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?"

 

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

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

 

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://technet.microsoft.com/en-us/library/dn786445(v=ws.11).aspx#BKMK_36871
SCHANNEL events https://technet.microsoft.com/en-us/library/dn786445(v=ws.11).aspx
SChannel error codes https://msdn.microsoft.com/en-us/library/windows/desktop/dd721886(v=vs.85).aspx
SChannel events https://technet.microsoft.com/en-us/library/dn786445(v=ws.11).aspx
SSL errors https://support.microsoft.com/en-us/help/305088/schannel-error-message-36871-when-receiving-an-ehlo-smtp-command
Troubleshooting https://docs.microsoft.com/en-us/iis/troubleshoot/security-issues/troubleshooting-ssl-related-issues-server-certificate

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