Internet DRAFT - draft-ietf-karp-routing-tcp-analysis
draft-ietf-karp-routing-tcp-analysis
Routing Working Group M. Jethanandani
Internet-Draft Ciena Corporation
Intended status: Informational K. Patel
Expires: October 10, 2013 Cisco Systems, Inc
L. Zheng
Huawei Technologies
April 08, 2013
Analysis of BGP, LDP, PCEP and MSDP Issues According to KARP Design
Guide
draft-ietf-karp-routing-tcp-analysis-07.txt
Abstract
This document analyzes TCP based routing protocols, Border Gateway
Protocol (BGP), Label Distribution Protocol (LDP), Path Computation
Element Communication Protocol (PCEP), and Multicast Source
Distribution Protocol (MSDP) according to guidelines set forth in
section 4.2 of Keying and Authentication for Routing Protocols Design
Guidelines (RFC6518).
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 October 10, 2013.
Copyright Notice
Copyright (c) 2013 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
publication of this document. Please review these documents
Jethanandani, et al. Expires October 10, 2013 [Page 1]
Internet-Draft BGP, LDP, PCEP and MSDP Analysis April 2013
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
1.1. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
2. Current Assessment of BGP, LDP, PCEP and MSDP . . . . . . . . 4
2.1. Transport layer . . . . . . . . . . . . . . . . . . . . . 5
2.2. Keying mechanisms . . . . . . . . . . . . . . . . . . . . 6
2.3. BGP . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.4. LDP . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.4.1. Spoofing attacks . . . . . . . . . . . . . . . . . . 7
2.4.2. Denial of Service Attacks . . . . . . . . . . . . . . 8
2.5. PCEP . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.6. MSDP . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3. Optimal State for BGP, LDP, PCEP, and MSDP . . . . . . . . . 10
3.1. LDP . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4. Gap Analysis for BGP, LDP, PCEP and MSDP . . . . . . . . . . 11
4.1. LDP . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.2. PCEP . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5. Transition and Deployment Considerations . . . . . . . . . . 13
6. Security Considerations . . . . . . . . . . . . . . . . . . . 13
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1. Normative References . . . . . . . . . . . . . . . . . . 14
9.2. Informative References . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
In March 2006, the Internet Architecture Board (IAB) described an
attack on core routing infrastructure as an ideal attack that would
inflict the greatest amount of damage, in their Report from the IAB
workshop on Unwanted Traffic March 9-10, 2006 [RFC4948], and suggests
steps to tighten the infrastructure against the attack. Four main
steps were identified for that tightening:
1. Create secure mechanisms and practices for operating routers.
2. Clean up the Internet Routing Registry (IRR) repository, and
securing both the database and the access, so that it can be used
for routing verifications.
Jethanandani, et al. Expires October 10, 2013 [Page 2]
Internet-Draft BGP, LDP, PCEP and MSDP Analysis April 2013
3. Create specifications for cryptographic validation of routing
message content.
4. Secure the routing protocols' packets on the wire.
In order to secure the routing protocols this document performs an
initial analysis of the current state of the following TCP based
protocols: BGP, LDP, PCEP, and MSDP according to the requirements of
KARP Design Guidelines [RFC6518]. Section 4.2 of the document uses
the term "state" which will be referred to as the "state of the
security method". Thus a term like "Define Optimal State" would be
referred to as "Define Optimal State of the Security Method". This
document builds on several previous analysis efforts into routing
security.
This document builds on several previous efforts into routing
security:
o Issues with existing Cryptographic Protection Methods for Routing
Protocols [RFC6039], describes issues with existing cryptographic
protection methods for routing protocols.
o Analysis of OSPF Security According to KARP Design Guide [RFC6863]
analyzes Open Shortest Path First (OSPF) security according to
KARP Design Guide.
Section 2 of this document looks at the current state of the security
method for the four routing protocols, BGP, LDP, PCEP and MSDP.
Section 3 examines what the optimal state of the security method
would be for the four routing protocols, according to KARP Design
Guidelines [RFC6518] and Section 4 does an analysis of the gap
between the existing state of the security method and the optimal
state of the security method for protocols and suggests some areas
where improvement is needed.
