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24 25 26 27 28 29 30 31 RFC 6749
Network Working Group E. Hammer-Lahav, Ed.
Internet-Draft Yahoo!
Obsoletes: 5849 (if approved) D. Recordon
Intended status: Standards Track Facebook
Expires: June 4, 2011 D. Hardt
Microsoft
December 1, 2010
The OAuth 2.0 Protocol Framework
draft-ietf-oauth-v2-11
Abstract
This specification describes the OAuth 2.0 protocol framework.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 4, 2011.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Notational Conventions . . . . . . . . . . . . . . . . . . 5
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
1.3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.4. Access Grants . . . . . . . . . . . . . . . . . . . . . . 8
1.4.1. Authorization Code . . . . . . . . . . . . . . . . . . 8
1.4.2. Resource Owner Password Credentials . . . . . . . . . 10
1.4.3. Client Credentials . . . . . . . . . . . . . . . . . . 10
1.4.4. Refresh Token . . . . . . . . . . . . . . . . . . . . 11
1.4.5. Assertion . . . . . . . . . . . . . . . . . . . . . . 12
2. Client Profiles . . . . . . . . . . . . . . . . . . . . . . . 12
2.1. Web Server . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2. User-Agent . . . . . . . . . . . . . . . . . . . . . . . . 14
2.3. Native Application . . . . . . . . . . . . . . . . . . . . 15
2.4. Autonomous . . . . . . . . . . . . . . . . . . . . . . . . 16
3. Client Credentials . . . . . . . . . . . . . . . . . . . . . . 17
3.1. Client Password Credentials . . . . . . . . . . . . . . . 17
3.2. Client Assertion Credentials . . . . . . . . . . . . . . . 18
4. Obtaining End-User Authorization . . . . . . . . . . . . . . . 20
4.1. Authorization Request . . . . . . . . . . . . . . . . . . 20
4.2. Authorization Response . . . . . . . . . . . . . . . . . . 22
4.3. Error Response . . . . . . . . . . . . . . . . . . . . . . 24
4.3.1. Error Codes . . . . . . . . . . . . . . . . . . . . . 25
5. Obtaining an Access Token . . . . . . . . . . . . . . . . . . 25
5.1. Access Grant Types . . . . . . . . . . . . . . . . . . . . 27
5.1.1. Authorization Code . . . . . . . . . . . . . . . . . . 27
5.1.2. Resource Owner Password Credentials . . . . . . . . . 27
5.1.3. Client Credentials . . . . . . . . . . . . . . . . . . 28
5.1.4. Refresh Token . . . . . . . . . . . . . . . . . . . . 28
5.1.5. Assertion . . . . . . . . . . . . . . . . . . . . . . 29
5.2. Access Token Response . . . . . . . . . . . . . . . . . . 30
5.3. Error Response . . . . . . . . . . . . . . . . . . . . . . 31
5.3.1. Error Codes . . . . . . . . . . . . . . . . . . . . . 32
6. Accessing a Protected Resource . . . . . . . . . . . . . . . . 33
6.1. Access Token Types . . . . . . . . . . . . . . . . . . . . 33
6.2. The WWW-Authenticate Response Header Field . . . . . . . . 33
6.2.1. Error Codes . . . . . . . . . . . . . . . . . . . . . 35
7. Extensibility . . . . . . . . . . . . . . . . . . . . . . . . 36
7.1. Defining New Client Credentials Types . . . . . . . . . . 36
7.2. Defining New Endpoint Parameters . . . . . . . . . . . . . 36
7.3. Defining New Header Field Parameters . . . . . . . . . . . 36
7.4. Defining New Access Grant Types . . . . . . . . . . . . . 37
8. Security Considerations . . . . . . . . . . . . . . . . . . . 37
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37
9.1. The OAuth Parameters Registry . . . . . . . . . . . . . . 37
9.1.1. Registration Template . . . . . . . . . . . . . . . . 37
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9.1.2. Example . . . . . . . . . . . . . . . . . . . . . . . 38
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 38
Appendix B. Contributors . . . . . . . . . . . . . . . . . . . . 38
Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . . 39
Appendix D. Document History . . . . . . . . . . . . . . . . . . 39
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 44
10.1. Normative References . . . . . . . . . . . . . . . . . . . 44
10.2. Informative References . . . . . . . . . . . . . . . . . . 45
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 46
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1. Introduction
With the increasing use of distributed web services and cloud
computing, third-party applications require access to server-hosted
resources. These resources are usually protected and require
authentication using the resource owner's credentials (typically a
username and password).
In the traditional client-server authentication model, the client
accesses a protected resource on the server by authenticating with
the server using the resource owner's credentials. In order to
provide third-party applications access to protected resources, the
resource owner shares its credentials with the third-party. This
creates several problems and limitations:
o Third-party applications are required to store the resource-
owner's credentials for future use, typically a password in clear-
text.
o Servers are required to support password authentication, despite
the security weaknesses created by passwords.
o Third-party applications gain overly broad access to the resource-
owner's protected resources, leaving resource owners without any
ability to restrict access to a limited subset of resources, to
limit access duration, or to limit access to the methods supported
by these resources.
o Resource owners cannot revoke access to an individual third-party
without revoking access to all third-parties, and must do so by
changing their password.
OAuth addresses these issues by separating the role of the client
from that of the resource owner. In OAuth, the client (which is
usually not the resource owner, but is acting on the resource owner's
behalf) requests access to resources controlled by the resource owner
and hosted by the resource server, and is issued a different set of
credentials than those of the resource owner.
Instead of using the resource owner's credentials to access protected
resources, the client obtains an access token - a string which
denotes a specific scope, duration, and other attributes. Access
tokens are issued to third-party clients by an authorization server
with the approval of the resource owner. The client uses the access
token to access the protected resources hosted by the resource
server.
For example, a web user (resource owner) can grant a printing service
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(client) access to her protected photos stored at a photo sharing
service (resource server), without sharing her username and password
with the printing service. Instead, she authenticates directly with
an authentication service trusted by the photo sharing service
(authorization server) which issues the printing service delegation-
specific credentials (token).
Access tokens can have different formats, structures, and methods of
utilization (e.g. cryptographic properties), based on the resource
server security requirements. Access token attributes and the
methods used to access protected resources are beyond the scope of
this specification and are defined by companion specifications. The
interaction between the authorization server and resource server is
beyond the scope of this specification.
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].
This document uses the Augmented Backus-Naur Form (ABNF) notation of
[I-D.ietf-httpbis-p1-messaging]. Additionally, the following rules
are included from [RFC3986]: URI-reference; and from
[I-D.ietf-httpbis-p1-messaging]: OWS, RWS, and quoted-string.
Unless otherwise noted, all the protocol parameter names and values
are case sensitive.
1.2. Terminology
protected resource
An access-restricted resource which can be obtained using an
OAuth-authenticated request.
resource server
A server capable of accepting and responding to protected
resource requests.
client
An application obtaining authorization and making protected
resource requests.
resource owner
An entity capable of granting access to a protected resource.
