org.apache.catalina.filters
Class AddDefaultCharsetFilter

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

All Implemented Interfaces:

Filter

public class AddDefaultCharsetFilter
extends FilterBase

Filter that explicitly sets the default character set for media subtypes of the "text" type to ISO-8859-1, or another user defined character set. RFC2616 explicitly states that browsers must use ISO-8859-1 if no character set is defined for media with subtype "text". However, browsers may attempt to auto-detect the character set. This may be exploited by an attacker to perform an XSS attack. Internet Explorer has this behaviour by default. Other browsers have an option to enable it.
This filter prevents the attack by explicitly setting a character set. Unless the provided character set is explicitly overridden by the user - in which case they deserve everything they get - the browser will adhere to an explicitly set character set, thus preventing the XSS attack.

Nested Class Summary

static class

AddDefaultCharsetFilter.ResponseWrapper Wrapper that adds a character set for text media types if no character set is specified.

Field Summary

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

sm

Constructor Summary

AddDefaultCharsetFilter()

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 Log	getLogger()
void	init(FilterConfig filterConfig) Called by the web container to indicate to a filter that it is being placed into service.
void	setEncoding(String encoding)

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

destroy, isConfigProblemFatal

Methods inherited from class java.lang.Object

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

Constructor Detail

AddDefaultCharsetFilter

public AddDefaultCharsetFilter()

Method Detail

setEncoding

public void setEncoding(String encoding)

getLogger

protected Log getLogger()

Specified by:

getLogger in class FilterBase

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