Internet DRAFT - draft-yang-sidr-fra
draft-yang-sidr-fra
Internet Engineering Task Force Yang, Ed.
Internet-Draft Shi
Intended status: Informational Xiang
Expires: September 12, 2017 Wang
Wu
Yin
Tsinghua Univ.
March 11, 2017
Fast route attestation on AS Path Segment
draft-yang-sidr-fra-04
Abstract
This draft proposes Fast Route Attestation (FRA), a mechanism for
securing AS paths and preventing prefix hijacking by signing and
verifying critical AS path segments (i.e., adjacent AS triples along
AS path). When full-deployed, FRA can achieve similar level of
security as BGPSec, but with much higher efficiency. When partial-
deployed, FRA offers more security benefits than BGPSec.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Background . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. FRA: Fast Route Attestation . . . . . . . . . . . . . . . . . 5
4.1. Neighbor Based Importing and Exporting . . . . . . . . . 5
4.2. Signing Critical AS Path Segments efficiently . . . . . . 6
4.3. More benefits in partial-deployment scenario . . . . . . 8
4.4. Other supports to FRA . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
In order to secure inter-domain routing, several extensions of BGP
have been proposed, which fall into two categories: anomaly detection
and cryptographic based authentication. However, anomaly detection
approaches [Whisper] [PGBGP] only detect and report routing
anomalies. They can not guarantee security in advance.
Cryptographic approaches, like S-BGP [S-BGP] and BGPSec [RFC7353],
use the Public Key Infrastructure (PKI) to authenticate routing
announcements. However, they may consume significant resources of
computation and storage. The other solutions either compromise in
the security [IRV] [I-D.ng-sobgp-bgp-extensions] [psBGP] [SPV], or
bring in more complexity on certification distribution [SA].
Towards these unsolved issues, we propose an efficient approach, FRA
(Fast Route Attestation), to secure AS path. Through signing and
verifying critical AS path segments (i.e., adjacent AS triples along
AS path), FRA can achieve similar level of security as S-BGP/BGPSec,
but with much higher efficiency. Besides, when partial-deployed, FRA
offers more security benefits than BGPSec, promoting ISPs to deploy
the security mechanism. It is the critical part of FS-BGP.
Analysis, evaluations, and more discussions of FRA can be found in
the recent technical report [TR-FSBGP].
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2. Terminology
(AS_i): AS i
<AS_n, ..., AS_0>: AS path from AS n to the origin AS 0
<AS_n, ..., AS_0>f: AS path of prefix f originated from AS 0
<AS_i+1, AS_i, AS_i-1>: critical AS path segment, adjacent AS triple
in a path
<AS_1, AS_0, f>: origin critical AS path segment in a path of prefix
f
{msg}i: signature on msg generated by AS i
3. Background
In BGP, UPDATE messages will not be validated, so neither the origin
AS nor the AS path is guaranteed to be correct. Secure BGP (S-BGP)
[S-BGP] is the dominant solution to this problem, and it is based on
RPKI [RFC6480] to help authenticating involved parties and messages.
Specifically, S-BGP uses Route Attestations (RAs) for path
authentication. On the basis of S-BGP, BGPSec [RFC7353] was proposed
to secure inter-domain routing, which has been standardized by IETF.
As shown in Figure 1, an RA is all signatures signed by ASes along
the path to authenticate the existence and position of ASes in the
path. We define {msg}i as the signature on msg generated with AS i's
private key. In Figure 1, each AS i equivalently signs the
corresponding extended AS path <AS_i+1, AS_i, ..., AS_0> and the
prefix f. The inclusion of the recipient AS i+1 in each signature is
necessary to prevent cut-and-paste attack.
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+---------------------------------------------------------------------------------+
| (AS_n+1) <-- (AS_n) <-- ... <-- (AS_i) <-- ... <-- (AS_1) <-- (AS_0) |
| s_0 s_0 s_0 s_0 |
| s_1 s_1 s_1 \\ |
| . . \\ {AS_1, AS_0, f}0 |
| . . {AS_2, AS_1, s_0}1 |
| . . \\ |
| s_i s_i {AS_2, AS_1, AS_0, f}1 |
| . \\ |
| . {AS_i+1, AS_i, s_i-1}i |
| . \\ |
| s_n {AS_i+1, AS_i, AS_i-1, ..., AS_1, AS_0, f}i |
| \\ |
| {AS_n+1, AS_n, s_n-1}n |
| \\ |
| {AS_n+1, AS_n, AS_n-1, ..., AS_1, AS_0, f}n |
+---------------------------------------------------------------------------------+
Figure 1: RA in BGPSec.
