Internet DRAFT - draft-ietf-sidrops-https-tal
draft-ietf-sidrops-https-tal
Network Working Group G. Huston
Internet-Draft APNIC
Obsoletes: 7730 (if approved) S. Weiler
Intended status: Standards Track W3C/MIT
Expires: November 1, 2019 G. Michaelson
APNIC
S. Kent
Unaffiliated
T. Bruijnzeels
NLnet Labs
April 30, 2019
Resource Public Key Infrastructure (RPKI) Trust Anchor Locator
draft-ietf-sidrops-https-tal-08
Abstract
This document defines a Trust Anchor Locator (TAL) for the Resource
Public Key Infrastructure (RPKI). TALs allow Relying Parties in the
RPKI to download the current Trust Anchor (TA) CA certificate from
one or more locations, and verify that the key of this self-signed
certificate matches the key on the TAL. Thus, Relying Parties can be
configured with TA keys, but allow these TAs to change the content of
their CA certificate. In particular it allows TAs to change the set
of IP Address Delegations and/or Autonomous System Identifier
Delegations included in the RFC3779 extension of their certificate.
This document obsoletes the previous definition of Trust Anchor
Locators in RFC 7730 by adding support for RFC3986 Uniform Resource
Identifiers (URIs) that use HTTPS as the scheme.
Status of This Memo
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 November 1, 2019.
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Copyright Notice
Copyright (c) 2019 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 Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Changes from RFC7730 . . . . . . . . . . . . . . . . . . 3
2. Trust Anchor Locator . . . . . . . . . . . . . . . . . . . . 3
2.1. Trust Anchor Locator Motivation . . . . . . . . . . . . . 3
2.2. Trust Anchor Locator File Format . . . . . . . . . . . . 4
2.3. TAL and Trust Anchor Certificate Considerations . . . . . 4
2.4. Example . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Relying Party Use . . . . . . . . . . . . . . . . . . . . . . 6
4. URI Scheme Considerations . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
This document defines a Trust Anchor Locator (TAL) for the Resource
Public Key Infrastructure (RPKI) [RFC6480]. This format may be used
to distribute trust anchor material using a mix of out-of-band and
online means. Procedures used by Relying Parties (RPs) to verify
RPKI signed objects SHOULD support this format to facilitate
interoperability between creators of trust anchor material and RPs.
This document obsoletes [RFC7730] by adding support for HTTPS URIs
[RFC7230] in a TAL.
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1.1. Terminology
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.
1.2. Changes from RFC7730
The TAL format defined in this document differs from the definition
in [RFC7730] in that:
o it allows for the use of the HTTPS scheme in URIs [RFC7230]; and
o it allows for the inclusion of an optional comment section.
Note that current Relying Parties may not support this new format
yet. Therefore it is RECOMMENDED that a Trust Anchor operator
maintains a [RFC7730] TAL file for a time as well until they are
satisfied that RP tooling has been updated.
2. Trust Anchor Locator
2.1. Trust Anchor Locator Motivation
This document does not propose a new format for trust anchor
material. A trust anchor in the RPKI is represented by a self-signed
X.509 Certification Authority (CA) certificate, a format commonly
used in PKIs and widely supported by RP software. This document
specifies a format for data used to retrieve and verify the
authenticity of a trust anchor in a very simple fashion. That data
is referred to as the TAL.
The motivation for defining the TAL is to enable selected data in the
trust anchor to change, without needing to redistribute the trust
anchor per se.
In the RPKI, certificates contain an RFC3779 extension, that can
contain a set of IP Address Delegations and/or Autonomous System
Identifier Delegations. In this document we refer to these
delegations as the Internet Number Resources (INR) contained in an
RPKI certificate.
The set of INRs associated with an entity acting as a trust anchor is
likely to change over time. Thus, if one were to use the common PKI
convention of distributing a trust anchor to RPs in a secure fashion,
then this procedure would need to be repeated whenever the INR set
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for the entity acting as a trust anchor changed. By distributing the
TAL (in a secure fashion), instead of distributing the trust anchor,
this problem is avoided, i.e., the TAL is constant so long as the
trust anchor's public key and its location do not change.
