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    SubjectRe: modules and securelevel
    On Fri, 12 Jul 1996, Kai Schulte wrote:

    > > Not to jump in or anything, but...
    > > How about a small kernel function to return the current securelevel value?
    > > int get_securelevel();
    > > Then export THAT to modules.
    >
    > I must be missing something here... if you really want to attack the
    > kernel you are running in you could always take the address of
    > get_securelevel(), follow it to see where the "mov" reads from, and then
    > write to that location.
    >
    > Protecting the kernel against each module would cause a lot of unnecessary
    > overhead. Is there any good reason why modules should not be "trusted"
    > code?

    I can't see any reason why modules can't be trusted code, and I've assumed
    them to be so for doing the POSIX.6 stuff - this requires having the
    sys_insmod/sys_rmmod privs to get the code into the kernel.

    Even in a non POSIX.6 system you need to be root to stuff module code into
    the kernel - an if you are root you can just as easily rebuild a bogus
    kernel.

    The only time I can see it being a problem is if you get a binary only
    module - then it is upto the systems security officer to make the judgment
    of it can be installed into the system.

    Basically I think that modules should be part of the TCB.

    What might be nice however is if securelevel could be raised only....


    --
    Darren J Moffat



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