draft-ietf-oauth-revocation-11.txt   rfc7009.txt 
OAuth Working Group T. Lodderstedt, Ed. Internet Engineering Task Force (IETF) T. Lodderstedt, Ed.
Internet-Draft Deutsche Telekom AG Request for Comments: 7009 Deutsche Telekom AG
Intended status: Standards Track S. Dronia Category: Standards Track S. Dronia
Expires: January 14, 2014 ISSN: 2070-1721
M. Scurtescu M. Scurtescu
Google Google
July 13, 2013 August 2013
OAuth 2.0 Token Revocation OAuth 2.0 Token Revocation
draft-ietf-oauth-revocation-11
Abstract Abstract
This document proposes an additional endpoint for OAuth authorization This document proposes an additional endpoint for OAuth authorization
servers, which allows clients to notify the authorization server that servers, which allows clients to notify the authorization server that
a previously obtained refresh or access token is no longer needed. a previously obtained refresh or access token is no longer needed.
This allows the authorization server to cleanup security credentials. This allows the authorization server to clean up security
A revocation request will invalidate the actual token and, if credentials. A revocation request will invalidate the actual token
applicable, other tokens based on the same authorization grant. and, if applicable, other tokens based on the same authorization
grant.
Requirements Language
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 RFC 2119 [RFC2119].
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
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 This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on January 14, 2014. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7009.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Token Revocation . . . . . . . . . . . . . . . . . . . . . . 3 2. Token Revocation . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Revocation Request . . . . . . . . . . . . . . . . . . . 3 2.1. Revocation Request . . . . . . . . . . . . . . . . . . . 4
2.2. Revocation Response . . . . . . . . . . . . . . . . . . . 5 2.2. Revocation Response . . . . . . . . . . . . . . . . . . . 5
2.2.1. Error Response . . . . . . . . . . . . . . . . . . . 5 2.2.1. Error Response . . . . . . . . . . . . . . . . . . . 6
2.3. Cross-Origin Support . . . . . . . . . . . . . . . . . . 6 2.3. Cross-Origin Support . . . . . . . . . . . . . . . . . . 6
3. Implementation Note . . . . . . . . . . . . . . . . . . . . . 6 3. Implementation Note . . . . . . . . . . . . . . . . . . . . . 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
4.1. OAuth Extensions Error Registration . . . . . . . . . . . 7 4.1. OAuth Extensions Error Registration . . . . . . . . . . . 8
4.1.1. The "unsupported_token_type" Error Value . . . . . . 7 4.1.1. The "unsupported_token_type" Error Value . . . . . . 8
4.1.2. OAuth Token Type Hint Registry . . . . . . . . . . . 8 4.1.2. OAuth Token Type Hints Registry . . . . . . . . . . . 8
4.1.2.1. Registration Template . . . . . . . . . . . . . . 8 4.1.2.1. Registration Template . . . . . . . . . . . . . . 9
4.1.2.2. Initial Registry Contents . . . . . . . . . . . . 8 4.1.2.2. Initial Registry Contents . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Normative References . . . . . . . . . . . . . . . . . . 10 7.1. Normative References . . . . . . . . . . . . . . . . . . 10
7.2. Informative References . . . . . . . . . . . . . . . . . 10 7.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction 1. Introduction
The OAuth 2.0 core specification [RFC6749] defines several ways for a The OAuth 2.0 core specification [RFC6749] defines several ways for a
client to obtain refresh and access tokens. This specification client to obtain refresh and access tokens. This specification
supplements the core specification with a mechanism to revoke both supplements the core specification with a mechanism to revoke both
types of tokens. A token is a string representing an authorization types of tokens. A token is a string representing an authorization
grant issued by the resource owner to the client. A revocation grant issued by the resource owner to the client. A revocation
request will invalidate the actual token and, if applicable, other request will invalidate the actual token and, if applicable, other
tokens based on the same authorization grant and the authorization tokens based on the same authorization grant and the authorization
grant itself. grant itself.
