On my work queue for tomorrow... -----Original Message----- From: Kathleen Moriarty [mailto:[email protected]] Sent: Tuesday, November 17, 2015 5:03 PM To: Mike Jones Cc: Manger, James; Jim Schaad; [email protected] Subject: Re: [jose] JWS Unencoded Payload Option spec addressing shepherd comments
Mike, When do you expect to have this ready? And assuming the shepherd agrees it's ready for AD review... Thanks, Kathleen On Thu, Nov 12, 2015 at 9:31 PM, Mike Jones <[email protected]> wrote: > Thanks, James. I’ll cover that case in the rewritten security > considerations. But at least in that case it “fails safe” by > rejecting the JWS due to the apparently bad signature. (That’s what > the first sentence of paragraph three of the current security > considerations section is about; I’ll try to make that clearer.) > > > > -- Mike > > > > From: Manger, James [mailto:[email protected]] > Sent: Thursday, November 12, 2015 6:23 PM > To: Mike Jones; Jim Schaad; [email protected] > > > Subject: RE: [jose] JWS Unencoded Payload Option spec addressing > shepherd comments > > > >> Do see any other cases in which there is a problem to address other >> than when the producer is intentionally emitting “b64”:true but >> signing as if “b64” was false? > > > > YES. > > The producer intentionally creates a proper "b64":false message, but > one of the recipients (that the producer might not have known about) > hasn’t implemented the new spec. That is less likely for a symmetric > MAC that will typically only be shared by 2 parties. But it is quite > realistic for an asymmetric digital signature that can, by design, be > verified by anyone. > > > >> In my analysis, if the recipient rejects a signature that it doesn’t >> understand, I didn’t consider that a security problem. Do you agree >> with that? > > > > YES, as long as it rejects the signature because the crypto doesn’t > verify, not just because the content will generally look wrong. > > > > -- > > James Manger > > > > From: jose [mailto:[email protected]] On Behalf Of Mike Jones > Sent: Friday, 13 November 2015 12:50 PM > To: Jim Schaad <[email protected]>; [email protected] > Subject: Re: [jose] JWS Unencoded Payload Option spec addressing > shepherd comments > > > > OK, I can take a stab at rewriting it that way. > > > > It’s not that I think there isn’t ever a problem but I do think that > there are lots of real cases in which there’s only a problem if the > producer is intentionally creating a JWS designed to confuse – in > which case the producer is an attacker. Do see any other cases in > which there is a problem to address other than when the producer is > intentionally emitting “b64”:true but signing as if “b64” was false? > > > > The current security considerations text was intended to do a case > analysis of when there is and isn’t a problem, breaking things down by > who implements the extension and who doesn’t. In my analysis, if the > recipient rejects a signature that it doesn’t understand, I didn’t > consider that a security problem. Do you agree with that? > > > > While, yes, in retrospect I wish we’d talked about in person too, in > fairness, I did write to the list in my November 2nd note that “I will > add the thoughts above to the Security Considerations section”, and > that’s what I did, keeping the factual content, but attempting to > change the tone from e-mail conversational to factual. > > > > But I’ll try it your way instead, while also keeping the case analysis > where appropriate. In the meantime, please let me know your thoughts > on the two questions I asked above. > > > > -- Mike > > > > From: Jim Schaad [mailto:[email protected]] > Sent: Thursday, November 12, 2015 2:24 PM > To: Mike Jones; [email protected] > Subject: RE: [jose] JWS Unencoded Payload Option spec addressing > shepherd comments > > > > Mike, > > > > I wish that we had talked about this last week at the F2F meeting. > > > > This does not read like a security consideration, it read like an > email that is sent to the list saying that there is nothing to talk > about here and it can be completely ignored. If that is the way that > you feel about this, you need to get census that there is no problem and kill > the text. > > > > How I would approach writing this consideration is as follows: > > > > 1. Describe what the problem is. While both James and I provided one > scenario that was easy to understand, it should not be thought of as > the only case that there is a problem. The basic description of the > problem is that