RPKI-Based Origin Validation Operation
draft-ietf-sidr-origin-ops-13
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Network Working Group R. Bush
Internet-Draft Internet Initiative Japan
Intended status: BCP November 14, 2011
Expires: May 17, 2012
RPKI-Based Origin Validation Operation
draft-ietf-sidr-origin-ops-13
Abstract
Deployment of RPKI-based BGP origin validation has many operational
considerations. This document attempts to collect and present them.
It is expected to evolve as RPKI-based origin validation is deployed
and the dynamics are better understood.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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 http://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 May 17, 2012.
Copyright Notice
Copyright (c) 2011 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
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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. Suggested Reading . . . . . . . . . . . . . . . . . . . . . . . 3
3. RPKI Distribution and Maintenance . . . . . . . . . . . . . . . 3
4. Within a Network . . . . . . . . . . . . . . . . . . . . . . . 5
5. Routing Policy . . . . . . . . . . . . . . . . . . . . . . . . 6
6. Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . . 8
10.2. Informative References . . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
RPKI-based origin validation relies on widespread deployment of the
Resource Public Key Infrastructure (RPKI) [I-D.ietf-sidr-arch]. How
the RPKI is distributed and maintained globally is a serious concern
from many aspects.
The global RPKI is in very initial stages of deployment, there is no
single root trust anchor, initial testing is being done by the IANA
and the RIRs, and there is a technical testbed. It is thought that
origin validation based on the RPKI will be deployed incrementally
over the next year to five years.
Origin validation needs to be done only by an AS's border routers and
is designed so that it can be used to protect announcements which are
originated by any network participating in Internet BGP routing:
large providers, upstreams and down-streams, and by small stub/
enterprise/edge routers.
Origin validation has been designed to be deployed on current routers
without significant hardware upgrade. It should be used in border
routers by operators from large backbones to small stub/entetprise/
edge networks.
RPKI-based origin validation has been designed so that, with prudent
local routing policies, there is little risk that what is seen as
today's normal Internet routing is threatened by imprudent deployment
of the global RPKI, see Section 5.
2. Suggested Reading
It is assumed that the reader understands BGP, [RFC4271], the RPKI,
see [I-D.ietf-sidr-arch], the RPKI Repository Structure, see
[I-D.ietf-sidr-repos-struct], ROAs, see [I-D.ietf-sidr-roa-format],
the RPKI to Router Protocol, see [I-D.ietf-sidr-rpki-rtr], RPKI-based
Prefix Validation, see [I-D.ietf-sidr-pfx-validate], and Ghostbusters
Records, see [I-D.ietf-sidr-ghostbusters].
3. RPKI Distribution and Maintenance
The RPKI is a distributed database containing certificates, CRLs,
manifests, ROAs, and Ghostbusters Records as described in
[I-D.ietf-sidr-repos-struct]. Policies and considerations for RPKI
object generation and maintenance are discussed elsewhere.
A local valid cache containing all RPKI data may be gathered from the
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global distributed database using the rsync protocol, [RFC5781], and
a validation tool such as rcynic [rcynic].
Validated caches may also be created and maintained from other
validated caches. Network operators SHOULD take maximum advantage of
this feature to minimize load on the global distributed RPKI
database. Of course, the recipient SHOULD re-validate the data.
Timing of inter-cache synchronization is outside the scope of this
document, but depends on things such as how often routers feed from
the caches, how often the operator feels the global RPKI changes
significantly, etc.
As inter-cache synchronization within an operator does not impact
global RPKI resources, an operator MAY choose to synchronize quite
frequently.
As RPKI-based origin validation relies on the availability of RPKI
data, operators SHOULD locate caches close to routers that require
these data and services. 'Close' is, of course, complex. One should
consider trust boundaries, routing bootstrap reachability, latency,
etc.
For redundancy, a router SHOULD peer with more than one cache at the
same time. Peering with two or more, at least one local and others
remote, is recommended.
If an operator trusts upstreams to carry their traffic, they MAY also
trust the RPKI data those upstreams cache, and SHOULD peer with
caches made available to them by those upstreams. Note that this
places an obligation on those upstreams to maintain fresh and
reliable caches, and to make them available to their customers. And,
as usual, the recipient SHOULD re-validate the data.
A transit provider or a network with peers SHOULD validate origins in
announcements made by upstreams, down-streams, and peers. They still
SHOULD trust the caches provided by their upstreams.