From an end-user's perspective, OAuth is often used to log into a From an end-user's perspective, OAuth is often used to log into a
certain site or application. This revocation mechanism allows a certain site or application. This revocation mechanism allows a
client to invalidate its tokens if the end-user logs out, changes client to invalidate its tokens if the end-user logs out, changes
identity, or uninstalls the respective application. Notifying the identity, or uninstalls the respective application. Notifying the
authorization server that the token is no longer needed allows the authorization server that the token is no longer needed allows the
authorization server to clean up data associated with that token authorization server to clean up data associated with that token
(e.g. session data) and the underlying authorization grant. This (e.g., session data) and the underlying authorization grant. This
behavior prevents a situation where there is still a valid behavior prevents a situation in which there is still a valid
authorization grant for a particular client which the end user is not authorization grant for a particular client of which the end-user is
aware of. This way, token revocation prevents abuse of abandoned not aware. This way, token revocation prevents abuse of abandoned
tokens and facilitates a better end-user experience since invalidated tokens and facilitates a better end-user experience since invalidated
authorization grants will no longer turn up in a list of authorization grants will no longer turn up in a list of
authorization grants the authorization server might present to the authorization grants the authorization server might present to the
end-user. end-user.
1.1. Requirements Language
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 RFC 2119 [RFC2119].
2. Token Revocation 2. Token Revocation
Implementations MUST support the revocation of refresh tokens and Implementations MUST support the revocation of refresh tokens and
SHOULD support the revocation of access tokens (see Implementation SHOULD support the revocation of access tokens (see Implementation
Note). Note).
The client requests the revocation of a particular token by making an The client requests the revocation of a particular token by making an
HTTP POST request to the token revocation endpoint URL. This URL HTTP POST request to the token revocation endpoint URL. This URL
MUST conform to the rules given in [RFC6749], section 3.1. Clients MUST conform to the rules given in [RFC6749], Section 3.1. Clients
MUST verify that the URL is an HTTPS URL. MUST verify that the URL is an HTTPS URL.
The means to obtain the location of the revocation endpoint is out of The means to obtain the location of the revocation endpoint is out of
scope of this specification. For example, the client developer may the scope of this specification. For example, the client developer
consult the server's documentation or automatic discovery may be may consult the server's documentation or automatic discovery may be
used. As this endpoint is handling security credentials, the used. As this endpoint is handling security credentials, the
endpoint location needs to be obtained from a trustworthy source. endpoint location needs to be obtained from a trustworthy source.
Since requests to the token revocation endpoint result in the Since requests to the token revocation endpoint result in the
transmission of plain text credentials in the HTTP request, URLs for transmission of plaintext credentials in the HTTP request, URLs for
token revocation endpoints MUST be HTTPS URLs. The authorization token revocation endpoints MUST be HTTPS URLs. The authorization
server MUST use Transport Layer Security (TLS) in a version compliant server MUST use Transport Layer Security (TLS) [RFC5246] in a version
with [RFC6749], section 1.6. Implementations MAY also support compliant with [RFC6749], Section 1.6. Implementations MAY also
additional transport-layer security mechanisms that meet their support additional transport-layer security mechanisms that meet
security requirements. their security requirements.
If the host of the token revocation endpoint can also be reached over If the host of the token revocation endpoint can also be reached over
HTTP, then the server SHOULD also offer a revocation service at the HTTP, then the server SHOULD also offer a revocation service at the
corresponding HTTP URI, but MUST NOT publish this URI as a token corresponding HTTP URI, but it MUST NOT publish this URI as a token
revocation endpoint. This ensures that tokens accidentally sent over revocation endpoint. This ensures that tokens accidentally sent over
HTTP will be revoked. HTTP will be revoked.
