Hi Hannes,
Let us start by the last argument of this email which is copied below:
Finally, there are still two questions that have been raised but
which have not yet been answered at this time:
* how can a client request a JWT compliant to /this/ profile, and
* how can a client be confident that it got a JWT compliant to
/this/ profile ?
[Hannes] Regarding the two questions: It cannot and it was never the
intention of this work.
If this document was limited to section 2, it would simply be a
description of a specific profile, but it is more than that
since it includes two additional sections:
3. Requesting a JWT Access Token
4. Validating JWT Access Tokens
In section 3, the text states:
If the request does not include a "resource" parameter, the
authorization server *MUST* use in the "aud" claim
as default resource indicator.
If the authorization server has no way to know that the client is
sending a request which implies compliance
with draft-ietf-oauth-access-token-jwt why should it behave in such a way ?
In section 4 the text states:
resource servers receiving a JWT access token *MUST* validate it in
the following manner
If the resource server has no way to know that it is checking a JWT
which is supposed to be compliant
with draft-ietf-oauth-access-token-jwt why should it behave in such a way ?
The responses to these two questions are important before handling the
other comments.
IMHO, a token type would be able to easily address the problem;
otherwise sections 3 and 4 should be deleted.
The remaining of my replies are within the text below prefixed with [Denis].
Hi Denis,
Please see my response below.
*From:* Denis <denis.i...@free.fr>
*Sent:* Wednesday, June 3, 2020 12:12 PM
*To:* Hannes Tschofenig <hannes.tschofe...@arm.com>
*Cc:* Rifaat Shekh-Yusef <rifaat.s.i...@gmail.com>; Vittorio Bertocci
<vittorio.berto...@auth0.com>; oauth@ietf.org
*Subject:* Re: [OAUTH-WG] Second WGLC on "JSON Web Token (JWT) Profile
for OAuth 2.0 Access Tokens"
Hi Hannes,
I do appreciate your efforts to attempt to get rid of the "MUST NOT"
in the "Privacy considerations" section.
Let us look at the following proposed sentence:
While this is technical possible, it is important to note that the
OAuth 2.0 protocol does not aim to expose the content of the access token
to the client. The access token is therefore, by design,
considered to be opaque to the client".
/
In the context of this document/, a detailed content of the JWT is
expected and thus, if a client receives a JWT compliant to this profile
(and if the token is not encrypted which is most often the case) it
will absolutely be sure to pick up any guaranteed field within the JWT.
So, /in the context of this document/, the access token cannot be
considered to be opaque to the client.
[Hannes] Here we have a disconnect. The OAuth 2.0 design does not
assume that the client inspects the access tokens if it flies by. This
document could not change that.
The purpose of this document is actually quite simple: Those who want
to use JWT as a format for access tokens they can use the claims
described in this document.
You are also free to use whatever format you want.
[Denis] You wrote: "The OAuth 2.0 design does not *assume *that the
client inspects the access tokens if it flies by". However, there are
cases where
the client may be interested to know which attributes have been placed
into the JWT, there should be some way(s) to be able to do it.
Using Token Introspection (extended to be used by clients) would be like
bringing in an elephant to kill a mouse. Using a local API would be a
simple
solution, however the IETF defines (most often) protocols rather than
local APIs.
The user's privacy cannot be fulfilled if the client is unable to know
which attributes have been placed into the JWT. A solution to address
this issue
would be to clearly advertise the following in the Privacy
Considerations section:
As the OAuth 2.0 design does not assume that the client inspects the
access tokens if it flies by, clients have no way to know which
identity
attributes have effectively been placed into the JWT. Since these
identity attributes may disclose more private information than what
is strictly
necessary to perform one or more operations, this may be a serious
concern for users that care about their privacy.
About the second paragraph, /in the context of this document (/besides
the case where the JWT is encrypted), it is neither difficult,
nor impossible to parse the token/.
/
About the second paragraph, let us look at the following proposed
sentence/in the context of this document/ :
" Additionally, there is no guarantee that the access token is
conveyed by value and the authorization server implementation may change
the token format at any time ".
The argumentation that the token format may change at any point of
time, while being valid in the general case, is invalid /in the
context of this document/.
This JWT profile will be stable over time. This means that this quoted
sentence is inappropriate /in the context of this document/.
[Hannes] Here is the issue. In a given deployment you do not know how
the access token is encoded nor whether the claims are in this format.
You don’t know whether the token is conveyed by reference or by value.
