The Resource Public Key Infrastructure (RPKI) to Router Protocol, Version 2
draft-ietf-sidrops-8210bis-11
| Document | Type | Active Internet-Draft (sidrops WG) | |
|---|---|---|---|
| Authors | Randy Bush , Rob Austein | ||
| Last updated | 2023-09-21 | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Proposed Standard | ||
| Formats | |||
| Reviews |
GENART Last Call review
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-06)
by Stewart Bryant
Ready w/issues
TSVART Last Call review
(of
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by Michael Tüxen
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||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Chris Morrow | ||
| Shepherd write-up | Show Last changed 2022-02-13 | ||
| IESG | IESG state | RFC Ed Queue | |
| Action Holders |
(None)
|
||
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | Warren "Ace" Kumari | ||
| Send notices to | morrowc@ops-netman.net | ||
| IANA | IANA review state | Version Changed - Review Needed | |
| IANA action state | RFC-Ed-Ack | ||
| RFC Editor | RFC Editor state | MISSREF | |
| Details |
draft-ietf-sidrops-8210bis-11
Network Working Group R. Bush
Internet-Draft IIJ Research, Arrcus, & DRL
Intended status: Standards Track R. Austein
Expires: 24 March 2024 Dragon Research Labs
21 September 2023
The Resource Public Key Infrastructure (RPKI) to Router Protocol,
Version 2
draft-ietf-sidrops-8210bis-11
Abstract
In order to verifiably validate the origin Autonomous Systems and
Autonomous System Paths of BGP announcements, routers need a simple
but reliable mechanism to receive Resource Public Key Infrastructure
(RFC 6480) prefix origin data and router keys from a trusted cache.
This document describes a protocol to deliver them.
This document describes version 2 of the RPKI-Router protocol. RFC
6810 describes version 0, and RFC 8210 describes version 1. This
document is compatible with both.
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 24 March 2024.
Copyright Notice
Copyright (c) 2023 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.
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Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
1.2. Changes from RFC 8210 . . . . . . . . . . . . . . . . . . 3
2. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Deployment Structure . . . . . . . . . . . . . . . . . . . . 5
4. Operational Overview . . . . . . . . . . . . . . . . . . . . 5
5. Protocol Data Units (PDUs) . . . . . . . . . . . . . . . . . 7
5.1. Fields of a PDU . . . . . . . . . . . . . . . . . . . . . 7
5.2. Serial Notify . . . . . . . . . . . . . . . . . . . . . . 10
5.3. Serial Query . . . . . . . . . . . . . . . . . . . . . . 11
5.4. Reset Query . . . . . . . . . . . . . . . . . . . . . . . 12
5.5. Cache Response . . . . . . . . . . . . . . . . . . . . . 12
5.6. IPv4 Prefix . . . . . . . . . . . . . . . . . . . . . . . 13
5.7. IPv6 Prefix . . . . . . . . . . . . . . . . . . . . . . . 14
5.8. End of Data . . . . . . . . . . . . . . . . . . . . . . . 15
5.9. Cache Reset . . . . . . . . . . . . . . . . . . . . . . . 16
5.10. Router Key . . . . . . . . . . . . . . . . . . . . . . . 16
5.11. Error Report . . . . . . . . . . . . . . . . . . . . . . 18
5.12. ASPA PDU . . . . . . . . . . . . . . . . . . . . . . . . 19
6. Protocol Timing Parameters . . . . . . . . . . . . . . . . . 21
7. Protocol Version Negotiation . . . . . . . . . . . . . . . . 22
8. Protocol Sequences . . . . . . . . . . . . . . . . . . . . . 24
8.1. Start or Restart . . . . . . . . . . . . . . . . . . . . 24
8.2. Typical Exchange . . . . . . . . . . . . . . . . . . . . 25
8.3. No Incremental Update Available . . . . . . . . . . . . . 25
8.4. Cache Has No Data Available . . . . . . . . . . . . . . . 26
9. Transport . . . . . . . . . . . . . . . . . . . . . . . . . . 26
9.1. SSH Transport . . . . . . . . . . . . . . . . . . . . . . 28
9.2. TLS Transport . . . . . . . . . . . . . . . . . . . . . . 28
9.3. TCP MD5 Transport . . . . . . . . . . . . . . . . . . . . 29
9.4. TCP-AO Transport . . . . . . . . . . . . . . . . . . . . 29
10. Router-Cache Setup . . . . . . . . . . . . . . . . . . . . . 30
11. ROA PDU Race Minimization . . . . . . . . . . . . . . . . . . 31
12. Deployment Scenarios . . . . . . . . . . . . . . . . . . . . 31
13. Error Codes . . . . . . . . . . . . . . . . . . . . . . . . . 32
14. Security Considerations . . . . . . . . . . . . . . . . . . . 33
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 35
16. References . . . . . . . . . . . . . . . . . . . . . . . . . 35
16.1. Normative References . . . . . . . . . . . . . . . . . . 35
16.2. Informative References . . . . . . . . . . . . . . . . . 38
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Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 38
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 39
1. Introduction
In order to verifiably validate the origin Autonomous Systems (ASes)
and AS paths of BGP announcements, routers need a simple but reliable
mechanism to receive cryptographically validated Resource Public Key
Infrastructure (RPKI) [RFC6480] prefix origin data and router keys
from a trusted cache. This document describes a protocol to deliver
them. The design is intentionally constrained to be usable on much
of the current generation of ISP router platforms.
This specification documents version 2 of the RPKI-RTR protocol.
Earlier versions are documented in [RFC6810] and [RFC8210]. Though
this version is, of course, preferred, the earlier versions are
expected to continue to be productively deployed indefinitely, and
Section 7 details how to downgrade from this version to earlier
versions as needed in order to interoperate.
Section 3 describes the deployment structure, and Section 4 then
presents an operational overview. The binary payloads of the
protocol are formally described in Section 5, and the expected
Protocol Data Unit (PDU) sequences are described in Section 8. The
transport protocol options are described in Section 9. Section 10
details how routers and caches are configured to connect and
authenticate. Section 12 describes likely deployment scenarios. The
traditional security and IANA considerations end the document.
The protocol is extensible in order to support new PDUs with new
semantics, if deployment experience indicates that they are needed.
PDUs are versioned should deployment experience call for change.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
1.2. Changes from RFC 8210
This section summarizes the significant changes between [RFC8210] and
the protocol described in this document.
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* A new ASPA (Autonomous System Provider Authorization) PDU type
(Section 5.12) has been added to support
[I-D.ietf-sidrops-aspa-profile].
* A small Section 11 has been added to handle two possible ROA
(Route Origination Authorization) PDU race conditions, Break
Before Make and Shorter Prefix First.
* Language was clarified when multiple caches are configured, and an
interesting affect is noted.
* The protocol version number incremented from 1 (one) to 2 (two)
and Section 7 has been updated accordingly.
2. Glossary
The following terms are used with special meaning.
Global RPKI: The authoritative data of the RPKI are published in a
distributed set of servers at the IANA, Regional Internet
Registries (RIRs), National Internet Registries (NIRs), and ISPs;
see [RFC6481].
CA: The authoritative data of the RPKI are meant to be published by
a distributed set of Certification Authorities (CAs) at the IANA,
RIRs, NIRs, and ISPs (see [RFC6481]).
Cache: A Cache, AKA Relying Party Cache, is a coalesced copy of the
published Global RPKI data, periodically fetched or refreshed,
directly or indirectly, using the rsync protocol [RFC5781] or some
successor. Relying Party software is used to gather and validate
the distributed data of the RPKI into a cache. Trusting this
cache further is a matter between the provider of the cache and a
Relying Party.
