Check for server certificate revocation

F5_Design_Engineer

MVP

Nov 17, 2023

For DYNAMIC CRL

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if you want to use external proxy server for forwarding the CRL request to the CRL server.

1. Crate DNS Resolver (Network-->DNS Resolvers-->DNS Resolver List-->Create)

2. Open DNS Resolver created in step 1, go to "Forward Zones" tab and add appropriate zones with DNS servers.

3. Create an internal proxy (GUI-->System-->Services-->Internal Proxies-->Create)

Assign DNS Resolver created in step 1 (no external proxy) or enable "Use Proxy Server" and specify LTM pool with proxy server (external proxy server).

4. Create Traffic Certificate Management CRL object (GUI-->System-->Certificate Management --> Traffic Certificate Management --> CRL)

Assign internal proxy created in step 3.

5. Assign CRL object created in step 5 to Client SSL profile with client authentication enabled:

Open GUI-->Local Traffic-->Profiles-->SSL-->Client-->profile_name

Go to Client Authentication section and set:

Client Certificate to request/require this will enable client authentication

Trusted Certificate Authorities to CA that you want to trust

CRL to object created in step 2.

Include root certificates to Advertised and Trusted bundle

From v15.1 onwards client SSL profiles support CRL validator objects as per this bug report:

Bug ID 743758 (f5.com)

In F5 in the client SSL profiles , please search for the following setting:

Notify Certificate Status to Virtual Server

Introduced in BIG-IP 13.0.0, this option specifies whether to propagate the status of the certificates associated with this client SSL profile to the virtual servers that are using this client SSL profile. Disabled by default.

Note: This option is used to communicate SSL certificate revocation status to the virtual server. This is typically implemented in conjunction with an OCSP stapling configuration.

This option is disabled by default.

You have to enable it on your CLIENT SSL profile by checking the option button

For that you have to import the CRL list and then apply that to the CRL option in the CLIET SSL profile

For STATIC CRL

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Having a CRL loaded as a local file into the BIGIP is probably the easiest way to get it to check a CRL since you are avoiding the use of MS Enterprise/Datacenter Servers with OCSP. I also had various issues that the F5 tech support could not explain with CRLDP and MS cert services. So the CRL is an easy fix for a lab environment. I also could not find the proper method to do this in the online knowledge-base for F5’s product either.

For starters, you need to get a copy of the CRL from your MS Certificate Server.

Download CRL
1) Browse to http://SERVERNAME/CertSrv Sign in if needed.
2) Click on Download a CA certificate, certificate chain, or CRL.
3) Select DER format and click on Download Latest Base CRL
4) Save the file to your machine.

Load the CRL to the BIGIP
1) Open up your BIGIP Admin Gui
2) Navigate to Sytem -> File Management -> SSL Certificate List -> Import
3) From the Import Type PullDown, Select ‘Certificate Revocation List’
4) Enter in the Name you want use when referencing this File in BIGIP. Select Create New or Overwrite as needed.
5) Use the Browse Button to select the cert file called ‘certcrl.crl’
6) Click Import to finish the Process.

Now that the CRL is imported, it can be used in any SSL Client Profile in the Certificate Revocation List (CRL) Dropdown.

This CRL is static. Any newly revoked certs on the MS Server will, of course, not be seen by the F5 until the CRL file

https://my.f5.com/manage/s/article/K14783

HTH

🙏