Internet DRAFT - draft-lodderstedt-oauth-rar
draft-lodderstedt-oauth-rar
Web Authorization Protocol T. Lodderstedt
Internet-Draft yes.com
Intended status: Standards Track J. Richer
Expires: May 6, 2020 Bespoke Engineering
B. Campbell
Ping Identity
November 3, 2019
OAuth 2.0 Rich Authorization Requests
draft-lodderstedt-oauth-rar-03
Abstract
This document specifies a new parameter "authorization_details" that
is used to carry fine grained authorization data in the OAuth
authorization request.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on May 6, 2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
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include Simplified BSD License text as described in Section 4.e of
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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 . . . . . . . . . . . . . . . 4
2. Request parameter "authorization_details" . . . . . . . . . . 4
2.1. Authorization data elements types . . . . . . . . . . . . 5
2.2. Relationship to "scope" parameter . . . . . . . . . . . . 8
2.2.1. Scope value "openid" and "claims" parameter . . . . . 8
2.3. Relationship to "resource" parameter . . . . . . . . . . 9
3. Using "authorization_details" . . . . . . . . . . . . . . . . 11
3.1. Authorization Request . . . . . . . . . . . . . . . . . . 11
3.2. Authorization Request Processing . . . . . . . . . . . . 14
3.3. Token Request . . . . . . . . . . . . . . . . . . . . . . 15
3.4. Token Response . . . . . . . . . . . . . . . . . . . . . 15
3.4.1. Token Content . . . . . . . . . . . . . . . . . . . . 16
3.5. Token Introspection Request . . . . . . . . . . . . . . . 18
3.6. Token Introspection Response . . . . . . . . . . . . . . 18
4. Metadata . . . . . . . . . . . . . . . . . . . . . . . . . . 19
5. Implementation Considerations . . . . . . . . . . . . . . . . 20
6. Security Considerations . . . . . . . . . . . . . . . . . . . 20
7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 20
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 21
10.1. Normative References . . . . . . . . . . . . . . . . . . 21
10.2. Informative References . . . . . . . . . . . . . . . . . 22
Appendix A. Additional Examples . . . . . . . . . . . . . . . . 23
A.1. OpenID Connect . . . . . . . . . . . . . . . . . . . . . 23
A.2. Remote Electronic Signing . . . . . . . . . . . . . . . . 25
A.3. Access to Tax Data . . . . . . . . . . . . . . . . . . . 26
A.4. eHealth . . . . . . . . . . . . . . . . . . . . . . . . . 27
Appendix B. Document History . . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30
1. Introduction
The OAuth 2.0 authorization framework [RFC6749] defines the parameter
"scope" that allows OAuth clients to specify the requested scope,
i.e., the permission, of an access token. This mechanism is
sufficient to implement static scenarios and coarse-grained
authorization requests, such as "give me read access to the resource
owner's profile" but it is not sufficient to specify fine-grained
authorization requirements, such as "please let me make a payment
with the amount of 45 Euros" or "please give me read access to folder
A and write access to file X".
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This draft introduces a new parameter "authorization_details" that
allows clients to specify their fine-grained authorization
requirements using the expressiveness of JSON data structures.
For example, a request for payment authorization can be represented
using a JSON object like this:
{
"type": "payment_initiation",
"locations": [
"https://example.com/payments"
],
"instructedAmount": {
"currency": "EUR",
"amount": "123.50"
},
"creditorName": "Merchant123",
"creditorAccount": {
"iban": "DE02100100109307118603"
},
"remittanceInformationUnstructured": "Ref Number Merchant"
}
This object contains detailed information about the intended payment,
such as amount, currency, and creditor, that are required to inform
the user and obtain her consent. The AS and the respective RS
(providing the payment initation API) will together enforce this
consent.
For a comprehensive discussion of the challenges arising from new use
cases in the open banking and electronic signing spaces see
[transaction-authorization].
In addition to facilitating custom authorization requests, this draft
also introduces a set of common data type fields for use across
different APIs.
Most notably, the field "locations" allows a client to specify where
it intends to use a certain authorization, i.e., it is now possible
to unambiguously assign permissions to resource servers. In
situations with multiple resource servers, this prevents unintended
client authorizations (e.g. a "read" scope value potentially
applicable for an email as well as a cloud service). In combination
with the "resource" token request parameter as specified in
[I-D.ietf-oauth-resource-indicators] it enables the AS to mint RS-
specific structured access tokens that only contain the permissions
applicable to the respective RS.
