| Rfc | 8183 |
|---|
| Title | An Out-of-Band Setup Protocol for Resource Public Key Infrastructure
(RPKI) Production Services |
|---|
| Author | R. Austein |
|---|
| Date | July 2017 |
|---|
| Format: | TXT,
HTML |
|---|
| Status: | PROPOSED STANDARD |
|---|
|
Internet Engineering Task Force (IETF) R. Austein
Request for Comments: 8183 Dragon Research Labs
Category: Standards Track July 2017
ISSN: 2070-1721
An Out-of-Band Setup Protocol for
Resource Public Key Infrastructure (RPKI) Production Services
Abstract
This note describes a simple out-of-band protocol to ease setup of
the Resource Public Key Infrastructure (RPKI) provisioning and
publication protocols between two parties. The protocol is encoded
in a small number of XML messages, which can be passed back and forth
by any mutually agreeable means which provides acceptable data
integrity and authentication.
This setup protocol is not part of the provisioning or publication
protocol; rather, it is intended to simplify configuration of these
protocols by setting up relationships and exchanging keying material
used to authenticate those relationships.
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
http://www.rfc-editor.org/info/rfc8183.
Copyright Notice
Copyright (c) 2017 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
(http://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 . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. History . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Overview of the BPKI . . . . . . . . . . . . . . . . . . . . 4
5. Protocol Elements . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Common Protocol Elements . . . . . . . . . . . . . . . . 6
5.2. Protocol Messages . . . . . . . . . . . . . . . . . . . . 7
5.2.1. <child_request/> . . . . . . . . . . . . . . . . . . 7
5.2.2. <parent_response/> . . . . . . . . . . . . . . . . . 8
5.2.3. <publisher_request/> . . . . . . . . . . . . . . . . 10
5.2.4. <repository_response/> . . . . . . . . . . . . . . . 11
5.3. <authorization/> . . . . . . . . . . . . . . . . . . . . 12
5.4. <error/> . . . . . . . . . . . . . . . . . . . . . . . . 13
6. Protocol Walk-Through . . . . . . . . . . . . . . . . . . . . 14
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
8. Security Considerations . . . . . . . . . . . . . . . . . . . 19
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
9.1. Normative References . . . . . . . . . . . . . . . . . . 20
9.2. Informative References . . . . . . . . . . . . . . . . . 21
Appendix A. RELAX NG Schema . . . . . . . . . . . . . . . . . . 22
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 23
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 23
1. Introduction
This note describes a small XML-based out-of-band protocol used to
set up relationships between parents and children in the RPKI
provisioning protocol [RFC6492] and between publishers and
repositories in the RPKI publication protocol [RFC8181].
The basic function of this protocol is public key exchange, in the
form of self-signed X.509 certificates, but workshop experience has
demonstrated that it's simpler for the user if we also bundle the
other configuration information needed to bring up a new player into
the messages used in the key exchange.
The underlying transport for this protocol 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 Quick
Response (QR) code, or a carrier pigeon.
Since much of the purpose of this protocol is key exchange,
authentication and integrity of the key exchange MUST be ensured via
external means. Typically, such means will tie directly to a new or
existing business relationship.
2. 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.
All of the protocols configured by this setup protocol have their own
terminology for their actors, but in the context of this protocol
that terminology becomes somewhat confusing. All of the players in
this setup protocol issue certificates, are the subjects of other
certificates, operate servers, and, in most cases, act as clients for
one protocol or another. Therefore, this note uses its own terms for
the actors in this protocol.
Child: An entity acting in the client ("subject") role of the
provisioning protocol defined in [RFC6492].
Parent: An entity acting in the server ("issuer") role of the
provisioning protocol defined in [RFC6492].
Publisher: An entity acting in the client role of the publication
protocol defined in [RFC8181].
Repository: An entity acting in the server role of the publication
protocol defined in [RFC8181].
Note that a given entity might act in more than one of these roles;
for example, in one of the simplest cases, the child is the same
entity as the publisher, while the parent is the same entity as the
repository.
3. History
The protocol described in this document grew out of a series of
workshops held starting in 2010, at which it became clear that manual
configuration of keying material and service URLs was both error
prone and unnecessarily confusing. The basic mechanism and semantics
have been essentially unchanged since the earliest versions of the
protocol, but there were several workshop-driven syntax changes and
simplifications before the protocol made its way into the IETF, and a
few more simplifications and minor extensions have occurred since
that time.