Hence, why should we suddenly even give developers the impression
that OAuth Clients should look at the token.
[Denis] OAuth clients SHOULD only look at the attributes placed into the
JWT, when/if they have privacy concerns about the identity attributes
that have been placed into the JWT. Otherwise, they would have no idea
on how they could be traced by the resources servers /and other servers //
//that don't use OAuth/. In the current situation, it appears necessary
to clearly advertise in the Privacy Considerations section that the
token opacity
may be a serious concern for users that care about their privacy.
It is also important to note that the /foundational design assumption
/of keeping access tokens opaque to clients (and their users) is closing
the door
to any confidence for clients that their privacy is indeed preserved by
the authorization servers.
The third proposed paragraph is stating :
"In scenarios where it is where it is desirable for the clients to
obtain information transmitted in the access token, OAuth 2.0 token
introspection
may provide a useful tool to enable such functionality (proper
authorization assumed) ".
RFC 7662 (OAuth 2.0 Token Introspection) is a protocol to be used by
protected resources, but is not a protocol to be used by clients.
As indicated, in order to be usable, a "proper authorization" also
needs to be managed. Besides the difficulty to support such a protocol
for clients
and to twist its original usage as defined in RFC 7662, it is simpler
to develop the code to examine the content of the JWT, since its
content is guaranteed
to be stable over time.
[Hannes] While it may be simpler to inspect the access token, the use
of token introspection is a better match for the OAuth architecture.
We can talk about updating the token introspection RFC to also
describe this use case, assuming there is interest.
[Denis] Updating the token introspection RFC would be like bringing a
bull in a china shop.
The question in general will surface why the client should get access
to the content of the access token in the first place.
For those cases where information is passed to the client other
mechanisms, such as the identity token in OIDC, have been developed.
[Denis] The reason has been explained above: it has to do with
correlation of the users by different resources servers,
but also by other servers when "globally unique identifiers" are being
used in the "sub" claim.
The last proposed paragraph is the following:
" Since the content of the access token is accessible to the
resource server it is important to evaluate whether the resource
server gained the proper entitlement
to have access to any content received in form of claims, /for
example through user consent in some form, policies and agreements
with the organization running /
/ the authorization servers, and so on/. The policies and the
user interfaces to enable this user consent are, however, part of a
specific deployment and therefore
outside the scope of this document ".
The sentence "for example through user consent in some form, policies
and agreements with the organization running the authorization
servers, and so on"
should be removed, since this example lets believe that the consent is
handled by the authorizations servers while it might be handled by the
resource servers.
[Hannes] The information is disclosed by the authorization server and
hence the consent has to be with the authorization server.
The last proposed paragraph would be solution neutral if the example
were removed. This would lead to the following sentence:
Since the content of the access token is accessible to the resource
server it is important to evaluate whether the resource server gained
the proper entitlement
to have access to any content received in form of claims. The policies
and the user interfaces to enable this user consent are, however, part
of a specific deployment
and therefore outside the scope of this document.
[Denis] A resource server may say: "In order to perform this operation ,
I need your date of birth". If the user agrees, then the client will ask
to the authorization
server to insert the date of birth of the user into the JWT. In this
way, the consent is given by the client when talking to the resource
server. The authorization
server is not involved with a consent given by the user. Obviously, this
is one scenario and other scenarios exist, but such a scenario should
not be prevented.
The AS does not need to know which operation will be performed by the
user, it only needs to know that the user is willing his birth date to
be included into the JWT.
However, at the moment, since there is no RFC supporting such a
possibility, asking for specific standardized attributes is not (yet)
possible.
Finally, there are still two questions that have been raised but which
have not yet been answered at this time:
* how can a client request a JWT compliant to /this/ profile, and
* how can a client be confident that it got a JWT compliant to
/this/ profile ?
[Hannes] Regarding the two questions: It cannot and it was never the
intention of this work.
[Denis] This point has been addressed at the top of this email. However,
I would like to add one point.
Let us suppose that a token type would be added both in the token
request and within the token itself,
and if, at the minimum, the client would be allowed to access to this
token type, saying "This token is conformant to RFC XXX",
then the client would be able to call a local API able to disclose the
content of the token.
This would be like using a piece of cheese to catch the mouse.
Denis
Ciao
Hannes
Denis
Let me try to jump in here in order to make a proposal for the
text in the privacy consideration section:
FROM:
*6*
<https://tools.ietf.org/html/draft-ietf-oauth-access-token-jwt-04#section-6>*.
