draft-ietf-gnap-core-protocol-06.txt   draft-ietf-gnap-core-protocol-07.txt 
GNAP J. Richer, Ed. GNAP J. Richer, Ed.
Internet-Draft Bespoke Engineering Internet-Draft Bespoke Engineering
Intended status: Standards Track A. Parecki Intended status: Standards Track A. Parecki
Expires: 13 January 2022 Okta Expires: 28 March 2022 Okta
F. Imbault F. Imbault
acert.io acert.io
12 July 2021 24 September 2021
Grant Negotiation and Authorization Protocol Grant Negotiation and Authorization Protocol
draft-ietf-gnap-core-protocol-06 draft-ietf-gnap-core-protocol-07
Abstract Abstract
GNAP defines a mechanism for delegating authorization to a piece of GNAP defines a mechanism for delegating authorization to a piece of
software, and conveying that delegation to the software. This software, and conveying that delegation to the software. This
delegation can include access to a set of APIs as well as information delegation can include access to a set of APIs as well as information
passed directly to the software. passed directly to the software.
Status of This Memo Status of This Memo
skipping to change at page 1, line 36 skipping to change at page 1, line 36
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Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
1.2. Roles . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.2. Roles . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3. Elements . . . . . . . . . . . . . . . . . . . . . . . . 8 1.3. Elements . . . . . . . . . . . . . . . . . . . . . . . . 9
1.4. Sequences . . . . . . . . . . . . . . . . . . . . . . . . 9 1.4. Trust relationships . . . . . . . . . . . . . . . . . . . 10
1.4.1. Redirect-based Interaction . . . . . . . . . . . . . 12 1.5. Sequences . . . . . . . . . . . . . . . . . . . . . . . . 11
1.4.2. User-code Interaction . . . . . . . . . . . . . . . . 15 1.5.1. Redirect-based Interaction . . . . . . . . . . . . . 15
1.4.3. Asynchronous Authorization . . . . . . . . . . . . . 17 1.5.2. User-code Interaction . . . . . . . . . . . . . . . . 18
1.4.4. Software-only Authorization . . . . . . . . . . . . . 19 1.5.3. Asynchronous Authorization . . . . . . . . . . . . . 20
1.4.5. Refreshing an Expired Access Token . . . . . . . . . 20 1.5.4. Software-only Authorization . . . . . . . . . . . . . 22
1.4.6. Requesting User Information . . . . . . . . . . . . . 22 1.5.5. Refreshing an Expired Access Token . . . . . . . . . 23
2. Requesting Access . . . . . . . . . . . . . . . . . . . . . . 23 1.5.6. Requesting User Information . . . . . . . . . . . . . 25
2.1. Requesting Access to Resources . . . . . . . . . . . . . 25 2. Requesting Access . . . . . . . . . . . . . . . . . . . . . . 26
2.1.1. Requesting a Single Access Token . . . . . . . . . . 25 2.1. Requesting Access to Resources . . . . . . . . . . . . . 28
2.1.2. Requesting Multiple Access Tokens . . . . . . . . . . 28 2.1.1. Requesting a Single Access Token . . . . . . . . . . 28
2.2. Requesting Subject Information . . . . . . . . . . . . . 30 2.1.2. Requesting Multiple Access Tokens . . . . . . . . . . 31
2.3. Identifying the Client Instance . . . . . . . . . . . . . 31 2.2. Requesting Subject Information . . . . . . . . . . . . . 33
2.3.1. Identifying the Client Instance by Reference . . . . 32 2.3. Identifying the Client Instance . . . . . . . . . . . . . 34
2.3.2. Providing Displayable Client Instance Information . . 33 2.3.1. Identifying the Client Instance by Reference . . . . 35
2.3.3. Authenticating the Client Instance . . . . . . . . . 33 2.3.2. Providing Displayable Client Instance Information . . 36
2.4. Identifying the User . . . . . . . . . . . . . . . . . . 34 2.3.3. Authenticating the Client Instance . . . . . . . . . 36
2.4.1. Identifying the User by Reference . . . . . . . . . . 35 2.4. Identifying the User . . . . . . . . . . . . . . . . . . 37
2.5. Interacting with the User . . . . . . . . . . . . . . . . 35 2.4.1. Identifying the User by Reference . . . . . . . . . . 38
2.5.1. Start Mode Definitions . . . . . . . . . . . . . . . 37 2.5. Interacting with the User . . . . . . . . . . . . . . . . 38
2.5.2. Finish Interaction Modes . . . . . . . . . . . . . . 38 2.5.1. Start Mode Definitions . . . . . . . . . . . . . . . 40
2.5.3. Hints . . . . . . . . . . . . . . . . . . . . . . . . 41 2.5.2. Finish Interaction Modes . . . . . . . . . . . . . . 41
2.5.4. Extending Interaction Modes . . . . . . . . . . . . . 41 2.5.3. Hints . . . . . . . . . . . . . . . . . . . . . . . . 44
2.6. Extending The Grant Request . . . . . . . . . . . . . . . 41 2.5.4. Extending Interaction Modes . . . . . . . . . . . . . 44
3. Grant Response . . . . . . . . . . . . . . . . . . . . . . . 42 2.6. Extending The Grant Request . . . . . . . . . . . . . . . 44
3.1. Request Continuation . . . . . . . . . . . . . . . . . . 43 3. Grant Response . . . . . . . . . . . . . . . . . . . . . . . 45
3.2. Access Tokens . . . . . . . . . . . . . . . . . . . . . . 44 3.1. Request Continuation . . . . . . . . . . . . . . . . . . 46
3.2.1. Single Access Token . . . . . . . . . . . . . . . . . 45 3.2. Access Tokens . . . . . . . . . . . . . . . . . . . . . . 47
3.2.2. Multiple Access Tokens . . . . . . . . . . . . . . . 48 3.2.1. Single Access Token . . . . . . . . . . . . . . . . . 48
3.3. Interaction Modes . . . . . . . . . . . . . . . . . . . . 49 3.2.2. Multiple Access Tokens . . . . . . . . . . . . . . . 51
3.3.1. Redirection to an arbitrary URL . . . . . . . . . . . 50 3.3. Interaction Modes . . . . . . . . . . . . . . . . . . . . 52
3.3.2. Launch of an application URL . . . . . . . . . . . . 51 3.3.1. Redirection to an arbitrary URL . . . . . . . . . . . 53
3.3.3. Display of a Short User Code . . . . . . . . . . . . 51 3.3.2. Launch of an application URL . . . . . . . . . . . . 54
3.3.4. Interaction Finish . . . . . . . . . . . . . . . . . 52 3.3.3. Display of a Short User Code . . . . . . . . . . . . 54
3.3.5. Extending Interaction Mode Responses . . . . . . . . 53 3.3.4. Interaction Finish . . . . . . . . . . . . . . . . . 55
3.4. Returning User Information . . . . . . . . . . . . . . . 53 3.3.5. Extending Interaction Mode Responses . . . . . . . . 56
3.5. Returning Dynamically-bound Reference Handles . . . . . . 54 3.4. Returning Subject Information . . . . . . . . . . . . . . 56
3.6. Error Response . . . . . . . . . . . . . . . . . . . . . 56 3.5. Returning Dynamically-bound Reference Handles . . . . . . 57
3.7. Extending the Response . . . . . . . . . . . . . . . . . 56 3.6. Error Response . . . . . . . . . . . . . . . . . . . . . 58
4. Determining Authorization and Consent . . . . . . . . . . . . 56 3.7. Extending the Response . . . . . . . . . . . . . . . . . 59
4.1. Interaction Start Methods . . . . . . . . . . . . . . . . 59 4. Determining Authorization and Consent . . . . . . . . . . . . 59
4.1.1. Interaction at a Redirected URI . . . . . . . . . . . 60 4.1. Interaction Start Methods . . . . . . . . . . . . . . . . 62
4.1.2. Interaction at the User Code URI . . . . . . . . . . 60 4.1.1. Interaction at a Redirected URI . . . . . . . . . . . 62
4.1.3. Interaction through an Application URI . . . . . . . 61 4.1.2. Interaction at the User Code URI . . . . . . . . . . 63
4.2. Post-Interaction Completion . . . . . . . . . . . . . . . 61 4.1.3. Interaction through an Application URI . . . . . . . 64
4.2. Post-Interaction Completion . . . . . . . . . . . . . . . 64
4.2.1. Completing Interaction with a Browser Redirect to the 4.2.1. Completing Interaction with a Browser Redirect to the
Callback URI . . . . . . . . . . . . . . . . . . . . 62 Callback URI . . . . . . . . . . . . . . . . . . . . 65
4.2.2. Completing Interaction with a Direct HTTP Request 4.2.2. Completing Interaction with a Direct HTTP Request
Callback . . . . . . . . . . . . . . . . . . . . . . 63 Callback . . . . . . . . . . . . . . . . . . . . . . 66
4.2.3. Calculating the interaction hash . . . . . . . . . . 64 4.2.3. Calculating the interaction hash . . . . . . . . . . 66
5. Continuing a Grant Request . . . . . . . . . . . . . . . . . 65 5. Continuing a Grant Request . . . . . . . . . . . . . . . . . 68
5.1. Continuing After a Completed Interaction . . . . . . . . 67 5.1. Continuing After a Completed Interaction . . . . . . . . 70
5.2. Continuing During Pending Interaction . . . . . . . . . . 68 5.2. Continuing During Pending Interaction . . . . . . . . . . 71
5.3. Modifying an Existing Request . . . . . . . . . . . . . . 69 5.3. Modifying an Existing Request . . . . . . . . . . . . . . 73
5.4. Canceling a Grant Request . . . . . . . . . . . . . . . . 75 5.4. Canceling a Grant Request . . . . . . . . . . . . . . . . 78
6. Token Management . . . . . . . . . . . . . . . . . . . . . . 75 6. Token Management . . . . . . . . . . . . . . . . . . . . . . 79
6.1. Rotating the Access Token . . . . . . . . . . . . . . . . 75 6.1. Rotating the Access Token . . . . . . . . . . . . . . . . 79
6.2. Revoking the Access Token . . . . . . . . . . . . . . . . 77 6.2. Revoking the Access Token . . . . . . . . . . . . . . . . 81
7. Securing Requests from the Client Instance . . . . . . . . . 78 7. Securing Requests from the Client Instance . . . . . . . . . 82
7.1. Key Formats . . . . . . . . . . . . . . . . . . . . . . . 78 7.1. Key Formats . . . . . . . . . . . . . . . . . . . . . . . 83
7.1.1. Key References . . . . . . . . . . . . . . . . . . . 80 7.1.1. Key References . . . . . . . . . . . . . . . . . . . 84
7.2. Presenting Access Tokens . . . . . . . . . . . . . . . . 80 7.2. Presenting Access Tokens . . . . . . . . . . . . . . . . 84
7.3. Proving Possession of a Key with a Request . . . . . . . 81 7.3. Proving Possession of a Key with a Request . . . . . . . 85
7.3.1. HTTP Message Signing . . . . . . . . . . . . . . . . 83 7.3.1. HTTP Message Signing . . . . . . . . . . . . . . . . 87
7.3.2. Mutual TLS . . . . . . . . . . . . . . . . . . . . . 87 7.3.2. Mutual TLS . . . . . . . . . . . . . . . . . . . . . 91
7.3.3. Detached JWS . . . . . . . . . . . . . . . . . . . . 89 7.3.3. Detached JWS . . . . . . . . . . . . . . . . . . . . 93
7.3.4. Attached JWS . . . . . . . . . . . . . . . . . . . . 93 7.3.4. Attached JWS . . . . . . . . . . . . . . . . . . . . 97
8. Resource Access Rights . . . . . . . . . . . . . . . . . . . 97 8. Resource Access Rights . . . . . . . . . . . . . . . . . . . 101
8.1. Requesting Resources By Reference . . . . . . . . . . . . 100 8.1. Requesting Resources By Reference . . . . . . . . . . . . 104
9. Discovery . . . . . . . . . . . . . . . . . . . . . . . . . . 102 9. Discovery . . . . . . . . . . . . . . . . . . . . . . . . . . 106
9.1. RS-first Method of AS Discovery . . . . . . . . . . . . . 103 9.1. RS-first Method of AS Discovery . . . . . . . . . . . . . 107
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 105 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 109
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 105 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 109
12. Security Considerations . . . . . . . . . . . . . . . . . . . 105 12. Security Considerations . . . . . . . . . . . . . . . . . . . 109
13. Privacy Considerations . . . . . . . . . . . . . . . . . . . 105 12.1. TLS Protection in Transit . . . . . . . . . . . . . . . 109
14. Normative References . . . . . . . . . . . . . . . . . . . . 105 12.2. Protection of Client Instance Key Material . . . . . . . 110
Appendix A. Document History . . . . . . . . . . . . . . . . . . 108 12.3. Protection of Authorization Server . . . . . . . . . . . 111
Appendix B. Compared to OAuth 2.0 . . . . . . . . . . . . . . . 110 12.4. Symmetric and Asymmetric Client Instance Keys . . . . . 112
Appendix C. Component Data Models . . . . . . . . . . . . . . . 113 12.5. Generation of Access Tokens . . . . . . . . . . . . . . 113
Appendix D. Example Protocol Flows . . . . . . . . . . . . . . . 113 12.6. Bearer Access Tokens . . . . . . . . . . . . . . . . . . 114
D.1. Redirect-Based User Interaction . . . . . . . . . . . . . 113 12.7. Key-Bound Token Access Tokens . . . . . . . . . . . . . 114
D.2. Secondary Device Interaction . . . . . . . . . . . . . . 117 12.8. Exposure of End-user Credentials to Client Instance . . 115
D.3. No User Involvement . . . . . . . . . . . . . . . . . . . 120 12.9. Mixing Up Authorization Servers . . . . . . . . . . . . 116
D.4. Asynchronous Authorization . . . . . . . . . . . . . . . 121 12.10. Processing of Client-Presented User Information . . . . 117
D.5. Applying OAuth 2.0 Scopes and Client IDs . . . . . . . . 124 12.11. Client Instance Pre-registration . . . . . . . . . . . . 118
Appendix E. JSON Structures and Polymorphism . . . . . . . . . . 126 12.12. Client Instance Impersonation . . . . . . . . . . . . . 119
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 127 12.13. Interception of Information in the Browser . . . . . . . 120
12.14. Callback URL Manipulation . . . . . . . . . . . . . . . 120
12.15. MTLS Deployment Patterns . . . . . . . . . . . . . . . . 121
12.16. Interception of Responses from the AS . . . . . . . . . 121
12.17. Key Distribution . . . . . . . . . . . . . . . . . . . . 122
12.18. Interaction Finish Modes and Polling . . . . . . . . . . 122
12.19. Storage of Information During Interaction and
Continuation . . . . . . . . . . . . . . . . . . . . . 123
12.20. Denial of Service (DoS) through Grant Continuation . . . 124
12.21. Exhaustion of Random Value Space . . . . . . . . . . . . 124
13. Privacy Considerations . . . . . . . . . . . . . . . . . . . 125
13.1. Surveillance . . . . . . . . . . . . . . . . . . . . . . 125
13.1.1. Surveillance by the Client . . . . . . . . . . . . . 125
13.1.2. Surveillance by the Authorization Server . . . . . . 125
13.2. Stored Data . . . . . . . . . . . . . . . . . . . . . . 126
13.3. Intrusion . . . . . . . . . . . . . . . . . . . . . . . 127
13.4. Correlation . . . . . . . . . . . . . . . . . . . . . . 127
13.4.1. Correlation by Clients . . . . . . . . . . . . . . . 127
13.4.2. Correlation by Resource Servers . . . . . . . . . . 127
13.4.3. Correlation by Authorization Servers . . . . . . . . 128
13.5. Disclosure in Shared References . . . . . . . . . . . . 128
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 128
14.1. Normative References . . . . . . . . . . . . . . . . . . 128
14.2. Informative References . . . . . . . . . . . . . . . . . 131
Appendix A. Document History . . . . . . . . . . . . . . . . . . 131
Appendix B. Compared to OAuth 2.0 . . . . . . . . . . . . . . . 134
Appendix C. Component Data Models . . . . . . . . . . . . . . . 136
Appendix D. Example Protocol Flows . . . . . . . . . . . . . . . 136
D.1. Redirect-Based User Interaction . . . . . . . . . . . . . 137
D.2. Secondary Device Interaction . . . . . . . . . . . . . . 140
D.3. No User Involvement . . . . . . . . . . . . . . . . . . . 143
D.4. Asynchronous Authorization . . . . . . . . . . . . . . . 144
D.5. Applying OAuth 2.0 Scopes and Client IDs . . . . . . . . 148
Appendix E. JSON Structures and Polymorphism . . . . . . . . . . 149
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 150
1. Introduction 1. Introduction
This protocol allows a piece of software, the client instance, to This protocol allows a piece of software, the client instance, to
request delegated authorization to resource servers and to request request delegated authorization to resource servers and to request
direct information. This delegation is facilitated by an direct information. This delegation is facilitated by an
authorization server usually on behalf of a resource owner. The end- authorization server usually on behalf of a resource owner. The end-
user operating the software may interact with the authorization user operating the software may interact with the authorization
server to authenticate, provide consent, and authorize the request. server to authenticate, provide consent, and authorize the request.
skipping to change at page 6, line 5 skipping to change at page 7, line 5
indicate line wrapping for long values, as per [RFC8792]. The "\" indicate line wrapping for long values, as per [RFC8792]. The "\"
character and leading spaces on wrapped lines are not part of the character and leading spaces on wrapped lines are not part of the
value. value.
