Internet Engineering Task Force (IETF) C. Martinez
Request for Comments: 9691 LACNIC
Category: Standards Track G. Michaelson
ISSN: 2070-1721 T. Harrison
APNIC
T. Bruijnzeels
RIPE NCC
R. Austein
Dragon Research Labs
November
December 2024
A Profile for Resource Public Key Infrastructure (RPKI) Signed Objects for Trust Anchor
Keys (TAKs)
Abstract
A Trust Anchor Locator (TAL) is used by Relying Parties (RPs) in the
Resource Public Key Infrastructure (RPKI) to locate and validate a
Trust Anchor (TA) Certification Authority (CA) certificates certificate used in
RPKI validation. This document defines an RPKI signed object for a
Trust Anchor Key (TAK) that (TAK). A TAK object can be used by a TA to signal
to RPs the location(s) of the accompanying CA certificate for the
current public
key to RPs, key, as well as the successor public key and the
location(s) of its CA certificate. This object helps to support
planned key rollovers without impacting RPKI validation.
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
https://www.rfc-editor.org/info/rfc9691.
Copyright Notice
Copyright (c) 2024 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
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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. Overview
1.1. Requirements Notation
2. TAK Object Definition
2.1. The TAK Object Content Type
2.2. The TAK Object eContent
2.2.1. TAKey
2.2.2. TAK
2.3. TAK Object Validation
3. TAK Object Generation and Publication
4. Relying Party Use
4.1. Manual Update of TA Public Key Details
5. Maintaining Multiple TA Key Pairs
6. Performing TA Key Rolls
6.1. Phase 1: Add a TAK for Key Pair 'A'
6.2. Phase 2: Add a Key Pair 'B'
6.3. Phase 3: Update TAL to point to 'B'
6.4. Phase 4: Remove Key Pair 'A'
7. Using TAK Objects to Distribute TAL Data
8. Deployment Considerations
8.1. Relying Party Support
8.2. Alternate Transition Models
9. Operational Considerations
9.1. Acceptance Timers
10. Security Considerations
10.1. Previous Keys
10.2. TA Compromise
10.3. Alternate Transition Models
11. IANA Considerations
11.1. Content Type
11.2. Signed Object
11.3. File Extension
11.4. Module Identifier
11.5. Registration of Media Type application/rpki-signed-tal
12. References
12.1. Normative References
12.2. Informative References
Appendix A. ASN.1 Module
Acknowledgments
Authors' Addresses
1. Overview
A Trust Anchor Locator (TAL) [RFC8630] is used by Relying Parties
(RPs) in the Resource Public Key Infrastructure (RPKI) to locate and
validate Trust Anchor (TA) Certification Authority (CA) certificates
used in RPKI validation. However, until now, there has been no in-
band way of notifying RPs of updates to a TAL. An in-band
notification means In-band notifications
mean that TA operators can be more confident of RPs being aware of
key rollover operations.
This document defines a new RPKI signed object that can be used to
document the location(s) of the TA CA certificate for the current TA
public key, as well as the value of the successor public key and the
location(s) of its TA CA certificate. This allows RPs to be notified
automatically of such changes and enables TAs to stage a successor
public key so that planned key rollovers can be performed without
risking the invalidation of the RPKI tree under the TA. We call this
object the Trust Anchor Key (TAK) object.
When RPs are first bootstrapped, they use a TAL to discover the
public key and location(s) of the CA certificate for a TA. The RP
can then retrieve and validate the CA certificate and subsequently
validate the manifest [RFC9286] and Certificate Revocation List (CRL)
published by that TA (Section 5 of [RFC6487]). However, before
processing any other objects, it will first validate the TAK object
if it is present. If the TAK object lists only the current public
key, then the RP continues processing as it would in the absence of a
TAK object. If the TAK object includes a successor public key, the
RP starts a 30-day acceptance timer for that key and then continues
standard top-down validation with the current public key. If, during During the
following validation runs up until the expiry of the acceptance
timer, the RP has not observed any changes to verifies that the public keys and the certificate URLs
listed in the TAK object, object remain unchanged. If they remain unchanged
as at that time, then the RP will fetch the successor public key,
update its local state with that public key and its associated certification
certificate location(s), and continue processing using that public
key.
