wdiff rfc7645.original rfc7645.txt

Routing Working Group
Internet Engineering Task Force (IETF) U. Chunduri
Internet-Draft
Request for Comments: 7645 A. Tian
Intended status:
Category: Informational W. Lu
Expires: January 7, 2016
ISSN: 2070-1721 Ericsson Inc.
July 6,
September 2015

KARP

The Keying and Authentication for Routing Protocol (KARP)
IS-IS security analysis
draft-ietf-karp-isis-analysis-07 Security Analysis

Abstract

This document analyzes the threats applicable for current state of Intermediate system System to
Intermediate system System (IS-IS) routing protocol and security gaps according to the KARP Design Guide. This document also provides
specific requirements to address the gaps with
set forth in Keying and Authentication for Routing Protocols (KARP)
Design Guidelines (RFC 6518) for both manual and auto automated key
management protocols.

Status of This Memo

This Internet-Draft document is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents not an Internet Standards Track specification; it is
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This Internet-Draft will expire on January 7, 2016.
http://www.rfc-editor.org/info/rfc7645.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
1.2. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Current State . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Key Usage . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.1. Sub network Subnetwork Independent . . . . . . . . . . . . . . . 4
2.1.2. Sub network Subnetwork dependent . . . . . . . . . . . . . . . . 4
2.2. Key Agility . . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Security Issues . . . . . . . . . . . . . . . . . . . . . 5
2.3.1. Replay Attacks . . . . . . . . . . . . . . . . . . . 5
2.3.1.1. Current Recovery mechanism Mechanism for LSPs . . . . . . . 6
2.3.2. Spoofing Attacks . . . . . . . . . . . . . . . . . . 7
2.3.3. DoS Attacks . . . . . . . . . . . . . . . . . . . . . 8
3. Gap Analysis and Security Requirements . . . . . . . . . . . 8
3.1. Manual Key Management . . . . . . . . . . . . . . . . . . 8
3.2. Key Management Protocols . . . . . . . . . . . . . . . . 9
4. IANA Security Considerations . . . . . . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . References . . . 10
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
7.
5.1. Normative References . . . . . . . . . . . . . . . . . . 10
5.2. Informative References . . . . . . . 10
7.1. Normative References . . . . . . . . . . 11
Acknowledgements . . . . . . . . 11
7.2. Informative References . . . . . . . . . . . . . . . . . 11 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12

1. Introduction

This document analyzes the current state of Intermediate system System to
Intermediate system System (IS-IS) protocol according to the requirements
set forth in "Keying and Authentication for Routing Protocols (KARP)
Design Guidelines" [RFC6518] for both manual and auto automated key
management protocols.

With currently published work, IS-IS meets some of the requirements
expected from a manually keyed routing protocol. Integrity
protection is expanded with by allowing more cryptographic algorithms and also to
be used [RFC 5310]. However, even with this expanded protection,
only limited algorithm agility (HMAC-SHA family) is provided with
[RFC5310]. Basic possible.
[RFC5310] makes possible a basic form of Intra-connection re-keying capability is
provided by the specification [RFC5310] intra-connection rekeying,
but with some gaps as explained analyzed in Section 3. 3 of this document.

This draft document summarizes the current state of cryptographic key usage
in the IS-IS protocol and several previous efforts to that analyze IS-IS
security. This includes the base IS-IS specification specifications: [RFC1195],
[RFC5304], [RFC5310] [RFC5310], and [RFC6039].

This document also analyzes applicability of various threats to IS-IS (as described in
[RFC6862]), lists gaps security gaps, and provide provides specific
recommendations to thwart the applicable threats for both manual keying and for auto
automated key management mechanisms.

1.1. Requirements Language

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 RFC 2119 [RFC2119].

1.2. Acronyms

DoS - Denial of Service. Service

GDOI - Group Domain of Interpretation

IGP - Interior Gateway Protocol. Protocol

IIH - IS-IS HELLO PDU.

