Re: [tcpinc] Adam Roach's Yes on draft-ietf-tcpinc-tcpcrypt-09: (with COMMENT)

[Adam Roach <[e-mail]>]

On 11/9/17 08:16, Kyle Rose wrote:
> On Thu, Nov 9, 2017 at 10:11 AM, Adam Roach <[e-mail]> wrote:
>> On 11/8/17 19:45, Mirja Kuehlewind (IETF) wrote:
>>> That’s not true. This is to cover the case where the packet got corrupted on
>>> the path, thus hopefully the retransmission will decrypt correctly.
>> So, to be clear, you're talking about packet corruption that happens to
>> produce a valid checksum, right? If that's the reasoning here, the authors
>> probably want to include that rationale in the document.
> Mirja's is my interpretation, as well.
>
> Off-path attackers wouldn't be able to sent segments with the right
> sequence number with high probability, so it's unlikely that this is a
> DoS vector; but giving implementations the option of simply dropping
> segments for which the authenticity check fails is not likely to cause
> recurring timeout problems for correct implementations.

Yes, and you're giving implementors options here without really 
explaining why -- which means they're probably just going to pick one 
randomly. Adding text that gives some notion about why one might choose 
one option over the other would allow them to make an informed choice 
rather than a random one.

Again, this remains a suggestion and not a blocking comment. You can 
feel free to proceed with the document as-is.

/a