2.1. Revocation Request 2.1. Revocation Request
The client constructs the request by including the following The client constructs the request by including the following
parameters using the "application/x-www-form-urlencoded" format in parameters using the "application/x-www-form-urlencoded" format in
the HTTP request entity-body: the HTTP request entity-body:
token REQUIRED. The token that the client wants to get revoked. token REQUIRED. The token that the client wants to get revoked.
token_type_hint OPTIONAL. A hint about the type of the token token_type_hint OPTIONAL. A hint about the type of the token
submitted for revocation. Clients MAY pass this parameter in submitted for revocation. Clients MAY pass this parameter in
order to help the authorization server to optimize the token order to help the authorization server to optimize the token
lookup. If the server is unable to locate the token using lookup. If the server is unable to locate the token using
the given hint, it MUST extend its search accross all of its the given hint, it MUST extend its search across all of its
supported token types. An authorization server MAY ignore supported token types. An authorization server MAY ignore
this parameter, particularly if it is able to detect the this parameter, particularly if it is able to detect the
token type automatically. This specification defines two token type automatically. This specification defines two
such values: such values:
* access_token: An Access Token as defined in [RFC6749], * access_token: An access token as defined in [RFC6749],
section 1.4 Section 1.4
* refresh_token: A Refresh Token as defined in [RFC6749], * refresh_token: A refresh token as defined in [RFC6749],
section 1.5 Section 1.5
Specific implementations, profiles, and extensions of this Specific implementations, profiles, and extensions of this
specification MAY define other values for this parameter specification MAY define other values for this parameter
using the registry defined in Section 4.1.2. using the registry defined in Section 4.1.2.
The client also includes its authentication credentials as described The client also includes its authentication credentials as described
in Section 2.3. of [RFC6749]. in Section 2.3. of [RFC6749].
For example, a client may request the revocation of a refresh token For example, a client may request the revocation of a refresh token
with the following request: with the following request:
skipping to change at page 4, line 45 skipping to change at page 5, line 22
token=45ghiukldjahdnhzdauz&token_type_hint=refresh_token token=45ghiukldjahdnhzdauz&token_type_hint=refresh_token
The authorization server first validates the client credentials (in The authorization server first validates the client credentials (in
case of a confidential client) and then verifies whether the token case of a confidential client) and then verifies whether the token
was issued to the client making the revocation request. If this was issued to the client making the revocation request. If this
validation fails, the request is refused and the client is informed validation fails, the request is refused and the client is informed
of the error by the authorization server as described below. of the error by the authorization server as described below.
In the next step, the authorization server invalidates the token. In the next step, the authorization server invalidates the token.
The invalidation takes place immediately, and the token can not be The invalidation takes place immediately, and the token cannot be
used again after the revocation. In practice there could be a used again after the revocation. In practice, there could be a
propagation delay, for example, in which some servers know about the propagation delay, for example, in which some servers know about the
invalidation while others do not. Implementations should minimize invalidation while others do not. Implementations should minimize
that window, and clients must not try to use the token after receipt that window, and clients must not try to use the token after receipt
of an HTTP 200 response from the server. of an HTTP 200 response from the server.
Depending on the authorization server's revocation policy, the Depending on the authorization server's revocation policy, the
revocation of a particular token may cause the revocation of related revocation of a particular token may cause the revocation of related
tokens and the underlying authorization grant. If the particular tokens and the underlying authorization grant. If the particular
token is a refresh token and the authorization server supports the token is a refresh token and the authorization server supports the
revocation of access tokens, then the authorization server SHOULD revocation of access tokens, then the authorization server SHOULD
also invalidate all access tokens based on the same authorization also invalidate all access tokens based on the same authorization
grant (see Implementation Note). If the token passed to the request grant (see Implementation Note). If the token passed to the request
is an access token, the server MAY revoke the respective refresh is an access token, the server MAY revoke the respective refresh
token as well. token as well.
Note: A client compliant with [RFC6749] must be prepared to handle Note: A client compliant with [RFC6749] must be prepared to handle
unexpected token invalidation at any time. Independent of the unexpected token invalidation at any time. Independent of the
revocation mechanism specified in this document, resource owners may revocation mechanism specified in this document, resource owners may
revoke authorization grants or the authorization server may revoke authorization grants, or the authorization server may
invalidate tokens in order to mitigate security threats. Thus having invalidate tokens in order to mitigate security threats. Thus,
different server policies with respect to cascading the revocation of having different server policies with respect to cascading the
tokens should not pose interoperability problems. revocation of tokens should not pose interoperability problems.
