check_immediate usage

Question

I'm implementing OpenID auth on a website and I'm using check_immediate. Now it works great with every big provider (google, myopenid, aol). But when a client from 1 certain OP tries to auth i always get Auth_OpenID_SetupNeededResponse. Now I've read that in this case the RP should retry without check_immediate (correct me if im wrong). But instead the OP sends me the error and does NOT specify a setup_url.

How can I fix this? Is this an error on the OP side or RP side?

Answer 1

openid.setup_url is not included in the OpenID 2.0 specification. Only OpenID 1.1 OPs are required to include it. So RPs should be prepared to not find that parameter in the checkid_immediate failure response and be able to synthesize the checkid_setup URL themselves without any help from the OP.