Internet DRAFT - draft-ietf-sidr-bgpsec-ops
draft-ietf-sidr-bgpsec-ops
Network Working Group R. Bush
Internet-Draft Internet Initiative Japan
Intended status: Best Current Practice January 5, 2017
Expires: July 9, 2017
BGPsec Operational Considerations
draft-ietf-sidr-bgpsec-ops-16
Abstract
Deployment of the BGPsec architecture and protocols has many
operational considerations. This document attempts to collect and
present the most critical and universal. It is expected to evolve as
BGPsec is formalized and initially deployed.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to
be interpreted as described in RFC 2119 [RFC2119] only when they
appear in all upper case. They may also appear in lower or mixed
case as English words, without normative meaning.
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
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Internet-Drafts are draft documents valid for a maximum of six months
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This Internet-Draft will expire on July 9, 2017.
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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Suggested Reading . . . . . . . . . . . . . . . . . . . . . . 3
3. RPKI Distribution and Maintenance . . . . . . . . . . . . . . 3
4. AS/Router Certificates . . . . . . . . . . . . . . . . . . . 3
5. Within a Network . . . . . . . . . . . . . . . . . . . . . . 3
6. Considerations for Edge Sites . . . . . . . . . . . . . . . . 4
7. Routing Policy . . . . . . . . . . . . . . . . . . . . . . . 5
8. Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
9. Security Considerations . . . . . . . . . . . . . . . . . . . 7
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
12.1. Normative References . . . . . . . . . . . . . . . . . . 7
12.2. Informative References . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Origin Validation based on the Resource Public Key Infrastructure
(RPKI), [RFC6811], is in its early phases. As BGPsec,
[I-D.ietf-sidr-bgpsec-protocol] may require larger memory and/or more
modern CPUs, it expected to be deployed incrementally over a longer
time span. BGPsec is a new protocol with many operational
considerations which this document attempts to describe. As with
most operational practices, this document will likely evolve.
BGPsec relies on widespread propagation of the RPKI [RFC6480]. How
the RPKI is distributed and maintained globally and within an
operator's infrastructure may be different for BGPsec than for origin
validation.
BGPsec needs to be spoken only by an AS's eBGP-speaking border
routers. It is designed so that it can be used to protect
announcements which are originated by resource constrained edge
routers. This has special operational considerations, see Section 6.
Different prefixes may have different timing and replay protection
considerations.
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2. Suggested Reading
It is assumed that the reader understands BGP, see [RFC4271], BGPsec,
[I-D.ietf-sidr-bgpsec-protocol], the RPKI, see [RFC6480], the RPKI
Repository Structure, see [RFC6481], and Route Origin Authorizations
(ROAs), see [RFC6482].
3. RPKI Distribution and Maintenance
The considerations for RPKI objects (Certificates, Certificate
Revocation Lists (CRLs), manifests, Ghostbusters Records [RFC6481]),
Trust Anchor Locators (TALs) [RFC7730], cache behaviours of
synchronisation and validation from the section on RPKI Distribution
and Maintenance of [RFC7115] apply. Specific considerations relating
to ROA objects do not apply to this document.
4. AS/Router Certificates
As described in [I-D.ietf-sidr-rtr-keying] BGPsec-speaking routers
are capable of generating their own public/private key-pairs and
having their certificates signed and published in the RPKI by the
RPKI CA system, and/or are given public/private key-pairs by the
operator.
A site/operator may use a single certificate/key in all their
routers, one certificate/key per router, or any granularity in
between.
A large operator, concerned that a compromise of one router's key
would make other routers vulnerable, may deploy a more complex
certificate/key distribution burden to reduce this exposure.
At the other end of the spectrum, an edge site with one or two
routers may choose to use a single certificate/key.
In anticipation of possible key compromise, a prudent operator SHOULD
pre-provision each router's 'next' key in the RPKI so there is no
propagation delay for provisioning the new key.
5. Within a Network
BGPsec is spoken by edge routers in a network, those which border
other networks/ASs.
In an AS where edge routers speak BGPsec and therefore inject BGPsec
paths into the iBGP, Route Reflectors MUST have BGPsec enabled if and
only if there are eBGP speakers in their client cone, i.e. an RR
client or the transitive closure of a client's customers.
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A BGPsec capable router MAY use the data it receives to influence
local policy within its network, see Section 7. In deployment this
policy should fit into the AS's existing policy, preferences, etc.
This allows a network to incrementally deploy BGPsec enabled border
routers.
eBGP speakers which face more critical peers or up/downstreams would
be candidates for early deployment. Both securing one's own
announcements and validating received announcements should be
considered in partial deployment.
