Forward incoming ssh connections for a single user into containers

Very simple example which demonstrates the concept..

My recomendation for the LXD host configuration for /etc/ssh/sshd_config are:-

  PasswordAuthentication no
  PermitUserEnvironment yes

Then add a 'sandbox' user on your Linux server...

Then install the ~sandbox/bin/gw, ~sandbox/etc/notice and a ~sandbox/.ssh/authorised_keys Limitation with this method is a key can only be used to forward to a single container. See the authorized_keys.example for the command="$HOME/bin/gw ssh-rsa syntax.

Make sure the permissions/ownership are correct..

  #chown -R sandbox:sandbow ~sandbox
  #chmod -R g-rewx,o-rwx ~ssandbox/bin

The containers I've been building are Ubuntu 20.10 they don't need to run ssh to work nor do they need networking.

e.g.

   #lxc launch ubuntu:20.10 container-X

Assuming thats all installed and working some examples of usage:-

ssh -i ~/.ssh/priv.key sandbox@<host address/ip>
sftp -i ~/.ssh/priv.key sandbox@<host address/ip>
scp -i ~/.ssh/priv.key /etc/hosts sandbox@<host address/ip>: