Global Routing Operations K. Sriram
Internet-Draft D. Montgomery
Intended status: Informational US NIST
Expires: September 10, 2015 D. McPherson
E. Osterweil
Verisign, Inc.
March 9, 2015
Problem Definition and Classification of BGP Route Leaks
draft-ietf-grow-route-leak-problem-definition-01
Abstract
A systemic vulnerability of the Border Gateway Protocol routing
system, known as 'route leaks', has received significant attention in
recent years. Frequent incidents that result in significant
disruptions to Internet routing are labeled "route leaks", but to
date we have lacked a common definition of the term. In this
document, we provide a working definition of route leaks, keeping in
mind the real occurrences that have received significant attention.
Further, we attempt to enumerate (though not exhaustively) different
types of route leaks based on observed events on the Internet. We
aim to provide a taxonomy that covers several forms of route leaks
that have been observed and are of concern to Internet user community
as well as the network operator community.
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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This Internet-Draft will expire on September 10, 2015.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Working Definition of Route Leaks . . . . . . . . . . . . . . 3
3. Classification of Route Leaks Based on Documented Events . . 3
4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
8. Informative References . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Frequent incidents [Huston2012][Cowie2013][Cowie2010][Madory][Zmijews
ki][Paseka][LRL][Khare] that result in significant disruptions to
Internet routing are commonly called "route leaks". Examination of
the details of some of these incidents reveals that they vary in
their form and technical details. Before we can discuss solutions to
"the route leak problem" we need a clear, technical definition of the
problem and its most common forms. In Section 2, we provide a
working definition of route leaks, keeping in view many recent
incidents that have received significant attention. Further, in
Section 3, we attempt to enumerate (though not exhaustively)
different types of route leaks based on observed events on the
Internet. We aim to provide a taxonomy that covers several forms of
route leaks that have been observed and are of concern to Internet
user community as well as the network operator community.
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2. Working Definition of Route Leaks
A proposed working definition of route leak is as follows:
A "route leak" is the propagation of routing announcement(s) beyond
their intended scope. That is, an AS's announcement of a learned BGP
route to another AS is in violation of the intended policies of the
receiver, the sender and/or one of the ASes along the preceding AS
path. The intended scope is usually defined by a set of local
redistribution/filtering policies distributed among the ASes
involved. Often, these intended policies are defined in terms of the
pair-wise peering business relationship between ASes (e.g., customer,
provider, peer). For literature related to AS relationships and
routing policies, see [Gao][Gill][Luckie]. For measurements of
valley-free violations in Internet routing, see [Giotsas][Wijchers].
The result of a route leak can be redirection of traffic through an
unintended path which may enable eavesdropping or traffic analysis,
and may or may not result in an overload or black-hole. Route leaks
can be accidental or malicious, but most often arise from accidental
misconfigurations.
The above definition is not intended to be all encompassing.
Perceptions vary widely about what constitutes a route leak. Our aim
here is to have a working definition that fits enough observed
incidents so that the IETF community has a basis for starting to work
on route leak mitigation methods.
3. Classification of Route Leaks Based on Documented Events
As illustrated in Figure 1, a common form of route leak occurs when a
multi-homed customer AS (such as AS1 in Figure 1) learns a prefix
update from one provider (ISP1) and leaks the update to another
provider (ISP2) in violation of intended routing policies, and
further the second provider does not detect the leak and propagates
the leaked update to its customers, peers, and transit ISPs.
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/\ /\
\ route-leak(P)/
\ propagated /
\ /
+------------+ peer +------------+
______| ISP1 (AS2) |----------->| ISP2 (AS3)|---------->
/ ------------+ prefix(P) +------------+ route-leak(P)
| prefix | \ update /\ \ propagated
\ (P) / \ / \
------- prefix(P) \ / \
update \ / \
\ /route-leak(P) \/
\/ /
+---------------+
| customer(AS1) |
+---------------+
Figure 1: Illustration of the basic notion of a route leak.
