Context

I installed an openWRT system, I want to connect to SSH on it.

After a fresh install only telnet is available.

One could always use telnet through the wan interface, but it's not a good choice

Dropbear

Dropbear is the lightweight SSH server for the situation.

It's installed by default, we just have to configure it

Allow TCP port 22 from wan (/etc/config/firewall)

The default behaviour is to REJECT any INPUT from wan:

      
        config zone
        option name             wan
        option input    REJECT
        option output   ACCEPT
        option forward  REJECT
        option masq             1
        option mtu_fix  1
That is the POLICY (default behaviour).

We are going to add a specific "rule" to allow TCP/22

        config rule
        option src              wan
        option proto            tcp
        option dest_port        22
        option target           ACCEPT
        option family   ipv4

Don't forget to setup a password for root, and we're done!