Network Working Group T. Hardjono, Ed.
Internet-Draft MIT
Intended status: Standards Track December 13, 2011
Expires: June 15, 2012
User-Managed Access (UMA) Core Protocol
draft-hardjono-oauth-umacore-02
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
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This Internet-Draft will expire on June 15, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Notational Conventions . . . . . . . . . . . . . . . . . . 5
1.2. Basic Terminology . . . . . . . . . . . . . . . . . . . . 5
1.3. Endpoints, Endpoint Protection, and Tokens . . . . . . . . 7
1.4. Scopes, Resource Sets, Permissions, and Authorization . . 8
1.5. AM Metadata . . . . . . . . . . . . . . . . . . . . . . . 9
2. Protecting a Resource . . . . . . . . . . . . . . . . . . . . 12
2.1. Host Looks Up AM Metadata . . . . . . . . . . . . . . . . 12
2.2. Host Registers with AM . . . . . . . . . . . . . . . . . . 13
2.3. Host Obtains Host Access Token . . . . . . . . . . . . . . 13
2.4. Host Registers Sets of Resources to Be Protected . . . . . 13
2.4.1. Scope Descriptions . . . . . . . . . . . . . . . . . . 14
2.4.2. Resource Set Descriptions . . . . . . . . . . . . . . 15
2.4.3. Resource Set Registration API . . . . . . . . . . . . 16
3. Getting Authorization and Accessing a Resource . . . . . . . . 21
3.1. Requester-Host: Attempt Access at Protected Resource . . . 22
3.1.1. Requester Presents No Access Token . . . . . . . . . . 23
3.1.2. Requester Presents an Invalid Access Token . . . . . . 23
3.1.3. Requester Presents a Valid Access Token . . . . . . . 23
3.2. Requester-AM: Requester Obtains Access Token . . . . . . . 25
3.3. Host-AM: Ask for Requester Access Token Status . . . . . . 25
3.4. Host-AM: Register a Permission . . . . . . . . . . . . . . 27
3.5. Requester-AM: Request Authorization to Add Permission . . 29
3.6. Authorization Flows . . . . . . . . . . . . . . . . . . . 31
3.6.1. Authorization Flow for Requester Apps Operated by
End-Users . . . . . . . . . . . . . . . . . . . . . . 32
4. Error Messages . . . . . . . . . . . . . . . . . . . . . . . . 33
4.1. OAuth Error Responses . . . . . . . . . . . . . . . . . . 33
4.2. UMA Error Responses . . . . . . . . . . . . . . . . . . . 33
5. Security Considerations . . . . . . . . . . . . . . . . . . . 34
6. Privacy Considerations . . . . . . . . . . . . . . . . . . . . 35
7. Conformance . . . . . . . . . . . . . . . . . . . . . . . . . 35
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36
9. AM Metadata Example . . . . . . . . . . . . . . . . . . . . . 36
10. Example of Registering Resource Sets . . . . . . . . . . . . . 37
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 43
12. Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 43
13.1. Normative References . . . . . . . . . . . . . . . . . . . 43
13.2. Informative References . . . . . . . . . . . . . . . . . . 44
Appendix A. Document History . . . . . . . . . . . . . . . . . . 45
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 45
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1. Introduction
The User-Managed Access (UMA) core protocol provides a method based
on [OAuth2] (currently draft 16) 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. 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 an access token. 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, 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"), is sent to obtain an access token from the AM if
it does not have one, and then must demonstrate to the AM that it
satisfies the user's authorization policy governing the sought-
for resource and scope of access if it does not already have the
required access permission ("D").
3. _Access a resource:_ This phase involves the requester
successfully presenting an access token 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.
The assignment in this document of URI labels is temporary, awaiting
final standardization in the eventual standards body within which
this specification is taken up as a work item.
1.2. Basic Terminology
UMA introduces the following terms, utilizing OAuth and other
identity and access management concepts.
authorizing user
An UMA-defined variant of an OAuth end-user resource owner; a
web user who configures an authorization manager with policies
that control how it assigns access permissions to requesters
for a protected resource.
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.
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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. If the
requesting party is a natural person, it 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.
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 is the "verb" portion of an entire policy that also
includes a "subject" (requesting party) and an "object"
(resource set).
