Grant Negotiation and Authorization Protocol
draft-ietf-gnap-core-protocol-04
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| Authors | Justin Richer , Aaron Parecki , Fabien Imbault | ||
| Last updated | 2021-02-22 | ||
| Replaces | draft-richer-transactional-authz | ||
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draft-ietf-gnap-core-protocol-04
GNAP J. Richer, Ed.
Internet-Draft Bespoke Engineering
Intended status: Standards Track A. Parecki
Expires: 26 August 2021 Okta
F. Imbault
acert.io
22 February 2021
Grant Negotiation and Authorization Protocol
draft-ietf-gnap-core-protocol-04
Abstract
GNAP defines a mechanism for delegating authorization to a piece of
software, and conveying that delegation to the software. This
delegation can include access to a set of APIs as well as information
passed directly to the software.
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
working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 26 August 2021.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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provided without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Roles . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3. Elements . . . . . . . . . . . . . . . . . . . . . . . . 6
1.4. Sequences . . . . . . . . . . . . . . . . . . . . . . . . 7
1.4.1. Redirect-based Interaction . . . . . . . . . . . . . 10
1.4.2. User-code Interaction . . . . . . . . . . . . . . . . 13
1.4.3. Asynchronous Authorization . . . . . . . . . . . . . 15
1.4.4. Software-only Authorization . . . . . . . . . . . . . 17
1.4.5. Refreshing an Expired Access Token . . . . . . . . . 18
2. Requesting Access . . . . . . . . . . . . . . . . . . . . . . 19
2.1. Requesting Access to Resources . . . . . . . . . . . . . 21
2.1.1. Requesting a Single Access Token . . . . . . . . . . 21
2.1.2. Requesting Multiple Access Tokens . . . . . . . . . . 24
2.2. Requesting Subject Information . . . . . . . . . . . . . 26
2.3. Identifying the Client Instance . . . . . . . . . . . . . 27
2.3.1. Identifying the Client Instance by Reference . . . . 28
2.3.2. Providing Displayable Client Instance Information . . 29
2.3.3. Authenticating the Client Instance . . . . . . . . . 30
2.4. Identifying the User . . . . . . . . . . . . . . . . . . 30
2.4.1. Identifying the User by Reference . . . . . . . . . . 31
2.5. Interacting with the User . . . . . . . . . . . . . . . . 32
2.5.1. Start Mode Definitions . . . . . . . . . . . . . . . 32
2.5.2. Finish Mode Definitions . . . . . . . . . . . . . . . 33
2.5.3. Hint Definitions . . . . . . . . . . . . . . . . . . 33
2.5.4. Example Interactions . . . . . . . . . . . . . . . . 33
2.5.5. Start Interaction Modes . . . . . . . . . . . . . . . 34
2.5.6. Finish Interaction Modes . . . . . . . . . . . . . . 35
2.5.7. Hints . . . . . . . . . . . . . . . . . . . . . . . . 37
2.5.8. Extending Interaction Modes . . . . . . . . . . . . . 38
2.6. Declaring Client Capabilities . . . . . . . . . . . . . . 38
2.7. Referencing an Existing Grant Request . . . . . . . . . . 38
2.8. Extending The Grant Request . . . . . . . . . . . . . . . 39
3. Grant Response . . . . . . . . . . . . . . . . . . . . . . . 39
3.1. Request Continuation . . . . . . . . . . . . . . . . . . 40
3.2. Access Tokens . . . . . . . . . . . . . . . . . . . . . . 41
3.2.1. Single Access Token . . . . . . . . . . . . . . . . . 42
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3.2.2. Multiple Access Tokens . . . . . . . . . . . . . . . 45
3.3. Interaction Modes . . . . . . . . . . . . . . . . . . . . 46
3.3.1. Redirection to an arbitrary URL . . . . . . . . . . . 47
3.3.2. Launch of an application URL . . . . . . . . . . . . 48
3.3.3. Post-interaction Callback to a Client Instance
Accessible URL . . . . . . . . . . . . . . . . . . . 48
3.3.4. Display of a Short User Code . . . . . . . . . . . . 49
3.3.5. Extending Interaction Mode Responses . . . . . . . . 50
3.4. Returning User Information . . . . . . . . . . . . . . . 50
3.5. Returning Dynamically-bound Reference Handles . . . . . . 51
3.6. Error Response . . . . . . . . . . . . . . . . . . . . . 53
3.7. Extending the Response . . . . . . . . . . . . . . . . . 53
4. Interaction at the AS . . . . . . . . . . . . . . . . . . . . 53
4.1. Interaction at a Redirected URI . . . . . . . . . . . . . 54
4.2. Interaction at the User Code URI . . . . . . . . . . . . 54
4.3. Interaction through an Application URI . . . . . . . . . 55
4.4. Post-Interaction Completion . . . . . . . . . . . . . . . 55
4.4.1. Completing Interaction with a Browser Redirect to the
Callback URI . . . . . . . . . . . . . . . . . . . . 55
4.4.2. Completing Interaction with a Direct HTTP Request
Callback . . . . . . . . . . . . . . . . . . . . . . 56
4.4.3. Calculating the interaction hash . . . . . . . . . . 57
5. Continuing a Grant Request . . . . . . . . . . . . . . . . . 58
5.1. Continuing After a Completed Interaction . . . . . . . . 60
5.2. Continuing During Pending Interaction . . . . . . . . . . 61
5.3. Modifying an Existing Request . . . . . . . . . . . . . . 62
5.4. Canceling a Grant Request . . . . . . . . . . . . . . . . 67
6. Token Management . . . . . . . . . . . . . . . . . . . . . . 68
6.1. Rotating the Access Token . . . . . . . . . . . . . . . . 68
6.2. Revoking the Access Token . . . . . . . . . . . . . . . . 70
7. Securing Requests from the Client Instance . . . . . . . . . 71
7.1. Key Formats . . . . . . . . . . . . . . . . . . . . . . . 71
7.1.1. Key References . . . . . . . . . . . . . . . . . . . 72
7.2. Presenting Access Tokens . . . . . . . . . . . . . . . . 73
7.3. Proving Possession of a Key with a Request . . . . . . . 74
7.3.1. Detached JWS . . . . . . . . . . . . . . . . . . . . 75
7.3.2. Attached JWS . . . . . . . . . . . . . . . . . . . . 77
7.3.3. Mutual TLS . . . . . . . . . . . . . . . . . . . . . 80
7.3.4. Demonstration of Proof-of-Possession (DPoP) . . . . . 82
7.3.5. HTTP Message Signing . . . . . . . . . . . . . . . . 83
7.3.6. OAuth Proof of Possession (PoP) . . . . . . . . . . . 85
8. Resource Access Rights . . . . . . . . . . . . . . . . . . . 86
8.1. Requesting Resources By Reference . . . . . . . . . . . . 90
9. Discovery . . . . . . . . . . . . . . . . . . . . . . . . . . 92
10. Resource Servers . . . . . . . . . . . . . . . . . . . . . . 93
10.1. Introspecting a Token . . . . . . . . . . . . . . . . . 93
10.2. Deriving a downstream token . . . . . . . . . . . . . . 95
10.3. Registering a Resource Handle . . . . . . . . . . . . . 97
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10.4. Requesting Resources With Insufficient Access . . . . . 98
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 98
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 99
13. Security Considerations . . . . . . . . . . . . . . . . . . . 99
14. Privacy Considerations . . . . . . . . . . . . . . . . . . . 99
15. Normative References . . . . . . . . . . . . . . . . . . . . 99
Appendix A. Document History . . . . . . . . . . . . . . . . . . 101
Appendix B. Component Data Models . . . . . . . . . . . . . . . 102
Appendix C. Example Protocol Flows . . . . . . . . . . . . . . . 103
C.1. Redirect-Based User Interaction . . . . . . . . . . . . . 103
C.2. Secondary Device Interaction . . . . . . . . . . . . . . 107
C.3. No User Involvement . . . . . . . . . . . . . . . . . . . 110
C.4. Asynchronous Authorization . . . . . . . . . . . . . . . 111
C.5. Applying OAuth 2 Scopes and Client IDs . . . . . . . . . 114
Appendix D. JSON Structures and Polymorphism . . . . . . . . . . 115
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 116
1. Introduction
This protocol allows a piece of software, the client instance, to
request delegated authorization to resource servers and to request
direct information. This delegation is facilitated by an
authorization server usually on behalf of a resource owner. The end-
user operating the software may interact with the authorization
server to authenticate, provide consent, and authorize the request.
The process by which the delegation happens is known as a grant, and
GNAP allows for the negotiation of the grant process over time by
multiple parties acting in distinct roles.
This protocol solves many of the same use cases as OAuth 2.0
[RFC6749], OpenID Connect [OIDC], and the family of protocols that
have grown up around that ecosystem. However, GNAP is not an
extension of OAuth 2.0 and is not intended to be directly compatible
with OAuth 2.0. GNAP seeks to provide functionality and solve use
cases that OAuth 2.0 cannot easily or cleanly address. Even so, GNAP
and OAuth 2.0 will exist in parallel for many deployments, and
considerations have been taken to facilitate the mapping and
transition from legacy systems to GNAP. Some examples of these can
be found in Appendix C.5.
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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1.2. Roles
The parties in GNAP perform actions under different roles. Roles are
defined by the actions taken and the expectations leveraged on the
role by the overall protocol.
Authorization Server (AS) server that grants delegated privileges to
a particular instance of client software in the form of an access
token and other information (such as subject information).
Client application operated by an end-user that consumes resources
from one or several RSs, possibly requiring access privileges from
one or several ASs.
Example: a client can be a mobile application, a web application,
etc.
Note: this specification differentiates between a specific
instance (the client instance, identified by its unique key) and
the software running the instance (the client software). For some
kinds of client software, there could be many instances of that
software, each instance with a different key.
Resource Server (RS) server that provides operations on protected
resources, where operations require a valid access token issued by
an AS.
Resource Owner (RO) subject entity that may grant or deny operations
on resources it has authority upon.
Note: the act of granting or denying an operation may be manual
(i.e. through an interaction with a physical person) or automatic
(i.e. through predefined organizational rules).
End-user natural person that operates a client instance.
Note: that natural person may or may not be the same entity as the
RO.
The design of GNAP does not assume any one deployment architecture,
but instead attempts to define roles that can be fulfilled in a
number of different ways for different use cases. As long as a given
role fulfills all of its obligations and behaviors as defined by the
protocol, GNAP does not make additional requirements on its structure
or setup.
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Multiple roles can be fulfilled by the same party, and a given party
can switch roles in different instances of the protocol. For
example, the RO and end-user in many instances are the same person,
where a user is authorizing the client instance to act on their own
behalf at the RS. In this case, one party fulfills both of the RO
and end-user roles, but the roles themselves are still defined
separately from each other to allow for other use cases where they
are fulfilled by different parties.
For another example, in some complex scenarios, an RS receiving
requests from one client instance can act as a client instance for a
downstream secondary RS in order to fulfill the original request. In
this case, one piece of software is both an RS and a client instance
from different perspectives, and it fulfills these roles separately
as far as the overall protocol is concerned.
A single role need not be deployed as a monolithic service. For
example, A client instance could have components that are installed
on the end-user's device as well as a back-end system that it
communicates with. If both of these components participate in the
delegation protocol, they are both considered part of the client
instance. If there are several copies of the client software that
run separately but all share the same key material, such as a
deployed cluster, then this cluster is considered a single client
instance.
For another example, an AS could likewise be built out of many
constituent components in a distributed architecture. The component
that the client instance calls directly could be different from the
component that the the RO interacts with to drive consent, since API
calls and user interaction have different security considerations in
many environments. Furthermore, the AS could need to collect
identity claims about the RO from one system that deals with user
attributes while generating access tokens at another system that
deals with security rights. From the perspective of GNAP, all of
these are pieces of the AS and together fulfill the role of the AS as
defined by the protocol.
1.3. Elements
In addition to the roles above, the protocol also involves several
elements that are acted upon by the roles throughout the process.
Attribute characteristics related to a subject.
Access Token a data artifact representing a set of rights and/or
attributes.
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Note: an access token can be first issued to an client instance
(requiring authorization by the RO) and subsequently rotated.
Grant (verb): to permit an instance of client software to receive
some attributes at a specific time and valid for a specific
duration and/or to exercise some set of delegated rights to access
a protected resource (noun): the act of granting.
Privilege right or attribute associated with a subject.
Note: the RO defines and maintains the rights and attributes
associated to the protected resource, and might temporarily
delegate some set of those privileges to an end-user. This
process is refered to as privilege delegation.
Protected Resource protected API (Application Programming Interface)
served by an RS and that can be accessed by a client, if and only
if a valid access token is provided.
Note: to avoid complex sentences, the specification document may
simply refer to resource instead of protected resource.
Right ability given to a subject to perform a given operation on a
resource under the control of an RS.
Subject person, organization or device.
Subject Information statement asserted locally by an AS about a
subject.
1.4. Sequences
GNAP can be used in a variety of ways to allow the core delegation
process to take place. Many portions of this process are
conditionally present depending on the context of the deployments,
and not every step in this overview will happen in all circumstances.
Note that a connection between roles in this process does not
necessarily indicate that a specific protocol message is sent across
the wire between the components fulfilling the roles in question, or
that a particular step is required every time. For example, for a
client instance interested in only getting subject information
directly, and not calling an RS, all steps involving the RS below do
not apply.
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In some circumstances, the information needed at a given stage is
communicated out of band or is preconfigured between the components
or entities performing the roles. For example, one entity can fulfil
multiple roles, and so explicit communication between the roles is
not necessary within the protocol flow.
+------------+ +------------+
| End-user | ~ ~ ~ ~ ~ ~ | Resource |
| | | Owner (RO) |
+------------+ +------------+
+ +
+ +
(A) (B)
+ +
+ +
+--------+ + +------------+
| Client |--------------(1)------+------>| Resource |
|Instance| + | Server |
| | +---------------+ | (RS) |
| |--(2)->| Authorization | | |
| |<-(3)--| Server | | |
| | | (AS) | | |
| |--(4)->| | | |
| |<-(5)--| | | |
| |--------------(6)------------->| |
| | | |<~(7)~~| |
| |<-------------(8)------------->| |
| |--(9)->| | | |
| |<-(10)-| | | |
| |--------------(11)------------>| |
| | | |<~(12)~| |
| |-(13)->| | | |
| | | | | |
+--------+ +---------------+ +------------+
Legend
+ + + indicates a possible interaction with a human
----- indicates an interaction between protocol roles
~ ~ ~ indicates a potential equivalence or out-of-band communication between roles
* (A) The end-user interacts with the client instance to indicate a
need for resources on behalf of the RO. This could identify the
RS the client instance needs to call, the resources needed, or the
RO that is needed to approve the request. Note that the RO and
end-user are often the same entity in practice.
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* (1) The client instance attempts to call the RS (Section 10.4) to
determine what access is needed. The RS informs the client
instance that access can be granted through the AS. Note that for
most situations, the client instance already knows which AS to
talk to and which kinds of access it needs.
* (2) The client instance requests access at the AS (Section 2).
* (3) The AS processes the request and determines what is needed to
fulfill the request. The AS sends its response to the client
instance (Section 3).
* (B) If interaction is required, the AS interacts with the RO
(Section 4) to gather authorization. The interactive component of
the AS can function using a variety of possible mechanisms
including web page redirects, applications, challenge/response
protocols, or other methods. The RO approves the request for the
client instance being operated by the end-user. Note that the RO
and end-user are often the same entity in practice.
* (4) The client instance continues the grant at the AS (Section 5).
* (5) If the AS determines that access can be granted, it returns a
response to the client instance (Section 3) including an access
token (Section 3.2) for calling the RS and any directly returned
information (Section 3.4) about the RO.
* (6) The client instance uses the access token (Section 7.2) to
call the RS.
* (7) The RS determines if the token is sufficient for the request
by examining the token, potentially calling the AS (Section 10.1).
Note that the RS could also examine the token directly, call an
internal data store, execute a policy engine request, or any
number of alternative methods for validating the token and its
fitness for the request.
* (8) The client instance calls the RS (Section 7.2) using the
access token until the RS or client instance determine that the
token is no longer valid.
* (9) When the token no longer works, the client instance fetches an
updated access token (Section 6.1) based on the rights granted in
(5).
* (10) The AS issues a new access token (Section 3.2) to the client
instance.
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* (11) The client instance uses the new access token (Section 7.2)
to call the RS.
* (12) The RS determines if the new token is sufficient for the
request by examining the token, potentially calling the AS
(Section 10.1).
* (13) The client instance disposes of the token (Section 6.2) once
the client instance has completed its access of the RS and no
longer needs the token.
The following sections and Appendix C contain specific guidance on
how to use GNAP in different situations and deployments.
1.4.1. Redirect-based Interaction
In this example flow, the client instance is a web application that
wants access to resources on behalf of the current user, who acts as
both the end-user and the resource owner (RO). Since the client
instance is capable of directing the user to an arbitrary URL and
receiving responses from the user's browser, interaction here is
handled through front-channel redirects using the user's browser.
The client instance uses a persistent session with the user to ensure
the same user that is starting the interaction is the user that
returns from the interaction.
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+--------+ +--------+ +------+
| Client | | AS | | User |
|Instance| | | | |
| |< (1) + Start Session + + + + + + + + + + + + + + + +| |
| | | | | |
| |--(2)--- Request Access --------->| | | |
| | | | | |
| |<-(3)-- Interaction Needed -------| | | |
| | | | | |
| |+ (4) + Redirect for Interaction + + + + + + + + + > | |
| | | | | |
| | | |<+ (5) +>| |
| | | | AuthN | |
| | | | | |
| | | |<+ (6) +>| |
| | | | AuthZ | |
| | | | | |
| |< (7) + Redirect for Continuation + + + + + + + + + +| |
| | | | +------+
| |--(8)--- Continue Request ------->| |
| | | |
| |<-(9)----- Grant Access ----------| |
| | | |
+--------+ +--------+
1. The client instance establishes a verifiable session to the user,
in the role of the end-user.
2. The client instance requests access to the resource (Section 2).
The client instance indicates that it can redirect to an
arbitrary URL (Section 2.5.5.1) and receive a redirect from the
browser (Section 2.5.6.1). The client instance stores
verification information for its redirect in the session created
in (1).
3. The AS determines that interaction is needed and responds
(Section 3) with a URL to send the user to (Section 3.3.1) and
information needed to verify the redirect (Section 3.3.3) in (7).
The AS also includes information the client instance will need to
continue the request (Section 3.1) in (8). The AS associates
this continuation information with an ongoing request that will
be referenced in (4), (6), and (8).
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4. The client instance stores the verification and continuation
information from (3) in the session from (1). The client
instance then redirects the user to the URL (Section 4.1) given
by the AS in (3). The user's browser loads the interaction
redirect URL. The AS loads the pending request based on the
incoming URL generated in (3).
5. The user authenticates at the AS, taking on the role of the RO.
6. As the RO, the user authorizes the pending request from the
client instance.
7. When the AS is done interacting with the user, the AS redirects
the user back (Section 4.4.1) to the client instance using the
redirect URL provided in (2). The redirect URL is augmented with
an interaction reference that the AS associates with the ongoing
request created in (2) and referenced in (4). The redirect URL
is also augmented with a hash of the security information
provided in (2) and (3). The client instance loads the
verification information from (2) and (3) from the session
created in (1). The client instance calculates a hash
(Section 4.4.3) based on this information and continues only if
the hash validates. Note that the client instance needs to
ensure that the parameters for the incoming request match those
that it is expecting from the session created in (1). The client
instance also needs to be prepared for the end-user never being
returned to the client instance and handle timeouts
appropriately.
8. The client instance loads the continuation information from (3)
and sends the interaction reference from (7) in a request to
continue the request (Section 5.1). The AS validates the
interaction reference ensuring that the reference is associated
with the request being continued.
9. If the request has been authorized, the AS grants access to the
information in the form of access tokens (Section 3.2) and direct
subject information (Section 3.4) to the client instance.
An example set of protocol messages for this method can be found in
Appendix C.1.
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1.4.2. User-code Interaction
In this example flow, the client instance is a device that is capable
of presenting a short, human-readable code to the user and directing
the user to enter that code at a known URL. The client instance is
not capable of presenting an arbitrary URL to the user, nor is it
capable of accepting incoming HTTP requests from the user's browser.
The client instance polls the AS while it is waiting for the RO to
authorize the request. The user's interaction is assumed to occur on
a secondary device. In this example it is assumed that the user is
both the end-user and RO, though the user is not assumed to be
interacting with the client instance through the same web browser
used for interaction at the AS.
+--------+ +--------+ +------+
| Client | | AS | | User |
|Instance|--(1)--- Request Access --------->| | | |
| | | | | |
| |<-(2)-- Interaction Needed -------| | | |
| | | | | |
| |+ (3) + + Display User Code + + + + + + + + + + + + >| |
| | | | | |
| | | |<+ (4) + | |
| | | |Open URI | |
| | | | | |
| | | |<+ (5) +>| |
| | | | AuthN | |
| |--(9)--- Continue Request (A) --->| | | |
| | | |<+ (6) +>| |
| |<-(10)- Not Yet Granted (Wait) ---| | Code | |
| | | | | |
| | | |<+ (7) +>| |
| | | | AuthZ | |
| | | | | |
| | | |<+ (8) +>| |
| | | |Completed| |
| | | | | |
| |--(11)-- Continue Request (B) --->| | +------+
| | | |
| |<-(12)----- Grant Access ---------| |
| | | |
+--------+ +--------+
1. The client instance requests access to the resource (Section 2).
The client instance indicates that it can display a user code
(Section 2.5.5.3).
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2. The AS determines that interaction is needed and responds
(Section 3) with a user code to communicate to the user
(Section 3.3.4). This could optionally include a URL to direct
the user to, but this URL should be static and so could be
configured in the client instance's documentation. The AS also
includes information the client instance will need to continue
the request (Section 3.1) in (8) and (10). The AS associates
this continuation information with an ongoing request that will
be referenced in (4), (6), (8), and (10).
3. The client instance stores the continuation information from (2)
for use in (8) and (10). The client instance then communicates
the code to the user (Section 4.1) given by the AS in (2).
4. The user's directs their browser to the user code URL. This URL
is stable and can be communicated via the client software's
documentation, the AS documentation, or the client software
itself. Since it is assumed that the RO will interact with the
AS through a secondary device, the client instance does not
provide a mechanism to launch the RO's browser at this URL.
5. The end-user authenticates at the AS, taking on the role of the
RO.
6. The RO enters the code communicated in (3) to the AS. The AS
validates this code against a current request in process.
7. As the RO, the user authorizes the pending request from the
client instance.
8. When the AS is done interacting with the user, the AS indicates
to the RO that the request has been completed.
9. Meanwhile, the client instance loads the continuation
information stored at (3) and continues the request (Section 5).
The AS determines which ongoing access request is referenced
here and checks its state.
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10. If the access request has not yet been authorized by the RO in
(6), the AS responds to the client instance to continue the
request (Section 3.1) at a future time through additional polled
continuation requests. This response can include updated
continuation information as well as information regarding how
long the client instance should wait before calling again. The
client instance replaces its stored continuation information
from the previous response (2). Note that the AS may need to
determine that the RO has not approved the request in a
sufficient amount of time and return an appropriate error to the
client instance.
11. The client instance continues to poll the AS (Section 5.2) with
the new continuation information in (9).
12. If the request has been authorized, the AS grants access to the
information in the form of access tokens (Section 3.2) and
direct subject information (Section 3.4) to the client instance.
An example set of protocol messages for this method can be found in
Appendix C.2.
1.4.3. Asynchronous Authorization
In this example flow, the end-user and RO roles are fulfilled by
different parties, and the RO does not interact with the client
instance. The AS reaches out asynchronously to the RO during the
request process to gather the RO's authorization for the client
instance's request. The client instance polls the AS while it is
waiting for the RO to authorize the request.
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+--------+ +--------+ +------+
| Client | | AS | | RO |
|Instance|--(1)--- Request Access --------->| | | |
| | | | | |
| |<-(2)-- Not Yet Granted (Wait) ---| | | |
| | | |<+ (3) +>| |
| | | | AuthN | |
| |--(6)--- Continue Request (A) --->| | | |
| | | |<+ (4) +>| |
| |<-(7)-- Not Yet Granted (Wait) ---| | AuthZ | |
| | | | | |
| | | |<+ (5) +>| |
| | | |Completed| |
| | | | | |
| |--(8)--- Continue Request (B) --->| | +------+
| | | |
| |<-(9)------ Grant Access ---------| |
| | | |
+--------+ +--------+
1. The client instance requests access to the resource (Section 2).
The client instance does not send any interactions modes to the
server, indicating that it does not expect to interact with the
RO. The client instance can also signal which RO it requires
authorization from, if known, by using the user request section
(Section 2.4).
2. The AS determines that interaction is needed, but the client
instance cannot interact with the RO. The AS responds
(Section 3) with the information the client instance will need to
continue the request (Section 3.1) in (6) and (8), including a
signal that the client instance should wait before checking the
status of the request again. The AS associates this continuation
information with an ongoing request that will be referenced in
(3), (4), (5), (6), and (8).
3. The AS determines which RO to contact based on the request in
(1), through a combination of the user request (Section 2.4), the
resources request (Section 2.1), and other policy information.
The AS contacts the RO and authenticates them.
4. The RO authorizes the pending request from the client instance.
5. When the AS is done interacting with the RO, the AS indicates to
the RO that the request has been completed.
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6. Meanwhile, the client instance loads the continuation information
stored at (3) and continues the request (Section 5). The AS
determines which ongoing access request is referenced here and
checks its state.
7. If the access request has not yet been authorized by the RO in
(6), the AS responds to the client instance to continue the
request (Section 3.1) at a future time through additional
polling. This response can include refreshed credentials as well
as information regarding how long the client instance should wait
before calling again. The client instance replaces its stored
continuation information from the previous response (2). Note
that the AS may need to determine that the RO has not approved
the request in a sufficient amount of time and return an
appropriate error to the client instance.
8. The client instance continues to poll the AS (Section 5.2) with
the new continuation information from (7).
9. If the request has been authorized, the AS grants access to the
information in the form of access tokens (Section 3.2) and direct
subject information (Section 3.4) to the client instance.
An example set of protocol messages for this method can be found in
Appendix C.4.
1.4.4. Software-only Authorization
In this example flow, the AS policy allows the client instance to
make a call on its own behalf, without the need for a RO to be
involved at runtime to approve the decision. Since there is no
explicit RO, the client instance does not interact with an RO.
+--------+ +--------+
| Client | | AS |
|Instance|--(1)--- Request Access --------->| |
| | | |
| |<-(2)---- Grant Access -----------| |
| | | |
+--------+ +--------+
1. The client instance requests access to the resource (Section 2).
The client instance does not send any interactions modes to the
server.
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2. The AS determines that the request is been authorized, the AS
grants access to the information in the form of access tokens
(Section 3.2) and direct subject information (Section 3.4) to the
client instance.
An example set of protocol messages for this method can be found in
Appendix C.3.
1.4.5. Refreshing an Expired Access Token
In this example flow, the client instance receives an access token to
access a resource server through some valid GNAP process. The client
instance uses that token at the RS for some time, but eventually the
access token expires. The client instance then gets a new access
token by rotating the expired access token at the AS using the
token's management URL.
+--------+ +--------+
| Client | | AS |
|Instance|--(1)--- Request Access ----------------->| |
| | | |
| |<-(2)--- Grant Access --------------------| |
| | | |
| | +--------+ | |
| |--(3)--- Access Resource --->| RS | | |
| | | | | |
| |<-(4)--- Error Response -----| | | |
| | +--------+ | |
| | | |
| |--(5)--- Rotate Token ------------------->| |
| | | |
| |<-(6)--- Rotated Token -------------------| |
| | | |
+--------+ +--------+
1. The client instance requests access to the resource (Section 2).
2. The AS grants access to the resource (Section 3) with an access
token (Section 3.2) usable at the RS. The access token response
includes a token management URI.
3. The client instance presents the token (Section 7.2) to the RS.
The RS validates the token and returns an appropriate response
for the API.
4. When the access token is expired, the RS responds to the client
instance with an error.
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5. The client instance calls the token management URI returned in
(2) to rotate the access token (Section 6.1). The client
instance presents the access token as well as the appropriate
key.
6. The AS validates the rotation request including the signature and
keys presented in (5) and returns a new access token
(Section 3.2.1). The response includes a new access token and
can also include updated token management information, which the
client instance will store in place of the values returned in
(2).
2. Requesting Access
To start a request, the client instance sends JSON [RFC8259] document
with an object as its root. Each member of the request object
represents a different aspect of the client instance's request. Each
field is described in detail in a section below.
access_token (object / array of objects) Describes the rights and
properties associated with the requested access token.
Section 2.1
subject (object) Describes the information about the RO that the
client instance is requesting to be returned directly in the
response from the AS. Section 2.2
client (object / string) Describes the client instance that is
making this request, including the key that the client instance
will use to protect this request and any continuation requests at
the AS and any user-facing information about the client instance
used in interactions at the AS. Section 2.3
user (object / string) Identifies the end-user to the AS in a manner
that the AS can verify, either directly or by interacting with the
end-user to determine their status as the RO. Section 2.4
interact (object) Describes the modes that the client instance has
for allowing the RO to interact with the AS and modes for the
client instance to receive updates when interaction is complete.
Section 2.5
capabilities (array of strings) Identifies named extension
capabilities that the client instance can use, signaling to the AS
which extensions it can use. Section 2.6
existing_grant (string) Identifies a previously-existing grant that
the client instance is extending with this request. Section 2.7
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Additional members of this request object can be defined by
extensions to this protocol as described in Section 2.8
A non-normative example of a grant request is below:
{
"access_token": {
"access": [
{
"type": "photo-api",
"actions": [
"read",
"write",
"dolphin"
],
"locations": [
"https://server.example.net/",
"https://resource.local/other"
],
"datatypes": [
"metadata",
"images"
]
},
"dolphin-metadata"
]
},
"client": {
"display": {
"name": "My Client Display Name",
"uri": "https://example.net/client"
},
"key": {
"proof": "jwsd",
"jwk": {
"kty": "RSA",
"e": "AQAB",
"kid": "xyz-1",
"alg": "RS256",
"n": "kOB5rR4Jv0GMeL...."
}
}
},
"interact": {
"start": ["redirect"],
"finish": {
"method": "redirect",
"uri": "https://client.example.net/return/123455",
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"nonce": "LKLTI25DK82FX4T4QFZC"
}
},
"capabilities": ["ext1", "ext2"],
"subject": {
"sub_ids": ["iss_sub", "email"],
"assertions": ["id_token"]
}
}
The request MUST be sent as a JSON object in the body of the HTTP
POST request with Content-Type "application/json", unless otherwise
specified by the signature mechanism.
2.1. Requesting Access to Resources
If the client instance is requesting one or more access tokens for
the purpose of accessing an API, the client instance MUST include an
"access_token" field. This field MUST be an object (for a single
access token (Section 2.1.1)) or an array of these objects (for
multiple access tokens (Section 2.1.2)), as described in the
following sections.
2.1.1. Requesting a Single Access Token
To request a single access token, the client instance sends an
"acccess_token" object composed of the following fields.
access (array of objects/strings) Describes the rights that the
client instance is requesting for one or more access tokens to be
used at RS's. This field is REQUIRED. Section 8
label (string) A unique name chosen by the client instance to refer
to the resulting access token. The value of this field is opaque
to the AS. If this field is included in the request, the AS MUST
include the same label in the token response (Section 3.2). This
field is REQUIRED if used as part of a multiple access token
request (Section 2.1.2), and is OPTIONAL otherwise.
flags (array of strings) A set of flags that indicate desired
attributes or behavior to be attached to the access token by the
AS. This field is OPTIONAL.
The values of the "flags" field defined by this specification are as
follows:
bearer If this flag is included, the access token being requested is
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a bearer token. If this flag is omitted, the access token is
bound to the key used by the client instance in this request, or
the key's most recent rotation. Methods for presenting bound and
bearer access tokens are described in Section 7.2. [[ See issue
#38 (https://github.com/ietf-wg-gnap/gnap-core-protocol/issues/38)
]]
split If this flag is included, the client instance is capable of
receiving a different number of tokens than specified in the token
request (Section 2.1), including receiving multiple access tokens
(Section 3.2.2) in response to any single token request
(Section 2.1.1) or a different number of access tokens than
requested in a multiple access token request (Section 2.1.2). The
"label" fields of the returned additional tokens are chosen by the
AS. The client instance MUST be able to tell from the token
response where and how it can use each of the access tokens. [[
See issue #37 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/37) ]]
Flag values MUST NOT be included more than once.
Additional flags can be defined by extensions using a registry TBD
(Section 12).
In the following example, the client instance is requesting access to
a complex resource described by a pair of access request object.
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"access_token": {
"access": [
{
"type": "photo-api",
"actions": [
"read",
"write",
"delete"
],
"locations": [
"https://server.example.net/",
"https://resource.local/other"
],
"datatypes": [
"metadata",
"images"
]
},
{
"type": "walrus-access",
"actions": [
"foo",
"bar"
],
"locations": [
"https://resource.other/"
],
"datatypes": [
"data",
"pictures",
"walrus whiskers"
]
}
],
"label": "token1-23",
"flags": [ "split" ]
}
If access is approved, the resulting access token is valid for the
described resource and is bound to the client instance's key (or its
most recent rotation). The token is labeled "token1-23" and could be
split into multiple access tokens by the AS, if the AS chooses. The
token response structure is described in Section 3.2.1.
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2.1.2. Requesting Multiple Access Tokens
To request multiple access tokens to be returned in a single
response, the client instance sends an array of objects as the value
of the "access_token" parameter. Each object MUST conform to the
request format for a single access token request, as specified in
requesting a single access token (Section 2.1.1). Additionally, each
object in the array MUST include the "label" field, and all values of
these fields MUST be unique within the request. If the client
instance does not include a "label" value for any entry in the array,
or the values of the "label" field are not unique within the array,
the AS MUST return an error.
The following non-normative example shows a request for two separate
access tokens, "token1" and "token2".
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"access_token": [
{
"label": "token1",
"access": [
{
"type": "photo-api",
"actions": [
"read",
"write",
"dolphin"
],
"locations": [
"https://server.example.net/",
"https://resource.local/other"
],
"datatypes": [
"metadata",
"images"
]
},
"dolphin-metadata"
]
},
{
"label": "token2",
"access": [
{
"type": "walrus-access",
"actions": [
"foo",
"bar"
],
"locations": [
"https://resource.other/"
],
"datatypes": [
"data",
"pictures",
"walrus whiskers"
]
}
],
"flags": [ "bearer" ]
}
]
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All approved access requests are returned in the multiple access
token response (Section 3.2.2) structure using the values of the
"label" fields in the request.
2.2. Requesting Subject Information
If the client instance is requesting information about the RO from
the AS, it sends a "subject" field as a JSON object. This object MAY
contain the following fields (or additional fields defined in a
registry TBD (Section 12)).
sub_ids (array of strings) An array of subject identifier subject
types requested for the RO, as defined by
[I-D.ietf-secevent-subject-identifiers].
assertions (array of strings) An array of requested assertion
formats. Possible values include "id_token" for an [OIDC] ID
Token and "saml2" for a SAML 2 assertion. Additional assertion
values are defined by a registry TBD (Section 12). [[ See issue
#41 (https://github.com/ietf-wg-gnap/gnap-core-protocol/issues/41)
]]
"subject": {
"sub_ids": [ "iss_sub", "email" ],
"assertions": [ "id_token", "saml2" ]
}
The AS can determine the RO's identity and permission for releasing
this information through interaction with the RO (Section 4), AS
policies, or assertions presented by the client instance
(Section 2.4). If this is determined positively, the AS MAY return
the RO's information in its response (Section 3.4) as requested.
Subject identifiers requested by the client instance serve only to
identify the RO in the context of the AS and can't be used as
communication channels by the client instance, as discussed in
Section 3.4.
The AS SHOULD NOT re-use subject identifiers for multiple different
ROs.
[[ See issue #42 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/42) ]]
Note: the "sub_ids" and "assertions" request fields are independent
of each other, and a returned assertion MAY omit a requested subject
identifier.
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[[ See issue #43 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/43) ]]
2.3. Identifying the Client Instance
When sending a non-continuation request to the AS, the client
instance MUST identify itself by including the "client" field of the
request and by signing the request as described in Section 7.3. Note
that for a continuation request (Section 5), the client instance is
identified by its association with the request being continued and so
this field is not sent under those circumstances.
When client instance information is sent by value, the "client" field
of the request consists of a JSON object with the following fields.
key (object / string) The public key of the client instance to be
used in this request as described in Section 7.1 or a reference to
a key as described in Section 7.1.1. This field is REQUIRED.
class_id (string) An identifier string that the AS can use to
identify the client software comprising this client instance. The
contents and format of this field are up to the AS. This field is
OPTIONAL.
display (object) An object containing additional information that
the AS MAY display to the RO during interaction, authorization,
and management. This field is OPTIONAL.
"client": {
"key": {
"proof": "httpsig",
"jwk": {
"kty": "RSA",
"e": "AQAB",
"kid": "xyz-1",
"alg": "RS256",
"n": "kOB5rR4Jv0GMeLaY6_It_r3ORwdf8ci_JtffXyaSx8xY..."
},
"cert": "MIIEHDCCAwSgAwIBAgIBATANBgkqhkiG9w0BAQsFA..."
},
"class_id": "web-server-1234",
"display": {
"name": "My Client Display Name",
"uri": "https://example.net/client"
}
}
Additional fields are defined in a registry TBD (Section 12).
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The client instance MUST prove possession of any presented key by the
"proof" mechanism associated with the key in the request. Proof
types are defined in a registry TBD (Section 12) and an initial set
of methods is described in Section 7.3.
Note that the AS MAY know the client instance's public key ahead of
time, and the AS MAY apply different policies to the request
depending on what has been registered against that key. If the same
public key is sent by value on subsequent access requests, the AS
SHOULD treat these requests as coming from the same client instance
for purposes of identification, authentication, and policy
application. If the AS does not know the client instance's public
key ahead of time, the AS MAY accept or reject the request based on
AS policy, attestations within the "client" request, and other
mechanisms.
[[ See issue #44 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/44) ]]
2.3.1. Identifying the Client Instance by Reference
If the client instance has an instance identifier that the AS can use
to determine appropriate key information, the client instance can
send this value in the "instance_id" field. The instance identifier
MAY be assigned to a client instance at runtime through the
Section 3.5 or MAY be obtained in another fashion, such as a static
registration process at the AS.
instance_id (string) An identifier string that the AS can use to
identify the particular instance of this client software. The
content and structure of this identifier is opaque to the client
instance.
"client": {
"instance_id": "client-541-ab"
}
If there are no additional fields to send, the client instance MAY
send the instance identifier as a direct reference value in lieu of
the object.
"client": "client-541-ab"
When the AS receives a request with an instance identifier, the AS
MUST ensure that the key used to sign the request (Section 7.3) is
associated with the instance identifier.
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If the "instance_id" field is sent, it MUST NOT be accompanied by
other fields unless such fields are explicitly marked safe for
inclusion alongside the instance identifier.
[[ See issue #45 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/45) ]]
If the AS does not recognize the instance identifier, the request
MUST be rejected with an error.
If the client instance is identified in this manner, the registered
key for the client instance MAY be a symmetric key known to the AS.
The client instance MUST NOT send a symmetric key by value in the
request, as doing so would expose the key directly instead of proving
possession of it.
2.3.2. Providing Displayable Client Instance Information
If the client instance has additional information to display to the
RO during any interactions at the AS, it MAY send that information in
the "display" field. This field is a JSON object that declares
information to present to the RO during any interactive sequences.
name (string) Display name of the client software
uri (string) User-facing web page of the client software
logo_uri (string) Display image to represent the client software
"display": {
"name": "My Client Display Name",
"uri": "https://example.net/client"
}
[[ See issue #48 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/48) ]]
Additional display fields are defined by a registry TBD (Section 12).
The AS SHOULD use these values during interaction with the RO. The
values are for informational purposes only and MUST NOT be taken as
authentic proof of the client instance's identity or source. The AS
MAY restrict display values to specific client instances, as
identified by their keys in Section 2.3.
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2.3.3. Authenticating the Client Instance
If the presented key is known to the AS and is associated with a
single instance of the client software, the process of presenting a
key and proving possession of that key is sufficient to authenticate
the client instance to the AS. The AS MAY associate policies with
the client instance identified by this key, such as limiting which
resources can be requested and which interaction methods can be used.
For example, only specific client instances with certain known keys
might be trusted with access tokens without the AS interacting
directly with the RO as in Appendix C.3.
The presentation of a key allows the AS to strongly associate
multiple successive requests from the same client instance with each
other. This is true when the AS knows the key ahead of time and can
use the key to authenticate the client instance, but also if the key
is ephemeral and created just for this series of requests. As such
the AS MAY allow for client instances to make requests with unknown
keys. This pattern allows for ephemeral client instances, such as
single-page applications, and client software with many individual
long-lived instances, such as mobile applications, to generate key
pairs per instance and use the keys within the protocol without
having to go through a separate registration step. The AS MAY limit
which capabilities are made available to client instances with
unknown keys. For example, the AS could have a policy saying that
only previously-registered client instances can request particular
resources, or that all client instances with unknown keys have to be
interactively approved by an RO.
