Internet DRAFT - draft-maler-oauth-umagrant
draft-maler-oauth-umagrant
Network Working Group E. Maler, Ed.
Internet-Draft ForgeRock
Intended status: Informational M. Machulak
Expires: August 17, 2019 HSBC
J. Richer
Bespoke Engineering
T. Hardjono
MIT
February 13, 2019
User-Managed Access (UMA) 2.0 Grant for OAuth 2.0 Authorization
draft-maler-oauth-umagrant-00
Abstract
This specification defines a means for a client, representing a
requesting party, to use a permission ticket to request an OAuth 2.0
access token to gain access to a protected resource asynchronously
from the time a resource owner authorizes access.
Status of This Memo
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This Internet-Draft will expire on August 17, 2019.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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to this document. Code Components extracted from this document must
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 4
1.2. Roles . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Abstract Flow . . . . . . . . . . . . . . . . . . . . . . 5
1.3.1. Authorization Process . . . . . . . . . . . . . . . . 7
2. Authorization Server Metadata . . . . . . . . . . . . . . . . 8
3. Flow Details . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1. Client Requests Resource Without Providing an Access
Token . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2. Resource Server Responds to Client's Tokenless Access
Attempt . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2.1. Resource Server Response to Client on Permission
Request Success . . . . . . . . . . . . . . . . . . . 10
3.2.2. Resource Server Response to Client on Permission
Request Failure . . . . . . . . . . . . . . . . . . . 10
3.3. Client Seeks RPT on Requesting Party's Behalf . . . . . . 11
3.3.1. Client Request to Authorization Server for RPT . . . 11
3.3.2. Client Redirect of Requesting Party to Authorization
Server for Interactive Claims-Gathering . . . . . . . 13
3.3.3. Authorization Server Redirect of Requesting Party
Back to Client After Interactive Claims-Gathering . . 15
3.3.4. Authorization Assessment and Results Determination . 16
3.3.5. Authorization Server Response to Client on
Authorization Success . . . . . . . . . . . . . . . . 18
3.3.6. Authorization Server Response to Client on
Authorization Failure . . . . . . . . . . . . . . . . 20
3.4. Client Requests Resource and Provides an RPT . . . . . . 23
3.5. Resource Server Responds to Client's RPT-Accompanied
Resource Request . . . . . . . . . . . . . . . . . . . . 23
3.6. Authorization Server Refreshes RPT . . . . . . . . . . . 24
3.7. Client Requests Token Revocation . . . . . . . . . . . . 24
4. Profiles and Extensions . . . . . . . . . . . . . . . . . . . 24
5. Security Considerations . . . . . . . . . . . . . . . . . . . 25
5.1. Cross-Site Request Forgery . . . . . . . . . . . . . . . 25
5.2. RPT and PCT Exposure . . . . . . . . . . . . . . . . . . 26
5.3. Strengthening RPT Protection Using Proof of Possession . 27
5.4. Credentials-Guessing . . . . . . . . . . . . . . . . . . 28
5.5. Permission Ticket Management . . . . . . . . . . . . . . 28
5.6. Naive Implementations of Default-Deny Authorization . . . 28
5.7. Requirements for Pre-Established Trust Regarding Claim
Tokens . . . . . . . . . . . . . . . . . . . . . . . . . 29
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5.8. Profiles and Trust Establishment . . . . . . . . . . . . 29
6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 30
6.1. Policy Condition Setting, Time-to-Live Management, and
Removal of Authorization Grants . . . . . . . . . . . . . 30
6.2. Requesting Party Information at the Authorization Server 30
6.3. Resource Owner Information at the Resource Server . . . . 31
6.4. Profiles and Trust Establishment . . . . . . . . . . . . 31
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31
7.1. Well-Known URI Registration . . . . . . . . . . . . . . . 31
7.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 31
7.2. OAuth 2.0 Authorization Server Metadata Registry . . . . 32
7.2.1. Registry Contents . . . . . . . . . . . . . . . . . . 32
7.3. OAuth 2.0 Dynamic Client Registration Metadata Registry . 32
7.3.1. Registry Contents . . . . . . . . . . . . . . . . . . 32
7.4. OAuth 2.0 Extension Grant Parameters Registration . . . . 33
7.4.1. Registry Contents . . . . . . . . . . . . . . . . . . 33
7.5. OAuth 2.0 Extensions Error Registration . . . . . . . . . 34
7.5.1. Registry Contents . . . . . . . . . . . . . . . . . . 34
7.6. OAuth Token Type Hints Registration . . . . . . . . . . . 35
7.6.1. Registry Contents . . . . . . . . . . . . . . . . . . 35
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 35
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 36
9.1. Normative References . . . . . . . . . . . . . . . . . . 36
9.2. Informative References . . . . . . . . . . . . . . . . . 37
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 38
1. Introduction
This specification defines an extension OAuth 2.0 [RFC6749] grant.
The grant enhances OAuth capabilities in the following ways:
o The resource owner authorizes protected resource access to clients
used by entities that are in a _requesting party_ role. This
enables party-to-party authorization, rather than authorization of
application access alone.
o The authorization server and resource server interact with the
client and requesting party in a way that is _asynchronous_ with
respect to resource owner interactions. This lets a resource
owner configure an authorization server with authorization grant
rules (policy conditions) at will, rather than authorizing access
token issuance synchronously just after authenticating.
For example, bank customer (resource owner) Alice with a bank account
service (resource server) can use a sharing management service
(authorization server) hosted by the bank to manage access to her
various protected resources by spouse Bob, accounting professional
Charline, and and financial information aggregation company Decide
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Account, all using different client applications. Each of her bank
accounts is a protected resource, and two different scopes of access
she can control on them are viewing account data and accessing
payment functions.
An OPTIONAL second specification, [UMAFedAuthz], defines a means for
an UMA-enabled authorization server and resource server to be loosely
coupled, or federated, in a resource owner context. This
specification, together with [UMAFedAuthz], constitutes UMA 2.0.
1.1. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
Unless otherwise noted, all parameter names and values are case
sensitive. JSON [RFC7159] data structures defined in this
specification MAY contain extension parameters that are not defined
in this specification. Any entity receiving or retrieving a JSON
data structure SHOULD ignore extension parameters it is unable to
understand. Extension names that are unprotected from collisions are
outside the scope of this specification.
1.2. Roles
The UMA grant enhances the OAuth definitions of entities in order to
accommodate the requesting party role.
resource owner
An entity capable of granting access to a protected resource, the
"user" in User-Managed Access. The resource owner MAY be an end-
user (natural person) or MAY be a non-human entity treated as a
person for limited legal purposes (legal person), such as a
corporation.
requesting party
A natural or legal person that uses a client to seek access to a
protected resource. The requesting party may or may not be the
same party as the resource owner.
client
An application that is capable of making requests for protected
resources with the resource owner's authorization and on the
requesting party's behalf.
resource server
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A server that hosts resources on a resource owner's behalf and is
capable of accepting and responding to requests for protected
resources.
authorization server
A server that protects, on a resource owner's behalf, resources
hosted at a resource server.
1.3. Abstract Flow
The UMA grant enhances the abstract protocol flow of OAuth.
Figure 1 shows an example flow illustrating a variety of messaging
paths and artifacts. The resource owner entity and its
communications with the authorization server are included for
completeness, although policy condition setting is outside the scope
of this specification and communications among the other four
entities are asynchrjonous with respect to resource owner actions.
Further, although both claims pushing and interactive claims
gathering are shown, both might not typically be used in one
scenario.
requesting authorization resource resource
party client server server owner
| | | | |
| | |Set policy| |
| | |conditions (anytime)|
| | |<- - - - - - - - - -|
| |Resource request (no access token) | |
| |------------------------------------->| |
| |401 response with initial permission | |
| |ticket, authz server location | |
| |<-------------------------------------| |
| |Access token (RPT) request | | |
| |with permission ticket, | | |
| |claim token (push claims) | | |
| |-------------------------->| | |
| | +----|Authz | |
| | +--->|assessment| |
| |403 response with new | | |
| |permission ticket, | | |
| |need_info error, | | |
| |redirect_user hint | | |
| |<--------------------------| | |
|Redirect | | | |
|user with | | | |
|permission | | | |
|ticket | | | |
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|<-----------| | | |
|Follow redirect to authz server | | |
|--------------------------------------->| | |
|Interactive claims gathering | | |
|<- - - - - - - - - - - - - - - - - - - >| | |
|Redirect back with new permission | | |
|ticket | | |
|<---------------------------------------| | |
|Follow | | | |
|redirect | | | |
|to client | | | |
|----------->| | | |
| |RPT request with permission| | |
| |ticket | | |
| |-------------------------->| | |
| | +----|Authz | |
| | +--->|assessment| |
| |Response with RPT and PCT | | |
| |<--------------------------| | |
| |Resource request with RPT | | |
| |------------------------------------->| |
| |Protected resource | | |
| |<-------------------------------------| |
Figure 1: Example Flow
Following are key concepts relevant to this specification, as
illustrated in the figure:
requesting party token (RPT) An OAuth access token associated with
the UMA grant. An RPT is unique to a requesting party, client,
authorization server, resource server, and resource owner.
permission Authorized access to a particular resource with some
number of scopes bound to that resource. A permission ticket
represents some number of requested permissions. An RPT
represents some number of granted permissions. Permissions are
part of the authorization server's process and are opaque to the
client.
permission ticket A correlation handle representing requested
permissions that is created and maintained by the authorization
server, initially passed to the client by the resource server, and
presented by the client at the token endpoint and during
requesting party redirects.
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authorization process The process through which the authorization
server determines whether it should issue an RPT to the client on
the requesting party's behalf, based on a variety of inputs. A
key component of the process is authorization assessment. (See
Section 1.3.1.)
claim A statement of the value or values of one or more attributes
of an entity. The authorization server typically needs to collect
and assess one or more claims of the requesting party or client
against policy conditions as part of protecting a resource. The
two methods available for UMA claims collection are claims pushing
and interactive claims gathering. Note: Claims collection might
involve authentication for unique user identification, but
depending on policy conditions might additionally or instead
involve the collection of non-uniquely identifying attributes,
authorization for some action (for example, see Section 3.3.3), or
other statements of agreement.
claim token A package of claims provided directly by the client to
the authorization server through claims pushing.
persisted claims token (PCT) A correlation handle issued by an
authorization server that represents a set of claims collected
during one authorization process, available for a client to use in
attempting to optimize a future authorization process.
Note: How the client acquired knowledge of the resource server's
interface and the specific endpoint of the desired protected resource
is outside the scope of this specification. For example, the
resource server might have a programmatic API or it might serve up
simple web pages, and the resource owner might have advertised the
endpoint publicly on a blog or other website, listed it in a
discovery service, or emailed a link to a particular intended
requesting party.
1.3.1. Authorization Process
The authorization process involves the following activities:
o Claims collection. Claims pushing by a client is defined in
Section 3.3.1, and interactive claims gathering with an end-user
requesting party is defined in Section 3.3.2.
o Authorization assessment (as defined in Section 3.3.4).
Authorization assessment involves the authorization server
assembling and evaluating policy conditions, scopes, claims, and
any other relevant information sourced outside of UMA claims
collection flows, in order to mitigate access authorization risk.
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o Authorization results determination (as defined in Section 3.3.4).
The authorization server either returns a success code (as defined
in Section 3.3.5), an RPT, and an optional PCT, or an error code
(as defined in Section 3.3.6). If the error code is "need_info"
or "request_submitted", the authorization server provides a
permission ticket, giving the client an opportunity to continue
within the same authorization process (including engaging in
further claims collection).
Different choices of claims collection methods, other inputs to
authorization assessment, and error codes might be best suited for
different deployment ecosystems. For example, where no pre-
established relationship is expected between the resource owner's
authorization server and the requesting party, initial requesting
party redirection might be a useful pattern, at which point the
authorization server might either authenticate the requesting party
locally or serve as a relying party for a remote identity provider.
Where a common authorization server functions as an identity provider
for all resource owners and requesting parties, having the client
push claim tokens sourced from that central server itself with a pre-
negotiated format and contents might be a useful pattern.
2. Authorization Server Metadata
The authorization server supplies metadata in a discovery document to
declare its endpoints. The client uses this discovery document to
discover these endpoints for use in the flows defined in Section 3.
The authorization server MUST make a discovery document available.
The structure of the discovery document MUST conform to that defined
in [OAuthMeta]. The discovery document MUST be available at an
endpoint formed by concatenating the string "/.well-known/
uma2-configuration" to the "issuer" metadata value defined in
[OAuthMeta], using the well-known URI syntax and semantics defined in
[RFC5785]. In addition to the metadata defined in [OAuthMeta], this
specification defines the following metadata for inclusion in the
discovery document:
claims_interaction_endpoint
OPTIONAL. A static endpoint URI at which the authorization
server declares that it interacts with end-user requesting
parties to gather claims. If the authorization server also
provides a claims interaction endpoint URI as part of its
"redirect_user" hint in a "need_info" response to a client on
authorization failure (see Section 3.3.6), that value overrides
this metadata value. Providing the static endpoint URI is
useful for enabling interactive claims gathering prior to any
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pushed-claims flows taking place, for example, for gathering
authorization for subsequent claim pushing (see Section 3.3.2).
uma_profiles_supported
OPTIONAL. UMA profiles and extensions supported by this
authorization server. The value is an array of string values,
where each string value is a URI identifying an UMA profile or
extension. As discussed in Section 4, an authorization server
supporting a profile or extension related to UMA SHOULD supply
the specification's identifying URI (if any) here.
If the authorization server supports dynamic client registration, it
MUST allow client applications to register "claims_redirect_uri"
metadata, as defined in Section 3.3.2, using the following metadata
field:
claims_redirect_uris
OPTIONAL. Array of one or more claims redirection URIs.
3. Flow Details
3.1. Client Requests Resource Without Providing an Access Token
The client requests a protected resource without providing any access
token.
Note: This process does not assume that any relevant policy
conditions have already been defined at the authorization server.
For an example of how the resource server can put resources under the
protection of an authorization server, see [UMAFedAuthz].
Example of a client request at a protected resource without providing
an access token:
GET /users/alice/album/photo.jpg HTTP/1.1 Host:
photoz.example.com ...
3.2. Resource Server Responds to Client's Tokenless Access Attempt
The resource server responds to the client's tokenless resource
request.
The resource server MUST obtain a permission ticket from the
authorization server to provide in its response, but the means of
doing so is outside the scope of this specification. For an example
of how the resource server can obtain the permission ticket, see
[UMAFedAuthz].
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The process of choosing what permissions to request from the
authorization server may require interpretation and mapping of the
client's resource request. The resource server SHOULD request a set
of permissions with scopes that is reasonable for the client's
resource request.
Note: In order for the resource server to know which authorization
server to approach for the permission ticket and on which resource
owner's behalf, it needs to derive the necessary information using
cues provided by the structure of the API where the resource request
was made, rather than by an access token. Commonly, this information
can be passed through the URI, headers, or body of the client's
request. Alternatively, the entire interface could be dedicated to
the use of a single resource owner and protected by a single
authorization server.
See Section 5.5 for permission ticket security considerations.