The primary motivation for this work is being able to migrate from a
Hardware Security Module (HSM) produced by one vendor to one produced
by another, where the first vendor does not support exporting private
keys for use by the second. There may be other scenarios in which
key rollover is useful, though.
1.1. Requirements Notation
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. TAK Object Definition
The TAK object makes use of the template for RPKI digitally signed
objects [RFC6488], which defines a Cryptographic Message Syntax (CMS)
[RFC5652] wrapper for the content, as well as a generic validation
procedure for RPKI signed objects. Therefore, to complete the
specification of the TAK object (see Section 4 of [RFC6488]), this
document defines the following:
* the OID (Section 2.1) that identifies the signed object as being a
TAK (this OID appears within the eContentType in the
encapContentInfo object, as well as the content-type signed
attribute in the signerInfo object)
* the ASN.1 syntax for the TAK eContent (Section 2.2)
* the additional steps required to validate a TAK (Section 2.3)
2.1. The TAK Object Content Type
This document specifies an OID for the TAK object as follows:
id-ct-signedTAL OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) ct(1) 50 }
This OID MUST appear in both the eContentType in the encapContentInfo
object and the content-type signed attribute in the signerInfo object
(see [RFC6488]).
2.2. The TAK Object eContent
The content of a TAK object is ASN.1 encoded using the Distinguished
Encoding Rules (DER) [X.690] and is defined per the module in
Appendix A.
2.2.1. TAKey
This structure defines a TA public key similar to that from
[RFC8630]. It contains a sequence of zero or more comments, one or
more certificate URIs, and a SubjectPublicKeyInfo.
comments: This field is semantically equivalent to the comment
section defined in Section 2.2 of [RFC8630]. Each comment is
human-readable informational UTF-8 text [RFC3629], conforming to
the restrictions defined in Section 2 of [RFC5198]. The leading
"#" character that is used to denote a comment in [RFC8630] is
omitted here.
certificateURIs: This field is semantically equivalent to the URI
section defined in Section 2.2 of [RFC8630]. It MUST contain at
least one CertificateURI element. Each CertificateURI element
contains the IA5String representation of either an rsync URI
[RFC5781] or an HTTPS URI [RFC9110].
subjectPublicKeyInfo: This field contains a SubjectPublicKeyInfo
(Section 4.1.2.7 of [RFC5280]) in the DER format [X.690].
2.2.2. TAK
version: The version number of the TAK object MUST be 0.
current: This field contains the TA public key of the repository in
which the TAK object is published.
predecessor: This field contains the TA public key that was in use
for this TA immediately prior to the current TA public key, if
applicable.
successor: This field contains the TA public key to be used in place
of the current public key, if applicable, after expiry of the
relevant acceptance timer.
2.3. TAK Object Validation
To determine whether a TAK object is valid, the RP MUST perform the
following checks in addition to those specified in [RFC6488]:
* The eContentType OID matches the OID described in Section 2.1.
* The TAK object appears as the product of a TA CA certificate
(i.e., the TA CA certificate itself is the issuer of the End-
Entity (EE) certificate of the TAK object).
* The TA CA has published only one TAK object in its repository for
this public key, and this object appears on the manifest as the
only entry using the ".tak" extension (see [RFC6481]).
* The EE certificate of this TAK object describes its Internet
Number Resources (INRs) using the "inherit" attribute.
* The decoded TAK content conforms to the format defined in
Section 2.2.
* The SubjectPublicKeyInfo value of the current TA public key in the
TAK object matches that of the TA CA certificate used to issue the
EE certificate of the TAK object.
If any of these checks do not succeed, the RP MUST ignore the TAK
object and proceed as though it were not listed on the manifest.
The RP is not required to compare its current set of certificateURIs
for the current public key with those listed in the TAK object. The
RP MAY alert the user that these sets of certificateURIs do not match
with a view to
match. If this happens, the user may opt to manually updating update the set
of certificateURIs in their configuration. However, the RP MUST NOT
automatically update its configuration to use these certificateURIs
in the event of
inconsistency inconsistency. This is because the migration of
users to new certificateURIs should happen by way of the successor
public key process.
