Perform checks first

[utkarsh2102]

My take is that this method will raise ProtocolError in the very first place (which is a good thing!) unless the request is a valid id_res response. Once it has been verified, the methods endpoint, message, and signed_fields contain the verified information.
Thereby making everything secure from any third party interference.

Closes #124

[tobiashm]

Why have you moved check_for_fields down? AFAIR its purpose is to check if all the required fields are provided before they're being used by the other checks.

[utkarsh2102]

@tobiashm,

Why have you moved check_for_fields down?

I did not move check_for_fields down but moved check_signature and check_nonce up. Because signature checking should come first and then the rest of it.

[tobiashm]

Okay, but I still think check_for_fields should go first, as it checks if the fields that the other methods rely on. E.g. check_signature uses the assoc_handle field which must be present.

[utkarsh2102]

I still think check_for_fields should go first..

Ack, fixed and pushed.

[tobiashm]

Thanks. Merged and released v2.9.2

[tobiashm]

Hm. Issue #125 suggests that there are some more internal assumptions about the execution order of the checks in id_res. Not sure if this has made it worse, but at least it's something that needs further investigation.

[utkarsh2102]

Aha! Shall try to look this up and reproduce :)