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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. Request parameter "authorization_details"
The request parameter "authorization_details" contains, in JSON
notation, an array of objects. Each JSON object contains the data to
specify the authorization requirements for a certain type of
resource. The type of resource or access requirement is determined
by the "type" field.
This example shows the specification of authorization details using
the payment authorization object shown above:
[
{
"type": "payment_initiation",
"actions": [
"initiate",
"status",
"cancel"
],
"locations": [
"https://example.com/payments"
],
"instructedAmount": {
"currency": "EUR",
"amount": "123.50"
},
"creditorName": "Merchant123",
"creditorAccount": {
"iban": "DE02100100109307118603"
},
"remittanceInformationUnstructured": "Ref Number Merchant"
}
]
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This example shows a combined request asking for access to account
information and permission to initiate a payment:
[
{
"type": "account_information",
"actions": [
"list_accounts",
"read_balances",
"read_transactions"
],
"locations": [
"https://example.com/accounts"
]
},
{
"type": "payment_initiation",
"actions": [
"initiate",
"status",
"cancel"
],
"locations": [
"https://example.com/payments"
],
"instructedAmount": {
"currency": "EUR",
"amount": "123.50"
},
"creditorName": "Merchant123",
"creditorAccount": {
"iban": "DE02100100109307118603"
},
"remittanceInformationUnstructured": "Ref Number Merchant"
}
]
The JSON objects with "type" fields of "account_information" and
"payment_initiation" represent the different authorization data to be
used by the AS to ask for consent and MUST subsequently also be made
available to the respective resource servers. The array MAY contain
several elements of the same "type".
2.1. Authorization data elements types
This draft defines a set of common data elements that are designed to
be usable across different types of APIs. These data elements MAY be
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combined in different ways depending on the needs of the API. Unless
otherwise noted, all data elements are OPTIONAL.
type:
The type of resource request as a string. This field MAY define
which other elements are allowed in the request. This element is
REQUIRED.
locations:
An array of strings representing the location of the resource or
resource server. This is typically composed of URIs.
actions:
An array of strings representing the kinds of actions to be taken
at the resource. The values of the strings are determined by the
API being protected.
datatypes:
An array of strings representing the kinds of data being requested
from the resource.
identifier:
A string identifier indicating a specific resource available at
the API.
When different element types are used in combination, the permissions
the client requests is the cartesian product of the values. In the
following example
[
{
"type": "customer_information",
"locations": [
"https://example.com/customers",
]
"actions": [
"read",
"write"
],
"datatypes": [
"contacts",
"photos"
]
}
]
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the client is requesting read and write access to both the contacts
and photos belonging to customers in a customer information API. If
the client wishes to have finer control over its access, it can send
multiple objects. For example:
[
{
"type": "customer_information",
"locations": [
"https://example.com/customers"
],
"actions": [
"read"
],
"datatypes": [
"contacts"
]
},
{
"type": "customer_information",
"locations": [
"https://example.com/customers"
],
"actions": [
"write"
],
"datatypes": [
"photos"
]
}
]
The client is asking for read access to the contacts and write access
to the photos in the same API endpoint.
An API MAY define its own extensions, subject to the "type" of the
respective authorization object. It is assumed that the full
structure of each of the authorization objects is tailored to the
needs of a certain application, API, or resource type. The example
structures shown above are based on certain kinds of APIs that can be
found in the Open Banking space.
Note: Applications MUST ensure that their authorization data types do
not collide. This is either achieved by using a namespace under the
control of the entity defining the type name or by registering the
type with the new "OAuth Authorization Data Type Registry" (see
Section 9).
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The following example shows how an implementation could utilize the
namespace "https://scheme.example.org/" to ensure collision resistant
element names.
{
"type": "https://scheme.example.org/files",
"locations": [
"https://example.com/files"
],
"permissions": [
{
"path": "/myfiles/A",
"access": [
"read"
]
},
{
"path": "/myfiles/A/X",
"access": [
"read",
"write"
]
}
]
}
2.2. Relationship to "scope" parameter
"authorization_details" and "scope" can be used in the same
authorization request for carrying independent authorization
requirements.
The AS MUST consider both sets of requirements in combination with
each other for the given authorization request. The details of how
the AS combines these parameters are specific to the APIs being
protected and outside the scope of this specification.
It is RECOMMENDED that a given API use only one form of requirement
specification.
When gathering user consent, the AS MUST present the merged set of
requirements represented by the authorization request.