4. Overview of the BPKI
Several protocols related to RPKI provisioning use signed
Cryptographic Message Syntax (CMS) messages [RFC5652] to authenticate
the underlying XML-based protocols. Verification of these CMS
messages requires X.509 certificates. The PKI that holds these
certificates is distinct from the RPKI and contains no RFC 3779
resources. We refer to this as the "Business PKI" (BPKI), to
distinguish it from the RPKI. The "B" is a hint that the certificate
relationships in the BPKI are likely to follow and become part of
existing contractual relationships between the issuers and subjects
of this PKI.
The RPKI provisioning protocol does not dictate a particular
structure for the BPKI, beyond the basic requirement that it be
possible for one party to sign and the other party to verify the CMS
messages. This allows a certain amount of flexibility to allow an
Internet registry to reuse an existing PKI as the BPKI if that makes
sense in their context.
In order to keep this protocol simple, we adopt a somewhat
constrained model of the BPKI. The first two operations in this
protocol are an exchange of public keys between child and parent for
use in the provisioning protocol; the latter two operations in this
protocol are an exchange of public keys between publisher and
repository for use in the publication protocol. In each of these
operations, the sending party includes its public key, in the form of
a self-signed X.509 Certification Authority (CA) certificate. The
private keys corresponding to the exchanged certificates are not used
to sign CMS messages directly; instead, the exchanged CA certificates
are the issuers of the BPKI end-entity (EE) certificates which will
be included in the CMS messages and can be used, along with the
exchanged certificates, to verify the CMS messages.
Details of how to tie the exchanged certificates into an
implementation's local BPKI are left to the implementation, but the
recommended approach is to cross-certify the received public key and
subject name under one's own BPKI, using a Basic Constraints
extension with cA = TRUE, pathLenConstraint = 0, indicating that the
cross-certified certificate is a CA certificate which is allowed to
issue EE certificates but is not allowed to issue CA certificates.
See Section 4.2.1.9 of [RFC5280] for more information about the Basic
Constraints extension.
For example, suppose that Alice and Bob each have their own self-
signed BPKI certificates:
Issuer: CN = Alice CA
Subject: CN = Alice CA
Public Key: [Alice CA Public Key]
BasicConstraints: cA = TRUE
Issuer: CN = Bob CA
Subject: CN = Bob CA
Public Key: [Bob CA Public Key]
BasicConstraints: cA = TRUE
Alice sends Bob her self-signed BPKI certificate, and Bob cross
certifies its public key and subject name under Bob's own self-signed
BPKI certificate:
Issuer: CN = Bob CA
Subject: CN = Alice CA
Public Key: [Alice CA Public Key]
BasicConstraints: cA = TRUE, pathLenConstraint = 0
Later, when Bob receives a CMS message from Alice, Bob can verify
this message via a trust chain back to Bob's own trust anchor:
Issuer: CN = Alice CA
Subject: CN = Alice EE
Public Key: [Alice EE Public Key]
A complete description of the certificates allowed here is beyond the
scope of this document, as it is determined primarily by what is
acceptable to the several other protocols for which this protocol is
handling setup. Furthermore, we expect the requirements to change
over time to track changes in cryptographic algorithms, required key
length, and so forth. Finally, since this protocol is restricted to
setting up pairwise relationships, all that's really required is that
the two parties involved in a particular conversation agree on what
constitutes an acceptable certificate.
All of that said, in practice, the certificates currently exchanged
by this protocol at the time this document was written are what a
reader familiar with the technology would probably expect: RSA keys
with lengths in the 2048-4096 bit range, SHA-2 digests, and a few
common X.509v3 extensions (principally Basic Constraints, Authority
Key Identifier, and Subject Key Identifier). Since the most likely
usage is a cross-certification operation in which the recipient
simply extracts the subject name and public key after checking the
self-signature and discards the rest of the incoming certificate, the
practical value of esoteric X.509v3 extensions is somewhat limited.
5. Protocol Elements
Each message in the protocol is a distinct XML element in the
<http://www.hactrn.net/uris/rpki/rpki-setup/> XML namespace.
