ssh-zone-handler 0.4.0

SSH commands to provide Secondary DNS self-service.

SSH Zone Handler

• You run your own DNS server(s), providing Secondary DNS to others?
• You want to provide your DNS tenants with a bit of debugging self-service?
• You like SSH, but you don't want to grant people not-you full shell access?

If so, then this might just be the tool for you.

Usage

Usage example, based on local Multipass setup.

$ make vm-create

$ alias ssh='ssh -F devel/.dynamic/ssh_conf'

$ ssh zones@szh-named help
usage: command [ZONE]

help                 Display this help message
list                 List available zones
dump ZONE            Output full content of ZONE
logs ZONE1 [ZONE2]   Output the last five days' log entries for ZONE(s)
retransfer ZONE      Trigger a full (AXFR) retransfer of ZONE
$

$ ssh zones@szh-named list
example.com
example.net
$

$ ssh zones@szh-named logs example.net
Apr 28 17:52:00 szh-named named[2821]: zone example.net/IN: Transfer started.
Apr 28 17:52:00 szh-named named[2821]: transfer of 'example.net/IN' from 192.168.63.10#53: connected using 192.168.63.10#53
Apr 28 17:52:00 szh-named named[2821]: zone example.net/IN: transferred serial 26281038
Apr 28 17:52:00 szh-named named[2821]: transfer of 'example.net/IN' from 192.168.63.10#53: Transfer status: success
Apr 28 17:52:00 szh-named named[2821]: transfer of 'example.net/IN' from 192.168.63.10#53: Transfer completed: 1 messages, 6 records, 190 bytes, 0.008 secs (23750 bytes/sec) (serial 26281038)
$

Setup instructions

Create user accounts

adduser --comment "SSH Zone Handler journalctl sudo access" --ingroup systemd-journal --system szh-logviewer
adduser --comment "SSH Zone Handler OpenSSH AuthorizedKeysCommandUser" --system szh-sshdcmd
adduser --comment "SSH Zone Handler shared login user" --disabled-password  zones

Create configuration

Create /etc/zone-handler.yaml based on either zone-handler.yaml.bind.example or zone-handler.yaml.knot.example.

Install application

python3 -m venv /opt/ssh-zone-handler
/opt/ssh-zone-handler/bin/pip3 install ssh-zone-handler

Generate sudoers rules

/opt/ssh-zone-handler/bin/szh-sudoers | EDITOR="tee" visudo -f /etc/sudoers.d/zone-handler

Configure sshd

Match User zones
     AuthorizedKeysFile none
     AuthorizedKeysCommandUser szh-sshdcmd
     AuthorizedKeysCommand /opt/ssh-zone-handler/bin/szh-sshkeys
     DisableForwarding yes
     PermitTTY no

Known limitations

• Might be Debian/Ubuntu distro specific