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1.3. Endpoints, Endpoint Protection, and Tokens
Various UMA entities present 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
access token (issued by the AM) for successful access (see
Section 2.3 for this issuance process).
o The AM presents an _authorization API_ to the requester, as
standardized by this specification. This API is OAuth-protected,
requiring a requester access token (issued by the AM) for
successful access (see Section 3.2 for this issuance process).
o The host presents a _protected resource_ to the requester, which
can be considered -- and may in fact be -- an application-specific
or proprietary API. This API is UMA-protected, requiring a
requester access token (issued by the AM) and sufficient
permissions (also issued by the AM) for successful access (see
Section 3.5 for this latter issuance process).
The AM presents the following endpoints to the host as part of its
protection API:
host access token endpoint Part of standard OAuth, as profiled by
UMA. The endpoint at which the host asks for a host access
token on the authorizing user's behalf. (The AM may also
choose to issue a refresh token.) It will use this token to
gain access to the other protection API endpoints.
host user authorization endpoint Part of standard OAuth, as profiled
by UMA. The endpoint to which the host redirects the
authorizing user to authorize the host to use this AM for
protecting resources, if the OAuth authorization code grant
type is being used.
resource set registration endpoint The endpoint at which the host
registers resource sets it wants the AM to protect.
permission registration endpoint The endpoint at which the host
registers permissions that it anticipates a requester will
shortly be asking for from the AM.
token status endpoint The endpoint at which the host submits
requester access tokens that have accompanied an access
request, to learn what currently valid permissions are
associated with them.
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The AM presents the following endpoints to the requester as part of
its authorization API:
requester access token endpoint Part of standard OAuth, as profiled
by UMA. The endpoint at which the requester asks for a
requester access token. (The AM may also choose to issue a
refresh token.) It will use this token to gain access to the
other authorization API endpoint.
permission endpoint The endpoint at which the requester asks for
authorization to have a new permission associated with its
requester access token.
Finally, the host presents one or more protected resource endpoints
to the requester:
protected resource endpoint An 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. The requester needs to
present a requester access token associated with sufficient
permissions in order to gain access.
Similarly to OAuth authorization servers, an UMA AM has the
opportunity to manage the validity periods of the access tokens, the
corresponding refresh tokens, 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.
Access tokens are currently assumed to be merely opaque strings (as
discussed in Section 1.5 and Section 7). Thus, when an AM associates
a permission with a requester access token, a host cannot
subsequently inspect such a token locally to assess whether a needed
permission has been granted. It must instead ask the AM to provide
the token's status.
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
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register resource sets and their scopes when there is not yet any
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_
authorization process for a requester to access a particular resource
set in a scoped (bounded) manner. Hosts register permission requests
on behalf of requesters that have attempted access. Requesters
subsequently ask AMs for permissions to be associated with their
tokens. AMs grant (or deny) permissions to requesters.
In order to represent meaningful, auditable, and potentially legally
enforceable authorization (see [UMA-trustmodel]), a permission is
bound to a particular set of UMA entities and parties. This includes
the requesting party, the requester (so that the same requesting
party would have to go through the authorization process for each
client application they use), the host, the resource set on which
access is being attempted, and therefore also the AM protecting it
and the authorizing user who is controlling access.
Unlike scopes (but similarly to tokens themselves; see Section 1.3),
permissions have a validity period.
1.5. AM Metadata
The AM MUST provide an XRD 1.0-formatted document at the hostmeta
location (see hostmeta [hostmeta]), documenting the following:
o Major conformance options supported by the AM (described further
in Section 7)
o Protection and authorization API endpoints (as described in
Section 1.3)
See Section 9 for a full example of AM metadata.
XRD property type values for conformance options:
http://docs.kantarainitiative.org/uma/1.0/client_reg
OPTIONAL (zero or one). Whether dynamic client registration,
such as through [OCDynClientReg], is supported for both hosts
and requesters. The only values for this property currently
available are "yes" (dynamic registration is supported, using
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an unspecified method) and "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.)
http://docs.kantarainitiative.org/uma/1.0/token_types
REQUIRED (one or more). An access token type produced by this
AM. Currently the only value for this property defined by this
specification is "artifact", meaning an opaque token string
whose associations the host MUST determine through a token
status interaction with the AM (see Section 3.3). The AM is
REQUIRED to support the artifact token type, and to supply this
value explicitly in the metadata. The AM MAY declare its
support for additional access token types by assigning each one
a unique absolute URI as the value of this property.