1.2. Roles 1.2. Roles
The parties in GNAP perform actions under different roles. Roles are The parties in GNAP perform actions under different roles. Roles are
defined by the actions taken and the expectations leveraged on the defined by the actions taken and the expectations leveraged on the
role by the overall protocol. role by the overall protocol.
+-------------+ +------------+ +-------------+ +------------+
| | | | | | | |
|Authorization| | Resource | |Authorization| | Resource |
| Server | | Server | | Server | | Server |
| |<-+ +---->| | | |<-+ +---->| |
+-------------+ | | +------------+ +-------------+ | | +------------+
+ | | + | |
+ | | + | |
+ | | + | |
+ | | + | |
+ | | + | |
+ +----------+ + +----------+
+ | Client | + | Client |
+ | Instance | + | Instance |
+ +----------+ + +----------+
+ + + +
+ + + +
+ + + +
+-----------+ + +------------+ +-----------+ + +------------+
| | + + + +| | | | + + + +| |
| Resource | | End | | Resource | | End |
| Owner | ~ ~ ~ ~ ~ ~ | User | | Owner | ~ ~ ~ ~ ~ ~ | User |
| | | | | | | |
+-----------+ +------------+ +-----------+ +------------+
Legend Legend
+ + + indicates interaction between a human and computer + + + indicates interaction between a human and computer
~ ~ ~ indicates a potential equivalence or out-of-band communication between roles ----- indicates interaction between two pieces of software
~ ~ ~ indicates a potential equivalence or out-of-band
communication between roles
Authorization Server (AS) server that grants delegated privileges to Authorization Server (AS) server that grants delegated privileges to
a particular instance of client software in the form of access a particular instance of client software in the form of access
tokens or other information (such as subject information). tokens or other information (such as subject information).
Client application operated by an end-user that consumes resources Client application operated by an end-user that consumes resources
from one or several RSs, possibly requiring access privileges from from one or several RSs, possibly requiring access privileges from
one or several ASs. one or several ASs. Example: a client can be a mobile
application, a web application, etc. Note: this specification
Example: a client can be a mobile application, a web application, differentiates between a specific instance (the client instance,
etc. identified by its unique key) and the software running the
instance (the client software). For some kinds of client
Note: this specification differentiates between a specific software, there could be many instances of that software, each
instance (the client instance, identified by its unique key) and instance with a different key.
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 Resource Server (RS) server that provides operations on protected
resources, where operations require a valid access token issued by resources, where operations require a valid access token issued by
an AS. an AS.
Resource Owner (RO) subject entity that may grant or deny operations Resource Owner (RO) subject entity that may grant or deny operations
on resources it has authority upon. on resources it has authority upon. Note: the act of granting or
denying an operation may be manual (i.e. through an interaction
Note: the act of granting or denying an operation may be manual with a physical person) or automatic (i.e. through predefined
(i.e. through an interaction with a physical person) or automatic organizational rules).
(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 End-user natural person that operates a client instance. Note: that
RO. natural person may or may not be the same entity as the RO.
The design of GNAP does not assume any one deployment architecture, The design of GNAP does not assume any one deployment architecture,
but instead attempts to define roles that can be fulfilled in a 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 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 role fulfills all of its obligations and behaviors as defined by the
protocol, GNAP does not make additional requirements on its structure protocol, GNAP does not make additional requirements on its structure
or setup. or setup.
Multiple roles can be fulfilled by the same party, and a given party Multiple roles can be fulfilled by the same party, and a given party
can switch roles in different instances of the protocol. For can switch roles in different instances of the protocol. For
skipping to change at page 8, line 32 skipping to change at page 9, line 32
communications mechanisms which are considered out of scope of GNAP. communications mechanisms which are considered out of scope of GNAP.
1.3. Elements 1.3. Elements
In addition to the roles above, the protocol also involves several In addition to the roles above, the protocol also involves several
elements that are acted upon by the roles throughout the process. elements that are acted upon by the roles throughout the process.
Attribute characteristics related to a subject. Attribute characteristics related to a subject.
Access Token a data artifact representing a set of rights and/or Access Token a data artifact representing a set of rights and/or
attributes. attributes. Note: an access token can be first issued to an
client instance (requiring authorization by the RO) and
Note: an access token can be first issued to an client instance subsequently rotated.
(requiring authorization by the RO) and subsequently rotated.
Grant (verb): to permit an instance of client software to receive Grant (verb): to permit an instance of client software to receive
some attributes at a specific time and valid for a specific some attributes at a specific time and valid for a specific
duration and/or to exercise some set of delegated rights to access duration and/or to exercise some set of delegated rights to access
a protected resource (noun): the act of granting. a protected resource (noun): the act of granting.
Privilege right or attribute associated with a subject. Privilege right or attribute associated with a subject. Note: the
RO defines and maintains the rights and attributes associated to
Note: the RO defines and maintains the rights and attributes the protected resource, and might temporarily delegate some set of
associated to the protected resource, and might temporarily those privileges to an end-user. This process is refered to as
delegate some set of those privileges to an end-user. This privilege delegation.
process is refered to as privilege delegation.
Protected Resource protected API (Application Programming Interface) Protected Resource protected API (Application Programming Interface)
served by an RS and that can be accessed by a client, if and only served by an RS and that can be accessed by a client, if and only
if a valid access token is provided. if a valid access token is provided. Note: to avoid complex
sentences, the specification document may simply refer to resource
Note: to avoid complex sentences, the specification document may instead of protected resource.
simply refer to resource instead of protected resource.
Right ability given to a subject to perform a given operation on a Right ability given to a subject to perform a given operation on a
resource under the control of an RS. resource under the control of an RS.
Subject person, organization or device. Subject person, organization or device.
Subject Information statement asserted by an AS about a subject. Subject Information statement asserted by an AS about a subject.
1.4. Sequences 1.4. Trust relationships
GNAP defines its trust objective as: "the RO trusts the AS to ensure
access validation and delegation of protected resources to end-users,
through third party clients."
This trust objective can be decomposed into trust relationships
between software elements and roles, especially the pairs end-user/
RO, end-user/client, client/AS, RS/RO, AS/RO, AS/RS. Trust of an
agent by its pair can exist if the pair is informed that the agent
has made a promise to follow the protocol in the past (e.g. pre-
registration, uncompromised cryptographic components) or if the pair
is able to infer by indirect means that the agent has made such a
promise (e.g. a compliant client request). Each agent defines its
own valuation function of promises given or received. Examples of
such valuations can be the benefits from interacting with other
agents (e.g. safety in client access, interoperability with identity
standards), the cost of following the protocol (including its
security and privacy requirements and recommendations), a ranking of
promise importance (e.g. a policy decision made by the AS), the
assessment of one's vulnerability or risk of not being able to defend
against threats, etc. Those valuations may depend on the context of
the request. For instance, the AS may decide to either take into
account or discard hints provided by the client, the RS may refuse
bearer tokens, etc. depending on the specific case in which GNAP is
used. Some promises can be conditional of some previous interactions
(e.g. repeated requests).
Looking back on each trust relationship:
* end-user/RO: this relationship exists only when the end-user and
the RO are different, in which case the end-user needs some out of
band mechanism of getting the RO consent (see Section 4). GNAP
generally assumes that humans can be authenticated thanks to
identity protocols (for instance, through an id_token assertion in
Section 2.2).
* end-user/client: the client acts as a user agent. Depending on
the technology used (browser, SPA, mobile application, IoT device,
etc.), some interactions may or may not be possible (as described
in Section 2.5.1). Client developers promise to implement
requirements and generally some recommendations or best practices,
so that the end-users may confidently use their software.
However, end-users might also be facing some attacker's client
software, without even realizing it.
* client/AS: An honest AS may be facing an attacker's client (as
discussed just above), or the reverse, and GNAP aims at making
common attacks impractical. The core specification makes access
tokens opaque to the client and defines the request/response
scheme in detail, therefore avoiding extra trust hypotheses from
this critical piece of software. Yet the AS may further define
cryptographic attestations or optional rules to simplify the
access of clients it already trusts, due to past behavior or
organizational policies (see Section 2.3).
* RS/RO: the RS promises it protects its resources from unauthorized
access, and only accepts valid access tokens issued by a trusted
AS. In case tokens are key bound, proper validation is expected
from the RS.
* AS/RO: the AS is expected to follow the decisions made by the RO,
either through interactive consent requests, repeated interactions
or automated rules (as described in Section 1.5). Privacy
considerations aim to reduce the risk of an honest but too curious
AS, or the consequences of an unexpected user data exposure.
* AS/RS: the AS promises to issue valid access tokens to legitimate
client requests (i.e. after carrying out appropriate due
diligence, as defined in the GNAP protocol). Some optional
configurations are covered by
[I-D.draft-ietf-gnap-resource-servers].
A global assumption made by GNAP is that authorization requests are
security and privacy sensitive, and appropriate measures are
respectively detailed in Section 12 and Section 13.
A formal trust model is out of scope of this specification, but might
be carried out thanks to [promise-theory].
1.5. Sequences
GNAP can be used in a variety of ways to allow the core delegation GNAP can be used in a variety of ways to allow the core delegation
process to take place. Many portions of this process are process to take place. Many portions of this process are
conditionally present depending on the context of the deployments, conditionally present depending on the context of the deployments,
and not every step in this overview will happen in all circumstances. and not every step in this overview will happen in all circumstances.
Note that a connection between roles in this process does not Note that a connection between roles in this process does not
necessarily indicate that a specific protocol message is sent across necessarily indicate that a specific protocol message is sent across
the wire between the components fulfilling the roles in question, or the wire between the components fulfilling the roles in question, or
that a particular step is required every time. For example, for a that a particular step is required every time. For example, for a
skipping to change at page 12, line 15 skipping to change at page 15, line 15
* (13) The client instance disposes of the token (Section 6.2) once * (13) The client instance disposes of the token (Section 6.2) once
the client instance has completed its access of the RS and no the client instance has completed its access of the RS and no
longer needs the token. longer needs the token.
The following sections and Appendix D contain specific guidance on The following sections and Appendix D contain specific guidance on
how to use GNAP in different situations and deployments. For how to use GNAP in different situations and deployments. For
example, it is possible for the client instance to never request an example, it is possible for the client instance to never request an
access token and never call an RS, just as it is possible for there access token and never call an RS, just as it is possible for there
not to be a user involved in the delegation process. not to be a user involved in the delegation process.
1.4.1. Redirect-based Interaction 1.5.1. Redirect-based Interaction
In this example flow, the client instance is a web application that 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 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 both the end-user and the resource owner (RO). Since the client
instance is capable of directing the user to an arbitrary URL and instance is capable of directing the user to an arbitrary URL and
receiving responses from the user's browser, interaction here is receiving responses from the user's browser, interaction here is
handled through front-channel redirects using the user's browser. handled through front-channel redirects using the user's browser.
The redirection URL used for interaction is a service hosted by the The redirection URL used for interaction is a service hosted by the
AS in this example. The client instance uses a persistent session AS in this example. The client instance uses a persistent session
with the user to ensure the same user that is starting the with the user to ensure the same user that is starting the
skipping to change at page 15, line 5 skipping to change at page 18, line 5
10. The client instance uses the access token (Section 7.2) to call 10. The client instance uses the access token (Section 7.2) to call
the RS. the RS.
11. The RS validates the access token and returns an appropriate 11. The RS validates the access token and returns an appropriate
response for the API. response for the API.
An example set of protocol messages for this method can be found in An example set of protocol messages for this method can be found in
Appendix D.1. Appendix D.1.
1.4.2. User-code Interaction 1.5.2. User-code Interaction
In this example flow, the client instance is a device that is capable 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 of presenting a short, human-readable code to the user and directing
the user to enter that code at a known URL. The URL the user enters the user to enter that code at a known URL. The URL the user enters
the code at is an interactive service hosted by the AS in this the code at is an interactive service hosted by the AS in this
example. The client instance is not capable of presenting an example. The client instance is not capable of presenting an
arbitrary URL to the user, nor is it capable of accepting incoming arbitrary URL to the user, nor is it capable of accepting incoming
HTTP requests from the user's browser. The client instance polls the 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 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 user's interaction is assumed to occur on a secondary device. In
skipping to change at page 17, line 26 skipping to change at page 20, line 26
13. The client instance uses the access token (Section 7.2) to call 13. The client instance uses the access token (Section 7.2) to call
the RS. the RS.
14. The RS validates the access token and returns an appropriate 14. The RS validates the access token and returns an appropriate
response for the API. response for the API.
An example set of protocol messages for this method can be found in An example set of protocol messages for this method can be found in
Appendix D.2. Appendix D.2.
1.4.3. Asynchronous Authorization 1.5.3. Asynchronous Authorization
In this example flow, the end-user and RO roles are fulfilled by In this example flow, the end-user and RO roles are fulfilled by
different parties, and the RO does not interact with the client different parties, and the RO does not interact with the client
instance. The AS reaches out asynchronously to the RO during the instance. The AS reaches out asynchronously to the RO during the
request process to gather the RO's authorization for the client request process to gather the RO's authorization for the client
instance's request. The client instance polls the AS while it is instance's request. The client instance polls the AS while it is
waiting for the RO to authorize the request. waiting for the RO to authorize the request.
+--------+ +--------+ +------+ +--------+ +--------+ +------+
| Client | | AS | | RO | | Client | | AS | | RO |
skipping to change at page 19, line 40 skipping to change at page 22, line 40
10. The client instance uses the access token (Section 7.2) to call 10. The client instance uses the access token (Section 7.2) to call
the RS. the RS.
11. The RS validates the access token and returns an appropriate 11. The RS validates the access token and returns an appropriate
response for the API. response for the API.
An example set of protocol messages for this method can be found in An example set of protocol messages for this method can be found in
Appendix D.4. Appendix D.4.
1.4.4. Software-only Authorization 1.5.4. Software-only Authorization
In this example flow, the AS policy allows the client instance to 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 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 involved at runtime to approve the decision. Since there is no
explicit RO, the client instance does not interact with an RO. explicit RO, the client instance does not interact with an RO.
+--------+ +--------+ +--------+ +--------+
| Client | | AS | | Client | | AS |
|Instance|--(1)--- Request Access --->| | |Instance|--(1)--- Request Access --->| |
| | | | | | | |
skipping to change at page 20, line 36 skipping to change at page 23, line 36
3. The client instance uses the access token (Section 7.2) to call 3. The client instance uses the access token (Section 7.2) to call
the RS. the RS.
