linux-kernel - Re: [tpmdd-devel] [PATCH RFC v3 5/5] tpm2: expose resource manager via a device link /dev/tpms<n>

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Message-ID: <1485120988.2504.21.camel@HansenPartnership.com>
Date:   Sun, 22 Jan 2017 13:36:28 -0800
From:   James Bottomley <James.Bottomley@...senPartnership.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     linux-security-module@...r.kernel.org,
        tpmdd-devel@...ts.sourceforge.net,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [tpmdd-devel] [PATCH RFC v3 5/5] tpm2: expose resource manager
 via    a device link /dev/tpms<n>

On Sun, 2017-01-22 at 23:04 +0200, Jarkko Sakkinen wrote:
> On Sun, Jan 22, 2017 at 11:01:07PM +0200, Jarkko Sakkinen wrote:
> > On Sun, Jan 22, 2017 at 10:30:55PM +0200, Jarkko Sakkinen wrote:
> > > On Sun, Jan 22, 2017 at 10:48:12AM -0800, James Bottomley wrote:
> > > > On Sun, 2017-01-22 at 09:49 -0800, James Bottomley wrote:
> > > > > On Fri, 2017-01-20 at 23:05 +0200, Jarkko Sakkinen wrote:
> > > > > > 'tabrm4' branch has been now rebased. It's now on top of
> > > > > > master
> > > > > > branch that contains Stefan's latest patch (min body length
> > > > > > check) 
> > > > > > that I've reviewed and tested. It also contains your
> > > > > > updated
> > > > > > /dev/tpms patch.
> > > > > > 
> > > > > > I guess the 5 commits that are there now are such that we
> > > > > > have 
> > > > > > fairly good consensus, don't we? If so, can I add your
> > > > > > reviewed-by 
> > > > > > and tested-by to my commits and vice versa?
> > > > > 
> > > > > We're still failing my test_transients.  This is the full
> > > > > python of 
> > > > > the test case:
> > > > > 
> > > > > 
> > > > >     def test_transients(self):
> > > > >         k = self.open_transients()
> > > > >         self.c.flush_context(k[0])
> > > > >         self.c.change_auth(self.c.SRK, k[1], None, pwd1)
> > > > >         ...
> > > > > 
> > > > > It's failing at self.c.flush_context(k[0]) with TPM_RC_VALUE.
> > > > >   It's 
> > > > > the same problem Ken complained about: TPM2_FlushContext
> > > > > doesn't have 
> > > > > a declared handle area so we don't translate the handle being
> > > > > sent
> > > > > down.  We have to fix this either by intercepting the flush
> > > > > and 
> > > > > manually translating the context, or by being dangerously
> > > > > clever and 
> > > > > marking flush as a command which takes one handle.
> > > > 
> > > > This is what the dangerously clever fix looks like.  With this
> > > > and a
> > > > few other changes, my smoke tests now pass.
> > > > 
> > > > James
> > > 
> > > I don't want to be clever here. I will rather intercept the body
> > > and
> > > try to keep the core code simple and easy to understand.
> > 
> > It came out quite clean actually.
> > 
> > I just encapsulated handle mapping and have this in the beginning
> > of
> > tpm2_map_command:
> > 
> > if (cc == TPM2_CC_FLUSH_CONTEXT)
> > 	return tpm2_map_to_phandle(space, &cmd[TPM_HEADER_SIZE]);
> > 
> > I think this documents better what is actually going on than
> > tinkering
> > cc_attr_tbl.
> > 
> > /Jarkko
> 
> Actually what you suggested is much better idea because it will also
> take care of validation.

Yes, that's why it's clever ... I'm just always wary of clever code
because of the Kernighan principle.

>  I'm still going to keep tpm2_map_to_phandle because it makes the 
> code flow a lot cleaner and probably sessions have to anyway make it
> even more complicated.

OK, there's one more thing that seems to be causing problems: when
tpm2_save_context fails because the handle no longer exists (like it's
been flushed) it returns TPM_RC_REFERENCE_H0 not TPM_RC_HANDLE (the
session code does seem to return TPM_RC_HANDLE under some
circumstances).

James