3. TAK Object Generation and Publication
A non-normative guideline for naming this object is that the filename
chosen for the TAK object in the publication repository
be a value derived from the public key part of the entity's key pair,
using the algorithm described for CRLs in Section 2.2 of [RFC6481] for
generation of filenames. [RFC6481].
The filename extension of ".tak" MUST be used to denote the object as
a TAK.
In order to generate a TAK object, the TA MUST perform the following
actions:
* The TA MUST generate a one-time-use EE certificate for the TAK.
* This EE certificate MUST have a unique key pair.
* This EE certificate MUST have a Subject Information Access (SIA)
[RFC6487] extension access description field with an accessMethod
OID value of id-ad-signedObject, where the associated
accessLocation references the publication point of the TAK as an
object URL.
* As described in [RFC6487], the EE certificate used for this object
must include an [RFC3779] extension. contain either the IP Address Delegation extension or the
Autonomous System Identifier Delegation extension [RFC3779], or
both. However, because the resource set is irrelevant to this
object type, this certificate MUST describe its INRs using the
"inherit" attribute rather than explicitly describing a resource
set.
* This EE certificate MUST have a "notBefore" time that matches or
predates the moment that the TAK will be published.
* This EE certificate MUST have a "notAfter" time that reflects the
intended duration for which this TAK will be published. If the EE
certificate for a TAK object is expired, it MUST no longer be
published, but it MAY be replaced by a newly generated TAK object
with equivalent content and an updated "notAfter" time.
* The current TA public key for the TAK MUST match that of the TA CA
certificate under which the TAK was issued.
In distribution contexts that support media types, the "application/
rpki-signed-tal" media type can be used for TAK objects.
4. Relying Party Use
RPs MUST keep a record of the current public key for each configured
TA, as well as the URI(s) where the CA certificate for this public
key may be retrieved. This record is typically bootstrapped by the
use of a pre-configured (and unsigned) TAL file [RFC8630].
When performing top-down validation, RPs MUST first validate and
process the TAK object for its current known public key by performing
the following steps:
* A CA certificate is retrieved and validated from the known URIs as
described in Sections 3 and 4 of [RFC8630].
* The manifest and CRL for this certificate are then validated as
described in [RFC6487] and [RFC9286].
* If the TAK object is present, it is validated as described in
Section 2.3.
If the TAK object includes a successor public key, then the RP must
verify the successor public key by doing the following: by:
* perform performing top-down validation using the successor public key in
order to validate the TAK object for the successor TA,
* ensure ensuring that a valid TAK object exists for the successor TA,
* ensure ensuring that the successor TAK object's current public key
matches the initial TAK object's successor public key, and
* ensure ensuring that the successor TAK object's predecessor public key
matches the initial TAK object's current public key.
If any of these steps fails, then the successor public key has failed
verification.
If the successor public key passes verification and the RP has not
seen that successor public key on the previous successful validation
run for this TA, then the RP:
* sets an acceptance timer of 30 days for this successor public key
for this TA,
* cancels the existing acceptance timer for this TA (if applicable),
and
* continues standard top-down validation as described in [RFC6487]
using the current public key.
If the successor public key passes verification and the RP has seen
that successor public key on the previous successful validation run
for this TA:
* if the relevant acceptance timer has not expired, TA, the RP continues standard top-down validation using the
current public key;
* otherwise, key if the relevant acceptance timer has not expired.
Otherwise, the RP updates its current known public key details for
this TA to be those of the successor public key, key and then begins top-down
validation again using the successor public key.
If the successor public key does not pass verification or if the TAK
object does not include a successor public key, the RP cancels the
existing acceptance timer for this TA (if applicable).
An RP MUST NOT use a successor public key for top-down validation
outside of the process described above, except for the purpose of
testing that the new public key is working correctly. This allows a
TA to publish a successor public key for a period of time, allowing
RPs to test it while still being able to rely on RPs using the
current public key for their production RPKI operations.
A successor public key may have the same SubjectPublicKeyInfo value
as the current public key; this will be the case where a TA is
updating the certificateURIs for that public key.
4.1. Manual Update of TA Public Key Details
A Relying Party
An RP may opt to not support the automatic transition of TA public
key data, as defined in Section 4. An alternative approach is for
the Relying Party RP to alert the user when a new successor public key is seen and
when the relevant acceptance timer has expired. The user can then
manually transition to the new TA public key data. This process
ensures that the benefits of the acceptance timer period are still
realised, as compared with TA public key update based on a TAL
distributed out of band by a TA.
