[Snort-users] Snort doc error (?) - rule option not optional?

Ricky Huang rhuang.work at ...11827...
Fri Mar 8 12:19:38 EST 2013


Thank you YM and Russ, my response below.

On Mar 8, 2013, at 7:44 AM, Russ Combs <rcombs at ...1935...> wrote:
> 
> On Fri, Mar 8, 2013 at 3:38 AM, Y M <snort at ...15979...> wrote:
> As far as I understand, the -T validates only the conf file of snort, and not the rules. 
> 
> `snort -c snort.conf -T` validates the whole snort configuration.  Any included files, such as rules files, are validated as well.
>  
> A rule must have an sid; which uniquely identifies each rule, it is a requirement.
> 
> This is essentially true, but if you forget to include a sid, it will default to zero.  And if multiple rules have the same sid, the one with the highest revision will be used.
> 
> You will see "WARNING"s under "Initializing rule chains..." if any of that is going on when Snort starts up.


It was more than a warning - if I forgot to specify a SID, like so:
	alert ICMP any any -> $HOME_NET any (msg:"Shut this rule off, it works now";)

Snort *dies* on a *fatal error*:
	Initializing rule chains...
	ERROR: ./rules/rhuang.rules(1) Each rule must contain a rule sid.
	Fatal Error, Quitting..

Fatal error is not a Warning...

1) I am fine with SID being a requirement, it was just not mentioned in the documentation.  Again, http://manual.snort.org/node28.html, says:
	"Note that the rule options section is not specifically required by any rule, they are just used for the sake of making tighter definitions…"
therefore I claim this as an error in documentation as it could have had a clause:
	"If any options were provided, a SID will be a require field"

2) If it's true that -T validates all included files, why isn't something that causes a Fatal error caught?


Please keep in mind that I am a brand-new user to Snort, some things that are obvious to the pro's are not really so to me unless they're explicitly documented somewhere.


Thanks again to all those that have responded!


> 
> YM
> From: Ricky Huang
> Sent: 3/7/2013 3:24 AM
> To: snort-users at lists.sourceforge.net
> Subject: [Snort-users] Snort doc error (?) - rule option not optional?
> 
> Hi all,
> 
> According to the rule doc (http://manual.snort.org/node28.html), 
>> Note that the rule options section is not specifically required by any rule, they are just used for the sake of making tighter definitions of packets to collect or alert on (or drop, for that matter).
> 
> 
> So I created a rule,
>> alert ICMP any any -> any any (msg:"Shut this rule off, it works now";)
> 
> which is included by snort.conf
> 
> If I run snort in test mode,
>> snort -T -i igb0 -u snort -g snort -c /usr/local/etc/snort/snort.conf
> 
> 
> it outputs success,
>> Snort successfully validated the configuration!
>> Snort exiting
> 
> Yet if I run it for production,
>> snort -i igb0 -u snort -g snort -c /usr/local/etc/snort/snort.conf
> 
> 
> it stops with the error,
>> Initializing rule chains...
>> ERROR: ./rules/myrules.rules(1) Each rule must contain a rule sid.
>> Fatal Error, Quitting..
> 
> If I change my rule to:
>> alert ICMP any any -> any any
> 
> 
> It validates and starts fine.
> 
> Here's my Snort built info:
>> # snort -V
>> 
>>    ,,_     -*> Snort! <*-
>>   o"  )~   Version 2.9.4 GRE (Build 40) FreeBSD
>>    ''''    By Martin Roesch & The Snort Team: http://www.snort.org/snort/snort-team
>>            Copyright (C) 1998-2012 Sourcefire, Inc., et al.
>>            Using libpcap version 1.1.1
>>            Using PCRE version: 8.31 2012-07-06
>>            Using ZLIB version: 1.2.5
> 
> 
> So I am wondering:
>   1) The optional section is not completely optional (?)
>   2)  If there's indeed a requirement, why doesn't -T catch it?
> 
> 
> Thanks!
> 
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