2.4. Identifying the User
If the client instance knows the identity of the end-user through one
or more identifiers or assertions, the client instance MAY send that
information to the AS in the "user" field. The client instance MAY
pass this information by value or by reference.
sub_ids (array of objects) An array of subject identifiers for the
end-user, as defined by [I-D.ietf-secevent-subject-identifiers].
assertions (object) An object containing assertions as values keyed
on the assertion type defined by a registry TBD (Section 12).
Possible keys include "id_token" for an [OIDC] ID Token and
"saml2" for a SAML 2 assertion. Additional assertion values are
defined by a registry TBD (Section 12). [[ See issue #41
(https://github.com/ietf-wg-gnap/gnap-core-protocol/issues/41) ]]
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"user": {
"sub_ids": [ {
"subject_type": "email",
"email": "user@example.com"
} ],
"assertions": {
"id_token": "eyj..."
}
}
Subject identifiers are hints to the AS in determining the RO and
MUST NOT be taken as declarative statements that a particular RO is
present at the client instance and acting as the end-user.
Assertions SHOULD be validated by the AS. [[ See issue #49
(https://github.com/ietf-wg-gnap/gnap-core-protocol/issues/49) ]]
If the identified end-user does not match the RO present at the AS
during an interaction step, the AS SHOULD reject the request with an
error.
[[ See issue #50 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/50) ]]
If the AS trusts the client instance to present verifiable
assertions, the AS MAY decide, based on its policy, to skip
interaction with the RO, even if the client instance provides one or
more interaction modes in its request.
2.4.1. Identifying the User by Reference
User reference identifiers can be dynamically issued by the AS
(Section 3.5) to allow the client instance to represent the same end-
user to the AS over subsequent requests.
If the client instance has a reference for the end-user at this AS,
the client instance MAY pass that reference as a string. The format
of this string is opaque to the client instance.
"user": "XUT2MFM1XBIKJKSDU8QM"
User reference identifiers are not intended to be human-readable user
identifiers or structured assertions. For the client instance to
send either of these, use the full user request object (Section 2.4)
instead.
[[ See issue #51 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/51) ]]
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If the AS does not recognize the user reference, it MUST return an
error.
2.5. Interacting with the User
Many times, the AS will require interaction with the RO in order to
approve a requested delegation to the client instance for both access
to resources and direct subject information. Many times the end-user
using the client instance is the same person as the RO, and the
client instance can directly drive interaction with the AS by
redirecting the end-user on the same device, or by launching an
application. Other times, the client instance can provide
information to start the RO's interaction on a secondary device, or
the client instance will wait for the RO to approve the request
asynchronously. The client instance could also be signaled that
interaction has completed by the AS making callbacks. To facilitate
all of these modes, the client instance declares the means that it
can interact using the "interact" field.
The "interact" field is a JSON object with three keys whose values
declare how the client can initiate and complete the request, as well
as provide hints to the AS about user preferences such as locale. A
client instance MUST NOT declare an interaction mode it does not
support. The client instance MAY send multiple modes in the same
request. There is no preference order specified in this request. An
AS MAY respond to any, all, or none of the presented interaction
modes (Section 3.3) in a request, depending on its capabilities and
what is allowed to fulfill the request.
start (list of strings/objects) Indicates how the client instance
can start an interaction.
finish (object) Indicates how the client instance can receive an
indication that interaction has finished at the AS.
hints (object) Provides additional information to inform the
interaction process at the AS.
The "interact" field MUST contain the "start" key, and MAY contain
the "finish" and "hints" keys. The value of each key is an array
which contains strings or JSON objects as defined below.
2.5.1. Start Mode Definitions
This specification defines the following interaction start modes as
an array of string values under the "start" key:
"redirect" Indicates that the client instance can direct the end-
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user to an arbitrary URL at the AS for interaction.
Section 2.5.5.1
"app" Indicates that the client instance can launch an application
on the end-user's device for interaction. Section 2.5.5.2
"user_code" Indicates that the client instance can communicate a
human-readable short code to the end-user for use with a stable
URL at the AS. Section 2.5.5.3
2.5.2. Finish Mode Definitions
This specification defines the following interaction completion
methods:
"redirect" Indicates that the client instance can receive a redirect
from the end-user's device after interaction with the RO has
concluded. Section 2.5.6.1
"push" Indicates that the client instance can receive an HTTP POST
request from the AS after interaction with the RO has concluded.
Section 2.5.6.2
2.5.3. Hint Definitions
This specification defines the following properties under the "hints"
key:
ui_locales (array of strings) Indicates the end-user's preferred
locales that the AS can use during interaction, particularly
before the RO has authenticated. Section 2.5.7.1
The following sections detail requests for interaction modes.
Additional interaction modes are defined in a registry TBD
(Section 12).
2.5.4. Example Interactions
In this non-normative example, the client instance is indicating that
it can redirect (Section 2.5.5.1) the end-user to an arbitrary URL
and can receive a redirect (Section 2.5.6.1) through a browser
request.
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"interact": {
"start": ["redirect"],
"finish": {
"method": "redirect",
"uri": "https://client.example.net/return/123455",
"nonce": "LKLTI25DK82FX4T4QFZC"
}
}
In this non-normative example, the client instance is indicating that
it can display a user code (Section 2.5.5.3) and direct the end-user
to an arbitrary URL (Section 2.5.5.1) on a secondary device, but it
cannot accept a redirect or push callback.
"interact": {
"start": ["redirect", "user_code"]
}
If the client instance does not provide a suitable interaction
mechanism, the AS cannot contact the RO asynchronously, and the AS
determines that interaction is required, then the AS SHOULD return an
error since the client instance will be unable to complete the
request without authorization.
The AS SHOULD apply suitable timeouts to any interaction mechanisms
provided, including user codes and redirection URLs. The client
instance SHOULD apply suitable timeouts to any callback URLs.
2.5.5. Start Interaction Modes
2.5.5.1. Redirect to an Arbitrary URL
If the client instance is capable of directing the end-user to a URL
defined by the AS at runtime, the client instance indicates this by
sending the "redirect" field with the boolean value "true". The
means by which the client instance will activate this URL is out of
scope of this specification, but common methods include an HTTP
redirect, launching a browser on the end-user's device, providing a
scannable image encoding, and printing out a URL to an interactive
console.
"interact": {
"start": ["redirect"]
}
If this interaction mode is supported for this client instance and
request, the AS returns a redirect interaction response
Section 3.3.1.
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2.5.5.2. Open an Application-specific URL
If the client instance can open a URL associated with an application
on the end-user's device, the client instance indicates this by
sending the "app" field with boolean value "true". The means by
which the client instance determines the application to open with
this URL are out of scope of this specification.
"interact": {
"start": ["app"]
}
If this interaction mode is supported for this client instance and
request, the AS returns an app interaction response with an app URL
payload Section 3.3.2.
[[ See issue #54 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/54) ]]
2.5.5.3. Display a Short User Code
If the client instance is capable of displaying or otherwise
communicating a short, human-entered code to the RO, the client
instance indicates this by sending the "user_code" field with the
boolean value "true". This code is to be entered at a static URL
that does not change at runtime, as described in Section 3.3.4.
"interact": {
"start": ["user_code"]
}
If this interaction mode is supported for this client instance and
request, the AS returns a user code and interaction URL as specified
in Section 4.2.
2.5.6. Finish Interaction Modes
If the client instance is capable of receiving a message from the AS
indicating that the RO has completed their interaction, the client
instance indicates this by sending the following members of an object
under the "finish" key.
method (string) REQUIRED. The callback method that the AS will use
to contact the client instance. Valid values include "redirect"
Section 2.5.6.1 and "push" Section 2.5.6.2, with other values
defined by a registry TBD (Section 12).
uri (string) REQUIRED. Indicates the URI that the AS will either
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send the RO to after interaction or send an HTTP POST request.
This URI MAY be unique per request and MUST be hosted by or
accessible by the client instance. This URI MUST NOT contain any
fragment component. This URI MUST be protected by HTTPS, be
hosted on a server local to the RO's browser ("localhost"), or use
an application-specific URI scheme. If the client instance needs
any state information to tie to the front channel interaction
response, it MUST use a unique callback URI to link to that
ongoing state. The allowable URIs and URI patterns MAY be
restricted by the AS based on the client instance's presented key
information. The callback URI SHOULD be presented to the RO
during the interaction phase before redirect.
nonce (string) REQUIRED. Unique value to be used in the calculation
of the "hash" query parameter sent to the callback URL, must be
sufficiently random to be unguessable by an attacker. MUST be
generated by the client instance as a unique value for this
request.
hash_method (string) OPTIONAL. The hash calculation mechanism to be
used for the callback hash in Section 4.4.3. Can be one of "sha3"
or "sha2". If absent, the default value is "sha3". [[ See issue
#56 (https://github.com/ietf-wg-gnap/gnap-core-protocol/issues/56)
]]
If this interaction mode is supported for this client instance and
request, the AS returns a nonce for use in validating the callback
response (Section 3.3.3). Requests to the callback URI MUST be
processed as described in Section 4.4, and the AS MUST require
presentation of an interaction callback reference as described in
Section 5.1.
[[ See issue #58 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/58) ]]
[[ See issue #59 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/59) ]]
2.5.6.1. Receive an HTTP Callback Through the Browser
A finish "method" value of "redirect" indicates that the client
instance will expect a request from the RO's browser using the HTTP
method GET as described in Section 4.4.1.
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"interact": {
"finish": {
"method": "redirect",
"uri": "https://client.example.net/return/123455",
"nonce": "LKLTI25DK82FX4T4QFZC"
}
}
Requests to the callback URI MUST be processed by the client instance
as described in Section 4.4.1.
Since the incoming request to the callback URL is from the RO's
browser, this method is usually used when the RO and end-user are the
same entity. As such, the client instance MUST ensure the end-user
is present on the request to prevent substitution attacks.
2.5.6.2. Receive an HTTP Direct Callback
A finish "method" value of "push" indicates that the client instance
will expect a request from the AS directly using the HTTP method POST
as described in Section 4.4.2.
"interact": {
"finish": {
"method": "push",
"uri": "https://client.example.net/return/123455",
"nonce": "LKLTI25DK82FX4T4QFZC"
}
}
Requests to the callback URI MUST be processed by the client instance
as described in Section 4.4.2.
Since the incoming request to the callback URL is from the AS and not
from the RO's browser, the client instance MUST NOT require the end-
user to be present on the incoming HTTP request.
[[ See issue #60 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/60) ]]
2.5.7. Hints
The "hints" key is an object describing one or more suggestions from
the client instance that the AS can use to help drive user
interaction.
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2.5.7.1. Indicate Desired Interaction Locales
If the client instance knows the end-user's locale and language
preferences, the client instance can send this information to the AS
using the "ui_locales" field with an array of locale strings as
defined by [RFC5646].
"interact": {
"hints": {
"ui_locales": ["en-US", "fr-CA"]
}
}
If possible, the AS SHOULD use one of the locales in the array, with
preference to the first item in the array supported by the AS. If
none of the given locales are supported, the AS MAY use a default
locale.
2.5.8. Extending Interaction Modes
Additional interaction modes are defined in a registry TBD
(Section 12).
2.6. Declaring Client Capabilities
If the client software supports extension capabilities, the client
instance MAY present them to the AS in the "capabilities" field.
This field is an array of strings representing specific extensions
and capabilities, as defined by a registry TBD (Section 12).
"capabilities": ["ext1", "ext2"]
2.7. Referencing an Existing Grant Request
If the client instance has a reference handle from a previously
granted request, it MAY send that reference in the "existing_grant"
field. This field is a single string consisting of the "value" of
the "access_token" returned in a previous request's continuation
response (Section 3.1).
"existing_grant": "80UPRY5NM33OMUKMKSKU"
The AS MUST dereference the grant associated with the reference and
process this request in the context of the referenced one. The AS
MUST NOT alter the existing grant associated with the reference.
[[ See issue #62 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/62) ]]
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2.8. Extending The Grant Request
The request object MAY be extended by registering new items in a
registry TBD (Section 12). Extensions SHOULD be orthogonal to other
parameters. Extensions MUST document any aspects where the extension
item affects or influences the values or behavior of other request
and response objects.
3. Grant Response
In response to a client instance's request, the AS responds with a
JSON object as the HTTP entity body. Each possible field is detailed
in the sections below
continue (object) Indicates that the client instance can continue
the request by making one or more continuation requests.
Section 3.1
access_token (object / array of objects) A single access token or
set of access tokens that the client instance can use to call the
RS on behalf of the RO. Section 3.2.1
interact (object) Indicates that interaction through some set of
defined mechanisms needs to take place. Section 3.3
subject (object) Claims about the RO as known and declared by the
AS. Section 3.4
instance_id (string) An identifier this client instance can use to
identify itself when making future requests. Section 3.5
user_handle (string) An identifier this client instance can use to
identify its current end-user when making future requests.
Section 3.5
error (object) An error code indicating that something has gone
wrong. Section 3.6
In this example, the AS is returning an interaction URL
(Section 3.3.1), a callback nonce (Section 3.3.3), and a continuation
response (Section 3.1).
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{
"interact": {
"redirect": "https://server.example.com/interact/4CF492MLVMSW9MKMXKHQ",
"push": "MBDOFXG4Y5CVJCX821LH"
},
"continue": {
"access_token": {
"value": "80UPRY5NM33OMUKMKSKU",
"bound": true
},
"uri": "https://server.example.com/tx"
}
}
In this example, the AS is returning a bearer access token
(Section 3.2.1) with a management URL and a subject identifier
(Section 3.4) in the form of an email address.
{
"access_token": {
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
"bound": false,
"manage": "https://server.example.com/token/PRY5NM33OM4TB8N6BW7OZB8CDFONP219RP1L"
},
"subject": {
"sub_ids": [ {
"subject_type": "email",
"email": "user@example.com",
} ]
}
}
3.1. Request Continuation
If the AS determines that the request can be continued with
additional requests, it responds with the "continue" field. This
field contains a JSON object with the following properties.
uri (string) REQUIRED. The URI at which the client instance can
make continuation requests. This URI MAY vary per request, or MAY
be stable at the AS if the AS includes an access token. The
client instance MUST use this value exactly as given when making a
continuation request (Section 5).
wait (integer) RECOMMENDED. The amount of time in integer seconds
the client instance SHOULD wait after receiving this continuation
handle and calling the URI.
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access_token (object) REQUIRED. A unique access token for
continuing the request, in the format specified in Section 3.2.1.
This access token MUST be bound to the client instance's key used
in the request and MUST NOT be a "bearer" token. As a
consequence, the "bound" field of this access token is always the
boolean value "true" and the "key" field MUST be omitted. This
access token MUST NOT be usable at resources outside of the AS.
The client instance MUST present the access token in all requests
to the continuation URI as described in Section 7.2. [[ See issue
#66 (https://github.com/ietf-wg-gnap/gnap-core-protocol/issues/66)
]]
{
"continue": {
"access_token": {
"value": "80UPRY5NM33OMUKMKSKU",
"bound": true
},
"uri": "https://server.example.com/continue",
"wait": 60
}
}
The client instance can use the values of this field to continue the
request as described in Section 5. Note that the client instance
MUST sign all continuation requests with its key as described in
Section 7.3 and MUST present the access token in its continuation
request.
This field SHOULD be returned when interaction is expected, to allow
the client instance to follow up after interaction has been
concluded.
3.2. Access Tokens
If the AS has successfully granted one or more access tokens to the
client instance, the AS responds with the "access_token" field. This
field contains either a single access token as described in
Section 3.2.1 or an array of access tokens as described in
Section 3.2.2.
The client instance uses any access tokens in this response to call
the RS as described in Section 7.2.
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3.2.1. Single Access Token
If the client instance has requested a single access token and the AS
has granted that access token, the AS responds with the
"access_token" field. The value of this field is an object with the
following properties.
value (string) REQUIRED. The value of the access token as a string.
The value is opaque to the client instance. The value SHOULD be
limited to ASCII characters to facilitate transmission over HTTP
headers within other protocols without requiring additional
encoding.
bound (boolean) RECOMMENDED. Flag indicating if the token is bound
to the client instance's key. If the boolean value is "true" or
the field is omitted, and the "key" field is omitted, the token is
bound to the key used by the client instance (Section 2.3) in its
request for access. If the boolean value is "true" or the field
is omitted, and the "key" field is present, the token is bound to
the key and proofing mechanism indicated in the "key" field. If
the boolean value is "false", the token is a bearer token with no
key bound to it and the "key" field MUST be omitted.
label (string) REQUIRED for multiple access tokens, OPTIONAL for
single access token. The value of the "label" the client instance
provided in the associated token request (Section 2.1), if
present. If the token has been split by the AS, the value of the
"label" field is chosen by the AS and the "split" field is
included and set to "true".
manage (string) OPTIONAL. The management URI for this access token.
If provided, the client instance MAY manage its access token as
described in Section 6. This management URI is a function of the
AS and is separate from the RS the client instance is requesting
access to. This URI MUST NOT include the access token value and
SHOULD be different for each access token issued in a request.
access (array of objects/strings) RECOMMENDED. A description of the
rights associated with this access token, as defined in Section 8.
If included, this MUST reflect the rights associated with the
issued access token. These rights MAY vary from what was
requested by the client instance.
expires_in (integer) OPTIONAL. The number of seconds in which the
access will expire. The client instance MUST NOT use the access
token past this time. An RS MUST NOT accept an access token past
this time. Note that the access token MAY be revoked by the AS or
RS at any point prior to its expiration.
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key (object / string) OPTIONAL. The key that the token is bound to,
if different from the client instance's presented key. The key
MUST be an object or string in a format described in Section 7.1,
describing a public key to which the client instance can use the
associated private key. The client instance MUST be able to
dereference or process the key information in order to be able to
sign the request.
durable (boolean) OPTIONAL. Flag indicating a hint of AS behavior
on token rotation. If this flag is set to the value "true", then
the client instance can expect a previously-issued access token to
continue to work after it has been rotated (Section 6.1) or the
underlying grant request has been modified (Section 5.3),
resulting in the issuance of new access tokens. If this flag is
set to the boolean value "false" or is omitted, the client
instance can anticipate a given access token will stop working
after token rotation or grant request modification. Note that a
token flagged as "durable" can still expire or be revoked through
any normal means.
split (boolean) OPTIONAL. Flag indicating that this token was
generated by issuing multiple access tokens in response to one of
the client instance's token request (Section 2.1) objects. This
behavior MUST NOT be used unless the client instance has
specifically requested it by use of the "split" flag.
The following non-normative example shows a single access token bound
to the client instance's key used in the initial request, with a
management URL, and that has access to three described resources (one
using an object and two described by reference strings).
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"access_token": {
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
"bound": true,
"manage": "https://server.example.com/token/PRY5NM33OM4TB8N6BW7OZB8CDFONP219RP1L",
"access": [
{
"type": "photo-api",
"actions": [
"read",
"write",
"dolphin"
],
"locations": [
"https://server.example.net/",
"https://resource.local/other"
],
"datatypes": [
"metadata",
"images"
]
},
"read", "dolphin-metadata"
]
}
The following non-normative example shows a single bearer access
token with access to two described resources.
"access_token": {
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
"bound": true,
"access": [
"finance", "medical"
]
}
If the client instance requested a single access token
(Section 2.1.1), the AS MUST NOT respond with the multiple access
token structure unless the client instance sends the "split" flag as
described in Section 2.1.1.
If the AS has split the access token response, the response MUST
include the "split" flag set to "true".
[[ See issue #69 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/69) ]]
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3.2.2. Multiple Access Tokens
If the client instance has requested multiple access tokens and the
AS has granted at least one of them, the AS responds with the
"access_token" field. The value of this field is a JSON array, the
members of which are distinct access tokens as described in
Section 3.2.1. Each object MUST have a unique "label" field,
corresponding to the token labels chosen by the client instance in
the multiple access token request (Section 2.1.2).
In this non-normative example, two bearer tokens are issued under the
names "token1" and "token2", and only the first token has a
management URL associated with it.
"access_token": [
{
"label": "token1",
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
"bound": true,
"manage": "https://server.example.com/token/PRY5NM33OM4TB8N6BW7OZB8CDFONP219RP1L",
"access": [ "finance" ]
},
{
"label": "token2",
"value": "UFGLO2FDAFG7VGZZPJ3IZEMN21EVU71FHCARP4J1",
"bound": true,
"access": [ "medical" ]
}
}
Each access token corresponds to one of the objects in the
"access_token" array of the client instance's request
(Section 2.1.2).
