Author: markt
Date: Fri May 7 17:38:03 2010
New Revision: 942157
URL: http://svn.apache.org/viewvc?rev=942157&view=rev
Log:
Add a simple CSRF prevention filter. It has been tested with the Tomcat 6
manager app and a back-port proposal will follow shortly.
Added:
tomcat/trunk/java/org/apache/catalina/filters/CsrfPreventionFilter.java
(with props)
Modified:
tomcat/trunk/java/org/apache/catalina/filters/Constants.java
tomcat/trunk/webapps/docs/config/filter.xml
Modified: tomcat/trunk/java/org/apache/catalina/filters/Constants.java
URL:
http://svn.apache.org/viewvc/tomcat/trunk/java/org/apache/catalina/filters/Constants.java?rev=942157&r1=942156&r2=942157&view=diff
==============================================================================
--- tomcat/trunk/java/org/apache/catalina/filters/Constants.java (original)
+++ tomcat/trunk/java/org/apache/catalina/filters/Constants.java Fri May 7
17:38:03 2010
@@ -31,4 +31,9 @@ public final class Constants {
public static final String Package = "org.apache.catalina.filters";
+ public static final String CSRF_NONCE_SESSION_ATTR_NAME =
+ "org.apache.catalina.filters.CSRF_NONCE";
+
+ public static final String CSRF_NONCE_REQUEST_PARAM =
+ "org.apache.catalina.filters.CSRF_NONCE";
}
Added: tomcat/trunk/java/org/apache/catalina/filters/CsrfPreventionFilter.java
URL:
http://svn.apache.org/viewvc/tomcat/trunk/java/org/apache/catalina/filters/CsrfPreventionFilter.java?rev=942157&view=auto
==============================================================================
--- tomcat/trunk/java/org/apache/catalina/filters/CsrfPreventionFilter.java
(added)
+++ tomcat/trunk/java/org/apache/catalina/filters/CsrfPreventionFilter.java Fri
May 7 17:38:03 2010
@@ -0,0 +1,190 @@
+/*
+ * 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.catalina.filters;
+
+import java.io.IOException;
+import java.util.Random;
+
+import javax.servlet.FilterChain;
+import javax.servlet.ServletException;
+import javax.servlet.ServletRequest;
+import javax.servlet.ServletResponse;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import javax.servlet.http.HttpServletResponseWrapper;
+
+import org.apache.juli.logging.Log;
+import org.apache.juli.logging.LogFactory;
+
+/**
+ * Provides basic CSRF protection for a web application. The filter assumes
+ * that:
+ * <ul>
+ * <li>The filter is mapped to /*</li>
+ * <li>{...@link HttpServletResponse#encodeRedirectURL(String)} and
+ * {...@link HttpServletResponse#encodeURL(String)} are used to encode all URLs
+ * returned to the client
+ * </ul>
+ */
+public class CsrfPreventionFilter extends FilterBase {
+
+ private static final Log log =
+ LogFactory.getLog(CsrfPreventionFilter.class);
+
+ private final Random randomSource = new Random();
+
+ @Override
+ protected Log getLogger() {
+ return log;
+ }
+
+ public void doFilter(ServletRequest request, ServletResponse response,
+ FilterChain chain) throws IOException, ServletException {
+
+ ServletResponse wResponse = null;
+
+ if (request instanceof HttpServletRequest &&
+ response instanceof HttpServletResponse) {
+
+ HttpServletRequest req = (HttpServletRequest) request;
+ HttpServletResponse res = (HttpServletResponse) response;
+
+ String previousNonce =
+ req.getParameter(Constants.CSRF_NONCE_REQUEST_PARAM);
+ String expectedNonce = (String) req.getSession(true).getAttribute(
+ Constants.CSRF_NONCE_SESSION_ATTR_NAME);
+
+ if (expectedNonce != null && !expectedNonce.equals(previousNonce))
{
+ res.sendError(HttpServletResponse.SC_FORBIDDEN);
+ return;
+ }
+
+ String newNonce = generateNonce();
+
+ req.getSession(true).setAttribute(
+ Constants.CSRF_NONCE_SESSION_ATTR_NAME, newNonce);
+
+ wResponse = new CsrfResponseWrapper(res, newNonce);
+ } else {
+ wResponse = response;
+ }
+
+ chain.doFilter(request, wResponse);
+ }
+
+ /**
+ * Generate a once time token (nonce) for authenticating subsequent
+ * requests. This will also add the token to the session. The nonce
+ * generation is a simplified version of ManagerBase.generateSessionId().