The main concern about deploying BGPSec in practice is its huge
computational cost for signing and verifying signatures while
authenticating AS path. So there are a bunch of solutions for
reducing the overhead of path authentication.
soBGP [I-D.ng-sobgp-bgp-extensions] maintains all authenticated AS
edges in a database, but faces the problem of forged paths. IRV
[IRV] builds an authentication server in each AS, but brings the
problem of maintaining and inter-connecting these servers, and
introduces query latencies. SPV [SPV] accelerates the signing
process by pre-generated one-time signatures based on a single root
value, but involves a significant amount of state information, and
its security can only be guaranteed probabilistically. Signature
Amortization (S-A) [SA] uses one bit vector for each neighbor of an
AS to indicate the allowed recipients of a route, such that only for
multiple recipients router only needs to sign once. However, each AS
will need to pre-establish a neighbor list corresponding to the bit
vector, and to distribute it to all other ASes.
As we can see, existing methods usually compromise security, and most
of them only improve the performance of signing. However,
verification happens more frequently than signing, since one
signature often needs to be verified at multiple places.
Besides, when BGPSec is partial-deployed, it can only improve limited
security benefits. This influence the deployment of BGPSec
seriously. Many ISPs insist that unless majority of ASes deploys
BGPSec, they would not benefit much from deploying BGPSec.
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To overcome these weeknesses, Path-End Validation [PATH-END] has been
proposed. Since AS paths of BGP updates are usually very short, most
attackers try to forge paths at their first two hops. Path-End
Validation aims to protect the two hops from modification. The
researchers show that if the first two hops of AS paths are
authenticated, attackers can only attract little traffic by forging
other parts of AS path. That is, Path-End Validation provides less
security protection than BGPSec when full-deployed. However,
according to simulation results, ASes can benefit more during the
long partial-deployed period. So Path-End Validation provides a
tangible path to significant improvements in inter-domain routing
security before BGPSec is fully deployed.
Though Path-End Validation provides a way to improve inter-domain
routing security, it has its own shortcoming. When deployed widely,
it cannot reach the security level of BGPSec. Thus we wonder if
there is a method which has higher computational efficiency than
BGPSec with the similar security benefit when full-deployed. In
addition, the method improves security obviously like Path-End
Validation during the long interim period. Our solution, Fast Route
Attestation (FRA), based on the assumption that RPKI has been used
for origin authentication, focuses on path authentication.
Importantly, FRA can satisfy such requirements well.
4. FRA: Fast Route Attestation
4.1. Neighbor Based Importing and Exporting
BGP is a policy-based routing protocol. An AS only exports a route
to a neighbor if it is willing to forward traffic to the
corresponding prefix from that neighbor. Although complex policies
(i.e. , route filters [RFC2622]) exist, AS usually does not
differentiate with prefixes or nonadjacent ASes. For example, in
Figure 2, when AS n decides whether routes learned from AS n-1 can be
exported to AS n+1, it only considers its relation with its two
direct neighbors, but does not consider other ASes along the path
(<AS_n-2, ..., AS_1, AS_0>). We call this the Neighbor Based
Importing and Exporting (NBIE).
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+-----------------------------------------------------------------------+
| / ... (AS_x_0) ... \ |
| / . \ |
| (AS_n+1) <-- (AS_n) <-- (AS_n-1) <-- ... . ... <-- (AS_0) |
| \ . / |
| \ ... (AS_x_k) ... / |
+-----------------------------------------------------------------------+
Figure 2: In BGPSec, AS n signs k paths which share a mutual AS path
segment <n+1, n, n-1>.
NBIE abstracts the basic functionality of BGP. According to our
measurement results in whois database, only a small portion of
routing polices (route filters) violate NBIE assumption.
Nevertheless, the purpose of route filters is to protect the routing
system against distribution of inaccurate routing information
[RFC2622]. In other words, the use of route filters is mainly due to
security considerations rather than policy requirements. We believe
that under a security environment (i.e., FRA/FS-BGP or BGPSec), these
ASes will not need filters any more. In deed, our schema can also
flexibly support complicated routing polices [TR-FSBGP].
4.2. Signing Critical AS Path Segments efficiently
Following NBIE assumption above, we propose Fast Route Attestation
(FRA) to guarantee the authentication of AS paths. Given a path
p=<AS_n+1, AS_n, ..., AS_0>, we define its set of critical path
segments as c_i, 0<i<=n, where
/ <AS_1,AS_0,f> , for i=0
c_i =
\ <AS_i+1,AS_i,AS_i-1> , for 0<i<=n
We call AS i as the owner of c_i. Particularly, c_0 is called the
originating critical path segment owned by AS 0. Under NBIE policy,
a critical path segment <AS_i+1, AS_i, AS_i-1> actually describes an
export policy of AS i, implying that AS i exports all routes imported
from AS i-1 to AS i+1.
