Re: [jose] New Version Notification for draft-barnes-jose-jsms-00.txt

["Jim Schaad" <[e-mail]>]

> -----Original Message-----
> From: John Bradley [mailto:[e-mail]]
> Sent: Tuesday, June 26, 2012 12:30 PM
> To: Richard L. Barnes
> Cc: Jim Schaad; [e-mail]
> Subject: Re: [jose] New Version Notification for draft-barnes-jose-jsms-
> 00.txt
> 
> There was a WG decision to not allow encryption without integrity.   Jim
and
> others call that sender verification.

Jim would not call that sender verification.  Jim would call that integrity
protection on the transmitted content.  There is no concept of data
origination with any type of AE algorithm.


> 
> Or on simple terms no AES-CBC without a mandatory MAC integrity.
> 
> The JWE/JWS specs don't control the body.   That is intended to be
arbitrary
> content.
> 
> We do have s JWT spec that covers the body for security tokens.   The idea
> was to separate that from signing and encryption so that signing and
> encryption can be used for other objects.
> 
> John B.
> 
> On 2012-06-26, at 1:43 PM, Richard L. Barnes wrote:
> 
> >> Now that we are mandating JWE sender verification people will be using
> JWE with symmetric keys or key agreement.
> >> In those cases one can easily argue that the header should be protected
> as much as in HMAC.
> >
> > Can you clarify the scope of "we are mandating"?
> >
> >
> >> There may well be signing_time or other elements that would go into the
> header as well for JWE.
> >
> > Why do these need to go into the header rather than the body?
> >
> > --Richard
> >
> >
> >
> >
> >> Regards
> >> John B.
> >>
> >> On 2012-06-25, at 7:48 PM, Jim Schaad wrote:
> >>
> >>> <personal>
> >>>
> >>> Richard,
> >>>
> >>>> -----Original Message-----
> >>>> From: [e-mail] [mailto:[e-mail]] On
> Behalf Of
> >>>> Richard L. Barnes
> >>>> Sent: Monday, June 25, 2012 2:35 PM
> >>>> To: Nat Sakimura
> >>>> Cc: Mike Jones; [e-mail]
> >>>> Subject: Re: [jose] New Version Notification for draft-barnes-jose-
> jsms-
> >>>> 00.txt
> >>>>
> >>>> Hi Nat,
> >>>>
> >>>> I'm not sure what X.509 fiasco you're referring to.  There was a
recent
> >>> MD5
> >>>> fiasco [1], but that's an attack on MD5, not X.509.  In fact, there
have
> >>> been
> >>>> recommendations for preventing this attack in X.509 since 2005 [2].
As
> >>> was
> >>>> noted on the SAAG list, the real news here is that Microsoft wasn't
> >>> following
> >>>> any of those recommendations.
> >>>>
> >>>> JWS would have had the same problem as X.509.  The attack did not
> modify
> >>>> the cryptographic parameters (anything that would have gone in the
> >>>> header), it would not have been thwarted by the integrity protection
> we're
> >>>> worrying about.
> >>>>
> >>>> Actually, the header signing that JWS does makes it even nicer for
the
> >>>> attacker: Flame used a "chosen prefix" attack, so since the JWS
header
> >>> value
> >>>> is entirely static for a given signer, it's easy to use as a fixed
prefix.
> >>> If JWS just
> >>>> signed the content, then the application could include a something
> random
> >>>> up front to prevent such prefix-based attacks.
> >>>>
> >>>
> >>> I don't believe that this is a true statement.  If you had a prefix or
just
> >>> signed what was given to you (i.e. no prefix), it would make no
> difference
> >>> in terms of the attack for Flame.  Flame could always use a fixed
prefix of
> >>> its own design rather than using the fixed header that is generated by
> >>> having JWS sign the header information.
> >>>
> >>>> It's tempting to say that we should just add randomness to the JOSE
> >>> format.
> >>>> But the real lesson of the Flame/MD5 attacks is operational:  If
you're
> >>> signing
> >>>> something that somebody else gave you, make sure that you're not
> signing
> >>>> exactly what they gave you.  Follow the recommendations of RFC 4270.
> In
> >>>> other contexts, there's no need of similar random elements; it just
> adds
> >>>> complexity.
> >>>
> >>> This is definitely a true statement in all events and is something
that
> >>> should be added to the Security Considerations section.
> >>>
> >>> That being said, I think that there are valid reasons for wanting to
protect
> >>> the header information by some authentication processing.  PKIX
> certificates
> >>> protect the signature algorithm information (by copying the data into
the
> to
> >>> be signed block) and CMS has long allowed for information to be
> included in
> >>> the signed attributes area that identifies the algorithms used, the
> >>> certificates used and so forth.  There are also other things that we
might
> >>> find to be convenient to be placed in the header information that is
> current
> >>> not there (a signing time and embedded content type comes to mind)
> that
> >>> would be a product either of specific types of signatures or becomes a
> >>> common attribute to be placed there.
> >>>
> >>> In terms of encryption operations, I remember in the past that I have
> had
> >>> either corrupted encrypted streams or corrupted IVs and had a
> successful
> >>> decryption that later generated other problems when trying to parse.
> This
> >>> is less of an issue with AEAD algorithms as they have a much stricter
rule
> >>> on when the stream decrypts correctly.
