| Internet-Draft | RPKI Signed Checklists | May 2022 |
| Snijders, et al. | Expires 27 November 2022 | [Page] |
This document defines a Cryptographic Message Syntax (CMS) profile for a general purpose listing of checksums (a 'checklist'), for use with the Resource Public Key Infrastructure (RPKI). The objective is to allow an attestation, in the form of a listing of one or more checksums of arbitrary digital objects (files), to be signed "with resources", and for validation to provide a means to confirm a specific Internet Resource Holder produced the Signed Checklist. The profile is intended to provide for the signing of an arbitrary checksum listing with a specific set of Internet Number Resources.¶
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 Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.¶
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."¶
This Internet-Draft will expire on 27 November 2022.¶
Copyright (c) 2022 IETF Trust and the persons identified as the document authors. All rights reserved.¶
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶
This document defines a Cryptographic Message Syntax (CMS) [RFC5652] profile for a general purpose listing of checksums (a 'checklist'), for use with the Resource Public Key Infrastructure (RPKI) [RFC6480]. The objective is to allow an attestation, in the form of a listing of one or more checksums of arbitrary files, to be signed "with resources", and for validation to provide a means to confirm a given Internet Resource Holder produced the RPKI Signed Checklist (RSC). The profile is intended to provide for the signing of a checksum listing with a specific set of Internet Number Resources.¶
Signed Checklists are expected to facilitate inter-domain business use-cases which depend on an ability to verify resource holdership. RPKI-based validation processes are expected to become the industry norm for automated Bring Your Own IP (BYOIP) on-boarding or establishment of physical interconnection between Autonomous Systems.¶
The RSC concept borrows heavily from RTA [I-D.ietf-sidrops-rpki-rta], Manifests [RFC6486], and OpenBSD's [signify] utility. The main difference between RSC and RTA is that the RTA profile allows multiple signers to attest a single digital object through a checksum of its content, while the RSC profile allows a single signer to attest the existence of multiple digital objects. A single signer profile is considered a simplification for both implementers and operators.¶
RSC follows the Signed Object Template for the RPKI [RFC6488] with one exception. Because RSCs MUST NOT be distributed through the global RPKI Repository system, the Subject Information Access (SIA) extension MUST be omitted from the RSC's X.509 End-Entity (EE) certificate.¶
What constitutes suitable transport for RSC files is deliberately unspecified. It might be a USB stick, a web interface secured with conventional HTTPS, PGP-signed email, a T-shirt printed with a QR code, or a carrier pigeon.¶
The CA MUST only sign one RSC with each EE Certificate, and MUST generate a new key pair for each new RSC. This form of use of the associated EE Certificate is termed a "one-time-use" EE certificate Section 3 of [RFC6487].¶
The ContentType for an RSC is defined as rpkiSignedChecklist, and has the numerical value of 1.2.840.113549.1.9.16.1.48.¶
This OID MUST appear both within the eContentType in the encapContentInfo object as well as the ContentType signed attribute in the signerInfo object (see [RFC6488]).¶
The content of an RSC indicates that a checklist for arbitrary digital objects has been signed "with resources". An RSC is formally defined as:¶
RpkiSignedChecklist-2022
{ iso(1) member-body(2) us(840) rsadsi(113549)
pkcs(1) pkcs9(9) smime(16) mod(0) TBD }
DEFINITIONS EXPLICIT TAGS ::=
BEGIN
IMPORTS
CONTENT-TYPE, Digest, DigestAlgorithmIdentifier
FROM CryptographicMessageSyntax-2010 -- in [RFC6268]
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
pkcs-9(9) smime(16) modules(0) id-mod-cms-2009(58) }
IPAddressOrRange, ASIdOrRange
FROM IPAddrAndASCertExtn -- in [RFC3779]
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) mod(0)
id-mod-ip-addr-and-as-ident(30) } ;
ct-rpkiSignedChecklist CONTENT-TYPE ::=
{ TYPE RpkiSignedChecklist IDENTIFIED BY
id-ct-signedChecklist }
id-ct-signedChecklist OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