2.2.1. Scope value "openid" and "claims" parameter
OpenID Connect [OIDC] specifies the JSON-based "claims" request
parameter that can be used to specify the claims a client (acting as
OpenID Connect Relying Party) wishes to receive in a fine-grained and
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privacy preserving way as well as assign those claims to a certain
delivery mechanisms, i.e. ID Token or userinfo response.
The combination of the scope value "openid" and the additional
parameter "claims" can be used beside "authorization_details" in the
same way as every non-OIDC scope value.
Alternatively, there could be an authorization data type for OpenID
Connect. Appendix A.1 gives an example of how such an authorization
data type could look like.
2.3. Relationship to "resource" parameter
The request parameter "resource" as defined in
[I-D.ietf-oauth-resource-indicators] indicates to the AS the
resource(s) where the client intends to use the access tokens issued
based on a certain grant. This mechanism is a way to audience-
restrict access tokens and to allow the AS to create resource server
specific access tokens.
If a client uses "authorization_details" with "locations" elements
and the "resource" parameter in the same authorization request, the
"locations" data take precedence over the data conveyed in the
"resource" parameter for that particular authorization details
object.
If such a client uses the "resource" parameter in a subsequent token
requests, the AS MUST utilize the data provided in the "locations"
elements to filter the authorization data objects applicable to the
respective resource server. The AS will select all authorization
details object where the "resource" string matches as prefix of one
of the URLs provided in the respective "locations" element.
This shall be illustrated using an example.
The client has sent an authorization request using the following
example authorization details.
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[
{
"type": "account_information",
"actions": [
"list_accounts",
"read_balances",
"read_transactions"
],
"locations": [
"https://example.com/accounts"
]
},
{
"type": "payment_initiation",
"actions": [
"initiate",
"status",
"cancel"
],
"locations": [
"https://example.com/payments"
],
"instructedAmount": {
"currency": "EUR",
"amount": "123.50"
},
"creditorName": "Merchant123",
"creditorAccount": {
"iban": "DE02100100109307118603"
},
"remittanceInformationUnstructured": "Ref Number Merchant"
}
]
If this client then sends the following token request to the AS,
POST /token HTTP/1.1
Host: as.example.com
Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW
Content-Type: application/x-www-form-urlencoded
grant_type=authorization_code&code=SplxlOBeZQQYbYS6WxSbIA
&redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb
&resource=https%3A%2F%2Fexample%2Ecom%2Fpayments
that contains a resource parameter with the value of
"https://example.com/payments", this value will be matched against
the locations elements ("https://example.com/accounts" and
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"https://example.com/payments") and will select the element of type
"payment_initiation" for inclusion in the access token as illustrated
by the following example JWT content.
{
"iss": "https://as.example.com",
"sub": "24400320",
"aud": "a7AfcPcsl2",
"exp": 1311281970,
...
"authorization_details": [
{
"type": "https://www.someorg.com/payment_initiation",
"actions": [
"initiate",
"status",
"cancel"
],
"locations": [
"https://example.com/payments"
],
"instructedAmount": {
"currency": "EUR",
"amount": "123.50"
},
"creditorName": "Merchant123",
"creditorAccount": {
"iban": "DE02100100109307118603"
},
"remittanceInformationUnstructured": "Ref Number Merchant"
}
],
...
}
3. Using "authorization_details"
3.1. Authorization Request
The request parameter can be used to specify authorization
requirements in all places where the "scope" parameter is used for
the same purpose, examples include:
o Authorization requests as specified in [RFC6749],
o Access token requests as specified in [RFC6749], if also used as
authorization requests, e.g. in the case of assertion grant types
[RFC7521],
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o Request objects as specified in [I-D.ietf-oauth-jwsreq],
o Device Authorization Request as specified in [RFC8628],
o Backchannel Authentication Requests as defined in [OpenID.CIBA].
Parameter encoding is determined by the respective context.
In the context of an authorization request according to [RFC6749],
the parameter is encoded using the "application/x-www-form-
urlencoded" format of the serialized JSON as shown in the following
example:
GET /authorize?response_type=code
&client_id=s6BhdRkqt3
&state=af0ifjsldkj
&redirect_uri=https%3A%2F%2Fclient.example.org%2Fcb
&code_challenge_method=S256
&code_challenge=K2-ltc83acc4h0c9w6ESC_rEMTJ3bww-uCHaoeK1t8U
&authorization_details=%5B%7B%22type%22%3A%22account%5Finformati
on%22%2C%22actions%22%3A%5B%22list%5Faccounts%22%2C%22read%5Fbal
ances%22%2C%22read%5Ftransactions%22%5D%2C%22locations%22%3A%5B%
22https%3A%2F%2Fexample%2Ecom%2Faccounts%22%5D%7D%5D HTTP/1.1
Host: server.example.com
Implementors MUST ensure to protect personal identifiable information
in transit. One way is to utilize encrypted request objects as
defined in [I-D.ietf-oauth-jwsreq]. In the context of a request
object, "authorization_details" is added as another top level JSON
element.
