OAuth 2.0 Pushed Authorization Requests
draft-ietf-oauth-par-03
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| Document | Type | Active Internet-Draft (oauth WG) | |
|---|---|---|---|
| Authors | Torsten Lodderstedt , Brian Campbell , Nat Sakimura , Dave Tonge , Filip Skokan | ||
| Last updated | 2020-07-31 | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text html xml htmlized pdfized bibtex | ||
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draft-ietf-oauth-par-03
Web Authorization Protocol T. Lodderstedt
Internet-Draft yes.com
Intended status: Standards Track B. Campbell
Expires: 1 February 2021 Ping Identity
N. Sakimura
NAT.Consulting
D. Tonge
Moneyhub Financial Technology
F. Skokan
Auth0
31 July 2020
OAuth 2.0 Pushed Authorization Requests
draft-ietf-oauth-par-03
Abstract
This document defines the pushed authorization request endpoint,
which allows clients to push the payload of an OAuth 2.0
authorization request to the authorization server via a direct
request and provides them with a request URI that is used as
reference to the data in a subsequent authorization request.
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 https://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 1 February 2021.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://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 . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions and Terminology . . . . . . . . . . . . . . . 5
2. Pushed Authorization Request Endpoint . . . . . . . . . . . . 5
2.1. Request . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2. Successful Response . . . . . . . . . . . . . . . . . . . 8
2.3. Error Response . . . . . . . . . . . . . . . . . . . . . 9
3. "request" Parameter . . . . . . . . . . . . . . . . . . . . . 10
4. Authorization Request . . . . . . . . . . . . . . . . . . . . 12
5. Authorization Server Metadata . . . . . . . . . . . . . . . . 13
6. Client Metadata . . . . . . . . . . . . . . . . . . . . . . . 13
7. Security Considerations . . . . . . . . . . . . . . . . . . . 14
7.1. Request URI Guessing . . . . . . . . . . . . . . . . . . 14
7.2. Open Redirection . . . . . . . . . . . . . . . . . . . . 14
7.3. Request Object Replay . . . . . . . . . . . . . . . . . . 14
7.4. Client Policy Change . . . . . . . . . . . . . . . . . . 14
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
9.1. OAuth Authorization Server Metadata . . . . . . . . . . . 15
9.2. OAuth Dynamic Client Registration Metadata . . . . . . . 15
9.3. OAuth URI Registration . . . . . . . . . . . . . . . . . 15
10. Normative References . . . . . . . . . . . . . . . . . . . . 15
11. Informative References . . . . . . . . . . . . . . . . . . . 16
Appendix A. Document History . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction
In OAuth [RFC6749] authorization request parameters are typically
sent as URI query parameters via redirection in the user-agent. This
is simple but also yields challenges:
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* There is no cryptographic integrity and authenticity protection.
An attacker could, for example, modify the ACR value requested by
the client or swap the context of a payment transaction
authorization by changing scope values. Although clients should
detect such changes by inspecting the token response data,
preventing such modifications early in the process would be a
better solution.
* There is no mechanism to ensure confidentiality of the request
parameters. This obviously is an issue if personal identifiable
information is sent in the authorization request, which might be
the case in identity and open banking scenarios.
* Authorization request URLs can become quite large, especially in
scenarios requiring fine-grained authorization data, which might
cause errors in request processing.
JWT Secured Authorization Request (JAR) [I-D.ietf-oauth-jwsreq]
provides solutions for the security challenges by allowing OAuth
clients to wrap authorization request parameters in a signed, and
optionally encrypted, JSON Web Token (JWT), the so-called "Request
Object". In order to cope with the size restrictions, JAR introduces
the "request_uri" parameter that allows clients to send a reference
to a request object instead of the request object itself.
This document complements JAR by providing an interoperable way to
push the payload of a request object directly to the authorization
server in exchange for a "request_uri".
