/**
 * 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.hdfs.server.datanode.web;

import static org.apache.hadoop.hdfs.client.HdfsClientConfigKeys.DFS_WEBHDFS_REST_CSRF_ENABLED_DEFAULT;
import static org.apache.hadoop.hdfs.client.HdfsClientConfigKeys.DFS_WEBHDFS_REST_CSRF_ENABLED_KEY;

import java.util.Enumeration;
import java.util.Map;
import javax.servlet.FilterConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;

import io.netty.bootstrap.ChannelFactory;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.http.HttpRequestDecoder;
import io.netty.handler.codec.http.HttpResponseEncoder;
import io.netty.handler.ssl.SslHandler;
import io.netty.handler.stream.ChunkedWriteHandler;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.permission.FsPermission;
import org.apache.hadoop.hdfs.DFSConfigKeys;
import org.apache.hadoop.hdfs.DFSUtil;
import org.apache.hadoop.hdfs.server.common.JspHelper;
import org.apache.hadoop.hdfs.server.datanode.BlockScanner;
import org.apache.hadoop.hdfs.server.datanode.DataNode;
import org.apache.hadoop.hdfs.server.datanode.web.webhdfs.DataNodeUGIProvider;
import org.apache.hadoop.http.HttpConfig;
import org.apache.hadoop.http.HttpServer2;
import org.apache.hadoop.net.NetUtils;
import org.apache.hadoop.security.authorize.AccessControlList;
import org.apache.hadoop.security.http.RestCsrfPreventionFilter;
import org.apache.hadoop.security.ssl.SSLFactory;

import java.io.Closeable;
import java.io.IOException;
import java.net.BindException;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.net.SocketException;
import java.net.URI;
import java.nio.channels.ServerSocketChannel;
import java.security.GeneralSecurityException;

import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_ADMIN;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_HTTPS_ADDRESS_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_HTTPS_ADDRESS_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_HTTP_ADDRESS_KEY;

public class DatanodeHttpServer implements Closeable {
  private final HttpServer2 infoServer;
  private final EventLoopGroup bossGroup;
  private final EventLoopGroup workerGroup;
  private final ServerSocketChannel externalHttpChannel;
  private final ServerBootstrap httpServer;
  private final SSLFactory sslFactory;
  private final ServerBootstrap httpsServer;
  private final Configuration conf;
  private final Configuration confForCreate;
  private final RestCsrfPreventionFilter restCsrfPreventionFilter;
  private InetSocketAddress httpAddress;
  private InetSocketAddress httpsAddress;
  static final Log LOG = LogFactory.getLog(DatanodeHttpServer.class);

  public DatanodeHttpServer(final Configuration conf,
      final DataNode datanode,
      final ServerSocketChannel externalHttpChannel)
    throws IOException {
    this.restCsrfPreventionFilter = createRestCsrfPreventionFilter(conf);
    this.conf = conf;

    Configuration confForInfoServer = new Configuration(conf);
    confForInfoServer.setInt(HttpServer2.HTTP_MAX_THREADS_KEY, 10);
    HttpServer2.Builder builder = new HttpServer2.Builder()
        .setName("datanode")
        .setConf(confForInfoServer)
        .setACL(new AccessControlList(conf.get(DFS_ADMIN, " ")))
        .hostName(getHostnameForSpnegoPrincipal(confForInfoServer))
        .addEndpoint(URI.create("http://localhost:0"))
        .setFindPort(true);

    final boolean xFrameEnabled = conf.getBoolean(
        DFSConfigKeys.DFS_XFRAME_OPTION_ENABLED,
        DFSConfigKeys.DFS_XFRAME_OPTION_ENABLED_DEFAULT);

    final String xFrameOptionValue = conf.getTrimmed(
        DFSConfigKeys.DFS_XFRAME_OPTION_VALUE,
        DFSConfigKeys.DFS_XFRAME_OPTION_VALUE_DEFAULT);

    builder.configureXFrame(xFrameEnabled).setXFrameOption(xFrameOptionValue);

    this.infoServer = builder.build();

    this.infoServer.setAttribute("datanode", datanode);
    this.infoServer.setAttribute(JspHelper.CURRENT_CONF, conf);
    this.infoServer.addServlet(null, "/blockScannerReport",
                               BlockScanner.Servlet.class);
    DataNodeUGIProvider.init(conf);
    this.infoServer.start();
    final InetSocketAddress jettyAddr = infoServer.getConnectorAddress(0);

