[Bug 1570788] Re: Makes mDNS ddos amplification attack possible

[Marcus Karlsson]

Apparently that wasn't the case, from another host I was able to
reproduce it with IPv4 as well.

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Title:
  Makes mDNS ddos amplification attack possible

Status in avahi package in Ubuntu:
  New

Bug description:
  Apparently mDNS can be used for ddos amplification, see for instance https://mdns.shadowserver.org/ and https://www.us-cert.gov/ncas/alerts/TA14-017A
   
  Steps to reproduce:

  dig @rusk.hpc2n.umu.se -p 5353 -t ptr _services._dns-sd._udp.local

  The response is supposedly 2-10 times the size of the query, making
  for a moderate but noticeable amplification.

  Workarounds are easy, but not responding outside localnet by default
  is probably reasonable for mDNS.

  Reproduced at at least trusty and precise, would be very surprised if
  it didn't also apply to xenial but I left my xenial laptop at home
  today. :)

  ProblemType: Bug
  DistroRelease: Ubuntu 12.04
  Package: avahi-daemon 0.6.30-5ubuntu2.1
  ProcVersionSignature: Ubuntu 3.13.0-83.127~precise1-generic 3.13.11-ckt35
  Uname: Linux 3.13.0-83-generic x86_64
  NonfreeKernelModules: openafs
  ApportVersion: 2.0.1-0ubuntu17.13
  Architecture: amd64
  Date: Fri Apr 15 12:12:22 2016
  MarkForUpload: True
  ProcEnviron:
   LANGUAGE=en_US:en
   TERM=xterm
   PATH=(custom, no user)
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: avahi
  UpgradeStatus: No upgrade log present (probably fresh install)

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