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OAuth Working Group N. Sakimura
Internet-Draft Nomura Research Institute
Intended status: Standards Track J. Bradley
Expires: August 3, 2017 Ping Identity
January 30, 2017
The OAuth 2.0 Authorization Framework: JWT Secured Authorization Request
(JAR)
draft-ietf-oauth-jwsreq-11
Abstract
The authorization request in OAuth 2.0 described in RFC 6749 utilizes
query parameter serialization, which means that Authorization Request
parameters are encoded in the URI of the request and sent through
user agents such as web browsers. While it is easy to implement, it
means that (a) the communication through the user agents are not
integrity protected and thus the parameters can be tainted, and (b)
the source of the communication is not authenticated. Because of
these weaknesses, several attacks to the protocol have now been put
forward.
This document introduces the ability to send request parameters in a
JSON Web Token (JWT) instead, which allows the request to be JWS
signed and/or JWE encrypted so that the integrity, source
authentication and confidentiality property of the Authorization
Request is attained. The request can be sent by value or by
reference.
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 August 3, 2017.
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Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1. Request Object . . . . . . . . . . . . . . . . . . . . . 6
2.2. Request Object URI . . . . . . . . . . . . . . . . . . . 6
3. Symbols and abbreviated terms . . . . . . . . . . . . . . . . 6
4. Request Object . . . . . . . . . . . . . . . . . . . . . . . 6
5. Authorization Request . . . . . . . . . . . . . . . . . . . . 8
5.1. Passing a Request Object by Value . . . . . . . . . . . . 9
5.2. Passing a Request Object by Reference . . . . . . . . . . 10
5.2.1. URL Referencing the Request Object . . . . . . . . . 12
5.2.2. Request using the "request_uri" Request Parameter . . 13
5.2.3. Authorization Server Fetches Request Object . . . . . 13
6. Validating JWT-Based Requests . . . . . . . . . . . . . . . . 13
6.1. Encrypted Request Object . . . . . . . . . . . . . . . . 13
6.2. JWS Signed Request Object . . . . . . . . . . . . . . . . 14
6.3. Request Parameter Assembly and Validation . . . . . . . . 14
7. Authorization Server Response . . . . . . . . . . . . . . . . 14
8. TLS Requirements . . . . . . . . . . . . . . . . . . . . . . 14
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . 15
10. Security Considerations . . . . . . . . . . . . . . . . . . . 15
10.1. Choice of Algorithms . . . . . . . . . . . . . . . . . . 15
10.2. Choice of Parameters to include in the Request Object . 15
10.3. Request Source Authentication . . . . . . . . . . . . . 16
10.4. Explicit Endpoints . . . . . . . . . . . . . . . . . . . 16
11. Privacy Considerations . . . . . . . . . . . . . . . . . . . 17
11.1. Collection limitation . . . . . . . . . . . . . . . . . 17
11.2. Disclosure Limitation . . . . . . . . . . . . . . . . . 18
11.2.1. Request Disclosure . . . . . . . . . . . . . . . . . 18
11.2.2. Tracking using Request Object URI . . . . . . . . . 18
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19
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13. Revision History . . . . . . . . . . . . . . . . . . . . . . 19
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
14.1. Normative References . . . . . . . . . . . . . . . . . . 22
14.2. Informative References . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction
The Authorization Request in OAuth 2.0 [RFC6749] utilizes query
parameter serialization and typically sent through user agents such
as web browsers.
For example, the parameters "response_type", "client_id", "state",
and "redirect_uri" are encoded in the URI of the request:
GET /authorize?response_type=code&client_id=s6BhdRkqt3&state=xyz
&redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb HTTP/1.1
Host: server.example.com
While it is easy to implement, the encoding in the URI does not allow
application layer security with confidentiality and integrity
protection to be used. While TLS is used to offer communication
security between the Client and the user-agent and the user-agent and
the Authorization Server, TLS sessions are terminated in the user-
agent. In addition, TLS sessions may be terminated prematurely at
some middlebox (such as a load balancer).
As the result, the Authorization Request of [RFC6749] has a property
that
(a) the communication through the user agents are not integrity
protected and thus the parameters can be tainted (integrity
protection failure);
(b) the source of the communication is not authenticated (source
authentication failure); and
(c) the communication through the user agents can be monitored
(containment / confidentiality failure).
Because of these weaknesses, several attacks against the protocol,
such as Redirection URI rewriting, has been discovered.
The use of application layer security mitigates these issues.
In addition, it allows requests to be prepared by a third party so
that a client application cannot request more permissions than
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previously agreed. This offers an additional degree of privacy
protection.
Furthermore, the request by reference allows the reduction of over-
the- wire overhead.