    this.confForCreate = new Configuration(conf);
    confForCreate.set(FsPermission.UMASK_LABEL, "000");

    this.bossGroup = new NioEventLoopGroup();
    this.workerGroup = new NioEventLoopGroup();
    this.externalHttpChannel = externalHttpChannel;
    HttpConfig.Policy policy = DFSUtil.getHttpPolicy(conf);

    if (policy.isHttpEnabled()) {
      this.httpServer = new ServerBootstrap().group(bossGroup, workerGroup)
        .childHandler(new ChannelInitializer<SocketChannel>() {
        @Override
        protected void initChannel(SocketChannel ch) throws Exception {
          ChannelPipeline p = ch.pipeline();
          p.addLast(new HttpRequestDecoder(),
            new HttpResponseEncoder());
          if (restCsrfPreventionFilter != null) {
            p.addLast(new RestCsrfPreventionFilterHandler(
                restCsrfPreventionFilter));
          }
          p.addLast(
              new ChunkedWriteHandler(),
              new URLDispatcher(jettyAddr, conf, confForCreate));
        }
      });

      this.httpServer.childOption(
          ChannelOption.WRITE_BUFFER_HIGH_WATER_MARK,
          conf.getInt(
              DFSConfigKeys.DFS_WEBHDFS_NETTY_HIGH_WATERMARK,
              DFSConfigKeys.DFS_WEBHDFS_NETTY_HIGH_WATERMARK_DEFAULT));
      this.httpServer.childOption(
          ChannelOption.WRITE_BUFFER_LOW_WATER_MARK,
          conf.getInt(
              DFSConfigKeys.DFS_WEBHDFS_NETTY_LOW_WATERMARK,
              DFSConfigKeys.DFS_WEBHDFS_NETTY_LOW_WATERMARK_DEFAULT));

      if (externalHttpChannel == null) {
        httpServer.channel(NioServerSocketChannel.class);
      } else {
        httpServer.channelFactory(new ChannelFactory<NioServerSocketChannel>() {
          @Override
          public NioServerSocketChannel newChannel() {
            return new NioServerSocketChannel(externalHttpChannel) {
              // The channel has been bounded externally via JSVC,
              // thus bind() becomes a no-op.
              @Override
              protected void doBind(SocketAddress localAddress) throws Exception {}
            };
          }
        });
      }
    } else {
      this.httpServer = null;
    }

    if (policy.isHttpsEnabled()) {
      this.sslFactory = new SSLFactory(SSLFactory.Mode.SERVER, conf);
      try {
        sslFactory.init();
      } catch (GeneralSecurityException e) {
        throw new IOException(e);
      }
      this.httpsServer = new ServerBootstrap().group(bossGroup, workerGroup)
        .channel(NioServerSocketChannel.class)
        .childHandler(new ChannelInitializer<SocketChannel>() {
          @Override
          protected void initChannel(SocketChannel ch) throws Exception {
            ChannelPipeline p = ch.pipeline();
            p.addLast(
                new SslHandler(sslFactory.createSSLEngine()),
                new HttpRequestDecoder(),
                new HttpResponseEncoder());
            if (restCsrfPreventionFilter != null) {
              p.addLast(new RestCsrfPreventionFilterHandler(
                  restCsrfPreventionFilter));
            }
            p.addLast(
                new ChunkedWriteHandler(),
                new URLDispatcher(jettyAddr, conf, confForCreate));
          }
        });
    } else {
      this.httpsServer = null;
      this.sslFactory = null;
    }
  }

  public InetSocketAddress getHttpAddress() {
    return httpAddress;
  }

  public InetSocketAddress getHttpsAddress() {
    return httpsAddress;
  }

  public void start() throws IOException {
    if (httpServer != null) {
      InetSocketAddress infoAddr = DataNode.getInfoAddr(conf);
      ChannelFuture f = httpServer.bind(infoAddr);
      try {
        f.syncUninterruptibly();
      } catch (Throwable e) {
        if (e instanceof BindException) {
          throw NetUtils.wrapException(null, 0, infoAddr.getHostName(),
              infoAddr.getPort(), (SocketException) e);
        } else {
          throw e;
        }
      }
      httpAddress = (InetSocketAddress) f.channel().localAddress();
      LOG.info("Listening HTTP traffic on " + httpAddress);
    }