IPv4 - Internet Protocol version 4. 4

KMP - Key Management Protocol (auto (automated key management). management)

LSP - IS-IS Link State PDU. PDU

MKM - Manual Key management Protocols. Management

NONCE - Number Once. Once

PDU - Protocol Data Unit. Unit

SA - Security Association. Association

SNP - Sequence number PDU. Number PDU

2. Current State

IS-IS is specified in International Standards Organization (ISO)
10589,
10589 [ISO10589], with extensions to support Internet Protocol
version 4 (IPv4) described in [RFC1195]. The specification includes
an authentication mechanism that allows for any authentication
algorithm and also specifies the algorithm for clear text passwords. Further
Further, [RFC5304] extends the authentication mechanism to work with
HMAC-MD5 and also modifies the base protocol for more effectiveness.
[RFC5310] provides algorithm agility, with a new generic crypto
cryptographic authentication mechanism (CRYPTO_AUTH) for IS-IS. The

CRYPTO_AUTH also introduces a Key ID mechanism that map maps to unique
IS-IS Security Associations
(SAs). SAs.

The following sections describe the current authentication key usage
for various IS-IS messages, current key change methodologies methodologies, and the
various potential security threats.

2.1. Key Usage

IS-IS can be provisioned with a per interface, per-interface, peer-to-peer key for
IS-IS HELLO (IIH)
IIH PDUs and a group key for Link State PDUs (LSPs) LSPs and
Sequence number PDUs (SNPs). SNPs. If provisioned, IIH
packets potentially can potentially use the same group key used for LSPs and
SNPs.

2.1.1. Sub network Subnetwork Independent

Link State PDUs, Complete and partial Sequence Number PDUs come under
Sub network Independent messages. For protecting Level-1 SNPs and
Level-1 LSPs, provisioned Area Authentication key is used. Level-2
SNPs as well as Level-2 LSPs use the provisioned domain
authentication key.

Since

Because authentication is performed on the LSPs transmitted by an IS,
rather than on the LSP packets transmitted to a specific neighbor, it
is implied that all the ISes within a single flooding domain must be
configured with the same key in order for authentication to work
correctly. This is also true for SNP packets, though they are
limited to link local link-local scope in broadcast networks.

If multiple instances share the circuits as specified in [RFC6822],
instance specific
instance-specific authentication credentials can be used to protect
the LSPs and SNPs within an area or domain. It is important to note, note
that [RFC6822] also allows usage of topology specific topology-specific authentication
credentials within an instance for the LSPs and SNPs.

2.1.2. Sub network dependent

IS-IS HELLO Subnetwork Dependent

IIH PDUs use the Link Level Authentication key, which may be
different from that of LSPs and SNPs. This could be particularly
true for point-to-point links. In broadcast networks networks, it is possible
to provision the same common key used for LSPs and SNPs, SNPs to protect
IIH messages. This allows neighbor discovery and adjacency formation
with more than one neighbor on the same physical interface. If
multiple instances share the circuits as specified in [RFC6822],
instance specific
instance-specific authentication credentials can be used to protect
Hello messages.

2.2. Key Agility

Key roll over without effecting the routing protocols operation in
general and IS-IS in particular, particular is necessary for effective key
management protocol integration.

Current HMAC-MD5 crypto cryptographic authentication as defined in
[RFC5304], suggests a transition mode, mode so that ISes use a set of keys
when verifying the authentication value, value to allow key changes. This
approach will allow changing the authentication key manually without
bringing down the adjacency and without dropping any control packet.
But, this can increase the load on the control plane for the key
transition duration duration, as each control packet may have to be verified
by more than one key key, and it also allows to mount a potential Denial of
Service (DoS) DoS attack in
the transition duration.

