wdiff draft-ietf-oauth-jwsreq-28.original draft-ietf-oauth-jwsreq-32-xml2.txt

OAuth Working Group N. Sakimura
Internet-Draft NAT.Consulting
Intended status: Standards Track J. Bradley
Expires: February 21, October 2, 2021 Yubico
M. Jones
Microsoft
August 20, 2020
March 31, 2021

The OAuth 2.0 Authorization Framework: JWT Secured Authorization Request
(JAR)
draft-ietf-oauth-jwsreq-28
draft-ietf-oauth-jwsreq-32

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 is 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 signed
with JSON Web Signature (JWS) and encrypted with JSON Web Encryption
(JWE) 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.

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This Internet-Draft will expire on February 21, October 2, 2021.

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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 . . . . . . . . . . . . . . . . . . . . . . . 7
5. Authorization Request . . . . . . . . . . . . . . . . . . . . 9
5.1. Passing a Request Object by Value . . . . . . . . . . . . 10
5.2. Passing a Request Object by Reference . . . . . . . . . . 10
5.2.1. URI Referencing the Request Object . . . . . . . . . 11
5.2.2. Request using the "request_uri" Request Parameter . . 12
5.2.3. Authorization Server Fetches Request Object . . . . . 12
6. Validating JWT-Based Requests . . . . . . . . . . . . . . . . 13
6.1. JWE Encrypted Request Object . . . . . . . . . . . . . . 13
6.2. JWS Signed Request Object . . . . . . . . . . . . . . . . 13
6.3. Request Parameter Assembly and Validation . . . . . . . . 14
7. Authorization Server Response . . . . . . . . . . . . . . . . 14
8. TLS Requirements . . . . . . . . . . . . . . . . . . . . . . 14
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . 15
9.1. OAuth Parameters Registration . . . . . . . . . . . . . . 15
9.2. OAuth Authorization Server Metadata Registry . . . . . . 16
9.3. OAuth Dynamic Client Registration Metadata Registry . . . 16
9.4. Media Type Registration . . . . . . . . . . . . . . . . . 17
9.4.1. Registry Contents . . . . . . . . . . . . . . . . . . 17
10. Security Considerations . . . . . . . . . . . . . . . . . . . 18
10.1. Choice of Algorithms . . . . . . . . . . . . . . . . . . 18
10.2. Request Source Authentication . . . . . . . . . . . . . 18
10.3. Explicit Endpoints . . . . . . . . . . . . . . . . . . . 19
10.4. Risks Associated with request_uri . . . . . . . . . . . 19
10.4.1. DDoS Attack on the Authorization Server . . . . . . 20 19
10.4.2. Request URI Rewrite . . . . . . . . . . . . . . . . 20
10.5. Downgrade Attack . . . . . . . . . . . . . . . . . . . . 20
10.6. TLS Security Considerations . . . . . . . . . . . . . . 21
10.7. Parameter Mismatches . . . . . . . . . . . . . . . . . . 21
10.8. Cross-JWT Confusion . . . . . . . . . . . . . . . . . . 21
11. Privacy Considerations . . . . . . . . . . . . . . . . . . . 22
11.1. Collection limitation . . . . . . . . . . . . . . . . . 22
11.2. Disclosure Limitation . . . . . . . . . . . . . . . . . 23
11.2.1. Request Disclosure . . . . . . . . . . . . . . . . . 23
11.2.2. Tracking using Request Object URI . . . . . . . . . 23
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 23 24
13. Revision History . . . . . . . . . . . . . . . . . . . . . . 24
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 31
14.1. Normative References . . . . . . . . . . . . . . . . . . 31 32
14.2. Informative References . . . . . . . . . . . . . . . . . 33
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 34 35

1. Introduction

The Authorization Request in OAuth 2.0 [RFC6749] utilizes query
parameter serialization and is 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 to be used to provide confidentiality and
integrity protection. While TLS is used to offer communication
security between the Client and the user-agent as well as 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
shortcomings in that:

(a) the communication through the user agents is 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)
(c) the communication through the user agents can be monitored
(containment / confidentiality failure).

Due to these inherent weaknesses, several attacks against the
protocol, such as Redirection URI rewriting and Mix-up attack [FETT], rewriting, have been identified.

The use of application layer security mitigates these issues.

The use of application layer security allows requests to be prepared
by a trusted third party so that a client application cannot request
more permissions than previously agreed. This offers an additional degree
of privacy protection.

Furthermore, passing 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 as a Proposed Standard, along with the
associated signing and encryption methods [RFC7515] [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. Note that, in contrast to RFC
7519, the elements of the Claims Set are encoded OAuth Request
Parameters [IANA.OAuth.Parameters], supplemented with only a few of
the IANA-managed JSON Web Token Claims [IANA.JWT.Claims] - in
particular "iss" and "aud". The JWT in the "request" parameter 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 (including at
and before user-agents).

(d) (collection minimization) The request can be signed by a trusted
third party attesting that the authorization request is
compliant with a certain policy. For example, a request can be
pre-examined by a trusted third party that all the personal data
requested is strictly necessary to perform the process that the
end-user asked for, and signed by that trusted third party. 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. When the client does not want to do the application level
cryptography. 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", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.