The multiple access token response MUST be used when multiple access
tokens are requested, even if only one access token is issued as a
result of the request. The AS MAY refuse to issue one or more of the
requested access tokens, for any reason. In such cases the refused
token is omitted from the response and all of the other issued access
tokens are included in the response the requested names appropriate
names.
If the client instance requested multiple access tokens
(Section 2.1.2), the AS MUST NOT respond with a single access token
structure, even if only a single access token is granted. In such
cases, the AS responds with a multiple access token structure
containing one access token.
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If the AS has split the access token response, the response MUST
include the "split" flag set to "true".
"access_token": [
{
"label": "split-1",
"value": "8N6BW7OZB8CDFONP219-OS9M2PMHKUR64TBRP1LT0",
"bound": true,
"split": true,
"manage": "https://server.example.com/token/PRY5NM33OM4TB8N6BW7OZB8CDFONP219RP1L",
"access": [ "fruits" ]
},
{
"label": "split-2",
"value": "FG7VGZZPJ3IZEMN21EVU71FHCAR-UFGLO2FDAP4J1",
"bound": true,
"split": true,
"access": [ "vegetables" ]
}
}
Each access token MAY be bound to different keys with different
proofing mechanisms.
If token management (Section 6) is allowed, each access token SHOULD
have different "manage" URIs.
[[ See issue #70 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/70) ]]
3.3. Interaction Modes
If the client instance has indicated a capability to interact with
the RO in its request (Section 2.5), and the AS has determined that
interaction is both supported and necessary, the AS responds to the
client instance with any of the following values in the "interact"
field of the response. There is no preference order for interaction
modes in the response, and it is up to the client instance to
determine which ones to use. All supported interaction methods are
included in the same "interact" object.
redirect (string) Redirect to an arbitrary URL. Section 3.3.1
app (string) Launch of an application URL. Section 3.3.2
finish (string) A nonce used by the client instance to verify the
callback after interaction is completed. Section 3.3.3
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user_code (object) Display a short user code. Section 3.3.4
Additional interaction mode responses can be defined in a registry
TBD (Section 12).
The AS MUST NOT respond with any interaction mode that the client
instance did not indicate in its request. The AS MUST NOT respond
with any interaction mode that the AS does not support. Since
interaction responses include secret or unique information, the AS
SHOULD respond to each interaction mode only once in an ongoing
request, particularly if the client instance modifies its request
(Section 5.3).
3.3.1. Redirection to an arbitrary URL
If the client instance indicates that it can redirect to an arbitrary
URL (Section 2.5.5.1) and the AS supports this mode for the client
instance's request, the AS responds with the "redirect" field, which
is a string containing the URL to direct the end-user to. This URL
MUST be unique for the request and MUST NOT contain any security-
sensitive information.
"interact": {
"redirect": "https://interact.example.com/4CF492MLVMSW9MKMXKHQ"
}
The interaction URL returned represents a function of the AS but MAY
be completely distinct from the URL the client instance uses to
request access (Section 2), allowing an AS to separate its user-
interactive functionality from its back-end security functionality.
[[ See issue #72 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/72) ]]
The client instance sends the end-user to the URL to interact with
the AS. The client instance MUST NOT alter the URL in any way. The
means for the client instance to send the end-user to this URL is out
of scope of this specification, but common methods include an HTTP
redirect, launching the system browser, displaying a scannable code,
or printing out the URL in an interactive console.
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3.3.2. Launch of an application URL
If the client instance indicates that it can launch an application
URL (Section 2.5.5.2) and the AS supports this mode for the client
instance's request, the AS responds with the "app" field, which is a
string containing the URL to direct the end-user to. This URL MUST
be unique for the request and MUST NOT contain any security-sensitive
information.
"interact": {
"app": "https://app.example.com/launch?tx=4CF492MLV"
}
The client instance launches the URL as appropriate on its platform,
and the means for the client instance to launch this URL is out of
scope of this specification. The client instance MUST NOT alter the
URL in any way. The client instance MAY attempt to detect if an
installed application will service the URL being sent before
attempting to launch the application URL.
[[ See issue #71 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/71) ]]
3.3.3. Post-interaction Callback to a Client Instance Accessible URL
If the client instance indicates that it can receive a
post-interaction redirect or push at a URL (Section 2.5.6) and the AS
supports this mode for the client instance's request, the AS responds
with a "finish" field containing a nonce that the client instance
will use in validating the callback as defined in Section 4.4.
"interact": {
"finish": "MBDOFXG4Y5CVJCX821LH"
}
When the RO completes interaction at the AS, the AS MUST either
redirect the RO's browser or send an HTTP POST to the client
instance's callback URL using the method indicated in the interaction
request (Section 2.5.6) as described in Section 4.4.
If the AS returns a nonce, the client instance MUST NOT continue a
grant request before it receives the associated interaction reference
on the callback URI.
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3.3.4. Display of a Short User Code
If the client instance indicates that it can display a short
user-typeable code (Section 2.5.5.3) and the AS supports this mode
for the client instance's request, the AS responds with a "user_code"
field. This field is an object that contains the following members.
code (string) REQUIRED. A unique short code that the user can type
into an authorization server. This string MUST be case-
insensitive, MUST consist of only easily typeable characters (such
as letters or numbers). The time in which this code will be
accepted SHOULD be short lived, such as several minutes. It is
RECOMMENDED that this code be no more than eight characters in
length.
url (string) RECOMMENDED. The interaction URL that the client
instance will direct the RO to. This URL MUST be stable at the AS
such that client instance's can be statically configured with it.
"interact": {
"user_code": {
"code": "A1BC-3DFF",
"url": "https://srv.ex/device"
}
}
The client instance MUST communicate the "code" to the end-user in
some fashion, such as displaying it on a screen or reading it out
audibly. The "code" is a one-time-use credential that the AS uses to
identify the pending request from the client instance. When the RO
enters this code (Section 4.2) into the AS, the AS MUST determine the
pending request that it was associated with. If the AS does not
recognize the entered code, the AS MUST display an error to the user.
If the AS detects too many unrecognized codes entered, it SHOULD
display an error to the user.
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The client instance SHOULD also communicate the URL if possible to
facilitate user interaction, but since the URL should be stable, the
client instance should be able to safely decide to not display this
value. As this interaction mode is designed to facilitate
interaction via a secondary device, it is not expected that the
client instance redirect the end-user to the URL given here at
runtime. Consequently, the URL needs to be stable enough that a
client instance could be statically configured with it, perhaps
referring the end-user to the URL via documentation instead of
through an interactive means. If the client instance is capable of
communicating an arbitrary URL to the end-user, such as through a
scannable code, the client instance can use the "redirect"
(Section 2.5.5.1) mode for this purpose instead of or in addition to
the user code mode.
The interaction URL returned represents a function of the AS but MAY
be completely distinct from the URL the client instance uses to
request access (Section 2), allowing an AS to separate its user-
interactive functionality from its back-end security functionality.
[[ See issue #72 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/72) ]]
3.3.5. Extending Interaction Mode Responses
Extensions to this specification can define new interaction mode
responses in a registry TBD (Section 12). Extensions MUST document
the corresponding interaction request.
3.4. Returning User Information
If information about the RO is requested and the AS grants the client
instance access to that data, the AS returns the approved information
in the "subject" response field. This field is an object with the
following OPTIONAL properties.
sub_ids (array of objects) An array of subject identifiers for the
RO, as defined by [I-D.ietf-secevent-subject-identifiers].
assertions (object) An object containing assertions as values keyed
on the assertion type defined by a registry TBD (Section 12). [[
See issue #41 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/41) ]]
updated_at (string) Timestamp as an ISO8610 date string, indicating
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when the identified account was last updated. The client instance
MAY use this value to determine if it needs to request updated
profile information through an identity API. The definition of
such an identity API is out of scope for this specification.
"subject": {
"sub_ids": [ {
"subject_type": "email",
"email": "user@example.com",
} ],
"assertions": {
"id_token": "eyj..."
}
}
The AS MUST return the "subject" field only in cases where the AS is
sure that the RO and the end-user are the same party. This can be
accomplished through some forms of interaction with the RO
(Section 4).
Subject identifiers returned by the AS SHOULD uniquely identify the
RO at the AS. Some forms of subject identifier are opaque to the
client instance (such as the subject of an issuer and subject pair),
while others forms (such as email address and phone number) are
intended to allow the client instance to correlate the identifier
with other account information at the client instance. The client
instance MUST NOT request or use any returned subject identifiers for
communication purposes (see Section 2.2). That is, a subject
identifier returned in the format of an email address or a phone
number only identifies the RO to the AS and does not indicate that
the AS has validated that the represented email address or phone
number in the identifier is suitable for communication with the
current user. To get such information, the client instance MUST use
an identity protocol to request and receive additional identity
claims. The details of an identity protocol and associated schema
are outside the scope of this specification.
[[ See issue #75 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/75) ]]
Extensions to this specification MAY define additional response
properties in a registry TBD (Section 12).
3.5. Returning Dynamically-bound Reference Handles
Many parts of the client instance's request can be passed as either a
value or a reference. The use of a reference in place of a value
allows for a client instance to optimize requests to the AS.
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Some references, such as for the client instance's identity
(Section 2.3.1) or the requested resources (Section 8.1), can be
managed statically through an admin console or developer portal
provided by the AS or RS. The developer of the client software can
include these values in their code for a more efficient and compact
request.
If desired, the AS MAY also generate and return some of these
references dynamically to the client instance in its response to
facilitate multiple interactions with the same software. The client
instance SHOULD use these references in future requests in lieu of
sending the associated data value. These handles are intended to be
used on future requests.
Dynamically generated handles are string values that MUST be
protected by the client instance as secrets. Handle values MUST be
unguessable and MUST NOT contain any sensitive information. Handle
values are opaque to the client instance.
All dynamically generated handles are returned as fields in the root
JSON object of the response. This specification defines the
following dynamic handle returns, additional handles can be defined
in a registry TBD (Section 12).
instance_id (string) A string value used to represent the
information in the "client" object that the client instance can
use in a future request, as described in Section 2.3.1.
user_handle (string) A string value used to represent the current
user. The client instance can use in a future request, as
described in Section 2.4.1.
This non-normative example shows two handles along side an issued
access token.
{
"user_handle": "XUT2MFM1XBIKJKSDU8QM",
"instance_id": "7C7C4AZ9KHRS6X63AJAO",
"access_token": {
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
"bound": true
}
}
[[ See issue #77 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/77) ]]
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[[ See issue #78 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/78) ]]
3.6. Error Response
If the AS determines that the request cannot be issued for any
reason, it responds to the client instance with an error message.
error (string) The error code.
{
"error": "user_denied"
}
The error code is one of the following, with additional values
available in a registry TBD (Section 12):
user_denied The RO denied the request.
too_fast The client instance did not respect the timeout in the wait
response.
unknown_request The request referenced an unknown ongoing access
request.
[[ See issue #79 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/79) ]]
3.7. Extending the Response
Extensions to this specification MAY define additional fields for the
grant response in a registry TBD (Section 12).
4. Interaction at the AS
If the client instance indicates that it is capable of driving
interaction with the RO in its request (Section 2.5), and the AS
determines that interaction is required and responds to one or more
of the client instance's interaction modes, the client instance
SHOULD initiate one of the returned interaction modes in the response
(Section 3.3).
When the RO is interacting with the AS, the AS MAY perform whatever
actions it sees fit, including but not limited to:
* authenticate the current user (who may be the end-user) as the RO
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* gather consent and authorization from the RO for access to
requested resources and direct information
* allow the RO to modify the parameters of the request (such as
disallowing some requested resources or specifying an account or
record)
* provide warnings to the RO about potential attacks or negative
effects of the requested information
4.1. Interaction at a Redirected URI
When the RO is directed to the AS through the "redirect"
(Section 3.3.1) mode, the AS can interact with the RO through their
web browser to authenticate the user as an RO and gather their
consent. Note that since the client instance does not add any
parameters to the URL, the AS MUST determine the grant request being
referenced from the URL value itself. If the URL cannot be
associated with a currently active request, the AS MUST display an
error to the RO and MUST NOT attempt to redirect the RO back to any
client instance even if a redirect is supplied (Section 2.5.6.1).
The interaction URL MUST be reachable from the RO's browser, though
note that the RO MAY open the URL on a separate device from the
client instance itself. The interaction URL MUST be accessible from
an HTTP GET request, and MUST be protected by HTTPS or equivalent
means.
With this method, it is common for the RO to be the same party as the
end-user, since the client instance has to communicate the
redirection URI to the end-user.
4.2. Interaction at the User Code URI
When the RO is directed to the AS through the "user_code"
(Section 3.3.4) mode, the AS can interact with the RO through their
web browser to collect the user code, authenticate the user as an RO,
and gather their consent. Note that since the URL itself is static,
the AS MUST determine the grant request being referenced from the
user code value itself. If the user code cannot be associated with a
currently active request, the AS MUST display an error to the RO and
MUST NOT attempt to redirect the RO back to any client instance even
if a redirect is supplied (Section 2.5.6.1).
The user code URL MUST be reachable from the RO's browser, though
note that the RO MAY open the URL on a separate device from the
client instance itself. The user code URL MUST be accessible from an
HTTP GET request, and MUST be protected by HTTPS or equivalent means.
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While it is common for the RO to be the same party as the end-user,
since the client instance has to communicate the user code to
someone, there are cases where the end-user and RO are separate
parties and the authorization happens asynchronously.
4.3. Interaction through an Application URI
When the client instance successfully launches an application through
the "app" mode (Section 3.3.2), the AS interacts with the RO through
that application to authenticate the user as the RO and gather their
consent. The details of this interaction are out of scope for this
specification.
4.4. Post-Interaction Completion
Upon completing an interaction with the RO, if a "callback"
(Section 3.3.3) mode is available with the current request, the AS
MUST follow the appropriate method at the end of interaction to allow
the client instance to continue. If this mode is not available, the
AS SHOULD instruct the RO to return to their client instance upon
completion. Note that these steps still take place in most error
cases, such as when the RO has denied access. This pattern allows
the client instance to potentially recover from the error state
without restarting the request from scratch by modifying its request
or providing additional information directly to the AS.
The AS MUST create an interaction reference and associate that
reference with the current interaction and the underlying pending
request. This value MUST be sufficiently random so as not to be
guessable by an attacker. The interaction reference MUST be one-
time-use.
The AS MUST calculate a hash value based on the client instance and
AS nonces and the interaction reference, as described in
Section 4.4.3. The client instance will use this value to validate
the return call from the AS.
The AS then MUST send the hash and interaction reference based on the
interaction finalization mode as described in the following sections.
4.4.1. Completing Interaction with a Browser Redirect to the Callback
URI
When using the "redirect" interaction finish method (Section 3.3.3),
the AS signals to the client instance that interaction is complete
and the request can be continued by directing the RO (in their
browser) back to the client instance's redirect URL sent in the
callback request (Section 2.5.6.1).
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The AS secures this redirect by adding the hash and interaction
reference as query parameters to the client instance's redirect URL.
hash REQUIRED. The interaction hash value as described in
Section 4.4.3.
interact_ref REQUIRED. The interaction reference generated for this
interaction.
The means of directing the RO to this URL are outside the scope of
this specification, but common options include redirecting the RO
from a web page and launching the system browser with the target URL.
https://client.example.net/return/123455
?hash=p28jsq0Y2KK3WS__a42tavNC64ldGTBroywsWxT4md_jZQ1R2HZT8BOWYHcLmObM7XHPAdJzTZMtKBsaraJ64A
&interact_ref=4IFWWIKYBC2PQ6U56NL1
When receiving the request, the client instance MUST parse the query
parameters to calculate and validate the hash value as described in
Section 4.4.3. If the hash validates, the client instance sends a
continuation request to the AS as described in Section 5.1 using the
interaction reference value received here.
4.4.2. Completing Interaction with a Direct HTTP Request Callback
When using the "callback" interaction mode (Section 3.3.3) with the
"push" method, the AS signals to the client instance that interaction
is complete and the request can be continued by sending an HTTP POST
request to the client instance's callback URL sent in the callback
request (Section 2.5.6.2).
The entity message body is a JSON object consisting of the following
two fields:
hash (string) REQUIRED. The interaction hash value as described in
Section 4.4.3.
interact_ref (string) REQUIRED. The interaction reference generated
for this interaction.
POST /push/554321 HTTP/1.1
Host: client.example.net
Content-Type: application/json
{
"hash": "p28jsq0Y2KK3WS__a42tavNC64ldGTBroywsWxT4md_jZQ1R2HZT8BOWYHcLmObM7XHPAdJzTZMtKBsaraJ64A",
"interact_ref": "4IFWWIKYBC2PQ6U56NL1"
}
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When receiving the request, the client instance MUST parse the JSON
object and validate the hash value as described in Section 4.4.3. If
the hash validates, the client instance sends a continuation request
to the AS as described in Section 5.1 using the interaction reference
value received here.
4.4.3. Calculating the interaction hash
The "hash" parameter in the request to the client instance's callback
URL ties the front channel response to an ongoing request by using
values known only to the parties involved. This security mechanism
allows the client instance to protect itself against several kinds of
session fixation and injection attacks. The AS MUST always provide
this hash, and the client instance MUST validate the hash when
received.
To calculate the "hash" value, the party doing the calculation first
takes the "nonce" value sent by the client instance in the
interaction section of the initial request (Section 2.5.6), the AS's
nonce value from the callback response (Section 3.3.3), and the
"interact_ref" sent to the client instance's callback URL. These
three values are concatenated to each other in this order using a
single newline character as a separator between the fields. There is
no padding or whitespace before or after any of the lines, and no
trailing newline character.
VJLO6A4CAYLBXHTR0KRO
MBDOFXG4Y5CVJCX821LH
4IFWWIKYBC2PQ6U56NL1
The party then hashes this string with the appropriate algorithm
based on the "hash_method" parameter of the "callback". If the
"hash_method" value is not present in the client instance's request,
the algorithm defaults to "sha3".
[[ See issue #56 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/56) ]]
4.4.3.1. SHA3-512
The "sha3" hash method consists of hashing the input string with the
512-bit SHA3 algorithm. The byte array is then encoded using URL
Safe Base64 with no padding. The resulting string is the hash value.
p28jsq0Y2KK3WS__a42tavNC64ldGTBroywsWxT4md_jZQ1R2HZT8BOWYHcLmObM7XHPAdJzTZMtKBsaraJ64A
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4.4.3.2. SHA2-512
The "sha2" hash method consists of hashing the input string with the
512-bit SHA2 algorithm. The byte array is then encoded using URL
Safe Base64 with no padding. The resulting string is the hash value.
62SbcD3Xs7L40rjgALA-ymQujoh2LB2hPJyX9vlcr1H6ecChZ8BNKkG_HrOKP_Bpj84rh4mC9aE9x7HPBFcIHw
5. Continuing a Grant Request
While it is possible for the AS to return a Section 3 with all the
client instance's requested information (including access tokens
(Section 3.2) and direct user information (Section 3.4)), it's more
common that the AS and the client instance will need to communicate
several times over the lifetime of an access grant. This is often
part of facilitating interaction (Section 4), but it could also be
used to allow the AS and client instance to continue negotiating the
parameters of the original grant request (Section 2).
To enable this ongoing negotiation, the AS provides a continuation
API to the client software. The AS returns a "continue" field in the
response (Section 3.1) that contains information the client instance
needs to access this API, including a URI to access as well as an
access token to use during the continued requests.
The access token is initially bound to the same key and method the
client instance used to make the initial request. As a consequence,
when the client instance makes any calls to the continuation URL, the
client instance MUST present the access token as described in
Section 7.2 and present proof of the client instance's key (or its
most recent rotation) by signing the request as described in
Section 7.3. The AS MUST validate all keys presented by the client
instance or referenced in an ongoing request for each call within
that request.
[[ See issue #85 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/85) ]]
For example, here the client instance makes a POST request to a
unique URI and signs the request with detached JWS:
POST /continue/KSKUOMUKM HTTP/1.1
Authorization: GNAP 80UPRY5NM33OMUKMKSKU
Host: server.example.com
Detached-JWS: ejy0...
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The AS MUST be able to tell from the client instance's request which
specific ongoing request is being accessed, using a combination of
the continuation URL, the provided access token, and the client
instance identified by the key signature. If the AS cannot determine
a single active grant request to map the continuation request to, the
AS MUST return an error.
The ability to continue an already-started request allows the client
instance to perform several important functions, including presenting
additional information from interaction, modifying the initial
request, and getting the current state of the request.
