Network Working Group T. Hardjono, Ed.
Internet-Draft MIT
Intended status: Standards Track March 29, 2012
Expires: September 30, 2012
User-Managed Access (UMA) Core Protocol
draft-hardjono-oauth-umacore-04
Abstract
This specification defines the User-Managed Access (UMA) core
protocol. This protocol provides a method for users to control
access to their protected resources, residing on any number of host
sites, through an authorization manager that governs access decisions
based on user policy.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 30, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Notational Conventions . . . . . . . . . . . . . . . . . . 6
1.2. Basic Terminology . . . . . . . . . . . . . . . . . . . . 6
1.3. Endpoints, Endpoint Protection, and Tokens . . . . . . . . 8
1.4. Scopes, Resource Sets, Permissions, and Authorization . . 10
1.5. AM Configuration Data . . . . . . . . . . . . . . . . . . 11
2. Protecting a Resource . . . . . . . . . . . . . . . . . . . . 13
2.1. Host Looks Up AM Configuration Data . . . . . . . . . . . 14
2.2. Host Registers with AM . . . . . . . . . . . . . . . . . . 15
2.3. Host Obtains Protection API Token . . . . . . . . . . . . 15
2.4. Host Registers Sets of Resources to Be Protected . . . . . 15
2.4.1. Scope Descriptions . . . . . . . . . . . . . . . . . . 16
2.4.2. Resource Set Descriptions . . . . . . . . . . . . . . 17
2.4.3. Resource Set Registration API . . . . . . . . . . . . 18
2.4.3.1. Create Resource Set Description . . . . . . . . . 19
2.4.3.2. Read Resource Set Description . . . . . . . . . . 20
2.4.3.3. Update Resource Set Description . . . . . . . . . 21
2.4.3.4. Delete Resource Set Description . . . . . . . . . 22
2.4.3.5. List Resource Set Descriptions . . . . . . . . . . 22
3. Getting Authorization and Accessing a Resource . . . . . . . . 23
3.1. Requester-Host: Attempt Access at Protected Resource . . . 24
3.1.1. Requester Presents No Requester Permission Token . . . 25
3.1.2. Requester Presents a Requester Permission Token
That Is Invalid Or Has Insufficient Permission . . . . 25
3.1.3. Requester Presents a Valid Requester Permission
Token . . . . . . . . . . . . . . . . . . . . . . . . 26
3.2. Host-AM: Register a Permission . . . . . . . . . . . . . . 26
3.3. Host-AM: Ask for Requester Permission Token Status . . . . 28
3.3.1. UMA Bearer Token Profile . . . . . . . . . . . . . . . 28
3.4. Requester-AM: Ask for Permission and Requester
Permission Token . . . . . . . . . . . . . . . . . . . . . 30
3.4.1. Requester Looks Up AM Configuration Data . . . . . . . 31
3.4.2. Requester Registers with AM . . . . . . . . . . . . . 31
3.4.3. Requester Obtains Authorization API Token . . . . . . 31
3.4.4. Requester-AM: Request Authorization to Add
Permission . . . . . . . . . . . . . . . . . . . . . . 32
3.5. Claims-Gathering Flows . . . . . . . . . . . . . . . . . . 34
3.5.1. Claims-Gathering Flow for Requester Apps Operated
by End-Users . . . . . . . . . . . . . . . . . . . . . 34
3.5.1.1. OpenID Connect Claim Profile . . . . . . . . . . . 35
4. Error Messages . . . . . . . . . . . . . . . . . . . . . . . . 36
4.1. OAuth Error Responses . . . . . . . . . . . . . . . . . . 36
4.2. UMA Error Responses . . . . . . . . . . . . . . . . . . . 36
5. Security Considerations . . . . . . . . . . . . . . . . . . . 37
6. Privacy Considerations . . . . . . . . . . . . . . . . . . . . 38
7. Conformance . . . . . . . . . . . . . . . . . . . . . . . . . 38
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8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39
9. Example of Registering Resource Sets . . . . . . . . . . . . . 39
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 45
11. Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 45
12.1. Normative References . . . . . . . . . . . . . . . . . . . 45
12.2. Informative References . . . . . . . . . . . . . . . . . . 46
Appendix A. Document History . . . . . . . . . . . . . . . . . . 47
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 48
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1. Introduction
The User-Managed Access (UMA) core protocol provides a method based
on OAuth 2.0 [OAuth2] for users to control access to their protected
resources, residing on any number of host sites, through a single
authorization manager (AM) that governs access decisions based on
user policy.
There are numerous use cases for UMA, where a resource owner elects
to have a third party to control access to these resources
potentially without the real-time presence of the resource owner. A
typical example is the following: a web user (authorizing user) can
authorize a web app (requester) to gain one-time or ongoing access to
a resource containing his home address stored at a "personal data
store" service (host), by telling the host to act on access decisions
made by his authorization decision-making service (authorization
manager or AM). The requesting party might be an e-commerce company
whose site is acting on behalf of the user himself to assist him/her
in arranging for shipping a purchased item, or it might be his friend
who is using an online address book service to collect addresses, or
it might be a survey company that uses an online service to compile
population demographics. Other scenarios and use cases for UMA usage
can be found in [UMA-usecases] and [UMA-userstories].
In enterprise settings, application access management often involves
letting back-office applications serve only as policy enforcement
points (PEPs), depending entirely on access decisions coming from a
central policy decision point (PDP) to govern the access they give to
requesters. This separation eases auditing and allows policy
administration to scale in several dimensions. UMA makes use of a
separation similar to this, letting the authorizing user serve as a
policy administrator crafting authorization strategies on his or her
own behalf.
The UMA protocol can be considered an advanced application of
[OAuth2] in that it profiles, extends, and embeds OAuth in various
ways. In the big picture, an AM can be thought of as an enhanced
OAuth authorization server; a host as an enhanced resource server;
and a requester as an enhanced client, acquiring an access token and
the requisite authorization to access a protected resource at the
host.
The UMA protocol has three broad phases, as shown in Figure 1.
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The Three Phases of the UMA Protocol
+-----+----------------+
| UA | authorizing |
+-------Manage (A)--| | user |
| +-----+----------------+
| Phase 1: | UA |
| protect a +----------------+
| resource |
| Control (B)
| |
v v
+-----------+ +-----+----------------+
| host |<-Protect-(C)-|prot | authorization |
| | | API | manager (AM) |
+-----------+ +-----+----------------+
| protected | | authorization |
| resource | | API |
+-----------+ +----------------+
^ |
| Phases 2 and 3: Authorize (D)
| get authz and |
| access a resource v
| +----------------+
+-------Access (E)--------| requester |
+----------------+
(requesting party)
Figure 1
In broad strokes, the phases are as follows:
1. Protect a resource (described in Section 2).
2. Get authorization (described in Section 3).
3. Access a resource (described along with Phase 2 in Section 3).
In more detail, the phases work as follows:
1. _Protect a resource:_ The authorizing user has chosen to use a
host for managing online resources ("A"), and introduces this
host to an AM using an OAuth-mediated interaction that results in
the AM giving the host a protection API token (PAT). The host
uses AM's protection API to tell the AM what sets of resources to
protect ("C"). Out of band of the UMA protocol, the authorizing
user instructs the AM what policies to attach to the registered
resource sets ("B"). Requesters are not yet in the picture.
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2. _Get authorization:_ This phase involves the requester (along
with its operator, the requesting party or that party's human
agent), host, and AM. It may also involve synchronous action by
the authorizing user if this person is the same person as the
requesting party. This phase is dominated by a loop of activity
in which the requester approaches the host seeking access to a
protected resource ("E"). In order to access the protected
resource at the host, the requester must obtain a requester
permission token (RPT) from the AM. The requester is then
directed to the AM ask for authorization for the permissions it
seeks. In doing so, it must demonstrate to the AM that it
satisfies the resource owner's authorization policy governing the
sought-for resource and scope of access if it does not already
have the required access permission ("D"). To use the AM's
authorization API in the first place, the requesting party has to
consent to deal with the AM in providing claims, which results in
the requester obtaining an authorization API token (AAT) from the
AM.
3. _Access a resource:_ This phase involves the requester
successfully presenting an RPT that has sufficient permission
associated with it to the host in order to gain access to the
desired resource ("E"). In this sense, it is the "happy path"
within phase 2.
1.1. Notational Conventions
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT',
'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and 'OPTIONAL' in this
document are to be interpreted as described in [RFC2119].
Unless otherwise noted, all the protocol properties and values are
case sensitive.
1.2. Basic Terminology
UMA introduces the following terms, utilizing OAuth and other
identity and access management concepts.
authorizing user
The "user" in User-Managed Access. An UMA-defined variant of
an OAuth resource owner, typically a web user who configures an
authorization manager with policies that control how it assigns
access permissions to requesters for a protected resource. The
authorizing user can also be corporation or other legal person.
