Re: [Curdle] Which curves are MUST and SHOULD ?

Daniel Migault <mglt.ietf@gmail.com> Mon, 04 January 2021 20:56 UTC

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From: Daniel Migault <mglt.ietf@gmail.com>
Date: Mon, 4 Jan 2021 15:56:31 -0500
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To: "Mark D. Baushke" <mdb=40juniper.net@dmarc.ietf.org>
Cc: Hubert Kario <hkario@redhat.com>, curdle <curdle@ietf.org>
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Subject: Re: [Curdle] Which curves are MUST and SHOULD ?
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Hi,

Thanks for the follow-up. Please find my responses. I would encourage the
WG to state his opinion as soon as possible. Would the end of the week fine
?

Yours,
Daniel

On Mon, Jan 4, 2021 at 3:21 PM Mark D. Baushke <mdb=
40juniper.net@dmarc.ietf.org> wrote:

> Hubert Kario <hkario@redhat.com> writes:
>
> > On Thursday, 17 December 2020 20:35:24 CET, Mark D. Baushke wrote:
> > > Ron Frederick <ronf@timeheart.net> writes:
> > >
> > >> On Dec 15, 2020, at 8:09 AM, Salz, Rich <rsalz@akamai.com> wrote:
> > >>>>   I’m not comfortable with algorithms going from REQUIRED to
> > >>>> SHOULD NOT without some kind of transitional period. My
> > >>>> suggestion would be to ease into this with SHOULD NOT for
> > >>>> now. If you want to discuss BCP in this draft, perhaps that
> > >>>> can be a separate section.
> > >>>
> > >>> We've done it before, MD5, short RSA/DH keys, etc.
> > >>>
> > >>> We shouldn't pretend that crypto-breaking advances haven't happened.
> > >>>
> > >>> Admins can make trade-offs anyway.
> > >
> > > I am under the impression that the audience here is the maintainers of
> > > SSHv2 software rather than the administrators that manage the sites
> > > using it.
> >
> > it's both
>
> Fair enough.
>
> Two kinds of stakeholders: a) "implementors" and b) "users" should mean
> more responses for the question.
>
> Okay. In the original RFC4253 specification both
>
>     diffie-hellman-group1-sha1
> and
>     diffie-hellman-group14-sha1
>
> were REQUIRED key exchanges.
>
> The group1 parameters in RFC4253 point to the 1024-bit MODP Second
> Oakley Group given in RFC2409 section 6.2 and RFC2412 section E.2.
>
> There are two issues with diffie-hellman-group1-sha1: 1) recent
> estimages are that it has roughly 80 bits of security strength, and 2)
> it uses SHA1 for hashing which is considered weak.
>
> If we choose "MUST NOT" for this key exchange, then we are going from
> "MUST" to "MUST NOT" which could be a hardship for low-end devices
> unable to run calculations to generate a shared secret using a larger
> MODP group if support is completely removed.
>
> If we choose "SHOULD NOT", then it is hoped that most implementors would
> default to not configuring this option by default, but may provide it
> for enviornments that need it.
>
> If we choose "MAY", then it is not certain if implementors or users will
> do much of anything different and this potentially insecure key exchange
> may continue to be used even when it may be a hazard to those that
> desire a more secure by default system.
>
> Are you an SSH impelmentor or user or both?
>
>   Implementor
>   User
>   Both
>
> user

> I would like to get a straw vote for the six *sha1* related key
> exchanges. I am proposing that the rsa1024-sha1-* kex be a MUST NOT and
> that all of the others be a SHOULD NOT.
>
> 1. For diffie-hellman-group1-sha1 what is your vote?
>
>   MUST          -- current for RFC4253
>   SHOULD
>   MAY
>   SHOULD NOT    -- proposed in the -13 draft
>   MUST NOT
>
> I am fine with the -13 draft

> 2. For diffie-hellman-group14-sha1 what is your vote?
>
>   MUST          -- current for RFC4253
>   SHOULD
>   MAY           -- proposed in the -13 draft
>   SHOULD NOT
>   MUST NOT
>
> I am fine with either MAY as well as SHOULD NOT

> 3. For diffie-hellman-group-exchange-sha1 what is your vote?
>
>   MUST
>   SHOULD
>   MAY           -- current for RFC4419
>   SHOULD NOT    -- proposed in the -13 draft
>   MUST NOT
>
> I am fine with the -13 draft

>

> 4. For rsa1024-sha1 what is your vote?
>
>   MUST
>   SHOULD
>   MAY           -- current for RFC4432
>   SHOULD NOT
>   MUST NOT      -- proposed in the -13 draft
>
> I am fine with the -13 draft

>

> 5. For gss-gex-sha1-* what is your vote?
>
>   MUST
>   SHOULD        -- current for RFC4462
>   MAY
>   SHOULD NOT    -- proposed in the -13 draft
>   MUST NOT
>
> I am fine with the -13 draft

>

> 6. For gss-group1-sha1-* what is your vote?
>
>   MUST
>   SHOULD        -- current for RFC4462
>   MAY
>   SHOULD NOT    -- proposed in the -13 draft
>   MUST NOT
>
> I am fine with the -13 draft

>

> You may direct your votes to the list or to the chairs and me.
>
>         Be safe, stay healthy,
>         -- Mark
>
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>


-- 
Daniel Migault
Ericsson