2.2. Revocation Response 2.2. Revocation Response
The authorization server responds with HTTP status code 200 if the The authorization server responds with HTTP status code 200 if the
token has been revoked sucessfully or if the client submitted an token has been revoked successfully or if the client submitted an
invalid token. invalid token.
Note: invalid tokens do not cause an error response since the client Note: invalid tokens do not cause an error response since the client
cannot handle such an error in a reasonable way. Moreover, the cannot handle such an error in a reasonable way. Moreover, the
purpose of the revocation request, invalidating the particular token, purpose of the revocation request, invalidating the particular token,
is already achieved. is already achieved.
The content of the response body is ignored by the client as all The content of the response body is ignored by the client as all
necessary information is conveyed in the response code. necessary information is conveyed in the response code.
An invalid token type hint value is ignored by the authorization An invalid token type hint value is ignored by the authorization
server and does not influence the revocation response. server and does not influence the revocation response.
2.2.1. Error Response 2.2.1. Error Response
The error presentation conforms to the definition in section 5.2 of The error presentation conforms to the definition in Section 5.2 of
[RFC6749]. The following additional error code is defined for the [RFC6749]. The following additional error code is defined for the
token revocation endpoint: token revocation endpoint:
unsupported_token_type The authorization server does not support the unsupported_token_type: The authorization server does not support
revocation of the presented token type. I.e. the client the revocation of the presented token type. That is, the
tried to revoke an access token on a server not supporting client tried to revoke an access token on a server not
this feature. supporting this feature.
If the server responds with HTTP status code 503, the client must If the server responds with HTTP status code 503, the client must
assume the token still exists and may retry after a reasonable delay. assume the token still exists and may retry after a reasonable delay.
The server may include a "Retry-After" header in the response to The server may include a "Retry-After" header in the response to
indicate how long the service is expected to be unavailable to the indicate how long the service is expected to be unavailable to the
requesting client. requesting client.
2.3. Cross-Origin Support 2.3. Cross-Origin Support
The revocation end-point MAY support CORS (Cross-Origin Resource The revocation endpoint MAY support Cross-Origin Resource Sharing
Sharing) if it is aimed at use in combination with user-agent-based (CORS) [W3C.WD-cors-20120403] if it is aimed at use in combination
applications. with user-agent-based applications.
In addition, for interoperability with legacy user-agents, it MAY In addition, for interoperability with legacy user-agents, it MAY
also offer JSONP (Remote JSON - JSONP) by allowing GET requests with also offer JSONP (Remote JSON - JSONP) [jsonp] by allowing GET
an additional parameter: requests with an additional parameter:
callback OPTIONAL. The qualified name of a JavaScript function. callback OPTIONAL. The qualified name of a JavaScript function.
For example, a client may request the revocation of an access token For example, a client may request the revocation of an access token
with the following request (line breaks are for display purposes with the following request (line breaks are for display purposes
only): only):
https://example.com/revoke?token=agabcdefddddafdd& https://example.com/revoke?token=agabcdefddddafdd&
callback=package.myCallback callback=package.myCallback
Successful response: Successful response:
package.myCallback(); package.myCallback();
Error response: Error response:
package.myCallback({"error":"unsupported_token_type"}); package.myCallback({"error":"unsupported_token_type"});
Clients should be aware that when relying on JSONP, a malicious Clients should be aware that when relying on JSONP, a malicious
revocation end-point may attempt to inject malicious code into the revocation endpoint may attempt to inject malicious code into the
client. client.
3. Implementation Note 3. Implementation Note
OAuth 2.0 allows deployment flexibility with respect to the style of OAuth 2.0 allows deployment flexibility with respect to the style of
access tokens. The access tokens may be self-contained so that an access tokens. The access tokens may be self-contained so that a
resource server needs no further interaction with an authorization resource server needs no further interaction with an authorization
server issuing these tokens to perform an authorization decision of server issuing these tokens to perform an authorization decision of
the client requesting access to a protected resource. A system the client requesting access to a protected resource. A system
design may, however, instead use access tokens that are handles design may, however, instead use access tokens that are handles
referring to authorization data stored at the authorization server. referring to authorization data stored at the authorization server.
