Re: [jose] Richard Barnes' Discuss on draft-ietf-jose-json-web-algorithms-33: (with DISCUSS and COMMENT)

[Richard Barnes <[e-mail]>]

On Sat, Oct 18, 2014 at 7:09 PM, Mike Jones <[e-mail]>
wrote:

> > > > Section 3.6.
> > > > I'm not going to object to "none", even though I think it's a very
> dangerous
> > > > feature because of the risk of confusion between Secured and
> Unsecured JWS.
> > > > But there needs to be stronger guidance:
> > > > 1. An implementation SHOULD NOT support "none" unless the implementer
> > > > knows that it will be used in application context s that require it.
> > > > 2. If an implementation does support "none", then it MUST NOT accept
> it as part
> > > > of generic JWS validation.  Instead, it should require the
> application to explicitly
> > > > signal that an Unsecured JWS is expected for a given validation
> operation.
> > >
> > > As discussed in the working group, your concern about applications
> inappropriately allowing the use of "none" actually is an instance of a
> more general concern that applications not allow *any* algorithms to be
> used that are not appropriate in their application contexts.  This concern
> is already addressed in the specification at the end of Section 5.2 as
> follows:
> > >
> > > "Finally, note that it is an application decision which algorithms are
> acceptable in a given context. Even if a JWS can be successfully validated,
> unless the algorithm(s) used in the JWS are acceptable to the application,
> it SHOULD reject the JWS."
> > >
> > > Since your specific concern is already handled in a more general way,
> I would like to request that you withdraw this DISCUSS on that basis.
> Also, you were one of the contributing authors to the security
> considerations on this topic in Section 8.5 of JWA (Unsecured JWS Security
> Considerations), so it's not clear that there's any cause for you to come
> back with additional wording change requests on this topic at this point.
> > >
> > > Thanks for reminding me about Section 8.5.  I think I would be
> satisfied here if the contents of Section 8.5 were just moved up to this
> section.  That way all of the requirements for implementing "none" will be
> together.
> >
> > Section 3.6 does end with the sentence "See Section 8.5 for security
> considerations associated with using this algorithm" so implementers are
> reminded to also pay attention to the security considerations.  If we were
> to do what you requested, this would be the only algorithm for which the
> security considerations were included in the algorithm description, rather
> than in the security considerations section, which would be fairly weird
> and non-parallel, editorially.
> >
> > Actually, "none" is the only algorithm for which there are additional
> normative requirements in the Security Considerations.  So it actually
> seems more sensible to move those requirements up.
> > I'm really just asking for a copy/paste here, shouldn't be invasive.
> But I do think the level of indirection creates security risk.
>
> I'm OK moving up the three sentences that actually do contain normative
> requirements.  Those are:
>
>    Implementations that support Unsecured JWS objects MUST NOT accept
>    such objects as valid unless the application specifies that it is
>    acceptable for a specific object to not be integrity-protected.
>    Implementations MUST NOT accept Unsecured JWS objects by default.
>    In order to mitigate downgrade attacks, applications MUST NOT signal
>    acceptance of Unsecured JWS objects at a global level, and SHOULD
>    signal acceptance on a per-object basis.
>
> I'm not OK cluttering up the normative description of the algorithm with
> the discussion text.  Assuming you're OK leaving the discussion text and
> "for example" text in 8.5, I think we have a way forward on this one.
> Please let me know if that works for you.
>

Sounds fine to me.  Thanks for the compromise.

--Richard



> > Again, given that you were an author of 8.5 and seemed fine with the
> resolution after the extensive discussion then, I'd ask you to clear the
> DISCUSS on that basis and not request that it be reworked again.
>
>                                 -- Mike
>
>