Privacy Considerations*
As JWT access tokens carry information by value, it now becomes
possible for requestors and receivers to directly peek inside the
token claims collection. The client MUST NOT inspect the
content of
the access token: the authorization server and the resource server
might decide to change token format at any time (for example by
switching from this profile to opaque tokens) hence any logic
in the
client relying on the ability to read the access token content
would
break without recourse. Nonetheless, authorization servers should
not assume that clients will comply with the above. Whenever
client
access to the access token content presents privacy issues for a
given scenario, the authorization server should take explicit steps
to prevent it as described below.
In scenarios in which JWT access tokens are accessible to the end
user, it should be evaluated whether the information can be
accessed
without privacy violations (for example, if an end user would
simply
access his or her own personal information) or if steps must be
taken
to enforce cofidentiality. Possible measures include:
encrypting the
access token, encrypting the sensitive claims, omitting the
sensitive
claims or not using this profile, falling back on opaque access
tokens.
In every scenario, the content of the JWT access token will
eventually be accessible to the resource server. It's important to
evaluate whether the resource server gained the proper
entitlement to
have access to any content received in form of claims, for example
through user consent in some form, policies and agreements with the
organization running the authorization servers, and so on.
TO:
*6
<https://tools.ietf.org/html/draft-ietf-oauth-access-token-jwt-04#section-6>.
Privacy Considerations*
The design of OAuth 2.0 envisions that access tokens are
created by
authorization servers and consumed by resource servers.
As JWT access tokens, as described in this document, carry
information by value, it is
possible for OAuth clients to peek inside the access token.
While this is technical possible, it is important to note that the
OAuth 2.0 protocol does not aim to expose the content of the
access token to the client. The access token is therefore, by
design, considered to be
opaque to the client.
A number of cases may make it difficult or impossible for
clients to
inspect the token, for example, the access token may be encrypted,
the access token may contain vendor-specific claims that have
not been
standardized or have been standardized in other consortia
making parsing
of the token difficult. Additionally, there is no guarantee
that the
access token is conveyed by value and the authorization server
implementation
may change the token format at any time.
In scenarios where it is desirable for the clients to obtain
information
transmitted in the access token, OAuth 2.0 token introspection
may provide
a useful tool to enable such functionality (proper
authorization assumed).
In scenarios where the content of the access token must not be
readable
by clients, encrypting the content of the access token is
RECOMMENDED.
Since the content of the access token is accessible to the
resource server
it is important to
evaluate whether the resource server gained the proper
entitlement to
have access to any content received in form of claims, for example
through user consent in some form, policies and agreements with the
organization running the authorization servers, and so on. The
policies
and the user interfaces to enable this user consent are,
however, part
of a specific deployment and therefore outside the scope of
this document.
How does this sound?
Ciao
Hannes
*From:* OAuth <oauth-boun...@ietf.org>
<mailto:oauth-boun...@ietf.org> *On Behalf Of *Rifaat Shekh-Yusef
*Sent:* Thursday, May 14, 2020 8:03 PM
*To:* Denis <denis.i...@free.fr> <mailto:denis.i...@free.fr>
*Cc:* Vittorio Bertocci <vittorio.berto...@auth0.com>
<mailto:vittorio.berto...@auth0.com>; oauth@ietf.org
<mailto:oauth@ietf.org>
*Subject:* Re: [OAUTH-WG] Second WGLC on "JSON Web Token (JWT)
Profile for OAuth 2.0 Access Tokens"
Denis,
You are rehashing the same issues that you have already discussed
on the mailing list multiple times,
You could not get the WG to agree with your points, because the WG
believe that this issue is outside the scope of this document.
The best the chairs can do at this stage is to capture your point
in the shepherd write-up to the IESG.
We think this document has the support of the WG and is ready to
move forward.
Regards,
Rifaat
On Thu, May 14, 2020 at 12:29 PM Denis <denis.i...@free.fr
<mailto:denis.i...@free.fr>> wrote:
Hi Vittorio,
I am referring to the email you sent on April the 29 th which
is copied below.
1) You wrote:
/> targeting of access tokens/
Let me think about that a bit longer.
I acknowledge that the decision of including an audience
has the effect of letting the AS track when the client
accesses a particular resource,
but at the same time that’s completely mainstream and very
much by design in a very large number of cases. As such, I
find the language
you are suggesting to be potentially confusing, as it
positions this as an exception vs a privacy protecting
mainstream that is in fact not common,
and ascribes to the client more latitude than I believe is
legitimate to expect or grant.