The above situation is improved with the introduction of the Key ID
mechanism as defined in [RFC5310]. With this, the receiver
determines the active security association (SA) SA by looking at the Key ID field in the
incoming PDU and need not try with other keys, keys when the integrity
check or digest verification fails. But, neither Key
co-ordination key coordination
across the group nor an exact key change mechanism is clearly
defined. [RFC5310] says: "

Normally, an implementation would allow the network operator to
configure a set of keys in a key chain, with each key in the chain
having a fixed lifetime. The actual operation of these mechanisms
is outside the scope of this document." document.

2.3. Security Issues

The following section analyzes various possible security threats possible, in
the current state for of the IS-IS protocol.

2.3.1. Replay Attacks

Replaying a captured protocol packet to cause damage is a common
threat for any protocol. Securing the packet with cryptographic
authentication information alone cannot mitigate this threat
completely. Though this problem is more prevalent in broadcast
networks
networks, it is important to note, note that most of the IGP deployments
use P2P-over-lan circuits [RFC5309], which makes it possible for an
adversary to replay 'easier' an IS-IS PDU more easily than the traditional P2P networks
networks.

In intra-session replay attacks attacks, a secured protocol packet of the
current session that is replayed, replayed can cause damage, if there is no
other mechanism to confirm this is a replay packet. In inter-session
replay attacks, a captured packet from one of the previous session sessions
can be replayed to cause the damage. IS-IS packets are vulnerable to
both of these attacks, as there is no sequence number verification
for IIH packets and SNP packets. Also with current manual key management management,
periodic key changes across the group are done rarely. Thus rarely done. Thus, the
intra-connection and inter-connection replay requirements are not
met.

IS-IS specifies the use of the HMAC-MD5 [RFC5304] and HMAC-SHA-1
family in [RFC5310], [RFC5310] to protect IS-IS packets. An adversary could
replay old IIHs or replay old SNPs that would cause churn in the
network or bring down the adjacencies.

1. At the time of adjacency bring up an IS sends IIH packet with
empty neighbor list (TLV 6) and with the authentication
information as per the provisioned authentication mechanism. If
this packet is replayed later on the broadcast network, all ISes
in the broadcast network can bounce the adjacency to create a huge
churn in the network.

2. Today Today, LSPs have intra-session replay protection as the LSP header
contains a 32-bit sequence number number, which is verified for every
received packet against the local LSP database. But, if a node in
the network is out of service (is undergoing some sort of high
availability condition, condition or an upgrade) for more than LSP refresh
time and the rest of the network ages out the LSPs of the node
under consideration, an adversary can potentially plunge in
inter-session inter-
session replay attacks in the network. If the key is not changed
in the above circumstances, attack can be launched by replaying an
old LSP with a higher sequence number and fewer prefixes or fewer
adjacencies. This may force the receiver to accept and remove the
routes from the routing table, which eventually causes traffic
disruption to those prefixes. However, as per the IS-IS specification
specification, there is a built-in recovery mechanism for LSPs
from inter-session replay attacks and it is further discussed in
Section 2.3.1.1.

3. In any IS-IS network (broadcast or otherwise), if an old and an
empty Complete Sequence Number packet Packet (CSNP) is replayed replayed, this can
cause LSP flood in the network. Similarly Similarly, a replayed Partial
Sequence Number Packet (PSNP) can cause LSP flood in the broadcast
network.

2.3.1.1. Current Recovery mechanism Mechanism for LSPs

In the event of inter-session replay attack by an adversary, as an
LSP with a higher sequence number gets accepted, it also gets
propagated until it reaches the originating node of the LSP. The
originator recognizes the LSP is "newer" than in the local database and this database,
which prompts the originator to flood a newer version of the LSP with
a higher sequence number than the that received. This newer version can
potentially replace any versions of the replayed LSP which that may exist
in the network.

But

However, in the above process, depending on where in the network the
replay is initiated, how quick quickly the nodes in the network react to
the replayed LSP LSP, and also how different the content in the accepted LSP
is determines the damage caused by the replayed LSP.

