No "Client Key Exchange" in Client to Server comms
 
  
 
  
 
 
 
 
 
 
    
        
        asked Jul 14 '2  
 
 RESRobert gravatar image  
 
 
 
 
 
I'm working on an issue where a piece of Client software tries to set up a handshake with it's Server side.
In the correct scenario, there should be 4 lines:
 
     
  • TLSv1.2 Client Hello
    •  
  • TLSv1.2 Server Hello, Certificate, Server Key Exchange, Server Hello Done
    •  
  • TLSv1.2 Client Key Exchange, Change Cipher Spec, Encrypted Handshake Message
    •  
  • TLSv1.2 Change Cypher Spec, Encrypted Handshake Message
    •  
 
In the faulting scenario, there's only 2 lines followed by an ACK and a FIN, ACK:
 
     
  • TLSv1.2 Client Hello
    •  
  • TLSv1.2 Server Hello, Certificate, Server Key Exchange, Server Hello Done
    •  
  • TCP [ACK]
    •  
  • TCP [FIN, ACK]
    •  
 
On the Client side there's an MS Server 2012R2 OS.
The odd thing is, some of the same OS machines in the same region work fine.
 
I would appreciate any clue as to what could be the cause of this.
 
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Comments
Your bullet list doesn't indicate the direction (src, dst) of the messages, but I would guess that it's the client closing the connection because it doesn't like something in the server response.
grahamb gravatar imagegrahamb (
    
        Jul 14 '2
    )
It's a log we created on the server-side of the client-server setup.
Any "Client" is the src received by the "Server"  dst.
Any "Server" is the src sending it to "Client" dst.
I was afraid someone might reply that. I could really use some pointer as to what that "something" in the response could be. Even where to look further would be much appreciated.
RESRobert gravatar imageRESRobert (
    
        Jul 14 '2
    )
If it is the client closing the connection, then client logs, either OS (i.e. event viewer) or application logs might be the place to look.
grahamb gravatar imagegrahamb (
    
        Jul 14 '2
    )
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