org.apache.catalina.filters
Class CsrfPreventionFilter

java.lang.Object
  org.apache.catalina.filters.FilterBase
      org.apache.catalina.filters.CsrfPreventionFilter

All Implemented Interfaces:

Filter

public class CsrfPreventionFilter
extends FilterBase

Provides basic CSRF protection for a web application. The filter assumes that:

• The filter is mapped to /*
• HttpServletResponse.encodeRedirectURL(String) and HttpServletResponse.encodeURL(String) are used to encode all URLs returned to the client

Nested Class Summary

protected static class

CsrfPreventionFilter.CsrfResponseWrapper

Field Summary

Fields inherited from class org.apache.catalina.filters.FilterBase

sm

Constructor Summary

CsrfPreventionFilter()

Method Summary

void	doFilter(ServletRequest request, ServletResponse response, FilterChain chain) The doFilter method of the Filter is called by the container each time a request/response pair is passed through the chain due to a client request for a resource at the end of the chain.
protected String	generateNonce() Generate a once time token (nonce) for authenticating subsequent requests.
protected Log	getLogger()
void	init(FilterConfig filterConfig) Called by the web container to indicate to a filter that it is being placed into service.
void	setEntryPoints(String entryPoints) Entry points are URLs that will not be tested for the presence of a valid nonce.
void	setNonceCacheSize(int nonceCacheSize) Sets the number of previously issued nonces that will be cached on a LRU basis to support parallel requests, limited use of the refresh and back in the browser and similar behaviors that may result in the submission of a previous nonce rather than the current one.
void	setRandomClass(String randomClass) Specify the class to use to generate the nonces.

Methods inherited from class org.apache.catalina.filters.FilterBase

destroy

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CsrfPreventionFilter

public CsrfPreventionFilter()

Method Detail

getLogger

protected Log getLogger()

Specified by:

getLogger in class FilterBase

setEntryPoints

public void setEntryPoints(String entryPoints)

Entry points are URLs that will not be tested for the presence of a valid nonce. They are used to provide a way to navigate back to a protected application after navigating away from it. Entry points will be limited to HTTP GET requests and should not trigger any security sensitive actions.

Parameters:

entryPoints - Comma separated list of URLs to be configured as entry points.

setNonceCacheSize

public void setNonceCacheSize(int nonceCacheSize)

Sets the number of previously issued nonces that will be cached on a LRU basis to support parallel requests, limited use of the refresh and back in the browser and similar behaviors that may result in the submission of a previous nonce rather than the current one. If not set, the default value of 5 will be used.

Parameters:

nonceCacheSize - The number of nonces to cache

setRandomClass

public void setRandomClass(String randomClass)

Specify the class to use to generate the nonces. Must be in instance of Random.

Parameters:

randomClass - The name of the class to use

init

public void init(FilterConfig filterConfig)
          throws ServletException

Description copied from interface: javax.servlet.Filter

Called by the web container to indicate to a filter that it is being placed into service. The servlet container calls the init method exactly once after instantiating the filter. The init method must complete successfully before the filter is asked to do any filtering work.

The web container cannot place the filter into service if the init method either
1.Throws a ServletException
2.Does not return within a time period defined by the web container

Specified by:

init in interface Filter

Overrides:

init in class FilterBase

Throws:

ServletException

doFilter

public void doFilter(ServletRequest request,
                     ServletResponse response,
                     FilterChain chain)
              throws IOException,
                     ServletException

Description copied from interface: javax.servlet.Filter

The doFilter method of the Filter is called by the container each time a request/response pair is passed through the chain due to a client request for a resource at the end of the chain. The FilterChain passed in to this method allows the Filter to pass on the request and response to the next entity in the chain.

A typical implementation of this method would follow the following pattern:-
1. Examine the request
2. Optionally wrap the request object with a custom implementation to filter content or headers for input filtering
3. Optionally wrap the response object with a custom implementation to filter content or headers for output filtering
4. a) Either invoke the next entity in the chain using the FilterChain object (chain.doFilter()),
4. b) or not pass on the request/response pair to the next entity in the filter chain to block the request processing
5. Directly set headers on the response after invocation of the next entity in the filter chain.

Throws:

IOException

ServletException

generateNonce

protected String generateNonce()

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().