2.3.2. Spoofing Attacks

IS-IS shares the same key between all neighbors in an area or in a
domain to protect the LSP, SNP packets packets, and in broadcast networks
even IIH packets. False advertisement by a router is not within the
scope of the KARP work. However, given the wide sharing of keys as
described above, there is a significant risk that an attacker can
compromise a key from one device, device and use it to falsely participate in
the routing, possibly even in a very separate part of the network.

If the same underlying topology is shared across multiple instances
to transport routing/application information as defined in [RFC6822],
it is necessary to use different authentication credentials for
different instances. In this connection, based on the deployment
considerations, if certain topologies in a particular IS-IS instance
require more protection from spoofing attacks and less exposure,
topology specific
topology-specific authentication credentials can be used for LSPs and
SNPs as facilitated in [RFC6822].

Currently

Currently, possession of the key itself is used as an authentication
check and there is no identity check done separately. Spoofing
occurs when an illegitimate device assumes the identity of a
legitimate one. An attacker can use spoofing as a means for
launching to launch various types
of attacks. For attacks, for example:

1. The attacker can send out unrealistic routing information that
might cause the disruption of network services services, such as block
holes.

2. A rogue system having that has access to the common key used to protect
the LSP, LSP can send flood an LSP, LSP by setting the Remaining Lifetime field
to zero, and flooding it thereby initiating a purge. Subsequently, this also can cause
the sequence number of all the LSPs to increase quickly to max out
the sequence number space, which can cause an IS to shut down for
MaxAge + ZeroAgeLifetime period to allow the old LSPs to age out
in other ISes of the same flooding domain.

2.3.3. DoS Attacks

Denial-of-service (DoS)

DoS attacks using the authentication mechanism is possible and an
attacker can send packets which that can overwhelm the security mechanism
itself. An example is initiating an overwhelming load of spoofed but integrity protected
integrity-protected protocol packets, so that the receiver needs to
process the integrity check, only to discard the packet. This can
cause significant CPU usage. DoS attacks are not generally
preventable within the routing protocol. As the attackers are often
remote, the DoS attacks are more damaging to area-scoped or
domain-scoped domain-
scoped packet receivers than link-local scoped link-local-scoped packet receivers.

3. Gap Analysis and Security Requirements

This section outlines the differences between the current state of
the IS-IS routing protocol and the desired state as specified in the
KARP Design Guidelines [RFC6518]. The This section focuses on where the
IS-IS protocol fails to meet general requirements as specified in the
threats and requirements document. document [RFC6862].

This section also describes security requirements that should be met
by IS-IS implementations that are secured by manual as well as auto
automated key management protocols.

3.1. Manual Key Management

1. With CRYPTO_AUTH specification [RFC5310], IS-IS packets can be
protected with the HMAC-SHA family of cryptographic algorithms.
The specification provides the limited algorithm agility (SHA family).
By using Key IDs, it also conceals the algorithm information from
the protected control messages.

2. Even though both intra intra- and inter session inter-session replay attacks are best
prevented by deploying key management protocols with frequent key
change capability, basic constructs for the sequence number should
be
there in the protocol messages. So, some basic or extended sequence
number mechanism should be in place to protect IIH packets and SNP
packets. The sequence number should be increased for each
protocol packet. This allows mitigation of some of the replay
threats as mentioned in Section 2.3.1.

3. Any common key mechanism with keys shared across a group of
routers is susceptible to spoofing attacks caused by a malicious
router. Separate A separate authentication check (apart from the integrity
check to verify the digest) with digital signatures as described
in [RFC2154], [RFC2154] can effectively nullify this attack. But this
approach was never deployed and one can only deployed, which we assume is due to operational
considerations at that time. The alternative approach to thwart
this threat would be by using to use the keys from the group key management
protocol. As the group key(s) are generated by authenticating the
member ISes in the group first, first and are then periodically rekeyed, per packet
per-packet identity or authentication check checks may not be needed.

4. In general general, DoS attacks may not be preventable with the mechanism
from the routing protocols protocol itself. But some form of Admin admin-
controlled lists (ACLs) at the forwarding plane can reduce the damage.
There are some other forms the of DoS attacks common to any protocol
that are not in scope as per the section Section 3.3 in of [RFC6862].