It also allows for clients to push the form encoded authorization
request parameters to the authorization server in order to exchange
them for a request URI that the client can use in a subsequent
authorization request.
For example, a client typically initiates an authorization request by
directing the user-agent to make an HTTP request like the following:
GET /authorize?response_type=code
&client_id=s6BhdRkqt3&state=af0ifjsldkj
&redirect_uri=https%3A%2F%2Fclient.example.org%2Fcb HTTP/1.1
Host: as.example.com
Such a request could instead be pushed directly to the authorization
server by the client as follows:
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POST /as/par HTTP/1.1
Host: as.example.com
Content-Type: application/x-www-form-urlencoded
Authorization: Basic czZCaGRSa3F0Mzo3RmpmcDBaQnIxS3REUmJuZlZkbUl3
response_type=code
&client_id=s6BhdRkqt3&state=af0ifjsldkj
&redirect_uri=https%3A%2F%2Fclient.example.org%2Fcb
The authorization server responds with a request URI:
HTTP/1.1 201 Created
Cache-Control: no-cache, no-store
Content-Type: application/json
{
"request_uri": "urn:example:bwc4JK-ESC0w8acc191e-Y1LTC2",
"expires_in": 90
}
The client uses the request URI value to create the subsequent
authorization request and directing the user-agent to make an HTTP
request like the following:
GET /authorize?client_id=s6BhdRkqt3&
request_uri=urn%3Aexample%3Abwc4JK-ESC0w8acc191e-Y1LTC2 HTTP/1.1
Host: as.example.com
The pushed authorization request endpoint fosters OAuth security by
providing all clients a simple means for a confidential and integrity
protected authorization request, but it also allows clients requiring
an even higher security level, especially cryptographically confirmed
non-repudiation, to explicitly adopt JWT-based request objects.
As a further benefit, the pushed authorization request allows the
authorization server to authenticate the clients before any user
interaction happens, i.e., the authorization server may refuse
unauthorized requests much earlier in the process and has much higher
confidence in the client's identity in the authorization process than
before. This generally improves security since it prevents attempts
to spoof confidential clients early in the process.
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This is directly utilized by this draft to allow confidential clients
to set the redirect URI for every authorization request, which gives
them more flexibility in building redirect URI. And if the client
IDs and credentials are managed by some external authority (e.g. a
certification authority), explicit client registration with the
particular authorization server could practically be skipped.
Note: HTTP POST requests to the authorization endpoint as described
in Section 3.1 of [RFC6749] and Section 3.1.2.1 of [OIDC] could also
be used to cope with the request size limitations described above.
Although this is a viable option for traditional web applications,
it's difficult to use with mobile apps. Those apps typically invoke
a custom tab with an URL that is translated into a GET request.
Using POST would require the app to first open a web page under its
control in the custom tab that in turn would initiate the form POST
towards the authorization server. PAR is simpler to use and has
additional security benefits as described above.
1.1. Conventions and Terminology
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.
This specification uses the terms "access token", "refresh token",
"authorization server", "resource server", "authorization endpoint",
"authorization request", "authorization response", "token endpoint",
"grant type", "access token request", "access token response", and
"client" defined by The OAuth 2.0 Authorization Framework [RFC6749].
2. Pushed Authorization Request Endpoint
The pushed authorization request endpoint is an HTTP API at the
authorization server that accepts POST requests with parameters in
the HTTP request entity-body using the "application/x-www-form-
urlencoded" format with a character encoding of UTF-8 as described in
Appendix B of [RFC6749]. The pushed authorization request endpoint
URL MUST use the "https" scheme.
Authorization servers supporting pushed authorization requests SHOULD
include the URL of their pushed authorization request endpoint in
their authorization server metadata document [RFC8414] using the
"pushed_authorization_request_endpoint" parameter as defined in
Section 5.