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authorization manager (AM)
An UMA-defined variant of an OAuth authorization server that
carries out an authorizing user's policies governing access to
a protected resource.
protected resource
An access-restricted resource at a host, which is being policy-
protected by an AM.
host
An UMA-defined variant of an OAuth resource server that
enforces access to the protected resources it hosts, as
governed by an authorization manager.
claim
A statement of the value or values of one or more identity
attributes of a requesting party. A requesting party may need
to provide claims to an authorization manager in order to
satisfy policy and gain permission for access to a protected
resource.
requester
An UMA-defined variant of an OAuth client that seeks access to
a protected resource.
requesting party
A web user, or a corporation or other legal person, that uses a
requester to seek access to a protected resource. The
requesting party may or may not be the same person as the
authorizing user.
resource set A host-managed set of one or more resources to be AM-
protected. In authorization policy terminology, a resource set
is the "object" being protected.
scope A bounded extent of access that is possible to perform on a
resource set. In authorization policy terminology, a scope is
one of the potentially many "verbs" that can logically apply to
a resource set. Whereas OAuth scopes apply to resource sets
that are implicit, UMA associates scopes with explicitly
labeled resource sets ("objects").
permission A scope of access over a particular resource set at a
particular host that is being asked for by, or being granted
to, a requester. In authorization policy terminology, a
permission includes a "subject" (requesting party), "verbs"
(one or more scopes of access), and an "object" (resource set).
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1.3. Endpoints, Endpoint Protection, and Tokens
Various UMA entities present protected APIs for other UMA entities to
use. These APIs are as follows:
o The AM presents a _protection API_ to the host, as standardized by
this specification. This API is OAuth-protected, requiring a host
to obtain from the AM an OAuth access token, referred to in this
specification as a _protection API token (PAT)_ to distinguish it
from other tokens with other purposes. The host must present the
PAT for successful use of OAuth-protected endpoints at this API.
o The AM presents an _authorization API_ to the requester, as
standardized by this specification. This API is OAuth-protected,
requiring a requester to obtain from the AM an OAuth access token,
referred to in this specification as an _authorization API token
(AAT)_ to distinguish it from other tokens with other purposes.
The requester must present the AAT for successful use of OAuth-
protected endpoints at this API.
o The host presents a _protected resource_ to the requester, which
can be considered an application-specific or proprietary API.
This API is UMA-protected, requiring a requester to obtain from
the AM an UMA-specific token referred to in this specification as
a _requester permission token (RPT)_ to distinguish it from other
tokens with other purposes. The requester must present the RPT
with sufficient permissions (also issued by the AM) for successful
access to an UMA-protected resource.
The AM presents standard OAuth endpoints for token issuance and user
authorization in protecting its own UMA APIs, as follows. Hosts
asking to use the protection API would be issued a PAT. Requesters
asking to use the authorization API would be issued an AAT.
token endpoint Part of standard OAuth, as profiled by UMA. The
endpoint at which the host asks for a PAT and the requester
asks for an AAT. (The AM may also choose to issue a refresh
token.) This specification makes the OAuth token profile
"bearer" mandatory for the AM to implement. The AM can declare
its ability to handle other token profiles.
user authorization endpoint Part of standard OAuth, as profiled by
UMA. The endpoint to which the host or requester redirects an
authorizing user or end-user requesting party, respectively, to
authorize it to use this AM in resource protection or
authorization, if the OAuth authorization code grant type
(mandatory for the AM to implement) is being used.
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The AM presents the following endpoints to the host as part of its
protection API; these endpoints are OAuth-protected and require a PAT
for access, for which the "protection" OAuth scope is required:
resource set registration endpoint The endpoint at which the host
registers resource sets it wants the AM to protect. The
operations available at this endpoint constitute a resource set
registration API that is a subset of the protection API (see
Section 2.4.3).
permission registration endpoint The endpoint at which the host
registers permissions that it anticipates a requester will
shortly be asking for from the AM.
RPT status endpoint The endpoint at which the host submits
(forwards) an RPT that has accompanied an access request, to
learn what currently valid permissions are associated with it.
This specification defines an UMA token profile, "bearer",
which is mandatory for the AM to implement and which, if used,
REQUIRES the host to use this endpoint (see Section 3.3).
The AM presents the following endpoint to the requester as part of
its authorization API; this endpoint is OAuth-protected and requires
an AAT for access, for which the "authorization" OAuth scope is
required:
permission request endpoint The endpoint at which the requester asks
for authorization to have permissions associated with an RPT
and, as necessary, asks for issuance of an RPT.
The host presents one or more protected resource endpoints to the
requester; these endpoints are UMA-protected and require an RPT with
sufficient permissions for access:
protected resource endpoint An application-specific endpoint at
which a requester attempts to access resources. This can be a
singular API endpoint, one of a set of API endpoints, a URI
corresponding to an HTML document, or any other URI.
Similarly to OAuth authorization servers, an UMA AM has the
opportunity to manage the validity periods of the access tokens, the
corresponding refresh tokens (in the case of the PAT and AAT), and
even the client credentials that it issues. Different lifetime
strategies may be suitable for different resources and scopes of
access, and the AM has the opportunity to give the authorizing user
control through policy. These options are all outside the scope of
this specification.
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1.4. Scopes, Resource Sets, Permissions, and Authorization
UMA extends the OAuth concept of a "scope" by defining scopes as
applying to particular labeled resource sets, rather than leaving the
relevant resources (such as API endpoints or URIs) implicit. A
resource set can have any number of scopes, which together describe
the universe of actions that _can be_ taken on this protected
resource set. For example, a resource set representing a status
update API might have scopes that include adding an update or reading
updates. A resource set representing a photo album might have scopes
that include viewing a slideshow or printing the album. Hosts
register resource sets and their scopes when there is not yet any
particular requesting party or requester in the picture.
Resource sets and scopes have meaning only to hosts and their users,
in the same way that application-specific host APIs have meaning only
to these entities. The AM is merely a conveyor of labels and
descriptions for these constructs, to help the authorizing user set
policies that guide eventual authorization processes.
In contrast to an UMA scope, an UMA permission reflects an _actual_
result of an authorization process for a specific requester (on
behalf of a specific requesting party) to access a particular
resource set in a scoped (bounded) manner. Hosts register permission
requests with AMs on behalf of requesters that have attempted access
there and transmit the resulting temporary permission tickets to
requesters. Requesters subsequently ask AMs for permissions to be
associated with their RPTs. AMs grant (or deny) permissions to
requesters.
An RPT is bound to a requesting party, the requester (client) being
used by that party, the host at which protected resources of interest
reside, and the AM that protects those resources. It becomes
associated with as many permissions as are appropriate for gaining
authorized access to resources protected at that host by any single
AM (even if those permissions apply to resources managed by two or
more different authorizing users at the same host using the same AM).
Each individual permission is associated, in addition, with the
authorizing user whose policies drove the authorization process.
This enables meaningful, auditable, and potentially legally
enforceable authorization for access (see [UMA-trustmodel]).
Unlike UMA scopes (but similarly to tokens themselves; see
Section 1.3), permissions have a validity period that the AM has the
opportunity to control independently or with input from the
authorizing user. These options are outside the scope of this
specification.
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1.5. AM Configuration Data
The AM MUST provide configuration data to other entities it interacts
with in aJSON [RFC4627] document that resides in an /uma-
configuration directory at at its hostmeta [RFC6415] location. The
configuration data documents major conformance options supported by
the AM (described further in Section 7) and protection and
authorization API endpoints (as described in Section 1.3).
The configuration data has the following properties and a Content-
Type of application/uma-configuration+json. All endpoint URIs
supplied SHOULD require the use of a transport-layer security
mechanism such as TLS.
version
REQUIRED. The version of the UMA core protocol to which this
AM conforms. The value MUST be the string "1.0".
issuer
REQUIRED. A URI indicating the party operating the AM.
dynamic_client_registration_supported
OPTIONAL. Whether dynamic client registration, such as through
[OCDynClientReg], is supported for both hosts and requesters.
The value, if this property is present, the value MUST be the
string "yes" (dynamic registration is supported, using an
unspecified method) or "no" (it is not supported; hosts and
requesters are required to pre-register). The default is AM-
specific. This property is not currently extensible. (This
conformance option is largely a placeholder for now.)
oauth_token_profiles_supported
REQUIRED. PAT and AAT profiles produced by this AM. The
property value is an array of string values. Currently the
only string value for this property defined by this
specification is "bearer", corresponding to the OAuth bearer
token profile [OAuth-bearer]. The AM is REQUIRED to support
this profile, and to supply this string value explicitly. The
AM MAY declare its support for additional access token profiles
by providing a unique absolute URI in a string value in the
array for each one.
uma_token_profiles_supported
REQUIRED. RPT types produced by this AM. The property value
is an array of string values. Currently the only string value
for this property defined by this specification is "bearer",
whose associations the host MUST determine through a token
status interaction with the AM (see Section 3.3 for the
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definition of this profile). The AM is REQUIRED to support the
UMA bearer token profile, and to supply this string value
explicitly. The AM MAY declare its support for RPTs using
additional UMA token profiles by providing a unique absolute
URI in a string value in the array for each one.
oauth_grant_types_supported
REQUIRED. OAuth grant types supported by this AM in issuing
PATs and AATs. The property value is an array of string
values. Each string value MUST be one of the grant_type values
defined in [OAuth2], or alternatively an extension grant type
indicated by a unique absolute URI.
claim_profiles_supported
OPTIONAL. Claim formats and associated sub-protocols for
gathering claims from requesting parties, as supported by this
AM. The property value is an array of string values.