The JWT [RFC7519] encoding has been chosen because of
(1) its close relationship with JSON, which is used as OAuth's
response format;
(2) its developer friendliness due to its textual nature;
(3) its relative compactness compared to XML;
(4) its development status that it is an RFC and so is its
associated signing and encryption methods as [RFC7515] and
[RFC7516];
(5) the relative ease of JWS and JWE compared to XML Signature and
Encryption.
The parameters "request" and "request_uri" are introduced as
additional authorization request parameters for the OAuth 2.0
[RFC6749] flows. The "request" parameter is a JSON Web Token (JWT)
[RFC7519] whose JWT Claims Set holds the JSON encoded OAuth 2.0
authorization request parameters. This JWT is integrity protected
and source authenticated using JWS.
The JWT [RFC7519] can be passed to the authorization endpoint by
reference, in which case the parameter "request_uri" is used instead
of the "request".
Using JWT [RFC7519] as the request encoding instead of query
parameters has several advantages:
(a) (integrity protection) The request can be signed so that the
integrity of the request can be checked;
(b) (source authentication) The request can be signed so that the
signer can be authenticated;
(c) (confidentiality protection) The request can be encrypted so
that end-to-end confidentiality can be provided even if the TLS
connection is terminated at one point or another; and
(d) (collection minimization) The request can be signed by a third
party attesting that the authorization request is compliant with
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a certain policy. For example, a request can be pre-examined by
a third party that all the personal data requested is strictly
necessary to perform the process that the end-user asked for,
and statically signed by that third party. The client would
then send the request along with dynamic parameters such as
"state". The authorization server then examines the signature
and shows the conformance status to the end-user, who would have
some assurance as to the legitimacy of the request when
authorizing it. In some cases, it may even be desirable to skip
the authorization dialogue under such circumstances.
There are a few cases that request by reference is useful such as:
1. When it is desirable to reduce the size of transmitted request.
The use of application layer security increases the size of the
request, particularly when public key cryptography is used.
2. The client can make a signed Request Object and put it in a place
that the Authorization Server can access. This may just be done
by a client utility or other process, so that the private key
does not have to reside on the client, simplifying programming.
The downside of it is that the signed portion just become a
token.
3. When the server wants the requests to be cacheable: The
"request_uri" may include a SHA-256 hash of the contents of the
resources referenced by the Request Object URI. With this, the
server knows if the resource has changed without fetching it, so
it does not have to re-fetch the same content, which is a win as
well. This is explained in Section 5.2.
4. When the client does not want to do the crypto: The Authorization
Server may provide an endpoint to accept the Authorization
Request through direct communication with the Client so that the
Client is authenticated and the channel is TLS protected.
This capability is in use by OpenID Connect [OpenID.Core].
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].
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2. Terminology
For the purposes of this specification, the following terms and
definitions in addition to what is defined in OAuth 2.0 Framework
[RFC6749], JSON Web Signature [RFC7515], and JSON Web Encryption
[RFC7519] apply.
2.1. Request Object
JWT [RFC7519] that holds an OAuth 2.0 authorization request as JWT
Claims Set
2.2. Request Object URI
Absolute URI from which the Request Object (Section 2.1) can be
obtained
3. Symbols and abbreviated terms
The following abbreviations are common to this specification.
JSON Javascript Object Notation
JWT JSON Web Token
JWS JSON Web Signature
JWE JSON Web Encryption
URI Uniform Resource Identifier
URL Uniform Resource Locator
WAP Wireless Application Protocol
4. Request Object
A Request Object (Section 2.1) is used to provide authorization
request parameters for an OAuth 2.0 authorization request. It
contains OAuth 2.0 [RFC6749] authorization request parameters
including extension parameters. The parameters are represented as
the JWT claims. Parameter names and string values MUST be included
as JSON strings. Since it is a JWT, JSON strings MUST be represented
in UTF-8. Numerical values MUST be included as JSON numbers. It MAY
include any extension parameters. This JSON [RFC7159] constitutes
the JWT Claims Set defined in JWT [RFC7519]. The JWT Claims Set is
then signed, encrypted, or signed and encrypted.
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To sign, JSON Web Signature (JWS) [RFC7515] is used. The result is a
JWS signed JWT [RFC7519]. If signed, the Authorization Request
Object SHOULD contain the Claims "iss" (issuer) and "aud" (audience)
as members, with their semantics being the same as defined in the JWT
[RFC7519] specification.
To encrypt, JWE [RFC7516] is used. Unless the algorithm used in JWE
allows for the source to be authenticated, JWS signature SHOULD also
be applied so that the source authentication can be done. When both
signature and encryption are being applied, the JWT MUST be signed
then encrypted as advised in the section 11.2 of [RFC7519]. The
result is a Nested JWT, as defined in [RFC7519].
The Authorization Request Object MAY be sent by value as described in
Section 5.1 or by reference as described in Section 5.2.