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The endpoint accepts the parameters defined in [RFC6749] for the
authorization endpoint as well as all applicable extensions defined
for the authorization endpoint. Some examples of such extensions
include PKCE [RFC7636], Resource Indicators [RFC8707], and OpenID
Connect [OIDC]. The endpoint also supports sending all authorization
request parameters as request object according to
[I-D.ietf-oauth-jwsreq].
The rules for client authentication as defined in [RFC6749] for token
endpoint requests, including the applicable authentication methods,
apply for the pushed authorization request endpoint as well. If
applicable, the "token_endpoint_auth_method" client metadata
parameter indicates the registered authentication method for the
client to use when making direct requests to the authorization
server, including requests to the pushed authorization request
endpoint.
Note that there's some potential ambiguity around the appropriate
audience value to use when JWT client assertion based authentication
is employed. To address that ambiguity the issuer identifier URL of
the authorization server according to [RFC8414] SHOULD be used as the
value of the audience. In order to facilitate interoperability the
authorization server MUST accept its issuer identifier, token
endpoint URL, or pushed authorization request endpoint URL as values
that identify it as an intended audience.
2.1. Request
A client can send all the parameters that usually comprise an
authorization request to the pushed authorization request endpoint.
A basic parameter set will typically include:
* "client_id"
* "response_type"
* "redirect_uri"
* "scope"
* "state"
* "code_challenge"
* "code_challenge_method"
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Depending on client type and authentication method, the request might
also include other parameters for client authentication such as the
"client_secret" parameter, the "client_assertion" parameter and the
"client_assertion_type" parameter. The "request_uri" authorization
request parameter MUST NOT be provided in this case (see Section 3).
The client adds the parameters in "x-www-form-urlencoded" format with
a character encoding of UTF-8 as described in Appendix B of [RFC6749]
to the body of an HTTP POST request. If applicable, the client also
adds client credentials to the request header or the request body
using the same rules as for token endpoint requests.
This is illustrated by the following example:
POST /as/par HTTP/1.1
Host: as.example.com
Content-Type: application/x-www-form-urlencoded
Authorization: Basic czZCaGRSa3F0Mzo3RmpmcDBaQnIxS3REUmJuZlZkbUl3
response_type=code&
state=af0ifjsldkj&
client_id=s6BhdRkqt3&
redirect_uri=https%3A%2F%2Fclient.example.org%2Fcb&
code_challenge=K2-ltc83acc4h0c9w6ESC_rEMTJ3bww-uCHaoeK1t8U&
code_challenge_method=S256&
scope=ais
The authorization server MUST process the request as follows:
1. Authenticate the client in the same way as at the token endpoint.
2. Reject the request if the "request_uri" authorization request
parameter is provided.
3. Validate the pushed request as it would an authorization request
sent to the authorization endpoint. For example, the
authorization server checks whether the redirect URI matches one
of the redirect URIs configured for the client and also checks
whether the client is authorized for the scope for which it is
requesting access. This validation allows the authorization
server to refuse unauthorized or fraudulent requests early. The
authorization server MAY omit validation steps that it is unable
to perform when processing the pushed request, however such
checks MUST then be performed at the authorization endpoint.
The authorization server MAY allow confidential clients to establish
per-authorization request redirect URIs with every pushed
authorization request. This is possible since, in contrast to
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[RFC6749], this specification gives the authorization server the
ability to authenticate and authorize clients before the actual
authorization request is performed.
This feature gives clients more flexibility in building redirect URIs
and, if the client IDs and credentials are managed by some authority
(CA or other type), the explicit client registration with the
particular authorization server (manually or via dynamic client
registration [RFC7591]) could practically be skipped. This makes
this mechanism especially useful for clients interacting with a
federation of authorization servers (or OpenID Connect Providers),
for example in Open Banking, where the certificate is provided as
part of a federated PKI.
2.2. Successful Response
If the verification is successful, the server MUST generate a request
URI and return a JSON response with the following members at the top
level with "201 Created" HTTP response code.