More specifically, FRA uses Critical Segment Attestations (CSA) to
authenticate paths. A CSA is simply the signature of the critical
path segment signed by its owner. In a path p=<n+1, n, ..., 0>, the
CSA s_i signed by AS i is defined as:
/ {1,0,f}0 , for i=0
s_i =
\ {i+1,i,i-1}i , for 0<i<=n
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Importantly, the prefixes f in s_0 is necessary, because AS 0 might
be multi-homing and can only announce part of its prefixes to AS 1 to
balance traffic.
Indeed, FRA have much higher efficiency than BGPSec. Figure 3 and
Figure 1 compare the signatures in FRA and BGPSec. Obviously, the
number of distinct critical path segments is far less than the number
of distinct paths. As a result, we can reduce the number of signing
and verifying operations in FRA by using a small cache. In Figure 2,
AS n needs to sign each of the k paths individually in BGPSec.
However, in FRA, all the k different paths can reuse one signature of
the common critical segment <AS_n+1, AS_n, AS_n-1>. Moreover, there
are situations where several distinct prefixes can be reached along
the same AS path. As BGPSec is sensitive to prefix, one AS must sign
several times if it deploys BGPSec. While adopting FRA mechanism,
the AS just signs critical path segment one time.
+---------------------------------------------------------------------------------+
| (AS_n+1) <-- (AS_n) <-- ... <-- (AS_i) <-- ... <-- (AS_1) <-- (AS_0) |
| s_0 s_0 s_0 s_0 |
| s_1 s_1 s_1 \\ |
| . . \\ {AS_1,AS_0,AS_f}0 |
| . . {AS_2,AS_1,AS_0}1 |
| . . |
| s_i s_i |
| . \\ |
| . {AS_i+1,AS_i,AS_i-1}i |
| . |
| s_n |
| \\ |
| {AS_n+1,AS_n,AS_n-1}n |
+---------------------------------------------------------------------------------+
Figure 3: CSAs in FRA.
Then we explain that FRA mechanism can achieve similar level of
security as S-BGP/BGPSec. For every secure path in BGPSec, it is
also authenticated in FRA. For instance, <AS_n, AS_n-1, ..., AS_0>
is secure in BGPSec. That is to say, ASes along the path all deploy
BGPSec, signing and verifying the path. If they adopt FRA, they also
sign its corresponding critical path segment. Since ASes along the
path are fully-deployed, the critical path segments can constitute
the complete path. If some attacker k intends to forge a link
between k and AS i, receivers will verify the CSA. Because the CSA
s_i (i.e. {AS_i+1,AS_i,AS_i-1}i) means i+1 is the true next-hop, the
forged update will be dropped.
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In this section, we argue that under the NBIE rule, if every AS along
a path signs its critical path segment, the path can be
authenticated. So as long as all the ASes along an AS path adopt FRA
mechanism, the path must be authenticated. Considering its
efficiency we discussed above, FRA can achieve similar level of
security as BGPSec with less time cost.
4.3. More benefits in partial-deployment scenario
As BGPSec is likely to coexist with legacy BGP for a long time, we
must consider the effects of them in partial-deployment period. In
general, when not fully deployed, FRA can prevent more attacks than
BGPSec.
In BGPSec, one AS regards a route secure/insecure according to those
ASes along the path. Only if they all have deployed BGPSec, this
route is regarded as a secure route. However, if there is any AS
which still runs legacy BGP, it would be regarded as an insecure one.
But under FRA mechanism, this changes. A route will not be regarded
secure/insecure roughly. Instead, FRA can provide different levels
of protections to authenticate AS path. For instance, suppose that
<AS_n, ..., AS_0> is a path of prefix f. If an attacker a intends to
forge a path <AS_n, ..., AS_i+1, AS_a, AS_i-1, ..., AS_0> but a is
not AS i-1's true neighbor, the forged path may be dropped by FRA
authentication. Specifically, if AS i-1 deploys FRA mechanism, it
should sign a critical path segment <AS_a, AS_i-1, AS_i-2>. Since AS
a is not AS i-1's neighbor, the critical path segment will not appear
in UPDATE messages. Thus, the attacker has to forge the CSA, which
can be detected by FRA adopters. Briefly speaking, even if it is
during partial-deployment period, FRA can provide more benefit than
BGPSec. According to the example aforementioned, the isolated
deployment on AS i-1 can prevent attackers from forging path to it.
However, the same benefit with BGPSec needs the deployment on all
ASes along the true path.
Since full-deployed BGPSec is not a short-term job, FRA makes sense
because of its better benefit in interim period. When majority still
runs legacy BGP, FRA guarantees users better security than BGPSec.
Besides, because FRA authenticates the whole path of BGP updates when
fully deployed, it can provide a similar security benefit as BGPSec.
