Re: [OAUTH-WG] Question lengths in draft-sakimura-oauth-tcse-03

Right but that's why I'm asking why not just put the limit on
code_challange rather than inferring it from code_verifyer + challenge
algorithm, which probably bounds it but doesn't necessarily do so? It's not
a big deal but would read more clearly, I think.

On Mon, May 12, 2014 at 3:48 PM, John Bradley <ve7jtb@ve7jtb.com> wrote:

> I think octets is more consistent with other JW* and OAuth specs.
>
> The code_challange is the same length as the code_verifyer or is a hash of
> the code_verifyer so likely smaller than 128octets (43 ish for base64 256
> bit)
>
> Limiting the code_verifyer size sets the upper bound for code_challange,
> unless someone comes up with a really creative code challenge algorithm.
>
> I will talk to nat about changing it to octets when I see him tomorrow.
>
> John B.
>
> On May 12, 2014, at 11:15 PM, Derek Atkins <warlord@MIT.EDU> wrote:
>
> > Brian Campbell <bcampbell@pingidentity.com> writes:
> >
> >> I notice that code_verifier is defined as "high entropy cryptographic
> random
> >> string of length less than 128 bytes"  [1], which brought a few
> questions and
> >> comments to mind. So here goes:
> >>
> >> Talking about the length of a string in terms of bytes is always
> potentially
> >> confusing. Maybe characters would be an easier unit for people like me
> to wrap
> >> their little brains around?
> >
> > It depends if it really is characters or bytes.  For example there are
> > many multi-byte UTF-8 characters, so if it really is bytes then saying
> > characters is wrong because it could overflow.  So let's make sure we
> > know what we're talking about.  Historically, if we're talking bytes the
> > IETF often uses the phrase "octets".  Would that be less confusing?
> >
> >> Why are we putting a length restriction on the code_verifier anyway? It
> seems
> >> like it'd be more appropriate to restrict the length of the
> code_challenge
> >> because that's the thing the AS will have to maintain somehow (store in
> a DB
> >> or memory or encrypt into the code). Am I missing something here?
> >>
> >> Let me also say that I hadn't looked at this document since its early
> days in
> >> draft -00 or -01 last summer but I like the changes and how it's been
> kept
> >> pretty simple for the common use-case while still allowing for crypto
> agility/
> >> extension. Nice work!
> >>
> >> [1] http://tools.ietf.org/html/draft-sakimura-oauth-tcse-03#section-3.3
> >
> > -derek
> >
> >> _______________________________________________
> >> OAuth mailing list
> >> OAuth@ietf.org
> >> https://www.ietf.org/mailman/listinfo/oauth
> >
> > --
> >       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
> >       Member, MIT Student Information Processing Board  (SIPB)
> >       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
> >       warlord@MIT.EDU                        PGP key available
>
>

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