This consequently requires a resource server to issue a request to This consequently requires a resource server to issue a request to
the respective authorization server to retrieve the content of the the respective authorization server to retrieve the content of the
access token every time a client presents an access token. access token every time a client presents an access token.
While these are not the only options they illustrate the implications While these are not the only options, they illustrate the
for revocation. In the latter case the authorization server is able implications for revocation. In the latter case, the authorization
to revoke an access token previously issued to a client when the server is able to revoke an access token previously issued to a
resource server relays a received access token. In the former case client when the resource server relays a received access token. In
some (currently non-standardized) backend interaction between the the former case, some (currently non-standardized) backend
authorization server and the resource server may be used when interaction between the authorization server and the resource server
immediate access token revocation is desired. Another design may be used when immediate access token revocation is desired.
alternative is to issue short-lived access tokens, which can be Another design alternative is to issue short-lived access tokens,
refreshed at any time using the corresponding refresh tokens. This which can be refreshed at any time using the corresponding refresh
allows the authorization server to impose a limit on the time revoked tokens. This allows the authorization server to impose a limit on
access tokens are in use. the time revoked when access tokens are in use.
Which approach of token revocation is chosen will depend on the Which approach of token revocation is chosen will depend on the
overall system design and on the application service provider's risk overall system design and on the application service provider's risk
analysis. The cost of revocation in terms of required state and analysis. The cost of revocation in terms of required state and
communication overhead is ultimately the result of the desired communication overhead is ultimately the result of the desired
security properties. security properties.
4. IANA Considerations 4. IANA Considerations
This specification registers an error value in the OAuth Extension This specification registers an error value in the "OAuth Extensions
Error registry and establishes the OAuth Token Type registry. Error Registry" and establishes the "OAuth Token Type Hints"
registry.
4.1. OAuth Extensions Error Registration 4.1. OAuth Extensions Error Registration
This specification registers the following error values in the OAuth This specification registers the following error value in the "OAuth
Extensions Error registry defined in [RFC6749]. Extensions Error Registry" defined in [RFC6749].
4.1.1. The "unsupported_token_type" Error Value 4.1.1. The "unsupported_token_type" Error Value
Error name unsupported_token_type Error name: unsupported_token_type
Error usage location revocation endpoint error response Error Usage Location: Revocation endpoint error response
Related protocol extension Token Revocation Endpoint Related Protocol Extension: Token Revocation Endpoint
Change controller IETF Change controller: IETF
Specification document(s) [this document] Specification document(s): [RFC7009]
4.1.2. OAuth Token Type Hint Registry 4.1.2. OAuth Token Type Hints Registry
This specification establishes the OAuth Token Type Hint registry. This specification establishes the "OAuth Token Type Hints" registry.
Possible values of the parameter "token_type_hint" (see Section 2.1) Possible values of the parameter "token_type_hint" (see Section 2.1)
are registered with a Specification Required ([RFC5226]) after a two- are registered with a Specification Required ([RFC5226]) after a two-
week review period on the TBD@ietf.org mailing list, on the advice of week review period on the oauth-ext-review@ietf.org mailing list, on
one or more Designated Experts. However, to allow for the allocation the advice of one or more Designated Experts. However, to allow for
of values prior to publication, the Designated Expert(s) may approve the allocation of values prior to publication, the Designated
registration once they are satisfied that such a specification will Expert(s) may approve registration once they are satisfied that such
be published. Registration requests must be sent to the TBD@ietf.org a specification will be published. Registration requests must be
mailing list for review and comment, with an appropriate subject sent to the oauth-ext-review@ietf.org mailing list for review and
(e.g., "Request for parameter: example"). Within the review period, comment, with an appropriate subject (e.g., "Request for parameter:
the Designated Expert(s) will either approve or deny the registration example"). Within the review period, the Designated Expert(s) will
request, communicating this decision to the review list and IANA. either approve or deny the registration request, communicating this
Denials should include an explanation and, if applicable, suggestions decision to the review list and IANA. Denials should include an
as to how to make the request successful. IANA must only accept explanation and, if applicable, suggestions as to how to make the
registry updates from the Designated Expert(s) and should direct all request successful. IANA must only accept registry updates from the
requests for registration to the review mailing list. Designated Expert(s) and should direct all requests for registration
to the review mailing list.
