Internet DRAFT - draft-wdenniss-incremental-auth
draft-wdenniss-incremental-auth
OAuth Working Group W. Denniss
Internet-Draft Google
Intended status: Standards Track July 3, 2017
Expires: January 4, 2018
OAuth 2.0 Incremental Authorization
draft-wdenniss-incremental-auth-00
Abstract
OAuth 2.0 authorization requests that include every scope the client
might ever need can result in over-scoped authorization and a sub-
optimal end-user consent experience. This specification enhances the
OAuth 2.0 authorization protocol by adding incremental authorization,
the ability to request specific authorization scopes as needed, when
they're needed, removing the requirement to request every possible
scope that might be needed upfront.
Status of This Memo
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This Internet-Draft will expire on January 4, 2018.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Notational Conventions . . . . . . . . . . . . . . . . . . . 2
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
4. Incremental Auth for Confidential Clients . . . . . . . . . . 3
5. Incremental Auth for Public Clients . . . . . . . . . . . . . 3
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6.1. OAuth Parameters Registry . . . . . . . . . . . . . . . . 4
7. Normative References . . . . . . . . . . . . . . . . . . . . 5
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 5
Appendix B. Document History . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
OAuth 2.0 clients may offer multiple features that requiring user
authorization, but commonly not every user will use each feature.
Without incremental authentication, applications need to either
request all the possible scopes they need upfront, potentially
resulting in a bad user experience, or track each authorization grant
separately, complicating development.
The goal of incremental authorization is to allow clients to request
just the scopes they need, when they need them, while allowing them
to store a single authorization grant for the user that contains the
sum of the scopes granted. Thus, each new authorization request
increments the scope of the authorization grant, without the client
needing to track a separate authorization grant for each group of
scopes.
2. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in Key
words for use in RFCs to Indicate Requirement Levels [RFC2119]. If
these words are used without being spelled in uppercase then they are
to be interpreted with their normal natural language meanings.
3. Terminology
In addition to the terms defined in referenced specifications, this
document uses the following terms:
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"OAuth" In this document, OAuth refers to OAuth 2.0 [RFC6749].
4. Incremental Auth for Confidential Clients
For confidential clients, such as web servers that can keep secrets,
the authorization endpoint SHOULD treat scopes that the user already
granted differently on the consent user interface. Typically such
scopes are hidden for new authorization requests, or at least there
is an indication that the user already approved them.
By itself, this property of the authorization endpoint enables
incremental authorization. The client can track every scope they've
ever requested, and include those scopes on every new authorization
request.
To avoid the need for confidential clients to re-request already
authorized scopes, authorization servers MAY support an additional
"include_granted_scopes" parameter in the authorization request.
This parameter, enables the client to request tokens during the
authorization grant exchange that represent the full scope of the
user's grant to the application including any previous grants,
without the app needing to track the scopes directly.
The client indicates they wish the new authorization grant to include
previously granted scopes by sending the following additional
parameter in the OAuth 2.0 Authorization Request (Section 4.1.1 of
[RFC6749].) using the following additional parameter:
include_granted_scopes OPTIONAL. Either "true" or "false". When
"true", the authorization server SHOULD include previously granted
scopes for this client in the new authorization grant.
5. Incremental Auth for Public Clients
Unlike with confidential clients, it is NOT RECOMMEND to
automatically approve OAuth requests for public clients without user
consent (see Section 10.2 of OAuth 2.0 [RFC6749]), thus authorization
grants shouldn't contain previously authorized scopes in the manner
described above for confidential clients.
Public clients (and confidential clients using this technique) should
instead track the scopes for every authorization grant, and only
request yet to be granted scopes during incremental authorization.
In the past, this would result in multiple discrete authorization
grants that would need to be tracked. To enable incrementing a
single authorization grant for public clients, the client supplies
their existing refresh token during the authorization code exchange,
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and receives new authorization tokens with the scope of the previous
and current authorization grants.
The client sends the previous refresh token in the OAuth 2.0 Access
Token Request (Section 4.1.3 of [RFC6749].) using the following
additional parameter:
existing_grant OPTIONAL. The refresh token from the existing
authorization grant.
When processing the token exchange, in addition to the normal
processing of such a request, the token endpoint MUST verify that
token provided in the "existing_grant" parameter is unexpired and
unrevoked, and was issued to the same client id and relates to the
same user as the current authorization grant. If this verification
succeeds, the new refresh token issued in the Access Token Response
(Section 4.1.4 of ) SHOULD include authorization for the scopes in
the previous grant.
6. IANA Considerations
This specification makes a registration request as follows:
6.1. OAuth Parameters Registry
This specification registers the following parameters in the IANA
OAuth Parameters registry defined in OAuth 2.0 [RFC6749].
o Parameter name: include_granted_scopes
o Parameter usage location: authorization request
o Change controller: IESG
o Specification document(s): this document
o Parameter name: existing_grant
o Parameter usage location: token request
o Change controller: IESG
o Specification document(s): this document
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7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012,
<http://www.rfc-editor.org/info/rfc6749>.
Appendix A. Acknowledgements
The following individuals contributed ideas, feedback, and wording
that shaped and formed the final specification:
Yanna Wu, Marius Scurtescu, Jason Huang, Nicholas Watson, and Breno
de Medeiros.
Appendix B. Document History
[[ to be removed by the RFC Editor before publication as an RFC ]]
-00
o Initial draft based on the implementation of incremental and
"appcremental" auth at Google.
Author's Address
William Denniss
Google
1600 Amphitheatre Pkwy
Mountain View, CA 94043
USA
Email: wdenniss@google.com
URI: http://wdenniss.com/incremental-auth
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