The OAuth 2.0 Authorization Framework: JWT-Secured Authorization Request (JAR)
NAT.Consulting
Kunitachi
Tokyo 186-0004
2-22-17 Naka
Japan
+81-42-580-7401
nat@nat.consulting
https://nat.sakimura.org/
Yubico
Casilla 177
Sucursal Talagante
Talagante
RM
Chile
+1.202.630.5272
rfc9101@ve7jtb.com
http://www.thread-safe.com/
Microsoft
One Microsoft Way
Redmond
Washington
98052
United States of America
mbj@microsoft.com
https://self-issued.info/
Security
OAuth Working Group
Assertion
Claim
Security Token
OAuth
JavaScript Object Notation
JSON
JSON Web Token
JWT
JSON Web Signature
JWS
JSON Web Encryption
JWE
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, b) the source of
the communication is not authenticated, and c) the communication
through the user agents can be monitored. 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
properties of the authorization request are attained. The request can
be sent by value or by reference.
Introduction
The authorization request in OAuth 2.0
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 a result, the authorization request of has
shortcomings in that:
- the communication through the user agents is
not integrity protected, and thus, the parameters can be tainted
(integrity protection failure);
- the source of the communication is not authenticated
(source authentication failure);
- 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, 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 upon.
Furthermore, passing the request by reference allows the reduction of over-the-wire overhead.
The JWT encoding has been chosen because of:
- its close relationship with JSON,
which is used as OAuth's response format
- its developer friendliness due to its textual nature
- its relative compactness compared to XML
- its development status as a Proposed Standard, along
with the associated signing and encryption methods
- 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 flows. The request parameter
is a JSON Web Token (JWT) 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 ,
supplemented with only a few of the IANA-managed JSON Web Token Claims
, in particular, iss and
aud. The JWT in the request parameter is integrity
protected and source authenticated using JWS.
The JWT can be passed to the authorization endpoint by reference,
in which case the parameter request_uri is
used instead of request.
Using JWT as the request encoding instead of query
parameters has several advantages:
- Integrity protection.
The request can be signed so that the integrity of the request can be checked.
- Source authentication.
The request can be signed so that the signer can be authenticated.
- 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).
- 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 to confirm that all the personal data requested is
strictly necessary to perform the process that the end user asked for;
the request would then be 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 where request by reference is useful, such as:
- when it is desirable to reduce the size of a transmitted request.
The use of application-layer security increases the size of the
request particularly when public-key cryptography is used.
- 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 .
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
when, and only when, they appear in all capitals,
as shown here.
Terminology
For the purposes of this specification, the following terms and
definitions apply in addition to what is defined in
OAuth 2.0 Framework,
JSON Web Signature, and
JSON Web Encryption.
Request Object
A Request Object is a JSON Web Token
(JWT) whose JWT Claims
Set holds the JSON-encoded OAuth 2.0 authorization request
parameters.
Request Object URI
A Request Object URI is an absolute URI that references the set of
parameters comprising an OAuth 2.0 authorization request. The content
of the resource referenced by the URI is a Request Object, 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 of the
authorization server. The content being a Request Object 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
that is 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.
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
Request Object
A Request Object 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
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 ,
these JSON strings MUST be encoded using UTF-8 .
Numerical values MUST be included as JSON numbers.
The Request Object MAY include any extension parameters.
This JSON object constitutes the
JWT Claims Set defined in JWT.
The JWT Claims Set is then signed or signed and encrypted.
To sign, JSON Web Signature (JWS) is
used. The result is a JWS-signed JWT. 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 specification. The value of aud
should be the value of the authorization server (AS) issuer, as
defined in RFC 8414.
To encrypt, JWE is used.
When both signature and encryption are being applied,
the JWT MUST be signed, then encrypted, as described in
.
The result is a Nested JWT, as defined in
.
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 , 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 , 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 ,
or by reference, as described in .
request and
request_uri parameters
MUST NOT be included in Request Objects.
A Request Object has the media
type
application/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 JSON Web Key (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"
}
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 that
holds authorization request parameters stated in
(OAuth 2.0).
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 RFC 3986, that is the Request Object URI referencing the
authorization request
parameters stated in (OAuth
2.0).
If this parameter is present in the authorization request,
request MUST NOT be present.
