Network Working Group E. Hammer-Lahav, Ed. Internet-Draft Yahoo! Obsoletes: 5849 (if approved) D. Recordon Intended status: Standards Track Facebook Expires: October 8, 2011 D. Hardt Microsoft April 6, 2011 The OAuth 2.0 Authorization Protocol draft-ietf-oauth-v2-15 Abstract The OAuth 2.0 authorization protocol enables granting third-party applications limited access to HTTP service on behalf of an end-user by orchestrating an approval interaction between the end-user and the HTTP service. 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 October 8, 2011. Copyright Notice Copyright (c) 2011 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 Hammer-Lahav, et al. Expires October 8, 2011 [Page 1]
Internet-Draft OAuth 2.0 April 2011 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Roles . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Protocol Flow . . . . . . . . . . . . . . . . . . . . . . 4 1.3. Access Token . . . . . . . . . . . . . . . . . . . . . . . 5 1.4. Authorization Grant . . . . . . . . . . . . . . . . . . . 6 1.5. Refresh Token . . . . . . . . . . . . . . . . . . . . . . 8 1.6. Document Structure . . . . . . . . . . . . . . . . . . . . 10 1.7. Notational Conventions . . . . . . . . . . . . . . . . . . 10 2. Protocol Endpoints . . . . . . . . . . . . . . . . . . . . . . 10 2.1. Authorization Endpoint . . . . . . . . . . . . . . . . . . 11 2.2. Token Endpoint . . . . . . . . . . . . . . . . . . . . . . 12 3. Client Authentication . . . . . . . . . . . . . . . . . . . . 13 3.1. Client Password Authentication . . . . . . . . . . . . . . 14 3.2. Other Client Authentication Methods . . . . . . . . . . . 14 4. Obtaining Authorization . . . . . . . . . . . . . . . . . . . 15 4.1. Authorization Code . . . . . . . . . . . . . . . . . . . . 15 4.2. Implicit Grant . . . . . . . . . . . . . . . . . . . . . . 21 4.3. Resource Owner Password Credentials . . . . . . . . . . . 27 4.4. Client Credentials . . . . . . . . . . . . . . . . . . . . 29 4.5. Extensions . . . . . . . . . . . . . . . . . . . . . . . . 31 5. Issuing an Access Token . . . . . . . . . . . . . . . . . . . 32 5.1. Successful Response . . . . . . . . . . . . . . . . . . . 32 5.2. Error Response . . . . . . . . . . . . . . . . . . . . . . 33 6. Refreshing an Access Token . . . . . . . . . . . . . . . . . . 35 7. Accessing Protected Resources . . . . . . . . . . . . . . . . 36 7.1. Access Token Types . . . . . . . . . . . . . . . . . . . . 36 8. Extensibility . . . . . . . . . . . . . . . . . . . . . . . . 37 8.1. Defining Access Token Types . . . . . . . . . . . . . . . 37 8.2. Defining New Endpoint Parameters . . . . . . . . . . . . . 37 8.3. Defining New Authorization Grant Types . . . . . . . . . . 38 8.4. Defining Additional Error Codes . . . . . . . . . . . . . 38 9. Security Considerations . . . . . . . . . . . . . . . . . . . 39 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39 10.1. The OAuth Access Token Type Registry . . . . . . . . . . . 39 10.2. The OAuth Parameters Registry . . . . . . . . . . . . . . 40 10.3. The OAuth Extensions Error Registry . . . . . . . . . . . 43 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 44 Appendix A. Editor's Notes . . . . . . . . . . . . . . . . . . . 45 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 46 12.1. Normative References . . . . . . . . . . . . . . . . . . . 46 12.2. Informative References . . . . . . . . . . . . . . . . . . 46 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 47 Hammer-Lahav, et al. Expires October 8, 2011 [Page 2]
Internet-Draft OAuth 2.0 April 2011 1. Introduction 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 duration or access to a limited subset of 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 introducing an authorization layer and separating the role of the client from that of the resource owner. In OAuth, the client 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 denoting a specific scope, duration, and other access 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 end-user (resource owner) can grant a printing service (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 a server trusted by the photo sharing service (authorization server) which issues the printing service delegation- specific credentials (access token). This specification is designed for use with HTTP [RFC2616]. The use of OAuth with any transport protocol other than HTTP is undefined. Hammer-Lahav, et al. Expires October 8, 2011 [Page 3]
Internet-Draft OAuth 2.0 April 2011 1.1. Roles OAuth includes four roles working together to grant and provide access to protected resources - access restricted resources which require authentication to access: resource owner An entity capable of granting access to a protected resource. When the resource owner is a person, it is referred to as an end- user. resource server The server hosting the protected resources, capable of accepting and responding to protected resource requests using access tokens. client An application making protected resource requests on behalf of the resource owner and with its authorization. authorization server The server issuing access tokens to the client after successfully authenticating the resource owner and obtaining authorization. The interaction between the authorization server and resource server is beyond the scope of this specification. The authorization server may be the same server as the resource server or a separate entity. A single authorization server may issue access tokens accepted by multiple resource servers. 1.2. Protocol Flow When interacting with the authorization server, the client identifies itself using a set of client credentials which include a client identifier and other authentication attributes. The means through which the client obtains its credentials are beyond the scope of this specification, but typically involve registration with the authorization server. Hammer-Lahav, et al. Expires October 8, 2011 [Page 4]
Internet-Draft OAuth 2.0 April 2011 +--------+ +---------------+ | |--(A)- Authorization Request ->| Resource | | | | Owner | | |<-(B)-- Authorization Grant ---| | | | +---------------+ | | | | Authorization Grant & +---------------+ | |--(C)--- Client Credentials -->| Authorization | | Client | | Server | | |<-(D)----- Access Token -------| | | | +---------------+ | | | | +---------------+ | |--(E)----- Access Token ------>| Resource | | | | Server | | |<-(F)--- Protected Resource ---| | +--------+ +---------------+ Figure 1: Abstract Protocol Flow The abstract flow illustrated in Figure 1 describes the interaction between the four roles 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 (as shown), or preferably indirectly via an intermediary such as an authorization server. (B) The client receives an authorization grant which represents the authorization provided by the resource owner. The authorization grant type depends on the method used by the client and supported by the authorization server to obtain it. (C) The client requests an access token by authenticating with the authorization server using its client credentials (prearranged between the client and authorization server) and presenting the authorization grant. (D) The authorization server validates the client credentials and the authorization grant, and if valid issues an access token. (E) The client requests the protected resource from the resource server and authenticates by presenting the access token. (F) The resource server validates the access token, and if valid, serves the request. 1.3. Access Token An access token is a string representing an authorization issued to the client. The string is usually opaque to the client. Tokens represent specific scopes and durations of access, granted by the Hammer-Lahav, et al. Expires October 8, 2011 [Page 5]