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

JSON Web Token (JWT) [RFC7519] whose JWT Claims Set holds the JSON
encoded OAuth 2.0 authorization request parameters.

2.2. Request Object URI

Absolute URI that references the set of parameters comprising an
OAuth 2.0 authorization request. The contents of the resource
referenced by the URI are a Request Object (Section 2.1), unless the
URI was provided to the client by the same Authorization Server, in
which case the content is an implementation detail at the discretion
the Authorization Server. The former is to ensure interoperability
in cases where the provider of the request_uri is a separate entity
from the consumer, such as when a client provides a URI referencing a
Request Object stored on the client's backend service and made
accessible via HTTPS. In the latter case where the Authorization
Server is both provider and consumer of the URI, such as when it
offers an endpoint that provides a URI in exchange for a Request
Object, this interoperability concern does not apply.

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

4. Request Object

A Request Object (Section 2.1) is used to provide authorization
request parameters for an OAuth 2.0 authorization request. It MUST
contain all the parameters (including extension parameters) used to
process the OAuth 2.0 [RFC6749] authorization request except the
"request" and "request_uri" parameters that are defined in this
document. The parameters are represented as the JWT claims of the
object. Parameter names and string values MUST be included as JSON
strings. Since Request Objects are handled across domains and
potentially outside of a closed ecosystem, per section 8.1 of
[RFC8259], these JSON strings MUST be encoded using UTF-8 [RFC3629].
Numerical values MUST be included as JSON numbers. It MAY include
any extension parameters. This JSON [RFC7159] [RFC8259] object constitutes the
JWT Claims Set defined in JWT [RFC7519]. The JWT Claims Set is then
signed or signed and encrypted.

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. The value of "aud" should be the value of
the Authorization Server (AS) "issuer" as defined in RFC8414
[RFC8414].

To encrypt, JWE [RFC7516] is used. When both signature and
encryption are being applied, the JWT MUST be signed then encrypted
as described in Section 11.2 of [RFC7519]. The result is a Nested
JWT, as defined in [RFC7519].

The client determines the algorithms used to sign and encrypt Request
Objects. The algorithms chosen need to be supported by both the
client and the authorization server. The client can inform the
authorization server of the algorithms that it supports in its
dynamic client registration metadata [RFC7591], specifically, the
metadata values "request_object_signing_alg",
"request_object_encryption_alg", and "request_object_encryption_enc".
Likewise, the authorization server can inform the client of the
algorithms that it supports in its authorization server metadata
[RFC8414], specifically, the metadata values
"request_object_signing_alg_values_supported",
"request_object_encryption_alg_values_supported", and
"request_object_encryption_enc_values_supported".

The Request Object MAY be sent by value as described in Section 5.1
or by reference as described in Section 5.2. "request" and
"request_uri" parameters MUST NOT be included in Request Objects.

A Request Object (Section 2.1) has the "mime-type" "application/
oauth.authz.req+jwt".
oauth-authz-req+jwt". Note that some existing deployments may
alternatively be using the type "application/jwt".

The following is an example of the Claims in a Request Object before
base64url encoding and signing. Note that it includes the extension
parameters "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
}

Signing it with the "RS256" algorithm results in this Request Object
value (with line wraps within values for display purposes only):

eyJhbGciOiJSUzI1NiIsImtpZCI6ImsyYmRjIn0.ewogICAgImlzcyI6ICJzNkJoZF
JrcXQzIiwKICAgICJhdWQiOiAiaHR0cHM6Ly9zZXJ2ZXIuZXhhbXBsZS5jb20iLAog
ICAgInJlc3BvbnNlX3R5cGUiOiAiY29kZSBpZF90b2tlbiIsCiAgICAiY2xpZW50X2
lkIjogInM2QmhkUmtxdDMiLAogICAgInJlZGlyZWN0X3VyaSI6ICJodHRwczovL2Ns
aWVudC5leGFtcGxlLm9yZy9jYiIsCiAgICAic2NvcGUiOiAib3BlbmlkIiwKICAgIC
JzdGF0ZSI6ICJhZjBpZmpzbGRraiIsCiAgICAibm9uY2UiOiAibi0wUzZfV3pBMk1q
IiwKICAgICJtYXhfYWdlIjogODY0MDAKfQ.Nsxa_18VUElVaPjqW_ToI1yrEJ67BgK
b5xsuZRVqzGkfKrOIX7BCx0biSxYGmjK9KJPctH1OC0iQJwXu5YVY-vnW0_PLJb1C2
HG-ztVzcnKZC2gE4i0vgQcpkUOCpW3SEYXnyWnKzuKzqSb1wAZALo5f89B_p6QA6j6
JwBSRvdVsDPdulW8lKxGTbH82czCaQ50rLAg3EYLYaCb4ik4I1zGXE4fvim9FIMs8O
CMmzwIB5S-ujFfzwFjoyuPEV4hJnoVUmXR_W9typPf846lGwA8h9G9oNTIuX8Ft2jf
pnZdFmLg3_wr3Wa5q3a-lfbgF3S9H_8nN3j1i7tLR_5Nz-g
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":"x5RbkAZkmpRxia65qRQ1wwSMSxQUnS7gcpVTV_cdHmfmG2ltd2yabEO9XadD8
pJNZubINPpmgHh3J1aD9WRwS05ucmFq3CfFsluLt13_7oX5yDRSKX7poXmT_5
ko8k4NJZPMAO8fPToDTH7kHYbONSE2FYa5GZ60CUsFhSonI-dcMDJ0Ary9lxI
w5k2z4TAdARVWcS7sD07VhlMMshrwsPHBQgTatlkxyIHXbYdtak8fqvNAwr7O
lVEvM_Ipf5OfmdB8Sd-wjzaBsyP4VhJKoi_qdgSzpC694XZeYPq45Sw-q51iF
UlcOlTCI7z6jltUtnR6ySn6XDGFnzH5Fe5ypw",
"e":"AQAB"
}

