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    SubjectRe: [tpmdd-devel] [TrouSerS-tech] [Ksummit-discuss] TPM MiniSummit @ LinuxCon Europe
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    On Tue, 2014-10-07 at 11:59 -0700, Andy Lutomirski wrote: 
    > On Tue, Oct 7, 2014 at 11:47 AM, Stefan Berger
    > <stefanb@linux.vnet.ibm.com> wrote:
    > > On 10/07/2014 02:02 PM, Jason Gunthorpe wrote:
    > >>
    > >> On Tue, Oct 07, 2014 at 01:54:41PM -0400, Stefan Berger wrote:
    > >>
    > >>> Why add the complexity of swapping of authenticated sessions and keys
    > >>> into the kernel if you can handle this in userspace? You need a library
    > >>> that is aware of the number of key slots and slots for sessions in the
    > >>> TPM and swaps them in at out when applications need them. Trousers is
    > >>> such a library that was designed to cope with the limitations of the
    > >>> device and make its functionality available to all applications that
    > >>> want to access it.
    > >>
    > >> How does trousers work with the kernel when the kernel is also using
    > >> TPM key slots for IMA/keyring/whatever?
    > >
    > >
    > > IIRC it only uses a single key slot and swaps all keys in and out of that
    > > one. If the kernel was to fill up all key (and sessions) slots, TSS would
    > > probably not work anymore.
    > >
    > > Another argument for the TSS is that you also wouldn't want applications to
    > > swap out each others keys and sessions and leave them out or assume that
    > > they would always cleanup if they do not currently need them.
    >
    > That argument seems backwards. If you're worried about applications
    > (or trousers itself!) failing to clean up, then shouldn't the kernel
    > driver clean up orphaned key slots itself?

    As I understand it, this isn't an issue of "cleaning up", but of
    mediating the limited resources, by "swapping" keys in and out as
    needed.

    Mimi

    > Also, what protects the kernel from having slot 0 get stomped on or,
    > worse, inappropriately used by a misbehaving or malicious user
    > program? Is the authorization session mechanism really secure against
    > intentional abuse by users of the same machine?
    >
    > --Andy



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