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.¶
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provisions of BCP 78 and BCP 79.¶
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The primary purpose of the Resource Public Key Infrastructure (RPKI) is to improve routing security [RFC6480].
As part of this infrastructure, a mechanism is needed to facilitate holders of Autonomous System (AS) identifiers in their capacity as Customer to authorize other ASes as their Provider(s).
A Provider AS (PAS) is a network that:¶
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offers its customers outbound (customer to Internet) data traffic connectivity and/or¶
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further propagates in all directions (towards providers, lateral peers, and customers) any BGP Updates that the customer may send.¶
The digitally signed Autonomous System Provider Authorization (ASPA) object described in this document provides the above-mentioned authorization mechanism.¶
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 listing meaning the listed AS is authorized to act as Provider network.
When the CAS has multiple Providers, all Provider ASes are listed in the ASPA, including any non-transparent Internet Exchange Point (IXP) Route Server (RS) ASes.
The common case for RS ASes at IXPs is to operate transparently (see Section 2.2.2.1 [RFC7947]), and in those instances the ASNs of IXP Route Servers are not 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 [I-D.ietf-sidrops-aspa-verification].
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 [RFC5652] protected content type definition conforms to the [RFC6488] template for RPKI signed objects.
In accordance with Section 4 of [RFC6488], this document defines:¶
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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.¶
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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 [X.680] Distinguished Encoding Rules (DER) [X.690].¶
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The steps required to validate an ASPA beyond the validation steps specified in [RFC6488].¶
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 [RFC6488]).¶
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 [I-D.ietf-sidrops-aspa-verification] 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 [X.680] 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 -- 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 ASID,
providers ProviderASSet }
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 [RFC6488].¶
The version number of the ASProviderAttestation that complies with this specification MUST be 1 and MUST be explicitly encoded.¶
The customerASID field contains 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:¶
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The CustomerASID value MUST NOT appear in any ASID in the providers field.¶
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The elements of providers MUST be ordered in ascending numerical order.¶
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Each value of ASID MUST be unique (with respect to the other elements of providers).¶
While the ASN.1 profile specified in Section 3 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 (Section 5.12 of [I-D.ietf-sidrops-8210bis]) is constrained to be 2^16.
In addition to protocol limitations in the supply chain, locally defined restrictions could exist for the maximum file size a Relying Party implementation is willing to accept for a signed object.¶
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.¶
This section is to be removed before publishing as an RFC.¶
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".¶
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A validator implementation [rpki-client] (version 8.5 and higher), written in C was provided by Job Snijders from Fastly.¶
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A validator implementation [routinator], written in Rust was provided by Martin Hoffman from NLnet Labs.¶
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A validator implementation [rpki-prover], written in Haskell was provided by Mikhail Puzanov.¶
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A Signer implementation [rpki-aspa-demo] in Perl was reported on Tom Harrison from APNIC.¶
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A signer implementation [rpki-commons] in Java was reported on by Ties de Kock from RIPE NCC.¶
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A signer implementation [krill] in Rust was reported on by Tim Bruijnzeels from NLnet Labs.¶