Measures against cache poisoning attacks using IP fragmentation in DNS
draft-fujiwara-dnsop-fragment-attack-01

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Network Working Group                                        K. Fujiwara
Internet-Draft                                                      JPRS
Intended status: Informational                            March 01, 2019
Expires: September 2, 2019

 Measures against cache poisoning attacks using IP fragmentation in DNS
                draft-fujiwara-dnsop-fragment-attack-01

Abstract

   Researchers proposed practical DNS cache poisoning attacks using IP
   fragmentation.  This document shows feasible and adequate measures at
   full-service resolvers and authoritative servers against these
   attacks.  To protect resolvers from these attacks, avoid
   fragmentation (limit requestor's UDP payload size to 1220/1232), drop
   fragmented UDP DNS responses and use TCP at resolver side.  To make a
   domain name robust against these attacks, limit EDNS0 Responder's
   maximum payload size to 1220, set DONTFRAG option to DNS response
   packets and use good random fragmentation ID at authoritative server
   side.

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Fujiwara                Expires September 2, 2019               [Page 1]
Internet-Draft               fragment-attack                  March 2019

   carefully, as they describe your rights and restrictions with respect
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Methodology of the attack . . . . . . . . . . . . . . . . . .   3
   3.  Current status  . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Possible measures . . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  Use DNSSEC  . . . . . . . . . . . . . . . . . . . . . . .   6
     4.2.  Limit requestor's UDP payload size to 1220/1232 on IPv6 .   6
     4.3.  Limit requestor's UDP payload size to 512 . . . . . . . .   6
     4.4.  Set IP_DONTFRAG / IPv6 DONTFRAG at authoritative servers    7
     4.5.  Drop path MTU discovery or filter ICMP related to path
           MTU discovery . . . . . . . . . . . . . . . . . . . . . .   7
     4.6.  Drop all fragmented packets . . . . . . . . . . . . . . .   7
     4.7.  Drop fragmented UDP DNS responses at full-service
           resolvers . . . . . . . . . . . . . . . . . . . . . . . .   7
     4.8.  Use TCP only  . . . . . . . . . . . . . . . . . . . . . .   7
     4.9.  Use good randomness for Fragmentation Identification
           field . . . . . . . . . . . . . . . . . . . . . . . . . .   8
   5.  Proposal  . . . . . . . . . . . . . . . . . . . . . . . . . .   8
   6.  Example firewall configuration  . . . . . . . . . . . . . . .   8
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   9
   10. Change History  . . . . . . . . . . . . . . . . . . . . . . .   9
     10.1.  00 . . . . . . . . . . . . . . . . . . . . . . . . . . .   9
     10.2.  01 . . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  10
     11.2.  Informative References . . . . . . . . . . . . . . . . .  10
   Appendix A.  How to know path MTU size  . . . . . . . . . . . . .  11
   Appendix B.  How to generate crafted ICMP packets . . . . . . . .  11
     B.1.  Example of crafted ICMP Need Fragmentation and DF set
           packet  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     B.2.  Example of crafted ICMPv6 Packet Too Big  . . . . . . . .  12
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction
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