Analysis of RSVP-TE Security According to KARP Design Guide
draft-mahesh-karp-rsvp-te-analysis-00.txt

Abstract

This document analyzes RSVP-TE according to guidelines set forth in section 4.2 of KARP Design Guidelines [RFC6518].

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Table of Contents

• 1. Introduction
• 1.1. Abbreviations
• 2. Current Security State of RSVP-TE
• 3. Gap Analysis for RSVP-TE
• 4. IANA Requirements
• 5. Acknowledgements
• 6. References
• 6.1. Normative References
• 6.2. Informative References
• Authors' Addresses

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.

This document performs the initial analysis of the current state of RSVP-TE according to the requirements of KARP Design Guidelines [RFC6518]. This draft builds on several previous analysis efforts into routing security. The OPSEC working group put together Issues with existing Cryptographic Protection Methods for Routing Protocols [RFC6039] an analysis of cryptographic issues with routing protocols and Analysis of BGP, LDP, PCEP, and MSDP Issues According to KARP Design Guide [draft-ietf-karp-routing-tcp-analysis] which is a analysis of the four routing protocols.

Section 2 looks at the current security state of RSVP-TE. Section 3 does a analysis of the gap between the existing and the optimal security state of the protocol and suggest some areas where we need to improve.

1.1. Abbreviations

BGP - Border Gateway Protocol

DoS - Denial of Service

KARP - Key and Authentication for Routing Protocols

KDF - Key Derivation Function

KEK - Key Encrypting Key

KMP - Key Management Protocol

LDP - Label Distribution Protocol

LSP - Label Switch Path

MAC - Message Authentication Code

MKT - Master Key Tuple

MPLS - Multi Protocol Label Switching

MSDP - Multicast Source Distribution Protocol

MD5 - Message Digest algorithm 5

PCEP - Path Computation Element Protocol

RSVP - Resource reSerVation Protocol

TCP - Transmission Control Protocol

UDP - User Datagram Protocol

2. Current Security State of RSVP-TE

This section looks at RSVP-TE and the underlying transport protocol and key mechanisms built for the protocol.

RSVP-TE is an extension of the RSVP protocol for traffic engineering. It supports the reservation of resources across IP networks and is used for establishing Multi Protocol Label Switching (MPLS) Label Switch Paths (LSPs). RSVP-TE signaling is used to establish both intra- and inter-domain TE LSPs. It is RSVP Cryptographic Authentication [RFC2747] that describes the format and use of RSVP's INTEGRITY objects to provide hop-by-hop integrity and authentication of RSVP messages. RSVP-TE which uses some of the same formats therefore can make use of some of the same authentication mechanisms. The rest of the document will therefore focus on current state of security for RSVP. Currently, there is no security approach specified for RSVP-TE particularly. However, the security mechanisms for RSVP RSVP Cryptographic Authentication [RFC2747] can be taken advantage of to provide the security protection for the RSVP-TE message transportation.

There is a requirement that RSVP-TE headers and payload be authenticated. There is no requirement that they be encrypted and that work is outside the scope of KARP WG. RSVP Cryptographic Authentication [RFC2747] outlines the use HMAC-MD5. When using HMAC-MD5, the length of the keyed digests is 128 bits. In these cases RSVP checksum can be disabled in lieu of message digest.

RSVP uses 64 bit monotonically increasing sequence numbers to prevent against replay attacks. The sequence number space is large enough to guarantee that a sequence number will never reach its maximum and roll back within a reasonable long period.

To address the issue of out-of-order message delivery, the solution allows administrators to specify a sequence number window corresponding to the worst case reordering behavior. Instead of requiring the sequence number of an incoming packet to be strictly larger than the ones previously received, a packet will be accepted if its sequence number is within the window. The solution provides three approaches to generate unique monotonically increasing sequence numbers across a failure or a restart. The solutions include:

1. Maintaining sequence numbers in stable memory
2. Introducing the data from a local time clock into the generation of sequence numbers after a restart
3. Introducing the timing information from a Network Recovered Clock into the generation of sequence numbers after a restart.

In addition, a handshake is defined for a receiver to get the latest value of a sequence number. Therefore, this solution is effective in addressing the issues caused by the rollback of sequence numbers across a system restart or failure. However, when a router uses the approach to generating sequence numbers with the time information from NTP, an attacker may try to deceive the router to generate a sequence number which is less than the sequence numbers it used to have, by sending replayed or foiled NTP information.

The protocol states that manual keying should be supported and states the need for a key management protocol to distribute keys. It even states that the Key Identifier be the hook between RSVP and the key management protocol. But it deliberately excludes defining a integrated key management protocol technique in the draft. However, it does define a key lifetime that should be recorded for all systems using values such as KeyStartValid and KeyEndValid. It even advises that the keys should be changed on a regular basis and that multiple keys should be used to transition from one key to another.

RSVP does not explicitly mention Denial of Service (DoS) attacks and how to prevent against it. However, RSVP-TE does know the peers that it should be communicating with and can therefore accept packets from known hosts only.

3. Gap Analysis for RSVP-TE

This section outlines the differences between the current state of RSVP-TE and the desired state as outlined in sections 4.1 and 4.2 of KARP Design Guidelines [RFC6518].

In RSVP Cryptographic Authentication [RFC2747], only the usage of MD5 to generate digests for RSVP-TE messages is mentioned. In order to fulfill the requirement of supporting strong algorithms, at least the support of SHA-2 needs to be provided.

In addition, in RSVP Cryptographic Authentication [RFC2747], three approaches to generating unique monotonically increasing sequence numbers across a failure and restart are introduced, but no approach is mandated. However, as mentioned above, when using Network Recovered Clocks into the generation of sequence numbers, the capability of RSVP-TE in tolerating inter-connection replay attacks will largely rely on the security of network timing protocols. Therefore, in future this approach should not be recommended.

4. IANA Requirements

None

5. Acknowledgements

6. References

6.1. Normative References

6.2. Informative References

Authors' Addresses