Re: [Curdle] State of draft-ietf-curdle-ssh-kex-sha2?
denis bider <denisbider.ietf@gmail.com> Sun, 12 July 2020 17:04 UTC
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From: denis bider <denisbider.ietf@gmail.com>
Date: Sun, 12 Jul 2020 12:04:11 -0500
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To: Ron Frederick <ronf@timeheart.net>
Cc: "Mark D. Baushke" <mdb@juniper.net>, curdle <curdle@ietf.org>,
curdle-chairs <curdle-chairs@ietf.org>
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Subject: Re: [Curdle] State of draft-ietf-curdle-ssh-kex-sha2?
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I think Ron's suggestions are all reasonable. On Sun, Jul 12, 2020 at 11:17 AM Ron Frederick <ronf@timeheart.net> wrote: > > On Jul 12, 2020, at 5:05 AM, denis bider <denisbider.ietf@gmail.com> > wrote: > > It looks like I found the key thing I missed: Google did not show me RFC > 8268 when I searched for "diffie-hellman-group14-sha256". It finds it now > when I search for "rfc diffie-hellman-group14-sha256". > > I could have found it in the IANA registry but I trusted the lack of > Google results in my first search. Alas. > > That resolves the key concern for me: that names like "diffie-hellman-group14-sha256" > are authoritatively defined. I was looking for this reference for the SSH > QUIC draft. > > With regard to MUST / MAY / SHOULD / etc assignments, I agree with all of > these: > > > curve25519-sha256 SHOULD > > curve448-sha512 MAY > > diffie-hellman-group-exchange-sha1 SHOULD NOT > > diffie-hellman-group-exchange-sha256 MAY > > diffie-hellman-group1-sha1 SHOULD NOT > > diffie-hellman-group14-sha1 SHOULD NOT > > diffie-hellman-group14-sha256 SHOULD > > diffie-hellman-group15-sha256 MAY > > I do not agree with this one: > > > diffie-hellman-group16-sha512 MUST > > I find this too computationally expensive to justify "MUST" for servers. > Last time I checked, this costs about 100 ms in server CPU time, more on > weaker CPUs, and makes it trivial to DoS a resource-constrained server - no > DDoS needed. > > > I’m good with group16-sha512 remaining a “MAY” along with group17-sha512 > and group18-sha512, What about group15-sha256, though? Should that perhaps > be a “SHOULD”, and also group14-sha256 changed to a “MUST”? I think we want > at least one DH algorithm to be listed as a “MUST”. > > > > I agree with all of these: > > > diffie-hellman-group17-sha512 MAY > > diffie-hellman-group18-sha512 MAY > > ecdh-sha2-* MAY > > ecdh-sha2-nistp256 SHOULD > > ecdh-sha2-nistp384 SHOULD > > ecmqv-sha2 MAY > > ext-info-c SHOULD > > ext-info-s SHOULD > > gss-* MAY > > I conditionally agree on these: > > > gss-curve25519-sha256-* SHOULD > > gss-curve448-sha512-* MAY > > gss-gex-sha1-* SHOULD NOT > > gss-group1-sha1-* SHOULD NOT > > gss-group14-sha256-* SHOULD > > gss-group15-sha512-* MAY > > gss-group16-sha512-* SHOULD > > gss-group17-sha512-* MAY > > gss-group18-sha512-* MAY > > gss-nistp256-sha256-* SHOULD > > gss-nistp384-sha384-* MAY > > gss-nistp521-sha512-* MAY > > The condition is that the reader understands that "SHOULD" for these > methods applies only if you implement any GSS-API key exchange methods at > all. In other words, the whole category of GSS-API needs to be "MAY", but > within the category the above SHOULDs are appropriate as long as the > decision is made to implement any of the GSS-API key exchange methods in > the first place. > > > With that condition in mind, I think all of these should match their > non-GSS equivalents in terms of MAY/SHOULD/MUST. So, if changes are made to > group14/15/16, they should be reflected here as well. > > > I agree with these: > > > rsa1024-sha1 MUST NOT > > rsa2048-sha256 MAY > > In summary - my main complaint is that "diffie-hellman-group16-sha512" is > too expensive to be a MUST. If that leaves no key exchange method that is a > "MUST", I'm fine with it. > > If there needs to be a method that's a "MUST", I vote for either > "curve25519-sha256" or "diffie-hellman-group14-sha256" as meeting > security requirements while being the most widely compatible. > > > I like having curve25519-sha256 as a strongly encouraged SHOULD, but I > think it might be better to stick with group14-sha256 as the MUST. > -- > Ron Frederick > ronf@timeheart.net > > > >
- [Curdle] State of draft-ietf-curdle-ssh-kex-sha2? denis bider
- Re: [Curdle] State of draft-ietf-curdle-ssh-kex-s… Salz, Rich
- Re: [Curdle] State of draft-ietf-curdle-ssh-kex-s… Salz, Rich
- Re: [Curdle] State of draft-ietf-curdle-ssh-kex-s… denis bider
- Re: [Curdle] State of draft-ietf-curdle-ssh-kex-s… Mark D. Baushke
- Re: [Curdle] State of draft-ietf-curdle-ssh-kex-s… denis bider
- Re: [Curdle] State of draft-ietf-curdle-ssh-kex-s… Ron Frederick
- Re: [Curdle] State of draft-ietf-curdle-ssh-kex-s… denis bider
- Re: [Curdle] State of draft-ietf-curdle-ssh-kex-s… Loganaden Velvindron
- Re: [Curdle] State of draft-ietf-curdle-ssh-kex-s… Mark D. Baushke
- Re: [Curdle] State of draft-ietf-curdle-ssh-kex-s… Salz, Rich
- Re: [Curdle] State of draft-ietf-curdle-ssh-kex-s… Ron Frederick
- Re: [Curdle] State of draft-ietf-curdle-ssh-kex-s… Mark D. Baushke
- Re: [Curdle] State of draft-ietf-curdle-ssh-kex-s… Mark D. Baushke
- Re: [Curdle] State of draft-ietf-curdle-ssh-kex-s… denis bider