Secure Inter-Domain Routing X. Lee
Internet-Draft X. Liu
Intended status: Informational Z. Yan
Expires: January 9, 2017 G. Geng
Y. Fu
CNNIC
July 8, 2016
RPKI Deployment Considerations: Problem Analysis and Alternative
Solutions
draft-lee-sidr-rpki-deployment-02
Abstract
With the global deployment of RPKI, a lot of concerns about technical
problems have been and will be raised. In this draft, we collect and
analyze the problems that have appeared or that seem likely to appear
during the process of RPKI deployment, and suggest some solutions to
address or mitigate these problems.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. RPKI Architecture . . . . . . . . . . . . . . . . . . . . 2
1.2. Status of RPKI Deployment . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Considerations of RPKI Deployment . . . . . . . . . . . . . . 4
3.1. More than One TA . . . . . . . . . . . . . . . . . . . . 4
3.2. Problems of CAs . . . . . . . . . . . . . . . . . . . . . 5
3.2.1. Operational Errors . . . . . . . . . . . . . . . . . 5
3.2.2. Unilateral Resource Revocation . . . . . . . . . . . 5
3.3. Mirror World Attacks . . . . . . . . . . . . . . . . . . 5
3.4. Data Synchronization . . . . . . . . . . . . . . . . . . 6
3.5. Problems of Staged and Incomplete Deployment . . . . . . 6
3.6. Low Validation Coverage . . . . . . . . . . . . . . . . . 7
4. Alternative Solutions to RPKI Deployment Problems . . . . . . 8
4.1. Solutions to Multiple TAs . . . . . . . . . . . . . . . . 8
4.2. Solutions to Misbehaving CAs . . . . . . . . . . . . . . 9
4.3. Solutions to Data Synchronization . . . . . . . . . . . . 9
4.4. Solutions to Incomplete Deployment and Low Validation
Coverage . . . . . . . . . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Normative References . . . . . . . . . . . . . . . . . . 10
8.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
1.1. RPKI Architecture
In RPKI, CAs (Certification Authorities) are organized in a
hierarchical structure which is aligned to the existing INR (Internet
Number Resources) allocation hierarchy (including IP prefixes and AS
numbers). Each INR allocation requires corresponding resource
certificates to attest to it, for security. In RPKI, two types of
resource certificates [RFC6480] are generated as adjuncts to this
allocation process: CA certificates and EE (End-entity) certificates.
CA certificates attest to the INR holdings; EE certificates are
primarily used for ROAs (Route Origin Authorizations) [RFC6482] and
Router Certificates. ROAs are used to bind IP prefixes to the ASes
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that is permitted to originate routes for these IP prefixes.
Manifests [RFC6486] are also validated using EE certificates.
Manifests are used to ensure the integrity of the RPKI repository
system.
The process of using the RPKI to verify the origin of a route is as
follows.
1. CAs, including IANA (Internet Assigned Numbers Authority), five
RIRs (Regional Internet Registries), NIRs (National Internet
Registries) and ISPs (Internet Service Providers), publish
authoritative objects (including resource certificates, ROAs,
Manifest and so on) into their repositories.
2. RPs (Relying Parties) all over the world collect (using rsync or
RRDP protocol [I-D.ietf-sidr-delta-protocol]) and verify (using
rcynic or RPSTIR) the RPKI objects from these repositories, and
provide the results of verification to BGP border routers or
other routing practices such as RPSL-based.
3. Finally, BGP border routers can make use of these results to
verify the route origin information in the BGP update messages
they receive. This may be done by generating route filters from
the validated RPKI data, or by using the RPKI-to-router protocol
[RFC6810].
1.2. Status of RPKI Deployment
Each of the five RIRs has initiated the deployment of RPKI, and each
now offers RPKI services to its members. A number of countries
(Ecuador, Japan, Bangladesh, etc.) have also started to test and
deploy RPKI internally. In order to promote the deployment of RPKI,
ICANN (Internet Corporation for Assigned Names and Numbers), the five
RIRs, many NIRs and companies have making continuous efforts to solve
the existing problems and improve the corresponding policies and
technical standards.
However, RPKI is still in its early stages of global deployment.
According to the data provided by RPKI Dashboard as of July 2016, the
current routing table holds about 659,271 IP prefixes in total, and
the RPKI validation state has been determined for 44983 IP prefixes,
which means that only 6.82% of the prefixes in the routing table can
be validated using the RPKI. Table 1 details of the RPKI "adoption
rate" (the percentage of members deployed RPKI) in each of the RIRs.