> >>>
> >>> Jim
> >>>
> >>>>
> >>>> --Richard
> >>>>
> >>>>
> >>>>
> >>>> [1] <http://trailofbits.files.wordpress.com/2012/06/flame-md5.pdf>
> >>>> [2] <http://tools.ietf.org/html/rfc4270#section-5.1>
> >>>>
> >>>>
> >>>> On Jun 21, 2012, at 11:11 AM, Nat Sakimura wrote:
> >>>>
> >>>>> Especially after the X.509 fiasco, I strongly believe that having
> >>> integrity
> >>>> check over the metadata is a good thing. It is such a little effort
that
> >>> gives us
> >>>> much more protection down the road. In this sense, I fully agree with
> Ben
> >>>> here. We should have integrity protection over the header.
> >>>>>
> >>>>> Nat
> >>>>>
> >>>>> On Thu, Jun 21, 2012 at 8:07 AM, Mike Jones
> >>>> <[e-mail]> wrote:
> >>>>> Two years ago when the developer community needing a JSON-
> friendly
> >>>> token format was designing the JSON Web Token (JWT), we explicitly
> asked
> >>>> security experts whether the header parameters should be integrity
> >>>> protected or not.  Among them, Ben Laurie was one of the voices
> saying
> >>> that
> >>>> securing them was the right thing to do.
> >>>>>
> >>>>>
> >>>>>
> >>>>> He argued that if the parameters can be protected in a practical
> manner,
> >>>> then they should.  Doing so provides an additional hurdle that
attackers
> >>>> would have to surmount.  For example, if they can try to substitute a
> >>> weaker
> >>>> authentication scheme, then they must figure out how to make it
> >>>> authenticate correctly despite some plaintext they can't control -
the
> >>> header
> >>>> parameters.
> >>>>>
> >>>>>
> >>>>>
> >>>>> Ben also took the position that paring security protocols down to
the
> >>> least
> >>>> you can get away with, given attacks you can think of, is not a good
> >>> design
> >>>> principle.  If there is not a strong argument against including a
feature
> >>> that
> >>>> may make it harder for attackers, then that feature should be
included.
> >>>>>
> >>>>>
> >>>>>
> >>>>> I agree with him.
> >>>>>
> >>>>>
> >>>>>
> >>>>> The decision to provide integrity protection for the headers is
> >>> documented
> >>>> in the session notes at http://self-issued.info/?p=361, which said:
> >>>>>
> >>>>>
> >>>>>
> >>>>> .  What to sign (envelope.payload or just payload)?
> >>>>>
> >>>>> Given that the envelope is extensible and therefore may contain
> >>> security-
> >>>> sensitive information, we reached a consensus (with input from Ben
> Laurie
> >>>> via IM) that the combination envelope.payload must be signed.
> >>>>>
> >>>>>
> >>>>> I believe that logic is as sound today as it was then.
> >>>>>
> >>>>>
> >>>>>
> >>>>> For all these reasons, I therefore personally stand by the
community's
> >>>> decision to provide integrity protection for the headers.
> >>>>>
> >>>>>
> >>>>>
> >>>>>                                                          Best
wishes,
> >>>>>
> >>>>>                                                          -- Mike
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> -----Original Message-----
> >>>>> From: [e-mail] [mailto:[e-mail]] On
> Behalf Of
> >>>> John Bradley
> >>>>> Sent: Wednesday, June 20, 2012 3:57 PM
> >>>>> To: Richard L.Barnes
> >>>>> Cc: [e-mail]
> >>>>> Subject: Re: [jose] New Version Notification for draft-barnes-jose-
> jsms-
> >>>> 00.txt
> >>>>>
> >>>>>
> >>>>>
> >>>>> Hi Richard,
> >>>>>
> >>>>>
> >>>>>
> >>>>> While for PKCS 1.5 the hash algorithm is baked into the padding and
> not
> >>>> susceptible to modification with ECDH or RSA-PSS it is not.
> >>>>>
> >>>>> There are possible hash truncation attacks by shortening SHA256 to
> >>> SHA224
> >>>> as an example (I know we preclude truncated hashes at the moment).
> >>>>>
> >>>>>
> >>>>>
> >>>>> The bad feeling I get around this is that if there is a scenario
where
> >>> the
> >>>> attacker controls the plaintext to be signed and there is no signer
> >>> controlled
> >>>> text contributed there are potential bad things that could happen
> down the
> >>>> road.
> >>>>>
> >>>>>
> >>>>>
> >>>>> This bit us with x509 certs not that long ago (yes with MD5
admittedly)
> >>>> where the attacker could use a certificate extension to include extra
> data
> >>> and
> >>>> cause a pre collided hash to be generated.
> >>>>>
> >>>>> Having part of the signed data outside the control of an attacker is
a
> >>> good
> >>>> thing.  (having a nonce or message ID in the envelope is possible
> though
> >>> not
> >>>> yet required in JWS.)
> >>>>>
> >>>>>
> >>>>>
> >>>>> I am still of the opinion that putting the base64 encoded envelope
> >>> inside
> >>>> the hash calculation is a valid way to allow additional attributes.
> >>>>>
> >>>>> Another structure to hold the attributes adds more complexity,  as
> would
> >>>> saying that they need to be inside the signed object.
> >>>>>
> >>>>>
> >>>>>
> >>>>> I think part of this is that as one of the openID Connect authors I
look
> >>> at this
> >>>> as a necessary security token format, for OAuth and Connect.
> >>>>>
> >>>>> For that simple processing with one signature is a high priority for
> >>> adoption.