5. Authorization Request

The client constructs the authorization request URI by adding the
following parameters to the query component of the authorization
endpoint URI using the "application/x-www-form-urlencoded" format:

request
REQUIRED unless "request_uri" is specified. The Request Object
(Section 2.1) that holds authorization request parameters stated
in section 4 of OAuth 2.0 [RFC6749]. If this parameter is present
in the authorization request, "request_uri" MUST NOT be present.

request_uri
REQUIRED unless "request" is specified. The absolute URI as
defined by RFC3986 [RFC3986] that is the Request Object URI
(Section 2.2) referencing the authorization request parameters
stated in section 4 of OAuth 2.0 [RFC6749]. If this parameter is
present in the authorization request, "request" MUST NOT be
present.

client_id
REQUIRED. OAuth 2.0 [RFC6749] "client_id". The value MUST match
the "request" or "request_uri" Request Object's (Section 2.1)
"client_id".

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?client_id=s6BhdRkqt3&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 one of the following:

(a) JWS signed

(b) JWS signed and JWE encrypted

The client MAY send the parameters included in the request object
duplicated in the query parameters as well for the backward
compatibility etc. However, the authorization server supporting this
specification MUST only use the parameters included in the request
object.

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.

The following is an example of an Authorization Request using the
"request" parameter (with line wraps within values for display
purposes only):

https://server.example.com/authorize?client_id=s6BhdRkqt3&
request=eyJhbGciOiJSUzI1NiIsImtpZCI6ImsyYmRjIn0.ewogICAgImlzcyI6
ICJzNkJoZFJrcXQzIiwKICAgICJhdWQiOiAiaHR0cHM6Ly9zZXJ2ZXIuZXhhbXBs
ZS5jb20iLAogICAgInJlc3BvbnNlX3R5cGUiOiAiY29kZSBpZF90b2tlbiIsCiAg
ICAiY2xpZW50X2lkIjogInM2QmhkUmtxdDMiLAogICAgInJlZGlyZWN0X3VyaSI6
ICJodHRwczovL2NsaWVudC5leGFtcGxlLm9yZy9jYiIsCiAgICAic2NvcGUiOiAi
b3BlbmlkIiwKICAgICJzdGF0ZSI6ICJhZjBpZmpzbGRraiIsCiAgICAibm9uY2Ui
OiAibi0wUzZfV3pBMk1qIiwKICAgICJtYXhfYWdlIjogODY0MDAKfQ.Nsxa_18VU
ElVaPjqW_ToI1yrEJ67BgKb5xsuZRVqzGkfKrOIX7BCx0biSxYGmjK9KJPctH1OC
0iQJwXu5YVY-vnW0_PLJb1C2HG-ztVzcnKZC2gE4i0vgQcpkUOCpW3SEYXnyWnKz
uKzqSb1wAZALo5f89B_p6QA6j6JwBSRvdVsDPdulW8lKxGTbH82czCaQ50rLAg3E
YLYaCb4ik4I1zGXE4fvim9FIMs8OCMmzwIB5S-ujFfzwFjoyuPEV4hJnoVUmXR_W
9typPf846lGwA8h9G9oNTIuX8Ft2jfpnZdFmLg3_wr3Wa5q3a-lfbgF3S9H_8nN3
j1i7tLR_5Nz-g

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 identified by the specified URI rather than passed by
value.

The entire Request URI MUST NOT exceed 512 ASCII characters. There
are three reasons for this restriction.

1. Many phones in the market as of this writing still do not accept
large payloads. The restriction is typically either 512 or 1024
ASCII characters.

2. 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 "request_uri" MUST be
a Request Object and MUST be reachable by the Authorization Server
unless the URI was provided to the client by the Authorization
Server. In the first case, the "request_uri" MUST be an "https" URI,
as specified in Section 2.7.2 of RFC7230 [RFC7230]. In the second
case, it MUST be a URN, as specified in RFC8141 [RFC8141].