Internet-Draft OAuth 2.0 April 2011 resource owner, and enforced by the resource server and authorization server. 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). Additional authentication credentials may be required in order for the client to use a token. The access token provides an abstraction layer, replacing different authorization constructs (e.g. username and password) with a single token understood by the resource server. This abstraction enables issuing access tokens more restrictive than the authorization grant used to obtain them, as well as removing the resource server's need to understand a wide range of authentication methods. 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. 1.4. Authorization Grant An authorization grant is a general term used to describe the intermediate credentials representing the resource owner authorization (to access its protected resources), and serves as an abstraction layer. An authorization grant is used by the client to obtain an access token. This specification defines four grant types: authorization code, implicit, resource owner password credentials, and client credentials, as well as an extensibility mechanism for defining additional types. 1.4.1. Authorization Code The authorization code is obtained by using an authorization server as an intermediary between the client and resource owner. Instead of requesting authorization directly from the resource owner, the client directs the resource owner to an authorization server (via its user- agent as defined in [RFC2616]), which in turns directs the resource owner back to the client with the authorization code. Before directing the resource owner back to the client with the authorization code, the authorization server authenticates the resource owner and obtains authorization. Because the resource owner only authenticates with the authorization server, the resource Hammer-Lahav, et al. Expires October 8, 2011 [Page 6]
Internet-Draft OAuth 2.0 April 2011 owner's credentials are never shared with the client. The authorization code provides a few important security benefits such as the ability to authenticate the client and issuing the access token directly to the client without potentially exposing it to others, including the resource owner. 1.4.2. Implicit When an access token is issued to the client directly as the result of the resource owner authorization, without an intermediary authorization grant (such as an authorization code), the grant is considered implicit. When issuing an implicit grant, the authorization server cannot verify the identity of the client, and the access token may be exposed to the resource owner or other applications with access to the resource owner's user-agent. Implicit grants improve the responsiveness and efficiency of some clients (such as a client implemented as an in-browser application) since it reduces the number of round trips required to obtain an access token. 1.4.3. Resource Owner Password Credentials The resource owner password credentials (e.g. a username and password) can be used directly as an authorization 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 authorization grant types are not available (such as an authorization code). Even though this grant type requires direct client access to the resource owner credentials, the resource owner 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 (when combined with a refresh token) eliminates the need for the client to store the resource-owner credentials for future use. 1.4.4. Client Credentials The client credentials can be used as an authorization grant when the authorization scope is limited to the protected resources under the control of the client, or to protected resources previously arranged with the authorization server. Client credentials are used as an authorization grant typically when the client is acting on its own Hammer-Lahav, et al. Expires October 8, 2011 [Page 7]
Internet-Draft OAuth 2.0 April 2011 behalf (the client is also the resource owner). 1.4.5. Extensions Additional grant types may be defined to provide a bridge between OAuth and other protocols. For example, [I-D.ietf-oauth-saml2-bearer] defines a SAML 2.0 [OASIS.saml-core-2.0-os] bearer assertion grant type, which can be used to obtain an access token. 1.5. Refresh Token A refresh token is optionally issued by the authorization server to the client together with an access token. The client can use the refresh token to request another access token based on the same authorization, without having to involve the resource owner again, or having to retain the original authorization grant used to obtain the initial access token. A refresh token is a string representing the authorization granted to the client by the resource owner. The string is usually opaque to the client. The token may denote an identifier used to retrieve the authorization information, or self-contain the authorization information in a verifiable manner. The refresh token is bound to the client it was issued to, and its usage requires client authentication. The refresh token can be used to obtain a new access token when the current access token expires (access tokens may have a shorter lifetime than authorized by the resource owner), no longer valid, or to obtain additional access tokens with identical or narrower scope. Hammer-Lahav, et al. Expires October 8, 2011 [Page 8]
Internet-Draft OAuth 2.0 April 2011 +--------+ Authorization Grant & +---------------+ | |--(A)-------- Client Credentials --------->| | | | | | | |<-(B)----------- Access Token -------------| | | | & Refresh Token | | | | | | | | +----------+ | | | |--(C)---- Access Token ---->| | | | | | | | | | | |<-(D)- Protected Resource --| Resource | | Authorization | | Client | | Server | | Server | | |--(E)---- Access Token ---->| | | | | | | | | | | |<-(F)- Invalid Token Error -| | | | | | +----------+ | | | | | | | | Refresh Token & | | | |--(G)-------- Client Credentials --------->| | | | | | | |<-(H)----------- Access Token -------------| | +--------+ & Optional Refresh Token +---------------+ Figure 2: Refreshing an Expired Access Token The flow illustrated in Figure 2 includes the following steps: (A) The client requests an access token by authenticating with the authorization server using its client credentials, and presenting an authorization grant. (B) The authorization server validates the client credentials and the authorization 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 knows the access token expired, it skips to step (G), otherwise it makes another protected resource request. (F) Since the access token is invalid, 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. Hammer-Lahav, et al. Expires October 8, 2011 [Page 9]
Internet-Draft OAuth 2.0 April 2011 (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). 1.6. Document Structure This specification is organized into the following sections: o Section 2 - describes the two endpoints used to obtain and utilize the various authorization grant types. o Section 3 - describes client identification and authentication in general, and provides one such method for client authentication using password credentials. o Section 4 - describes the complete flow for each authorization grant type, including requesting authorization, authorization response, and requesting an access token. o Section 5 - describes the common access token response used for all non-implicit authorization grant types. o Section 6 - describes the use of a refresh token to obtain additional access tokens using the same resource owner authorization. o Section 7 - describes how access tokens are used to access protected resources. o Section 8 - describes how to extend certain elements of the protocol. o Section 9 - provides a security analysis of the protocol. 1.7. Notational Conventions The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and 'OPTIONAL' in this specification are to be interpreted as described in [RFC2119]. This specification uses the Augmented Backus-Naur Form (ABNF) notation of [RFC5234]. Unless otherwise noted, all the protocol parameter names and values are case sensitive. 2. Protocol Endpoints The authorization process utilizes two endpoints (HTTP resources): o Authorization endpoint - used to obtain authorization from the resource owner via user-agent redirection. Hammer-Lahav, et al. Expires October 8, 2011 [Page 10]
Internet-Draft OAuth 2.0 April 2011 o Token endpoint - used to exchange an authorization grant for an access token, typically with client authentication. Not every authorization grant type utilizes both endpoints. Extension grant types MAY define additional endpoints as needed. 2.1. Authorization Endpoint The authorization endpoint is used to interact with the resource owner and obtain authorization which is expressed explicitly as an authorization code (exchanged for an access token), or implicitly by direct issuance of an access token. The authorization server MUST first verify the identity of the resource owner. The way in which the authorization server authenticates the resource owner (e.g. username and password login, session cookies) is beyond the scope of this specification. The means through which the client obtains the location of the authorization endpoint are beyond the scope of this specification but is typically provided in the service documentation. The 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 authorization endpoint result in user authentication and the transmission of clear-text credentials (in the HTTP response), the authorization server MUST require the use of a transport-layer security mechanism when sending requests to the token endpoints. The authorization server MUST support TLS 1.2 as defined in [RFC5246], and MAY support additional transport-layer mechanisms meeting its security requirements. The authorization server MUST support the use of the HTTP "GET" method [RFC2616] for the authorization endpoint, and MAY support the use of the "POST" method as well. The REQUIRED "response_type" request parameter is used to identify which grant type the client is requesting: authorization code or implicit, described in Section 4.1.1 and Section 4.2.1 respectively. If the request is missing the "response_type" parameter, the authorization server SHOULD return an error response as described in Section 4.1.2.1. Parameters sent without a value MUST be treated as if they were omitted from the request. The authorization server SHOULD ignore unrecognized request parameters. Request and response parameters MUST NOT repeat more than once, Hammer-Lahav, et al. Expires October 8, 2011 [Page 11]
