Secure BFD Sequence Numbers
draft-ietf-bfd-secure-sequence-numbers-07
Network Working Group M. Jethanandani
Internet-Draft Kloud Services
Updates: 5880 (if approved) S. Agarwal
Intended status: Standards Track Cisco Systems, Inc
Expires: June 19, 2021 A. Mishra
O3b Networks
A. Saxena
Ciena Corporation
A. Dekok
Network RADIUS SARL
December 16, 2020
Secure BFD Sequence Numbers
draft-ietf-bfd-secure-sequence-numbers-07
Abstract
This document describes a security enhancement for the sequence
number used in BFD control packets. This document updates RFC 5880.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on June 19, 2021.
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Internet-Draft Securing next sequence number December 2020
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2
3. Theory of operation . . . . . . . . . . . . . . . . . . . . . 2
4. Impact of using a hash . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
BFD [RFC5880] section 6.7 describes the use of monotonically
incrementing 32-bit sequence numbers for use in authentication of BFD
packets. While this method protects against simple replay attacks,
the monotonically incrementing sequence numbers are predictable and
vulnerable to more complex attack vectors. This document proposes
the use of non-monotonically-incrementing sequence numbers in the BFD
authentication section to enhance the security of BFD sessions.
Specifically, the document presents a method to generate pseudo-
random sequence numbers on the frame by algorithmically hashing
monotonically increasing sequence numbers. Since the monotonically
increasing sequence number does not appear on the wire, it is
difficult for a third party to launch a replay attack.
2. 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].
3. Theory of operation
Instead of inserting a monotonically, sometimes occasionally,
increasing sequence number in BFD control packets, the ciphertext
result from a symmetric key algorithm operation (Symmetric-key
algorithms require both the sender and the recipient of a message to
have the same shared secret key) is inserted. The result is
computed, using a shared key, on the sequence number. That
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