Currently the only string value for this property defined by
this specification is "openid", for which details are supplied
in Section 3.5.1.1. The AM MAY declare its support for
additional claim profiles by assigning a unique absolute URI in
a string value in the array for each one.
token_endpoint
REQUIRED. The endpoint URI at which the host or requester asks
the AM for a PAT or AAT, respectively. A requested scope of
"protection" results in a PAT. A requested scope of
"authorization" results in an AAT. Available HTTP methods are
as defined by [OAuth2] for a token endpoint.
user_endpoint
REQUIRED. The endpoint URI at which the host gathers the
consent of the authorizing user or end-user requesting party,
if the "authorization_code" grant type is used. Available HTTP
methods are as defined by [OAuth2] for an end-user
authorization endpoint.
resource_set_registration_endpoint
REQUIRED. The endpoint URI at which the host registers
resource sets with the AM to put them under its protection (see
Section 2.4.3). A PAT MUST accompany requests to this
protected endpoint.
permission_registration_endpoint
REQUIRED. The endpoint URI at which the host registers
permissions with the AM for which a requester will be seeking
authorization (see Section 3.2). A PAT MUST accompany requests
to this protected endpoint.
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rpt_status_endpoint
REQUIRED. The endpoint URI at which the host requests the
status of an RPT presented to it by a requester (see
Section 3.3). A PAT MUST accompany requests to this protected
endpoint.
permission_request_endpoint
REQUIRED. The endpoint URI at which the requester asks for
authorization to have a new permission associated with its RPT
(possibly assigned dynamically if it had not existed before).
An AAT MUST accompany requests to this protected endpoint.
Example of AM configuration data that resides at
https://example.com/.well-known/uma-configuration (note the use of
https: for endpoints throughout):
{
"version":"1.0",
"issuer":"https://example.com",
"dynamic_client_registration_supported":"yes",
"oauth_token_profiles_supported":[
"bearer"
],
"uma_token_profiles_supported":[
"bearer"
],
"oauth_grant_types_supported":[
"authorization_code"
],
"claim_profiles_supported":[
"openid"
],
"token_endpoint":"https://am.example.com/token_uri",
"user_endpoint":"https://am.example.com/user_uri",
"resource_set_registration_endpoint":"https://am.example.com/host/rsrc_uri",
"rpt_status_endpoint":"https://am.example.com/host/status_uri",
"permission_registration_endpoint":"https://am.example.com/host/perm_uri",
"permission_request_endpoint":"https://am.example.com/requester/perm_uri"
}
AM configuration data MAY contain extension properties that are not
defined in this specification. Extension names that are unprotected
from collisions are outside the scope of the current specification.
2. Protecting a Resource
Phase 1 of UMA is protecting a resource. The user, host, and AM
perform the following steps in order to successfully complete Phase
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1:
1. The host (having learned the general location of the relevant AM
out of band) looks up the AM's configuration data and learns
about its relevant endpoints and supported formats.
2. If the host has not yet obtained a unique OAuth client identifier
and optional secret from the AM, it registers with the AM as
required. It MAY do this using [OCDynClientReg], if the AM
supports it.
3. The host obtains a protection API token (PAT) from the AM with
the authorizing user's consent, by asking for the "protection"
scope.
4. The host registers any resource sets with the AM that are
intended to be protected. (This step is repeated when and as
needed.)
If the host undertakes these actions successfully, the results are as
follows:
o The host has received configuration data about the AM, such as
endpoints it needs to use in interacting with the AM.
o The host has received a PAT that represents this authorizing
user's approval for the host to work with the AM in protecting
resources.
o The AM has acquired information about resource sets at this host
that it is supposed to protect on behalf of this authorizing user.
2.1. Host Looks Up AM Configuration Data
The host needs to learn the AM's protection API endpoints before they
can begin interacting. To get the host started in this process, the
authorizing user might provide the AM's location to it, for example,
by typing a URL into a web form field or clicking a button.
Alternatively, the host might already be configured to work with a
single AM without requiring any user input. The exact process is
beyond the scope of this specification, and it is up to the host to
choose a method to learn the AM's general location.
From the data provided, discovered, or configured, the host MUST
retrieve the AM's configuration data document, as described in
Section 2 of hostmeta [RFC6415]. For example, if the user supplied
"example.com" as the Authorization Manager's domain, the host creates
the URL "https://example.com/.well-known/uma-configuration" and
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performs a GET request on it. The AM MUST return content that
includes UMA protection API endpoints as defined in Section 1.5.
2.2. Host Registers with AM
If the host has not already obtained an OAuth client identifier and
optional secret from this AM, in this step it MUST do so in order to
engage in OAuth-based interactions with the AM. It MAY do this using
[OCDynClientReg], if the AM supports it (see Section 1.5 for how the
AM MAY indicate support).
2.3. Host Obtains Protection API Token
In this step, the host acquires a PAT from the AM. The token
represents the approval of the authorizing user for this host to
trust this AM for protecting resources belonging to this user.
The host MUST use OAuth 2.0 [OAuth2] to obtain the protection API
token. Here the host acts in the role of an OAuth client requesting
the "protection" scope; the authorizing user acts in the role of an
OAuth end-user resource owner; and the AM acts in the role of an
OAuth authorization server. Once the host has obtained its PAT, it
presents it to the AM at various protection API endpoints; in
presenting these endpoints the AM acts in the role of a resource
server.
The AM MAY support the use of any grant type, but MUST support the
authorization_code grant type, and SHOULD support the SAML bearer
token grant type [OAuth-SAML]
(urn:ietf:params:oauth:grant-type:saml2-bearer) if it anticipates
working with hosts that are operating in environments where the use
of SAML is prevalent. The AM MUST indicate all grant types it
supports in its configuration data, as defined in Section 1.5.
The host has completed this step successfully when it possesses a PAT
it can use to get access to the AM's protection API on this user's
behalf.
2.4. Host Registers Sets of Resources to Be Protected
Once the host has received a PAT, for any of the user's sets of
resources that are to be protected by this AM, it MUST register these
resource sets at the AM's registration endpoint.
Note that the host is free to offer the option to protect any subset
of the user's resources using different AMs or other means entirely,
or to protect some resources and not others. Additionally, the
choice of protection regimes can be made explicitly by the user or
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implicitly by the host. Any such partitioning by the host or user is
outside the scope of this specification.
See Section 9 for an extended example of registering resource sets.
2.4.1. Scope Descriptions
A scope is a bounded extent of access that is possible to perform on
a resource set. A scope description is a JSON document with the
following properties and a Content-Type of application/
uma-scope+json:
name REQUIRED. A human-readable string describing some scope
(extent) of access. This name is intended for ultimate use in the
AM's user interface to assist the user in setting policies for
protected resource sets that have this available scope.
icon_uri OPTIONAL. A URI for a graphic icon representing the scope.
The referenced icon is intended for ultimate use in the AM's user
interface to assist the user in setting policies for protected
resource sets that have this available scope.
For example, this description characterizes a scope that involves
reading or viewing resources (vs. creating them or editing them in
some fashion):
{
"name": "View",
"icon_uri": "http://www.example.com/icons/reading-glasses"
}
Scope descriptions MAY contain extension properties that are not
defined in this specification. Extension names that are unprotected
from collisions are outside the scope of the current specification.
A host MUST list a resource set's available scopes using URI
references (as defined in Section 2.4.2). The scopes available for
use at any one host MUST have unique URI references so that the
host's scope descriptions are uniquely distinguishable. A scope URI
reference MAY include a fragment identifier. Scope descriptions MAY
reside anywhere. The host is not required to self-host scope
descriptions and may wish to point to standardized scope descriptions
residing elsewhere. Scope description documents MUST be accessible
to AMs through GET calls made to these URI references
See Section 1.4 for further discussion of scope-related concepts, and
Section 9 for a long-form example of scopes used in resource set
registration.
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2.4.2. Resource Set Descriptions
The host defines a resource set that needs protection by registering
a resource set description at the AM. The host registers the
description and manages its lifecycle at the AM's host resource set
registration endpoint by using the resource set registration API, as
defined in Section 2.4.3.
A resource set description is a JSON document with the following
properties and a Content-Type of application/uma-resource-set+json:
name REQUIRED. A human-readable string describing a set of one or
more resources. The AM SHOULD use the name in its user interface
to assist the user in setting policies for protecting this
resource set.
icon_uri OPTIONAL. A URI for a graphic icon representing the
resource set. If provided, the AM SHOULD use the referenced icon
in its user interface to assist the user in setting policies for
protecting this resource set.
scopes REQUIRED. An array providing the URI references of scope
descriptions that are available for this resource set. The AM
SHOULD use the scope names and any icons defined as part of the
referenced scopes in its user interface to assist the user in
setting policies for protecting this resource set.
