On Wed, Jul 4, 2018 at 11:07 AM, Stephen Farrell <stephen.farr...@cs.tcd.ie> wrote:
> > Hiya, > > Just on this bit... > > On 04/07/18 18:20, Eric Rescorla wrote: > > The structure started a bit simpler and got new features to > > deal with new issues. Specifically: > > > > - The checksum is intended to deal with corruption > > I'm not sure I see why that's needed, but I believe you if > you say it might help with some home routers. (Though I'd > also be interested in information/citation about the > details of the problems seen there.) > Sure. that's a fair question. Kazuho proposed this, so I'd be interested in his view. > > > - The keys and cipher suites seem kind of mandatory > > Yep. OTOH, given we need to support >1 value for the RR, if > mostly people just need one key+CS per-RR, it may be possible > to use multiple RRs to provide additional keys/CSes. (If most > uses would have a variable number of keys/CSes then I agree > the current structure is better.) > I think it's bad to provide multiple options that aren't coupled together. Moreover, from the perspective of the TLS stack, it's actually easier to have them all bundled. > - I think it's clear what not_before and not_after are for. If you have > > more concrete feedback about better ways to do that, we'd welcome > > this. > > With not_before/not_after (and the TTL) there'll need to be some > consideration of the various overlaps, which has been a source of > bugs and ops screw-ups in other scenarios. I also don't like the > forced expiry of not_after - people will just put in 2038 all over, > Note that this is 64 bits, so you can go far past 2038 :) > - Extensions is just there because we're trying to be safe. > > Sure, but I hope we consider dropping 'em if there's no need. > New RRTYPEs could always be used for extensions (if new RRTYPEs > are cheap, that is:-) > I would not be in favor of this. It's trivial to parse and ignore. > (thus making the internal structure opaque to DNS). Removing > > things won't make it much smaller because a big chunk of > > the data is in the keys. For instance, in my implementation, > > the object is 70 bytes long and 34 bytes of that is key (X25519) > > and 8 bytes is cipher suite (each of these has 2 bytes of length). > > That's good. But I was more thinking about how friendly this > would be for the DNS admin folks. One thing I like about TLSA > and CAA is that (for my use-cases:-) I can just cut'n'paste > the values into zone files and they'll be good until a CA root > key or name changes, which is pretty rare and would be widely > advertised ahead of time. > > With RRSIGs and similar, I can also easily inspect values by > just looking at zonefiles and/or using dig, which is helpful > for me at least. But I don't have to deal with large zones so > that kind of inspection may not be of much use to larger > operators. So, I'd defer to real DNS server folks on whether > or not being able to directly view the internals of ESNIKeys > encoding makes any difference. > > All that said, I did just suggest adding in the dummy sni > value:-) So I mostly think if this goes ahead (as I hope it > does), we spend a bit of time considering the above issues > before we're done. > Sure, that seems reasonable. I think you are getting to something important here: my philosophy here is that this should be a more or less opaque blob which you provide to the TLS stack. So I'm optimizing for what's convenient for that. I can understand that others might feel differently. -Ekr > Cheers, > S. > >
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