The outermost XML element of each message contains a version
attribute. This document describes version 1 of the protocol.
Appendix A is a [RELAX-NG] schema for this protocol. The schema is
normative: in the event of a disagreement between the schema and the
following textual description, the schema is authoritative.
Since "1" is currently the only value allowed for the version
attribute in the schema, an incorrect protocol version can be
detected either by checking the version attribute directly or as a
schema validation error.
5.1. Common Protocol Elements
Most messages contain, among other things, a self-signed BPKI X.509
certificate. These certificates are represented as XML elements
whose text value is the Base64 text ([RFC4648], Section 4, with line
breaks within the Base64 text permitted but not required) encoding
the DER representation of the X.509 certificate.
A number of attributes contain "handles". A handle in this protocol
is a text string in the US-ASCII character set consisting of letters,
digits, and the special characters "/", "-", and "_". This protocol
places no special semantics on the structure of these handles,
although implementations might. Handles are protocol elements, not
necessarily meaningful to humans, thus the simplicity of a restricted
character set makes more sense than the complex rules which would be
needed for internationalized text.
Most messages allow an optional "tag" attribute. This is an opaque
cookie supplied by the client in a particular exchange and echoed by
the server; the intent is to simplify the process of matching a
response received by the client with an outstanding request.
5.2. Protocol Messages
The core of this protocol consists of four message types,
representing the basic request and response semantics needed to
configure an RPKI engine to talk to its parent and its repository via
the provisioning and publication protocols, respectively.
5.2.1. <child_request/>
The <child_request/> message is an initial setup request from a
provisioning protocol child to its provisioning protocol parent.
Fields in the <child_request/> message:
version: The version attribute specifies the protocol version. This
note describes protocol version 1.
tag: The child MAY include a "tag" attribute in the request message.
child_handle: The child_handle attribute is what the child calls
itself. This is just a hint from the child to the parent, and the
parent need not honor it.
child_bpki_ta: The <child_bpki_ta/> element is the child's BPKI
identity, a self-signed X.509 BPKI certificate, encoded in Base64.
This CA certificate will be the issuer of the BPKI EE certificates
corresponding to private keys that the child will use when sending
provisioning protocol messages to the parent.
---------------------------------------------------------------------
<child_request
xmlns="http://www.hactrn.net/uris/rpki/rpki-setup/"
version="1"
child_handle="Bob">
<child_bpki_ta>
R29kIGlzIHJlYWwgdW5sZXNzIGRlY2xhcmVkIGludGVnZXI=
</child_bpki_ta>
</child_request>
---------------------------------------------------------------------
5.2.2. <parent_response/>
The <parent_response/> message is a response from a provisioning
protocol parent to a provisioning protocol child that had previously
sent a <child_request/> message.
Fields in the <parent_response/> message:
version: The version attribute specifies the protocol version. This
note describes protocol version 1.
tag: If the <child_request/> message included a "tag" attribute, the
parent MUST include an identical "tag" attribute in the
<parent_response/> message; if the request did not include a tag
attribute, the response MUST NOT include a tag attribute either.
service_uri: The service_uri attribute contains an HTTP or HTTPS URL
[RFC7230] that the child should contact for up-down [RFC6492]
service.
child_handle: The child_handle attribute is the parent's name for
the child. This MAY match the child_handle from the
<child_request/> message. If they do not match, the parent wins,
because the parent gets to dictate the names in the provisioning
protocol. This value is the sender field in provisioning protocol
request messages and the recipient field in provisioning protocol
response messages.
parent_handle: The parent_handle attribute is the parent's name for
itself. This value is the recipient field in provisioning
protocol request messages and the sender field in provisioning
protocol response messages.
parent_bpki_ta: The <parent_bpki_ta/> element is the parent's BPKI
identity, a self-signed X.509 BPKI certificate.
This certificate is the issuer of the BPKI EE certificates
corresponding to private keys that the parent will use to sign
provisioning protocol messages to the child.
offer: If an <offer/> element is present, the parent is offering
publication service to the child. The <offer/> element, if
present, is empty.
referral: If <referral/> elements are present, they suggest third-
party publication services which the child might use, and contain:
referrer: A referrer attribute, containing the handle by which
the publication repository knows the parent,
contact_uri: An optional contact_uri attribute that the child may
be able to follow for more information, and
Authorization token: The text of the <referral/> element is the
Base64 encoding of a signed authorization token granting the
child the right to use a portion of the parent's namespace at
the publication repository in question. See Section 5.3 for
details on the authorization token.