5. Maintaining Multiple TA Key Pairs
Although an
An RP that can process TAK objects will only ever use one public key
for validation (either validation: either the current public key key, or the successor
public key once the relevant acceptance timer has expired), expired. By
contrast, an RP that cannot process TAK objects will continue to use
the public key details per its TAL (or equivalent manual
configuration) indefinitely. As a result, even when a TA is using a
TAK object in order to migrate clients to a new public key, the TA
may have to maintain the previous key pair for a period of time
alongside the new key pair in order to ensure continuity of service
for older clients.
For each TA key pair that a TA maintains, the signed material for
these key pairs MUST be published under different directories in the
context of the 'id-ad-caRepository' and 'id-ad-rpkiManifest' Subject
Information Access SIA
descriptions contained on the CA certificates [RFC6487]. Publishing
objects under the same directory is potentially confusing for RPs and
could lead to object invalidity in the event of filename collisions.
Also, the CA certificates for each maintained key pair and the
content published for each key pair MUST be equivalent (except for
the TAK object). In other words, for the purposes of RPKI
validation, it MUST NOT make a difference which of the public keys is
used as a starting point.
This means that the IP and Autonomous System (AS) resources contained
on all current CA certificates for the maintained TA key pairs MUST
be the same. Furthermore, for any delegation of IP and AS resources
to a child CA, the TA MUST have an equivalent CA certificate
published under each of its key pairs. Any updates in delegations
MUST be reflected under each of its key pairs. A TA SHOULD NOT
publish any other objects besides a CRL, a manifest, a single TAK
object, and any number of CA certificates for delegation to child
CAs.
If a TA uses a single remote publication server (per [RFC8181]) for
its key pairs per
[RFC8181], pairs, then it MUST include all <publish/> and <withdraw/>
Protocol Data Units (PDUs) for the products of each of its key pairs
in a single query in order to reduce the risk of RPs seeing
inconsistent data in the TA's RPKI repositories.
If a TA uses multiple publication servers, then the content for
different key pairs will be out of sync at times. The TA SHOULD
ensure that the duration of these moments is limited to the shortest
possible time. Furthermore, the following should be observed:
* In cases where a CA certificate is revoked or replaced by a
certificate with a reduced set of resources, these changes will
not take effect fully until all the relevant repository
publication points have been updated. Given that TA private key
operations are normally performed infrequently, this is unlikely
to be a problem; problem: if the revocation or shrinking of an issued CA
certificate is staged for days/weeks, then experiencing a delay of
several minutes for the repository publication points to be
updated is relatively insignificant.
* In cases where a CA certificate is replaced by a certificate with
an extended set of resources, the TA MUST inform the receiving CA
only after all of its repository publication points have been
updated. This ensures that the receiving CA will not issue any
products that could be invalid if an RP uses a TA public key just
before the CA certificate was due to be updated.
Finally, note that the publication locations of CA certificates for
delegations to child CAs under each key pair will be different;
therefore, the Authority Information Access 'id-ad-caIssuers' values
(Section 4.8.7 of [RFC6487]) on certificates issued by the child CAs
may not be as expected when performing top-down validation, depending
on the TA public key that is used. However, these values are not
critical to top-down validation, so RPs performing such validation
MUST NOT reject a certificate simply because this value is not as
expected.
6. Performing TA Key Rolls
This section describes how present-day RPKI TAs that use only one key
pair and do not use TAK objects can use a TAK object to perform a
planned key rollover.
6.1. Phase 1: Add a TAK for Key Pair 'A'
Before adding a successor public key, a TA may want to confirm that
it can maintain a TAK object for its current key pair only. We will
refer to this key pair as key pair 'A' throughout this section.
6.2. Phase 2: Add a Key Pair 'B'
The TA can now generate a new key pair called 'B'. The private key
of this key pair MUST now be used to create a new CA certificate for
the associated public key and issue equivalent CA certificates for
delegations to child CAs as described in Section 5.
At this point, the TA can also construct a new TAL file [RFC8630] for
the public key of key pair 'B' and locally test that the validation
outcome for the new public key is equivalent to that of the other
current public key(s).