Internet-Draft OAuth 2.0 April 2011 unless noted otherwise. 2.1.1. Redirection URI The client directs the resource owner's user-agent to the authorization endpoint and includes a redirection URI to which the authorization server will redirect the user-agent back once authorization has been obtained (or denied). The client MAY omit the redirection URI if one has been established between the client and authorization server via other means, such as during the client registration process. The redirection URI MUST be an absolute URI and MAY include a query component, which MUST be retained by the authorization server when adding additional query parameters. The authorization server SHOULD require the client to pre-register their redirection URI or at least certain components such as the scheme, host, port and path. If a redirection URI was registered, the authorization server MUST compare any redirection URI received at the authorization endpoint with the registered URI. 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 the resource owner directly of the error. 2.2. Token Endpoint The token endpoint is used by the client to obtain an access token by authenticating with the authorization server and presenting its authorization grant or refresh token. The token endpoint is used with every authorization grant except for the implicit grant type (since an access token is issued directly). The means through which the client obtains the location of the token endpoint are beyond the scope of this specification but is typically provided in the service documentation. The endpoint URI MAY include a query component, which MUST be retained when adding additional query parameters. Since requests to the token endpoint result in the transmission of clear-text credentials (in the HTTP request and response), the authorization server MUST require the use of a transport-layer security mechanism when sending requests to the token endpoints. The authorization server MUST support TLS 1.2 as defined in [RFC5246], and MAY support additional transport-layer mechanisms meeting its Hammer-Lahav, et al. Expires October 8, 2011 [Page 12]
Internet-Draft OAuth 2.0 April 2011 security requirements. The token endpoint requires client authentication as described in Section 3. The authorization server MAY accept any form of client authentication meeting its security requirements. The client MUST NOT use more than one authentication method in each request. The client MUST use the HTTP "POST" method when making access token requests. Parameters sent without a value MUST be treated as if they were omitted from the request. The authorization server SHOULD ignore unrecognized request parameters. Request and response parameters MUST NOT repeat more than once, unless noted otherwise. 3. Client Authentication Client credentials are used to identify and authenticate the client. The client credentials include a client identifier - a unique string issued to the client to identify itself to the authorization server. The client identifier is not a secret, it is exposed to the resource owner, and MUST NOT be used alone for client authentication. Client authentication is accomplished via additional means such as a matching client password. The methods through which the client obtains its client credentials are beyond the scope of this specification. However, the client registration process typically includes gathering relevant information used to inform the resource owner about the client when requesting authorization. Due to the nature of some clients, the authorization server should not make assumptions about the confidentiality of client credentials without establishing trust with the client. The authorization server SHOULD NOT issue client credentials to clients incapable of keeping their credentials confidential (typically determined during the client registration process). In addition, 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. For readability purposes only, this specification is written under the assumption that the authorization server requires some form of client authentication. However, such language does not affect the authorization server's discretion in allowing Hammer-Lahav, et al. Expires October 8, 2011 [Page 13]
Internet-Draft OAuth 2.0 April 2011 unauthenticated client requests. 3.1. Client Password Authentication The client password authentication uses a shared symmetric secret to authenticate the client. The client identifier and password are included in the request 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 3.2. Other Client Authentication Methods In cases where client password authentication is not suitable or sufficient, the authorization server MAY support other existing HTTP authentication schemes or define new methods. For example, the authorization server MAY support using the HTTP Basic authentication scheme as defined in [RFC2617] to include the client identifier as the username and client password as the password (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 When using a method other than client password authentication to exchange an authorization code grant type, the authorization server Hammer-Lahav, et al. Expires October 8, 2011 [Page 14]
Internet-Draft OAuth 2.0 April 2011 MUST define a method for mapping the client credentials to the client identifier used to obtain the authorization code. 4. Obtaining Authorization To request an access token, the client obtains authorization from the resource owner. The authorization is expressed in the form of an authorization grant which the client uses to request the access token. OAuth defines four grant types: authorization code, implicit, resource owner password credentials, and client credentials. It also provides an extension mechanism for defining additional grant types. 4.1. Authorization Code The authorization code grant type is suitable for clients capable of maintaining their client credentials confidential (for authenticating with the authorization server) such as a client implemented on a secure server. As a redirection-based flow, the client must be capable of interacting with the resource owner's user-agent (typically a web browser) and capable of receiving incoming requests (via redirection) from the authorization server. Hammer-Lahav, et al. Expires October 8, 2011 [Page 15]
Internet-Draft OAuth 2.0 April 2011 +----------+ | resource | | owner | | | +----------+ ^ | (B) +----|-----+ Client Identifier +---------------+ | -+----(A)--- & Redirect URI ------>| | | User- | | Authorization | | Agent -+----(B)-- User authenticates --->| Server | | | | | | -+----(C)-- Authorization Code ---<| | +-|----|---+ +---------------+ | | ^ v (A) (C) | | | | | | ^ v | | +---------+ | | | |>---(D)-- Client Credentials, --------' | | | Authorization Code, | | Client | & Redirect URI | | | | | |<---(E)----- Access Token -------------------' +---------+ (w/ Optional Refresh Token) Figure 3: Authorization Code Flow The flow illustrated in Figure 3 includes the following steps: (A) The client initiates the flow by directing the resource owner's user-agent to the 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 resource owner (via the user-agent) and establishes whether the resource owner grants or denies the client's access request. (C) Assuming the resource owner grants access, the authorization server redirects the user-agent back to the client using the redirection URI provided earlier. The redirection URI includes an authorization code and any local state provided by the client earlier. Hammer-Lahav, et al. Expires October 8, 2011 [Page 16]