> >>>>>
> >>>>>
> >>>>>
> >>>>> From a general signing/encrypting of documents point of view you
> >>>> legitimately have different priorities.
> >>>>>
> >>>>>
> >>>>>
> >>>>> I know it is hard to prove a negative but It is also going to be
> >>> difficult for me
> >>>> to go back to security people at google Facebook and other places and
> >>>> explain how not integrity protecting the header could be better than
> >>>> integrity protecting it.
> >>>>>
> >>>>>
> >>>>>
> >>>>> It seems that I would be reduced to arguing that this is no worse
than
> >>> CMS
> >>>> and that hasn't been proven insecure yet.
> >>>>>
> >>>>>
> >>>>>
> >>>>> Allowing a possible attacker to control the hash output, and not
> >>> integrity
> >>>> protecting the additional data, seems like something I am bound to
> regret
> >>> in
> >>>> the future.
> >>>>>
> >>>>>
> >>>>>
> >>>>> Regards
> >>>>>
> >>>>> John B.
> >>>>>
> >>>>>
> >>>>>
> >>>>> On 2012-06-19, at 7:00 PM, Richard L. Barnes wrote:
> >>>>>
> >>>>>
> >>>>>
> >>>>>> Hey John,
> >>>>>
> >>>>>>
> >>>>>
> >>>>>> Interesting points, but I don't think they actually apply here.
> >>>>>
> >>>>>>
> >>>>>
> >>>>>> With regard to downgrade attacks:
> >>>>>
> >>>>>>
> >>>>>
> >>>>>> The attack that RFC 5752 is concerned with is when an attacker
strips
> >>>> signatures from a signed message, so that the only ones left are ones
> he
> >>> can
> >>>> tamper with.  So the integrity protection here is "horizontal"; it
goes
> >>> across
> >>>> signatures.  The integrity protection in JWS/JWE is "vertical" -- it
only
> >>> protects
> >>>> one signer's parameters -- so it is, so to speak, orthogonal.
> >>>>>
> >>>>>>
> >>>>>
> >>>>>>
> >>>>>
> >>>>>> With regard to "brown bag" attacks:
> >>>>>
> >>>>>>
> >>>>>
> >>>>>> The root of this attack is ambiguity about what content is *signed*
> >>>>>
> >>>>>> vs. what content is *used*.  If an application doesn't verify that
> >>>>>
> >>>>>> it's actually using the stuff that's signed, then it can be tricked
> >>>>>
> >>>>>> into accepting something unsigned. (Cf.
> >>>>>
> >>>>>> <http://en.wikipedia.org/wiki/Confused_Deputy>)
> >>>>>
> >>>>>>
> >>>>>
> >>>>>> However, I don't think any of the current proposals have that
> problem.
> >>>> In JWE/JWS, the signed content is right there between the dots, and
in
> >>> JSMS,
> >>>> it's in the "content" element.  The current JSMS draft does allow
> detached
> >>>> signatures, but with a "voids your warranty" sticker on it.
> >>>>>
> >>>>>>
> >>>>>
> >>>>>> In any case, these attacks have nothing to do with whether the
> >>>> cryptographic parameters are integrity-protected with the content.
> The
> >>>> example attacks in the IBM still work regardless -- the whole point
of
> the
> >>>> attack is that the cryptographic processing is the same, only the
> >>> (non-crypto)
> >>>> matching of content is flawed.
> >>>>>
> >>>>>>
> >>>>>
> >>>>>>
> >>>>>
> >>>>>> With regard to "arbitrary attributes":
> >>>>>
> >>>>>>
> >>>>>
> >>>>>> We can have that here, too, but you need canonicalization.  And
> >>> base64-
> >>>> encoding is not not canonicalization -- it just waves its hands over
the
> >>>> question of equivalence.  In my opinion, we should keep the
> cryptographic
> >>>> object simple by disallowing attributes, and push the attributes you
> would
> >>>> sign inside of the thing being signed.  If people really do want
> >>> attributes, it
> >>>> doesn't seem to me like JSON canonicalization is very hard.  I can do
it
> >>> in 19
> >>>> lines of python:
> >>>>>
> >>>>>> <http://pastebin.com/ptUfn0c3>
> >>>>>
> >>>>>>
> >>>>>
> >>>>>>
> >>>>>
> >>>>>> With regard too "meta-data in the body":
> >>>>>
> >>>>>>
> >>>>>
> >>>>>> It seems to me like if we're trying to define a general format for
> >>> applying
> >>>> security protections, then we ought to keep out things that aren't
> >>> strictly
> >>>> security relevant.  Those things can go in application-specific
content
> >>> types
> >>>> (e.g., SAML) without polluting the general purpose header.
> >>>>>
> >>>>>>
> >>>>>
> >>>>>>
> >>>>>
> >>>>>> With regard to "defense in depth" and selling this to government
> >>>> agencies:
> >>>>>
> >>>>>>
> >>>>>
> >>>>>> CMS, via S/MIME, is in broad use across multiple federal agencies
> and
> >>>> large enterprises.  JSMS is essentially a profile of CMS (see Section
7),
> >>> and
> >>>> has the same security properties.