When the TA is certain that the content for both public keys is
equivalent and wants to initiate the migration from 'A' to 'B', it
issues a new TAK object under key pair 'A', with the public key from
that key pair as the current public key for that object, the public
key from key pair 'B' as the successor public key, and no predecessor
public key. It also issues a TAK object under key pair 'B', with the
public key from that key pair as the current public key for that
object, the public key from key pair 'A' as the predecessor public
key, and no successor public key.
Once this has happened, RP clients will start seeing the new public
key and setting acceptance timers accordingly.
6.3. Phase 3: Update TAL to point to 'B'
At about the time that the TA expects clients to start setting the
public key from key pair 'B' as the current public key, the TA must
release a new TAL file for that public key. It SHOULD use a
different set of URIs in the TAL compared to the TAK file so that the
TA can learn the proportion of RPs that can successfully validate and
use the updated TAK objects.
To support RPs that do not take account of TAK objects, the TA should
continue operating key pair 'A' for a period of time after the
expected migration of clients to the public key from 'B'. The length
of that period of time is a local policy matter for that TA; TA: for
example, it might operate the key pair until no clients are
attempting to validate using the associated public key.
6.4. Phase 4: Remove Key Pair 'A'
The TA SHOULD now remove all content from the repository used by key
pair 'A' and destroy the private key for that key pair. RPs
attempting to rely on a TAL for the public key from key pair 'A' from
this point will not be able to perform RPKI validation for the TA and
will have to update their local state manually by way of a new TAL
file.
7. Using TAK Objects to Distribute TAL Data
Relying Parties
RPs must be configured with RPKI Trust Anchor TA data in order to function
correctly. This Trust Anchor TA data is typically distributed in the TAL format
defined in [RFC8630]. A TAK object can also serve as a format for
distribution of this data, though, because the TAKey data stored in
the TAK object contains the same data that would appear in a TAL for
the associated Trust Anchor.
Relying Parties TA.
RPs may support conversion of TAK objects into TAL files.
Relying Parties RPs that
support conversion MUST validate the TAK object using the process
from Section 2.3. One exception to the standard validation process
in this context is that a Relying Party an RP MAY treat a TAK object as valid, even
though it is associated with a Trust
Anchor TA that the Relying Party RP is not currently
configured to trust. If the Relying Party RP is relying on this exception when
converting a given TAK object, the Relying Party RP MUST communicate that fact to
the user.
When converting a TAK object, a Relying Party an RP MUST default to producing a TAL
file based on the 'current' TAKey in the TAK object, though it MAY
optionally support producing TAL files based on the 'predecessor' and
'successor' TAKeys.
When converting a TAK object, a Relying Party
If the TAKey that is being converted has comments, an RP MUST include any
those comments from the corresponding TAKey in the TAL file.
If TAK object validation fails, then the Relying Party RP MUST NOT produce a TAL
file based on the TAK object.
Users should be aware that TAK objects distributed out of band have
similar security properties to TAL files (i.e., there is no
authentication). In particular, TAK objects that are not signed by
TAs with which the Relying Party RP is currently configured should only be used if
the source that distributes them is one the user trusts to distribute
TAL files.
If a Relying Party an RP is not transitioning to new Trust Anchor TA data using the automatic
process described in Section 4 or the partially manual process
described in Section 4.1, then the user will have to rely on an out-of-band out-
of-band mechanism for validating and updating the
Trust Anchor TA data for the Relying Party. RP.
Users in this situation should take similar care when updating a trust anchor TA
using a TAK object file as when using a TAL file to update TA data.
8. Deployment Considerations
8.1. Relying Party Support
Publishing TAK objects while RPs do not support this standard will
result in those RPs rejecting these objects. It is not expected that
this will result in the invalidation of any other object under a
Trust Anchor. TA.
Some RPs may purposefully not support this mechanism; mechanism: for example,
they may be implemented or configured such that they are unable to
update local current public key data. TA operators should take this
into consideration when planning key rollover. However, these RPs
would ideally still notify their operators of planned key rollovers
so that the operator could update the relevant configuration
manually.