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end-user
A human resource owner.
token
A string representing an access authorization issued to the
client. The string is usually opaque to the client. Tokens
represent specific scopes and durations of access, granted by
the resource owner, and enforced by the resource server and
authorization servers. The token may denote an identifier used
to retrieve the authorization information, or self-contain the
authorization information in a verifiable manner (i.e. a token
string consisting of some data and a signature). Tokens may be
pure capabilities. Specific additional authentication
credentials may be required in order for a client to use a
token.
access token
A token used by the client to make authenticated requests on
behalf of the resource owner.
refresh token
A token used by the client to obtain a new access token without
having to involve the resource owner.
authorization code A short-lived token representing the
authorization provided by the end-user. The authorization code
is used to obtain an access token and a refresh token.
access grant A general term used to describe the intermediate
credentials (such as an end-user password or authorization
code) representing the resource owner authorization. Access
grants are used by the client to obtain an access token. By
exchanging access grants of different types for an access
token, the resource server is only required to support a single
authentication scheme.
authorization server
A server capable of issuing tokens after successfully
authenticating the resource owner and obtaining authorization.
The authorization server may be the same server as the resource
server, or a separate entity. A single authorization server
may issue tokens for multiple resource servers.
end-user authorization endpoint
The authorization server's HTTP endpoint capable of
authenticating the end-user and obtaining authorization. The
end-user authorization endpoint is described in Section 4.
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token endpoint
The authorization server's HTTP endpoint capable of issuing
tokens and refreshing expired tokens. The token endpoint is
described in Section 5.
client identifier
A unique identifier issued to the client to identify itself to
the authorization server. Client identifiers may have a
matching secret. The client identifier is described in
Section 3.
1.3. Overview
OAuth provides a method for clients to access a protected resource on
behalf of a resource owner. Before a client can access a protected
resource, it must first obtain authorization (access grant) from the
resource owner, then exchange the access grant for an access token
(representing the grant's scope, duration, and other attributes).
The client accesses the protected resource by presenting the access
token to the resource server.
The access token provides an abstraction layer, replacing different
authorization constructs (e.g. username and password, assertion) for
a single token understood by the resource server. This abstraction
enables issuing access tokens valid for a short time period, as well
as removing the resource server's need to understand a wide range of
authentication schemes.
+--------+ +---------------+
| |--(A)- Authorization Request ->| Resource |
| | | Owner |
| |<-(B)----- Access Grant -------| |
| | +---------------+
| |
| | Access Grant & +---------------+
| |--(C)--- Client Credentials -->| Authorization |
| Client | | Server |
| |<-(D)----- Access Token -------| |
| | +---------------+
| |
| | +---------------+
| |--(E)----- Access Token ------>| Resource |
| | | Server |
| |<-(F)--- Protected Resource ---| |
+--------+ +---------------+
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Figure 1: Abstract Protocol Flow
The abstract flow illustrated in Figure 1 describes the overall
protocol architecture and includes the following steps:
(A) The client requests authorization from the resource owner. The
authorization request can be made directly to the resource
owner, or preferably indirectly via an intermediary such as an
authorization server.
(B) The client receives an access grant which represents the
authorization provided by the resource owner.
(C) The client requests an access token by authenticating with the
authorization server using its client credentials, and
presenting the access grant.
(D) The authorization server validates the client credentials and
the access grant, and if valid issues an access token.
(E) The client makes a protected resource request to the resource
server by presenting the access token.
(F) The resource server validates the access token, and if valid,
serves the request.
1.4. Access Grants
The access grant represents the authorization provided by the
resource owner. The access grant type depends on the method used by
the client and supported by the authorization server to obtain it.
1.4.1. Authorization Code
The authorization code is an access grant obtained by directing the
end-user to an authorization server. The authorization server
authenticates the end-user, obtains authorization, and issues the an
authorization code to the client. Because the end-user only
authenticates with the authorization server, the end-user's password
is never shared with the client.
The authorization code access grant is suitable when the client is
interacting with an end-user via a user-agent.
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+----------+
| |
| End-User |
| |
+----------+
^
|
(B)
+----|-----+ Client Identifier +---------------+
| -+--(A)--- & Redirect URI ----->| |
| User- | | Authorization |
| Agent -|--(B)-- User authenticates -->| Server |
| | | |
| -+--(C)-- Authorization Code --<| |
+-|----|---+ +---------------+
(A) (C)
| |
^ v
+---------+
| |
| Client |
| |
+---------+
Figure 2: Obtaining an Authorization Code
The authorization code flow illustrated in Figure 2 includes the
following steps:
(A) The client initiates the flow by directing the end-user's user-
agent to the authorization server's end-user authorization
endpoint. The client includes its client identifier, requested
scope, local state, and a redirection URI (to which the
authorization server will send the user-agent back once access
is granted or denied).
(B) The authorization server authenticates the end-user (via the
user-agent) and establishes whether the end-user grants or
denies the client's access request.
(C) If access is granted, the authorization server directs the user-
agent back to the client using the redirection URI provided.
The authorization server includes an authorization code for the
client to use to obtain an access token.
Once the client obtains an authorization code, it requests an access
token by authenticating with the authorization server (using its
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client credentials) and presenting the authorization code (access
grant).
In cases where the client is incapable of maintaining its client
credentials secret (such as native applications or an application
implemented as a user-agent script), the authorization server issues
an access token directly to the client in step (C), instead of
issuing an authorization code.
Obtaining an authorization code is described in Section 4.
1.4.2. Resource Owner Password Credentials
The resource owner password credentials (e.g. a username and
password) can be used directly as an access grant to obtain an access
token. The credentials should only be used when there is a high
degree of trust between the resource owner and the client (e.g. its
computer operating system or a highly privileged application), and
when other access grant types are not available (such as an
authorization code).
Even though this grant type requires direct client access to the
resource owner's credentials, the resource owner's credentials are
used for a single request and are exchanged for an access token.
Unlike the HTTP Basic authentication scheme defined in [RFC2617],
this grant type eliminates the need for the client to store the
resource-owner's credentials for future use.
In Figure 3, the client requests authorization from the resource
owner directly. When the resource owner is an end-user, the client
typically prompts the end-user for the username and password.
+--------+ +----------+
| |--(A)- Authorization Request ->| Resource |
| Client | | Owner |
| |<-(B)-- Username & Password ---| |
+--------+ +----------+
Figure 3: Obtaining Resource Owner Password Credentials
1.4.3. Client Credentials
The client credentials can be used as an access grant when the
authorization scope is limited to the protected resources under the
control of the client, or other protected resources previously
arranged with the authorization server. Client credentials are used
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as an access grant typically when the client is acting on its own
behalf (the client is also the resource owner).
1.4.4. Refresh Token
Access tokens usually have a shorter lifetime than authorized by the
resource owner. When issuing an access token, the authorization
server can include a refresh token which is used by the client to
obtain a new access token when the current access token expires.
When requesting a new access token, the refresh token acts as an
access grant. Using a refresh token removes the need to interact
with the resource owner again, or to store the original access grant
used to obtain the access token and refresh token.
+--------+ Access Grant & +---------------+
| |--(A)-- Client Credentials -->| Authorization |
| | | Server |
| |<-(B)---- Access Token -------| |
| | & Refresh Token +---------------+
| |
| | +---------------+
| |--(C)----- Access Token ----->| |
| | | |
| |<-(D)-- Protected Resource ---| Resource |
| Client | | Server |
| |--(E)----- Access Token ----->| |
| | | |
| |<-(F)-- Invalid Token Error --| |
| | +---------------+
| |
| | Refresh Token & +---------------+
| |--(G)-- Client Credentials -->| Authorization |
| | | Server |
| |<-(H)----- Access Token ------| |
+--------+ & Optional Refresh Token +---------------+
Figure 4: Refreshing an Access Token
The refresh token flow illustrated in Figure 4 includes the following
steps:
(A) The client requests an access token by authenticating with the
authorization server using its client credentials, and
presenting an access grant.
