[Bro-Dev] [JIRA] (BIT-1238) High false-positive for application/x-tar signature

Brian O'Berry (JIRA) jira at bro-tracker.atlassian.net
Sat Oct 11 05:55:07 PDT 2014


    [ https://bro-tracker.atlassian.net/browse/BIT-1238?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18303#comment-18303 ] 

Brian O'Berry commented on BIT-1238:
------------------------------------

I guess more likely, any regular text file containing lines padded with at least 24 spaces after the 100th character will match, including a line of at least 124 spaces.  Or, lines padded with spaces followed by digits in the case of left-justified descriptions followed by right-justified integers.  Point being this pattern seems likely to match many text files, period, not just those in our environment.

> High false-positive for application/x-tar signature
> ---------------------------------------------------
>
>                 Key: BIT-1238
>                 URL: https://bro-tracker.atlassian.net/browse/BIT-1238
>             Project: Bro Issue Tracker
>          Issue Type: Problem
>          Components: Bro
>    Affects Versions: 2.3
>            Reporter: Brian O'Berry
>              Labels: file, mime, signature
>
> The following signature in base/frameworks/files/magic/general.sig frequently triggers on text files in our environment, and includes a strength value higher than GNU and POSIX tar signatures in libmagic.sig.
> {code}
> signature file-tar {
>     file-magic /([[:print:]\x00]){100}(([[:digit:]\x00\x20]){8}){3}/
>     file-mime "application/x-tar", 150
> }
> {code}



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