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

Fernando Gont <fgont@si6networks.com> Fri, 26 May 2023 15:04 UTC

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Date: Fri, 26 May 2023 17:04:28 +0200
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To: Brian E Carpenter <brian.e.carpenter@gmail.com>, "Manfredi (US), Albert E" <albert.e.manfredi@boeing.com>, Tom Herbert <tom@herbertland.com>
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Subject: Re: [IPv6] [v6ops] [EXTERNAL] Re: [OPSEC] Why folks are blocking IPv6 extension headers? (Episode 1000 and counting) (Linux DoS)
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On 25/5/23 23:13, Brian E Carpenter wrote:
[....]
> 
> It's perfectly fine if a host chooses to block incoming packets for any 
> reason whatever, including unknown extension headers. That's quite 
> consistent with the *network* allowing permissionless innovation.
> 
> The problem arises when any upstream intermediate node drops a packet 
> because it doesn't like it for some reason. There, you immediately 
> create the tussle between transparency and security, and I strore is no universal way of avoiding that tussle. Not 
> every new feature has backing from Google.

Since you mention Google... rumor has it that they block EHs. :-)



>> The ISP has its own concerns, to protect its network, but I, in my 
>> enterprise or household, have different concerns. I'm not going to 
>> trust the ISP's security mechanisms to provide my own security needs.
>>
>> Honestly don’t see how IPv6 is going to change that. Over time, 
>> perhaps, some specific extensions used out in the wild will be seen as 
>> crucially important to my enterprise or household, and maybe those 
>> will not be blocked. But "trust me, you must accept all these EHs"? 
>> More likely, those potential innovations will go unused and maybe will 
>> eventually be implemented in a different way.
> 
> A well-implemented host will not be troubled by unkown extension headers 
> or options.

Search for IPv6-related CVE's, and you'll probably find that the vast 
majority of them are associated with EHs.

IPv4 options were already a issue at the time -- and it just became much 
worse with EHs.


> If my "smart" TV isn't capable of ignoring unkown extension 
> headers, its vendor will have to give me my money back. I don't want my 
> ISP or my CE router to block any extension header.

You might care. How many other would care?




>> Security evolved as it did, over IPv4, for a reason, methinks.
> 
> There is really no difference between the story of IPv4 options and IPv6 
> extension headers, except that extensibility was a sales argument for 
> IPv6, so naturally people have tried to use them. 

The sales argument also argued that the packet structure led to improved 
packet processing performance. -- which has not been well connected with 
reality, though! :-)

Thanks!

Cheers,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
PGP Fingerprint: F242 FF0E A804 AF81 EB10 2F07 7CA1 321D 663B B494