All requests to the continuation API are protected by this bound
access token. For example, here the client instance makes a POST
request to a stable continuation endpoint URL with the interaction
reference (Section 5.1), includes the access token, and signs with
detached JWS:
POST /continue HTTP/1.1
Host: server.example.com
Content-Type: application/json
Authorization: GNAP 80UPRY5NM33OMUKMKSKU
Detached-JWS: ejy0...
{
"interact_ref": "4IFWWIKYBC2PQ6U56NL1"
}
If a "wait" parameter was included in the continuation response
(Section 3.1), the client instance MUST NOT call the continuation URI
prior to waiting the number of seconds indicated. If no "wait"
period is indicated, the client instance SHOULD wait at least 5
seconds. If the client instance does not respect the given wait
period, the AS MUST return an error. [[ See issue #86
(https://github.com/ietf-wg-gnap/gnap-core-protocol/issues/86) ]]
The response from the AS is a JSON object and MAY contain any of the
fields described in Section 3, as described in more detail in the
sections below.
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If the AS determines that the client instance can make a further
continuation request, the AS MUST include a new "continue" response
(Section 3.1). The new "continue" response MUST include a bound
access token as well, and this token SHOULD be a new access token,
invalidating the previous access token. If the AS does not return a
new "continue" response, the client instance MUST NOT make an
additional continuation request. If a client instance does so, the
AS MUST return an error. [[ See issue #87 (https://github.com/ietf-
wg-gnap/gnap-core-protocol/issues/87) ]]
For continuation functions that require the client instance to send a
message body, the body MUST be a JSON object.
5.1. Continuing After a Completed Interaction
When the AS responds to the client instance's "callback" parameter as
in Section 4.4.1, this response includes an interaction reference.
The client instance MUST include that value as the field
"interact_ref" in a POST request to the continuation URI.
POST /continue HTTP/1.1
Host: server.example.com
Content-Type: application/json
Authorization: GNAP 80UPRY5NM33OMUKMKSKU
Detached-JWS: ejy0...
{
"interact_ref": "4IFWWIKYBC2PQ6U56NL1"
}
Since the interaction reference is a one-time-use value as described
in Section 4.4.1, if the client instance needs to make additional
continuation calls after this request, the client instance MUST NOT
include the interaction reference. If the AS detects a client
instance submitting the same interaction reference multiple times,
the AS MUST return an error and SHOULD invalidate the ongoing
request.
The Section 3 MAY contain any newly-created access tokens
(Section 3.2) or newly-released subject claims (Section 3.4). The
response MAY contain a new "continue" response (Section 3.1) as
described above. The response SHOULD NOT contain any interaction
responses (Section 3.3). [[ See issue #89 (https://github.com/ietf-
wg-gnap/gnap-core-protocol/issues/89) ]]
For example, if the request is successful in causing the AS to issue
access tokens and release subject claims, the response could look
like this:
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{
"access_token": {
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
"bound": true,
"manage": "https://server.example.com/token/PRY5NM33OM4TB8N6BW7OZB8CDFONP219RP1L"
},
"subject": {
"sub_ids": [ {
"subject_type": "email",
"email": "user@example.com",
} ]
}
}
With this example, the client instance can not make an additional
continuation request because a "continue" field is not included.
[[ See issue #88 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/88) ]]
5.2. Continuing During Pending Interaction
When the client instance does not include a "callback" parameter, the
client instance will often need to poll the AS until the RO has
authorized the request. To do so, the client instance makes a POST
request to the continuation URI as in Section 5.1, but does not
include a message body.
POST /continue HTTP/1.1
Host: server.example.com
Content-Type: application/json
Authorization: GNAP 80UPRY5NM33OMUKMKSKU
Detached-JWS: ejy0...
The Section 3 MAY contain any newly-created access tokens
(Section 3.2) or newly-released subject claims (Section 3.4). The
response MAY contain a new "continue" response (Section 3.1) as
described above. If a "continue" field is included, it SHOULD
include a "wait" field to facilitate a reasonable polling rate by the
client instance. The response SHOULD NOT contain interaction
responses (Section 3.3).
For example, if the request has not yet been authorized by the RO,
the AS could respond by telling the client instance to make another
continuation request in the future. In this example, a new, unique
access token has been issued for the call, which the client instance
will use in its next continuation request.
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{
"continue": {
"access_token": {
"value": "33OMUKMKSKU80UPRY5NM",
"bound": true
},
"uri": "https://server.example.com/continue",
"wait": 30
}
}
[[ See issue #90 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/90) ]]
[[ See issue #91 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/91) ]]
If the request is successful in causing the AS to issue access tokens
and release subject claims, the response could look like this
example:
{
"access_token": {
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
"bound": true,
"manage": "https://server.example.com/token/PRY5NM33OM4TB8N6BW7OZB8CDFONP219RP1L"
},
"subject": {
"sub_ids": [ {
"subject_type": "email",
"email": "user@example.com",
} ]
}
}
5.3. Modifying an Existing Request
The client instance might need to modify an ongoing request, whether
or not tokens have already been issued or claims have already been
released. In such cases, the client instance makes an HTTP PATCH
request to the continuation URI and includes any fields it needs to
modify. Fields that aren't included in the request are considered
unchanged from the original request.
The client instance MAY include the "access_token" and "subject"
fields as described in Section 2.1 and Section 2.2. Inclusion of
these fields override any values in the initial request, which MAY
trigger additional requirements and policies by the AS. For example,
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if the client instance is asking for more access, the AS could
require additional interaction with the RO to gather additional
consent. If the client instance is asking for more limited access,
the AS could determine that sufficient authorization has been granted
to the client instance and return the more limited access rights
immediately. [[ See issue #92 (https://github.com/ietf-wg-gnap/gnap-
core-protocol/issues/92) ]]
The client instance MAY include the "interact" field as described in
Section 2.5. Inclusion of this field indicates that the client
instance is capable of driving interaction with the RO, and this
field replaces any values from a previous request. The AS MAY
respond to any of the interaction responses as described in
Section 3.3, just like it would to a new request.
The client instance MAY include the "user" field as described in
Section 2.4 to present new assertions or information about the end-
user. [[ See issue #93 (https://github.com/ietf-wg-gnap/gnap-core-
protocol/issues/93) ]]
The client instance MUST NOT include the "client" section of the
request. [[ See issue #94 (https://github.com/ietf-wg-gnap/gnap-core-
protocol/issues/94) ]]
The client instance MAY include post-interaction responses such as
described in Section 5.1. [[ See issue #95 (https://github.com/ietf-
wg-gnap/gnap-core-protocol/issues/95) ]]
Modification requests MUST NOT alter previously-issued access tokens.
Instead, any access tokens issued from a continuation are considered
new, separate access tokens. The AS MAY revoke existing access
tokens after a modification has occurred. [[ See issue #96
(https://github.com/ietf-wg-gnap/gnap-core-protocol/issues/96) ]]
If the modified request can be granted immediately by the AS, the
Section 3 MAY contain any newly-created access tokens (Section 3.2)
or newly-released subject claims (Section 3.4). The response MAY
contain a new "continue" response (Section 3.1) as described above.
If interaction can occur, the response SHOULD contain interaction
responses (Section 3.3) as well.
For example, a client instance initially requests a set of resources
using references:
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POST /tx HTTP/1.1
Host: server.example.com
Content-Type: application/json
Detached-JWS: ejy0...
{
"access": [
"read", "write"
],
"interact": {
"start": ["redirect"],
"finish": {
"method": "redirect",
"uri": "https://client.example.net/return/123455",
"nonce": "LKLTI25DK82FX4T4QFZC"
}
},
"client": "987YHGRT56789IOLK"
}
Access is granted by the RO, and a token is issued by the AS. In its
final response, the AS includes a "continue" field, which includes a
separate access token for accessing the continuation API:
{
"continue": {
"access_token": {
"value": "80UPRY5NM33OMUKMKSKU",
"bound": true
},
"uri": "https://server.example.com/continue",
"wait": 30
},
"access_token": {
"value": "RP1LT0-OS9M2P_R64TB",
"bound": true,
"access": [
"read", "write"
]
}
}
This "continue" field allows the client instance to make an eventual
continuation call. In the future, the client instance realizes that
it no longer needs "write" access and therefore modifies its ongoing
request, here asking for just "read" access instead of both "read"
and "write" as before.
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PATCH /continue HTTP/1.1
Host: server.example.com
Content-Type: application/json
Authorization: GNAP 80UPRY5NM33OMUKMKSKU
Detached-JWS: ejy0...
{
"access_token": {
"access": [
"read"
]
}
...
}
The AS replaces the previous "access" from the first request,
allowing the AS to determine if any previously-granted consent
already applies. In this case, the AS would likely determine that
reducing the breadth of the requested access means that new access
tokens can be issued to the client instance. The AS would likely
revoke previously-issued access tokens that had the greater access
rights associated with them, unless they had been issued with the
"durable" flag.
{
"continue": {
"access_token": {
"value": "M33OMUK80UPRY5NMKSKU",
"bound": true
},
"uri": "https://server.example.com/continue",
"wait": 30
},
"access_token": {
"value": "0EVKC7-2ZKwZM_6N760",
"bound": true,
"access": [
"read"
]
}
}
For another example, the client instance initially requests read-only
access but later needs to step up its access. The initial request
could look like this example.
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POST /tx HTTP/1.1
Host: server.example.com
Content-Type: application/json
Detached-JWS: ejy0...
{
"access_token": {
"access": [
"read"
]
},
"interact": {
"start": ["redirect"],
"finish": {
"method": "redirect",
"uri": "https://client.example.net/return/123455",
"nonce": "LKLTI25DK82FX4T4QFZC"
}
},
"client": "987YHGRT56789IOLK"
}
Access is granted by the RO, and a token is issued by the AS. In its
final response, the AS includes a "continue" field:
{
"continue": {
"access_token": {
"value": "80UPRY5NM33OMUKMKSKU",
"bound": true
},
"uri": "https://server.example.com/continue",
"wait": 30
},
"access_token": {
"value": "RP1LT0-OS9M2P_R64TB",
"bound": true,
"access": [
"read"
]
}
}
This allows the client instance to make an eventual continuation
call. The client instance later realizes that it now needs "write"
access in addition to the "read" access. Since this is an expansion
of what it asked for previously, the client instance also includes a
new interaction section in case the AS needs to interact with the RO
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again to gather additional authorization. Note that the client
instance's nonce and callback are different from the initial request.
Since the original callback was already used in the initial exchange,
and the callback is intended for one-time-use, a new one needs to be
included in order to use the callback again.
[[ See issue #97 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/97) ]]
PATCH /continue HTTP/1.1
Host: server.example.com
Content-Type: application/json
Authorization: GNAP 80UPRY5NM33OMUKMKSKU
Detached-JWS: ejy0...
{
"access_token": {
"access": [
"read", "write"
]
},
"interact": {
"start": ["redirect"],
"finish": {
"method": "redirect",
"uri": "https://client.example.net/return/654321",
"nonce": "K82FX4T4LKLTI25DQFZC"
}
}
}
From here, the AS can determine that the client instance is asking
for more than it was previously granted, but since the client
instance has also provided a mechanism to interact with the RO, the
AS can use that to gather the additional consent. The protocol
continues as it would with a new request. Since the old access
tokens are good for a subset of the rights requested here, the AS
might decide to not revoke them. However, any access tokens granted
after this update process are new access tokens and do not modify the
rights of existing access tokens.
5.4. Canceling a Grant Request
If the client instance wishes to cancel an ongoing grant request, it
makes an HTTP DELETE request to the continuation URI.
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DELETE /continue HTTP/1.1
Host: server.example.com
Content-Type: application/json
Authorization: GNAP 80UPRY5NM33OMUKMKSKU
Detached-JWS: ejy0...
If the request is successfully cancelled, the AS responds with an
HTTP 202. The AS SHOULD revoke all associated access tokens.
6. Token Management
If an access token response includes the "manage" parameter as
described in Section 3.2.1, the client instance MAY call this URL to
manage the access token with any of the actions defined in the
following sections. Other actions are undefined by this
specification.
The access token being managed acts as the access element for its own
management API. The client instance MUST present proof of an
appropriate key along with the access token.
If the token is sender-constrained (i.e., not a bearer token), it
MUST be sent with the appropriate binding for the access token
(Section 7.2).
If the token is a bearer token, the client instance MUST present
proof of the same key identified in the initial request (Section 2.3)
as described in Section 7.3.
The AS MUST validate the proof and assure that it is associated with
either the token itself or the client instance the token was issued
to, as appropriate for the token's presentation type.
6.1. Rotating the Access Token
The client instance makes an HTTP POST to the token management URI,
sending the access token in the appropriate header and signing the
request with the appropriate key.
POST /token/PRY5NM33OM4TB8N6BW7OZB8CDFONP219RP1L HTTP/1.1
Host: server.example.com
Authorization: GNAP OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0
Detached-JWS: eyj0....
The AS validates that the token presented is associated with the
management URL, that the AS issued the token to the given client
instance, and that the presented key is appropriate to the token.
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If the access token has expired, the AS SHOULD honor the rotation
request to the token management URL since it is likely that the
client instance is attempting to refresh the expired token. To
support this, the AS MAY apply different lifetimes for the use of the
token in management vs. its use at an RS. An AS MUST NOT honor a
rotation request for an access token that has been revoked, either by
the AS or by the client instance through the token management URI
(Section 6.2).
If the token is validated and the key is appropriate for the request,
the AS MUST invalidate the current access token associated with this
URL, if possible, and return a new access token response as described
in Section 3.2.1, unless the "multi_token" flag is specified in the
request. The value of the access token MUST NOT be the same as the
current value of the access token used to access the management API.
The response MAY include an updated access token management URL as
well, and if so, the client instance MUST use this new URL to manage
the new access token. [[ See issue #101 (https://github.com/ietf-wg-
gnap/gnap-core-protocol/issues/101) ]]
[[ See issue #102 (https://github.com/ietf-wg-gnap/gnap-core-
protocol/issues/102) ]]
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{
"access_token": {
"value": "FP6A8H6HY37MH13CK76LBZ6Y1UADG6VEUPEER5H2",
"bound": true,
"manage": "https://server.example.com/token/PRY5NM33OM4TB8N6BW7OZB8CDFONP219RP1L",
"access": [
{
"type": "photo-api",
"actions": [
"read",
"write",
"dolphin"
],
"locations": [
"https://server.example.net/",
"https://resource.local/other"
],
"datatypes": [
"metadata",
"images"
]
},
"read", "dolphin-metadata"
]
}
}
[[ See issue #103 (https://github.com/ietf-wg-gnap/gnap-core-
protocol/issues/103) ]]
6.2. Revoking the Access Token
If the client instance wishes to revoke the access token proactively,
such as when a user indicates to the client instance that they no
longer wish for it to have access or the client instance application
detects that it is being uninstalled, the client instance can use the
token management URI to indicate to the AS that the AS should
invalidate the access token for all purposes.
The client instance makes an HTTP DELETE request to the token
management URI, presenting the access token and signing the request
with the appropriate key.
DELETE /token/PRY5NM33OM4TB8N6BW7OZB8CDFONP219RP1L HTTP/1.1
Host: server.example.com
Authorization: GNAP OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0
Detached-JWS: eyj0....
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If the key presented is associated with the token (or the client
instance, in the case of a bearer token), the AS MUST invalidate the
access token, if possible, and return an HTTP 204 response code.
204 No Content
Though the AS MAY revoke an access token at any time for any reason,
the token management function is specifically for the client
instance's use. If the access token has already expired or has been
revoked through other means, the AS SHOULD honor the revocation
request to the token management URL as valid, since the end result is
still the token not being usable.
7. Securing Requests from the Client Instance
In GNAP, the client instance secures its requests to the AS and RS by
presenting an access token, presenting proof of a key that it
possesses, or both an access token and key proof together.
* When an access token is used with a key proof, this is a bound
token request. This type of request is used for calls to the RS
as well as the AS during negotiation.
* When a key proof is used with no access token, this is a non-
authorized signed request. This type of request is used for calls
to the AS to initiate a negotiation.
* When an access token is used with no key proof, this is a bearer
token request. This type of request is used only for calls to the
RS, and only with access tokens that are not bound to any key as
described in Section 3.2.1.
* When neither an access token nor key proof are used, this is an
unsecured request. This type of used only for calls to the RS
during a discovery phase as described in Section 10.4.
7.1. Key Formats
Several different places in GNAP require the presentation of key
material by value. Proof of this key material MUST be bound to a
request, the nature of which varies with the location in the protocol
the key is used. For a key used as part of a client instance's
initial request in Section 2.3, the key value is the client
instance's public key, and proof of that key MUST be presented in
that request. For a key used as part of an access token response in
Section 3.2.1, the proof of that key MUST be used when presenting the
access token.
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A key presented by value MUST be a public key in at least one
supported format. If a key is sent in multiple formats, all the key
format values MUST be equivalent. Note that while most formats
present the full value of the public key, some formats present a
value cryptographically derived from the public key.
proof (string) The form of proof that the client instance will use
when presenting the key. The valid values of this field and the
processing requirements for each are detailed in Section 7.3. The
"proof" field is REQUIRED.
jwk (object) Value of the public key as a JSON Web Key [RFC7517].
The object MUST contain an "alg" field which is used to validate
the signature. The object MUST contain the "kid" field to
identify the key.
cert (string) PEM serialized value of the certificate used to sign
the request, with optional internal whitespace per [RFC7468]. The
PEM header and footer are optionally removed.
cert#S256 (string) The certificate thumbprint calculated as per
OAuth-MTLS [RFC8705] in base64 URL encoding. Note that this
format does not include the full public key.
Additional key formats are defined in a registry TBD (Section 12).
This non-normative example shows a single key presented in multiple
formats. This key is intended to be used with the detached JWS
(Section 7.3.1) proofing mechanism, as indicated by the "proof"
field.
"key": {
"proof": "jwsd",
"jwk": {
"kty": "RSA",
"e": "AQAB",
"kid": "xyz-1",
"alg": "RS256",
"n": "kOB5rR4Jv0GMeLaY6_It_r3ORwdf8ci_JtffXyaSx8xY..."
},
"cert": "MIIEHDCCAwSgAwIBAgIBATANBgkqhkiG9w0BAQsFA..."
}
7.1.1. Key References
Keys in GNAP can also be passed by reference such that the party
receiving the reference will be able to determine the appropriate
keying material for use in that part of the protocol.
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"key": "S-P4XJQ_RYJCRTSU1.63N3E"
Keys referenced in this manner MAY be shared symmetric keys. The key
reference MUST NOT contain any unencrypted private or shared
symmetric key information.
Keys referenced in this manner MUST be bound to a single proofing
mechanism.
The means of dereferencing this value are out of scope for this
specification.
7.2. Presenting Access Tokens
The method the client instance uses to send an access token depends
on whether the token is bound to a key, and if so which proofing
method is associated with the key. This information is conveyed in
the "key" and "proof" parameters in the access token response
(Section 3.2.1).
If the "key" value is the boolean "false", the access token is a
bearer token sent using the HTTP Header method defined in [RFC6750].
Authorization: Bearer OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0
The form parameter and query parameter methods of [RFC6750] MUST NOT
be used.
If the "key" value is the boolean "true", the access token MUST be
sent using the same key and proofing mechanism that the client
instance used in its initial request (or its most recent rotation).
If the "key" value is an object as described in Section 7.1, the
value of the "proof" field within the key indicates the particular
proofing mechanism to use. The access token is sent using the HTTP
authorization scheme "GNAP" along with a key proof as described in
Section 7.3 for the key bound to the access token. For example, a
"jwsd"-bound access token is sent as follows:
Authorization: GNAP OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0
Detached-JWS: eyj0....
[[ See issue #104 (https://github.com/ietf-wg-gnap/gnap-core-
protocol/issues/104) ]]
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7.3. Proving Possession of a Key with a Request
Any keys presented by the client instance to the AS or RS MUST be
validated as part of the request in which they are presented. The
type of binding used is indicated by the proof parameter of the key
object in Section 7.1. Values defined by this specification are as
follows:
jwsd A detached JWS signature header
jws Attached JWS payload
mtls Mutual TLS certificate verification
dpop OAuth Demonstration of Proof-of-Possession key proof header
httpsig HTTP Signing signature header
oauthpop OAuth PoP key proof authentication header
Additional proofing methods are defined by a registry TBD
(Section 12).
All key binding methods used by this specification MUST cover all
relevant portions of the request, including anything that would
change the nature of the request, to allow for secure validation of
the request by the AS. Relevant aspects include the URI being
called, the HTTP method being used, any relevant HTTP headers and
values, and the HTTP message body itself. The recipient of the
signed message MUST validate all components of the signed message to
ensure that nothing has been tampered with or substituted in a way
that would change the nature of the request.
