Signature Validation + CA Chain Validation with Only An I-rule

Hi,

 

I would like to know what the possiblities are for :

 

Signature Validation + CA Chain Validation with Only An I-rule. Basically the certificate + Signatureblock has been send in the payload, & we also have the orginal data stored.

 

I would like to know if you can validate the signature somehow. + also validate the ca chain from within an I-rule. ( & what my options are )