Internet-Draft OAuth 2.0 April 2011 (D) The client requests an access token from the authorization server's token endpoint by authenticating using its client credentials, and includes the authorization code received in the previous step. The client includes the redirection URI used to obtain the authorization code for verification. (E) The authorization server validates the client credentials, the authorization code, and ensures the redirection URI received matches the URI used to redirect the client in step (C). If valid, responds back with an access token. 4.1.1. Authorization Request The client constructs the request URI by adding the following parameters to the query component of the authorization endpoint URI using the "application/x-www-form-urlencoded" format as defined by [W3C.REC-html401-19991224]: response_type REQUIRED. Value MUST be set to "code". 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. Described in Section 2.1.1. scope OPTIONAL. The scope of the access request expressed as a list of space-delimited, case sensitive strings. The value 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 resource owner to the constructed URI using an HTTP redirection response, or by other means available to it via the user-agent. For example, the client directs the 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& Hammer-Lahav, et al. Expires October 8, 2011 [Page 17]
Internet-Draft OAuth 2.0 April 2011 redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb HTTP/1.1 Host: server.example.com The authorization server validates the request to ensure all required parameters are present and valid. If the request is valid, the authorization server authenticates the resource owner and obtains an authorization decision (by asking the resource owner or by establishing approval via other means). When a decision is established, the authorization server directs the user-agent to the provided client redirection URI using an HTTP redirection response, or by other means available to it via the user- agent. 4.1.2. Authorization Response If the resource owner grants the access request, the authorization server issues an authorization code and delivers it to the client by adding the following parameters to the query component of the redirection URI using the "application/x-www-form-urlencoded" format: code REQUIRED. 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. 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 user-agent by sending the following HTTP response: HTTP/1.1 302 Found Location: https://client.example.com/cb?code=i1WsRn1uB1 The client SHOULD ignore unrecognized response parameters. The authorization code string size is left undefined by this specification. The client should avoid making assumptions about code value sizes. The authorization server should document the size of Hammer-Lahav, et al. Expires October 8, 2011 [Page 18]
Internet-Draft OAuth 2.0 April 2011 any value it issues. 4.1.2.1. Error Response If the request fails due to a missing, invalid, or mismatching redirection URI, or if the client identifier provided is invalid, the authorization server SHOULD inform the resource owner of the error, and MUST NOT redirect the user-agent to the invalid redirection URI. If the resource owner 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 query component of the redirection URI using the "application/x-www-form-urlencoded" format: error REQUIRED. A single error code from the following: invalid_request The request is missing a required parameter, includes an unsupported parameter or parameter value, or is otherwise malformed. unauthorized_client The client is not authorized to request an authorization code using this method. access_denied The resource owner or authorization server denied the request. unsupported_response_type The authorization server does not support obtaining an authorization code using this method. invalid_scope The requested scope is invalid, unknown, or malformed. a 4xx or 5xx HTTP status code (except for 400 and 401) [[ Pending Consensus ]] The authorization server MAY set the "error" parameter value to a numerical HTTP status code from the 4xx or 5xx range, with the exception of the 400 (Bad Request) and 401 (Unauthorized) status codes. For example, if the service is temporarily unavailable, the authorization server MAY return an error response with "error" set to "503". error_description OPTIONAL. A human-readable text providing additional information, used to assist in the understanding and resolution of the error occurred. Hammer-Lahav, et al. Expires October 8, 2011 [Page 19]
Internet-Draft OAuth 2.0 April 2011 error_uri OPTIONAL. A URI identifying a human-readable web page with information about the error, used to provide the resource owner with additional information about the error. state REQUIRED if a valid "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 user-agent by sending the following HTTP response: HTTP/1.1 302 Found Location: https://client.example.com/cb?error=access_denied 4.1.3. Access Token Request The client makes a request to the token endpoint by adding the following parameter using the "application/x-www-form-urlencoded" format in the HTTP request entity-body: grant_type REQUIRED. Value MUST be set to "authorization_code". code REQUIRED. The authorization code received from the authorization server. redirect_uri REQUIRED. The redirection URI used by the authorization server to return the authorization response in the previous step. The client includes its authentication credentials as described in Section 3 For example, the client makes the following HTTP request by including its client credentials via the "client_id" and "client_secret" parameters, 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 Hammer-Lahav, et al. Expires October 8, 2011 [Page 20]
Internet-Draft OAuth 2.0 April 2011 The authorization server MUST: o Validate the client credentials and ensure that the authorization code was issued to that client. o Verify that the authorization code is valid, and that the redirection URI matches the redirection URI used by the authorization server to deliver the authorization code. 4.1.4. Access Token Response If the access token request is valid and authorized, the authorization server issues an access token and optional refresh token as described in Section 5.1. If the request client authentication failed or is invalid, the authorization server returns an error response as described in Section 5.2. An example successful response: 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", "example_parameter":"example_value" } 4.2. Implicit Grant The implicit grant type is suitable for clients incapable of maintaining their client credentials confidential (for authenticating with the authorization server) such as client applications residing in a user-agent, typically implemented in a browser using a scripting language such as JavaScript. As a redirection-based flow, the client must be capable of interacting with the resource owner's user-agent (typically a web browser) and capable of receiving incoming requests (via redirection) from the authorization server. Unlike the authorization code grant type in which the client makes separate requests for authorization and access token, the client receives the access token as the result of the authorization request. Hammer-Lahav, et al. Expires October 8, 2011 [Page 21]
Internet-Draft OAuth 2.0 April 2011 Using the implicit grant type does not include client authentication since the client is unable to maintain their credential confidentiality (the client resides on the resource owner's computer or device which makes the client credentials accessible and exploitable). Because the access token is encoded into the redirection URI, it may be exposed to the resource owner and other applications residing on its computer or device. +----------+ | Resource | | Owner | | | +----------+ ^ | (B) +----|-----+ Client Identifier +---------------+ | -+----(A)--- & Redirect URI ----->| | | User- | | Authorization | | Agent -|----(B)-- User authenticates -->| Server | | | | | | |<---(C)---- Redirect URI ------<| | | | with Access Token +---------------+ | | in Fragment | | +---------------+ | |----(D)---- Redirect URI ------>| Web Server | | | without Fragment | with Client | | | | Resource | | (F) |<---(E)------- Script ---------<| | | | +---------------+ +-|--------+ | | (A) (G) Access Token | | ^ v +---------+ | | | Client | | | +---------+ Figure 4: Implicit Grant Flow The flow illustrated in Figure 4 includes the following steps: Hammer-Lahav, et al. Expires October 8, 2011 [Page 22]