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{
"iss": "s6BhdRkqt3",
"aud": "https://server.example.com",
"response_type": "code",
"client_id": "s6BhdRkqt3",
"redirect_uri": "https://client.example.com/cb",
"state": "af0ifjsldkj",
"code_challenge_method": "S256",
"code_challenge": "K2-ltc83acc4h0c9w6ESC_rEMTJ3bww-uCHaoeK1t8U",
"authorization_details": [
{
"type": "account_information",
"actions": [
"list_accounts",
"read_balances",
"read_transactions"
],
"locations": [
"https://example.com/accounts"
]
},
{
"type": "payment_initiation",
"actions": [
"initiate",
"status",
"cancel"
],
"locations": [
"https://example.com/payments"
],
"instructedAmount": {
"currency": "EUR",
"amount": "123.50"
},
"creditorName": "Merchant123",
"creditorAccount": {
"iban": "DE02100100109307118603"
},
"remittanceInformationUnstructured": "Ref Number Merchant"
}
]
}
Authorization request URIs containing authorization details in a
request parameter or a request object can become very long.
Implementers SHOULD therefore consider using the "request_uri"
parameter as defined in [I-D.ietf-oauth-jwsreq] in combination with
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the pushed request object mechanism as defined in
[I-D.lodderstedt-oauth-par] to pass authorization details in a
reliable and secure manner. Here is an example of such a pushed
authorization request that sends the authorization request data
directly to the AS via a HTTPS-protected connection:
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
&code_challenge_method=S256
&code_challenge=K2-ltc83acc4h0c9w6ESC_rEMTJ3bww-uCHaoeK1t8U
&authorization_details=%7B%22iss%22%3A%22s6BhdRkqt3%22%2C%22aud%22%
3A%22https%3A%2F%2Fserver%2Eexample%2Ecom%22%2C%22response%5Ftype%2
2%3A%22code%22%2C%22client%5Fid%22%3A%22s6BhdRkqt3%22%2C%22redirect
%5Furi%22%3A%22https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb%22%2C%22st
ate%22%3A%22af0ifjsldkj%22%2C%22code%5Fchallenge%5Fmethod%22%3A%22S
256%22%2C%22code%5Fchallenge%22%3A%22K2%2Dltc83acc4h0c9w6ESC%5FrEMT
J3bww%2DuCHaoeK1t8U%22%2C%22authorization%5Fdetails%22%3A%5B%7B%22t
ype%22%3A%22account%5Finformation%22%2C%22actions%22%3A%5B%22list%5
Faccounts%22%2C%22read%5Fbalances%22%2C%22read%5Ftransactions%22%5D
%2C%22locations%22%3A%5B%22https%3A%2F%2Fexample%2Ecom%2Faccounts%2
2%5D%7D%2C%7B%22type%22%3A%22payment%5Finitiation%22%2C%22actions%2
2%3A%5B%22initiate%22%2C%22status%22%2C%22cancel%22%5D%2C%22locatio
ns%22%3A%5B%22https%3A%2F%2Fexample%2Ecom%2Fpayments%22%5D%2C%22ins
tructedAmount%22%3A%7B%22currency%22%3A%22EUR%22%2C%22amount%22%3A%
22123%2E50%22%7D%2C%22creditorName%22%3A%22Merchant123%22%2C%22cred
itorAccount%22%3A%7B%22iban%22%3A%22DE02100100109307118603%22%7D%2C
%22remittanceInformationUnstructured%22%3A%22Ref%20Number%20Merchan
t%22%7D%5D%7D
3.2. Authorization Request Processing
Based on the data provided in the "authorization_details" parameter
the AS will ask the user for consent to the requested access
permissions.
The AS MUST refuse to process any unknown authorization data type.
If the "authorization_details" contain any unknown authorization data
type, the AS MUST abort processing and respond with an error
"invalid_authorization_details" to the client.