pkcs-9(9) id-smime(16) id-ct(1) 48 }
RpkiSignedChecklist ::= SEQUENCE {
version [0] INTEGER DEFAULT 0,
resources ResourceBlock,
digestAlgorithm DigestAlgorithmIdentifier,
checkList SEQUENCE (SIZE(1..MAX)) OF FileNameAndHash }
FileNameAndHash ::= SEQUENCE {
fileName PortableFilename OPTIONAL,
hash Digest }
PortableFilename ::= IA5String (FROM("a".."z" | "A".."Z" | "0".."9" | "." | "_" | "-"))
ResourceBlock ::= SEQUENCE {
asID [0] ConstrainedASIdentifiers OPTIONAL,
ipAddrBlocks [1] ConstrainedIPAddrBlocks OPTIONAL }
-- at least one of asID or ipAddrBlocks MUST be present
( WITH COMPONENTS { ..., asID PRESENT} |
WITH COMPONENTS { ..., ipAddrBlocks PRESENT } )
ConstrainedIPAddrBlocks ::= SEQUENCE (SIZE(1..MAX)) OF ConstrainedIPAddressFamily
ConstrainedIPAddressFamily ::= SEQUENCE {
addressFamily OCTET STRING (SIZE(2)),
addressesOrRanges SEQUENCE (SIZE(1..MAX)) OF IPAddressOrRange }
ConstrainedASIdentifiers ::= SEQUENCE {
asnum [0] SEQUENCE (SIZE(1..MAX)) OF ASIdOrRange }
END
¶
The version number of the RpkiSignedChecklist MUST be 0.¶
The resources contained here are the resources used to mark the attestation, and MUST be a subset of the set of resources listed by the EE Certificate carried in the CMS certificates field.¶
If the asID field is present, it MUST contain an instance of ConstrainedASIdentifiers.¶
If the ipAddrBlocks field is present, it MUST contain an instance of ConstrainedIPAddrBlocks.¶
Each of ConstrainedASIdentifiers and ConstrainedIPAddrBlocks are specified such that the resulting DER-encoded data instances are binary compatible with, respectively, ASIdentifiers and IPAddrBlocks defined in [RFC3779].¶
Implementations encountering decoding errors whilst attempting to read DER-encoded data using this specification SHOULD be aware of the possibility that the data may have been encoded using an implementation intended for use with [RFC3779]. Such data may contain elements prohibited by the current specification.¶
Attempting to decode the errored data using the more permissive specification conatained in [RFC3779] may enable implementors to gather additional context for use when reporting errors to the user.¶
However, implementations MUST NOT ignore errors resulting from the more restrictive definitions contained herein: in particular, such errors MUST cause the validation procedure described in Section 5 to fail.¶
ConstrainedASIdentifiers is a SEQUENCE, constisting of a single field "asnum", itself containing a SEQUENCE OF one or more ASIdOrRange instances as defined in [RFC3779].¶
ConstrainedASIdentifiers is defined such that the resulting DER-encoded data are binary compatible with ASIdentifiers defined in [RFC3779].¶
ConstrainedIPAddrBlocks is a SEQUENCE OF one or more instances of ConstrainedIPAddressFamily.¶
There MUST be only one instance of ConstrainedIPAddressFamily per unique AFI.¶
The elements of ConstrainedIPAddressFamily MUST be ordered by ascending addressFamily values (treating the octets as unsigned numbers). Thus, when both IPv4 and IPv6 addresses are specified, the IPv4 addresses MUST precede the IPv6 addresses (since the IPv4 AFI of 0001 is less than the IPv6 AFI of 0002).¶
ConstrainedIPAddrBlocks is defined such that the resulting DER-encoded data are binary compatible with IPAddrBlocks defined in [RFC3779].¶
The addressFamily field is an OCTET STRING containing a two-octet Address Family Identifier (AFI), in network byte order. Unlike IPAddrBlocks [RFC3779], a third octet containing a SAFI MUST NOT be present. AFIs are specified in [ADDRESS-FAMILY-NUMBERS].¶
The addressesOrRanges element is a SEQUENCE OF one or more IPAddressOrRange values, as defined in [RFC3779]. The rules for canonicalization and encoding defined in Section 2.2.3.6 of [RFC3779] apply to the value of addressesOrRanges.¶
The digest algorithm used to create the message digest of the attested digital object. This algorithm MUST be a hashing algorithm defined in [RFC7935].¶
This field is a SEQUENCE OF one or more FileNameAndHash values. There is one FileNameAndHash entry for each digital object referenced on the Signed Checklist.¶
Each FileNameAndHash is an ordered pair of the name of the directory entry containing the digital object and the message digest of the digital object.¶