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(B) The authorization server validates the client credentials and
the access grant, and if valid issues an access token and a
refresh token.
(C) The client makes a protected resource requests to the resource
server by presenting the access token.
(D) The resource server validates the access token, and if valid,
serves the request.
(E) Steps (C) and (D) repeat until the access token expires. If the
client does not know the access token expired, it makes another
protected resource request. Otherwise, it skips to step (G).
(F) Since the access token is invalid (expired), the resource server
returns an invalid token error.
(G) The client requests a new access token by authenticating with
the authorization server using its client credentials, and
presenting the refresh token (as the access grant).
(H) The authorization server validates the client credentials and
the refresh token, and if valid issues a new access token (and
optionally, a new refresh token).
1.4.5. Assertion
Assertions provide a bridge between OAuth and other trust frameworks.
They enable the client to utilize existing trust relationships in
order to obtain an access token. The access grant represented by an
assertion depends on the assertion type, its content, and how it was
issued, which are beyond the scope of this specification.
Assertions are used as part of the protocol extensibility model,
providing a way for authorization servers to support additional
access grant types.
2. Client Profiles
[[ add intro and find new names for the profiles. this section will
have normative language in future drafts, similar to -05 and earlier.
]]
2.1. Web Server
The web server profile is suitable for clients capable of interacting
with the end-user's user-agent (typically a web browser) and capable
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of receiving incoming requests (via redirection) from the
authorization server (capable of acting as an HTTP server).
+----------+ Client Identifier +---------------+
| -+----(A)--- & Redirect URI ------>| |
| End-user | | Authorization |
| at |<---(B)-- User authenticates --->| Server |
| Browser | | |
| -+----(C)-- Authorization Code ---<| |
+-|----|---+ +---------------+
| | ^ v
(A) (C) | |
| | | |
^ v | |
+---------+ | |
| |>---(D)-- Client Credentials, --------' |
| Server | Authorization Code, |
| -Based | & Redirect URI |
| Client | |
| |<---(E)----- Access Token -------------------'
+---------+ (w/ Optional Refresh Token)
Figure 5: Web Server Flow
The web server flow illustrated in Figure 5 includes the following
steps:
(A) The web client initiates the flow by redirecting the end-user's
user-agent to the end-user authorization endpoint as described
in Section 4. The client includes its client identifier,
requested scope, local state, and a redirect URI to which the
authorization server will send the end-user back once access is
granted (or denied).
(B) The authorization server authenticates the end-user (via the
user-agent) and establishes whether the end-user grants or
denies the client's access request.
(C) Assuming the end-user granted access, the authorization server
redirects the user-agent back to the client to the redirection
URI provided earlier. The authorization includes an
authorization code for the client to use to obtain an access
token.
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(D) The client requests an access token from the authorization
server by authenticating and including the authorization code
received in the previous step as described in Section 5.
(E) The authorization server validates the client credentials and
the authorization code and responds back with the access token.
2.2. User-Agent
The user-agent profile is suitable for client applications residing
in a user-agent, typically implemented in a browser using a scripting
language such as JavaScript. These clients cannot keep client
secrets confidential and the authentication of the client is based on
the user-agent's same-origin policy.
Unlike other profiles in which the client makes separate requests for
end-user authorization and access token, the client receives the
access token as a result of the end-user authorization request in the
form of an HTTP redirection. The client requests the authorization
server to redirect the user-agent to another web server or local
resource accessible to the user-agent which is capable of extracting
the access token from the response and passing it to the client.
This user-agent profile does not utilize the client secret since the
client executables reside on the end-user's computer or device which
makes the client secret accessible and exploitable. Because the
access token is encoded into the redirection URI, it may be exposed
to the end-user and other applications residing on the computer or
device.
+----------+ Client Identifier +----------------+
| |>---(A)-- & Redirection URI --->| |
| | | |
End <--+ - - - +----(B)-- User authenticates -->| Authorization |
User | | | Server |
| |<---(C)--- Redirect URI -------<| |
| Client | with Access Token | |
| in | in Fragment +----------------+
| Browser |
| | +----------------+
| |>---(D)--- Redirect URI ------->| |
| | without Fragment | Web Server |
| | | with Client |
| (F) |<---(E)--- Web Page with ------<| Resource |
| Access | Script | |
| Token | +----------------+
+----------+
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Figure 6: User-Agent Flow
The user-agent flow illustrated in Figure 6 includes the following
steps:
(A) The client sends the user-agent to the end-user authorization
endpoint as described in Section 4. The client includes its
client identifier, requested scope, local state, and a redirect
URI to which the authorization server will send the end-user
back once authorization is granted (or denied).
(B) The authorization server authenticates the end-user (via the
user-agent) and establishes whether the end-user grants or
denies the client's access request.
(C) If the end-user granted access, the authorization server
redirects the user-agent to the redirection URI provided
earlier. The redirection URI includes the access token in the
URI fragment.
(D) The user-agent follows the redirection instructions by making a
request to the web server which does not include the fragment.
The user-agent retains the fragment information locally.
(E) The web server returns a web page (typically an HTML page with
an embedded script) capable of accessing the full redirection
URI including the fragment retained by the user-agent, and
extracting the access token (and other parameters) contained in
the fragment.
(F) The user-agent executes the script provided by the web server
locally, which extracts the access token and passes it to the
client.
2.3. Native Application
Native applications are clients running as native code on the end-
user's computer or device (i.e. executing outside a user-agent or as
a desktop program). These clients are often capable of interacting
with (or embedding) the end-user's user-agent but are limited in how
such interaction affects their end-user experience. In many cases,
native applications are incapable of receiving direct callback
requests from the server (e.g. firewall, operating system
restrictions).
Native application clients can be implemented in different ways based
on their requirements and desired end-user experience. Native
application clients can:
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o Utilize the end-user authorization endpoint as described in
Section 4 by launching an external user-agent. The client can
capture the response by providing a redirection URI with a custom
URI scheme (registered with the operating system to invoke the
client application), or by providing a redirection URI pointing to
a server-hosted resource under the client's control which makes
the response available to the client (e.g. using the window title
or other locations accessible from outside the user-agent).
o Utilize the end-user authorization endpoint as described in
Section 4 by using an embedded user-agent. The client obtains the
response by directly communicating with the embedded user-agent.
o Prompt end-users for their password and use them directly to
obtain an access token. This is generally discouraged, as it
hands the end-user's password directly to the third-party client
which in turn has to store it in clear-text. It also requires the
server to support password-based authentication.
When choosing between launching an external browser and an embedded
user-agent, developers should consider the following:
o External user-agents may improve completion rate as the end-user
may already be logged-in and not have to re-authenticate.
o Embedded user-agents often offer a better end-user flow, as they
remove the need to switch context and open new windows.
o Embedded user-agents pose a security challenge because users are
authenticating in an unidentified window without access to the
visual protections offered by many user-agents.
2.4. Autonomous
Autonomous clients utilize an existing trust relationship or
framework to establish authorization. Autonomous clients can be
implemented in different ways based on their requirements and the
existing trust framework they rely upon. Autonomous clients can:
o Obtain an access token by authenticating with the authorization
server using their client credentials. The scope of the access
token is limited to the protected resources under the control of
the client, or that of another resource owner previously arranged
with the authorization server.
o Use an existing access grant expressed as an assertion using an
assertion format supported by the authorization server. Using
assertions requires the client to obtain an assertion (such as a
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SAML [OASIS.saml-core-2.0-os] assertion) from an assertion issuer
or to self-issue an assertion. The assertion format, the process
by which the assertion is obtained, and the method of validating
the assertion are defined by the assertion issuer and the
authorization server, and are beyond the scope of this
specification.