For example, this description characterizes a resource set (a photo
album) that can potentially be only viewed, or alternatively to which
full access can be granted; the URIs point to scope descriptions as
defined in Section 2.4.1:
{
"name": "Photo Album",
"icon_uri": "http://www.example.com/icons/flower.png",
"scopes": [
"http://photoz.example.com/dev/scopes/view",
"http://photoz.example.com/dev/scopes/all"
]
}
Resource set descriptions MAY contain extension properties that are
not defined in this specification. Extension names that are
unprotected from collisions are outside the scope of the current
specification.
When a host creates or updates a resource set description (see
Section 2.4.3), the AM MUST attempt to retrieve the referenced scope
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descriptions. It MAY cache such descriptions as long as indicated in
the HTTP cache-control header for the scope description resource
unless the resource set description is subsequently updated within
the validity period. At the beginning of an authorizing user's login
session at the AM, the AM MUST attempt to re-retrieve scope
descriptions applying to that user whose cached versions have
expired.
2.4.3. Resource Set Registration API
The host uses the RESTful API at the AM's resource set registration
endpoint to create, read, update, and delete resource set
descriptions, along with listing groups of such descriptions. The
host MUST use its valid PAT obtained previously to gain access to
this endpoint. The resource set registration API is a subset of the
protection API.
(Note carefully the similar but distinct senses in which the word
"resource" is used in this section. UMA resource set descriptions
are themselves managed as web resources at the AM through this API.)
The AM MUST present an API for registering resource set descriptions
at a set of URIs with the structure "{rsreguri}/resource_set/{rsid}",
where the PAT provides sufficient context to distinguish between
identical resource set identifiers assigned by different hosts.
The components of these URIs are defined as follows:
{rsreguri} The AM's resource set registration endpoint as advertised
in its configuration data (see Section 1.5).
{rsid} An identifier for a resource set description.
Without a specific resource set identifier path component, the URI
applies to the set of resource set descriptions already registered.
Following is a summary of the five registration operations the AM is
REQUIRED to support. Each is defined in its own section below. All
other methods are unsupported. This API uses ETag and If-Match to
ensure the desired resource at the AM is targeted.
o Create resource set description: PUT /resource_set/{rsid}
o Read resource set description: GET /resource_set/{rsid}
o Update resource set description: PUT /resource_set/{rsid} with If-
Match
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o Delete resource set description: DELETE /resource_set/{rsid}
o List resource set descriptions: GET /resource_set/ with If-Match
If the request to the resource set registration endpoint is
incorrect, then the AM responds with an error message (see
Section 4.2) by including one of the following error codes with the
response:
unsupported_method_type The host request used an unsupported HTTP
method. The AM MUST respond with the HTTP 405 (Method Not
Allowed) status code and MUST fail to act on the request.
not_found The resource set requested from the AM cannot be found.
The AM MUST respond with HTTP 404 (Not Found) status code.
precondition_failed The resource set that was requested to be
deleted or updated at the AM did not match the If-Match value
present in the request. The AM MUST respond with HTTP 412
(Precondition Failed) status code and MUST fail to act on the
request.
2.4.3.1. Create Resource Set Description
Adds a new resource set description using the PUT method, thereby
putting it under the AM's protection. If the request is successful,
the AM MUST respond with a status message that includes an ETag
header and _id and _rev properties for managing resource set
description versioning.
The host is free to use its own methods of identifying and describing
resource sets. The AM MUST treat them as opaque for the purpose of
authorizing access, other than associating them with the authorizing
user represented by the PAT used to access the API. On successfully
registering a resource set, the host MUST use UMA mechanisms to limit
access to any resources corresponding to this resource set, relying
on the AM to supply currently valid permissions for authorized
access.
Form of a "create resource set description" HTTP request:
PUT /resource_set/{rsid} HTTP/1.1
Content-Type: application/uma-resource-set+json
...
(body contains JSON resource set description to be created)
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Form of a successful HTTP response:
HTTP/1.1 201 Created
Content-Type: application/uma-status+json
ETag: (matches "_rev" property in returned object)
...
{
"status": "created",
"_id": (id of created resource set),
"_rev": (ETag of created resource set)
}
On successful registration, the AM MAY return a redirect policy URI
to the host in a property with the name "policy_uri". This URI
allows the host to redirect the user to a specific user interface
within the AM where the user can immediately set or modify access
policies for the resource set that was just registered.
Form of a successful HTTP response:
HTTP/1.1 201 Created
Content-Type: application/uma-status+json
ETag: (matches "_rev" property in returned object)
...
{
"status": "created",
"_id": (id of created resource set),
"_rev": (ETag of created resource set)
"policy_uri":"http://am.example.com/host/222/resource/333/policy"
}
2.4.3.2. Read Resource Set Description
Reads a previously registered resource set description using the GET
method. If the request is successful, the AM MUST respond with a
status message that includes an ETag header and _id and _rev
properties for managing resource set description versioning.
Form of a "read resource set description" HTTP request:
GET /resource_set/{rsid} HTTP/1.1
...
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Form of a successful HTTP response:
HTTP/1.1 200 OK
Content-Type: application/uma-resource-set+json
...
(body contains JSON resource set description, including _id and _rev)
If the referenced resource does not exist, the AM MUST produce an
error response with an error property value of "not_found", as
defined in Section 2.4.3.
On successful read, the AM MAY return a redirect policy URI to the
host in a property with the name "policy_uri". This URI allows the
host to redirect the user to a specific user interface within the AM
where the user can immediately set or modify access policies for the
resource set that was read.
2.4.3.3. Update Resource Set Description
Updates a previously registered resource set description using the
PUT method, thereby changing the resource set's protection
characteristics. If the request is successful, the AM MUST respond
with a status message that includes an ETag header and _id and _rev
properties for managing resource set description versioning.
Form of an "update resource set description" HTTP request:
PUT /resource_set/{rsid} HTTP/1.1
Content-Type: application/resource-set+json
If-Match: (entity tag of resource)
...
(body contains JSON resource set description to be updated)
Form of a successful HTTP response:
HTTP/1.1 204 No Content
ETag: "2"
...
If the entity tag does not match, the AM MUST produce an error
response with an error property value of "precondition_failed", as
defined in Section 2.4.3.
On successful update, the AM MAY return a redirect policy URI to the
host in a property with the name "policy_uri". This URI allows the
host to redirect the user to a specific user interface within the AM
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where the user can immediately set or modify access policies for the
resource set that was just updated.
2.4.3.4. Delete Resource Set Description
Deletes a previously registered resource set description using the
DELETE method, thereby removing it from the AM's protection regime.
Form of a "delete resource set description" HTTP request:
DELETE /resource_set/{rsid}
If-Match: (entity tag of resource)
...
Form of a successful HTTP response:
HTTP/1.1 204 No content
...
As defined in Section 2.4.3, if the referenced resource does not
exist the AM MUST produce an error response with an error property
value of "not_found", and if the entity tag does not match the AM
MUST produce an error response with an error property value of
"precondition_failed".
2.4.3.5. List Resource Set Descriptions
Lists all previously registered resource set identifiers for this
user using the GET method. The AM MUST return the list in the form
of a JSON array of {rsid} values.
The host uses this method as a first step in checking whether its
understanding of protected resources is in full synchronization with
the AM's understanding.
Form of a "list resource set descriptions" HTTP request:
GET /resource_set HTTP/1.1
...
HTTP response:
HTTP/1.1 200 OK
Content-Type: application/json
...
(body contains JSON array of {rsid} values)
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3. Getting Authorization and Accessing a Resource
Phase 2 of UMA is getting authorization, and Phase 3 is accessing a
resource. In these phases, an AM orchestrates and controls
requesting parties' access to an authorizing user's protected
resources at a host, under conditions dictated by that user.
Phase 3 is merely the successful completion of a requester's access
attempt that initially involved several embedded interactions among
the requester, AM, and host in Phase 2. Phase 2 always begins with
the requester attempting access at a protected resource endpoint at
the host. How the requester came to learn about this endpoint is out
of scope for this specification. The authorizing user might, for
example, have advertised its availability publicly on a blog or other
website, listed it in a discovery service, or emailed a link to a
particular intended requesting party.
The host responds to the requester's access request in one of several
ways depending on the circumstances of the request, either
immediately or having first performed one or more embedded
interactions with the AM. Depending on the nature of the host's
response to an failed access attempt, the requester itself engages in
embedded interactions with the AM before re-attempting access.
The interactions are as follows. Each interaction MAY be the last,
if the requester chooses not to continue pursuing the access attempt
or the host chooses not to continue facilitating it.
1. The requester attempts access at a particular protected resource
at a host (see Section 3.1).
A. If the access attempt is unaccompanied by a requester
permission token (RPT) (see Section 3.1.1), the host
registers a suitable permission request with the AM (see
Section 3.2). On receiving a permission ticket from the AM,
the host delivers it to the requester through an HTTP 401
(Unauthorized) response message with instructions on where to
go to obtain the permission (and, necessarily, an RPT).
B. If the access attempt was accompanied by an RPT, the host
checks the token's status (see Section 3.3).