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Note: If the authorization request also contained the "scope"
parameter, the AS MUST present the merged set of requirements
represented by the authorization request in the user consent.
If the resource owner grants the client the requested access, the AS
will issue tokens to the client that are associated with the
respective "authorization_details" (and scope values, if applicable).
Note: The AS MUST make the "authorization_details" available to the
respective resource servers. The AS MAY add the
"authorization_details" element to access tokens in JWT format and to
Token Introspection responses (see below).
3.3. Token Request
Clients utilizing authorization details are RECOMMENDED to use the
"resource" token request parameter to allow the AS to issue audience
restricted access tokens as recommended in
[I-D.ietf-oauth-security-topics].
For example the following token request selects authorization details
applicable for the resource server represented by the URI
"https://example.com/payments".
POST /token HTTP/1.1
Host: as.example.com
Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW
Content-Type: application/x-www-form-urlencoded
grant_type=authorization_code&code=SplxlOBeZQQYbYS6WxSbIA
&redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb
&resource=https%3A%2F%2Fexample%2Ecom%2Fpayments
3.4. Token Response
In addition to the token response parameters as defined in [RFC6749],
the authorization server MUST also return the authorization details
as granted by the resource owner and assigned to the respective
access token.
This is shown in the following example:
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HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-cache, no-store
{
"access_token": "2YotnFZFEjr1zCsicMWpAA",
"token_type": "example",
"expires_in": 3600,
"refresh_token": "tGzv3JOkF0XG5Qx2TlKWIA",
"authorization_details": [
{
"type": "https://www.someorg.com/payment_initiation",
"actions": [
"initiate",
"status",
"cancel"
],
"locations": [
"https://example.com/payments"
],
"instructedAmount": {
"currency": "EUR",
"amount": "123.50"
},
"creditorName": "Merchant123",
"creditorAccount": {
"iban": "DE02100100109307118603"
},
"remittanceInformationUnstructured": "Ref Number Merchant"
}
]
}
3.4.1. Token Content
In order to enable the RS to enforce the authorization details as
approved in the authorization process, the AS MUST make this data
available to the RS.
If the access token is a JWT [RFC7519], the AS is RECOMMENDED to add
the "authorization_details" object, filtered to the specific
audience, as top-level claim.
The AS will typically also add further claims to the JWT the RS
requires for request processing, e.g., user id, roles, and
transaction specific data. What claims the particular RS requires is
defined by the RS-specific policy with the AS.
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The following shows the contents of an example JWT for the payment
initation example above:
{
"iss": "https://as.example.com",
"sub": "24400320",
"aud": "a7AfcPcsl2",
"exp": 1311281970,
"acr": "psd2_sca",
"txn": "8b4729cc-32e4-4370-8cf0-5796154d1296",
"authorization_details": [
{
"type": "https://www.someorg.com/payment_initiation",
"actions": [
"initiate",
"status",
"cancel"
],
"locations": [
"https://example.com/payments"
],
"instructedAmount": {
"currency": "EUR",
"amount": "123.50"
},
"creditorName": "Merchant123",
"creditorAccount": {
"iban": "DE02100100109307118603"
},
"remittanceInformationUnstructured": "Ref Number Merchant"
}
],
"debtorAccount": {
"iban": "DE40100100103307118608",
"user_role": "owner"
}
]
In this case, the AS added the following example claims:
o "sub": conveys the user on which behalf the client is asking for
payment initation
o "txn": transaction id used to trace the transaction across the
services of provider "example.com"
o "debtorAccount": API-specific element containing the debtor
account. In the example, this account was not passed in the
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authorization details but selected by the user during the
authorization process. The field "user_role" conveys the role the
user has with respect to this particuar account. In this case,
she is the owner. This data is used for access control at the
payment API (the RS).
3.5. Token Introspection Request
In case of opaque access tokens, the data provided to a certain RS is
determined using the RS's identifier with the AS (see
[I-D.ietf-oauth-jwt-introspection-response], section 3).
3.6. Token Introspection Response
The token endpoint response provides the RS with the authorization
details applicable to it as a top-level JSON element along with the
claims the RS requires for request processing.
