[maemo-developers] Remotely Nuking a device (was Re: becomeroot once again but with password)

[From: marc zonzon]

On 2/22/07, Paul Klapperich <maemo.org at bobpaul.org> wrote:

> You could setup pubkey authentication on your home ssh server. Then you
> could add a script to the device such that when it connects it runs
> something like:
> ssh -n -R2022:localhost:22
>
Good idea, as your ssh is an outbound connection the local firewall
may accept it. But your command is incomplete, we must have something
like:
ssh -n -R2022:localhost:22 myusername at myserver.com sleep 3600
and you must be sure that the public key of the nokia user is accepted by
myusername at myserver.com
It would be helpful to replace sleep by a script that  warn you, then sleep

> Then on your local computer you could "ssh user at localhost -p2022" to connect
> into your device whenever it's on the internet, regardless of where it's
> connected from. You could manually erase the data, something like:
> for i in /home/user /media/mmc1 /media/mmc2; do
>   rm -rf $i
> done

We can do like that but it might be frustrating when you miss the
connection, or when it is interrupted before you finish, ...
I think this can only be an add-on to the second option.

> Another trick I've used--actually to update computer labs--is to keep a
> script on your server, then have the device use scp to copy that script from
> the server and run it whenever it connects. In my case, the script was
> simple. In your case the script would do nothing. To nuke your nokia,
> replace it with one that erases stuff. This will get it the next time it
> connects and wouldn't require you find know when the device connects.

That's fine we use the same "download at boot and execute" to keep our
clients up-to-date. We just need to find how the script can be
triggered when the tablet connect to internet (must not be difficult,
but I have not looked upon the tablet networking). Your emergency
script can of course erase sensible data but also add a startup
service in /etc/init.d that shutdown the tablet if some special action
(say use some key) is not triggered. Making the use of the tablet
impossible except for you  without reflashing.

Better than scp you can download the script from an httpd server using
netcat, because outbound http connection on port 80 are always open on
any
access point your tablet may use.

> Other options would include writing a lot file to your home machine with the
> IP connecting from. This could be used to track your device so you might be
> able help police recover it. Or you could delete important system files and
> your personal data to make the device worthless without a reflash.

Too complicated just mail a message when you connect "I'm connected
from ip n° xxx.xxx.xxx.xxx gateway xxx.xxx.xxx.xxx", if you have
traceroute you can even traceroute to a known point to help locate the
device. but I suppose it's of no use, some people complain that the
police is not even looking for their stolen child, what do you expect
for your tablet!


At this point I'm wondering if it is not an otion to put on our tablet
(at least when we are on the go), this "shut down if not
authenticated" service.
Of course the tablet policy forbid to authenticate as user before
loging in, because the second part of the boot process is done as
user. But why not put a simple query that the user must answer during
the first 5mn of connection? A startup script may popup a window and
shutdown the device if not answered. If you keep a ssh access to user
or root you have some emergency solution if ever you forget the
password.

Marc