1) Definition

The “security filter” is in charge of protecting URL, requesting authentication and optionally authorization.

In some cases, you may want to bypass this “security filter” and this can be done using the matchers parameter which is generally a list of matcher names. A matcher is generally defined in the security configuration.

The matchers can also be used to always apply some logic on the URLs, like adding some security headers.

2) Available matchers

A matcher can be defined by implementing the Matcher interface. It has only one method: boolean matches(WebContext context) to say if the “security filter” must be applied.

A few matchers are available (but you can of course develop your own matchers):

• the PathMatcher allows you to exclude some paths from the security checks

• the HeaderMatcher allows you to check if a given header is null or matches a regular expression

• the HttpMethodMatcher allows you to check if the method of the HTTP request is one of the expected defined methods.

3) Default matchers

Most pac4j implementations use the pac4j logics and matchers and thus the DefaultMatchingChecker component. In that case, the following matchers are automatically available via the following short keywords:

• the get, post, put and delete keywords for the related configurations of the HttpMethodMatcher (if they do not already exist)
• the hsts keyword for the StrictTransportSecurityMatcher
• the nosniff keyword for the XContentTypeOptionsMatcher
• the noframe keyword for the XFrameOptionsMatcher
• the xssprotection keyword for the XSSProtectionMatcher
• the nocache keyword for the CacheControlMatcher
• the securityheaders keyword as a shortcut for hsts,nosniff,noframe,xssprotection,nocache
• the csrfToken keyword for the CsrfTokenGeneratorMatcher with the DefaultCsrfTokenGenerator (it generates a CSRF token and saves it as the pac4jCsrfToken request attribute and in the pac4jCsrfToken cookie)
• the allowAjaxRequests keyword for a default configuration of the CorsMatcher with the Access-Control-Allow-Origin header set to *.
• the none keyword for no matchers at all.

These short names are defined as constants in DefaultMatchers. You can override them with your own matchers using the same names.