*I’ll try to come up with concise language that clarifies
to the reader that the current mechanism does allow AS
tracking*.
Since the last draft has been published on the 27 th, you have
not proposed any "concise language that clarifies to the reader
that the current mechanism does allow AS tracking".
2) You also wrote about the "sub" uniqueness:
As long as an identifier identifies one resource only, it
satisfies uniqueness. It doesn’t have to be a singleton.
RFC 7519 defines in section 4.1.2 the semantics of the "sub"
claim using the following sentence:
The subject value MUST either be scoped to be locally
unique in the context of the issuer or be globally unique.
The text does NOT say that the subject value "MUST be scoped
to be locally unique in the context of the *resource server*".
Changing the semantics of an already defined claim is not
permitted. If you would like to have such a semantics available,
a new claim should be defined (and it would be very nice to
have it !).
3) The text is the privacy considerations section states:
Although the ability to correlate requests might be
required by design in many scenarios, there are scenarios
where the authorization
server might want to prevent correlation to preserve the
desired level of privacy.
In the real world, it is also clients or end-users which would
like to prevent correlation to preserve their desired level of
privacy.
A better sentence would be:
Although the ability to correlate requests might be
required by design in many scenarios, there are scenarios
where the authorization
server *or the client* might want to prevent correlation to
preserve the desired level of privacy.
4) The text continues with:
Authorization servers should choose how to assign "sub"
values according to the level of privacy required by each
situation. For instance: if a solution requires preventing
tracking principal activities across multiple resource servers,
the authorization server should ensure that JWT access
tokens meant for different resource servers have distinct "sub"
values that cannot be correlated in the event of resource
servers collusion.
Authorization servers are not necessarily able to choose the
level of privacy required by each situation. When there are
different
situations for the same resource server, the scope is
(unfortunately at the moment) the only way to select the
"level of privacy that is required".
The example ("For instance:") is only an example that provides
a vague recommendation for the ASs which is NOT conformant
with the semantics of the "sub" claim as defined in RFC 7519.
What should be discussed here are not "examples" or what an
authorization server should do, but explanations about the
implications
for the end-user or for the client for the various values that
can be placed into the "sub" claim by an AS. The problem is
wider that simply
a collusion between resource servers, but also with other
servers that DO NOT participate in any OAuth exchange.
RFC 6973 (Privacy Considerations) states in section 7 : Guidelines
This section provides guidance for document authors in the
form of a questionnaire about a protocol being designed.
The questionnaire may be useful at any point in the design
process, particularly after document authors have developed
a high-level protocol model as described in [RFC4101].
One of the questions is:
f. *Correlation*. Does the protocol allow for correlation
of identifiers ? Are there expected ways that information
exposed
by the protocol will be combined or *correlated with
information obtained outside the protocol* ?
It is important to provide an answer to these two questions.
Hereafter is some text that is fully conformant with RFC 7519
which should be incorporated into the privacy considerations
section
which explains the implications of the two (and only two)
flavours of the "sub" claim.
When the sub claim contains a locally unique identifier in
the context of the issuer, this allows the tracking of
principal activities
across multiple resource servers.
When the sub claim contains a globally unique identifier,
this allows to correlate principal activities across
multiple resource
servers, while in addition, this globally unique
identifier may also allow to correlate the principal
activities on servers where
no access has been performed by the principals to these
servers but where the same globally unique identifiers are
being used
by these servers.
Denis
Thanks Denis for the thorough commentary.
/> The title of this spec./
Fixed, thanks!
/> The client MUST NOT inspect the content of the access
token/
This is really a sticky point. I really want to
acknowledge your PoV on this, but at the same time I found
this to be one of the biggest sources of issues in the use
of JWT for access tokens hence I feel we really need to
give solid guidance here. Let me expand further on the
reasoning behind it, and perhaps we can get to language
that satisfies both PoVs.
To me the key point is that clients should not write
/code/ that inspects access tokens. Taking a dependency on
the ability to do so is ignoring fundamental information
about the architecture and relationships between OAuth
roles, and suggests an ability of the client to understand
the semantic of the content that cannot be assumed in the
general case. I expanded on the details in my former reply
to you on this topic, I would recommend referring to it.
