On Mon, Jan 02, 2017 at 01:40:48PM -0800, James Bottomley wrote: > On Mon, 2017-01-02 at 21:33 +0200, Jarkko Sakkinen wrote: > > On Mon, Jan 02, 2017 at 08:36:20AM -0800, James Bottomley wrote: > > > On Mon, 2017-01-02 at 15:22 +0200, Jarkko Sakkinen wrote: > > > > This patch set adds support for TPM spaces that provide a context > > > > for isolating and swapping transient objects. This patch set does > > > > not yet include support for isolating policy and HMAC sessions > > > > but it is trivial to add once the basic approach is settled (and > > > > that's why I created an RFC patch set). > > > > > > The approach looks fine to me. The only basic query I have is > > > about the default: shouldn't it be with resource manager on rather > > > than off? I can't really think of a use case that wants the RM off > > > (even if you're running your own, having another doesn't hurt > > > anything, and it's still required to share with in-kernel uses). > > > > This is a valid question and here's a longish explanation. > > > > In TPM2_GetCapability and maybe couple of other commands you can get > > handles in the response body. I do not want to have special cases in > > the kernel for response bodies because there is no a generic way to > > do the substitution. What's worse, new commands in the standard > > future revisions could have such commands requiring special cases. In > > addition, vendor specific commans could have handles in the response > > bodies. > > OK, in general I buy this ... what you're effectively saying is that we > need a non-RM interface for certain management type commands.
Not only that. Doing virtualization for commands like GetCapability is just a better fit for doing in the user space. You could have a thin translation layer in your TSS library for example to handle these specific messages. > However, let me expand a bit on why I'm fretting about the non-RM use > case. Right at the moment, we have a single TPM device which you use > for access to the kernel TPM. The current tss2 just makes direct use > of this, meaning it has to have 0666 permissions. This means that any > local user can simply DoS the TPM by running us out of transient > resources if they don't activate the RM. If they get a connection > always via the RM, this isn't a worry. Perhaps the best way of fixing > this is to expose two separate device nodes: one raw to the TPM which > we could keep at 0600 and one with an always RM connection which we can > set to 0666. That would mean that access to the non-RM connection is > either root only or governed by a system set ACL. I'm not sure about this. Why you couldn't have a very thin daemon that prepares the file descriptor and sends it through UDS socket to a client. The non-RFC version will also have whitelisting ioctl for further restricting the file descriptor to only specific TPM commands. This is also architecture I preseted in my LSS presentation and I think it makes sense especially when I add the whitelisting to the pack. > James I'm more dilated to keep things way they are now. I'll stick to that at least with the first non-RFC version and hopefully get the tpm2-space.c part reviewed as I split that stuff to a separate commit. /Jarkko
