Package org.apache.catalina.filters

## Class CsrfPreventionFilter

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

All Implemented Interfaces:
  `Filter`

    public class CsrfPreventionFilter
    extends CsrfPreventionFilterBase

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

Nested Classes
`protected static class` `CsrfPreventionFilter.CsrfResponseWrapper`
`protected static class` `CsrfPreventionFilter.LruCache<T>` Despite its name, this is a FIFO cache not an LRU cache.
`protected static interface` `CsrfPreventionFilter.NonceCache<T>`

### Field Summary

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

`sm`

### Constructor Summary

Constructors
`CsrfPreventionFilter()`

### Method Summary

All Methods Instance Methods Concrete Methods
`protected CsrfPreventionFilter.NonceCache<java.lang.String>` `createNonceCache​(HttpServletRequest request, HttpSession session)` Create a new `CsrfPreventionFilter.NonceCache` and store in the `HttpSession`.
`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 CsrfPreventionFilter.NonceCache<java.lang.String>` `getNonceCache​(HttpServletRequest request, HttpSession session)` Obtain the `CsrfPreventionFilter.NonceCache` associated with the request and/or session.
`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` `setEntryPoints​(java.lang.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` `setNonceRequestParameterName​(java.lang.String parameterName)` Sets the request parameter name to use for CSRF nonces.
`protected boolean` `skipNonceCheck​(HttpServletRequest request)`
`protected boolean` `skipNonceGeneration​(HttpServletRequest request)` Determines whether a nonce should be created.

### Methods inherited from class org.apache.catalina.filters.CsrfPreventionFilterBase

`generateNonce, generateNonce, getDenyStatus, getLogger, getRequestedPath, isConfigProblemFatal, setDenyStatus, setRandomClass`

### Methods inherited from class java.lang.Object

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

### Methods inherited from interface javax.servlet.Filter

`destroy`

### Constructor Detail

#### CsrfPreventionFilter

    public CsrfPreventionFilter()

### Method Detail

#### setEntryPoints

    public void setEntryPoints​(java.lang.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

#### setNonceRequestParameterName

    public void setNonceRequestParameterName​(java.lang.String parameterName)

Sets the request parameter name to use for CSRF nonces.

Parameters:
  `parameterName` - The request parameter name to use for CSRF nonces.

#### 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 `CsrfPreventionFilterBase`
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: `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.

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

#### skipNonceCheck

    protected boolean skipNonceCheck​(HttpServletRequest request)

#### skipNonceGeneration

    protected boolean skipNonceGeneration​(HttpServletRequest request)

Determines whether a nonce should be created. This method is provided primarily for the benefit of sub-classes that wish to customise this behaviour.

Parameters:
  `request` - The request that triggered the need to potentially create the nonce.
Returns:
  `true` if a nonce should be created, otherwise `false`

#### createNonceCache

    protected CsrfPreventionFilter.NonceCache<java.lang.String> createNonceCache​(HttpServletRequest request,
                                                                                 HttpSession session)

Create a new `CsrfPreventionFilter.NonceCache` and store in the `HttpSession`. This method is provided primarily for the benefit of sub-classes that wish to customise this behaviour.

Parameters:
  `request` - The request that triggered the need to create the nonce cache. Unused by the default implementation.
  `session` - The session associated with the request.
Returns:
  A newly created `CsrfPreventionFilter.NonceCache`

#### getNonceCache

    protected CsrfPreventionFilter.NonceCache<java.lang.String> getNonceCache​(HttpServletRequest request,
                                                                              HttpSession session)

Obtain the `CsrfPreventionFilter.NonceCache` associated with the request and/or session. This method is provided primarily for the benefit of sub-classes that wish to customise this behaviour.

Parameters:
  `request` - The request that triggered the need to obtain the nonce cache. Unused by the default implementation.
  `session` - The session associated with the request.
Returns:
  The `CsrfPreventionFilter.NonceCache` currently associated with the request and/or session