Tag: IPv6

Breaking
by Enno Rey

Evasion of Cisco ACLs by (Ab)Using IPv6 & Discussion of Mitigation Techniques

This is a guest post of Antonios Atlasis.

During our blogpost regarding DHCPv6 Guard evasion, one of the side-effects was that Access Control Lists (ACLs) configured to block access to UDP ports 546 can be evaded by abusing (again) IPv6 Extension headers. Having that in mind, we decided to check the effectiveness of Cisco IPv6 ACLs under various scenarios. Our goal was to examine whether the IPv6 ACLs of Cisco routers can be evaded, as well as under which conditions this can take place. To this end, several representative scenarios from enterprise environments or other potential ones are examined.

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Building
by Enno Rey

Evaluation of IPv6 Capabilities of Commercial IPAM Solutions

Originating from a customer IPv6 deployment project, in early 2014 we defined a number of requirements as for the IPv6 capabilities of IPAM solutions, with a certain focus on security-related requirements (due to the specific environment of the project). We subsequently performed a practical evaluation of several commercial solutions, based on documentation, lab implementation and vendor communication.

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Events
by Christopher Werny

Observations from the Cisco Live Europe Wifi Infrastructure

Given that Enno and I are network geeks, and that I am responsible for setting up the Troopers Wifi network I was curious which components might be used at Cisco Live and which IPv6 related configuration was done for the Wifi network to ensure a reliable network and reduce the chatty nature of IPv6. Andrew Yourtchenko (@ayourtch) already did an amazing job last year at Cisco Live Europe explaining in detail (at the time session BRKEWN-2666) the intricacies of IPv6 in Wifi networks, and how to optimize IPv6 for these networks. He was also a great inspiration for me when setting up the Troopers Wifi network a couple of weeks later. Thank You!

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Building
by Enno Rey

How To Configure Snort to Stop IPv6 Evasion Attacks

This is a guest post from Antonios Atlasis.

Hi all,

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:

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Building
by Enno Rey

DHCPv6 Guard: Do It Like RA Guard Evasion

Or: When Cisco ACL Can Count Up to Five 🙂

This is a guest post by Antonios Atlasis.

Hi all,

RA Guard Evasion is well-known in the IPv6 “circles”; there is RFC 7113 Advice for IPv6 Router Advertisement Guard (RA-Guard) and many interesting blog-posts like this one here, here, and this excellent write-up here that discuss this issue.
Moreover, as Jim Smalls states in his comprehensive “IPv6 Attacks and Countermeasures” presentation given at the North American IPv6 Summit 2013, DHCPv6 Guard or a corresponding IPv6 ACL can stop a DHCPv6 Rogue Servers, but (only?) for non-malicious/non-fragmented DHCPv6 packets (slide 35). However, at that time there wasn’t any known attack tool in the wild that had the fragmentation evasion built in.

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Building
by Enno Rey

Should IPv6 Packets With Source Address ::1 Be Processed When Received on an External Interface?

This is a guest post from Antonis Atlasis.

Most of you are probably aware of the recently discovered/-closed severe ntpd vulnerabilities (CVE-2014-9293, CVE-2014-9294, CVE-2014-9295, CVE-2014-9296, see also the initial ntp.org security notice). Some days ago the Project Zero team at Google published a blog post “Finding and exploiting ntpd vulnerabilities” with additional details. In this one they mentioned a seemingly minor but quite important detail: on a default OS X installation one of the built-in protection mechanisms of ntpd (that is the restriction to process certain packets only if they are sourced on the local machine) can easily be circumvented by sending IPv6 packets with a spoofed source address of ::1 (the equivalent to 127.0.0.1 in IPv4 which would be discarded by the kernel once received from an external source).

This brought up a number of more generic questions:

a) Should such packets having as source address the IPv6 loopback one be processed at all?
b) Which OSs process such packets?
c) How can we protect our systems from them?

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Building
by Enno Rey

IPv6 Hardening Guide for Linux Servers

We were recently approached by a customer asking us for support along the lines of “do you have any recommendations as for strict hardening of IPv6 parameters on Linux systems?”. It turned out that the systems in question process quite sensitive data and are located in certain, not too big network segments with very high security requirements.

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