[EN] Open Finance Brasil Financial-grade API Dynamic Client Registration 1.0 Implementers Draft 3

Foreword

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The Open Finance Brasil Initial Structure is responsible for creating standards and specifications necessary to meet the requirements and obligations of the Brasil Open Finance Legislation as originally outlined by the Brasil Central Bank. There is a possibility that some of the elements of this document may be the subject to patent rights. OFBIS shall not be held responsible for identifying any or all such patent rights.

Open Finance Brasil Financial-grade API Security Profile 1.0 consists of the following parts:

• Open Finance Brasil Financial-grade API Security Profile 1.0

• Open Finance Brasil Dynamic Client Registration Profile 1.0

These parts are intended to be used with RFC6749, RFC6750, RFC7636, OIDC, OIDR, RFC7591, RFC7592, FAPI-1-Baseline and FAPI-1-Advanced

Introduction

The Open Finance Brasil Financial-grade API Dynamic Client Registration Profile is a profile of RFC7591, RFC7592 and OIDR that aims to provide specific implementation guidelines for security and interoperability which can be applied to the identification, registration and management of OAuth Clients operating in the Brasil Open Finance ecosystem.

Although it is possible to code an OpenID Provider and Relying Party from scratch using this specification, the main audience for this specification are parties who already have a certified implementation of OpenID Connect and seek to obtain certification for the Brasil Open Finance programme.

Notational Conventions

The key words "shall", "shall not", "should", "should not", "may", and "can" in this document are to be interpreted as described in ISO Directive Part 2. These key words are not to be used as lexicon terms such that any occurrence of them shall be interpreted as key words and are not to be interpreted with their natural language meanings.

Scope

This document specifies the method of

• applications registered in the Open Finance Directory of Participants to discover OpenID Providers offering services in the Open Finance Brasil ecosystem;

• applications to use OpenID Connect Registration to onboard their applications with Bank OpenID Providers; and

• applications to use OAuth 2.0 Dynamic Client Registration Management Protocol to manage their applications with OpenID Providers;

This document is applicable to all participants engaging in Open Finance in Brasil.

Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applied. For undated references, the latest edition of the referenced document (including any amendments) applies.

ISODIR2 - ISO/IEC Directives Part 2

RFC6749 - The OAuth 2.0 Authorization Framework

RFC6750 - The OAuth 2.0 Authorization Framework: Bearer Token Usage

RFC7636 - Proof Key for Code Exchange by OAuth Public Clients

RFC6819 - OAuth 2.0 Threat Model and Security Considerations

RFC7519 - JSON Web Token (JWT)

RFC7591 - OAuth 2.0 Dynamic Client Registration Protocol

RFC7592 - OAuth 2.0 Dynamic Client Registration Management Protocol

BCP195 - Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)

OIDC - OpenID Connect Core 1.0 incorporating errata set 1

FAPI-CIBA - Financial-grade API: Client Initiated Backchannel Authentication Profile

RFC4514 - Lightweight Directory Access Protocol (LDAP): String Representation of Distinguished Names

RFC4517 - Lightweight Directory Access Protocol (LDAP): Syntaxes and Matching Rules

OIDD - OpenID Connect Discovery 1.0 incorporating errata set 1

OIDR - OpenID Connect Registration 1.0 incorporating errata set 1

RFC8705 - OAuth 2.0 Mutual TLS Client Authentication and Certificate Bound Access Tokens

JARM - Financial-grade API: JWT Secured Authorization Response Mode for OAuth 2.0 (JARM)

PAR - OAuth 2.0 Pushed Authorization Requests

JAR - OAuth 2.0 JWT Secured Authorization Request

FAPI-1-Baseline - Financial-grade API Security Profile 1.0 - Part 1: Baseline

FAPI-1-Advanced - Financial-grade API Security Profile 1.0 - Part 2: Advanced

OFB-FAPI - Open Finance Brasil Financial-grade API Security Profile 1.0

OFB-Cert-Standards - Open Finance Brasil x.509 Certificate Standards

OFB-DCR/DCM-Swagger - DCR & DCM Swagger

Terms and definitions

For the purpose of this document, the terms defined in RFC6749, RFC6750, RFC7636, OpenID Connect Core and ISO29100 apply.

Symbols and Abbreviated terms

• API - Application Programming Interface

• DCR - Dynamic Client Registration

• FAPI - Financial-grade API

• HTTP - Hyper Text Transfer Protocol

• OIDF - OpenID Foundation

• REST - Representational State Transfer

• SS - Software Statement

• SSA - Software Statement Assertion

• TLS - Transport Layer Security

Introduction

Brasil Open Finance ecosystem leverages a federation trust provider or directory of participants as the golden source of information on accredited participants and software that are authorized to partake in the Open Finance Brasil ecosystem.

The services by the Directory include

• Software registration and management.