When a key proofing mechanism is bound to an access token, the access
token MUST be covered by the signature method of the proofing
mechanism.
When used for delegation in GNAP, these key binding mechanisms allow
the AS to ensure that the keys presented by the client instance in
the initial request are in control of the party calling any follow-up
or continuation requests. To facilitate this requirement, the
continuation response (Section 3.1) includes an access token bound to
the client instance's key (Section 2.3), and that key (or its most
recent rotation) MUST be proved in all continuation requests
Section 5. Token management requests Section 6 are similarly bound
to either the access token's own key or, in the case of bearer
tokens, the client instance's key.
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[[ See issue #105 (https://github.com/ietf-wg-gnap/gnap-core-
protocol/issues/105) ]]
7.3.1. Detached JWS
This method is indicated by "jwsd" in the "proof" field. A JWS
[RFC7515] signature object is created as follows:
The header of the JWS MUST contain the "kid" field of the key bound
to this client instance for this request. The JWS header MUST
contain an "alg" field appropriate for the key identified by kid and
MUST NOT be "none". The "b64" field MUST be set to "false" and the
"crit" field MUST contain at least "b64" as specified in [RFC7797]
To protect the request, the JWS header MUST contain the following
additional fields.
htm (string) The HTTP Method used to make this request, as an
uppercase ASCII string.
htu (string) The HTTP URI used for this request, including all path
and query components.
ts (integer) A timestamp of the request in integer seconds
at_hash (string) When to bind a request to an access token, the
access token hash value. Its value is the base64url encoding of
the left-most half of the hash of the octets of the ASCII
representation of the "access_token" value, where the hash
algorithm used is the hash algorithm used in the "alg" header
parameter of the JWS's JOSE Header. For instance, if the "alg" is
"RS256", hash the "access_token" value with SHA-256, then take the
left-most 128 bits and base64url encode them.
The payload of the JWS object is the serialized body of the request,
and the object is signed according to detached JWS [RFC7797].
The client instance presents the signature in the Detached-JWS HTTP
Header field.
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POST /tx HTTP/1.1
Host: server.example.com
Content-Type: application/json
Detached-JWS: eyJiNjQiOmZhbHNlLCJhbGciOiJSUzI1NiIsImtpZCI6Inh5ei0xIn0.
.Y287HMtaY0EegEjoTd_04a4GC6qV48GgVbGKOhHdJnDtD0VuUlVjLfwne8AuUY3U7e8
9zUWwXLnAYK_BiS84M8EsrFvmv8yDLWzqveeIpcN5_ysveQnYt9Dqi32w6IOtAywkNUD
ZeJEdc3z5s9Ei8qrYFN2fxcu28YS4e8e_cHTK57003WJu-wFn2TJUmAbHuqvUsyTb-nz
YOKxuCKlqQItJF7E-cwSb_xULu-3f77BEU_vGbNYo5ZBa2B7UHO-kWNMSgbW2yeNNLbL
C18Kv80GF22Y7SbZt0e2TwnR2Aa2zksuUbntQ5c7a1-gxtnXzuIKa34OekrnyqE1hmVW
peQ
{
"access_token": {
"access": [
"dolphin-metadata"
]
},
"interact": {
"start": ["redirect"],
"finish": {
"method": "redirect",
"uri": "https://client.foo",
"nonce": "VJLO6A4CAYLBXHTR0KRO"
}
},
"client": {
"proof": "jwsd",
"key": {
"jwk": {
"kty": "RSA",
"e": "AQAB",
"kid": "xyz-1",
"alg": "RS256",
"n": "kOB5rR4Jv0GMeLaY6_It_r3ORwdf8ci_JtffXyaSx8
xYJCNaOKNJn_Oz0YhdHbXTeWO5AoyspDWJbN5w_7bdWDxgpD-y6jnD1u9YhBOCWObNPF
vpkTM8LC7SdXGRKx2k8Me2r_GssYlyRpqvpBlY5-ejCywKRBfctRcnhTTGNztbbDBUyD
SWmFMVCHe5mXT4cL0BwrZC6S-uu-LAx06aKwQOPwYOGOslK8WPm1yGdkaA1uF_FpS6LS
63WYPHi_Ap2B7_8Wbw4ttzbMS_doJvuDagW8A1Ip3fXFAHtRAcKw7rdI4_Xln66hJxFe
kpdfWdiPQddQ6Y1cK2U3obvUg7w"
}
}
"display": {
"name": "My Client Display Name",
"uri": "https://example.net/client"
},
}
}
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If the request being made does not have a message body, such as an
HTTP GET, OPTIONS, or DELETE method, the JWS signature is calculated
over an empty payload.
When the server (AS or RS) receives the Detached-JWS header, it MUST
parse its contents as a detached JWS object. The HTTP Body is used
as the payload for purposes of validating the JWS, with no
transformations.
7.3.2. Attached JWS
This method is indicated by "jws" in the "proof" field. A JWS
[RFC7515] signature object is created as follows:
The header of the JWS MUST contain the "kid" field of the key bound
to this client instance for this request. The JWS header MUST
contain an "alg" field appropriate for the key identified by "kid"
and MUST NOT be "none".
To protect the request, the JWS header MUST contain the following
additional fields.
htm (string) The HTTP Method used to make this request, as an
uppercase ASCII string.
htu (string) The HTTP URI used for this request, including all path
and query components.
ts (integer) A timestamp of the request in integer seconds
at_hash (string) When to bind a request to an access token, the
access token hash value. Its value is the base64url encoding of
the left-most half of the hash of the octets of the ASCII
representation of the "access_token" value, where the hash
algorithm used is the hash algorithm used in the "alg" header
parameter of the JWS's JOSE Header. For instance, if the "alg" is
"RS256", hash the "access_token" value with SHA-256, then take the
left-most 128 bits and base64url encode them.
The payload of the JWS object is the JSON serialized body of the
request, and the object is signed according to JWS and serialized
into compact form [RFC7515].
The client instance presents the JWS as the body of the request along
with a content type of "application/jose". The AS MUST extract the
payload of the JWS and treat it as the request body for further
processing.
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POST /tx HTTP/1.1
Host: server.example.com
Content-Type: application/jose
eyJhbGciOiJSUzI1NiIsImtpZCI6IktBZ05wV2JSeXk5T
WYycmlrbDQ5OExUaE1ydmtiWldIVlNRT0JDNFZIVTQiLC
JodG0iOiJwb3N0IiwiaHR1IjoiL3R4IiwidHMiOjE2MDM
4MDA3ODN9.eyJjYXBhYmlsaXRpZXMiOltdLCJjbGllbnQ
iOnsia2V5Ijp7Imp3ayI6eyJrdHkiOiJSU0EiLCJlIjoi
QVFBQiIsImtpZCI6IktBZ05wV2JSeXk5TWYycmlrbDQ5O
ExUaE1ydmtiWldIVlNRT0JDNFZIVTQiLCJuIjoibGxXbU
hGOFhBMktOTGRteE9QM2t4RDlPWTc2cDBTcjM3amZoejk
0YTkzeG0yRk5xb1NQY1JaQVBkMGxxRFM4TjNVaWE1M2RC
MjNaNTlPd1k0YnBNX1ZmOEdKdnZwdExXbnhvMVB5aG1Qc
i1lY2RTQ1JRZFRjX1pjTUY0aFJWNDhxcWx2dUQwbXF0Y0
RiSWtTQkR2Y2NKbVpId2ZUcERIaW5UOHR0dmNWUDhWa0F
NQXE0a1ZhenhPcE1vSVJzb3lFcF9lQ2U1cFN3cUhvMGRh
Q1dOS1ItRXBLbTZOaU90ZWRGNE91bXQ4TkxLVFZqZllnR
khlQkRkQ2JyckVUZDR2Qk13RHRBbmpQcjNDVkN3d3gyYk
FRVDZTbHhGSjNmajJoaHlJcHE3cGM4clppYjVqTnlYS3d
mQnVrVFZZWm96a3NodC1Mb2h5QVNhS3BZVHA4THROWi13
In0sInByb29mIjoiandzIn0sIm5hbWUiOiJNeUZpcnN0Q
2xpZW50IiwidXJpIjoiaHR0cDovL2xvY2FsaG9zdC9jbG
llbnQvY2xpZW50SUQifSwiaW50ZXJhY3QiOnsic3RhcnQ
iOlsicmVkaXJlY3QiXSwiZmluaXNoIjp7Im1ldGhvZCI6
InJlZGlyZWN0Iiwibm9uY2UiOiJkOTAyMTM4ODRiODQwO
TIwNTM4YjVjNTEiLCJ1cmkiOiJodHRwOi8vbG9jYWxob3
N0L2NsaWVudC9yZXF1ZXN0LWRvbmUifX0sImFjY2Vzc19
0b2tlbiI6eyJhY2Nlc3MiOlt7ImFjdGlvbnMiOlsicmVh
ZCIsInByaW50Il0sImxvY2F0aW9ucyI6WyJodHRwOi8vb
G9jYWxob3N0L3Bob3RvcyJdLCJ0eXBlIjoicGhvdG8tYX
BpIn1dfSwic3ViamVjdCI6eyJzdWJfaWRzIjpbImlzc19
zdWIiLCJlbWFpbCJdfX0.LUyZ8_fERmxbYARq8kBYMwzc
d8GnCAKAlo2ZSYLRRNAYWPrp2XGLJOvg97WK1idf_LB08
OJmLVsCXxCvn9mgaAkYNL_ZjHcusBvY1mNo0E1sdTEr31
CVKfC-6WrZCscb8YqE4Ayhh0Te8kzSng3OkLdy7xN4xeK
uHzpF7yGsM52JZ0cBcTo6WrYEfGdr08AWQJ59ht72n3jT
smYNy9A6I4Wrvfgj3TNxmwYojpBAicfjnzA1UVcNm9F_x
iSz1_y2tdH7j5rVqBMQife-k9Ewk95vr3lurthenliYSN
iUinVfoW1ybnaIBcTtP1_YCxg_h1y-B5uZEvYNGCuoCqa
6IQ
This example's JWS header decodes to:
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{
"alg": "RS256",
"kid": "KAgNpWbRyy9Mf2rikl498LThMrvkbZWHVSQOBC4VHU4",
"htm": "POST",
"htu": "https://server.example.com/tx",
"ts": 1603800783
}
And the JWS body decodes to:
{
"capabilities": [],
"client": {
"key": {
"jwk": {
"kty": "RSA",
"e": "AQAB",
"kid": "KAgNpWbRyy9Mf2rikl498LThMrvkbZWHVSQOBC4VHU4",
"n": "llWmHF8XA2KNLdmxOP3kxD9OY76p0Sr37jfhz94a93xm2FNqoSPc
RZAPd0lqDS8N3Uia53dB23Z59OwY4bpM_Vf8GJvvptLWnxo1PyhmPr-ecd
SCRQdTc_ZcMF4hRV48qqlvuD0mqtcDbIkSBDvccJmZHwfTpDHinT8ttvcV
P8VkAMAq4kVazxOpMoIRsoyEp_eCe5pSwqHo0daCWNKR-EpKm6NiOtedF4
Oumt8NLKTVjfYgFHeBDdCbrrETd4vBMwDtAnjPr3CVCwwx2bAQT6SlxFJ3
fj2hhyIpq7pc8rZib5jNyXKwfBukTVYZozksht-LohyASaKpYTp8LtNZ-w"
},
"proof": "jws"
},
"name": "My First Client",
"uri": "http://localhost/client/clientID"
},
"interact": {
"start": ["redirect"],
"finish": {
"method": "redirect",
"nonce": "d90213884b840920538b5c51",
"uri": "http://localhost/client/request-done"
}
},
"access_token": {
"access": [
{
"actions": [
"read",
"print"
],
"locations": [
"http://localhost/photos"
],
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"type": "photo-api"
}
]
}
"subject": {
"sub_ids": [
"iss_sub",
"email"
]
}
}
If the request being made does not have a message body, such as an
HTTP GET, OPTIONS, or DELETE method, the JWS signature is calculated
over an empty payload and passed in the "Detached-JWS" header as
described in Section 7.3.1.
[[ See issue #109 (https://github.com/ietf-wg-gnap/gnap-core-
protocol/issues/109) ]]
7.3.3. Mutual TLS
This method is indicated by "mtls" in the "proof" field. The client
instance presents its TLS client certificate during TLS negotiation
with the server (either AS or RS). The AS or RS takes the thumbprint
of the TLS client certificate presented during mutual TLS negotiation
and compares that thumbprint to the thumbprint presented by the
client instance application as described in [RFC8705] section 3.
POST /tx HTTP/1.1
Host: server.example.com
Content-Type: application/json
SSL_CLIENT_CERT: MIIEHDCCAwSgAwIBAgIBATANBgkqhkiG9w0BAQsFADCBmjE3MDUGA1UEAwwuQmVz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Y2xpZW50LmxvY2FsMA0GCSqGSIb3DQEBCwUAA4IBAQCKKv8WlLrT4Z5NazaUrYtl
TF+2v0tvZBQ7qzJQjlOqAcvxry/d2zyhiRCRS/v318YCJBEv4Iq2W3I3JMMyAYEe
2573HzT7rH3xQP12yZyRQnetdiVM1Z1KaXwfrPDLs72hUeELtxIcfZ0M085jLboX
hufHI6kqm3NCyCCTihe2ck5RmCc5l2KBO/vAHF0ihhFOOOby1v6qbPHQcxAU6rEb
907/p6BW/LV1NCgYB1QtFSfGxowqb9FRIMD2kvMSmO0EMxgwZ6k6spa+jk0IsI3k
lwLW9b+Tfn/daUbIDctxeJneq2anQyU2znBgQl6KILDSF4eaOqlBut/KNZHHazJh
{
"access_token": {
"access": [
"dolphin-metadata"
]
},
"interact": {
"start": ["redirect"],
"finish": {
"method": "redirect",
"uri": "https://client.foo",
"nonce": "VJLO6A4CAYLBXHTR0KRO"
}
},
"client": {
"display": {
"name": "My Client Display Name",
"uri": "https://example.net/client"
},
"key": {
"proof": "mtls",
"cert": "MIIEHDCCAwSgAwIBAgIBATANBgkqhkiG9w0BAQsFADCBmjE3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/p6BW/LV1NCgYB1QtFSfGxowqb9FRIMD2kvMSmO0EMxgwZ6k6spa+jk0IsI3klwLW
9b+Tfn/daUbIDctxeJneq2anQyU2znBgQl6KILDSF4eaOqlBut/KNZHHazJh"
}
}
[[ See issue #110 (https://github.com/ietf-wg-gnap/gnap-core-
protocol/issues/110) ]]
7.3.4. Demonstration of Proof-of-Possession (DPoP)
This method is indicated by "dpop" in the "proof" field. The client
instance creates a Demonstration of Proof-of-Possession signature
header as described in [I-D.ietf-oauth-dpop] section 2. In addition
to the required fields, the DPoP body MUST also contain a digest of
the request body:
digest (string) Digest of the request body as the value of the
Digest header defined in [RFC3230].
POST /tx HTTP/1.1
Host: server.example.com
Content-Type: application/json
DPoP: eyJ0eXAiOiJkcG9wK2p3dCIsImFsZyI6IlJTMjU2IiwiandrIjp7Imt0eSI6Il
JTQSIsImUiOiJBUUFCIiwia2lkIjoieHl6LWNsaWVudCIsImFsZyI6IlJTMjU2Iiwibi
I6Inp3Q1RfM2J4LWdsYmJIcmhlWXBZcFJXaVk5SS1uRWFNUnBablJySWpDczZiX2VteV
RrQmtEREVqU3lzaTM4T0M3M2hqMS1XZ3hjUGRLTkdaeUlvSDNRWmVuMU1LeXloUXBMSk
cxLW9MTkxxbTdwWFh0ZFl6U2RDOU8zLW9peXk4eWtPNFlVeU5aclJSZlBjaWhkUUNiT1
9PQzhRdWdtZzlyZ05ET1NxcHBkYU5lYXMxb3Y5UHhZdnhxcnoxLThIYTdna0QwMFlFQ1
hIYUIwNXVNYVVhZEhxLU9fV0l2WVhpY2c2STVqNlM0NFZOVTY1VkJ3dS1BbHluVHhRZE
1BV1AzYll4VlZ5NnAzLTdlVEpva3ZqWVRGcWdEVkRaOGxVWGJyNXlDVG5SaG5oSmd2Zj
NWakRfbWFsTmU4LXRPcUs1T1NEbEhUeTZnRDlOcWRHQ20tUG0zUSJ9fQ.eyJodHRwX21
ldGhvZCI6IlBPU1QiLCJodHRwX3VyaSI6Imh0dHA6XC9cL2hvc3QuZG9ja2VyLmludGV
ybmFsOjk4MzRcL2FwaVwvYXNcL3RyYW5zYWN0aW9uIiwiaWF0IjoxNTcyNjQyNjEzLCJ
qdGkiOiJIam9IcmpnbTJ5QjR4N2pBNXl5RyJ9.aUhftvfw2NoW3M7durkopReTvONng1
fOzbWjAlKNSLL0qIwDgfG39XUyNvwQ23OBIwe6IuvTQ2UBBPklPAfJhDTKd8KHEAfidN
B-LzUOzhDetLg30yLFzIpcEBMLCjb0TEsmXadvxuNkEzFRL-Q-QCg0AXSF1h57eAqZV8
SYF4CQK9OUV6fIWwxLDd3cVTx83MgyCNnvFlG_HDyim1Xx-rxV4ePd1vgDeRubFb6QWj
iKEO7vj1APv32dsux67gZYiUpjm0wEZprjlG0a07R984KLeK1XPjXgViEwEdlirUmpVy
T9tyEYqGrTfm5uautELgMls9sgSyE929woZ59elg
{
"access_token": {
"access": [
"dolphin-metadata"
]
},
"interact": {
"start": ["redirect"],
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"finish": {
"method": "redirect",
"uri": "https://client.foo",
"nonce": "VJLO6A4CAYLBXHTR0KRO"
}
},
"client": {
"display": {
"name": "My Client Display Name",
"uri": "https://example.net/client"
},
"proof": "dpop",
"key": {
"jwk": {
"kty": "RSA",
"e": "AQAB",
"kid": "xyz-1",
"alg": "RS256",
"n": "kOB5rR4Jv0GMeLaY6_It_r3ORwdf8ci_JtffXyaSx8xYJ
CCNaOKNJn_Oz0YhdHbXTeWO5AoyspDWJbN5w_7bdWDxgpD-y6jnD1u9YhBOCWObNPFvpkTM
8LC7SdXGRKx2k8Me2r_GssYlyRpqvpBlY5-ejCywKRBfctRcnhTTGNztbbDBUyDSWmFMVCH
e5mXT4cL0BwrZC6S-uu-LAx06aKwQOPwYOGOslK8WPm1yGdkaA1uF_FpS6LS63WYPHi_Ap2
B7_8Wbw4ttzbMS_doJvuDagW8A1Ip3fXFAHtRAcKw7rdI4_Xln66hJxFekpdfWdiPQddQ6Y
1cK2U3obvUg7w"
}
}
}
}
7.3.5. HTTP Message Signing
This method is indicated by "httpsig" in the "proof" field. The
client instance creates an HTTP Signature header as described in
[I-D.ietf-httpbis-message-signatures] section 4. The client instance
MUST calculate and present the Digest header as defined in [RFC3230]
and include this header in the signature.
POST /tx HTTP/1.1
Host: server.example.com
Content-Type: application/json
Content-Length: 716
Signature: keyId="xyz-client", algorithm="rsa-sha256",
headers="(request-target) digest content-length",
signature="TkehmgK7GD/z4jGkmcHS67cjVRgm3zVQNlNrrXW32Wv7d
u0VNEIVI/dMhe0WlHC93NP3ms91i2WOW5r5B6qow6TNx/82/6W84p5jqF
YuYfTkKYZ69GbfqXkYV9gaT++dl5kvZQjVk+KZT1dzpAzv8hdk9nO87Xi
rj7qe2mdAGE1LLc3YvXwNxuCQh82sa5rXHqtNT1077fiDvSVYeced0UEm
rWwErVgr7sijtbTohC4FJLuJ0nG/KJUcIG/FTchW9rd6dHoBnY43+3Dzj
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CIthXpdH5u4VX3TBe6GJDO6Mkzc6vB+67OWzPwhYTplUiFFV6UZCsDEeu
Sa/Ue1yLEAMg=="]}
Digest: SHA=oZz2O3kg5SEFAhmr0xEBbc4jEfo=
{
"access_token": {
"access": [
"dolphin-metadata"
]
},
"interact": {
"start": ["redirect"],
"finish": {
"method": "push",
"uri": "https://client.foo",
"nonce": "VJLO6A4CAYLBXHTR0KRO"
}
},
"client": {
"display": {
"name": "My Client Display Name",
"uri": "https://example.net/client"
},
"proof": "httpsig",
"key": {
"jwk": {
"kty": "RSA",
"e": "AQAB",
"kid": "xyz-1",
"alg": "RS256",
"n": "kOB5rR4Jv0GMeLaY6_It_r3ORwdf8ci_J
tffXyaSx8xYJCCNaOKNJn_Oz0YhdHbXTeWO5AoyspDWJbN5w_7bdWDxgpD-
y6jnD1u9YhBOCWObNPFvpkTM8LC7SdXGRKx2k8Me2r_GssYlyRpqvpBlY5-
ejCywKRBfctRcnhTTGNztbbDBUyDSWmFMVCHe5mXT4cL0BwrZC6S-uu-LAx
06aKwQOPwYOGOslK8WPm1yGdkaA1uF_FpS6LS63WYPHi_Ap2B7_8Wbw4ttz
bMS_doJvuDagW8A1Ip3fXFAHtRAcKw7rdI4_Xln66hJxFekpdfWdiPQddQ6
Y1cK2U3obvUg7w"
}
}
}
}
When used to present an access token as in Section 7.2, the
Authorization header MUST be included in the signature.