http://docs.kantarainitiative.org/uma/1.0/host_authz_grant_types
REQUIRED (one or more). An OAuth grant type supported by this
AM. The value MUST be one of the grant_type values defined in
[OAuth2], or alternatively an extension grant type indicated by
a unique absolute URI. The AM is REQUIRED to support the
authorization_code and client_credentials grant types, and to
supply these values explicitly in the metadata. The
authorization_code grant type is primarily intended for use
with hosts, and the client_credentials grant type is primarily
intended for use with requesters.
http://docs.kantarainitiative.org/uma/1.0/claim_types
OPTIONAL (zero or more). A claim format and associated sub-
protocol for gathering claims from requesting parties, as
supported by this AM. Currently the only value for this
property defined by this specification is "openid", for which
details are supplied in Section 3.6.1.1. The AM MAY declare
its support for claim types other than "openid" by assigning
each one a unique absolute URI as the value of this property.
XRD link relationship rel values for protection API endpoints:
http://docs.kantarainitiative.org/uma/1.0/host_token_uri
REQUIRED. The host access token endpoint. Available HTTP
methods are as defined by [OAuth2] for a token endpoint.
Supplies the endpoint the host uses to ask for a host access
token.
http://docs.kantarainitiative.org/uma/1.0/host_user_uri
REQUIRED. The host user authorization endpoint. Available
HTTP methods are as defined by [OAuth2] for an end-user
authorization endpoint. Supplies the endpoint the host uses to
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gather the consent of the authorizing user for a host-AM
relationship if it is using the authorization code grant type.
The AM MUST support the authorization code grant type method of
obtaining the authorizing user's consent.
http://docs.kantarainitiative.org/uma/1.0/host_resource_reg_uri
REQUIRED. The resource set registration endpoint. Requests to
this endpoint require a host access token to be present.
Supplies the endpoint the host uses for registering resource
sets with the AM to be protected (see Section 2.4.3). This
endpoint SHOULD require the use of a transport-layer security
mechanism such as TLS.
http://docs.kantarainitiative.org/uma/1.0/host_token_status_uri
REQUIRED. The token status endpoint. Requests to this
endpoint require a host access token to be present. Supplies
the endpoint the host uses to request the status of access
tokens presented to them by requesters with respect to
currently valid permissions. This endpoint SHOULD require the
use of a transport-layer security mechanism such as TLS.
http://docs.kantarainitiative.org/uma/1.0/host_perm_reg_uri
REQUIRED. The permission registration endpoint. Requests to
this endpoint require a host access token to be present.
Supplies the endpoint the host uses for registering permissions
with the AM for which a requester will be seeking authorization
(see Section 3.4). This endpoint SHOULD require the use of a
transport-layer security mechanism such as TLS.
XRD link relationship rel values for authorization API endpoints:
http://docs.kantarainitiative.org/uma/1.0/req_token_uri
REQUIRED. The requester access token endpoint. Available HTTP
methods are as defined by [OAuth2] for a token issuance
endpoint. Supplies the endpoint the requester uses to ask for
an access token. This endpoint SHOULD require the use of a
transport-layer security mechanism such as TLS.
http://docs.kantarainitiative.org/uma/1.0/req_perm_uri
REQUIRED. The permission endpoint. Supplies the endpoint the
requester uses to ask for authorization to have a new
permission associated with its existing requester access token,
which MUST accompany the request. This endpoint SHOULD require
the use of a transport-layer security mechanism such as TLS.
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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
1:
1. The host (having learned the general location of the relevant AM
out of band) looks up the AM's metadata and learns about its
protection API 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 host access token from the AM with the
authorizing user's consent.
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 metadata about the AM, such as endpoints it
needs to use in interacting with the AM.
o The host has received an OAuth host access token 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 Metadata
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 use
the process described in Section 2 of hostmeta [hostmeta] to retrieve
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the AM hostmeta document. For example, if the user supplied
"am.example.com" as the Authorization Manager's domain, the host
creates the URL "https://am.example.com/.well-known/host-meta" and
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 Host Access Token
In this step, the host acquires a host access token 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 OAuth2 [OAuth2] to obtain the host access token.
Here the host acts in the role of an OAuth client; 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 an access token, 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 metadata, as defined in Section 1.5.
