/*
 * 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.logging.log4j.core.net.ssl;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.NoSuchFileException;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Arrays;

PasswordProvider that reads password from a file.

This is a relatively secure way to handle passwords:

    
Managing file access privileges can be delegated to the operating system.
    
The password file can be in a separate location from the logging configuration.
      This gives flexibility to have different passwords in different environments while
      using the same logging configuration. It also allows for separation of responsibilities:
      developers don't need to know the password that is used in the production environment.
    
There is only a small window of opportunity for attackers to obtain the password from a memory dump: the password data is only resident in memory from the moment the caller calls the getPassword() method and the password file is read until the moment that the caller completes authentication and overwrites the password char[] array.

 Less secure implementations are MemoryPasswordProvider and EnvironmentPasswordProvider. 
/**
 * PasswordProvider that reads password from a file.
 * <p>
 * This is a relatively secure way to handle passwords:
 * <ul>
 *     <li>Managing file access privileges can be delegated to the operating system.</li>
 *     <li>The password file can be in a separate location from the logging configuration.
 *       This gives flexibility to have different passwords in different environments while
 *       using the same logging configuration. It also allows for separation of responsibilities:
 *       developers don't need to know the password that is used in the production environment.</li>
 *     <li>There is only a small window of opportunity for attackers to obtain the password from a memory
 *       dump: the password data is only resident in memory from the moment the caller calls the
 *       {@link #getPassword()} method and the password file is read until the moment that the caller
 *       completes authentication and overwrites the password char[] array.</li>
 * </ul>
 * </p><p>
 * Less secure implementations are {@link MemoryPasswordProvider} and {@link EnvironmentPasswordProvider}.
 * </p>
 */
class FilePasswordProvider implements PasswordProvider {
    private final Path passwordPath;

    
Constructs a new FilePasswordProvider with the specified path.
Params:
passwordFile – the path to the password file
Throws:
NoSuchFileException – if the password file does not exist when this FilePasswordProvider is constructed/**
     * Constructs a new FilePasswordProvider with the specified path.
     * @param passwordFile the path to the password file
     * @throws NoSuchFileException if the password file does not exist when this FilePasswordProvider is constructed
     */
    public FilePasswordProvider(final String passwordFile) throws NoSuchFileException {
        this.passwordPath = Paths.get(passwordFile);
        if (!Files.exists(passwordPath)) {
            throw new NoSuchFileException("PasswordFile '" + passwordFile + "' does not exist");
        }
    }

    @Override
    public char[] getPassword() {
        byte[] bytes = null;
        try {
            bytes = Files.readAllBytes(passwordPath);
            final ByteBuffer bb = ByteBuffer.wrap(bytes);
            final CharBuffer decoded = Charset.defaultCharset().decode(bb);
            final char[] result = new char[decoded.limit()];
            decoded.get(result, 0, result.length);
            decoded.rewind();
            decoded.put(new char[result.length]); // erase decoded CharBuffer
            return result;
        } catch (final IOException e) {
            throw new IllegalStateException("Could not read password from " + passwordPath + ": " + e, e);
        } finally {
            if (bytes != null) {
                Arrays.fill(bytes, (byte) 0x0);
            }
        }
    }
}