Network Working Group D. Recordon, Ed.
Internet-Draft B. Goldman
Intended status: Standards Track Facebook
Expires: January 2, 2011 Jul 2010
OAuth 2.0 Device Profile
draft-recordon-oauth-v2-device-00
Abstract
The device profile is suitable for OAuth 2.0 clients executing on
devices which do not have an easy data-entry method (e.g. game
consoles or media hubs), but where the end-user has separate access
to a user-agent on another computer or device (e.g. home computer, a
laptop, or a smart phone).
Status of this Memo
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This Internet-Draft will expire on January 2, 2011.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Notational Conventions . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4. Client Requests Authorization . . . . . . . . . . . . . . . 5
1.5. Client Requests Access Token . . . . . . . . . . . . . . . 7
1.6. Additional Error Responses . . . . . . . . . . . . . . . . 7
2. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
3. Normative References . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
1.1. Notational Conventions
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT',
'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and 'OPTIONAL' in this
document are to be interpreted as described in [RFC2119].
1.2. Terminology
device endpoint
The authorization server's HTTP endpoint capable of issuing
verification codes, user codes, and verification URLs.
device verification code
A short-lived token representing an authorization session.
end-user verificition code
A short-lived token which the device displays to the end user,
is entered by the end-user on the authorization sever, and is
thus used to bind the device to the end-user.
1.3. Overview
The device profile is suitable for clients executing on devices which
do not have an easy data-entry method (e.g. game consoles or media
hubs), but where the end-user has separate access to a user-agent on
another computer or device (e.g. home computer, a laptop, or a smart
phone). The client is incapable of receiving incoming requests from
the authorization server (incapable of acting as an HTTP server).
Instead of interacting with the end-user's user-agent, the client
instructs the end-user to use another computer or device and connect
to the authorization server to approve the access request. Since the
client cannot receive incoming requests, it polls the authorization
server repeatedly until the end-user completes the approval process.
This device flow does not utilize the client secret since the client
executables reside on a local device which makes the client secret
accessible and exploitable.
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+----------+ +----------------+
| |>---(A)-- Client Identifier --->| |
| | | |
| |<---(B)-- Verification Code, --<| |
| | User Code, | |
| | & Verification URI | |
| Device | | |
| Client | Client Identifier & | |
| |>---(E)-- Verification Code --->| |
| | ... | |
| |>---(E)---> | |
| | | Authorization |
| |<---(F)-- Access Token --------<| Server |
+----------+ (w/ Optional Refresh Token) | |
v | |
: | |
(C) User Code & Verification URI | |
: | |
v | |
+----------+ | |
| End-user | | |
| at |<---(D)-- User authenticates -->| |
| Browser | | |
+----------+ +----------------+
Figure 1: Device Flow
The device flow illustrated in Figure 1 includes the following steps:
(A) The client requests access from the authorization server and
includes its client identifier in the request.
(B) The authorization server issues a verification code, an end-user
code, and provides the end-user verification URI.
(C) The client instructs the end-user to use its user-agent
(elsewhere) and visit the provided end-user verification URI.
The client provides the end-user with the end-user code to enter
in order to grant access.
(D) The authorization server authenticates the end-user (via the
user-agent) and prompts the end-user to grant the client's
access request. If the end-user agrees to the client's access
request, the end-user enters the end-user code provided by the
client. The authorization server validates the end-user code
provided by the end-user.
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(E) While the end-user authorizes (or denies) the client's request
(D), the client repeatedly polls the authorization server to
find out if the end-user completed the end-user authorization
step. The client includes the verification code and its client
identifier.
(F) Assuming the end-user granted access, the authorization server
validates the verification code provided by the client and
responds back with the access token.
1.4. Client Requests Authorization
The client initiates the flow by requesting a set of verification
codes from the authorization server by making an HTTP "POST" request
to the device endpoint. The client constructs a request URI by
adding the following parameters to the request:
response_type
REQUIRED. The parameter value MUST be set to "device_code".
client_id
REQUIRED. The client identifier as described in Section 2 of
[I-D.ietf.oauth-v2].
scope
OPTIONAL. The scope of the access request expressed as a list
of space-delimited strings. The value of the "scope" parameter
is defined by the authorization server. If the value contains
multiple space-delimited strings, their order does not matter,
and each string adds an additional access range to the
requested scope.
For example, the client makes the following HTTPS request (line
breaks are for display purposes only):
POST /token HTTP/1.1
Host: server.example.com
Content-Type: application/x-www-form-urlencoded
response_type=device_code&client_id=s6BhdRkqt3
In response, the authorization server generates a verification code
and an end-user code and includes them in the HTTP response body
using the "application/json" format with a 200 status code (OK). The
response contains the following parameters:
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device_code
REQUIRED. The verification code.
user_code
REQUIRED. The end-user verification code.
verification_uri
REQUIRED. The end-user verification URI on the authorization
server. The URI should be short and easy to remember as end-
users will be asked to manually type it into their user-agent.
expires_in
OPTIONAL. The duration in seconds of the verification code
lifetime.
interval
OPTIONAL. The minimum amount of time in seconds that the
client SHOULD wait between polling requests to the token
endpoint.
For example:
HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-store
{
"device_code":"74tq5miHKB",
"user_code":"94248",
"verification_uri":"http://www.example.com/device",
"interval"=5
}
The client displays the end-user code and the end-user verification
URI to the end-user, and instructs the end-user to visit the URI
using a user-agent and enter the end-user code.
The end-user manually types the provided verification URI and
authenticates with the authorization server. The authorization
server prompts the end-user to authorize the client's request by
entering the end-user code provided by the client. Once the end-user
approves or denies the request, the authorization server informs the
end-user to return to the device for further instructions.
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1.5. Client Requests Access Token
Since the client is unable to receive incoming requests from the
authorization server, it polls the authorization server repeatedly
until the end-user grants or denies the request, or the verification
code expires.
The client makes the following request at an arbitrary but reasonable
interval which MUST NOT exceed the minimum interval rate provided by
the authorization server (if present via the "interval" parameter).
Alternatively, the client MAY provide a user interface for the end-
user to manually inform it when authorization was granted.
The client requests an access token by making an HTTP "POST" request
to the token endpoint as described in Section 4.1.1 of
[I-D.ietf.oauth-v2]. The "redirect_uri" parameter is NOT REQUIRED as
part of this request.
1.6. Additional Error Responses
The following error responses are defined in addition to those within
Section 4.3.1 of [I-D.ietf.oauth-v2].
authorization_pending
The authorization request is still pending as the end-user
hasn't yet visited the authorization server and entered their
verification code.
slow_down
The client is polling too quickly and should back off at a
reasonable rate.
2. Security Considerations
Length of codes (Google has done some research here).
3. Normative References
[I-D.ietf.oauth-v2]
Hammer-Lahav, E., Ed., Recordon, D., and D. Hardt, "The
OAuth 2.0 Protocol", Jun 2010.
[RFC2119] Bradner, B., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119.
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Authors' Addresses
David Recordon (editor)
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Email: davidrecordon@facebook.com
Brent Goldman
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Email: brent@facebook.com
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