* "request_uri" : The request URI corresponding to the authorization
request posted. This URI is used as reference to the respective
request data in the subsequent authorization request only. The
way the authorization process obtains the authorization request
data is at the discretion of the authorization server and out of
scope of this specification. There is no need to make the
authorization request data available to other parties via this
URI.
* "expires_in" : A JSON number that represents the lifetime of the
request URI in seconds. The request URI lifetime is at the
discretion of the authorization server and will typically be
relatively short.
The format of the "request_uri" value is at the discretion of the
authorization server but it MUST contain some part generated using a
cryptographically strong pseudorandom algorithm such that it is
computationally infeasible to predict or guess a valid value. The
authorization server MAY construct the "request_uri" value using the
form "urn:ietf:params:oauth:request_uri:<reference-value>" with
"<reference-value>" as the random part of the URI that references the
respective authorization request data. The string representation of
a UUID as a URN per [RFC4122] is also an option for authorization
servers to construct "request_uri" values.
The "request_uri" MUST be bound to the client that posted the
authorization request.
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Since parts of the request content, e.g. the "code_challenge"
parameter value, is unique to a certain authorization request, a
"request_uri" SHOULD be limited to one-time use.
The following is an example of such a response:
HTTP/1.1 201 Created
Content-Type: application/json
Cache-Control: no-cache, no-store
{
"request_uri":
"urn:ietf:params:oauth:request_uri:bwc4JK-ESC0w8acc191e-Y1LTC2",
"expires_in": 60
}
2.3. Error Response
For an error the authorization server sets an appropriate HTTP status
code and MAY include additional error parameters in the entity-body
of the HTTP response using the format specified for the token
endpoint in Section 5.2 of [RFC6749].
If the authorization server sets an error code, it SHOULD be one of
the defined codes for the token endpoint in Section 5.2 or for the
authorization endpoint in Sections 4.1.2.1 and 4.2.2.1 of [RFC6749],
or by an OAuth extension if one is involved in the initial processing
of authorization request that was pushed. Since initial processing
of the pushed authorization request doesn't involve resource owner
interaction, error codes related to user interaction, such as
"consent_required" defined by [OIDC], are not returned.
If the client is required to use signed request objects, either by
authorization server or client policy (see [I-D.ietf-oauth-jwsreq],
section 10.5), the authorization server MUST only accept requests
complying with the definition given in Section 3 and MUST refuse any
other request with HTTP status code 400 and error code
"invalid_request".
In addition to the error codes above, the pushed authorization
request endpoint can also make use of the following HTTP status
codes:
* 405: If the request did not use POST, the authorization server
responds with an HTTP 405 (Method Not Allowed) status code.
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* 413: If the request size was beyond the upper bound that the
authorization server allows, the authorization server responds
with an HTTP 413 (Payload Too Large) status code.
* 429: If the request from the client for a time period goes beyond
the number the authorization server allows, the authorization
server responds with an HTTP 429 (Too Many Requests) status code.
The following is an example of an error response from the pushed
authorization request endpoint:
HTTP/1.1 400 Bad Request
Content-Type: application/json
Cache-Control: no-cache, no-store
{
"error": "invalid_request",
"error_description":
"The redirect_uri is not valid for the given client"
}
3. "request" Parameter
Clients MAY use the "request" parameter as defined in JAR
[I-D.ietf-oauth-jwsreq] to push a request object JWT to the
authorization server. The rules for processing, signing, and
encryption of the request object as defined in JAR
[I-D.ietf-oauth-jwsreq] apply. When the "application/x-www-form-
urlencoded" HTTP entity-body "request" parameter is used, the request
object MUST contain all the authorization request parameters as
claims of the JWT. Additional request parameters as required by the
given client authentication method are to be included as
'application/x-www-form-urlencoded' parameters in the HTTP request
entity-body (e.g. Mutual TLS client authentication
[I-D.ietf-oauth-mtls] uses the "client_id" HTTP request parameter
while JWT assertion based client authentication [RFC7523] uses
"client_assertion" and "client_assertion_type").