> >>>>>
> >>>>>>
> >>>>>
> >>>>>>
> >>>>>
> >>>>>> Cheers,
> >>>>>
> >>>>>> --Richard
> >>>>>
> >>>>>>
> >>>>>
> >>>>>>
> >>>>>
> >>>>>>
> >>>>>
> >>>>>>
> >>>>>
> >>>>>> On Jun 19, 2012, at 5:10 PM, John Bradley wrote:
> >>>>>
> >>>>>>
> >>>>>
> >>>>>>> Hi Richard,
> >>>>>
> >>>>>>>
> >>>>>
> >>>>>>> Originally we only integrity protected the header for signing.  We
> >>> added
> >>>> the integrity protection to encryption as part of AEAD, as encryption
> can
> >>> also
> >>>> be used for sender verification.
> >>>>>
> >>>>>>>
> >>>>>
> >>>>>>> I understand the argument that it makes things simpler if we don't
> >>>> integrity protect the header information.
> >>>>>
> >>>>>>>
> >>>>>
> >>>>>>> However xmldsig,  provides integrity over those elements to
> prevent
> >>>> possible downgrade attacks by manipulating the algorithms.
> >>>>>
> >>>>>>>
> >>>>>
> >>>>>>> CMS may not typically provide that integrity protection but I
think
> >>> Jim
> >>>> Schaad and Sean Terner created RFC5752 to address downgrade
> attacks.
> >>>>>
> >>>>>>> Given they are on this list they can speak to their view on
integrity
> >>> over
> >>>> the crypto parameters.
> >>>>>
> >>>>>>>
> >>>>>
> >>>>>>> I also recall when working on InfoCards there was a Monte
> Carlo/Brown
> >>>> Bag attack that needs to be considered if we move to something more
> like a
> >>>> detached signature.
> >>>>>
> >>>>>>>
> >>>>>
> >>>>>>> The other design consideration is that we wanted to be able to
sign
> >>>> arbitrary byte strings not just JSON.   You could sign XML if you
wanted.
> >>>>>
> >>>>>>> That prevented us from including meta-data in the body as we
> didn't
> >>>> want to touch it.   That left us with the header to include
additional
> >>> elements
> >>>> in.
> >>>>>
> >>>>>>> Not integrity protecting those elements as well would be a
> problem.
> >>>>>
> >>>>>>>
> >>>>>
> >>>>>>> I am not a CMS expert but I believe it allows for signing of
> >>> arbitrary
> >>>> attributes not unlike the current JOSE spec.
> >>>>>
> >>>>>>>
> >>>>>
> >>>>>>> Especially for something that will be used with JWT security
tokens I
> >>> will
> >>>> have a hard time making the argument to NIST and others that need to
> >>>> approve this format that not integrity protecting the header
> parameters is
> >>>> appropriate defence in depth, for something that might be replacing
> signed
> >>>> SAML assertions in some applications.
> >>>>>
> >>>>>>>
> >>>>>
> >>>>>>> I do understand how not integrity protecting the header will make
> >>> some
> >>>> things easier, however I can't agree that the benefit outweighs the
> >>>> disadvantages.
> >>>>>
> >>>>>>>
> >>>>>
> >>>>>>> Regards
> >>>>>
> >>>>>>> John B.
> >>>>>
> >>>>>>>
> >>>>>
> >>>>>>>
> >>>>>
> >>>>>>> On 2012-06-18, at 10:02 PM, Richard L. Barnes wrote:
> >>>>>
> >>>>>>>
> >>>>>
> >>>>>>>> Hey Mike,
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> Thanks for having some back-and-forth with me on this.  I think
> this
> >>> is a
> >>>> good discussion to have right now.  I would like to discuss some
> >>> high-level
> >>>> points, and then I'll respond inline to your precise points.
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> tl;dr: In order to meet its deliverables, the WG needs to define
> >>> JSON-
> >>>> based formats for integrity and confidentiality protections.  JWE and
> JWS
> >>>> don't fit that requirement, so we should re-consider their adoption
and
> >>> call
> >>>> for new candidates.
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> Major points:
> >>>>>
> >>>>>>>> 1. JOSE is JSON
> >>>>>
> >>>>>>>> 2. JSON does not imply canonicalization 3. Compactness and
> >>>>>
> >>>>>>>> URL-safeness are still OK, as derivatives
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> Part 1: JOSE is JSON
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> The JOSE WG charter calls out four deliverables, three of which
> are
> >>>> explicitly required to be JSON:
> >>>>>
> >>>>>>>> -- "JSON-structured integrity protection"
> >>>>>
> >>>>>>>> -- "JSON-structured encryption"
> >>>>>
> >>>>>>>> -- "public keys as JSON-structured objects"
> >>>>>
> >>>>>>>> (The fourth is just a list of algorithms, which should be JSON as
> >>>>>
> >>>>>>>> well, just as RFC 3370 is ASN.1.)
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> In light of these requirements, JWE and JWS are clearly not
> suitable
> >>>>>
> >>>>>>>> candidates to fulfill the working group's milestones.  (At least
in
> >>>>>
> >>>>>>>> their current form.)  So ISTM that we need to step back and
> >>>>>
> >>>>>>>> re-evaluate alternatives for the three above milestones,
> especially
> >>>>>
> >>>>>>>> the first two.  (JWK is not as far off.)
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> As JSON-based mechanisms, though, the "JSON serialization"
> drafts
> >>>> are pretty half-hearted.  Because JWS and JWE include the
> cryptographic
> >>>> parameters within the integrity protection, they have to have the
> headers
> >>>> included as base64-encoded strings.  That obviously adds a lot of
> >>> complexity
> >>>> to encoding and decoding -- for example, you have to keep the
> encoded
> >>>> header around even after you've decoded it! -- and just plain more
> octets.