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+---------------+---------+-------+-------+--------+----------+
| RIR | AFRINIC | APNIC | ARIN | LACNIC | RIPE NCC |
+---------------+---------+-------+-------+--------+----------+
| Adoption Rate | 0% | 3.44% | 1.22% | 20.66% | 12.14% |
+---------------+---------+-------+-------+--------+----------+
Table 1.Adoption rate of RPKI in 5 RIRs
As we can see from Table 1, LACNIC has the highest adoption rate,
which is about 20.66%. While the adoption rates in ARIN and AFRINIC
are much lower, which are only 1.22% and 0% respectively.
RIPE NCC provides some statistics regarding the number of resource
certificates and ROAs in each RIR. From these statistics we find a
good sign that the global deployment status of RPKI rises gradually,
and with its further evolution, the global adoption rate of RPKI
should achieve a faster growth.
2. Terminology
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 [RFC2119].
3. Considerations of RPKI Deployment
During the process of incremental deployment of RPKI, several
technical problems have appeared and others may appear. In this
section, we attempt to collect and analyze the problems that seem
most critical.
3.1. More than One TA
A TA (Trust Anchor) is an authoritative entity represented by a
public key and its associated data [RFC5914]. The public key is used
to verify digital signatures and the associated data describes the
types of information and actions for which the TA is authoritative.
There are multiple TAs in the RPKI architecture today, for example,
the five RIRs are generally viewed as default TAs.
With more than one TA, there is no technical mechanism to prevent two
or more TAs from asserting control over the same set of INRs
accidentally or maliciously, which means that certificates might be
issued for allocations of the overlapping INRs. This, in turn, may
lead to inconsistent and conflicting assertions about to whom the
specific INRs have been allocated. This kind of problem obviously
may cause resource conflicts on the Internet.
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3.2. Problems of CAs
3.2.1. Operational Errors
Operatioanl errors by CAs are inevitable and may cause significant
impact on Internet routing. Thus such errors by CAs in RPKI
constitute a risk to widespread deployment.
Operatioanl errors by CAs in the RPKI may lead to serious
consequences similar to those caused by malicious attacks (black-hole
routes, traffic interception, and denial-of-service attacks). For
example, an error in using a ROA (such as adding a new erroneous ROA
or whacking an existing ROA) may cause all routes covered by the
(original) ROA to become invalid (or to assume an "unknown" security
status [RFC6483]). Note that, if the old validating ROA still
matches (not just covers) the announce prefix, the announcement will
still be marked as valid.
3.2.2. Unilateral Resource Revocation
In the RPKI architecture, there is a risk that CAs have the power to
unilaterally revoke the INRs that have been allocated to their
descendants, e.g., by revoking corresponding CA certificates
[RFC6480].
This is a natural aspect of PKIs and it is a necessary capability for
CAs as they manage re-allocation of resources within their domains.
However, if revocation occurs accidentally, or because the CA has
been compelled by authorities, the results can be significant.
Specifically, all RPs will view the origin assertions by the CA (and
its descendants) to be not found. This may cause ISPs to
depreference routes to the affected prefixes.
3.3. Mirror World Attacks
In mirror world attacks, a malicious CA presents one view of the RPKI
repository (that it manages) to some RPs, and a different view to
others. (Because repository data may be cached by ISPs, it may not
be possible for a malicious CA to provide erroneous results to a
narrowly targeted set of RPs.)
Since a CA in the RPKI controls everything in its own repository, it
may be easy for a malicious CA to perform such a attack. For
example, a malicious CA presents the correct view of its repository
to some RPs, but a forged view (e.g., the CA adds a specific,
erroneous ROA) to the others. When these deceived RPs offer their
validation results to BGP routers, the routers may abandon the
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legitimate routes that are considered to be invalid according to the
(erroneous) validation results they have received.
3.4. Data Synchronization
It is required in [RFC6480] that all repositories must be accessible
via rsync protocol which is used by RPs to get the RPKI objects in
the global distributed repositories. However, the rsync protocol is
considered to be controversial with respect to the following
disadvantages:
1. Lack of standards and non-modular implementation: Although rsync
is widely adopted in backup, restore, and file transfer, it has
not been standardized by IETF. And the rsync implementation is
non-modular, making it difficult to use its source code.
2. Underlying overhead caused by repository updates during active
data transmissions: During data transmissions between RPs and the
repository, a new update to the repository may cause data
inconsistency between them. In order to rectify this
inconsistency, extra overhead costs (such as performing the
synchronization once more) are required.
