Why do I receive SSL alert number 40 with selfsigned certificates?

ortiz — Wed, 25 Jan 2023 21:08:56 GMT

Dear all,

We are on process of ingesting Check Point EDR logs in our Splunk Cloud Platform. This should be done through a Heavy Forwarder. Checkpoint sends encrypted data to HFW.

For that purpose, we used the following guide provided by CheckPoint for generating and configure the certificates which contains specific instructions for Splunk:
https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk122323

As summary, there are two certificates that needs to be configured on the Splunk side:

- splunk.pem It is a combination of SyslogServer.crt + SyslogServer.key + RootCa.pem configured in /opt/splunk/etc/apps/CheckPointAPP/local/inputs.conf
- ca.pem configured in /opt/splunk/etc/system/local/server.conf

This configuration is not working because the certificate splunk.pem is giving a handshake error "SSL alert number 40".

The following setting in server.conf as the CheckPoint guide specifies, returns an error in Splunk: "Invalid key in stanza [SSL]".

[SSL] cipherSuite = TLSv1+HIGH:TLSv1.2+HIGH:@STRENGTH

We also have tried with this configuration with the same result:

[SSL] cipherSuite = ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA:AES256-SHA:DHE-RSA-AES128-SHA:AES128-SHA:AES256-SHA:AES128-SHA

In Splunk internal wereceive the following error:

Received fatal SSL3 alert. ssl_state='SSLv3 read client certificate A', alert_description='unknown CA'.

Do you know which could be the point of failure? Why the certificate is returning an error 40 or if the configuration should be set in a different way?

Best regards

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Why do I receive SSL alert number 40 with selfsigned certificates?