Internet-Draft OAuth 2.0 April 2011 (A) The client initiates the flow by directing the resource owner's user-agent to the 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 resource owner (via the user-agent) and establishes whether the resource owner grants or denies the client's access request. (C) Assuming the resource owner grants access, the authorization server redirects the user-agent back to the client using 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 (does not include the fragment). The user-agent retains the fragment information locally. (E) The web server returns a web page (typically an HTML document 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. 4.2.1. Authorization Request The client constructs the request URI by adding the following parameters to the query component of the authorization endpoint URI using the "application/x-www-form-urlencoded" format: response_type REQUIRED. Value MUST be set to "token". 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. Described in Section 2.1.1. scope OPTIONAL. The scope of the access request expressed as a list of space-delimited, case sensitive strings. The value 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. Hammer-Lahav, et al. Expires October 8, 2011 [Page 23]
Internet-Draft OAuth 2.0 April 2011 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 resource owner to the constructed URI using an HTTP redirection response, or by other means available to it via the user-agent. For example, the client directs the user-agent to make the following HTTP request using transport-layer security (line breaks are for display purposes only): GET /authorize?response_type=token&client_id=s6BhdRkqt3& redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb HTTP/1.1 Host: server.example.com The authorization server validates the request to ensure all required parameters are present and valid. If the request is valid, the authorization server authenticates the resource owner and obtains an authorization decision (by asking the resource owner or by establishing approval via other means). When a decision is established, the authorization server directs the user-agent to the provided client redirection URI using an HTTP redirection response, or by other means available to it via the user- agent. 4.2.2. Access Token Response If the resource owner grants the access request, the authorization server issues an access token and delivers it to the client by adding the following parameters to the fragment component of the redirection URI using the "application/x-www-form-urlencoded" format: access_token REQUIRED. The access token issued by the authorization server. token_type REQUIRED. The type of the token issued as described in Section 7.1. Value is case insensitive. 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. Hammer-Lahav, et al. Expires October 8, 2011 [Page 24]
Internet-Draft OAuth 2.0 April 2011 scope OPTIONAL. The scope of the access request expressed as a list of space-delimited, case sensitive strings. The value 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. For example, the authorization server redirects the 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 The client SHOULD ignore unrecognized response parameters. The access token string size is left undefined by this specification. The client should avoid making assumptions about value sizes. The authorization server should document the size of any value it issues. 4.2.2.1. Error Response If the request fails due to a missing, invalid, or mismatching redirection URI, or if the client identifier provided is invalid, the authorization server SHOULD inform the resource owner of the error, and MUST NOT redirect the user-agent to the invalid redirection URI. If the resource owner 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 fragment component of the redirection URI using the "application/x-www-form-urlencoded" format: error REQUIRED. A single error code from the following: Hammer-Lahav, et al. Expires October 8, 2011 [Page 25]
Internet-Draft OAuth 2.0 April 2011 invalid_request The request is missing a required parameter, includes an unsupported parameter or parameter value, or is otherwise malformed. unauthorized_client The client is not authorized to request an access token using this method. access_denied The resource owner or authorization server denied the request. unsupported_response_type The authorization server does not support obtaining an access token using this method. invalid_scope The requested scope is invalid, unknown, or malformed. a 4xx or 5xx HTTP status code (except for 400 and 401) [[ Pending Consensus ]] The authorization server MAY set the "error" parameter value to a numerical HTTP status code from the 4xx or 5xx range, with the exception of the 400 (Bad Request) and 401 (Unauthorized) status codes. For example, if the service is temporarily unavailable, the authorization server MAY return an error response with "error" set to "503". 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 resource owner with additional information about the error. state REQUIRED if a valid "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 user-agent by sending the following HTTP response: HTTP/1.1 302 Found Location: https://client.example.com/cb#error=access_denied Hammer-Lahav, et al. Expires October 8, 2011 [Page 26]
Internet-Draft OAuth 2.0 April 2011 4.3. Resource Owner Password Credentials The resource owner password credentials grant type is suitable in cases where the resource owner has a trust relationship with the client, such as its computer operating system or a highly privileged application. The authorization server should take special care when enabling the grant type, and only when other flows are not viable. The grant type is suitable for clients capable of obtaining the resource owner credentials (username and password, typically using an interactive form). It is also used to migrate existing clients using direct authentication schemes such as HTTP Basic or Digest authentication to OAuth by converting the stored credentials with an access token. +----------+ | Resource | | Owner | | | +----------+ v | (A) Password Credentials | v +---------+ +---------------+ | | Client Credentials | | | |>--(B)---- & Resource Owner ----->| | | Client | Password Credentials | Authorization | | | | Server | | |<--(C)---- Access Token ---------<| | | | (w/ Optional Refresh Token) | | +---------+ +---------------+ Figure 5: Resource Owner Password Credentials Flow The flow illustrated in Figure 5 includes the following steps: (A) The resource owner provides the client with its username and password. (B) The client requests an access token from the authorization server's token endpoint by authenticating using its client credentials, and includes the credentials received from the resource owner. Hammer-Lahav, et al. Expires October 8, 2011 [Page 27]
Internet-Draft OAuth 2.0 April 2011 (C) The authorization server validates the resource owner credentials and the client credentials and issues an access token. 4.3.1. Authorization Request and Response The method through which the client obtains the resource owner credentials is beyond the scope of this specification. The client MUST discard the credentials once an access token has been obtained. 4.3.2. Access Token Request The client makes a request to the token endpoint by adding the following parameter using the "application/x-www-form-urlencoded" format in the HTTP request entity-body: grant_type REQUIRED. Value MUST be set to "password". username REQUIRED. The resource owner username. password REQUIRED. The resource owner password. scope OPTIONAL. The scope of the access request expressed as a list of space-delimited, case sensitive strings. The value 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 client includes its authentication credentials as described in Section 3 For example, the client makes the following HTTP request by including its client credentials via the "client_id" and "client_secret" parameters, 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: Hammer-Lahav, et al. Expires October 8, 2011 [Page 28]