The host has completed this step successfully when it possesses a
host access token it can use at the AM's protection API.
2.4. Host Registers Sets of Resources to Be Protected
Once the host has received a host access token, 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
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choice of protection regimes can be made explicitly by the user or
implicitly by the host. Any such partitioning by the host or user is
outside the scope of this specification.
See Section 10 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 [RFC4627] 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. The names of extension properties
MUST consist of a fully qualified URL, or begin with "x-" or "X-".
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 10 for a long-form example of scopes used in resource set
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registration.
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 [RFC4627] 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. The names of extension properties
MUST consist of a fully qualified URL or begin with "x-" or "X-".
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When a host creates or updates a resource set description (see
Section 2.4.3), the AM MUST attempt to retrieve the referenced scope
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 host access token obtained previously to gain
access to this endpoint.
(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 host access token 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 metadata (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}
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o Update resource set description: PUT /resource_set/{rsid} with If-
Match
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 host access token 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.
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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)
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)
}
Optionally, upon successful registration by the host, the AM may
return a redirect policy URI to the host. This policy URI allows the
user to set access policies at the AM for the resource set that was
successfully registered by the Host.
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)
"x-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.
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Form of a "read resource set description" HTTP request:
GET /resource_set/{rsid} HTTP/1.1
...
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.
Optionally, upon a successful Read by the host, the AM may return a
redirect policy URI to the host. This policy URI allows the user to
set access policies at the AM for the resource set that are already
registered.
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.
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Optionally, upon a successful Update by the host, the AM may return a
redirect policy URI to the host. This policy URI allows the user to
set access policies at the AM for the resource set that were 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
...
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HTTP response:
HTTP/1.1 200 OK
Content-Type: application/json
...
(body contains JSON array of {rsid} values)
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 a 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 (see Section 3.1.3.2) 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 UMA. 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. The interaction summarized in each
top-level list item MAY be the last interaction engaged in, if the
requester chooses not to continue pursuing the access attempt, or the
host chooses not to continue facilitating it.
o The requester attempts access at a particular protected resource
at a host (see Section 3.1).
* If the access attempt is unaccompanied by a requester access
token, the host responds immediately with an HTTP 401
(Unauthorized) response and instructions on where to go to
obtain one (see Section 3.1.1).
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o If the access attempt was accompanied by a requester access token,
the host checks the token's status at the AM (see Section 3.3).
* If the AM reports that the requester access token is invalid
(see Section 3.1.2), the host responds to the requester with an
HTTP 401 (Unauthorized) response and instructions on where to
go to obtain a token (see Section 3.1.1).
o If the AM supplies a token status description for a valid
requester access token (see Section 3.1.3) but none of the
permissions associated with the token match the scope of attempted
access, the host registers a suitable permission on the
requester's behalf at the AM (see Section 3.4) and then responds
to the requester with an HTTP 403 (Forbidden) response and
instructions on where to go to request authorization to associate
that permission with its token (see Section 3.1.3.1).
o If the requester received instructions on where to get a token, it
requests a token from the appropriate AM (see Section 3.2).
o If the requester received instructions on where to get
authorization for adding a permission, it requests the permission
from the appropriate AM (see Section 3.5).
* If the requester asked the AM to add a permission, the AM
engages in an authorization flow that MAY require requesting
claims from the requesting party (see Section 3.6).
o If the AM gave status back on a valid requester access token, and
at least one of the permissions associated with the token match
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).
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
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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.
The host responds in one of the following ways.
3.1.1. Requester Presents No Access Token
If the requester does not present any access token with the request,
the host MUST return an HTTP 401 (Unauthorized) status code, along
with providing the AM's URI to facilitate AM metadata discovery by
the requester.
For example:
HTTP/1.1 401 Unauthorized
WWW-Authenticate: UMA realm="example",
host_id="photoz.example.com",
am_uri="http://am.example.com"
...
3.1.2. Requester Presents an Invalid Access Token
If the requester presents an access token with its request, the host
asks the AM to give it the requester access token's status (see
Section 3.3). If the AM reports that the token is invalid, the host
MUST return an HTTP 401 (Unauthorized) status code, along with
providing the AM's URI to facilitate AM metadata discovery by the
requester.