An operator should be aware that BGPsec, as any other policy change,
can cause traffic shifts in their network. And, as with normal
policy shift practice, a prudent operator has tools and methods to
predict, measure, modify, etc.
On the other hand, an operator wanting to monitor router loading,
shifts in traffic, etc. might deploy incrementally while watching
those and similar effects.
BGPsec does not sign over communities, so they are not formally
trustable. Additionally, outsourcing verification is not prudent
security practice. Therefore an eBGP listener SHOULD NOT strongly
trust unsigned security signaling, such as communities, received
across a trust boundary.
6. Considerations for Edge Sites
An edge site which does not provide transit and trusts its
upstream(s) may only originate a signed prefix announcement and not
validate received announcements.
An Operator might need to use hardware with limited resources. In
such cases, BGPsec protocol capability negotiation allows for a
resource constrained edge router to hold only its own signing key(s)
and sign its announcements, but not receive signed announcements.
Therefore, the router would not have to deal with the majority of the
RPKI, potentially saving the need for additional hardware.
As the vast majority of ASs are stubs, and they announce the majority
of prefixes, this allows for simpler and less expensive incremental
deployment. It may also mean that edge sites concerned with routing
security will be attracted to upstreams which support BGPsec.
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7. Routing Policy
Unlike origin validation based on the RPKI, BGPsec marks a received
announcement as Valid or Not Valid, there is no explicit NotFound
state. In some sense, an unsigned BGP4 path is the equivalent of
NotFound. How this is used in routing is up to the operator's local
policy, similar to origin validation as in [RFC6811].
As BGPsec will be rolled out over years and does not allow for
intermediate non-signing edge routers, coverage will be spotty for a
long time. This presents a dilemma; should a router evaluating an
inbound BGPsec_Path as Not Valid be very strict and discard it? On
the other hand, it might be the only path to that prefix, and a very
low local-preference would cause it to be used and propagated only if
there was no alternative. Either choice is reasonable, but we
recommend dropping because of the next point.
Operators should be aware that accepting Not Valid announcements, no
matter the local preference, will often be the equivalent of treating
them as fully Valid. Local preference affects only routes to the
same set of destinations. Consider having a Valid announcement from
neighbor V for prefix 10.0.0.0/16 and an Not Valid announcement for
10.0.666.0/24 from neighbor I. If local policy on the router is not
configured to discard the Not Valid announcement from I, then longest
match forwarding will send packets to neighbor I no matter the value
of local preference.
Validation of signed paths is usually deployed at the eBGP edge.
Local policy on the eBGP edge MAY convey the validation state of a
BGP signed path through normal local policy mechanisms, e.g. setting
a BGP community for internal use, or modifying a metric value such as
local-preference or multi-exit discriminator (MED). Some may choose
to use the large Local-Pref hammer. Others may choose to let AS-Path
rule and set their internal metric, which comes after AS-Path in the
BGP decision process.
As the mildly stochastic timing of RPKI propagation may cause version
skew across routers, an AS Path which does not validate at router R0
might validate at R1. Therefore, signed paths that are Not Valid and
yet propagated (because they are chosen as best path) MUST NOT have
signatures stripped and MUST be signed if sent to external BGPsec
speakers.
This implies that updates which a speaker judges to be Not Valid MAY
be propagated to iBGP peers. Therefore, unless local policy ensures
otherwise, a signed path learned via iBGP may be Not Valid. If
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needed, the validation state should be signaled by normal local
policy mechanisms such as communities or metrics.
On the other hand, local policy on the eBGP edge might preclude iBGP
or eBGP announcement of signed AS Paths which are Not Valid.
A BGPsec speaker receiving a path SHOULD perform origin validation
per [RFC6811] and [RFC7115].
A route server is usually 'transparent', i.e. does not insert an AS
into the path so as not to increase the AS hop count and thereby
affect downstream path choices. But, with BGPsec, a client router R
needs to be able to validate paths which are forward signed to R.
But the sending router can not generate signatures to all the
possible clients. Therefore a BGPsec-aware route server needs to
validate the incoming BGPsec_Path, and to forward updates which can
be validated by clients which must therefore know the route server's
AS. This implies that the route server creates signatures per client
including its own AS in the BGPsec_Path, forward signing to each
client AS, see [I-D.ietf-sidr-bgpsec-protocol]. The route server
uses pCount of zero to not increase the effective AS hop count,
thereby retaining the intent of 'transparency'.
If it is known that a BGPsec neighbor is not a transparent route
server, or is otherwise validly using pCount=0 (e,g, see
[I-D.ietf-sidr-as-migration]), and the router provides a knob to
disallow a received pCount (of zero, that knob SHOULD be applied.