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7.3.6. OAuth Proof of Possession (PoP)
This method is indicated by "oauthpop" in the "proof" field. The
client instance creates an HTTP Authorization PoP header as described
in [I-D.ietf-oauth-signed-http-request] section 4, with the following
additional requirements:
* The "at" (access token) field MUST be omitted unless this method
is being used in conjunction with an access token as in
Section 7.2. [[ See issue #112 (https://github.com/ietf-wg-gnap/
gnap-core-protocol/issues/112) ]]
* The "b" (body hash) field MUST be calculated and supplied, unless
there is no entity body (such as a GET, OPTIONS, or DELETE
request).
* All components of the URL MUST be calculated and supplied
* The m (method) field MUST be supplied
POST /tx HTTP/1.1
Host: server.example.com
Content-Type: application/json
PoP: eyJhbGciOiJSUzI1NiIsImp3ayI6eyJrdHkiOiJSU0EiLCJlIjoi
QVFBQiIsImtpZCI6Inh5ei1jbGllbnQiLCJhbGciOiJSUzI1NiIsIm4iO
iJ6d0NUXzNieC1nbGJiSHJoZVlwWXBSV2lZOUktbkVhTVJwWm5ScklqQ3
M2Yl9lbXlUa0JrRERFalN5c2kzOE9DNzNoajEtV2d4Y1BkS05HWnlJb0g
zUVplbjFNS3l5aFFwTEpHMS1vTE5McW03cFhYdGRZelNkQzlPMy1vaXl5
OHlrTzRZVXlOWnJSUmZQY2loZFFDYk9fT0M4UXVnbWc5cmdORE9TcXBwZ
GFOZWFzMW92OVB4WXZ4cXJ6MS04SGE3Z2tEMDBZRUNYSGFCMDV1TWFVYW
RIcS1PX1dJdllYaWNnNkk1ajZTNDRWTlU2NVZCd3UtQWx5blR4UWRNQVd
QM2JZeFZWeTZwMy03ZVRKb2t2allURnFnRFZEWjhsVVhicjV5Q1RuUmhu
aEpndmYzVmpEX21hbE5lOC10T3FLNU9TRGxIVHk2Z0Q5TnFkR0NtLVBtM
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lPYkdOeERhZVBTZnc3NnFjamtqSXNFRmxDb3g5bTU5NFM0M0RkU0xBIiw
idSI6Imhvc3QuZG9ja2VyLmludGVybmFsIiwiaCI6W1siQWNjZXB0Iiwi
Q29udGVudC1UeXBlIiwiQ29udGVudC1MZW5ndGgiXSwiVjQ2OUhFWGx6S
k9kQTZmQU5oMmpKdFhTd3pjSGRqMUloOGk5M0h3bEVHYyJdLCJtIjoiUE
9TVCIsInRzIjoxNTcyNjQyNjEwfQ.xyQ47qy8bu4fyK1T3Ru1Sway8wp6
5rfAKnTQQU92AUUU07I2iKoBL2tipBcNCC5zLH5j_WUyjlN15oi_lLHym
fPdzihtt8_Jibjfjib5J15UlifakjQ0rHX04tPal9PvcjwnyZHFcKn-So
Y3wsARn-gGwxpzbsPhiKQP70d2eG0CYQMA6rTLslT7GgdQheelhVFW29i
27NcvqtkJmiAG6Swrq4uUgCY3zRotROkJ13qo86t2DXklV-eES4-2dCxf
cWFkzBAr6oC4Qp7HnY_5UT6IWkRJt3efwYprWcYouOVjtRan3kEtWkaWr
G0J4bPVnTI5St9hJYvvh7FE8JirIg
{
"access_token": {
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"access": [
"dolphin-metadata"
]
},
"interact": {
"redirect": true,
"callback": {
"method": "redirect",
"uri": "https://client.foo",
"nonce": "VJLO6A4CAYLBXHTR0KRO"
}
},
"client": {
"display": {
"name": "My Client Display Name",
"uri": "https://example.net/client"
},
"proof": "oauthpop",
"key": {
"jwk": {
"kty": "RSA",
"e": "AQAB",
"kid": "xyz-1",
"alg": "RS256",
"n": "kOB5rR4Jv0GMeLaY6_It_r3ORwdf8ci_J
tffXyaSx8xYJCCNaOKNJn_Oz0YhdHbXTeWO5AoyspDWJbN5w_7bdWDxgpD-
y6jnD1u9YhBOCWObNPFvpkTM8LC7SdXGRKx2k8Me2r_GssYlyRpqvpBlY5-
ejCywKRBfctRcnhTTGNztbbDBUyDSWmFMVCHe5mXT4cL0BwrZC6S-uu-LAx
06aKwQOPwYOGOslK8WPm1yGdkaA1uF_FpS6LS63WYPHi_Ap2B7_8Wbw4ttz
bMS_doJvuDagW8A1Ip3fXFAHtRAcKw7rdI4_Xln66hJxFekpdfWdiPQddQ6
Y1cK2U3obvUg7w"
}
}
}
}
[[ See issue #113 (https://github.com/ietf-wg-gnap/gnap-core-
protocol/issues/113) ]]
8. Resource Access Rights
GNAP provides a rich structure for describing the protected resources
hosted by RSs and accessed by client software. This structure is
used when the client instance requests an access token (Section 2.1)
and when an access token is returned (Section 3.2).
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The root of this structure is a JSON array. The elements of the JSON
array represent rights of access that are associated with the the
access token. The resulting access is the union of all elements
within the array.
The access associated with the access token is described using
objects that each contain multiple dimensions of access. Each object
contains a REQUIRED "type" property that determines the type of API
that the token is used for.
type (string) The type of resource request as a string. This field
MAY define which other fields are allowed in the request object.
This field is REQUIRED.
The value of the "type" field is under the control of the AS. This
field MUST be compared using an exact byte match of the string value
against known types by the AS. The AS MUST ensure that there is no
collision between different authorization data types that it
supports. The AS MUST NOT do any collation or normalization of data
types during comparison. It is RECOMMENDED that designers of
general-purpose APIs use a URI for this field to avoid collisions
between multiple API types protected by a single AS.
While it is expected that many APIs will have its own properties, a
set of common properties are defined here. Specific API
implementations SHOULD NOT re-use these fields with different
semantics or syntax. The available values for these properties are
determined by the API being protected at the RS.
actions (array of strings) The types of actions the client instance
will take at the RS as an array of strings. For example, a client
instance asking for a combination of "read" and "write" access.
locations (array of strings) The location of the RS as an array of
strings. These strings are typically URIs identifying the
location of the RS.
datatypes (array of strings) The kinds of data available to the
client instance at the RS's API as an array of strings. For
example, a client instance asking for access to raw "image" data
and "metadata" at a photograph API.
identifier (string) A string identifier indicating a specific
resource at the RS. For example, a patient identifier for a
medical API or a bank account number for a financial API.
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The following non-normative example is describing three kinds of
access (read, write, delete) to each of two different locations and
two different data types (metadata, images) for a single access token
using the fictitious "photo-api" type definition.
"access": [
{
"type": "photo-api",
"actions": [
"read",
"write",
"delete"
],
"locations": [
"https://server.example.net/",
"https://resource.local/other"
],
"datatypes": [
"metadata",
"images"
]
}
]
The access requested for a given object when using these fields is
the cross-product of all fields of the object. That is to say, the
object represents a request for all "action" values listed within the
object to be used at all "locations" values listed within the object
for all "datatype" values listed within the object. Assuming the
request above was granted, the client instance could assume that it
would be able to do a "read" action against the "images" on the first
server as well as a "delete" action on the "metadata" of the second
server, or any other combination of these fields, using the same
access token.
To request a different combination of access, such as requesting one
"action" against one "location" and a different "action" against a
different "location", the client instance can include multiple
separate objects in the "resources" array. The following non-
normative example uses the same fictitious "photo-api" type
definition to request a single access token with more specifically
targeted access rights by using two discrete objects within the
request.
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"access": [
{
"type": "photo-api",
"actions": [
"read"
],
"locations": [
"https://server.example.net/"
],
"datatypes": [
"images"
]
},
{
"type": "photo-api",
"actions": [
"write",
"delete"
],
"locations": [
"https://resource.local/other"
],
"datatypes": [
"metadata"
]
}
]
The access requested here is for "read" access to "images" on one
server while simultaneously requesting "write" and "delete" access
for "metadata" on a different server, but importantly without
requesting "write" or "delete" access to "images" on the first
server.
It is anticipated that API designers will use a combination of common
fields defined in this specification as well as fields specific to
the API itself. The following non-normative example shows the use of
both common and API-specific fields as part of two different
fictitious API "type" values. The first access request includes the
"actions", "locations", and "datatypes" fields specified here as well
as the API-specific "geolocation" field. The second access request
includes the "actions" and "identifier" fields specified here as well
as the API-specific "currency" field.
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"access": [
{
"type": "photo-api",
"actions": [
"read",
"write"
],
"locations": [
"https://server.example.net/",
"https://resource.local/other"
],
"datatypes": [
"metadata",
"images"
],
"geolocation": [
{ lat: -32.364, lng: 153.207 },
{ lat: -35.364, lng: 158.207 }
]
},
{
"type": "financial-transaction",
"actions": [
"withdraw"
],
"identifier": "account-14-32-32-3",
"currency": "USD"
}
]
If this request is approved, the resulting access token
(Section 3.2.1)'s access rights will be the union of the requested
types of access for each of the two APIs, just as above.
8.1. Requesting Resources By Reference
Instead of sending an object describing the requested resource
(Section 8), access rights MAY be communicated as a string known to
the AS or RS representing the access being requested. Each string
SHOULD correspond to a specific expanded object representation at the
AS.
"access": [
"read", "dolphin-metadata", "some other thing"
]
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This value is opaque to the client instance and MAY be any valid JSON
string, and therefore could include spaces, unicode characters, and
properly escaped string sequences. However, in some situations the
value is intended to be seen and understood by the client software's
developer. In such cases, the API designer choosing any such human-
readable strings SHOULD take steps to ensure the string values are
not easily confused by a developer, such as by limiting the strings
to easily disambiguated characters.
This functionality is similar in practice to OAuth 2's "scope"
parameter [RFC6749], where a single string represents the set of
access rights requested by the client instance. As such, the
reference string could contain any valid OAuth 2 scope value as in
Appendix C.5. Note that the reference string here is not bound to
the same character restrictions as in OAuth 2's "scope" definition.
A single "access" array MAY include both object-type and string-type
resource items. In this non-normative example, the client instance
is requesting access to a "photo-api" and "financial-transaction" API
type as well as the reference values of "read", "dolphin-metadata",
and "some other thing".
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"access": [
{
"type": "photo-api",
"actions": [
"read",
"write",
"delete"
],
"locations": [
"https://server.example.net/",
"https://resource.local/other"
],
"datatypes": [
"metadata",
"images"
]
},
"read",
"dolphin-metadata",
{
"type": "financial-transaction",
"actions": [
"withdraw"
],
"identifier": "account-14-32-32-3",
"currency": "USD"
},
"some other thing"
]
The requested access is the union of all elements of the array,
including both objects and reference strings.
9. Discovery
By design, the protocol minimizes the need for any pre-flight
discovery. To begin a request, the client instance only needs to
know the endpoint of the AS and which keys it will use to sign the
request. Everything else can be negotiated dynamically in the course
of the protocol.
However, the AS can have limits on its allowed functionality. If the
client instance wants to optimize its calls to the AS before making a
request, it MAY send an HTTP OPTIONS request to the grant request
endpoint to retrieve the server's discovery information. The AS MUST
respond with a JSON document containing the following information:
grant_request_endpoint (string) REQUIRED. The full URL of the AS's
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grant request endpoint. This MUST match the URL the client
instance used to make the discovery request.
capabilities (array of strings) OPTIONAL. A list of the AS's
capabilities. The values of this result MAY be used by the client
instance in the capabilities section (Section 2.6) of the request.
interaction_methods (array of strings) OPTIONAL. A list of the AS's
interaction methods. The values of this list correspond to the
possible fields in the interaction section (Section 2.5) of the
request.
key_proofs (array of strings) OPTIONAL. A list of the AS's
supported key proofing mechanisms. The values of this list
correspond to possible values of the "proof" field of the key
section (Section 7.1) of the request.
sub_ids (array of strings) OPTIONAL. A list of the AS's supported
identifiers. The values of this list correspond to possible
values of the subject identifier section (Section 2.2) of the
request.
assertions (array of strings) OPTIONAL. A list of the AS's
supported assertion formats. The values of this list correspond
to possible values of the subject assertion section (Section 2.2)
of the request.
The information returned from this method is for optimization
purposes only. The AS MAY deny any request, or any portion of a
request, even if it lists a capability as supported. For example, a
given client instance can be registered with the "mtls" key proofing
mechanism, but the AS also returns other proofing methods, then the
AS will deny a request from that client instance using a different
proofing mechanism.
10. Resource Servers
In some deployments, a resource server will need to be able to call
the AS for a number of functions.
[[ See issue #114 (https://github.com/ietf-wg-gnap/gnap-core-
protocol/issues/114) ]]
10.1. Introspecting a Token
When the RS receives an access token, it can call the introspection
endpoint at the AS to get token information. [[ See issue #115
(https://github.com/ietf-wg-gnap/gnap-core-protocol/issues/115) ]]
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+--------+ +------+ +------+
| Client |--(1)->| RS | | AS |
|Instance| | |--(2)->| |
| | | |<-(3)--| |
| | | | +------+
| |<-(4)--| |
+--------+ +------+
1. The client instance calls the RS with its access token.
2. The RS introspects the access token value at the AS. The RS
signs the request with its own key (not the client instance's key
or the token's key).
3. The AS validates the token value and the client instance's
request and returns the introspection response for the token.
4. The RS fulfills the request from the client instance.
The RS signs the request with its own key and sends the access token
as the body of the request.
POST /introspect HTTP/1.1
Host: server.example.com
Content-Type: application/json
Detached-JWS: ejy0...
{
"access_token": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
}
The AS responds with a data structure describing the token's current
state and any information the RS would need to validate the token's
presentation, such as its intended proofing mechanism and key
material.
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Content-Type: application/json
{
"active": true,
"access": [
"dolphin-metadata", "some other thing"
],
"client": {
"key": {
"proof": "httpsig",
"jwk": {
"kty": "RSA",
"e": "AQAB",
"kid": "xyz-1",
"alg": "RS256",
"n": "kOB5rR4Jv0GMeL...."
}
}
}
}
10.2. Deriving a downstream token
Some architectures require an RS to act as a client instance and
request a derived access token for a secondary RS. This internal
token is issued in the context of the incoming access token.
+--------+ +-------+ +------+ +-------+
| Client |--(1)->| RS1 | | AS | | RS2 |
|Instance| | |--(2)->| | | |
| | | |<-(3)--| | | |
| | | | +------+ | |
| | | | | |
| | | |-----------(4)------->| |
| | | |<----------(5)--------| |
| |<-(6)--| | | |
+--------+ +-------+ +-------+
1. The client instance calls RS1 with an access token.
2. RS1 presents that token to the AS to get a derived token for use
at RS2. RS1 indicates that it has no ability to interact with
the RO. RS1 signs its request with its own key, not the token's
key or the client instance's key.
3. The AS returns a derived token to RS1 for use at RS2.
4. RS1 calls RS2 with the token from (3).
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5. RS2 fulfills the call from RS1.
6. RS1 fulfills the call from client instance.
If the RS needs to derive a token from one presented to it, it can
request one from the AS by making a token request as described in
Section 2 and presenting the existing access token's value in the
"existing_access_token" field.
The RS MUST identify itself with its own key and sign the request.
[[ See issue #116 (https://github.com/ietf-wg-gnap/gnap-core-
protocol/issues/116) ]]
POST /tx HTTP/1.1
Host: server.example.com
Content-Type: application/json
Detached-JWS: ejy0...
{
"access_token": {
"access": [
{
"actions": [
"read",
"write",
"dolphin"
],
"locations": [
"https://server.example.net/",
"https://resource.local/other"
],
"datatypes": [
"metadata",
"images"
]
},
"dolphin-metadata"
]
},
"client": "7C7C4AZ9KHRS6X63AJAO",
"existing_access_token": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0"
}
The AS responds with a token for the downstream RS2 as described in
Section 3.2.
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10.3. Registering a Resource Handle
If the RS needs to, it can post a set of resources as described in
Section 8 to the AS's resource registration endpoint.
The RS MUST identify itself with its own key and sign the request.
POST /resource HTTP/1.1
Host: server.example.com
Content-Type: application/json
Detached-JWS: ejy0...
{
"access": [
{
"actions": [
"read",
"write",
"dolphin"
],
"locations": [
"https://server.example.net/",
"https://resource.local/other"
],
"datatypes": [
"metadata",
"images"
]
},
"dolphin-metadata"
],
"client": "7C7C4AZ9KHRS6X63AJAO"
}
The AS responds with a handle appropriate to represent the resources
list that the RS presented.
Content-Type: application/json
{
"resource_handle": "FWWIKYBQ6U56NL1"
}
The RS MAY make this handle available as part of a response
(Section 10.4) or as documentation to developers.
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[[ See issue #117 (https://github.com/ietf-wg-gnap/gnap-core-
protocol/issues/117) ]]
10.4. Requesting Resources With Insufficient Access
If the client instance calls an RS without an access token, or with
an invalid access token, the RS MAY respond to the client instance
with an authentication header indicating that GNAP needs to be used
to access the resource. The address of the GNAP endpoint MUST be
sent in the "as_uri" parameter. The RS MAY additionally return a
resource reference that the client instance MAY use in its access
token request (Section 2.1). This resource reference handle SHOULD
be sufficient for at least the action the client instance was
attempting to take at the RS. The RS MAY use the dynamic resource
handle request (Section 10.3) to register a new resource handle, or
use a handle that has been pre-configured to represent what the AS is
protecting. The content of this handle is opaque to the RS and the
client instance.
WWW-Authenticate: GNAP as_uri=https://server.example/tx,resource=FWWIKYBQ6U56NL1
The client instance then makes a call to the "as_uri" as described in
Section 2, with the value of "resource" as one of the members of the
"access" array Section 2.1.1. The client instance MAY request
additional resources and other information, and MAY request multiple
access tokens.
[[ See issue #118 (https://github.com/ietf-wg-gnap/gnap-core-
protocol/issues/118) ]]
11. Acknowledgements
The editors would like to thank the feedback of the following
individuals for their reviews, implementations, and contributions:
Aaron Parecki, Annabelle Backman, Dick Hardt, Dmitri Zagidulin,
Dmitry Barinov, Fabien Imbault, Francis Pouatcha, George Fletcher,
Haardik Haardik, Hamid Massaoud, Jacky Yuan, Joseph Heenan, Justin
Richer, Kathleen Moriarty, Mike Jones, Mike Varley, Nat Sakimura,
Takahiko Kawasaki, Takahiro Tsuchiya.
The editors would also like to thank the GNAP working group design
team of Kathleen Moriarty, Fabien Imbault, Dick Hardt, Mike Jones,
and Justin Richer, who incorporated elements from the XAuth and XYZ
proposals to create the first version of this document.
In addition, the editors would like to thank Aaron Parecki and Mike
Jones for insights into how to integrate identity and authentication
systems into the core protocol, and Justin Richer and Dick Hardt for
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the use cases, diagrams, and insights provided in the XYZ and XAuth
proposals that have been incorporated here. The editors would like
to especially thank Mike Varley and the team at SecureKey for
feedback and development of early versions of the XYZ protocol that
fed into this standards work.
