The last text that has been proposed on the list about this thread is
the following:
Implementers should be aware that a token introspection request lets the
AS know when the client is accessing the RS,
which can also indicate when the user is using the client. If
this implication is not acceptable, implementers can use other means
to carry access token data, e.g. directly transferring the data
needed by the RS within the access token.
The concerns of the implementers have nothing to do with the concerns of
the Users. Such a text proposal has nothing to do with a "User consent".
*Towards an RFC Errata to RFC 7662*
Mike Jones wrote:
I agree with Dick’s observation about the privacy implications of using
an Introspection Endpoint. That’s why it’s preferable to not use one at all
and instead directly have the Resource understand the Access
Token. One way of doing this is the JWT Access Token spec. There are
plenty of others.
I fully agree.
RFC 7662 should have incorporated a more detailed content such as:
In OAuth 2.0 [RFC6749], the contents of tokens are opaque to
clients. However, the contents of tokens is not intended to be opaque to
RSs.
Token introspection is an OPTIONAL feature of an AS described in
OAuth Introspection [RFC 7662] intended for clients that are unable
to support structured access tokens including their validation.
The use of this call allows an AS to track where and when its clients
have indeed
presented an issued access token. As soon as the RS knows the
format of the access token, e.g. using structured token formats such as
JWT [RFC7519], and is able to validate its security features, the
call described in OAuth Introspection [RFC 7662] should be avoided,
otherwise
the AS will know exactly when the introspection call has been made
and thus be able to make sure which client has attempted perform an access
to that RS and at which instant of time. As soon as this call is
supported by an AS, the client or the user have no way to prevent the RS
to use it.
It might be useful to add it, e.g. using an RFC Errata.
*Differences with RFC 7662*
RFC 7662 defines a protocol that allows authorized protected resources
to query the authorization server to determine
the set of metadata for a given token that was presented to them by an
OAuth 2.0 client.
At a first glance, draft-ietf-oauth-jwt-introspection-response-09 seems
to be simply a JWT Response for OAuth Token Introspection
instead of a JSON document representing the meta information surrounding
the token.
However, this is not the case since major differences can be identified.
RFC 7662 describes an OPTIONAL call able to return a JSON object with
the following top-level members: active (REQUIRED), scope (OPTIONAL),
client_id (OPTIONAL), username (OPTIONAL), token_type (OPTIONAL), exp
(OPTIONAL), iat (OPTIONAL), nbf (OPTIONAL), sub (OPTIONAL),
aud (OPTIONAL), iss (OPTIONAL), jti (OPTIONAL) and claims from the "JSON
Web Token Claims" registry (OPTIONAL).
draft-ietf-oauth-jwt-introspection-response-09 is able to return a JWT
as the introspection response. However, the request and the returned
information
are not the same.
Section 4 (Requesting a JWT Response) only provides an example and does
not describe the mandatory and optional parameters from the request.
Are they identical to those described in RFC 7662 ? No one is able to say.
draft-ietf-oauth-jwt-introspection-response-09 describes a response
structure which is different from RFC 7662 where a single top-level
member is required,
i.e. active. The text from
draft-ietf-oauth-jwt-introspection-response-09 requires three (in fact
four) top-level members. The text states:
The JWT MUST include the following top-level claims:
* issMUST be set to the issuer URL of the authorization server.
* audMUST identify the resource server receiving the token
introspection response.
* iatMUST be set to the time when the introspection response was
created by the authorization server.
Note that the text about "active" (i.e. the fourth top-level member) is
misplaced in the middle of the token_introspection claim and does not allow
to easily understand that the top-level claim "active" MUST be set to
either true or false.
The text states:
The AS determines based on its RS-specific policy what claims about the
resource owner to return in the token introspection response.
Such a sentence (which does not exist in RFC 7662) is a door wide-opened
to return claims that are NOT included into the access token.
This protocol should NOT be a protocol that allows authorized RSs to
query the AS to obtain metadata that was NOT included into an access token
that was presented to them.
Torsten wrote:
Token introspection has several advantages over structured access
tokens, also when it comes to privacy. If one uses a structured access
token
in conjunction with different *services*, then this access token
needs to contain ALL data required to call ALL these services. This
effectively means
the services learn more data than required. One could try to
mitigate this by carrying encrypted compartments in the same token, each
of them
encrypted with for a certain service. That would be complex and
is not covered by current technical standards. Introspection, however,
allows the AS
issue a minimal access token (even without any id) and mint
specific response for the different RSs.