1.1. Abbreviations
AES - Advanced Encryption Standard
AO - Authentication Option
AS - Autonomous Systems
BGP - Border Gateway Protocol
CMAC - Ciper Based MAC
DoS - Denial of Service
Jethanandani, et al. Expires October 10, 2013 [Page 3]
Internet-Draft BGP, LDP, PCEP and MSDP Analysis April 2013
GTSM - Generalized TTL Security Mechanism
HMAC - Hash Based MAC
KARP - Key and Authentication for Routing Protocols
KDF - Key Derivation Function
KEK - Key Encrypting Key
KMP - Key Management Protocol
LDP - Label Distribution Protocol
LSR - Label Switching Routers
MAC - Message Authentication Code
MKT - Master Key Tuple
MSDP - Multicast Source Distribution Protocol
MD5 - Message Digest algorithm 5
OSPF - Open Shortest Path First
PCEP - Path Computation Element Communication Protocol
PCC - Path Computation Client
PCE - Path Computation Element
SHA - Security Hash Algorithm
TCP - Transmission Control Protocol
TTL - Time To Live
UDP - User Datagram Protocol
WG - Working Group
2. Current Assessment of BGP, LDP, PCEP and MSDP
This section assesses the transport protocols for any authentication
or integrity mechanisms used by the protocol. It describes the
current security mechanisms if any used by BGP, LDP, PCEP and MSDP.
Jethanandani, et al. Expires October 10, 2013 [Page 4]
Internet-Draft BGP, LDP, PCEP and MSDP Analysis April 2013
2.1. Transport layer
At a transport layer, routing protocols are subject to a variety of
DoS attacks, as outlined in Internet Denial-of-Service Considerations
[RFC4732]. Such attacks can cause the routing protocol to become
congested with the result that routing updates are supplied too
slowly to be useful. In extreme cases, these attacks prevent routers
from converging after a change.
Routing protocols use several methods to protect themselves. Those
that use TCP as a transport protocol use access lists to accept
packets only from known sources. These access lists also help
protect edge routers from attacks originating outside the protected
domain. In addition, for edge routers running eBGP, TCP LISTEN is
run only on interfaces on which its peers have been discovered or via
which routing sessions are expected (as specified in router
configuration databases).
Generalized TTL Security Mechanism (GTSM) [RFC5082] describes a
generalized Time to Live (TTL) security mechanism to protect a
protocol stack from CPU-utilization based attacks.TCP Robustness
[RFC5961] recommends some TCP level mitigations against spoofing
attacks targeted towards long-lived routing protocol sessions.
Even when BGP, LDP, PCEP and MSDP sessions use access lists, they are
vulnerable to spoofing and man in the middle attacks. Authentication
and integrity checks allow the receiver of a routing protocol update
to know that the message genuinely comes from the node that claims to
have sent it, and to know whether the message has been modified.
Sometimes routers can be subjected to a large number of
authentication and integrity requests, exhausting connection
resources on the router in a way that could lead to deny genuine
requests.
TCP MD5 [RFC2385] has been obsoleted by TCP-AO [RFC5925]. However,
it is still widely used to authenticate TCP based routing protocols
such as BGP. It provides a way for carrying a MD5 digest in a TCP
segment. This digest is computed using information known only to the
end points and this ensures authenticity and integrity of messages.
The MD5 key used to compute the digest is stored locally on the
router. This option is used by routing protocols to provide for
session level protection against the introduction of spoofed TCP
segments into any existing TCP streams, in particular TCP Reset
segments. TCP MD5 does not provide a generic mechanism to support
key roll-over. It also does not support algorithm agility.
The Message Authentication Codes (MACs) used by TCP MD5 option, is
considered too weak both because of the use of the hash function and
Jethanandani, et al. Expires October 10, 2013 [Page 5]
Internet-Draft BGP, LDP, PCEP and MSDP Analysis April 2013
because of the way the secret key used by TCP MD5 is managed.
Furthermore, TCP MD5 does not support any algorithm agility. TCP-AO
[RFC5925], and its companion document Crypto Algorithms for TCP-AO
[RFC5926], describe steps towards correcting both the MAC weakness
and the management of secret keys. For MAC it requires that two MAC
algorithms be supported. They are HMAC-SHA-1-96 as specified in HMAC
[RFC2104], and AES-128-CMAC-96 as specified in NIST-SP800-38B
[NIST-SP800-38B]. Cryptographic research suggests that both these
MAC algorithms defined are fairly secure. By supporting multiple MAC
algorithms, TCP-AO supports algorithm agility. TCP-AO also allows
additional MACs to be added in the future.