4. The RS validates the access token and returns an appropriate 4. The RS validates the access token and returns an appropriate
response for the API. response for the API.
An example set of protocol messages for this method can be found in An example set of protocol messages for this method can be found in
Appendix D.3. Appendix D.3.
1.4.5. Refreshing an Expired Access Token 1.5.5. Refreshing an Expired Access Token
In this example flow, the client instance receives an access token to In this example flow, the client instance receives an access token to
access a resource server through some valid GNAP process. The client access a resource server through some valid GNAP process. The client
instance uses that token at the RS for some time, but eventually the instance uses that token at the RS for some time, but eventually the
access token expires. The client instance then gets a new access access token expires. The client instance then gets a new access
token by rotating the expired access token at the AS using the token by rotating the expired access token at the AS using the
token's management URL. token's management URL.
+--------+ +--------+ +--------+ +--------+
| Client | | AS | | Client | | AS |
skipping to change at page 22, line 12 skipping to change at page 25, line 12
as the appropriate key, see the token rotation section for as the appropriate key, see the token rotation section for
details. details.
8. The AS validates the rotation request including the signature and 8. The AS validates the rotation request including the signature and
keys presented in (5) and returns a new access token keys presented in (5) and returns a new access token
(Section 3.2.1). The response includes a new access token and (Section 3.2.1). The response includes a new access token and
can also include updated token management information, which the can also include updated token management information, which the
client instance will store in place of the values returned in client instance will store in place of the values returned in
(2). (2).
1.4.6. Requesting User Information 1.5.6. Requesting User Information
In this scenario, the client instance does not call an RS and does In this scenario, the client instance does not call an RS and does
not request an access token. Instead, the client instance only not request an access token. Instead, the client instance only
requests and is returned direct subject information (Section 3.4). requests and is returned direct subject information (Section 3.4).
Many different interaction modes can be used in this scenario, so Many different interaction modes can be used in this scenario, so
these are shown only in the abstract as functions of the AS here. these are shown only in the abstract as functions of the AS here.
+--------+ +--------+ +------+ +--------+ +--------+ +------+
| Client | | AS | | User | | Client | | AS | | User |
|Instance| | | | | |Instance| | | | |
skipping to change at page 33, line 18 skipping to change at page 36, line 18
RO during any interactions at the AS, it MAY send that information in RO during any interactions at the AS, it MAY send that information in
the "display" field. This field is a JSON object that declares the "display" field. This field is a JSON object that declares
information to present to the RO during any interactive sequences. information to present to the RO during any interactive sequences.
name (string) Display name of the client software name (string) Display name of the client software
uri (string) User-facing web page of the client software uri (string) User-facing web page of the client software
logo_uri (string) Display image to represent the client software logo_uri (string) Display image to represent the client software
"display": { "display": {
"name": "My Client Display Name", "name": "My Client Display Name",
"uri": "https://example.net/client" "uri": "https://example.net/client"
} }
[[ See issue #48 (https://github.com/ietf-wg-gnap/gnap-core-protocol/ [[ See issue #48 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/48) ]] issues/48) ]]
Additional display fields are defined by a registry TBD (Section 11). Additional display fields are defined by a registry TBD (Section 11).
The AS SHOULD use these values during interaction with the RO. The The AS SHOULD use these values during interaction with the RO. The
values are for informational purposes only and MUST NOT be taken as values are for informational purposes only and MUST NOT be taken as
authentic proof of the client instance's identity or source. The AS authentic proof of the client instance's identity or source. The AS
MAY restrict display values to specific client instances, as MAY restrict display values to specific client instances, as
skipping to change at page 34, line 44 skipping to change at page 37, line 44
"id": "J2G8G8O4AZ" "id": "J2G8G8O4AZ"
} ], } ],
"assertions": { "assertions": {
"id_token": "eyj..." "id_token": "eyj..."
} }
} }
Subject identifiers are hints to the AS in determining the RO and Subject identifiers are hints to the AS in determining the RO and
MUST NOT be taken as declarative statements that a particular RO is MUST NOT be taken as declarative statements that a particular RO is
present at the client instance and acting as the end-user. present at the client instance and acting as the end-user.
Assertions SHOULD be validated by the AS. [[ See issue #49 Assertions SHOULD be validated by the AS. [[ See issue #49
(https://github.com/ietf-wg-gnap/gnap-core-protocol/issues/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 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 during an interaction step, the AS SHOULD reject the request with an
error. error.
[[ See issue #50 (https://github.com/ietf-wg-gnap/gnap-core-protocol/ [[ See issue #50 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/50) ]] issues/50) ]]
If the AS trusts the client instance to present verifiable If the AS trusts the client instance to present verifiable
assertions, the AS MAY decide, based on its policy, to skip assertions, the AS MAY decide, based on its policy, to skip
interaction with the RO, even if the client instance provides one or interaction with the RO, even if the client instance provides one or
more interaction modes in its request. more interaction modes in its request.
2.4.1. Identifying the User by Reference 2.4.1. Identifying the User by Reference
User reference identifiers can be dynamically issued by the AS The AS can identify the current end-user to the client instance with
(Section 3.5) to allow the client instance to represent the same end- a reference which can be used by the client instance to refer to the
user to the AS over subsequent requests. end-user across multiple requests. If the client instance has a
reference for the end-user at this AS, the client instance MAY pass
If the client instance has a reference for the end-user at this AS, that reference as a string. The format of this string is opaque to
the client instance MAY pass that reference as a string. The format the client instance.
of this string is opaque to the client instance.
"user": "XUT2MFM1XBIKJKSDU8QM" "user": "XUT2MFM1XBIKJKSDU8QM"
One means of dynamically obtaining such a user reference is from the
AS returning an "opaque" subject identifier as described in
Section 3.4. Other means of configuring a client instance with a
user identifier are out of scope of this specification.
User reference identifiers are not intended to be human-readable user User reference identifiers are not intended to be human-readable user
identifiers or structured assertions. For the client instance to identifiers or structured assertions. For the client instance to
send either of these, use the full user request object (Section 2.4) send either of these, use the full user request object (Section 2.4)
instead. instead.
[[ See issue #51 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/51) ]]
If the AS does not recognize the user reference, it MUST return an If the AS does not recognize the user reference, it MUST return an
error. error.
2.5. Interacting with the User 2.5. Interacting with the User
Often, the AS will require interaction with the RO (Section 4) in Often, the AS will require interaction with the RO (Section 4) in
order to approve a requested delegation to the client instance for order to approve a requested delegation to the client instance for
both access to resources and direct subject information. Many times both access to resources and direct subject information. Many times
the end-user using the client instance is the same person as the RO, the end-user using the client instance is the same person as the RO,
and the client instance can directly drive interaction with the end and the client instance can directly drive interaction with the end
skipping to change at page 42, line 23 skipping to change at page 45, line 23
Section 3.1 Section 3.1
access_token (object / array of objects) A single access token or access_token (object / array of objects) A single access token or
set of access tokens that the client instance can use to call the set of access tokens that the client instance can use to call the
RS on behalf of the RO. Section 3.2.1 RS on behalf of the RO. Section 3.2.1
interact (object) Indicates that interaction through some set of interact (object) Indicates that interaction through some set of
defined mechanisms needs to take place. Section 3.3 defined mechanisms needs to take place. Section 3.3
subject (object) Claims about the RO as known and declared by the subject (object) Claims about the RO as known and declared by the
AS. Section 3.4 AS, as described in Section 3.4.
instance_id (string) An identifier this client instance can use to instance_id (string) An identifier this client instance can use to
identify itself when making future requests. Section 3.5 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 error (object) An error code indicating that something has gone
wrong. Section 3.6 wrong. Section 3.6
In this example, the AS is returning an interaction URL In this example, the AS is returning an interaction URL
(Section 3.3.1), a callback nonce (Section 3.3.4), and a continuation (Section 3.3.1), a callback nonce (Section 3.3.4), and a continuation
response (Section 3.1). response (Section 3.1).
NOTE: '\' line wrapping per RFC 8792
{ {
"interact": { "interact": {
"redirect": "https://server.example.com/interact/4CF492ML\ "redirect": "https://server.example.com/interact/4CF492ML\
VMSW9MKMXKHQ", VMSW9MKMXKHQ",
"finish": "MBDOFXG4Y5CVJCX821LH" "finish": "MBDOFXG4Y5CVJCX821LH"
}, },
"continue": { "continue": {
"access_token": { "access_token": {
"value": "80UPRY5NM33OMUKMKSKU", "value": "80UPRY5NM33OMUKMKSKU",
}, },
"uri": "https://server.example.com/tx" "uri": "https://server.example.com/tx"
} }
} }
In this example, the AS is returning a bearer access token In this example, the AS is returning a bearer access token
(Section 3.2.1) with a management URL and a subject identifier (Section 3.2.1) with a management URL and a subject identifier
(Section 3.4) in the form of an opaque identifier. (Section 3.4) in the form of an opaque identifier.
NOTE: '\' line wrapping per RFC 8792
{ {
"access_token": { "access_token": {
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0", "value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
"flags": ["bearer"], "flags": ["bearer"],
"manage": "https://server.example.com/token/PRY5NM33O\ "manage": "https://server.example.com/token/PRY5NM33O\
M4TB8N6BW7OZB8CDFONP219RP1L", M4TB8N6BW7OZB8CDFONP219RP1L",
}, },
"subject": { "subject": {
"sub_ids": [ { "sub_ids": [ {
"format": "opaque", "format": "opaque",
skipping to change at page 47, line 5 skipping to change at page 50, line 5
Flag values MUST NOT be included more than once. Flag values MUST NOT be included more than once.
Additional flags can be defined by extensions using a registry TBD Additional flags can be defined by extensions using a registry TBD
(Section 11). (Section 11).
The following non-normative example shows a single access token bound The following non-normative example shows a single access token bound
to the client instance's key used in the initial request, with a to the client instance's key used in the initial request, with a
management URL, and that has access to three described resources (one management URL, and that has access to three described resources (one
using an object and two described by reference strings). using an object and two described by reference strings).
NOTE: '\' line wrapping per RFC 8792
"access_token": { "access_token": {
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0", "value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
"manage": "https://server.example.com/token/PRY5NM33O\ "manage": "https://server.example.com/token/PRY5NM33O\
M4TB8N6BW7OZB8CDFONP219RP1L", M4TB8N6BW7OZB8CDFONP219RP1L",
"access": [ "access": [
{ {
"type": "photo-api", "type": "photo-api",
"actions": [ "actions": [
"read", "read",
"write", "write",
skipping to change at page 48, line 19 skipping to change at page 51, line 19
"access_token" field. The value of this field is a JSON array, the "access_token" field. The value of this field is a JSON array, the
members of which are distinct access tokens as described in members of which are distinct access tokens as described in
Section 3.2.1. Each object MUST have a unique "label" field, Section 3.2.1. Each object MUST have a unique "label" field,
corresponding to the token labels chosen by the client instance in corresponding to the token labels chosen by the client instance in
the multiple access token request (Section 2.1.2). the multiple access token request (Section 2.1.2).
In this non-normative example, two tokens are issued under the names In this non-normative example, two tokens are issued under the names
"token1" and "token2", and only the first token has a management URL "token1" and "token2", and only the first token has a management URL
associated with it. associated with it.
NOTE: '\' line wrapping per RFC 8792
"access_token": [ "access_token": [
{ {
"label": "token1", "label": "token1",
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0", "value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
"manage": "https://server.example.com/token/PRY5NM33O\ "manage": "https://server.example.com/token/PRY5NM33O\
M4TB8N6BW7OZB8CDFONP219RP1L", M4TB8N6BW7OZB8CDFONP219RP1L",
"access": [ "finance" ] "access": [ "finance" ]
}, },
{ {
"label": "token2", "label": "token2",
skipping to change at page 53, line 25 skipping to change at page 56, line 25
If the AS returns a nonce, the client instance MUST NOT continue a If the AS returns a nonce, the client instance MUST NOT continue a
grant request before it receives the associated interaction reference grant request before it receives the associated interaction reference
on the callback URI. See details in Section 4.2. on the callback URI. See details in Section 4.2.
3.3.5. Extending Interaction Mode Responses 3.3.5. Extending Interaction Mode Responses
Extensions to this specification can define new interaction mode Extensions to this specification can define new interaction mode
responses in a registry TBD (Section 11). Extensions MUST document responses in a registry TBD (Section 11). Extensions MUST document
the corresponding interaction request. the corresponding interaction request.
3.4. Returning User Information 3.4. Returning Subject Information
If information about the RO is requested and the AS grants the client If information about the RO is requested and the AS grants the client
instance access to that data, the AS returns the approved information instance access to that data, the AS returns the approved information
in the "subject" response field. This field is an object with the in the "subject" response field. The AS MUST return the "subject"
following OPTIONAL properties. 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).
This field is an object with the following OPTIONAL properties.
sub_ids (array of objects) An array of subject identifiers for the sub_ids (array of objects) An array of subject identifiers for the
RO, as defined by [I-D.ietf-secevent-subject-identifiers]. RO, as defined by [I-D.ietf-secevent-subject-identifiers].
assertions (object) An object containing assertions as values keyed assertions (object) An object containing assertions as values keyed
on the assertion type defined by a registry TBD (Section 11). [[ on the assertion type defined by a registry TBD (Section 11). [[
See issue #41 (https://github.com/ietf-wg-gnap/gnap-core-protocol/ See issue #41 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/41) ]] issues/41) ]]
updated_at (string) Timestamp as an ISO8610 date string, indicating updated_at (string) Timestamp as an ISO8610 date string, indicating
when the identified account was last updated. The client instance when the identified account was last updated. The client instance
MAY use this value to determine if it needs to request updated MAY use this value to determine if it needs to request updated
profile information through an identity API. The definition of profile information through an identity API. The definition of
such an identity API is out of scope for this specification. such an identity API is out of scope for this specification.
"subject": { "subject": {
"sub_ids": [ { "sub_ids": [ {
"format": "opaque", "format": "opaque",
"id": "J2G8G8O4AZ" "id": "XUT2MFM1XBIKJKSDU8QM"
} ], } ],
"assertions": { "assertions": {
"id_token": "eyj..." "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 Subject identifiers returned by the AS SHOULD uniquely identify the
RO at the AS. Some forms of subject identifier are opaque to 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), client instance (such as the subject of an issuer and subject pair),
while others forms (such as email address and phone number) are while others forms (such as email address and phone number) are
intended to allow the client instance to correlate the identifier intended to allow the client instance to correlate the identifier
with other account information at the client instance. The AS MUST with other account information at the client instance. The AS MUST
ensure that the returned subject identifiers only apply to the ensure that the returned subject identifiers only apply to the
authenticated end user. The client instance MUST NOT request or use authenticated end user. The client instance MUST NOT request or use
any returned subject identifiers for communication purposes (see any returned subject identifiers for communication purposes (see
Section 2.2). That is, a subject identifier returned in the format Section 2.2). That is, a subject identifier returned in the format
skipping to change at page 55, line 26 skipping to change at page 58, line 15
sending the associated data value. These handles are intended to be sending the associated data value. These handles are intended to be
used on future requests. used on future requests.
Dynamically generated handles are string values that MUST be Dynamically generated handles are string values that MUST be
protected by the client instance as secrets. Handle values MUST be protected by the client instance as secrets. Handle values MUST be
unguessable and MUST NOT contain any sensitive information. Handle unguessable and MUST NOT contain any sensitive information. Handle
values are opaque to the client instance. values are opaque to the client instance.
All dynamically generated handles are returned as fields in the root All dynamically generated handles are returned as fields in the root
JSON object of the response. This specification defines the JSON object of the response. This specification defines the
following dynamic handle returns, additional handles can be defined following dynamic handle return, additional handles can be defined in
in a registry TBD (Section 11). a registry TBD (Section 11).
instance_id (string) A string value used to represent the instance_id (string) A string value used to represent the
information in the "client" object that the client instance can information in the "client" object that the client instance can
use in a future request, as described in Section 2.3.1. use in a future request, as described in Section 2.3.1.
user_handle (string) A string value used to represent the current This non-normative example shows one handle along side an issued
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. access token.
