Hi, Ole, On 04/18/2017 12:44 PM, otr...@employees.org wrote: >>> The ping pong attack is mitigated in RFC4443. >> >> I must be missing something.. what does RFC4443 have to do with this? A >> ping pong attack does not require the attack packets to be ICMPv6 echo >> requests... > > https://tools.ietf.org/html/rfc4443#section-3.1 > One specific case in which a Destination Unreachable message is sent > with a code 3 is in response to a packet received by a router from a > point-to-point link, destined to an address within a subnet assigned > to that same link (other than one of the receiving router's own > addresses). In such a case, the packet MUST NOT be forwarded back > onto the arrival link. > > Most implementations I'm aware of now implement this.
Why wouldn't an attacker send *any* packet meant for the p2p link, but that not correspond to the address of any of the two endpoints? i.e., I don't see the need to focus on a specific kind of packet... I guess I'm missing something? >>> I am not convinced there is justification that this document should >>> recommend /127 for "security reasons". >> >> Besides ping-pong, there's NCE. While I do agree that the real solution >> to the above two issues is *not* to use a /127, this document being an >> operational one, I can see why the authors may want to recommend /127. > > Neighbour cache exhaustion has to be mitigated anyway. > On router-router links that's a relatively simple problem compared to > links with hosts. > I'm still not convinced that /127 should be recommended over any of the > other addressing models for router to router links. > /64, link-local only, /128s. How do you mitigate it when the implementation does not limit the number of NC entries? (i.e., operationally) >>> Section 2.2: >>> I am not sure that extension headers are one of the most critical >>> differentiators between IPv4 and IPv6. IPv4 had variable length >>> options... >> >> The packet structure does make a big difference. For instance, it's >> trivial to find (in IPv4-based packets) the upper layer protocol type >> and protocol header, while in IPv6 it actually isn't. > > It isn't supposed to be. Which for people running networks translates to "broken by design". >>> Section 2.3.2: >>> Consider Secure DHCPv6? >> >> Question: is that doable? (i.e., widely supported) > > You expect this document to have a short lifetime? > (Which I guess is the exact problem of publishing this type of advice as > an IETF RFC). I didn't even think about the lifetime. But I wouldn't suggest a mitigation that isn't doable at the time of publication. If Secure DHCPv6 is not widely implemented, this would be like saying "secure ND with SEND" ("yeah... in your dreams!"). FWIW, I do support this document. I think it contains valuable and much needed information. >>> Section 3.1: >>> In general update references. e.g. ipv6-eh-filtering is outdated. >>> I question referencing opsec-ipv6-eh-filtering. It has wrong and >>> outdated advice. E.g. on section of HBH header. >>> The advice in ipv6-eh-filtering is essentially to ossify the network. >> >> Have you read the I-D? Because the I-D boils down to: "pass all EHs >> unless they are known to be very harmdful". > > Hmm, I see the latest opsec version has put this right, thanks. > I must have read the earlier individual draft, cause that said "should > drop HBH". We've certainly been improving th document as part of the process. Thanks! Cheers, -- Fernando Gont SI6 Networks e-mail: fg...@si6networks.com PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492 _______________________________________________ OPSEC mailing list OPSEC@ietf.org https://www.ietf.org/mailman/listinfo/opsec