Protecting Internet Key Exchange (IKE) Implementations from Distributed Denial of Service Attacks
draft-ietf-ipsecme-ddos-protection-00

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Last updated 2014-10-27
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IPSecME Working Group                                             Y. Nir
Internet-Draft                                               Check Point
Intended status: Standards Track                        October 27, 2014
Expires: April 30, 2015

Protecting Internet Key Exchange (IKE) Implementations from Distributed
                       Denial of Service Attacks
                 draft-ietf-ipsecme-ddos-protection-00

Abstract

   This document recommends implementation and configuration best
   practices for Internet-connected IPsec Responders, to allow them to
   resist Denial of Service and Distributed Denial of Service attacks.
   Additionally, the document introduces a new mechanism called "Client
   Puzzles" that help accomplish this task.

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 April 30, 2015.

Copyright Notice

   Copyright (c) 2014 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
   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

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions Used in This Document . . . . . . . . . . . .   3
   2.  The Vulnerability . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Puzzles . . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Retention Periods for Half-Open SAs . . . . . . . . . . . . .   7
   5.  Rate Limiting . . . . . . . . . . . . . . . . . . . . . . . .   8
   6.  Plan for Defending a Responder  . . . . . . . . . . . . . . .   9
   7.  Operational Considerations  . . . . . . . . . . . . . . . . .  11
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     10.2.  Informative References . . . . . . . . . . . . . . . . .  12
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   The IKE_SA_INIT Exchange described in section 1.2 of [RFC7296]
   involves the Initiator sending a single message.  The Responder
   replies with a single message and also allocates memory for a
   structure called a half-open IKE SA (Security Association).  This
   half-open SA is later authenticated in the IKE_AUTH Exchange, but if
   that IKE_AUTH request never comes, the half-open SA is kept for an
   unspecified amount of time.  Depending on the algorithms used and
   implementation, such a half-open SA will use from around 100 bytes to
   several thousands bytes of memory.

   This creates an easy attack vector against an Internet Key Exchange
   (IKE) Responder.  Generating the Initial request is cheap, and
   sending multiple such requests can either cause the Responder to
   allocate too much resources and fail, or else if resource allocation
   is somehow throttled, legitimate Initiators would also be prevented
   from setting up IKE SAs.

   An obvious defense, which is described in Section 5, is limiting the
   number of half-open SAs opened by a single peer.  However, since all
   that is required is a single packet, an attacker can use multiple
   spoofed source IP addresses.

   Section 2.6 of RFC 7296 offers a mechanism to mitigate this DoS
   attack: the stateless cookie.  When the server is under load, the
   Responder responds to the Initial request with a calculated
   "stateless cookie" - a value that can be re-calculated based on

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