Internet Engineering Task Force Yang, Ed.
Internet-Draft Shi
Intended status: Informational Xiang
Expires: August 20, 2017 Wang
Wu
Yin
Tsinghua Univ.
February 16, 2017
Fast route attestation on AS Path Segment
draft-yang-sidr-fra-02
Abstract
This draft proposes Fast Route Attestation (FRA), an efficient
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 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.
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 August 20, 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
(http://trustee.ietf.org/license-info) in effect on the date of
Yang, et al. Expires August 20, 2017 [Page 1]
Internet-Draft FRA February 2017
publication of this document. 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 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 . . . . . . . . . . . . . . . . . . . . . . . . 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 period . . . . . . . 8
4.4. Contents of FRA Certificates . . . . . . . . . . . . . . 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 and correctness in
advance. Cryptographic approaches, which are being pursued by the
SIDR WG, use the Public Key Infrastructure (PKI) to authenticate
routing announcements. There are a bunch of solutions including
S-BGP [S-BGP], BGPSec [RFC7353] and many others. 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
Yang, et al. Expires August 20, 2017 [Page 2]
Internet-Draft FRA February 2017
[TR-FSBGP]. Analysis, evaluations, and more discussions of FRA can
be found in the recent technical report [TR-FSBGP].
2. Terminology
(i): AS i
<n, ..., 0>: AS path from AS n to the origin AS 0
<n, ..., 0>f: AS path of prefix f originated from AS 0
<i+1, i, i-1>: critical AS path segment, adjacent AS triple in a path
<1, 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 can 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, a 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 <i+1, i, ..., 0> and the prefix f.
The inclusion of the recipient AS i+1 in each signature is necessary
to prevent cut-and-paste attack.
Yang, et al. Expires August 20, 2017 [Page 3]
Internet-Draft FRA February 2017
+-------------------------------------------------------------+
| (n+1) <-- (n) <-- ... <-- (i) <-- ... <-- (1) <-- (0) |
| s_0 s_0 s_0 s_0 |
| s_1 s_1 s_1 \\ |
| . . \\ {1, 0, f}0 |
| . . {2, 1, s_0}1 |
| . . \\ |
| s_i s_i {2, 1, 0, f}1 |
| . \\ |
| . {i+1, i, s_i-1}i |
| . \\ |
| s_n {i+1, i, i-1, ..., 1, 0, f}i |
| \\ |
| {n+1, n, s_n-1}n |
| \\ |
| {n+1, n, n-1, ..., 1, 0, f}n |
+-------------------------------------------------------------+
Figure 1: RA in BGPSec.
The main concern about deploying BGPSec in practice is the huge
computational cost for signing and verifying signatures. The
dominating barrier for adopting them is the overhead of processing
RAs, that is to authenticate paths. Toward this direction, 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 one
signing is needed for multiple recipients. 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
Yang, et al. Expires August 20, 2017 [Page 4]
Internet-Draft FRA February 2017
seriously. Many ISPs insist that unless majority of ASes deploys
BGPSec, they would not benefit much from deploying BGPSec.
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 path are
authenticated, attackers can only attract little traffic by forging
other part 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 interdomain routing
security before BGPSec is fully deployed.
Though Path-End Validation provides a way to improve interdomain
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 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, FRA, builds on the assumption that
RPKI has been used for origin authentication, focusing 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
(<n-2, ..., 1, 0>). We call this the Neighbor Based Importing and
Exporting (NBIE).
Yang, et al. Expires August 20, 2017 [Page 5]
Internet-Draft FRA February 2017
+----------------------------------------------------------+
| / ... (x_0) ... \ |
| / . \ |
| (n+1) <-- (n) <-- (n-1) <-- ... . ... <-- (0) |
| \ . / |
| \ ... (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 the 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), more
ASes will not need these filters. In deed, our schema can also
flexibly support complicated routing polices [TR-FSBGP].
4.2. Signing Critical AS Path Segments efficiently
Following our key observation above, we propose Fast Route
Attestation (FRA) to guarantee the authenticate AS paths. Given a
path p=<n+1, n, ..., 0>, we define its set of critical path segments
as c_i, 0<i<=n, where
/ <1,0,f> , for i=0
c_i =
\ <i+1,i,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 <i+1, i, 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
Yang, et al. Expires August 20, 2017 [Page 6]
Internet-Draft FRA February 2017
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 <n+1, n, 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 using FRA mechanism, the
AS just signs critical path segment one time.
+------------------------------------------------------------+
| (n+1) <-- (n) <-- ... <-- (i) <-- ... <-- (1) <-- (0) |
| s_0 s_0 s_0 s_0 |
| s_1 s_1 s_1 \\ |
| . . \\ {1,0,f}0 |
| . . {2,1,0}1 |
| . . |
| s_i s_i |
| . \\ |
| . {i+1,i,i-1}i |
| . |
| s_n |
| \\ |
| {n+1,n,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, <n, n-1, ..., 0> is secure
in BGPSec. That is to say, ASes along the path all deploy BGPSec,
signing and verifying the path. If they use 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 path. Because the CSA s_i (i.e.
{i+1,i,i-1}i) means i+1 is the true next-hop, the forged update will
be dropped.
Yang, et al. Expires August 20, 2017 [Page 7]
Internet-Draft FRA February 2017
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 use FRA
mechanism, the path must be authenticated. Considering its
efficiency we discussed above, FRA can achieve similar level of
security as S-BGP/BGPSec with less time cost.
4.3. More benefits in partial-deployment period
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 it, this route
is a secure route. However, if there is any AS which still runs
legacy BGP, the route is regarded as an insecure one.
But under FRA mechanism, it 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
<n, ..., 0> is a path of prefix f. If an attacker a intends to forge
a path <n, ..., i+1, a, i-1, ..., 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 <a, i-1, 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 users. 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. When majority still runs legacy BGP,
FRA guarantees users better security than BGPSec. Besides, because
FRA authenticates the whole path of BGP updates, it can provide a
similar security benefit as BGPSec.
4.4. Contents of FRA Certificates
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.
Yang, et al. Expires August 20, 2017 [Page 8]
Internet-Draft FRA February 2017
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, the certificates also
include the private keys of ASes. ASes' public keys 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 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 when partially-
deployed. 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.
Yang, et al. Expires August 20, 2017 [Page 9]
Internet-Draft FRA February 2017
[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.
Yang, et al. Expires August 20, 2017 [Page 10]
Internet-Draft FRA February 2017
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
Yang, et al. Expires August 20, 2017 [Page 11]
Internet-Draft FRA February 2017
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
Yang, et al. Expires August 20, 2017 [Page 12]