A Profile for Autonomous System Provider Authorization

The primary purpose of the Resource Public Key Infrastructure (RPKI) is to improve security in the global Internet routing system. As part of this infrastructure, a mechanism is needed for Autonomous Systems (AS) operators, in their capacity as customer, to designate and authorize other ASes as their Provider(s). A Provider AS (PAS) is a network providing connectivity between networks - it provides transit services to the customer, that is: the provider may propagate Network Layer Reachability Information (NLRI) received from any direction (e.g., routes the provider learned from its own providers, lateral peers, and other customers), or default route advertisements, towards the customer; the provider may propagate NLRI received from the customer towards any direction (e.g. towards the provider's providers, lateral peers, and other customers). The digitally signed Autonomous System Provider Authorization (ASPA) object profile specified in this document provides the authorization mechanism mentioned above and can be used to facilitate detection and mitigation of route leaks. An ASPA object is a cryptographically verifiable attestation signed by the holder of an Autonomous System identifier (hereafter called the "Customer AS", or CAS). An ASPA contains a list of one or more ASes, each entry meaning the listed AS is authorized to act as Provider network for the CAS. When the CAS makes use of multiple providers, all Provider ASes are to be listed in the ASPA, including any non-transparent Internet Exchange Point (IXP) Route Server (RS) ASes. Note that the common case for RS ASes at IXPs is to operate transparently (see Section 2.2.2.1 ), and transparent IXP Route Servers need not be listed as PAS in ASPAs. The BGP Roles that an Autonomous System (AS) may have in its peering relationships with eBGP neighbors are discussed in . The details of ASPA registration requirements for ASes in different scenarios are also specified in that document. In addition, the procedures for verifying AS_PATHs in BGP UPDATE messages using Validated ASPA Payloads (VAPs) are described in that document. This CMS protected content type definition conforms to the template for RPKI signed objects. In accordance with Section 4 of , this document defines: The object identifier (OID) that identifies the ASPA signed object. This OID appears in the eContentType field of the encapContentInfo object as well as the content-type signed attribute within the signerInfo structure. The ASN.1 syntax for the ASPA content, which is the payload signed by the CAS. The ASPA content is encoded using the ASN.1 Distinguished Encoding Rules (DER) . The steps required to validate an ASPA beyond the validation steps specified in .

The content-type for an ASPA is defined as id-ct-ASPA, which has the numerical value of 1.2.840.113549.1.9.16.1.49. This OID MUST appear both within the eContentType in the encapContentInfo structure as well as the content-type signed attribute within the signerInfo structure (see ).

The content of an ASPA identifies the Customer AS (CAS) as well as the Set of Provider ASes (SPAS) that are authorized by the CAS to be its Providers. A user registering ASPA(s) must be cognizant of Sections 2, 3, and 4 of and the user (or their software tool) must comply with the ASPA registration recommendations in Section 4 of that document. It is highly recommended that for a given Customer AS, a single ASPA object be maintained which contains all providers, including any non-transparent RS ASes. Such a practice helps prevent race conditions during ASPA updates. Otherwise, said race conditions might affect route propagation. The software that provides hosting for ASPA records SHOULD support enforcement of this recommendation. In the case of the transition process between different CA registries, the ASPA records SHOULD be kept identical in all registries in terms of their authorization contents. The eContent of an ASPA is an instance of ASProviderAttestation, formally defined by the following ASN.1 module: RPKI-ASPA-2023 { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) modules(0) id-mod-rpki-aspa-2023(TBD) } DEFINITIONS EXPLICIT TAGS ::= BEGIN IMPORTS CONTENT-TYPE FROM CryptographicMessageSyntax-2010 -- From RFC 6268 { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) modules(0) id-mod-cms-2009(58) } ; id-ct-ASPA OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) id-smime(16) id-ct(1) aspa(49) } ct-ASPA CONTENT-TYPE ::= { TYPE ASProviderAttestation IDENTIFIED BY id-ct-ASPA } ASProviderAttestation ::= SEQUENCE { version [0] INTEGER DEFAULT 0, customerASID CAS, providers ProviderASSet } CAS ::= INTEGER (1..4294967295) ProviderASSet ::= SEQUENCE (SIZE(1..MAX)) OF ASID ASID ::= INTEGER (0..4294967295) END Note that this content appears as the eContent within the encapContentInfo as specified in .

