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Currently i'm working with ADFS to establish a federated trust between two separated domains.

My question is simple: does ADFS v. 2.0 support transitive trust across federated identity providers? And if so, see the questions below. (I'm not talking about AD forest trusts but about compleatly separated domains using pure ADFS 2.0 in a federation scenario)

I know that ADFS v 1.0 does not, as stated in this document on page 9. But when looking on the claims rules that come with ADFS 2.0 it seems to be possible, as a Microsoft partner confirmed. However: the documentation on this topic is a mess! Simply no ADFS v. 2.0 related statements on this topic that i was able to find (IF you got any documentation on this PLEASE help me out guys!).

To be more clear, lets assume this scenario:

Federation provider (A) trust federation provider (B) which trusts identity provider (C).
So, does (A) trust identities comming from (C) across (B)?

Fruther questions in case of support of transitive trust:

  • Is it possible to restrict the transitive trust in ADFS in any way? If so, how? (Powershell Command or ADFS GUI menü entry where to find it)
  • How does the transitive trust affect the Issuer and OriginalIssuer properties of the claims?
  • If transitive trust is used together with claims transformations and provider (B) would transform incomming claims from (C) in a way that they are transformed into (new) claims of same type an value, how would this affect the Issuer and OriginalIssuer properties?

IMPORTANT: whether it's supported or not, I need some official sources on this. However, if nobody else will be able to provide them and someone is able to answer the questions with his experience, i'm willed to give the bounty to him / her even without official sources.

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1 Answer 1

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Well, since nobody did answer, i took the time, setup a test lab and sniffed the HTTPS traffic. Here are my research results in case anybody else will ever come across this thing:

  • I still got no official source for this questions
  • First off: yes, transitive trust is possible and there is no way to block it except of legal affairs. A propper SLA is the basis for any federation scenario anyways.
  • There is no special "setting" to disable or enable it, but using the claims rule engine a trusted partner may configure ANY kind of outgoing claims IF ANY kind of incomming claims are detected, so there is no way to "protect" illegal access.
  • In my tests, none of the rule templates that come with ADFS changed the OriginalIssuer property of the claims. One may think: Okay so i can use that property to verify the original source of any claim and build a filter to only allow claims comming directly from (and not traversed through, which by default only affects the Issuer but not the OriginalIssuer property) a trusted partner. But thats wrong, why? Look at the next line.
  • As i said, the default templates don't touch the OriginalIssuer property. But you may create custom rules using the rule engine. Using that one, you can change pretty much every claim type, value and their properties. And yes: also the OriginalIssuer. So to the federation provider it looks as the claims are comming directy from the trusted partner, where in reality they're only transformed there.

So, what i would suggest to atleast minimize "transitive" scenarios if they're unwanted, is to check for the OriginalIssuer. It dosn't protect from transitive logins, but a admin would have to explicitly configure it - which would make legal affiars much more easier in a case of SLA voilation. Also, i'm not thinking of the possibility to change the OriginalIssuer as a "bug", in fact: even without that feature, every thrid party software could always make it able to act as a proxy between backend systems and the trusted identity provider. For example the IdP could create shadow accounts for partner (C) - so there will always be a workaround since when using federation, you're giving away the control on who is able to delegate access rights to specific ressources.

Anyway - if you have been as curious as i about how ADFS 2.0 handles transitive trusts, now you know without the need to build a testlab and sniff HTTPS traffic.

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