The TAL is analogous to the TrustAnchorInfo data structure specified
in [RFC5914], which is on the Standards Track. That specification
could be used to represent the TAL, if one defined an rsync or HTTPS
URI extension for that data structure. However, the TAL format was
adopted by RPKI implementors prior to the PKIX trust anchor work, and
the RPKI implementer community has elected to utilize the TAL format,
rather than define the requisite extension. The community also
prefers the simplicity of the ASCII encoding of the TAL, versus the
binary (ASN.1) encoding for TrustAnchorInfo.
2.2. Trust Anchor Locator File Format
In this document we define a Trust Anchor URI as a URI that can be
used to retrieved a current Trust Anchor certificate. This URI MUST
be either an rsync URI [RFC5781], or an HTTPS URI [RFC7230].
The TAL is an ordered sequence of:
1. an optional comment section consisting of one or more lines each
starting with the '#' character, followed by human readable
informational UTF-8 text, conforming to the restrictions defined
in section 2 of [RFC5198], and ending with a line break,
2. a URI section, that is comprised of one or more ordered lines,
each containing a Trust Anchor URI, and ending with a line break,
3. a line break,
4. a subjectPublicKeyInfo [RFC5280] in DER format [X.509], encoded
in Base64 (see Section 4 of [RFC4648]). To avoid long lines,
line breaks MAY be inserted into the Base64-encoded string.
Note that line breaks in this file can use either "<CRLF>" or "<LF>".
2.3. TAL and Trust Anchor Certificate Considerations
Each Trust Anchor URI in the TAL MUST reference a single object. It
MUST NOT reference a directory or any other form of collection of
objects. The referenced object MUST be a self-signed CA certificate
that conforms to the RPKI certificate profile [RFC6487]. This
certificate is the trust anchor in certification path discovery
[RFC4158] and validation [RFC5280] [RFC3779].
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The validity interval of this trust anchor is chosen such that the
"notBefore" time predates the moment that this certificate is
published, and the "notAfter" time is after the planned time of re-
issuance of this certificate.
The INR extension(s) of this trust anchor MUST contain a non-empty
set of number resources. It MUST NOT use the "inherit" form of the
INR extension(s). The INR set described in this certificate is the
set of number resources for which the issuing entity is offering
itself as a putative trust anchor in the RPKI [RFC6480].
The public key used to verify the trust anchor MUST be the same as
the subjectPublicKeyInfo in the CA certificate and in the TAL.
The trust anchor MUST contain a stable key which does not change when
the certificate is reissued due to changes in the INR extension(s),
when the certificate is renewed prior to expiration.
Because the public key in the TAL and the trust anchor MUST be
stable, this motivates operation of that CA in an offline mode. In
that case a subordinate CA certificate containing the same INRs, or
in theory any sub-set of INRs, can be issued for online operations.
This allows the entity that issues the trust anchor to keep the
corresponding private key of this certificate offline, while issuing
all relevant child certificates under the immediate subordinate CA.
This measure also allows the Certificate Revocation List (CRL) issued
by that entity to be used to revoke the subordinate CA certificate in
the event of suspected key compromise of this online operational key
pair that is potentially more vulnerable.
The trust anchor MUST be published at a stable URI. When the trust
anchor is reissued for any reason, the replacement CA certificate
MUST be accessible using the same URI.
Because the trust anchor is a self-signed certificate, there is no
corresponding CRL that can be used to revoke it, nor is there a
manifest [RFC6486] that lists this certificate.
If an entity wishes to withdraw a self-signed CA certificate as a
putative trust anchor, for any reason, including key rollover, the
entity MUST remove the object from the location referenced in the
TAL.
Where the TAL contains two or more Trust Anchor URIs, then the same
self-signed CA certificate MUST be found at each referenced location.
