Social-to-SAML Gateway Attributes

The following attributes contribute to a minimal gateway attribute bundle:

  1. eduPersonTargetedID (ePTID)
  2. eduPersonPrincipalName (ePPN)
  3. mail
  4. displayName OR (givenName AND sn)


  • Set ePPN to the user’s email address
    • Use ePPN at your own risk
  • Set the mail attribute to the user’s email address
  • Set the person name as appropriate
  • Optionally set the NameID to one of the following:
    1. the user’s email address
    2. ePTID (i.e., a SAML2 Persistent NameID)
    3. SAML2 Transient NameID (default)

The most difficult mapping is ePTID. The goal is to assert a value of ePTID that persists with or without the gateway in the middle.

Recall that ePTID is a triple: (IdP entityID, SP entityID, persistent opaque blob)

All three components must persist regardless of whether or not the gateway is functioning as an intermediary. For the Google OpenID Gateway, we can do this as follows.

Let’s assume that the entityID of the Google IdP is:

and the entityID of the end SP is:

(The latter is in fact the entityID of the Federation Manager.) Then the ePTID computed and asserted by the gateway is given by the triple:

IdP entityID:
SP entityID:
User ID: persistent_opaque_value

This remains true even if the Google OpenID Gateway goes away.

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