Re: [OAUTH-WG] draft-ietf-oauth-spop-10

Is there anyone who has problems changing it to a MUST?
On 2015年2月18日(水) at 18:48 Hannes Tschofenig <hannes.tschofenig@gmx.net>
wrote:

> I think that the "controlled environment" is a risky idea. I believe we
> should definitely go for a MUST.
>
> On 02/18/2015 10:26 AM, Nat Sakimura wrote:
> > Hi Hannes,
> >
> > The reason I have put SHOULD there instead of MUST is
> > that there may be a valid reason not to in a controlled
> > environment, and it does not interfere the interoperability.
> > The deployment may opt to use other control than entropy,
> > and SHOULD allows it while MUST does not.
> >
> > Having said that, if the WG is OK with a MUST there,
> > I am fine with incorporating the proposed change.
> >
> > Cheers,
> >
> > Nat
> >
> >
> > On Wed, 18 Feb 2015 09:43:30 +0100
> > Hannes Tschofenig <hannes.tschofenig@gmx.net> wrote:
> >
> >> Hi Nat,
> >>
> >> thanks for the quick response.
> >>
> >> I was hoping to see a statement like "The code verifier MUST have
> >> enough entropy to make it impractical to guess the value." in the
> >> text rather than the SHOULD. Given all the other statements in the
> >> draft I am not sure what the should actually means. Under what
> >> conditions would an implementer not provide enough entropy to make
> >> guessing impractical?
> >>
> >> Ciao
> >> Hannes
> >>
> >> On 02/18/2015 05:13 AM, Nat Sakimura wrote:
> >>> Hi Hannes,
> >>>
> >>> I hereby confirm that I have submit the draft  in full conformance
> >>> with the  provisions of BCP 78 and BCP 79.
> >>>
> >>> Re: Security Consideration (7.1) and section 4.1
> >>>
> >>> The first part of the 7.1 is a non-normative prose explaining that
> >>> the implementers got to make sure that the code verifier is hard to
> >>> guessed or modeled. In a way, this is laying out the basic security
> >>> property requirment on the code verifier.
> >>>
> >>> Then, it goes onto the implementation guideance that one need to
> >>> use a cryptographic random number generator instead of relying on a
> >>> rand() in some language that are  not cryptographically random to
> >>> generate 32-octet sequence. The same text is in 4.1 as well.
> >>>
> >>> We did not copy "code verifier SHOULD have enough entropy to make
> >>> it impractical to guess the value" here because that looked
> >>> needlessly repeating, but if you want, I have no objection in
> >>> adding it to 7.1.
> >>>
> >>> Alternatively, in 7.1, after explaining the rationale, we can just
> >>> point to 4.1 for the control and implementation guidance.
> >>>
> >>> Re: 32-octet
> >>>
> >>> We chose it because we are using SHA256 in generating the code
> >>> challange. Having more entropy does not help us here, while having
> >>> less octets increases the risk.
> >>>
> >>> Best,
> >>>
> >>> Nat
> >>>
> >>>
> >>>
> >>> On Tue, 17 Feb 2015 17:56:33 +0100
> >>> Hannes Tschofenig <hannes.tschofenig@gmx.net> wrote:
> >>>
> >>>> Hi Nat, John, Naveen,
> >>>>
> >>>> thanks a lot for your work on the document.
> >>>>
> >>>> I still need responses to this mail to complete the shepherd
> >>>> writeup:
> >>>> http://www.ietf.org/mail-archive/web/oauth/current/msg14100.html
> >>>>
> >>>> I definitely need the IPR confirmation.
> >>>>
> >>>> It would also be helpful to have someone who implemented the
> >>>> specification as it currently is. I asked Brian and Thorsten for
> >>>> clarification regarding their statements that they implemented
> >>>> earlier versions of the spec.
> >>>>
> >>>> As a final remark I still believe that the text regarding the
> >>>> randomness is still a bit inconsistent. Here are two examples:
> >>>>
> >>>> 1) In the Security Consideration you write that "The security model
> >>>> relies on the fact that the code verifier is not learned or
> >>>> guessed by the attacker.  It is vitally important to adhere to
> >>>> this principle. "
> >>>>
> >>>> 2) In Section 4.1 you, however, write: "NOTE: code verifier SHOULD
> >>>> have enough entropy to make it impractical to guess the value.  It
> >>>> is RECOMMENDED that the output of a suitable random number
> >>>> generator be used to create a 32-octet sequence."
> >>>>
> >>>> There is clearly a long way from a SHOULD have enough entropy to
> >>>> the text in the security consideration section where you ask for
> >>>> 32 bytes entropy.
> >>>>
> >>>> It is also not clear why you ask for 32 bytes of entropy in
> >>>> particular.
> >>>>
> >>>> Ciao
> >>>> Hannes
> >>>>
> >>>
> >>>
> >>
> >
> >
>
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