[Bro-Dev] [JIRA] (BIT-1240) TCP gaps inserted in wrong place

Jimmy Jones (JIRA) jira at bro-tracker.atlassian.net
Sat Sep 6 13:46:07 PDT 2014

Jimmy Jones created BIT-1240:

             Summary: TCP gaps inserted in wrong place
                 Key: BIT-1240
                 URL: https://bro-tracker.atlassian.net/browse/BIT-1240
             Project: Bro Issue Tracker
          Issue Type: Problem
          Components: Bro
    Affects Versions: 2.3, git/master
         Environment: CentOS 6
            Reporter: Jimmy Jones
         Attachments: get-hole1.trace

Using attached test file, I tried using the file analysis framework to extract out the payload, which is a copy of one of the bro testcases but with a packet removed.

However the extracted file has nulls padded at the beginning, but they should be at offset 1448. Looking at what happens, the gap is signalled to File::Gap before the data is received in File::DataIn, which calculates the offset to write the payload by adding the seen bytes to the missing byte count. Should gaps always be signalled in order with the data - this also affects users of content_gap, who would receive the data and hole "out of order"?

Used the following bro script:

event file_new(f: fa_file)
  Files::add_analyzer(f, Files::ANALYZER_EXTRACT, [$extract_filename=f$id]);

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