Current File(s): conf/authn/function-authn-config.xml, conf/authn/authn.properties (V4.1+)
Format: Native Spring, Properties (V4.1+)
Overview
The authn/Function login flow is an extension point that allows authentication to be handled by a deployer-supplied Function object, which can be written in Java, a scripting language, etc. It simplifies authoring certain kinds of custom login flows (essentially it provides the "flow" part) and potentially simplifies some MultiFactorAuthnConfiguration scenarios by moving some of the logic into a separate component.
Enabling Module (V4.1+)
For V4.1+, configuring and using this feature requires that you first enable the "idp.authn.Function" module if it isn't already enabled. Systems upgraded from older releases generally come pre-enabled due to the prior state of the configuration tree.
(Windows) C:\opt\shibboleth-idp> bin\module.bat -t idp.authn.Function || bin\module.bat -e idp.authn.Function (Other) $ bin/module.sh -t idp.authn.Function || bin/module.sh -e idp.authn.Function
General Configuration
The core of the flow is a required bean named shibboleth.authn.Function.ResultLookupStrategy, of type Function<ProfileRequestContext,Object>
If the Function returns a null, then authentication fails (this is how to signal a controlled failure). Otherwise, the Function can return a String (the username), a Principal, or a Subject, and the system will construct an appropriate AuthenticationResult around whatever is returned.
Use of Cookies
Since a common use case is to be able to read and write cookies, note that there's already a component that handles this called a CookieManager. There are built-in objects of this type that will reuse standard properties controlling cookie domain, path, flags, etc. and that's usually the best way to do things. Simply inject an instance of shibboleth.CookieManager or shibboleth.PersistentCookieManager into a Java-based Function implementation, or as a customObject-ref property of a bean inheriting from shibboleth.ContextFunctions.Scripted or shibboleth.ContextFunctions.Expression, to use it to read and write cookies for you.