Kathleen, thanks for the review. Responses inline, though I'm going to
let the other authors talk about their sections (deployment org,
software version, etc) directly.
On 2/11/2015 6:06 PM, Kathleen Moriarty wrote:
Thank you for your work on this draft and sorry for the delay in my
review. Before we progress to IETF last call, I'd like to see what we
can resolve from the list below. I am looking at the IPR issues to
see if we can resolve the outstanding questions as well.
The Shepherd report says the following:
The document shepherd has raised concerns regarding the fuzzy
description
of the actors (deployment organization, software API publisher, client
developer) and their impact on the protocol execution. The working
group did not seem to worry about these aspects though.
I can see the point after reading the draft. The interactions are
written much more clearly in the security considerations section than
where the flows are described. Can something be done to address these
concerns?
Section 1.2
Deployment Organization definition:
I highly recommend replacing the phrase "simple cloud deployment" with
a description that accurately reflects what is intended. If that's
within a single service provider's network, a single data center, or a
single hosted data center, I think it would be more clear.
Section 1.2 nit:
Add the word "be" into the following term definition after "may":
Software API Publisher
The organization that defines a particular web accessible API that
may deployed in one or more deployment environments.
[deferred to original author of this text Phil et. al for better wording]
Section 2:
Why isn't a more secure option offered and set as the default for
authentication types? I know I've asked this before and the answer was
just that you can add something to the registry, but setting HTTP
Basic as the default seems like a really bad choice. HOBA is on it's
way to becoming an RFC from the HTTPAuth working group. HTTPAuth also
has an updated version of Basic that is in IETF last call, but I know
you are pointing to the OAuth 2.0 document, so it would be that
document that gets updated and not this draft. The new version of
HTTP Basic fixes some internationalization problems and spells out the
security issues much more clearly, so it probably doesn't matter too
much to update the reference, but maybe makes it more clear that basic
is not a secure form of authentication.
Can you provide some justification as to why this is okay to set basic
as the default and add that to the draft? Section 2.3.1 of OAuth 2.0
just says this MUST be implemented, but that any HTTP schemes can be
used. Why not register another method and use that instead as the
default? You could use digest and there is library support. It's not
a great answer, but slightly better than passwords with basic. You
could register HOBA and use that instead, the only downside is limited
library support at the moment.
It was our intent to document the methods already defined for use with
OAuth and provide a registration mechanism for distinguishing between
them, not to create new client authentication mechanisms. Digest and
HOBA simply aren't defined for use with OAuth clients yet. It would be
simple to do: put the client id in the "username" field and the client
secret in the "password" field of both algorithms. However, I don't
believe it's a good idea to conflate those two goals in a single
specification. We actually had other, more secure definitions in an
earlier draft of this document (using a JWT signed with a private key or
a JWT signed with a shared key, specifically), but those were removed in
order to focus on solving just the client registration problem. I agree
with that decision of the WG.
As other methods of client authentication are defined in the OAuth
ecosystem, they can register as valid values in the registry. I think it
would be a valuable output of this WG to define other client
authentication mechanisms as a separate draft or an eventual update to
RFC6749 (or both?).
Section 2: Contacts:
I noticed privacy is not dealt with until you get to the security
considerations section. I'd prefer to see it with the definition,
stating the address should be a general help address at the domain
rather than directly to an identifiable individual. It may be good to
set a default for what this should be for consistency or give an
example (think back to ab...@domain.com <mailto:ab...@domain.com>)?
The problem that I see with putting it inside the definition is that it
makes the definition text very long, as the definition sits in a list of
other metadata items. We could add a forward pointer and an example
easily enough, though. Or we could move the privacy considerations
section up as a subsection here, though I don't know if that runs afoul
of the RFC style guidelines for this new section.
Software_id and software_version:
Are there any guidelines as to how these should be represented? There
are several specifications on software_id (and platform). Does
consistency here matter or is this just meant to be human readable?
Section 2.2 specifies some metadata values that are to be human
readable, should the above be in the list? I would expect this list
to be comprehensive for clarity, rather than just examples since there
aren't too many defined here.
[mostly deferred to Phil et. al, but note that software_id and
software_version are not intended to be human readable and don't need
the multi-language support]
Section 3.2.1 & Privacy section
For client_name and client_id and associated information, how is user
privacy affected and what can be done to mitigate concerns? The
definition should state that this is a public value and that it is
specific to the software, not a person. You have to get to the
security consideration section before that is clear. References are
fine too, but some more information is needed in the privacy section.
I'm left with a bunch of questions:
Can the client_name and client_id be tied to a person?
The client name is common across all copies of the software (usually),
so no worries there. The ID represents an individual piece of software,
not a person, though if that person is the sole user of the instance of
software then I believe you're right that there are some privacy
considerations that we should point that out. However, dynamic
registration can actually help mitigate this as well, since in the
normal case (with no software statements) there's no way to correlate
instances of clients with each other.
Can the person be tracked by this?
Can other information be gathered about a system (and it's user)
during this process?
Nothing gathered about the user during registration, as this happens in
the back channel outside the user's purview.
The information is used to dynamically register clients, what is logged?
What data is aggregated?
What can you tell about a client (time, location, travel, other
personal details that may be considered sensitive)? I don't think
this was covered in the OAuth 2.0 RFC.
How is this addressed at the authorization server and other points?
The Security considerations talks about client_id as being short
lived, so they expire, but are these event logged or is that prohibited?
Many of these questions seem to be completely dependent on the
implementation of the authorization server, and I'm not really sure how
(or if) to address them in this draft. Any suggestions would be welcomed
here.
The client_id *could* be short lived, but they usually aren't. I don't
see any particular logging or tracking concerns using a dynamic OAuth
client above using any other piece of software, ever. As such, I don't
think it requires special calling out here.
5. Security considerations
The first paragraph is a repeat of text. Can this just be in one
place and use a pointer to the full text? I like the requirement, but
reading it once is enough.
I think it was less onerous of a repeat when both simply said "use TLS",
so some refactoring after the expansion of the text makes sense to me.
Would it be better to have it upfront in the endpoint definition, or in
the security considerations?
--
Best regards,
Kathleen
Thanks again for your review!
-- Justin
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