The following is an example of a pushed authorization request using a
signed request object. The client is authenticated by its client
secret using the HTTP Basic Authentication scheme specified in
Section 2.3.1 of [RFC6749]:
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POST /as/par HTTP/1.1
Host: as.example.com
Content-Type: application/x-www-form-urlencoded
Authorization: Basic czZCaGRSa3F0Mzo3RmpmcDBaQnIxS3REUmJuZlZkbUl3
request=eyJraWQiOiJrMmJkYyIsImFsZyI6IlJTMjU2In0.eyJpc3MiOiJzNkJoZ
FJrcXQzIiwiYXVkIjoiaHR0cHM6Ly9zZXJ2ZXIuZXhhbXBsZS5jb20iLCJyZXNwb2
5zZV90eXBlIjoiY29kZSIsImNsaWVudF9pZCI6InM2QmhkUmtxdDMiLCJyZWRpcmV
jdF91cmkiOiJodHRwczovL2NsaWVudC5leGFtcGxlLm9yZy9jYiIsInNjb3BlIjoi
YWlzIiwic3RhdGUiOiJhZjBpZmpzbGRraiIsImNvZGVfY2hhbGxlbmdlIjoiSzItb
HRjODNhY2M0aDBjOXc2RVNDX3JFTVRKM2J3dy11Q0hhb2VLMXQ4VSIsImNvZGVfY2
hhbGxlbmdlX21ldGhvZCI6IlMyNTYifQ.O49ffUxRPdNkN3TRYDvbEYVr1CeAL64u
W4FenV3n9WlaFIRHeFblzv-wlEtMm8-tusGxeE9z3ek6FxkhvvLEqEpjthXnyXqqy
Jfq3k9GSf5ay74ml_0D6lHE1hy-kVWg7SgoPQ-GB1xQ9NRhF3EKS7UZIrUHbFUCF0
MsRLbmtIvaLYbQH_Ef3UkDLOGiU7exhVFTPeyQUTM9FF-u3K-zX-FO05_brYxNGLh
VkO1G8MjqQnn2HpAzlBd5179WTzTYhKmhTiwzH-qlBBI_9GLJmE3KOipko9TfSpa2
6H4JOlMyfZFl0PCJwkByS0xZFJ2sTo3Gkk488RQohhgt1I0onw
The authorization server needs to take the following steps beyond the
processing rules defined in Section 2.1:
1. If applicable, decrypt the request object as specified in JAR
[I-D.ietf-oauth-jwsreq], section 6.1.
2. Validates the request object signature as specified in JAR
[I-D.ietf-oauth-jwsreq], section 6.2.
3. If the client is a confidential client, the authorization server
MUST check whether the authenticated "client_id" matches the
"client_id" claim in the request object. If they do not match,
the authorization server MUST refuse to process the request. It
is at the authorization server's discretion to require the "iss"
claim to match the "client_id" as well.