The following is an 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):

5.2.1. URI Referencing the Request Object

The Client stores the Request Object resource either locally or
remotely at a URI the Authorization Server can access. Such facility
may be provided by the authorization server or a trusted third party.
For example, the authorization server may provide a URL to which the
client POSTs the request object and obtains the Request URI. This
URI 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 so that
the URI is not guessable if publicly retrievable. For the guidance,
refer to 5.1.4.2.2 of [RFC6819] and Good Practices for Capability
URLs [CapURLs]. It is RECOMMENDED that it be removed after a
reasonable timeout unless access control measures are taken.

The following is an example of a Request Object URI value (with line
wraps within values for display purposes only). In this example, a
trusted third-party Trust Framework Provider (TFP) service hosts the Request Object.

https://tfp.example.org/request.jwt/
GkurKxf5T0Y-mnPFCHqWOMiZi4VS138cQO_V7PZHAdM

5.2.2. Request using the "request_uri" Request Parameter

The Client sends the Authorization Request to the Authorization
Endpoint.

The following is an example of an Authorization Request using the
"request_uri" parameter (with line wraps within values for display
purposes only):

https://server.example.com/authorize?
client_id=s6BhdRkqt3
&request_uri=https%3A%2F%2Ftfp.example.org%2Frequest.jwt
%2FGkurKxf5T0Y-mnPFCHqWOMiZi4VS138cQO_V7PZHAdM

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 stored in a way so that it can retrieve
it through other mechanism securely, and parse it to recreate the
Authorization Request parameters.

The following is an example of this fetch process. In this example,
a trusted third-party Trust Framework Provider (TFP) service hosts the Request Object.

GET /request.jwt/GkurKxf5T0Y-mnPFCHqWOMiZi4VS138cQO_V7PZHAdM HTTP/1.1
Host: tfp.example.org
The following is an example of the fetch response:

HTTP/1.1 200 OK
Date: Thu, 20 Aug 2020 23:52:39 GMT
Server: Apache/2.4.43 (tfp.example.org)
Content-type: application/oauth.authz.req+jwt application/oauth-authz-req+jwt
Content-Length: 797
Last-Modified: Wed, 19 Aug 2020 23:52:32 GMT

6. Validating JWT-Based Requests

6.1. JWE Encrypted Request Object

If the request object is encrypted, the Authorization Server MUST
decrypt the JWT in accordance with the JSON Web Encryption [RFC7516]
specification.

The result is a signed request object.

If decryption fails, the Authorization Server MUST return an
"invalid_request_object" error.

6.2. JWS Signed Request Object

The Authorization Server MUST validate the signature of the JSON Web
Signature [RFC7515] signed Request Object. The signature MUST be
validated using the a key for that "client_id" associated with the client and the algorithm
specified in the "alg" Header Parameter. If a "kid" Header Parameter
is present, the key identified MUST be the key used, and MUST be a
key associated with the client. Algorithm verification MUST be
performed, as specified in Sections 3.1 and 3.2 of [RFC8725].

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 extract the set of Authorization
Request parameters from the Request Object value. The Authorization
Server MUST only use the parameters in the Request Object even if the
same parameter is provided in the query parameter. The Client ID
values in the "client_id" request parameter and in the Request Object
"client_id" claim MUST be identical. The Authorization Server then
validates the request as specified in OAuth 2.0 [RFC6749].

If the validation fails, then the Authorization Server MUST return an
error 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)
[BCP195].

To protect against information disclosure and tampering,
confidentiality protection MUST be applied using TLS with a cipher
suite that provides confidentiality and integrity protection.

HTTP clients MUST also verify the TLS server certificate, using DNS-
ID [RFC6125], to avoid man-in-the-middle attacks. The rules and
guidelines defined in [RFC6125] apply here, with the following
considerations:

o Support for DNS-ID identifier type (that is, the dNSName identity
in the subjectAltName extension) is REQUIRED. Certification
authorities which issue server certificates MUST support the DNS-
ID identifier type, and the DNS-ID identifier type MUST be present
in server certificates.

o DNS names in server certificates MAY contain the wildcard
character "*".

o Clients MUST NOT use CN-ID identifiers; a CN field may be present
in the server certificate's subject name, but MUST NOT be used for
authentication within the rules described in [BCP195].

o SRV-ID and URI-ID as described in Section 6.5 of [RFC6125] MUST
NOT be used for comparison.

9. IANA Considerations

9.1. OAuth Parameters Registration

Since the request object is a JWT, the core JWT claims cannot be used
for any purpose in the request object other than for what JWT
dictates. Thus, they need to be registered as OAuth Authorization
Request parameters to avoid future OAuth extensions using them with
different meanings.

