Package org.apache.catalina.filters

Class 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

      Nested Classes 
      Modifier and Type Class Description
      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

      Constructors 
      Constructor Description
      AddDefaultCharsetFilter()
      Constructs a new AddDefaultCharsetFilter.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      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()
      Returns the logger for this filter.
      void init​(FilterConfig filterConfig)
      Iterates over the configuration parameters and either logs a warning, or throws an exception for any parameter that does not have a matching setter in this filter.
      void setEncoding​(java.lang.String encoding)
      Sets the character encoding to use.

      • Methods inherited from class java.lang.Object

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

    • Constructor Detail

      • AddDefaultCharsetFilter

        public AddDefaultCharsetFilter()
        Constructs a new AddDefaultCharsetFilter.

    • Method Detail

      • setEncoding

        public void setEncoding​(java.lang.String encoding)
        Sets the character encoding to use.
        Parameters:
        encoding - The character encoding

      • getLogger

        protected Log getLogger()
        Description copied from class: FilterBase
        Returns the logger for this filter.
        Specified by:
        getLogger in class FilterBase
        Returns:
        the logger

      • init

        public void init​(FilterConfig filterConfig)
          throws ServletException
        Description copied from class: FilterBase
        Iterates over the configuration parameters and either logs a warning, or throws an exception for any parameter that does not have a matching setter in this filter.
        Specified by:
        init in interface Filter
        Overrides:
        init in class FilterBase
        Parameters:
        filterConfig - The configuration information associated with the filter instance being initialised
        Throws:
        ServletException - if FilterBase.isConfigProblemFatal() returns true and a configured parameter does not have a matching setter

      • doFilter

        public void doFilter​(ServletRequest request,
                     ServletResponse response,
                     FilterChain chain)
              throws java.io.IOException,
                     ServletException
        Description copied from interface: jakarta.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.

        Parameters:
        request - The request to process
        response - The response associated with the request
        chain - Provides access to the next filter in the chain for this filter to pass the request and response to for further processing
        Throws:
        java.io.IOException - if an I/O error occurs during this filter's processing of the request
        ServletException - if the processing fails for any other reason