sshd support

[Informatic]

We are currently only supporting unauthenticated telnet-based remote access. We should prefer some safer solution by default - like SSH.

• Bundle static dropbear sshd binary with the app
• Figure out emergency situations (do we fall back to enabling telnetd in case homebrew channel gets removed, or do we copy over required binaries to some known location outside of /media/developer?)
• Authentication bootstraping problem
  • We have no way of overlaying /etc/shadow to set some default root password for a user (yet) - can we make dropbear accept unauthenticated users unless authorized_keys has been populated?
• Ensure this works well enough with ares-install and other SDK tools

[DavidBuchanan314]

RE: authentication, could we just put this in our init script:

if [ ! -f /home/root/.ssh/authorized_keys ]; then 
  sed s/root:.:/root:xGVw8H4GqkKg6:/ /etc/shadow > /tmp/shadow
  chmod 400 /tmp/shadow
  mount --bind /tmp/shadow /etc/shadow
fi

i.e. if authorized_keys does not exist, set the root password to alpine via bind mount

[Informatic]

That makes sense.

If we put that shadowfile somewhere persistent (/var/luna/preferences/webosbrew_shadow?) we could also use it as a go-to solution for remote access for people inexperienced with ssh public key authentication. passwd should work as is with this setup, right?

Update: just realized this (persistence) is not a great idea, in case someone does a software update, as we don't have any guarantees regarding passwd/shadow not changing.

[Informatic]

Initial dropbear integration is finished in 957d29f - UI is working, tools/build-dropbear.sh can be used to build a working customized dropbear sshd binary to be bundled with the application. Not sure how to distribute this - should we just commit the binary into the repo and call it a day?

Fully static builds seemed to fail to link when built with meta-lg-webos-ndk - not sure how to go about this, I don't have much practice with general subject of crosscompilation.

[mariotaku]

Fully static build may not work - IIRC the NDK I built doen't come with any archive files. Thus no way to static link with libc. But I think if crypto libraries could be statically linked, then it's good enough.