HDFS-9711. Integrate CSRF prevention filter in WebHDFS. Contributed by Chris Nauroth.

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/http/RestCsrfPreventionFilter.java

@@ -18,7 +18,9 @@
 package org.apache.hadoop.security.http;
 
 import java.io.IOException;
+import java.util.HashMap;
 import java.util.HashSet;
+import java.util.Map;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 import java.util.Set;
@@ -32,6 +34,13 @@ import javax.servlet.ServletResponse;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.conf.Configuration;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 /**
  * This filter provides protection against cross site request forgery (CSRF)
  * attacks for REST APIs. Enabling this filter on an endpoint results in the
@@ -39,7 +48,13 @@ import javax.servlet.http.HttpServletResponse;
  * with every request. In the absense of this header the filter will reject the
  * attempt as a bad request.
  */
+@InterfaceAudience.Public
+@InterfaceStability.Evolving
 public class RestCsrfPreventionFilter implements Filter {
+
+  private static final Logger LOG =
+      LoggerFactory.getLogger(RestCsrfPreventionFilter.class);
+
   public static final String HEADER_USER_AGENT = "User-Agent";
   public static final String BROWSER_USER_AGENT_PARAM =
       "browser-useragents-regex";
@@ -72,6 +87,9 @@ public class RestCsrfPreventionFilter implements Filter {
       agents = BROWSER_USER_AGENTS_DEFAULT;
     }
     parseBrowserUserAgents(agents);
+    LOG.info("Adding cross-site request forgery (CSRF) protection, "
+        + "headerName = {}, methodsToIgnore = {}, browserUserAgents = {}",
+        headerName, methodsToIgnore, browserUserAgents);
   }
 
   void parseBrowserUserAgents(String userAgents) {
@@ -118,22 +136,152 @@ public class RestCsrfPreventionFilter implements Filter {
     return false;
   }
 
-  @Override
+  /**
-  public void doFilter(ServletRequest request, ServletResponse response,
+   * Defines the minimal API requirements for the filter to execute its
-      FilterChain chain) throws IOException, ServletException {
+   * filtering logic.  This interface exists to facilitate integration in
-    HttpServletRequest httpRequest = (HttpServletRequest)request;
+   * components that do not run within a servlet container and therefore cannot
-    if (!isBrowser(httpRequest.getHeader(HEADER_USER_AGENT)) ||
+   * rely on a servlet container to dispatch to the {@link #doFilter} method.
-        methodsToIgnore.contains(httpRequest.getMethod()) ||
+   * Applications that do run inside a servlet container will not need to write
-        httpRequest.getHeader(headerName) != null) {
+   * code that uses this interface.  Instead, they can use typical servlet
-      chain.doFilter(request, response);
+   * container configuration mechanisms to insert the filter.
+   */
+  public interface HttpInteraction {
+
+    /**
+     * Returns the value of a header.
+     *
+     * @param header name of header
+     * @return value of header
+     */
+    String getHeader(String header);
+
+    /**
+     * Returns the method.
+     *
+     * @return method
+     */
+    String getMethod();
+
+    /**
+     * Called by the filter after it decides that the request may proceed.
+     *
+     * @throws IOException if there is an I/O error
+     * @throws ServletException if the implementation relies on the servlet API
+     *     and a servlet API call has failed
+     */
+    void proceed() throws IOException, ServletException;
+
+    /**
+     * Called by the filter after it decides that the request is a potential
+     * CSRF attack and therefore must be rejected.
+     *
+     * @param code status code to send
+     * @param message response message
+     * @throws IOException if there is an I/O error
+     */
+    void sendError(int code, String message) throws IOException;
+  }
+
+  /**
+   * Handles an {@link HttpInteraction} by applying the filtering logic.
+   *
+   * @param httpInteraction caller's HTTP interaction
+   * @throws IOException if there is an I/O error
+   * @throws ServletException if the implementation relies on the servlet API
+   *     and a servlet API call has failed
+   */
+  public void handleHttpInteraction(HttpInteraction httpInteraction)
+      throws IOException, ServletException {
+    if (!isBrowser(httpInteraction.getHeader(HEADER_USER_AGENT)) ||
+        methodsToIgnore.contains(httpInteraction.getMethod()) ||
+        httpInteraction.getHeader(headerName) != null) {
+      httpInteraction.proceed();
     } else {
-      ((HttpServletResponse)response).sendError(
+      httpInteraction.sendError(HttpServletResponse.SC_BAD_REQUEST,
-          HttpServletResponse.SC_BAD_REQUEST,
           "Missing Required Header for CSRF Vulnerability Protection");
     }
   }
 