For example:
HTTP/1.1 401 Unauthorized
WWW-Authenticate: UMA realm="example",
host_id="photoz.example.com",
am_uri="http://am.example.com"
...
3.1.3. Requester Presents a Valid Access Token
If the requester presents an access token with its request, the host
SHOULD ask the AM to give it the requester access token's status (see
Section 3.3). If the AM supplies a token status description for a
valid requester access token, the host examines the token status
description.
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When a requester presents a valid access token, the host SHOULD
provide the requester with access to the desired resource. Note that
that access to resources at a host remains at the discretion of the
host, even in cases where the requester has presented a valid access
token.
3.1.3.1. Requester's Token Has Insufficient Permission
If the token status is not associated with any currently valid
permission that applies to the scope of access attempted by the
requester, the Host SHOULD register the desired permission with the
AM (see Section 3.4) and then respond to the requester with the HTTP
403 (Forbidden) status code indicating that the token has
"insufficient_scope" (see Section 2.4.1 of [OAuth-bearer]), along
with providing the AM's URI to facilitate AM metadata discovery by
the requester, and the permission ticket it just received from the AM
iin the body of the response in JSON form.
For example:
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"
}
3.1.3.2. Requester's Token Has Sufficient Permission
If the token status is associated with at least one currently valid
permission that applies to the scope of access attempted by the
requester, the host MUST give access to the desired resource.
For example:
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.
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The host MUST NOT give access where its request for token status did
not reveal at least one currently active permission for that scope of
access.
3.2. Requester-AM: Requester Obtains Access Token
When a requester does not possess a valid access token for accessing
resources of a particular user at a particular host, it requests one
from the AM's requester token endpoint.
The requester learns about this endpoint by retrieving the AM's
hostmeta document (see Section 1.5) based on the "am_uri" information
that was provided by the host in its previous response, as described
in Section 2 of hostmeta [hostmeta]. For example, if the "am_uri" is
"am.example.com", the requester creates the URI
"https://am.example.com/.well-known/host-meta" and performs a GET
request on it.
Each such token represents the set of permissions for that requesting
party to access potentially many different resource sets (all
controlled by a single authorizing user), with a variety of scopes,
at that same host, on behalf of the same requesting party.
The requester SHOULD use the OAuth 2.0 client_credentials
authorization grant type (see Section 4.4 of [OAuth2]).
If the requester does not yet have a client identifier and optional
client secret prior to requesting an access token, it MAY request
these using [OCDynClientReg], if the AM supports it (see Section 1.5
for how the AM MAY indicate support).
(Note that in UMA, unlike in plain OAuth, obtaining an access token
does not automatically convey permission for access to any protected
resource. The token must first be associated with at least one
suitable permission for scoped access in order for the requester to
succeed in accessing the resource.)
3.3. Host-AM: Ask for Requester Access Token Status
On receiving a requester access token in an access attempt, the host
asks the AM for that token's status. If it has a cached token status
description available that has not expired yet, it MAY use it
instead.
The host makes the request to the AM with a POST request to the AM's
token status endpoint. The body of the HTTP request message contains
a JSON [RFC4627] document providing the requester access token and
the IP address of the requester's request. The host MAY, at its
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discretion, instead supply the originating IP address indicated in
the requester's X-Forwarded-For: header value. The IP address or
originating IP address is advisory only; the AM MAY ignore it for
purposes of its own token validation process.
The host gains access to the token status endpoint by presenting its
own host access token in the request.
Example of a request to the token validation endpoint that provides
the host access token in the header:
POST /token_status HTTP/1.1
Host: am.example.com
Authorization: Bearer vF9dft4qmT
Content-Type: application/json
...
{
"token": "sbjsbhs(/SSJHBSUSSJHVhjsgvhsgvshgsv",
"resource_set_id": "112210f47de98100",
"host_id": "photoz.example.com",
"ipaddr": "192.168.1.1"
}
The AM returns the token's status in an HTTP response using the 200
OK status code, containing a JSON [RFC4627] document supplying the
token status description. The token status description either
contains all of the permissions that are currently valid for this
requester access token (and thus for the requesting party on whose
behalf it is acting), or indicates that the token is invalid. The AM
MAY set a cache period for the returned token status description that
allows the host to reuse it over some period of time when it later
sees the same requester access token.
The token status description for a valid access token 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.
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.
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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-token-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 access token is a JSON
structure, as follows.
