draft-ietf-oauth-device-flow-07.txt   draft-ietf-oauth-device-flow-08.txt 
OAuth W. Denniss OAuth W. Denniss
Internet-Draft Google Internet-Draft Google
Intended status: Standards Track J. Bradley Intended status: Standards Track J. Bradley
Expires: May 3, 2018 Ping Identity Expires: September 20, 2018 Ping Identity
M. Jones M. Jones
Microsoft Microsoft
H. Tschofenig H. Tschofenig
ARM Limited ARM Limited
October 30, 2017 March 19, 2018
OAuth 2.0 Device Flow for Browserless and Input Constrained Devices OAuth 2.0 Device Flow for Browserless and Input Constrained Devices
draft-ietf-oauth-device-flow-07 draft-ietf-oauth-device-flow-08
Abstract Abstract
This OAuth 2.0 authorization flow for browserless and input This OAuth 2.0 authorization flow for browserless and input
constrained devices, often referred to as the device flow, enables constrained devices, often referred to as the device flow, enables
OAuth clients to request user authorization from devices that have an OAuth clients to request user authorization from devices that have an
Internet connection, but don't have an easy input method (such as a Internet connection, but don't have an easy input method (such as a
smart TV, media console, picture frame, or printer), or lack a smart TV, media console, picture frame, or printer), or lack a
suitable browser for a more traditional OAuth flow. This suitable browser for a more traditional OAuth flow. This
authorization flow instructs the user to perform the authorization authorization flow instructs the user to perform the authorization
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 3, 2018. This Internet-Draft will expire on September 20, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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3. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Device Authorization Request . . . . . . . . . . . . . . 5 3.1. Device Authorization Request . . . . . . . . . . . . . . 5
3.2. Device Authorization Response . . . . . . . . . . . . . . 6 3.2. Device Authorization Response . . . . . . . . . . . . . . 6
3.3. User Interaction . . . . . . . . . . . . . . . . . . . . 7 3.3. User Interaction . . . . . . . . . . . . . . . . . . . . 7
3.3.1. Non-textual Verification URI Optimization . . . . . . 8 3.3.1. Non-textual Verification URI Optimization . . . . . . 8
3.4. Device Access Token Request . . . . . . . . . . . . . . . 9 3.4. Device Access Token Request . . . . . . . . . . . . . . . 9
3.5. Device Access Token Response . . . . . . . . . . . . . . 10 3.5. Device Access Token Response . . . . . . . . . . . . . . 10
4. Discovery Metadata . . . . . . . . . . . . . . . . . . . . . 11 4. Discovery Metadata . . . . . . . . . . . . . . . . . . . . . 11
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
5.1. User Code Brute Forcing . . . . . . . . . . . . . . . . . 11 5.1. User Code Brute Forcing . . . . . . . . . . . . . . . . . 11
5.2. Device Trustworthiness . . . . . . . . . . . . . . . . . 11 5.2. Device Trustworthiness . . . . . . . . . . . . . . . . . 12
5.3. Remote Phishing . . . . . . . . . . . . . . . . . . . . . 11 5.3. Remote Phishing . . . . . . . . . . . . . . . . . . . . . 12
5.4. Session Spying . . . . . . . . . . . . . . . . . . . . . 12 5.4. Session Spying . . . . . . . . . . . . . . . . . . . . . 12
5.5. Non-confidential Clients . . . . . . . . . . . . . . . . 12 5.5. Non-confidential Clients . . . . . . . . . . . . . . . . 12
5.6. Non-Visual Code Transmission . . . . . . . . . . . . . . 12 5.6. Non-Visual Code Transmission . . . . . . . . . . . . . . 13
6. Usability Considerations . . . . . . . . . . . . . . . . . . 12 6. Usability Considerations . . . . . . . . . . . . . . . . . . 13
6.1. User Code Recommendations . . . . . . . . . . . . . . . . 13 6.1. User Code Recommendations . . . . . . . . . . . . . . . . 13
6.2. Non-Browser User Interaction . . . . . . . . . . . . . . 13 6.2. Non-Browser User Interaction . . . . . . . . . . . . . . 14
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
7.1. OAuth URI Registration . . . . . . . . . . . . . . . . . 14 7.1. OAuth URI Registration . . . . . . . . . . . . . . . . . 14
7.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 14 7.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 14
7.2. OAuth Extensions Error Registration . . . . . . . . . . . 14 7.2. OAuth Extensions Error Registration . . . . . . . . . . . 14
7.2.1. Registry Contents . . . . . . . . . . . . . . . . . . 14 7.2.1. Registry Contents . . . . . . . . . . . . . . . . . . 14
7.3. OAuth 2.0 Authorization Server Metadata . . . . . . . . . 14 7.3. OAuth 2.0 Authorization Server Metadata . . . . . . . . . 15
7.3.1. Registry Contents . . . . . . . . . . . . . . . . . . 15 7.3.1. Registry Contents . . . . . . . . . . . . . . . . . . 15
8. Normative References . . . . . . . . . . . . . . . . . . . . 15 8. Normative References . . . . . . . . . . . . . . . . . . . . 15
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 15 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 16
Appendix B. Document History . . . . . . . . . . . . . . . . . . 16 Appendix B. Document History . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction 1. Introduction
This OAuth 2.0 protocol flow for browserless and input constrained This OAuth 2.0 protocol flow for browserless and input constrained
devices, often referred to as the device flow, enables OAuth clients devices, often referred to as the device flow, enables OAuth clients
to request user authorization from devices that have an internet to request user authorization from devices that have an internet
connection, but don't have an easy input method (such as a smart TV, connection, but don't have an easy input method (such as a smart TV,
media console, picture frame, or printer), or lack a suitable browser media console, picture frame, or printer), or lack a suitable browser
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following metadata: following metadata:
device_authorization_endpoint device_authorization_endpoint
OPTIONAL. URL of the authorization server's device authorization OPTIONAL. URL of the authorization server's device authorization
endpoint defined in Section 3.1. endpoint defined in Section 3.1.
