RFC 9323: A Profile for RPKI Signed Checklists (RSCs)

RFC 9323: A Profile for RPKI Signed Checklists (RSCs)
RFC 9323
RPKI Signed Checklists (RSCs)
November 2022
Snijders, et al.
Standards Track
[Page]
Stream:
Internet Engineering Task Force (IETF)
RFC:
9323
Category:
Standards Track
Published:
November 2022
ISSN:
2070-1721
Authors:
J. Snijders
Fastly
T. Harrison
APNIC
B. Maddison
Workonline
RFC 9323
A Profile for RPKI Signed Checklists (RSCs)
Abstract
This document defines a Cryptographic Message Syntax (CMS) protected content type for use with the Resource Public Key Infrastructure (RPKI) to carry a general-purpose listing of checksums (a 'checklist').
The objective is to allow for the creation of an attestation, termed an "RPKI Signed Checklist (RSC)", which contains one or more checksums of arbitrary digital objects (files) that are signed with a specific set of Internet Number Resources. When validated, an RSC confirms that the respective Internet resource holder produced the RSC.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by
the Internet Engineering Steering Group (IESG). Further
information on Internet Standards is available in Section 2 of
RFC 7841.
Information about the current status of this document, any
errata, and how to provide feedback on it may be obtained at
Copyright Notice
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
) 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.
Table of Contents
1.
Introduction
This document defines a Cryptographic Message Syntax (CMS)
RFC5652
RFC6268
protected content type for a general-purpose listing of checksums (a 'checklist'), for use with the Resource Public Key Infrastructure (RPKI)
RFC6480
The CMS protected content type is intended to provide for the creation and validation of an RPKI Signed Checklist (RSC), a checksum listing signed with a specific set of Internet Number Resources.
The objective is to allow for the creation of an attestation that, when validated, provides a means to confirm a given Internet resource holder produced the RSC.
RPKI Signed Checklists are expected to facilitate inter-domain business use cases that 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 interconnections between Autonomous Systems (ASes).
The RSC concept borrows heavily from Resource Tagged Attestation (RTA)
RPKI-RTA
, Manifests
RFC9286
, and OpenBSD's signify utility
signify
The main difference between an 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 content of multiple digital objects.
A single signer profile is considered a simplification for both implementers and operators.
1.1.
Requirements Language
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.
2.
RSC Profile and Distribution
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.
For example, it might be a USB stick, a web interface secured with HTTPS, an email signed with Pretty Good Privacy (PGP), a T-shirt printed with a QR code, or a carrier pigeon.
2.1.
RSC EE Certificates
The Certification Authority (CA)
MUST
only sign one RSC with each EE certificate and
MUST
generate a new key pair for each new RSC.
This type of EE certificate is termed a "one-time-use" EE certificate (see
Section 3
of [
RFC6487
).
3.
The RSC eContentType
The eContentType for an RSC is defined as id-ct-signedChecklist, with Object Identifier (OID) 1.2.840.113549.1.9.16.1.48.
This OID
MUST
appear within both the eContentType in the encapContentInfo object and the ContentType signed attribute in the signerInfo object (see
RFC6488
).
4.
The RSC eContent
The content of an RSC indicates that a checklist for arbitrary digital objects has been signed with a specific set of Internet Number Resources.
An RSC is formally defined as follows:
RpkiSignedChecklist-2022
{ iso(1) member-body(2) us(840) rsadsi(113549)
pkcs(1) pkcs9(9) smime(16) mod(0)
id-mod-rpkiSignedChecklist-2022(73) }

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
4.1.
Version
The version number of the RpkiSignedChecklist
MUST
be 0.
4.2.
Resources
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.
At least one of asID or ipAddrBlocks
MUST
be present.
ConstrainedASIdentifiers and ConstrainedIPAddrBlocks are specified such that the resulting DER-encoded data instances are binary compatible with ASIdentifiers and IPAddrBlocks (defined in
RFC3779
), respectively.
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 contained 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.
4.2.1.
ConstrainedASIdentifiers Type
ConstrainedASIdentifiers is a SEQUENCE consisting of a single field, asnum, which in turn contains 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
4.2.2.
ConstrainedIPAddrBlocks Type
ConstrainedIPAddrBlocks is a SEQUENCE OF one or more instances of ConstrainedIPAddressFamily.
There
MUST
be only one instance of ConstrainedIPAddressFamily per unique Address Family Identifier (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
4.2.2.1.
ConstrainedIPAddressFamily Type
4.2.2.1.1.
addressFamily Field
The addressFamily field is an OCTET STRING containing a 2-octet AFI, in network byte order.
Unlike IPAddrBlocks
RFC3779
, a third octet containing a Subsequent Address Family Identifier (SAFI)
MUST NOT
be present.
AFIs are specified in the "Address Family Numbers" registry
IANA.ADDRESS-FAMILY-NUMBERS
maintained by IANA.
4.2.2.1.2.
addressesOrRanges Field
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.