As discussed in Section 2.2, though the Key ID mechanism described in
[RFC5310] helps, a better key co-ordination coordination mechanism for key roll
over is desirable even with manual key management. But, it fell short of
specifying [RFC5310]
does not specify the exact mechanism other than using requiring use of key
chains. The specific
requirements: requirements are as follows:

a. Keys SHOULD be able to change without affecting effecting the established
adjacency and even better
adjacency, ideally without any control packet loss.

b. Keys SHOULD be able to change without effecting the protocol
operations,
operations; for example, LSP flooding should not be held for a
specific Key ID availability.

c. Any proposed mechanism SHOULD also be further incrementally deployable
with key management protocols.

3.2. Key Management Protocols

In broadcast deployments, the keys used for protecting IS-IS
protocols messages can, in particular, be group keys. A mechanism is
needed to distribute group keys to a group of ISes in a Level-1 area
or Level-2 domain, using the Group Domain of Interpretation (GDOI)
protocol as specified in [RFC6407]. An example policy and payload
format was is described in [I-D.weis-gdoi-mac-tek]. [GDOI].

If a group key is used, the authentication granularity becomes group
membership of devices, not peer authentication between devices.
Group The
deployed group key management protocol deployed SHOULD be capable of
supporting rekeying support. support rekeying.

In some deployments, where IS-IS point-to-point (P2P) mode is used
for adjacency bring-up, sub network dependent subnetwork-dependent messages (IIHs) (e.g., IIHs)
can use a different key shared between the two point-to-point P2P peers, while all
other messages use a group key. When a group keying mechanism is
deployed, even the P2P IIHs can be protected with the common group
keys. This approach facilitates one key management mechanism instead
of both pair-wise keying and group keying protocols to be being deployed
together. If the same circuits are shared across multiple instances,
the granularity of the group can become per instance for IIHs and per
instance/topology for LSPs and SNPs as specified in the [RFC6822].

Effective key change capability within the routing protocol which that
allows key roll over without impacting the routing protocol
operation, operation
is one of the requirements for deploying any group key mechanism.
Once such mechanism is in place with the deployment of group key
management protocol, protocol; IS-IS can be protected from various threats and
is not limited to intra intra- and inter session inter-session replay attacks and
spoofing attacks.

Specific use of crypto cryptographic tables [RFC7210] should be defined for
the IS-IS protocol.

4. IANA Considerations

This document defines no new namespaces.

5. Security Considerations

This document is mostly about security considerations of the IS-IS
protocol, and it lists potential threats and security requirements
for
solving those mitigating these threats. This document does not introduce any
new security threats for the IS-IS protocol. In view of openly
published attack vectors, as noted in Section 1 of [RFC5310] on HMAC-MD5 HMAC-
MD5 cryptographic authentication mechanism, IS-IS deployments SHOULD
use the HMAC-SHA family [RFC5310] instead of HMAC-MD5 [RFC5304] for
protecting to
protect IS-IS PDUs. For more detailed security considerations considerations,
please refer the Security Considerations section of the IS-IS Generic
Cryptographic Authentication [RFC5310], the KARP Design Guide
[RFC6518]
document document, as well as the KARP threat document [RFC6862].

6. Acknowledgements

Authors would like to thank Joel Halpern for initial discussions on
this document and giving valuable review comments. Authors would
like to acknowledge Naiming Shen for reviewing and providing feedback
on this document. Thanks to Russ White, Brian Carpenter and Amanda
Barber for reviewing the document during IESG review process.

5. References

7.1.

5.1. Normative References

[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
dual environments", RFC 1195, DOI 10.17487/RFC1195,
December 1990. 1990, <http://www.rfc-editor.org/info/rfc1195>.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997. 1997,
<http://www.rfc-editor.org/info/rfc2119>.

[RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, DOI 10.17487/RFC5304, October 2008.
2008, <http://www.rfc-editor.org/info/rfc5304>.

[RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic
Authentication", RFC 5310, DOI 10.17487/RFC5310, February 2009.

7.2.
2009, <http://www.rfc-editor.org/info/rfc5310>.

5.2. Informative References

[I-D.weis-gdoi-mac-tek]

[GDOI] Weis, B. and S. Rowles, "GDOI Generic Message
Authentication Code Policy", draft-weis-gdoi-mac-tek-03
(work Work in progress), Progress,
draft-weis-gdoi-mac-tek-03, September 2011.

[ISO10589] International Organization for Standardization,
"Intermediate System to Intermediate System intra-domain
routeing information exchange protocol for use in
conjunction with the protocol for providing the
connectionless-mode network service (ISO 8473)", ISO/IEC
10589:2002, Second Edition, November 2002.

[RFC2154] Murphy, S., Badger, M., and B. Wellington, "OSPF with
Digital Signatures", RFC 2154, DOI 10.17487/RFC2154, June 1997.
1997, <http://www.rfc-editor.org/info/rfc2154>.

[RFC5309] Shen, N. N., Ed., and A. Zinin, Ed., "Point-to-Point
Operation over LAN in Link State Routing Protocols",
RFC 5309, DOI 10.17487/RFC5309, October 2008. 2008,
<http://www.rfc-editor.org/info/rfc5309>.

[RFC6039] Manral, V., Bhatia, M., Jaeggli, J., and R. White, "Issues
with Existing Cryptographic Protection Methods for Routing
Protocols", RFC 6039, DOI 10.17487/RFC6039, October 2010. 2010,
<http://www.rfc-editor.org/info/rfc6039>.

[RFC6407] Weis, B., Rowles, S., and T. Hardjono, "The Group Domain
of Interpretation", RFC 6407, DOI 10.17487/RFC6407,
October 2011. 2011, <http://www.rfc-editor.org/info/rfc6407>.

[RFC6518] Lebovitz, G. and M. Bhatia, "Keying and Authentication for
Routing Protocols (KARP) Design Guidelines", RFC 6518,
DOI 10.17487/RFC6518, February 2012. 2012,
<http://www.rfc-editor.org/info/rfc6518>.

[RFC6822] Previdi, S., Ed., Ginsberg, L., Shand, M., Roy, A., and
D. Ward, "IS-IS Multi-Instance", RFC 6822,
DOI 10.17487/RFC6822, December 2012. 2012,
<http://www.rfc-editor.org/info/rfc6822>.

[RFC6862] Lebovitz, G., Bhatia, M., and B. Weis, "Keying and
Authentication for Routing Protocols (KARP) Overview,
Threats, and Requirements", RFC 6862,
DOI 10.17487/RFC6862, March 2013. 2013,
<http://www.rfc-editor.org/info/rfc6862>.

[RFC7210] Housley, R., Polk, T., Hartman, S., and D. Zhang,
"Database of Long-Lived Symmetric Cryptographic Keys",
RFC 7210, DOI 10.17487/RFC7210, April 2014. 2014,
<http://www.rfc-editor.org/info/rfc7210>.

Acknowledgements

Authors would like to thank Joel Halpern for initial discussions on
this document and for giving valuable review comments. The authors
would like to acknowledge Naiming Shen for reviewing and providing
feedback on this document. Thanks to Russ White, Brian Carpenter,
and Amanda Barber for reviewing the document during the IESG review
process.

Authors' Addresses

Uma Chunduri
Ericsson Inc.
300 Holger Way,
San Jose, California 95134
USA
United States
Phone: 408 750-5678
Email: uma.chunduri@ericsson.com

Albert Tian
Ericsson Inc.
300 Holger Way,
San Jose, California 95134
USA
United States
Phone: 408 750-5210
Email: albert.tian@ericsson.com

Wenhu Lu
Ericsson Inc.
300 Holger Way,
San Jose, California 95134
USA
United States
Email: wenhu.lu@ericsson.com