The fileName field is OPTIONAL. This is to allow Signed Checklists to be used in a "stand-alone" fashion in which nameless digital objects are addressed directly through their respective message digest rather than through a file system abstraction.¶
If the fileName field is present then its value:¶
Conversely, if the fileName field is omitted, then the value of the hash field MUST be unique with respect to the other FileNameAndHash elements of checkList for which the fileName field is also omitted.¶
Before a Relying Party can use an RSC to validate a set of digital objects, the Relying Party MUST first validate the RSC. To validate an RSC, the Relying Party MUST perform all the validation checks specified in [RFC6488] (except checking for the presence of a SIA extension, which MUST NOT be present in the EE X.509 certificate Section 4.8.8.2 of [RFC6487]), and perform the following additional RSC-specific validation steps:¶
To verify a set of digital objects with an RSC:¶
For every digital object to be verified:¶
If the verification procedure is provided with a file name for the object being verified (e.g. because the user has provided a file system path from which to read the object) then verification SHOULD proceed in "filename-aware" mode. Otherwise, verification SHOULD proceed in "filename-unaware" mode.¶
Implementations MAY provide an option to override the verification mode, for example to ignore the fact that the object is to be read from a file.¶
The message digest MUST be computed from the file contents or data using the digest algorithm specified in the digestAlgorithm field of the RSC.¶
The digest computed in step 2 MUST be compared to the value appearing in the hash field of all FileNameAndHash elements of the checkList field of the RSC.¶
One or more FileNameAndHash elements MUST be found with a matching hash value, otherwise verification MUST fail and the error SHOULD be reported to the user.¶
If the mode selected in step 1 is "filename-aware" then exactly one of the FileNameAndHash elements matched in step 3 MUST contain a fileName field value exactly matching the file name of the object being verified.¶
Alternatively, if the mode selected in step 1 is "filename-unaware" then exactly one of the FileNameAndHash elements matched in step 3 MUST have the fileName field omitted.¶
Otherwise, verification MUST fail, and the error SHOULD be reported to the user.¶
Note that in the above procedure, not all elements of checkList necessarily need be used. That is, it is not an error if the length of checkList is greater than the size of the set of digital objects to be verified. However, in this situation, implementations SHOULD issue a warning to the user, allowing for corrective action to be taken if necessary.¶
When creating digital objects of a plain-text nature (such as ASCII, UTF-8, HTML, Javascript, XML, etc) it is RECOMMENDED to convert such objects into a lossless compressed form. Distributing plain-text objects within a compression envelope (such as GZIP [RFC1952]) might help avoid unexpected canonicalization at intermediate systems (which in turn would lead to checksum verification errors). Validator implementations are expected to treat a checksummed digital object as string of arbitrary single octets.¶
If a fileName field is present, but no referenced digital object has a filename that matches the content of that field, a validator implementation SHOULD compare the message digest of each digital object to the value from the hash field of the associated FileNameAndHash, and report matches to the client for further consideration.¶
Relying parties are hereby warned that the data in a RPKI Signed Checklist is self-asserted. When determining the meaning of any data contained in an RPKI Signed Checklist, Relying Parties MUST NOT make any assumptions about the signer beyond the fact that it had sufficient control of the issuing CA to create the object. These data have not been verified by the Certificate Authority (CA) that issued the CA certificate to the entity that issued the EE Certificate used to validate the Signed Checklist.¶
RPKI Certificates are not bound to real world identities, see [I-D.ymbk-sidrops-rpki-has-no-identity] for an elaboration. Relying Parties can only associate real world entities to Internet Number Resources by additionally consulting an exogenous authority. Signed Checklists are a tool to communicate assertions 'signed with Internet Number Resources', not about any other aspect of the resource holder's business operations such as the identity of the resource holder itself.¶
