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ZakJ96
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Nov 21, 2024

Client SSL Profile set to Require Client Certificate breaks RDP in APM

Hello,

I have a policy set up in the BIG-IP F5 VE 15.1.10.5 APM to allow access to a handful of Remote Desktop (RDP) links. I'm attempting to set the authentication to require Common Access Card (CAC) Certificate login. In my access policy visual editor, I have a Client Cert Inspection branch that leads into OCSP Authentication and then if successful assigns the RDP resources through LDAP. This all works perfectly fine as long as the Client SSL profile connected to the access policy has Client Authentication > Client Certificate set to "Request" or "Require."

 If set properly, when a user attempts to connect to the webtop URL they are prompted for their certificate, authorized against the OCSP, and given access to the resources as corresponds to LDAP group. However when attempting to use one of the Remote Desktop Links it'll download the RDPconnection as intended and fail to connect with "There was a problem connecting to the remote resource. Ask your network administrator for help." I know this is because of the Client SSL profile because if i change it back to "Ignore" and have the user click the Remote Desktop link, it downloads and connects to the specified resource with no issue.

 The server the RDP connects to is configured with a client certificate that is trusted by the Root and Intermediate CA in the "Trusted Certificate Authorities" under the Client SSL Client Authentication profile.

I was originally able to get around this by, instead of using Client Cert Inspection in my access policy, using On-Demand Cert Auth and leaving the Client SSL profile to "Ignore" client certificate. This allowed the user to be prompted and authenticated when originally accessing the webtop and utilize the RDP resources assigned. Unfortunately, On-Demand Cert Auth recently broke and users are not being prompted for their certificate and as such cannot connect to the webtop without the Client SSL profile being set to "Request" or "Require" to force the certificate prompt. 

https://my.f5.com/manage/s/article/K63123740

I've read the above KB where it says "the RDP client doesn't like the certificate request." but I'm not sure why, RDP should support certificate requests, users authenticate with token certificates all the time when RDP'ing to resources unless I'm misunderstanding what is happening? With that article I thought maybe the Server SSL profile would be an issue, but only changing the Client SSL profile certificate settings affects login. Any help would be appreciated, thanks!

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