/*
 * Copyright (c) 1997, 2021 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package com.sun.enterprise.security.store;

import static com.sun.enterprise.util.SystemPropertyConstants.INSTANCE_ROOT_PROPERTY;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.security.Key;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.UnrecoverableKeyException;
import java.security.cert.CertificateException;
import java.util.Enumeration;

import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

/**
 * This class implements an adapter for password manipulation a JCEKS. Note that although it uses locks ('synchronized'), it
 * tends to be created anew with each use, an inefficient and potentially problematic use that could create more than one
 * instance accessing the same keystore at a time.
 */
public final class PasswordAdapter {
    public static final String PASSWORD_ALIAS_KEYSTORE = "domain-passwords";

    private KeyStore _pwdStore;
    private final File _keyFile;
    private char[] _masterPassword;

    private char[] getMasterPassword() {
        return _masterPassword;
    }

    private static String getDefaultKeyFileName() {
        return System.getProperty(INSTANCE_ROOT_PROPERTY) + File.separator + "config" + File.separator + PASSWORD_ALIAS_KEYSTORE;
    }

    /**
     * Construct a PasswordAdapter with given Shared Master Password, SMP using the default keyfile (domain-passwords.jceks)
     *
     * @param smp master password
     * @throws CertificateException
     * @throws IOException
     * @throws KeyStoreException
     * @throws NoSuchAlgorithmException
     */
    public PasswordAdapter(char[] masterPassword) throws CertificateException, IOException, KeyStoreException, NoSuchAlgorithmException {
        this(getDefaultKeyFileName(), masterPassword);
    }

    /**
     * Construct a PasswordAdapter with given Shared Master Password, SMP.
     *
     * @param keyfileName the jceks key file name
     * @param smp master password
     * @throws CertificateException
     * @throws IOException
     * @throws KeyStoreException
     * @throws NoSuchAlgorithmException
     */
    public PasswordAdapter(final String keyStoreFileName, final char[] masterPassword)
        throws CertificateException, IOException, KeyStoreException, NoSuchAlgorithmException {
        final File keyStoreFile = new File(keyStoreFileName);

        _pwdStore = loadKeyStore(keyStoreFile, masterPassword);

        // assign these only once the store is good; no need to keep copies otherwise!
        _keyFile = keyStoreFile;
        _masterPassword = masterPassword;

        //debugState( "PasswordAdapter constructor" );
    }

    /**
     * Construct a PasswordAdapter with given Shared Master Password, SMP.
     *
     * @param keyfileName the jceks key file name
     * @param smp the master password
     * @exception CertificateException
     * @exception IOException
     * @exception KeyStoreException
     * @exception NoSuchAlgorithmException
     */
    private static KeyStore loadKeyStore(final File keyStoreFile, final char[] masterPassword)
        throws CertificateException, IOException, KeyStoreException, NoSuchAlgorithmException {
        final KeyStore keyStore = KeyStore.getInstance("JCEKS");

        if (keyStoreFile.exists()) {
            // don't buffer keystore; it's tiny anyway
            final FileInputStream input = new FileInputStream(keyStoreFile);
            try (input) {
                keyStore.load(input, masterPassword);
            }
        } else {
            keyStore.load(null, masterPassword);
        }

        return keyStore;
    }

    /**
     * This methods returns password String for a given alias and SMP.
     *
     * @param alias
     * @return corresponding password or null if the alias does not exist.
     * @exception KeyStoreException
     * @exception NoSuchAlgorithmException
     * @exception UnrecoverableKeyException
     */
    public synchronized String getPasswordForAlias(final String alias)
        throws KeyStoreException, NoSuchAlgorithmException, UnrecoverableKeyException {
        String passwordString = null;

        final Key key = _pwdStore.getKey(alias, getMasterPassword());
        if (key != null) {
            passwordString = new String(key.getEncoded());
        }

        return passwordString;
    }

    /**
     * This methods returns password SecretKey for a given alias and SMP.
     *
     * @param alias
     * @return corresponding password SecretKey or null if the alias does not exist.
     * @exception KeyStoreException
     * @exception NoSuchAlgorithmException
     * @exception UnrecoverableKeyException
     */
    public synchronized SecretKey getPasswordSecretKeyForAlias(String alias)
        throws KeyStoreException, NoSuchAlgorithmException, UnrecoverableKeyException {

        return (SecretKey) _pwdStore.getKey(alias, getMasterPassword());
    }

    /**
     * See if the given alias exists
     *
     * @param alias the alias name
     * @return true if the alias exists in the keystore
     */
    public synchronized boolean aliasExists(final String alias) throws KeyStoreException {
        return _pwdStore.containsAlias(alias);
    }

    /**
     * Remove an alias from the keystore
     *
     * @param alias The name of the alias to remove
     * @throws KeyStoreException
     * @throws IOException
     * @throws NoSuchAlgorithmException
     * @throws CertificateException
     */
    public synchronized void removeAlias(final String alias)
        throws KeyStoreException, IOException, NoSuchAlgorithmException, CertificateException, UnrecoverableKeyException {
        _pwdStore.deleteEntry(alias);
        writeStore();
    }

    /**
     * Return the aliases from the keystore.
     *
     * @return An enumeration containing all the aliases in the keystore.
     */
    public synchronized Enumeration<String> getAliases() throws KeyStoreException {
        return _pwdStore.aliases();
    }