HTTP/1.1 200 OK
Content-Type: application/uma-token-status+json
...
{
"token_status": "invalid"
}
3.4. Host-AM: Register a Permission
If the permissions returned by the AM from a token status request are
insufficient to allow this requester's access attempt, the host
SHOULD register a permission with the AM that it believes would be
sufficient for the type of access sought. As a result of the host
registering a permission to the AM, the AM returns a permission
ticket for the host to give to the requester in its response (see
Section 3.1.3.1).
The permission ticket is a short-lived opaque structure whose form is
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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
structure from the point of view of the requester, the AM MAY include
information regarding expiration time within the opaque ticket.
Later, when the requester asks the AM to add permissions to the
requester's token (see Section 3.5 it will submit this ticket to the
AM. It is therefore the task of the AM to perform binding of this
ticket to the requester and its token.
The host registers the permission using the POST method at the AM's
permission registration endpoint, providing its host access token to
get authorized access to this endpoint. The body of the HTTP request
message contains a JSON [RFC4627] document providing the requester's
access token and the requested permission.
The requested scope is an object with the name "requested_permission"
and the following properties:
resource_set_id REQUIRED. A string that uniquely identifies a
resource set, access to which this requester is seeking access.
The identifier MUST correspond to a resource set that was
previously registered as protected.
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
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body.
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 fails, the AM responds with an HTTP 400
(Bad Request) status code and includes one of the following 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.
invalid_requester_token The requester access token was not
recognized by the AM.
expired_requester_token The requester access token has expired.
3.5. Requester-AM: Request Authorization to Add Permission
In this interaction, the requester asks the AM to grant it permission
for access. It does this at the AM's permission endpoint by
supplying the permission ticket it got from the host, along with its
requester access token and other pertinent information. 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 3.6), and ultimately
responds to the request positively or negatively.
The requester learns about this endpoint by retrieving the AM's
hostmeta document (see Section 1.5) based on the "am_uri" information
that was provided by the host in its previous response, as described
in Section 2 of hostmeta [hostmeta]. For example, if the "am_uri" is
"am.example.com", the requester creates the URI
"https://am.example.com/.well-known/host-meta" and performs a GET
request on it.
The requester performs a GET or POST on the permission endpoint,
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supplying:
o The permission ticket it received from the host
o Its own requester access token
o A state property (to help avoid replay attacks)
o A redirect URL
o A callback URL
The AM MUST support GET requests to this endpoint and MAY support
POST requests; if it supports POST, the endpoint MUST use SSL/TLS.
(Requesters will tend to prefer POST when they want to sign the
request message and preserve certain URL information; however, GET
typically provides a smoother user experience.)
If the AM determines that the requesting party meets the
authorization criteria set out by the authorizing user's policy (see
Section 3.6), it responds with an HTTP 201 (Created) status code and
provides an updated token:
For example:
HTTP/1.1 201 Created
Content-Type: application/uma-access-token+json
{
"token": "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 requester
access token or requires higher privileges at this endpoint than
provided by the access token, the AM responds with an OAuth error
(see Section 4.1).
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For example:
HTTP/1.1 401 Unauthorized
WWW-Authenticate: Bearer realm="example",
error="invalid_token",
error_description="The access token expired"
If the AM ultimately 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.
For example:
HTTP/1.1 400 Bad Request
Content-Type: application/uma-status+json
Cache-Control: no-store
...
{
"status": "error",
"error": "expired_requester_ticket"
}
3.6. Authorization Flows
The AM MUST base its decisions to add permissions to requester access
tokens 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
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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 XRD
metadata through the claim_types property (see Section 1.5). For the
business-level and legal implications of different technical
authorization flows, see [UMA-trustmodel].
3.6.1. Authorization 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:
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).
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 end-user
operating the requester app 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. If the AM succeeds in
adding the requested permission, it MUST redirect the end-user
requesting party back to the requester app when reporting success.
3.6.1.1. Gathering Claims from Requesting End-Users with OpenID Connect
An AM MAY use OpenID Connect as one means of gathering claims from an
end-user requesting party, leveraging OpenID Connect mechanisms to
transmit claims from distributed sources. If it supports this
option, the AM MUST supply the "openid" value for one of its
claim_types properties in its AM metadata (see Section 1.5 for how to
formulate this metadata).