12. IANA Considerations
[[ TBD: There are a lot of items in the document that are expandable
through the use of value registries. ]]
13. Security Considerations
[[ TBD: There are a lot of security considerations to add. ]]
All requests have to be over TLS or equivalent as per [BCP195]. Many
handles act as shared secrets, though they can be combined with a
requirement to provide proof of a key as well.
14. Privacy Considerations
[[ TBD: There are a lot of privacy considerations to add. ]]
Handles are passed between parties and therefore should not contain
any private data.
When user information is passed to the client instance, the AS needs
to make sure that it has the permission to do so.
15. Normative References
[BCP195] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", May 2015,
<https://www.rfc-editor.org/info/bcp195>.
[I-D.ietf-httpbis-message-signatures]
Backman, A., Richer, J., and M. Sporny, "Signing HTTP
Messages", Work in Progress, Internet-Draft, draft-ietf-
httpbis-message-signatures-01, 17 November 2020,
<http://www.ietf.org/internet-drafts/draft-ietf-httpbis-
message-signatures-01.txt>.
[I-D.ietf-oauth-dpop]
Fett, D., Campbell, B., Bradley, J., Lodderstedt, T.,
Jones, M., and D. Waite, "OAuth 2.0 Demonstrating Proof-
of-Possession at the Application Layer (DPoP)", Work in
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Progress, Internet-Draft, draft-ietf-oauth-dpop-02, 18
November 2020, <http://www.ietf.org/internet-drafts/draft-
ietf-oauth-dpop-02.txt>.
[I-D.ietf-oauth-signed-http-request]
Richer, J., Bradley, J., and H. Tschofenig, "A Method for
Signing HTTP Requests for OAuth", Work in Progress,
Internet-Draft, draft-ietf-oauth-signed-http-request-03, 8
August 2016, <http://www.ietf.org/internet-drafts/draft-
ietf-oauth-signed-http-request-03.txt>.
[I-D.ietf-secevent-subject-identifiers]
Backman, A. and M. Scurtescu, "Subject Identifiers for
Security Event Tokens", Work in Progress, Internet-Draft,
draft-ietf-secevent-subject-identifiers-06, 4 September
2020, <http://www.ietf.org/internet-drafts/draft-ietf-
secevent-subject-identifiers-06.txt>.
[OIDC] Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., and
C. Mortimore, "OpenID Connect Core 1.0 incorporating
errata set 1", November 2014,
<https://openiD.net/specs/openiD-connect-core-1_0.html>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3230] Mogul, J. and A. Van Hoff, "Instance Digests in HTTP",
RFC 3230, DOI 10.17487/RFC3230, January 2002,
<https://www.rfc-editor.org/info/rfc3230>.
[RFC5646] Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying
Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646,
September 2009, <https://www.rfc-editor.org/info/rfc5646>.
[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012,
<https://www.rfc-editor.org/info/rfc6749>.
[RFC6750] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization
Framework: Bearer Token Usage", RFC 6750,
DOI 10.17487/RFC6750, October 2012,
<https://www.rfc-editor.org/info/rfc6750>.
[RFC7468] Josefsson, S. and S. Leonard, "Textual Encodings of PKIX,
PKCS, and CMS Structures", RFC 7468, DOI 10.17487/RFC7468,
April 2015, <https://www.rfc-editor.org/info/rfc7468>.
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[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <https://www.rfc-editor.org/info/rfc7515>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<https://www.rfc-editor.org/info/rfc7517>.
[RFC7797] Jones, M., "JSON Web Signature (JWS) Unencoded Payload
Option", RFC 7797, DOI 10.17487/RFC7797, February 2016,
<https://www.rfc-editor.org/info/rfc7797>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>.
[RFC8693] Jones, M., Nadalin, A., Campbell, B., Ed., Bradley, J.,
and C. Mortimore, "OAuth 2.0 Token Exchange", RFC 8693,
DOI 10.17487/RFC8693, January 2020,
<https://www.rfc-editor.org/info/rfc8693>.
[RFC8705] Campbell, B., Bradley, J., Sakimura, N., and T.
Lodderstedt, "OAuth 2.0 Mutual-TLS Client Authentication
and Certificate-Bound Access Tokens", RFC 8705,
DOI 10.17487/RFC8705, February 2020,
<https://www.rfc-editor.org/info/rfc8705>.
Appendix A. Document History
* -04
- Updated terminology.
- Refactored key presentation and binding.
- Refactored "interact" request to group start and end modes.
- Changed access token request and response syntax.
- Removed closed issue links.
- Removed function to read state of grant request by client.
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- Closed issues related to reading and updating access tokens.
* -03
- Changed "resource client" terminology to separate "client
instance" and "client software".
- Removed OpenID Connect "claims" parameter.
- Dropped "short URI" redirect.
- Access token is mandatory for continuation.
- Removed closed issue links.
- Editorial fixes.
* -02
- Moved all "editor's note" items to GitHub Issues.
- Added JSON types to fields.
- Changed "GNAP Protocol" to "GNAP".
- Editorial fixes.
* -01
- "updated_at" subject info timestamp now in ISO 8601 string
format.
- Editorial fixes.
- Added Aaron and Fabien as document authors.
* -00
- Initial working group draft.
Appendix B. Component Data Models
While different implementations of this protocol will have different
realizations of all the components and artifacts enumerated here, the
nature of the protocol implies some common structures and elements
for certain components. This appendix seeks to enumerate those
common elements.
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TBD: Client has keys, allowed requested resources, identifier(s),
allowed requested subjects, allowed
TBD: AS has "grant endpoint", interaction endpoints, store of trusted
client keys, policies
TBD: Token has RO, user, client, resource list, RS list,
Appendix C. Example Protocol Flows
The protocol defined in this specification provides a number of
features that can be combined to solve many different kinds of
authentication scenarios. This section seeks to show examples of how
the protocol would be applied for different situations.
Some longer fields, particularly cryptographic information, have been
truncated for display purposes in these examples.
C.1. Redirect-Based User Interaction
In this scenario, the user is the RO and has access to a web browser,
and the client instance can take front-channel callbacks on the same
device as the user. This combination is analogous to the OAuth 2
Authorization Code grant type.
The client instance initiates the request to the AS. Here the client
instance identifies itself using its public key.
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POST /tx HTTP/1.1
Host: server.example.com
Content-Type: application/json
Detached-JWS: ejy0...
{
"access_token": {
"access": [
{
"actions": [
"read",
"write",
"dolphin"
],
"locations": [
"https://server.example.net/",
"https://resource.local/other"
],
"datatypes": [
"metadata",
"images"
]
}
],
},
"client": {
"key": {
"proof": "jwsd",
"jwk": {
"kty": "RSA",
"e": "AQAB",
"kid": "xyz-1",
"alg": "RS256",
"n": "kOB5rR4Jv0GMeLaY6_It_r3ORwdf8ci_JtffXyaSx8xY..."
}
}
},
"interact": {
"start": ["redirect"],
"finish": {
"method": "redirect",
"uri": "https://client.example.net/return/123455",
"nonce": "LKLTI25DK82FX4T4QFZC"
}
}
}
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The AS processes the request and determines that the RO needs to
interact. The AS returns the following response giving the client
instance the information it needs to connect. The AS has also
indicated to the client instance that it can use the given instance
identifier to identify itself in future requests (Section 2.3.1).
Content-Type: application/json
{
"interact": {
"redirect": "https://server.example.com/interact/4CF492MLVMSW9MKMXKHQ",
"push": "MBDOFXG4Y5CVJCX821LH"
}
"continue": {
"access_token": {
"value": "80UPRY5NM33OMUKMKSKU",
"bound": true
},
"uri": "https://server.example.com/continue"
},
"instance_id": "7C7C4AZ9KHRS6X63AJAO"
}
The client instance saves the response and redirects the user to the
interaction_url by sending the following HTTP message to the user's
browser.
HTTP 302 Found
Location: https://server.example.com/interact/4CF492MLVMSW9MKMXKHQ
The user's browser fetches the AS's interaction URL. The user logs
in, is identified as the RO for the resource being requested, and
approves the request. Since the AS has a callback parameter, the AS
generates the interaction reference, calculates the hash, and
redirects the user back to the client instance with these additional
values added as query parameters.
HTTP 302 Found
Location: https://client.example.net/return/123455
?hash=p28jsq0Y2KK3WS__a42tavNC64ldGTBroywsWxT4md_jZQ1R2HZT8BOWYHcLmObM7XHPAdJzTZMtKBsaraJ64A
&interact_ref=4IFWWIKYBC2PQ6U56NL1
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The client instance receives this request from the user's browser.
The client instance ensures that this is the same user that was sent
out by validating session information and retrieves the stored
pending request. The client instance uses the values in this to
validate the hash parameter. The client instance then calls the
continuation URL and presents the handle and interaction reference in
the request body. The client instance signs the request as above.
POST /continue HTTP/1.1
Host: server.example.com
Content-Type: application/json
Authorization: GNAP 80UPRY5NM33OMUKMKSKU
Detached-JWS: ejy0...
{
"interact_ref": "4IFWWIKYBC2PQ6U56NL1"
}
The AS retrieves the pending request based on the handle and issues a
bearer access token and returns this to the client instance.
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Content-Type: application/json
{
"access_token": {
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
"bound": true,
"manage": "https://server.example.com/token/PRY5NM33OM4TB8N6BW7OZB8CDFONP219RP1L",
"access": [{
"actions": [
"read",
"write",
"dolphin"
],
"locations": [
"https://server.example.net/",
"https://resource.local/other"
],
"datatypes": [
"metadata",
"images"
]
}]
},
"continue": {
"access_token": {
"value": "80UPRY5NM33OMUKMKSKU",
"bound": true
},
"uri": "https://server.example.com/continue"
}
}
C.2. Secondary Device Interaction
In this scenario, the user does not have access to a web browser on
the device and must use a secondary device to interact with the AS.
The client instance can display a user code or a printable QR code.
The client instance is not able to accept callbacks from the AS and
needs to poll for updates while waiting for the user to authorize the
request.
The client instance initiates the request to the AS.
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POST /tx HTTP/1.1
Host: server.example.com
Content-Type: application/json
Detached-JWS: ejy0...
{
"access_token": {
"access": [
"dolphin-metadata", "some other thing"
],
},
"client": "7C7C4AZ9KHRS6X63AJAO",
"interact": {
"start": ["redirect", "user_code"]
}
}
The AS processes this and determines that the RO needs to interact.
The AS supports both redirect URIs and user codes for interaction, so
it includes both. Since there is no "callback" the AS does not
include a nonce, but does include a "wait" parameter on the
continuation section because it expects the client instance to poll
for results.
Content-Type: application/json
{
"interact": {
"redirect": "https://srv.ex/MXKHQ",
"user_code": {
"code": "A1BC-3DFF",
"url": "https://srv.ex/device"
}
},
"continue": {
"access_token": {
"value": "80UPRY5NM33OMUKMKSKU",
"bound": true
},
"uri": "https://server.example.com/continue/VGJKPTKC50",
"wait": 60
}
}
The client instance saves the response and displays the user code
visually on its screen along with the static device URL. The client
instance also displays the short interaction URL as a QR code to be
scanned.
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If the user scans the code, they are taken to the interaction
endpoint and the AS looks up the current pending request based on the
incoming URL. If the user instead goes to the static page and enters
the code manually, the AS looks up the current pending request based
on the value of the user code. In both cases, the user logs in, is
identified as the RO for the resource being requested, and approves
the request. Once the request has been approved, the AS displays to
the user a message to return to their device.
Meanwhile, the client instance periodically polls the AS every 60
seconds at the continuation URL. The client instance signs the
request using the same key and method that it did in the first
request.
POST /continue/VGJKPTKC50 HTTP/1.1
Host: server.example.com
Authorization: GNAP 80UPRY5NM33OMUKMKSKU
Detached-JWS: ejy0...
The AS retrieves the pending request based on the handle and
determines that it has not yet been authorized. The AS indicates to
the client instance that no access token has yet been issued but it
can continue to call after another 60 second timeout.
Content-Type: application/json
{
"continue": {
"access_token": {
"value": "G7YQT4KQQ5TZY9SLSS5E",
"bound": true
},
"uri": "https://server.example.com/continue/ATWHO4Q1WV",
"wait": 60
}
}
Note that the continuation URL and access token have been rotated
since they were used by the client instance to make this call. The
client instance polls the continuation URL after a 60 second timeout
using this new information.
POST /continue/ATWHO4Q1WV HTTP/1.1
Host: server.example.com
Authorization: GNAP G7YQT4KQQ5TZY9SLSS5E
Detached-JWS: ejy0...
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The AS retrieves the pending request based on the URL and access
token, determines that it has been approved, and issues an access
token for the client to use at the RS.
Content-Type: application/json
{
"access_token": {
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
"bound": true,
"manage": "https://server.example.com/token/PRY5NM33OM4TB8N6BW7OZB8CDFONP219RP1L",
"access": [
"dolphin-metadata", "some other thing"
]
}
}
C.3. No User Involvement
In this scenario, the client instance is requesting access on its own
behalf, with no user to interact with.
The client instance creates a request to the AS, identifying itself
with its public key and using MTLS to make the request.
POST /tx HTTP/1.1
Host: server.example.com
Content-Type: application/json
{
"access_token": {
"access": [
"backend service", "nightly-routine-3"
],
},
"client": {
"key": {
"proof": "mtls",
"cert#S256": "bwcK0esc3ACC3DB2Y5_lESsXE8o9ltc05O89jdN-dg2"
}
}
}
The AS processes this and determines that the client instance can ask
for the requested resources and issues an access token.
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Content-Type: application/json
{
"access_token": {
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
"bound": true,
"manage": "https://server.example.com/token",
"access": [
"backend service", "nightly-routine-3"
]
}
}
C.4. Asynchronous Authorization
In this scenario, the client instance is requesting on behalf of a
specific RO, but has no way to interact with the user. The AS can
asynchronously reach out to the RO for approval in this scenario.
The client instance starts the request at the AS by requesting a set
of resources. The client instance also identifies a particular user.
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POST /tx HTTP/1.1
Host: server.example.com
Content-Type: application/json
Detached-JWS: ejy0...
{
"access_token": {
"access": [
{
"type": "photo-api",
"actions": [
"read",
"write",
"dolphin"
],
"locations": [
"https://server.example.net/",
"https://resource.local/other"
],
"datatypes": [
"metadata",
"images"
]
},
"read", "dolphin-metadata",
{
"type": "financial-transaction",
"actions": [
"withdraw"
],
"identifier": "account-14-32-32-3",
"currency": "USD"
},
"some other thing"
],
},
"client": "7C7C4AZ9KHRS6X63AJAO",
"user": {
"sub_ids": [ {
"subject_type": "email",
"email": "user@example.com"
} ]
}
}
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The AS processes this and determines that the RO needs to interact.
The AS determines that it can reach the identified user
asynchronously and that the identified user does have the ability to
approve this request. The AS indicates to the client instance that
it can poll for continuation.
Content-Type: application/json
{
"continue": {
"access_token": {
"value": "80UPRY5NM33OMUKMKSKU",
"bound": true
},
"uri": "https://server.example.com/continue",
"wait": 60
}
}
The AS reaches out to the RO and prompts them for consent. In this
example, the AS has an application that it can push notifications in
to for the specified account.
Meanwhile, the client instance periodically polls the AS every 60
seconds at the continuation URL.
POST /continue HTTP/1.1
Host: server.example.com
Authorization: GNAP 80UPRY5NM33OMUKMKSKU
Detached-JWS: ejy0...
The AS retrieves the pending request based on the handle and
determines that it has not yet been authorized. The AS indicates to
the client instance that no access token has yet been issued but it
can continue to call after another 60 second timeout.
Content-Type: application/json
{
"continue": {
"access_token": {
"value": "BI9QNW6V9W3XFJK4R02D",
"bound": true
},
"uri": "https://server.example.com/continue",
"wait": 60
}
}
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Note that the continuation handle has been rotated since it was used
by the client instance to make this call. The client instance polls
the continuation URL after a 60 second timeout using the new handle.
POST /continue HTTP/1.1
Host: server.example.com
Authorization: GNAP BI9QNW6V9W3XFJK4R02D
Detached-JWS: ejy0...
The AS retrieves the pending request based on the handle and
determines that it has been approved and it issues an access token.
Content-Type: application/json
{
"access_token": {
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
"bound": true,
"manage": "https://server.example.com/token/PRY5NM33OM4TB8N6BW7OZB8CDFONP219RP1L",
"access": [
"dolphin-metadata", "some other thing"
]
}
}
C.5. Applying OAuth 2 Scopes and Client IDs
While GNAP is not designed to be directly compatible with OAuth 2
[RFC6749], considerations have been made to enable the use of OAuth 2
concepts and constructs more smoothly within GNAP.
In this scenario, the client developer has a "client_id" and set of
"scope" values from their OAuth 2 system and wants to apply them to
the new protocol. Traditionally, the OAuth 2 client developer would
put their "client_id" and "scope" values as parameters into a
redirect request to the authorization endpoint.
HTTP 302 Found
Location: https://server.example.com/authorize
?client_id=7C7C4AZ9KHRS6X63AJAO
&scope=read%20write%20dolphin
&redirect_uri=https://client.example.net/return
&response_type=code
&state=123455
Now the developer wants to make an analogous request to the AS using
GNAP. To do so, the client instance makes an HTTP POST and places
the OAuth 2 values in the appropriate places.
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POST /tx HTTP/1.1
Host: server.example.com
Content-Type: application/json
Detached-JWS: ejy0...
{
"access_token": {
"access": [
"read", "write", "dolphin"
],
"flags": [ "bearer" ]
},
"client": "7C7C4AZ9KHRS6X63AJAO",
"interact": {
"start": ["redirect"],
"finish": {
"method": "redirect",
"uri": "https://client.example.net/return?state=123455",
"nonce": "LKLTI25DK82FX4T4QFZC"
}
}
}
The client_id can be used to identify the client instance's keys that
it uses for authentication, the scopes represent resources that the
client instance is requesting, and the "redirect_uri" and "state"
value are pre-combined into a "callback" URI that can be unique per
request. The client instance additionally creates a nonce to protect
the callback, separate from the state parameter that it has added to
its return URL.
From here, the protocol continues as above.
Appendix D. JSON Structures and Polymorphism
GNAP makes use of polymorphism within the JSON [RFC8259] structures
used for the protocol. Each portion of this protocol is defined in
terms of the JSON data type that its values can take, whether it's a
string, object, array, boolean, or number. For some fields,
different data types offer different descriptive capabilities and are
used in different situations for the same field. Each data type
provides a different syntax to express the same underlying semantic
protocol element, which allows for optimization and simplification in
many common cases.
Even though JSON is often used to describe strongly typed structures,
JSON on its own is naturally polymorphic. In JSON, the named members
of an object have no type associated with them, and any data type can
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be used as the value for any member. In practice, each member has a
semantic type that needs to make sense to the parties creating and
consuming the object. Within this protocol, each object member is
defined in terms of its semantic content, and this semantic content
might have expressions in different concrete data types for different
specific purposes. Since each object member has exactly one value in
JSON, each data type for an object member field is naturally mutually
exclusive with other data types within a single JSON object.
For example, a resource request for a single access token is composed
of an array of resource request descriptions while a request for
multiple access tokens is composed of an object whose member values
are all arrays. Both of these represent requests for access, but the
difference in syntax allows the client instance and AS to
differentiate between the two request types in the same request.
Another form of polymorphism in JSON comes from the fact that the
values within JSON arrays need not all be of the same JSON data type.
However, within this protocol, each element within the array needs to
be of the same kind of semantic element for the collection to make
sense, even when the data types are different from each other.
For example, each aspect of a resource request can be described using
an object with multiple dimensional components, or the aspect can be
requested using a string. In both cases, the resource request is
being described in a way that the AS needs to interpret, but with
different levels of specificity and complexity for the client
instance to deal with. An API designer can provide a set of common
access scopes as simple strings but still allow client software
developers to specify custom access when needed for more complex
APIs.
Extensions to this specification can use different data types for
defined fields, but each extension needs to not only declare what the
data type means, but also provide justification for the data type
representing the same basic kind of thing it extends. For example,
an extension declaring an "array" representation for a field would
need to explain how the array represents something akin to the non-
array element that it is replacing.
Authors' Addresses
Justin Richer (editor)
Bespoke Engineering
Email: ietf@justin.richer.org
URI: https://bspk.io/
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Aaron Parecki
Okta
Email: aaron@parecki.com
URI: https://aaronparecki.com
Fabien Imbault
acert.io
Email: fabien.imbault@acert.io
URI: https://acert.io/
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