3. Client Credentials
When interacting with the authorization server, the client identifies
itself using a set of client credentials which include a client
identifier and other properties for client authentication. The means
through which the client obtains its credentials are beyond the scope
of this specification, but typically involve registration with the
authorization server.
Due to the nature of some clients, authorization servers SHOULD NOT
make assumptions about the confidentiality of client secrets without
establishing trust with the client. Authorization servers SHOULD NOT
issue client secrets to clients incapable of keeping their secrets
confidential.
The authorization server MAY authenticate the client using any
appropriate set of credentials and authentication schemes. The
client MUST NOT include more than one set of credentials or
authentication mechanism with each request.
3.1. Client Password Credentials
The client password credentials use a shared symmetric secret to
authenticate the client. The client identifier and password are
included in the request using the HTTP Basic authentication scheme as
defined in [RFC2617] by including the client identifier as the
username and client password as the password.
For example (line breaks are for display purposes only):
POST /token HTTP/1.1
Host: server.example.com
Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW
Content-Type: application/x-www-form-urlencoded
grant_type=authorization_code&code=i1WsRn1uB1&
redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb
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Alternatively, the client MAY include the password in the request
body using the following parameters:
client_id
REQUIRED. The client identifier.
client_secret REQUIRED. The client password.
For example (line breaks are for display purposes only):
POST /token HTTP/1.1
Host: server.example.com
Content-Type: application/x-www-form-urlencoded
grant_type=authorization_code&client_id=s6BhdRkqt3&
client_secret=gX1fBat3bV&code=i1WsRn1uB1&
redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb
The authorization server MUST accept the client credentials using
both the request parameter, and the HTTP Basic authentication scheme.
The authorization server MAY support additional authentication
schemes suitable for the transmission of password credentials.
3.2. Client Assertion Credentials
The client assertion credentials are used in cases where a password
(clear-text shared symmetric secret) is unsuitable or does not
provide sufficient security for client authentication. In such cases
it is common to use other mechanisms such as HMAC or digital
signatures that do not require sending clear-text secrets. The
client assertion credentials provide an extensible mechanism to use
an assertion format supported by the authorization server for
authentication the client.
Using assertions requires the client to obtain an assertion (such as
a SAML [OASIS.saml-core-2.0-os] assertion) from an assertion issuer
or to self-issue an assertion. The assertion format, the process by
which the assertion is obtained, and the method of validating the
assertion are defined by the assertion issuer and the authorization
server, and are beyond the scope of this specification.
When using a client assertion, the client includes the following
parameters:
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client_assertion_type REQUIRED. The format of the assertion as
defined by the authorization server. The value MUST be an
absolute URI.
client_assertion REQUIRED. The client assertion.
For example, the client sends the following access token request
using a SAML 2.0 assertion to authenticate itself (line breaks are
for display purposes only):
POST /token HTTP/1.1
Host: server.example.com
Content-Type: application/x-www-form-urlencoded
grant_type=authorization_code&code=i1WsRn1uB1&
client_assertion=PHNhbWxwOl[...omitted for brevity...]ZT4%3D&
client_assertion_type=
urn%3Aoasis%3Anames%sAtc%3ASAML%3A2.0%3Aassertion&
redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb
When obtaining an access token using a client assertion together with
an authorization code (as described in Section 5.1.1), a mechanism is
needed to map between the value of "client_id" parameter used to
obtain the authorization code, and the client assertion. Such
mechanism is beyond the out of scope for this specification, but MUST
be specified for any client assertion type used in combination with
an authorization code.
The authorization server MUST reject access token requests using
client assertion credentials that do not contain HMAC or signed
values that:
o State the assertion was specifically issued to be consumed by the
receiving endpoint (typically via an audience or recipient value
containing the receiving endpoint's identifier).
o Identify the entity that issued the assertion (typically via an
issuer value).
o Identify when the assertion expires as an absolute time (typically
via an expiration value containing a UTC date/time value). The
authorization server MUST reject expired assertions.
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4. Obtaining End-User Authorization
Before the client can access a protect resource, it MUST first obtain
authorization from the end-user. To obtain an end-user
authorization, the client sends the end-user to the end-user
authorization endpoint. Once obtained, the end-user access grant is
expressed as an authorization code which the client uses to obtain an
access token.
At the end-user authorization endpoint, the end-user first
authenticates with the authorization server, and then grants or
denies the access request. The way in which the authorization server
authenticates the end-user (e.g. username and password login, OpenID,
session cookies) and in which the authorization server obtains the
end-user's authorization, including whether it uses a secure channel
such as TLS, is beyond the scope of this specification. However, the
authorization server MUST first verify the identity of the end-user.
The location of the end-user authorization endpoint can be found in
the service documentation. The end-user authorization endpoint URI
MAY include a query component as defined by [RFC3986] section 3,
which must be retained when adding additional query parameters.
Since requests to the end-user authorization endpoint result in user
authentication and the transmission of sensitive information, the
authorization server SHOULD require the use of a transport-layer
security mechanism such as TLS when sending requests to the end-user
authorization endpoint.
4.1. Authorization Request
In order to direct the end-user's user-agent to the authorization
server, the client constructs the request URI by adding the following
parameters to the end-user authorization endpoint URI query component
using the "application/x-www-form-urlencoded" format as defined by
[W3C.REC-html401-19991224]:
response_type
REQUIRED. The requested response: an access token, an
authorization code, or both. The parameter value MUST be set
to "token" for requesting an access token, "code" for
requesting an authorization code, or "code_and_token" to
request both. The authorization server MAY decline to provide
one or more of these response types.
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client_id
REQUIRED. The client identifier as described in Section 3.
redirect_uri
REQUIRED, unless a redirection URI has been established between
the client and authorization server via other means. An
absolute URI to which the authorization server will redirect
the user-agent to when the end-user authorization step is
completed. The authorization server SHOULD require the client
to pre-register their redirection URI.
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.
state
OPTIONAL. An opaque value used by the client to maintain state
between the request and callback. The authorization server
includes this value when redirecting the user-agent back to the
client.
The client directs the end-user to the constructed URI using an HTTP
redirection response, or by other means available to it via the end-
user's user-agent. The authorization server MUST support the use of
the HTTP "GET" method for the end-user authorization endpoint, and
MAY support the use of the "POST" method as well.
For example, the client directs the end-user's user-agent to make the
following HTTP request using transport-layer security (line breaks
are for display purposes only):
GET /authorize?response_type=code&client_id=s6BhdRkqt3&
redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb HTTP/1.1
Host: server.example.com
If the client has previously registered a redirection URI with the
authorization server, the authorization server MUST verify that the
redirection URI received matches the registered URI associated with
the client identifier. The authorization server SHOULD NOT redirect
the user-agent to unregistered or untrusted URIs to prevent the
endpoint from being used as an open redirector. If no valid
redirection URI is available, the authorization server SHOULD inform
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the end-user of the error occured. [[ provide guidance on how to
perform matching ]]
Parameters sent without a value MUST be treated as if they were
omitted from the request. The authorization server SHOULD ignore
unrecognized request parameters.
The authorization server validates the request to ensure all required
parameters are present and valid. If the request is invalid, the
authorization server redirects the user-agent back to the client
using the redirection URI provided with the appropriate error code as
described in Section 4.3.
