Set up a ssh tunnel only user
In order to give someone access to hosts that are available only by ssh "bouncing" (
add a user for this specific purpose.
We have an internal openstack where instances get IPs on per-tenant networks. Each tenant has a 'bastion' host that has a "public" ip (floating ip). You can access other instances by bouncing through the bastion. From time to time I want to let someone else into an instance. This could be done either with:
a.) just give them shell access to the bastion and let them hop through. Sharing an unrestricted shell account on my bastion is less than ideal. b.) assign a floating/"public" IP to the instance so they could go directly in. Floating IPs are limited, so this is less than ideal.
So instead, I have set up a single user as described here that can only be used for ProxyJump. It allows others proxied access to my instances but without granting them full shell access.
Heres how you can set this up.
Pick a name
We match by
Match Userhere, but could also use
Match Group. Add the following to your
/etc/ssh/sshd_config, and make sure to adjust
Match User sshjump AllowAgentForwarding no AllowTcpForwarding yes X11Forwarding no PermitTunnel no GatewayPorts no ForceCommand echo 'This account can only be used for ProxyJump (ssh -J)'
Then, restart sshd:
sudo systemctl restart ssh
Add the user
The shell can actually be
/bin/true, but then you will not get the
ForceCommanddirective to do anything, which can be useful for a user connecting.
sudo useradd "$JUMP_USER" "--home-dir=/home/$JUMP_USER" --create-home --shell=/bin/rbash # if you want to, set a password. sudo passwd "$JUMP_USER"
Add some ssh keys
sudo -Hu "$JUMP_USER" ssh-import-id smoser
Try it out
assuming you want to give access to
email@example.com your host is
ssh -J sshjump@jumphost firstname.lastname@example.org
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