Re: [TLS] TLS1.3 + PSK with multiple identities
Eric Rescorla <ekr@rtfm.com> Mon, 19 September 2016 12:48 UTC
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From: Eric Rescorla <ekr@rtfm.com>
Date: Mon, 19 Sep 2016 05:46:09 -0700
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To: David Woodhouse <dwmw2@infradead.org>
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Subject: Re: [TLS] TLS1.3 + PSK with multiple identities
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On Mon, Sep 19, 2016 at 5:26 AM, David Woodhouse <dwmw2@infradead.org> wrote: > On Mon, 2016-09-19 at 04:41 -0700, Eric Rescorla wrote: > > > Do we care that the '0x00 0x12' bytes on my third line above are > > > entirely redundant on the wire? Or have I interpreted it wrong? > > > > Not enough to fix it, this is just the way TLS rolls. > > An interesting contrast to Nikos's observation that using the index in > the response is "used nowhere else in TLS" — which he could have > phrased using similar words. But I suppose in that case you're saving a > *lot* more than two bytes in the ServerHello, so it makes sense to > deviate from "the way TLS rolls" :) > Yes. > > Is there no way the PSK identities for session resumption could be made > > > smaller? Of the data which RFC5077 suggests that we put into a session > > > ticket (and thus the PSK identity), is there *none* of it which could > > > be sent later in a ClientKeyExchange packet? > > > > No. Also, there isn't a CKE record in TLS 1.3. All information needed to > derive > > the key needs to be in the CH. > > Well, that was kind of my point. Information needed to derive the *key* > needs to be in the ClientHello. > > But if it's auxiliary information which isn't actually *needed* to > derive the key or to select which {identity to use,session to resume}, > then perhaps the client could be required to supply it afterwards. > You need the complete ticket to make sensible decisions. And then the client only needs to supply one copy of it for the > identity which the server actually selected, not one for *each* > identity which was being offered by the client. > We're most likely going to allow only on PSK anyway. I share Nikos's concern about using the PSK identity for two completely > different types of identifiers — especially given that one type has > historically been defined as UTF-8 text, while the other is binary. > > The reason I care about this right now is that we're looking at using > PSK to bootstrap a DTLS connection in the context of an SSL VPN, > currently using DTLS 1.2 and draft-jay-tls-psk-identity-extension. I recommend against this: I very much doubt that we are going to adopt this draft in TLS. So it would be useful to have some clarity on the UTF-8 requirement > from RFC4279, and whether it's being completely abandoned with TLS 1.3. > It's being abandoned. PR welcome. -Ekr
- Re: [TLS] TLS1.3 + PSK with multiple identities Nikos Mavrogiannopoulos
- Re: [TLS] TLS1.3 + PSK with multiple identities Ilari Liusvaara
- [TLS] TLS1.3 + PSK with multiple identities Nikos Mavrogiannopoulos
- Re: [TLS] TLS1.3 + PSK with multiple identities David Woodhouse
- Re: [TLS] TLS1.3 + PSK with multiple identities Eric Rescorla
- Re: [TLS] TLS1.3 + PSK with multiple identities David Woodhouse
- Re: [TLS] TLS1.3 + PSK with multiple identities Eric Rescorla
- Re: [TLS] TLS1.3 + PSK with multiple identities David Woodhouse
- Re: [TLS] TLS1.3 + PSK with multiple identities Eric Rescorla
- Re: [TLS] TLS1.3 + PSK with multiple identities David Woodhouse
- Re: [TLS] TLS1.3 + PSK with multiple identities Eric Rescorla
- Re: [TLS] TLS1.3 + PSK with multiple identities David Woodhouse
- Re: [TLS] TLS1.3 + PSK with multiple identities Eric Rescorla
- [TLS] application-specific identifier was: TLS1.3… Nikos Mavrogiannopoulos
- Re: [TLS] TLS1.3 + PSK with multiple identities Olivier Levillain
- Re: [TLS] TLS1.3 + PSK with multiple identities Andreas Walz
- Re: [TLS] TLS1.3 + PSK with multiple identities Hannes Tschofenig