topic ASA VPN with ISE and diffrent OTP backends for authentication in Network Access Control

ASA VPN with ISE and diffrent OTP backends for authentication

Mattias Andersson — Mon, 11 Mar 2019 02:09:26 GMT

Hi,

I have an AAA-problem I hope to get some help solving.

The problem in short is: How to make the ASA via ISE send Radius Access Requests to diffrent given OTP backends given a connection to a certain Tunnel Group.

BACKGROUND:

I will try to give you a brief picture of the scenario this is what I currently have.

A VPN system ( ASA 8.4(4) ) where I allow my users to choose from 3 different authentication methods being

1) Certificate (on smart-card)

2) Pledge - OTP token (One-Time-Password delivered via application in smartphone: using pledge from Nordic Edge OTP-Server)

3) SMS - OTP token (OTP via SMS from Nordic Edge OTP-Server)

The choice corresponds to different Connection Profiles/Tunnel Groups.

Today all authentication requests go directly to the OTP-servers and authorization goes directly to AD via LDAP.

THE PROBLEM:

The problem arises when I try to put in the ISE into the mix.

What I obviously(?) would like to do is to have all network authentication/autorization go thru my ISE platform to take advantage of centralized administration, monitoring etc.

Still I would need to use the different backend databases such as AD and Nordic Edge OTP-Server, but then proxied via ISE.

For me to be able to know to which backend AAA system to proxy I must somehow be able to distinguish the incoming Radius Access-Requests.

WHAT IS KNOWN:

As of ASA 8.4.3 the Radius Access-Request contains 2 new attributes, Tunnel Group Name and Client Type, when a VPN user connects.

http://www.cisco.com/en/US/docs/security/asa/asa84/configuration/guide/ref_extserver.html#wp1802187

QUESTION:

So, in theory is seams I can achive what I want looking at the Radius Access-Request attribute "Tunnel Group Name" and forward my request to diffrent OTP backends for the Autentication part. But, how do I actually go ahead and configure that in ISE?

I do not see this attribute when I look at the Radius Authentication details for a AAA autentication from the ASA to the ISE.

Best regards

/Mattias

ASA VPN with ISE and diffrent OTP backends for authentication

Mattias Andersson — Tue, 12 Jun 2012 11:54:17 GMT

Hi,

I have an update for this quite broad question.

I have now came a bit further on the path.

Now the needed Radius Access Attribute are available in ISE after adding them in

"Policy Elements" -> "Dictionaris" -> "System" -> "Radius" -> "Cisco-VPN3000".

I added both the attribute 146 Tunnel-Group-Name which I realy need to achive what I want(select diffrent OTP-backends depending on Tunnel Group in ASA) and the other new attribute 150 Client-Type which could be intresting to look at as well.

Here the "Diagnostics Tools" -> "Generel tools" -> "TCP Dump" and Wireshare helped me understand how this worked.

With that I could really see the attributes in the radius access requests going in to the ASA.

Now looking at a request in "Radius Authentication details" I have

---

Other Attributes:

ConfigVersionId=29,Device Port=1025,DestinationPort=1812,RadiusPacketType=AccessRequest,Protocol=Radius,CVPN3000/ASA/PIX7.x-Tunnel-Group-Name=SMHI-TG-RA-ISESMS,CVPN3000/ASA/PIX7.x-Client-Type=,CPMSessionID=ac100865000006294FD60A7F,.....

----

Ok, the tunnel group name attribute seems to be understood correct, but Client-Type just say =, no value for that.

That is strange, I must have defined that wrong(?), but lets leave that for now, I do not really need it for the moment being.

So now when I have this Tunnel-Group-Name attribute available I want to use it in my Rule-Based Authentication Policy.

Problem now is that as soon as I in an expression add a criteria containing Cisco-VPN3000:CVPN3000/ASA/PIX7.x-Tunnel-Group-Name matches .* (just anything), then that row does not match any more. It still work matching against NAS-IP and other attributes.

What could it be I have missed?

Best regards

/Mattias

ASA VPN with ISE and diffrent OTP backends for authentication

jrabinow — Tue, 12 Jun 2012 12:17:22 GMT

I think you may be hitting the following issue:

CSCtz49846: ISE does not match condition with VPN attribute 146 Tunnel-Group-Name

This issue is not specific to this attribute as can be seen from the workaround in the release note

Workaround

Ensure that attribute name does not include a '.' character. This also applies to some of the existing attributes in the Cisco-VPN300 dictionary. The attribute names should similarly be modified so that they do not include a '.' character.

ASA VPN with ISE and diffrent OTP backends for authentication

Mattias Andersson — Tue, 12 Jun 2012 13:47:14 GMT

Thanks alot, that was it!

It also solved the problem that I did not see any values for the Client-Type attribute.

I renamed both thoose attributes to not include a . in the name.

After changing the attribute name in the dictonary the authentication policy changed to reflect that.

I hoped it would now directly work, but that was not the case. Looking at the "Authentication Details" the name for the attribute was still the old name. I figured some component must be restarted to fetch the new attribute name. Don't knowing exacly which one I restarted the whole primary ISE-box and the it just worked.

I have been spending a lot of hours on this one and thought I have missunderstood the whole concept. I'm really glad to hear it was a bug and not me...