2.2. Keying mechanisms
For TCP-AO [RFC5925] there is no Key Management Protocol (KMP) used
to manage the keys that are employed to generate the Message
Authentication Code (MAC). TCP-AO talks about coordinating keys
derived from Master Key Table (MKT) between endpoints and allows for
a master key to be configured manually or for it to be managed via a
out of band mechanism.
It should be noted that most routers configured with static keys have
not seen the key changed ever. The common reason given for not
changing the key is the difficulty in coordinating the change between
pairs of routers when using TCP MD5. It is well known that the
longer the same key is used, the greater the chance that it can be
guessed or exposed e.g. when an administrator with knowledge of the
keys leaves the company.
For point-to-point key management IKEv2 [RFC5996] protocol provides
for automated key exchange under a SA, and can be used for a
comprehensive Key Management Protocol (KMP) solution for routers.
IKEv2 can be used for both IPsec SAs [RFC4301] and other types of
SAs. For example, Fibre Channel SAs [RFC4595] are currently
negotiated with IKEv2. Using IKEv2 to negotiate TCP-AO is a possible
option.
2.3. BGP
All BGP communications take place over TCP. Therefore, all security
vulnerabilities for BGP can be categorised as relating to the
security of the transport protocol itself, or to the compromising of
individual routers and the data they handle. This document examines
the issues for the transport protocol, while the SIDR Working Group
(WG) looks at ways to sign and secure the data exchanged in BGP as
described in An Infrastructure to Support Secure Internet Protocol
[RFC6480].
Jethanandani, et al. Expires October 10, 2013 [Page 6]
Internet-Draft BGP, LDP, PCEP and MSDP Analysis April 2013
2.4. LDP
Security Framework for MPLS and GMPLS Networks [RFC5920] outlines
security aspects that are relevant in the context of MPLS and GMPLS.
It describes the security threats, the related defensive techniques,
and the mechanism for detection and reporting.
Section 5 of LDP [RFC5036] states that LDP is subject to two
different types of attacks: spoofing, and denial of service attacks.
2.4.1. Spoofing attacks
A spoofing attack against LDP can occur both during the discovery
phase and during the session communication phase.
2.4.1.1. Discovery exchanges using UDP
Label Switching Routers (LSRs) indicate their willingness to
establish and maintain LDP sessions by periodically sending Hello
messages. Reception of a Hello message serves to create a new "Hello
adjacency", if one does not already exist, or to refresh an existing
one.
There are two variants of the discovery mechanism. A Basic Discovery
mechanism that is used to discover LSR neighbors that are directly
connected at the link level and a Extended Discovery mechanism that
is used by LSRs that are more than one hop away.
Unlike all other LDP messages, the Hello messages are sent using UDP.
This means that they cannot benefit from the security mechanisms
available with TCP. LDP [RFC5036] does not provide any security
mechanisms for use with Hello messages except for some configuration
which may help protect against bogus discovery events. These
configurations include directly connected links and interfaces.
Routers that do not use directly connected links have to use Extended
Discovery mechanism, and will not be able to use configuration to
protect against bogus discovery events.
Spoofing a Hello packet for an existing adjacency can cause the
adjacency to time out and result in termination of the associated
session. This can occur when the spoofed Hello message specifies a
small Hold Time, causing the receiver to expect Hello messages within
this interval, while the true neighbor continues sending Hello
messages at the lower, previously agreed to frequency.
Spoofing a Hello packet can also cause the LDP session to be
terminated. This can occur when the spoofed Hello specifies a
different Transport Address from the previously agreed one between
Jethanandani, et al. Expires October 10, 2013 [Page 7]
Internet-Draft BGP, LDP, PCEP and MSDP Analysis April 2013
neighbors. Spoofed Hello messages are observed and reported as real
problem in production networks.