> >>>> The support for multiple recipients and multiple signatures is both
> >>> unweildy
> >>>> (matching up parallel indices for headers and signatures) and
inefficient
> >>>> (multiple integrity check values in encrypted objects).
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> By contrast, JSMS takes advantage of the cryptographic wisdom
> that
> >>>> went into CMS, while making the syntax pure JSON and as simple as
> >>> possible.
> >>>> Multiple signatures and multiple recipients are supported with
absolute
> >>>> minimum overhead.  So I think it's worth consideration by the working
> >>> group.
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> Part 2: JSON !=> canonicalization
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> I would like to dispel the myth that a JSON-based format requires
> >>>>>
> >>>>>>>> canonicalization.  In JWE/JWS, the JSON header requires
> >>>>>
> >>>>>>>> "canonicalization" (via base64url encoding) because it's included
> >>>>>
> >>>>>>>> within the integrity protection.  I'm not aware of any reason for
> >>>>>
> >>>>>>>> including the cryptographic parameters in the integrity check,
> >>>>>
> >>>>>>>> instead of only integrity-protecting the content itself.  Indeed,
if
> >>>>>
> >>>>>>>> there were an attack based on non-integrity-protected
> cryptographic
> >>>>>
> >>>>>>>> parameters, it would be a pretty big deal, since neither CMS nor
> IKE
> >>>>>
> >>>>>>>> nor provides this protection.  (TLS does provide a signature over
> >>>>>
> >>>>>>>> the algorithms, but only as a way to bind the public key to the
> >>>>>
> >>>>>>>> session.)
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> Indeed CMS doesn't require canonicalization at all, except for
> >>>> attributes that are included in the protected content (signedAttrs /
> >>>> authenticatedAttrs), which need to be DER-encoded.  In JSMS, we
> don't
> >>>> allow those parameters, so there is no need for canonicalization at
all.
> >>> All the
> >>>> "canonicalization" that's needed is to base64url-encode the protected
> >>>> content.  In that regard, JSMS is even simpler than JWE/JWS.
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> Part 3: Compactness and URL-safeness are still OK, as derivatives
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> I have absolutely no objection to defining a compact, URL-safe
> >>> format.
> >>>> Indeed, I did so in the JSMS draft, in Section 5.  Encoding the
example
> >>> from
> >>>> Section 3.1 of the JWS spec, we get the following JSMS object:
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> {
> >>>>>
> >>>>>>>> "v":1,
> >>>>>
> >>>>>>>> "t":"au",
> >>>>>
> >>>>>>>> "a":"hs256",
> >>>>>
> >>>>>>>> "c":"eyJpc3MiOiJqb2...0cnVlfQ",
> >>>>>
> >>>>>>>> "mac":"pwM0gJNMLFxn8G1-juQFLrJtMEOR8_FeKIH3wIM_OAo",
> >>>>>
> >>>>>>>> "ki":"rSIilRk8Ego"
> >>>>>
> >>>>>>>> }
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> If we remove the decorative spaces and base64url-encode, we
> only
> >>>> use
> >>>>>
> >>>>>>>> 88 octets more than JWS (267 vs. 179).  If we take this a step
> >>>>>
> >>>>>>>> further and define an explicit compact format for
> AuthenticatedData,
> >>>>>
> >>>>>>>> we can emulate JWS by moving the content and MAC fields
> outside
> >>>> and
> >>>>>
> >>>>>>>> dot-combining.  That avoids double-base64url-encoding, and only
> >>>>>
> >>>>>>>> takes up 11 more octets than a JWS (190 vs 179).  (I've put the
> code
> >>>>>
> >>>>>>>> to generate these in the Github project linked earlier.)
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> So it's fine to have a compact, URL-safe format for an objective,
> >>> but it
> >>>> makes *much* more sense to derive that from a full-size, usable, JSON
> >>>> format than the other way around.
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> Responses to specific points inline below.
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>> Fair enough.  I'll briefly respond to each in turn.  Before
doing
> >>> so, I'll
> >>>> say that I'm writing in the spirit of trying to increase mutual
> >>> understanding
> >>>> and consensus, rather than taking the point of view that the status
quo
> is
> >>> the
> >>>> only reasonable outcome.
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>> -- Not being JSON
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>> This was by design, so that the results are URL-safe.  This is
> >>> required,
> >>>> for instance, for them to be used as OAuth Bearer Tokens.  At the
> request
> >>> of
> >>>> the working group, closely related pure-JSON drafts were also
> published.
> >>>> See:
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>> http://tools.ietf.org/html/draft-jones-json-web-signature-json-
> seri
> >>>>>
> >>>>>>>>> alization-01 and
> >>>>>
> >>>>>>>>> http://tools.ietf.org/html/draft-jones-json-web-encryption-
> json-ser
> >>>>>
> >>>>>>>>> ialization-01
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>> Use them if you prefer if they better suit your use cases.  They
> >>> could
> >>>> be adopted as working group documents, if there's interest.
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> See above.  These are super-clunky, and the need to be the main
> >>>> focus of the WG, not an afterthought.
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>> -- Not supporting multiple recipients
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>> The JSON serialization drafts above do, again, in response to
use
> >>>> cases presented by the working group.
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> See above.  Because of the unnecessary inclusion of the header in
> >>> the
> >>>> integrity check, this is far less efficient than it should be.