• Software credential registration and management using ICP Certificates.

• Software Statement Assertion (SSA) generation

Participants within the ecosystem must leverage these services to facilitate API driven OAuth client registration using the process outlined in clause 3.1.1 of RFC7591 with additional metadata necessary to support OpenID Connect defined in OpenID Connect Registration.

It's important to remember that the client registration payload has most of its attributes as non-mandatory, and that assigned values that conflict with those in the software statement assertion will be overridden by the values of the software statement assertion issued by the Directory of Participants. Not all metadata a client wishes to provide may be contained in a software statement, e.g alternative Metadata Languages and Script values. There are some cases where the client metadata are subset of the existing values in the SSA, such as redirect_URIs.

Open Finance Brasil OpenID Connect Discovery provisions

Authorization server

The Authorization Server shall support OpenID Connect Discovery as required by Financial-grade API Security Profile 1.0 - Part 1: Baseline. This support shall be explicit in Participant Directory configurations, and in the declaration of its attributes in the Discovery file (well-known), respecting the authentication mechanisms certified by the institution through the Open Finance Brazil compliance tests.

In addition, the Authorization Server:

1. shall advertise its presence in the Open Finance Brasil ecosystem by being listed on the Directory of Participants;

2. shall advertise all Open Finance Brasil REST API resources protected by the OpenID Provider on the Directory of Participants;

3. shall advertise support for all signing, encryption, authentication mechanisms and standards required to support Open Finance Brasil Financial API;

4. shall advertise support for OpenID Dynamic Client Registration;

5. shall advertise mtls_endpoint_aliases as per clause 5 RFC 8705 OAuth 2.0 Mutual-TLS Client Authentication and Certificate-Bound Access Tokens the token_endpoint, registration_endpoint and userinfo_endpoint;

6. if supporting OAuth 2.0 Pushed Authorization Requests shall advertise through OIDD mtls_endpoint_aliases the pushed_authorization_request_endpoint;

7. if supporting Financial API - Client Initiated Back Channel Authentication shall advertise through OIDD mtls_endpoint_aliases the backchannel_authentication_endpoint;

Client

The Client shall support OpenID Connect Discovery as required by Financial-grade API Security Profile 1.0 - Part 1: Baseline

In addition, the Client

1. shall rely on ecosystem discovery services provided by Directory of Participants only;

2. shall derive necessary Authorisation Server metadata by relying on an Authorization Servers OpenID Connect Discovery services only;

3. where present, shall use endpoints advertised in mtls_endpoint_aliases as per clause 5 RFC 8705 OAuth 2.0 Mutual-TLS Client Authentication and Certificate-Bound Access Tokens;

Open Finance Brasil OpenID Connect Registration Provisions

7.1. Authorization server

The Authorization Server shall support the RFC RFCs Dynamic Client Registration (DCR) RFC7591, Dynamic Client Management (DCM) RFC7592 and OpenID Registration

In addition, the Authorization Server

1. shall reject dynamic client registration requests not performed over a connection secured with mutual tls using certificates issued by Brazil ICP (production) or the Directory of Participants (sandbox);

2. shall validate that the request contains software_statement JWT signed using the PS256 algorithim issued by the Open Finance Brasil directory of participants;

3. shall validate that the software_statement was issued (iat) not more than 5 minutes prior to the request being received;

4. shall validate that the attribute jwks (key set by value) was not included; but declared as a reference in the jwks_uri attribute;

5. shall, when informed, validate that jwks_uri matches the software_jwks_uri provided in the software_statement;

6. shall require and validate that redirect_uris matches or contains a sub set of software_redirect_uris provided in the software_statement;

7. shall require and validate that all client authentication mechanism adhere to the requirements defined in RFC7591 and RFC7592, validating the registration_access_token and, through a secure connection, the certificate chain of ICP-Brasil;

8. removed;

9. shall validate that the requested scopes are adequate for accredited institutions and their regulatory roles and contained in the software_statement. The list of regulatory permissions and the corresponding scopes are described in the following sections;

10. where possible, shall compare client metadata asserted by a client to the metadata provided in the software_statement, choosing values in the SSA with precedence;

11. shall accept all x.500 AttributeType name strings defined in the Distinguished Name of the x.509 Certificate Profiles defined in Open Finance Brasil x.509 Certificate Standards;

12. if supporting tls_client_auth client authentication mechanism as defined in RFC8705 shall only accept tls_client_auth_subject_dn as an indication of the certificate subject value as defined in clause 2.1.2 RFC8705;

13. The value of the field UID of the certificate should match the one sent in the SSA, where the UID field should contain the value of the software_id field of the SSA.