    if (httpsServer != null) {
      InetSocketAddress secInfoSocAddr =
          NetUtils.createSocketAddr(conf.getTrimmed(
              DFS_DATANODE_HTTPS_ADDRESS_KEY,
              DFS_DATANODE_HTTPS_ADDRESS_DEFAULT));
      ChannelFuture f = httpsServer.bind(secInfoSocAddr);

      try {
        f.syncUninterruptibly();
      } catch (Throwable e) {
        if (e instanceof BindException) {
          throw NetUtils.wrapException(null, 0, secInfoSocAddr.getHostName(),
              secInfoSocAddr.getPort(), (SocketException) e);
        } else {
          throw e;
        }
      }
      httpsAddress = (InetSocketAddress) f.channel().localAddress();
      LOG.info("Listening HTTPS traffic on " + httpsAddress);
    }
  }

  @Override
  public void close() throws IOException {
    bossGroup.shutdownGracefully();
    workerGroup.shutdownGracefully();
    if (sslFactory != null) {
      sslFactory.destroy();
    }
    if (externalHttpChannel != null) {
      externalHttpChannel.close();
    }
    try {
      infoServer.stop();
    } catch (Exception e) {
      throw new IOException(e);
    }
  }

  private static String getHostnameForSpnegoPrincipal(Configuration conf) {
    String addr = conf.getTrimmed(DFS_DATANODE_HTTP_ADDRESS_KEY, null);
    if (addr == null) {
      addr = conf.getTrimmed(DFS_DATANODE_HTTPS_ADDRESS_KEY,
                             DFS_DATANODE_HTTPS_ADDRESS_DEFAULT);
    }
    InetSocketAddress inetSocker = NetUtils.createSocketAddr(addr);
    return inetSocker.getHostString();
  }

  /**
   * Creates the {@link RestCsrfPreventionFilter} for the DataNode.  Since the
   * DataNode HTTP server is not implemented in terms of the servlet API, it
   * takes some extra effort to obtain an instance of the filter.  This method
   * takes care of configuration and implementing just enough of the servlet API
   * and related interfaces so that the DataNode can get a fully initialized
   * instance of the filter.
   *
   * @param conf configuration to read
   * @return initialized filter, or null if CSRF protection not enabled
   */
  private static RestCsrfPreventionFilter createRestCsrfPreventionFilter(
      Configuration conf) {
    if (!conf.getBoolean(DFS_WEBHDFS_REST_CSRF_ENABLED_KEY,
        DFS_WEBHDFS_REST_CSRF_ENABLED_DEFAULT)) {
      return null;
    }
    String restCsrfClassName = RestCsrfPreventionFilter.class.getName();
    Map<String, String> restCsrfParams = RestCsrfPreventionFilter
        .getFilterParams(conf, "dfs.webhdfs.rest-csrf.");
    RestCsrfPreventionFilter filter = new RestCsrfPreventionFilter();
    try {
      filter.init(new MapBasedFilterConfig(restCsrfClassName, restCsrfParams));
    } catch (ServletException e) {
      throw new IllegalStateException(
          "Failed to initialize RestCsrfPreventionFilter.", e);
    }
    return filter;
  }

  /**
   * A minimal {@link FilterConfig} implementation backed by a {@link Map}.
   */
  private static final class MapBasedFilterConfig implements FilterConfig {

    private final String filterName;
    private final Map<String, String> parameters;

    /**
     * Creates a new MapBasedFilterConfig.
     *
     * @param filterName filter name
     * @param parameters mapping of filter initialization parameters
     */
    public MapBasedFilterConfig(String filterName,
        Map<String, String> parameters) {
      this.filterName = filterName;
      this.parameters = parameters;
    }

    @Override
    public String getFilterName() {
      return this.filterName;
    }

    @Override
    public String getInitParameter(String name) {
      return this.parameters.get(name);
    }

    @Override
    public Enumeration<String> getInitParameterNames() {
      throw this.notImplemented();
    }

    @Override
    public ServletContext getServletContext() {
      throw this.notImplemented();
    }

    /**
     * Creates an exception indicating that an interface method is not
     * implemented.  These should never be seen in practice, because it is only
     * used for methods that are not called by {@link RestCsrfPreventionFilter}.
     *
     * @return exception indicating method not implemented
     */
    private UnsupportedOperationException notImplemented() {
      return new UnsupportedOperationException(this.getClass().getSimpleName()
          + " does not implement this method.");
    }
  }
}