{ {
"user_handle": "XUT2MFM1XBIKJKSDU8QM",
"instance_id": "7C7C4AZ9KHRS6X63AJAO", "instance_id": "7C7C4AZ9KHRS6X63AJAO",
"access_token": { "access_token": {
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0" "value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0"
} }
} }
[[ See issue #77 (https://github.com/ietf-wg-gnap/gnap-core-protocol/ [[ See issue #77 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/77) ]] issues/77) ]]
[[ See issue #78 (https://github.com/ietf-wg-gnap/gnap-core-protocol/ [[ See issue #78 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
skipping to change at page 63, line 5 skipping to change at page 65, line 35
hash REQUIRED. The interaction hash value as described in hash REQUIRED. The interaction hash value as described in
Section 4.2.3. Section 4.2.3.
interact_ref REQUIRED. The interaction reference generated for this interact_ref REQUIRED. The interaction reference generated for this
interaction. interaction.
The means of directing the RO to this URL are outside the scope of The means of directing the RO to this URL are outside the scope of
this specification, but common options include redirecting the RO this specification, but common options include redirecting the RO
from a web page and launching the system browser with the target URL. from a web page and launching the system browser with the target URL.
NOTE: '\' line wrapping per RFC 8792
https://client.example.net/return/123455\ https://client.example.net/return/123455\
?hash=p28jsq0Y2KK3WS__a42tavNC64ldGTBroywsWxT4md_jZQ1R2\ ?hash=p28jsq0Y2KK3WS__a42tavNC64ldGTBroywsWxT4md_jZQ1R2\
HZT8BOWYHcLmObM7XHPAdJzTZMtKBsaraJ64A\ HZT8BOWYHcLmObM7XHPAdJzTZMtKBsaraJ64A\
&interact_ref=4IFWWIKYBC2PQ6U56NL1 &interact_ref=4IFWWIKYBC2PQ6U56NL1
When receiving the request, the client instance MUST parse the query When receiving the request, the client instance MUST parse the query
parameters to calculate and validate the hash value as described in parameters to calculate and validate the hash value as described in
Section 4.2.3. If the hash validates, the client instance sends a Section 4.2.3. If the hash validates, the client instance sends a
continuation request to the AS as described in Section 5.1 using the continuation request to the AS as described in Section 5.1 using the
interaction reference value received here. interaction reference value received here.
skipping to change at page 63, line 33 skipping to change at page 66, line 22
The entity message body is a JSON object consisting of the following The entity message body is a JSON object consisting of the following
two fields: two fields:
hash (string) REQUIRED. The interaction hash value as described in hash (string) REQUIRED. The interaction hash value as described in
Section 4.2.3. Section 4.2.3.
interact_ref (string) REQUIRED. The interaction reference generated interact_ref (string) REQUIRED. The interaction reference generated
for this interaction. for this interaction.
NOTE: '\' line wrapping per RFC 8792
POST /push/554321 HTTP/1.1 POST /push/554321 HTTP/1.1
Host: client.example.net Host: client.example.net
Content-Type: application/json Content-Type: application/json
{ {
"hash": "p28jsq0Y2KK3WS__a42tavNC64ldGTBroywsWxT4md_jZQ1R\ "hash": "p28jsq0Y2KK3WS__a42tavNC64ldGTBroywsWxT4md_jZQ1R\
2HZT8BOWYHcLmObM7XHPAdJzTZMtKBsaraJ64A", 2HZT8BOWYHcLmObM7XHPAdJzTZMtKBsaraJ64A",
"interact_ref": "4IFWWIKYBC2PQ6U56NL1" "interact_ref": "4IFWWIKYBC2PQ6U56NL1"
} }
skipping to change at page 65, line 5 skipping to change at page 67, line 44
[[ See issue #56 (https://github.com/ietf-wg-gnap/gnap-core-protocol/ [[ See issue #56 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/56) ]] issues/56) ]]
4.2.3.1. SHA3-512 4.2.3.1. SHA3-512
The "sha3" hash method consists of hashing the input string with the The "sha3" hash method consists of hashing the input string with the
512-bit SHA3 algorithm. The byte array is then encoded using URL 512-bit SHA3 algorithm. The byte array is then encoded using URL
Safe Base64 with no padding. The resulting string is the hash value. Safe Base64 with no padding. The resulting string is the hash value.
NOTE: '\' line wrapping per RFC 8792
p28jsq0Y2KK3WS__a42tavNC64ldGTBroywsWxT4md_jZQ1R2HZT8BOWYHcLmObM\ p28jsq0Y2KK3WS__a42tavNC64ldGTBroywsWxT4md_jZQ1R2HZT8BOWYHcLmObM\
7XHPAdJzTZMtKBsaraJ64A 7XHPAdJzTZMtKBsaraJ64A
4.2.3.2. SHA2-512 4.2.3.2. SHA2-512
The "sha2" hash method consists of hashing the input string with the The "sha2" hash method consists of hashing the input string with the
512-bit SHA2 algorithm. The byte array is then encoded using URL 512-bit SHA2 algorithm. The byte array is then encoded using URL
Safe Base64 with no padding. The resulting string is the hash value. Safe Base64 with no padding. The resulting string is the hash value.
NOTE: '\' line wrapping per RFC 8792
62SbcD3Xs7L40rjgALA-ymQujoh2LB2hPJyX9vlcr1H6ecChZ8BNKkG_HrOKP_Bp\ 62SbcD3Xs7L40rjgALA-ymQujoh2LB2hPJyX9vlcr1H6ecChZ8BNKkG_HrOKP_Bp\
j84rh4mC9aE9x7HPBFcIHw j84rh4mC9aE9x7HPBFcIHw
5. Continuing a Grant Request 5. Continuing a Grant Request
While it is possible for the AS to return a Section 3 with all the While it is possible for the AS to return a Section 3 with all the
client instance's requested information (including access tokens client instance's requested information (including access tokens
(Section 3.2) and direct user information (Section 3.4)), it's more (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 common that the AS and the client instance will need to communicate
several times over the lifetime of an access grant. This is often several times over the lifetime of an access grant. This is often
skipping to change at page 68, line 8 skipping to change at page 71, line 8
The Section 3 MAY contain any newly-created access tokens The Section 3 MAY contain any newly-created access tokens
(Section 3.2) or newly-released subject claims (Section 3.4). The (Section 3.2) or newly-released subject claims (Section 3.4). The
response MAY contain a new "continue" response (Section 3.1) as response MAY contain a new "continue" response (Section 3.1) as
described above. The response SHOULD NOT contain any interaction described above. The response SHOULD NOT contain any interaction
responses (Section 3.3). [[ See issue #89 (https://github.com/ietf- responses (Section 3.3). [[ See issue #89 (https://github.com/ietf-
wg-gnap/gnap-core-protocol/issues/89) ]] wg-gnap/gnap-core-protocol/issues/89) ]]
For example, if the request is successful in causing the AS to issue For example, if the request is successful in causing the AS to issue
access tokens and release opaque subject claims, the response could access tokens and release opaque subject claims, the response could
look like this: look like this:
NOTE: '\' line wrapping per RFC 8792
{ {
"access_token": { "access_token": {
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0", "value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
"manage": "https://server.example.com/token/PRY5NM33O\ "manage": "https://server.example.com/token/PRY5NM33O\
M4TB8N6BW7OZB8CDFONP219RP1L", M4TB8N6BW7OZB8CDFONP219RP1L",
}, },
"subject": { "subject": {
"sub_ids": [ { "sub_ids": [ {
"format": "opaque", "format": "opaque",
"id": "J2G8G8O4AZ" "id": "J2G8G8O4AZ"
skipping to change at page 69, line 31 skipping to change at page 72, line 31
[[ See issue #90 (https://github.com/ietf-wg-gnap/gnap-core-protocol/ [[ See issue #90 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/90) ]] issues/90) ]]
[[ See issue #91 (https://github.com/ietf-wg-gnap/gnap-core-protocol/ [[ See issue #91 (https://github.com/ietf-wg-gnap/gnap-core-protocol/
issues/91) ]] issues/91) ]]
If the request is successful in causing the AS to issue access tokens If the request is successful in causing the AS to issue access tokens
and release subject claims, the response could look like this and release subject claims, the response could look like this
example: example:
NOTE: '\' line wrapping per RFC 8792
{ {
"access_token": { "access_token": {
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0", "value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
"manage": "https://server.example.com/token/PRY5NM33O\ "manage": "https://server.example.com/token/PRY5NM33O\
M4TB8N6BW7OZB8CDFONP219RP1L", M4TB8N6BW7OZB8CDFONP219RP1L",
}, },
"subject": { "subject": {
"sub_ids": [ { "sub_ids": [ {
"format": "opaque", "format": "opaque",
"id": "J2G8G8O4AZ" "id": "J2G8G8O4AZ"
skipping to change at page 70, line 14 skipping to change at page 73, line 23
The client instance MAY include the "access_token" and "subject" The client instance MAY include the "access_token" and "subject"
fields as described in Section 2.1 and Section 2.2. Inclusion of fields as described in Section 2.1 and Section 2.2. Inclusion of
these fields override any values in the initial request, which MAY these fields override any values in the initial request, which MAY
trigger additional requirements and policies by the AS. For example, trigger additional requirements and policies by the AS. For example,
if the client instance is asking for more access, the AS could if the client instance is asking for more access, the AS could
require additional interaction with the RO to gather additional require additional interaction with the RO to gather additional
consent. If the client instance is asking for more limited access, consent. If the client instance is asking for more limited access,
the AS could determine that sufficient authorization has been granted the AS could determine that sufficient authorization has been granted
to the client instance and return the more limited access rights to the client instance and return the more limited access rights
immediately. [[ See issue #92 (https://github.com/ietf-wg-gnap/gnap- immediately. [[ See issue #92 (https://github.com/ietf-wg-gnap/gnap-
core-protocol/issues/92) ]] core-protocol/issues/92) ]]
The client instance MAY include the "interact" field as described in The client instance MAY include the "interact" field as described in
Section 2.5. Inclusion of this field indicates that the client Section 2.5. Inclusion of this field indicates that the client
instance is capable of driving interaction with the RO, and this instance is capable of driving interaction with the RO, and this
field replaces any values from a previous request. The AS MAY field replaces any values from a previous request. The AS MAY
respond to any of the interaction responses as described in respond to any of the interaction responses as described in
Section 3.3, just like it would to a new request. Section 3.3, just like it would to a new request.
The client instance MAY include the "user" field as described in The client instance MAY include the "user" field as described in
Section 2.4 to present new assertions or information about the end- Section 2.4 to present new assertions or information about the end-
user. [[ See issue #93 (https://github.com/ietf-wg-gnap/gnap-core- user. [[ See issue #93 (https://github.com/ietf-wg-gnap/gnap-core-
protocol/issues/93) ]] protocol/issues/93) ]]
The client instance MUST NOT include the "client" section of the The client instance MUST NOT include the "client" section of the
request. [[ See issue #94 (https://github.com/ietf-wg-gnap/gnap-core- request. [[ See issue #94 (https://github.com/ietf-wg-gnap/gnap-core-
protocol/issues/94) ]] protocol/issues/94) ]]
The client instance MAY include post-interaction responses such as The client instance MAY include post-interaction responses such as
described in Section 5.1. [[ See issue #95 (https://github.com/ietf- described in Section 5.1. [[ See issue #95 (https://github.com/ietf-
wg-gnap/gnap-core-protocol/issues/95) ]] wg-gnap/gnap-core-protocol/issues/95) ]]
Modification requests MUST NOT alter previously-issued access tokens. Modification requests MUST NOT alter previously-issued access tokens.
Instead, any access tokens issued from a continuation are considered Instead, any access tokens issued from a continuation are considered
new, separate access tokens. The AS MAY revoke existing access new, separate access tokens. The AS MAY revoke existing access
tokens after a modification has occurred. [[ See issue #96 tokens after a modification has occurred. [[ See issue #96
(https://github.com/ietf-wg-gnap/gnap-core-protocol/issues/96) ]] (https://github.com/ietf-wg-gnap/gnap-core-protocol/issues/96) ]]
If the modified request can be granted immediately by the AS, the If the modified request can be granted immediately by the AS, the
Section 3 MAY contain any newly-created access tokens (Section 3.2) Section 3 MAY contain any newly-created access tokens (Section 3.2)
or newly-released subject claims (Section 3.4). The response MAY or newly-released subject claims (Section 3.4). The response MAY
contain a new "continue" response (Section 3.1) as described above. contain a new "continue" response (Section 3.1) as described above.
If interaction can occur, the response SHOULD contain interaction If interaction can occur, the response SHOULD contain interaction
responses (Section 3.3) as well. responses (Section 3.3) as well.
For example, a client instance initially requests a set of resources For example, a client instance initially requests a set of resources
using references: using references:
skipping to change at page 77, line 4 skipping to change at page 81, line 4
in Section 3.2.1, unless the "multi_token" flag is specified in the 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 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. current value of the access token used to access the management API.
The response MAY include an updated access token management URL as 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 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- the new access token. [[ See issue #101 (https://github.com/ietf-wg-
gnap/gnap-core-protocol/issues/101) ]] gnap/gnap-core-protocol/issues/101) ]]
[[ See issue #102 (https://github.com/ietf-wg-gnap/gnap-core- [[ See issue #102 (https://github.com/ietf-wg-gnap/gnap-core-
protocol/issues/102) ]] protocol/issues/102) ]]
NOTE: '\' line wrapping per RFC 8792
{ {
"access_token": { "access_token": {
"value": "FP6A8H6HY37MH13CK76LBZ6Y1UADG6VEUPEER5H2", "value": "FP6A8H6HY37MH13CK76LBZ6Y1UADG6VEUPEER5H2",
"manage": "https://server.example.com/token/PRY5NM33O\ "manage": "https://server.example.com/token/PRY5NM33O\
M4TB8N6BW7OZB8CDFONP219RP1L", M4TB8N6BW7OZB8CDFONP219RP1L",
"access": [ "access": [
{ {
"type": "photo-api", "type": "photo-api",
"actions": [ "actions": [
"read", "read",
skipping to change at page 83, line 5 skipping to change at page 87, line 5
to either the access token's own key or, in the case of bearer to either the access token's own key or, in the case of bearer
tokens, the client instance's key. tokens, the client instance's key.
[[ See issue #105 (https://github.com/ietf-wg-gnap/gnap-core- [[ See issue #105 (https://github.com/ietf-wg-gnap/gnap-core-
protocol/issues/105) ]] protocol/issues/105) ]]
In the following sections, unless otherwise noted, the "RS256" JOSE In the following sections, unless otherwise noted, the "RS256" JOSE
Signature Algorithm is applied using the following RSA key (presented Signature Algorithm is applied using the following RSA key (presented
here in JWK format): here in JWK format):
NOTE: '\' line wrapping per RFC 8792
{ {
"kid": "gnap-rsa", "kid": "gnap-rsa",
"p": "xS4-YbQ0SgrsmcA7xDzZKuVNxJe3pCYwdAe6efSy4hdDgF9-vhC5gjaRk\ "p": "xS4-YbQ0SgrsmcA7xDzZKuVNxJe3pCYwdAe6efSy4hdDgF9-vhC5gjaRk\
i1wWuERSMW4Tv44l5HNrL-Bbj_nCJxr_HAOaesDiPn2PnywwEfg3Nv95Nn-\ i1wWuERSMW4Tv44l5HNrL-Bbj_nCJxr_HAOaesDiPn2PnywwEfg3Nv95Nn-\
eilhqXRaW-tJKEMjDHu_fmJBeemHNZI412gBnXdGzDVo22dvYoxd6GM", eilhqXRaW-tJKEMjDHu_fmJBeemHNZI412gBnXdGzDVo22dvYoxd6GM",
"kty": "RSA", "kty": "RSA",
"q": "rVdcT_uy-CD0GKVLGpEGRR7k4JO6Tktc8MEHkC6NIFXihk_6vAIOCzCD6\ "q": "rVdcT_uy-CD0GKVLGpEGRR7k4JO6Tktc8MEHkC6NIFXihk_6vAIOCzCD6\
LMovMinOYttpRndKoGTNdJfWlDFDScAs8C5n2y1STCQPRximBY-bw39-aZq\ LMovMinOYttpRndKoGTNdJfWlDFDScAs8C5n2y1STCQPRximBY-bw39-aZq\
JXMxOLyPjzuVgiTOCBIvLD6-8-mvFjXZk_eefD0at6mQ5qV3U1jZt88", JXMxOLyPjzuVgiTOCBIvLD6-8-mvFjXZk_eefD0at6mQ5qV3U1jZt88",
"d": "FHlhdTF0ozTliDxMBffT6aJVKZKmbbFJOVNten9c3lXKB3ux3NAb_D2dB\ "d": "FHlhdTF0ozTliDxMBffT6aJVKZKmbbFJOVNten9c3lXKB3ux3NAb_D2dB\
skipping to change at page 85, line 5 skipping to change at page 89, line 5
Other covered content MAY also be included. Other covered content MAY also be included.
