How do i verify & validate Base64 encoded SAML in Apigee in IDP initiated Flow

[rraghuna]

Hello, 

I am new to Apigee..  . We have an application which would post the SAML (Base 64 ) encoded  SAML to the Apigee Proxy. Wanted to know how to decode the base 64 SAML & verify the saml assertions and extract a user attribute... which i use it for the futher flows.