[Bro-Dev] [JIRA] (BIT-1535) conn.log conn_state field or documentation is wrong

Justin Azoff (JIRA) jira at bro-tracker.atlassian.net
Wed Feb 10 11:40:00 PST 2016


Justin Azoff created BIT-1535:
---------------------------------

             Summary: conn.log conn_state field or documentation is wrong
                 Key: BIT-1535
                 URL: https://bro-tracker.atlassian.net/browse/BIT-1535
             Project: Bro Issue Tracker
          Issue Type: Problem
          Components: Bro
    Affects Versions: 2.4
            Reporter: Justin Azoff


There is an issue where the conn.log conn_state field will contain RSTR, which according to the documentation means "Established, responder aborted."

The problem that I notice is that I see log entries where conn_state is RSTR, but conn_history does not contain an 'h'.  Additionally, the resp_h is absolutely not running a service on resp_p and the orig_h is usually in the process of a tcp scan.

Here are the top frequencies of RSTR without an h over about a weeks worth of conn logs:

{code}
38193 RSTR      Fr
3662 RSTR       DFr
1801 RSTR       DFdrR
1248 RSTR       DRr
432 RSTR        DrF
232 RSTR        Far
128 RSTR        DdAFrR
79 RSTR DFadrR
64 RSTR DrR
58 RSTR DdAFarR
{code}

Compared to histories that did contain an h:

{code}
425398 RSTR     ShADadFr
204149 RSTR     ShADadFrR
156303 RSTR     ShADdFar
141795 RSTR     ShADadFRRr
105704 RSTR     ShADadfr
79697 RSTR      ShADadr
63493 RSTR      ShADaFr
51704 RSTR      ShADadFrrrr
42075 RSTR      ShADdar
37678 RSTR      ShADadfRr
{code}

I don't have a pcap for this, but I believe many of the weird connections are related to scans or backscatter.

I'm not sure if the code is wrong or the documentation is wrong, but I don't see how a fin+reset connection could be classified as established.

Also, One thing that would be a nice documentation addition is the answer to this question:

Given a conn.log entry, how do determine if there was a connection established?  I thought it would be if the state was in 'SF S1 S2 S3 RSTO RSTR', but RSTR is problematic...




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