We propose the following taxonomy for classification of route leaks
aiming to cover several types of recently observed route leaks, while
acknowledging that the list is not meant to be exhaustive. In what
follows, we refer to the AS that announces a route that is in
violation of the intended policies as the "offending AS".
o Type 1 "U-Turn with Full Prefix": A multi-homed AS learns a prefix
route from one upstream ISP and simply propagates the prefix to
another upstream ISP. Neither the prefix nor the AS path in the
update is altered. This is similar to a straight forward path-
poisoning attack [Kapela-Pilosov], but with full prefix. It
should be noted that attacks or leaks of this type are often
accidental (i.e. not malicious). The update basically makes a
U-turn at the attacker's multi-homed AS. The attack (accidental
or deliberate) often succeeds because the second ISP prefers
customer announcement over peer announcement of the same prefix.
Data packets would reach the legitimate destination albeit via the
offending AS, unless they are dropped at the offending AS due to
its inability to handle resulting large volumes of traffic.
* Example incidents: Examples of Type 1 route-leak incidents are
(1) the Dodo-Telstra incident in March 2012 [Huston2012], (2)
the Moratel-PCCW leak of Google prefixes in November 2012
[Paseka], and (3) the VolumeDrive-Atrato incident in September
2014 [Madory].
o Type 2 "U-Turn with More Specific Prefix": A multi-homed AS learns
a prefix route from one upstream ISP and announces a sub-prefix
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(subsumed in the prefix) to another upstream ISP. The AS path in
the update is not altered. Update is crafted by the attacker to
have a subprefix to maximize the success of the attack while
reverse path is kept open by the path poisoning techniques as in
[Kapela-Pilosov]. Data packets reach the legitimate destination
albeit via the offending AS.
* Example incidents: An example of Type 2 route-leak incident is
the demo performed at DEFCON-16 in August 2008
[Kapela-Pilosov]. An attacker who deliberately performs a Type
1 route leak (with full prefix) can just as easily perform a
Type 2 route leak (with subprefix) to achieve a greater impact.
o Type 3 "Prefix Hijack with Data Path to Legitimate Origin": A
multi-homed AS learns a prefix route from one upstream ISP and
announces the prefix to another upstream ISP as if it is being
originated by it (i.e. strips the received AS path, and re-
originates the prefix). This amounts to straightforward
hijacking. However, somehow (not attributable to the use of path
poisoning trick by the attacker) a reverse path is present, and
data packets reach the legitimate destination albeit via the
offending AS. But sometimes the reverse path may not be there,
and data packets get dropped following receipt by the offending
AS.
* Example incidents: Examples of Type 3 route leak include (1)
the China Telecom incident in April 2010
[Hiran][Cowie2010][Labovitz], (2) the Belarusian GlobalOneBel
route leak incidents in February-March 2013 and May 2013
[Cowie2013], (3) the Icelandic Opin Kerfi-Simmin route leak
incidents in July-August 2013 [Cowie2013], and (4) the Indosat
route leak incident in April 2014 [Zmijewski].
o Type 4 "Leak of Internal Prefixes and Accidental Deaggregation":
An offending AS simply leaks its internal prefixes to one or more
of its transit ASes and/or ISP peers. The leaked internal
prefixes are often deaggregated subprefixes (i.e. more specifics)
of already announced aggregate prefixes. Further, the AS
receiving those leaks fails to filter them. Typically these
leaked announcements are due to some transient failures within the
AS; they are short-lived, and typically withdrawn quickly
following the announcements.
* Example incidents: Leaks of internal prefix-routes occur
frequently (e.g. multiple times in a week), and the number of
prefixes leaked range from hundreds to thousands per incident.