A parent is unlikely to need to send both <offer> and <referral>
elements, but strictly speaking they are not mutually exclusive, so a
parent which really needs to express that it both offers repository
service to its child and is also willing to refer its child to one or
more other repository servers can do so.
---------------------------------------------------------------------
<parent_response
xmlns="http://www.hactrn.net/uris/rpki/rpki-setup/"
version="1"
service_uri="http://a.example/up-down/Alice/Bob-42"
child_handle="Bob-42"
parent_handle="Alice">
<parent_bpki_ta>
WW91IGNhbiBoYWNrIGFueXRoaW5nIHlvdSB3YW50IHdpdGggVEVDTyBhbmQgRERU
</parent_bpki_ta>
<offer/>
</parent_response>
---------------------------------------------------------------------
---------------------------------------------------------------------
<parent_response
xmlns="http://www.hactrn.net/uris/rpki/rpki-setup/"
version="1"
service_uri="http://bob.example/up-down/Bob/Carol"
child_handle="Carol"
parent_handle="Bob">
<parent_bpki_ta>
R29kIGlzIHJlYWwgdW5sZXNzIGRlY2xhcmVkIGludGVnZXI=
</parent_bpki_ta>
<referral
referrer="Alice/Bob-42">
R28sIGxlbW1pbmdzLCBnbyE=
</referral>
</parent_response>
---------------------------------------------------------------------
5.2.3. <publisher_request/>
The <publisher_request/> message is a setup request from a publisher
to a repository. Generally, this will not take place until after the
publisher has set up the provisioning protocol via a <child_request/>
/ <parent_response/> exchange: in particular, the <referral> sub-
element here requires an <authorization/> token provided by the
provisioning protocol exchange.
Fields in the <publisher_request/> message:
version: The version attribute specifies the protocol version. This
note describes protocol version 1.
tag: The publisher MAY include a "tag" attribute in the request
message.
publisher_handle: The publisher_handle attribute is the publisher's
name for itself. This is just a hint; the repository need not
honor it.
publisher_bpki_ta: The <publisher_bpki_ta/> element is the
publisher's BPKI identity, a self-signed X.509 BPKI certificate.
This certificate is the issuer of the BPKI EE certificates
corresponding to private keys that the publisher will use to sign
publication protocol messages to the repository.
referral: If a <referral/> element is present, it contains:
referrer: A referrer attribute containing the publication handle
of the referring parent, and
Authorization token: The text of the <referral/> element is the
Base64 encoding of a signed authorization token granting the
publisher the right to use a portion of its parent's namespace
at this repository. See Section 5.3 for details on the
authorization token.
These fields are copies of values that a parent provided to the
child in the <parent_response/> message (see Section 5.2.2). The
referrer attribute is present to aid lookup of the corresponding
certificate by the repository. Note that the repository operator
makes the final decision on whether to grant publication service
to the prospective publisher. The <referral/> element just
conveys a parent's grant of permission to use a portion of that
parent's namespace.
---------------------------------------------------------------------
<publisher_request
xmlns="http://www.hactrn.net/uris/rpki/rpki-setup/"
version="1"
tag="A0001"
publisher_handle="Bob">
<publisher_bpki_ta>
R29kIGlzIHJlYWwgdW5sZXNzIGRlY2xhcmVkIGludGVnZXI=
</publisher_bpki_ta>
</publisher_request>
---------------------------------------------------------------------
5.2.4. <repository_response/>
The <repository_response/> message is a repository's response to a
publisher which has previously sent a <publisher_request/> message.
