As you may know, we published a whitepaper discussing the behavior of different operating systems once they receive IPv6 configuration parameters from different sources two years ago. At that time, the results were quite a mess. We were curious whether the situation is still so “dire” like two years ago. We fired up the lab, updated the tested operating systems and performed the tests again.
To summarize, at least in scenarios were only one router is involved, the results look way more consistent (even cross operating system) then two years ago. So we made progress on this front. Unfortunately, as soon as a second router is introduced into the segment it gets messy and the operating systems do show inconsistent behavior.
It is a pleasant surprise for many (us included) that Microsoft implemented support for the RDNSS (RFC 8106) option in Router Advertisements beginning with the Windows 10 Creators Update. Interestingly, I wasn’t able to find any official documents from Microsoft stating this. As we are involved in a lot of IPv6 related projects for our customers, the lack of RDNSS support for Windows and DHCPv6 for Android is a major pain point when implementing IPv6 in mixed client segments, as you need to implement both mechanisms to ensure that all clients do get the relevant network parameters. I won’t beat on the dead horse, but Microsoft’s decision is a huge step in the right direction and one can hope that one day Google finds a “compelling use case” to implement at least stateless DHCPv6 for Android.
Since BlackNurse was released on 10th of November, we asked ourselves whether this problem does also apply to ICMPv6 traffic. To answer this question, Christian Tanck (one of our students) build a lab with several firewall appliances. Kudos to him for testing and the following blog post.
Intro
On 10^(th) of November, 2016 the TDC Security Operations Center in Denmark published the BlackNurse Denial of Service Attack Report as an PDF download on their website and a blog post written by Erik Hjelmvik from NETRESEC. He was involved in the project by helping with the analysis of packet dumps, testing different systems, with ideas for test scenarios and at least inspired me with his blog post on how to build a test lab described later in this post. The attack on its own was discovered by the TDC analysts Kenneth B. Jørgensen and Lenny Hansson.
As you may have already noticed, Cisco released an urgent security advisory describing an IPv6 Neighbor Discovery DoS Vulnerability in several flavors of Cisco’s operating systems. Currently IOS-XR, XE and NX-OS are affected while ASA and “classic” IOS are under investigation. At first glance, it might look like yet another IPv6 DoS vulnerability. Looking closer, Cisco is mentioning an unauthenticated, remote attacker due to insufficient processing logic for crafted IPv6 NDP packets that are sent to an affected device. Following the public discussion about the vulnerability, it seems that these packets will reach the, probably low rate-limited, LPTS filter/queue on IOS XR devices “crowding” out legitimate NDP packets resulting in a DoS for IPv6 traffic, or in general a high CPU load as these packets will be processed by the CPU. More details are currently not available, but this might indicate the affected systems aren’t doing proper message validation checks on NDP packets (in addition to the LPTS filter/queue problem).
Troopers is (unfortunately) over. It was a blast (but I may be biased ;-))! After things have settled, I want to take the opportunity to reflect my thoughts and impressions on the IPv6-only WiFi we had deployed during the conference. To make sure that everybody is on the same page let’s start at the beginning.
In the last couple of years we had provided Dual-Stack connectivity on the main “Troopers” SSID but also had an additional IPv6-only SSID. This year we decided to spice things up and made the “Troopers“ SSID IPv6-only (with NAT64) while providing Dual-Stack connectivity on the “Legacy“ SSID. We wanted to get a feeling how many clients and applications can work properly in an IPv6-only environment. We intentionally didn’t announce it vastly beforehand, hoping that attendees would just connect to the main SSID without noticing anything. We were aware that some applications might expose issues but, as I said , we wanted to get a feeling to which degree problems actually occured.
today we want to examine the behavior of Cisco devices when they receive spoofed IPv6 Neighbor Advertisement packets from an untrusted system pretending to be the default router for the local segment. We start with a quick refresher how Cisco devices behave in the legacy (IPv4) world when they receive a spoofed broadcast ARP packet containing the IP address of the device but with a different MAC address, followed by a discussion of the corresponding behavior in the IPv6 world.
Enno and I spent the first day on Cisco Live Europe in Berlin today attending the “Advanced Practical Knowledge for Enterprise Deploying IPv6” technical breakout held by Tim Martin and Jim Bailey. It was a good breakout session, and thanks again Tim for the honorable mention of our work in your slides! We really appreciate it. Like last year, we were curious how the Wifi network was setup this year as I face a corresponding task for Troopers in March, with some major changes in comparison to the last years. The Wifi infastructure in Berlin looked very similar to the one from last year in Milan, we had the “standard” Cisco Live SSID as well as an IPv6-only (with NAT64 as translation mechanism) SSID. The standard SSID looked identical to last year with the exception that now the RA Throttling feature on the WLC was active from the beginning! Neither the M nor the O flag are set which means that my client has to use the legacy protocol to resolve AAAA records. As I am running Windows, it does not support RA option 25 but the option wasn’t included in the RAs anyway. The preference was configured to the default “medium”. One thing I noticed, but haven’t had a chance to ask Andrew Yourtchenko, was that for the legacy (IPv4) connection they use HSRPv2 as an FHRP protocol (indicated by the MAC address 00:00:0c:9f:f0:01 I received from the gateway) but for IPv6 I received Router Advertisements from two different MAC addresses (which both belong to Cisco, so I don’t think anyone sent spoofed RAs). I am curious about the reasoning for this approach 🙂
What i also encountered was that the Peer-to-Peer Blocking feature was apparently not enabled on the SSID as I was able to enumerate approx. 1600 active clients at the time. No worries, I haven’t done anything else, just was curious whether the feature was activated or not…
It’s me again with another teaser for an upcoming workshop at the IPv6 Security Summit. This one is a classic! If you happen to deploy IPv6 in your environment in the near future, but didn’t had the time to think about the security implications, this workshop is the right place to start.
We will start the workshop with a quick refresher of the core behavior of IPv6 to make sure that every attendee is on the same page. Before we start discussing and demonstrating various IPv6 attacks, we dive into (a little more abstract) topic of why IPv6 security actually isn’t that easy to implement. We will continue with IPv6 attacks targeted at the local link. Rafael and I will introduce commonly used IPv6 attack tools as well as performing various attacks in a dedicated lab environment. Every attendee is encouraged to participate in these exercises. We will provide you with the necessary tools; you just have to bring a laptop with (ideally) Linux installed. We will prepare some virtual machines including VMware Player in case your corporate laptop runs Windows.
today I want to talk about OSPFv3. I won’t cover the glory details of OSPFv3, there are smarter guys than me out there who did that already 😉 and there are great resources to familiarize yourself with the protocol. However, it should be noted that OSPFv3 is not only OSPF for IPv6, OSPFv3 brought some major enhancements compared to OSPFv2. Wouldn’t it be cool to benefit from the enhancements in the IPv4 world as well?
Today I want to give you a little teaser about my upcoming talk at the IPv6 Security Summit about First-Hop-Security on HP devices. In the past I presented on about First-Hop-Security in the Cisco realm and in virtualized environments. Until recently, Cisco was mostly the only vendor who had a sufficient implementation of various IPv6 security features on their access-layer switches, but HP closed the gap considerably and it’s time to have an in-depth look at their implementation of those features.
