A driver gains root with sudo -S and puts the password in front of stdin.
A sudo that does not prompt -- NOPASSWD, a cached timestamp -- leaves it
there, and the cat under sudo wrote it into the drop-in as its first line.
Seen on the first real run (NetOrk/netork#1027): sshd -t rejected the file
and the rollback removed it, but the password was in a 0644 file for a
moment and in the error the caller showed.
The content now goes without privilege to a mktemp file only the login user
can read; root installs that file (mode 644, root-owned) and removes it.
The fake host in the tests prepends the password to every privileged stdin,
as a non-prompting sudo does.
Bumps to 4.5.1. NetOrk/netork#1027, NetOrk/netork#1029
christianmanivong