If the signer's key presented is a JWK, the "keyid" parameter of the If the signer's key presented is a JWK, the "keyid" parameter of the
signature MUST be set to the "kid" value of the JWK, the signing signature MUST be set to the "kid" value of the JWK, the signing
algorithm used MUST be the JWS algorithm denoted by the key's "alg" algorithm used MUST be the JWS algorithm denoted by the key's "alg"
field, and the explicit "alg" signature parameter MUST NOT be field, and the explicit "alg" signature parameter MUST NOT be
included. included.
In this example, the message body is the following JSON object: In this example, the message body is the following JSON object:
NOTE: '\' line wrapping per RFC 8792
{ {
"access_token": { "access_token": {
"access": [ "access": [
"dolphin-metadata" "dolphin-metadata"
] ]
}, },
"interact": { "interact": {
"start": ["redirect"], "start": ["redirect"],
"finish": { "finish": {
"method": "redirect", "method": "redirect",
skipping to change at page 86, line 5 skipping to change at page 90, line 5
} }
This body is hashed for the Digest header using SHA-256 into the This body is hashed for the Digest header using SHA-256 into the
following encoded value: following encoded value:
SHA-256=98QzyNVYpdgTrWBKpC4qFSCmmR+CrwwvUoiaDCSjKxw= SHA-256=98QzyNVYpdgTrWBKpC4qFSCmmR+CrwwvUoiaDCSjKxw=
The HTTP message signature input string is calculated to be the The HTTP message signature input string is calculated to be the
following: following:
NOTE: '\' line wrapping per RFC 8792
"@request-target": post /gnap "@request-target": post /gnap
"host": server.example.com "host": server.example.com
"content-type": application/json "content-type": application/json
"digest": SHA-256=98QzyNVYpdgTrWBKpC4qFSCmmR+CrwwvUoiaDCSjKxw= "digest": SHA-256=98QzyNVYpdgTrWBKpC4qFSCmmR+CrwwvUoiaDCSjKxw=
"content-length": 986 "content-length": 986
"@signature-params": ("@request-target" "host" "content-type" \ "@signature-params": ("@request-target" "host" "content-type" \
"digest" "content-length");created=1618884475;keyid="gnap-rsa" "digest" "content-length");created=1618884475;keyid="gnap-rsa"
This leads to the following full HTTP message request: This leads to the following full HTTP message request:
NOTE: '\' line wrapping per RFC 8792
POST /gnap HTTP/1.1 POST /gnap HTTP/1.1
Host: server.example.com Host: server.example.com
Content-Type: application/json Content-Type: application/json
Content-Length: 986 Content-Length: 986
Digest: SHA-256=98QzyNVYpdgTrWBKpC4qFSCmmR+CrwwvUoiaDCSjKxw= Digest: SHA-256=98QzyNVYpdgTrWBKpC4qFSCmmR+CrwwvUoiaDCSjKxw=
Signature-Input: sig1=("@request-target" "host" "content-type" \ Signature-Input: sig1=("@request-target" "host" "content-type" \
"digest" "content-length");created=1618884475;keyid="gnap-rsa" "digest" "content-length");created=1618884475;keyid="gnap-rsa"
Signature: \ Signature: \
sig1=:axj8FLOvEWBcwh+Xk6VTTKXxqo4XNygleTDJ8h3ZJfi1sSmWrRtyo9RG/dc\ sig1=:axj8FLOvEWBcwh+Xk6VTTKXxqo4XNygleTDJ8h3ZJfi1sSmWrRtyo9RG/dc\
miZmdszRjWbg+/ixVZpA4BL3AOwEOxxtmHAXNB8uJ0I3tfbs6Suyk4sEo8zPr+MJq\ miZmdszRjWbg+/ixVZpA4BL3AOwEOxxtmHAXNB8uJ0I3tfbs6Suyk4sEo8zPr+MJq\
skipping to change at page 87, line 40 skipping to change at page 91, line 44
In this example, the certificate is communicated to the application In this example, the certificate is communicated to the application
through the "Client-Cert" header from a TLS reverse proxy, leading to through the "Client-Cert" header from a TLS reverse proxy, leading to
the following full HTTP request message: the following full HTTP request message:
POST /gnap HTTP/1.1 POST /gnap HTTP/1.1
Host: server.example.com Host: server.example.com
Content-Type: application/jose Content-Type: application/jose
Content-Length: 1567 Content-Length: 1567
Client-Cert: \ Client-Cert: \
MIIC6jCCAdKgAwIBAgIGAXjw74xPMA0GCSqGSIb3DQEBCwUAMDYxNDAyBgNVBAMM \ :MIIC6jCCAdKgAwIBAgIGAXjw74xPMA0GCSqGSIb3DQEBCwUAMDYxNDAyBgNVBAMM\
K05JWU15QmpzRGp5QkM5UDUzN0Q2SVR6a3BEOE50UmppOXlhcEV6QzY2bVEwHhcN \ K05JWU15QmpzRGp5QkM5UDUzN0Q2SVR6a3BEOE50UmppOXlhcEV6QzY2bVEwHhcN\
MjEwNDIwMjAxODU0WhcNMjIwMjE0MjAxODU0WjA2MTQwMgYDVQQDDCtOSVlNeUJq \ MjEwNDIwMjAxODU0WhcNMjIwMjE0MjAxODU0WjA2MTQwMgYDVQQDDCtOSVlNeUJq\
c0RqeUJDOVA1MzdENklUemtwRDhOdFJqaTl5YXBFekM2Nm1RMIIBIjANBgkqhkiG \ c0RqeUJDOVA1MzdENklUemtwRDhOdFJqaTl5YXBFekM2Nm1RMIIBIjANBgkqhkiG\
9w0BAQEFAAOCAQ8AMIIBCgKCAQEAhYOJ+XOKISdMMShn/G4W9m20mT0VWtQBsmBB \ 9w0BAQEFAAOCAQ8AMIIBCgKCAQEAhYOJ+XOKISdMMShn/G4W9m20mT0VWtQBsmBB\
kI2cmRt4Ai8BfYdHsFzAtYKOjpBR1RpKpJmVKxIGNy0g6Z3ad2XYsh8KowlyVy8I \ kI2cmRt4Ai8BfYdHsFzAtYKOjpBR1RpKpJmVKxIGNy0g6Z3ad2XYsh8KowlyVy8I\
kZ8NMwSrcUIBZGYXjHpwjzvfGvXH/5KJlnR3/uRUp4Z4Ujk2bCaKegDn11V2vxE4 \ kZ8NMwSrcUIBZGYXjHpwjzvfGvXH/5KJlnR3/uRUp4Z4Ujk2bCaKegDn11V2vxE4\
1hqaPUnhRZxe0jRETddzsE3mu1SK8dTCROjwUl14mUNo8iTrTm4n0qDadz8BkPo+ \ 1hqaPUnhRZxe0jRETddzsE3mu1SK8dTCROjwUl14mUNo8iTrTm4n0qDadz8BkPo+\
uv4BC0bunS0K3bA/3UgVp7zBlQFoFnLTO2uWp/muLEWGl67gBq9MO3brKXfGhi3k \ uv4BC0bunS0K3bA/3UgVp7zBlQFoFnLTO2uWp/muLEWGl67gBq9MO3brKXfGhi3k\
OzywzwPTuq+cVQDyEN7aL0SxCb3Hc4IdqDaMg8qHUyObpPitDQIDAQABMA0GCSqG \ OzywzwPTuq+cVQDyEN7aL0SxCb3Hc4IdqDaMg8qHUyObpPitDQIDAQABMA0GCSqG\
SIb3DQEBCwUAA4IBAQBnYFK0eYHy+hVf2D58usj39lhL5znb/q9G35GBd/XsWfCE \ SIb3DQEBCwUAA4IBAQBnYFK0eYHy+hVf2D58usj39lhL5znb/q9G35GBd/XsWfCE\
wHuLOSZSUmG71bZtrOcx0ptle9bp2kKl4HlSTTfbtpuG5onSa3swRNhtKtUy5NH9 \ wHuLOSZSUmG71bZtrOcx0ptle9bp2kKl4HlSTTfbtpuG5onSa3swRNhtKtUy5NH9\
W/FLViKWfoPS3kwoEpC1XqKY6l7evoTCtS+kTQRSrCe4vbNprCAZRxz6z1nEeCgu \ W/FLViKWfoPS3kwoEpC1XqKY6l7evoTCtS+kTQRSrCe4vbNprCAZRxz6z1nEeCgu\
NMk38yTRvx8ihZpVOuU+Ih+dOtVe/ex5IAPYxlQsvtfhsUZqc7IyCcy72WHnRHlU \ NMk38yTRvx8ihZpVOuU+Ih+dOtVe/ex5IAPYxlQsvtfhsUZqc7IyCcy72WHnRHlU\
fn3pJm0S5270+Yls3Iv6h3oBAP19i906UjiUTNH3g0xMW+V4uLxgyckt4wD4Mlyv \ fn3pJm0S5270+Yls3Iv6h3oBAP19i906UjiUTNH3g0xMW+V4uLxgyckt4wD4Mlyv\
jnaQ7Z3sR6EsXMocAbXHIAJhwKdtU/fLgdwL5vtx jnaQ7Z3sR6EsXMocAbXHIAJhwKdtU/fLgdwL5vtx:
{ {
"access_token": { "access_token": {
"access": [ "access": [
"dolphin-metadata" "dolphin-metadata"
] ]
}, },
"interact": { "interact": {
"start": ["redirect"], "start": ["redirect"],
"finish": { "finish": {
skipping to change at page 91, line 5 skipping to change at page 95, line 5
"alg": "RS256", "alg": "RS256",
"kid": "gnap-rsa", "kid": "gnap-rsa",
"uri": "https://server.example.com/gnap", "uri": "https://server.example.com/gnap",
"htm": "POST", "htm": "POST",
"typ": "gnap-binding+jwsd", "typ": "gnap-binding+jwsd",
"created": 1618884475 "created": 1618884475
} }
The request body is the following JSON object: The request body is the following JSON object:
NOTE: '\' line wrapping per RFC 8792
{ {
"access_token": { "access_token": {
"access": [ "access": [
"dolphin-metadata" "dolphin-metadata"
] ]
}, },
"interact": { "interact": {
"start": ["redirect"], "start": ["redirect"],
"finish": { "finish": {
"method": "redirect", "method": "redirect",
skipping to change at page 92, line 5 skipping to change at page 96, line 5
}, },
} }
} }
This is hashed to the following Base64 encoded value: This is hashed to the following Base64 encoded value:
PGiVuOZUcN1tRtUS6tx2b4cBgw9mPgXG3IPB3wY7ctc PGiVuOZUcN1tRtUS6tx2b4cBgw9mPgXG3IPB3wY7ctc
This leads to the following full HTTP request message: This leads to the following full HTTP request message:
NOTE: '\' line wrapping per RFC 8792
POST /gnap HTTP/1.1 POST /gnap HTTP/1.1
Host: server.example.com Host: server.example.com
Content-Type: application/json Content-Type: application/json
Content-Length: 983 Content-Length: 983
Detached-JWS: eyJhbGciOiJSUzI1NiIsImNyZWF0ZWQiOjE2MTg4ODQ0NzUsImh0b\ Detached-JWS: eyJhbGciOiJSUzI1NiIsImNyZWF0ZWQiOjE2MTg4ODQ0NzUsImh0b\
SI6IlBPU1QiLCJraWQiOiJnbmFwLXJzYSIsInR5cCI6ImduYXAtYmluZGluZytqd3\ SI6IlBPU1QiLCJraWQiOiJnbmFwLXJzYSIsInR5cCI6ImduYXAtYmluZGluZytqd3\
NkIiwidXJpIjoiaHR0cHM6Ly9zZXJ2ZXIuZXhhbXBsZS5jb20vZ25hcCJ9.PGiVuO\ NkIiwidXJpIjoiaHR0cHM6Ly9zZXJ2ZXIuZXhhbXBsZS5jb20vZ25hcCJ9.PGiVuO\
ZUcN1tRtUS6tx2b4cBgw9mPgXG3IPB3wY7ctc.fUq-SV-A1iFN2MwCRW_yolVtT2_\ ZUcN1tRtUS6tx2b4cBgw9mPgXG3IPB3wY7ctc.fUq-SV-A1iFN2MwCRW_yolVtT2_\
TZA2h5YeXUoi5F2Q2iToC0Tc4drYFOSHIX68knd68RUA7yHqCVP-ZQEd6aL32H69e\ TZA2h5YeXUoi5F2Q2iToC0Tc4drYFOSHIX68knd68RUA7yHqCVP-ZQEd6aL32H69e\
9zuMiw6O_s4TBKB3vDOvwrhYtDH6fX2hP70cQoO-47OwbqP-ifkrvI3hVgMX9TfjV\ 9zuMiw6O_s4TBKB3vDOvwrhYtDH6fX2hP70cQoO-47OwbqP-ifkrvI3hVgMX9TfjV\
skipping to change at page 95, line 5 skipping to change at page 99, line 5
"kid": "gnap-rsa", "kid": "gnap-rsa",
"uri": "https://server.example.com/gnap", "uri": "https://server.example.com/gnap",
"htm": "POST", "htm": "POST",
"typ": "gnap-binding+jwsd", "typ": "gnap-binding+jwsd",
"created": 1618884475 "created": 1618884475
} }
The request body, used as the JWS Payload, is the following JSON The request body, used as the JWS Payload, is the following JSON
object: object:
NOTE: '\' line wrapping per RFC 8792
{ {
"access_token": { "access_token": {
"access": [ "access": [
"dolphin-metadata" "dolphin-metadata"
] ]
}, },
"interact": { "interact": {
"start": ["redirect"], "start": ["redirect"],
"finish": { "finish": {
"method": "redirect", "method": "redirect",
skipping to change at page 96, line 5 skipping to change at page 100, line 5
"uri": "https://client.foo/" "uri": "https://client.foo/"
}, },
}, },
"subject": { "subject": {
"formats": ["iss_sub", "opaque"] "formats": ["iss_sub", "opaque"]
} }
} }
This leads to the following full HTTP request message: This leads to the following full HTTP request message:
NOTE: '\' line wrapping per RFC 8792
POST /gnap HTTP/1.1 POST /gnap HTTP/1.1
Host: server.example.com Host: server.example.com
Content-Type: application/jose Content-Type: application/jose
Content-Length: 1047 Content-Length: 1047
eyJhbGciOiJSUzI1NiIsImNyZWF0ZWQiOjE2MTg4ODQ0NzUsImh0bSI6IlBPU1QiLCJ\ eyJhbGciOiJSUzI1NiIsImNyZWF0ZWQiOjE2MTg4ODQ0NzUsImh0bSI6IlBPU1QiLCJ\
raWQiOiJnbmFwLXJzYSIsInR5cCI6ImduYXAtYmluZGluZytqd3NkIiwidXJpIjoiaH\ raWQiOiJnbmFwLXJzYSIsInR5cCI6ImduYXAtYmluZGluZytqd3NkIiwidXJpIjoiaH\
R0cHM6Ly9zZXJ2ZXIuZXhhbXBsZS5jb20vZ25hcCJ9.CnsKICAgICJhY2Nlc3NfdG9r\ R0cHM6Ly9zZXJ2ZXIuZXhhbXBsZS5jb20vZ25hcCJ9.CnsKICAgICJhY2Nlc3NfdG9r\
ZW4iOiB7CiAgICAgICAgImFjY2VzcyI6IFsKICAgICAgICAgICAgImRvbHBoaW4tbWV\ ZW4iOiB7CiAgICAgICAgImFjY2VzcyI6IFsKICAgICAgICAgICAgImRvbHBoaW4tbWV\
0YWRhdGEiCiAgICAgICAgXQogICAgfSwKICAgICJpbnRlcmFjdCI6IHsKICAgICAgIC\ 0YWRhdGEiCiAgICAgICAgXQogICAgfSwKICAgICJpbnRlcmFjdCI6IHsKICAgICAgIC\
skipping to change at page 104, line 9 skipping to change at page 108, line 9
with an authentication header indicating that GNAP needs to be used with an authentication header indicating that GNAP needs to be used
to access the resource. The address of the GNAP endpoint MUST be to access the resource. The address of the GNAP endpoint MUST be
sent in the "as_uri" parameter. The RS MAY additionally return a sent in the "as_uri" parameter. The RS MAY additionally return a
resource reference that the client instance MAY use in its access resource reference that the client instance MAY use in its access
token request. This resource reference MUST be sufficient for at token request. This resource reference MUST be sufficient for at
least the action the client instance was attempting to take at the RS least the action the client instance was attempting to take at the RS
and MAY be more powerful. The means for the RS to determine the and MAY be more powerful. The means for the RS to determine the
resource reference are out of scope of this specification, but some resource reference are out of scope of this specification, but some
dynamic methods are discussed in dynamic methods are discussed in
[I-D.draft-ietf-gnap-resource-servers]. The content of the resource [I-D.draft-ietf-gnap-resource-servers]. The content of the resource
handle is opaque to the client instance. reference is opaque to the client instance.