Serial Number: "Serial Number" is a 32-bit strictly increasing
unsigned integer which wraps from 2^32-1 to 0. It denotes the
logical version of a cache. A cache increments the value when it
successfully updates its data from a parent cache or from primary
RPKI data. While a cache is receiving updates, new incoming data
and implicit deletes are associated with the new Serial Number but
MUST NOT be sent until the fetch is complete. A Serial Number is
not commensurate between different caches or different protocol
versions, nor need it be maintained across resets of the cache
server. See [RFC1982] on DNS Serial Number Arithmetic for too
much detail on the topic.
Session ID: When a cache server is started, it generates a Session
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ID to uniquely identify the instance of the cache and to bind it
to the sequence of Serial Numbers that cache instance will
generate. This allows the router to restart a failed session
knowing that the Serial Number it is using is commensurate with
that of the cache.
Payload PDU: A payload PDU is a protocol message which contains data
for use by the router, as opposed to a PDU which conveys the
control mechanisms of this protocol. Prefixes and Router Keys are
examples of payload PDUs.
3. Deployment Structure
Deployment of the RPKI to reach routers has a three-level structure
as follows:
Global RPKI: The authoritative data of the RPKI are published in a
distributed set of servers at the IANA, RIRs, NIRs, and ISPs (see
[RFC6481]).
Local Caches: Local caches are a local set of one or more collected
and verified caches of RPKI data. A Relying Party, e.g., router
or other client, MUST have a trust relationship with, and a
trusted transport channel to, any cache(s) it uses.
Routers: A router fetches data from a local cache using the protocol
described in this document. It is said to be a client of the
cache. There MAY be mechanisms for the router to assure itself of
the authenticity of the cache and to authenticate itself to the
cache (see Section 9).
4. Operational Overview
A router establishes and keeps open a transport connection to one or
more caches with which it has client/server relationships. It is
configured with a semi-ordered list of caches and establishes a
connection to the most preferred cache, or set of caches with that
same priority, which accept the connections.
The router MUST choose the most preferred, by configuration, cache or
set of caches so that the operator may control load on their caches
and the Global RPKI.
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A VRP is effective if it is in the fetched set from any of the
currently preferred caches. Therefore, a VRP takes effect on the
router when the first cache serves that VRP, and the VRP is in effect
until the last cache withdraws that VRP. Thus, in a global sense,
the effect of a VRP announcement propagates more quickly than a
withdraw,
Periodically, the router sends a Serial Query to the cache the most
recent Serial Number for which it has received data from that cache,
i.e., the router's current Serial Number, in the form of a Serial
Query. When a router establishes a new session with a cache or
wishes to reset a current relationship, it sends a Reset Query.
The cache responds to the Serial Query with all data changes which
took place since the given Serial Number. This may be the null set,
in which case the End of Data PDU (Section 5.8) is still sent. Note
that the Serial Number comparison used to determine "since the given
Serial Number" MUST take wrap-around into account; see [RFC1982].
When the router has received all data records from the cache, it sets
its current Serial Number to that of the Serial Number in the
received End of Data PDU.
When the cache updates its database, it sends a Notify PDU to every
currently connected router. This is a hint that now would be a good
time for the router to poll for an update, but it is only a hint.
The protocol requires the router to poll for updates periodically in
any case.
Strictly speaking, a router could track a cache simply by asking for
a complete data set every time it updates, but this would be very
inefficient. The Serial-Number-based incremental update mechanism
allows an efficient transfer of just the data records which have
changed since the last update. As with any update protocol based on
incremental transfers, the router must be prepared to fall back to a
full transfer if for any reason the cache is unable to provide the
necessary incremental data. Unlike some incremental transfer
protocols, this protocol requires the router to make an explicit
request to start the fallback process; this is deliberate, as the
cache has no way of knowing whether the router has also established
sessions with other caches that may be able to provide better
service.
As a cache server must evaluate certificates and ROAs (Route Origin
Authorizations; see [RFC6480]), which are time dependent, servers'
clocks MUST be correct to a tolerance of an hour.
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Barring errors, transport connections remain up as long as the cache
and router remain up and the router is not reconfigured to no longer
use the cache.
Should a transport connection be lost for unknown reasons, the router
SHOULD try to reestablish one; being careful to not abuse the cache
with two many failed requests.
5. Protocol Data Units (PDUs)
The exchanges between the cache and the router are sequences of
exchanges of the following PDUs according to the rules described in
Section 8.
Reserved fields (marked "zero" in PDU diagrams) MUST be zero on
transmission and MUST be ignored on receipt.
5.1. Fields of a PDU
PDUs contain the following data elements:
Protocol Version: An 8-bit unsigned integer, currently 2, denoting
the version of this protocol.
PDU Type: An 8-bit unsigned integer, denoting the type of the PDU,
e.g., IPv4 Prefix.
Serial Number: A 32-bit unsigned integer serializing the RPKI cache
epoch when this set of PDUs was received from an upstream cache
server or gathered from the Global RPKI. A cache increments its
Serial Number when completing a validated update from a parent
cache or the Global RPKI.
Session ID: A 16-bit unsigned integer. When a cache server is
started, it generates a Session ID to identify the instance of the
cache and to bind it to the sequence of Serial Numbers that cache
instance will generate. This allows the router to restart a
failed session knowing that the Serial Number it is using is
commensurate with that of the cache. If, at any time after the
protocol version has been negotiated (Section 7), either the
router or the cache finds that the value of the Session ID is not
the same as the other's, the party which detects the mismatch MUST
immediately terminate the session with an Error Report PDU with
code 0 ("Corrupt Data"), and the router MUST flush all data
learned from that cache.
Note that sessions are specific to a particular protocol version.
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That is, if a cache server supports multiple versions of this
protocol, happens to use the same Session ID value for multiple
protocol versions, and further happens to use the same Serial
Number values for two or more sessions using the same Session ID
but different Protocol Version values, the Serial Numbers are not
commensurate. The full test for whether Serial Numbers are
commensurate requires comparing Protocol Version, Session ID, and
Serial Number. To reduce the risk of confusion, cache servers
SHOULD NOT use the same Session ID across multiple protocol
versions, but even if they do, routers MUST treat sessions with
different Protocol Version fields as separate sessions even if
they do happen to have the same Session ID.
Should a cache erroneously reuse a Session ID so that a router
does not realize that the session has changed (old Session ID and
new Session ID have the same numeric value), the router may become
confused as to the content of the cache. The time it takes the
router to discover that it is confused will depend on whether the
Serial Numbers are also reused. If the Serial Numbers in the old
and new sessions are different enough, the cache will respond to
the router's Serial Query with a Cache Reset, which will solve the
problem. If, however, the Serial Numbers are close, the cache may
respond with a Cache Response, which may not be enough to bring
the router into sync. In such cases, it's likely but not certain
that the router will detect some discrepancy between the state
that the cache expects and its own state. For example, the Cache
Response may tell the router to drop a record which the router
does not hold or may tell the router to add a record which the
router already has. In such cases, a router will detect the error
and reset the session. The one case in which the router may stay
out of sync is when nothing in the Cache Response contradicts any
data currently held by the router.
Using persistent storage for the Session ID or a clock-based
scheme for generating Session IDs should avoid the risk of Session
ID collisions.
The Session ID might be a pseudorandom value, a strictly
increasing value if the cache has reliable storage, et cetera. A
seconds-since-epoch timestamp value such as the low order 16 bits
of unsigned integer seconds since 1970-01-01T00:00:00Z ignoring
leap seconds might make a good Session ID value.
Length: A 32-bit unsigned integer which has as its value the count
of the bytes in the entire PDU, including the 8 bytes of header
which includes the length field.