4.4. Other supports to FRA
FRA uses certificates to handle UPDATE messages. As FRA takes effect
even if some ASes along the path don't deploy it, the certificates of
FRA must involve extra info.
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Based on RPKI [RFC6480], FRA can also validate source address of BGP.
Thus, FRA certificates must include ASNs, prefixes and their maximum
length, which are similar to RPKI's ROAs.
In order to sign critical AS path segments, any AS must be accessible
to public keys of all ASes. They are stored in some public
repositories. Relying parties can download them to their local
caches and validate UPDATEs with FRA.
Besides, ASNs of all the ASes having deployed FRA are also involved
in certificates. When FRA is partial-deployed, ASes can check all
adopters' CSAs along the path. Thus, attackers cannot remove any
CSAs to forge path.
5. IANA Considerations
This document includes no request to IANA.
6. Security Considerations
The entire document is about security consideration. More
theoretical analysis and experiment results can be found in our
technical report [TR-FSBGP].
7. Conclusions
This draft proposes Fast Route Attestation (FRA), an efficient
mechanism for securing AS paths and preventing prefix hijacking by
signing critical AS path segments with cache machenism. FRA can
achieve provide higher security benefits than BGPSec even in very
limited partial adoption. Also, we believe it can achieve higher
level of security than Path-End validation when full-deployed.
8. References
8.1. Normative References
[I-D.ng-sobgp-bgp-extensions]
Ng, J., "Extensions to BGP to Support Secure Origin BGP
(soBGP)", 2004.
[IRV] Goodell, G., Aiello, W., Griffin, T., Ioannidis, J.,
McDaniel, P., and A. Rubin, "Working around BGP: An
Incremental Approach to Improving Security and Accuracy in
Interdomain Routing", 2003.
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[PATH-END]
Cohen, Avichai., Gilad, Yossi., Herzberg, Amir., and
Michael. Schapira, "Jumpstarting BGP Security with Path-
End Validation", 2016.
[psBGP] van Oorschot, P., Wan, T., and E. Kranakis, "On
interdomain routing security and pretty secure BGP
(psBGP)", 2007.
[RFC2622] Alaettinoglu, C., Villamizar, C., Gerich, E., Kessens, D.,
Meyer, D., Bates, T., Karrenberg, D., and M. Terpstra,
"Routing Policy Specification Language (RPSL)", RFC 2622,
DOI 10.17487/RFC2622, June 1999,
<http://www.rfc-editor.org/info/rfc2622>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<http://www.rfc-editor.org/info/rfc4271>.
[RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support
Secure Internet Routing", RFC 6480, DOI 10.17487/RFC6480,
February 2012, <http://www.rfc-editor.org/info/rfc6480>.
[RFC7353] Bellovin, S., Bush, R., and D. Ward, "Security
Requirements for BGP Path Validation", RFC 7353,
DOI 10.17487/RFC7353, August 2014,
<http://www.rfc-editor.org/info/rfc7353>.
[S-BGP] Kent, S., Lynn, C., Mikkelson, J., and K. Seo, "Secure
Border Gateway Protocol (S-BGP)", 2000.
[SA] Nicol, D., Smith, S., and M. Zhao, "Evaluation of
efficient security for BGP route announcements using
parallel simulation", 2004.
[SPV] Hu, Y., Perrig, A., and M. Sirbu, "SPV: secure path vector
routing for securing BGP", 2004.
[TR-FSBGP]
Xiang, Yang., Wang, Zhiliang., Yin, Xia., Shi, Xingang.,
and Jianping. Wu, "FS-BGP: An Efficient Approach to
Securing AS Paths", 2011.
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8.2. Informative References
[PGBGP] Karlin, J., Forrest, S., and J. Rexford, "Pretty Good BGP:
Improving BGP by Cautiously Adopting Routes", 2006.
[Whisper] Subramanian, L., Roth, V., Stoica, I., Shenker, S., and R.
Katz, "Listen and Whisper: Security Mechanisms for BGP",
2004.
Authors' Addresses
Yan Yang (editor)
Tsinghua Univ.
Beijing
CN
Email: yangyan15@mails.tsinghua.edu.cn
Xingang Shi
Tsinghua Univ.
Beijing
CN
Email: shixg@cernet.edu.cn
Yang Xiang
Tsinghua Univ.
Beijing
CN
Email: xiangy08@csnet1.cs.tsinghua.edu.cn
Zhiliang Wang
Tsinghua Univ.
Beijing
CN
Email: wzl@csnet1.cs.tsinghua.edu.cn
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Jianping Wu
Tsinghua Univ.
Beijing
CN
Email: jianping@csnet1.cs.tsinghua.edu.cn
Xia Yin
Tsinghua Univ.
Beijing
CN
Email: yxia@csnet1.cs.tsinghua.edu.cn
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