1. If the RPT is invalid (for example, not applicable to
this host or expired), or has insufficient permissions
(see Section 3.1.2), the host registers a suitable
permission request at the AM (see Section 3.2) and then
responds to the requester with an HTTP 403 (Forbidden)
response and instructions on where to go to request
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authorization for that permission (and, as required, a
valid RPT for this host).
2. If the RPT is valid, and at least one of the permissions
associated with the token matches the scope of attempted
access, the host responds to the requester's access
attempt with an HTTP 200 (OK) response and a
representation of the resource (see Section 3.1.3).
2. If the requester received a permission ticket, it requests the
permission (and a valid RPT for the host in question, as
necessary) from the AM (Section 3.4). The AM MAY then engage in
a claims-gathering flow with the requesting party prior to
authorizing a new permission to be associated with an RPT (see
Section 3.5).
A. If the requester does not already have an AAT at the
appropriate AM to be able to use its permission request
endpoint, it first engages in an OAuth grant flow to obtain
one (see Section 3.4.3).
The interactions are described in detail in the following sections.
3.1. Requester-Host: Attempt Access at Protected Resource
This interaction assumes that the host has previously registered with
an AM one or more resource sets that correspond to the resource to
which access is being attempted, such that the host considers this
resource to be UMA-protected by a particular AM.
The requester typically attempts to access the desired resource at
the host directly (for example, when a human operator of the
requester software clicks on a thumbnail representation of the
resource). The requester is expected to discover, or be provisioned
or configured with, knowledge of the protected resource and its
location out of band. Further, the requester is expected to acquire
its own knowledge about the application-specific methods made
available by the host for operating on this protected resource (such
as viewing it with a GET method, or transforming it with some complex
API call) and the possible scopes of access.
Example of a request carrying no RPT:
GET /album/photo.jpg HTTP/1.1
Host: photoz.example.com
...
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Example of a request carrying an RPT:
GET /album/photo.jpg HTTP/1.1
Authorization: Bearer vF9dft4qmT
Host: photoz.example.com
...
The host responds in one of the following ways.
3.1.1. Requester Presents No Requester Permission Token
If the requester does not present an RPT with the request, the Host
SHOULD register a permission with the AM that would suffice for that
scope of access (see Section 3.2), and then respond to the requester
with the HTTP 401 (Unauthorized) status code, along with providing
the AM's URI in the header of the message and the permission ticket
it just received from the AM in the body in JSON form.
Example of the host's response:
HTTP/1.1 401 Unauthorized
WWW-Authenticate: UMA realm="example",
host_id="photoz.example.com",
am_uri="http://am.example.com"
{
"ticket": "016f84e8-f9b9-11e0-bd6f-0021cc6004de"
}
3.1.2. Requester Presents a Requester Permission Token That Is Invalid
Or Has Insufficient Permission
If the requester presents an RPT with its request, the host SHOULD
determine the RPT's status (see Section 3.3). If the token is
invalid or has insufficient permission for the type of access sought,
the Host SHOULD register a permission with the AM that would suffice
for that scope of access (see Section 3.2), and then respond to the
requester with the HTTP 403 (Forbidden) status code, along with
providing the AM's URI in the header of the message and the
permission ticket it just received from the AM in the body in JSON
form.
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Example of the host's response:
HTTP/1.1 403 Forbidden
WWW-Authenticate: UMA realm="example",
host_id="photoz.example.com",
am_uri="http://am.example.com"
{
"ticket": "016f84e8-f9b9-11e0-bd6f-0021cc6004de"
}
3.1.3. Requester Presents a Valid Requester Permission Token
If the RPT's status is associated with at least one currently valid
permission that applies to the scope of access attempted by the
requester (see Section 3.3), the host MUST give access to the desired
resource.
Example of the host's response:
HTTP/1.1 200 OK
Content-Type: image/jpeg
...
/9j/4AAQSkZJRgABAgAAZABkAAD/7AARRHVja
3kAAQAEAAAAPAAA/+4ADkFkb2JlAGTAAAAAAf
/bAIQABgQEBAUEBgUFBgkGBQYJCwgGBggLDAo
KCwoKDBAMDAwMDAwQDA4PEA8ODBMTFBQTExwb
This response constitutes the conclusion of Phase 3 of UMA.
The host MUST NOT give access where the token's status is not
associated with at least one currently active permission that
suffices for that scope of access.
3.2. Host-AM: Register a Permission
In response to receiving an access request unaccompanied by an RPT or
accompanied by an RPT that is invalid or has insufficient
permissions, the host SHOULD register a permission with the AM that
would be sufficient for the type of access sought. The AM returns a
permission ticket for the host to give to the requester in its
response.
The permission ticket is a short-lived opaque structure whose form is
determined by the AM. The ticket value MUST be securely random (for
example, not merely part of a predictable sequential series), to
avoid denial-of-service attacks. Since the ticket is an opaque
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structure from the point of view of the requester, the AM is free to
include information regarding expiration time within the opaque
ticket for its own consumption. When the requester subsequently asks
the AM to add permissions to its RPT, it will submit this ticket to
the AM.
The host registers the permission using the POST method at the AM's
permission registration endpoint, providing its PAT to get access to
this endpoint. The body of the HTTP request message contains a JSON
document providing the requested permission.
The requested scope is an object with the name "requested_permission"
and the following properties:
resource_set_id REQUIRED. The identifier for a resource set, access
to which this requester is seeking access. The identifier MUST
correspond to a resource set that was previously registered.
scopes REQUIRED. An array referencing one or more identifiers of
scopes to which access is needed for this resource set. Each
scope identifier MUST correspond to a scope that was registered by
this host for the referenced resource set.
Example of an HTTP request that registers a permission at the AM's
permission registration endpoint:
POST /host/scope_reg_uri/photoz.example.com HTTP/1.1
Content-Type: application/uma-requested-permission+json
Host: am.example.com
{
"resource_set_id": "112210f47de98100",
"scopes": [
"http://photoz.example.com/dev/actions/view",
"http://photoz.example.com/dev/actions/all"
]
}
If the registration request is successful, the AM responds with an
HTTP 201 (Created) status code and includes the Location header in
its response as well as the "ticket" property in the JSON-formatted
body.
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For example:
HTTP/1.1 201 Created
Content-Type: application/uma-permission-ticket+json
Location: https://am.example.com/permreg/host/photoz.example.com/5454345rdsaa4543
...
{
"ticket": "016f84e8-f9b9-11e0-bd6f-0021cc6004de"
}
If the registration request is authenticated properly but fails due
to other reasons, the AM responds with an HTTP 400 (Bad Request)
status code and includes one of the following UMA error codes (see
Section 4.2):
invalid_resource_set_id The provided resource set identifier was not
found at the AM.
invalid_scope At least one of the scopes included in the request was
not registered previously by this host.
3.3. Host-AM: Ask for Requester Permission Token Status
On receiving an RPT, the host MUST ascertain its status before
granting or denying access to the requester. An RPT that a requester
provides to a host in order to get access is associated with a set of
permissions that govern whether the requester is authorized for
access. The token's nature and format are dictated by its defined
profile; the profile might allow it to be self-contained, such that
the host is able to ascertain its status locally, or might require or
allow the host to make a run-time status request of the AM that
issued the token.
This specification makes one type of RPT mandatory to implement: the
UMA bearer token profile, as defined in Section 3.3.1. Alternate RPT
profiles MAY define their own unique token formats and MAY require,
allow, or prohibit use of the RPT status endpoint.
3.3.1. UMA Bearer Token Profile
This section defines the format and protocol requirements for the UMA
bearer token profile. An AM MUST support the UMA bearer token
profile and must indicate its support in the
"uma_token_profiles_supported" property in the configuration data
(see Section 1.5).
On receiving an RPT of the "Bearer" type in an authorization header
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from a requester making an access attempt, the host MUST ask the AM
for the RPT's status unless it has an unexpired cached status
description for this RPT, which it MAY use instead. In order to ask
the AM for an RPT's status, the host makes the request to the AM with
a POST request to the AM's RPT status endpoint. The body of the HTTP
request message contains a JSON document providing the RPT. The host
gains access to the RPT status endpoint by presenting its own PAT in
the request.
Note that although the host's request is a safe operation, which
normally would use the GET operation, this specification dictates the
use of POST because it is advantageous for security of bearer tokens.
Since the host provides its own PAT in the authorization header of
the request, the RPT appears in the request body. A GET operation
would expose the message to being recorded in AM access logs.
Example of a request to the RPT status endpoint that provides the PAT
in the header:
POST /token_status HTTP/1.1
Host: am.example.com
Authorization: Bearer vF9dft4qmT
Content-Type: application/json
...
{
"rpt": "sbjsbhs(/SSJHBSUSSJHVhjsgvhsgvshgsv",
"resource_set_id": "112210f47de98100",
"host_id": "photoz.example.com"
}
The AM returns the RPT's status in an HTTP response using the 200 OK
status code, containing a JSON document supplying the RPT status
description. The RPT status description either contains all of the
permissions that are currently valid for this RPT or indicates that
the RPT is invalid (see Section 1.4). The AM MAY set a cache period
for the returned RPT status description that allows the host to reuse
it over some period of time when it later sees the same RPT.