14. The organizationIdentifier field will be found in the subject_DN in ASN.1 format and must be decoded respecting the corresponding encoding string. The value of the organizationIdentifier field of the certificate which must contain the prefix corresponding to the Registration Reference OFBBR- followed by the value of the org_id field of the SSA. You must convert the values ​​of the OID 2.5.4.97 field from ASN.1 format to human-readable text. For certificates issued before August 31, 2022: The value of the OR field of the certificate must contain the value of the org_id field of the SSA.

15. shall, during the TLS handshake process, use the distinguishedNameMatch rule to compare the DN values as defined in RFC4517.

16. shall ensure the integrity of the stock of active consents, even after any systemic changes, so that such changes are transparent to the data receiver institutions (TPP).

17. shall perform a recertification on OIDF FAPI and DCR after any systemic changes.

These provisions apply equally to the processing of RFC7591, RFC7592 and OpenID Registration requests

Applying Server Defaults

Whenever properties of a DCR request are not included nor mandatory in the specification, the Authorisation Server shall apply client defaults in the following manner:

1. shall select and apply the encryption algorithm and cipher choice from the most recommended of the IANA cipher suites that is supported by the Authorisation Server;

2. shall populate defaults from values within the software_statement assertion where possible;

3. shall grant the client permission to the complete set of potential scopes based on the softwares regulatory permissions included in the software_statement;

Certificate Distinguished Name Parsing

Clause 3 of Lightweight Directory Access Protocol (LDAP): String Representation of Distinguished Names defines the mandatory OIDs whose AttributeType strings (descriptors) must be recognized by implementers. This mandatory list does not include several of the OIDs defined in Open Finance Brasil x.509 Certificate Standards nor is there a defined mechanism for Authorisation Servers to publish information regarding the format that they would expect a Dynamic Client Registration request that includes a tls_client_auth_subject_dn to be presented in.

To address this ambiguity, the Authorization Server shall accept only the AttributeTypes (descriptors) defined in the last paragraph of clause 3 RFC4514 in string format, it shall also accept in OID format, with their values in ASN.1, all the AttributeTypes defined in Distinguished Name Open Finance Brasil x.509 Certificate Standards or added by the Certificate Authority.

In case of non-compliance with these requirements, the Authorization Server shall reject the registration.

In terms of format, follow below how decoding should be done:

• Obtain in reverse order the certificate attributes.

• Append each RDN (RelativeDistinguishedName) segment with a comma ','.

• Use the RFC strings (CN, L, ST, O, OR, C, Street, DC, UID) with the value of their attributes in human-readable format.

• Use the OIDs of the attributes defined in this specification for use in the OFB (businessCategory = OID 2.5.4.15, jurisdictionCountryName = OID 1.3.6.1.4.1.311.60.2.1.3, serialNumber = OID 2.5.4.5, organizationIdentifier = OID 2.5.4.97) with values in ASN.1 format, following the RFC4514, being that:

  • Attribute names shall be defined according to dot-decimal notation, without adding the prefix "OID", ie. "2.5.4.15", followed by ('=#') plus the hexadecimal value of the attribute, here follows a complete example: 2.5.4.15=#0C1450726976617465204F7267616E697A6174696F6E

  • There are no restrictions for encoding and formatting attribute values. The hexadecimal value presented on the utilized attribute must be respected (PrintableString, UTF8String, etc). This item complies with opcionality of the format stabilished by the AC face ICP normatives and items 2.3, 2.4 e 5.2 of the RFC4514. -To comply with DCR standard, convert ASN.1 values from OID 2.5.4.97 organizationIdentifier to human readable text, use features of your API gateway or a standard library of type ASN.1 or if necessary still develop manually. To do so, retrieve the full value of the OID 2.5.4.97 contained in the subject_DN. Remove dot-decimal notation (2.5.4.97). Remove the ('=#') signs. Convert the hex value to text. Apply a filter using regular expression to retrieve the org_id after ('OFBBR-'), for example: 2.5.4.97=#132A4F464242522D36376335373838322D303433622D313165632D396130332D303234326163313330303033. Remove dot-decimal notation and signs ('=#'): 2.5.4.97=#. Convert the hexadecimal value 132A4F464242522D36376335373838322D303433622D313165632D396130332D303234326163313330303033 to text: **OFBBR-67c57882-043b-031ec Apply the regular expression and retrieve the org_id that is contained after 'OFBBR-':67c57882-043b-11ec-9a03-0242ac130003.

Below are examples of required attributes for CAs active until August 31, 2022:

Below are examples of required attributes for CAs active after August 31, 2022:

Regulatory Roles for OpenID and OAuth 2.0 Mappings

To participate in the Open Finance ecosystem, accredited institutions must register themselves in the directory of participants according to their regulatory roles. Those roles reflect the institutions authorization from the Central Bank and, consequently, the APIs they are allowed to use.