+ *
+ */
+ protected String generateNonce() {
+ byte random[] = new byte[16];
+
+ // Render the result as a String of hexadecimal digits
+ StringBuilder buffer = new StringBuilder();
+
+ randomSource.nextBytes(random);
+
+ for (int j = 0; j < random.length; j++) {
+ byte b1 = (byte) ((random[j] & 0xf0) >> 4);
+ byte b2 = (byte) (random[j] & 0x0f);
+ if (b1 < 10)
+ buffer.append((char) ('0' + b1));
+ else
+ buffer.append((char) ('A' + (b1 - 10)));
+ if (b2 < 10)
+ buffer.append((char) ('0' + b2));
+ else
+ buffer.append((char) ('A' + (b2 - 10)));
+ }
+
+ return buffer.toString();
+ }
+
+ private static class CsrfResponseWrapper
+ extends HttpServletResponseWrapper {
+
+ private String nonce;
+
+ public CsrfResponseWrapper(HttpServletResponse response, String nonce)
{
+ super(response);
+ this.nonce = nonce;
+ }
+
+ @Override
+ @Deprecated
+ public String encodeRedirectUrl(String url) {
+ return encodeRedirectURL(url);
+ }
+
+ @Override
+ public String encodeRedirectURL(String url) {
+ return addNonce(super.encodeRedirectURL(url));
+ }
+
+ @Override
+ @Deprecated
+ public String encodeUrl(String url) {
+ return encodeURL(url);
+ }
+
+ @Override
+ public String encodeURL(String url) {
+ return addNonce(super.encodeURL(url));
+ }
+
+ /**
+ * Return the specified URL with the nonce added to the query string
+ *
+ * @param url URL to be modified
+ * @param nonce The nonce to add
+ */
+ private String addNonce(String url) {
+
+ if ((url == null) || (nonce == null))
+ return (url);
+
+ String path = url;
+ String query = "";
+ String anchor = "";
+ int question = url.indexOf('?');
+ if (question >= 0) {
+ path = url.substring(0, question);
+ query = url.substring(question);
+ }
+ int pound = path.indexOf('#');
+ if (pound >= 0) {
+ anchor = path.substring(pound);
+ path = path.substring(0, pound);
+ }
+ StringBuilder sb = new StringBuilder(path);
+ sb.append(anchor);
+ if (query.length() >0) {
+ sb.append(query);
+ sb.append('&');
+ } else {
+ sb.append('?');
+ }
+ sb.append(Constants.CSRF_NONCE_REQUEST_PARAM);
+ sb.append('=');
+ sb.append(nonce);
+ return (sb.toString());
+ }
+ }
+}
Propchange:
tomcat/trunk/java/org/apache/catalina/filters/CsrfPreventionFilter.java
------------------------------------------------------------------------------
svn:eol-style = native
Modified: tomcat/trunk/webapps/docs/config/filter.xml
URL:
http://svn.apache.org/viewvc/tomcat/trunk/webapps/docs/config/filter.xml?rev=942157&r1=942156&r2=942157&view=diff
==============================================================================
--- tomcat/trunk/webapps/docs/config/filter.xml (original)
+++ tomcat/trunk/webapps/docs/config/filter.xml Fri May 7 17:38:03 2010
@@ -87,6 +87,41 @@
</section>
+<section name="CSRF Prevention Filter">
+
+ <subsection name="Introduction">
+
+ <p>This filter provides basic CSRF protection for a web application. The
+ filter assumes that it is mapped to <code>/*</code> and that all URLs
+ returned to the client are encoded via a call to
+ <code>HttpServletResponse#encodeRedirectURL(String)</code> or
+ <code>HttpServletResponse#encodeURL(String)</code>.</p>
+
+ <p>This filter prevents CSRF by generating a nonce and storing it in the
+ session. URLs are also encoded with the same nonce. When the next request
is
+ received the nonce in the request is compared to the nonce in the session
+ and only if they are the same is the request allowed to continue.</p>
+
+ </subsection>
+
+ <subsection name="Filter Class Name">
+
+ <p>The filter class name for the CSRF Prevention Filter is
+ <strong><code>org.apache.catalina.filters.CsrfPreventionFilter</code>
+ </strong>.</p>
+
+ </subsection>
+
+ <subsection name="Initialisation parameters">
+
+ <p>The CSRF Prevention Filter does not support any initialization
+ parameters.</p>
+
+ </subsection>
+
+</section>
+
+
<section name="Remote Address Filter">
<subsection name="Introduction">
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