Snort mailing list archives

Re: preprocessors and thresholding broken with latest rules tarball?


From: JJC <cummingsj () gmail com>
Date: Fri, 20 May 2011 09:14:57 -0600

Eoin,

Thanks for the update and followup!  I'll have a look at the bug that you
just submitted and make the apt changes.

JJC

On Fri, May 20, 2011 at 8:50 AM, Eoin Miller <
eoin.miller () trojanedbinaries com> wrote:

On 5/20/2011 7:54 AM, carlopmart wrote:

On 05/19/2011 11:15 PM, Eoin Miller wrote:

So I guess there are two issues discovered here.

Snort:
=========================================
Still generates alerts despite threshold.conf settings for preprocessors
if the preproc_rules/*.rules file is loaded up inside of the
snort.rules. I don't know how or why this would start happening now. Or
why there are now preprocessor rules located in two locations, compiled
into the code (I assume?) and also in a seperate rules file. Would this
cause double alerting or something? Why did this happen?


PulledPork:
=========================================
Does not allow you to specify the disabling of the files inside of the
VRT tarball for the preproc's:
   - preproc_rules/decoder.rules
   - preproc_rules/preprocessor.rules
   - preproc_rules/sensitive-data.rules

I have tried including sensitive-data.rules inside of the ignore= line
of pulledpork.conf, but the file still gets included into the
snort.rules output.


-- Eoin

 This is the same problem that I have reported some weeks ago without
response:


http://groups.google.com/group/snortusers/browse_thread/thread/b7692ecee12bce77/19ae04f0ce59fc75?lnk=gst&q=Snort+decoder+alerts+are+fired+when+are+disabled+in+config+file#19ae04f0ce59fc75
(last message).

 I think I may have figured out the issue with pulledpork not allowing you
to ignore the specific files if you just supply the name of them. As it
looks through the @ignore array, it looks for values you have supplied that
contain .preproc inside of them. Only these values will replace .preproc
with .rules for files located in the preproc_rules/ subdirectory of the
extracted tarball.

---SNIP---
       elsif ( $_ =~ /\.preproc/ ) {
           print "\tIgnoring preprocessor rules: $_\n"
             if ( $Verbose && !$Quiet );
           my $preprocfile = $_;
           $preprocfile =~ s/preproc/rules/;
           $tar->remove("preproc_rules/$preprocfile");
       }
---SNIP---

So if you add the following to your ignore= list in your pulledpork.conf
file, they *should* no longer be in your rules file (except there is a bug
in this code, so keep reading):
decoder.preproc,preprocessor.preproc,sensitive-data.preproc

However, there is a bug in this above code that is borking everything up.
If you just replace the string "preproc" with "rules" and one of your files
you are trying to disable is "preprocessor.rules" and you are specifying the
element "preprocessor.preproc" into the ignore array; then when you apply
this search replace to the "preprocessor.preproc" then you end up with
"rulesessor.rules" as the file name that pulledpork tries to remove. Since
that file doesn't exist, then you end up still having all the preprocessor
rules dumped into your snort.rules file. To fix this, update the below line
inside of pulledpork.pl:

From:
           $preprocfile =~ s/preproc/rules/;

To:
           $preprocfile =~ s/\.preproc/\.rules/;


This fixes the bug and allows you to keep using pulledpork.pl in a
completely automated fashion. Still some weirdness going on here though.
Can't figure out why this only startered happening to me after I got SO
rules working or did VRT just start adding all of these into the tarball
with their last release? Why does Snort's threshold.conf file get ignored if
the preprocessor rule is in the rules file?

-- Eoin

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