The version number of the ASProviderAttestation that complies with this specification MUST be 1 and MUST be explicitly encoded.

The customerASID field contains a positive integer that represents the AS number of the Customer Autonomous System that is the authorizing entity.

The providers field contains the listing of ASes that are authorized as providers. Each element contained in the providers field is an instance of ASID. Each ASID element contains the AS number of an AS that has been authorized by the customer AS as its provider or RS. In addition to the constraints described by the formal ASN.1 definition, the contents of the providers field MUST satisfy the following constraints: The CustomerASID value MUST NOT appear in any ASID in the providers field. The elements of providers MUST be ordered in ascending numerical order. Each value of ASID MUST be unique (with respect to the other elements of providers). An ASID value of 0 can only be encoded in the providers field as a single item list, i.e., an element for AS 0 MUST NOT appear alongside any other elements.

Before a relying party can use an ASPA to validate a routing announcement, the relying party MUST first validate the ASPA object itself. To validate an ASPA, the relying party MUST perform all the validation checks specified in as well as the following additional ASPA-specific validation steps. The Autonomous System Identifier Delegation Extension MUST be present in the end-entity (EE) certificate (contained within the ASPA), and the Customer ASID in the ASPA eContent MUST match the ASId specified by the EE certificate's Autonomous System Identifier Delegation Extension. The Autonomous System Identifier Delegation Extension MUST contain exactly one "id" element () and MUST NOT contain any "inherit" elements () or "range" elements (). The IP Address Delegation Extension MUST be absent.

IANA is requested to allocate for id-mod-rpki-aspa-2023 in the "SMI Security for S/MIME Module Identifier (1.2.840.113549.1.9.16.0)" registry as follows:

Decimal	Description	Specification
TBD2	id-mod-rpki-aspa-2023	[RFC-to-be]

IANA is requested to make permanent in the "SMI Security for S/MIME CMS Content Type (1.2.840.113549.1.9.16.1)" registry as follows:

Decimal	Description	Specification
49	id-ct-ASPA	[RFC-to-be]

IANA is requested to make permanent in the "RPKI Signed Object" registry as follows:

Name	OID	Specification
Autonomous System Provider Authorization	1.2.840.113549.1.9.16.1.49	[RFC-to-be]

IANA is requested to make permanent in the "RPKI Repository Name Scheme" registry as follows:

Filename Extension	RPKI Object	Reference
.asa	Autonomous System Provider Authorization	[RFC-to-be]

The IANA is requested to register the media type application/rpki-aspa in the "Media Type" registry as follows: Intended usage: COMMON Restrictions on usage: None Change controller: IETF ]]>

Use of One-Time Use End Entity Certificates CA are RECOMMENDED to generate a new key pair for each new ASPA and only sign one ASPA with each EE certificate. This type of EE certificate is termed a "one-time-use" EE certificate (see ).

ASPA Object Filenames CAs are RECOMMENDED to follow the guidelines for naming ASPA objects based on , i.e., convert the 160-bit hash of the EE's public key value into a 27-character string using Base 64 Encoding with the URL and Filename Safe Alphabet (see ). See for more information and considerations.