3.2.1. Resource Server Response to Client on Permission Request Success
If the resource server is able to provide a permission ticket from
the authorization server, it responds to the client by providing a
"WWW-Authenticate" header with the authentication scheme "UMA", with
the "issuer" URI from the authorization server's discovery document
in an "as_uri" parameter and the permission ticket in a "ticket"
parameter.
For example:
HTTP/1.1 401 Unauthorized WWW-Authenticate: UMA
realm="example", as_uri="https://as.example.com",
ticket="016f84e8-f9b9-11e0-bd6f-0021cc6004de" ...
3.2.2. Resource Server Response to Client on Permission Request Failure
If the resource server is unable to provide a permission ticket from
the authorization server, then it includes a header of the following
form in its response to the client: "Warning: 199 - "UMA
Authorization Server Unreachable"".
For example:
HTTP/1.1 403 Forbidden Warning: 199 - "UMA Authorization
Server Unreachable" ...
Without an authorization server location and permission ticket, the
client is unable to continue.
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3.3. Client Seeks RPT on Requesting Party's Behalf
The client seeks issuance of an RPT.
This process assumes that:
o The client has obtained a permission ticket and an authorization
server location from the resource server.
o The client has retrieved the authorization server's discovery
document as needed.
o The client has obtained a client identifier or a full set of
client credentials as appropriate, either statically or
dynamically (for example, through [RFC7591] or
[OIDCDynClientReg]). This grant works with clients of both
confidential and public types.
Initiation of this process has two options. One option is for the
client to request an RPT from the token endpoint immediately, as
defined in Section 3.3.1. Claim pushing is available at this
endpoint. The other option, if the authorization server's discovery
document statically provided a claims interaction endpoint, is for
the client to redirect the requesting party immediately to that
endpoint for interactive claims gathering, as defined in
Section 3.3.2.
3.3.1. Client Request to Authorization Server for RPT
The client makes a request to the token endpoint by sending the
following parameters:
grant_type REQUIRED. MUST be the value
"urn:ietf:params:oauth:grant-type:uma-ticket".
ticket REQUIRED. The most recent permission ticket received by the
client as part of this authorization process.
claim_token OPTIONAL. If this parameter is used, it MUST appear
together with the "claim_token_format" parameter. A string
containing directly pushed claim information in the indicated
format. It MUST be base64url encoded unless specified otherwise
by the claim token format. The client MAY provide this
information on both first and subsequent requests to this
endpoint. The client and authorization server together might need
to establish proper audience restrictions for the claim token
prior to claims pushing. See Section 5.7 and Section 6.2 for
security and privacy considerations regarding pushing of claims.
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claim_token_format OPTIONAL. If this parameter is used, it MUST
appear together with the "claim_token" parameter. A string
specifying the format of the claim token in which the client is
directly pushing claims to the authorization server. The string
MAY be a URI. Examples of potential types of claim token formats
are [OIDCCore] ID Tokens and SAML assertions.
pct OPTIONAL. If the authorization server previously returned a PCT
along with an RPT, the client MAY include the PCT in order to
optimize the process of seeking a new RPT. Given that some claims
represented by a PCT are likely to contain identity information
about a requesting party, a client supplying a PCT in its RPT
request MUST make a best effort to ensure that the requesting
party using the client now is the same as the requesting party
that was associated with the PCT when it was issued. See
Section 5.7 and Section 6.2 for additional security and privacy
considerations regarding persistence of claims. The client MAY
use the PCT for the same requesting party when seeking an RPT for
a resource different from the one sought when the PCT was issued,
or a protected resource at a different resource server entirely.
See Section 5.2 for additional PCT security considerations. See
Section 3.3.5 for the form of the authorization server's response
with a PCT.
rpt OPTIONAL. Supplying an existing RPT (which MAY be expired)
gives the authorization server the option of upgrading that RPT
instead of issuing a new one (see Section 3.3.5.1 for more about
this option).
scope OPTIONAL. A string of space-separated values representing
requested scopes. For the authorization server to consider any
requested scope in its assessment, the client MUST have been pre-
registered for the same scope with the authorization server. The
client should consult the resource server's API documentation for
details about which scopes it can expect the resource server's
initial returned permission ticket to represent as part of the
authorization assessment (see Section 3.3.4).
Example of a request message with no optional parameters (line breaks
are shown only for display convenience):
POST /token HTTP/1.1 Host: as.example.com Authorization:
Basic jwfLG53^sad$#f ...
grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Auma-ticket
&ticket=016f84e8-f9b9-11e0-bd6f-0021cc6004de
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Example of a request message that includes an existing RPT for
upgrading, a scope being sought that was previously registered with
the authorization server, and a PCT and a claim token for
consideration in the authorization process:
POST /token HTTP/1.1 Host: as.example.com Authorization:
Basic jwfLG53^sad$#f ...
grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Auma-ticket
&ticket=016f84e8-f9b9-11e0-bd6f-0021cc6004de
&claim_token=eyj0...
&claim_token_format=http%3A%2F%2Fopenid.net%2Fspecs%2Fopenid-connect-core-1_0.html%23IDToken
&pct=c2F2ZWRjb25zZW50
&rpt=sbjsbhs(/SSJHBSUSSJHVhjsgvhsgvshgsv
&scope=read
This specification provides a means to define profiles of claim token
formats for use with UMA (see Section 4). The authorization server
SHOULD document the profiles it supports in its discovery document.
3.3.2. Client Redirect of Requesting Party to Authorization Server for
Interactive Claims-Gathering
The client redirects an end-user requesting party to the
authorization server's claims interaction endpoint for one or more
interactive claims-gathering processes as the authorization server
requires. These can include direct interactions, such as account
registration and authentication local to the authorization server as
an identity provider, filling out a questionnaire, or asking the user
to authorize subsequent collection of claims by interaction or
pushing, and persistent storage of such claims (for example, as
associated with a PCT). Interactions could also involve further
redirection, for example, for federated (such as social)
authentication at a remote identity provider, and other federated
claims gathering. See Section 5.7 and Section 6.2 for security and
privacy considerations regarding pushing and persistence of claims.
The client might have initiated redirection immediately on receiving
an initial permission ticket from the resource server, or, for
example, in response to receiving a "redirect_user" hint in a
"need_info" error (see Section 3.3.6).
In order for the client to redirect the requesting party immediately
on receiving the initial permission ticket from the resource server,
this process assumes that the authorization server has statically
declared its claims interaction endpoint in its discovery document.
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The client constructs the request URI by adding the following
parameters to the query component of the claims interaction endpoint
URI using the "application/x-www-form-urlencoded" format:
client_id REQUIRED. The client's identifier issued by the
authorization server.
ticket REQUIRED. The most recent permission ticket received by the
client as part of this authorization process.
claims_redirect_uri REQUIRED if the client has pre-registered
multiple claims redirection URIs or has pre-registered no claims
redirection URI; OPTIONAL only if the client has pre-registered a
single claims redirection URI. The URI to which the client wishes
the authorization server to direct the requesting party's user
agent after completing its interaction. The URI MUST be absolute,
MAY contain an "application/x-www-form-urlencoded"-formatted query
parameter component that MUST be retained when adding additional
parameters, and MUST NOT contain a fragment component. The client
SHOULD pre-register its "claims_redirect_uri" with the
authorization server, and the authorization server SHOULD require
all clients, and MUST require public clients, to pre-register
their claims redirection endpoints (see Section 2). Claims
redirection URIs are different from the redirection URIs defined
in [RFC6749] in that they are intended for the exclusive use of
requesting parties and not resource owners. Therefore,
authorization servers MUST NOT redirect requesting parties to pre-
registered redirection URIs defined in [RFC6749] unless such URIs
are also pre-registered specifically as claims redirection URIs.