One highly conspicuous and widely disruptive leak of internal
prefixes happened recently in August 2014 when AS701 and AS705
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leaked about 22,000 more specifics of already announced
aggregates [Huston2014][Toonk].
o Type 5 "Lateral ISP-ISP-ISP Leak": This type of route leak
typically occurs when, for example, three sequential ISP peers
(e.g. ISP-A, ISP-B and ISP-C) are involved, and ISP-B receives a
prefix-route from ISP-A and in turn leaks it to ISP-C. The
typical routing policy between laterally (i.e. non-hierarchically)
peering ISPs is that they should only propagate to each other
their respective customer prefixes.
* Example incidents: In [Mauch-nanog][Mauch], route leaks of this
type are reported by monitoring updates in the global BGP
system and finding three or more very large ISP ASNs in a
sequence in a BGP update's AS path. Mauch [Mauch] observes
that these are anomalies and potentially route leaks because
very large ISPs such as ATT, Sprint, Verizon, and
Globalcrossing do not in general buy transit services from each
other. However, he also notes that there are exceptions when
one very large ISP does indeed buy transit from another very
large ISP, and accordingly exceptions are made in his detection
algorithm for known cases.
o Type 6 "Leak of Provider Prefixes to Peer": This type of route
leak occurs when an offending AS leaks prefix-routes learned from
its provider to a lateral peer.
* Example incidents: The incidents reported in [Mauch] include
the Type 6 leaks.
o Type 7 "Leak of Peer Prefixes to Provider": This type of route
leak occurs when an offending AS leaks prefix-routes learned from
a lateral peer to its (the AS's) own provider. These leaked
prefix-routes typically originate from the customer cone of the
lateral peer.
* Example incidents: Some of the example incidents cited for Type
1 route leaks above are also inclusive of Type 7 route leaks.
For instance, in the Dodo-Telstra incident [Huston2012], the
leaked routes from Dodo to Telstra included routes that Dodo
learned from its providers as well as lateral peers.
4. Summary
We attempted to provide a working definition of route leak. We also
presented a taxonomy for categorizing route leaks. It covers not all
but at least several forms of route leaks that have been observed and
are of concern to Internet user and network operator communities. We
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hope that this work provides the IETF community a basis for pursuing
possible BGP enhancements for route leak detection and mitigation.
5. Security Considerations
No security considerations apply since this is a problem definition
document.
6. IANA Considerations
No updates to the registries are suggested by this document.
7. Acknowledgements
The authors wish to thank Danny McPherson and Eric Osterweil for
discussions related to this work. Also, thanks are due to Jared
Mauch, Jeff Haas, Warren Kumari, Brian Dickson, Amogh Dhamdhere,
Jakob Heitz, Geoff Huston, Randy Bush, Ruediger Volk, Andrei
Robachevsky, Chris Morrow, and Sandy Murphy for comments,
suggestions, and critique. The authors are also thankful to Padma
Krishnaswamy, Oliver Borchert, and Okhee Kim for their comments and
review.
8. Informative References
[Cowie2010]
Cowie, J., "China's 18 Minute Mystery", Dyn Research/
Renesys Blog, November 2010,
<http://research.dyn.com/2010/11/
chinas-18-minute-mystery/>.
[Cowie2013]
Cowie, J., "The New Threat: Targeted Internet Traffic
Misdirection", Dyn Research/Renesys Blog, November 2013,
<http://research.dyn.com/2013/11/
mitm-internet-hijacking/>.
[Gao] Gao, L. and J. Rexford, "Stable Internet routing without
global coordination", IEEE/ACM Transactions on Networking,
December 2001, <http://www.cs.princeton.edu/~jrex/papers/
sigmetrics00.long.pdf>.
[Gill] Gill, P., Schapira, M., and S. Goldberg, "A Survey of
Interdomain Routing Policies", ACM SIGCOMM Computer
Communication Review, January 2014,
<https://www.cs.bu.edu/~goldbe/papers/survey.pdf>.
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[Giotsas] Giotsas, V. and S. Zhou, "Valley-free violation in
Internet routing - Analysis based on BGP Community data",
IEEE ICC 2012, June 2012,
<http://www0.cs.ucl.ac.uk/staff/V.Giotsas/files/
giotsas.icc.2012.pdf>.