Flags: An 8-bit binary field, with the lowest-order bit being 1 for
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an announcement and 0 for a withdrawal. For a Prefix PDU (IPv4 or
IPv6), the announce/withdraw flag indicates whether this PDU
announces a new right to announce the prefix or withdraws a
previously announced right; a withdraw effectively deletes one
previously announced Prefix PDU with the exact same Prefix,
Length, Max-Len, and Autonomous System Number (ASN).
Similarly, for a Router Key PDU, the flag indicates whether this
PDU announces a new Router Key or deletes one previously announced
Router Key PDU with the exact same AS Number,
subjectKeyIdentifier, and subjectPublicKeyInfo.
The remaining bits in the Flags field are reserved for future use.
Prefix Length: An 8-bit unsigned integer denoting the shortest
prefix allowed by the Prefix element.
Max Length: An 8-bit unsigned integer denoting the longest prefix
allowed by the Prefix element. This MUST NOT be less than the
Prefix Length element.
Prefix: The IPv4 or IPv6 prefix of the ROA.
Autonomous System Number: A 32-bit unsigned integer representing an
ASN allowed to announce a prefix or associated with a router key.
Subject Key Identifier: The 20-octet Subject Key Identifier (SKI)
value of a router key, as described in [RFC6487].
Subject Public Key Info: A variable length field holding a router
key's subjectPublicKeyInfo value, as described in [RFC8608]. This
is the full ASN.1 DER encoding of the subjectPublicKeyInfo,
including the ASN.1 tag and length values of the
subjectPublicKeyInfo SEQUENCE.
Refresh Interval: A 32-bit interval in seconds between normal cache
polls. See Section 6.
Retry Interval: A 32-bit interval in seconds between cache poll
retries after a failed cache poll. See Section 6.
Expire Interval: A 32-bit interval in seconds during which data
fetched from a cache remains valid in the absence of a successful
subsequent cache poll. See Section 6.
AFI Flags: An 8-bit field of the ASPA PDU where the low order bit is
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set if the AS relationships are for IPv4 (AFI 1), and the second
lowest bit is set for IPv6 (AFI 2). Currently, both bits MUST be
set.
Provider AS Count: A 16-bit count of Provider Autonomous System
Numbers in the PDU.
Customer Autonomous System Number: The 32-bit AS number of the
Autonomous System that authorizes the upstream providers listed in
the Provider Autonomous System list to propagate prefixes of the
specified address family to other ASes.
Provider Autonomous System Numbers: The set of 32-bit AS numbers
authorized to propagate prefixes of the specified AFI which were
received from the customer AS.
5.2. Serial Notify
The cache notifies the router that the cache has new data.
The Session ID reassures the router that the Serial Numbers are
commensurate, i.e., the cache session has not been changed.
Upon receipt of a Serial Notify PDU, the router MAY issue an
immediate Serial Query (Section 5.3) or Reset Query (Section 5.4)
without waiting for the Refresh Interval timer (see Section 6) to
expire.
Serial Notify is the only message that the cache can send that is not
in response to a message from the router.
If the router receives a Serial Notify PDU during the initial startup
period where the router and cache are still negotiating to agree on a
protocol version, the router MUST simply ignore the Serial Notify
PDU, even if the Serial Notify PDU is for an unexpected protocol
version. See Section 7 for details.
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0 8 16 24 31
.-------------------------------------------.
| Protocol | PDU | |
| Version | Type | Session ID |
| 2 | 0 | |
+-------------------------------------------+
| |
| Length=12 |
| |
+-------------------------------------------+
| |
| Serial Number |
| |
`-------------------------------------------'
5.3. Serial Query
The router sends a Serial Query to ask the cache for all
announcements and withdrawals which have occurred since the Serial
Number specified in the Serial Query.
The cache replies to this query with a Cache Response PDU
(Section 5.5) if the cache has a (possibly null) record of the
changes since the Serial Number specified by the router, followed by
zero or more payload PDUs and an End Of Data PDU (Section 5.8).
When replying to a Serial Query, the cache MUST return the minimum
set of changes needed to bring the router into sync with the cache.
That is, if a particular prefix or router key underwent multiple
changes between the Serial Number specified by the router and the
cache's current Serial Number, the cache MUST merge those changes to
present the simplest possible view of those changes to the router.
In general, this means that, for any particular prefix or router key,
the data stream will include at most one withdrawal followed by at
most one announcement, and if all of the changes cancel out, the data
stream will not mention the prefix or router key at all.
The rationale for this approach is that the entire purpose of the
RPKI-Router protocol is to offload work from the router to the cache,
and it should therefore be the cache's job to simplify the change
set, thus reducing work for the router.
If the cache does not have the data needed to update the router,
perhaps because its records do not go back to the Serial Number in
the Serial Query, then it responds with a Cache Reset PDU
(Section 5.9).
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The Session ID tells the cache what instance the router expects to
ensure that the Serial Numbers are commensurate, i.e., the cache
session has not been changed.
0 8 16 24 31
.-------------------------------------------.
| Protocol | PDU | |
| Version | Type | Session ID |
| 2 | 1 | |
+-------------------------------------------+
| |
| Length=12 |
| |
+-------------------------------------------+
| |
| Serial Number |
| |
`-------------------------------------------'
5.4. Reset Query
The router tells the cache that it wants to receive the total active,
current, non-withdrawn database. The cache responds with a Cache
Response PDU (Section 5.5), followed by zero or more payload PDUs and
an End of Data PDU (Section 5.8).
0 8 16 24 31
.-------------------------------------------.
| Protocol | PDU | |
| Version | Type | zero |
| 2 | 2 | |
+-------------------------------------------+
| |
| Length=8 |
| |
`-------------------------------------------'
5.5. Cache Response
The cache responds to queries with zero or more payload PDUs. When
replying to a Serial Query (Section 5.3), the cache sends the set of
announcements and withdrawals that have occurred since the Serial
Number sent by the client router. When replying to a Reset Query
(Section 5.4), the cache sends the set of all data records it has; in
this case, the announce/withdraw field in the payload PDUs MUST have
the value 1 (announce).
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In response to a Reset Query, the new value of the Session ID tells
the router the instance of the cache session for future confirmation.
In response to a Serial Query, the Session ID being the same
reassures the router that the Serial Numbers are commensurate, i.e.,
the cache session has not been changed.
0 8 16 24 31
.-------------------------------------------.
| Protocol | PDU | |
| Version | Type | Session ID |
| 2 | 3 | |
+-------------------------------------------+
| |
| Length=8 |
| |
`-------------------------------------------'
5.6. IPv4 Prefix
0 8 16 24 31
.-------------------------------------------.
| Protocol | PDU | |
| Version | Type | zero |
| 2 | 4 | |
+-------------------------------------------+
| |
| Length=20 |
| |
+-------------------------------------------+
| | Prefix | Max | |
| Flags | Length | Length | zero |
| | 0..32 | 0..32 | |
+-------------------------------------------+
| |
| IPv4 Prefix |
| |
+-------------------------------------------+
| |
| Autonomous System Number |
| |
`-------------------------------------------'
This PDU carries an [RFC6811] Validated ROA Payload (VRP) for an IPv4
ROA.
The lowest-order bit of the Flags field is 1 for an announcement and
0 for a withdrawal.
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In the RPKI, nothing prevents a signing certificate from issuing two
identical ROAs. In this case, there would be no semantic difference
between the objects, merely a process redundancy.
In the RPKI, there is also an actual need for what might appear to a
router as identical IPvX PDUs. This can occur when an upstream
certificate is being reissued or there is an address ownership
transfer up the validation chain. The ROA would be identical in the
router sense, i.e., have the same {Prefix, Len, Max-Len, ASN}, but it
would have a different validation path in the RPKI. This is
important to the RPKI but not to the router.