Routers should disallow pCount 0 by default.
To prevent exposure of the internals of BGP Confederations [RFC5065],
a BGPsec speaker exporting to a non-member removes all intra-
confederation Secure_Path segments. Therefore signing within the
confederation will not cause external confusion even if non-unique
private ASs are used.
8. Notes
For protection from attacks replaying BGP data on the order of a day
or longer old, re-keying routers with new keys (previously)
provisioned in the RPKI is sufficient. For one approach, see
[I-D.ietf-sidr-bgpsec-rollover]
A router that once negotiated (and/or sent) BGPsec should not be
expected to always do so.
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 or router
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than another cache or router. There is no 'fix' for this, it is the
nature of distributed data with distributed caches.
Operators who manage certificates SHOULD have RPKI GhostBuster
Records (see [RFC6493]), signed indirectly by End Entity
certificates, for those certificates on which others' routing depends
for certificate and/or ROA validation.
Operators should be aware of impending algorithm transitions, which
will be rare and slow-paced, see [RFC6916]. They should work with
their vendors to ensure support for new algorithms.
As a router must evaluate certificates and ROAs which are time
dependent, routers' clocks MUST be correct to a tolerance of
approximately an hour. The common approach is for operators to
deploy servers that provide time service, such as [RFC5905], to
client routers.
If a router has reason to believe its clock is seriously incorrect,
e.g. it has a time earlier than 2011, it SHOULD NOT attempt to
validate incoming updates. It SHOULD defer validation until it
believes it is within reasonable time tolerance.
9. Security Considerations
This document describes operational considerations for the deployment
of BGPsec. The security considerations for BGPsec are described in
[I-D.ietf-sidr-bgpsec-protocol].
10. IANA Considerations
This document has no IANA Considerations.
11. Acknowledgments
The author wishes to thank Thomas King, Arnold Nipper, and Alvaro
Retana, and the BGPsec design group.
12. References
12.1. Normative References
[I-D.ietf-sidr-bgpsec-protocol]
Lepinski, M., "BGPSEC Protocol Specification", draft-ietf-
sidr-bgpsec-protocol-07 (work in progress), February 2013.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC6493] Bush, R., "The Resource Public Key Infrastructure (RPKI)
Ghostbusters Record", RFC 6493, February 2012.
[RFC6811] Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R.
Austein, "BGP Prefix Origin Validation", RFC 6811, January
2013.
[RFC7115] Bush, R., "Origin Validation Operation Based on the
Resource Public Key Infrastructure (RPKI)", BCP 185,
RFC 7115, DOI 10.17487/RFC7115, January 2014,
<http://www.rfc-editor.org/info/rfc7115>.
[RFC7730] Huston, G., Weiler, S., Michaelson, G., and S. Kent,
"Resource Public Key Infrastructure (RPKI) Trust Anchor
Locator", RFC 7730, DOI 10.17487/RFC7730, January 2016,
<http://www.rfc-editor.org/info/rfc7730>.
12.2. Informative References
[I-D.ietf-sidr-as-migration]
George, W. and S. Murphy, "BGPSec Considerations for AS
Migration", draft-ietf-sidr-as-migration-06 (work in
progress), December 2016.
[I-D.ietf-sidr-bgpsec-rollover]
Gagliano, R., Patel, K., and B. Weis, "BGPSEC router key
rollover as an alternative to beaconing", draft-ietf-sidr-
bgpsec-rollover-01 (work in progress), October 2012.
[I-D.ietf-sidr-rtr-keying]
Turner, S., Patel, K., and R. Bush, "Router Keying for
BGPsec", draft-ietf-sidr-rtr-keying-01 (work in progress),
February 2013.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous
System Confederations for BGP", RFC 5065, August 2007.
[RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, June 2010.
[RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support
Secure Internet Routing", RFC 6480, February 2012.
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[RFC6481] Huston, G., Loomans, R., and G. Michaelson, "A Profile for
Resource Certificate Repository Structure", RFC 6481,
February 2012.
[RFC6482] Lepinski, M., Kent, S., and D. Kong, "A Profile for Route
Origin Authorizations (ROAs)", RFC 6482, February 2012.
[RFC6916] Gagliano, R., Kent, S., and S. Turner, "Algorithm Agility
Procedure for the Resource Public Key Infrastructure
(RPKI)", BCP 182, RFC 6916, DOI 10.17487/RFC6916, April
2013, <http://www.rfc-editor.org/info/rfc6916>.
Author's Address
Randy Bush
Internet Initiative Japan
5147 Crystal Springs
Bainbridge Island, Washington 98110
US
Email: randy@psg.com
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