🚀 go-pugleaf

holland@dutiws.tudelft.nl (Gerhard den Hollander) writes:
>If machine B mounts machine A,
>I can execute (on machine B) my root-script on machine A
>meaning I am root on machine B.

Generally speaking, if you import information at this kind of security level,
the source had better be trustworthy.  Even if you allow users to mount floppy
disks, they can edit them with a sector editor on their own machine (esp. the
same kind of machine running a different OS, like a mac running mac OS if we're
talking about an a/ux disk) and create setuid shells.

>How can I prevent this ????
>Mounting with the nosuid option does NOT work.

Do you mean it's not implemented on your system (quite common), or that it
fails to perform the documented function?  What kind of system is it?

Nosuid isn't good enough, though.  For example, people can still create device
files and mount them.  Being able to write /dev/kmem should be good enough to
get you in, and all you have to do (on "machine A") is mknod myfile c 3 1;
chmod 666 myfile.  Also, you may have root-run programs which "trust" files on
some filesystems imported from machine A; or for that matter, if you're root on
machine A you can edit any non-root file it imports (how to do this is left as
an exercise for the reader).