8.2. Alternate Transition Models
Alternate models of for TAL updates update exist and are complementary to this
mechanism. For example, TAs can liaise directly with RP software
developers to include updated and reissued TAL files in new code
releases and use existing code update mechanisms in the RP community
to distribute the changes.
Additionally, these non-TA channels for distributing TAL data may
themselves rely on monitoring monitor for TAK objects and then update the TAL data in
their distributions or packages accordingly. In this way, TAK
objects may be useful even for RPs that don't implement in-band
support for the protocol.
Non-TA channels for distributing TAL data should ensure, so far as is
possible, that their update mechanisms take account of any changes
that a user has made to their local TA public key configuration. For
example, if a new public key is published for a TA, but the non-TA
channel's mechanism is able to detect that a user had removed the
TA's previous public key from their local TA public key configuration
such that the user no longer relies on it, then the mechanism should
not add the new public key to the user's TA public key configuration
by default.
9. Operational Considerations
9.1. Acceptance Timers
Acceptance timers are used in TAK objects in order to permit RPs to
test that the new public key is working correctly. In turn, this
means that the TA operator will be able to gain confidence in the
correct functioning of the new public key before RPs are relying on
that public key in their production RPKI operations. If a successor
public key is not working correctly, a TA may remove that public key
from the current TAK object.
A TA that removes a successor public key from a TAK object SHOULD NOT
add the same successor public key back into the TAK object for that
TA. This is because there may be an RP that has fetched the TAK
object while the successor public key was listed in it and has
started an acceptance timer accordingly but has not fetched the TAK
object during the period when the successor public key was not listed
in it. If the unchanged successor public key is added back into the
TA, such an RP will transition to using the new TA public key more
quickly than other RPs, which may, in turn, may make debugging and similar
processes more complicated. A simple way of addressing this problem
in a situation where the TA operator doesn't want to reissue the
SubjectPublicKeyInfo content for the successor public key that was
withdrawn is to update the URL set for the successor public key since key.
Since RPs must take that URL set into account for the purposes of
initiating and cancelling acceptance timers. timers, an RP that observes a
change to that URL set will cancel any existing acceptance timer it
has and initiate a new acceptance timer in its place.
10. Security Considerations
10.1. Previous Keys
A TA needs to consider the length of time for which it will maintain
previously current key pairs and their associated repositories. An
RP that is seeded with old TAL data will run for 30 days using the
previous public key before migrating to the next public key due to
the acceptance timer requirements, and this 30-day delay applies to
each new key pair that has been issued since the old TAL data was
initially published. In these instances, it may be better for the TA
to send error responses when receiving requests for the old
publication URLs so that the RP reports an error to its operator and
the operator seeds it with up-to-date TAL data immediately.
Once a TA has decided not to maintain a previously current key pair
and its associated repository, the TA SHOULD destroy the associated
private key. The TA SHOULD also reuse the TA CA certificate URLs
from the previous TAL data for the next TAL that it generates. These
measures will help to mitigate the risk of an adversary gaining
access to the private key and its associated publication points in
order to send invalid or incorrect data to RPs seeded with the TAL
data for the corresponding public key.
10.2. TA Compromise
TAK objects do not offer protection against compromise of the current
TA private key or the successor TA private key. TA private key
compromise in general is out of scope for this document.
While it is possible for a malicious actor to use TAK objects to
cause RPs to transition from the current TA public key to a successor
TA public key, such action is predicated on the malicious actor
having compromised the current TA private key in the first place;
thus, place.
Since a malicious actor who has compromised the current TA private
key has complete control over the TA anyway, TAK objects do not alter
the security considerations relevant to this scenario.
10.3. Alternate Transition Models
Section 8.2 describes other ways in which a TA may transition from
one key pair to another. Transition by way of an in-band process
reliant on TAK objects is not mandatory for TAs or RPs, though the
fact that the TAK objects are verifiable by way of the currently
trusted TA public key is a benefit compared to with existing out-of-band
mechanisms for TA public key distribution.
There will be a period of time where both the current public key and
the successor public key are available for use, and RPs that are
initialised at different points of the transition process or from
different out-of-band sources may be using either the current public
key or the successor public key. TAs are required to ensure, so far
as is possible, that there is no difference which public key is used
for RPKI validation outcomes are the purposes same regardless
of RPKI validation. which of the two keys is used.
