/**
 * 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.hadoop.fs.http.server;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hdfs.web.WebHdfsConstants;
import org.apache.hadoop.security.authentication.server.AuthenticationFilter;
import org.apache.hadoop.security.token.delegation.web.DelegationTokenAuthenticationFilter;
import org.apache.hadoop.security.token.delegation.web.KerberosDelegationTokenAuthenticationHandler;

import javax.servlet.FilterConfig;
import javax.servlet.ServletException;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
import java.nio.charset.StandardCharsets;
import java.util.Map;
import java.util.Properties;

/**
 * Subclass of hadoop-auth <code>AuthenticationFilter</code> that obtains its configuration
 * from HttpFSServer's server configuration.
 */
@InterfaceAudience.Private
public class HttpFSAuthenticationFilter
    extends DelegationTokenAuthenticationFilter {

  private static final String CONF_PREFIX = "httpfs.authentication.";

  private static final String SIGNATURE_SECRET_FILE = SIGNATURE_SECRET + ".file";

  /**
   * Returns the hadoop-auth configuration from HttpFSServer's configuration.
   * <p>
   * It returns all HttpFSServer's configuration properties prefixed with
   * <code>httpfs.authentication</code>. The <code>httpfs.authentication</code>
   * prefix is removed from the returned property names.
   *
   * @param configPrefix parameter not used.
   * @param filterConfig parameter not used.
   *
   * @return hadoop-auth configuration read from HttpFSServer's configuration.
   */
  @Override
  protected Properties getConfiguration(String configPrefix,
      FilterConfig filterConfig) throws ServletException{
    Properties props = new Properties();
    Configuration conf = HttpFSServerWebApp.get().getConfig();

    props.setProperty(AuthenticationFilter.COOKIE_PATH, "/");
    for (Map.Entry<String, String> entry : conf) {
      String name = entry.getKey();
      if (name.startsWith(CONF_PREFIX)) {
        String value = conf.get(name);
        name = name.substring(CONF_PREFIX.length());
        props.setProperty(name, value);
      }
    }

    String signatureSecretFile = props.getProperty(SIGNATURE_SECRET_FILE, null);
    if (signatureSecretFile == null) {
      throw new RuntimeException("Undefined property: " + SIGNATURE_SECRET_FILE);
    }

    try {
      StringBuilder secret = new StringBuilder();
      Reader reader = new InputStreamReader(new FileInputStream(
          signatureSecretFile), StandardCharsets.UTF_8);
      int c = reader.read();
      while (c > -1) {
        secret.append((char)c);
        c = reader.read();
      }
      reader.close();
      props.setProperty(AuthenticationFilter.SIGNATURE_SECRET, secret.toString());
    } catch (IOException ex) {
      throw new RuntimeException("Could not read HttpFS signature secret file: " + signatureSecretFile);
    }
    setAuthHandlerClass(props);
    String dtkind = WebHdfsConstants.WEBHDFS_TOKEN_KIND.toString();
    if (conf.getBoolean("httpfs.ssl.enabled", false)) {
      dtkind = WebHdfsConstants.SWEBHDFS_TOKEN_KIND.toString();
    }
    props.setProperty(KerberosDelegationTokenAuthenticationHandler.TOKEN_KIND,
                      dtkind);
    return props;
  }

  protected Configuration getProxyuserConfiguration(FilterConfig filterConfig) {
    Map<String, String> proxyuserConf = HttpFSServerWebApp.get().getConfig().
        getValByRegex("httpfs\\.proxyuser\\.");
    Configuration conf = new Configuration(false);
    for (Map.Entry<String, String> entry : proxyuserConf.entrySet()) {
      conf.set(entry.getKey().substring("httpfs.".length()), entry.getValue());
    }
    return conf;
  }

}