NOTE: '\' line wrapping per RFC 8792
WWW-Authenticate: \ WWW-Authenticate: \
GNAP as_uri=https://server.example/tx,access=FWWIKYBQ6U56NL1 GNAP as_uri=https://server.example/tx,access=FWWIKYBQ6U56NL1
The client instance then makes a request to the "as_uri" as described The client instance then makes a request to the "as_uri" as described
in Section 2, with the value of "access" as one of the members of the in Section 2, with the value of "access" as one of the members of the
"access" array in the "access_token" portion of the request. The "access" array in the "access_token" portion of the request. The
client instance MAY request additional resources and other client instance MAY request additional resources and other
information. The client instance MAY request multiple access tokens. information. The client instance MAY request multiple access tokens.
skipping to change at page 105, line 36 skipping to change at page 109, line 36
feedback and development of early versions of the XYZ protocol that feedback and development of early versions of the XYZ protocol that
fed into this standards work. fed into this standards work.
11. IANA Considerations 11. IANA Considerations
[[ TBD: There are a lot of items in the document that are expandable [[ TBD: There are a lot of items in the document that are expandable
through the use of value registries. ]] through the use of value registries. ]]
12. Security Considerations 12. Security Considerations
[[ TBD: There are a lot of security considerations to add. ]] 12.1. TLS Protection in Transit
All requests have to be over TLS or equivalent as per [BCP195]. Many All requests in GNAP have to be made over TLS or equivalent as
handles act as shared secrets, though they can be combined with a outlined in [BCP195] to protect the contents of the request and
requirement to provide proof of a key as well. response from manipulation and interception by an attacker. This
includes all requests from a client instance to the AS, all requests
from the client instance to an RS, any requests back to a client
instance such as the push-based interaction finish method, and any
back-end communications such as from an RS to an AS as described in
[I-D.draft-ietf-gnap-resource-servers]. Additionally, all requests
between a browser and other components, such as during redirect-based
interaction, need to be made over TLS or use equivalent protection.
Even though requests from the client instance to the AS are signed,
the signature method alone does not protect the request from
interception by an attacker. TLS protects the response as well as
the request, preventing an attacker from intercepting requested
information as it is returned. This is particularly important in the
core protocol for security artifacts such as nonces and for personal
information such as subject information.
The use of key-bound access tokens does not negate the requirement
for protecting calls to the RS with TLS. While the keys and
signatures associated a bound access token will prevent an attacker
from using a stolen token, without TLS an attacker would be able to
watch the data being sent to the RS and returned from the RS during
legitimate use of the client instance under attack. Additionally,
without TLS an attacker would be able to profile the calls made
between the client instance and RS, possibly gaining information
about the functioning of the API between the client software and RS
software that would be otherwise unknown to the attacker.
TLS or equivalent protection also needs to be used between the
browser and any other components. This applies during initial
redirects to an AS's components during interaction, during any
interaction with the resource owner, and during any redirect back to
the client instance. Without TLS protection on these portions of the
process, an attacker could wait for a valid request to start and then
take over the resource owner's interaction session.
12.2. Protection of Client Instance Key Material
Client instances are identified by their unique keys, and anyone with
access to a client instance's key material will be able to
impersonate that client instance to all parties. This is true for
both calls to the AS as well as calls to an RS using a key-bound
access token.
Different types of client software have different methods available
for creating, managing, and registering keys. GNAP explicitly allows
for ephemeral clients, such as SPAs, and single-user clients, such as
mobile applications, to create and present their own keys during the
initial grant request. The client software can securely generate a
keypair on-device and present the public key, along with proof of
holding that public key, to the AS as part of the initial request.
To facilitate trust in these ephemeral keys, GNAP further allows for
an extensible set of client information to be passed with the
request. This information can include device posture and third-party
attestations of the client software's provenance and authenticity,
depending on the needs and capabilities of the client software and
its deployment.
From GNAP's perspective, each distinct key is a different client
instance. However, multiple client instances can be grouped together
by an AS policy and treated similarly to each other. For instance,
if an AS knows of several different keys for different servers within
a cluster, the AS can decide that authorization of one of these
servers applies to all other servers within the cluster. An AS that
chooses to do this needs to be careful with how it groups different
client keys together in its policy, since the breach of one instance
would have direct effects on the others in the cluster.
Additionally, if an end user controls multiple instances of a single
type of client software, such as having an application installed on
multiple devices, each of these instances is expected to have a
separate key and be issued separate access tokens. However, if the
AS is able to group these separate instances together as described
above, it can streamline the authorization process for new instances
of the same client software. For example, if two client instances
can present proof of a valid installation of a piece of client
software, the AS would be able to associate the approval of the first
instance of this software to all related instances. The AS could
then choose to bypass an explicit prompt of the resource owner for
approval during authorization, since such approval has already been
given. An AS doing such a process would need to take assurance
measures that the different instances are in fact correlated and
authentic, as well as ensuring the expected resource owner is in
control of the client instance.
Finally, if multiple instances of client software each have the same
key, then from GNAP's perspective, these are functionally the same
client instance as GNAP has no reasonable way to differentiate
between them. This situation could happen if multiple instances
within a cluster can securely share secret information among
themselves. Even though there are multiple copies of the software,
the shared key makes these copies all present as a single instance.
It is considered bad practice to share keys between copies of
software unless they are very tightly integrated with each other and
can be closely managed. It is particularly bad practice to allow an
end-user to copy keys between client instances and to willingly use
the same key in multiple instances.
12.3. Protection of Authorization Server
The AS performs critical functions in GNAP, including authenticating
client software, managing interactions with end-users to gather
consent and provide notice, and issuing access tokens for client
instances to present to resource servers. As such, protecting the AS
is central to any GNAP deployment.
If an attacker is able to gain control over an AS, they would be able
to create fraudulent tokens and manipulate registration information
to allow for malicious clients. These tokens and clients would be
trusted by other components in the ecosystem under the protection of
the AS.
If the AS is using signed access tokens, an attacker in control of
the AS's signing keys would be able to manufacture fraudulent tokens
for use at RS's under the protection of the AS.
If an attacker is able to impersonate an AS, they would be able to
trick legitimate client instances into making signed requests for
information which could potentially be proxied to a real AS. To
combat this, all communications to the AS need to be made over TLS or
its equivalent, and the software making the connection has to
validate the certificate chain of the host it is connecting to.
Consequently, protecting, monitoring, and auditing the AS is
paramount to preserving the security of a GNAP-protected ecosystem.
12.4. Symmetric and Asymmetric Client Instance Keys
The cryptographic methods used by GNAP for key-proofing can support
both asymmetric and symmetric cryptography, and can be extended to
use a wide variety of mechanisms. While symmetric cryptographic
systems have some benefits in speed and simplicity, they have a
distinct drawback that both parties need access to the same key in
order to do both signing and verification of the message. This means
that when the client instance calls the AS to request a token, the AS
needs to know the exact value of the client instance's key (or be
able to derive it) in order to validate the key proof signature.
With asymmetric keys, the client needs only to send its public key to
the AS to allow for verification that the client holds the associated
private key, regardless of whether that key was pre-registered or not
with the AS.
When used to bind to an access token, a key value must be known by
the RS in order to validate the proof signature on the request.
Common methods for communicating these proofing keys include putting
information in a structured access token and allowing the RS to look
up the associated key material against the value of the access token.
With symmetric cryptography, both of these methods would expose the
signing key to the RS, and in the case of an structured access token,
potentially to any party that can see the access token itself unless
the token's payload has been encrypted. Any of these parties would
then be able to make calls using the access token by creating a valid
signature. With asymmetric cryptography, the RS only needs to know
the public key associated with the token in order to validate, and
therefore cannot create any new calls.
Symmetric keys also have the expected advantage of providing better
protection against quantum threats in the future. Also, these types
of keys (and their secure derivations) are widely supported among
many cloud-based key management systems.
While both signing approaches are allowed, GNAP treats these two
classes of keys somewhat differently. Only the public portion of
asymmetric keys are allowed to be sent by value in requests to the AS
when establishing a connection. Since sending a symmetric key (or
the private portion of an asymmetric key) would expose the signing
material to any parties on the request path, including any attackers,
sending these kinds of keys is prohibited. Symmetric keys can still
be used by client instances, but only a reference to the key and not
its value can be sent. This allows the AS to use pre-registered
symmetric keys as well as key derivation schemes to take advantage of
symmetric cryptography but without requiring key distribution at
runtime, which would expose the keys in transit.
Both the AS and client software can use systems such as hardware
security modules to strengthen their key security storage and
generation for both asymmetric and symmetric keys.
12.5. Generation of Access Tokens
The content of access tokens need to be such that only the generating
AS would be able to create them, and the contents cannot be
manipulated by an attacker to gain different or additional access
rights.
One method for accomplishing this is to use a cryptographically
random value for the access token, generated by the AS using a secure
randomization function with sufficiently high entropy. The odds of
an attacker guessing the output of the randomization function to
collide with a valid access token are exceedingly small, and even
then the attacker would not have any control over what the access
token would represent since that information would be held close by
the AS.
Another method for accomplishing this is to use a structured token
that is cryptographically signed. In this case, the payload of the
access token declares to the RS what the token is good for, but the
signature applied by the AS during token generation covers this
payload. Only the AS can create such a signature and therefore only
the AS can create such a signed token. The odds of an attacker being
able to guess a signature value with a useful payload are exceedingly
small. This technique only works if all targeted RS's check the
signature of the access token. Any RS that does not validate the
signature of all presented tokens would be susceptible to injection
of a modified or falsified token. Furthermore, an AS has to
carefully protect the keys used to sign access tokens, since anyone
with access to these signing keys would be able to create seemingly-
valid access tokens using them.
12.6. Bearer Access Tokens
Bearer access tokens can be used by any party that has access to the
token itself, without any additional information. As a natural
consequence, any RS that a bearer token is presented to has the
technical capability of presenting that bearer token to another RS,
as long as the token is valid. It also means that any party that is
able capture of the token value in storage or in transit is able to
use the access token. While bearer tokens are inherently simpler,
this simplicity has been misapplied and abused in making needlessly
insecure systems.
In GNAP, key-bound access tokens are the default due to their higher
security properties. While bearer tokens can be used in GNAP, their
use should be limited onto to cases where the simplicity benefits
outweigh the significant security downsides.
12.7. Key-Bound Token Access Tokens
Key-bound access tokens, as the name suggests, are bound to a
specific key and must be presented along with proof of that key
during use. The key itself is not presented at the same time as the
token, so even if a token value is captured, it cannot be used to
make a new request. This is particularly true for an RS, which will
see the token value but will not see the keys used to make the
request.
Key-bound access tokens provide this additional layer of protection
only when the RS checks the signature of the message presented with
the token. Acceptance of an invalid presentation signature, or
failure to check the signature entirely, would allow an attacker to
make calls with a captured access token without having access to the
related signing key material.
In addition to validating the signature of the presentation message
itself, the RS also needs to ensure that the signing key used is
appropriate for the presented token. If an RS does not ensure that
the right keys were used to sign a message with a specific token, an
attacker would be able to capture an access token and sign the
request with their own keys, thereby negating the benefits of using
key-bound access tokens.
The RS also needs to ensure that a sufficient portions of the message
are covered by the signature. Any items outside the signature could
still affect the API's processing decisions, but these items would
not be strongly bound to the token presentation. As such, an
attacker could capture a valid request, then manipulate portions of
the request outside of the signature envelope in order to cause
unwanted actions at the protected API.
Some key-bound tokens are susceptible to replay attacks, depending on
the details of the signing method used. If a signature method covers
only portions of a given request, that same signature proof can be
used by an attacker to make a similar call, potentially even varying
elements that are outside of the protection of the signature. Key
proofing mechanisms used with access tokens therefore need to use
replay protection mechanisms covered under the signature such as a
per-message nonce, a reasonably short time validity window, or other
uniqueness constraints. The details of using these will vary
depending on the key proofing mechanism in use, but for example, HTTP
Message Signatures has both a "created" and "nonce" signature
parameter as well as the ability to cover significant portions of the
HTTP message.
12.8. Exposure of End-user Credentials to Client Instance
As a delegation protocol, one of the main goals of GNAP is to prevent
the client software from being exposed to any credentials or
information about the end-user or resource owner as a requirement of
the delegation process. By using the variety of interaction
mechanisms, the resource owner can interact with the AS without ever
authenticating to the client software, and without the client
software having to impersonate the resource owner through replay of
their credentials.
Consequently, no interaction methods defined in the GNAP core require
the end-user to enter their credentials, but it is technologically
possible for an extension to be defined to carry such values. Such
an extension would be dangerous as it would allow rogue client
software to directly collect, store, and replay the end-user's
credentials outside of any legitimate use within a GNAP request.
The concerns of such an extension could be mitigated through use of a
challenge and response unlocked by the end user's credentials. For
example, the AS presents a challenge as part of an interaction start
method, and the client instance signs that challenge using a key
derived from a password presented by the end user. It would be
possible for the client software to collect this password in a secure
software enclave without exposing the password to the rest of the
client software or putting it across the wire to the AS. The AS can
validate this challenge response against a known password for the
identified end user. While an approach such as this does not remove
all of the concerns surrounding such a password-based scheme, it is
at least possible to implement in a more secure fashion than simply
collecting and replaying the password. Even so, such schemes should
only ever be used by trusted clients due to the ease of abusing them.
12.9. Mixing Up Authorization Servers
If a client instance is able to work with multiple AS's
simultaneously, it is more possible for an attacker to add a
compromised AS to the client instance's configuration and cause the
client software to start a request at the compromised AS. This AS
could then proxy the client's request to a valid AS in order to
attempt to get the resource owner to approve access for the
legitimate client instance.