11. IANA Considerations
11.1. Content Type
IANA has registered an OID for one content type in the "SMI Security
for S/MIME CMS Content Type (1.2.840.113549.1.9.16.1)" registry as
follows:
+=========+=================+=============+
| Decimal | Description | References |
+=========+=================+=============+
| 50 | id-ct-signedTAL | Section 2.1 |
+---------+-----------------+-------------+
Table 1
Description: id-ct-signedTAL
OID: 1.2.840.113549.1.9.16.1.50
Specification: Section 2.1
11.2. Signed Object
IANA has added the following to the "RPKI Signed Objects" registry:
+==================+============================+=============+
| Name | OID | Reference |
+==================+============================+=============+
| Trust Anchor Key | 1.2.840.113549.1.9.16.1.50 | Section 2.1 |
+------------------+----------------------------+-------------+
Table 2
IANA has also added the following note to the "RPKI Signed Objects"
registry:
| Objects of the types listed in this registry, as well as RPKI
| resource certificates and CRLs, are expected to be validated using
| the RPKI.
11.3. File Extension
IANA has added the following item for the Signed TAL file extension
to the "RPKI Repository Name Schemes" registry created by [RFC6481]:
+====================+==================+===========+
| Filename Extension | RPKI Object | Reference |
+====================+==================+===========+
| .tak | Trust Anchor Key | RFC 9691 |
+--------------------+------------------+-----------+
Table 3
11.4. Module Identifier
IANA has registered an OID for one module identifier in the "SMI
Security for S/MIME Module Identifier (1.2.840.113549.1.9.16.0)"
registry as follows:
+=========+================================+============+
| Decimal | Description | References |
+=========+================================+============+
| 74 | RPKISignedTrustAnchorList-2021 | RFC 9691 |
+---------+--------------------------------+------------+
Table 4
Description: RPKISignedTrustAnchorList-2021
OID: 1.2.840.113549.1.9.16.0.74
Specification: RFC 9691
11.5. Registration of Media Type application/rpki-signed-tal
IANA has registered the media type "application/rpki-signed-tal" in
the "Media Types" registry as follows:
Type name: application
Subtype name: rpki-signed-tal
Required parameters: N/A
Optional parameters: N/A
Encoding considerations: binary
Security considerations: Carries an RPKI Signed TAL. This media
type contains no active content. See the Security Considerations
section of RFC 9691 for further information.
Interoperability considerations: N/A
Published specification: RFC 9691
Applications that use this media type: RPKI operators
Fragment identifier considerations: N/A
Additional information:
Content: This media type is for a signed object, as defined in
RFC 6488, which contains trust anchor key material as defined
in RFC 9691.
Magic number(s): N/A
File extension(s): .tak
Macintosh file type code(s): N/A
Person & email address to contact for further information:
iesg@ietf.org
Intended usage: COMMON
Restrictions on usage: N/A
Author: sidrops WG
Change controller: IESG
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <https://www.rfc-editor.org/info/rfc3629>.
[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,
<https://www.rfc-editor.org/info/rfc3779>.
[RFC5198] Klensin, J. and M. Padlipsky, "Unicode Format for Network
Interchange", RFC 5198, DOI 10.17487/RFC5198, March 2008,
<https://www.rfc-editor.org/info/rfc5198>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
[RFC5781] Weiler, S., Ward, D., and R. Housley, "The rsync URI
Scheme", RFC 5781, DOI 10.17487/RFC5781, February 2010,
<https://www.rfc-editor.org/info/rfc5781>.
[RFC6481] Huston, G., Loomans, R., and G. Michaelson, "A Profile for
Resource Certificate Repository Structure", RFC 6481,
DOI 10.17487/RFC6481, February 2012,
<https://www.rfc-editor.org/info/rfc6481>.
[RFC6487] Huston, G., Michaelson, G., and R. Loomans, "A Profile for
X.509 PKIX Resource Certificates", RFC 6487,
DOI 10.17487/RFC6487, February 2012,
<https://www.rfc-editor.org/info/rfc6487>.
[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,
<https://www.rfc-editor.org/info/rfc6488>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8181] Weiler, S., Sonalker, A., and R. Austein, "A Publication
Protocol for the Resource Public Key Infrastructure
(RPKI)", RFC 8181, DOI 10.17487/RFC8181, July 2017,
<https://www.rfc-editor.org/info/rfc8181>.