The following RSA key pair, represented in JWK [RFC7517] format, can
be used to validate or recreate the request object signature in the
above example (line wraps within values for display purposes only):
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{
"kty": "RSA",
"kid":"k2bdc",
"n": "y9Lqv4fCp6Ei-u2-ZCKq83YvbFEk6JMs_pSj76eMkddWRuWX2aBKGHAtKlE
5P7_vn__PCKZWePt3vGkB6ePgzAFu08NmKemwE5bQI0e6kIChtt_6KzT5Oa
aXDFI6qCLJmk51Cc4VYFaxgqevMncYrzaW_50mZ1yGSFIQzLYP8bijAHGVj
dEFgZaZEN9lsn_GdWLaJpHrB3ROlS50E45wxrlg9xMncVb8qDPuXZarvghL
L0HzOuYRadBJVoWZowDNTpKpk2RklZ7QaBO7XDv3uR7s_sf2g-bAjSYxYUG
sqkNA9b3xVW53am_UZZ3tZbFTIh557JICWKHlWj5uzeJXaw",
"e": "AQAB",
"d": "LNwG_pCKrwowALpCpRdcOKlSVqylSurZhE6CpkRiE9cpDgGKIkO9CxPlXOL
zjqxXuQc8MdMqRQZTnAwgd7HH0B6gncrruV3NewI-XQV0ckldTjqNfOTz1V
Rs-jE-57KAXI3YBIhu-_0YpIDzdk_wBuAk661Svn0GsPQe7m9DoxdzenQu9
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cSgwjmKsFzDBbQNJc7qMG1N6EssJUwgGJxz1eAUFf0w4YAQ",
"qi": "J-mG0swR4FTy3atrcQ7dd0hhYn1E9QndN-
-sDG4EQO0RnFj6wIefCvwIc4
7hCtVeFnCTPYJNc_JyV-mU-9vlzS5GSNuyR5qdpsMZXUMpEvQcwKt23ffPZ
YGaqfKyEesmf_Wi8fFcE68H9REQjnniKrXm7w2-IuG_IrVJA9Ox-uU",
"q": "4hlMYAGa0dvogdK1jnxQ7J_Lqpqi99e-AeoFvoYpMPhthChTzwFZO9lQmUo
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"p": "5sd9Er3I2FFT9R-gy84_oakEyCmgw036B_nfYEEOCwpSvi2z7UcIVK3bSEL
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"dq": "Nz2PF3XM6bEc4XsluKZO70ErdYdKgdtIJReUR7Rno_tOZpejwlPGBYVW19
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"dp": "Zc877jirkkLOtyTs2vxyNe9KnMNAmOidlUc2tE_-0gAL4Lpo1hSwKCtKwe
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KozRCugf1WXkU9GZAH2_x8PUopdNUEa70ISowPRh04HANKX4fkjWAE"
}
4. Authorization Request
The client uses the "request_uri" value returned by the authorization
server to build an authorization request as defined in
[I-D.ietf-oauth-jwsreq]. This is shown in the following example
where the client directs the user-agent to make the following HTTP
request:
GET /authorize?client_id=s6BhdRkqt3&request_uri=urn%3Aietf%3Aparams
%3Aoauth%3Arequest_uri%3Abwc4JK-ESC0w8acc191e-Y1LTC2 HTTP/1.1
Host: as.example.com
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The authorization server MUST validate authorization requests arising
from a pushed request as it would any other authorization request.
The authorization server MAY omit validation steps that it performed
when the request was pushed, provided that it can validate that the
request was a pushed request, and that the request or the
authorization server's policy has not been modified in a way that
would affect the outcome of the omitted steps.
Authorization server policy MAY dictate, either globally or on a per-
client basis, that pushed authorization requests are the only means
for a client to pass authorization request data. In this case, the
authorization server will refuse, using the "invalid_request" error
code, to process any request to the authorization endpoint that does
not have a "request_uri" parameter with a value obtained from the
pushed authorization request endpoint.
Note: authorization server and clients MAY use metadata as defined in
Section 5 and Section 6 to signal the desired behavior.
5. Authorization Server Metadata
The following authorization server metadata [RFC8414] parameters are
introduced to signal the server's capability and policy with respect
to pushed authorization requests.
"pushed_authorization_request_endpoint" The URL of the pushed
authorization request endpoint at which the client can post an
authorization request and get a request URI in exchange.
"require_pushed_authorization_requests" Boolean parameter indicating
whether the authorization server accepts authorization request
data only via the pushed authorization request method. If
omitted, the default value is "false".
6. Client Metadata
The Dynamic Client Registration Protocol [RFC7591] defines an API for
dynamically registering OAuth 2.0 client metadata with authorization
servers. The metadata defined by [RFC7591], and registered
extensions to it, also imply a general data model for clients that is
useful for authorization server implementations even when the Dynamic
Client Registration Protocol isn't in play. Such implementations
will typically have some sort of user interface available for
managing client configuration. The following client metadata
parameter is introduced by this document to indicate whether pushed
authorization requests are reqired for the given client.
