal(role, null, null);
                    subject.getPrincipals().add(roleGp);
                    this.roles.add(roleGp);
                }
            }
        }

        committed = true;
        return true;
    }


    @Override
    public void initialize(Subject subject, CallbackHandler callbackHandler, Map<String,?> sharedState,
            Map<String,?> options) {
        if (log.isTraceEnabled()) {
            log.trace("Init");
        }

        // Save configuration values
        this.subject = subject;
        this.callbackHandler = callbackHandler;
        this.sharedState = sharedState;
        this.options = options;

        // Perform instance-specific initialization
        Object option = options.get("pathname");
        if (option instanceof String) {
            this.pathname = (String) option;
        }

        CredentialHandler credentialHandler = null;
        option = options.get("credentialHandlerClassName");
        if (option instanceof String) {
            try {
                Class<?> clazz = Class.forName((String) option);
                credentialHandler = (CredentialHandler) clazz.getConstructor().newInstance();
            } catch (ReflectiveOperationException e) {
                throw new IllegalArgumentException(e);
            }
        }
        if (credentialHandler == null) {
            credentialHandler = new MessageDigestCredentialHandler();
        }

        for (Entry<String,?> entry : options.entrySet()) {
            if ("pathname".equals(entry.getKey())) {
                continue;
            }
            if ("credentialHandlerClassName".equals(entry.getKey())) {
                continue;
            }
            // Skip any non-String values since any value we are interested in
            // will be a String.
            if (entry.getValue() instanceof String) {
                IntrospectionUtils.setProperty(credentialHandler, entry.getKey(), (String) entry.getValue());
            }
        }
        setCredentialHandler(credentialHandler);

        // Load our defined Principals
        load();
    }


    @Override
    public boolean login() throws LoginException {
        // Set up our CallbackHandler requests
        if (callbackHandler == null) {
            throw new LoginException(sm.getString("jaasMemoryLoginModule.noCallbackHandler"));
        }
        Callback[] callbacks = new Callback[10];
        callbacks[0] = new NameCallback("Username: ");
        callbacks[1] = new PasswordCallback("Password: ", false);
        callbacks[2] = new TextInputCallback("nonce");
        callbacks[3] = new TextInputCallback("nc");
        callbacks[4] = new TextInputCallback("cnonce");
        callbacks[5] = new TextInputCallback("qop");
        callbacks[6] = new TextInputCallback("realmName");
        callbacks[7] = new TextInputCallback("digestA2");
        callbacks[8] = new TextInputCallback("algorithm");
        callbacks[9] = new TextInputCallback("authMethod");

        // Interact with the user to retrieve the username and password
        String username;
        String password;
        String nonce;
        String nc;
        String cnonce;
        String qop;
        String realmName;
        String digestA2;
        String algorithm;
        String authMethod;

        try {
            callbackHandler.handle(callbacks);
            username = ((NameCallback) callbacks[0]).getName();
            char[] passwordArray = ((PasswordCallback) callbacks[1]).getPassword();
            password = (passwordArray == null) ? null : new String(passwordArray);
            nonce = ((TextInputCallback) callbacks[2]).getText();
            nc = ((TextInputCallback) callbacks[3]).getText();
            cnonce = ((TextInputCallback) callbacks[4]).getText();
            qop = ((TextInputCallback) callbacks[5]).getText();
            realmName = ((TextInputCallback) callbacks[6]).getText();
            digestA2 = ((TextInputCallback) callbacks[7]).getText();
            algorithm = ((TextInputCallback) callbacks[8]).getText();
            authMethod = ((TextInputCallback) callbacks[9]).getText();
        } catch (IOException | UnsupportedCallbackException e) {
            throw new LoginException(sm.getString("jaasMemoryLoginModule.callbackHandlerError", e.toString()));
        }

        // Validate the username and password we have received
        if (authMethod == null) {
            // BASIC or FORM
            principal = super.authenticate(username, password);
        } else if (authMethod.equals(HttpServletRequest.DIGEST_AUTH)) {
            principal = super.authenticate(username, password, nonce, nc, cnonce, qop, realmName, digestA2, algorithm);
        } else if (authMethod.equals(HttpServletRequest.CLIENT_CERT_AUTH)) {
            principal = super.getPrincipal(username);
        } else {
            throw new LoginException(sm.getString("jaasMemoryLoginModule.unknownAuthenticationMethod"));
        }

        if (log.isDebugEnabled()) {
            log.debug(sm.getString("jaasMemoryLoginModule.login", username, principal));
        }

        // Report results based on success or failure
        if (principal != null) {
            return true;
        } else {
            throw new FailedLoginException(sm.getString("jaasMemoryLoginModule.invalidCredentials"));
        }
    }


    @Override
    public boolean logout() throws LoginException {
        subject.getPrincipals().remove(principal);
        if (principal instanceof GenericPrincipal) {
            for (Principal role : roles) {
                subject.getPrincipals().remove(role);
            }
        }
        committed = false;
        principal = null;
        roles = null;
        return true;
    }


    // ---------------------------------------------------------- Realm Methods
    // ------------------------------------------------------ Protected Methods

    /**
     * Load the contents of our configuration file.
     */
    protected void load() {
        // Validate the existence of our configuration file
        File file = new File(pathname);
        if (!file.isAbsolute()) {
            String catalinaBase = getCatalinaBase();
            if (catalinaBase == null) {
                log.error(sm.getString("jaasMemoryLoginModule.noCatalinaBase", pathname));
                return;
            } else {
                file = new File(catalinaBase, pathname);
            }
        }
        if (!file.canRead()) {
            log.error(sm.getString("jaasMemoryLoginModule.noConfig", file.getAbsolutePath()));
            return;
        }

        // Load the contents of our configuration file
        Digester digester = new Digester();
        digester.setValidating(false);
        digester.addRuleSet(new MemoryRuleSet());
        try {
            digester.push(this);
            digester.parse(file);
        } catch (Exception e) {
            log.error(sm.getString("jaasMemoryLoginModule.parseError", file.getAbsolutePath()), e);
        } finally {
            digester.reset();
        }
    }

    private String getCatalinaBase() {
        // Have to get this via a callback as that is the only link we have back
        // to the defining Realm. Can't use the system property as that may not
        // be set/correct in an embedded scenario

        if (callbackHandler == null) {
            return null;
        }

        Callback[] callbacks = new Callback[1];
        callbacks[0] = new TextInputCallback("catalinaBase");

        String result;

        try {
            callbackHandler.handle(callbacks);
            result = ((TextInputCallback) callbacks[0]).getText();
        } catch (IOException | UnsupportedCallbackException e) {
            return null;
        }

        return result;
    }
}