The cache server MUST ensure that it has told the router client to
have one and only one IPvX PDU for a unique {Prefix, Len, Max-Len,
ASN} at any one point in time. Should the router client receive an
IPvX PDU with a {Prefix, Len, Max-Len, ASN} identical to one it
already has active, it SHOULD raise a Duplicate Announcement Received
error.
5.7. IPv6 Prefix
0 8 16 24 31
.-------------------------------------------.
| Protocol | PDU | |
| Version | Type | zero |
| 2 | 6 | |
+-------------------------------------------+
| |
| Length=32 |
| |
+-------------------------------------------+
| | Prefix | Max | |
| Flags | Length | Length | zero |
| | 0..128 | 0..128 | |
+-------------------------------------------+
| |
+--- ---+
| |
+--- IPv6 Prefix ---+
| |
+--- ---+
| |
+-------------------------------------------+
| |
| Autonomous System Number |
| |
`-------------------------------------------'
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This PDU carries an [RFC6811] Validated ROA Payload (VRP) for an IPv6
ROA.
Analogous to the IPv4 Prefix PDU, it has 96 more bits and no magic.
5.8. End of Data
The cache tells the router it has no more data for the request.
The Session ID and Protocol Version MUST be the same as that of the
corresponding Cache Response which began the (possibly null) sequence
of payload PDUs.
0 8 16 24 31
.-------------------------------------------.
| Protocol | PDU | |
| Version | Type | Session ID |
| 2 | 7 | |
+-------------------------------------------+
| |
| Length=24 |
| |
+-------------------------------------------+
| |
| Serial Number |
| |
+-------------------------------------------+
| |
| Refresh Interval |
| |
+-------------------------------------------+
| |
| Retry Interval |
| |
+-------------------------------------------+
| |
| Expire Interval |
| |
`-------------------------------------------'
The Refresh Interval, Retry Interval, and Expire Interval are all
32-bit elapsed times measured in seconds. They express the timing
parameters which the cache expects the router to use in deciding when
to send subsequent Serial Query or Reset Query PDUs to the cache.
See Section 6 for an explanation of the use and the range of allowed
values for these parameters.
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Note that the End of Data PDU changed significantly between versions
0 and 1. Version 2 End of Data is the same as Version 1.
5.9. Cache Reset
The cache may respond to a Serial Query informing the router that the
cache cannot provide an incremental update starting from the Serial
Number specified by the router. The router must decide whether to
issue a Reset Query or switch to a different cache.
0 8 16 24 31
.-------------------------------------------.
| Protocol | PDU | |
| Version | Type | zero |
| 2 | 8 | |
+-------------------------------------------+
| |
| Length=8 |
| |
`-------------------------------------------'
5.10. Router Key
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0 8 16 24 31
.-------------------------------------------.
| Protocol | PDU | | |
| Version | Type | Flags | zero |
| 2 | 9 | | |
+-------------------------------------------+
| |
| Length |
| |
+-------------------------------------------+
| |
+--- ---+
| Subject Key Identifier |
+--- ---+
| |
+--- ---+
| (20 octets) |
+--- ---+
| |
+-------------------------------------------+
| |
| AS Number |
| |
+-------------------------------------------+
| |
| Subject Public Key Info |
| |
`-------------------------------------------'
The Router Key PDU transports an [RFC8635] Router key.
The lowest-order bit of the Flags field is 1 for an announcement and
0 for a withdrawal.
The cache server MUST ensure that it has told the router client to
have one and only one Router Key PDU for a unique {SKI, ASN, Subject
Public Key} at any one point in time. Should the router client
receive a Router Key PDU with a {SKI, ASN, Subject Public Key}
identical to one it already has active, it SHOULD raise a Duplicate
Announcement Received error.
Note that a particular ASN may appear in multiple Router Key PDUs
with different Subject Public Key values, while a particular Subject
Public Key value may appear in multiple Router Key PDUs with
different ASNs. In the interest of keeping the announcement and
withdrawal semantics as simple as possible for the router, this
protocol makes no attempt to compress either of these cases.
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Also note that it is possible, albeit very unlikely, for multiple
distinct Subject Public Key values to hash to the same SKI. For this
reason, implementations MUST compare Subject Public Key values as
well as SKIs when detecting duplicate PDUs.
As the Subject Public Key Info is a variable length field, it must be
decoded to determine where the PDU terminates.
5.11. Error Report
This PDU is used by either party to report an error to the other.
Error reports are only sent as responses to other PDUs, not to report
errors in Error Report PDUs.
Error codes are described in Section 13.
The Erroneous PDU field is a binary copy of the PDU causing the error
condition, including all fields.
If the error is generic (e.g., "Internal Error") and not associated
with the PDU to which it is responding, the Erroneous PDU field MUST
be empty and the Length of Encapsulated PDU field MUST be zero.
An Error Report PDU MUST NOT be sent for an Error Report PDU. If an
erroneous Error Report PDU is received, the session SHOULD be
dropped.
If the error is associated with a PDU of excessive length, i.e., too
long to be any legal PDU other than another Error Report, or a
possibly corrupt length, the Erroneous PDU field MAY be truncated.
The Arbitrary Text field is optional; if not present, the Length of
Arbitrary text field MUST be zero. If Arbitrary Text is present, it
MUST be a string in UTF-8 encoding (see [RFC3629]) in the Queen's
English.
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0 8 16 24 31
.-------------------------------------------.
| Protocol | PDU | |
| Version | Type | Error Code |
| 2 | 10 | |
+-------------------------------------------+
| |
| Length |
| |
+-------------------------------------------+
| |
| Length of Encapsulated PDU |
| |
+-------------------------------------------+
| |
~ Erroneous PDU ~
| |
+-------------------------------------------+
| |
| Length of Arbitrary Text |
| |
+-------------------------------------------+
| |
| Arbitrary Text |
~ of ~
| Error Diagnostic Message |
| |
`-------------------------------------------'
5.12. ASPA PDU
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0 8 16 24 31
.-------------------------------------------.
| Protocol | PDU | |
| Version | Type | zero |
| 2 | 11 | |
+-------------------------------------------+
| |
| Length |
| |
+-------------------------------------------+
| | | |
| Flags | AFI Flags| Provider AS Count |
| | | |
+-------------------------------------------+
| |
| Customer Autonomous System Number |
| |
+-------------------------------------------+
| |
~ Provider Autonomous System Numbers ~
| |
~-------------------------------------------~
The ASPA PDU supports [I-D.ietf-sidrops-aspa-profile]. An ASPA PDU
represents one single customer AS and its provider ASes. Receipt of
an ASPA PDU announcement (announce/withdraw flag == 1) when the
router already has an ASPA PDU with the same Customer Autonomous
System Number replaces the previous one. The cache MUST deliver the
complete data of an ASPA record in a single ASPA PDU.
The router MUST see at most one ASPA from a cache for a particular
Customer Autonomous System Number active at any time. As a number of
conditions in the global RPKI may present multiple valid ASPA RPKI
records for a single customer to a particular RP cache, this places a
burden on the cache to form the union of multiple ASPA records it has
received from the global RPKI into one ASPA PDU.
The Flags field is as described in Section 5.
For the ASPA PDU, the announce/withdraw Flag is set to 1 to indicate
either the announcement of a new ASPA record or a replacement for a
previously announced record with the same Customer Autonomous System
Number.
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If the announce/withdraw flag is set to 0, it indicates removal of
the entire ASPA record for that Customer AS. Here, the customer AS
of the ASPA record MUST be provided, the Provider AS Count must be
zero, the Provider AS Numbers list MUST be null, and these last two
fields MUST be ignored by the router.