2.4.1.2. Session communication using TCP
LDP like other TCP based routing protocols specifies use of the TCP
MD5 Signature Option to provide for the authenticity and integrity of
session messages. As stated in section 2.1 of this document and in
section 2.9 of LDP [RFC5036], MD5 authentication is considered too
weak for this application as outlined in MD5 and HMAC-MD5 Security
Considerations [RFC6151]. It also does not support algorithm
agility. A stronger hashing algorithm e.g SHA1, which is supported
by TCP-AO [RFC5925] could be deployed to take care of the weakness.
Alternatively, one could move to using TCP-AO which provides for
stronger MAC algorithms, makes it easier to setup manual keys and
protects against replay attacks.
2.4.2. Denial of Service Attacks
LDP is subject to Denial of Service (DoS) attacks both in its
discovery mode and in session mode. These are documented in
Section 5.3 of LDP [RFC5036].
2.5. PCEP
For effective selection by PCCs, a PCC needs to know the location of
PCEs in its domain along with some information relevant for PCE
selection. Such PCE information could be learned through manual
configuration, on each PCC, along with their capabilities or
automatically through a PCE discovery mechanism as outlined in
Requirements for PCE Discovery [RFC4674].
Attacks on PCEP [RFC5440] may result in damage to active networks.
These include computation responses, which if changed can cause
protocols like RSVP-TE [RFC3209] to setup sub-optimal or
inappropriate LSPs. In addition, PCE itself can attacked by a
variety of DoS attacks. Such attacks can cause path computations to
be supplied too slowly to be of any value particularly as it relates
to recovery or establishment of LSPs.
Finally, PCE discovery as outlined in OSPF Protocol Extensions for
PCE Discovery [RFC5088] and IS-IS Protocol Extensions for PCE
Discovery [RFC5089] is a significant feature for the successful
deployment of PCEP in large networks. These mechanisms allow PCC to
discover the existence of PCEs within the network. If the discovery
mechanism is compromised, it will impair the ability of the nodes to
function as described below.
Jethanandani, et al. Expires October 10, 2013 [Page 8]
Internet-Draft BGP, LDP, PCEP and MSDP Analysis April 2013
As RFC 5440 states, PCEP which makes use of TCP as a transport, could
be the target of the following attacks:
o Spoofing (PCC or PCE implementation)
o Snooping (message interception)
o Falsification
o Denial of Service
In inter-Autonomous Systems (AS) scenarios where PCE-to-PCE
communication is required, attacks may be particularly significant
with commercial as well as service-level agreement implications.
Additionally, snooping of PCEP requests and responses may give an
attacker information about the operation of the network. By viewing
the PCEP messages an attacker can determine the pattern of service
establishment in the network, and can know where traffic is being
routed, thereby making the network susceptible to targeted attacks
and the data within specific LSPs vulnerable.
Ensuring PCEP communication privacy is of key importance, especially
in an inter-AS context, where PCEP communication end-points do not
reside in the same AS. An attacker that intercepts a PCE message
could obtain sensitive information related to computed paths and
resources.
At the time PCEP was documented in [RFC5440], TCP-AO had not been
fully specified. Therefore, [RFC5440] mandates that PCEP
implementations include support for TCP-MD5, and that use of the
function should be configurable by the operator. [RFC5440] also
describes the vulnerabilities and weaknesses of TCP-MD5 as noted in
this document. [RFC5440] goes on to state that PCEP implementations
should include support for TCP-AO as soon as that specification is
complete. Since TCP-AO [RFC5925] has now been published, new PCEP
implementation should fully support TCP-AO.
2.6. MSDP
Similar to BGP and LDP, Multicast Source Distribution Protocol (MSDP)
uses TCP MD5 [RFC2385] to protect TCP sessions via the TCP MD5
option. But with a weak MD5 authentication, TCP MD5 is not
considered strong enough for this application. It also does not
support algorithm agility.
MSDP also advocates imposing a limit on number of source address and
group addresses (S,G) that can be cached within the protocol and
Jethanandani, et al. Expires October 10, 2013 [Page 9]
Internet-Draft BGP, LDP, PCEP and MSDP Analysis April 2013
thereby mitigate state explosion due to any denial of service and
other attacks.
3. Optimal State for BGP, LDP, PCEP, and MSDP
The ideal state of the security method for BGP, LDP, PCEP and MSDP
protocols are when they can withstand any of the known types of
attacks. The protocols also need to support algorithm agility, i.e.
they must not hardwire themselves to one algorithm.