Here is an example for the payment initation example RS:
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{
"active": true,
"sub": "24400320",
"aud": "s6BhdRkqt3",
"exp": 1311281970,
"acr": "psd2_sca",
"txn": "8b4729cc-32e4-4370-8cf0-5796154d1296",
"authorization_details": [
{
"type": "https://www.someorg.com/payment_initiation",
"actions": [
"initiate",
"status",
"cancel"
],
"locations": [
"https://example.com/payments"
],
"instructedAmount": {
"currency": "EUR",
"amount": "123.50"
},
"creditorName": "Merchant123",
"creditorAccount": {
"iban": "DE02100100109307118603"
},
"remittanceInformationUnstructured": "Ref Number Merchant"
}
],
"debtorAccount": {
"iban": "DE40100100103307118608",
"user_role": "owner"
}
}
4. Metadata
The AS advertises support for "authorization_details" using the
metadata parameter "authorization_details_supported" of type boolean.
The authorization data types supported can be determined using the
metadata parameter "authorization_data_types_supported", which is an
JSON array.
Clients announce the authorization data types they use in the new
dynamic client registration parameter "authorization_data_types".
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The registration of new authorization data types with the AS is out
of scope of this draft.
5. Implementation Considerations
The scheme and processing will vary significantly among different
authorization data types. Any implementation of this draft is
therefore supposed to allow the customization of the user consent and
the handling of access token data.
One option would be to have a mechanism allowing the registration of
extension modules, each of them responsible for rendering the
respective user consent and any transformation needed to provide the
data needed to the resource server by way of structured access tokens
or token introspection responses.
6. Security Considerations
Authorization details are sent through the user agent in case of an
OAuth authorization request, which makes them vulnerable to
modifications by the user. In order to ensure their integrity, the
client SHOULD send authorization details in a signed request object
as defined in [I-D.ietf-oauth-jwsreq] or use the "request_uri"
authorization request parameter as defined in [I-D.ietf-oauth-jwsreq]
to pass the URI of the request object to the authorization server.
All strings MUST be compared using the exact byte representation of
the characters as defined by [RFC8259]. This is especially true for
the "type" field, which dictates which other fields and functions are
allowed in the request. The server MUST NOT perform any form of
collation, transformation, or equivalence on the string values.
7. Privacy Considerations
Implementers MUST design and use authorization details in a privacy
preserving manner.
Any sensitive personal data included in authorization details MUST be
prevented from leaking, e.g., through referrer headers.
Implementation options include encrypted request objects as defined
in [I-D.ietf-oauth-jwsreq] or transmission of authorization details
via end-to-end encrypted connections between client and authorization
server by utilizing the "request_uri" authorization request parameter
as defined in [I-D.ietf-oauth-jwsreq].
Even if the request data are encrypted, an attacker could use the
authorization server to learn the user data by injecting the
encrypted request data into an authorization request on a device
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under his control and use the authorization server's user consent
screens to show the (decrypted) user data in the clear.
Implementations MUST consider this attacker vector and implement
appropriate counter measures, e.g. by only showing portions of the
data or, if possible, determing whether the assumed user context is
still the same (after user authentication).
The AS MUST take into consideration the privacy implications when
sharing authorization details with the resource servers. The AS
SHOULD share this data with the resource servers on a "need to know"
basis.
8. Acknowledgements
We would would like to thank Daniel Fett, Sebastian Ebling, Dave
Tonge, Mike Jones, Nat Sakimura, and Rob Otto for their valuable
feedback during the preparation of this draft.
We would also like to thank Daniel Fett, Dave Tonge, Travis Spencer,
Joergen Binningsboe, Aamund Bremer, Steinar Noem, and Aaron Parecki
for their valuable feedback to this draft.
9. IANA Considerations
TBD
o "authorization_details" as JWT claim
o "authorization_details_supported" and
"authorization_data_types_supported" as metadata parameters
o "authorization_data_types" as dynamic client registration
parameter
o establish authorization data type registry
o register type "openid_claims"
10. References
10.1. Normative References
[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>.
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[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>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/info/rfc7519>.
[RFC7521] Campbell, B., Mortimore, C., Jones, M., and Y. Goland,
"Assertion Framework for OAuth 2.0 Client Authentication
and Authorization Grants", RFC 7521, DOI 10.17487/RFC7521,
May 2015, <https://www.rfc-editor.org/info/rfc7521>.
[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>.
[RFC8628] Denniss, W., Bradley, J., Jones, M., and H. Tschofenig,
"OAuth 2.0 Device Authorization Grant", RFC 8628,
DOI 10.17487/RFC8628, August 2019,
<https://www.rfc-editor.org/info/rfc8628>.
10.2. Informative References
[CSC] Consortium, C. S., "Architectures and protocols for remote
signature applications", Jun 2019,
<https://cloudsignatureconsortium.org/wp-
content/uploads/2019/07/CSC_API_V1_1.0.4.0.pdf>.