"require_pushed_authorization_requests" Boolean parameter indicating
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whether the only means of initiating an authorization request the
client is allowed to use is a pushed authorization request.
7. Security Considerations
7.1. Request URI Guessing
An attacker could attempt to guess and replay a valid request URI
value and try to impersonate the respective client. The
authorization server MUST consider the considerations given in JAR
[I-D.ietf-oauth-jwsreq], section 10.2, clause (d) on request URI
entropy.
7.2. Open Redirection
An attacker could try register a redirect URI pointing to a site
under his control in order to obtain authorization codes or lauch
other attacks towards the user. The authorization server MUST only
accept new redirect URIs in the PAR request from confidential clients
after successful authentication and authorization.
7.3. Request Object Replay
An attacker could replay a request URI captured from a legitimate
authorization request. In order to cope with such attacks, the
authorization server SHOULD make the request URIs one-time use.
7.4. Client Policy Change
The client policy might change between the lodging of the request
object and the authorization request using a particular request
object. It is therefore recommended that the authorization server
check the request parameter against the client policy when processing
the authorization request.
8. Acknowledgements
This specification is based on the work towards Pushed Request Object
(https://bitbucket.org/openid/fapi/src/master/
Financial_API_Pushed_Request_Object.md) conducted at the Financial-
grade API working group at the OpenID Foundation. We would like to
thank the members of the WG for their valuable contributions.
We would like to thank Vladimir Dzhuvinov, Aaron Parecki, Justin
Richer, Sascha Preibisch, Daniel Fett, Michael B. Jones, Annabelle
Backman, Joseph Heenan, Sean Glencross, Maggie Hung, Neil Madden, and
Takahiko Kawasaki for their valuable feedback on this draft.
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9. IANA Considerations
9.1. OAuth Authorization Server Metadata
This specification requests registration of the following values in
the IANA "OAuth Authorization Server Metadata" registry of
[IANA.OAuth.Parameters] established by [RFC8414].
Metadata Name: "pushed_authorization_request_endpoint"
Metadata Description: URL of the authorization server's pushed
authorization request endpoint
Change Controller: IESG
Specification Document(s): Section 5 of [[ this document ]]
Metadata Name: "require_pushed_authorization_requests"
Metadata Description: Indicates whether the authorization server
accepts authorization request only via the pushed authorization
request method.
Change Controller: IESG
Specification Document(s): Section 5 of [[ this document ]]
9.2. OAuth Dynamic Client Registration Metadata
This specification requests registration of the following value in
the IANA "OAuth Dynamic Client Registration Metadata" registry of
[IANA.OAuth.Parameters] established by [RFC7591].
Metadata Name: "require_pushed_authorization_requests"
Metadata Description: Indicates whether the client is required to
use the pushed authorization request method to initiate
authorization requests.
Change Controller: IESG
Specification Document(s): Section 6 of [[ this document ]]
9.3. OAuth URI Registration
This specification requests registration of the following value in
the "OAuth URI" registry of [IANA.OAuth.Parameters] established by
[RFC6755].
URN: "urn:ietf:params:oauth:request_uri:"
Common Name: A URN Sub-Namespace for OAuth Request URIs.
Change Controller: IESG
Specification Document(s): Section 2.2 of [[ this document ]]
10. Normative References
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[I-D.ietf-oauth-jwsreq]
Sakimura, N. and J. Bradley, "The OAuth 2.0 Authorization
Framework: JWT Secured Authorization Request (JAR)", Work
in Progress, Internet-Draft, draft-ietf-oauth-jwsreq-26,
27 July 2020,
<https://tools.ietf.org/html/draft-ietf-oauth-jwsreq-26>.
[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>.
[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>.
[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>.
