[Bug 1240912] Re: ssh produces superfluous key mismatch warning when network uses DHCP

[Robie Basak]

Thank you for reporting this bug and helping to make Ubuntu better.

I believe that this behaviour is by design, as designed by the upstream
authors. Additionally it can be turned off with the CheckHostIP option.

I'm not sure if it is a good idea to change the default of this option
in Ubuntu. Please seek consensus upstream in the first instance, or in
Debian or Ubuntu first.

Since there's no clear action we can take on this bug, the behaviour is
by design, it's just a warning, and the warning can be trivially
suppressed on your own system, I'm marking this bug as Invalid.

** Changed in: openssh (Ubuntu)
       Status: New => Invalid

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https://bugs.launchpad.net/bugs/1240912

Title:
  ssh produces superfluous key mismatch warning when network uses DHCP

Status in “openssh” package in Ubuntu:
  Invalid

Bug description:
  To replicate:
  1: In terminal type:
      ssh user at host1.local
  2: Type "yes" to add certificate to known hosts.
  3: Exit ssh
  4: In terminal type:
     ssh user at host2.local
  5: Type "yes", confirm certificate again.
  6: Shut down all computers on the network, wait until the router's DHCP cache has cleared, start up computers in such an order that host1.local and host2.local have each others' IP addresses when compared to before shutting down.
  7: In terminal type:
     ssh user at host1.local

  What should happen:
  ssh should accept the certificate automatically because it's the correct certificate for host1.local

  What actually happens:
  Warning: the ECDSA host key for 'host1.local' differs from the key for the IP address '192.168.1.104'
  Offending key for IP in /home/user/.ssh/known_hosts:2
  Matching host key in /home/user/.ssh/known_hosts:7

  ProblemType: Bug
  DistroRelease: Ubuntu 13.04
  Package: ssh 1:6.1p1-4
  ProcVersionSignature: Ubuntu 3.8.0-31.46-generic 3.8.13.8
  Uname: Linux 3.8.0-31-generic x86_64
  ApportVersion: 2.9.2-0ubuntu8.3
  Architecture: amd64
  Date: Thu Oct 17 18:21:11 2013
  InstallationDate: Installed on 2013-08-19 (58 days ago)
  InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424)
  MarkForUpload: True
  PackageArchitecture: all
  SourcePackage: openssh
  UpgradeStatus: No upgrade log present (probably fresh install)

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