The status description for a valid RPT is a JSON array of zero or
more permission objects, each with the following properties:
resource_set_id REQUIRED. A string that uniquely identifies the
resource set, access to which has been granted to this requester
on behalf of this requesting party. The identifier MUST
correspond to a resource set that was previously registered as
protected.
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scopes REQUIRED. An array referencing one or more URIs of scopes to
which access was granted for this resource set. Each scope MUST
correspond to a scope that was registered by this host for the
referenced resource set.
exp REQUIRED. An integer representing the expiration time on or
after which the permission MUST NOT be accepted for authorized
access. The processing of the exp property requires that the
current date/time MUST be before the expiration date/time listed
in the exp claim. Host implementers MAY provide for some small
leeway, usually no more than a few minutes, to account for clock
skew.
Example:
HTTP/1.1 200 OK
Content-Type: application/uma-rpt-status+json
Cache-Control: no-store
...
[
{
"resource_set_id": "112210f47de98100",
"scopes": [
"http://photoz.example.com/dev/actions/view",
"http://photoz.example.com/dev/actions/all"
],
"exp": 1300819380
}
]
The token status description for an invalid RPT is a JSON structure,
as follows.
HTTP/1.1 200 OK
Content-Type: application/uma-rpt-status+json
...
{
"rpt_status": "invalid"
}
3.4. Requester-AM: Ask for Permission and Requester Permission Token
If a requester has received a permission ticket in an Unauthorized or
Forbidden response to an access attempt, this means that the
requester originally presented no RPT, or presented an RPT that was
invalid, or presented a valid RPT that had insufficient permissions
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associated with it. The requester uses the permission ticket to ask
for the necessary permission -- and an RPT with which to associate
it, as required -- from the AM's permission request endpoint. This
process necessarily involves the requesting party (the natural or
legal person who is operating the requester).
The requester takes action in the following ways.
3.4.1. Requester Looks Up AM Configuration Data
The requester needs to learn the AM's permission request endpoint
before they can begin interacting. From the "am_uri" information
provided in the host's previous response containing the permission
ticket, the requester MUST retrieve the AM's configuration data
document, as described in Section 2 of hostmeta [RFC6415]. For
example, if the "am_uri" is "example.com", the requester creates the
URL "https://example.com/.well-known/uma-configuration" and performs
a GET request on it. The AM MUST return content that includes UMA
authorization API endpoints as defined in Section 1.5.
3.4.2. Requester Registers with AM
If the requester has not already obtained an OAuth client identifier
and optional secret from this AM, in this step it MUST do so in order
to engage in OAuth-based interactions with the AM. It MAY do this
using [OCDynClientReg], if the AM supports it (see Section 1.5 for
how the AM MAY indicate support).
3.4.3. Requester Obtains Authorization API Token
In this step, the requester acquires an AAT from the AM. The token
represents the approval of this requesting party for this requester
to engage with this AM for to supply claims, ask for permissions, and
perform any other tasks needed for obtaining authorization for access
to resources at all hosts that use this AM.
The requester MUST use OAuth 2.0 [OAuth2] to obtain the AAT. Here
the requester acts in the role of an OAuth client requesting the
"authorization" scope; the requesting party acts in the role of an
OAuth resource owner; and the AM acts in the role of an OAuth
authorization server. Once the requester has obtained its AAT, it
presents it to the AM at the permission request API endpoint; in
presenting this endpoint the AM acts in the role of a resource
server.
By virtue of being able to identify this requester/requesting party
pair uniquely across all hosts, the AM is able to manage the process
of authorization and claims-gathering efficiently. These management
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processes are outside the scope of this specificaiton.
The AM MAY support the use of any grant type, but MUST support the
authorization_code grant type, and SHOULD support the SAML bearer
token grant type [OAuth-SAML]
(urn:ietf:params:oauth:grant-type:saml2-bearer) if it anticipates
working with requesters that are operating in environments where the
use of SAML is prevalent. The AM MUST indicate all grant types it
supports in its configuration data, as defined in Section 1.5.
The requester has completed this step successfully when it possesses
a AAT it can use to get access to the AM's authorization API on the
requesting party's behalf.
3.4.4. Requester-AM: Request Authorization to Add Permission
Once in possession of a permission ticket and an AAT, the requester
asks the AM to authorize it to have the permission for the sought-for
access. The requester performs a POST on the permission endpoint,
supplying:
o The permission ticket it received from the host
o Its RPT for this host, if it already has one
o Its own AAT in the header in order to gain access to the
permission endpoint
Example of a request message containing a permission ticket and RPT:
POST /token_status HTTP/1.1
Host: am.example.com
Authorization: Bearer jwfLG53^sad$#f
Content-Type: application/json
...
{
"rpt": "sbjsbhs(/SSJHBSUSSJHVhjsgvhsgvshgsv",
"ticket": "016f84e8-f9b9-11e0-bd6f-0021cc6004de"
}
In this interaction, the requester uses the AM's permission request
endpoint. The AM uses the ticket to look up the previously
registered permission, maps the requested permission to operative
user policies, undergoes any authorization flows required (see
Section 3.5), and ultimately responds to the request positively or
negatively.
If the AM determines that the requesting party meets the
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authorization criteria set out by the authorizing user's policy (see
Section 3.5), it responds with an HTTP 201 (Created) status code and
provides a new or updated RPT:
For example:
HTTP/1.1 201 Created
Content-Type: application/uma-rpt+json
{
"rpt": "sbjsbhs(/SSJHBSUSSJHVhjsgvhsgvshgsv"
}
If the content-type of the request is not recognized by the AM, the
AM MUST produce an HTTP error.
If the request fails due to missing or invalid parameters, or is
otherwise malformed, the AM SHOULD inform the requester of the error
by sending an HTTP error response.
If the request fails due to an invalid, missing, or expired AAT or
requires higher privileges at this endpoint than provided by the AAT,
the AM responds with an OAuth error (see Section 4.1).
For example:
HTTP/1.1 401 Unauthorized
WWW-Authenticate: Bearer realm="example",
error="invalid_token",
error_description="The access token expired"
If the AM does not add the requested permission, it responds using
the appropriate HTTP status code (typically 400 or 403), and includes
one of the following error codes in the response (see Section 4.2):
invalid_requester_ticket The provided ticket was not found at the
AM. The AM SHOULD respond with the HTTP 400 (Bad Request) status
code.
expired_requester_ticket The provided ticket has expired. The AM
SHOULD respond with the HTTP 400 (Bad Request) status code.
not_authorized_permission The requester is definitively not
authorized for this permission according to user policy. The AM
SHOULD respond with the HTTP 403 (Forbidden) status code.
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need_claims The AM is unable to determine whether the requester is
authorized for this permission without gathering claims from the
requesting party. The AM SHOULD respond with the HTTP 403
(Forbidden) status code. The requester is therefore not
authorized, but has the opportunity to engage the requesting party
in a claims-gathering flow with the AM (see Section 3.5) to
potentially become authorized.
For example:
HTTP/1.1 400 Bad Request
Content-Type: application/uma-status+json
Cache-Control: no-store
...
{
"status": "error",
"error": "expired_requester_ticket"
}
3.5. Claims-Gathering Flows
The AM MUST base its decisions to add permissions to RPTs on user
policies. The nature of these policies is outside the scope of UMA,
but generally speaking, they can be thought of as either independent
of requesting-party features (for example, time of day) or dependent
on requesting-party features (for example, whether they are over 18).
This latter case requires the requesting party to transmit identity
claims to the AM in some fashion.
The process for requesting and providing claims is extensible and may
have a variety of dependencies on the type of requesting party (for
example, natural person or legal person) and the type of requester
application (for example, browser, native app, or autonomously
running web service). UMA currently provides a framework for
handling human-driven requester apps and an optional solution for
gathering standardized claims from that end-user, and allows for
extensions to support other solutions for this use case and other use
cases. The AM SHOULD document its claims-handling ability in its
configuration data through the claim_profiles_supported property (see
Section 1.5). For the business-level and legal implications of
different technical authorization flows, see [UMA-trustmodel].
3.5.1. Claims-Gathering Flow for Requester Apps Operated by End-Users
A requester app, whether browser-based or native, is operated by a
natural person (human end-user) in one of two typical situations:
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o The requesting party is a natural person (for example, a friend of
the authorizing user); the requesting party may even be the
authorizing user herself.
o The requesting party is a legal person such as a corporation, and
the human being operating the requester app is acting as an agent
of that legal person (for example, a customer support specialist
representing a credit card company).
For convenience, this specification refers to the human end-user as a
"requesting end-user" to cover both cases, which differ only at the
level of business agreements (and potentially law), rather than
technology. The AM has a variety of options at this point for
satisfying the authorizing user's policy; this specification does not
dictate a single answer. For example, the AM could require the
requesting end-user to register for and/or log in to a local AM
account, or to fill in a questionnaire, or to complete a purchase.
It could even require several of these operations, where the order is
significant.
