[Snort-devel] IPv6 rule options syntax

김무성 kimms at ...3084...
Thu May 5 21:49:27 EDT 2011

Let's think tunneled packet.

The packet has two IP. (IPv4 and IPv6)
So there are two value of ttl(HL).
Where field is TTL option matched?
But, if IDS/IPS is on below Router, Maybe there is a IP.

RA packet have a two itype. (icmpv6 type and icmpv6 option type)
One thing is itype:134. This means RA packet.
Other thing is itype:3. This is icmpv6 option's type. This means prefix information.
This will be created a new option. Ex) iopts_type:3

-----Original Message-----
From: Steven Sturges [mailto:ssturges at ...402...] 
Sent: Wednesday, May 04, 2011 9:59 PM
To: Martin Schütte
Cc: snort-devel at lists.sourceforge.net; 김무성
Subject: Re: [Snort-devel] IPv6 rule options syntax

Martin is correct.

Snort does not expose all of the values from the IPv6 extension
headers via rule options, however where there is an IPv4 equivalent,
we do leverage those.

1) Hop limit is akin to the ttl value in the IPv4 header, so you can use 
the ttl rule option for that.

2) For ICMP, Snort handles both IPv4 and IPv6 versions of ICMP the same

Other examples are the fragmentation offset, fragmentation ID, and
traffic class, which map to the offset, id, and tos fields of IPv4.


On 5/4/11 7:33 AM, Martin Schütte wrote:
> On 05/04/11 07:30, 김무성 wrote:
>> Are there any options for IPv6 which already created or will be created.
>> Example) IPv6 Hop Limit ->  HL:50;
>> Example) ICMPv6 type ->  itype6:134
> There are no IPv6 specific options (yet?).
> But nearly all fields are mapped to their IPv4 counterparts, so your
> examples are expressed with the rules:
> alert ip icmp any ->  any any                           \
>      (msg:"IPv6 ICMP Router Advertisement"; itype:134;  \
>      classtype:icmp-event; sid:2000001; rev:1;)
> alert ip any any ->  any any                            \
>      (msg:"TTL or Hop Limit = 50"; ttl:50;              \
>      classtype:attempted-recon; sid:2000002; rev:1;)
> BTW, I am currently writing an IPv6 preprocessor to detect more issues
> and to track autoconfiguration. It is not released yet, but feel free to
> contact me off list.
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