Before issuing a ROA for a super-block, an operator MUST ensure that
any sub-allocations from that block which are announced by other ASs,
e.g. customers, have correct ROAs in the RPKI. Otherwise, issuing a
ROA for the super-block will cause the announcements of sub-
allocations with no ROAs to be viewed as Invalid, see
[I-D.ietf-sidr-pfx-validate].
Use of RPKI-based origin validation removes any need to originate
more specifics into BGP to protect against mis-origination of a less
specific prefix. Having a ROA for the covering prefix should protect
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it.
To aid translation of ROAs into efficient search algorithms in
routers, ROAs SHOULD be as precise as possible, i.e. match prefixes
as announced in BGP. E.g. software and operators SHOULD avoid use of
excessive max length values in ROAs unless operationally necessary.
One advantage of minimal ROA length is that the forged origin attack
does not work for sub-prefixes that are not covered by overly long
max length. E.g. if, instead of 10.0.0.0/16-24, one issues
10.0.0.0/16 and 10.0.42.0/24, a forged origin attack can not succeed
against 10.0.66.0/24. They must attack the whole /16, which is more
likely to be noticed because of its size.
Therefore, ROA generation software MUST use the prefix length as the
max length if the user does not specify a max length.
Operators SHOULD be conservative in use of max length in ROAs. E.g.,
if a prefix will have only a few sub-prefixes announced, multiple
ROAs for the specific announcements SHOULD be used as opposed to one
ROA with a long max length.
If a prefix is legitimately announced by more than one AS, ROAs for
all of the ASs SHOULD be issued so that all are considered Valid.
An environment where private address space is announced in eBGP the
operator MAY have private RPKI objects which cover these private
spaces. This will require a trust anchor created and owned by that
environment, see [I-D.ietf-sidr-ltamgmt].
Operators owning prefix P should issue ROAs for all ASs which may
announce P.
Operators issuing ROAs may have customers which announce their own
prefixes and ASs into global eBGP but who do not wish to go though
the work to manage the relevant certificates and ROAs. Operators
SHOULD offer to provision the RPKI data for these customers just as
they provision many other things for them.
While an operator using RPKI data MAY choose any polling frequency
they wish for ensuring they have a fresh RPKI cache. However, if
they use RPKI data as an input to operational routing decisions, they
SHOULD ensure local cache freshness at least every four to six hours.
4. Within a Network
Origin validation need only be done by edge routers in a network,
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those which border other networks/ASs.
A validating router will use the result of origin validation to
influence local policy within its network, see Section 5. In
deployment this policy should fit into the AS's existing policy,
preferences, etc. This allows a network to incrementally deploy
validation-capable border routers.
eBGP speakers which face more critical peers or up/down-streams are
candidates for the earliest deployment. Validating more critical
received announcements should be considered in partial deployment.
5. Routing Policy
Origin validation based on the RPKI marks a received announcement as
having an origin which is Valid, NotFound, or Invalid. See
[I-D.ietf-sidr-pfx-validate]. How this is used in routing SHOULD be
specified by the operator's local policy.
Local policy using relative preference is suggested to manage the
uncertainty associated with a system in early deployment, applying
local policy to eliminate the threat of unroutability of prefixes due
to ill-advised certification policies and/or incorrect certification
data. E.g. until the community feels comfortable relying on RPKI
data, routing on Invalid origin validity, though at a low preference,
MAY occur.
As origin validation will be rolled out incrementally, coverage will
be incomplete for a long time. Therefore, routing on NotFound
validity state SHOULD be done for a long time. As the transition
moves forward, the number of BGP announcements with validation state
NotFound should decrease. Hence an operator's policy SHOULD NOT be
overly strict, preferring Valid announcements, attaching a lower
preference to, but still using, NotFound announcements, and dropping
or giving very low preference to Invalid announcements.
Some providers may choose to set Local-Preference based on the RPKI
validation result. Other providers may not want the RPKI validation
result to be more important than AS-path length -- these providers
would need to map RPKI validation result to some BGP attribute that
is evaluated in BGP's path selection process after AS-path is
evaluated. Routers implementing RPKI-based origin validation MUST
provide such options to operators.
Local-Preference may be used to carry both the validity state of a
prefix along with it's traffic engineering characteristic(s). It is
likely that an operator already using Local-Preference will have to
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change policy so they can encode these two separate characteristics
in the same BGP attribute without negatively impact or opening
privilege escalation attacks.
When using a metric which is also influenced by other local policy,
an operator should be careful not to create privilege upgrade
vulnerabilities. E.g. if Local Pref is set depending on validity
state, be careful that peer community signaling MAY NOT upgrade an
Invalid announcement to Valid or better.