An end-user-driven requester app MUST redirect the end-user to the AM
to complete the process of authorization. The redirection MUST
include a URI query parameter with the name "ticket" whose value
conveys the permission ticket for which the need_claims error was
received; for example, "ticket=016f84e8-f9b9-11e0-bd6f-0021cc6004de".
Each claim profile MUST provide the following capabilities:
redirect URI A means by which the requester MUST supply the URI to
which the AM MUST redirect the requesting end-user at the end of
the claims-gathering process.
callback URI A means by which the requester OPTIONALLY supplies a
callback URI for the AM to use.
state A means by which the requester SHOULD supply an opaque value
used to maintain state between the request and the callback;
serves as a protection against XSRF attacks.
An AM MAY support any number of claim profiles. One potential such
profile is defined in this specification: the "openid" claim profile,
which leverages OpenID Connect for gathering generally useful user
claims (see Section 3.5.1.1).
3.5.1.1. OpenID Connect Claim Profile
If an AM supports the OpenID Connect claim profile, it MUST supply
the "openid" value for one of its claim_profiles_supported values in
its AM configuration data (see Section 1.5 for how to formulate this
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data).
To conform to this option, the AM MUST do the following:
o Serve as a conforming OpenID Relying Party and Claims Client
according to [OCStandard]
o Be able to utilize at least all of the reserved claims defined in
[OCMessages] in assessing policy and granting permissions
o Use the OpenID Connect "redirect_uri" and "state" request
parameters as appropriate
The AM can then use any conforming OpenID Connect mechanisms and
typical user interfaces for engaging with the UserInfo endpoints of
OpenID Providers and Claims Providers, potentially allowing for the
delivery of "trusted claims" (such as a verified email address or a
date or birth) on which authorization policy may depend.
4. Error Messages
Ultimately the host is responsible for either granting the access the
requester attempted, or returning an error response to the requester
with a reason for the failure. [OAuth2] defines several error
responses for a resource server to return. UMA makes use of these
error responses, but requires the host to "outsource" the
determination of some error conditions to the AM. UMA defines its
own additional error responses that the AM may give to the host and
requester as they interact with it, and that the host may give to the
requester.
4.1. OAuth Error Responses
When a client (host or requester) attempts to access one of the AM
endpoints Section 1.5 or a client (requester) attempts to access a
protected resource at the host, it has to make an authenticated
request by including an OAuth access token in the HTTP request as
described in [OAuth2] Section 7.
If the client's request failed authentication, the AM or the host
responds with an OAuth error message as described throughout
Section 2 and Section 3.
4.2. UMA Error Responses
When a client (host or requester) attempts to access one of the AM
endpoints Section 1.5 or a client (requester) attempts to access a
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protected resource at the host, if the client request is successfully
authenticated by OAuth means, but is invalid for another reason, the
AM or host responds with an UMA error response by adding the
following properties to the entity body of the HTTP response using
the "application/json" media type:
error REQUIRED. A single error code. Value for this property is
defined in the specific AM endpoint description.
error_description OPTIONAL. A human-readable text providing
additional information, used to assist in the understanding and
resolution of the error occurred.
error_uri OPTIONAL. A URI identifying a human-readable web page
with information about the error, used to provide the end-user
with additional information about the error.
Common error codes:
invalid_request The request is missing a required parameter or is
otherwise malformed. The AM MUST respond with the HTTP 400 (Bad
Request) status code.
For example:
HTTP/1.1 400 Bad Request
Content-Type: application/uma-status+json
Cache-Control: no-store
...
{
"status": "error",
"error": "invalid_request",
"error_description": "There is already a resource with this identifier.",
"error_uri": "http://am.example.com/errors/resource_exists"
}
5. Security Considerations
This specification relies mainly on OAuth security mechanisms for
protecting the host registration endpoint at the AM so that only a
properly authorized host can access it on behalf of the intended
user. For example, the host needs to use a valid protection API
token (PAT) issued through a user authorization process at the
endpoint, and the interaction SHOULD take place over TLS. It is
expected that the host will protect its client secret (if it was
issued one) and its PAT, particularly if used in "bearer token"
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fashion.
In addition, this specification dictates a binding between the PAT
and the host-specific registration area on the AM to prevent a host
from interacting with a registration area not its own.
This specification defines a number of JSON-based data formats. As a
subset of the JavaScript scripting language, JSON data SHOULD be
consumed through a process that does not dynamically execute it as
code, to avoid malicious code execution. One way to achieve this is
to use a JavaScript interpreter rather than the built-in JavaScript
eval() function.
For information about the technical, operational, and legal elements
of trust establishment between UMA entities and parties, which
affects security considerations, see [UMA-trustmodel].
6. Privacy Considerations
The AM comes to be in possession of resource set information (such as
names and icons) that may reveal information about the user, which
the AM's trust relationship with the host is assumed to accommodate.
However, the requester is a less-trusted party (in fact, entirely
untrustworthy until it acquires permissions for an RPT in UMA
protocol phase 2. This specification recommends obscuring resource
set identifiers in order to avoid leaking personally identifiable
information to requesters through the "scope" mechanism.
For information about the technical, operational, and legal elements
of trust establishment between UMA entities and parties, which
affects privacy considerations, see [UMA-trustmodel].
7. Conformance
This section outlines conformance requirements for various entities
implementing UMA endpoints.
This specification has dependencies on other specifications, as
follows:
o OAuth 2.0: AMs, hosts, and requesters MUST support [OAuth2]
features named in this specification for conformance. For
example, AMs MUST support the authorization_code and
client_credentials grant types.
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o hostmeta: AMs, hosts, and requesters MUST support the [RFC6415]
features named in this specification.
o OpenID Connect: AMs MAY support [OCDynClientReg], and MAY choose
to conform to the "openid" claim format option, corresponding to
the OpenID Connect RP role defined in [OCStandard] and support for
OpenID Connect reserved claims defined in [OCMessages].
The AM's configuration data provides a machine-readable method for an
AM to indicate certain of the conformance options it has chosen.
Several of the data properties allow for extensibility. Where this
specification does not already require optional features to be
documented, it is RECOMMENDED that AM developers and deployers
document any profiled or extended features explicitly and use
configuration data to indicate their usage. See Section 1.5 for
information about providing and extending AM configuration data.
8. IANA Considerations
Several UMA-specific JSON-based media types are being proposed, as
follows: (TBS)
9. Example of Registering Resource Sets
The following example illustrates the intent and usage of resource
set descriptions and scope descriptions as part of resource set
registration.
This example contains some steps that are exclusively in the realm of
user experience rather than web protocol, to achieve realistic
illustration. These steps are labeled "User experience only". Some
other steps are exclusively internal to the operation of the entity
being discussed. These are labeled "Internal only".
An authorizing user, Alice Adams, has just uploaded a photo of her
new puppy to a host, Photoz.example.com, and wants to ensure that
this specific photo is not publicly accessible.
Alice has already introduced this host to her AM,
CopMonkey.example.com, and thus Photoz has already obtained a PAT
from CopMonkey. However, Alice has not previously instructed Photoz
to use CopMonkey to protect any other photos of hers.
Alice has previously visited CopMonkey to map a default "do not share
with anyone" policy to any resource sets registered by Photoz, until
such time as she maps some other more permissive policies to those
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resources. (User experience only. This may have been done at the
time Alice introduced the host to the AM, and/or it could have been a
global or host-specific preference setting. A different constraint
or no constraint at all might be associated with newly protected
resources.) Other kinds of policies she may eventually map to
particular photos or albums might be "Share only with
husband@email.example.net" or "Share only with people in my 'family'
group".
Photoz itself has a publicly documented application-specific API that
offers two dozen different methods that apply to single photos, such
as "addTags" and "getSizes", but rolls them up into two photo-related
scopes of access: "view" (consisting of various read-only operations)
and "all" (consisting of various reading, editing, and printing
operations). It defines two scope descriptions that represent these
scopes, which it is able to reuse for all of its users (not just
Alice), and ensures that these scope description documents are
available through HTTP GET requests that may be made by AMs.
The "name" property values are intended to be seen by Alice when she
maps authorization constraints to specific resource sets and actions
while visiting CopMonkey, such that Alice would see the strings "View
Photo and Related Info" and "All Actions", likely accompanied by the
referenced icons, in the CopMonkey interface. (Other users of Photoz
might similarly see the same labels at CopMonkey or whatever other AM
they use. Photoz could distinguish natural-language labels per user
if it wishes, by pointing to scopes with differently translated
names.)
Example of the viewing-related scope description document available
at http://photoz.example.com/dev/scopes/view with a Content-Type of
application/uma-scope+json:
{
"name": "View Photo and Related Info",
"icon_uri": "http://www.example.com/icons/reading-glasses.png"
}
Example of the broader scope description document available at
http://photoz.example.com/dev/scopes/all, likewise with a Content-
Type of application/uma-scope+json:
{
"name": "All Actions",
"icon_uri": "http://www.example.com/icons/galaxy.png"
}
While visiting Photoz, Alice selects a link or button that instructs
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the site to "Protect" or "Share" this single photo (user experience
only; Photoz could have made this a default or preference setting).