This specification adds the following values to the "OAuth
Parameters" registry [IANA.OAuth.Parameters] established by
[RFC6749].

o Name: "iss"
o Parameter Usage Location: authorization request
o Change Controller: IESG IETF
o Specification Document(s): Section 4.1.1 of [RFC7519] and this
document.

o Name: "sub"
o Parameter Usage Location: authorization request
o Change Controller: IESG IETF
o Specification Document(s): Section 4.1.2 of [RFC7519] and this
document.

o Name: "aud"
o Parameter Usage Location: authorization request
o Change Controller: IETF
o Specification Document(s): Section 4.1.3 of [RFC7519] and this
document.

o Name: "exp"
o Parameter Usage Location: authorization request
o Change Controller: IETF
o Specification Document(s): Section 4.1.4 of [RFC7519] and this
document.

o Name: "nbf"
o Parameter Usage Location: authorization request
o Change Controller: IETF
o Specification Document(s): Section 4.1.5 of [RFC7519] and this
document.

o Name: "iat"
o Parameter Usage Location: authorization request
o Change Controller: IESG IETF
o Specification Document(s): Section 4.1.6 of [RFC7519] and this
document.

o Name: "jti"
o Parameter Usage Location: authorization request
o Change Controller: IESG IETF
o Specification Document(s): Section 4.1.7 of [RFC7519] and this
document.

9.2. OAuth Authorization Server Metadata Registry

This specification adds the following values to the "OAuth
Authorization Server Metadata" registry [IANA.OAuth.Parameters]
established by [RFC8414].

o Metadata Name: "require_signed_request_object"
o Metadata Description: Indicates where authorization request needs
to be protected as Request Object and provided through either
"request" or "request_uri parameter".
o Change Controller: IESG IETF
o Specification Document(s): Section 10.5 of this document.

9.3. OAuth Dynamic Client Registration Metadata Registry

This specification adds the following values to the "OAuth Dynamic
Client Registration Metadata" registry [IANA.OAuth.Parameters]
established by [RFC7591].

9.4. Media Type Registration

9.4.1. Registry Contents

This section registers the "application/oauth.authz.req+jwt" "application/oauth-authz-req+jwt" media
type [RFC2046] in the "Media Types" registry [IANA.MediaTypes] in the
manner described in [RFC6838], which can be used to indicate that the
content is a JWT containing Request Object claims.

o Type name: application
o Subtype name: oauth.authz.req+jwt oauth-authz-req+jwt
o Required parameters: n/a
o Optional parameters: n/a
o Encoding considerations: binary; A Request Object is a JWT; JWT
values are encoded as a series of base64url-encoded values (some
of which may be the empty string) separated by period ('.')
characters.
o Security considerations: See Section 10 of [[ this specification
]]
o Interoperability considerations: n/a
o Published specification: Section 4 of [[ this specification ]]
o Applications that use this media type: Applications that use
Request Objects to make an OAuth 2.0 Authorization Request
o Fragment identifier considerations: n/a
o Additional information:

Magic number(s): n/a
File extension(s): n/a
Macintosh file type code(s): n/a

o Person & email address to contact for further information:
Nat Sakimura, nat@nat.consulting
o Intended usage: COMMON
o Restrictions on usage: none
o Author: Nat Sakimura, nat@nat.consulting
o Change controller: IESG IETF
o Provisional registration? No

10. Security Considerations

In addition to the all the security considerations discussed in OAuth
2.0 [RFC6819], the security considerations in [RFC7515], [RFC7516],
[RFC7518], and [RFC8725] need 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 signed
then encrypted using JWS [RFC7515] and JWE [RFC7516] respectively,
with then considered appropriate algorithms.

10.2. Request Source Authentication

The source of the Authorization Request MUST always be verified.
There are several ways to do it:

(a) Verifying the JWS Signature of the Request Object.

(b) Verifying that the symmetric key for the JWE encryption is the
correct one if the JWE is using symmetric encryption. Note
however, that if public key encryption is used, no source
authentication is enabled by the encryption, as any party can
encrypt content to the public key.

(c) 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.

(d) When an Authorization Server implements a service that returns a
Request Object URI in exchange for a Request Object, 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. It MUST validate the
signature, per (a). 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.

(e) When a third party, such as a Trust Framework Provider(TFP),
implements a trusted third-party service that returns a Request Object URI
in exchange for a Request Object, it MUST validate the
signature, per (a). In addition, the Authorization Server MUST
be a member
of trusted by the trust framework third-party service and MUST know out-of-band
that the client is also uses the trust framework. trusted by it.

10.3. 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 following endpoints defined in
[RFC6749], [RFC6750], and [RFC8414] are RECOMMENDED by this
specification to use this practice :

(a) Protected Resources ("protected_resources")

(b) Authorization Endpoint ("authorization_endpoint")

(d) Token Endpoint ("token_endpoint")

Further, if dynamic discovery is used, then this practice also
applies to the discovery related endpoints.

In [RFC6749], while Redirection URI is included in the Authorization
Request, others are not. As a result, the same applies to
Authorization Request Object.

The lack of linkage among those endpoints is cited as the cause of
the Cross-Phase Attacks described in [FETT]. An extension
specification could be created providing this linkage as a means to
address the risks.

10.4. Risks Associated with request_uri

The introduction of "request_uri" introduces several attack
possibilities. Consult the security considerations in Section 7 of
RFC3986 [RFC3986] for more information regarding risks associated
with URIs.

10.4.1. DDoS Attack on the Authorization Server

A set of malicious client can launch a DoS attack to the
authorization server by pointing the "request_uri" to a URI that
returns extremely large content or extremely slow to respond. Under
such an attack, the server may use up its resource and start failing.