The AFI Flags field is defined in Section 15 Currently, the two low
order bits MUST always be set, i.e. 1, and the rest unset, i.e. 0.
This allows the router to prepare for less change should the AFIs be
separated in a future version.
The Provider AS Count is the number of 32-bit Provider Autonomous
System Numbers in the PDU.
The Customer Autonomous System Number is the 32-bit Autonomous System
Number of the customer which authenticated the ASPA RPKI data. There
MUST be one and only one ASPA for a Customer Autonomous System Number
active in the router at any time.
There are zero or more 32-bit Provider Autonomous System Number
fields as indicated in the Provider AS Count; see
[I-D.ietf-sidrops-aspa-profile].
6. Protocol Timing Parameters
Since the data the cache distributes via the RPKI-Router protocol are
retrieved from the Global RPKI system at intervals which are only
known to the cache, only the cache can really know how frequently it
makes sense for the router to poll the cache, or how long the data
are likely to remain valid (or, at least, unchanged). For this
reason, as well as to allow the cache some control over the load
placed on it by its client routers, the End Of Data PDU includes
three values that allow the cache to communicate timing parameters to
the router:
Refresh Interval: This parameter tells the router how long to wait
before next attempting to poll the cache and between subsequent
attempts, using a Serial Query or Reset Query PDU. The router
SHOULD NOT poll the cache sooner than indicated by this parameter.
Note that receipt of a Serial Notify PDU overrides this interval
and suggests that the router issue an immediate query without
waiting for the Refresh Interval to expire. Countdown for this
timer starts upon receipt of the containing End Of Data PDU.
Minimum allowed value: 1 second.
Maximum allowed value: 86400 seconds (1 day).
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Recommended default: 3600 seconds (1 hour).
Retry Interval: This parameter tells the router how long to wait
before retrying a failed Serial Query or Reset Query. The router
SHOULD NOT retry sooner than indicated by this parameter. Note
that a protocol version mismatch overrides this interval: if the
router needs to downgrade to a lower protocol version number, it
MAY send the first Serial Query or Reset Query immediately.
Countdown for this timer starts upon failure of the query and
restarts after each subsequent failure until a query succeeds.
Minimum allowed value: 1 second.
Maximum allowed value: 7200 seconds (2 hours).
Recommended default: 600 seconds (10 minutes).
Expire Interval: This parameter tells the router how long it can
continue to use the current version of the data while unable to
perform a successful subsequent query. The router MUST NOT retain
the data past the time indicated by this parameter. Countdown for
this timer starts upon receipt of the containing End Of Data PDU.
Minimum allowed value: 600 seconds (10 minutes).
Maximum allowed value: 172800 seconds (2 days).
Recommended default: 7200 seconds (2 hours).
If the router has never issued a successful query against a
particular cache, it SHOULD retry periodically using the default
Retry Interval, above.
Caches MUST set Expire Interval to a value larger than both the
Refresh Interval and the Retry Interval.
7. Protocol Version Negotiation
A router MUST start each transport connection by issuing either a
Reset Query or a Serial Query. This query MUST tell the cache the
highest version of this protocol the router implements.
If a cache which supports version N receives a Reset Query with
Version Q < N, the cache MUST downgrade to protocol version Q
[RFC6810] or [RFC8210]. If the router's Reset Request was Q > N, the
cache MUST send a version 2 Error Report PDU with Error Code 4
("Unsupported Protocol Version"), and the router MUST send another
Reset Query with a lower Version Q. This MAY repeat. If the router
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requests Q == 0 and it still fails, then the router MUST abort the
session, sending a version 2 Error Report PDU with Error Code 4
("Unsupported Protocol Version").
If a router which supports version N sends a query to a cache which
only supports version C < N, one of two things will happen:
1. The cache may terminate the connection, perhaps with a version 2
Error Report PDU with Error Code 4 ("Unsupported Protocol
Version"). In this case, the router MAY retry the connection
using protocol version C.
2. The cache may reply with a version C response. In this case, the
router MUST either downgrade to version C or terminate the
connection.
In any of the downgraded combinations above, the new features of the
higher version will not be available, and all PDUs MUST have the
negotiated lower version number in their version fields.
If either party receives a PDU containing an unrecognized Protocol
Version (neither 0, 1, nor 2) during this negotiation, it MUST either
downgrade to a known version or terminate the connection, with an
Error Report PDU unless the received PDU is itself an Error Report
PDU.
The router MUST ignore any Serial Notify PDUs it might receive from
the cache during this initial startup period, regardless of the
Protocol Version field in the Serial Notify PDU. Since Session ID
and Serial Number values are specific to a particular protocol
version, the values in the notification are not useful to the router.
Even if these values were meaningful, the only effect that processing
the notification would have would be to trigger exactly the same
Reset Query or Serial Query that the router has already sent as part
of the not-yet-complete version negotiation process, so there is
nothing to be gained by processing notifications until version
negotiation completes.
Caches SHOULD NOT send Serial Notify PDUs before version negotiation
completes. Routers, however, MUST handle such notifications (by
ignoring them) for backwards compatibility with caches serving
protocol version 0.
Once the cache and router have agreed upon a Protocol Version via the
negotiation process above, that version is stable for the life of the
session. See Section 5.1 for a discussion of the interaction between
Protocol Version and Session ID.
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If either party receives a PDU for a different Protocol Version once
the above negotiation completes, that party MUST drop the session;
unless the PDU containing the unexpected Protocol Version was itself
an Error Report PDU, the party dropping the session SHOULD send an
Error Report with an error code of 8 ("Unexpected Protocol Version").
8. Protocol Sequences
The sequences of PDU transmissions fall into four conversations as
follows:
8.1. Start or Restart
Cache Router
~ ~
| <----- Reset Query -------- | R requests data (or Serial Query)
| |
| ----- Cache Response -----> | C confirms request
| ------- Payload PDU ------> | C sends zero or more
| ------- Payload PDU ------> | IPv4 Prefix, IPv6 Prefix,
| ------- Payload PDU ------> | ASPA, or Router Key PDUs
| ------- End of Data ------> | C sends End of Data
| | and sends new serial
~ ~
When a transport connection is first established, the router MUST
send either a Reset Query or a Serial Query. A Serial Query would be
appropriate if the router has unexpired data from a broken session
with the same cache and remembers the Session ID of that session, in
which case a Serial Query containing the Session ID from the previous
session will allow the router to bring itself up to date while
ensuring that the Serial Numbers are commensurate and that the router
and cache are speaking compatible versions of the protocol. In all
other cases, the router lacks the necessary data for fast
resynchronization and therefore MUST fall back to a Reset Query.
The Reset Query sequence is also used when the router receives a
Cache Reset, chooses a new cache, or fears that it has otherwise lost
its way.
See Section 7 for details on version negotiation.
To limit the length of time a cache must keep the data necessary to
generate incremental updates, a router MUST send either a Serial
Query or a Reset Query periodically. This also acts as a keep-alive
at the application layer. See Section 6 for details on the required
polling frequency.
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8.2. Typical Exchange
Cache Router
~ ~
| -------- Notify ----------> | (optional)
| |
| <----- Serial Query ------- | R requests data
| |
| ----- Cache Response -----> | C confirms request
| ------- Payload PDU ------> | C sends zero or more
| ------- Payload PDU ------> | IPv4 Prefix, IPv6 Prefix,
| ------- Payload PDU ------> | ASPA. or Router Key PDUs
| ------- End of Data ------> | C sends End of Data
| | and sends new serial
~ ~
The cache server SHOULD send a Notify PDU with its current Serial
Number when the cache's serial changes, with the expectation that the
router MAY then issue a Serial Query earlier than it otherwise might.