Required OAuth 2.0 Authorization Request parameters that are not
included in the Request Object MUST be sent as query parameters. If
a required parameter is missing from both the query parameters and
the Request Object, the request is malformed.
"request" and "request_uri" parameters MUST NOT be included in
Request Objects.
If the parameter exists in both the query string and the
Authorization Request Object, the values in the Request Object take
precedence. This means that if it intends to use a cached request
object, it cannot include parameters such as "state" that are
expected to differ in every request. It is fine to include them in
the request object if it is going to be prepared afresh every time.
The following is a non-normative example of the Claims in a Request
Object before base64url encoding and signing. Note that it includes
extension variables such as "nonce" and "max_age".
{
"iss": "s6BhdRkqt3",
"aud": "https://server.example.com",
"response_type": "code id_token",
"client_id": "s6BhdRkqt3",
"redirect_uri": "https://client.example.org/cb",
"scope": "openid",
"state": "af0ifjsldkj",
"nonce": "n-0S6_WzA2Mj",
"max_age": 86400
}
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Signing it with the "RS256" algorithm results in this Request Object
value (with line wraps within values for display purposes only):
eyJhbGciOiJSUzI1NiIsImtpZCI6ImsyYmRjIn0.ew0KICJpc3MiOiAiczZCaGRSa3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.nwwnNsk1-Zkbmnvs
F6zTHm8CHERFMGQPhos-EJcaH4Hh-sMgk8ePrGhw_trPYs8KQxsn6R9Emo_wHwajyF
KzuMXZFSZ3p6Mb8dkxtVyjoy2GIzvuJT_u7PkY2t8QU9hjBcHs68PkgjDVTrG1uRTx
0GxFbuPbj96tVuj11pTnmFCUR6IEOXKYr7iGOCRB3btfJhM0_AKQUfqKnRlrRscc8K
ol-cSLWoYE9l5QqholImzjT_cMnNIznW9E7CDyWXTsO70xnB4SkG6pXfLSjLLlxmPG
iyon_-Te111V8uE83IlzCYIb_NMXvtTIVc1jpspnTSD7xMbpL-2QgwUsAlMGzw
The following RSA public key, represented in JWK format, can be used
to validate the Request Object signature in this and subsequent
Request Object examples (with line wraps within values for display
purposes only):
{
"kty":"RSA",
"kid":"k2bdc",
"n":"y9Lqv4fCp6Ei-u2-ZCKq83YvbFEk6JMs_pSj76eMkddWRuWX2aBKGHAtKlE5P
7_vn__PCKZWePt3vGkB6ePgzAFu08NmKemwE5bQI0e6kIChtt_6KzT5OaaXDF
I6qCLJmk51Cc4VYFaxgqevMncYrzaW_50mZ1yGSFIQzLYP8bijAHGVjdEFgZa
ZEN9lsn_GdWLaJpHrB3ROlS50E45wxrlg9xMncVb8qDPuXZarvghLL0HzOuYR
adBJVoWZowDNTpKpk2RklZ7QaBO7XDv3uR7s_sf2g-bAjSYxYUGsqkNA9b3xV
W53am_UZZ3tZbFTIh557JICWKHlWj5uzeJXaw",
"e":"AQAB"
}
5. Authorization Request
The client constructs the authorization request URI by adding one of
the following parameters but not both to the query component of the
authorization endpoint URI using the "application/x-www-form-
urlencoded" format:
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request The Request Object (Section 2.1) that holds authorization
request parameters stated in section 4 of OAuth 2.0 [RFC6749].
request_uri The absolute URL that points to the Request Object
(Section 2.1) that holds authorization request parameters stated
in section 4 of OAuth 2.0 [RFC6749].
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 end user's user-agent to make the
following HTTPS request:
GET /authz?request=eyJhbG..AlMGzw HTTP/1.1
Host: server.example.com
The value for the request parameter is abbreviated for brevity.
The authorization request object MUST be either
(a) JWS signed; or
(b) JWE encrypted (when symmetric keys are being used); or
(c) JWS signed and JWE encrypted.
When the Request Object is used, the OAuth 2.0 request parameter
values contained in the JWS Signed and/or JWE Encrypted JWT supersede
those passed using the OAuth 2.0 request syntax. Parameters MAY also
be passed using the OAuth 2.0 request syntax even when a Request
Object is used in the cases such as (a) to achieve backward
compatibility with [RFC6749] or (b) to enable a cached, pre-signed
(and possibly pre-encrypted) Request Object value to be used
containing the fixed request parameters, while parameters that can
vary with each request, such as "state" and "nonce" of OpenID
Connect, are passed as OAuth 2.0 parameters. In such case, one needs
to carefully assess the risk associated with it as unprotected
parameters would create additional attack surfaces. See Section 10.2
as well.