Additionally, Key Management Protocol (KMP) for the routing sessions
should help negotiate unique, pair wise random keys without
administrator involvement. It should also negotiate Security
Association (SA) parameters required for the session connection,
including key life times. It should keep track of those lifetimes
and negotiate new keys and parameters before they expire and do so
without administrator involvement. In the event of a breach,
including when an administrator with knowledge of the keys leaves the
company, the keys should be changed immediately.
The DoS attacks for BGP, LDP, PCEP and MSDP are attacks to the
transport protocol, TCP for the most part and UDP in case of
discovery phase of LDP. TCP and UDP should be able to withstand any
of DoS scenarios by dropping packets that are attack packets in a way
that does not impact legitimate packets.
The routing protocols should provide a mechanism to authenticate the
routing information carried within the payload and administrators
should enable it.
3.1. LDP
To harden LDP against its current vulnerability to spoofing attacks,
LDP needs to be upgraded such that an implementation is able to
determine the authenticity of the neighbors sending the Hello
message.
Labels are similar to routing information which is distributed in the
clear. However, there is currently no requirement that the labels be
encrypted. And stated before, is currently out of scope of this
document.
Similarly, it is important to ensure that routers exchanging labels
are mutually authenticated, and that there are no rogue peers or
unauthenticated peers that can compromise the stability of the
network.
Jethanandani, et al. Expires October 10, 2013 [Page 10]
Internet-Draft BGP, LDP, PCEP and MSDP Analysis April 2013
4. Gap Analysis for BGP, LDP, PCEP and MSDP
This section outlines the differences between the current state of
the security methods for routing protocols, and the desired state of
the security methods as outlined in section 4.2 of KARP Design
Guidelines [RFC6518]. As that document states, these routing
protocols fall into the category of one-to-one peering messages and
will use peer keying protocol. It covers issues that are common to
the four protocols in this section, leaving protocol specific issues
to sub-sections.
At a transport level these routing protocols are subject to some of
the same attacks that TCP applications are subject to. These include
DoS and spoofing attacks. Internet Denial-of-Service Considerations
[RFC4732] outlines some solutions. Defending TCP Against Spoofing
Attacks [RFC4953] recommends ways to prevent spoofing attacks. In
addition, the recommendations in [RFC5961] should also be followed
and implemented to strengthen TCP.
Routers lack comprehensive key management and keys derived from it
that they can use to authenticate data. As an example TCP-AO
[RFC5925], talks about coordinating keys derived from Master Key
Table (MKT) between endpoints, but the MKT itself has to be
configured manually or through an out of band mechanism. Also TCP-AO
does not address the issue of connectionless reset, as it applies to
routers that do not store MKT across reboots.
Authentication, integrity protection, and encryption all require the
use of keys by sender and receiver. An automated KMP therefore has
to include a way to distribute key material between two end points
with little or no administration overhead. It has to cover automatic
key rollover. It is expected that authentication will cover the
packet, i.e. the payload and the TCP header and will not cover the
frame i.e. the link layer 2 header.
There are two methods of automatic key rollover. Implicit key
rollover can be initiated after certain volume of data gets exchanged
or when a certain time has elapsed. This does not require explicit
signaling nor should it result in a reset of the TCP connection in a
way that the links/adjacencies are affected. On the other hand,
explicit key rollover requires an out of band key signaling
mechanism. It can be triggered by either side and can be done
anytime a security parameter changes e.g. an attack has happened, or
a system administrator with access to the keys has left the company.
An example of this is IKEv2 [RFC5996], but it could be any other new
mechanisms also.
Jethanandani, et al. Expires October 10, 2013 [Page 11]
Internet-Draft BGP, LDP, PCEP and MSDP Analysis April 2013
As stated earlier TCP-AO [RFC5925], and its accompanying document
Crypto Algorithms for TCP-AO [RFC5926], requires that two MAC
algorithms be supported, and they are HMAC-SHA-1-96 as specified in
HMAC [RFC2104], and AES-128-CMAC-96 as specified in NIST-SP800-38B
[NIST-SP800-38B]. Therefore, TCP-AO meets the algorithm agility
requirement.
There is a need to protect authenticity and validity of the routing/
label information that is carried in the payload of the sessions.
However, that is outside the scope of this document and is being
addressed by SIDR WG. Similar mechanisms could be used for intra-
domain protocols.