The following table describes the regulatory roles for Open Finance and the related OAuth 2.0 scopes mapping. If the scopes are omitted during the DCR process, the authorization server shall grant the complete set of potential scopes based on the registering bank's regulatory roles, as described in the Server Defaults section.

It is requiread that the active roles in the application's software_statement are validated. The field _software_statement_roles shall be used for validation and currently listed roles shall be active.

Client Registration

Section 4.2.11 of RFC 4517 (caseIgnoreMatch) must be respected. Upon registering using the tls_client_auth authentication method, the client shall forward the tls_client_auth_subject_dn field with the AttibuteTypes(Descriptors) using the defined format under item Certificate Distinguished Name Parsing. Non adherence to this format shall cause rejection of the registration.

Software Statement Assertion

A Software Statement Assertion (software_statement) is a JSON Web Token (JWT) RFC7519 that asserts the metadata values of the client software as a whole. On the Open Finance Brasil structure, this software_statement is signed by the Participants Directory and it's signature MUST be validated by the Authorization Servers using the public keys available on the following session.

Attributes of the Software Statement Assertion (Claims)

The following example contains all attributes currently included in a software_statement:

{
  "software_mode": "Live",
  "software_redirect_uris": [
    "https://www.raidiam.com/accounting/cb"
  ],
  "software_statement_roles": [
    {
      "role": "DADOS",
      "authorisation_domain": "Open Banking",
      "status": "Active"
    },
    {
      "role": "PAGTO",
      "authorisation_domain": "Open Banking",
      "status": "Active"
    }
  ],
  "software_client_name": "Raidiam Accounting",
  "org_status": "Active",
  "software_client_id": "Cki1EbvjwyhPB12NGLlz2",
  "iss": "Open Banking Open Banking Brasil prod SSA issuer",
  "software_tos_uri": "https://www.raidiam.com/accounting/tos.html",
  "software_client_description": "Raidiam Accounting leverage cutting edge open banking access to bring you real time up to date views of your finances",
  "software_jwks_uri": "https://keystore.directory.openbankingbrasil.org.br/b961c4eb-509d-4edf-afeb-35642b38185d/25556d5a-b9dd-4e27-aa1a-cce732fe74de/application.jwks",
  "software_policy_uri": "https://www.raidiam.com/accounting/policy.html",
  "software_id": "25556d5a-b9dd-4e27-aa1a-cce732fe74de",
  "software_client_uri": "https://www.raidiam.com/accounting.html",
  "software_jwks_inactive_uri": "https://keystore.directory.openbankingbrasil.org.br/b961c4eb-509d-4edf-afeb-35642b38185d/25556d5a-b9dd-4e27-aa1a-cce732fe74de/inactive/application.jwks",
  "software_jwks_transport_inactive_uri": "https://keystore.directory.openbankingbrasil.org.br/b961c4eb-509d-4edf-afeb-35642b38185d/25556d5a-b9dd-4e27-aa1a-cce732fe74de/inactive/transport.jwks",
  "software_jwks_transport_uri": "https://keystore.directory.openbankingbrasil.org.br/b961c4eb-509d-4edf-afeb-35642b38185d/25556d5a-b9dd-4e27-aa1a-cce732fe74de/transport.jwks",
  "software_logo_uri": "https://www.raidiam.com/accounting/logo.png",
  "org_id": "b961c4eb-509d-4edf-afeb-35642b38185d",
  "org_number": "112233445566",
  "software_environment": "production",
  "software_version": "1.1",
  "software_roles": [
    "DADOS",
    "PAGTO"
  ],
  "org_name": "Open Banking Brasil",
  "iat": 1620060821,
  "organisation_competent_authority_claims": [
    {
      "authorisation_domain": "Open Banking",
      "authorisations": [],
      "registration_id": "13353236-OBB-CONTA",
      "authority_id": "687a1c94-b360-4e04-9589-0fa5cb16451b",
      "authority_name": "Banco Central",
      "authorisation_role": "CONTA",
      "authority_code": "BCB",
      "status": "Active"
    },
    {
      "authorisation_domain": "Open Banking",
      "authorisations": [],
      "registration_id": "13353236-OBB-DADOS",
      "authority_id": "687a1c94-b360-4e04-9589-0fa5cb16451b",
      "authority_name": "Banco Central",
      "authorisation_role": "DADOS",
      "authority_code": "BCB",
      "status": "Active"
    },
    {
      "authorisation_domain": "Open Banking",
      "authorisations": [],
      "registration_id": "13353236-OBB-PAGTO",
      "authority_id": "687a1c94-b360-4e04-9589-0fa5cb16451b",
      "authority_name": "Banco Central",
      "authorisation_role": "PAGTO",
      "authority_code": "BCB",
      "status": "Active"
    }
  ]
}

Processing of the Dynamic Client Registration claim

The steps of the subject_DN extraction process are described in section Certificate Distinguished Name Parsing