5.1. Passing a Request Object by Value
The Client sends the Authorization Request as a Request Object to the
Authorization Endpoint as the "request" parameter value.
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The following is a non-normative example of an Authorization Request
using the "request" parameter (with line wraps within values for
display purposes only):
https://server.example.com/authorize?
request=eyJhbGciOiJSUzI1NiIsImtpZCI6ImsyYmRjIn0.ew0KICJpc3MiOiA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.nwwnNsk1-ZkbmnvsF6zTHm8CHERFMGQPhos-EJcaH4H
h-sMgk8ePrGhw_trPYs8KQxsn6R9Emo_wHwajyFKzuMXZFSZ3p6Mb8dkxtVyjoy2
GIzvuJT_u7PkY2t8QU9hjBcHs68PkgjDVTrG1uRTx0GxFbuPbj96tVuj11pTnmFC
UR6IEOXKYr7iGOCRB3btfJhM0_AKQUfqKnRlrRscc8Kol-cSLWoYE9l5QqholImz
jT_cMnNIznW9E7CDyWXTsO70xnB4SkG6pXfLSjLLlxmPGiyon_-Te111V8uE83Il
zCYIb_NMXvtTIVc1jpspnTSD7xMbpL-2QgwUsAlMGzw
5.2. Passing a Request Object by Reference
The "request_uri" Authorization Request parameter enables OAuth
authorization requests to be passed by reference, rather than by
value. This parameter is used identically to the "request"
parameter, other than that the Request Object value is retrieved from
the resource at the specified URL, rather than passed by value.
When the "request_uri" parameter is used, the OAuth 2.0 authorization
request parameter values contained in the referenced JWT supersede
those passed using the OAuth 2.0 request syntax. Parameters MAY also
be passed using the OAuth 2.0 request syntax even when a Request
Object is used in the cases such as (a) to achieve backward
compatibility with [RFC6749] or (b) to enable a cached, pre-signed
(and possibly pre-encrypted) Request Object value to be used
containing the fixed request parameters, while parameters that can
vary with each request, such as "state" and "nonce" of OpenID
Connect, are passed as OAuth 2.0 parameters. In such case, one needs
to carefully assess the risk associated with it as unprotected
parameters would create additional attack surfaces. See Section 10.2
as well.
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Servers MAY cache the contents of the resources referenced by Request
Object URIs. If the contents of the referenced resource could ever
change, the URI SHOULD include the base64url encoded SHA-256 hash as
defined in RFC6234 [RFC6234] of the referenced resource contents as
the fragment component of the URI. If the fragment value used for a
URI changes, it signals the server that any cached value for that URI
with the old fragment value is no longer valid.
The entire Request URI MUST NOT exceed 512 ASCII characters. There
are three reasons for this restriction.
1. Many WAP / feature phones do not accept large payloads. The
restriction is typically either 512 or 1024 ASCII characters.
2. The maximum URL length supported by older versions of Internet
Explorer is 2083 ASCII characters.
3. On a slow connection such as 2G mobile connection, a large URL
would cause the slow response and therefore the use of such is
not advisable from the user experience point of view.
The contents of the resource referenced by the URL MUST be a Request
Object. The scheme used in the "request_uri" value MUST be "https",
unless the target Request Object is signed in a way that is
verifiable by the Authorization Server. The "request_uri" value MUST
be reachable by the Authorization Server, and SHOULD be reachable by
the Client.
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The following is a non-normative example of the contents of a Request
Object resource that can be referenced by a "request_uri" (with line
wraps within values for display purposes only):
eyJhbGciOiJSUzI1NiIsImtpZCI6ImsyYmRjIn0.ew0KICJpc3MiOiAiczZCaGRSa3
F0MyIsDQogImF1ZCI6ICJodHRwczovL3NlcnZlci5leGFtcGxlLmNvbSIsDQogInJl
c3BvbnNlX3R5cGUiOiAiY29kZSBpZF90b2tlbiIsDQogImNsaWVudF9pZCI6ICJzNk
JoZFJrcXQzIiwNCiAicmVkaXJlY3RfdXJpIjogImh0dHBzOi8vY2xpZW50LmV4YW1w
bGUub3JnL2NiIiwNCiAic2NvcGUiOiAib3BlbmlkIiwNCiAic3RhdGUiOiAiYWYwaW
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ODY0MDAsDQogImNsYWltcyI6IA0KICB7DQogICAidXNlcmluZm8iOiANCiAgICB7DQ
ogICAgICJnaXZlbl9uYW1lIjogeyJlc3NlbnRpYWwiOiB0cnVlfSwNCiAgICAgIm5p
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ICAgInBpY3R1cmUiOiBudWxsDQogICAgfSwNCiAgICJpZF90b2tlbiI6IA0KICAgIH
sNCiAgICAgImdlbmRlciI6IG51bGwsDQogICAgICJiaXJ0aGRhdGUiOiB7ImVzc2Vu
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F6zTHm8CHERFMGQPhos-EJcaH4Hh-sMgk8ePrGhw_trPYs8KQxsn6R9Emo_wHwajyF
KzuMXZFSZ3p6Mb8dkxtVyjoy2GIzvuJT_u7PkY2t8QU9hjBcHs68PkgjDVTrG1uRTx
0GxFbuPbj96tVuj11pTnmFCUR6IEOXKYr7iGOCRB3btfJhM0_AKQUfqKnRlrRscc8K
ol-cSLWoYE9l5QqholImzjT_cMnNIznW9E7CDyWXTsO70xnB4SkG6pXfLSjLLlxmPG
iyon_-Te111V8uE83IlzCYIb_NMXvtTIVc1jpspnTSD7xMbpL-2QgwUsAlMGzw
5.2.1. URL Referencing the Request Object
The Client stores the Request Object resource either locally or
remotely at a URL the Authorization Server can access. The URL MUST
be HTTPS URL. This URL is the Request Object URI, "request_uri".