    /**
     * Writes the keystore to disk
     *
     * @throws KeyStoreException
     * @throws IOException
     * @throws NoSuchAlgorithmException
     * @throws CertificateException
     */
    public void writeStore()
        throws KeyStoreException, IOException, NoSuchAlgorithmException, CertificateException, UnrecoverableKeyException {
        writeKeyStoreSafe(getMasterPassword());
    }

    /**
     * This methods set alias, secretKey into JCEKS keystore.
     *
     * @param alias
     * @param secretKey
     * @exception CertificateException
     * @exception IOException
     * @exception KeyStoreException
     * @exception NoSuchAlgorithmException
     */
    public synchronized void setPasswordForAlias(final String alias, final byte[] keyBytes)
        throws CertificateException, IOException, KeyStoreException, NoSuchAlgorithmException, UnrecoverableKeyException {
        final Key key = new SecretKeySpec(keyBytes, "AES");
        _pwdStore.setKeyEntry(alias, key, getMasterPassword(), null);
        writeStore();
    }

    /**
     * Make a new in-memory KeyStore with all the keys secured with the new master password.
     */
    private KeyStore duplicateKeyStore(final char[] newMasterPassword)
        throws KeyStoreException, IOException, NoSuchAlgorithmException, CertificateException, UnrecoverableKeyException {
        final char[] oldMasterPassword = getMasterPassword();

        final KeyStore oldStore = _pwdStore;
        final KeyStore newKeyStore = KeyStore.getInstance("JCEKS", _pwdStore.getProvider());
        newKeyStore.load(null, newMasterPassword);

        final Enumeration<String> aliasesEnum = oldStore.aliases();
        while (aliasesEnum.hasMoreElements()) {
            final String alias = aliasesEnum.nextElement();

            if (!oldStore.isKeyEntry(alias)) {
                throw new IllegalArgumentException("Expecting keys only");
            }

            final Key key = oldStore.getKey(alias, oldMasterPassword);
            newKeyStore.setKeyEntry(alias, key, newMasterPassword, null);
        }

        return newKeyStore;
    }

    /**
     * Write the KeyStore to disk. Calling code should protect against overwriting any original file.
     *
     * @param keyStore
     * @param file
     * @param masterPassword
     */
    private static void writeKeyStoreToFile(final KeyStore keyStore, final File file, final char[] masterPassword)
        throws KeyStoreException, IOException, NoSuchAlgorithmException, CertificateException {
        final FileOutputStream out = new FileOutputStream(file);
        try (out) {
            keyStore.store(out, masterPassword);
        }
    }

    /**
     * Writes the current KeyStore to disk in a manner that preserves its on-disk representation from being destroyed if something
     * goes wrong; a temporary file is used.
     */
    private synchronized void writeKeyStoreSafe(final char[] masterPassword)
        throws KeyStoreException, IOException, NoSuchAlgorithmException, CertificateException, UnrecoverableKeyException {
        final boolean keystoreExists = _keyFile.exists();

        // if the KeyStore exists, update it in a manner that doesn't destroy
        // the existing store if a failure occurs.
        if (keystoreExists) {
            final KeyStore newKeyStore = duplicateKeyStore(masterPassword);

            // 'newKeyStore' is now complete; rename the old KeyStore, the write the new one in its place
            final File saveOld = new File(_keyFile.toString() + ".save");

            if (!_keyFile.renameTo(saveOld)) {
                throw new IOException("Can't rename " + _keyFile + " to " + saveOld);
            }

            try {
                writeKeyStoreToFile(newKeyStore, _keyFile, masterPassword);
                _pwdStore = newKeyStore;
                _masterPassword = masterPassword;
            } catch (final Throwable t) {
                try {
                    if (!saveOld.renameTo(_keyFile)) {
                        throw new RuntimeException("Could not write new KeyStore, and " + "cannot restore KeyStore to original state", t);
                    }
                } catch (final Throwable tt) {
                    /* best effort failed */
                    throw new RuntimeException("Could not write new KeyStore, and " + "cannot restore KeyStore to original state", tt);
                }

                throw new RuntimeException("Can't write new KeyStore", t);
            }

            try {
                if (!saveOld.delete()) {
                    throw new RuntimeException("Can't remove old KeyStore \"" + _keyFile + "\"");
                }
            } catch (Throwable t) {
                throw new RuntimeException("Can't remove old KeyStore \"" + _keyFile + "\"", t);
            }
        } else {
            writeKeyStoreToFile(_pwdStore, _keyFile, masterPassword);
        }

        loadKeyStore(_keyFile, getMasterPassword());
    }

    /**
     * Changes the keystore password, including the encoding of the keys within it.
     * <p>
     * There are several error conditions that could occur:
     * <ul>
     * <li>Problem extracting existing alias keys with new ones.</li>
     * <li>Problem writing the keystore, including destroying it if an I/O problem occurs.</li>
     * <li></li>
     * </ul>
     * For these reasons, make a new KeyStore and write it, then swap it with the old one.
     *
     * @param newpassword the new keystore password
     * @throws KeyStoreException
     * @throws IOException
     * @throws NoSuchAlgorithmException
     * @throws CertificateException
     */
    public synchronized void changePassword(char[] newMasterPassword)
        throws KeyStoreException, IOException, NoSuchAlgorithmException, CertificateException, UnrecoverableKeyException {

        writeKeyStoreSafe(newMasterPassword);
    }
}