Re: [OAUTH-WG] I-D Action: draft-ietf-oauth-spop-09.txt

Brian Campbell <bcampbell@pingidentity.com> Thu, 05 February 2015 18:09 UTC

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From: Brian Campbell <bcampbell@pingidentity.com>
Date: Thu, 5 Feb 2015 11:09:04 -0700
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To: John Bradley <ve7jtb@ve7jtb.com>
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Subject: Re: [OAUTH-WG] I-D Action: draft-ietf-oauth-spop-09.txt
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22-chars (128 bits) as a lower limit seems just fine for this case.

"ccm" works for me but I don't feel strongly about it either way.



On Thu, Feb 5, 2015 at 9:49 AM, John Bradley <ve7jtb@ve7jtb.com> wrote:

> Inline
>
>
> > On Feb 4, 2015, at 10:43 PM, Manger, James <
> James.H.Manger@team.telstra.com> wrote:
> >
> >>    Title           : Proof Key for Code Exchange by OAuth Public Clients
> >>      Filename        : draft-ietf-oauth-spop-09.txt
> >> https://tools.ietf.org/html/draft-ietf-oauth-spop-09
> >
> >
> > Some nits on this draft:
> >
> > 1. 42 chars.
> > The lower limit of 42 chars for code_verifier: is not mentioned in prose
> (just the upper limit); is too high (128-bits=22-chars is sufficient); and
> doesn't correspond to 256-bits (BASE64URL-ENCODE(32 bytes) gives 43 chars,
> not 42).
>
> In my editors draft I fixed the 43 octet base64url encoding of 32bytes.  I
> originally had 43 but it got changed at some point
>
> Is there working group feedback on making the lower limit clear in the
> prose and if so what should it be?  22-chars (128 bits) or 43 char (256
> bits)?
>
>
> >
> > 2.
> > Quotes around "code_verifier" and "code_challenge" in prose are okay,
> though not really necessary as the underscore is enough to distinguish them
> as technical labels. Quotes around these terms in formula is bad as it
> looks like the formula applies to the 13 or 14 chars of the label. The
> quoting is also used inconsistently.
> > Suggestion: remove all quotes around "code_verifier" and
> "code_challenge" in prose and formula.
> > For example, change ASCII("code_verifier") to ASCII(code_verifier).
> >
>
> I am going to leave this for a later formatting cleanup at the moment, I
> need to find a good style compromise that works with rfcmarkup.
>
> > 3.
> > Two ways to check code_verifier are given in appendix B, whereas only
> one of these is mentioned in section 4.6.
> >  SHA256(verifier) === B64-DECODE(challenge)
> >  B64-ENCODE(SHA256(verifier)) === challenge
> >
> > I suggest only mentioning the 2nd (change 4.6 to use the 2nd, and drop
> the 1st from appendix B). It is simpler to mention only one. It also means
> base64url-decoding is never done, and doesn't need to be mentioned in the
> spec.
> >
> Yes when I added the example I realized that the normative text was the
> more complicated way to do the comparison.
>
> I will go back and refactor the main text to talk about the simpler
> comparison and drop the base64url-decode references.
> >
> > 4.
> > Expand "MTI" to "mandatory to implement".
>
> Done in editors draft.
> >
> > P.S. Suggesting code challenge method names not exceed 8 chars to be
> compact is a bit perverse given the field holding these values has the long
> name "code_challenge_method" ;)
>
>   On the topic of the parameter  name  "code_challange_method",  James has
> a point in that it is a bit long.
>
> We could shorten it to "ccm".   If we want to change the name sooner is
> better than later.
>
> It is that balance between compactness and clear parameter names for
> developers, that we keep running into.
>
> I don't know that encouraging longer parameter values is the best
> direction.
>
> Feedback please
>
> John B.
> >
> > --
> > James Manger
> >
> > _______________________________________________
> > OAuth mailing list
> > OAuth@ietf.org
> > https://www.ietf.org/mailman/listinfo/oauth
>
>
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