Internet-Draft OAuth 2.0 April 2011 o Validate the client credentials. o Validate the resource owner password credentials. 4.3.3. Access Token Response If the access token request is valid and authorized, the authorization server issues an access token and optional refresh token as described in Section 5.1. If the request failed client authentication or is invalid, the authorization server returns an error response as described in Section 5.2. An example successful response: 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", "example_parameter":"example_value" } 4.4. Client Credentials The client can request an access token using only its client credentials when 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). +---------+ +---------------+ | | | | | |>--(A)--- Client Credentials ---->| Authorization | | Client | | Server | | |<--(B)---- Access Token ---------<| | | | (w/ Optional Refresh Token) | | +---------+ +---------------+ Figure 6: Client Credentials Flow The flow illustrated in Figure 6 includes the following steps: Hammer-Lahav, et al. Expires October 8, 2011 [Page 29]
Internet-Draft OAuth 2.0 April 2011 (A) The client requests an access token from the token endpoint by authenticating using its client credentials. (B) The authorization server validates the client credentials and issues an access token. 4.4.1. Authorization Request and Response Since the client credentials are used as the authorization grant, no additional authorization request is needed as the client is already in the possession of its client credentials. 4.4.2. Access Token Request The client makes a request to the token endpoint by adding the following parameter using the "application/x-www-form-urlencoded" format in the HTTP request entity-body: grant_type REQUIRED. Value MUST be set to "client_credentials". scope OPTIONAL. The scope of the access request expressed as a list of space-delimited, case sensitive strings. The value 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 client includes its authentication credentials as described in Section 3 For example, the client makes the following HTTP request by including its client credentials via the "client_id" and "client_secret" parameters, 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=client_credentials&client_id=s6BhdRkqt3& client_secret=47HDu8s The authorization server MUST validate the client credentials. Hammer-Lahav, et al. Expires October 8, 2011 [Page 30]
Internet-Draft OAuth 2.0 April 2011 4.4.3. Access Token Response If the access token request is valid and authorized, the authorization server issues an access token and optional refresh token as described in Section 5.1. If the request failed client authentication or is invalid, the authorization server returns an error response as described in Section 5.2. An example successful response: 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", "example_parameter":"example_value" } 4.5. Extensions The client uses an extension grant type by specifying the grant type using an absolute URI (defined by the authorization server) as the value of the "grant_type" parameter of the token endpoint, and by adding any additional parameters necessary. For example, to request an access token using a SAML 2.0 assertion grant type as defined by [I-D.ietf-oauth-saml2-bearer], the client makes the following HTTP request 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=http%3A%2F%2Foauth.net%2Fgrant_type%2Fassertion%2F saml%2F2.0%2Fbearer&assertion=PEFzc2VydGlvbiBJc3N1ZUluc3RhbnQ [...omitted for brevity...]V0aG5TdGF0ZW1lbnQ-PC9Bc3NlcnRpb24- Hammer-Lahav, et al. Expires October 8, 2011 [Page 31]
Internet-Draft OAuth 2.0 April 2011 5. Issuing an Access Token If the access token request is valid and authorized, the authorization server issues an access token and optional refresh token as described in Section 5.1. If the request failed client authentication or is invalid, the authorization server returns an error response as described in Section 5.2. 5.1. Successful Response The authorization server issues an 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: access_token REQUIRED. The access token issued by the authorization server. token_type REQUIRED. The type of the token issued as described in Section 7.1. Value is case insensitive. 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. refresh_token OPTIONAL. The refresh token which can be used to obtain new access tokens using the same authorization grant as described in Section 6. scope OPTIONAL. The scope of the access request expressed as a list of space-delimited, case sensitive strings. The value 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. The parameters are included 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 [RFC2616] with a value of "no-store" in any response containing tokens, secrets, or other sensitive information. Hammer-Lahav, et al. Expires October 8, 2011 [Page 32]
Internet-Draft OAuth 2.0 April 2011 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", "example_parameter":"example_value" } The client SHOULD ignore unrecognized response parameters. The sizes of tokens and other values received from the authorization server are left undefined. The client should avoid making assumptions about value sizes. The authorization server should document the size of any value it issues. 5.2. Error Response The authorization server responds with an HTTP 400 (Bad Request) status code and includes the following parameters with the response: error REQUIRED. A single error code from the following: 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 Client authentication failed (e.g. unknown client, no client credentials included, multiple client credentials included, or unsupported credentials type). The authorization server MAY return an HTTP 401 (Unauthorized) status code to indicate which HTTP authentication schemes are supported. If the client attempted to authenticate via the "Authorization" request header field, the authorization server MUST respond with an HTTP 401 (Unauthorized) status code, and include the "WWW-Authenticate" response header field matching the authentication scheme used by the client. Hammer-Lahav, et al. Expires October 8, 2011 [Page 33]
Internet-Draft OAuth 2.0 April 2011 invalid_grant The provided authorization grant is invalid, expired, revoked, does not match the redirection URI used in the authorization request, or was issued to another client. unauthorized_client The authenticated client is not authorized to use this authorization grant type. unsupported_grant_type The authorization grant type is not supported by the authorization server. invalid_scope The requested scope is invalid, unknown, malformed, or exceeds the scope granted by the resource owner. 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 resource owner with additional information about the error. The parameters are included 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. For example: HTTP/1.1 400 Bad Request Content-Type: application/json Cache-Control: no-store { "error":"invalid_request" } [[ Pending Consensus ]] If the authorization server encounters an error condition other than the 400 (Bad Request) and 401 (Unauthorized) responses described above (e.g. the service is temporarily unavailable), the authorization server SHOULD include an error response in the entity body, and set the "error" parameter value to the numerical HTTP status code returned. Hammer-Lahav, et al. Expires October 8, 2011 [Page 34]
Internet-Draft OAuth 2.0 April 2011 For example: HTTP/1.1 503 Service Unavailable Content-Type: application/json { "error":"503" } 6. Refreshing an Access Token The client makes a request to the token endpoint by adding the following parameter using the "application/x-www-form-urlencoded" format in the HTTP request entity-body: grant_type REQUIRED. Value MUST be set to "refresh_token". refresh_token REQUIRED. The refresh token issued to the client. scope OPTIONAL. The scope of the access request expressed as a list of space-delimited, case sensitive strings. The value 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 requested scope MUST be equal or lesser than the scope originally granted by the resource owner, and if omitted is treated as equal to the scope originally granted by the resource owner. The client includes its authentication credentials as described in Section 3. For example, the client makes the following HTTP request by including its client credentials via the "client_id" and "client_secret" parameters, 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 Hammer-Lahav, et al. Expires October 8, 2011 [Page 35]
