linux-kernel - Re: [PATCH 1/7] ima: on soft reboot, restore the measurement list

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Message-Id: <1470751618.2881.140.camel@linux.vnet.ibm.com>
Date:	Tue, 09 Aug 2016 10:06:58 -0400
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>
Cc:	Michael Ellerman <mpe@...erman.id.au>,
	linux-security-module@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-ima-devel@...ts.sourceforge.net,
	Dave Young <dyoung@...hat.com>
Subject: Re: [PATCH 1/7] ima: on soft reboot, restore the measurement list

On Tue, 2016-08-09 at 09:55 -0400, Mimi Zohar wrote:
> On Tue, 2016-08-09 at 10:19 -0300, Thiago Jung Bauermann wrote:
> > Am Dienstag, 09 August 2016, 09:01:13 schrieb Mimi Zohar:
> > > On Tue, 2016-08-09 at 20:59 +1000, Michael Ellerman wrote:
> > > > Mimi Zohar <zohar@...ux.vnet.ibm.com> writes:
> > > > > diff --git a/security/integrity/ima/ima.h
> > > > > b/security/integrity/ima/ima.h
> > > > > index b5728da..84e8d36 100644
> > > > > --- a/security/integrity/ima/ima.h
> > > > > +++ b/security/integrity/ima/ima.h
> > > > > @@ -102,6 +102,13 @@ struct ima_queue_entry {
> > > > > 
> > > > >  };
> > > > >  extern struct list_head ima_measurements;	/* list of all 
> > measurements
> > > > >  */
> > > > > 
> > > > > +/* Some details preceding the binary serialized measurement list */
> > > > > +struct ima_kexec_hdr {
> > > > > +	unsigned short version;
> > > > > +	unsigned long buffer_size;
> > > > > +	unsigned long count;
> > > > > +} __packed;
> > > > > +
> > > > 
> > > > Am I understanding it correctly that this structure is passed between
> > > > kernels?
> > > Yes, the header prefixes the measurement list, which is being passed on
> > > the same computer to the next kernel.  Could the architecture (eg.
> > > LE/BE) change between soft re-boots?
> > 
> > Yes. I am able to boot a BE kernel from an LE kernel with my patches. 
> > Whether we want to support that or not is another question...
> 
> The <securityfs/ima/binary_runtime_measurements is system architecture
> dependent.  It looks like the khdr->version check in
> ima_restore_measurement_list() would fail if the architecture changes.
> 
> If/when we update the binary measurement list format to support multiple
> TPM PCRs, we should address the endianness as well.

That should have been "TPM PCR banks".  TPM 2.0 allows for multiple TPM
PCR banks.

Mimi