Similarly, a malicious client can specify the "request_uri" value
that itself points to an authorization request URI that uses
"request_uri" to cause the recursive lookup.

To prevent such attack to succeed, the server should (a) check that
the value of "request_uri" parameter does not point to an unexpected
location, (b) check the content type of the response is "application/
oauth.authz.req+jwt",
oauth-authz-req+jwt", (c) implement a time-out for obtaining the
content of "request_uri", and (d) not perform recursive GET on the
"request_uri".

10.4.2. Request URI Rewrite

The value of "request_uri" is not signed thus it can be tampered by
Man-in-the-browser attacker. Several attack possibilities rise
because of this, e.g., (a) attacker may create another file that the
rewritten URI points to making it possible to request extra scope (b)
attacker launches a DoS attack to a victim site by setting the value
of "request_uri" to be that of the victim.

To prevent such attack to succeed, the server should (a) check that
the value of "request_uri" parameter does not point to an unexpected
location, (b) check the content type of the response is "application/
oauth.authz.req+jwt",
oauth-authz-req+jwt", and (c) implement a time-out for obtaining the
content of "request_uri".

10.5. Downgrade Attack

Unless the protocol used by client and the server is locked down to
use OAuth JAR, it is possible for an attacker to use RFC6749 requests
to bypass all the protection provided by this specification.

To prevent it, this specification defines a new client metadata and
server metadata "require_signed_request_object" whose value is a
boolean.

When the value of it as a client metadata is "true", then the server
MUST reject the authorization request from the client that does not
conform to this specification. It MUST also reject the request if
the request object uses "alg":"none". If omitted, the default value
is "false".

When the value of it as a server metadata is "true", then the server
MUST reject the authorization request from any client that does not
conform to this specification. It MUST also reject the request if
the request object uses "alg":"none". If omitted, the default value
is "false".

10.6. TLS Security Considerations

Current security considerations can be found in Recommendations for
Secure Use of TLS and DTLS [BCP195]. This supersedes the TLS version
recommendations in OAuth 2.0 [RFC6749].

10.7. Parameter Mismatches

Given that OAuth parameter values are being sent in two different
places, as normal OAuth parameters and as Request Object claims,
implementations must guard against attacks that could use mismatching
parameter values to obtain unintended outcomes. That is the reason
that the two Client ID values MUST match, the reason that only the
parameter values from the Request Object are to be used, and the
reason that neither "request" nor "request_uri" can appear in a
Request Object.

10.8. Cross-JWT Confusion

As described in Section 2.8 of [RFC8725], attackers may attempt to
use a JWT issued for one purpose in a context that it was not
intended for. The mitigations described for these attacks can be
applied to Request Objects.

One way that an attacker might attempt to repurpose a Request Object
is to try to use it as a client authentication JWT, as described in
Section 2.2 of [RFC7523]. A simple way to prevent this is to never
use the Client ID as the "sub" value in a Request Object.

Another way to prevent cross-JWT confusion is to use explicit typing,
as described in Section 3.11 of [RFC8725]. One would explicitly type
a Request Object by including a "typ" Header Parameter with the value
"oauth.authz.req+jwt"
"oauth-authz-req+jwt" (which is registered in Section 9.4.1. Note
however, that requiring explicitly typed Requests Objects at existing
authorization servers will break most existing deployments, as
existing clients are already commonly using untyped Request Objects,
especially with OpenID Connect [OpenID.Core]. However, requiring
explicit typing would be a good idea for new OAuth deployment
profiles where compatibility with existing deployments is not a
consideration.

Finally, yet another way to prevent cross-JWT confusion is to use a
key management regime in which keys used to sign Request Objects are
identifiably distinct from those used for other purposes. Then, if
an adversary attempts to repurpose the Request Object in another
context, a key mismatch will occur, thwarting the attack.

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. RFC 6973 Privacy
Considerations for Internet Protocols [RFC6973] gives excellent
guidance 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 are 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 trusted third-party service 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 trusted third-party service
to obtain the Request Object URI. This process is two steps:

(1) (Certification Process) The TFP examines the business process of
the client and determines what claims they need: This is the
certification process. Once the client is certified, then they
are issued a client credential to authenticate against to push
request objects to the TFP to get the "request_uri".

(2) (Translation Process) The client uses the client credential that
it got to push the request object to the TFP to get the
"request_uri". The TFP also verifies that the Request Object is
consistent with the claims that the client is eligible for, per
prior step.

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. trusted third-
party service. Then, the Authorization Server issues HTTP GET
request to 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 trusted third-party service 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 static per-user
Request Object URIs are used. A third party may observe it through
browser history etc. and start correlating the user's activity using
it. In a way, it is a data disclosure as well and should be avoided.

Therefore, per-user persistent Request Object URIs should be avoided.
Single-use Request Object URIs are one alternative.

12. Acknowledgements

The following people contributed to the creation of this document in
the OAuth working group and other IETF roles. (Affiliations at the
time of the contribution are used.)