It is possible for the Request Object to include values that are to
be revealed only to the Authorization Server. As such, the
"request_uri" MUST have appropriate entropy for its lifetime. It is
RECOMMENDED that it be removed if it is known that it will not be
used again or after a reasonable timeout unless access control
measures are taken.
Unless the access to the "request_uri" over TLS provides adequate
authentication of the source of the Request Object, the Request
Object MUST be JWS Signed.
The following is a non-normative example of a Request Object URI
value (with line wraps within values for display purposes only):
https://client.example.org/request.jwt#
GkurKxf5T0Y-mnPFCHqWOMiZi4VS138cQO_V7PZHAdM
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5.2.2. Request using the "request_uri" Request Parameter
The Client sends the Authorization Request to the Authorization
Endpoint.
The following is a non-normative example of an Authorization Request
using the "request_uri" parameter (with line wraps within values for
display purposes only):
https://server.example.com/authorize?
response_type=code%20id_token
&client_id=s6BhdRkqt3
&request_uri=https%3A%2F%2Fclient.example.org%2Frequest.jwt
%23GkurKxf5T0Y-mnPFCHqWOMiZi4VS138cQO_V7PZHAdM
&state=af0ifjsldkj
5.2.3. Authorization Server Fetches Request Object
Upon receipt of the Request, the Authorization Server MUST send an
HTTP "GET" request to the "request_uri" to retrieve the referenced
Request Object, unless it is already cached, and parse it to recreate
the Authorization Request parameters.
Note that the client SHOULD use a unique URI for each request
containing distinct parameters values, or otherwise prevent the
Authorization Server from caching the "request_uri".
The following is a non-normative example of this fetch process:
GET /request.jwt HTTP/1.1
Host: client.example.org
6. Validating JWT-Based Requests
6.1. Encrypted Request Object
The Authorization Server MUST decrypt the JWT in accordance with the
JSON Web Encryption [RFC7516] specification. If the result is a
signed request object, signature validation MUST be performed as
defined in Section 6.2 as well.
If decryption fails, the Authorization Server MUST return an
"invalid_request_object" error.
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6.2. JWS Signed Request Object
To perform JWS Signature Validation, the "alg" Header Parameter in
the JOSE Header MUST match the value of the pre-registered algorithm.
The signature MUST be validated against the appropriate key for that
"client_id" and algorithm.
If signature validation fails, the Authorization Server MUST return
an "invalid_request_object" error.
6.3. Request Parameter Assembly and Validation
The Authorization Server MUST assemble the set of Authorization
Request parameters to be used from the Request Object value and the
OAuth 2.0 Authorization Request parameters (minus the "request" or
"request_uri" parameters). If the same parameter exists both in the
Request Object and the OAuth Authorization Request parameters, the
parameter in the Request Object is used. Using the assembled set of
Authorization Request parameters, the Authorization Server then
validates the request as specified in OAuth 2.0 [RFC6749].
7. Authorization Server Response
Authorization Server Response is created and sent to the client as in
Section 4 of OAuth 2.0 [RFC6749] .
In addition, this document uses these additional error values:
invalid_request_uri The "request_uri" in the Authorization Request
returns an error or contains invalid data.
invalid_request_object The request parameter contains an invalid
Request Object.
request_not_supported The Authorization Server does not support the
use of the "request" parameter.
request_uri_not_supported The Authorization Server does not support
the use of the "request_uri" parameter.
8. TLS Requirements
Client implementations supporting the Request Object URI method MUST
support TLS following Recommendations for Secure Use of Transport
Layer Security (TLS) and Datagram Transport Layer Security (DTLS)
[RFC7525].
