[Bug 1698317] Re: AllowUsers *@*.local in /etc/ssh/sshd_config does not work

[Trent Lloyd]

If you want to block access to the local LAN only, then that is correct.

My best suggestion would be to secure your SSH and thus not worry so
much if it's accessed by some other host on the network.  If you
restrict it to one user, have a very secure password and/or SSH key only
then your attack surface is relatively limited.  But that's a personal
choice ultimately.

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https://bugs.launchpad.net/bugs/1698317

Title:
  AllowUsers *@*.local in /etc/ssh/sshd_config does not work

Status in avahi package in Ubuntu:
  Invalid
Status in openssh package in Ubuntu:
  Invalid

Bug description:
  I installed Ubuntu Mate 16.04 on two of my computers. The software has
  been brought uptodate to at least May 2017.

  They are both on my local wifi network and should both be using Zeroconf/Avahi/Bonjour.
  I have the same username on both machines.

  I copied /usr/share/doc/avahi-daemon/examples/ssh.service 
  to /etc/avahi/services
  $ sudo service avahi-daemon restart

  I installed sshd on "faustino"
  $ sudo apt-get install openssh-server 

  With the default /etc/ssh/sshd_config I can succesfully ssh to faustino thus
  $ ssh -v localhost			/* from faustino */
  $ ssh -v faustino.local		/* from faustino */
  $ ssh -v faustino.local		/* from the other computer */

  I modified /etc/ssh/sshd_config) to add
  LogLevel VERBOSE
  PermitRootLogin no
  AllowUsers  *@*.local

  $ sudo systemctl restart ssh

  Now I get, for example

  $ ssh faustino.local
  username at faustino.local's password: 
  Permission denied, please try again.

  That fails from the same machine, from another machine and if I try
  ssh localhost. All those worked before I put those directives in.

  I expected all attempts to ssh from .local addresses to work and all
  others to fail.

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