[Hiran] Hiran, R., Carlsson, N., and P. Gill, "Characterizing
Large-scale Routing Anomalies: A Case Study of the China
Telecom Incident", PAM 2013, March 2013,
<http://www3.cs.stonybrook.edu/~phillipa/papers/
CTelecom.html>.
[Huston2012]
Huston, G., "Leaking Routes", March 2012,
<http://labs.apnic.net/blabs/?p=139/>.
[Huston2014]
Huston, G., "What's so special about 512?", September
2014, <http://labs.apnic.net/blabs/?p=520/>.
[Kapela-Pilosov]
Pilosov, A. and T. Kapela, "Stealing the Internet: An
Internet-Scale Man in the Middle Attack", DEFCON-16 Las
Vegas, NV, USA, August 2008,
<https://www.defcon.org/images/defcon-16/dc16-
presentations/defcon-16-pilosov-kapela.pdf/>.
[Khare] Khare, V., Ju, Q., and B. Zhang, "Concurrent Prefix
Hijacks: Occurrence and Impacts", IMC 2012, Boston, MA,
November 2012, <http://www.cs.arizona.edu/~bzhang/
paper/12-imc-hijack.pdf/>.
[LRL] Khare, V., Ju, Q., and B. Zhang, "Large Route Leaks",
Project web page, 2012,
<http://nrl.cs.arizona.edu/projects/
lsrl-events-from-2003-to-2009/>.
[Labovitz]
Labovitz, C., "Additional Discussion of the April China
BGP Hijack Inciden", Arbor Networks IT Security Blog,
November 2010,
<http://www.arbornetworks.com/asert/2010/11/additional-
discussion-of-the-april-china-bgp-hijack-incident/>.
[Luckie] Luckie, M., Huffaker, B., Dhamdhere, A., Giotsas, V., and
kc. claffy, "AS Relationships, Customer Cones, and
Validation", IMC 2013, October 2013,
<http://www.caida.org/~amogh/papers/asrank-IMC13.pdf>.
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[Madory] Madory, D., "Why Far-Flung Parts of the Internet Broke
Today", Dyn Research/Renesys Blog, September 2014,
<http://research.dyn.com/2014/09/
why-the-internet-broke-today/>.
[Mauch] Mauch, J., "BGP Routing Leak Detection System", Project
web page, 2014,
<http://puck.nether.net/bgp/leakinfo.cgi/>.
[Mauch-nanog]
Mauch, J., "Detecting Routing Leaks by Counting", NANOG-41
Albuquerque, NM, USA, October 2007,
<https://www.nanog.org/meetings/nanog41/presentations/
mauch-lightning.pdf/>.
[Paseka] Paseka, T., "Why Google Went Offline Today and a Bit about
How the Internet Works", CloudFare Blog, November 2012,
<http://blog.cloudflare.com/
why-google-went-offline-today-and-a-bit-about/>.
[Toonk] Toonk, A., "What Caused Today's Internet Hiccup", August
2014, <http://www.bgpmon.net/
what-caused-todays-internet-hiccup/>.
[Wijchers]
Wijchers, B. and B. Overeinder, "Quantitative Analysis of
BGP Route Leaks", RIPE-69, November 2014,
<https://ripe69.ripe.net/presentations/157-RIPE-69-
Routing-WG.pdf>.
[Zmijewski]
Zmijewski, E., "Indonesia Hijacks the World", Dyn
Research/Renesys Blog, April 2014,
<http://research.dyn.com/2014/04/
indonesia-hijacks-world/>.
Authors' Addresses
Kotikalapudi Sriram
US NIST
Email: ksriram@nist.gov
Doug Montgomery
US NIST
Email: dougm@nist.gov
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Danny McPherson
Verisign, Inc.
Email: dmcpherson@verisign.com
Eric Osterweil
Verisign, Inc.
Email: eosterweil@verisign.com
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