This is analogous to DNS NOTIFY in [RFC1996]. The cache MUST rate-
limit Serial Notifies to no more frequently than one per minute.
When the transport layer is up and either a timer has gone off in the
router or the cache has sent a Notify PDU, the router queries for new
data by sending a Serial Query, and the cache sends all data newer
than the serial in the Serial Query.
To limit the length of time a cache must keep old withdraws, a router
MUST send either a Serial Query or a Reset Query periodically. See
Section 6 for details on the required polling frequency.
8.3. No Incremental Update Available
Cache Router
~ ~
| <------ Serial Query ------ | R requests data
| ------- Cache Reset ------> | C cannot supply update
| | from specified serial
| <------ Reset Query ------- | R requests new data
| ----- Cache Response -----> | C confirms request
| ------- Payload PDU ------> | C sends zero or more
| ------- Payload PDU ------> | IPv4 Prefix, IPv6 Prefix,
| ------- Payload PDU ------> | ASPA, or Router Key PDUs
| ------- End of Data ------> | C sends End of Data
| | and sends new serial
~ ~
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The cache may respond to a Serial Query with a Cache Reset, informing
the router that the cache cannot supply an incremental update from
the Serial Number specified by the router. This might be because the
cache has lost state, or because the router has waited too long
between polls and the cache has cleaned up old data that it no longer
believes it needs, or because the cache has run out of storage space
and had to expire some old data early. Regardless of how this state
arose, the cache replies with a Cache Reset to tell the router that
it cannot honor the request. When a router receives this, the router
SHOULD attempt to connect to any more-preferred caches in its cache
list. If there are no more-preferred caches, it MUST issue a Reset
Query and get an entire new load from the cache.
8.4. Cache Has No Data Available
Cache Router
~ ~
| <------ Serial Query ------ | R requests data
| ---- Error Report PDU ----> | C No Data Available
~ ~
Cache Router
~ ~
| <------ Reset Query ------- | R requests data
| ---- Error Report PDU ----> | C No Data Available
~ ~
The cache may respond to either a Serial Query or a Reset Query
informing the router that the cache cannot supply any update at all.
The most likely cause is that the cache has lost state, perhaps due
to a restart, and has not yet recovered. While it is possible that a
cache might go into such a state without dropping any of its active
sessions, a router is more likely to see this behavior when it
initially connects and issues a Reset Query while the cache is still
rebuilding its database.
When a router receives this kind of error, the router SHOULD attempt
to connect to any other caches in its cache list, in preference
order. If no other caches are available, the router MUST issue
periodic Reset Queries until it gets a new usable load from the
cache; maybe once a minute so as not to DoS the cache.
9. Transport
The transport-layer session between a router and a cache carries the
binary PDUs in a persistent session.
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To prevent cache spoofing and DoS attacks by illegitimate routers, it
is highly desirable that the router and the cache be authenticated to
each other. Integrity protection for payloads is also desirable to
protect against monkey-in-the-middle (MITM) attacks. Unfortunately,
there is no protocol to do so on all currently used platforms.
Therefore, as of the writing of this document, there is no mandatory-
to-implement transport which provides authentication and integrity
protection.
To reduce exposure to dropped but non-terminated sessions, both
caches and routers SHOULD enable keep-alives when available in the
chosen transport protocol.
It is expected that, when the TCP Authentication Option (TCP-AO)
[RFC5925] is available on all platforms deployed by operators, it
will become the mandatory-to-implement transport.
Caches and routers MUST implement unprotected transport over TCP
using a port, rpki-rtr (323); see Section 15. Operators SHOULD use
procedural means, e.g., access control lists (ACLs), to reduce the
exposure to authentication issues.
If unprotected TCP is the transport, the cache and routers MUST be on
the same trusted and controlled network.
If available to the operator, caches and routers MUST use one of the
following more protected protocols:
* Caches and routers SHOULD use TCP-AO transport [RFC5925] over the
rpki-rtr port.
* Caches and routers MAY use Secure Shell version 2 (SSHv2)
transport [RFC4252] using the normal SSH port. For an example,
see Section 9.1.
* Caches and routers MAY use TCP MD5 transport [RFC2385] using the
rpki-rtr port if no other protected transport is available. Note
that TCP MD5 has been obsoleted by TCP-AO [RFC5925].
* Caches and routers MAY use TCP over IPsec transport [RFC4301]
using the rpki-rtr port.
* Caches and routers MAY use Transport Layer Security (TLS)
transport [RFC8446] using port rpki-rtr-tls (324); see Section 15.
Conformance to [RFC7525] modern cipher suites is REQUIRED.
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9.1. SSH Transport
To run over SSH, the client router first establishes an SSH transport
connection using the SSHv2 transport protocol, and the client and
server exchange keys for message integrity and encryption. The
client then invokes the "ssh-userauth" service to authenticate the
application, as described in the SSH authentication protocol
[RFC4252]. Once the application has been successfully authenticated,
the client invokes the "ssh-connection" service, also known as the
SSH connection protocol.
After the ssh-connection service is established, the client opens a
channel of type "session", which results in an SSH session.
Once the SSH session has been established, the application invokes
the application transport as an SSH subsystem called "rpki-rtr".
Subsystem support is a feature of SSHv2 and is not included in SSHv1.
Running this protocol as an SSH subsystem avoids the need for the
application to recognize shell prompts or skip over extraneous
information, such as a system message that is sent at shell startup.
It is assumed that the router and cache have exchanged keys out of
band by some reasonably secured means.
Cache servers supporting SSH transport MUST accept RSA authentication
and SHOULD accept Elliptic Curve Digital Signature Algorithm (ECDSA)
authentication. User authentication "publickey") MUST be supported;
host authentication "hostbased") MAY be supported. Implementations
MAY support password authentication "password"). "None"
authentication MUST NOT be used. Client routers SHOULD verify the
public key of the cache to avoid MITM attacks.
9.2. TLS Transport
Client routers using TLS transport MUST present client-side
certificates to authenticate themselves to the cache in order to
allow the cache to manage the load by rejecting connections from
unauthorized routers. In principle, any type of certificate and
Certification Authority (CA) may be used; however, in general, cache
operators will wish to create their own small-scale CA and issue
certificates to each authorized router. This simplifies credential
rollover; any unrevoked, unexpired certificate from the proper CA may
be used.
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Certificates used to authenticate client routers in this protocol
MUST include a subjectAltName extension [RFC5280] containing one or
more iPAddress identities; when authenticating the router's
certificate, the cache MUST check the IP address of the TLS
connection against these iPAddress identities and SHOULD reject the
connection if none of the iPAddress identities match the connection.
Routers MUST also verify the cache's TLS server certificate, using
subjectAltName dNSName identities as described in [RFC6125], to avoid
MITM attacks. The rules and guidelines defined in [RFC6125] apply
here, with the following considerations:
* Support for the DNS-ID identifier type (that is, the dNSName
identity in the subjectAltName extension) is REQUIRED in rpki-rtr
server and client implementations which use TLS. Certification
authorities which issue rpki-rtr server certificates MUST support
the DNS-ID identifier type, and the DNS-ID identifier type MUST be
present in rpki-rtr server certificates.
* DNS names in rpki-rtr server certificates SHOULD NOT contain the
wildcard character "*".
* rpki-rtr implementations which use TLS MUST NOT use Common Name
(CN-ID) identifiers; a CN field may be present in the server
certificate's subject name but MUST NOT be used for authentication
within the rules described in [RFC6125].