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To protect against information disclosure and tampering,
confidentiality protection MUST be applied using TLS with a cipher
suite that provides confidentiality and integrity protection.
Whenever TLS is used, the identity of the service provider encoded in
the TLS server certificate MUST be verified using the procedures
described in Section 6 of [RFC6125].
9. IANA Considerations
This specification requests no actions by IANA.
10. Security Considerations
In addition to the all the security considerations discussed in OAuth
2.0 [RFC6819], the security considerations in [RFC7515], [RFC7516],
and [RFC7518] needs to be considered. Also, there are several
academic papers such as [BASIN] that provide useful insight into the
security properties of protocols like OAuth.
In consideration of the above, this document advises taking the
following security considerations into account.
10.1. Choice of Algorithms
When sending the authorization request object through "request"
parameter, it MUST either be signed using JWS [RFC7515] or encrypted
using JWE [RFC7516] with then considered appropriate algorithm.
10.2. Choice of Parameters to include in the Request Object
Unless there is a compelling reason to do otherwise, it is strongly
recommended to create a request object that covers all the parameters
so that the entire request is integrity protected.
This means that the request object is going to be prepared fresh each
time an authorization request is made and caching cannot be used. It
has a performance disadvantage, but where such disadvantage is
permissible, it should be considered.
Unless the server and the client have agreed prior to the
authorization request to use the non-protected parameters, the
authorization server SHOULD reject a request that is not fully
integrity protected and source authenticated. Note that such
agreement needs to be done in a secure fashion. For example, the
developers from the server side and the client side can have a face
to face meeting to come to such an agreement.
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10.3. Request Source Authentication
The source of the Authorization Request MUST always be verified.
There are several ways to do it in this specification.
(a) Verifying the JWS Signature of the Request Object.
(b) Verifying the TLS Server Identity of the Request Object URI. In
this case, the Authorization Server MUST know out-of-band that
the Client uses Request Object URI and only the Client is
covered by the TLS certificate. In general, it is not a
reliable method.
(c) Authorization Server is providing an endpoint that provides a
Request Object URI in exchange for a Request Object. In this
case, the Authorization Server MUST perform Client
Authentication to accept the Request Object and bind the Client
Identifier to the Request Object URI it is providing. Since
Request Object URI can be replayed, the lifetime of the Request
Object URI MUST be short and preferably one-time use. The
entropy of the Request Object URI MUST be sufficiently large.
The adequate shortness of the validity and the entropy of the
Request Object URI depends on the risk calculation based on the
value of the resource being protected. A general guidance for
the validity time would be less than a minute and the Request
Object URI is to include a cryptographic random value of 128bit
or more at the time of the writing of this specification.
(d) A third party, such as a Trust Framework Provider, provides an
endpoint that provides a Request Object URI in exchange for a
Request Object. The same requirements as (b) above apply. In
addition, the Authorization Server MUST know out-of-band that
the Client utilizes the Trust Framework Operator.
10.4. Explicit Endpoints
Although this specification does not require them, research such as
[BASIN] points out that it is a good practice to explicitly state the
intended interaction endpoints and the message position in the
sequence in a tamper evident manner so that the intent of the
initiator is unambiguous. The endpoints that come into question in
this specification are
(a) Protected Resources ("protected_resources");
(b) Authorization Endpoint ("authorization_endpoint");
(c) Redirection URI ("redirect_uri"); and
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(d) Token Endpoint ("token_endpoint").
While Redirection URI is included, others are not included in the
Authorization Request Object. It is probably a good idea to include
these in it to reduce the attack surface. An extension specification
should be created as a preventive measure to address potential
vulnerabilities that have not yet been identified.
11. Privacy Considerations
When the Client is being granted access to a protected resource
containing personal data, both the Client and the Authorization
Server need to adhere to Privacy Principles. ISO/IEC 29100
[ISO29100] is a freely accessible International Standard and its
Privacy Principles are good to follow.
While ISO/IEC 29100 [ISO29100] is a high-level document that gives
general guidance, RFC 6973 Privacy Considerations for Internet
Protocols [RFC6973] gives more specific guidances on the privacy
consideration for Internet Protocols. It gives excellent guidances
on the enhancement of protocol design and implementation. The
provision listed in it should be followed.
Most of the provision would apply to The OAuth 2.0 Authorization
Framework [RFC6749] and The OAuth 2.0 Authorization Framework: Bearer
Token Usage [RFC6750] and not specific to this specification. In
what follows, only the specific provisions to this specification are
noted.
11.1. Collection limitation
When the Client is being granted access to a protected resource
containing personal data, the Client SHOULD limit the collection of
personal data to that which is within the bounds of applicable law
and strictly necessary for the specified purpose(s).