The authorization server authenticates the end-user and obtains an
authorization decision (by asking the end-user or by establishing
approval via other means). When a decision has been established, the
authorization server directs the end-user's user-agent to the
provided client redirection URI using an HTTP redirection response,
or by other means available to it via the end-user's user-agent.
4.2. Authorization Response
If the end-user grants the access request, the authorization server
issues an access token, an authorization code, or both, and delivers
them to the client by adding the following parameters to the
redirection URI (as described below):
code
REQUIRED if the response type is "code" or "code_and_token",
otherwise MUST NOT be included. The authorization code
generated by the authorization server. The authorization code
SHOULD expire shortly after it is issued to minimize the risk
of leaks. The client MUST NOT reuse the authorization code.
If an authorization code is used more than once, the
authorization server MAY revoke all tokens previously issued
based on that authorization code. The authorization code is
bound to the client identifier and redirection URI.
access_token
REQUIRED if the response type is "token" or "code_and_token",
otherwise MUST NOT be included. The access token issued by the
authorization server.
token_type
REQUIRED if the response includes an access token. The type of
the token issued. The token type informs the client how the
access token is to be used when accessing a protected resource
as described in Section 6.1.
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expires_in
OPTIONAL. The duration in seconds of the access token lifetime
if an access token is included. For example, the value "3600"
denotes that the access token will expire in one hour from the
time the response was generated by the authorization server.
scope
OPTIONAL. The scope of the access token as a list of space-
delimited strings if an access token is included. 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. The authorization server
SHOULD include the parameter if the requested scope is
different from the one requested by the client.
state
REQUIRED if the "state" parameter was present in the client
authorization request. Set to the exact value received from
the client.
The method in which the authorization server adds the parameter to
the redirection URI is determined by the response type requested by
the client in the authorization request using the "response_type"
parameter.
If the response type is "code", the authorization server adds the
parameters to the redirection URI query component using the
"application/x-www-form-urlencoded" format as defined by
[W3C.REC-html401-19991224].
For example, the authorization server redirects the end-user's user-
agent by sending the following HTTP response:
HTTP/1.1 302 Found
Location: https://client.example.com/cb?code=i1WsRn1uB1
If the response type is "token" or "code_and_token", the
authorization server adds the parameters to the redirection URI
fragment component using the "application/x-www-form-urlencoded"
format as defined by [W3C.REC-html401-19991224].
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For example, the authorization server redirects the end-user's user-
agent by sending the following HTTP response (URI line breaks are for
display purposes only):
HTTP/1.1 302 Found
Location: http://example.com/rd#access_token=FJQbwq9&
token_type=example&expires_in=3600
Clients SHOULD ignore unrecognized response parameters. The sizes of
tokens and other values received from the authorization server, are
left undefined by this specification. Clients should avoid making
assumptions about value sizes. Servers should document the expected
size of any value they issue.
4.3. Error Response
If the end-user denies the access request or if the request fails for
reasons other than a missing or invalid redirection URI, the
authorization server informs the client by adding the following
parameters to the redirection URI query component using the
"application/x-www-form-urlencoded" format as defined by
[W3C.REC-html401-19991224]:
error
REQUIRED. A single error code as described in Section 4.3.1.
error_description OPTIONAL. A human-readable text providing
additional information, used to assist in the understanding and
resolution of the error occurred.
error_uri OPTIONAL. A URI identifying a human-readable web page
with information about the error, used to provide the end-user
with additional information about the error.
state
REQUIRED if the "state" parameter was present in the client
authorization request. Set to the exact value received from
the client.
For example, the authorization server redirects the end-user's user-
agent by sending the following HTTP response:
HTTP/1.1 302 Found
Location: https://client.example.com/cb?error=access_denied
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If the request fails due to a missing or invalid redirection URI, the
authorization server SHOULD inform the end-user of the error, and
MUST NOT redirect the end-user's user-agent to the invalid
redirection URI.
4.3.1. Error Codes
The authorization server includes one of the following error codes
with the error response:
invalid_request
The request is missing a required parameter, includes an
unsupported parameter or parameter value, or is otherwise
malformed.
invalid_client
The client identifier provided is invalid.
unauthorized_client
The client is not authorized to use the requested response
type.
redirect_uri_mismatch
The redirection URI provided does not match a pre-registered
value.
access_denied
The end-user or authorization server denied the request.
unsupported_response_type
The requested response type is not supported by the
authorization server.
invalid_scope
The requested scope is invalid, unknown, or malformed.
[[ Add mechanism for extending error codes ]]
5. Obtaining an Access Token
The client obtains an access token by authenticating with the
authorization server and presenting its access grant (in the form of
an authorization code, resource owner credentials, an assertion, or a
refresh token).
Since requests to the token endpoint result in the transmission of
clear-text credentials in the HTTP request and response, the
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authorization server MUST require the use of a transport-layer
security mechanism when sending requests to the token endpoints.
Servers MUST support TLS 1.2 as defined in [RFC5246], and MAY support
additional transport-layer security mechanisms.
The client requests an access token by making an HTTP "POST" request
to the token endpoint. The location of the token endpoint can be
found in the service documentation. The token endpoint URI MAY
include a query component.
The client authenticates with the authorization server by adding its
client credentials to the request as described in Section 3. The
authorization server MAY allow unauthenticated access token requests
when the client identity does not matter (e.g. anonymous client) or
when the client identity is established via other means (e.g. using
an assertion access grant).
The client constructs the request by including the following
parameters using the "application/x-www-form-urlencoded" format in
the HTTP request entity-body:
grant_type
REQUIRED. The access grant type included in the request.
Value MUST be one of "authorization_code", "password",
"refresh_token", "client_credentials", or an absolute URI
identifying an assertion format supported by the authorization
server.
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. If the access grant being used already
represents an approved scope (e.g. authorization code,
assertion), the requested scope MUST be equal or lesser than
the scope previously granted, and if omitted is treated as
equal to the previously approved scope.
In addition, the client MUST include the appropriate parameters
listed for the selected access grant type as described in
Section 5.1.
Parameters sent without a value MUST be treated as if they were
omitted from the request. The authorization server SHOULD ignore
unrecognized request parameters.
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5.1. Access Grant Types
The client requests an access token using an authorization code,
resource owner password credentials, client credentials, refresh
token, or assertion.
5.1.1. Authorization Code
The client includes the authorization code using the
"authorization_code" access grant type and the following parameters:
code
REQUIRED. The authorization code received from the
authorization server.
redirect_uri
REQUIRED. The redirection URI used in the initial request.
For example, the client makes the following HTTP request by including
its client credentials via the "client_secret" parameter described in
Section 3 and using transport-layer security (line breaks are for
display purposes only):
POST /token HTTP/1.1
Host: server.example.com
Content-Type: application/x-www-form-urlencoded
grant_type=authorization_code&client_id=s6BhdRkqt3&
client_secret=gX1fBat3bV&code=i1WsRn1uB1&
redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb
The authorization server MUST:
o Validate the client credentials (if present) and ensure they match
the authorization code.
o Verify that the authorization code and redirection URI are all
valid and match its stored association.
If the request is valid, the authorization server issues a successful
response as described in Section 5.2.
5.1.2. Resource Owner Password Credentials
The client includes the resource owner credentials using the
"password" access grant type and the following parameters: [[ add
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internationalization consideration for username and password ]]
username
REQUIRED. The resource owner's username.
password
REQUIRED. The resource owner's password.