A client instance needs to always be aware of which AS it is talking
to throughout a grant process, and ensure that any callback for one
AS does not get conflated with the callback to different AS. The
interaction finish hash calculate allows a client instance to protect
against this kind of substitution, but only if the client instance
validates the hash. If the client instance does not use an
interaction finish method or does not check the interaction finish
hash value, the compromised AS can be granted a valid access token on
behalf of the resource owner. See [attack-surfaces] for details of
one such attack, which has been since addressed in this document by
including the grant endpoint in the interaction hash calculation.
The client instance still needs to validate the hash for the attack
to be prevented.
12.10. Processing of Client-Presented User Information
GNAP allows the client instance to present assertions and identifiers
of the current user to the AS as part of the initial request. This
information should only ever be taken by the AS as a hint, since the
AS has no way to tell if the represented person is present at the
client software, without using an interaction mechanism. This
information does not guarantee the given user is there, but it does
constitute a statement by the client software that the AS can take
into account.
For example, if a specific user is claimed to be present prior to
interaction, but a different user is shown to be present during
interaction, the AS can either determine this to be an error or
signal to the client instance through returned subject information
that the current user has changed from what the client instance
thought. This user information can also be used by the AS to
streamline the interaction process when the user is present. For
example, instead of having the user type in their account identifier
during interaction at a redirected URL, the AS can immediately
challenge the user for their account credentials. Alternatively, if
an existing session is detected, the AS can determine that it matches
the identifier provided by the client and subsequently skip an
explicit authentication event by the resource owner.
In cases where the AS trusts the client software more completely, due
to policy or by previous approval of a given client instance, the AS
can take this user information as a statement that the user is
present and could issue access tokens and release subject information
without interaction. The AS should only take such action in very
limited circumstances, as a client instance could assert whatever it
likes for the user's identifiers in its request.
When a client instance presents an assertion to the AS, the AS needs
to evaluate that assertion. Since the AS is unlikely to be the
intended audience of an assertion held by the client software, the AS
will need to evaluate the assertion in a different context. Even in
this case, the AS can still evaluate that the assertion was generated
by a trusted party, was appropriately signed, and is within any time
validity windows stated by the assertion. If the client instance's
audience identifier is known to the AS and can be associated with the
client instance's presented key, the AS can also evaluate that the
appropriate client instance is presenting the claimed assertion. All
of this will prevent an attacker from presenting a manufactured
assertion, or one captured from an untrusted system. However,
without validating the audience of the assertion, a captured
assertion could be presented by the client instance to impersonate a
given end user. In such cases, the assertion offers little more
protection than a simple identifier would.
A special case exists where the AS is the generator of the assertion
being presented by the client instance. In these cases, the AS can
validate that it did issue the assertion and it is associated with
the client instance presenting the assertion.
12.11. Client Instance Pre-registration
Each client instance is identified by its own unique key, and for
some kinds of client software such as a web server or backend system,
this identification can be facilitated by registering a single key
for a piece of client software ahead of time. This registration can
be associated with a set of display attributes to be used during the
authorization process, identifying the client software to the user.
In these cases, it can be assumed that only one instance of client
software will exist, likely to serve many different users.
A client's registration record needs to include its identifying key.
Furthermore, it is the case that any clients using symmetric
cryptography for key proofing mechanisms need to have their keys pre-
registered. The registration should also include any information
that would aid in the authorization process, such as a display name
and logo. The registration record can also limit a given client to
ask for certain kinds of information and access, or be limited to
specific interaction mechanisms at runtime.
It also is sensible to pre-register client instances when the
software is acting on its own behalf, without the need for a runtime
approval by a resource owner or any interaction with an end-user. In
these cases, an AS needs to rest on the trust decisions that have
been determined prior to runtime in determining what rights and
tokens to grant to a given client instance.
However, it does not make sense to pre-register many types of
clients. Single-page applications (SPAs) and mobile/desktop
applications in particular present problems with pre-registration.
For SPAs, the instances are ephemeral in nature and long-term
registration of a single instance leads to significant storage and
management overhead at the AS. For mobile applications, each
installation of the client software is a separate instance, and
sharing a key among all instances would be detrimental to security as
the compromise of any single installation would compromise all copies
for all users.
An AS can treat these classes of client software differently from
each other, perhaps by allowing access to certain high-value APIs
only to pre-registered known clients, or by requiring an active end-
user delegation of authority to any client software not pre-
registered.
An AS can also provide warnings and caveats to resource owners during
the authorization process, allowing the user to make an informed
decision regarding the software they are authorizing. For example,
if the AS has done vetting of the client software and this specific
instance, it can present a different authorization screen compared to
a client instance that is presenting all of its information at
runtime.
12.12. Client Instance Impersonation
If client instances are allowed to set their own user-facing display
information, such as a display name and website URL, a malicious
client instance could impersonate legitimate client software for the
purposes of tricking users into authorizing the malicious client.
Requiring clients to pre-register does not fully mitigate this
problem since many pre-registration systems have self-service portals
for management of client registration, allowing authenticated
developers to enter self-asserted information into the management
portal.
An AS can mitigate this by actively filtering all self-asserted
values presented by client software, both dynamically as part of GNAP
and through a registration portal, to limit the kinds of
impersonation that would be done.
An AS can also warn the resource owner about the provenance of the
information it is displaying, allowing the resource owner to make a
more informed delegation decision. For example, an AS can visually
differentiate between a client instance that can be traced back to a
specific developer's registration and an instance that has self-
asserted its own key and display information.
12.13. Interception of Information in the Browser
Most information passed through the web-browser is susceptible to
interception and possible manipulation by elements within the browser
such as scripts loaded within pages. Information in the URL is
exposed through browser and server logs, and can also leak to other
parties through HTTP "Referrer" headers.
GNAP's design limits the information passed directly through the
browser, allowing for opaque URLs in most circumstances. For the
redirect-based interaction finish mechanism, named query parameters
are used to carry unguessable opaque values. For these, GNAP
requires creation and validation of a cryptographic hash to protect
the query parameters added to the URL and associate them with an
ongoing grant process. The client instance has to properly validate
this hash to prevent an attacker from injecting an interaction
reference intended for a different AS or client instance.
Several interaction start mechanisms use URLs created by the AS and
passed to the client instance. While these URLs are opaque to the
client instance, it's possible for the AS to include parameters,
paths, and other pieces of information that could leak security data
or be manipulated by a party in the middle of the transaction.
12.14. Callback URL Manipulation
The callback URL used in interaction finish mechanisms is defined by
the client instance. This URL is opaque to the AS, but can contain
information relevant to the client instance's operations. In
particular, the client instance can include state information to
allow the callback request to be associated with an ongoing grant
request.
Since this URL is exposed to the end-user's browser, it is
susceptible to both logging and manipulation in transit before the
request is made to the client software. As such, a client instance
should never put security-critical or private information into the
callback URL in a cleartext form. For example, if the client
software includes a post-redirect target URL in its callback URL to
the AS, this target URL could be manipulated by an attacker, creating
an open redirector at the client. Instead, a client instance can use
an unguessable identifier into the URL that can then be used by the
client software to look up the details of the pending request. Since
this approach requires some form of statefulness by the client
software during the redirection process, clients that are not capable
of holding state through a redirect should not use redirect-based
interaction mechanisms.
12.15. MTLS Deployment Patterns
GNAP does not specify how a client instance's keys could be made
known to the AS ahead of time. Public Key Infrastructure (PKI) can
be used to manage the keys used by client instances when calling the
AS, allowing the AS to trust a root key from a trusted authority.
This method is particularly relevant to the MTLS signature method,
where the client instance presents its certificate to the AS as part
of the TLS connection. An AS using PKI to validate the MTLS
connection would need to ensure that the presented certificate was
issued by a trusted certificate authority before allowing the
connection to continue. PKI-based certificates would allow a key to
be revoked and rotated through management at the certificate
authority without requiring additional registration or management at
the AS. PKI has historically been difficult to deploy, especially at
scale, but it remains an appropriate solution for systems where the
required overhead is not an impediment.
MTLS need not use a PKI backing, as self-signed certificates and
certificates from untrusted authorities can still be presented as
part of a TLS connection. In this case, the AS or RS would validate
the connection but accept whatever certificate was presented by the
client software. This specific certificate would then be bound to
all future connections from that client software by being bound to
the resulting access tokens.
12.16. Interception of Responses from the AS
Responses from the AS contain information vital to both the security
and privacy operations of GNAP. This information includes nonces
used in cryptographic calculations, subject identifiers, assertions,
public keys, and information about what client software is requesting
and was granted.
In addition, if bearer tokens are used or keys are issued alongside a
bound access token, the response from the AS contains all information
necessary for use of the contained access token. Any party that is
capable of viewing such a response, such as an intermediary proxy,
would be able to exfiltrate and use this token. If the access token
is instead bound to the client instance's presented key,
intermediaries no longer have sufficient information to use the
token. They can still, however, gain information about the end user
as well as the actions of the client software.
12.17. Key Distribution
The keys for client instances could be distributed as part of the
deployment process of instances of the client software. For example,
an application installation framework could generate a keypair for
each copy of client software, then both install it into the client
software upon installation and registering that instance with the AS.
Additionally, it's possible for the AS to generate keys to be used
with access tokens that are separate from the keys used by the client
instance to request tokens. In this method, the AS would generate
the asymmetric keypair or symmetric key and return the entire key,
including all private signing information, to the client instance
alongside the access token itself. This approach would make
interception of the return from the token endpoint equivalent to that
of a bearer token, since all information required to use the access
token would be present in the request.
12.18. Interaction Finish Modes and Polling
During the interaction process, the client instance usually hands
control of the user experience over to another component, beit the
system browser, another application, or some action the resource
owner is instructed to take on another device. By using an
interaction finish method, the client instance can be securely
notified by the AS when the interaction is completed and the next
phase of the protocol should occur. This process includes
information that the client instance can use to validate the finish
call from the AS and prevent some injection, session hijacking, and
phishing attacks.
Some types of client deployment are unable to receive an interaction
finish message. Without an interaction finish method to notify it,
the client instance will need to poll the grant continuation API
while waiting for the resource owner to approve or deny the request.
An attacker could take advantage of this situation by capturing the
interaction start parameters and phishing a legitimate user into
authorizing the attacker's waiting client instance, which would in
turn have no way of associating the completed interaction with the
start of the request.
However, it is important to note that this pattern is practically
indistinguishable from some legitimate use cases. For example, a
smart device emits a code for the resource owner to enter on a
separate device. The smart device has to poll because the expected
behavior is that the interaction will take place on the separate
device, without a way to return information to the original device's
context.
As such, developers need to weigh the risks of forgoing an
interaction finish method against the deployment capabilities of the
client software and its environment. Due to the increased security,
an interaction finish method should be employed whenever possible.
12.19. Storage of Information During Interaction and Continuation
When starting an interactive grant request, a client application has
a number of protocol elements that it needs to manage, including
nonces, references, keys, access tokens, and other elements. During
the interaction process, the client instance usually hands control of
the user experience over to another component, beit the system
browser, another application, or some action the resource owner is
instructed to take on another device. In order for the client
instance to make its continuation call, it will need to recall all of
these protocol elements. Usually this means the client instance will
need to store these protocol elements in some retrievable fashion.
If the security protocol elements are stored on the end-user's
device, such as in browser storage or in local application data
stores, capture and exfiltration of this information could allow an
attacker to continue a pending transaction instead of the client
instance. Client software can make use of secure storage mechanisms,
including hardware-based key and data storage, to prevent such
exfiltration.
Note that in GNAP, the client instance has to choose its interaction
finish URL prior to making the first call to the AS. As such, the
interaction finish URL will often have a unique identifier for the
ongoing request, allowing the client instance to access the correct
portion of its storage. Since this URL is passed to other parties
and often used through a browser, this URL should not contain any
security-sensitive information that would be valuable to an attacker,
such as any token identifier, nonce, or user information. Instead, a
cryptographically random value is suggested.
12.20. Denial of Service (DoS) through Grant Continuation
When a client instance starts off an interactive process, it will
eventually need to continue the grant request in a subsequent message
to the AS. It's possible for a naive client implementation to
continuously send continuation requests to the AS while waiting for
approval, especially if no interaction finish method is used. Such
constant requests could overwhelm the AS's ability to respond to both
these and other requests.
To mitigate this for well-behaved client software, the continuation
response contains a "wait" parameter that is intended to tell the
client instance how long it should wait until making its next
request. This value can be used to back off client software that is
checking too quickly by returning increasing wait times for a single
client instance.
If client software ignores the "wait" value and makes its
continuation calls too quickly, or if the client software assumes the
absence of the "wait" values means it should poll immediately, the AS
can choose to return errors to the offending client instance,
including possibly canceling the ongoing grant request. With well-
meaning client software these errors can indicate a need to change
the client software's programmed behavior.
12.21. Exhaustion of Random Value Space
Several parts of the GNAP process make use of unguessable randomized
values, such as nonces, tokens, and randomized URLs. Since these
values are intended to be unique, a sufficiently powerful attacker
could make a large number of requests to trigger generation of
randomized values in an attempt to exhaust the random number
generation space. While this attack is particularly applicable to
the AS, client software could likewise be targeted by an attacker
triggering new grant requests against an AS.
To mitigate this, software can ensure that its random values are
chosen from a significantly large pool that exhaustion of that pool
is prohibitive for an attacker. Additionally, the random values can
be time-boxed in such a way as their validity windows are reasonably
short. Since many of the random values used within GNAP are used
within limited portions of the protocol, it is reasonable for a
particular random value to be valid for only a small amount of time.
For example, the nonces used for interaction finish hash calculation
need only to be valid while the client instance is waiting for the
finish callback and can be functionally expired when the interaction
has completed. Similarly, artifacts like access tokens and the
interaction reference can be limited to have lifetimes tied to their
functional utility. Finally, each different category of artifact
(nonce, token, reference, identifier, etc.) can be generated from a
separate random pool of values instead of a single global value
space.
13. Privacy Considerations 13. Privacy Considerations
[[ TBD: There are a lot of privacy considerations to add. ]] The privacy considerations in this section are modeled after the list
of privacy threats in [[RFC6973]], "Privacy Considerations for
Internet Protocols", and either explain how these threats are
mitigated or advise how the threats relate to GNAP.
Handles are passed between parties and therefore should not contain 13.1. Surveillance
any private data.
When user information is passed to the client instance, the AS needs Surveillance is the observation or monitoring of an individual's
to make sure that it has the permission to do so. communications or activities. Surveillance can be conducted by
observers or eavesdroppers at any point along the communications
path.
14. Normative References GNAP assumes the TLS protection used throughout the spec is intact.
Without the protection of TLS, there are many points throughout the
use of GNAP that would lead to possible surveillance.
13.1.1. Surveillance by the Client
The purpose of GNAP is to authorize clients to be able to access
information on behalf of a user. So while it is expected that the
client may be aware of the user's identity as well as data being
fetched for that user, in some cases the extent of the client may be
beyond what the user is aware of. For example, a client may be
implemented as multiple distinct pieces of software, such as a
logging service or a mobile app that reports usage data to an
external backend service.
13.1.2. Surveillance by the Authorization Server
The role of the authorization server is to manage the authorization
of client instances to protect access to the user's data. In this
role, the authorization server is by definition aware of each
authorization of a client instance by a user. When the authorization
server shares user information with the client instance, it needs to
make sure that it has the permission from that user to do so.
Additionally, as part of the authorization grant process, the
authorization server may be aware of which resource servers the
client intends to use an access token at. However, it is possible to
design a system using GNAP in which this knowledge is not made
available to the authorization server, such as by avoiding the use of
the "locations" object in the authorization request.
If the authorization server's implementation of access tokens is such
that it requires a resource server call back to the authorization
server to validate them, then the authorization server will be aware
of which resource servers are actively in use and by which users and
which clients. To avoid this possibility, the authorization server
would need to structure access tokens in such a way that they can be
validated by the resource server without notifying the authorization
server that the token is being validated.
13.2. Stored Data
Several parties in the GNAP process are expected to persist data at
least temporarily, if not semi-permanently, for the normal
functioning of the system. If compromised, this could lead to
exposure of sensitive information. This section documents the
potentially sensitive information each party in GNAP is expected to
store for normal operation. Naturally it is possible that any party
is storing information for longer than technically necessary of the
protocol mechanics (such as audit logs, etc).