- client_id
-
REQUIRED. OAuth 2.0
client_id. The value MUST match the
request or request_uri
Request Object's
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:
- JWS signed
- JWS signed and JWE encrypted
The client MAY send the parameters included in
the Request Object duplicated in the query parameters as well
for backward compatibility, etc.
However, the authorization server supporting this specification
MUST only use the parameters included in the Request Object.
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
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, except that the Request Object value is
retrieved from the resource identified by the specified URI rather
than passed by value.
The entire Request URI SHOULD NOT exceed 512 ASCII characters.
There are two reasons for this restriction:
- Many phones on the market as of this writing still do not accept
large payloads. The restriction is typically either 512 or 1024
ASCII characters.
- On a slow connection such as a 2G mobile connection, a large URL
would cause a slow response; 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 .
In the second case, it MUST be a URN,
as specified in .
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):
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
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 a 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
and
"" .
It is RECOMMENDED that the request_uri 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 service hosts the Request Object.
https://tfp.example.org/request.jwt/
GkurKxf5T0Y-mnPFCHqWOMiZi4VS138cQO_V7PZHAdM
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
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 the Request Object is stored in a way so that the server can
retrieve it through other mechanisms 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 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
Content-Length: 797
Last-Modified: Wed, 19 Aug 2020 23:52:32 GMT
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
Validating JWT-Based Requests
JWE Encrypted Request Object
If the Request Object is encrypted,
the authorization server MUST decrypt the JWT in accordance with
the JSON Web Encryption
specification.
The result is a signed Request Object.
If decryption fails, the authorization server MUST
return an invalid_request_object error to the client in
response to the authorization request.
JWS-Signed Request Object
The authorization server MUST validate the
signature of the JWS-signed Request
Object. If a kid Header Parameter is present, the key identified
MUST be the key used and MUST be a
key associated with the client. The signature MUST
be validated using a key associated with the client and the
algorithm specified in the alg Header Parameter. Algorithm verification MUST be performed, as specified in Sections and of .
If the key is not associated with the client or if signature
validation fails, the authorization server MUST
return an invalid_request_object error to the client in response to the authorization request.
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.
If the Client ID check or the request validation fails, then the
authorization server MUST return an error to the
client in response to the authorization request, as specified in
(OAuth 2.0).
Authorization Server Response
The authorization server response is created and sent to the client as in
(OAuth 2.0).
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.
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)".
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
, to avoid man-in-the-middle attacks.
The rules and guidelines defined in
apply here, with the following considerations:
-
Support for DNS-ID identifier type (that is, the dNSName identity
in the subjectAltName extension) is REQUIRED. Certification
authorities that issue server certificates
MUST support
the DNS-ID identifier type, and the DNS-ID identifier type MUST
be present in server certificates.
-
DNS names in server certificates MAY contain the
wildcard character *.
-
Clients MUST NOT use CN-ID identifiers; a Common Name
field (CN field) may be present in the server certificate's subject
name but MUST NOT be used for authentication within
the rules described in .
-
SRV-ID and URI-ID as described in
MUST NOT be used for comparison.
IANA Considerations
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 have been 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
established by .
- Name:
- iss
- Parameter Usage Location:
- authorization request
- Change Controller:
- IETF
- Specification Document(s):
- This document and .
- Name:
- sub
- Parameter Usage Location:
- authorization request
- Change Controller:
- IETF
- Specification Document(s):
- This document and .
- Name:
- aud
- Parameter Usage Location:
- authorization request
- Change Controller:
- IETF
- Specification Document(s):
- This document and .
- Name:
- exp
- Parameter Usage Location:
- authorization request
- Change Controller:
- IETF
- Specification Document(s):
- This document and .
- Name:
- nbf
- Parameter Usage Location:
- authorization request
- Change Controller:
- IETF
- Specification Document(s):
- This document and .
- Name:
- iat
- Parameter Usage Location:
- authorization request
- Change Controller:
- IETF
- Specification Document(s):
- This document and .
- Name:
- jti
- Parameter Usage Location:
- authorization request
- Change Controller:
- IETF
- Specification Document(s):
- This document and .
OAuth Authorization Server Metadata Registry
This specification adds the following value to the "OAuth
Authorization Server Metadata" registry established by .
