2.1. Request Object

A Request Object is a JSON Web Token (JWT) [RFC7519] whose JWT Claims Set holds the JSON-encoded OAuth 2.0 authorization request parameters.¶

2.2. 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 (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 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.¶

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, 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:¶

1. 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.¶
2. 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 Section 2.7.2 of [RFC7230]. In the second case, it MUST be a URN, as specified in [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):¶

  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

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

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

GET /request.jwt/GkurKxf5T0Y-mnPFCHqWOMiZi4VS138cQO_V7PZHAdM HTTP/1.1
Host: tfp.example.org

  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

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 to the client in response to the authorization request.¶

6.2. JWS-Signed Request Object

The authorization server MUST validate the signature of the JWS-signed [RFC7515] 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 3.1 and 3.2 of [RFC8725].¶

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.¶

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 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 Section 5.2 of [RFC6749] (OAuth 2.0).¶

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 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 [IANA.OAuth.Parameters] established by [RFC6749].¶

Name:

iss¶

Parameter Usage Location:

authorization request¶

Change Controller:

IETF¶

Specification Document(s):

This document and Section 4.1.1 of [RFC7519].¶

Name:

sub¶

Parameter Usage Location:

authorization request¶

Change Controller:

IETF¶

Specification Document(s):

This document and Section 4.1.2 of [RFC7519].¶

Name:

aud¶

Parameter Usage Location:

authorization request¶

Change Controller:

IETF¶

Specification Document(s):

This document and Section 4.1.3 of [RFC7519].¶

Name:

exp¶

Parameter Usage Location:

authorization request¶

Change Controller:

IETF¶

Specification Document(s):

This document and Section 4.1.4 of [RFC7519].¶

Name:

nbf¶

Parameter Usage Location:

authorization request¶

Change Controller:

IETF¶

Specification Document(s):

This document and Section 4.1.5 of [RFC7519].¶

Name:

iat¶

Parameter Usage Location:

authorization request¶

Change Controller:

IETF¶

Specification Document(s):

This document and Section 4.1.6 of [RFC7519].¶

Name:

jti¶

Parameter Usage Location:

authorization request¶

Change Controller:

IETF¶

Specification Document(s):

This document and Section 4.1.7 of [RFC7519].¶

9.2. OAuth Authorization Server Metadata Registry

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

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):

Section 10.5 of this document.¶

9.3. OAuth Dynamic Client Registration Metadata Registry

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

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):

Section 10.5 of this document.¶

9.4. Media Type Registration

10.1. Choice of Algorithms

When sending the Authorization Request Object through the request parameter, it MUST be either signed using JWS [RFC7515] or signed and then encrypted using JWS [RFC7515] and JWE [RFC7516], respectively, with algorithms considered appropriate at the time.¶

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 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 the Request Object URI and only the client is covered by the TLS certificate. In general, this 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 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.¶

(e)

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.¶

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. It is RECOMMENDED by this specification to use this practice for the following endpoints defined in [RFC6749], [RFC6750], and [RFC8414]:¶

(a)

Protected resources (protected_resources)¶

(b)

Authorization endpoint (authorization_endpoint)¶

(c)

Redirection URI (redirect_uri)¶

(d)

Token endpoint (token_endpoint)¶

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

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

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] for more information regarding risks associated with URIs.¶

10.5. 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 Section 4.¶

10.6. TLS Security Considerations

Current security considerations can be found in "Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)" [RFC7525]. 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 (which is registered in Section 9.4.1). 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 [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.¶

11.1. 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 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:¶

(1)

(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.¶

(2)

(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.¶

11.2. Disclosure Limitation