Fields in the <repository_response/> message:
version: The version attribute specifies the protocol version. This
note describes protocol version 1.
tag: If the <publisher_request/> message included a "tag" attribute,
the repository MUST include an identical "tag" attribute in the
<repository_response/> message; if the request did not include a
tag attribute, the response MUST NOT include a tag attribute
either.
service_uri: The service_uri attribute contains an HTTP or HTTPS URL
[RFC7230] that the publisher should contact for publication
service [RFC8181].
publisher_handle: The publisher_handle attribute is the repository's
name for the publisher. This may or may not match the
publisher_handle attribute in the publisher's <publisher_request/>
message.
sia_base: The sia_base attribute is the rsync:// URI for the base of
the publication space allocated to the publisher.
rrdp_notification_uri: The optional rrdp_notification_uri attribute
is the URI for the RPKI Repository Delta Protocol (RRDP)
notification file covering the publication space allocated to the
publisher [RFC8182].
repository_bpki_ta: The <repository_bpki_ta/> element is the
repository's BPKI identity, a self-signed X.509 BPKI certificate.
---------------------------------------------------------------------
<repository_response
xmlns="http://www.hactrn.net/uris/rpki/rpki-setup/"
version="1"
tag="A0001"
service_uri="http://a.example/publication/Alice/Bob-42"
publisher_handle="Alice/Bob-42"
sia_base="rsync://a.example/rpki/Alice/Bob-42/"
rrdp_notification_uri="https://rpki.example/rrdp/notify.xml">
<repository_bpki_ta>
WW91IGNhbiBoYWNrIGFueXRoaW5nIHlvdSB3YW50IHdpdGggVEVDTyBhbmQgRERU
</repository_bpki_ta>
</repository_response>
---------------------------------------------------------------------
5.3. <authorization/>
The <authorization/> element is a separate message which is signed
with CMS and then included as the Base64 content of <referral/>
elements in other messages.
The eContentType for the signed CMS message is id-ct-xml [RFC6492].
Fields in the <authorization/> element:
version: The version attribute specifies the protocol version. This
note describes protocol version 1.
authorized_sia_base: The value of the authorized_sia_base attribute
is the rsync:// URI of the base of the namespace which the
referrer is delegating.
BPKI TA: The text of the <authorization/> element is the identity of
the entity to whom the referrer is delegating the portion of the
namespace named in the authorized_sia_base attribute, represented
as a Base64-encoded self-signed X.509 BPKI certificate.
---------------------------------------------------------------------
<authorization
xmlns="http://www.hactrn.net/uris/rpki/rpki-setup/"
version="1"
authorized_sia_base="rsync://a.example/rpki/Alice/Bob-42/Carol/">
SSd2ZSBoYWQgZnVuIGJlZm9yZS4gIFRoaXMgaXNuJ3QgaXQu
</authorization>
---------------------------------------------------------------------
5.4. <error/>
The <error/> element is an optional message which can be used in
response to any of the core protocol messages described in
Section 5.2.
Whether an <error/> element is an appropriate way to signal errors
back to the sender of a protocol message depends on details of the
implementation, which are outside this specification. For example,
if this protocol is embedded in a web portal interface which is
designed to let a human being upload and download these messages via
upload and download forms, a human-readable error message may be more
appropriate. On the other hand, a portal intended to be driven by a
robotic client might well want to use an <error/> message to signal
errors. Similar arguments apply to non-web encapsulations (such as
email or a USB stick); the primary factor is likely to be whether the
implementation expects the error to be handled by a human being or by
a program.
Fields in the <error/> message:
version: The version attribute specifies the protocol version. This
note describes protocol version 1.
reason: The reason attribute contains a code indicating what was
wrong with the message. This version of the protocol defines the
following codes:
syntax-error: Receiver could not parse the offending message.
authentication-failure: Receiver could not authenticate the
offending message.
refused: Receiver refused to perform the requested action.
Offending message: The <error/> element contains a verbatim copy of
the message to which this error applies.
---------------------------------------------------------------------
<error
xmlns="http://www.hactrn.net/uris/rpki/rpki-setup/"
version="1"
reason="refused">
<child_request
xmlns="http://www.hactrn.net/uris/rpki/rpki-setup/"
version="1"
child_handle="Carol">
<child_bpki_ta>
SSd2ZSBoYWQgZnVuIGJlZm9yZS4gIFRoaXMgaXNuJ3QgaXQu
</child_bpki_ta>
</child_request>
</error>
---------------------------------------------------------------------
6. Protocol Walk-Through
This section walks through a few simple examples of the protocol in
use and stars our old friends, Alice, Bob, and Carol. In this
example, Alice is the root of an RPKI tree, Bob wants to get address
and Autonomous System Number (ASN) resources from Alice, and Carol
wants to get some of those resources in turn from Bob. Alice offers
publication service, which is used by all three.