+  @Override
+  public void doFilter(ServletRequest request, ServletResponse response,
+      final FilterChain chain) throws IOException, ServletException {
+    final HttpServletRequest httpRequest = (HttpServletRequest)request;
+    final HttpServletResponse httpResponse = (HttpServletResponse)response;
+    handleHttpInteraction(new ServletFilterHttpInteraction(httpRequest,
+        httpResponse, chain));
+  }
+
   @Override
   public void destroy() {
   }
+
+  /**
+   * Constructs a mapping of configuration properties to be used for filter
+   * initialization.  The mapping includes all properties that start with the
+   * specified configuration prefix.  Property names in the mapping are trimmed
+   * to remove the configuration prefix.
+   *
+   * @param conf configuration to read
+   * @param confPrefix configuration prefix
+   * @return mapping of configuration properties to be used for filter
+   *     initialization
+   */
+  public static Map<String, String> getFilterParams(Configuration conf,
+      String confPrefix) {
+    Map<String, String> filterConfigMap = new HashMap<>();
+    for (Map.Entry<String, String> entry : conf) {
+      String name = entry.getKey();
+      if (name.startsWith(confPrefix)) {
+        String value = conf.get(name);
+        name = name.substring(confPrefix.length());
+        filterConfigMap.put(name, value);
+      }
+    }
+    return filterConfigMap;
+  }
+
+  /**
+   * {@link HttpInteraction} implementation for use in the servlet filter.
+   */
+  private static final class ServletFilterHttpInteraction
+      implements HttpInteraction {
+
+    private final FilterChain chain;
+    private final HttpServletRequest httpRequest;
+    private final HttpServletResponse httpResponse;
+
+    /**
+     * Creates a new ServletFilterHttpInteraction.
+     *
+     * @param httpRequest request to process
+     * @param httpResponse response to process
+     * @param chain filter chain to forward to if HTTP interaction is allowed
+     */
+    public ServletFilterHttpInteraction(HttpServletRequest httpRequest,
+        HttpServletResponse httpResponse, FilterChain chain) {
+      this.httpRequest = httpRequest;
+      this.httpResponse = httpResponse;
+      this.chain = chain;
+    }
+
+    @Override
+    public String getHeader(String header) {
+      return httpRequest.getHeader(header);
+    }
+
+    @Override
+    public String getMethod() {
+      return httpRequest.getMethod();
+    }
+
+    @Override
+    public void proceed() throws IOException, ServletException {
+      chain.doFilter(httpRequest, httpResponse);
+    }
+
+    @Override
+    public void sendError(int code, String message) throws IOException {
+      httpResponse.sendError(code, message);
+    }
+  }
 }

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/client/HdfsClientConfigKeys.java

@@ -41,6 +41,18 @@ public interface HdfsClientConfigKeys {
   String DFS_WEBHDFS_OAUTH_ENABLED_KEY = "dfs.webhdfs.oauth2.enabled";
   boolean DFS_WEBHDFS_OAUTH_ENABLED_DEFAULT = false;
 
+  String DFS_WEBHDFS_REST_CSRF_ENABLED_KEY = "dfs.webhdfs.rest-csrf.enabled";
+  boolean DFS_WEBHDFS_REST_CSRF_ENABLED_DEFAULT = false;
+  String DFS_WEBHDFS_REST_CSRF_CUSTOM_HEADER_KEY =
+      "dfs.webhdfs.rest-csrf.custom-header";
+  String DFS_WEBHDFS_REST_CSRF_CUSTOM_HEADER_DEFAULT = "X-XSRF-HEADER";
+  String DFS_WEBHDFS_REST_CSRF_METHODS_TO_IGNORE_KEY =
+      "dfs.webhdfs.rest-csrf.methods-to-ignore";
+  String DFS_WEBHDFS_REST_CSRF_METHODS_TO_IGNORE_DEFAULT =
+      "GET,OPTIONS,HEAD,TRACE";
+  String DFS_WEBHDFS_REST_CSRF_BROWSER_USERAGENTS_REGEX_KEY =
+      "dfs.webhdfs.rest-csrf.browser-useragents-regex";
+
   String OAUTH_CLIENT_ID_KEY = "dfs.webhdfs.oauth2.client.id";
   String OAUTH_REFRESH_URL_KEY = "dfs.webhdfs.oauth2.refresh.url";
 

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/web/WebHdfsFileSystem.java

@@ -18,6 +18,13 @@
 
 package org.apache.hadoop.hdfs.web;
 
+import static org.apache.hadoop.hdfs.client.HdfsClientConfigKeys.DFS_WEBHDFS_REST_CSRF_CUSTOM_HEADER_DEFAULT;
+import static org.apache.hadoop.hdfs.client.HdfsClientConfigKeys.DFS_WEBHDFS_REST_CSRF_CUSTOM_HEADER_KEY;
+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 static org.apache.hadoop.hdfs.client.HdfsClientConfigKeys.DFS_WEBHDFS_REST_CSRF_METHODS_TO_IGNORE_DEFAULT;
+import static org.apache.hadoop.hdfs.client.HdfsClientConfigKeys.DFS_WEBHDFS_REST_CSRF_METHODS_TO_IGNORE_KEY;
+
 import java.io.BufferedInputStream;
 import java.io.BufferedOutputStream;
 import java.io.EOFException;
@@ -33,8 +40,10 @@ import java.net.URL;
 import java.security.PrivilegedExceptionAction;
 import java.util.ArrayList;
 import java.util.EnumSet;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.StringTokenizer;
 
 import javax.ws.rs.core.HttpHeaders;
@@ -129,6 +138,8 @@ public class WebHdfsFileSystem extends FileSystem
   private InetSocketAddress nnAddrs[];
   private int currentNNAddrIndex;
   private boolean disallowFallbackToInsecureCluster;
+  private String restCsrfCustomHeader;
+  private Set<String> restCsrfMethodsToIgnore;
   private static final ObjectReader READER =
       new ObjectMapper().reader(Map.class);
 
