Messages in this thread | | | From | Andy Lutomirski <> | Date | Tue, 7 Oct 2014 10:58:27 -0700 | Subject | Re: [TrouSerS-tech] [Ksummit-discuss] TPM MiniSummit @ LinuxCon Europe |
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On Tue, Oct 7, 2014 at 10:54 AM, Stefan Berger <stefanb@linux.vnet.ibm.com> wrote: > On 09/23/2014 12:42 PM, Andy Lutomirski wrote: >> >> On Sep 22, 2014 2:07 AM, "Peter Huewe" <PeterHuewe@gmx.de> wrote: >>> >>> Hi, >>> >>> I would like to 'invite' all interested parties in a short TPM minisummit >>> where we can discuss the following hot topics of the TPM subsystem over a >>> beer or two: >>> - State of the TPM Subsystem >>> - De-/Initialization Mess >>> - Devm'ification >>> - Testing >>> - TPM 2.0 Support >>> - Dependencies / interaction with other subsystems (e.g. keyring / IMA) >>> - Status of old 1.1b TPM drivers, deprecation plans >>> - ... >>> >> I am unlikely to be there, but I have a feature request / food for >> thought: >> >> Using a mandatory userspace daemon (e.g. trousers) for TPM access >> sucks. Might it be possible to teach the kernel to handle context >> save and restore and let multiple processes open the device at once? >> Then a daemon wouldn't be necessary. > > > 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. >
Trousers is a daemon, not a library, and it's really quite scary.
Admittedly, my information may be a bit out of date, but trousers contains way too much code (it has layers in the server!), it has parsers and serializers of questionable safety (I found one critical bug *by accident* a couple years ago), it listens on a TCP socket (this should really be a UNIX socket under /run), it's heavy-weight, and it does far more than necessary (all it needs to do is context switching).
Also, Trousers is quite unfriendly to non-Trousers-using programs (e.g. chapsd/trunks).
If the kernel helped with context switching, then user programs that actually want Trousers' functionality could run their own copies.
--Andy
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