To conform to this option, the AM MUST do the following:
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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
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
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:
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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 host access token
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 host
access token, particularly if used in "bearer token" fashion.
In addition, this specification dictates a binding between the host
access token and the host-specific registration area on the AM to
prevent a host from interacting with a registration area not its own.
For information about the technical, operational, and legal elements
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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 a requester access
token in UMA protocol step 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.
o hostmeta: AMs, hosts, and requesters MUST support the [hostmeta]
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 and support for OpenID Connect reserved
claims.
The AM's XRD metadata provides a machine-readable method for an AM to
indicate certain of the conformance options it has chosen. Several
of the metadata fields 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 XRD
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metadata to indicate their usage. See Section 1.5 for information
about providing and extending AM metadata.
8. IANA Considerations
Several UMA-specific JSON-based media types are being proposed, as
follows: (TBS)
9. AM Metadata Example
Following is a conforming XRD metadata document for an AM (line
breaks and spaces are provided for readability only):
<!-- AM conformance options -->
<Property type="http://docs.kantarainitiative.org/uma/1.0/client_reg">
yes
</Property>
<Property type="http://docs.kantarainitiative.org/uma/1.0/token_types">
artifact
</Property>
<Property type="http://docs.kantarainitiative.org/uma/1.0/host_authz_grant_types">
authorization_code
</Property>
<Property type="http://docs.kantarainitiative.org/uma/1.0/host_authz_grant_types">
client_credentials
</Property>
<Property type="http://docs.kantarainitiative.org/uma/1.0/claim_types">
openid
</Property>
<!-- Host protection API -->
<Link
rel="http://docs.kantarainitiative.org/uma/1.0/host_token_uri"
href="https://am.example.com/host/token_uri">
</Link>
<Link
rel="http://docs.kantarainitiative.org/uma/1.0/host_user_uri"
href="https://am.example.com/host/user_uri">
</Link>
<Link
rel="http://docs.kantarainitiative.org/uma/1.0/host_resource_reg_uri"
href="https://am.example.com/host/resource_details_uri">
</Link>
<Link
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rel="http://docs.kantarainitiative.org/uma/1.0/host_token_status_uri"
href="https://am.example.com/host/token_validation_uri">
</Link>
<Link
rel="http://docs.kantarainitiative.org/uma/1.0/host_perm_reg_uri"
href="https://am.example.com/host/scope_reg_uri">
</Link>
<!-- Requester authorization API -->
<Link
rel="http://docs.kantarainitiative.org/uma/1.0/req_token_uri"
href="https://am.example.com/requester/token_uri">
</Link>
<Link
rel="http://docs.kantarainitiative.org/uma/1.0/req_perm_uri"
href="https://am.example.com/requester/perm_uri">
</Link>
10. 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 host
access token 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
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
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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
the site to "Protect" or "Share" this single photo (user experience
only; Photoz could have made this a default or preference setting).
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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 host access token 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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11. 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 Maciej Machulak, Newcastle University
o Eve Maler, XMLgrrl.com
o Lukasz Moren, Newcastle University
o Christian Scholz, COMlounge GmbH (former editor)
Additional contributors to this specification include the Kantara UMA
Work Group participants, a list of whom can be found at
[UMAnitarians].
12. Issues
All issues are now captured at the project's GitHub site
(<https://github.com/xmlgrrl/UMA-Specifications/issues>).
13. References
13.1. 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-08>.
[OAuth-bearer]
Jones, M., "The OAuth 2.0 Protocol: Bearer Tokens",
June 2011,
<http://tools.ietf.org/html/
draft-ietf-oauth-v2-bearer-06>.
[OAuth2] Hammer-Lahav, E., "The OAuth 2.0 Protocol",
September 2011,
<http://tools.ietf.org/html/draft-ietf-oauth-v2>.
[OCDynClientReg]
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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.
[hostmeta]
Hammer-Lahav, E., "Web Host Metadata", May 2011,
<http://tools.ietf.org/html/draft-hammer-hostmeta-16>.
13.2. 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", 2011, <http://
kantarainitiative.org/confluence/display/uma/
Participant+Roster>.
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Appendix A. Document History
NOTE: To be removed by RFC editor before publication as an RFC.
Author's Address
Thomas Hardjono (editor)
MIT
Email: hardjono@mit.edu
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