@@ -227,9 +238,52 @@ public class WebHdfsFileSystem extends FileSystem
     this.disallowFallbackToInsecureCluster = !conf.getBoolean(
         CommonConfigurationKeys.IPC_CLIENT_FALLBACK_TO_SIMPLE_AUTH_ALLOWED_KEY,
         CommonConfigurationKeys.IPC_CLIENT_FALLBACK_TO_SIMPLE_AUTH_ALLOWED_DEFAULT);
+    this.initializeRestCsrf(conf);
     this.delegationToken = null;
   }
 
+  /**
+   * Initializes client-side handling of cross-site request forgery (CSRF)
+   * protection by figuring out the custom HTTP headers that need to be sent in
+   * requests and which HTTP methods are ignored because they do not require
+   * CSRF protection.
+   *
+   * @param conf configuration to read
+   */
+  private void initializeRestCsrf(Configuration conf) {
+    if (conf.getBoolean(DFS_WEBHDFS_REST_CSRF_ENABLED_KEY,
+        DFS_WEBHDFS_REST_CSRF_ENABLED_DEFAULT)) {
+      this.restCsrfCustomHeader = conf.getTrimmed(
+          DFS_WEBHDFS_REST_CSRF_CUSTOM_HEADER_KEY,
+          DFS_WEBHDFS_REST_CSRF_CUSTOM_HEADER_DEFAULT);
+      this.restCsrfMethodsToIgnore = new HashSet<>();
+      this.restCsrfMethodsToIgnore.addAll(getTrimmedStringList(conf,
+          DFS_WEBHDFS_REST_CSRF_METHODS_TO_IGNORE_KEY,
+          DFS_WEBHDFS_REST_CSRF_METHODS_TO_IGNORE_DEFAULT));
+    } else {
+      this.restCsrfCustomHeader = null;
+      this.restCsrfMethodsToIgnore = null;
+    }
+  }
+
+  /**
+   * Returns a list of strings from a comma-delimited configuration value.
+   *
+   * @param conf configuration to check
+   * @param name configuration property name
+   * @param defaultValue default value if no value found for name
+   * @return list of strings from comma-delimited configuration value, or an
+   *     empty list if not found
+   */
+  private static List<String> getTrimmedStringList(Configuration conf,
+      String name, String defaultValue) {
+    String valueString = conf.get(name, defaultValue);
+    if (valueString == null) {
+      return new ArrayList<>();
+    }
+    return new ArrayList<>(StringUtils.getTrimmedStringCollection(valueString));
+  }
+
   @Override
   public URI getCanonicalUri() {
     return super.getCanonicalUri();
@@ -601,6 +655,11 @@ public class WebHdfsFileSystem extends FileSystem
       final boolean doOutput = op.getDoOutput();
       conn.setRequestMethod(op.getType().toString());
       conn.setInstanceFollowRedirects(false);
+      if (restCsrfCustomHeader != null &&
+          !restCsrfMethodsToIgnore.contains(op.getType().name())) {
+        // The value of the header is unimportant.  Only its presence matters.
+        conn.setRequestProperty(restCsrfCustomHeader, "\"\"");
+      }
       switch (op.getType()) {
       // if not sending a message body for a POST or PUT operation, need
       // to ensure the server/proxy knows this

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -1041,6 +1041,8 @@ Release 2.8.0 - UNRELEASED
 
     HDFS-9244. Support nested encryption zones. (zhz)
 
+    HDFS-9711. Integrate CSRF prevention filter in WebHDFS. (cnauroth)
+
   IMPROVEMENTS
 
     HDFS-9257. improve error message for "Absolute path required" in INode.java

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/DatanodeHttpServer.java

@@ -17,6 +17,15 @@
  */
 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.ServerBootstrap;
 import io.netty.channel.ChannelFactory;
 import io.netty.channel.ChannelFuture;
@@ -46,6 +55,7 @@ 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;
@@ -73,6 +83,7 @@ public class DatanodeHttpServer implements Closeable {
   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);
@@ -81,6 +92,7 @@ public class DatanodeHttpServer implements Closeable {
       final DataNode datanode,
       final ServerSocketChannel externalHttpChannel)
     throws IOException {
+    this.restCsrfPreventionFilter = createRestCsrfPreventionFilter(conf);
     this.conf = conf;
 
