[Snort-devel] [PATCH]: Snort manual fixes for 2.9.1-beta

Russ Combs rcombs at ...402...
Wed Jun 15 11:14:15 EDT 2011


Thanks, we'll try to address these before release.

On Wed, Jun 15, 2011 at 2:19 AM, <Joshua.Kinard at ...3108...> wrote:

>
> Hi snort-devel,
>
> I've worked up three additional patches for the Snort manual to clarify
> two little details and fix a typo.
>
>
> snort-291beta-manual-fast_pattern-no_http_method.patch:
>
> Per discussion earlier on the mailing list and the latest entry in the
> ChangeLog, 'http_method' is no longer compatible with the 'fast_pattern'
> modifier.  This patch annotates 'http_method' to indicate this.  It also
> adds a mention to 'fast_pattern'.
>
> It also removes the following line:
> "Note, however, that it is okay to use the fast pattern modifier if
> another http content modifier not mentioned above is used in combination
> with one of the above to modify the same content."
>
> I cannot ever foresee such a scenario where one would use two distinct
> HTTP modifiers on the same content:
> (content:"foobar"; http_header; http_client_body;)
>
> This lines up with the change I submitted a few months ago to clarify
> 'uricontent', which states that 'uricontent' is not compatible with any
> of the other HTTP modifiers.
>
> I've done scans through the VRT rule set as of April 2011 and the
> Emerging Threats all-rules files, and cannot find this particular
> construct in use (but I did not do thorough scans).
>
>
>
> snort-291beta-manual-flowbits-with-tag.patch:
>
> The example under 'tag' that describes using two 'flowbits' keywords to
> allow tag to work correctly need a clarification of /where/ to place
> them.  The example currently reads:
>
> alert tcp any any <> 10.1.1.1 any (flowbits:isnotset,tagged;
> flowbits:set,tagged; tag:host,600,seconds,src;)
>
> This does not offer any guidance on where to place any payload detection
> keywords.  Before?  After?  The patch fixes this and changes this
> example to:
>
> alert tcp any any <> 10.1.1.1 any (flowbits:isnotset,tagged;
> content:"foobar"; nocase; flowbits:set,tagged;
> tag:host,600,seconds,src;)
>
> The idea being the first flowbit will check that the 'tagged' state is
> set, and if not, allow the content check to procede BEFORE setting the
> tagged state.  That way, if the content check fails, the flowbit state
> will not get set on that flow (incase a further packet down the line has
> the content being searched for).  If the content check succeeds, then
> the 'tagged' state is set so that subsequent alerts will not reset the
> tagging.
>
>
>
> snort-291beta-manual-tag-flags-example.patch:
>
> This is a minor typo fix just after the 'tag' fix above:
>
> alert tcp any any -> any 23 (flags:s,CE; tag:session,10,seconds;)
>
> The 's' in 'flags' is converted to uppercase.
>
>
>
> Cheers!,
>
> --J
>
>
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