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Who has done this
Yale University.
Renew evaluated client-side
CAS 2.0 offers a request parameter "renew" on service ticket validation. Setting renew=true requires that the ST was issued in the same transaction as that which issued its granting ticket – that is, the user presented primary crendentials simultaneous with specifying the target for which the ST was issued.
WIND includes this boolean in the ticket validation response. Doing so enables clients to determine client-side whether to require this of a ST.
Use case
Suppose a service wishes to allow users to opt into Single Sign On. If this attribute of STs is communicated in the validation response, then the client can examine the authenticated username and whether the ST was issued simultaneous with user presentation of primary credentials. If the user has opted into SSO, great. If the user has not opted into SSO, but the user presented primary credentials at the time the ST was issued, great. If the user has not opted into SSO but the ticket was issued via SSO, then the service can redirect back to CAS login with renew=true.