Annabelle Backman (Amazon), Sergey Beryozkin, Ben Campbell (as AD),
Brian Campbell (Ping Identity), Roman Danyliw (as AD), Vladimir
Dzhuvinov (Connect2id), Joel Halpern (as GENART), Benjamin Kaduk (as
AD), Stephen Kent (as SECDIR), Murray Kucherawy (as AD), Warren
Kumari (as OPSDIR), Watson Ladd (as SECDIR), Torsten Lodderstedt
(yes.com), Jim Manico, Axel Nennker (Deutsche Telecom), Hannes
Tschofenig (ARM), Dirk Balfanz (Google), James H. Manger (Telstra),
Kathleen Moriarty (as AD), John Panzer (Google), David Recordon
(Facebook), Marius Scurtescu (Google), Luke Shepard (Facebook), Filip
Skokan (Auth0), Eric Vyncke (as AD), and Robert Wilton (as AD).

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), Breno de Medeiros (Google), Hideki
Nara (TACT), Justin Richer (MITRE).

13. Revision History

Note to the RFC Editor: Please remove this section from the final
RFC.

-32

o Addressed SecDir review comments by Watson Ladd.

-30

o Changed the MIME Type from "oauth.authz.req+jwt" to "oauth-authz-
req+jwt", per advice from the designated experts.

-29

o Uniformly use the Change Controller "IETF".

-28

o Removed unused references, as suggested by Roman Danyliw.

-27
o Edits by Mike Jones to address IESG and working group review
comments, including:

o Added Security Considerations text saying not to use the Client ID
as the "sub" value to prevent Cross-JWT Confusion.

o Added Security Considerations text about using explicit typing to
prevent Cross-JWT Confusion.

o Addressed Eric Vyncke's review comments.

o Addressed Robert Wilton's review comments.

o Addressed Murray Kucherawy's review comments.

o Addressed Benjamin Kaduk's review comments.

o Applied spelling and grammar corrections.

-20

o BK comments

o Section 3 Removed WAP

o Section 4. Clarified authorization request object parameters,
removed extension parameters from examples

o Section 4. Specifies application/oauth.authz.req+jwt as mime-type
fore request objects

o Section 5.2.1 Added reference to Capability URLs

o Section 5.2.3. Added entropy fragment to example request

o Section 8. Replaced "subjectAltName dnsName" with "DNS-ID"

o Section 9. Registers authorization request parameters in JWT
Claims Registry.

o Section 9. Registers application/oauth.authz.req in IANA mime-
types registry

o Section 10.1. Clarified encrypted request objects are "signed
then encrypted" to maintain consistency

o Section 10.2. Clarifies trust between AS and TFP
o Section 10.3. Clarified endpoints subject to the practice

o Section 10.4 Replaced "redirect_uri" to "request_uri"

o Section 10.4. Added reference to RFC 3986 for risks

o Section 10.4.1.d Deleted "do" to maintain grammar flow

o Section 10.4.1, 10.4.2 Replaced "application/jose" to
"application/jwt"

o Section 12.1. Extended description for submitting authorization
request to TFP to obtain request object

o Section 12.2.2. Replaced per-user Request Object URI with static
per-user Request URIs

o Section 13. Combined OAuth WG contributors together

o Section Whole doc Replaced application/jwt with application/
oauth.authz.req+jwt

-19

o AD comments

o Section 5.2.1. s/Requiest URI/Request URI/

o Section 8 s/[BCP195] ./[BCP195]./

o Section 10.3. s/sited/cited/

o Section 11. Typo. s/Curent/Current/

-17

o #78 Typos in content-type

-16

o Treated remaining Ben Campbell comments.

-15

o Removed further duplication

-14
o #71 Reiterate dynamic params are included.

o #70 Made clear that AS must return error.

o #69 Inconsistency of the need to sign.

o Fixed Mimetype.

o #67 Inconsistence in requiring HTTPS in request URI.

o #66 Dropped ISO 29100 reference.

o #25 Removed Encrypt only option.

o #59 Same with #25.

-13

o add TLS Security Consideration section

o replace RFC7525 reference with BCP195

o moved front tag in FETT reference to fix XML structure

o changes reference from SoK to FETT

-12

o fixes #62 - Alexey Melnikov Discuss

o fixes #48 - OPSDIR Review : General - delete semicolons after list
items

o fixes #58 - DP Comments for the Last Call

o fixes #57 - GENART - Remove "non-normative ... " from examples.

o fixes #45 - OPSDIR Review : Introduction - are attacks discovered
or already opened

o fixes #49 - OPSDIR Review : Introduction - Inconsistent colons
after initial sentence of list items.