Finally, replay protection is required. The replay mechanism needs
to be sufficient to prevent an attacker from creating a denial of
service or disrupting the integrity of the routing protocol by
replaying packets. It is important that an attacker not be able to
disrupt service by capturing packets and waiting for replay state to
be lost.
4.1. LDP
As described in LDP [RFC5036], the threat of spoofed Basic Hellos can
be reduced by only accepting Basic Hellos on interfaces that LSRs
trust, employing GTSM [RFC5082] and ignoring Basic Hellos not
addressed to the "all routers on this subnet" multicast group.
Spoofing attacks via Targeted Hellos are potentially a more serious
threat. An LSR can reduce the threat of spoofed Extended Hellos by
filtering them and accepting Hellos from sources permitted by an
access lists. However, performing the filtering using access lists
requires LSR resource, and the LSR is still vulnerable to the IP
source address spoofing. Spoofing attacks can be solved by being
able to authenticate the Hello messages, and an LSR can be configured
to only accept Hello messages from specific peers when authentication
is in use.
LDP Hello Cryptographic Authentication
[draft-zheng-mpls-ldp-hello-crypto-auth-04] suggest a new
Cryptographic Authentication TLV that can be used as an
authentication mechanism to secure Hello messages.
4.2. PCEP
Path Computation Element (PCE) discovery according to its RFC
[RFC5440], is a significant feature for the successful deployment of
PCEP in large networks. This mechanism allows a Path Computation
Client (PCC) to discover the existence of suitable PCEs within the
network without the necessity of configuration. It should be obvious
Jethanandani, et al. Expires October 10, 2013 [Page 12]
Internet-Draft BGP, LDP, PCEP and MSDP Analysis April 2013
that, where PCEs are discovered and not configured, the PCC cannot
know the correct key to use. There are different approaches to
retain some aspect of security, but all of them require use of a keys
and a keying mechanism, the need for which has been discussed above.
5. Transition and Deployment Considerations
As stated in KARP Design Guidelines [RFC6518], it is imperative that
the new authentication, security mechanisms defined, and key
management protocol support incremental deployment, as it is not
feasible to deploy the new routing protocol authentication mechanism
overnight.
Typically, authentication and security in a peer-to-peer protocol
requires that both parties agree to the mechanisms that will be used.
If an agreement is not reached the setup of the new mechanism will
fail or will be deferred. Upon failure, the routing protocols can
fallback to the mechanisms that were already in place e.g. use
static keys if that was the mechanism in place. The fallback should
be configurable on a per-node or per-interface. It is usually not
possible for one end to use the new mechanism while the other end
uses the old. Policies can be put in place to retry upgrading after
a said period of time, so a manual coordination is not required.
If the automatic KMP requires use of Public Key Infrastructure
Certificates [RFC5280] to exchange key material, the required
Certificate Authority (CA) root certificates may need to be installed
to verify authenticity of requests initiated by a peer. Such a step
does not require coordination with the peer except to decide what CA
authority will be used.
6. Security Considerations
This section describes security considerations that BGP, LDP, PCEP
and MSDP should try to meet.
As with all routing protocols, they need protection from both on-path
and off-path blind attacks. A better way to protect them would be
with per-packet protection using a cryptographic MAC. In order to
provide for the MAC, keys are needed.
The routing protocols need to support algorithm agility, i.e. they
must not hardwire themselves to one algorithm.
Once keys are used, mechanisms are required to support key rollover.
This should cover both manual and automatic key rollover. Multiple
approaches could be used. However, since the existing mechanisms
provide a protocol field to identify the key as well as management
Jethanandani, et al. Expires October 10, 2013 [Page 13]
Internet-Draft BGP, LDP, PCEP and MSDP Analysis April 2013
mechanisms to introduce and retire new keys, focusing on the existing
mechanism as a starting point is prudent.
Furthermore, it is strongly suggested that these routing protocols
need to support algorithm agility. It has been proven that
algorithms weaken over time. Supporting algorithm agility assists in
smooth transition from old to new algorithms.
7. IANA Considerations
None.
8. Acknowledgements
We would like to thank Brian Weis for encouraging us to write this
draft, and to Anantha Ramaiah and Mach Chen for providing comments on
it.