Internet-Draft OAuth 2.0 April 2011 The authorization server MUST validate the client credentials, ensure that the refresh token was issued to the authenticated client, validate the refresh token, and verify that the resource owner's authorization is still valid. If valid and authorized, the authorization server issues an access token as described in Section 5.1. If the request failed verification or is invalid, the authorization server returns an error 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. 7. Accessing Protected Resources The client accesses protected resources by presenting the 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 (as well as any error responses) are beyond the scope of this specification, but generally involve an interaction or coordination between the resource server and the 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. Typically, it involves using the HTTP "Authorization" request header field [RFC2617] with an authentication scheme defined by the access token type specification. 7.1. Access Token Types The access token type provides the client with the information required to successfully utilize the access token to make a protected resource request (along with type-specific attributes). For example, the "bearer" token type defined in [I-D.ietf-oauth-v2-bearer] is utilized by simply including the access token string in the request: GET /resource/1 HTTP/1.1 Host: example.com Authorization: Bearer h480djs93hd8 Hammer-Lahav, et al. Expires October 8, 2011 [Page 36]
Internet-Draft OAuth 2.0 April 2011 while the "mac" token type defined in [I-D.hammer-oauth-v2-mac-token] is utilized by issuing a token secret together with the access token which is used to sign certain components of the HTTP requests: GET /resource/1 HTTP/1.1 Host: example.com Authorization: MAC token="h480djs93hd8", timestamp="137131200", nonce="dj83hs9s", signature="kDZvddkndxvhGRXZhvuDjEWhGeE=" Each access token type definition specifies the additional attributes (if any) sent to the client together with the "access_token" response parameter. It also defines the HTTP authentication method used to include the access token when making a protected resource request. 8. Extensibility 8.1. Defining Access Token Types Access token types can be defined in one of two ways: registered in the access token type registry (following the procedures in Section 10.1), or use a unique absolute URI as its name. Types utilizing a URI name SHOULD be limited to vendor-specific implementations that are not commonly applicable, and are specific to the implementation details of the resource server where they are used. All other types MUST be registered. Type names MUST conform to the type-name ABNF. If the type definition includes a new HTTP authentication scheme, the type name SHOULD be identical to the HTTP authentication scheme name (as defined by [RFC2617]). type-name = 1*name-char name-char = "-" / "." / "_" / DIGIT / ALPHA 8.2. Defining New Endpoint Parameters New request or response parameters for use with the authorization endpoint or the token endpoint are defined and registered in the parameters registry following the procedure in Section 10.2. Hammer-Lahav, et al. Expires October 8, 2011 [Page 37]
Internet-Draft OAuth 2.0 April 2011 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 Unregistered vendor-specific parameter extensions that are not commonly applicable, and are specific to the implementation details of the authorization server where they are used SHOULD utilize a vendor-specific prefix that is not likely to conflict with other registered values (e.g. begin with 'companyname_'). 8.3. Defining New Authorization Grant Types New authorization grant types can be defined by assigning them a unique absolute URI for use with the "grant_type" parameter. If the extension grant type requires additional token endpoint parameters, they MUST be registered in the OAuth parameters registry as described by Section 10.2. 8.4. Defining Additional Error Codes [[ Pending Consensus ]] In cases where protocol extensions (i.e. access token types, extension parameters, or extension grant types) require additional error codes to be used with the authorization code grant error response (Section 4.1.2.1), the implicit grant error response (Section 4.2.2.1), or the token error response (Section 5.2), such error codes MAY be defined. Extension error codes MUST be registered (following the procedures in Section 10.3) if the extension they are used in conjunction with is registered. Additional error codes used with unregistered extensions MAY be registered. Error codes MUST conform to the error-code ABNF, and SHOULD be prefixed by an identifying name when possible. For example, an error identifying an invalid value set to the extension parameter "example" should be named "example_invalid". error-code = ALPHA *error-char error-char = "-" / "." / "_" / DIGIT / ALPHA Hammer-Lahav, et al. Expires October 8, 2011 [Page 38]
Internet-Draft OAuth 2.0 April 2011 9. Security Considerations [[ TBD ]] 10. IANA Considerations 10.1. The OAuth Access Token Type Registry This specification establishes the OAuth access token type registry. Access token types 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 access toke type: 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. ]] Within at most 14 days of the request, the Designated Expert(s) will either approve or deny the registration request, communicating this decision to the review list and IANA. Denials should include an explanation and, if applicable, suggestions as to how to make the request successful. Decisions (or lack thereof) made by the Designated Expert can be first appealed to Application Area Directors (contactable using app-ads@tools.ietf.org email address or directly by looking up their email addresses on http://www.iesg.org/ website) and, if the appellant is not satisfied with the response, to the full IESG (using the iesg@iesg.org mailing list). IANA should only accept registry updates from the Designated Expert(s), and should direct all requests for registration to the review mailing list. 10.1.1. Registration Template Type name: The name requested (e.g., "example"). Hammer-Lahav, et al. Expires October 8, 2011 [Page 39]
Internet-Draft OAuth 2.0 April 2011 Additional Token Endpoint Response Parameters: Additional response parameters returned together with the "access_token" parameter. New parameters MUST be separately registered in the OAuth parameters registry as described by Section 10.2. HTTP Authentication Scheme(s): The HTTP authentication scheme name(s), if any, used to authenticate protected resources requests using access token of this type. 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. 10.2. The OAuth Parameters Registry This specification establishes the OAuth parameters registry. Additional parameters for inclusion in the authorization endpoint request, the authorization endpoint response, the token endpoint request, or the token endpoint response, 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. ]] Within at most 14 days of the request, the Designated Expert(s) will either approve or deny the registration request, communicating this decision to the review list and IANA. Denials should include an explanation and, if applicable, suggestions as to how to make the request successful. Decisions (or lack thereof) made by the Designated Expert can be first appealed to Application Area Directors (contactable using app-ads@tools.ietf.org email address or directly by looking up their email addresses on http://www.iesg.org/ website) and, if the Hammer-Lahav, et al. Expires October 8, 2011 [Page 40]
Internet-Draft OAuth 2.0 April 2011 appellant is not satisfied with the response, to the full IESG (using the iesg@iesg.org mailing list). IANA should only accept registry updates from the Designated Expert(s), and should direct all requests for registration to the review mailing list. 10.2.1. Registration Template Parameter name: The name requested (e.g., "example"). Parameter usage location: The location(s) where parameter can be used. The possible locations are: authorization request, authorization response, token request, or token response. 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. 10.2.2. Initial Registry Contents The OAuth Parameters Registry's initial contents are: o Parameter name: client_id o Parameter usage location: authorization request, token request o Change controller: IETF o Specification document(s): [[ this document ]] o Parameter name: client_secret o Parameter usage location: token request o Change controller: IETF o Specification document(s): [[ this document ]] o Parameter name: response_type o Parameter usage location: authorization request o Change controller: IETF o Specification document(s): [[ this document ]] o Parameter name: redirect_uri o Parameter usage location: authorization request, token request Hammer-Lahav, et al. Expires October 8, 2011 [Page 41]