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>> -- Lacking clear distinctions between signing and MAC
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>> Functionally, these are very similar operations, at least from
an
> >>>> implementation perspective, so it's not clear that making a clear
> >>> distinction
> >>>> would help either developers or adoption in any practical way.  They
> >>> achieve
> >>>> overlapping, but admittedly sometimes different goals.  I believe
that
> >>>> developers can be trusted to use the algorithms that achieve their
> >>>> applications' goals without making a hard distinction between the
two.
> >>> But
> >>>> I'd be interested in hearing your thoughts on why you believe a
> >>> brighter-line
> >>>> distinction might be useful or necessary.
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> It's important if you want to do MACs with anything other than
> pre-
> >>>> shared keys.  If you want to do anything more advanced, you need to
> have
> >>>> wrapped keys, in which case an object with a MAC starts to look a lot
> more
> >>>> like a JWE than a JWS.
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>> -- Lacking clear processing instructions for different key
> >>>>>
> >>>>>>>>> establishment modalities
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>> This seems like an area where the existing drafts could be
> refined
> >>> to
> >>>> add descriptions for additional establishment modalities, possibly
> based
> >>>> upon your ideas and descriptions, should the working group decide to
> do
> >>> so.
> >>>> What additional modalities do you have use cases for that you believe
> are
> >>>> not achievable or straightforward with the existing drafts?  The
existing
> >>>> modalities supported are largely those that existing developers had
> told
> >>> us
> >>>> they needed and draw both from the precursor draft-jones-json-web-
> *
> >>>> documents and draft-rescorla-jsms.
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>> Bear in mind that the balance that the current drafts try to
strike
> >>> is
> >>>> keeping the Mandatory to Implement (MTI) feature footprint small
> enough
> >>>> that developers, including Web developers, are likely to adopt the
> specs,
> >>>> while still providing enough functionality to make them generally
> useful.
> >>> As
> >>>> in any balance, it's often possible to shift things a bit and still
> >>> maintain the
> >>>> balance, but I'd like people to keep the ubiquitous adoption goal
> >>> front-and-
> >>>> center when proposing additional functionality.
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>> Ubiquitous deployment and usefulness trump theoretical
> >>>>>
> >>>>>>>>> completeness.  (Just look at XMLDSIG and XMLENC to
> understand
> >>>>>
> >>>>>>>>> that!)
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> I agree that we need to find a reasonable MTI.  The current JSMS
> >>> draft
> >>>> doesn't really specify which parts are MTI, beyond basic things like
> >>> base64url
> >>>> encoding and ignoring unknown fields.
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> My main concern is that JWS and JWE don't really tell me which
> >>> fields
> >>>> need to be present for which use case.  If I'm putting a MAC on a JWS
> vs.
> >>> a
> >>>> signature, do I need "jwk" or "jku" fields to be populated?  Whereas
in
> >>> JSMS,
> >>>> I think these things are much clearer due to the separation of the
use
> >>> cases
> >>>> (Signed/Authenticated/Encrypted) and the isolation of signatures and
> >>>> wrapped keys into sub-objects.
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>> -- Lack of clear typing of objects
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>> Most JSON documents aren't clearly typed; instead, developers
> and
> >>>> implementations understand from context what the meaning of each
> field is.
> >>>> XML is clearly typed, but developers are voting with their feet by
> moving
> >>> to
> >>>> JSON.
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>> What practical advantages resulting from overlaying a typing
> >>>> infrastructure on JSON do you believe are worth the potential costs
of
> >>> doing
> >>>> so?  BTW, I'm not opposed to having a JSON schema description of the
> JOSE
> >>>> JSON data structures like JSMS did in
http://tools.ietf.org/html/draft-
> >>>> rescorla-jsms-00#appendix-A, but I'll remark that this an informative
> >>> tool, not
> >>>> a normative one.
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> I actualy don't have a hugely urgent requirement here either.
It's
> >>>> something that others in the WG had requested, which is trivial to
add
> in
> >>>> JSMS, but not in JWE/JWS -- again because of the unnecessary
integrity
> >>>> protection of the header.
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>> -- Lack of versioning for future extensibility
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>> An optional version field could be added if the working group
> >>>>>
> >>>>>>>>> desires, however the last time the working group discussed it,
> they
> >>>>>
> >>>>>>>>> decided not to do so.  Rather, specs like this effectively
become
> >>>>>
> >>>>>>>>> "versioned" when revised in a way that new fields are added.  If
> >>>>>
> >>>>>>>>> you understand the new fields, you support that new version.
> (Note
> >>>>>
> >>>>>>>>> that this is independent of whether there is a version number
> >>>>>
> >>>>>>>>> field, which according to some participants in the previous
> >>>>>
> >>>>>>>>> discussion, they regarded as therefore being redundant
> >>>>>
> >>>>>>>>> information.)
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>> I'm not religious about not having a version number field, but
> >>> often
> >>>> "less is more".
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> Indeed, I'm not religious either.  It just seems like a general
good
> >>> idea
> >>>> to state this directly as opposed to having parsers divine it based
on
> >>> which
> >>>> fields are present.  To quote RFC 5652:
> >>>>>
> >>>>>>>> "
> >>>>>
> >>>>>>>> Each of the major data structures includes a version number as
> the
> >>>>>
> >>>>>>>> first item in the data structure.  The version numbers are
intended
> >>>>>
> >>>>>>>> to avoid ASN.1 decode errors.  Some implementations do not
> check
> >>>> the
> >>>>>
> >>>>>>>> version number prior to attempting a decode, and if a decode
> error
> >>>>>
> >>>>>>>> occurs, then the version number is checked as part of the error
> >>>>>
> >>>>>>>> handling routine.  This is a reasonable approach; it places error
> >>>>>
> >>>>>>>> processing outside of the fast path.  This approach is also
> >>>>>
> >>>>>>>> forgiving  when an incorrect version number is used by the
> sender.