If the URI is pre-registered, this URI MUST exactly match one of
the pre-registered claims redirection URIs, with the matching
performed as described in Section 6.2.1 of [RFC3986] (Simple
String Comparison).
state RECOMMENDED. An opaque value used by the client to maintain
state between the request and callback. The authorization server
includes this value when redirecting the user agent back to the
client. The use of this parameter is for preventing cross-site
request forgery (see Section 5.1 for further security
information).
Example of a request issued by a client application (line breaks are
shown only for display convenience):
GET /rqp_claims?client_id=some_client_id
&ticket=016f84e8-f9b9-11e0-bd6f-0021cc6004de
&claims_redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fredirect_claims
&state=abc HTTP/1.1 Host: as.example.com
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3.3.3. Authorization Server Redirect of Requesting Party Back to Client
After Interactive Claims-Gathering
At the conclusion of a successful interaction with the requesting
party, the authorization server returns the requesting party to the
client, adding the following parameters to the query component of the
claims redirection URI using the "application/x-www-form-urlencoded"
format:
ticket REQUIRED. A permission ticket that allows the client to make
further requests to the authorization server during this
authorization process. The value MUST NOT be the same as the one
the client used to make its request.
state OPTIONAL. The same state value that the client provided in
the request. It MUST be present if and only if the client
provided it (see Section 5.1 for further security information).
Note: Interactive claims-gathering processes are outside the scope of
this specification. The purpose of the interaction is for the
authorization server to gather information for its own authorization
assessment purposes. This redirection does not involve sending any
of the information back to the client.
The authorization server MAY use interactive claims-gathering to
request authorization from the requesting party for persisting claims
across authorization processes. Such persisted claims will be
represented by a PCT issued to the client in a subsequent step.
The client MUST ignore unrecognized response parameters. If the
request fails due to a missing, invalid, or mismatching claims
redirection URI, or if the client identifier is missing or invalid,
the authorization server SHOULD inform the requesting party of the
error and MUST NOT automatically redirect the user agent to the
invalid redirection URI.
If the request fails for reasons other than a missing or invalid
claims redirection URI, the authorization server informs the client
by adding an "error" parameter to the query component of the claims
redirection URI as defined in Section 4.1.2.1 of [RFC6749].
Example of a response issued by an authorization server (line breaks
are shown only for display convenience):
HTTP/1.1 302 Found Location:
https://client.example.com/redirect_claims?
ticket=cHJpdmFjeSBpcyBjb250ZXh0LCBjb250cm9s&state=abc
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3.3.4. Authorization Assessment and Results Determination
When the authorization server has received a request for an RPT from
a client as defined in Section 3.3.1, it assesses whether the client
is authorized to receive the requested RPT and determines the
results.
The authorization server MUST apply the following conceptual
authorization assessment calculation in determining authorization
results. Note: As this calculation is internal to authorization
server operations, its particulars are outside the scope of this
specification.
1. Assemble a set called _RegisteredScopes_ containing the scopes
for which the client is pre-registered (either dynamically or
through some static process) at the authorization server.
Assemble a set called _RequestedScopes_ containing the scopes the
client most recently requested at the token endpoint. The
permission ticket that was presented by the client at the token
endpoint represents some number of resources, each with some
number of scopes; for each of those resources, assemble a set
called _TicketScopes(resource)_ containing the scopes associated
with that resource.
2. For each resource in the permission ticket, determine a final set
of requested scopes as follows:
_RequestedScopes(resource)={TicketScopes(resource) ∪
{RegisteredScopes ∩ RequestedScopes}}_. Treat each scope in
_{RegisteredScopes ∩ RequestedScopes}_ as matching any
available scope associated with a resource found in the
permission ticket.
3. For each _RequestedScopes(resource)_ set, determine all operative
policy conditions, and claims and other relevant information
serving as input to them, and evaluate its authorization status.
4. For each scope in _RequestedScopes(resource)_ that passes the
evaluation, add it to a set called
_CandidateGrantedScopes(resource)_.
Note: Claims and other information gathered during one authorization
process may become out of date in terms of their relevance for future
authorization processes. The authorization server is responsible for
managing such relevance wherever information associated with a PCT,
or other persistently stored information, is used as input to
authorization, including policy conditions themselves.
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Note: Since the authorization server's policy expression and
evaluation capabilities are outside the scope of this specification,
any one implementation might take a simple or arbitrarily complex
form, with varying abilities to combine or perform calculations over
claims and their values. For example, logical operations such as
accepting "either claim value A or claim value B" as correct are
possible to implement.
In the authorization results phase, the authorization server examines
each _CandidateGrantedScopes(resource)_ set to determine whether to
issue an RPT and what permissions should be associated with it. If
all _RequestedScopes(resource)_ sets can be granted, then the
authorization server subsequently responds with a success code and
issues an RPT containing _CandidateGrantedScopes_ for each resource.
Otherwise, the authorization server subsequently issues either an RPT
containing _CandidateGrantedScopes_ for each resource, or one of the
error codes, as appropriate. The reason for the two options is that
granting only partial scopes might not be useful for the client's and
requesting party's purposes in seeking authorization for access. The
choice of error depends on policy conditions and the authorization
server's implementation choices. The conditions for the "need_info",
"request_denied", and "request_submitted" error codes are dependent
on authorization assessment and thus these codes might be more likely
than the others to be issued subsequent to such a calculation.
The following example illustrates authorization assessment and
partial results.
o The resource server has three of the resource owner's resources of
interest to the client and requesting party, "photo1" and "photo2"
with scopes "view", "resize", "print", and "download", and "album"
with scopes "view", "edit", and "download". It considers "photo1"
and "photo2" to be logically "inside" "album".
o Though the exact contents of RPTs, permissions, and permission
requests are opaque to the client, the resource server has
documented its API, available scopes, and permission requesting
practices. For example, if the client requests an album resource,
it expects that the resource server will request a permission for
the album with a scope that approximates the attempted client
operation, but will also request permissions for all the photos
"inside" the album, with "view" scope only.
o The client has a pre-registered scope of "download" with the
authorization server. This enables the client later to request
this scope dynamically on behalf of its requesting party from the
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token endpoint. The authorization server assembles the set
_RegisteredScopes_ with contents of scope "download".
o The client requests the album resource in an attempt to edit it,
so the resource server obtains a permission ticket with three
permissions in it: for "album" with a scope of "edit", and for
"photo1" and "photo2", each with a scope of "view". The
authorization server assembles the following sets:
_TicketScopes_("album") containing "edit",
_TicketScopes_("photo1") containing "view", and
_TicketScopes_("photo2") containing "view".
o While asking for an RPT at the token endpoint, the client requests
"download" scope on the requesting party's behalf. The
authorization server determines the contents of the following
sets: _RequestedScopes_("album") containing "edit" and "download",
_RequestedScopes_("photo1") containing "view" and "download", and
_RequestedScopes_("photo2") containing "view" and "download".
o The resource owner has set policy conditions that allow access by
this particular requesting party only to "photo1" and only for
"view" scope.
o Based on the authorization server's authorization assessment
calculation, it determines the contents of the following sets:
_CandidateGrantedScopes_("album") containing no scopes,
_CandidateGrantedScopes_("photo1") containing "view", and
_CandidateGrantedScopes_("photo2") containing no scopes. This
adds up to less than in the corresponding _RequestedScopes_ sets.
The authorization server therefore has a choice whether to issue
an RPT (in this case, containing a permission for "photo1" with
"view" scope) or an error (say, "request_denied", or
"request_submitted" if has a way to notify the resource owner
about the album editing resource request and seek an added policy
covering it).
See Section 5.6 for a discussion of authorization implementation
threats.
3.3.5. Authorization Server Response to Client on Authorization Success
If the authorization server's assessment process results in issuance
of permissions, it issues the RPT with which it has associated the
permissions by using the successful response form defined in
Section 5.1 of [RFC6749].