4.3.
digestAlgorithm
The digest algorithm is used to create the message digest of the attested digital object(s).
This algorithm
MUST
be a hashing algorithm defined in
RFC7935
4.4.
checkList
This field is a SEQUENCE OF one or more FileNameAndHash values.
There is one FileNameAndHash entry for each digital object referenced on the RSC.
4.4.1.
FileNameAndHash
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 hash field is mandatory.
The value of the hash field is the calculated message digest of the digital object.
The hashing algorithm is specified in the digestAlgorithm field.
The fileName field is
OPTIONAL
This is to allow RSCs 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:
MUST
contain only characters specified in the Portable Filename Character Set as defined in
POSIX
MUST
be unique with respect to the other FileNameAndHash elements of checkList for which the fileName field is also present.
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.
5.
RSC Validation
Before a Relying Party (RP) can use an RSC to validate a set of digital objects, the RP
MUST
first validate the RSC.
To validate an RSC, the RP
MUST
perform all the validation checks specified in
RFC6488
, except for checking for the presence of an SIA extension, which
MUST NOT
be present in the EE certificate (see
Section 2
).
In addition, the RP
MUST
perform the following RSC-specific validation steps:
The contents of the CMS eContent field
MUST
conform to all of the constraints described in
Section 4
, including the constraints described in
Section 4.4.1
If the asID field is present within the contents of the resources field, then the AS identifier delegation extension
RFC3779
MUST
be present in the EE certificate contained in the CMS certificates field. The AS identifiers present in the eContent resources field
MUST
be a subset of those present in the certificate extension. The EE certificate's AS identifier delegation extension
MUST NOT
contain "inherit" elements.
If the ipAddrBlocks field is present within the contents of the resources field, then the IP address delegation extension
RFC3779
MUST
be present in the EE certificate contained in the CMS certificates field. The IP addresses present in the eContent resources field
MUST
be a subset of those present in the certificate extension. The EE certificate's IP address delegation extension
MUST NOT
contain "inherit" elements.
6.
Verifying Files or Data Using RSC
To verify a set of digital objects with an RSC:
The RSC
MUST
be validated according to the procedure described in
Section 5
If the RSC cannot be validated, verification
MUST
fail.
This error
SHOULD
be reported to the user.
For every digital object to be verified:
If the verification procedure is provided with a filename 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
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
is "filename-aware", then exactly one of the FileNameAndHash elements matched in Step
MUST
contain a fileName field value exactly matching the filename of the object being verified.
Alternatively, if the mode selected in Step
is "filename-unaware", then exactly one of the FileNameAndHash elements matched in Step
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.
7.
Operational Considerations
When creating digital objects of a plain-text nature (such as ASCII, UTF-8, HTML, Javascript, and XML), converting such objects into a lossless compressed form is
RECOMMENDED
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 a string of arbitrary single octets.
If a fileName field is present, but no digital object within the set of to-be-verified digital objects 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 user for further consideration.
8.
Security Considerations
RPs are hereby warned that the data in an RSC is self-asserted.
When determining the meaning of any data contained in an RSC, RPs
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 RSC.
RPKI certificates are not bound to real-world identities; see
RFC9255
for an elaboration.
RPs can only associate real-world entities to Internet Number Resources by additionally consulting an exogenous authority.
RSCs are a tool to communicate assertions signed with Internet Number Resources and do not communicate 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 Certificate Revocation List (CRL) that does not match any published object, an observer could postulate that an RSC EE certificate was revoked.
Conversely, a gap in serial numbers does not imply that an RSC exists.
Nor does the presence in a CRL of a serial number unknown to the RP imply an RSC object exists: the implicitly referenced object might not be an RSC, it might have never been published, or it may have been 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 a 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 key pair.
Any RSC objects sharing the same EE certificate cannot be revoked individually.
9.
IANA Considerations
9.1.
SMI Security for S/MIME CMS Content Type (1.2.840.113549.1.9.16.1)
IANA has allocated the following in the "SMI Security for S/MIME CMS Content Type (1.2.840.113549.1.9.16.1)" registry:
Table 1
Decimal
Description
References
48
id-ct-signedChecklist
RFC 9323
9.2.
RPKI Signed Objects
IANA has registered the OID for the RSC in the "RPKI Signed Objects" registry
RFC6488
as follows:
Table 2
Name
OID
Reference
Signed Checklist
1.2.840.113549.1.9.16.1.48
RFC 9323
9.3.
RPKI Repository Name Schemes
IANA has added the Signed Checklist file extension to the "RPKI Repository Name Schemes" registry
RFC6481
as follows:
Table 3
Filename Extension
RPKI Object
Reference
.sig
Signed Checklist
RFC 9323
9.4.
SMI Security for S/MIME Module Identifier (1.2.840.113549.1.9.16.0)
IANA has allocated the following in the "SMI Security for S/MIME Module Identifier (1.2.840.113549.1.9.16.0)" registry:
Table 4
Decimal
Description
References
73
id-mod-rpkiSignedChecklist-2022
RFC 9323
9.5.
