Re: [v6ops] [EXTERNAL] Re: [IPv6] [OPSEC] Why folks are blocking IPv 6 extension headers? (Episode 1000 and counting) (Linux DoS)

[Andrew Alston <[e-mail]>]

Speaking strictly in my personal capacity wearing no hats.

I sit on both sides of this fence - there are many extension headers that I wouldn’t block - there are others that I certainly will - mainly because they represent a fundamental security risk my view.

So that leaves me with a choice - permit the headers through my network because people wish to use them - or filter them to protect myself and my customers. I choose in the case of certain headers (srh would be top on that list - for all the reasons detailed at https://mailarchive.ietf.org/arch/msg/v6ops/GbWiie-bjQ_Bp1JKB1PlDh_fPdc/) to err on the side of caution and filter.

Keep in mind that what may seem like an arbitrary decision may well be driven my conscious decision that is simply not as public as some would like.

I point out that the standards mandate support of certain things - but they do not - and cannot - mandate how operators choose to run their networks. If I feel something poses a security threat - or if I know for a fact it does - I'm gonna block it all day long.

Just my thoughts

Andrew

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________________________________
From: v6ops <[e-mail]> on behalf of Manfredi (US), Albert E <[e-mail]>
Sent: Sunday, May 28, 2023 12:16:09 AM
To: Tom Herbert <[e-mail]>
Cc: [e-mail] <[e-mail]>; [e-mail] <[e-mail]>; [e-mail] <[e-mail]>
Subject: Re: [v6ops] [EXTERNAL] Re: [IPv6] [OPSEC] Why folks are blocking IPv 6 extension headers? (Episode 1000 and counting) (Linux DoS)

-----Original Message-----
From: Tom Herbert <[e-mail]>

> Correct, that's the fundamental problem. When public network providers apply ad hoc protocol filtering, that limits the capabilities and opportunities to provide value to the users. For instance, if someone came up with a new transport protocol that improves user security by 10x, we couldn't deploy it because some network providers would block it. So the very security policies that are ostensibly in place to protect the users can actually harm them.

Potentially, I agree. Problem is, each of the players has to determine what is an acceptable risk. If an ISP wants to keep his infrastructure secure, he's got the responsibility to make it so, as best he can. He can’t trust mechanisms that either don’t exist yet or that might introduce their own new vulnerabilities. Someone says, trust me, these extensions will be for your own good, and yet he is fully cognizant that those extensions could also be used in ddos attacks, he'll say thanks but no thanks. Maybe I'll let those through after we're satisfied with testing and experience.

> As for what constitutes the "the greater good", like pretty much everything else in IETF shouldn't that be something determined by "rough consensus"?

Yes, but unfortunately, that does not absolve the players of their own responsibilities. In matters of security, no one will blindly follow "rough consensus." We are 180 degrees from the Postel principle:

"Be conservative in what you do, be liberal in what you accept from others," is turned on its head, as we know. For system security, you cannot be liberal in what you accept from others.

> Even if the consensus were that extension headers need to be deprecated, to me that would be better than the current situation where we, specifically application and host developers, need to deal with a patchwork of anonymous and seemingly arbitrary network provider policies that degenerate the end to end services we can provide to users to rely only on least common denominator of protocols which we can only deduce by guess work.

I get your point completely. We don’t have an IETF dictatorship though, so what happens is that over time, smart people have to decide how best to do their jobs, given the realities of today. There is a lot of infrastructure flexibility, and apps, thought really cool when they were developed, that go unused for just this reason. Such as, you might be better off, in your network, to use proxy-MLD and to block PIM-SM. Same goes for some or even much of ICMP. It's the tussle Brian C talks about.

Bert

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