[Openid-specs-heart] Resources vs Resource sets

Mon Aug 1 13:54:35 UTC 2016

Justin 

Thank you for explaining this consideration.  I especially like the
statement you make toward the end that:

.        "Protected service discovery is a thorny problem, and not one I've
seen an elegant solution for yet."

Does WebFinger have the vulnerability you describe as well?  I don't know if
it is an stated precondition of HEART that it support Protected Service
Discovery but I suspect that the consumer has that expectation and as such
either we have to explicitly inform them of the risk as part of our offering
or look to another approach, right?

Aaron Seib, CEO

@CaptBlueButton 

 (o) 301-540-2311

(m) 301-326-6843

From: Openid-specs-heart
[mailto:openid-specs-heart-bounces at lists.openid.net] On Behalf Of Justin
Richer
Sent: Monday, August 01, 2016 8:30 AM
To: Adrian Gropper; Debbie Bucci
Cc: HEART List; Dixie Baker
Subject: Re: [Openid-specs-heart] Resources vs Resource sets

As far as what matters, you're missing a key point: it very much matters to
HEART that an RS and AS that are both *run* by the same group don't have to
be *built* by the same group. Runtime choice matters for more than just
patients. 

As far as the patient choice of AS at all times, there are two very real
consequences to discovery that we need to be aware of as a group. Both of
these have been discussed here in HEART before (as well as elsewhere,
particularly in the UMA working group) but to reiterate:

 1) To have the AS selectable at runtime by a client with no token (ie: a
"dry start" to get to the resource, like we have in UMA), you need to limit
the type of API you protect. The RS needs to know *which* AS to get to
without a hint from the security layer. This puts APIs styled like OpenID
Connect's UserInfo Endpoint out of reach since they use the access token to
dispatch to the appropriate resource owner and therefore appropriate
resource. In general, FHIR records are going to have a patient or record
identifier in the URL, but this of course has privacy implications as you're
leaking identifying information in an unprotected component (the URL
itself). 

2) The above leads us to an interesting attack. Let's say I get (or guess) a
patient's record URL, /PXZ-1234. I don't know who it's for and I don't have
access to it. But I use my generic client to call said URL, and the RS
dutifully goes and figures out that this is Alice's record and it's
protected by Alice's AS, alicehealth.org. This is Alice's own personal AS
and she's the only one that uses it. I can go to alicehealth.org and see
that stamped right on the front page. What have we learned? That /PXZ-1234
belongs to Alice, a real-life person that we can probably find now. And
we've got her medical record number, she can become a target for other
attacks, online and off. Remember, all of this is required by the current
protocols and would be universal if it were "patient always gets to choose
the AS no matter what" as Adrian suggests (though I'll note that this is NOT
in the HEART charter or mission). 

Protected service discovery is a thorny problem, and not one I've seen an
elegant solution for yet. Not to say it's intractable but rather to get us
to be aware of the consequences of our decisions here.

 -- Justin

On 7/31/2016 7:04 PM, Adrian Gropper wrote:

Debbie, 

Thanks for giving me another opportunity to explain what's at stake for all
of us.

As far as the substantive point of this interchange, it doesn't matter if
only 5% or 10% of the AS are independent - it will be enough to make every
authorization service patient-centered and make transparency and
longitudinal health records the norm for all of us.

I don't understand why any AS operated by an RS matters in the HEART
context. It's entirely captive and not an interoperability issue. The only
AS that matters to HEART is the one a patient has a choice over.

Adrian

On Sunday, July 31, 2016, Debbie Bucci <debbucci at gmail.com> wrote:

Adrian - 

My sincere apologies if I offended you.   I just voiced a personal opinion.
That was not the point of the paragraph though - I failed to state the point
I was trying to make - sorry to send you off on a tangent. 

Totally agree with the following statement.

The degree to which HEART chooses to profile particular subsets of FHIR has
nothing to do with whether a person chooses to outsource his / her
authorization server. It simply has to do with the person's user experience
in setting policies that HIPAA-covered-entities and FTC-covered-entities and
42-CFR-covered-entities as resource servers will need to follow. In some
cases, the resource servers will voluntarily take advantage of the FHIR
standard while in others it will not apply at all.  

I do not see the rise of totally independent AS.   I see it more as a
federate authorization model (kind of what MIT is thinking about with
Datahub - DUMA - PDS).  All RS will have their own AS processes to deal with
- even if trusted, most likely the sharing preference/consent/ROI would be
replicated to the RA AS to manage ongoing requests.  

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