For example, the client makes the following HTTP request by including
its client credentials via the "client_secret" parameter described in
Section 3 and using transport-layer security (line breaks are for
display purposes only):
POST /token HTTP/1.1
Host: server.example.com
Content-Type: application/x-www-form-urlencoded
grant_type=password&client_id=s6BhdRkqt3&
client_secret=47HDu8s&username=johndoe&password=A3ddj3w
The authorization server MUST validate the client credentials (if
present) and end-user credentials and if valid issue an access token
response as described in Section 5.2.
5.1.3. Client Credentials
The client can request an access token using only its client
credentials using the "client_credentials" access grant type. When
omitting an explicit access grant, the client is requesting access to
the protected resources under its control, or those of another
resource owner which has been previously arranged with the
authorization server (the method of which is beyond the scope of this
specification).
5.1.4. Refresh Token
The client includes the refresh token using the "refresh_token"
access grant type and the following parameter:
refresh_token
REQUIRED. The refresh token associated with the access token
to be refreshed.
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For example, the client makes the following HTTP request by including
its client credentials via the "client_secret" parameter described in
Section 3 and using transport-layer security (line breaks are for
display purposes only):
POST /token HTTP/1.1
Host: server.example.com
Content-Type: application/x-www-form-urlencoded
grant_type=refresh_token&client_id=s6BhdRkqt3&
client_secret=8eSEIpnqmM&refresh_token=n4E9O119d
The authorization server MUST verify the client credentials (if
present), the validity of the refresh token, and that the resource
owner's authorization is still valid. If the request is valid, the
authorization server issues an access token response as described in
Section 5.2. The authorization server MAY issue a new refresh token,
in which case, the client MUST discard the old refresh token and
replace it with the new refresh token.
5.1.5. Assertion
The client includes an assertion by specifying the assertion format
using an absolute URI (as defined by the authorization server) as the
value of the "grant_type" parameter and by adding the following
parameter:
assertion
REQUIRED. The assertion.
For example, the client makes the following HTTP request using
transport-layer security, and client authentication is achieved via
the assertion (line breaks are for display purposes only):
POST /token HTTP/1.1
Host: server.example.com
Content-Type: application/x-www-form-urlencoded
grant_type=urn%3Aoasis%3Anames%3Atc%3ASAML%3A2.0%3Aassertion&
assertion=PHNhbWxwOl[...omitted for brevity...]ZT4%3D
The authorization server MUST validate the client credentials (if
present) and the assertion and if valid issues an access token
response as described in Section 5.2. The authorization server
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SHOULD NOT issue a refresh token (instead, it should require the
client to use the same or new assertion).
Authorization servers SHOULD issue access tokens with a limited
lifetime and require clients to refresh them by requesting a new
access token using the same assertion if it is still valid.
Otherwise the client MUST obtain a new valid assertion.
5.2. Access Token Response
After receiving and verifying a valid and authorized access token
request from the client, the authorization server issues the access
token and optional refresh token, and constructs the response by
adding the following parameters to the entity body of the HTTP
response with a 200 (OK) status code:
The token response contains the following parameters:
access_token
REQUIRED. The access token issued by the authorization server.
token_type
REQUIRED. The type of the token issued. The token type
informs the client how the access token is to be used when
accessing a protected resource as described in Section 6.1.
expires_in
OPTIONAL. The duration in seconds of the access token
lifetime. For example, the value "3600" denotes that the
access token will expire in one hour from the time the response
was generated by the authorization server.
refresh_token
OPTIONAL. The refresh token used to obtain new access tokens
using the same end-user access grant as described in
Section 5.1.4. The authorization server SHOULD NOT issue a
refresh token when the access grant type is an assertion or a
set of client credentials.
scope
OPTIONAL. The scope of the access token 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. The authorization server SHOULD include the
parameter if the requested scope is different from the one
requested by the client.
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The parameters are including in the entity body of the HTTP response
using the "application/json" media type as defined by [RFC4627]. The
parameters are serialized into a JSON structure by adding each
parameter at the highest structure level. Parameter names and string
values are included as JSON strings. Numerical values are included
as JSON numbers.
The authorization server MUST include the HTTP "Cache-Control"
response header field with a value of "no-store" in any response
containing tokens, secrets, or other sensitive information.
For example:
HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-store
{
"access_token":"SlAV32hkKG",
"token_type":"example",
"expires_in":3600,
"refresh_token":"8xLOxBtZp8"
}
Clients SHOULD ignore unrecognized response parameters. The sizes of
tokens and other values received from the authorization server, are
left undefined by this specification. Clients should avoid making
assumptions about value sizes. Servers should document the expected
size of any value they issue.
5.3. Error Response
If the token request is invalid or unauthorized, the authorization
server constructs the response by adding the following parameter to
the entity body of the HTTP response using the "application/json"
media type:
error
REQUIRED. A single error code as described in Section 5.3.1.
error_description OPTIONAL. A human-readable text providing
additional information, used to assist in the understanding and
resolution of the error occurred.
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error_uri OPTIONAL. A URI identifying a human-readable web page
with information about the error, used to provide the end-user
with additional information about the error.
For example:
HTTP/1.1 400 Bad Request
Content-Type: application/json
Cache-Control: no-store
{
"error":"invalid_request"
}
If the client provided invalid credentials using an HTTP
authentication scheme via the "Authorization" request header field,
the authorization server MUST respond with the HTTP 401
(Unauthorized) status code. Otherwise, the authorization server
SHALL respond with the HTTP 400 (Bad Request) status code.
5.3.1. Error Codes
The authorization server includes one of the following error codes
with the error response:
invalid_request
The request is missing a required parameter, includes an
unsupported parameter or parameter value, repeats a parameter,
includes multiple credentials, utilizes more than one mechanism
for authenticating the client, or is otherwise malformed.
invalid_client
The client identifier provided is invalid, the client failed to
authenticate, the client did not include its credentials,
provided multiple client credentials, or used unsupported
credentials type.
unauthorized_client
The authenticated client is not authorized to use the access
grant type provided.
invalid_grant
The provided access grant is invalid, expired, or revoked (e.g.
invalid assertion, expired authorization token, bad end-user
password credentials, or mismatching authorization code and
redirection URI).
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unsupported_grant_type
The access grant included - its type or another attribute - is
not supported by the authorization server.
invalid_scope
The requested scope is invalid, unknown, malformed, or exceeds
the previously granted scope.
[[ Add mechanism for extending error codes ]]
6. Accessing a Protected Resource
Clients access protected resources by presenting an access token to
the resource server. The resource server MUST validate the access
token and ensure it has not expired and that its scope covers the
requested resource. The methods used by the resource server to
validate the access token are beyond the scope of this specification,
but generally involve an interaction or coordination between the
resource server and authorization server.
The method in which the client utilized the access token to
authenticate with the resource server depends on the type of access
token issued by the authorization server.