3. This is being solved by the new RRDP protocol, now in deployment.
3.5. Problems of Staged and Incomplete Deployment
Since the global deployment of RPKI is an incremental and staged
process, unexpected problems may appear during this process. Let's
take an example to explain why the incomplete deployment of RPKI may
cause legitimate routes to be misclassified into invalid. In Fig.1,
we make the following assumptions:
1. CNNIC, ISP1 and ISP2 have deployed the RPKI, but ISP3 has not
yet. ISP1 and ISP2 received allocations form CNNIC, and ISP3
received its allocation from ISP1.
2. CNNIC allocated IP prefix 218.241.104.0/22 to ISP1 and
218.241.108.0/22 to ISP2.
3. Three ROAs (ROA1, ROA2, ROA3) are issued respectively by CNNIC,
ISP1 and ISP2.
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------- --------------
|APNIC| | Resource |
------- |Certificates|
| --------------
| ..............
................. ------- . ROA .
. ROA1: . | | ..............
.218.241.96.0/20.<--|CNNIC|
. AS1 . | |
................. -------
/ \
/ \
.................. ------ ------ ..................
. ROA2: . | | | | . ROA3: .
.218.241.104.0/22.<--|ISP1| |ISP2|-->.218.241.108.0/22.
. AS2 . | | | | . AS3 .
.................. ------ ------ ..................
|
|
------
| |
|ISP3|
| |
------
Fig.1: An example of incomplete deployment
Now ISP3 announces to be the origin of 218.241.106.0/23. When other
entities receive this announcement, they can validate it with ROAs
information. Since prefix 218.241.104.0/22 described in ROA2
encompasses prefix 218.241.106.0/23 and no matching ROA describes
218.241.106.0/23 could be found [RFC6483], the announcement for
prefix 218.241.106.0/23 will be considered to be invalid. This
example illustrates why careful coordination is needed when (non-
leaf) ISPs incrementally deploy the RPKI. This example illustrates
why careful coordination is needed when (non-leaf) ISPs incrementally
deploy the RPKI.
Therefore, if an ISP knows its customer is not creating a ROA, it is
the ISP's responsibility to create that ROA, just as it is that ISP's
responsibility to do 42 other things for their 'customer'.
3.6. Low Validation Coverage
The route origin validation coverage refers to the percentage of
valid routes attested to by the RPKI. i.e., Coverage =
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number_of_valid_routes / (number_of_valid_routes +
number_of_invalid_routes).
As we can see from Table 2, the coverage of route origin validation
in the five RIRs differs a lot. LACNIC and RIPE NCC have the highest
validation coverage and both of them are over 90%, while the coverage
in APNIC is less than 70%. Many reasons may account for the low
validation coverage, such as misconfigurations, low RPKI adoption
rates, etc.
+---------+-------+-------+---------+---------+----------+----------+
| RIR | Total | Valid | Invalid | Unknown | Accuracy | Adoption |
| | | | | | | Rate |
+---------+-------+-------+---------+---------+----------+----------+
| AFRI- | 14948 | 242 | 5 | 14701 | 97.98% | 1.65% |
| NIC | | | | | | |
| APNIC | 15802 | 3332 | 1564 | 153124 | 68.06% | 3.1% |
| | 0 | | | | | |
| ARIN | 21977 | 1911 | 337 | 217531 | 85.01% | 1.02% |
| | 9 | | | | | |
| LACNIC | 76841 | 13379 | 736 | 62726 | 94.79% | 18.37% |
| RIPE | 15925 | 16771 | 1307 | 141178 | 92.77% | 11.35% |
| NCC | 6 | | | | | |
+---------+-------+-------+---------+---------+----------+----------+
Table 2. Route Origin Validation Accuracy in 5 RIRs
4. Alternative Solutions to RPKI Deployment Problems
In this section, we propose and analyze the alternative solutions and
strategies to solve or mitigate the problems mentioned in Section 3.
4.1. Solutions to Multiple TAs
The RIRs say they are trying to continually evolve RPKI. ICANN
(IANA) and RIRs have developed a technical testbed with an RPKI GTA.
It's assumed that there must be a single root trust anchor
eventually. With this single root trust anchor deployed, the risks
of resource conflicts (at the level of RIR certificates) could be
significantly reduced.
However, this solution cedes more power to ICANN (IANA) and thus
might exacerbate the risk of "Unilateral Resource Revocation" (power
imbalance) mentioned in Section 3.2.2.
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4.2. Solutions to Misbehaving CAs
S. Kent et al. put forward a collection of mechanisms named
"Suspenders". "Suspenders" is designed to address the adverse
effects on INR holders which were caused by CAs' accidental or
deliberate misbehavior or attacks on CAs and repositories. This
mechanism imports two new objects: an INRD (Internet Number Resource
Declaration) file and a LOCK object. The INRD file is external to
the RPKI repository, and it contains the most recent changes that
were made by the INR holder. The LOCK object is published in the INR
holder's repository. It contains a URL which points to the INRD
file, and a public key used to verify the signature of INRD file.