     Configuration confForInfoServer = new Configuration(conf);
@@ -117,7 +129,7 @@ public class DatanodeHttpServer implements Closeable {
         @Override
         protected void initChannel(SocketChannel ch) throws Exception {
           ch.pipeline().addLast(new PortUnificationServerHandler(jettyAddr,
-              conf, confForCreate));
+              conf, confForCreate, restCsrfPreventionFilter));
         }
       });
 
@@ -167,7 +179,12 @@ public class DatanodeHttpServer implements Closeable {
             p.addLast(
                 new SslHandler(sslFactory.createSSLEngine()),
                 new HttpRequestDecoder(),
-              new HttpResponseEncoder(),
+                new HttpResponseEncoder());
+            if (restCsrfPreventionFilter != null) {
+              p.addLast(new RestCsrfPreventionFilterHandler(
+                  restCsrfPreventionFilter));
+            }
+            p.addLast(
                 new ChunkedWriteHandler(),
                 new URLDispatcher(jettyAddr, conf, confForCreate));
           }
@@ -252,4 +269,87 @@ public class DatanodeHttpServer implements Closeable {
     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.");
+    }
+  }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/PortUnificationServerHandler.java

@@ -23,6 +23,7 @@ import java.util.List;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hdfs.server.datanode.web.dtp.DtpHttp2Handler;
+import org.apache.hadoop.security.http.RestCsrfPreventionFilter;
 
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ByteBufUtil;
@@ -51,19 +52,32 @@ public class PortUnificationServerHandler extends ByteToMessageDecoder {
 
   private final Configuration confForCreate;
 
+  private final RestCsrfPreventionFilter restCsrfPreventionFilter;
+
   public PortUnificationServerHandler(InetSocketAddress proxyHost,
-      Configuration conf, Configuration confForCreate) {
+      Configuration conf, Configuration confForCreate,
+      RestCsrfPreventionFilter restCsrfPreventionFilter) {
     this.proxyHost = proxyHost;
     this.conf = conf;
     this.confForCreate = confForCreate;
+    this.restCsrfPreventionFilter = restCsrfPreventionFilter;
   }
 
   private void configureHttp1(ChannelHandlerContext ctx) {
-    ctx.pipeline().addLast(new HttpServerCodec(), new ChunkedWriteHandler(),
+    ctx.pipeline().addLast(new HttpServerCodec());
+    if (this.restCsrfPreventionFilter != null) {
+      ctx.pipeline().addLast(new RestCsrfPreventionFilterHandler(
+          this.restCsrfPreventionFilter));
+    }
+    ctx.pipeline().addLast(new ChunkedWriteHandler(),
         new URLDispatcher(proxyHost, conf, confForCreate));
   }
 
   private void configureHttp2(ChannelHandlerContext ctx) {
+    if (this.restCsrfPreventionFilter != null) {
+      ctx.pipeline().addLast(new RestCsrfPreventionFilterHandler(
+          this.restCsrfPreventionFilter));
+    }
     ctx.pipeline().addLast(new DtpHttp2Handler());
   }
 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/RestCsrfPreventionFilterHandler.java