It is often hard for the user to find out if the personal data asked
for is strictly necessary. A Trust Framework Provider can help the
user by examining the Client request and comparing to the proposed
processing by the Client and certifying the request. After the
certification, the Client, when making an Authorization Request, can
submit Authorization Request to the Trust Framework Provider to
obtain the Request Object URI.
Upon receiving such Request Object URI in the Authorization Request,
the Authorization Server first verifies that the authority portion of
the Request Object URI is a legitimate one for the Trust Framework
Provider. Then, the Authorization Server issues HTTP GET request to
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the Request Object URI. Upon connecting, the Authorization Server
MUST verify the server identity represented in the TLS certificate is
legitimate for the Request Object URI. Then, the Authorization
Server can obtain the Request Object, which includes the "client_id"
representing the Client.
The Consent screen MUST indicate the Client and SHOULD indicate that
the request has been vetted by the Trust Framework Operator for the
adherence to the Collection Limitation principle.
11.2. Disclosure Limitation
11.2.1. Request Disclosure
This specification allows extension parameters. These may include
potentially sensitive information. Since URI query parameter may
leak through various means but most notably through referrer and
browser history, if the authorization request contains a potentially
sensitive parameter, the Client SHOULD JWE [RFC7516] encrypt the
request object.
Where Request Object URI method is being used, if the request object
contains personally identifiable or sensitive information, the
"request_uri" SHOULD be used only once, have a short validity period,
and MUST have large enough entropy deemed necessary with applicable
security policy unless the Request Object itself is JWE [RFC7516]
Encrypted. The adequate shortness of the validity and the entropy of
the Request Object URI depends on the risk calculation based on the
value of the resource being protected. A general guidance for the
validity time would be less than a minute and the Request Object URI
is to include a cryptographic random value of 128bit or more at the
time of the writing of this specification.
11.2.2. Tracking using Request Object URI
Even if the protected resource does not include a personally
identifiable information, it is sometimes possible to identify the
user through the Request Object URI if persistent per-user Request
Object URI is used. A third party may observe it through browser
history etc. and start correlating the user's activity using it. It
is in a way a data disclosure as well and should be avoided.
Therefore, per-user Request Object URI should be avoided.
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12. Acknowledgements
The following people contributed to the creation of this document in
the OAuth WG. (Affiliations at the time of the contribution is
used.)
Sergey Beryozkin, Brian Campbell (Ping Identity), Vladimir Dzhuvinov
(Connect2id), Michael B. Jones (Microsoft), Torsten Lodderstedt
(Deutsche Telecom) Jim Manico, Axel Nenker(Deutsche Telecom), Hannes
Tschofenig (ARM), Denis Pinkas, Kathleen Moriarty (as AD), and Steve
Kent (as SECDIR).
The following people contributed to creating this document through
the OpenID Connect Core 1.0 [OpenID.Core].
Brian Campbell (Ping Identity), George Fletcher (AOL), Ryo Itou
(Mixi), Edmund Jay (Illumila), Michael B. Jones (Microsoft), Breno
de Medeiros (Google), Hideki Nara (TACT), Justin Richer (MITRE).
In addition, the following people contributed to this and previous
versions through the OAuth Working Group.
Dirk Balfanz (Google), James H. Manger (Telstra), John Panzer
(Google), David Recordon (Facebook), Marius Scurtescu (Google), Luke
Shepard (Facebook).
13. Revision History
-11
o s/bing/being/
o Added history for -10
-10
o #20: KM1 -- some wording that is awkward in the TLS section.
o #21: KM2 - the additional attacks against OAuth 2.0 should also
have a pointer
o #22: KM3 -- Nit: in the first line of 10.4:
o #23: KM4 -- Mention RFC6973 in Section 11 in addition to ISO 29100
o #24: SECDIR review: Section 4 -- Confusing requirements for
sign+encrypt
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o #25: SECDIR review: Section 6 -- authentication and integrity need
not be provided if the requestor encrypts the token?
o #26: SECDIR Review: Section 10 -- why no reference for JWS
algorithms?
o #27: SECDIR Review: Section 10.2 - how to do the agreement between
client and server "a priori"?
o #28: SECDIR Review: Section 10.3 - Indication on "large entropy"
and "short lifetime" should be indicated
o #29: SECDIR Review: Section 10.3 - Typo
o #30: SECDIR Review: Section 10.4 - typos and missing articles
o #31: SECDIR Review: Section 10.4 - Clearer statement on the lack
of endpoint identifiers needed
o #32: SECDIR Review: Section 11 - ISO29100 needs to be moved to
normative reference
o #33: SECDIR Review: Section 11 - Better English and Entropy
language needed
o #34: Section 4: Typo
o #35: More Acknowledgment
o #36: DP - More precise qualification on Encryption needed.
-09
o Minor Editorial Nits.
o Section 10.4 added.
o Explicit reference to Security consideration (10.2) added in
section 5 and section 5.2.
o , (add yourself) removed from the acknowledgment.
