/*
 * 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.util.Objects;

PasswordProvider implementation that obtains the password value from a system environment variable.

This implementation is not very secure because the Java interface to obtain system environment variable values
requires us to use String objects. String objects are immutable and Java does not provide a way to erase this
sensitive data from the application memory. The password data will stay resident in memory until the String object
and its associated char[] array object are garbage collected and the memory is overwritten by another object.
 This is slightly more secure than MemoryPasswordProvider because the actual password string does not need to be passed to the application. The actual password string is not pulled into memory until it is needed (so the password string does not need to be passed in from the command line or in a configuration file). This gives an attacker a smaller window of opportunity to obtain the password from a memory dump. 
 A more secure implementation is FilePasswordProvider. 
/**
 * PasswordProvider implementation that obtains the password value from a system environment variable.
 * <p>
 * This implementation is not very secure because the Java interface to obtain system environment variable values
 * requires us to use String objects. String objects are immutable and Java does not provide a way to erase this
 * sensitive data from the application memory. The password data will stay resident in memory until the String object
 * and its associated char[] array object are garbage collected and the memory is overwritten by another object.
 * </p><p>
 * This is slightly more secure than {@link MemoryPasswordProvider} because the actual password string does not
 * need to be passed to the application.
 * The actual password string is not pulled into memory until it is needed
 * (so the password string does not need to be passed in from the command line or in a configuration file).
 * This gives an attacker a smaller window  of opportunity to obtain the password from a memory dump.
 * </p><p>
 * A more secure implementation is {@link FilePasswordProvider}.
 * </p>
 */
class EnvironmentPasswordProvider implements PasswordProvider {
    private final String passwordEnvironmentVariable;

    
Constructs a new EnvironmentPasswordProvider with the specified environment variable name
Params:
passwordEnvironmentVariable – name of the system environment variable that holds the password/**
     * Constructs a new EnvironmentPasswordProvider with the specified environment variable name
     * @param passwordEnvironmentVariable name of the system environment variable that holds the password
     */
    public EnvironmentPasswordProvider(final String passwordEnvironmentVariable) {
        this.passwordEnvironmentVariable = Objects.requireNonNull(
                passwordEnvironmentVariable, "passwordEnvironmentVariable");
    }

    @Override
    public char[] getPassword() {
        final String password = System.getenv(passwordEnvironmentVariable);
        return password == null ? null : password.toCharArray();
    }
}