* The client router MUST set its "reference identifier" (see
Section 6.2 of [RFC6125]) to the DNS name of the rpki-rtr cache.
9.3. TCP MD5 Transport
If TCP MD5 is used, implementations MUST support key lengths of at
least 80 printable ASCII bytes, per Section 4.5 of [RFC2385].
Implementations MUST also support hexadecimal sequences of at least
32 characters, i.e., 128 bits.
Key rollover with TCP MD5 is problematic. Cache servers SHOULD
support [RFC4808].
9.4. TCP-AO Transport
Implementations MUST support key lengths of at least 80 printable
ASCII bytes. Implementations MUST also support hexadecimal sequences
of at least 32 characters, i.e., 128 bits. Message Authentication
Code (MAC) lengths of at least 96 bits MUST be supported, per
Section 5.1 of [RFC5925].
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The cryptographic algorithms and associated parameters described in
[RFC5926] MUST be supported.
10. Router-Cache Setup
A cache has the public authentication data for each router it is
configured to support.
A router may be configured to peer with a selection of caches, and a
cache may be configured to support a selection of routers. Each must
have the name of, and authentication data for, each peer. In
addition, in a router, this list has a non-unique preference value
for each cache. This preference is intended to be based on
proximity, a la RTT, not trust, preferred belief, et cetera. The
client router attempts to establish a session with each potential
serving cache in preference order and then starts to load data from
the most preferred cache to which it can connect and authenticate.
The router's list of caches has the following elements:
Preference: An unsigned integer denoting the router's preference to
connect to that cache; the lower the value, the more preferred.
Name: The IP address or fully qualified domain name of the cache.
Cache Credential(s): Any credential (such as a public key) needed to
authenticate the cache's identity to the router.
Router Credential(s): Any credential (such as a private key or
certificate) needed to authenticate the router's identity to the
cache.
Due to the distributed nature of the RPKI, caches simply cannot be
rigorously synchronous. A client may hold data from multiple caches
but MUST keep the data marked as to source, as later updates MUST
affect the correct data.
Just as there may be more than one covering ROA from a single cache,
there may be multiple covering ROAs from multiple caches. The
results are as described in [RFC6811].
If data from multiple caches are held, implementations MUST NOT
distinguish between data sources when performing validation of BGP
announcements.
When a more-preferred cache becomes available, if resources allow, it
would be prudent for the client to start fetching from that cache.
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The client SHOULD attempt to maintain at least one set of data,
regardless of whether it has chosen a different cache or established
a new connection to the previous cache.
A client MAY drop the data from a particular cache when it is fully
in sync with one or more other caches.
See Section 6 for details on what to do when the client is not able
to refresh from a particular cache.
If a client loses connectivity to a cache it is using or otherwise
decides to switch to a new cache, it SHOULD retain the data from the
previous cache until it has a full set of data from one or more other
caches. Note that this may already be true at the point of
connection loss if the client has connections to more than one cache.
11. ROA PDU Race Minimization
When a cache is sending ROA (IPv4 or IPv6) PDUs to a router,
especially an initial full load in response to a Reset Query PDU, two
undesirable race conditions are possible:
Break Before Make: For some prefix P, an AS may announce two (or
more) ROAs because they are in the process of changing what
provider AS is announcing P. This is a case of "make before
break." If a cache is feeding a router and sends the one not yet
in service a significant time before sending the one currently in
service, then BGP data could be marked invalid during the
interval. To minimize that interval, the cache SHOULD announce
all ROAs for the same prefix as close to sequentially as possible.
Shorter Prefix First: If an AS has issued a ROA for P0, and another
AS (likely their customer) has issued a ROA for P1 which is a sub-
prefix of P0, a router which receives the ROA for P0 before that
for P1 is likely to mark a BGP prefix P1 invalid. Therefore, the
cache SHOULD announce the sub-prefix P1 before the covering prefix
P0.
12. Deployment Scenarios
For illustration, we present three likely deployment scenarios:
Small End Site: The small multihomed end site may wish to outsource
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the RPKI cache to one or more of their upstream ISPs. They would
exchange authentication material with the ISP using some out-of-
band mechanism, and their router(s) would connect to the cache(s)
of one or more upstream ISPs. The ISPs would likely deploy caches
intended for customer use separately from the caches with which
their own BGP speakers peer.
Large End Site: A larger multihomed end site might run one or more
caches, arranging them in a hierarchy of client caches, each
fetching from a serving cache which is closer to the Global RPKI.
They might configure fallback peerings to upstream ISP caches.
ISP Backbone: A large ISP would likely have one or more redundant
caches in each major point of presence (PoP), and these caches
would fetch from each other in an ISP-dependent topology so as not
to place undue load on the Global RPKI.
Experience with large DNS cache deployments has shown that complex
topologies are ill-advised, as it is easy to make errors in the
graph, e.g., not maintain a loop-free condition.
Of course, these are illustrations, and there are other possible
deployment strategies. It is expected that minimizing load on the
Global RPKI servers will be a major consideration.
To keep load on Global RPKI services from unnecessary peaks, it is
recommended that caches which fetch from the Global RPKI not do so
all at the same times, e.g., on the hour. Choose a random time,
perhaps the ISP's AS number modulo 60, and jitter the inter-fetch
timing.
13. Error Codes
This section describes the meaning of the error codes. There is an
IANA registry where valid error codes are listed; see [iana-err].
Errors which are considered fatal MUST cause the session to be
dropped, and the router MUST flush all data learned from that cache.
0: Corrupt Data (fatal): The receiver believes the received PDU to
be corrupt in a manner not specified by another error code.
1: Internal Error (fatal): The party reporting the error experienced
some kind of internal error unrelated to protocol operation (ran
out of memory, a coding assertion failed, et cetera).
2: No Data Available: The cache believes itself to be in good
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working order but is unable to answer either a Serial Query or a
Reset Query because it has no useful data available at this time.
This is likely to be a temporary error and most likely indicates
that the cache has not yet completed pulling down an initial
current data set from the Global RPKI system after some kind of
event that invalidated whatever data it might have previously held
(reboot, network partition, et cetera).
3: Invalid Request (fatal): The cache server believes the client's
request to be invalid.
4: Unsupported Protocol Version (fatal): The Protocol Version is not
known by the receiver of the PDU.
5: Unsupported PDU Type (fatal): The PDU Type is not known by the
receiver of the PDU.
6: Withdrawal of Unknown Record (fatal): The received PDU has
Flag=0, but a matching record ({Prefix, Len, Max-Len, ASN} tuple
for an IPvX PDU, or {SKI, ASN, Subject Public Key} tuple for a
Router Key PDU), or Customer Autonomous System for an ASPA PDU
does not exist in the receiver's database.
7: Duplicate Announcement Received (fatal): The received PDU has
Flag=1, but a matching record ({Prefix, Len, Max-Len, ASN} tuple
for an IPvX PDU or {SKI, ASN, Subject Public Key} tuple for a
Router Key PDU), or Customer Autonomous System for an ASPA PDU is
already active in the router.
8: Unexpected Protocol Version (fatal): The received PDU has a
Protocol Version field that differs from the protocol version
negotiated in Section 7.
14. Security Considerations
As this document describes a security protocol, many aspects of
security interest are described in the relevant sections. This
section points out issues which may not be obvious in other sections.
Cache Validation: In order for a collection of caches as described
in Section 12 to provide a consistent view, they need to be given
consistent trust anchors of the Certification Authorities to use
in their internal validation process. Distribution of a
consistent trust anchor set to validating caches is assumed to be
out of band.
Cache Peer Identification: The router initiates a transport
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connection to a cache, which it identifies by either IP address or
fully qualified domain name. Be aware that a DNS or address
spoofing attack could make the correct cache unreachable. No
session would be established, as the authorization keys would not
match.