4.1.2.1. Registration Template 4.1.2.1. Registration Template
Hint Value: The additional value, which can be used to indicate a Hint Value: The additional value, which can be used to indicate a
certain token type to the authorization server. certain token type to the authorization server.
Change controller: For Standards Track RFCs, state "IETF". For Change controller: For Standards Track RFCs, state "IETF". For
others, give the name of the responsible party. Other details others, give the name of the responsible party. Other details
(e.g., postal address, email address, home page URI) may also be (e.g., postal address, email address, and home page URI) may also
included. be included.
Specification document(s): Reference to the document(s) that specify Specification document(s): Reference to the document(s) that
the type, preferably including a URI that can be used to retrieve specifies the type, preferably including a URI that can be used to
a copy of the document(s). An indication of the relevant sections retrieve a copy of the document(s). An indication of the relevant
may also be included but is not required. sections may also be included but is not required.
4.1.2.2. Initial Registry Contents 4.1.2.2. Initial Registry Contents
The OAuth Token Type Hint registry's initial contents are: The OAuth Token Type Hint registry's initial contents are as follows.
o Hint Value: access_token
o Change controller: IETF
o Specification document(s): [this document]
o Hint Value: refresh_token +---------------+-------------------+-----------+
| Hint Value | Change Controller | Reference |
+---------------+-------------------+-----------+
| access_token | IETF | [RFC7009] |
| refresh_token | IETF | [RFC7009] |
+---------------+-------------------+-----------+
o Change controller: IETF Table 1: OAuth Token Type Hints initial registry contents
o Specification document(s): [this document]
5. Security Considerations 5. Security Considerations
If the authorization server does not support access token revocation, If the authorization server does not support access token revocation,
access tokens will not be immediately invalidated when the access tokens will not be immediately invalidated when the
corresponding refresh token is revoked. Deployments must take this corresponding refresh token is revoked. Deployments must take this
into account when conducting their security risk analysis. into account when conducting their security risk analysis.
Cleaning up tokens using revocation contributes to overall security Cleaning up tokens using revocation contributes to overall security
and privacy since it reduces the likelihood for abuse of abandoned and privacy since it reduces the likelihood for abuse of abandoned
tokens. This specification in general does not intend to provide tokens. This specification in general does not intend to provide
countermeasures against token theft and abuse. For a discussion of countermeasures against token theft and abuse. For a discussion of
respective threats and countermeasures, consult the security respective threats and countermeasures, consult the security
considerations given in section 10 of the OAuth core specification considerations given in Section 10 of the OAuth core specification
[RFC6749] and the OAuth threat model document [RFC6819]. [RFC6749] and the OAuth threat model document [RFC6819].
Malicious clients could attempt to use the new endpoint to launch Malicious clients could attempt to use the new endpoint to launch
denial of service attacks on the authorization server. Appropriate denial-of-service attacks on the authorization server. Appropriate
countermeasures, which should be in place for the token endpoint as countermeasures, which should be in place for the token endpoint as
well, MUST be applied to the revocation endpoint (see [RFC6819], well, MUST be applied to the revocation endpoint (see [RFC6819],
section 4.4.1.11). Specifically, invalid token type hints may Section 4.4.1.11). Specifically, invalid token type hints may
misguide the authorization server and cause additional database misguide the authorization server and cause additional database
lookups. Care MUST be taken to prevent malicious clients from lookups. Care MUST be taken to prevent malicious clients from
exploiting this feature to launch denial of service attacks. exploiting this feature to launch denial-of-service attacks.
A malicious client may attempt to guess valid tokens on this endpoint A malicious client may attempt to guess valid tokens on this endpoint
by making revocation requests against potential token strings. by making revocation requests against potential token strings.