[RFC8630] Huston, G., Weiler, S., Michaelson, G., Kent, S., and T.
Bruijnzeels, "Resource Public Key Infrastructure (RPKI)
Trust Anchor Locator", RFC 8630, DOI 10.17487/RFC8630,
August 2019, <https://www.rfc-editor.org/info/rfc8630>.
[RFC9110] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", STD 97, RFC 9110,
DOI 10.17487/RFC9110, June 2022,
<https://www.rfc-editor.org/info/rfc9110>.
[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,
<https://www.rfc-editor.org/info/rfc9286>.
[X.690] 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 Recommendation X.690, ISO/IEC 8825-1:2002,
2002, <https://www.itu.int/rec/T-REC-X.690-200207-S/en>. 8825-1:2021,
February 2021,
<https://www.itu.int/rec/T-REC-X.690-202102-I/en>.
12.2. Informative References
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<https://www.rfc-editor.org/info/rfc5652>.
[RFC5911] Hoffman, P. and J. Schaad, "New ASN.1 Modules for
Cryptographic Message Syntax (CMS) and S/MIME", RFC 5911,
DOI 10.17487/RFC5911, June 2010,
<https://www.rfc-editor.org/info/rfc5911>.
[RFC5912] Hoffman, P. and J. Schaad, "New ASN.1 Modules for the
Public Key Infrastructure Using X.509 (PKIX)", RFC 5912,
DOI 10.17487/RFC5912, June 2010,
<https://www.rfc-editor.org/info/rfc5912>.
Appendix A. ASN.1 Module
This appendix includes the ASN.1 module for the TAK object.
<CODE BEGINS>
RPKISignedTrustAnchorList-2021
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
pkcs9(9) smime(16) mod(0) 74 }
DEFINITIONS EXPLICIT TAGS ::=
BEGIN
IMPORTS
CONTENT-TYPE
FROM CryptographicMessageSyntax-2009 -- in [RFC5911]
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
pkcs-9(9) smime(16) modules(0) id-mod-cms-2004-02(41) }
SubjectPublicKeyInfo
FROM PKIX1Explicit-2009 -- in [RFC5912]
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-pkix1-explicit-02(51) } ;
ct-signedTAL CONTENT-TYPE ::=
{ TYPE TAK IDENTIFIED BY
id-ct-signedTAL }
id-ct-signedTAL OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs9(9) smime(16) ct(1) 50 }
CertificateURI ::= IA5String
TAKey ::= SEQUENCE {
comments SEQUENCE SIZE (0..MAX) OF UTF8String,
certificateURIs SEQUENCE SIZE (1..MAX) OF CertificateURI,
subjectPublicKeyInfo SubjectPublicKeyInfo
}
TAK ::= SEQUENCE {
version INTEGER DEFAULT 0,
current TAKey,
predecessor [0] TAKey OPTIONAL,
successor [1] TAKey OPTIONAL
}
END
<CODE ENDS>
Acknowledgments
The authors wish to thank Martin Hoffmann for a thorough review of
the document, Russ Housley for multiple reviews of the ASN.1
definitions and for providing a new module for the TAK object, Job
Snijders for the extensive suggestions around TAK object structure/
distribution and rpki-client implementation work, and Ties de Kock
for text/suggestions around TAK/TAL distribution and general security
considerations.
Authors' Addresses
Carlos Martinez
LACNIC
Rambla Mexico 6125
11400 Montevideo
Uruguay
Email: carlos@lacnic.net
URI: https://www.lacnic.net/
George G. Michaelson
Asia Pacific Network Information Centre
6 Cordelia St
South Brisbane QLD 4101
Australia
Email: ggm@apnic.net
Tom Harrison
Asia Pacific Network Information Centre
6 Cordelia St
South Brisbane QLD 4101
Australia
Email: tomh@apnic.net
Tim Bruijnzeels
RIPE NCC
Stationsplein 11
Amsterdam
The Netherlands
Email: tim@ripe.net
URI: https://www.ripe.net/
Rob Austein
Dragon Research Labs
Email: sra@hactrn.net