o fixes #53 - OPSDIR Review : 6.2 JWS Signed Request Object -
Clarify JOSE Header

o fixes #42 - OPSDIR Review : Introduction - readability of 'and' is
confusing
o fixes #50 - OPSDIR Review : Section 4 Request Object - Clarify
'signed, encrypted, or signed and encrypted'

o fixes #39 - OPSDIR Review : Abstract - Explain/Clarify JWS and JWE

o fixed #50 - OPSDIR Review : Section 4 Request Object - Clarify
'signed, encrypted, or signed and encrypted'

o fixes #43 - OPSDIR Review : Introduction - 'properties' sounds
awkward and are not exactly 'properties'

o fixes #56 - OPSDIR Review : 12 Acknowledgements - 'contribution
is' => 'contribution are'

o fixes #55 - OPSDIR Review : 11.2.2 Privacy Considerations - ' It
is in a way' => 'In a way, it is'

o fixes #54 - OPSDIR Review : 11 Privacy Considerations - 'and not
specific' => 'and are not specific'

o fixes #51 - OPSDIR Review : Section 4 Request Object - 'It is
fine' => 'It is recommended'

o fixes #47 - OPSDIR Review : Introduction - 'over- the- wire' =>
'over-the-wire'

o fixes #46 - OPSDIR Review : Introduction - 'It allows' => 'The use
of application security' for

o fixes #44 - OPSDIR Review : Introduction - 'has' => 'have'

o fixes #41 - OPSDIR Review : Introduction - missing 'is' before
'typically sent'

o fixes #38 - OPSDIR Review : Section 11 - Delete 'freely
accessible' regarding ISO 29100

-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

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/.

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.

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

[BCP195] 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, May 2015.

[IANA.MediaTypes]
IANA, "Media Types",
<http://www.iana.org/assignments/media-types>.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.

[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <https://www.rfc-editor.org/info/rfc3629>.

[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.

[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, <https://www.rfc-editor.org/info/rfc6125>.

[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012,
<https://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,
<https://www.rfc-editor.org/info/rfc6750>.

[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <https://www.rfc-editor.org/info/rfc7159>.

[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014,
<https://www.rfc-editor.org/info/rfc7230>.

[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <https://www.rfc-editor.org/info/rfc7515>.

[RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
RFC 7516, DOI 10.17487/RFC7516, May 2015,
<https://www.rfc-editor.org/info/rfc7516>.

[RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
DOI 10.17487/RFC7518, May 2015,
<https://www.rfc-editor.org/info/rfc7518>.

[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/info/rfc7519>.

[RFC8141] Saint-Andre, P. and J. Klensin, "Uniform Resource Names
(URNs)", RFC 8141, DOI 10.17487/RFC8141, April 2017,
<https://www.rfc-editor.org/info/rfc8141>.

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.

[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>.

[RFC8414] Jones, M., Sakimura, N., and J. Bradley, "OAuth 2.0
Authorization Server Metadata", RFC 8414,
DOI 10.17487/RFC8414, June 2018,
<https://www.rfc-editor.org/info/rfc8414>.

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>.

[CapURLs] Tennison, J., "Good Practices for Capability URLs",
W3C Working Draft, February 2014,
<https://www.w3.org/TR/capability-urls/>.

[FETT] Fett, D., Kusters, R., and G. Schmitz, "A Comprehensive
Formal Security Analysis of OAuth 2.0", CCS '16
Proceedings of the 2016 ACM SIGSAC Conference on Computer
and Communications Security Pages 1204-1215 , October
2016, <https://arxiv.org/pdf/1601.01229v2.pdf>.

[IANA.JWT.Claims]
IANA, "JSON Web Token Claims",
<http://www.iana.org/assignments/jwt>.

[IANA.OAuth.Parameters]
IANA, "OAuth Parameters",
<http://www.iana.org/assignments/oauth-parameters>.

[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>.

[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
DOI 10.17487/RFC2046, November 1996,
<https://www.rfc-editor.org/info/rfc2046>.

[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,
<https://www.rfc-editor.org/info/rfc6819>.

[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013,
<https://www.rfc-editor.org/info/rfc6838>.

[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,
<https://www.rfc-editor.org/info/rfc6973>.

[RFC7523] Jones, M., Campbell, B., and C. Mortimore, "JSON Web Token
(JWT) Profile for OAuth 2.0 Client Authentication and
Authorization Grants", RFC 7523, DOI 10.17487/RFC7523, May
2015, <https://www.rfc-editor.org/info/rfc7523>.

[RFC7591] Richer, J., Ed., Jones, M., Bradley, J., Machulak, M., and
P. Hunt, "OAuth 2.0 Dynamic Client Registration Protocol",
RFC 7591, DOI 10.17487/RFC7591, July 2015,
<https://www.rfc-editor.org/info/rfc7591>.

[RFC8725] Sheffer, Y., Hardt, D., and M. Jones, "JSON Web Token Best
Current Practices", BCP 225, RFC 8725,
DOI 10.17487/RFC8725, February 2020,
<https://www.rfc-editor.org/info/rfc8725>.

Authors' Addresses

Nat Sakimura
NAT.Consulting
2-22-17 Naka
Kunitachi, Tokyo 186-0004
Japan

Phone: +81-42-580-7401
Email: nat@nat.consulting
URI: http://nat.sakimura.org/

John Bradley
Yubico
Casilla 177, Sucursal Talagante
Talagante, RM
Chile

Phone: +1.202.630.5272
Email: ve7jtb@ve7jtb.com
URI: http://www.thread-safe.com/

Michael B. Jones
Microsoft
One Microsoft Way
Redmond, Washington 98052
United States of America

Email: mbj@microsoft.com
URI: https://self-issued.info/