6.1. Access Token Types
[[ add token type explanation, maybe with links to other token specs
]]
6.2. The WWW-Authenticate Response Header Field
If the protected resource request does not include authentication
credentials, contains an invalid access token, or is malformed, the
resource server MUST include the HTTP "WWW-Authenticate" response
header field. The "WWW-Authenticate" header field uses the framework
defined by [RFC2617] as follows:
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challenge = "OAuth2" [ RWS 1#param ]
param = scope /
error / error-desc / error-uri /
( token "=" ( token / quoted-string ) )
scope = "scope" "=" <"> scope-v *( SP scope-v ) <">
scope-v = 1*quoted-char
quoted-char = ALPHA / DIGIT /
"!" / "#" / "$" / "%" / "&" / "'" / "(" / ")" /
"*" / "+" / "-" / "." / "/" / ":" / "<" / "=" /
">" / "?" / "@" / "[" / "]" / "^" / "_" / "`" /
"{" / "|" / "}" / "~" / "\" / "," / ";"
error = "error" "=" quoted-string
error-desc = "error_description" "=" quoted-string
error-uri = "error_uri" = <"> URI-reference <">
The "scope" attribute is a space-delimited list of scope values
indicating the required scope of the access token for accessing the
requested resource. The "scope" attribute MUST NOT appear more than
once.
If the protected resource request included an access token and failed
authentication, the resource server SHOULD include the "error"
attribute to provide the client with the reason why the access
request was declined. The parameter value is described in
Section 6.2.1. In addition, the resource server MAY include the
"error_description" attribute to provide a human-readable
explanation, and the "error-uri" attribute with an absolute URI
identifying a human-readable web page explaining the error. The
"error", "error_description", and "error_uri" attribute MUST NOT
appear more than once.
For example, in response to a protected resource request without
authentication:
HTTP/1.1 401 Unauthorized
WWW-Authenticate: OAuth2
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And in response to a protected resource request with an
authentication attempt using an expired access token:
HTTP/1.1 401 Unauthorized
WWW-Authenticate: OAuth2
error="invalid_token",
error_description="The access token expired"
6.2.1. Error Codes
When a request fails, the resource server responds using the
appropriate HTTP status code (typically, 400, 401, or 403), and
includes one of the following error codes in the response:
invalid_request
The request is missing a required parameter, includes an
unsupported parameter or parameter value, repeats the same
parameter, uses more than one method for including an access
token, or is otherwise malformed. The resource server SHOULD
respond with the HTTP 400 (Bad Request) status code.
invalid_token
The access token provided is expired, revoked, malformed, or
invalid for other reasons. The resource SHOULD respond with
the HTTP 401 (Unauthorized) status code. The client MAY
request a new access token and retry the protected resource
request.
insufficient_scope
The request requires higher privileges than provided by the
access token. The resource server SHOULD respond with the HTTP
403 (Forbidden) status code and MAY include the "scope"
attribute with the scope necessary to access the protected
resource.
[[ Add mechanism for extending error codes ]]
If the request lacks any authentication information (i.e. the client
was unaware authentication is necessary or attempted using an
unsupported authentication method), the resource server SHOULD not
include an error code or other error information.
For example:
HTTP/1.1 401 Unauthorized
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WWW-Authenticate: OAuth2
7. Extensibility
7.1. Defining New Client Credentials Types
[[ TBD ]]
7.2. Defining New Endpoint Parameters
Applications that wish to define new request or response parameters
for use with the end-user authorization endpoint or the token
endpoint SHALL do so in one of two ways: register them in the
parameters registry (following the procedures in Section 9.1), or use
the "x_" parameter name prefix.
Parameters utilizing the "x_" parameter name prefix MUST be limited
to vendor-specific extensions that are not commonly applicable, and
are specific to the implementation details of the authorization
server where they are used. All other new parameters MUST be
registered, and MUST NOT use the "x_" parameter name prefix.
Parameter names MUST conform to the param-name ABNF, and parameter
values syntax MUST be well-defined (e.g., using ABNF, or a reference
to the syntax of an existing parameter).
param-name = 1*name-char
name-char = "-" / "." / "_" / DIGIT / ALPHA
7.3. Defining New Header Field Parameters
Applications that wish to define new parameters for use in the OAuth
"WWW-Authenticate" header field MUST register them in the parameters
registry, following the procedures in Section 9.1.
Parameter names MUST conform to the param-name ABNF and MUST NOT
begin with "x_". Parameter values MUST conform to the param-value
ABNF and their syntax MUST be well-defined (e.g., using ABNF, or a
reference to the syntax of an existing parameter).
param-value = quoted-value | quoted-string
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7.4. Defining New Access Grant Types
The assertion access grant type allows the authorization server to
accept additional access grants not specified. Applications that
wish to define additional access grant types can do so by utilizing a
new or existing assertion type and format.
8. Security Considerations
[[ TBD ]]
9. IANA Considerations
9.1. The OAuth Parameters Registry
This document establishes the OAuth parameters registry.
Additional parameters to be use in the end-user authorization
endpoint request, the end-user authorization endpoint response, the
token endpoint request, the token endpoint response, or the
"WWW-Authenticate" header field, are registered on the advice of one
or more Designated Experts (appointed by the IESG or their delegate),
with a Specification Required (using terminology from [RFC5226]).
However, to allow for the allocation of values prior to publication,
the Designated Expert(s) may approve registration once they are
satisfied that such a specification will be published.
Registration requests should be sent to the [TBD]@ietf.org mailing
list for review and comment, with an appropriate subject (e.g.,
"Request for parameter: example"). [[ Note to RFC-EDITOR: The name of
the mailing list should be determined in consultation with the IESG
and IANA. Suggested name: oauth-ext-review. ]]
Before a period of 14 days has passed, the Designated Expert(s) will
either approve or deny the registration request, communicating this
decision both to the review list and to IANA. Denials should include
an explanation and, if applicable, suggestions as to how to make the
request successful. Registration requests that are undetermined for
a period longer than 21 days can be brought to the IESG's attention
(using the iesg@iesg.org mailing list) for resolution.
9.1.1. Registration Template
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Parameter name: The name requested (e.g., "example").
Parameter usage location: The location(s) where parameter can be
used. The possible locations are: the end-user authorization
endpoint request, the end-user authorization endpoint response,
the token endpoint request, the token endpoint response, the or
the "WWW-Authenticate" header field.
Change controller: For standards-track RFCs, state "IETF". For
others, give the name of the responsible party. Other details
(e.g., postal address, e-mail address, home page URI) may also be
included.
Specification document(s): Reference to document that specifies the
parameter, preferably including a URI that can be used to retrieve
a copy of the document. An indication of the relevant sections
may also be included, but is not required.
Related information: Optionally, citations to additional documents
containing further relevant information.
9.1.2. Example
The following is the parameter registration request for the "scope"
parameter as defined in this specification:
Parameter name: scope
Parameter usage location: The end-user authorization endpoint
request, the end-user authorization endpoint response, the token
endpoint request, the token endpoint response, and the
"WWW-Authenticate" header field.
Change controller: IETF
Specification document(s): [[ this document ]]
Related information: None
Appendix A. Examples
[[ TBD ]]
Appendix B. Contributors
The following people contributed to preliminary versions of this
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document: Blaine Cook (BT), Brian Eaton (Google), Yaron Goland
(Microsoft), Brent Goldman (Facebook), Raffi Krikorian (Twitter),
Luke Shepard (Facebook), and Allen Tom (Yahoo!). The content and
concepts within are a product of the OAuth community, WRAP community,
and the OAuth Working Group.
The OAuth Working Group has dozens of very active contributors who
proposed ideas and wording for this document, including: [[ If your
name is missing or you think someone should be added here, please
send Eran a note - don't be shy ]]
Michael Adams, Andrew Arnott, Dirk Balfanz, Brian Campbell, Leah
Culver, Bill de hOra, Brian Ellin, Igor Faynberg, George Fletcher,
Tim Freeman, Evan Gilbert, Kristoffer Gronowski, Justin Hart, Mike
Jones, John Kemp, Chasen Le Hara, Torsten Lodderstedt, Alastair Mair,
Eve Maler, James Manger, Laurence Miao, Chuck Mortimore, Justin
Richer, Peter Saint-Andre, Nat Sakimura, Rob Sayre, Marius Scurtescu,
Naitik Shah, Justin Smith, Jeremy Suriel, Christian Stuebner, Paul
Tarjan, Franklin Tse, and Nick Walker.