Announcements with Valid origins SHOULD be preferred over those with
NotFound or Invalid origins, if the latter are accepted at all.
Announcements with NotFound origins SHOULD be preferred over those
with Invalid origins.
Announcements with Invalid origins SHOULD NOT be used, but MAY be
used to meet special operational needs. In such circumstances, the
announcement SHOULD have a lower preference than that given to Valid
or NotFound.
Validity state signialing SHOULD NOT be accepted from a neighbor AS.
The validity state of a received announcement has only local scope
due to issues such as scope of trust, RPKI synchrony, and
[I-D.ietf-sidr-ltamgmt].
6. Notes
Like the DNS, the global RPKI presents only a loosely consistent
view, depending on timing, updating, fetching, etc. Thus, one cache
or router may have different data about a particular prefix than
another cache or router. There is no 'fix' for this, it is the
nature of distributed data with distributed caches.
It is hoped that testing and deployment will produce advice on
relying party cache loading and timing.
There is some uncertainty about the origin AS of aggregates and what,
if any, ROA can be used. The long range solution to this is the
deprecation of AS-SETs, see [I-D.wkumari-deprecate-as-sets].
Operators who manage certificates SHOULD associate RPKI Ghostbusters
Records (see [I-D.ietf-sidr-ghostbusters]) with each publication
point they control. These are publication points holding the CRL,
ROAs, and other signed objects issued by the operator, and made
available to other ASs in support of routing on the public Internet.
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7. Security Considerations
As the BGP origin AS of an update is not signed, origin validation is
open to malicious spoofing. Therefore, RPKI-based origin validation
is designed to deal only with inadvertent mis-advertisement.
Origin validation does not address the problem of AS-Path validation.
Therefore paths are open to manipulation, either malicious or
accidental.
As BGP does not ensure that traffic will flow via the paths it
advertises, the data plane may not follow the control plane.
Be aware of the class of privilege escalation issues discussed in
Section 5 above.
8. IANA Considerations
This document has no IANA Considerations.
9. Acknowledgments
The author wishes to thank Shane Amante, Rob Austein, Steve Bellovin,
Jay Borkenhagen, Steve Kent, Pradosh Mohapatra, Chris Morrow, Sandy
Murphy, Keyur Patel, Heather and Jason Schiller, John Scudder,
Kotikalapudi Sriram, Maureen Stillman, and Dave Ward.
10. References
10.1. Normative References
[I-D.ietf-sidr-arch]
Lepinski, M. and S. Kent, "An Infrastructure to Support
Secure Internet Routing", draft-ietf-sidr-arch-13 (work in
progress), May 2011.
[I-D.ietf-sidr-ghostbusters]
Bush, R., "The RPKI Ghostbusters Record",
draft-ietf-sidr-ghostbusters-15 (work in progress),
October 2011.
[I-D.ietf-sidr-ltamgmt]
Reynolds, M. and S. Kent, "Local Trust Anchor Management
for the Resource Public Key Infrastructure",
draft-ietf-sidr-ltamgmt-02 (work in progress), June 2011.
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[I-D.ietf-sidr-pfx-validate]
Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R.
Austein, "BGP Prefix Origin Validation",
draft-ietf-sidr-pfx-validate-03 (work in progress),
October 2011.
[I-D.ietf-sidr-repos-struct]
Huston, G., Loomans, R., and G. Michaelson, "A Profile for
Resource Certificate Repository Structure",
draft-ietf-sidr-repos-struct-09 (work in progress),
July 2011.
[I-D.ietf-sidr-roa-format]
Lepinski, M., Kent, S., and D. Kong, "A Profile for Route
Origin Authorizations (ROAs)",
draft-ietf-sidr-roa-format-12 (work in progress),
May 2011.
[I-D.ietf-sidr-rpki-rtr]
Bush, R. and R. Austein, "The RPKI/Router Protocol",
draft-ietf-sidr-rpki-rtr-19 (work in progress),
October 2011.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5781] Weiler, S., Ward, D., and R. Housley, "The rsync URI
Scheme", RFC 5781, February 2010.
10.2. Informative References
[I-D.wkumari-deprecate-as-sets]
Kumari, W., "Deprecation of BGP AS_SET, AS_CONFED_SET.",
draft-wkumari-deprecate-as-sets-01 (work in progress),
September 2010.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
[rcynic] "rcynic read-me",
<http://subvert-rpki.hactrn.net/rcynic/README>.
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Author's Address
Randy Bush
Internet Initiative Japan
5147 Crystal Springs
Bainbridge Island, Washington 98110
US
Phone: +1 206 780 0431 x1
Email: randy@psg.com
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