during our BlackHat US 2014 talk titled “Evasion of High-End IPS Devices in the Age of IPv6”, among others we discussed a Snort preprocessor rule (116:456) which, when enabled (not the case by default), triggers an alert when an IPv6 datagram with nine (9) or more IPv6 Extension Headers is used (such a header was used by us to evade Snort). However, we mentioned that:
In the “A Novel Way of Abusing IPv6 Extension Headers to Evade IPv6 Security Devices” blogpost I described a way to evade a high-end commercial IDPS device, the Tipping Point IDPS (TOS Tipping Point, Package 126.96.36.19936 and vaccine 188.8.131.5230 digital), by abusing a minor detail at the IPv6 specification. As I promised at the end of that blogpost, this is not the end. In this blogpost I am going to describe several new and different ways of evading another popular IDPS, an open-source one this time, Suricata.
As it is well known to the IPv6 enthusiasts, one of the most significant changes that IPv6 brings with it, apart from supporting a really huge address space, is the improved support for Extensions and Options, which is achieved by the usage of IPv6 Extension headers. According to RFC 2460, “changes in the way IP header options are encoded allows for more efficient forwarding, less stringent limits on the length of options, and greater flexibility for introducing new options in the future.” So, by adding IPv6 Extension headers, according to the designers of the protocol, flexibility and efficiency in the IP layer is improved.
We had a great day today at the Troopers IPv6 Security Summit. Good conversations, quite some technical discussion and a prevailing overall will to improve actual IPv6 network security.
Here are the slides of Antonios Atlasis’ great talk on extension headers and these are some of his accompanying Python/Scapy scripts. My own presentation on high secure IPv6 networks can be found here. The slides of the real-world capabilities workshop will not be published yet as we first have to discuss some stuff with a vendor.
Looking forward to tomorrow, have a great evening everybody
This illustrates once more the huge security problems related to IPv6 extension headers and IPv6 fragmentation and in particular to the combination of those two. Antonios Atlasis will discuss those in detail at the event (see his announcements here and here). It would be really helpful if major security products had some simple global properties/command line parameters/checkboxes like “drop all fragmented IPv6 packets”, “drop all IPv6 packets with extension headers” (ok, maybe “drop all IPv6 with multiple extension headers”; besides HBH in MLD packets – which shouldn’t traverse L3 hops – we don’t see too much ext headers in production networks anyway, as of early 2013) or at least “drop all packets with a combination of fragmentation and ext headers other than the fragmentation header”. But this will probably need another some years to show up and unfortunately we’ll probably see such problems still for a very long time…
Again, you should see Antonios’ presentations on this stuff (I had the chance to look at them already, it’s great research with scary results). For those of you who can’t join us: they’ll be made available for download after the conference.
Looking forward to an active discussion of these topics at the IPv6 Sec Summit,
IPv6 introduces a lot of new features and consequently, a lot of new capabilities. Obviously, the most significant of them is the huge address space that it offers. However, this is not the only one. IPv6 also introduces the use of the IPv6 Extension Headers. The IPv6 header has been considerably simplified in comparison with IPv4 one. On the other hand, the IPv6 Extension Headers, not only do the “job” of most of the fields which were removed from the main header, but, additionally, they add many more. However, any new “technology” creates new attack opportunities and a “new” protocol, such as IPv6 could not be an exception, especially since its design and implementation is more complicated than it’s predecessor.