Upper Bound on the Number of Providers While the ASN.1 profile specified in imposes no limit on the number of Provider ASes that can be listed for a given Customer ASID, consideration will need to be given to limitations existing in validators and elsewhere in the RPKI supply chain. For example, the number of Provider ASes that can be listed in a single RPKI-To-Router protocol ASPA PDU (following the Length field constraints in ) is 16,380 providers. In addition to protocol limitations in the supply chain, locally defined restrictions could exist for the maximum file size of signed objects a Relying Party implementation is willing to accept. Relying Party implementations are RECOMMENDED to impose an upper bound on the number of Provider ASes for a given Customer ASID. An upper bound value between 4,000 and 10,000 Provider ASes is suggested. If this threshold is exceeded, Relying Party implementations SHOULD treat all ASPA objects related to the Customer ASID invalid; e.g. not emit a partial list of Provider ASes. Additionally, an error SHOULD be logged in the local system, indicating the Customer ASID for which the threshold was exceeded. Implementers and operators SHOULD periodically review whether imposed upper bounds still are reasonable in context of the global Internet routing system.

The security considerations of , , and also apply to ASPAs.

Implementation status This section records the status of known implementations of the protocol defined by this specification at the time of posting of this Internet-Draft, and is based on a proposal described in RFC 7942. The description of implementations in this section is intended to assist the IETF in its decision processes in progressing drafts to RFCs. Please note that the listing of any individual implementation here does not imply endorsement by the IETF. Furthermore, no effort has been spent to verify the information presented here that was supplied by IETF contributors. This is not intended as, and must not be construed to be, a catalog of available implementations or their features. Readers are advised to note that other implementations may exist. According to RFC 7942, "this will allow reviewers and working groups to assign due consideration to documents that have the benefit of running code, which may serve as evidence of valuable experimentation and feedback that have made the implemented protocols more mature. It is up to the individual working groups to use this information as they see fit".

A validator implementation written in C was provided by Job Snijders.
A validator implementation written in Rust was provided by Martin Hoffman from NLnet Labs.
A validator implementation written in Haskell was provided by Mikhail Puzanov.
A signer implementation written in Perl was provided by Tom Harrison from APNIC.
A signer implementation in Java was reported on by Ties de Kock from RIPE NCC.
A signer implementation in Rust was reported on by Tim Bruijnzeels.

The authors would like to thank Keyur Patel for helping kick-start the ASPA profile project, Ties de Kock & Tim Bruijnzeels for suggesting that the ProviderASSet be in a canonical form, and Claudio Jeker, Martin Hoffman & Lancheng Qin for review and several suggestions for improvements.

The following people made significant contributions to this document:

