Extracting agreementRef from IPMode?

[MakakWasTaken]

I am currently using a custom implementation of IAS4PModeAwareCryptoFactory to get the ids of the initiator and responder. I the use these to determine what certificates to use. I would however like to use the agreementRef instead as it also contains the version of the certificate that should be used.
I have looked at the entire IPMode interface and have not been able to find anything. The getter getAgreement() returns urn:as4:agreement

An example of an agreementRef with versioning looks like this:
http://entsog.eu/communication/agreements/EIC_A/EIC_B/V where EIC_A, EIC_B are the party’s EIC codes in alphabetical order and V is a number which increments which each certificate update.

[phax]

Lets try to reverse engineer the meaning of agreement and agreementRef

ebMS Core 3.0 spec:

1172 Agreeing on a P-Mode operation set is essential for two parties in order for their MSHs to interoperate.
1173 P-Modes are the MSH-level expression of a prior agreement between partners. A reference to such an
1174 agreement may be present in the message header (see eb:AgreementRef element in Section 5.2.2.7).
and
1647 AgreementRef is a string value that identifies the agreement that governs the exchange. The P-Mode
1648 under which the MSH operates for this message should be aligned with this agreement.
1649 The value of an AgreementRef element MUST be unique within a namespace mutually agreed by the two
1650 parties. This could be a concatenation of the From and To PartyId values, a URI containing the Internet
1651 domain name of one of the parties, or a namespace offered and managed by some other naming or
1652 registry service. It is RECOMMENDED that the AgreementRef be a URI.

The agreementRef is something that is soley contained in the UserMessage and not in the PMode. See below example (for the Peppol AS4 profile):

        <eb:CollaborationInfo>
          <eb:AgreementRef>urn:fdc:peppol.eu:2017:agreements:tia:ap_provider</eb:AgreementRef>
          <eb:Service type="cenbii-procid-ubl">urn:fdc:peppol.eu:2017:poacc:billing:01:1.0</eb:Service>
          <eb:Action>busdox-docid-qns::urn:oasis:names:specification:ubl:schema:xsd:Invoice-2::Invoice##urn:cen.eu:en16931:2017#compliant#urn:fdc:peppol.eu:2017:poacc:billing:3.0::2.1</eb:Action>
          <eb:ConversationId>phase4@Conv7764093634010523874</eb:ConversationId>
        </eb:CollaborationInfo>

I think what you need is first a custom IPModeResolver implementation that lets you select a PMode based on the agreementRef value.

Now my detailed knowledge about ENTSOG is de facto zero. Do you need point-to-point PModes or do you use "general PModes" that only differ by certificate(s) and endpoint URL? In the latter case, you could define n PModes - one for each agreementRef....

hth