The authorization server MAY return a refresh token. See Section 3.6
for more information about refreshing an RPT.
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The authorization server MAY add the following parameters to its
response:
pct OPTIONAL. A correlation handle representing claims and other
information collected during this authorization process, which the
client is able to present later in order to optimize future
authorization processes on behalf of a requesting party. The PCT
MUST be unguessable by an attacker. The PCT MUST NOT disclose
claims from the requesting party directly to possessors of the
PCT. Instead, such claims SHOULD be associated by reference to
the PCT or expressed in an encrypted format that can be decrypted
only by the authorization server that issued the PCT. See
Section 3.3.2 for more information about the end-user requesting
party interaction option. See Section 5.2 for additional PCT
security considerations.
upgraded OPTIONAL. Boolean value. If the client submits an RPT in
the request and the authorization server includes the permissions
of the RPT from the request as part of the newly issued RPT, then
it MUST set this value to "true". If it sets the value to "false"
or the value is absent, the client MUST act as if the newly issued
RPT does not include the permissions associated with the RPT from
the request. (See Section 3.3.5.1.)
The authorization server MAY include any of the parameters defined in
Section 5.1 of [RFC6749] on its response, except that it SHOULD NOT
include the "scope" parameter. This is because for an RPT's
permissions, each scope is associated with a specific resource, even
though this association is opaque to the client. Note: The outcome
of authorization assessment may result in expiration periods for
RPTs, permissions, and refresh tokens that can affect the client's
later requests for refreshing the RPT.
Example:
HTTP/1.1 200 OK Content-Type: application/json ... {
"access_token":"sbjsbhs(/SSJHBSUSSJHVhjsgvhsgvshgsv",
"token_type":"Bearer" }
Example with a PCT in the response:
HTTP/1.1 200 OK Content-Type: application/json ... {
"access_token":"sbjsbhs(/SSJHBSUSSJHVhjsgvhsgvshgsv",
"token_type":"Bearer", "pct":"c2F2ZWRjb25zZW50" }
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3.3.5.1. Authorization Server Upgrades RPT
The authorization server MAY implement RPT upgrading. The
authorization server SHOULD document its practices regarding RPT
upgrades and to act consistently with respect to RPT upgrades so as
to enable clients to manage received RPTs efficiently.
If the authorization server has implemented RPT upgrading, the client
has submitted an RPT in its request, and the result is success, the
authorization server adds the permissions from the client's previous
RPT to the RPT it is about to issue, setting the value of "upgraded"
in its response containing the upgraded RPT to "true".
If the authorization server is upgrading an RPT, and the RPT string
is new rather than repeating the RPT provided by the client in the
request, then the authorization server SHOULD revoke the existing
RPT, if possible, and the client MUST discard its previous RPT. If
the authorization server does not upgrade the RPT but issues a new
RPT, the client MAY retain the existing RPT.
Example with "upgraded" in the response:
HTTP/1.1 200 OK Content-Type: application/json ... {
"access_token":"sbjsbhs(/SSJHBSUSSJHVhjsgvhsgvshgsv",
"token_type":"Bearer", "upgraded":true }
3.3.6. Authorization Server Response to Client on Authorization Failure
If the client's request to the token endpoint results in failure, the
authorization server responds with an error, as defined in
Section 5.2 of [RFC6749] and as follows.
invalid_grant If the provided permission ticket was not found at the
authorization server, or the provided permission ticket has
expired, or any other original reasons to use this error code are
found as defined in [RFC6749], the authorization server responds
with the HTTP 400 (Bad Request) status code.
invalid_scope At least one of the scopes included in the request
does not match an available scope for any of the resources
associated with requested permissions for the permission ticket
provided by the client. The authorization server MAY also return
this error when at least one of the scopes included in the request
does not match a scope for which the client is pre-registered with
the authorization server. The authorization server responds with
the HTTP 400 (Bad Request) status code.
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need_info The authorization server needs additional information in
order for a request to succeed, for example, a provided claim
token was invalid or expired, or had an incorrect format, or
additional claims are needed to complete the authorization
assessment. The authorization server responds with the HTTP 403
(Forbidden) status code. It MUST include a "ticket" parameter,
and it MUST also include either the "required_claims" parameter or
the "redirect_user" parameter, or both, as hints about the
information it needs.
ticket REQUIRED. A permission ticket that allows the client to
make a further request to the authorization server's token
endpoint as part of this same authorization process,
potentially immediately. The value MUST NOT be the same as the
one the client used to make its request.
required_claims An array of objects that describe the required
claims, with the following subparameters:
claim_token_format OPTIONAL. An array of strings specifying a
set of acceptable formats for a claim token pushed by the
client containing this claim, as defined in Section 3.3.1.
Any one of the referenced formats would satisfy the
authorization server's requirements. Each string MAY be a
URI.
claim_type OPTIONAL. A string, indicating the expected
interpretation of the provided claim value. The string MAY
be a URI.
friendly_name OPTIONAL. A string that provides a human-
readable form of the claim's name. This can be useful as a
"display name" for use in user interfaces in cases where the
actual name is complex or opaque, such as an OID or a UUID.
issuer OPTIONAL. An array of strings specifying a set of
acceptable issuing authorities for the claim. Any one of
the referenced authorities would satisfy the authorization
server's requirements. Each string MAY be a URI.
name OPTIONAL. A string (which MAY be a URI) representing the
name of the claim; the "key" in a key-value pair.
redirect_user The claims interaction endpoint URI to which to
redirect the end-user requesting party at the authorization
server to continue the process of interactive claims gathering,
as defined in Section 3.3.2. For example, the authorization
server could require the requesting party to log in to an
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account, or fill out a CAPTCHA to help prove humanness, or
perform any number of other interactive tasks. If the
requesting party is not an end-user, then no client action is
possible on receiving the hint. If a static claims interaction
endpoint was also provided in the authorization server's
discovery document, then this value overrides the static value.
Providing a value in this response might be appropriate, for
example, if the URI needs to be customized per requesting party
with a query parameter.
request_denied The client is not authorized to have these
permissions. The authorization server responds with the HTTP 403
(Forbidden) status code.
request_submitted The authorization server requires intervention by
the resource owner to determine whether the client is authorized
to have these permissions. The authorization server responds with
the HTTP 403 (Forbidden) status code. It MUST include a "ticket"
parameter and MAY include an "interval" parameter.
ticket REQUIRED. A permission ticket that allows the client to
make one or more later polling requests to the token endpoint
as part of this same authorization process, when the resource
owner might have completed some approval (or denial) action.
The value MUST NOT be the same as the one the client used to
make its request.
interval OPTIONAL. The minimum amount of time in seconds that
the client SHOULD wait between polling requests to the token
endpoint. See Section 5.5 for security considerations in
scenarios involving polling and consequences for permission
ticket lifetimes.
Example when the permission ticket was not found or has expired:
HTTP/1.1 400 Bad Request Content-Type: application/json
Cache-Control: no-store ... { "error":"invalid_grant" }
Example of a "need_info" response with hints about required claims:
HTTP/1.1 403 Forbidden Content-Type: application/json
Cache-Control: no-store ... { "error":"need_info",
"ticket":"ZXJyb3JfZGV0YWlscw==", "required_claims":[ {
"claim_token_format":[
"http://openid.net/specs/openid-connect-core-1_0.html#IDToken" ],
"claim_type":"urn:oid:0.9.2342.19200300.100.1.3",
"friendly_name":"email", "issuer":[ "https://example.com/idp" ],
"name":"email23423453ou453" } ] }
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Example of a "need_info" response with a hint to redirect the
requesting party to a claims interaction endpoint:
HTTP/1.1 403 Forbidden Content-Type: application/json
Cache-Control: no-store ... { "error":"need_info",
"ticket":"ZXJyb3JfZGV0YWlscw==",
"redirect_user":"https://as.example.com/rqp_claims?id=2346576421"
}
Example when the client was not authorized to have the permissions:
HTTP/1.1 403 Forbidden Content-Type: application/json
Cache-Control: no-store ... { "error":"request_denied" }
Example when the authorization server requires resource owner
intervention, including the optional "interval" parameter:
HTTP/1.1 403 Forbidden Content-Type: application/json
Cache-Control: no-store ... { "error":"request_submitted",
"ticket?:?ZXJyb3JfZGV0YWlscw==", "interval": 5 }
3.4. Client Requests Resource and Provides an RPT
The client requests the resource, now in possession of an RPT. The
client uses [RFC6750] for a bearer token, and any other suitable
presentation mechanism for an RPT of another access token type.