Clients violating this simple principle has been one of
the most common sources of production issues I had to deal
with in the past few years, and one of the hardest to
remediate given that clients are hard to update and
sometimes the things they relied on were irremediably
lost. This is why I am inclined to put in here strong
language.
That said: I have nothing against client developers
examining a network trace and drawing conclusions based on
the content of what they see. That doesn’t create any hard
dependencies and has no implications in respect to changes
in the solution behavior. However I am not sure how to
phrase that in the specification, given that referring to
the client inevitably refers to its code. I am open to
suggestions.
> 3)…
I have a pretty hard time following the chain of reasoning
in this section. Let me attempt to tackle it to the best
of my understanding.
I think the key might be
/> a client should be able to choose whether it wishes the
sub claim to contain [..]/
I don’t think that should be a choice left to the client.
In business systems, my experience is that the type of
identifiers to be used (when the IdP gives any choice at
all) is established at resource provisioning time. I am
not aware of mechanisms thru which a client signals the
nature of the identifier to be used, nor that would be
fully feasible (the resource knows what it needs to
perform its function).
Furthermore:
/> which has nothing to do with uniqueness since the value
changes for every generated token./
Again, this is something that was touched on in my former
reply to your message. As long as an identifier identifies
one resource only, it satisfies uniqueness. It doesn’t
have to be a singleton.
Finally, the scope is optional (for good reasons: 1^st
party and non delegation scenarios don’t require it) hence
it cannot be relied upon for properties that should hold
in every scenario.
In summary: per the preceding thread on this topic, the
consensus was that varying the sub content was a
satisfactory way of protecting against correlation. I
don’t a gree that clients should have a mechanism to
request different sub flavors, as that decision should be
done out of band by the AS and RS; and the scope isn’t
always available anyway.
/> targeting of access tokens/
Let me think about that a bit longer.
I acknowledge that the decision of including an audience
has the effect of letting the AS track when the client
accesses a particular resource, but at the same time
that’s completely mainstream and very much by design in a
very large number of cases. As such, I find the language
you are suggesting to be potentially confusing, as it
positions this as an exception vs a privacy protecting
mainstream that is in fact not common, and ascribes to the
client more latitude than I believe is legitimate to
expect or grant.
I’ll try to come up with concise language that clarifies
to the reader that the current mechanism does allow AS
tracking.
*From: *OAuth <oauth-boun...@ietf.org>
<mailto:oauth-boun...@ietf.org> on behalf of Denis
<denis.i...@free.fr> <mailto:denis.i...@free.fr>
*Date: *Wednesday, April 29, 2020 at 09:12
*To: *"oauth@ietf.org" <mailto:oauth@ietf.org>
<oauth@ietf.org> <mailto:oauth@ietf.org>
*Subject: *Re: [OAUTH-WG] Second WGLC on "JSON Web Token
(JWT) Profile for OAuth 2.0 Access Tokens"
You will find four comments numbered 1) to 4).
*1) *The title of this spec. is:
JSON Web Token (JWT) Profile for OAuth *2.0* Access Tokens
So, this spec. is supposed to be targeted to OAuth *2.0.
* However, the header at the top of the page omits to
mention it.
Currently, it is :
Internet-Draft OAuth Access Token JWT Profile
April 2020
It should rather be:
Internet-Draft OAuth *2.0* Access Token JWT Profile April 2020
*2)* The following text is within section 6.
The client MUST NOT inspect the content of
the access token: the authorization server and the
resource server
might decide to change token format at any time (for
example by
switching from this profile to opaque tokens) hence any
logic in the
client relying on the ability to read the access token
content would
break without recourse.
Nonetheless, authorization servers should
not assume that clients will comply with the above.
It is of a primary importance that clients MAY be able to
inspect tokens before transmitting them.
The "MUST NOT" is not acceptable.
The above text should be replaced with:
Reading the access token content may be useful for the
user to verify that
the access token content matches with its expectations.
However,
the authorization server and the resource server might
decide to change the
token format at any time. Thus, the client should not
expect to always be
in a position to read the access token content.
The remaining of the text about this topic is fine.
*3) *The next topic is about the sub claim.
The text states:
Although the ability to correlate requests might be
required by
design in many scenarios, there are scenarios where the
authorization
server might want to prevent correlation to preserve the
desired
level of privacy. Authorization servers should choose how
to assign
sub values according to the level of privacy required by each
situation.
I have a set of questions:
1. How can authorization servers choose how to assign sub
values according to the level of privacy required "by
each situation" ?