Alice, Bob, and Carol each generate his or her own self-signed BPKI
certificate.
Bob constructs a <child_request/> message and sends it to Alice:
---------------------------------------------------------------------
<child_request
xmlns="http://www.hactrn.net/uris/rpki/rpki-setup/"
version="1"
child_handle="Bob">
<child_bpki_ta>
R29kIGlzIHJlYWwgdW5sZXNzIGRlY2xhcmVkIGludGVnZXI=
</child_bpki_ta>
</child_request>
---------------------------------------------------------------------
o Bob's preferred handle is "Bob", so Bob uses that when setting
child_handle.
o <child_bpki_ta/> is Bob's self-signed BPKI certificate.
Alice replies with a <parent_response/> message, but Alice already
has 41 other children named Bob, so she calls this one "Bob-42".
Alice's provisioning protocol server happens to use a RESTful URL
scheme so that it can find the expected validation context for the
provisioning protocol CMS message just by looking at the URL, so the
service URL she provides to Bob includes both her name and Bob's.
Alice offers publication service, so she offers to let Bob use it;
Alice doesn't have to do this, she could just omit this and leave Bob
to find publication service on his own, but Alice is trying to be
helpful to her customer Bob. Bob doesn't have to accept Alice's
offer, but may choose to do so.
---------------------------------------------------------------------
<parent_response
xmlns="http://www.hactrn.net/uris/rpki/rpki-setup/"
version="1"
service_uri="http://a.example/up-down/Alice/Bob-42"
child_handle="Bob-42"
parent_handle="Alice">
<parent_bpki_ta>
WW91IGNhbiBoYWNrIGFueXRoaW5nIHlvdSB3YW50IHdpdGggVEVDTyBhbmQgRERU
</parent_bpki_ta>
<offer/>
</parent_response>
---------------------------------------------------------------------
o <parent_bpki_ta/> is Alice's own self-signed BPKI certificate.
Bob receives Alice's <parent_response/> and extracts the fields Bob's
RPKI engine will need to know about (child_handle, parent_handle,
service_uri, and <parent_bpki_ta/>). Bob also sees the repository
offer, decides to take Alice up on this offer, and constructs a
<publisher_request/> message accordingly:
---------------------------------------------------------------------
<publisher_request
xmlns="http://www.hactrn.net/uris/rpki/rpki-setup/"
version="1"
tag="A0001"
publisher_handle="Bob">
<publisher_bpki_ta>
R29kIGlzIHJlYWwgdW5sZXNzIGRlY2xhcmVkIGludGVnZXI=
</publisher_bpki_ta>
</publisher_request>
---------------------------------------------------------------------
Alice receives Bob's request to use Alice's publication service,
decides to honor the offer she made, and sends back a
<repository_response/> message in response. Alice recognizes Bob as
one of her own children, because she's already seen Bob's self-signed
BPKI certificate, so she allocates publication space to Bob under her
own publication space, so that relying parties who rsync her products
will pick up Bob's products automatically without needing an
additional fetch operation.
---------------------------------------------------------------------
<repository_response
xmlns="http://www.hactrn.net/uris/rpki/rpki-setup/"
version="1"
tag="A0001"
service_uri="http://a.example/publication/Alice/Bob-42"
publisher_handle="Alice/Bob-42"
sia_base="rsync://a.example/rpki/Alice/Bob-42/"
rrdp_notification_uri="https://rpki.example/rrdp/notify.xml">
<repository_bpki_ta>
WW91IGNhbiBoYWNrIGFueXRoaW5nIHlvdSB3YW50IHdpdGggVEVDTyBhbmQgRERU
</repository_bpki_ta>
</repository_response>
---------------------------------------------------------------------
Bob should now have everything he needs to talk to Alice for both
provisioning and publication.
A more interesting case is Bob's child, Carol. Carol wants to get
her resources from Bob and, like Bob, does not particularly want to
operate a publication service. Bob doesn't have a publication
service of his own to offer, but he can refer Carol to Alice, along
with his permission for Carol to use a portion of the namespace that
Alice gave him.