@@ -0,0 +1,137 @@
+/**
+ * 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 io.netty.handler.codec.http.HttpHeaderNames.CONNECTION;
+import static io.netty.handler.codec.http.HttpHeaderValues.CLOSE;
+import static io.netty.handler.codec.http.HttpResponseStatus.INTERNAL_SERVER_ERROR;
+import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;
+
+import io.netty.channel.ChannelFutureListener;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.SimpleChannelInboundHandler;
+import io.netty.handler.codec.http.DefaultHttpResponse;
+import io.netty.handler.codec.http.HttpRequest;
+import io.netty.handler.codec.http.HttpResponseStatus;
+import io.netty.util.ReferenceCountUtil;
+
+import org.apache.commons.logging.Log;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.security.http.RestCsrfPreventionFilter;
+import org.apache.hadoop.security.http.RestCsrfPreventionFilter.HttpInteraction;
+
+/**
+ * Netty handler that integrates with the {@link RestCsrfPreventionFilter}.  If
+ * the filter determines that the request is allowed, then this handler forwards
+ * the request to the next handler in the Netty pipeline.  Otherwise, this
+ * handler drops the request and immediately sends an HTTP 400 response.
+ */
+@InterfaceAudience.Private
+final class RestCsrfPreventionFilterHandler
+    extends SimpleChannelInboundHandler<HttpRequest> {
+
+  private static final Log LOG = DatanodeHttpServer.LOG;
+
+  private final RestCsrfPreventionFilter restCsrfPreventionFilter;
+
+  /**
+   * Creates a new RestCsrfPreventionFilterHandler.  There will be a new
+   * instance created for each new Netty channel/pipeline serving a new request.
+   * To prevent the cost of repeated initialization of the filter, this
+   * constructor requires the caller to pass in a pre-built, fully initialized
+   * filter instance.  The filter is stateless after initialization, so it can
+   * be shared across multiple Netty channels/pipelines.
+   *
+   * @param restCsrfPreventionFilter initialized filter
+   */
+  public RestCsrfPreventionFilterHandler(
+      RestCsrfPreventionFilter restCsrfPreventionFilter) {
+    this.restCsrfPreventionFilter = restCsrfPreventionFilter;
+  }
+
+  @Override
+  protected void channelRead0(final ChannelHandlerContext ctx,
+      final HttpRequest req) throws Exception {
+    restCsrfPreventionFilter.handleHttpInteraction(new NettyHttpInteraction(
+        ctx, req));
+  }
+
+  @Override
+  public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
+    LOG.error("Exception in " + this.getClass().getSimpleName(), cause);
+    sendResponseAndClose(ctx,
+        new DefaultHttpResponse(HTTP_1_1, INTERNAL_SERVER_ERROR));
+  }
+
+  /**
+   * Finish handling this pipeline by writing a response with the
+   * "Connection: close" header, flushing, and scheduling a close of the
+   * connection.
+   *
+   * @param ctx context to receive the response
+   * @param resp response to send
+   */
+  private static void sendResponseAndClose(ChannelHandlerContext ctx,
+      DefaultHttpResponse resp) {
+    resp.headers().set(CONNECTION, CLOSE);
+    ctx.writeAndFlush(resp).addListener(ChannelFutureListener.CLOSE);
+  }
+
+  /**
+   * {@link HttpInteraction} implementation for use in a Netty pipeline.
+   */
+  private static final class NettyHttpInteraction implements HttpInteraction {
+
+    private final ChannelHandlerContext ctx;
+    private final HttpRequest req;
+
+    /**
+     * Creates a new NettyHttpInteraction.
+     *
+     * @param ctx context to receive the response
+     * @param req request to process
+     */
+    public NettyHttpInteraction(ChannelHandlerContext ctx, HttpRequest req) {
+      this.ctx = ctx;
+      this.req = req;
+    }
+
+    @Override
+    public String getHeader(String header) {
+      return req.headers().get(header);
+    }
+
+    @Override
+    public String getMethod() {
+      return req.method().name();
+    }
+
+    @Override
+    public void proceed() {
+      ReferenceCountUtil.retain(req);
+      ctx.fireChannelRead(req);
+    }
+
+    @Override
+    public void sendError(int code, String message) {
+      HttpResponseStatus status = new HttpResponseStatus(code, message);
+      sendResponseAndClose(ctx, new DefaultHttpResponse(HTTP_1_1, status));
+    }
+  }
+}

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNodeHttpServer.java

@@ -17,6 +17,8 @@
  */
 package org.apache.hadoop.hdfs.server.namenode;
 
+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.io.IOException;
 import java.net.InetSocketAddress;
@@ -45,6 +47,7 @@ import org.apache.hadoop.http.HttpServer2;
 import org.apache.hadoop.net.NetUtils;
 import org.apache.hadoop.security.SecurityUtil;
 import org.apache.hadoop.security.UserGroupInformation;
+import org.apache.hadoop.security.http.RestCsrfPreventionFilter;
 
 /**
  * Encapsulates the HTTP server started by the NameNode. 
@@ -90,6 +93,16 @@ public class NameNodeHttpServer {
     HttpServer2.LOG.info("Added filter '" + name + "' (class=" + className
         + ")");
 
+    // add REST CSRF prevention filter
+    if (conf.getBoolean(DFS_WEBHDFS_REST_CSRF_ENABLED_KEY,
+        DFS_WEBHDFS_REST_CSRF_ENABLED_DEFAULT)) {
+      Map<String, String> restCsrfParams = RestCsrfPreventionFilter
+          .getFilterParams(conf, "dfs.webhdfs.rest-csrf.");
+      String restCsrfClassName = RestCsrfPreventionFilter.class.getName();
+      HttpServer2.defineFilter(httpServer.getWebAppContext(), restCsrfClassName,
+          restCsrfClassName, restCsrfParams, new String[] {pathSpec});
+    }
+
     // add webhdfs packages
     httpServer.addJerseyResourcePackage(NamenodeWebHdfsMethods.class
         .getPackage().getName() + ";" + Param.class.getPackage().getName(),

hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml

@@ -2762,4 +2762,56 @@
   </description>
 </property>
 
+<property>
+  <name>dfs.webhdfs.rest-csrf.enabled</name>
+  <value>false</value>
+  <description>
+    If true, then enables WebHDFS protection against cross-site request forgery
+    (CSRF).  The WebHDFS client also uses this property to determine whether or
+    not it needs to send the custom CSRF prevention header in its HTTP requests.
+  </description>
+</property>
+
+<property>
+  <name>dfs.webhdfs.rest-csrf.custom-header</name>
+  <value>X-XSRF-HEADER</value>
+  <description>
+    The name of a custom header that HTTP requests must send when protection
+    against cross-site request forgery (CSRF) is enabled for WebHDFS by setting
+    dfs.webhdfs.rest-csrf.enabled to true.  The WebHDFS client also uses this
+    property to determine whether or not it needs to send the custom CSRF
+    prevention header in its HTTP requests.
+  </description>
+</property>
+
+<property>
+  <name>dfs.webhdfs.rest-csrf.methods-to-ignore</name>
+  <value>GET,OPTIONS,HEAD,TRACE</value>
+  <description>
+    A comma-separated list of HTTP methods that do not require HTTP requests to
+    include a custom header when protection against cross-site request forgery
+    (CSRF) is enabled for WebHDFS by setting dfs.webhdfs.rest-csrf.enabled to
+    true.  The WebHDFS client also uses this property to determine whether or
+    not it needs to send the custom CSRF prevention header in its HTTP requests.
+  </description>
+</property>
+
+<property>
+  <name>dfs.webhdfs.rest-csrf.browser-useragents-regex</name>
+  <value>^Mozilla.*,^Opera.*</value>
+  <description>
+    A comma-separated list of regular expressions used to match against an HTTP
+    request's User-Agent header when protection against cross-site request
+    forgery (CSRF) is enabled for WebHDFS by setting
+    dfs.webhdfs.reset-csrf.enabled to true.  If the incoming User-Agent matches
+    any of these regular expressions, then the request is considered to be sent
+    by a browser, and therefore CSRF prevention is enforced.  If the request's
+    User-Agent does not match any of these regular expressions, then the request
+    is considered to be sent by something other than a browser, such as scripted
+    automation.  In this case, CSRF is not a potential attack vector, so
+    the prevention is not enforced.  This helps achieve backwards-compatibility
+    with existing automation that has not been updated to send the CSRF
+    prevention header.
+  </description>
+</property>
 </configuration>

hadoop-hdfs-project/hadoop-hdfs/src/main/webapps/hdfs/explorer.html

@@ -269,6 +269,7 @@
     </script><script type="text/javascript" src="/static/dust-helpers-1.1.1.min.js">
     </script><script type="text/javascript" src="/static/dfs-dust.js">
     </script><script type="text/javascript" src="/static/json-bignum.js">
+    </script><script type="text/javascript" src="/static/rest-csrf.js">
     </script><script type="text/javascript" src="explorer.js">
     </script><script type="text/javascript" src="/static/moment.min.js">
     </script>

hadoop-hdfs-project/hadoop-hdfs/src/main/webapps/static/rest-csrf.js

@@ -0,0 +1,91 @@
+/**
+ * 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.
+ */
+
+"use strict";
+
+// Initializes client-side handling of cross-site request forgery (CSRF)
+// protection by figuring out the custom HTTP headers that need to be sent in
+// requests and which HTTP methods are ignored because they do not require CSRF
+// protection.
+(function() {
+  var restCsrfCustomHeader = null;
+  var restCsrfMethodsToIgnore = null;
+
+  $.ajax({'url': '/conf', 'dataType': 'xml', 'async': false}).done(
+    function(data) {
+      function getBooleanValue(element) {
+        return ($(element).find('value').text().trim().toLowerCase() === 'true')
+      }
+
+      function getTrimmedStringValue(element) {
+        return $(element).find('value').text().trim();
+      }
+
+      function getTrimmedStringArrayValue(element) {
+        var str = $(element).find('value').text().trim();
+        var array = [];
+        if (str) {
+          var splitStr = str.split(',');
+          for (var i = 0; i < splitStr.length; i++) {
+            array.push(splitStr[i].trim());
+          }
+        }
+        return array;
+      }
+
+      // Get all relevant configuration properties.
+      var $xml = $(data);
+      var csrfEnabled = false;
+      var header = null;
+      var methods = [];
+      $xml.find('property').each(function(idx, element) {
+        var name = $(element).find('name').text();
+        if (name === 'dfs.webhdfs.rest-csrf.enabled') {
+          csrfEnabled = getBooleanValue(element);
+        } else if (name === 'dfs.webhdfs.rest-csrf.custom-header') {
+          header = getTrimmedStringValue(element);
+        } else if (name === 'dfs.webhdfs.rest-csrf.methods-to-ignore') {
+          methods = getTrimmedStringArrayValue(element);
+        }
+      });
+
+      // If enabled, set up all subsequent AJAX calls with a pre-send callback
+      // that adds the custom headers if necessary.
+      if (csrfEnabled) {
+        restCsrfCustomHeader = header;
+        restCsrfMethodsToIgnore = {};
+        methods.map(function(method) { restCsrfMethodsToIgnore[method] = true; });
+        $.ajaxSetup({
+          beforeSend: addRestCsrfCustomHeader
+        });
+      }
+    });
+
+  // Adds custom headers to request if necessary.  This is done only for WebHDFS
+  // URLs, and only if it's not an ignored method.
+  function addRestCsrfCustomHeader(xhr, settings) {
+    if (settings.url == null || !settings.url.startsWith('/webhdfs/')) {
+      return;
+    }
+    var method = settings.type;
+    if (restCsrfCustomHeader != null && !restCsrfMethodsToIgnore[method]) {
+      // The value of the header is unimportant.  Only its presence matters.
+      xhr.setRequestHeader(restCsrfCustomHeader, '""');
+    }
+  }
+})();

hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/WebHDFS.md

@@ -23,6 +23,7 @@ WebHDFS REST API
         * [HDFS Configuration Options](#HDFS_Configuration_Options)
     * [Authentication](#Authentication)
     * [Proxy Users](#Proxy_Users)
+    * [Cross-Site Request Forgery Prevention](#Cross-Site_Request_Forgery_Prevention)
     * [File and Directory Operations](#File_and_Directory_Operations)
         * [Create and Write to a File](#Create_and_Write_to_a_File)
         * [Append to a File](#Append_to_a_File)
@@ -263,6 +264,41 @@ When the proxy user feature is enabled, a proxy user *P* may submit a request on
 
         curl -i "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?delegation=<TOKEN>&op=..."
 
+Cross-Site Request Forgery Prevention
+-------------------------------------
+
+WebHDFS supports an optional, configurable mechanism for cross-site request
+forgery (CSRF) prevention.  When enabled, WebHDFS HTTP requests to the NameNode
+or DataNode must include a custom HTTP header.  Configuration properties allow
+adjusting which specific HTTP methods are protected and the name of the HTTP
+header.  The value sent in the header is not relevant.  Only the presence of a
+header by that name is required.
+
+Enabling CSRF prevention also sets up the `WebHdfsFileSystem` class to send the
+required header.  This ensures that CLI commands like
+[`hdfs dfs`](./HDFSCommands.html#dfs) and
+[`hadoop distcp`](../../hadoop-distcp/DistCp.html) continue to work correctly
+when used with `webhdfs:` URIs.
+
+Enabling CSRF prevention also sets up the NameNode web UI to send the required
+header.  After enabling CSRF prevention and restarting the NameNode, existing
+users of the NameNode web UI need to refresh the browser to reload the page and
+find the new configuration.
+
+The following properties control CSRF prevention.
+
+| Property | Description | Default Value |
+|:---- |:---- |:----
+| `dfs.webhdfs.rest-csrf.enabled` | If true, then enables WebHDFS protection against cross-site request forgery (CSRF).  The WebHDFS client also uses this property to determine whether or not it needs to send the custom CSRF prevention header in its HTTP requests. | `false` |
+| `dfs.webhdfs.rest-csrf.custom-header` | The name of a custom header that HTTP requests must send when protection against cross-site request forgery (CSRF) is enabled for WebHDFS by setting dfs.webhdfs.rest-csrf.enabled to true.  The WebHDFS client also uses this property to determine whether or not it needs to send the custom CSRF prevention header in its HTTP requests. | `X-XSRF-HEADER` |
+| `dfs.webhdfs.rest-csrf.methods-to-ignore` | A comma-separated list of HTTP methods that do not require HTTP requests to include a custom header when protection against cross-site request forgery (CSRF) is enabled for WebHDFS by setting dfs.webhdfs.rest-csrf.enabled to true.  The WebHDFS client also uses this property to determine whether or not it needs to send the custom CSRF prevention header in its HTTP requests. | `GET,OPTIONS,HEAD,TRACE` |
+| `dfs.webhdfs.rest-csrf.browser-useragents-regex` | A comma-separated list of regular expressions used to match against an HTTP request's User-Agent header when protection against cross-site request forgery (CSRF) is enabled for WebHDFS by setting dfs.webhdfs.reset-csrf.enabled to true.  If the incoming User-Agent matches any of these regular expressions, then the request is considered to be sent by a browser, and therefore CSRF prevention is enforced.  If the request's User-Agent does not match any of these regular expressions, then the request is considered to be sent by something other than a browser, such as scripted automation.  In this case, CSRF is not a potential attack vector, so the prevention is not enforced.  This helps achieve backwards-compatibility with existing automation that has not been updated to send the CSRF prevention header. | `^Mozilla.*,^Opera.*` |
+
+The following is an example `curl` call that uses the `-H` option to include the
+custom header in the request.
+
+        curl -i -L -X PUT -H 'X-XSRF-HEADER: ""' 'http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=CREATE'
+
 File and Directory Operations
 -----------------------------
 

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/web/TestWebHdfsWithRestCsrfPreventionFilter.java