In order to increase operational resilience, it is RECOMMENDED that
the domain name parts of each of these URIs resolve to distinct IP
addresses that are used by a diverse set of repository publication
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points, and these IP addresses be included in distinct Route Origin
Authorizations (ROAs) objects signed by different CAs.
2.4. Example
# This TAL is intended for documentation purposes only.
# Do not attempt to use this in a production setting.
rsync://rpki.example.org/rpki/hedgehog/root.cer
https://rpki.example.org/rpki/hedgehog/root.cer
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAovWQL2lh6knDx
GUG5hbtCXvvh4AOzjhDkSHlj22gn/1oiM9IeDATIwP44vhQ6L/xvuk7W6
Kfa5ygmqQ+xOZOwTWPcrUbqaQyPNxokuivzyvqVZVDecOEqs78q58mSp9
nbtxmLRW7B67SJCBSzfa5XpVyXYEgYAjkk3fpmefU+AcxtxvvHB5OVPIa
BfPcs80ICMgHQX+fphvute9XLxjfJKJWkhZqZ0v7pZm2uhkcPx1PMGcrG
ee0WSDC3fr3erLueagpiLsFjwwpX6F+Ms8vqz45H+DKmYKvPSstZjCCq9
aJ0qANT9OtnfSDOS+aLRPjZryCNyvvBHxZXqj5YCGKtwIDAQAB
3. Relying Party Use
In order to use the TAL to retrieve and validate a (putative) trust
anchor, an RP SHOULD:
1. Retrieve the object referenced by (one of) the Trust Anchor
URI(s) contained in the TAL.
2. Confirm that the retrieved object is a current, self-signed RPKI
CA certificate that conforms to the profile as specified in
[RFC6487].
3. Confirm that the public key in the TAL matches the public key in
the retrieved object.
4. Perform other checks, as deemed appropriate (locally), to ensure
that the RP is willing to accept the entity publishing this self-
signed CA certificate to be a trust anchor. These tests apply to
the validity of attestations made in the context of the RPKI
relating to all resources described in the INR extension of this
certificate.
An RP SHOULD perform these functions for each instance of TAL that it
is holding for this purpose every time the RP performs a
resynchronization across the local repository cache. In any case, an
RP also SHOULD perform these functions prior to the expiration of the
locally cached copy of the retrieved trust anchor referenced by the
TAL.
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In the case where a TAL contains multiple Trust Anchor URIs, an RP
MAY use a locally defined preference rule to select the URI to
retrieve the self-signed RPKI CA certificate that is to be used as a
trust anchor. Some examples are:
o Using the order provided in the TAL
o Selecting the Trust Anchor URI randomly from the available list
o Creating a prioritized list of URIs based on RP-specific
parameters, such as connection establishment delay
If the connection to the preferred URI fails, or the retrieved CA
certificate public key does not match the TAL public key, the RP
SHOULD retrieve the CA certificate from the next URI, according to
the local preference ranking of URIs.
4. URI Scheme Considerations
Please note that the RSYNC protocol provides neither transport
security nor any means by which the Relying Party can validate that
they are connected to the proper host. There it is RECOMMENDED that
HTTPS is used as the preferred scheme.
Note that, although a Man in the Middle (MITM) cannot produce a CA
certificate that would be considered valid according to the process
described in Section 3, this attack can prevent that the Relying
Party learns about an updated CA certificate.
Relying Parties MUST do TLS certificate and host name validation when
they fetch a CA certificate using an HTTPS URI on a TAL. RPs SHOULD
log any TLS certificate or host name validation issues found, so that
an operator can investigate the cause.
It is RECOMMENDED that Relying Parties and Repository Servers follow
the Best Current Practices outlined in [RFC7525] on the use of HTTP
over TLS (HTTPS) [RFC7230]. Relying Parties SHOULD do TLS
certificate and host name validation using subjectAltName dNSName
identities as described in [RFC6125]. The rules and guidelines
defined in [RFC6125] apply here, with the following considerations:
o Relying Parties and Repository Servers SHOULD support the DNS-ID
identifier type. The DNS-ID identifier type SHOULD be present in
Repository Server certificates.
o DNS names in Repository Server certificates SHOULD NOT contain the
wildcard character "*".
