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Looking for pointers on putting Cribl between Splunk UF and Indexer with TLS Encryption

  • March 11, 2025
  • 12 replies
  • 12 views

hello All, As a cribl beginner, I am looking for resources/guide to achieve below ---I am trying to place Cribl between splunk UF and indexer with TLS encryption enabled.Any pointers/lead/direction will be highly appreciated. more details in thread below...

12 replies

  • Author
  • Known Participant
  • March 11, 2025

I am not currently facing any issue or error, rather i am trying to understand/preparing to deliver -- with what will be provided --outputs.conf on UF andinputs.conf on the indexer


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  • Participating Frequently
  • March 11, 2025

Do you wanna do mTLS or just TLS on the receiving side?


  • Author
  • Known Participant
  • March 11, 2025

on the windows UF side, i must use`sslVerifyServerCert = true` in outputs.conf -- so i suppose mutual TLS is needed for this, right


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  • Participating Frequently
  • March 11, 2025

Mutual means that the client (sending side) also needs to present a valid cert


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  • Participating Frequently
  • March 11, 2025

In Splunk that's requireClientCert


  • Author
  • Known Participant
  • March 11, 2025

yes.I would need to use below in my splunk UF outputs.conf --```clientCert = <path>sslVerifyServerCert = trueindexerDiscovery = somethingABCDEFGHuseACK = true```I will keep indexerDiscovery out of the scope of our discussion for now andfocus more on `clientCert` and `sslVerifyServerCert` as a must to place on the windows UF -- while i am reproducing scenario in my lab.


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  • Participating Frequently
  • March 11, 2025

Yeah, the question is if proper client cert authentication is part of your requirements.


  • Author
  • Known Participant
  • March 11, 2025

yes. it is


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  • Participating Frequently
  • March 11, 2025

In Cribl, you enable TLS on the input, enable client cert validation, give Cribl the root CA of the UF client cert.


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  • Participating Frequently
  • March 11, 2025

Okay. So you already have that config for the UF. You might have to add the root CA cert that the Cribl receiving side cert has been issued by


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  • Participating Frequently
  • March 11, 2025

On Cribl output, configure a valid client cert, on the IDX side configure inputs.conf for splunktcp-ssl, give it a root CA that issued the Cribl client cert


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  • Participating Frequently
  • March 11, 2025

Well, whatever cert you got for that box Cribl runs on