-08
o Applied changes proposed by Hannes on 2016-06-29 on IETF OAuth
list recorded as https://bitbucket.org/Nat/oauth-jwsreq/
issues/12/.
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o TLS requirements added.
o Security Consideration reinforced.
o Privacy Consideration added.
o Introduction improved.
-07
o Changed the abbrev to OAuth JAR from oauth-jar.
o Clarified sig and enc methods.
o Better English.
o Removed claims from one of the example.
o Re-worded the URI construction.
o Changed the example to use request instead of request_uri.
o Clarified that Request Object parameters take precedence
regardless of request or request_uri parameters were used.
o Generalized the language in 4.2.1 to convey the intent more
clearly.
o Changed "Server" to "Authorization Server" as a clarification.
o Stopped talking about request_object_signing_alg.
o IANA considerations now reflect the current status.
o Added Brian Campbell to the contributors list. Made the lists
alphabetic order based on the last names. Clarified that the
affiliation is at the time of the contribution.
o Added "older versions of " to the reference to IE uri length
limitations.
o Stopped talking about signed or unsigned JWS etc.
o 1.Introduction improved.
-06
o Added explanation on the 512 chars URL restriction.
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o Updated Acknowledgements.
-05
o More alignment with OpenID Connect.
-04
o Fixed typos in examples. (request_url -> request_uri, cliend_id ->
client_id)
o Aligned the error messages with the OAuth IANA registry.
o Added another rationale for having request object.
-03
o Fixed the non-normative description about the advantage of static
signature.
o Changed the requirement for the parameter values in the request
itself and the request object from 'MUST MATCH" to 'Req Obj takes
precedence.
-02
o Now that they are RFCs, replaced JWS, JWE, etc. with RFC numbers.
-01
o Copy Edits.
14. References
14.1. Normative References
[ISO29100]
"ISO/IEC 29100 Information technology - Security
techniques - Privacy framework", December 2011,
<http://standards.iso.org/ittf/PubliclyAvailableStandards/
c045123_ISO_IEC_29100_2011.zip>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
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[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
2011, <http://www.rfc-editor.org/info/rfc6125>.
[RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234,
DOI 10.17487/RFC6234, May 2011,
<http://www.rfc-editor.org/info/rfc6234>.
[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012,
<http://www.rfc-editor.org/info/rfc6749>.
[RFC6750] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization
Framework: Bearer Token Usage", RFC 6750,
DOI 10.17487/RFC6750, October 2012,
<http://www.rfc-editor.org/info/rfc6750>.
[RFC6819] Lodderstedt, T., Ed., McGloin, M., and P. Hunt, "OAuth 2.0
Threat Model and Security Considerations", RFC 6819,
DOI 10.17487/RFC6819, January 2013,
<http://www.rfc-editor.org/info/rfc6819>.
[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M., and R. Smith, "Privacy
Considerations for Internet Protocols", RFC 6973,
DOI 10.17487/RFC6973, July 2013,
<http://www.rfc-editor.org/info/rfc6973>.
[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <http://www.rfc-editor.org/info/rfc7159>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <http://www.rfc-editor.org/info/rfc7515>.
[RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
RFC 7516, DOI 10.17487/RFC7516, May 2015,
<http://www.rfc-editor.org/info/rfc7516>.
[RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
DOI 10.17487/RFC7518, May 2015,
<http://www.rfc-editor.org/info/rfc7518>.
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[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<http://www.rfc-editor.org/info/rfc7519>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <http://www.rfc-editor.org/info/rfc7525>.
14.2. Informative References
[BASIN] Basin, D., Cremers, C., and S. Meier, "Provably Repairing
the ISO/IEC 9798 Standard for Entity Authentication",
Journal of Computer Security - Security and Trust
Principles Volume 21 Issue 6, Pages 817-846, November
2013,
<https://www.cs.ox.ac.uk/people/cas.cremers/downloads/
papers/BCM2012-iso9798.pdf>.
[OpenID.Core]
Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., and
C. Mortimore, "OpenID Connect Core 1.0", OpenID
Foundation Standards, February 2014,
<http://openid.net/specs/openid-connect-core-1_0.html>.
Authors' Addresses
Nat Sakimura
Nomura Research Institute
1-6-5 Marunouchi, Marunouchi Kitaguchi Bldg.
Chiyoda-ku, Tokyo 100-0005
Japan
Phone: +81-3-5533-2111
Email: n-sakimura@nri.co.jp
URI: http://nat.sakimura.org/
John Bradley
Ping Identity
Casilla 177, Sucursal Talagante
Talagante, RM
Chile
Phone: +44 20 8133 3718
Email: ve7jtb@ve7jtb.com
URI: http://www.thread-safe.com/
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