@@ -0,0 +1,166 @@
+/**
+ * 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.web;
+
+import static org.apache.hadoop.hdfs.client.HdfsClientConfigKeys.DFS_WEBHDFS_REST_CSRF_BROWSER_USERAGENTS_REGEX_KEY;
+import static org.apache.hadoop.hdfs.client.HdfsClientConfigKeys.DFS_WEBHDFS_REST_CSRF_ENABLED_KEY;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+
+import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.net.URI;
+import java.util.Arrays;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hdfs.DFSTestUtil;
+import org.apache.hadoop.hdfs.MiniDFSCluster;
+import org.apache.hadoop.io.IOUtils;
+import org.apache.hadoop.net.NetUtils;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+import org.junit.runners.Parameterized.Parameters;
+
+/**
+ * Tests use of the cross-site-request forgery (CSRF) prevention filter with
+ * WebHDFS.  This is a parameterized test that covers various combinations of
+ * CSRF protection enabled or disabled at the NameNode, the DataNode and the
+ * WebHDFS client.  If the server is configured with CSRF prevention, but the
+ * client is not, then protected operations are expected to fail.
+ */
+@RunWith(Parameterized.class)
+public class TestWebHdfsWithRestCsrfPreventionFilter {
+
+  private static final Path FILE = new Path("/file");
+
+  private final boolean nnRestCsrf;
+  private final boolean dnRestCsrf;
+  private final boolean clientRestCsrf;
+
+  private MiniDFSCluster cluster;
+  private FileSystem fs, webhdfs;
+
+  @Rule
+  public ExpectedException exception = ExpectedException.none();
+
+  public TestWebHdfsWithRestCsrfPreventionFilter(boolean nnRestCsrf,
+      boolean dnRestCsrf, boolean clientRestCsrf) {
+    this.nnRestCsrf = nnRestCsrf;
+    this.dnRestCsrf = dnRestCsrf;
+    this.clientRestCsrf = clientRestCsrf;
+  }
+
+  @Parameters
+  public static Iterable<Object[]> data() {
+    return Arrays.asList(new Object[][] {
+        { false, false, false },
+        { true, true, true },
+        { true, true, false },
+        { true, false, true },
+        { true, false, false },
+        { false, true, true },
+        { false, true, false },
+        { false, false, true }});
+  }
+
+  @Before
+  public void before() throws Exception {
+    Configuration nnConf = new Configuration();
+    nnConf.setBoolean(DFS_WEBHDFS_REST_CSRF_ENABLED_KEY, nnRestCsrf);
+    // Set configuration to treat anything as a browser, so that CSRF prevention
+    // checks actually get enforced.
+    nnConf.set(DFS_WEBHDFS_REST_CSRF_BROWSER_USERAGENTS_REGEX_KEY, ".*");
+    cluster = new MiniDFSCluster.Builder(nnConf).numDataNodes(0).build();
+
+    Configuration dnConf = new Configuration(nnConf);
+    dnConf.setBoolean(DFS_WEBHDFS_REST_CSRF_ENABLED_KEY, dnRestCsrf);
+    cluster.startDataNodes(dnConf, 1, true, null, null, null, null, false);
+
+    cluster.waitActive();
+    fs = cluster.getFileSystem();
+
+    Configuration clientConf = new Configuration();
+    clientConf.setBoolean(DFS_WEBHDFS_REST_CSRF_ENABLED_KEY, clientRestCsrf);
+    InetSocketAddress addr = cluster.getNameNode().getHttpAddress();
+    webhdfs = FileSystem.get(URI.create("webhdfs://" +
+        NetUtils.getHostPortString(addr)), clientConf);
+  }
+
+  @After
+  public void after() {
+    IOUtils.closeStream(webhdfs);
+    IOUtils.closeStream(fs);
+    if (cluster != null) {
+      cluster.shutdown();
+    }
+  }
+
+  @Test
+  public void testCreate() throws Exception {
+    // create is a HTTP PUT that redirects from NameNode to DataNode, so we
+    // expect CSRF prevention on either server to block an unconfigured client.
+    if ((nnRestCsrf || dnRestCsrf) && !clientRestCsrf) {
+      expectException();
+    }
+    assertTrue(webhdfs.createNewFile(FILE));
+  }
+
+  @Test
+  public void testDelete() throws Exception {
+    DFSTestUtil.createFile(fs, FILE, 1024, (short)1, 0L);
+    // delete is an HTTP DELETE that executes solely within the NameNode as a
+    // metadata operation, so we expect CSRF prevention configured on the
+    // NameNode to block an unconfigured client.
+    if (nnRestCsrf && !clientRestCsrf) {
+      expectException();
+    }
+    assertTrue(webhdfs.delete(FILE, false));
+  }
+
+  @Test
+  public void testGetFileStatus() throws Exception {
+    // getFileStatus is an HTTP GET, not subject to CSRF prevention, so we
+    // expect it to succeed always, regardless of CSRF configuration.
+    assertNotNull(webhdfs.getFileStatus(new Path("/")));
+  }
+
+  @Test
+  public void testTruncate() throws Exception {
+    DFSTestUtil.createFile(fs, FILE, 1024, (short)1, 0L);
+    // truncate is an HTTP POST that executes solely within the NameNode as a
+    // metadata operation, so we expect CSRF prevention configured on the
+    // NameNode to block an unconfigured client.
+    if (nnRestCsrf && !clientRestCsrf) {
+      expectException();
+    }
+    assertTrue(webhdfs.truncate(FILE, 0L));
+  }
+
+  private void expectException() {
+    exception.expect(IOException.class);
+    exception.expectMessage("Missing Required Header");
+  }
+}