Carol's <child_request/> to Bob looks very similar to Bob's earlier
request to Alice:
---------------------------------------------------------------------
<child_request
xmlns="http://www.hactrn.net/uris/rpki/rpki-setup/"
version="1"
child_handle="Carol">
<child_bpki_ta>
SSd2ZSBoYWQgZnVuIGJlZm9yZS4gIFRoaXMgaXNuJ3QgaXQu
</child_bpki_ta>
</child_request>
---------------------------------------------------------------------
Bob's <parent_response/> to Carol also looks a lot like Alice's
response to Bob, except that Bob includes a <referral/> element
instead of an <offer/> element. Carol is an only child, so Bob
leaves her name alone:
---------------------------------------------------------------------
<parent_response
xmlns="http://www.hactrn.net/uris/rpki/rpki-setup/"
version="1"
service_uri="http://bob.example/up-down/Bob/Carol"
child_handle="Carol"
parent_handle="Bob">
<parent_bpki_ta>
R29kIGlzIHJlYWwgdW5sZXNzIGRlY2xhcmVkIGludGVnZXI=
</parent_bpki_ta>
<referral
referrer="Alice/Bob-42">
R28sIGxlbW1pbmdzLCBnbyE=
</referral>
</parent_response>
---------------------------------------------------------------------
Bob's response includes a <referral/> element with a referrer
attribute of "Alice/Bob-42", since that's Bob's name in Alice's
repository. The Base64-encoded authorization token is an
<authorization/> element in a CMS message that can be verified
against Bob's self-signed BPKI certificate, using a BPKI EE
certificate included in the CMS wrapper. The <authorization/> text
is Carol's self-signed BPKI certificate; Bob's signature over this
element indicates Bob's permission for Carol to use the indicated
portion of Bob's publication space.
---------------------------------------------------------------------
<authorization
xmlns="http://www.hactrn.net/uris/rpki/rpki-setup/"
version="1"
authorized_sia_base="rsync://a.example/rpki/Alice/Bob-42/Carol/">
SSd2ZSBoYWQgZnVuIGJlZm9yZS4gIFRoaXMgaXNuJ3QgaXQu
</authorization>
---------------------------------------------------------------------
Carol, not wanting to have to run a publication service, presents
Bob's referral to Alice in the hope that Alice will let Carol use
Alice's publication service. So Carol constructs a
<publisher_request/> message, including the referral information
received from Bob, and sends it all to Alice:
---------------------------------------------------------------------
<publisher_request
xmlns="http://www.hactrn.net/uris/rpki/rpki-setup/"
version="1"
tag="A0002"
publisher_handle="Carol">
<publisher_bpki_ta>
SSd2ZSBoYWQgZnVuIGJlZm9yZS4gIFRoaXMgaXNuJ3QgaXQu
</publisher_bpki_ta>
<referral
referrer="Alice/Bob-42">
R28sIGxlbW1pbmdzLCBnbyE=
</referral>
</publisher_request>
---------------------------------------------------------------------
Alice sees the signed authorization token Bob gave to Carol, checks
its signature, and unpacks it. When the signature proves valid and
the contained BPKI trust anchor (TA) matches Carol's, Alice knows
that Bob is willing to let Carol use a portion of Bob's namespace.
Given this, Alice is willing to provide publication service to Carol
in the subtree allocated by Bob for this purpose, so Alice sends back
a <repository_response/>:
---------------------------------------------------------------------
<repository_response
xmlns="http://www.hactrn.net/uris/rpki/rpki-setup/"
version="1"
tag="A0002"
service_uri="http://a.example/publication/Alice/Bob-42/Carol"
publisher_handle="Alice/Bob-42/Carol"
sia_base="rsync://a.example/rpki/Alice/Bob-42/Carol/">
<repository_bpki_ta>
WW91IGNhbiBoYWNrIGFueXRoaW5nIHlvdSB3YW50IHdpdGggVEVDTyBhbmQgRERU
</repository_bpki_ta>
</repository_response>
---------------------------------------------------------------------
Once Carol receives this response, Carol should be good to go.
In theory, the publication referral mechanism can extend indefinitely
(for example, Carol can refer her child Dave to Alice for publication
service, and it should all work). In practice, this has not yet been
implemented, much less tested. In order to keep the protocol
relatively simple, we've deliberately ignored perverse cases such as
Bob being willing to refer Carol to Alice but not wanting Carol to be
allowed to refer Dave to Alice.