2. How can authorization servers know the level of
privacy required "by each situation" ?
3. How can the users be informed of the level of privacy
required "by each situation" ?
4. How can the users *consent* with the level of privacy
required "by each situation" ?
Currently, the request MUST include either a resource
parameter or an aud claim parameter, while it MAY include
a scope parameter.
The syntax of the scope parameter is a list of
space-delimited, case-sensitive strings (RFC 6749). It is
thus subject to private agreements
between clients and Authorization Servers. Since the scope
is being returned, it is a primary importance that the
returned scope matches
with its expectations before transmitting the token to a
Resource Server.
In theory, a client should be able to choose whether it
wishes the sub claim to contain :
* a global unique identifier for all ASs ("globally
unique"),
* a unique identifier for each AS ("locally unique in
the context of the issuer"),
* a different pseudonym for each RS, or
* a different pseudonym for each authorization token
request.
The only variable parameter that it can use for this
purpose in the token request is the scope parameter.
RFC 7519 states is section 4.1.2:
The subject value MUST either be scoped to be locally
unique in the context of the issuer
or be globally unique.
It is quite hard to recognize that the sub claim is able
to carry a different pseudonym for each RS, i.e. for case
(c), or
a different pseudonym for each authorization token
request, i.e. for case (d), which has nothing to do with
uniqueness
since the value changes for every generated token.
This has implications about the following text:
For instance: if a solution requires preventing tracking
principal activities across multiple resource servers, the
authorization server should ensure that JWT access tokens
meant for
different resource servers have distinct sub values that
cannot be
correlated in the event of resource servers collusion.
Since it addresses case (c).
and also about the following text:
4.b) Similarly: if a solution requires preventing a
resource server from
correlating the principal’s activity within the resource
itself, the
authorization server should assign different sub values
for every JWT
access token issued.
Since it addresses case (d).
This means that the current text placed in the privacy
considerations section was a good attempt to address the
case,
but that the text needs to be revised.
Proposed text replacement for all the previously quoted
sentences:
According to RFC 7519 (4.1.2): The subject value MUST
either be scoped to be locally unique in the context of
the issuer or be globally unique.
When the sub claim contains a globally unique identifier,
this allows to correlate principal activities across
multiple resource servers, while in addition,
this globally unique identifier may also allow to
correlate the principal activities on servers where no
access has been performed by the principals
to these servers but where the same globally unique
identifiers are being used by these servers.
When the sub claim contains a locally unique identifier in
the context of the issuer, this also allows the tracking
of principal activities across multiple resource servers.
The scope request parameter is the only way to influence
on the content of the sub claim parameter. Its meaning is
subject to a private agreement
between the client and the AS, which means that the use of
the scope parameter is the only way to choose between a
locally unique identifier
in the context of the issuer or a globally unique identifier.
Since the scope parameter is being returned, it is a
primary importance that the returned scope matches with
the expectations of the client before transmitting
the token to a Resource Server.
However, there are other cases where the client would like
to be able to choose whether it wishes the sub claim to
contain :
- a different pseudonym for each RS so that different
resource servers will be unable to correlate its
activities, or
- a different pseudonym for each authorization token
request, so that the same resource server cannot correlate
its activities performed at different instant of time.
Considering the semantics of the sub claim, these two
cases cannot be currently supported.
*4) *The next topic is about the targeting of access tokens
Text had been proposed before the last conference call.
Then, the topic has been presented at the very end of the
last conference call, but no text has been included
in the next draft.
Here is a revised text be included in the privacy
considerations section:
For security reasons, some clients may be willing to
target their access tokens but, for privacy reasons, may
be unwilling to disclose to Authorization Servers
an identification of the Resource Servers they are going
to access, so that Authorization Servers will be unable to
know which resources servers are being accessed.
The disclosure of the Resource Servers names allows the
Authorization Servers to list all the Resource Servers
being access by all its users and in addition to list pairs
of (Principal, Resource Servers) which allow to trace all
the users accesses to Resource Servers performed through a
given Authorization Server. When a token is targeted,
this profile does not contain provisions to address these
two threats.
Denis
Hi all,
This is a second working group last call for "JSON Web
Token (JWT) Profile for OAuth 2.0 Access Tokens".
Here is the document:
https://tools.ietf.org/html/draft-ietf-oauth-access-token-jwt-06
Please send your comments to the OAuth mailing list by
April 29, 2020.
Regards,
Rifaat & Hannes
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