tpmd to listen on a privileged port

[alban]

At the moment, unprivileged users can bind on the tcp port before tpmd is started. That could DoS tpmclient.

See rkt/rkt#1816

[alban]

/cc @mjg59 @jonboulle

[jonboulle]

I don't quite understand what you want here. To have it listen on a fixed port and remove the option of configuring it?

[alban]

oh, I forgot that the port was configurable. I think it is fine to be configurable.

Then the suggestion is to pick a port < 1024, document it and write it in tpmd.service. Then, get rkt to use that port. So, non-root processes cannot steal that port.

Or, if rkt does not use tpmd over a network, we could add an additional option in tpmd to listen on a socket file in /run/tpmd/tpmd.socket (with /run/tpmd/ only writeable by root).