Example of a client request for the resource carrying an RPT:
GET /users/alice/album/photo.jpg HTTP/1.1 Authorization:
Bearer sbjsbhs(/SSJHBSUSSJHVhjsgvhsgvshgsv Host: photoz.example.com
...
3.5. Resource Server Responds to Client's RPT-Accompanied Resource
Request
The resource server responds to the client's RPT-accompanied resource
request.
If the resource request fails, the resource server responds as if the
request were unaccompanied by an access token, as defined in
Section 3.2.
The resource server MUST NOT give access in the case of an invalid
RPT or an RPT associated with insufficient authorization.
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For an example of how the resource server can introspect the RPT and
its permissions at the authorization server prior to responding to
the client's request, see [UMAFedAuthz].
3.6. Authorization Server Refreshes RPT
As noted in Section 3.3.5, when issuing an RPT, the authorization
server MAY also issue a refresh token.
Having previously received a refresh token from the authorization
server, the client MAY use the refresh token grant as defined in
[RFC6749] to attempt to refresh an expired RPT. If the client
includes the "scope" parameter in its request, the authorization
server MAY limit the scopes in the permissions associated with any
resulting refreshed RPT to the scopes requested by the client.
The authorization server MUST NOT perform an authorization assessment
calculation on receiving the client's request to refresh an RPT.
3.7. Client Requests Token Revocation
If the authorization server presents a token revocation endpoint as
defined in [RFC7009], the client MAY use the endpoint to request
revocation of an RPT (access token), refresh token, or PCT previously
issued to it on behalf of a requesting party. This specification
defines the following token type hint value:
pct Helps the authorization server optimize lookup of a PCT for
revocation.
4. Profiles and Extensions
An UMA profile restricts UMA's available options. An UMA extension
defines how to use UMA's extensibility points. The two can be
combined. Some reasons for creating profiles and extensions include:
o A profile restricting options in order to tighten security
o A profile/extension restricting options and adding messaging
parameters for use with a specific industry API
o A profile that documents a specific URI, format, and
interpretation for pushed claim tokens (see Section 3.3.1)
o An extension that defines additional metadata for the
authorization server discovery document to define machine-readable
usage details
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The following actions are RECOMMENDED regarding the creation and use
of profiles and extensions:
o The creator of a profile or extension related to UMA SHOULD assign
it a uniquely identifying URI.
o The authorization server supporting a profile or extension related
to UMA with such a URI SHOULD supply the identifying URI in its
"uma_profiles_supported" metadata (see Section 2).
5. Security Considerations
This specification relies mainly on OAuth 2.0 security mechanisms as
well as transport-level security. Thus, implementers are strongly
advised to read [BCP195] and the security considerations in [RFC6749]
(Section 10) and [RFC6750] (Section 5) along with the security
considerations of any other OAuth token-defining specifications in
use, along with the entire [RFC6819] specification, and apply the
countermeasures described therein. As well, implementers should take
into account the security considerations in all other normatively
referenced specifications.
The following sections describe additional security considerations.
5.1. Cross-Site Request Forgery
Redirection used for gathering claims interactively from an end-user
requesting party (described in Section 3.3.2) creates the potential
for cross-site request forgery (CSRF). This may be the result of an
open redirect if the authorization server does not force the client
to pre-register its claims redirection endpoint, and server-side
artifact tampering if the client does not avail itself of the "state"
parameter.
A CSRF attack against the authorization server's claims interaction
endpoint can result in an attacker obtaining authorization for access
through a malicious client without involving or alerting the end-user
requesting party. The authorization server MUST implement CSRF
protection for its claims interaction endpoint and ensure that a
malicious client cannot obtain authorization without the awareness
and involvement of the requesting party.
If the client uses the interactive claims gathering feature, it MUST
implement CSRF protection for its claims redirection URI. It SHOULD
use the "state" parameter when redirecting the requesting party to
the claims interaction endpoint. The value of the "state" parameter
MUST be unguessable by an attacker. Once the authorization server
redirects the requesting party back, with the required binding value
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contained in the "state" parameter, the client MUST check that the
value of the "state" parameter received is equal to the value sent in
the initial redirection request. Depending on the type of
application, a client has several methods for storing and later
verifying the value of the "state" parameter in between the initial
redirect and the eventual resulting request to the claims redirection
URI, including storage in a server-side session-bound variable,
cryptographic derivation from a browser cookie, or secure
application-level storage. The client MUST treat requests containing
an invalid or unknown "state" parameter value as an error.
The "state" parameter SHOULD NOT include sensitive client or
requesting party information in plain text, as it is transmitted
through third-party components (the requesting party's user agent)
and could be stored insecurely.
5.2. RPT and PCT Exposure
When a client redirects an end-user requesting party to the claims
interaction endpoint, the client provides no a priori context to the
authorization server about which user is appearing at the endpoint,
other than implicitly through the permission ticket. Thus, a
malicious client has the opportunity to switch end-users -- say,
enabling malicious end-user Carlos to impersonate legitimate end-user
Bob, who might be represented by a PCT already in that client's
possession and might even have authorized the issuance of that PCT --
after the redirect completes and before it returns to the token
endpoint to seek permissions.
To mitigate this threat, the authorization server, with the support
of the resource owner, should consider the following strategies in
combination.
o Require that the requesting party legitimately represent the
wielder of the RPT on a legal or contractual level. This solution
alone does not reduce the risk from a technical perspective.
o Gather claims interactively from an end-user requesting party that
demonstrate that some sufficiently strong level of authentication
was performed.
o Require claims to have a high degree of freshness in order for
them to satify policy conditions.
o Tighten time-to-live strategies around RPTs and their associated
permissions (see Section 6.1).
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The client MUST only share the RPT (access token) with the resource
server and authorization server, as explained in Section 10.3 of
[RFC6749], and thus MUST keep it confidential from the requesting
party. Because a malicious requesting party (the user of the client
in the UMA grant) may have incentives to steal an RPT that the
resource owner (the user of the client in other OAuth grants) does
not, this security consideration takes on especial importance.
The PCT is similar to a refresh token in that it allows non-
interactive issuance of access tokens. The authorization server and
client MUST keep the PCT confidential in transit and storage, and
MUST NOT share the PCT with any entity other than each other. The
authorization server MUST maintain the binding between the PCT and
the client to which it was issued.
Given that the PCT represents a set of requesting party claims, a
client supplying a PCT in its RPT request MUST make a best effort to
ensure that the requesting party using the client now is the same as
the requesting party that was associated with the PCT when it was
issued. Different clients will have different capabilities in this
respect; for example, some applications are single-user and perform
no local authentication, associating all PCTs with the "current
user", while others might have more sophisticated authentication and
user mapping capabilities.
If the authorization server has reason to believe that a PCT is
compromised, for example, if the PCT has been supplied by a client
that has "impossible geography" parameters, the authorization server
should consider not using the claims based on that PCT in its
authorization assessment.
