Many people think of AD FS as merely a federated authentication service. And with a name like Active Directory Federation Services, it’s easy to see why. However, it also has the capacity to make authorisation decisions within its Claims Engine. This may be most familiar as the Office 365 Client Access Policies, but those policies are basically just a flavour of AD FS Issuance Authorisation Rules. An AD FS Issuance Authorisation rule provides a gate at AD FS, where permissions can be granted or denied to authentic users, per-Relying Party, before giving the user Claims for the requested Relying Party. In most cases we will think about these rules as coarse controls, to block a wide category of requests, such as those originating from outside the network, for members of a group, or for any combination of request-based, device-based and user attribute-based Claims. We can even create authorisation rules based on the user’s Identity Provider, or from additional factors of authentication. We will typically still implement most of our authorisation logic within the Relying Parties we are authenticating to, but in some cases it’s very useful to control access at this intermediary tier – especially if a large class of users, devices or networks should be treated as higher risk.
These concepts are not new, and the TechNet documentation I reference here dates back to the earliest wave of AD FS 2.0 RTW content:
Ultimately, I think these articles do answer the question of how to create an AD FS Issuance Authorisation rule, but I can’t point very clearly to the place on these pages that spells it out, and I do think there is a lot of confusing information about this in other places which may lead people astray. Namely, there is a lot of information that only concerns itself with the default Active Directory Claims Provider Rules and the Claims that come from request headers. Also, some of the most referenced AD FS + SharePoint content seems to have been written without authorisation rules in-mind. I want to try to clear some of that up in this post.
I’ve added a fairly significant update regarding the new MFA stage in the pipeline half-way down this post.
Continue reading “The Rules of AD FS Claims Rules”
Back in February, I posted a question on the Geneva forum about Adjusting token lifetimes at the Web Application Proxy (WAP) for external access:
Does the Web Application Proxy or AD FS have any separate controls for adjusting token lifetimes to a different value via WAP than directly at AD FS? I can see there’s a session cookie for EdgeAccessCookie that WAP issues but this seems to be entirely undocumented at present. I’ve poked around in C:\Windows\ADFS\Config\microsoft.identityServer.proxyservice.exe.config (also undocumented as far as I can tell) but I’m not finding anything there either. We used to have some of these controls (sort of) with TMG/UAG. Are they totally gone now? With the AD FS Proxy this was less of an issue because it was only publishing AD FS but this is something that I’d hope to be able to control with a Reverse Proxy. Any ideas?
I didn’t get any replies, but after carrying out some tests of my own, I noticed the EdgeAccessCookie, and found a bit of information on TechNet:
After the user is authenticated, the AD FS server issues a security token, the ‘edge token’, containing the following information and redirects the HTTPS request back to the Web Application Proxy server:
- The resource identifier that the user attempted to access.
- The user’s identity as a user principal name (UPN).
- The expiry of the access grant approval; that is, the user is granted access for a limited period of time, after which they are required to authenticate again.
- Signature of the information in the edge token.
Web Application Proxy receives the redirected HTTPS request from the AD FS server with the edge token and validates and uses the token as follows:
- Validates that the edge token signature is from the federation service that is configured in the Web Application Proxy configuration.
- Validates that the token was issued for the correct application.
- Validates that the token has not expired.
- Uses the user identity when required; for example to obtain a Kerberos ticket if the backend server is configured to use Integrated Windows authentication.
If the edge token is valid, Web Application Proxy forwards the HTTPS request to the published web application using either HTTP or HTTPS.
This quickly became one of those things where there was insufficient documentation and limited project time, so I had to put this inquiry on hold. Then in July, I posted a question on the Application Proxy blog (a great resource), to see if this is something that they planned to document. The response that I got from Ian Parramore was unexpected and pleasing:
Continue reading “Coordinating AD FS 2012 R2 token lifetimes to reduce logon prompts, enforce revocation and limit session duration over public networks”