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o A Common Name (CN) field may be present in a Repository Server
certificate's subject name but SHOULD NOT be used for
authentication within the rules described in [RFC6125].
o This protocol does not require the use of SRV-IDs.
o This protocol does not require the use of URI-IDs.
5. Security Considerations
Compromise of a trust anchor private key permits unauthorized parties
to masquerade as a trust anchor, with potentially severe
consequences. Reliance on an inappropriate or incorrect trust anchor
has similar potentially severe consequences.
This TAL does not directly provide a list of resources covered by the
referenced self-signed CA certificate. Instead, the RP is referred
to the trust anchor itself and the INR extension(s) within this
certificate. This provides necessary operational flexibility, but it
also allows the certificate issuer to claim to be authoritative for
any resource. Relying parties should either have great confidence in
the issuers of such certificates that they are configuring as trust
anchors, or they should issue their own self-signed certificate as a
trust anchor and, in doing so, impose constraints on the subordinate
certificates.
6. IANA Considerations
This document has no actions for IANA.
7. Acknowledgements
This approach to trust anchor material was originally described by
Robert Kisteleki.
The authors acknowledge the contributions of Rob Austein and Randy
Bush, who assisted with drafting this document and with helpful
review comments.
The authors acknowledge work of Roque Gagliano, Terry Manderson, and
Carlos Martinez Cagnazzo in developing the ideas behind the inclusion
of multiple URIs in the TAL.
The authors acknowledge Job Snijders for suggesting the inclusion of
comments at the start of the TAL.
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8. References
8.1. 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>.
[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>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/info/rfc4648>.
[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>.
[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
2011, <https://www.rfc-editor.org/info/rfc6125>.
[RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support
Secure Internet Routing", RFC 6480, DOI 10.17487/RFC6480,
February 2012, <https://www.rfc-editor.org/info/rfc6480>.
[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>.
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[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014,
<https://www.rfc-editor.org/info/rfc7230>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <https://www.rfc-editor.org/info/rfc7525>.
[RFC7730] Huston, G., Weiler, S., Michaelson, G., and S. Kent,
"Resource Public Key Infrastructure (RPKI) Trust Anchor
Locator", RFC 7730, DOI 10.17487/RFC7730, January 2016,
<https://www.rfc-editor.org/info/rfc7730>.
[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>.
[X.509] ITU-T, "The Directory: Public-key and attribute
certificate frameworks", October 2012.
8.2. Informative References
[RFC4158] Cooper, M., Dzambasow, Y., Hesse, P., Joseph, S., and R.
Nicholas, "Internet X.509 Public Key Infrastructure:
Certification Path Building", RFC 4158,
DOI 10.17487/RFC4158, September 2005,
<https://www.rfc-editor.org/info/rfc4158>.
[RFC5914] Housley, R., Ashmore, S., and C. Wallace, "Trust Anchor
Format", RFC 5914, DOI 10.17487/RFC5914, June 2010,
<https://www.rfc-editor.org/info/rfc5914>.
[RFC6486] Austein, R., Huston, G., Kent, S., and M. Lepinski,
"Manifests for the Resource Public Key Infrastructure
(RPKI)", RFC 6486, DOI 10.17487/RFC6486, February 2012,
<https://www.rfc-editor.org/info/rfc6486>.
Authors' Addresses
Geoff Huston
APNIC
Email: gih@apnic.net
URI: https://www.apnic.net
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Samuel Weiler
W3C/MIT
Email: weiler@csail.mit.edu
George Michaelson
APNIC
Email: ggm@apnic.net
URI: https://www.apnic.net
Stephen Kent
Unaffiliated
Email: kent@alum.mit.edu
Tim Bruijnzeels
NLnet Labs
Email: tim@nlnetlabs.nl
URI: https://www.nlnetlabs.nl
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