According to this specification, a client's request must contain a According to this specification, a client's request must contain a
valid client_id, in the case of a public client, or valid client valid client_id, in the case of a public client, or valid client
credentials, in the case of a confidential client. The token being credentials, in the case of a confidential client. The token being
revoked must also belong to the requesting client. If an attacker is revoked must also belong to the requesting client. If an attacker is
able to successfully guess a public client's client_id and one of able to successfully guess a public client's client_id and one of
their tokens, or a private client's credentials and one of their their tokens, or a private client's credentials and one of their
tokens, they could do much worse damage by using the token elsewhere tokens, they could do much worse damage by using the token elsewhere
than by revoking it. If they chose to revoke the token, the than by revoking it. If they chose to revoke the token, the
legitimate client will lose its authorization grant and will need to legitimate client will lose its authorization grant and will need to
prompt the user again. No further damage is done and the guessed prompt the user again. No further damage is done and the guessed
token is now worthless. token is now worthless.
Since the revocation endpoint is handling security credentials, Since the revocation endpoint is handling security credentials,
clients need to obtain its location from a trustworthy source only. clients need to obtain its location from a trustworthy source only.
Otherwise, an attacker could capture valid security tokens by Otherwise, an attacker could capture valid security tokens by
utilizing a counterfeit revocation endpoint. Moreover in order to utilizing a counterfeit revocation endpoint. Moreover, in order to
detect counterfeit revocation endpoints, clients MUST authenticate detect counterfeit revocation endpoints, clients MUST authenticate
the revocation endpoint (certificate validation etc.). the revocation endpoint (certificate validation, etc.).
6. Acknowledgements 6. Acknowledgements
We would like to thank Peter Mauritius, Amanda Anganes, Mark Wubben, We would like to thank Peter Mauritius, Amanda Anganes, Mark Wubben,
Hannes Tschofenig, Michiel de Jong, Doug Foiles, Paul Madsen, George Hannes Tschofenig, Michiel de Jong, Doug Foiles, Paul Madsen, George
Fletcher, Sebastian Ebling, Christian Stuebner, Brian Campbell, Igor Fletcher, Sebastian Ebling, Christian Stuebner, Brian Campbell, Igor
Faynberg, Lukas Rosenstock, and Justin Richer for their valuable Faynberg, Lukas Rosenstock, and Justin Richer for their valuable
feedback. feedback.
7. References 7. References
7.1. Normative References 7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
RFC 2246, January 1999.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008. May 2008.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008. (TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC6749] Hardt, D., "The OAuth 2.0 Authorization Framework", RFC [RFC6749] Hardt, D., "The OAuth 2.0 Authorization Framework",
6749, October 2012. RFC 6749, October 2012.
7.2. Informative References 7.2. Informative References
[RFC6819] Lodderstedt, T., McGloin, M., and P. Hunt, "OAuth 2.0 [RFC6819] Lodderstedt, T., McGloin, M., and P. Hunt, "OAuth 2.0
Threat Model and Security Considerations", RFC 6819, Threat Model and Security Considerations", RFC 6819,
January 2013. January 2013.
[W3C.WD-cors-20120403] [W3C.WD-cors-20120403]
Kesteren, A., "Cross-Origin Resource Sharing", World Wide Kesteren, A., "Cross-Origin Resource Sharing", World Wide
Web Consortium LastCall WD-cors-20120403, April 2012, Web Consortium LastCall WD-cors-20120403, April 2012,
<http://www.w3.org/TR/2012/WD-cors-20120403>. <http://www.w3.org/TR/2012/WD-cors-20120403>.
[jsonp] Ippolito, B., "Remote JSON - JSONP", December 2005, <http: [jsonp] Ippolito, B., "Remote JSON - JSONP", December 2005,
//bob.pythonmac.org/archives/2005/12/05/remote-json- <http://bob.pythonmac.org/archives/2005/12/05/
jsonp>. remote-json-jsonp>.
Authors' Addresses Authors' Addresses
Torsten Lodderstedt (editor) Torsten Lodderstedt (editor)
Deutsche Telekom AG Deutsche Telekom AG
Email: torsten@lodderstedt.net EMail: torsten@lodderstedt.net
Stefanie Dronia Stefanie Dronia
Email: sdronia@gmx.de EMail: sdronia@gmx.de
Marius Scurtescu Marius Scurtescu
Google Google
Email: mscurtescu@google.com EMail: mscurtescu@google.com
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