Re: [secdir] Secdir review of draft-murchison-nntp-compress-05
Julien ÉLIE <julien@trigofacile.com> Mon, 24 October 2016 20:28 UTC
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To: Barry Leiba <barryleiba@computer.org>, draft-murchison-nntp-compress.all@ietf.org, Michael Bäuerle <michael.baeuerle@stz-e.de>
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From: Julien ÉLIE <julien@trigofacile.com>
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Subject: Re: [secdir] Secdir review of draft-murchison-nntp-compress-05
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Hi Barry, Thanks again for your valuable comments on the document. They were very much appreciated, and permitted to fix a few issues. I've just finalized a revised draft, taking into account all the comments received during Last Call. I just want to highlight the following change in wording. Ken and Michael, as respectively co-author and document shepherd, please tell if you think the new wording is not the right thing to do. Personally, I think this document (draft-murchison-nntp-compress) should only focus on standardizing the COMPRESS command and not try to fix how authentication works in another kind of compression (TLS-level compression). It would otherwise be an update to RFC 4643. Updating TLS usage with NNTP is the aim of a second, separate document (draft-elie-nntp-tls-recommendations) that updates RFC 4643 with best current practices. That one discourages the use of TLS-level compression, thus dealing with authentication layered with a TLS-level compression method. >> In order to help mitigate leaking authentication credentials via for >> instance a CRIME attack [CRIME], authentication SHOULD NOT be >> attempted when a compression layer is active. Consequently, a server >> SHOULD NOT return any arguments with the AUTHINFO capability label >> (or SHOULD NOT advertise it at all) in response to a CAPABILITIES >> command received from an unauthenticated client after a compression >> layer is active, and such a client SHOULD NOT attempt to utilize any >> AUTHINFO [RFC4643] commands. It implies that a server SHOULD reply >> with a 502 response code if a syntactically valid AUTHINFO command is >> received while a compression layer is already active. >> >> Why are these SHOULD, and not MUST? Under what conditions would it be >> necessary or reasonable for an implementation not to abide by these, >> and what considerations need to be considered when making that >> determination? (And this is also directly referred to in Section 6.) [...] > OK. I've adopted your suggestion. [...] > Hmm... I think I should now do a pass on the document and explicitly > say when "compression layer" only means the one negotiated with COMPRESS. > As a matter of fact, I do not think it's a good idea to say in this > draft that authentication MUST NOT be attempted when TLS-level > compression is active! It would otherwise be a change in how > authentication works (RFC 4643 heavily mentions the preferred use of > AUTHINFO along with TLS, and RFC 4642 allows TLS-level compression). > This document would otherwise be an update to RFC 4643, by no longer > allowing AUTHINFO when TLS-level compression is active. Pass done. I updated the wording in a few parts of the document. The above quoted paragraph becomes: In order to help mitigate leaking authentication credentials via for instance a CRIME attack [CRIME], authentication MUST NOT be attempted after a successful use of the COMPRESS command. Consequently, a server MUST either list the AUTHINFO capability with no arguments or not advertise it at all, in response to a CAPABILITIES command received from an unauthenticated client after a successful use of the COMPRESS command, and such a client MUST NOT attempt to utilize any AUTHINFO [RFC4643] commands. It implies that a server MUST reply with a 502 response code if a syntactically valid AUTHINFO command is received after a successful use of the COMPRESS command. (Note that this specification does not change the behaviour of AUTHINFO as described in [RFC4643] independently of TLS-level compression. Authentication is therefore still allowed, even though TLS-level compression is active.) I hope you're all fine with that. Have a nice day, -- Julien ÉLIE « Aut bibas aut abeas. »
- [secdir] Secdir review of draft-murchison-nntp-co… Barry Leiba
- Re: [secdir] Secdir review of draft-murchison-nnt… Julien ÉLIE
- Re: [secdir] Secdir review of draft-murchison-nnt… Barry Leiba
- Re: [secdir] Secdir review of draft-murchison-nnt… Julien ÉLIE
- Re: [secdir] Secdir review of draft-murchison-nnt… Julien ÉLIE
- Re: [secdir] Secdir review of draft-murchison-nnt… Barry Leiba
- Re: [secdir] Secdir review of draft-murchison-nnt… Julien ÉLIE
- Re: [secdir] Secdir review of draft-murchison-nnt… Julien ÉLIE
- Re: [secdir] Secdir review of draft-murchison-nnt… Julien ÉLIE
- Re: [secdir] Secdir review of draft-murchison-nnt… Ken Murchison
- Re: [secdir] Secdir review of draft-murchison-nnt… Michael Bäuerle
- Re: [secdir] Secdir review of draft-murchison-nnt… Alexey Melnikov
- Re: [secdir] Secdir review of draft-murchison-nnt… Julien ÉLIE