- Metadata Name:
- require_signed_request_object
- Metadata Description:
- Indicates where authorization
request needs to be protected as Request Object and provided through
either request or request_uri parameter.
- Change Controller:
- IETF
- Specification Document(s):
- of this document.
OAuth Dynamic Client Registration Metadata Registry
This specification adds the following value to the "OAuth Dynamic
Client Registration Metadata" registry established by .
- Metadata Name:
- require_signed_request_object
- Metadata Description:
- Indicates where authorization
request needs to be protected as Request Object and provided through
either request or request_uri parameter.
- Change Controller:
- IETF
- Specification Document(s):
- of this document.
Media Type Registration
Registry Contents
This section registers the
application/oauth-authz-req+jwt
media type in the "Media Types"
registry in the manner
described in . It can be used to
indicate that the content is a JWT containing Request
Object claims.
- Type name:
- application
- Subtype name:
- oauth-authz-req+jwt
- Required parameters:
- N/A
- Optional parameters:
- N/A
- 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.
- Security considerations:
- See
of RFC 9101
- Interoperability considerations:
- N/A
- Published specification:
- of RFC 9101
- Applications that use this media type:
- Applications
that use Request Objects to make an OAuth 2.0 authorization
request
- Fragment identifier considerations:
- N/A
- Additional information:
-
- Deprecated alias names for this type:
- N/A
- Magic number(s):
- N/A
- File extension(s):
- N/A
- Macintosh file type code(s):
- N/A
- Person & email address to contact for further
information:
Nat Sakimura <nat@nat.consulting>
- Intended usage:
- COMMON
- Restrictions on usage:
- none
- Author:
- Nat Sakimura <nat@nat.consulting>
- Change controller:
- IETF
- Provisional registration?
- No
Security Considerations
In addition to all the security
considerations discussed in OAuth 2.0, the security
considerations in , ,
, and need to be
considered. Also, there are several academic papers such as 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.
Choice of Algorithms
When sending the Authorization Request Object through the
request parameter, it MUST be either
signed using JWS
or signed and then encrypted using JWS and
JWE, respectively,
with algorithms considered appropriate at the time.
Request Source Authentication
The source of the authorization request MUST always be
verified. There are several ways to do it:
- Verifying the JWS Signature of the Request Object.
- 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 to the public
key.
- 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 the Request Object URI and
only the client is covered by the TLS certificate.
In general, this is not a reliable method.
- 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 the 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 128 bits or more at the time of the
writing of this specification.
- When a trusted third-party service 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 trusted by the third-party service and
MUST know out-of-band that the client is also trusted by it.
Explicit Endpoints
Although this specification does not require them,
research such as 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. It
is RECOMMENDED by this specification to use this
practice for the following endpoints defined in , , and :
- Protected resources (protected_resources)
- Authorization endpoint (authorization_endpoint)
- Redirection URI (redirect_uri)
- Token endpoint (token_endpoint)
Further, if dynamic discovery is used, then this practice also applies
to the discovery-related endpoints.
In ,
while the redirection URI is included in the authorization request, others
are not. As a result, the same applies to the Authorization
Request Object.
Risks Associated with request_uri
The introduction of request_uri
introduces several attack possibilities.
Consult the security considerations in
for more information
regarding
risks associated with URIs.
DDoS Attack on the Authorization Server
A set of malicious clients can launch a DoS attack
to the authorization server by pointing the
request_uri to a URI
that returns extremely large content or is extremely slow to respond.
Under such an attack, the server may use up its resource
and start failing.
Similarly, a malicious client can specify a
request_uri value
that itself points to an authorization request URI
that uses request_uri to
cause the recursive lookup.
To prevent such an attack from succeeding, the server should
a) check that the value of the request_uri
parameter does not point to an unexpected location,
b) check that the media type of the response is
application/oauth-authz-req+jwt,
c) implement a timeout for obtaining the content of
request_uri, and
d) not perform recursive GET on the
request_uri.
Request URI Rewrite
The value of request_uri is not signed;
thus, it can be tampered with by a man-in-the-browser attacker.
Several attack possibilities arise because of this. For
example,
a) an attacker may create another file that the rewritten
URI points to, making it possible to request extra scope, or
b) an attacker may launch a DoS attack on a victim site
by setting the value of request_uri
to be that of the victim.