> >>>>>
> >>>>>>>> "
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> Best,
> >>>>>
> >>>>>>>> --Richard
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>>                                                Best wishes,
> >>>>>
> >>>>>>>>>                                                -- Mike
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>> -----Original Message-----
> >>>>>
> >>>>>>>>> From: Richard L. Barnes [mailto:[e-mail]]
> >>>>>
> >>>>>>>>> Sent: Friday, June 15, 2012 3:00 PM
> >>>>>
> >>>>>>>>> To: Mike Jones
> >>>>>
> >>>>>>>>> Cc: [e-mail]
> >>>>>
> >>>>>>>>> Subject: Re: [jose] Fwd: New Version Notification for
> >>>>>
> >>>>>>>>> draft-barnes-jose-jsms-00.txt
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>> Ok, so maybe I should have phrased my lead-in differently.
> IMO,
> >>> the
> >>>> current JW* specs are deficient in several ways, e.g.:
> >>>>>
> >>>>>>>>> -- Not being JSON
> >>>>>
> >>>>>>>>> -- Not supporting multiple recipients
> >>>>>
> >>>>>>>>> -- Lacking clear distinctions between signing and MAC
> >>>>>
> >>>>>>>>> -- Lacking clear processing instructions for different key
> >>>>>
> >>>>>>>>> establishment modalities
> >>>>>
> >>>>>>>>> -- Lack of clear typing of objects
> >>>>>
> >>>>>>>>> -- Lack of versioning for future extensibility
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>> Looking at the current specs, it didn't seem to me that it would
> be
> >>>> simple to adapt them to address these deficiencies.  So I just did a
> >>> re-write.
> >>>> If you think they can be addressed within the current framework,
> please
> >>>> explain.  I just found it simpler to start from whole cloth.
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>> Cheers,
> >>>>>
> >>>>>>>>> --Richard
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>> On Jun 15, 2012, at 5:43 PM, Mike Jones wrote:
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>>> Hi Richard,
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>> If you're puzzled by specific design decisions in the JOSE
> >>> documents,
> >>>> I encourage you to ask about them on the list.  The documents have
> >>>> significant history going back to mid-2010 when convergence
> discussions
> >>>> started among people with four different JSON signing & encryption
> >>>> proposals.  JWT and the current JOSE specs and implementations are
> the
> >>>> result.  I realize that not all the JOSE participants were part of
those
> >>>> discussions from the beginning (although many were) and so teasing
> out the
> >>>> rationale for specific decisions might help people better understand
> the
> >>>> choices made, and hopefully thereby increase consensus behind the
> >>>> eventual working group choices.
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>> If the list that you're puzzled by is the bulleted list below,
> >>> maybe we
> >>>> can start a discussion on that basis.
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>>                                              Best wishes,
> >>>>>
> >>>>>>>>>>                                              -- Mike
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>> -----Original Message-----
> >>>>>
> >>>>>>>>>> From: [e-mail] [mailto:[e-mail]]
> On
> >>>>>
> >>>>>>>>>> Behalf Of Richard L. Barnes
> >>>>>
> >>>>>>>>>> Sent: Friday, June 15, 2012 2:08 PM
> >>>>>
> >>>>>>>>>> To: [e-mail]
> >>>>>
> >>>>>>>>>> Subject: [jose] Fwd: New Version Notification for
> >>>>>
> >>>>>>>>>> draft-barnes-jose-jsms-00.txt
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>> Dear JOSE WG,
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>> Like Mr. Manger, once I finally got around to doing a thorough
> >>>> review of the JW* specs, I was kind of puzzled by some of the design
> >>>> decisions.  So I also went through and wrote an alternative format,
this
> >>> time
> >>>> taking a more of a cue from CMS.  A link to the document is below.
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>> Summary of differences:
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>> o  JSMS is pure JSON, whereas in JWE and JWS only the header
> >>>>>
> >>>>>>>>>> parameters are represented in JSON.
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>> o  JSMS allows for full algorithm agility in key agreement,
while
> >>> JWE
> >>>>>
> >>>>>>>>>> only allows ECDH-ES.
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>> o  JSMS supports multiple recipients for EncryptedData and
> >>>>>
> >>>>>>>>>> AuthenticatedData objects via the inclusion of multiple
> >>>> WrappedKey
> >>>>>
> >>>>>>>>>> objects.  Sending a JWE to multiple recipients requires re-
> >>>>>
> >>>>>>>>>> encryption of the entire object for each recipient.
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>> o  The signature and MAC functions of the JWS object are
> separated
> >>>>>
> >>>>>>>>>> into SignedData and AuthenticatedData JSMS objects.
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>> o  JSMS parameters are not integrity-protected, as they are in
> JWE
> >>>>>
> >>>>>>>>>> and JWS.
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>> o  The "typ" and "zip" parameters are not defined in JSMS, but
> >>> could
> >>>>>
> >>>>>>>>>> be added without significant change.
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>> o  JSMS requires that recipients MUST ignore unknown header
> >>>>>
> >>>>>>>>>> parameters, in order to facilitate extensibility.
