There is no way to define authentication processing filter per particular Relying Party

[cicnavi]

We should try and mimic the possibility to enable particular authentication processing filter for particular Relying Party, similar in how this is possible for SAML Service Providers described in https://simplesamlphp.org/docs/stable/simplesamlphp-authproc.html#filters-in-metadata

[cicnavi]

Hint from @tvdijen: check filter precondition as per https://simplesamlphp.org/docs/stable/simplesamlphp-authproc.html#preconditional-filters

Sample:

'%precondition' => 'return strcmp($state["core:SP"], "my-sp-entity-id-that-should-run-this-filter") === 0;',