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: <20170122210441.ivzujugb3urzndhj@intel.com>
Date:   Sun, 22 Jan 2017 23:04:41 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     James Bottomley <James.Bottomley@...senPartnership.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, 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. 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.

/Jarkko