Instead of attempting to imagine complex mechanisms like "encrypted
compartments in the same token", it is much simpler to use different
access tokens.
AFAIK, in addition, there is no notion of "services" in OAuth in RFC
6749, but only a notion of "server". A "server" is not a "service".
resource server
The server hosting the protected resources, capable of accepting
and responding to protected resource requests using access tokens.
RFC 6750 is using the wording "audience restriction" to restrict the use
of a token to "the intended relying party or set of relying parties"
(i.e. to one or more RSs).
So if the access token is targeted to one or more RSs, it should only
contain what is necessary to accomplish the call on these RSs.
This means the RS(s) learn(s) exactly the data that it required. If it
is not the case, several access tokens should be used.
The principle of "data minimization" implies that an access token should
only contain what is necessary to accomplish a call to a given RS.
Since this new call is meant to be OPTIONAL, there should be no
difference whether the RS decodes and validates the access token by itself
or sub-contracts the same operations to the AS.
The explanations from Torsten imply that there can be a difference ....
which furthermore is left at the full discretion of the AS.
*About the secondary use*
I wrote:
This concern is identified in RFC 6973 as:
5.2.3.Secondary Use
Secondary use is the use of collected information about an individual
without the individual’s consent for a purpose different from that
for which the information was collected.Secondary use may violate
people’s expectations or desires.The potential for secondary use
can generate uncertainty as to how one’s information will be used in
the future, potentially discouraging information exchange in the
first place.Secondary use encompasses any use of data, including
disclosure.
Torsten replied:
This is no secondary use, it’s the primary use *the user
consented with*.
No "user consent" phase is ever mentioned in order to allow a RS to ask
and receive a jwt-introspection-response.
The text states:
The AS MUST ensure the release of any privacy-sensitive data is legally
based.
Such a statement does not make sense in practice. A different legal
system applies depending upon three factors:
the location of the client, the location of the AS and the location of
the RS.
Unless these three entities are located within the same country (e.g.
Switzerland), the same state (e.g. Maryland) or
the same union (e.g. the European Union), the AS will be unable to know
how to enforce such a statement.
The release of any privacy-sensitive data must be under the control of
the user who must consent to the release
of that privacy-sensitive data. This makes it independent from any legal
system.
*About the token introspection endpoint
*
The token introspection endpoint is advertised in RFC 8414 in the
following way:
introspection_endpoint
OPTIONAL.URL of the authorization server’s OAuth 2.0 introspection
endpoint [RFC7662].
This endpoint is intended to explicitly support RFC 7662, but not
anything else. This draft is intended to support a new functionality
that is different
from RFC 7662. This means that the AS should not use the same token
introspection endpoint. If supported, this new functionality should be
supported
using a new endpoint, e.g. an introspection_JWT_endpoint.
When this new functionality is advertised by an AS by the disclosure of
an access point, this does not necessarily mean that it is supported for
all the RSs
with which that AS has a relationship.
The current situation is that the User and his client have no way to
know whether or not this new call will indeed be supported by the AS for
a given RS.
Even the RS can't know it directly, since the only way to know it is to
use a "trial and error" mechanism.
*A proposal on how to solve the issue*
Hereafter is one way on how to solve the issue.
The User is the entity that is the best placed to give the User Consent.
It would be simpler if the user could ask to the AS to provide to his
client
a JWT for a given RS that could be used to issue certificates usable for
creating qualified electronic signatures. A specific scope could be defined
for such a purpose which would detail the claims to be incorporated into
the access token and say that these claims shall be verified according to
sections 6.2.2 (Initial identity validation) of both ETSI EN 319 411-1
and ETSI EN 319 411-2.
The client supporting the user would then communicate that JWT to the RS
of its choice. The scope placed into the access token would testify
that the claims have indeed been verified according to sections 6.2.2 of
both ETSI EN 319 411-1 and ETSI EN 319 411-2.
Such a functionality cannot be supported using
draft-ietf-oauth-jwt-introspection-response.
In case the RS would be unable to decode the access token and/or to
validate it, it might make attempt to make a call to the AS according to
RFC 7662,
if this service is available (but the user has no way to indicate that
he consents for making such a call).
As a conclusion, since draft-ietf-oauth-jwt-introspection-response harms
the user's privacy and fully by-passes the User consent,
this draft should not be progressed to the RFC level.
Denis
The "can" works better, agreed. Thanks!