Internet-Draft OAuth 2.0 April 2011 o Change controller: IETF o Specification document(s): [[ this document ]] o Parameter name: scope o Parameter usage location: authorization request, authorization response, token request, token response o Change controller: IETF o Specification document(s): [[ this document ]] o Parameter name: state o Parameter usage location: authorization request, authorization response o Change controller: IETF o Specification document(s): [[ this document ]] o Parameter name: code o Parameter usage location: authorization response, token request o Change controller: IETF o Specification document(s): [[ this document ]] o Parameter name: error_description o Parameter usage location: authorization response, token response o Change controller: IETF o Specification document(s): [[ this document ]] o Parameter name: error_uri o Parameter usage location: authorization response, token response o Change controller: IETF o Specification document(s): [[ this document ]] o Parameter name: grant_type o Parameter usage location: token request o Change controller: IETF o Specification document(s): [[ this document ]] o Parameter name: access_token o Parameter usage location: authorization response, token response o Change controller: IETF o Specification document(s): [[ this document ]] o Parameter name: token_type o Parameter usage location: authorization response, token response o Change controller: IETF o Specification document(s): [[ this document ]] o Parameter name: expires_in Hammer-Lahav, et al. Expires October 8, 2011 [Page 42]
Internet-Draft OAuth 2.0 April 2011 o Parameter usage location: authorization response, token response o Change controller: IETF o Specification document(s): [[ this document ]] o Parameter name: username o Parameter usage location: token request o Change controller: IETF o Specification document(s): [[ this document ]] o Parameter name: password o Parameter usage location: token request o Change controller: IETF o Specification document(s): [[ this document ]] o Parameter name: refresh_token o Parameter usage location: token request, token response o Change controller: IETF o Specification document(s): [[ this document ]] 10.3. The OAuth Extensions Error Registry [[ Pending Consensus ]] This specification establishes the OAuth extensions error registry. Additional error codes used together with other protocol extensions (i.e. extension grant types, access token types, or extension parameters) 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 error code: 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. ]] Within at most 14 days of the request, the Designated Expert(s) will either approve or deny the registration request, communicating this decision to the review list and IANA. Denials should include an explanation and, if applicable, suggestions as to how to make the request successful. Decisions (or lack thereof) made by the Designated Expert can be first appealed to Application Area Directors (contactable using Hammer-Lahav, et al. Expires October 8, 2011 [Page 43]
Internet-Draft OAuth 2.0 April 2011 app-ads@tools.ietf.org email address or directly by looking up their email addresses on http://www.iesg.org/ website) and, if the appellant is not satisfied with the response, to the full IESG (using the iesg@iesg.org mailing list). IANA should only accept registry updates from the Designated Expert(s), and should direct all requests for registration to the review mailing list. 10.3.1. Registration Template Error name: The name requested (e.g., "example"). Error usage location: The location(s) where the error can be used. The possible locations are: authorization code grant error response (Section 4.1.2.1), implicit grant error response (Section 4.2.2.1), or token error response (Section 5.2). Related protocol extension: The name of the extension grant type, access token type, or extension parameter, the error code is used in conjunction with. 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 error code, 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. 11. Acknowledgements This specification is the work of the OAuth Working Group which includes dozens of active and dedicated participants. In particular, the following individuals contributed ideas, feedback, and wording which shaped and formed the final specification: Michael Adams, Andrew Arnott, Dirk Balfanz, Blaine Cook, Brian Campbell, Leah Culver, Bill de hOra, Brian Eaton, Brian Ellin, Igor Faynberg, George Fletcher, Tim Freeman, Evan Gilbert, Yaron Goland, Brent Goldman, Kristoffer Gronowski, Justin Hart, Craig Heath, Phil Hunt, Michael B. Jones, John Kemp, Mark Kent, Raffi Krikorian, Chasen Le Hara, Rasmus Lerdorf, Torsten Lodderstedt, Hui-Lan Lu, Paul Madsen, Alastair Mair, Eve Maler, James Manger, Laurence Miao, Chuck Mortimore, Justin Richer, Peter Saint-Andre, Nat Sakimura, Rob Sayre, Marius Scurtescu, Naitik Shah, Luke Shepard, Justin Smith, Jeremy Hammer-Lahav, et al. Expires October 8, 2011 [Page 44]
Internet-Draft OAuth 2.0 April 2011 Suriel, Christian Stuebner, Paul Tarjan, Allen Tom, Franklin Tse, Nick Walker, Skylar Woodward. The initial OAuth 2.0 protocol specification was edited by David Recordon, based on two previous publications: the OAuth 1.0 community specification [RFC5849], and OAuth WRAP (OAuth Web Resource Authorization Profiles) [I-D.draft-hardt-oauth-01]. The OAuth 1.0 community specification was edited by Eran Hammer-Lahav and authored by Mark Atwood, Dirk Balfanz, Darren Bounds, Richard M. Conlan, Blaine Cook, Leah Culver, Breno de Medeiros, Brian Eaton, Kellan Elliott-McCrea, Larry Halff, Eran Hammer-Lahav, Ben Laurie, Chris Messina, John Panzer, Sam Quigley, David Recordon, Eran Sandler, Jonathan Sergent, Todd Sieling, Brian Slesinsky, and Andy Smith. The OAuth WRAP specification was edited by Dick Hardt and authored by Brian Eaton, Yaron Goland, Dick Hardt, and Allen Tom. Appendix A. Editor's Notes While many people contributed to this specification throughout its long journey, the editor would like to acknowledge and thank a few individuals for their outstanding and invaluable efforts leading up to the publication of this specification. It is these individuals without whom this work would not have existed, or reached its successful conclusion. David Recordon for continuously being one of OAuth's most valuable assets, bringing pragmatism and urgency to the work, and helping shape it from its very beginning, as well as being one of the best collaborators I had the pleasure of working with. Mark Nottingham for introducing OAuth to the IETF and setting the community on this course. Lisa Dusseault for her support and guidance as the Application area director. Blaine Cook, Peter Saint- Andre, and Hannes Tschofenig for their work as working group chairs. James Manger for his creative ideas and always insightful feedback. Brian Campbell, Torsten Lodderstedt, Chuck Mortimore, Justin Richer, Marius Scurtescu, and Luke Shepard for their continued participation and valuable feedback. Special thanks goes to Mike Curtis and Yahoo! for their unconditional support of this work for over three years. Hammer-Lahav, et al. Expires October 8, 2011 [Page 45]
Internet-Draft OAuth 2.0 April 2011 12. References 12.1. Normative References [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., Leach, P., Luotonen, A., and L. Stewart, "HTTP Authentication: Basic and Digest Access Authentication", RFC 2617, June 1999. [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. [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, August 2008. [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>. 12.2. Informative References [I-D.draft-hardt-oauth-01] Hardt, D., Ed., Tom, A., Eaton, B., and Y. Goland, "OAuth Web Resource Authorization Profiles", January 2010. [I-D.hammer-oauth-v2-mac-token] Hammer-Lahav, E., "HTTP Authentication: MAC Authentication", draft-hammer-oauth-v2-mac-token-02 (work Hammer-Lahav, et al. Expires October 8, 2011 [Page 46]
Internet-Draft OAuth 2.0 April 2011 in progress), January 2011. [I-D.ietf-oauth-saml2-bearer] Campbell, B. and C. Mortimore, "SAML 2.0 Bearer Assertion Grant Type Profile for OAuth 2.0", draft-ietf-oauth-saml2-bearer-03 (work in progress), February 2011. [I-D.ietf-oauth-v2-bearer] Jones, M., Hardt, D., and D. Recordon, "The OAuth 2.0 Protocol: Bearer Tokens", draft-ietf-oauth-v2-bearer-02 (work in progress), January 2011. [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- 2.0-os, March 2005. [RFC5849] Hammer-Lahav, E., "The OAuth 1.0 Protocol", RFC 5849, April 2010. Authors' Addresses Eran Hammer-Lahav (editor) Yahoo! Email: eran@hueniverse.com URI: http://hueniverse.com David Recordon Facebook Email: dr@fb.com URI: http://www.davidrecordon.com/ Dick Hardt Microsoft Email: dick.hardt@gmail.com URI: http://dickhardt.org/ Hammer-Lahav, et al. Expires October 8, 2011 [Page 47]