Any RPKI operator is free to run their own publication service should
they feel a need to do so, and a child need not accept any particular
<offer/> or <referral/>. In general, having a smaller number of
larger publication repositories is probably good for overall system
performance, because it will tend to reduce the number of distinct
repositories from which each relying party will need to fetch, but
the decision on where to publish is up to individual RPKI CA
operators and out of scope for this protocol.
7. IANA Considerations
This document does not require any IANA actions.
8. Security Considerations
As stated in Section 1, the basic function of this protocol is an
exchange of public keys to be used as BPKI trust anchors. Integrity
and authentication of these exchanges MUST be ensured via external
mechanisms deliberately left unspecified in this protocol.
9. References
9.1. Normative References
[RELAX-NG] Clark, J., "RELAX NG Compact Syntax", OASIS Committee
Specification, November 2002,
<https://www.oasis-open.org/committees/relax-ng/
compact-20021121.html>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<http://www.rfc-editor.org/info/rfc4648>.
[RFC6492] Huston, G., Loomans, R., Ellacott, B., and R. Austein, "A
Protocol for Provisioning Resource Certificates",
RFC 6492, DOI 10.17487/RFC6492, February 2012,
<http://www.rfc-editor.org/info/rfc6492>.
[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,
<http://www.rfc-editor.org/info/rfc7230>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <http://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,
<http://www.rfc-editor.org/info/rfc8181>.
[RFC8182] Bruijnzeels, T., Muravskiy, O., Weber, B., and R. Austein,
"The RPKI Repository Delta Protocol (RRDP)", RFC 8182,
DOI 10.17487/RFC8182, July 2017,
<http://www.rfc-editor.org/info/rfc8182>.
9.2. Informative References
[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,
<http://www.rfc-editor.org/info/rfc5280>.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<http://www.rfc-editor.org/info/rfc5652>.
Appendix A. RELAX NG Schema
Here is a [RELAX-NG] schema describing the protocol elements.
This schema is normative: in the event of a disagreement between this
schema and the document text above, this schema is authoritative.
default namespace = "http://www.hactrn.net/uris/rpki/rpki-setup/"
version = "1"
base64 = xsd:base64Binary { maxLength="512000" }
handle = xsd:string { maxLength="255" pattern="[\-_A-Za-z0-9/]*" }
uri = xsd:anyURI { maxLength="4096" }
any = element * { attribute * { text }*, ( any | text )* }
tag = xsd:token { maxLength="1024" }
authorization_token = base64
bpki_ta = base64
start |= element child_request {
attribute version { version },
attribute child_handle { handle },
attribute tag { tag }?,
element child_bpki_ta { bpki_ta }
}
start |= element parent_response {
attribute version { version },
attribute service_uri { uri },
attribute child_handle { handle },
attribute parent_handle { handle },
attribute tag { tag }?,
element parent_bpki_ta { bpki_ta },
element offer { empty }?,
element referral {
attribute referrer { handle },
attribute contact_uri { uri }?,
authorization_token
}*
}
start |= element publisher_request {
attribute version { version },
attribute publisher_handle { handle },
attribute tag { tag }?,
element publisher_bpki_ta { bpki_ta },
element referral {
attribute referrer { handle },
authorization_token
}*
}
start |= element repository_response {
attribute version { version },
attribute service_uri { uri },
attribute publisher_handle { handle },
attribute sia_base { uri },
attribute rrdp_notification_uri { uri }?,
attribute tag { tag }?,
element repository_bpki_ta { bpki_ta }
}
start |= element authorization {
attribute version { version },
attribute authorized_sia_base { uri },
bpki_ta
}
start |= element error {
attribute version { version },
attribute reason {
"syntax-error" |
"authentication-failure" |
"refused"
},
any?
}
Acknowledgements
The author would like to thank: Byron Ellacott, George Michaelson,
Leif Johansson, Matsuzaki Yoshinobu, Michael Elkins, Randy Bush,
Seiichi Kawamura, Tim Bruijnzeels, and anybody else who helped along
the way but whose name the author has temporarily forgotten.
Author's Address
Rob Austein
Dragon Research Labs
Email: sra@hactrn.net