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>> I've also thrown together an initial JavaScript implementation
> >>> (based
> >>>> on NodeJS for some python crypto glue), which is on github:
> >>>>>
> >>>>>>>>>> <https://github.com/bifurcation/jsms>
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>> Comments are very welcome.
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>> Thanks,
> >>>>>
> >>>>>>>>>> --Richard
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>> Begin forwarded message:
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>>> From: [e-mail]
> >>>>>
> >>>>>>>>>>> Subject: New Version Notification for
> >>>>>
> >>>>>>>>>>> draft-barnes-jose-jsms-00.txt
> >>>>>
> >>>>>>>>>>> Date: June 15, 2012 4:56:09 PM EDT
> >>>>>
> >>>>>>>>>>> To: [e-mail]
> >>>>>
> >>>>>>>>>>>
> >>>>>
> >>>>>>>>>>>
> >>>>>
> >>>>>>>>>>> A new version of I-D, draft-barnes-jose-jsms-00.txt has been
> >>>>>
> >>>>>>>>>>> successfully submitted by Richard Barnes and posted to the
> IETF
> >>>>>
> >>>>>>>>>>> repository.
> >>>>>
> >>>>>>>>>>>
> >>>>>
> >>>>>>>>>>> Filename:             draft-barnes-jose-jsms
> >>>>>
> >>>>>>>>>>> Revision:              00
> >>>>>
> >>>>>>>>>>> Title:                     JavaScript Message Security Format
> >>>>>
> >>>>>>>>>>> Creation date:    2012-06-15
> >>>>>
> >>>>>>>>>>> WG ID:                  Individual Submission
> >>>>>
> >>>>>>>>>>> Number of pages: 25
> >>>>>
> >>>>>>>>>>> URL:
> >>> http://www.ietf.org/internet-drafts/draft-barnes-jose-
> >>>> jsms-00.txt
> >>>>>
> >>>>>>>>>>> Status:
> >>> http://datatracker.ietf.org/doc/draft-barnes-jose-jsms
> >>>>>
> >>>>>>>>>>> Htmlized:
> >>> http://tools.ietf.org/html/draft-barnes-jose-jsms-00
> >>>>>
> >>>>>>>>>>>
> >>>>>
> >>>>>>>>>>>
> >>>>>
> >>>>>>>>>>> Abstract:
> >>>>>
> >>>>>>>>>>> Many applications require the ability to send
cryptographically
> >>>>>
> >>>>>>>>>>> secured messages.  While the IETF has defined a number of
> >>>> formats
> >>>>>
> >>>>>>>>>>> for such messages (e.g.  CMS) those formats use encodings
> which
> >>>>>
> >>>>>>>>>>> are not easy to use in modern applications.  This document
> >>>>>
> >>>>>>>>>>> describes the JavaScript Message Security format (JSMS), a
> new
> >>>>>
> >>>>>>>>>>> cryptographic message format which is based on JavaScript
> Object
> >>>>>
> >>>>>>>>>>> Notation (JSON) and thus is easy for many applications to
> >>> generate
> >>>> and parse.
> >>>>>
> >>>>>>>>>>>
> >>>>>
> >>>>>>>>>>>
> >>>>>
> >>>>>>>>>>>
> >>>>>
> >>>>>>>>>>>
> >>>>>
> >>>>>>>>>>> The IETF Secretariat
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>> _______________________________________________
> >>>>>
> >>>>>>>>>> jose mailing list
> >>>>>
> >>>>>>>>>> [e-mail]
> >>>>>
> >>>>>>>>>> https://www.ietf.org/mailman/listinfo/jose
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>>
> >>>>>
> >>>>>>>>>> _______________________________________________
> >>>>>
> >>>>>>>>>> jose mailing list
> >>>>>
> >>>>>>>>>> [e-mail]
> >>>>>
> >>>>>>>>>> https://www.ietf.org/mailman/listinfo/jose
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>>
> >>>>>
> >>>>>>>>> _______________________________________________
> >>>>>
> >>>>>>>>> jose mailing list
> >>>>>
> >>>>>>>>> [e-mail]
> >>>>>
> >>>>>>>>> https://www.ietf.org/mailman/listinfo/jose
> >>>>>
> >>>>>>>>
> >>>>>
> >>>>>>>> _______________________________________________
> >>>>>
> >>>>>>>> jose mailing list
> >>>>>
> >>>>>>>> [e-mail]
> >>>>>
> >>>>>>>> https://www.ietf.org/mailman/listinfo/jose
> >>>>>
> >>>>>>>
> >>>>>
> >>>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> _______________________________________________
> >>>>> jose mailing list
> >>>>> [e-mail]
> >>>>> https://www.ietf.org/mailman/listinfo/jose
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> --
> >>>>> Nat Sakimura (=nat)
> >>>>> Chairman, OpenID Foundation
> >>>>> http://nat.sakimura.org/
> >>>>> @_nat_en
> >>>>>
> >>>>> _______________________________________________
> >>>>> jose mailing list
> >>>>> [e-mail]
> >>>>> https://www.ietf.org/mailman/listinfo/jose
> >>>>
> >>>> _______________________________________________
> >>>> jose mailing list
> >>>> [e-mail]
> >>>> https://www.ietf.org/mailman/listinfo/jose
> >>>
> >>> _______________________________________________
> >>> jose mailing list
> >>> [e-mail]
> >>> https://www.ietf.org/mailman/listinfo/jose
> >>
> >> _______________________________________________
> >> jose mailing list
> >> [e-mail]
> >> https://www.ietf.org/mailman/listinfo/jose
> >