Hi all, This is a "preliminary" review only because there's some strangeness relating to the Updates: (and Obsoletes:) headers, and any changes there would make me need to go and recheck the relationship of this document to the ones listed. So, I haven't done any of that yet, in an attempt to only have to do it once.
Specifically, there's skew between the list of documents updated in the top header and the list in Section 1.1. Evern more annoyingly, the (tools) HTML version seems to be missing some numbers from the document header, that are present in the TXT version. (Henrik is going to take a look, per https://mailarchive.ietf.org/arch/msg/tools-discuss/Maeh0f_WfOy5sfnGQpwGPs_sYcU .) Additionally, Section 1.1 lists some RFCs that "have been obsoleted", but there is no "Obsoletes:" header at the top of the document. I think nits is right about references (square-bracketed "[RFC6347]") in the Abstract; we should change those to normal textual (parenthesed "(RFC 6347)") before IETF LC. Some other notes from a quick pass over the main text (though I'll probably read it again once the above are addressed) follow. Section 1 It feels a little backwards for a "primary technical reason" to deprecate a protocol version being that "at least one widely-used library has plans to drop [it]". I do appreciate that we give discussion about what we intend "deprecation" to mean and for whom -- thank you for that! Section 2 TLS 1.3, specified in TLSv1.3 [RFC8446], represents a significant change to TLS that aims to address threats that have arisen over the years. Among the changes are a new handshake protocol, a new key derivation process that uses the HMAC-based Extract-and-Expand Key Derivation Function (HKDF), and the removal of cipher suites that use static RSA or DH key exchanges, the CBC mode of operation, or SHA-1. The list of extensions that can be used with TLS 1.3 has been reduced considerably. While it's true that the initial list of extensions usable with TLS 1.3 is smaller than the list of extensions usable at TLS 1.2 taken at the same time, it's also true that the requirements for allocating a new extension codepoint have been reduced dramatically. So I think I'd say that this reflects not a desire to reduce the attack surface (as "measured" by number of extensions) but rather a paradigm shift in how the protocol works, which leaves some existing functionality incompatible with the new model. I don't really get a clear sense of what this current last sentence is trying to say (i.e., whether it's one of those two descriptions I offered above). Section 3 Similarly, the authentication of the handshake depends on signatures made using SHA-1 hash or a not stronger concatenation of MD-5 and SHA-1 hashes, allowing the attacker to impersonate a server when it is able to break the severely weakened SHA-1 hash. My recollection of the WG discussions (which I will go review) is that we don't really have consensus on the "not stronger" portion of this. Is that a key component of the document here? (N.B. this is *not* an invitation to rehash that discussion again! The chairs or I can provide a summary of points not resolved by previous discussion and points believed to be adequately agreed upon, which would be a trigger for any additional discussion that might be needed.) Thanks for putting this document together (I know that getting all the long list of references/updates/etc. right is really tedious and frustrating), and sorry to have been sitting on it for so long. -Ben _______________________________________________ TLS mailing list TLS@ietf.org https://www.ietf.org/mailman/listinfo/tls