Appendix C. Acknowledgements
[[ Add OAuth 1.0a authors + WG contributors ]]
Appendix D. Document History
[[ to be removed by RFC editor before publication as an RFC ]]
-11
o Many editorial changes. Fixed user authorization section
structure. Removed unused normative references. Adjusted
language regarding single use of authorization codes.
o Fixed header ABNF.
o Change access token description from shared symmetric secret to
password.
o Moved access grant 'none' to a separate section, renamed to
'client_credentials'.
o Demoted the HTTP status code requirement from MUST to SHOULD in
protected resource response error.
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o Removed 'expired_token' error code.
o Moved all the 'code_and_token' parameter to the fragment (from
code being in the query).
o Removed 'assertion_type' parameter (moved to 'grant_type').
o Added note about redirecting to invalid redirection URIs (open
redirectors).
o Removed bearer token section, added new required 'token_type'
parameter with extensibility.
o 'error-uri' parameter value changed to absolute URI.
o OAuth 2.0 HTTP authentication scheme name changed to 'OAuth2'.
o Dropped the 'WWW-Authenticate' header field 'realm' parameter.
o Removed definition of access token characters.
o Added instructions for dealing with error and an invalid
redirection URI.
-10
o Fixed typos. Many editorial changes. Rewrote introduction.
removed terminology grouping.
o Allowed POST for end-user authorization endpoint.
o Fixed token endpoint to not require client authentication.
o Made URI query and POST body 'oauth_token' parameter optional.
o Moved all parameter names and values to use underscores.
o Changed 'basic_credentials' to 'password',
'invalid_client_credentials' and 'invalid_client_id' to
'invalid_client'.
o Added note that access token requests without an access grant
should not include a refresh token.
o Changed scheme name from 'Token' to 'OAuth', simplified request
format to simple string for token instead of key=value pair (still
supported for extensions).
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o Defined permitted access token string characters (suitable for
inclusion in an HTTP header).
o Added a note about conflicts with previous versions.
o Moved 'client_id' definition from client authentication to access
token endpoint.
o Added definition for 'access grant'.
-09
o Fixed typos, editorial changes.
o Added token expiration example.
o Added scope parameter to end-user authorization endpoint response.
o Added note about parameters with empty values (same as omitted).
o Changed parameter values to use '-' instead of '_'. Parameter
names still use '_'.
o Changed authorization endpoint client type to response type with
values: code, token, and both.
o Complete cleanup of error codes. Added support for error
description and URI.
o Add initial extensibility support.
-08
o Renamed verification code to authorization code.
o Revised terminology, structured section, added new terms.
o Changed flows to profiles and moved to introduction.
o Added support for access token rescoping.
o Cleaned up client credentials section.
o New introduction overview.
o Added error code for invalid username and password, and renamed
error code to be more consistent.
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o Added access grant type parameter to token endpoint.
-07
o Major rewrite of entire document structure.
o Removed device profile.
o Added verification code support to user-agent flow.
o Removed multiple formats support, leaving JSON as the only format.
o Changed assertion "assertion_format" parameter to
"assertion_type".
o Removed "type" parameter from token endpoint.
-06
o Editorial changes, corrections, clarifications, etc.
o Removed conformance section.
o Moved authors section to contributors appendix.
o Added section on native applications.
o Changed error response to use the requested format. Added support
for HTTP "Accept" header.
o Flipped the order of the web server and user-agent flows.
o Renamed assertion flow "format" parameter name to
"assertion_format" to resolve conflict.
o Removed the term identifier from token definitions. Added a
cryptographic token definition.
o Added figure titles.
o Added server response 401 when client tried to authenticate using
multiple credentials.
o Clarified support for TLS alternatives, and added requirement for
TLS 1.2 support for token endpoint.
o Removed all signature and cryptography.
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o Removed all discovery.
o Updated HTML4 reference.
-05
o Corrected device example.
o Added client credentials parameters to the assertion flow as
OPTIONAL.
o Added the ability to send client credentials using an HTTP
authentication scheme.
o Initial text for the "WWW-Authenticate" header (also added scope
support).
o Change authorization endpoint to end-user endpoint.
o In the device flow, change the "user_uri" parameter to
"verification_uri" to avoid confusion with the end-user endpoint.
o Add "format" request parameter and support for XML and form-
encoded responses.
-04
o Changed all token endpoints to use "POST"
o Clarified the authorization server's ability to issue a new
refresh token when refreshing a token.
o Changed the flow categories to clarify the autonomous group.
o Changed client credentials language not to always be server-
issued.
o Added a "scope" response parameter.
o Fixed typos.
o Fixed broken document structure.
-03
o Fixed typo in JSON error examples.
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o Fixed general typos.
o Moved all flows sections up one level.
-02
o Removed restriction on "redirect_uri" including a query.
o Added "scope" parameter.
o Initial proposal for a JSON-based token response format.
-01
o Editorial changes based on feedback from Brian Eaton, Bill Keenan,
and Chuck Mortimore.
o Changed device flow "type" parameter values and switch to use only
the token endpoint.
-00
o Initial draft based on a combination of WRAP and OAuth 1.0a.
10. References
10.1. Normative References
[I-D.ietf-httpbis-p1-messaging]
Fielding, R., Gettys, J., Mogul, J., Nielsen, H.,
Masinter, L., Leach, P., Berners-Lee, T., and J. Reschke,
"HTTP/1.1, part 1: URIs, Connections, and Message
Parsing", draft-ietf-httpbis-p1-messaging-09 (work in
progress), March 2010.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
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Leach, P., Luotonen, A., and L. Stewart, "HTTP
Authentication: Basic and Digest Access Authentication",
RFC 2617, June 1999.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC2828] Shirey, R., "Internet Security Glossary", RFC 2828,
May 2000.
[RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media
Types", RFC 3023, January 2001.
[RFC3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography
Standards (PKCS) #1: RSA Cryptography Specifications
Version 2.1", RFC 3447, February 2003.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC4627] Crockford, D., "The application/json Media Type for
JavaScript Object Notation (JSON)", RFC 4627, July 2006.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC5849] Hammer-Lahav, E., "The OAuth 1.0 Protocol", RFC 5849,
April 2010.
[W3C.REC-html401-19991224]
Raggett, D., Hors, A., and I. Jacobs, "HTML 4.01
Specification", World Wide Web Consortium
Recommendation REC-html401-19991224, December 1999,
<http://www.w3.org/TR/1999/REC-html401-19991224>.
10.2. Informative References
[OASIS.saml-core-2.0-os]
Cantor, S., Kemp, J., Philpott, R., and E. Maler,
"Assertions and Protocol for the OASIS Security Assertion
Markup Language (SAML) V2.0", OASIS Standard saml-core-
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2.0-os, March 2005.
Authors' Addresses
Eran Hammer-Lahav (editor)
Yahoo!
Email: eran@hueniverse.com
URI: http://hueniverse.com
David Recordon
Facebook
Email: davidrecordon@facebook.com
URI: http://www.davidrecordon.com/
Dick Hardt
Microsoft
Email: dick.hardt@gmail.com
URI: http://dickhardt.org/
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