5. Security Considerations 5. Security Considerations
5.1. User Code Brute Forcing 5.1. User Code Brute Forcing
Since the user code is typed by the user, the entropy is typically Since the user code is typed by the user, shorter codes are more
desirable for usability reasons. This means the entropy is typically
less than would be used for the device code or other OAuth bearer less than would be used for the device code or other OAuth bearer
token types. It is therefore recommended that the server rate-limit token types where the code length does not impact usability. It is
user code attempts. The user code SHOULD have enough entropy that therefore recommended that the server rate-limit user code attempts.
when combined with rate limiting makes a brute-force attack The user code SHOULD have enough entropy that when combined with rate
infeasible. limiting and other mitigations makes a brute-force attack infeasible.
A successful brute forcing of the user code would enable the attacker
to authenticate with their own credentials and make an authorization
grant to the device. This is the opposite scenario to an OAuth
bearer token being brute forced, whereby the attacker gains control
of the victim's authorization grant. In some applications this
attack may not make much economic sense, for example for a video app,
the owner of the device may then be able to purchase movies with the
attacker's account, however there are still privacy considerations in
that case as well as other uses of the device flow whereby the
granting account may be able to perform sensitive actions such as
controlling the victim's device.
The precise length of the user code and the entropy contained within
is at the discretion of the authorization server, which needs to
consider the sensitivity of their specific protected resources, the
practicality of the code length from a usability standpoint, and any
mitigations that are in place such as rate-limiting, when determining
the user code format.
5.2. Device Trustworthiness 5.2. Device Trustworthiness
Unlike other native application OAuth 2.0 flows, the device Unlike other native application OAuth 2.0 flows, the device
requesting the authorization is not the same as the device that the requesting the authorization is not the same as the device that the
user grants access from. Thus, signals from the approving user's user grants access from. Thus, signals from the approving user's
session and device are not relevant to the trustworthiness of the session and device are not relevant to the trustworthiness of the
client device. client device.
5.3. Remote Phishing 5.3. Remote Phishing
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OAuth 2.0 protocol specification removed prior to publication due to OAuth 2.0 protocol specification removed prior to publication due to
a then lack of sufficient deployment expertise. Thank you to the a then lack of sufficient deployment expertise. Thank you to the
OAuth working group members who worked on this specification through OAuth working group members who worked on this specification through
2010. 2010.
The following individuals contributed ideas, feedback, and wording The following individuals contributed ideas, feedback, and wording
that shaped and formed the final specification: that shaped and formed the final specification:
Roshni Chandrashekhar, Marius Scurtescu, Breno de Medeiros, Stein Roshni Chandrashekhar, Marius Scurtescu, Breno de Medeiros, Stein
Myrseth, Simon Moffatt, Brian Campbell, James Manger, Justin Richer, Myrseth, Simon Moffatt, Brian Campbell, James Manger, Justin Richer,
Ken Wang, Steven E. Wright, Nat Sakimura, and Torsten Lodderstedt. Ken Wang, Steven E. Wright, Nat Sakimura, and Torsten Lodderstedt.
Appendix B. Document History Appendix B. Document History
[[ to be removed by the RFC Editor before publication as an RFC ]] [[ to be removed by the RFC Editor before publication as an RFC ]]
-07 -07
o Replaced the "user_code" URI parameter optimization with o Replaced the "user_code" URI parameter optimization with
verification_uri_complete following the IETF99 working group verification_uri_complete following the IETF99 working group
discussion. discussion.
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