5.3. Strengthening RPT Protection Using Proof of Possession
After the client's resource request with an RPT, assuming the client
sent an RPT of the bearer style such as defined in [RFC6750], the
resource server will have received from the client the entire secret
portion of the token. This specification assumes only bearer-type
tokens because they are the only type standardized as of this
specification's publication. However, to strengthen protection for
RPTs using a proof-of-possession approach, the resource server could
receive an RPT that consists of only a cryptographically signed token
identifier, and then to validate the signature, it could, for
example, submit the token identifier to the token introspection
endpoint to obtain the necessary key information. The details of
this usage are outside the scope of this specification.
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5.4. Credentials-Guessing
Permission tickets and PCTs are additional credentials that the
authorization server MUST prevent attackers from guessing, as defined
in Section 10.10 of [RFC6749].
5.5. Permission Ticket Management
Within the constraints of making permission ticket values
unguessable, the authorization server MAY format the permission
ticket however it chooses, for example, either as a random string
that references data held on the server or by including data within
the ticket itself.
Permission tickets MUST be single-use. This prevents susceptibility
to a session fixation attack.
The authorization server MUST invalidate a permission ticket when the
client presents the permission ticket to either the token endpoint or
the claims interaction endpoint, or when the permission ticket
expires, whichever occurs first.
The client SHOULD check that the value of the "ticket" parameter it
receives back from the authorization server in each response and each
redirect of the requesting party back to it differs from the one it
sent to the server in the initial request or redirect.
If the authorization server has reason to believe that a permission
ticket is compromised, for example, because it has seen the
permission ticket before and it believes the first appearance was
from a legitimate client and the second appearance is from an
attacker, it should consider invalidating any access tokens based on
this evidence.
Given that scenarios involving the "request_submitted" error code are
likely to involve polling intervals, the permission ticket needs to
last long enough to give the client a chance to attempt a polling
request, which then needs to figure into other permission ticket
security considerations.
5.6. Naive Implementations of Default-Deny Authorization
While a reasonable approach for most scenarios is to implement the
classic stance of default-deny ("everything that is not expressly
allowed is forbidden"), corner cases can inadvertently result in
default-permit behavior. For example, it is insufficient to create
default "empty" policy conditions stating "no claims are needed", and
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then accept an empty set of supplied claims as sufficient for access
during authorization assessment.
5.7. Requirements for Pre-Established Trust Regarding Claim Tokens
When a client makes an RPT request, it has the opportunity to push a
claim token to attempt to satisfy policy conditions (see
Section 3.3.1).
Claim tokens of any format typically contain audience restrictions,
and an authorization server would not typically be in the primary
audience for a claim token held or generated by a client. It is
RECOMMENDED to document how the client, authorization server,
requesting party, and any additional ecosystem entities and parties
will establish a trust relationship and communicate any required
keying material in a claim token profile, as described in Section 4.
Authorization servers are RECOMMENDED not to accept claim tokens
pushed by untrusted clients and not to ignore audience restrictions
found in claim tokens pushed by clients.
A malicious client could push a claim token to the authorization
server (revealing the claims therein; see Section 6.2) to seek
resource access on its own behalf prior to any opportunity for an
end-user requesting party to authorize claims collection. It is
RECOMMENDED either for trust relationships established by the
ecosystem parties to include prior requesting party authorization as
required, or for end-user requesting party authorization to be
gathered interactively prior to claims pushing, as described in
Section 3.3.2.
Some deployments could have exceptional circumstances allowing the
authorization server to validate claim tokens. For example, if the
authorization server itself is also the identity provider for the
requesting party, then it would be able to validate any ID token that
the client pushes as a claim token and also validate the client to
which it was issued.
5.8. Profiles and Trust Establishment
Parties that are operating and using UMA software entities may need
to establish agreements about the parties' rights and
responsibilities on a legal or contractual level, along with common
interpretations of UMA constructs for consistent and expected
software behavior. These agreements can be used to improve the
parties' respective security postures. Written profiles are a key
mechanism for conveying and enforcing these agreements. Section 4
discusses profiling. See [UMA-legal] to learn about frameworks and
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tools to assist in the legal and contractual elements of deploying
UMA-enabled services.
6. Privacy Considerations
UMA has the following privacy considerations.
6.1. Policy Condition Setting, Time-to-Live Management, and Removal of
Authorization Grants
The setting of policy conditions, the resource owner-authorization
server interface, and the resource owner-resource server interface
are outside the scope of this specification. (For an example of how
a secure and authorized resource owner context can be established
between the resource server and authorization server, see
[UMAFedAuthz].)
A variety of flows and user interfaces for policy condition setting
involving user agents for both of these servers are possible, each
with different privacy consequences for end-user resource owners. As
well, various authorization, security, and time-to-live strategies
could be applied on a per-resource owner basis or a per-authorization
server basis, as the entities see fit. Validity periods of RPTs,
refresh tokens, permissions, caching periods for responses, and even
OAuth client credentials are all subject to management. Different
time-to-live strategies might be suitable for different resources and
scopes.
In order to account for modifications of policy conditions that
result in the withdrawal of authorization grants (for example, fewer
scopes, fewer resources, or resources available for a shorter time)
in as timely a fashion as possible, the authorization server should
align its strategies for management of these factors with resource
owner needs and actions rather than those of clients and requesting
parties. For example, the authorization server may want to
invalidate a client's RPT and refresh token as soon as a resource
owner changes policy conditions in such a way as to deny the client
and its requesting party future access to a full set of previously
held permissions.
6.2. Requesting Party Information at the Authorization Server
Claims are likely to contain personal, personally identifiable, and
sensitive information, particularly in the case of requesting parties
who are end-users.
If the authorization server supports persisting claims for any length
of time (for example, to support issuance of PCTs), then it SHOULD
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provide a secure and privacy-protected means of storing claim data.
It is also RECOMMENDED for the authorization server to use an
interactive claims-gathering flow to ask an end-user requesting party
for authorization to collect any claims subsequently and to persist
their claims (for example, before issuing a PCT), if no prior
requesting party authorization has been established among the
ecosystem parties (see Section 5.7).
6.3. Resource Owner Information at the Resource Server
Since the client's initial request for a protected resource is made
in an unauthorized and unauthenticated context, such requests are by
definition open to all users. The response to that request includes
the authorization server's location to enable the client to request
an access token and present claims. If it is known out of band that
authorization server is owned and controlled by a single user, or
visiting the authorization server contains other identifying
information, then an unauthenticated and unauthorized client would be
able to tell which resource owner is associated with a given
resource. Other information about the resource owner, such as
organizational affiliation or group membership, may be gained from
this transaction as well.
6.4. Profiles and Trust Establishment
Parties that are operating and using UMA software entities may need
to establish agreements about mutual rights, responsibilities, and
common interpretations of UMA constructs for consistent and expected
software behavior. These agreements can be used to improve the
parties' respective privacy postures. See Section 5.8 for more
information. Additional considerations related to Privacy by Design
concepts are discussed in [UMA-PbD].
7. IANA Considerations
This document makes the following requests of IANA.
7.1. Well-Known URI Registration
This specification registers the well-known URI defined in Section 2,
as required by Section 5.1 of [RFC5785].
7.1.1. Registry Contents
o URI suffix: "uma2-configuration"
o Change controller: Kantara Initiative User-Managed Access Work
Group - staff@kantarainitiative.org
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o Specification document: Section 2 in this document
7.2. OAuth 2.0 Authorization Server Metadata Registry
This specification registers OAuth 2.0 authorization server metadata
defined in Section 2, as required by Section 7.1 of [OAuthMeta].
7.2.1. Registry Contents
o Metadata name: "claims_interaction_endpoint"
o Metadata description: endpoint metadata
o Change controller: Kantara Initiative User-Managed Access Work
Group - staff@kantarainitiative.org
o Specification document: Section 2 in this document
o Metadata name: "uma_profiles_supported"
o Metadata description: profile/extension feature metadata
o Change controller: Kantara Initiative User-Managed Access Work
Group - staff@kantarainitiative.org
o Specification document: Section 2 in this document
7.3. OAuth 2.0 Dynamic Client Registration Metadata Registry
This specification registers OAuth 2.0 dynamic client registration
metadata defined in Section 2, as required by Section 4.1 of
[RFC7591].
7.3.1. Registry Contents
o Metadata name: "claims_redirect_uris"
o Metadata description: claims redirection endpoints
o Change controller: Kantara Initiative User-Managed Access Work
Group - staff@kantarainitiative.org
o Specification document: Section 2 in this document
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7.4. OAuth 2.0 Extension Grant Parameters Registration
This specification registers the parameters defined in Section 3.3.1,
as required by Section 11.2 of [RFC6749].
7.4.1. Registry Contents
o Parameter name: "claim_token"
o Parameter usage location: client request, token endpoint
o Change controller: Kantara Initiative User-Managed Access Work
Group - staff@kantarainitiative.org
o Specification document: Section 3.3.1 in this document
o Parameter name: "pct"
o Parameter usage location: client request, token endpoint
o Change controller: Kantara Initiative User-Managed Access Work
Group - staff@kantarainitiative.org
o Specification document: Section 3.3.1 in this document
o Parameter name: "pct"
o Parameter usage location: authorization server response, token
endpoint
o Change controller: Kantara Initiative User-Managed Access Work
Group - staff@kantarainitiative.org
o Specification document: Section 3.3.5 in this document
o Parameter name: "rpt"
o Parameter usage location: client request, token endpoint
o Change controller: Kantara Initiative User-Managed Access Work
Group - staff@kantarainitiative.org
o Specification document: Section 3.3.1 in this document
o Parameter name: "ticket"
o Parameter usage location: client request, token endpoint
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o Change controller: Kantara Initiative User-Managed Access Work
Group - staff@kantarainitiative.org
o Specification document: Section 3.3.1 in this document
o Parameter name: "upgraded"
o Parameter usage location: authorization server response, token
endpoint
o Change controller: Kantara Initiative User-Managed Access Work
Group - staff@kantarainitiative.org
o Specification document: Section 3.3.5 in this document
7.5. OAuth 2.0 Extensions Error Registration
This specification registers the errors defined in Section 3.3.6, as
required by Section 11.4 of [RFC6749].
7.5.1. Registry Contents
o Error name: "need_info" (and its subsidiary parameters)
o Change controller: Kantara Initiative User-Managed Access Work
Group - staff@kantarainitiative.org
o Specification document: Section 3.3.6 in this document
o Error usage location: authorization server response, token
endpoint
o Error name: "request_denied"
o Change controller: Kantara Initiative User-Managed Access Work
Group - staff@kantarainitiative.org
o Specification document: Section 3.3.6 in this document
o Error usage location: authorization server response, token
endpoint
o Error name: "request_submitted" (and its subsidiary parameters)
o Change controller: Kantara Initiative User-Managed Access Work
Group - staff@kantarainitiative.org
o Specification document: Section 3.3.6 in this document
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o Error usage location: authorization server response, token
endpoint
7.6. OAuth Token Type Hints Registration
This specification registers the errors defined in Section 3.7, as
required by Section 4.1.2 of [RFC7009].
7.6.1. Registry Contents
o Hint value: "pct"
o Change controller: Kantara Initiative User-Managed Access Work
Group - staff@kantarainitiative.org
o Specification document: Section 3.7 in this document
8. Acknowledgments
The following people made significant text contributions to the
specification:
o Paul C. Bryan, ForgeRock US, Inc. (former editor)
o Domenico Catalano, Oracle (former author)
o Mark Dobrinic, Cozmanova
o George Fletcher, AOL
o Thomas Hardjono, MIT (former editor)
o Andrew Hindle, Hindle Consulting Limited
o Lukasz Moren, Cloud Identity Ltd
o James Phillpotts, ForgeRock
o Christian Scholz, COMlounge GmbH (former editor)
o Mike Schwartz, Gluu
o Cigdem Sengul, Nominet UK
o Jacek Szpot, Newcastle University
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Additional contributors to this specification include the Kantara UMA
Work Group participants, a list of whom can be found at
[UMAnitarians].
9. References
9.1. Normative References
[BCP195] Sheffer, Y., "Recommendations for Secure Use of Transport
Layer Security (TLS) and Datagram Transport Layer Security
(DTLS)", May 2015, <https://tools.ietf.org/html/bcp195>.
[OAuthMeta]
Jones, M., "OAuth 2.0 Authorization Server Metadata",
November 2017, <https://tools.ietf.org/html/
draft-ietf-oauth-discovery-08>.
[OIDCCore]
Sakimura, N., "OpenID Connect Core 1.0 incorporating
errata set 1", November 2014,
<http://openid.net/specs/openid-connect-core-1_0.html>.
[OIDCDynClientReg]
Sakimura, N., "OpenID Connect Dynamic Client Registration
1.0 incorporating errata set 1", November 2014,
<http://openid.net/specs/
openid-connect-registration-1_0.html>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
Uniform Resource Identifiers (URIs)", RFC 5785,
DOI 10.17487/RFC5785, April 2010,
<https://www.rfc-editor.org/info/rfc5785>.
[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012,
<https://www.rfc-editor.org/info/rfc6749>.
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[RFC6750] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization
Framework: Bearer Token Usage", RFC 6750,
DOI 10.17487/RFC6750, October 2012,
<https://www.rfc-editor.org/info/rfc6750>.
[RFC6819] Lodderstedt, T., Ed., McGloin, M., and P. Hunt, "OAuth 2.0
Threat Model and Security Considerations", RFC 6819,
DOI 10.17487/RFC6819, January 2013,
<https://www.rfc-editor.org/info/rfc6819>.
[RFC7009] Lodderstedt, T., Ed., Dronia, S., and M. Scurtescu, "OAuth
2.0 Token Revocation", RFC 7009, DOI 10.17487/RFC7009,
August 2013, <https://www.rfc-editor.org/info/rfc7009>.
[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <https://www.rfc-editor.org/info/rfc7159>.
[RFC7591] Richer, J., Ed., Jones, M., Bradley, J., Machulak, M., and
P. Hunt, "OAuth 2.0 Dynamic Client Registration Protocol",
RFC 7591, DOI 10.17487/RFC7591, July 2015,
<https://www.rfc-editor.org/info/rfc7591>.
[UMAFedAuthz]
Maler, E., "Federated Authorization for User-Managed
Access (UMA) 2.0", January 2019,
<https://docs.kantarainitiative.org/uma/
rec-oauth-uma-federated-authz-2.0.html>.
9.2. Informative References
[UMA-legal]
Maler, E., "UMA Legal", 2017,
<http://kantarainitiative.org/confluence/display/uma/
UMA+Legal>.
[UMA-PbD] Maler, E., "Privacy by Design Implications of UMA", 2018,
<https://kantarainitiative.org/confluence/display/uma/
Privacy+by+Design+Implications+of+UMA>.
[UMAnitarians]
Maler, E., "UMA Participant Roster", 2017,
<https://kantarainitiative.org/confluence/display/uma/
Participant+Roster>.
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Authors' Addresses
Eve Maler (editor)
ForgeRock
Email: eve.maler@forgerock.com
Maciej Machulak
HSBC
Email: maciej.p.machulak@hsbc.com
Justin Richer
Bespoke Engineering
Email: justin@bspk.io
Thomas Hardjono
MIT
Email: hardjono@mit.edu
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