[ETSI] ETSI, "ETSI TS 119 432, Electronic Signatures and
Infrastructures (ESI); Protocols for remote digital
signature creation", Mar 2019,
<https://www.etsi.org/deliver/
etsi_ts/119400_119499/119432/01.01.01_60/
ts_119432v010101p.pdf>.
[I-D.ietf-oauth-jwsreq]
Sakimura, N. and J. Bradley, "The OAuth 2.0 Authorization
Framework: JWT Secured Authorization Request (JAR)",
draft-ietf-oauth-jwsreq-20 (work in progress), October
2019.
[I-D.ietf-oauth-jwt-introspection-response]
Lodderstedt, T. and V. Dzhuvinov, "JWT Response for OAuth
Token Introspection", draft-ietf-oauth-jwt-introspection-
response-08 (work in progress), September 2019.
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[I-D.ietf-oauth-resource-indicators]
Campbell, B., Bradley, J., and H. Tschofenig, "Resource
Indicators for OAuth 2.0", draft-ietf-oauth-resource-
indicators-08 (work in progress), September 2019.
[I-D.ietf-oauth-security-topics]
Lodderstedt, T., Bradley, J., Labunets, A., and D. Fett,
"OAuth 2.0 Security Best Current Practice", draft-ietf-
oauth-security-topics-13 (work in progress), July 2019.
[I-D.lodderstedt-oauth-par]
Lodderstedt, T., Campbell, B., Sakimura, N., Tonge, D.,
and F. Skokan, "OAuth 2.0 Pushed Authorization Requests",
draft-lodderstedt-oauth-par-00 (work in progress),
September 2019.
[OIDC] Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., and
C. Mortimore, "OpenID Connect Core 1.0 incorporating
errata set 1", Nov 2014,
<http://openid.net/specs/openid-connect-core-1_0.html>.
[OpenID.CIBA]
Fernandez, G., Walter, F., Nennker, A., Tonge, D., and B.
Campbell, "OpenID Connect Client Initiated Backchannel
Authentication Flow - Core 1.0", January 2019,
<https://openid.net/specs/openid-client-initiated-
backchannel-authentication-core-1_0.html>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>.
[transaction-authorization]
Lodderstedt, T., "Transaction Authorization or why we need
to re-think OAuth scopes", Apr 2019, <https://medium.com/
oauth-2/transaction-authorization-or-why-we-need-to-re-
think-oauth-scopes-2326e2038948>.
Appendix A. Additional Examples
A.1. OpenID Connect
These hypothetical examples try to encapsulate all details specific
to the OpenID Connect part of an authorization process into an
authorization JSON object.
The top-level elements are based on the definitions given in [OIDC]:
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o "claim_sets": names of predefined claim sets, replacement for
respective scope values, such as "profile"
o "max_age": Maximum Authentication Age
o "acr_values": array of ACR values
o "claims": the "claims" JSON structure as defined in [OIDC]
This is a simple request for some claim sets.
[
{
"type": "openid",
"locations": [
"https://op.example.com/userinfo"
],
"claim_sets": [
"email",
"profile"
]
}
]
Note: "locations" specifies the location of the userinfo endpoint
since this is the only place where an access token is used by a
client (RP) in OpenID Connect to obtain claims.
A more sophisticated example is shown in the following
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[
{
"type": "openid",
"locations": [
"https://op.example.com/userinfo"
],
"max_age": 86400,
"acr_values": "urn:mace:incommon:iap:silver",
"claims": {
"userinfo": {
"given_name": {
"essential": true
},
"nickname": null,
"email": {
"essential": true
},
"email_verified": {
"essential": true
},
"picture": null,
"http://example.info/claims/groups": null
},
"id_token": {
"auth_time": {
"essential": true
}
}
}
}
]
A.2. Remote Electronic Signing
The following example is based on the concept layed out for remote
electronic signing in ETSI TS 119 432 [ETSI] and the CSC API for
remote signature creation [CSC].