ᐧ
On Sat, Aug 29, 2020 at 8:25 AM Justin Richer <jric...@mit.edu
<mailto:jric...@mit.edu>> wrote:
Thanks, Dick. I agree with removing the excess parenthetical, but
I intentionally avoided using a lowercase “may” in the middle of
the text (in favor of “can”) to avoid normative-sounding
non-normative language, so I’d recommend that change be kept:
Implementers should be aware that a token introspection request
lets the AS know when the client
is accessing the RS, which can also indicate when the user is
using
the client. If this implication is not acceptable,
implementers can use other means to carry
access token data, e.g. directly transferring the data needed
by the RS within the access token.
On Aug 27, 2020, at 12:15 PM, Dick Hardt <dick.ha...@gmail.com
<mailto:dick.ha...@gmail.com>> wrote:
Here is a crisper revision.
Implementers should be aware that a token introspection request
lets the AS know when the client
is accessing the RS, which may indicate when the user is using
the client. If this implication is not acceptable,
implementers can use other means to carry
access token data, e.g. directly transferring the data needed
by the RS within the access token.
ᐧ
On Thu, Aug 27, 2020 at 7:19 AM Justin Richer <jric...@mit.edu
<mailto:jric...@mit.edu>> wrote:
I would clarify that this doesn’t necessarily say that the
user’s there, and remove the normative requirement (which
doesn’t have enforceable teeth in this context):
Implementers should be aware that a token introspection
request lets the AS know when the client
(and potentially the user) is accessing the RS, which
*can also indicate* when the user is using
the client. If this implication is not acceptable,
*implementers can use other means* to carry
access token data, e.g. directly transferring the data
needed by the RS within the access token.
— Justin
On Aug 27, 2020, at 9:48 AM, Torsten Lodderstedt
<torsten=40lodderstedt....@dmarc.ietf.org
<mailto:torsten=40lodderstedt....@dmarc.ietf.org>> wrote:
Will the following text work for you?
Implementers should be aware that a token introspection
request lets the AS know when the client
(and potentially the user) is accessing the RS, which is
also an indication of when the user is using
the client. If this impliction is not accepatable,
implementars MUST use other means to carry
access token data, e.g. directly transferring the data
needed by the RS within the access token.
On 26. Aug 2020, at 23:12, Mike Jones
<Michael.Jones=40microsoft....@dmarc.ietf.org
<mailto:Michael.Jones=40microsoft....@dmarc.ietf.org>> wrote:
I agree with Dick’s observation about the privacy
implications of using an Introspection Endpoint. That’s why
it’s preferable to not use one at all and instead directly
have the Resource understand the Access Token. One way of
doing this is the JWT Access Token spec. There are plenty
of others.
The downsides of using an Introspection Endpoint should be
described in the Privacy Considerations section.
-- Mike
From: OAuth <oauth-boun...@ietf.org
<mailto:oauth-boun...@ietf.org>> On Behalf Of Dick Hardt
Sent: Wednesday, August 26, 2020 9:52 AM
To: Torsten Lodderstedt
<torsten=40lodderstedt....@dmarc.ietf.org
<mailto:torsten=40lodderstedt....@dmarc.ietf.org>>
Cc: last-c...@ietf.org <mailto:last-c...@ietf.org>; oauth
<oauth@ietf.org <mailto:oauth@ietf.org>>
Subject: Re: [OAUTH-WG] Last Call:
<draft-ietf-oauth-jwt-introspection-response-09.txt> (JWT
Response for OAuth Token Introspection) to Proposed Standard
On Wed, Aug 26, 2020 at 4:37 AM Torsten Lodderstedt
<torsten=40lodderstedt....@dmarc.ietf.org
<mailto:torsten=40lodderstedt....@dmarc.ietf.org>> wrote:
Hi Denis,
On 25. Aug 2020, at 16:55, Denis <denis.i...@free.fr
<mailto:denis.i...@free.fr>> wrote:
The fact that the AS will know exactly when the
introspection call has been made and thus be able to make
sure which client
has attempted perform an access to that RS and at which
instant of time. The use of this call allows an AS to
track where and when
its clients have indeed presented an issued access token.
That is a fact. I don’t think it is an issue per se. Please
explain the privacy implications.
As I see it, the privacy implication is that the AS knows
when the client (and potentially the user) is accessing the
RS, which is also an indication of when the user is using
the client.
I think including this implication would be important to
have in a Privacy Considerations section.
/Dick
ᐧ
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