RSC objects are not distributed through the RPKI Repository system. From this, it follows that third parties who do not have a copy of a given RSC, may not be aware of the existence of that RSC. Since RSC objects use EE Certificates, but all other currently defined types of RPKI object profiles are published in public CA repositories, an observer may infer from discrepancies in the Repository that RSC object(s) may exist. For example, if a CA does not use random serial numbers for Certificates, an observer could detect gaps between the serial numbers of the published EE Certificates. Similarly, if the CA includes a serial number on a CRL that does not match any published object, an observer could postulate an RSC EE Certificate was revoked.¶
Conversely, a gap in serial numbers does not imply that an RSC exists. Nor does an arbitrary (to the RP unknown) serial in a CRL imply an RSC object exists: the implicitly referenced object might not be a RSC, it might never have been published, or was revoked before it was visible to RPs. In general, it is not possible to confidently infer the existence or non-existence of RSCs from the Repository state without access to a given RSC.¶
While an one-time-use EE Certificate must only be used to generate and sign a single RSC object, CAs technically are not restricted from generating and signing multiple different RSC objects with a single keypair. Any RSC objects sharing the same EE Certificate can not be revoked individually.¶
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".¶
The IANA has permanently allocated for this document in the SMI Security for S/MIME CMS Content Type (1.2.840.113549.1.9.16.1) registry:¶
Decimal Description References --------------------------------------------------------------- 48 id-ct-signedChecklist [draft-ietf-sidrops-rpki-rsc]¶
Upon publication of this document, IANA is requested to reference the RFC publication instead of this draft.¶
The IANA is requested to register the OID for the RPKI Signed Checklist in the registry created by [RFC6488] as following:¶
Name OID Specification ------------------------------------------------------------- Signed Checklist 1.2.840.113549.1.9.16.1.48 [draft-ietf-sidrops-rpki-rsc]¶
The IANA is requested to add an item for the Signed Checklist file extension to the "RPKI Repository Name Scheme" registry created by [RFC6481] as follows:¶
Filename Extension RPKI Object Reference
-------------------------------------------------------------------
.sig Signed Checklist [draft-ietf-sidrops-rpki-rsc]
¶
The IANA is requested to add an item to the "SMI Security for S/MIME Module Identifier" registry as follows:¶
Decimal Description References
-----------------------------------------------------------------------
TBD id-mod-rpkiSignedChecklist-2021 [draft-ietf-sidrops-rpki-rsc]
¶
The IANA is requested to register the media type application/rpki-checklist in the Provisional Standard Media Type registry as follows:¶
Type name: application
Subtype name: rpki-checklist
Required parameters: None
Optional parameters: None
Encoding considerations: binary
Security considerations: Carries an RPKI Signed Checklist
[RFC-TBD].
Interoperability considerations: None
Published specification: This document.
Applications that use this media type: RPKI operators.
Additional information:
Content: This media type is a signed object, as defined
in [RFC6488], which contains a payload of a list of
checksums as defined above in this document.
Magic number(s): None
File extension(s): .sig
Macintosh file type code(s):
Person & email address to contact for further information:
Job Snijders <job@fastly.com>
Intended usage: COMMON
Restrictions on usage: None
Author: Job Snijders <job@fastly.com>
Change controller: Job Snijders <job@fastly.com>
¶
The authors wish to thank George Michaelson, Geoff Huston, Randy Bush, Stephen Kent, Matt Lepinski, Rob Austein, Ted Unangst, and Marc Espie for prior art. The authors thank Russ Housley for reviewing the ASN.1 notation and providing suggestions. The authors would like to thank Nimrod Levy, Tim Bruijnzeels, Alberto Leiva, Ties de Kock, Peter Peele, Claudio Jeker, and Theo Buehler for document review and suggestions.¶
This section is to be removed before publishing as an RFC.¶