As a result, Photoz defines for itself a resource set that represents
this photo (internal only; Photoz is the only application that knows
how to map a particular photo to a particular resource set). Photoz
also prepares the following resource set description, which is
specific to Alice and her photo. The "name" property value is
intended to be seen by Alice in mapping authorization policies to
specific resource sets and actions when she visits CopMonkey. Alice
would see the string "Steve the puppy!", likely accompanied by the
referenced icon, in the CopMonkey interface. The possible scopes of
access on this resource set are indicated with URI references to the
scope descriptions, as shown just above.
{
"name": "Steve the puppy!",
"icon_uri": "http://www.example.com/icons/flower",
"scopes": [
"http://photoz.example.com/dev/scopes/view",
"http://photoz.example.com/dev/scopes/all"
]
}
Photoz uses the "create resource set description" method of
CopMonkey's standard UMA resource set registration API, presenting
its Alice-specific PAT there, to register and assign an identifier to
the resource set description.
PUT /resource_set/112210f47de98100 HTTP/1.1
Content-Type: application/uma-resource-set+json
...
{
"name": "Steve the puppy!",
"icon_uri": "http://www.example.com/icons/flower.png",
"scopes": [
"http://photoz.example.com/dev/scopes/view",
"http://photoz.example.com/dev/scopes/all"
]
}
If the registration attempt succeeds, CopMonkey responds in the
following fashion.
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HTTP/1.1 201 Created
Content-Type: application/uma-status+json
ETag: "1"
...
{
"status": "created",
"_id": "112210f47de98100",
"_rev": "1"
}
At the time Alice indicates she would like this photo protected,
Photoz can choose to redirect Alice to CopMonkey for further policy
setting, access auditing, and other AM-related tasks (user experience
only).
Once it has successfully registered this description, Photoz is
responsible for outsourcing to CopMonkey all questions of
authorization for access attempts made to this photo.
Over time, as Alice uploads other photos and creates and organizes
photo albums, and as Photoz makes new action functionality available,
Photoz can use additional methods of the resource set registration
API to ensure that CopMonkey's understanding of Alice's protected
resources matches its own.
For example, if Photoz suspects that somehow its understanding of the
resource set has gotten out of sync with CopMonkey's, it can ask to
read the resource set description as follows.
GET /resource_set/112210f47de98100 HTTP/1.1
Host: am.example.com
...
CopMonkey responds with the full content of the resource set
description, including its _id and its current _rev, as follows:
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Example of an HTTP response to a "read resource set description"
request, containing a resource set description from the AM:
HTTP/1.1 200 OK
Content-Type: application/uma-resource-set+json
ETag: "1"
...
{
"_id": "112210f47de98100",
"_rev": "1",
"name": "Photo album",
"icon_uri": "http://www.example.com/icons/flower.png",
"scopes": [
"http://photoz.example.com/dev/scopes/view",
"http://photoz.example.com/dev/scopes/all"
]
}
If for some reason Photoz and CopMonkey have gotten dramatically out
of sync, Photoz can ask for the list of resource set identifiers
CopMonkey currently knows about:
GET /resource_set HTTP/1.1
Host: am.example.com
...
CopMonkey's response might look as follows:
HTTP/1.1 200 OK
Content-Type: application/json
...
[ "112210f47de98100", "34234df47eL95300" ]
If Alice later changes the photo's title (user experience only) on
Photoz from "Steve the puppy!" to "Steve on October 14, 2011", Photoz
would use the "update resource set description" method to ensure that
Alice's experience of policy-setting at CopMonkey remains consistent
with what she sees at Photoz. Following is an example of this
request.
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PUT /resource_set/112210f47de98100 HTTP/1.1
Content-Type: application/uma-resource-set+json
Host: am.example.com
If-Match: "1"
...
{
"name": "Steve on October 14, 2011",
"icon_uri": "http://www.example.com/icons/flower.png",
"scopes": [
"http://photoz.example.com/dev/scopes/view",
"http://photoz.example.com/dev/scopes/all"
]
}
CopMonkey would respond as follows.
HTTP/1.1 201 Created
Content-Type: application/uma-status+json
ETag: "2"
...
{
"status": "updated",
"_id": "112210f47de98100",
"_rev": "2"
}
There are other reasons Photoz might want to update resource set
descriptions, having nothing to do with Alice's actions or wishes.
For example, it might extend its API to include new features, and
want to add new scopes to all of Alice's and other users' resource
set descriptions.
if Alice later decides to entirely remove sharing protection (user
experience only) on this photo while visiting Photoz, ensuring that
the public can get access without any UMA-based protection, Photoz is
responsible for deleting the relevant resource set registration, as
follows:
DELETE /resource_set/112210f47de98100 HTTP/1.1
Host: am.example.com
If-Match: "2"
...
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10. Acknowledgments
The current editor of this specification is Thomas Hardjono of MIT.
The following people are co-authors:
o Paul C. Bryan, ForgeRock US, Inc. (former editor)
o Domenico Catalano, Oracle Corp.
o George Fletcher, AOL
o Maciej Machulak, Newcastle University
o Eve Maler, XMLgrrl.com
o Lukasz Moren, Newcastle University
o Christian Scholz, COMlounge GmbH (former editor)
o Jacek Szpot, Newcastle University
Additional contributors to this specification include the Kantara UMA
Work Group participants, a list of whom can be found at
[UMAnitarians].
11. Issues
All issues are now captured at the project's GitHub site
(<https://github.com/xmlgrrl/UMA-Specifications/issues>).
12. References
12.1. Normative References
[OAuth-SAML]
Campbell, B., "SAML 2.0 Bearer Assertion Grant Type
Profile for OAuth 2.0", August 2011,
<http://tools.ietf.org/html/
draft-ietf-oauth-saml2-bearer>.
[OAuth-bearer]
"The OAuth 2.0 Authorization Protocol: Bearer Tokens",
March 2012,
<http://tools.ietf.org/html/draft-ietf-oauth-v2-bearer>.
[OAuth2] Hammer-Lahav, E., "The OAuth 2.0 Protocol",
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September 2011,
<http://tools.ietf.org/html/draft-ietf-oauth-v2>.
[OCDynClientReg]
Sakimura, N., "OpenID Connect Dynamic Client Registration
1.0", September 2011, <http://openid.net/specs/
openid-connect-registration-1_0.html>.
[OCMessages]
Sakimura, N., "OpenID Connect Messages 1.0",
September 2011,
<http://openid.net/specs/
openid-connect-messages-1_0.html>.
[OCStandard]
Sakimura, N., "OpenID Connect Standard 1.0",
September 2011,
<http://openid.net/specs/
openid-connect-standard-1_0.html>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4627] Crockford, D., "The application/json Media Type for
JavaScript Object Notation (JSON)", RFC 4627, July 2006.
[RFC6415] Hammer-Lahav, E., "Web Host Metadata", October 2011,
<http://tools.ietf.org/html/rfc6415>.
12.2. Informative References
[UMA-trustmodel]
Maler, E., "UMA Trust Model", February 2011, <http://
kantarainitiative.org/confluence/display/uma/
UMA+Trust+Model>.
[UMA-usecases]
Maler, E., "UMA Scenarios and Use Cases", October 2010, <h
ttp://kantarainitiative.org/confluence/display/uma/
UMA+Scenarios+and+Use+Cases>.
[UMA-userstories]
Maler, E., "UMA User Stories", November 2010, <http://
kantarainitiative.org/confluence/display/uma/
User+Stories>.
[UMAnitarians]
Maler, E., "UMA Participant Roster", 2012, <http://
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kantarainitiative.org/confluence/display/uma/
Participant+Roster>.
Appendix A. Document History
NOTE: To be removed by RFC editor before publication as an RFC.
From I-D rev 03 to rev 04, the following major changes have been
made:
o The requirement to support the client_credentials flow has been
removed.
o The requester access token has been split into two tokens, and all
of the tokens have been renamed. The host access token is now the
PAT. The requester access token used at the AM's API is now the
AAT, and consists of vanilla OAuth. The requester access token
used at the host is now the RPT.
o The token and user authorization endpoints for the different APIs
at the AM have been joined together, and are now distinguished
through the "protection" scope (for the protection API) and the
"authorization" scope (for the authorization API).
o The token status description format and JSON media type, and the
RPT/permission delivery response, have been updated to reflect the
RPT naming.
o The configuration data format has changed to reflect the changes
above.
o The Phase 2/3 flow has changed and been simplified to match the
requirements of the new AAT and RPT.
o Token types are now called token profiles, and this is reflected
in the configuration parameter names. Claim types are now called
claim profiles, and this is also reflected in the configuration
parameter name.
o The requester now asks for permission in a back-channel
interaction, and the AM now produces a need_claims error that
instructs the requester to use a claims-gathering flow (renamed
from "authorization flow").
o Named subsections for token and claim profiles have been added so
that they show up in the TOC.
Hardjono Expires September 30, 2012 [Page 47]
Internet-Draft UMA Core Protocol March 2012
Author's Address
Thomas Hardjono (editor)
MIT
Email: hardjono@mit.edu
Hardjono Expires September 30, 2012 [Page 48]