[OIDC] Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., and
C. Mortimore, "OpenID Connect Core 1.0 incorporating
errata set 1", 8 November 2014,
<http://openid.net/specs/openid-connect-core-1_0.html>.
[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>.
11. Informative References
[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>.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122,
DOI 10.17487/RFC4122, July 2005,
<https://www.rfc-editor.org/info/rfc4122>.
[I-D.ietf-oauth-mtls]
Campbell, B., Bradley, J., Sakimura, N., and T.
Lodderstedt, "OAuth 2.0 Mutual-TLS Client Authentication
and Certificate-Bound Access Tokens", Work in Progress,
Internet-Draft, draft-ietf-oauth-mtls-17, 23 August 2019,
<https://tools.ietf.org/html/draft-ietf-oauth-mtls-17>.
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[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<https://www.rfc-editor.org/info/rfc7517>.
[IANA.OAuth.Parameters]
IANA, "OAuth Parameters",
<http://www.iana.org/assignments/oauth-parameters>.
[RFC6755] Campbell, B. and H. Tschofenig, "An IETF URN Sub-Namespace
for OAuth", RFC 6755, DOI 10.17487/RFC6755, October 2012,
<https://www.rfc-editor.org/info/rfc6755>.
[RFC7636] Sakimura, N., Ed., Bradley, J., and N. Agarwal, "Proof Key
for Code Exchange by OAuth Public Clients", RFC 7636,
DOI 10.17487/RFC7636, September 2015,
<https://www.rfc-editor.org/info/rfc7636>.
[RFC8707] Campbell, B., Bradley, J., and H. Tschofenig, "Resource
Indicators for OAuth 2.0", RFC 8707, DOI 10.17487/RFC8707,
February 2020, <https://www.rfc-editor.org/info/rfc8707>.
[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>.
Appendix A. Document History
[[ To be removed from the final specification ]]
-03
* Editorial updates
* Mention that https is required for the PAR endpoint
* Add some discussion of browser form posting an authz request vs.
the benefits of PAR for any application
* Added text about motivations behind PAR - integrity,
confidentiality and early client auth
* Better explain one-time use recommendation of the request_uri
* Drop the section on special error responses for request objects
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* Clarify authorization request examples to say that the client
directs the user-agent to make the HTTP GET request (vs. making
the request itself)
-02
* Update Resource Indicators reference to the somewhat recently
published RFC 8707
* Added metadata in support of pushed authorization requests only
feature
* Update to comply with draft-ietf-oauth-jwsreq-21, which requires
"client_id" in the authorization request in addition to the
"request_uri"
* Clarified timing of request validation
* Add some guidance/options on the request URI structure
* Add the key used in the request object example so that a reader
could validate or recreate the request object signature
* Update to draft-ietf-oauth-jwsreq-25 and added note regarding
"require_signed_request_object"
-01
* Use the newish RFC v3 XML and HTML format
* Added IANA registration request for
"pushed_authorization_request_endpoint"
* Changed abbrev to "OAuth PAR"
-00 (WG draft)
* Reference RFC6749 sec 2.3.1 for client secret basic rather than
RFC7617
* further clarify that a request object JWT contains all the
authorization request parameters while client authentication
params, if applicable, are outside that JWT as regular form
encoded params in HTTP body
-01
* List "client_id" as one of the basic parameters
* Explicitly forbid "request_uri" in the processing rules
* Clarification regarding client authentication and that public
clients are allowed
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* Added option to let clients register per-authorization request
redirect URIs
* General clean up and wording improvements
-00
* first draft
Authors' Addresses
Torsten Lodderstedt
yes.com
Email: torsten@lodderstedt.net
Brian Campbell
Ping Identity
Email: bcampbell@pingidentity.com
Nat Sakimura
NAT.Consulting
Email: nat@sakimura.org
Dave Tonge
Moneyhub Financial Technology
Email: dave@tonge.org
Filip Skokan
Auth0
Email: panva.ip@gmail.com
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