Minutes from last week's TLS meetings in Prague are now online [1]. They're also copied at the end of this message. Please have a look and send any issues to the list.
Many thanks to Richard Barnes and Robin Wilton for taking notes! Best, Chris, Joe, and Sean [1] https://datatracker.ietf.org/doc/minutes-104-tls/ ----- TLS working Group IETF 104 Monday, 25 March, 2019 Prague, CZ # Working Group Drafts ## TLS 1.3 Extension for Certificate-based Authentication with an External Pre-Shared Key - Russ Housley - Draft defines an extension to the TLS handshake, adding an optional parameter allowing the External PSK to be combined with EC(DHE) as secret inputs to the key schedule. - Watson Ladd: does this enable the sending of early data? - RH: No; explicitly stated to be out of scope in the draft. - ANO: formal review would be desirable. - Ekr: don’t think we should pass this until someone has implemented it. - RH: as the first slide notes, this is experimental. - one hand in response to question about implementations. - * Next Steps: additional review (probably WGLC). # Individual Drafts ## TLS Resumption across Server Name Indications for TLS 1.3 - Erik Sy - TLS 1.3 recommends against, but doesn’t give a good indication of what criteria to consider, or a signalling mechanism to say if the server supports Resumption. - Performance benefits, CPU time and elapsed time improvements may be valid criteria - TLS extension would be needed to signal that this option is available, e.g, a simple flag. - Privacy impact could be reduced by enforcing shorter session lengths. - Ekr: where should the extension go? - in the EE. Needs to be made clearer in the doc. - Ekr: should also be clear about whether resumption should require a fresh DNS request - Ekr: is a 1-bit flag really sufficient? - yes, otherwise would need to specify a list of values for which Resumption is OK, and that would make implementation harder. - Ekr: should TLS, in principle, define a general-purpose extension space rather than a bunch of specific flags? - Yoav Nir: 1-bit flag may introduce address space/scope clashes at the server, and different servers might have different requirements. Not a good idea to allow reconnection to “any server”. - Server identification could be aided by reference to the X.509 cert. - Viktor: recommends using a session ticket extension for this, not the handshake itself. - Viktor: shortening the acceptable resumption period, as proposed, is rational, but privacy implications probably need further examination. - 10 muinutes is a figure of merit. - Nick Sullivan: Where an X.509 cert has broad scope (across multiple servers), additional parameters may be needed to ensure Yoav’s concern isn’t an issue. Relying only on the -.509 cert makes unreasonable assumptions. ## Importing External PSKs for TLS - Christopher Wood - TLS 1.3 imposes restriction on PSK usage with hash functions; TLS 1.2 did not impose this restriction - so the resulting incompatibility (and potential for inappropriate use of PSKs) must be handled (ideally) without changing the key schedule. - Christian Huitema: working on a draft that generalizes DNS-SD technique for external PSK identifiers in TLS. - Jon Mattsson: question about using one hash algorithm to generate keys for use with another. - ANO: Does the PSK constitute a channel binding? Depending how the External PSK is generated, this and the Resumption issue may overlap. A subsequent session has no way of knowing how the previous session was established. - Ekr: reusing hashes as proposed is secure. [Discussion inconclusive, needs further examination]. - * No objections to adoption as a work item. Take to list. ## TLS Client Network Address Extension - Tommy Pauly - Purpose: NAT detection in secure transport protocols - Relates to these drafts specifying extensions: - TLS, draft-kinnear-tls-client-net-address - QUIC, draft-pauly-quic-address-extension - Wes H.: is this specific to NATv4? - it applies everywhere. - Wes H: Why is this a TLS-specific problem? - for QUIC, this is a transport handshake question. For TLS, it would be more complicated to put it elsewhere (?). - DKG: what would a client do with this information? - the only real purpose of this is to check that you’re not behind a NAT. - * Discussion moved to the list for timekeeping reasons. ## Using Identity as Raw Public Key in Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) - Haiguang Wang - Using Identity Based Signature exempts the server from having to maintain records of the binding between a raw public key and the entity presenting it. - * Next steps: ask to reserve specific code points for this mechanism to use in implementation and testing. Tuesday, 26 March, 2019 # Working Group Drafts ## Deprecating TLS 1.0 and 1.1 - TODO: update to deprecate DTLS 1.0 - Update to require NNTP to do the right thing - * Hearing no objection, headed for WGLC ## DTLS 1.3 - Issue 78 - we will say MUST limit amplification until the path is validated somehow. - - … and we will separately say that though there is a CID, there is not a migration piece - that is, endpoints don't send to new addresses in response to receiving valid records from those addresses. - Issue 72 - No change. - Implementation status - NSS, Mint, mbedTLS. ## Cert Compression - Add decompressed certificate to transcript? No. - * Will write up changes, then WGLC. ## Delegated credentials - * Ready for LC? Yes, most likely. ## ESNI - Current solution with PR#137 as an extension? Unclear from the room. - Will an ESNI RRType Diverge from the A/AAAA results? - [[lots of discussion, no resolutions]] # Individual Drafts ## OPAQUE in TLS 1.3 - We should wait for CFRG to opine. - Cisco has a use case, some possibility of web API? - * No action, due to novelty. ## Hybrid key exchange - Probably too early, given that research on combinations still active. ## CWTs in TLS / DTLS - Would need to restrict to PoP tokens. - * No action, due to novelty ## Fake SNI - Should be compared to earlier draft on attacks against SNI approaches. - * No action, due to novelty. _______________________________________________ TLS mailing list TLS@ietf.org https://www.ietf.org/mailman/listinfo/tls