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[
{
"type": "sign",
"locations": [
"https://signing.example.com/signdoc"
],
"credentialID": "60916d31-932e-4820-ba82-1fcead1c9ea3",
"documentDigests": [
{
"hash": "sTOgwOm+474gFj0q0x1iSNspKqbcse4IeiqlDg/HWuI=",
"label": "Credit Contract"
},
{
"hash": "HZQzZmMAIWekfGH0/ZKW1nsdt0xg3H6bZYztgsMTLw0=",
"label": "Contract Payment Protection Insurance"
}
],
"hashAlgorithmOID": "2.16.840.1.101.3.4.2.1"
}
]
The top-level elements have the following meaning:
o "credentialID": identifier of the certificate to be used for
signing
o "documentDigests": array containing the hash of every document to
be signed ("hash" elements). Additionally, the corresponding
"label" element identifies the respective document to the user,
e.g. to be used in user consent.
o "hashAlgorithm": algomrithm that was used to calculate the hash
values.
The AS is supposed to ask the user for consent for the creation of
signatues for the documents listed in the structure. The client uses
the access token issued as result of the process to call the sign doc
endpoint at the respective signing service to actually create the
signature. This access token is bound to the client, the user id and
the hashes (and signature algorithm) as consented by the user.
A.3. Access to Tax Data
This example is inspired by an API allowing third parties to access
citizen's tax declarations and income statements, for example to
determine their credit worthiness.
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[
{
"type": "tax_data",
"locations": [
"https://taxservice.govehub.no"
],
"actions":"read_tax_declaration",
"periods": ["2018"],
"duration_of_access": 30,
"tax_payer_id": "23674185438934"
}
]
The top-level elements have the following meaning:
o "periods": determines the periods the client wants to access
o "duration_of_access": how long does the client intend to access
the data in days
o "tax_payer_id": identifier of the tax payer (if known to the
client)
A.4. eHealth
This example is inspired by an API used in the Norwegian eHealth
system.
In this use case the physical therapist sits in front of her computer
using a local Electronic Health Records (EHR) system. She wants to
look at the electronic patient records of a certain patient and she
also wants to fetch the patients journal entries in another system,
perhaps at another institution or a national service. Access to this
data is provided by an API.
The information necessary to authorize the request at the API is only
known by the EHR system, and must be presented to the API.
Here is an example authorization details object:
[
{
"type": "patient_record",
"location": "https://fhir.example.com/patient",
"actions": [
"read"
],
"patient_identifier": [
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{
"system": "urn:oid:2.16.578.1.12.4.1.4.1",
"value": "12345678901"
}
],
"reason_for_request": "Clinical treatment",
"requesting_entity": {
"type": "Practitioner",
"practicioner_identifier": [
{
"system": " urn:oid:2.16.578.1.12.4.1.4.4",
"value": "1234567"
}
],
"practitioner_role": {
"organization": {
"organization_identifier": [
{
"system": "urn:oid:2.16.578.1.12.4.1.2.101",
"value": "<organizational number>"
}
],
"organization_type": {
"coding": [
{
"system":
"http://hl7.org/fhir/organization-type",
"code": "dept",
"display": "Hospital Department"
}
]
},
"name": "Akuttmottak"
},
"role": {
"coding": [
{
"system": "http://snomed.info/sct",
"code": "36682004",
"display": "Physical therapist"
}
]
}
}
}
}
]
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Description of the elements:
o "patient_identifier": the identifier of the patient composed of a
system identifier in OID format (namespace) and the acutal value
within this namespace.
o "reason_for_request": the reason why the user wants to access a
certain API
o "requesting_entity": specification of the requester by means of
identity, role and organizational context. This data is provided
to facilitate authorization and for auditing purposes.
In this use case, the AS authenticates the requester, who is not the
patient, and approves access based on policies.
Appendix B. Document History
[[ To be removed from the final specification ]]
-03
o Reworked examples to illustrate privacy preserving use of
"authorization_details"
o Added text on audience restriction
o Added description of relationship between "scope" and
"authorization_details"
o Added text on token request & response and "authorization_details"
o Added text on how authorization details are conveyed to RSs by
JWTs or token endpoint response
o Added description of relationship between "claims" and
"authorization_details"
o Added more example from different sectors
o Clarified string comparison to be byte-exact without collation
-02
o Added Security Considerations
o Added Privacy Considerations
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o Added notes on URI size and authorization details
o Added requirement to return the effective authorization details
granted by the resource owner in the token response
o changed "authorization_details" structure from object to array
o added Justin Richer & Brian Campbell as Co-Authors
-00 / -01
o first draft
Authors' Addresses
Torsten Lodderstedt
yes.com
Email: torsten@lodderstedt.net
Justin Richer
Bespoke Engineering
Email: ietf@justin.richer.org
Brian Campbell
Ping Identity
Email: bcampbell@pingidentity.com
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