The authorization server is expected to store subject identifiers for
user indefinitely, in order to be able to include them in the
responses to clients. The authorization server is also expected to
store client key identifiers associated with display information
about the client such as its name and logo.
The client is expected to store its client instance key indefinitely,
in order to authenticate to the authorization server for the normal
functioning of the GNAP flows. Additionally, the client will be
temporarily storing artifacts issued by the authorization server
during a flow, and these artifacts SHOULD be discarded by the client
when the transaction is complete.
The resource server is not required to store any state for its normal
operation. Depending on the implementation of access tokens, the
resource server may need to cache public keys from the authorization
server in order to validate access tokens.
13.3. Intrusion
Intrusion refers to the ability of various parties to send
unsolicited messages or cause denial of service for unrelated
parties.
If the resource owner is different from the end user, there is an
opportunity for the end user to cause unsolicited messages to be sent
to the resource owner if the system prompts the resource owner for
consent when an end user attempts to access their data.
The format and contents of subject identifiers are intentionally not
defined by GNAP. If the authorization server uses values for subject
identifiers that are also identifiers for communication channels,
(e.g. an email address or phone number), this opens up the
possibility for a client to learn this information when it was not
otherwise authorized to access this kind of data about the user.
13.4. Correlation
The threat of correlation is the combination of various pieces of
information related to an individual in a way that defies their
expectations of what others know about them.
13.4.1. Correlation by Clients
The biggest risk of correlation in GNAP is when an authorization
server returns stable consistent user identifiers to multiple
different applications. In this case, applications created by
different parties would be able to correlate these user identifiers
out of band in order to know which users they have in common.
The most common example of this in practice is tracking for
advertising purposes, such that client A shares their list of user
IDs with an ad platform that is then able to retarget ads to
applications created by other parties. In contrast, a positive
example of correlation is a corporate acquisition where two
previously unrelated clients now do need to be able to identify the
same user between the two clients.
13.4.2. Correlation by Resource Servers
Unrelated resource servers also have an opportunity to correlate
users if the authorization server includes stable user identifiers in
access tokens or in access token introspection responses.
In some cases a resource server may not actually need to be able to
identify users, (such as a resource server providing access to a
company cafeteria menu which only needs to validate whether the user
is a current employee), so authorization servers should be thoughtful
of when user identifiers are actually necessary to communicate to
resource servers for the functionining of the system.
13.4.3. Correlation by Authorization Servers
Clients are expected to be identified by their client instance key.
If a particular client instance key is used at more than one
authorization server, this could open up the possibility for multiple
unrelated authorization servers to correlate client instances. This
is especially a problem in the common case where a client instance is
used by a single individual, as it would allow the authorization
servers to correlate that individual between them. If this is a
concern of a client, the client should use distinct keys with each
authorization server.
13.5. Disclosure in Shared References
Throughout many parts of GNAP, the parties pass shared references
between each other, sometimes in place of the values themselves. For
example the "interact_ref" value used throughout the flow. These
references are intended to be random strings and should not contain
any private or sensitive data that would potentially leak information
between parties.
14. References
14.1. Normative References
[BCP195] Sheffer, Y., Holz, R., and P. Saint-Andre, [BCP195] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer "Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security Security (TLS) and Datagram Transport Layer Security
(DTLS)", May 2015, (DTLS)", May 2015,
<https://www.rfc-editor.org/info/bcp195>. <https://www.rfc-editor.org/info/bcp195>.
[I-D.draft-ietf-gnap-resource-servers] [I-D.draft-ietf-gnap-resource-servers]
Richer, J., Parecki, A., and F. Imbault, "Grant Richer, J., Parecki, A., and F. Imbault, "Grant
Negotiation and Authorization Protocol Resource Server Negotiation and Authorization Protocol Resource Server
Connections", Work in Progress, Internet-Draft, draft- Connections", Work in Progress, Internet-Draft, draft-
ietf-gnap-resource-servers-00, 28 April 2021, ietf-gnap-resource-servers-00, 28 April 2021,
<https://www.ietf.org/archive/id/draft-ietf-gnap-resource- <https://www.ietf.org/archive/id/draft-ietf-gnap-resource-
servers-00.txt>. servers-00.txt>.
[I-D.ietf-httpbis-message-signatures] [I-D.ietf-httpbis-message-signatures]
Backman, A., Richer, J., and M. Sporny, "Signing HTTP Backman, A., Richer, J., and M. Sporny, "HTTP Message
Messages", Work in Progress, Internet-Draft, draft-ietf- Signatures", Work in Progress, Internet-Draft, draft-ietf-
httpbis-message-signatures-05, 8 June 2021, httpbis-message-signatures-06, 13 August 2021,
<https://www.ietf.org/archive/id/draft-ietf-httpbis- <https://www.ietf.org/archive/id/draft-ietf-httpbis-
message-signatures-05.txt>. message-signatures-06.txt>.
[I-D.ietf-oauth-rar] [I-D.ietf-oauth-rar]
Lodderstedt, T., Richer, J., and B. Campbell, "OAuth 2.0 Lodderstedt, T., Richer, J., and B. Campbell, "OAuth 2.0
Rich Authorization Requests", Work in Progress, Internet- Rich Authorization Requests", Work in Progress, Internet-
Draft, draft-ietf-oauth-rar-05, 15 May 2021, Draft, draft-ietf-oauth-rar-07, 12 September 2021,
<https://www.ietf.org/archive/id/draft-ietf-oauth-rar- <https://www.ietf.org/archive/id/draft-ietf-oauth-rar-
05.txt>. 07.txt>.
[I-D.ietf-oauth-signed-http-request] [I-D.ietf-oauth-signed-http-request]
Richer, J., Bradley, J., and H. Tschofenig, "A Method for Richer, J., Bradley, J., and H. Tschofenig, "A Method for
Signing HTTP Requests for OAuth", Work in Progress, Signing HTTP Requests for OAuth", Work in Progress,
Internet-Draft, draft-ietf-oauth-signed-http-request-03, 8 Internet-Draft, draft-ietf-oauth-signed-http-request-03, 8
August 2016, <https://www.ietf.org/archive/id/draft-ietf- August 2016, <https://www.ietf.org/archive/id/draft-ietf-
oauth-signed-http-request-03.txt>. oauth-signed-http-request-03.txt>.
[I-D.ietf-secevent-subject-identifiers] [I-D.ietf-secevent-subject-identifiers]
Backman, A. and M. Scurtescu, "Subject Identifiers for Backman, A. and M. Scurtescu, "Subject Identifiers for
skipping to change at page 108, line 21 skipping to change at page 131, line 10
Lodderstedt, "OAuth 2.0 Mutual-TLS Client Authentication Lodderstedt, "OAuth 2.0 Mutual-TLS Client Authentication
and Certificate-Bound Access Tokens", RFC 8705, and Certificate-Bound Access Tokens", RFC 8705,
DOI 10.17487/RFC8705, February 2020, DOI 10.17487/RFC8705, February 2020,
<https://www.rfc-editor.org/info/rfc8705>. <https://www.rfc-editor.org/info/rfc8705>.
[RFC8792] Watsen, K., Auerswald, E., Farrel, A., and Q. Wu, [RFC8792] Watsen, K., Auerswald, E., Farrel, A., and Q. Wu,
"Handling Long Lines in Content of Internet-Drafts and "Handling Long Lines in Content of Internet-Drafts and
RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020, RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020,
<https://www.rfc-editor.org/info/rfc8792>. <https://www.rfc-editor.org/info/rfc8792>.
14.2. Informative References
[attack-surfaces]
Axeland, Å. and O. Oueidat, "Security Analysis of Attack
Surfaces on the Grant Negotiation and Authorization
Protocol", 2021,
<https://odr.chalmers.se/handle/20.500.12380/304105>.
[promise-theory]
Burgess, M. and J. Bergstra, "Promise theory", January
2014, <http://markburgess.org/promises.html>.
[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M., and R. Smith, "Privacy
Considerations for Internet Protocols", RFC 6973,
DOI 10.17487/RFC6973, July 2013,
<https://www.rfc-editor.org/info/rfc6973>.
Appendix A. Document History Appendix A. Document History
* -07
- Replace user handle by opaque identifier
- Added trust relationships
- Added privacy considerations section
- Added security considerations.
* -06 * -06
- Removed "capabilities" and "existing_grant" protocol fields. - Removed "capabilities" and "existing_grant" protocol fields.
- Removed separate "instance_id" field. - Removed separate "instance_id" field.
- Split "interaction_methods_supported" into - Split "interaction_methods_supported" into
"interaction_start_modes_supported" and "interaction_start_modes_supported" and
"interaction_finish_methods_supported". "interaction_finish_methods_supported".
skipping to change at page 115, line 35 skipping to change at page 139, line 4
}, },
"instance_id": "7C7C4AZ9KHRS6X63AJAO" "instance_id": "7C7C4AZ9KHRS6X63AJAO"
} }
The client instance saves the response and redirects the user to the The client instance saves the response and redirects the user to the
interaction_url by sending the following HTTP message to the user's interaction_url by sending the following HTTP message to the user's
browser. browser.
HTTP 302 Found HTTP 302 Found
Location: https://server.example.com/interact/4CF492MLVMSW9MKM Location: https://server.example.com/interact/4CF492MLVMSW9MKM
The user's browser fetches the AS's interaction URL. The user logs 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 in, is identified as the RO for the resource being requested, and
approves the request. Since the AS has a callback parameter, the AS approves the request. Since the AS has a callback parameter, the AS
generates the interaction reference, calculates the hash, and generates the interaction reference, calculates the hash, and
redirects the user back to the client instance with these additional redirects the user back to the client instance with these additional
values added as query parameters. values added as query parameters.
NOTE: '\' line wrapping per RFC 8792
HTTP 302 Found HTTP 302 Found
Location: https://client.example.net/return/123455\ Location: https://client.example.net/return/123455\
?hash=p28jsq0Y2KK3WS__a42tavNC64ldGTBroywsWxT4md_jZQ1R2\ ?hash=p28jsq0Y2KK3WS__a42tavNC64ldGTBroywsWxT4md_jZQ1R2\
HZT8BOWYHcLmObM7XHPAdJzTZMtKBsaraJ64A\ HZT8BOWYHcLmObM7XHPAdJzTZMtKBsaraJ64A\
&interact_ref=4IFWWIKYBC2PQ6U56NL1 &interact_ref=4IFWWIKYBC2PQ6U56NL1
The client instance receives this request from the user's browser. The client instance receives this request from the user's browser.
The client instance ensures that this is the same user that was sent The client instance ensures that this is the same user that was sent
out by validating session information and retrieves the stored out by validating session information and retrieves the stored
pending request. The client instance uses the values in this to pending request. The client instance uses the values in this to
skipping to change at page 117, line 5 skipping to change at page 140, line 5
Signature: sig1=... Signature: sig1=...
Digest: sha256=... Digest: sha256=...
{ {
"interact_ref": "4IFWWIKYBC2PQ6U56NL1" "interact_ref": "4IFWWIKYBC2PQ6U56NL1"
} }
The AS retrieves the pending request based on the handle and issues a The AS retrieves the pending request based on the handle and issues a
bearer access token and returns this to the client instance. bearer access token and returns this to the client instance.
NOTE: '\' line wrapping per RFC 8792
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/json Content-Type: application/json
Cache-Control: no-store Cache-Control: no-store
{ {
"access_token": { "access_token": {
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0", "value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
"manage": "https://server.example.com/token/PRY5NM33O\ "manage": "https://server.example.com/token/PRY5NM33O\
M4TB8N6BW7OZB8CDFONP219RP1L", M4TB8N6BW7OZB8CDFONP219RP1L",
"access": [{ "access": [{
skipping to change at page 120, line 20 skipping to change at page 143, line 20
Host: server.example.com Host: server.example.com
Authorization: GNAP G7YQT4KQQ5TZY9SLSS5E Authorization: GNAP G7YQT4KQQ5TZY9SLSS5E
Signature-Input: sig1=... Signature-Input: sig1=...
Signature: sig1=... Signature: sig1=...
Digest: sha256=... Digest: sha256=...
The AS retrieves the pending request based on the URL and access The AS retrieves the pending request based on the URL and access
token, determines that it has been approved, and issues an access token, determines that it has been approved, and issues an access
token for the client to use at the RS. token for the client to use at the RS.
NOTE: '\' line wrapping per RFC 8792
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/json Content-Type: application/json
Cache-Control: no-store Cache-Control: no-store
{ {
"access_token": { "access_token": {
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0", "value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
"manage": "https://server.example.com/token/PRY5NM33O\ "manage": "https://server.example.com/token/PRY5NM33O\
M4TB8N6BW7OZB8CDFONP219RP1L", M4TB8N6BW7OZB8CDFONP219RP1L",
"access": [ "access": [
skipping to change at page 124, line 32 skipping to change at page 147, line 32
POST /continue HTTP/1.1 POST /continue HTTP/1.1
Host: server.example.com Host: server.example.com
Authorization: GNAP BI9QNW6V9W3XFJK4R02D Authorization: GNAP BI9QNW6V9W3XFJK4R02D
Signature-Input: sig1=... Signature-Input: sig1=...
Signature: sig1=... Signature: sig1=...
The AS retrieves the pending request based on the handle and The AS retrieves the pending request based on the handle and
determines that it has been approved and it issues an access token. determines that it has been approved and it issues an access token.
NOTE: '\' line wrapping per RFC 8792
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/json Content-Type: application/json
Cache-Control: no-store Cache-Control: no-store
{ {
"access_token": { "access_token": {
"value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0", "value": "OS9M2PMHKUR64TB8N6BW7OZB8CDFONP219RP1LT0",
"manage": "https://server.example.com/token/PRY5NM33O\ "manage": "https://server.example.com/token/PRY5NM33O\
M4TB8N6BW7OZB8CDFONP219RP1L", M4TB8N6BW7OZB8CDFONP219RP1L",
"access": [ "access": [
skipping to change at page 125, line 11 skipping to change at page 148, line 17
While GNAP is not designed to be directly compatible with OAuth 2.0 While GNAP is not designed to be directly compatible with OAuth 2.0
[RFC6749], considerations have been made to enable the use of OAuth [RFC6749], considerations have been made to enable the use of OAuth
2.0 concepts and constructs more smoothly within GNAP. 2.0 concepts and constructs more smoothly within GNAP.
In this scenario, the client developer has a "client_id" and set of In this scenario, the client developer has a "client_id" and set of
"scope" values from their OAuth 2.0 system and wants to apply them to "scope" values from their OAuth 2.0 system and wants to apply them to
the new protocol. Traditionally, the OAuth 2.0 client developer the new protocol. Traditionally, the OAuth 2.0 client developer
would put their "client_id" and "scope" values as parameters into a would put their "client_id" and "scope" values as parameters into a
redirect request to the authorization endpoint. redirect request to the authorization endpoint.
NOTE: '\' line wrapping per RFC 8792
HTTP 302 Found HTTP 302 Found
Location: https://server.example.com/authorize Location: https://server.example.com/authorize\
?client_id=7C7C4AZ9KHRS6X63AJAO ?client_id=7C7C4AZ9KHRS6X63AJAO\
&scope=read%20write%20dolphin &scope=read%20write%20dolphin\
&redirect_uri=https://client.example.net/return &redirect_uri=https://client.example.net/return\
&response_type=code &response_type=code\
&state=123455 &state=123455
Now the developer wants to make an analogous request to the AS using 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 GNAP. To do so, the client instance makes an HTTP POST and places
the OAuth 2.0 values in the appropriate places. the OAuth 2.0 values in the appropriate places.
POST /tx HTTP/1.1 POST /tx HTTP/1.1
Host: server.example.com Host: server.example.com
Content-Type: application/json Content-Type: application/json
Signature-Input: sig1=... Signature-Input: sig1=...
 End of changes. 81 change blocks. 
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