Media Types
IANA has registered the media type "application/rpki-checklist" in the "Media Types" registry as follows:
Type name:
application
Subtype name:
rpki-checklist
Required parameters:
N/A
Optional parameters:
N/A
Encoding considerations:
binary
Security considerations:
Carries an RPKI Signed Checklist. This media type contains no active content. See
Section 5
of RFC 9323 for further information.
Interoperability considerations:
N/A
Published specification:
RFC 9323
Applications that use this media type:
RPKI operators
Fragment identifier considerations:
N/A
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 in RFC 9323.
Magic number(s):
N/A
File extension(s):
.sig
Macintosh file type code(s):
N/A
Person & email address to contact for further information:
Job Snijders (job@fastly.com)
Intended usage:
COMMON
Restrictions on usage:
N/A
Author:
Job Snijders (job@fastly.com)
Change controller:
IETF
10.
References
10.1.
Normative References
[POSIX]
IEEE and The Open Group
"Base Specifications"
Issue 7
DOI 10.1109/IEEESTD.2016.7582338
2016
[RFC2119]
Bradner, S.
"Key words for use in RFCs to Indicate Requirement Levels"
BCP 14
RFC 2119
DOI 10.17487/RFC2119
March 1997
[RFC3779]
Lynn, C.
Kent, S.
, and
K. Seo
"X.509 Extensions for IP Addresses and AS Identifiers"
RFC 3779
DOI 10.17487/RFC3779
June 2004
[RFC5652]
Housley, R.
"Cryptographic Message Syntax (CMS)"
STD 70
RFC 5652
DOI 10.17487/RFC5652
September 2009
[RFC6481]
Huston, G.
Loomans, R.
, and
G. Michaelson
"A Profile for Resource Certificate Repository Structure"
RFC 6481
DOI 10.17487/RFC6481
February 2012
[RFC6487]
Huston, G.
Michaelson, G.
, and
R. Loomans
"A Profile for X.509 PKIX Resource Certificates"
RFC 6487
DOI 10.17487/RFC6487
February 2012
[RFC6488]
Lepinski, M.
Chi, A.
, and
S. Kent
"Signed Object Template for the Resource Public Key Infrastructure (RPKI)"
RFC 6488
DOI 10.17487/RFC6488
February 2012
[RFC7935]
Huston, G.
and
G. Michaelson, Ed.
"The Profile for Algorithms and Key Sizes for Use in the Resource Public Key Infrastructure"
RFC 7935
DOI 10.17487/RFC7935
August 2016
[RFC8174]
Leiba, B.
"Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words"
BCP 14
RFC 8174
DOI 10.17487/RFC8174
May 2017
[RFC9286]
Austein, R.
Huston, G.
Kent, S.
, and
M. Lepinski
"Manifests for the Resource Public Key Infrastructure (RPKI)"
RFC 9286
DOI 10.17487/RFC9286
June 2022
10.2.
Informative References
[IANA.ADDRESS-FAMILY-NUMBERS]
IANA
"Address Family Numbers"
[RFC1952]
Deutsch, P.
"GZIP file format specification version 4.3"
RFC 1952
DOI 10.17487/RFC1952
May 1996
[RFC6268]
Schaad, J.
and
S. Turner
"Additional New ASN.1 Modules for the Cryptographic Message Syntax (CMS) and the Public Key Infrastructure Using X.509 (PKIX)"
RFC 6268
DOI 10.17487/RFC6268
July 2011
[RFC6480]
Lepinski, M.
and
S. Kent
"An Infrastructure to Support Secure Internet Routing"
RFC 6480
DOI 10.17487/RFC6480
February 2012
[RFC9255]
Bush, R.
and
R. Housley
"The 'I' in RPKI Does Not Stand for Identity"
RFC 9255
DOI 10.17487/RFC9255
June 2022
[RPKI-RTA]
Michaelson, G.
Huston, G.
Harrison, T.
Bruijnzeels, T.
, and
M. Hoffman
"A profile for Resource Tagged Attestations (RTAs)"
Work in Progress
Internet-Draft, draft-ietf-sidrops-rpki-rta-00
17 January 2021
[signify]
Unangst, T.
and
M. Espie
"signify - cryptographically sign and verify files"
Acknowledgements
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
Theo Buehler
Donald Eastlake 3rd
Erik Kline
Robert Wilton
Roman Danyliw
Éric Vyncke
Lars Eggert
Paul Wouters
and
Murray S. Kucherawy
for document review and suggestions.
Authors' Addresses
Job Snijders
Fastly
Amsterdam
Netherlands
Email:
job@fastly.com
Tom Harrison
Asia Pacific Network Information Centre
6 Cordelia St
South Brisbane
QLD
4101
Australia
Email:
tomh@apnic.net
Ben Maddison
Workonline Communications
Cape Town
South Africa
Email:
benm@workonline.africa