Transport Security: The RPKI relies on object, not server or
transport, trust. That is, the IANA root trust anchor is
distributed to all caches through some out-of-band means and can
then be used by each cache to validate certificates and ROAs all
the way down the tree. The inter-cache relationships are based on
this object security model; hence, the inter-cache transport can
be lightly protected.
However, this protocol document assumes that the routers cannot do
the validation cryptography. Hence, the last link, from cache to
router, SHOULD be secured by server authentication and transport-
level security to prevent monkey in the middle attacks; though it
might not be. Not using transport security is dangerous, as
server authentication and transport have very different threat
models than object security.
So the strength of the trust relationship and the transport
between the router(s) and the cache(s) are critical. You're
betting your routing on this.
While we cannot say the cache must be on the same LAN, if only due
to the issue of an enterprise wanting to offload the cache task to
their upstream ISP(s), locality, trust, and control are very
critical issues here. The cache(s) really SHOULD be as close, in
the sense of controlled and protected (against DDoS, MITM)
transport, to the router(s) as possible. It also SHOULD be
topologically close so that a minimum of validated routing data
are needed to bootstrap a router's access to a cache.
Authenticating transport protocols (i.e. not raw TCP) will
authenticate the identity of the cache server to the router
client, and vice versa, before any data are exchanged.
Transports which cannot provide the necessary authentication and
integrity (see Section 9) must rely on network design and
operational controls to provide protection against spoofing/
corruption attacks. As pointed out in Section 9, TCP-AO is the
long-term plan. Protocols which provide integrity and
authenticity SHOULD be used, and if they cannot, i.e., TCP is used
as the transport, the router and cache MUST be on the same
trusted, controlled network.
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15. IANA Considerations
This section only discusses updates required in the existing IANA
protocol registries to accommodate version 2 of this protocol. See
[RFC8210] for IANA considerations of the previous (version 1)
protocol.
All of the PDU types in the IANA "rpki-rtr-pdu" registry [iana-pdu]
in protocol versions 0 and 1 are also allowed in protocol version 2,
with the addition of the new ASPA PDU.
The "rpki-rtr-pdu" registry [iana-pdu] has been updated as follows:
Protocol PDU
Version Type Description
-------- ---- ---------------
0-2 0 Serial Notify
0-2 1 Serial Query
0-2 2 Reset Query
0-2 3 Cache Response
0-2 4 IPv4 Prefix
0-2 6 IPv6 Prefix
0-2 7 End of Data
0-2 8 Cache Reset
0 9 Reserved
1-2 9 Router Key
0-2 10 Error Report
0-1 11 Reserved
2 11 ASPA
0-2 255 Reserved
This document requests the IANA to create a registry for ASPA AFI
Flags 0 to 7. The name of the registry should be rpki-rtr-afi. The
policy for adding to the registry is Expert Review per [RFC8126],
where the responsible IESG area director should appoint the Expert
Reviewer. The initial entries should be as follows:
Bit Bit Name
---- -------------------
0 IPv4 AFI 1, currently MUST be set
1 IPv6 AFI 2, currently MUST be set
2-7 Reserved, MUST be zero
16. References
16.1. Normative References
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[I-D.ietf-sidrops-aspa-profile]
Azimov, A., Uskov, E., Bush, R., Snijders, J., Housley,
R., and B. Maddison, "A Profile for Autonomous System
Provider Authorization", Work in Progress, Internet-Draft,
draft-ietf-sidrops-aspa-profile-16, 10 July 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-sidrops-
aspa-profile-16>.
[iana-err] IANA, "rpki-rtr-error",
<https://www.iana.org/assignments/rpki#rpki-rtr-error>.
[iana-pdu] IANA, "rpki-rtr-pdu",
<https://www.iana.org/assignments/rpki#rpki-rtr-pdu>.
[RFC1982] Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982,
DOI 10.17487/RFC1982, August 1996,
<https://www.rfc-editor.org/info/rfc1982>.
[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>.
[RFC2385] Heffernan, A., "Protection of BGP Sessions via the TCP MD5
Signature Option", RFC 2385, DOI 10.17487/RFC2385, August
1998, <https://www.rfc-editor.org/info/rfc2385>.
[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>.
[RFC4252] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
Authentication Protocol", RFC 4252, DOI 10.17487/RFC4252,
January 2006, <https://www.rfc-editor.org/info/rfc4252>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <https://www.rfc-editor.org/info/rfc4301>.
[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>.
[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
June 2010, <https://www.rfc-editor.org/info/rfc5925>.
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[RFC5926] Lebovitz, G. and E. Rescorla, "Cryptographic Algorithms
for the TCP Authentication Option (TCP-AO)", RFC 5926,
DOI 10.17487/RFC5926, June 2010,
<https://www.rfc-editor.org/info/rfc5926>.
[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>.
[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>.
[RFC6810] Bush, R. and R. Austein, "The Resource Public Key
Infrastructure (RPKI) to Router Protocol", RFC 6810,
DOI 10.17487/RFC6810, January 2013,
<https://www.rfc-editor.org/info/rfc6810>.
[RFC6811] Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R.
Austein, "BGP Prefix Origin Validation", RFC 6811,
DOI 10.17487/RFC6811, January 2013,
<https://www.rfc-editor.org/info/rfc6811>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", RFC 7525, DOI 10.17487/RFC7525, May 2015,
<https://www.rfc-editor.org/info/rfc7525>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[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>.
[RFC8210] Bush, R. and R. Austein, "The Resource Public Key
Infrastructure (RPKI) to Router Protocol, Version 1",
RFC 8210, DOI 10.17487/RFC8210, September 2017,
<https://www.rfc-editor.org/info/rfc8210>.
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[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[RFC8608] Turner, S. and O. Borchert, "BGPsec Algorithms, Key
Formats, and Signature Formats", RFC 8608,
DOI 10.17487/RFC8608, June 2019,
<https://www.rfc-editor.org/info/rfc8608>.
[RFC8635] Bush, R., Turner, S., and K. Patel, "Router Keying for
BGPsec", RFC 8635, DOI 10.17487/RFC8635, August 2019,
<https://www.rfc-editor.org/info/rfc8635>.
16.2. Informative References
[RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone
Changes (DNS NOTIFY)", RFC 1996, DOI 10.17487/RFC1996,
August 1996, <https://www.rfc-editor.org/info/rfc1996>.
[RFC4808] Bellovin, S., "Key Change Strategies for TCP-MD5",
RFC 4808, DOI 10.17487/RFC4808, March 2007,
<https://www.rfc-editor.org/info/rfc4808>.
[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>.
[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>.
[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>.
Acknowledgements
The authors wish to thank Nils Bars, Steve Bellovin, Oliver Borchert,
Mohamed Boucadair, Tim Bruijnzeels, Roman Danyliw, Rex Fernando,
Richard Hansen, Martin Hoffmann, Paul Hoffman, Fabian Holler, Russ
Housley, Pradosh Mohapatra, Keyur Patel, David Mandelberg, Sandy
Murphy, Robert Raszuk, Andreas Reuter, Thomas Schmidt, John Scudder,
Ruediger Volk, Matthias Waehlisch, and David Ward. Particular thanks
go to Hannes Gredler for showing us the dangers of unnecessary
fields.
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No doubt this list is incomplete. We apologize to any contributor
whose name we missed.
Authors' Addresses
Randy Bush
IIJ Research, Arrcus, & DRL
5147 Crystal Springs
Bainbridge Island, Washington 98110
United States of America
Email: randy@psg.com
Rob Austein
Dragon Research Labs
Email: sra@hactrn.net
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