there are now two different strings that will generate > the same signature value, without there being a weakness in the hash > algorithm. > > 2. Describe the set of things that can be done to address this problem. > > a. Use the “crit” parameter > > b. Use a profile of the application that states there is only one > possible value > > c. Make sure that all implementations support the b64 parameter > > > > Jim > > > > > > > > > > > > From: jose [mailto:[email protected]] On Behalf Of Manger, James > Sent: Wednesday, November 11, 2015 4:21 PM > To: Mike Jones <[email protected]>; [email protected] > Subject: Re: [jose] JWS Unencoded Payload Option spec addressing > shepherd comments > > > > Mike, thanks for trying to explain with a page of Security > Considerations the ambiguity arising since existing (OLD) JWS > implementations will silently ignore the "b64":false signal. > > > > It is still wrong. The extra text starts by saying “there is no > security problem… since the signature will fail” when "b64":false is > ignored, but then ends by saying "crit":["b64"] is necessary when "b64":false > is ignored. > It cannot be both! > > > > There is no security problem if a JWS correctly created using "b64" > > with a "false" value is received by an implementation not > supporting > > the "b64" Header Parameter, since the signature will fail to verify > > and the JWS will therefore be rejected. > > … > > Only if the application dynamically switches between "false" and > > "true" values for "b64" (something NOT RECOMMENDED in Section 6), > > would it be necessary for the application to require the use of > > "crit" with a value of "["b64"]" in such application contexts. > > > > > > The signature can, in fact, still verify when "b64":false is ignored — > giving the verifier the wrong content. > > We could have chosen a different signing input to avoid all ambiguity, > but decided against that (as it was aesthetically nice to keep a > lower-layer invariant somewhere inside JWS implementations of > signing-up-to-the-2nd-dot). > > We could have required "crit":["b64"], but would prefer to avoid the > extra handful of bytes (and probably aren’t that confident that > everyone implements "crit" properly anyway). > > We could leave it to users to avoid the ambiguity at higher layers by > having totally separate contexts that do & don’t use "b64":false, > trying to help them get it right with advice about “application > profiles”, “application context”, a “NOT RECOMMENDED”, and 5 extra > Security Considerations paragraphs (though what “application” means here is > not that clear). > > > > To me, this is a design failure. > > > > > > > > The extra text about trust is dangerous. > > > > If the trust established by > > verifying the signer's key does not actually establish that the > > creator is a trusted party, then this case in which JWS libraries > > supporting and not supporting the extension may respectively > > interpret the attacker's payload as being encoded or unencoded is > the > > least of the application's worries. > > > > CAs issuing certificates to millions of HTTPS web sites (used to > verify the signer’s key) absolutely DO NOT establish that the creator > (web site) is a trusted party, merely what the creator’s name is. > Misinterpreting what a signer means is bad regardless of trust. > > > > -- > > James Manger > > > > > > From: jose [mailto:[email protected]] On Behalf Of Mike Jones > Sent: Thursday, 12 November 2015 2:37 AM > To: [email protected] > Subject: [jose] JWS Unencoded Payload Option spec addressing shepherd > comments > > > > Draft -04 of the JWS Unencoded Payload Option specification addresses > the shepherd comments. Thanks to Jim Schaad for his careful review. > The primary change was adding additional security considerations text, > including describing when “crit” should be used. > > > > The specification is available at: > > · > https://tools.ietf.org/html/draft-ietf-jose-jws-signing-input-options- > 04 > > > > An HTML formatted version is also available at: > > · > http://self-issued.info/docs/draft-ietf-jose-jws-signing-input-options > -04.html > > > > -- > Mike > > > > P.S. This note was also published at http://self-issued.info/?p=1474 > and as @selfissued. > > > > > _______________________________________________ > jose mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/jose > -- Best regards, Kathleen _______________________________________________ jose mailing list [email protected] https://www.ietf.org/mailman/listinfo/jose