To prevent such an attack from succeeding, the server should
a) check that the value of the request_uri
parameter does not point to an unexpected location,
b) check that the media type of the response is
application/oauth-authz-req+jwt, and
c) implement a timeout for obtaining the content of
request_uri.
Downgrade Attack
Unless the protocol used by the client and the server is locked down to
use an OAuth JWT-Secured Authorization Request (JAR), it is possible
for an attacker to use RFC 6749 requests
to bypass all the protection provided by this specification.
To prevent this kind of attack, this specification defines new
client metadata and server metadata values, both named
require_signed_request_object, whose values are both
booleans.
When the value of it as 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 an alg value of none when this server
metadata value is true. If omitted, the default value is
false.
When the value of it as 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 an alg value of none. If omitted, the
default value is false.
Note that even if require_signed_request_object metadata
values are not present, the client MAY use signed Request Objects,
provided that there are signing algorithms mutually supported by the
client and the server. Use of signing algorithm metadata is described
in .
TLS Security Considerations
Current security
considerations can be found in "" . This
supersedes the TLS version recommendations in OAuth
2.0.
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.
Cross-JWT Confusion
As described in ,
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 .
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 .
One would explicitly type a Request Object by including a
typ Header Parameter with the value
oauth-authz-req+jwt
(which is registered in ).
Note, however, that requiring explicitly typed Request Objects
at existing authorization servers will break most existing deployments,
as existing clients are already commonly using untyped Request Objects,
especially with OpenID Connect .
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.
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.
""
gives excellent guidance on the
enhancement of protocol design and implementation.
The provisions listed in it should be followed.
Most of the provisions would apply to
""
and ""
and are not specific to this specification.
In what follows, only the provisions specific
to this specification are noted.
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 trusted third-party service can help the
user by examining the client request, comparing it to the proposed
processing by the client, and certifying the request. After the
certification, the client, when making an authorization request, can
submit an authorization request to the trusted third-party service to
obtain the Request Object URI. This process has two steps:
- (Certification Process) The trusted third-party service examines
the business process of the client and determines what claims they
need; this is the certification process. Once the client is
certified, they are issued a client credential to authenticate
against to push Request Objects to the trusted third-party service
to get the request_uri.
- (Translation Process) The client uses the client credential that
it got to push the Request Object to the trusted third-party service
to get the request_uri. The trusted third-party service
also verifies that the Request Object is consistent with the claims
that the client is eligible for, per the prior step.
Upon receiving such a 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 trusted third-party
service. Then, the authorization server issues an HTTP GET request to
the Request Object URI. Upon connecting, the authorization server
MUST verify that 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
trusted third-party service for the adherence to the collection
limitation principle.
Disclosure Limitation
Request Disclosure
This specification allows extension parameters.
These may include potentially sensitive information.
Since URI query parameters 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 encrypt
the Request Object using JWE.
Where the 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
and have a short validity period, and it MUST have
sufficient entropy for the applicable security policies unless the
Request Object itself is encrypted using JWE. 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 128 bits or more at the time of the
writing of this specification.
Tracking Using Request Object URI
Even if the protected resource does not include
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.
References
Normative References
Informative References
Media Types
IANA
OAuth Parameters
IANA
JSON Web Token (JWT)
IANA
OpenID Connect Core 1.0 incorporating errata set 1
NAT Consulting
Ping Identity
Microsoft
Google
Salesforce
OpenID Foundation Standards
Provably Repairing the ISO/IEC 9798 Standard for Entity Authentication
Journal of Computer Security - Security and Trust Principles, Volume 21, Issue 6, pp. 817-846
Good Practices for Capability URLs
W3C First Public Working Draft
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.)
(Amazon),
(Google),
,
(as AD),
(Ping Identity),
(as AD),
(as AD),
(Connect2id),
(as AD),
(as GENART),
(as AD),
(as SECDIR),
(as AD),
(as OPSDIR),
(as SECDIR),
(yes.com),
,
(Telstra),
(as AD),
(Deutsche Telecom),
(Google),
(as AD),
(Facebook),
(Google),
(Facebook),
(Auth0),
(ARM),
(as AD),
and
(as AD).
The following people contributed to creating this document through
the OpenID Connect Core 1.0.
(Ping Identity), (AOL),
(Mixi), (Illumila), (Google), (TACT), and (MITRE).