Key words for use in RFCs to Indicate Requirement Levels In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. X.509 Extensions for IP Addresses and AS Identifiers This document defines two X.509 v3 certificate extensions. The first binds a list of IP address blocks, or prefixes, to the subject of a certificate. The second binds a list of autonomous system identifiers to the subject of a certificate. These extensions may be used to convey the authorization of the subject to use the IP addresses and autonomous system identifiers contained in the extensions. [STANDARDS-TRACK] Cryptographic Message Syntax (CMS) This document describes the Cryptographic Message Syntax (CMS). This syntax is used to digitally sign, digest, authenticate, or encrypt arbitrary message content. [STANDARDS-TRACK] A Profile for Resource Certificate Repository Structure This document defines a profile for the structure of the Resource Public Key Infrastructure (RPKI) distributed repository. Each individual repository publication point is a directory that contains files that correspond to X.509/PKIX Resource Certificates, Certificate Revocation Lists and signed objects. This profile defines the object (file) naming scheme, the contents of repository publication points (directories), and a suggested internal structure of a local repository cache that is intended to facilitate synchronization across a distributed collection of repository publication points and to facilitate certification path construction. [STANDARDS-TRACK] The Profile for Algorithms and Key Sizes for Use in the Resource Public Key Infrastructure (RPKI) This document specifies the algorithms, algorithms' parameters, asymmetric key formats, asymmetric key size, and signature format for the Resource Public Key Infrastructure (RPKI) subscribers that generate digital signatures on certificates, Certificate Revocation Lists, and signed objects as well as for the relying parties (RPs) that verify these digital signatures. [STANDARDS-TRACK] Signed Object Template for the Resource Public Key Infrastructure (RPKI) This document defines a generic profile for signed objects used in the Resource Public Key Infrastructure (RPKI). These RPKI signed objects make use of Cryptographic Message Syntax (CMS) as a standard encapsulation format. [STANDARDS-TRACK] Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. BGP AS_PATH Verification Based on Autonomous System Provider Authorization (ASPA) Objects Yandex Qrator Labs Internet Initiative Japan & Arrcus, Inc. Arrcus USA National Institute of Standards and Technology This document describes procedures that make use of Autonomous System Provider Authorization (ASPA) objects in the Resource Public Key Infrastructure (RPKI) to verify the Border Gateway Protocol (BGP) AS_PATH attribute of advertised routes. This AS_PATH verification enhances routing security by adding means to detect and mitigate route leaks and AS_PATH manipulations. The Resource Public Key Infrastructure (RPKI) to Router Protocol, Version 2 Arrcus, DRL, & IIJ Research Dragon Research Labs Asia Pacific Network Information Centre In order to validate the origin Autonomous Systems (ASes) and Autonomous System relationships behind BGP announcements, routers need a simple but reliable mechanism to receive Resource Public Key Infrastructure (RFC6480) prefix origin data, Router Keys, and ASPA data from a trusted cache. This document describes a protocol to deliver them. This document describes version 2 of the RPKI-Router protocol. [RFC6810] describes version 0, and [RFC8210] describes version 1. This document is compatible with both. Information technology - Abstract Syntax Notation One (ASN.1): Specification of basic notation ITU-T Information Technology - ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER) ITU-T Best Practises for Operating Resource Public Key Infrastructure (RPKI) Publication Services RIPE NCC RIPE NCC ARIN APNIC BSD Software Development This document describes best current practices for operating an RFC 8181 RPKI publication engine and its associated publicly accessible rsync (RFC 5781) and RRDP (RFC 8182) repositories. The Base16, Base32, and Base64 Data Encodings This document describes the commonly used base 64, base 32, and base 16 encoding schemes. It also discusses the use of line-feeds in encoded data, use of padding in encoded data, use of non-alphabet characters in encoded data, use of different encoding alphabets, and canonical encodings. [STANDARDS-TRACK] An Infrastructure to Support Secure Internet Routing This document describes an architecture for an infrastructure to support improved security of Internet routing. The foundation of this architecture is a Resource Public Key Infrastructure (RPKI) that represents the allocation hierarchy of IP address space and Autonomous System (AS) numbers; and a distributed repository system for storing and disseminating the data objects that comprise the RPKI, as well as other signed objects necessary for improved routing security. As an initial application of this architecture, the document describes how a legitimate holder of IP address space can explicitly and verifiably authorize one or more ASes to originate routes to that address space. Such verifiable authorizations could be used, for example, to more securely construct BGP route filters. This document is not an Internet Standards Track specification; it is published for informational purposes. A Profile for X.509 PKIX Resource Certificates This document defines a standard profile for X.509 certificates for the purpose of supporting validation of assertions of "right-of-use" of Internet Number Resources (INRs). The certificates issued under this profile are used to convey the issuer's authorization of the subject to be regarded as the current holder of a "right-of-use" of the INRs that are described in the certificate. This document contains the normative specification of Certificate and Certificate Revocation List (CRL) syntax in the Resource Public Key Infrastructure (RPKI). This document also specifies profiles for the format of certificate requests and specifies the Relying Party RPKI certificate path validation procedure. [STANDARDS-TRACK] Internet Exchange BGP Route Server This document outlines a specification for multilateral interconnections at Internet Exchange Points (IXPs). Multilateral interconnection is a method of exchanging routing information among three or more External BGP (EBGP) speakers using a single intermediate broker system, referred to as a route server. Route servers are typically used on shared access media networks, such as IXPs, to facilitate simplified interconnection among multiple Internet routers. OpenBSD rpki-client rpki-aspa-demo APNIC rpki-commons RIPE NCC krill NLnet Labs rpki-prover routinator NLnet Labs

Example ASPA eContent Payload Below an example of a DER encoded ASPA eContent is provided with annotation following the '#' character. Below is a complete Base64 encoded RPKI ASPA Signed Object. The above should decode as following: