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

[Brian E Carpenter <[e-mail]>]

On 26-May-23 08:33, Manfredi (US), Albert E wrote:
> -----Original Message-----
> From: Tom Herbert <[e-mail]>
> 
>> It's more than a preference to have host security, it is an absolute requirement that each host provides security for its applications and users. This requirement applies to SmartTVs, SmartPhones, home computers, and pretty much all the several billion end user devices connected to the Internet. No host device would ever assume that the network consistently provides any adequate level of security, for real security we need to assume that the host is the first and last line of defense (i.e. zero trust model).
> 
> I could not agree more, Tom. So, as Fernando and others have said, the impulse is to block everything coming in from the Internet that you figure you don't need **right now**. Such as weird complicated header extensions.

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 strongly suspect that there is no universal way of avoiding that tussle. Not every new feature has backing from Google.

> 
> 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. 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 headers.

> 
> 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. And it would be exactly the same for IPvN where N>6.

    Brian