9. References
9.1. Normative References
[RFC5926] Lebovitz, G. and E. Rescorla, "Cryptographic Algorithms
for the TCP Authentication Option (TCP-AO)", RFC 5926,
June 2010.
[RFC6518] Lebovitz, G. and M. Bhatia, "Keying and Authentication for
Routing Protocols (KARP) Design Guidelines", RFC 6518,
February 2012.
9.2. Informative References
[NIST-SP800-38B]
Dworking, , "Recommendation for Block Cipher Modes of
Operation: The CMAC Mode for Authentication", May 2005.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104, February
1997.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2385] Heffernan, A., "Protection of BGP Sessions via the TCP MD5
Signature Option", RFC 2385, August 1998.
Jethanandani, et al. Expires October 10, 2013 [Page 14]
Internet-Draft BGP, LDP, PCEP and MSDP Analysis April 2013
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC3618] Fenner, B. and D. Meyer, "Multicast Source Discovery
Protocol (MSDP)", RFC 3618, October 2003.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
[RFC4595] Maino, F. and D. Black, "Use of IKEv2 in the Fibre Channel
Security Association Management Protocol", RFC 4595, July
2006.
[RFC4674] Le Roux, J.L., "Requirements for Path Computation Element
(PCE) Discovery", RFC 4674, October 2006.
[RFC4732] Handley, M., Rescorla, E., IAB, "Internet Denial-of-
Service Considerations", RFC 4732, December 2006.
[RFC4948] Andersson, L., Davies, E., and L. Zhang, "Report from the
IAB workshop on Unwanted Traffic March 9-10, 2006", RFC
4948, August 2007.
[RFC4953] Touch, J., "Defending TCP Against Spoofing Attacks", RFC
4953, July 2007.
[RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP
Specification", RFC 5036, October 2007.
[RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., and C.
Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, October 2007.
[RFC5088] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
"OSPF Protocol Extensions for Path Computation Element
(PCE) Discovery", RFC 5088, January 2008.
[RFC5089] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
"IS-IS Protocol Extensions for Path Computation Element
(PCE) Discovery", RFC 5089, January 2008.
Jethanandani, et al. Expires October 10, 2013 [Page 15]
Internet-Draft BGP, LDP, PCEP and MSDP Analysis April 2013
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008.
[RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element
(PCE) Communication Protocol (PCEP)", RFC 5440, March
2009.
[RFC5920] Fang, L., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, July 2010.
[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, June 2010.
[RFC5961] Ramaiah, A., Stewart, R., and M. Dalal, "Improving TCP's
Robustness to Blind In-Window Attacks", RFC 5961, August
2010.
[RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
"Internet Key Exchange Protocol Version 2 (IKEv2)", RFC
5996, September 2010.
[RFC6039] Manral, V., Bhatia, M., Jaeggli, J., and R. White, "Issues
with Existing Cryptographic Protection Methods for Routing
Protocols", RFC 6039, October 2010.
[RFC6151] Turner, S. and L. Chen, "Updated Security Considerations
for the MD5 Message-Digest and the HMAC-MD5 Algorithms",
RFC 6151, March 2011.
[RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support
Secure Internet Routing", RFC 6480, February 2012.
[RFC6863] Hartman, S. and D. Zhang, "Analysis of OSPF Security
According to the Keying and Authentication for Routing
Protocols (KARP) Design Guide", RFC 6863, March 2013.
[draft-zheng-mpls-ldp-hello-crypto-auth-04]
Zheng, , "LDP Hello Cryptographic Authentication", May
2012.
Authors' Addresses
Jethanandani, et al. Expires October 10, 2013 [Page 16]
Internet-Draft BGP, LDP, PCEP and MSDP Analysis April 2013
Mahesh Jethanandani
Ciena Corporation
1741 Technology Drive
San Jose, CA 95110
USA
Phone: + (408) 436-3313
Email: mjethanandani@gmail.com
Keyur Patel
Cisco Systems, Inc
170 Tasman Drive
San Jose, CA 95134
USA
Phone: +1 (408) 526-7183
Email: keyupate@cisco.com
Lianshu Zheng
Huawei Technologies
China
Phone: +86 (10) 82882008
Email: vero.zheng@huawei.com
Jethanandani, et al. Expires October 10, 2013 [Page 17]