Whenever the RPs detect the inconsistencies between the actual
changes and the INRD file, they can determine individually whether to
accept these changes or not. (This proposal is being revised to
address operational concerns, but it is anticipated that a subsequent
version of Suspenders will preserve the primary features noted
above.)
4.3. Solutions to Data Synchronization
A number of alternative protocols have been presented to take the
place of "rsync" protocol due to its shortcomings mentioned above.
1) RRDP
T. Bruijnzeels et al. have proposed an alternative protocol (RRDP,
RPKI Repository Delta Protocol) for RPs to keep their local caches in
sync with the repository system [I-D.ietf-sidr-delta-protocol]. This
new protocol is based on notification, snapshot and delta files.
When RPs query a repository for updates, they will use delta files
(and snapshot files as needed) to keep their local caches updated.
Moreover, RRDP protocol can work with the existing rsync URIs.
Compared with rsync protocol, RRDP is considered to be effective as a
way to eliminate a number of consistency related issues, help to
reduce the load on publication servers, and have improved
scalability.
RRDP is in current RIPE and DRL software.
2) Improved Rsync Protocol
CNNIC also proposed an improved rsync mechanism which transfers the
work of checksums calculation to RPs in order to reduce the
computation load on the rsync server side. The mechanism also
offered a NOTIFY method that send NOTIFY message to make some
important RPs to actively fetch the updated RPKI objects in time.
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4.4. Solutions to Incomplete Deployment and Low Validation Coverage
Both of the two problems (incomplete deployment and low validation
accuracy) are caused by the partial deployment of RPKI. With the
widely deployment of RPKI in the near future, these two problems
ought to be mitigated.
5. Security Considerations
TBD
6. IANA Considerations
This draft does not request any IANA action.
7. Acknowledgements
The authors would like to thanks the valuable comments made by
Stephen Kent and other members of sidr WG.
This document was produced using the xml2rfc tool [RFC2629].
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[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>.
[RFC6482] Lepinski, M., Kent, S., and D. Kong, "A Profile for Route
Origin Authorizations (ROAs)", RFC 6482,
DOI 10.17487/RFC6482, February 2012,
<http://www.rfc-editor.org/info/rfc6482>.
[RFC6483] Huston, G. and G. Michaelson, "Validation of Route
Origination Using the Resource Certificate Public Key
Infrastructure (PKI) and Route Origin Authorizations
(ROAs)", RFC 6483, DOI 10.17487/RFC6483, February 2012,
<http://www.rfc-editor.org/info/rfc6483>.
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[RFC6486] Austein, R., Huston, G., Kent, S., and M. Lepinski,
"Manifests for the Resource Public Key Infrastructure
(RPKI)", RFC 6486, DOI 10.17487/RFC6486, February 2012,
<http://www.rfc-editor.org/info/rfc6486>.
8.2. Informative References
[I-D.ietf-sidr-delta-protocol]
Bruijnzeels, T., Muravskiy, O., Weber, B., and R. Austein,
"RPKI Repository Delta Protocol", draft-ietf-sidr-delta-
protocol-03 (work in progress), July 2016.
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
DOI 10.17487/RFC2629, June 1999,
<http://www.rfc-editor.org/info/rfc2629>.
[RFC5914] Housley, R., Ashmore, S., and C. Wallace, "Trust Anchor
Format", RFC 5914, DOI 10.17487/RFC5914, June 2010,
<http://www.rfc-editor.org/info/rfc5914>.
[RFC6810] Bush, R. and R. Austein, "The Resource Public Key
Infrastructure (RPKI) to Router Protocol", RFC 6810,
DOI 10.17487/RFC6810, January 2013,
<http://www.rfc-editor.org/info/rfc6810>.
Authors' Addresses
Xiaodong Lee
CNNIC
No.4 South 4th Street, Zhongguancun
Beijing, 100190
P.R. China
Email: xl@cnnic.cn
Xiaowei Liu
CNNIC
No.4 South 4th Street, Zhongguancun
Beijing, 100190
P.R. China
Email: liuxiaowei@cnnic.cn
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Zhiwei Yan
CNNIC
No.4 South 4th Street, Zhongguancun
Beijing, 100190
P.R. China
Email: yanzhiwei@cnnic.cn
Guanggang Geng
CNNIC
No.4 South 4th Street, Zhongguancun
Beijing, 100190
P.R. China
Email: gengguanggang@cnnic.cn
Yu Fu
CNNIC
No.4 South 4th Street, Zhongguancun
Beijing, 100190
P.R. China
Email: fuyu@cnnic.cn
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