SCHANNEL event logging

First, my thanks to Bhuvnesh Kumar for his help!

 

Time to figure out what’s going on behind the curtain!

 

 

Are you seeing System Event Log, Event ID 36871 events?

 

Why does this matter?

 

Depending on OS versions and patches, the TLS Cipher Suites may not match on the various SCOM servers.

  1. If you’re setting up TLS1.2, you need the SCOM servers to talk
  2. The bad part, is this isn’t logged much on the GW but log more often on MS
  3. Sometimes the 36871 events come with 36874, but in my experience they occur after Event Logging is enabled.

 

The unanswered question is “why are we seeing the 36871 events?”

 

In my example, the events only happened once a day, roughly 24 hours

 

Event Viewer

 

Are events related to the Cipher Suite, or is it a MP trying to run the old SQLOLEDB method?

 

This article will focus on verifying Cipher Suite on a server

See this article for MP analysis for SQL methods

 

 

 

SCHANNEL event logging setup

 

From Holman’s blog

Decimal Description
0 Do not log
1 Log Error messages
2 Log Warnings
3 Log Error and Warning messages
4 Log Informational and Success events
5 Log Error, Informational and Success events
6 Log Warnings, Informational and Success events
7 Log Everything (Warnings, Errors, Informational and Success events

 

I’d recommend setting it to 3 to see errors and warnings, or 7 to see everything.

Remember to set this back to 1 when done resolving any issues.

 

Add

From Command Prompt or PowerShell (as administrator)

reg add “HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL” /v “EventLogging” /t REG_DWORD /d 7 /f

Disable

reg delete “HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL” /v “EventLogging”

Verification

reg query “HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL” /v “EventLogging”

 

PowerShell verification

RegEdit Verification

Time to reboot!

 

 

Verify SCHANNEL events

Look at the System Event log, and filter for 36880 and 36874 events for clues

 

36880 provides Cipher Suite details

 

Event ID 36874 definitely describes the scenario

 

The easy answer to solve the cipher suite is to ask – is this server patched with latest security and .NET patches?

After all this, in my example, we confirmed that simple step was assumed, and inaccurate.

 

 

 

 

References
36871 event https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2012-R2-and-2012/dn786445(v=ws.11)

SCHANNEL events https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2012-R2-and-2012/dn786445(v=ws.11)

SChannel error codes https://docs.microsoft.com/en-us/windows/win32/secauthn/schannel-error-codes-for-tls-and-ssl-alerts

SChannel events https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2012-R2-and-2012/dn786445(v=ws.11)

SSL errors https://www.experts-exchange.com/questions/28996780/event-id-36871-Schannel.html

Troubleshooting https://docs.microsoft.com/en-us/iis/troubleshoot/security-issues/troubleshooting-ssl-related-issues-server-certificate

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