linux-kernel - Re: [PATCH 2/2] ima: Support appraise_type=imasig

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Date:	Wed, 13 Feb 2013 08:29:21 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	"Kasatkin, Dmitry" <dmitry.kasatkin@...el.com>
Cc:	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] ima: Support appraise_type=imasig_optional

On Wed, Feb 13, 2013 at 02:14:55PM +0200, Kasatkin, Dmitry wrote:
> Hello Vivek,
> 
> Can you please send to us how your IMA policy looks like.

Hi Dmitry,

For testing purposes, I am using following.

appraise fowner=0 func=BPRM_CHECK appraise_type=imasig_optional

I set this using /sys/kernel/security/policy interface after boot.

Thanks
Vivek

> 
> Thanks,
> Dmitry
> 
> On Tue, Feb 12, 2013 at 8:57 PM, Vivek Goyal <vgoyal@...hat.com> wrote:
> > On Tue, Feb 12, 2013 at 01:52:03PM -0500, Vivek Goyal wrote:
> >> On Tue, Feb 12, 2013 at 12:14:07PM -0500, Mimi Zohar wrote:
> >>
> >> [..]
> >> > > > > --- a/security/integrity/ima/ima_appraise.c
> >> > > > > +++ b/security/integrity/ima/ima_appraise.c
> >> > > > > @@ -124,19 +124,26 @@ int ima_appraise_measurement(int func, struct integrity_iint_cache *iint,
> >> > > > >       enum integrity_status status = INTEGRITY_UNKNOWN;
> >> > > > >       const char *op = "appraise_data";
> >> > > > >       char *cause = "unknown";
> >> > > > > -     int rc;
> >> > > > > +     int rc, audit_info = 0;
> >> > > > >
> >> > > > >       if (!ima_appraise)
> >> > > > >               return 0;
> >> > > > > -     if (!inode->i_op->getxattr)
> >> > > > > +     if (!inode->i_op->getxattr) {
> >> > > > > +             /* getxattr not supported. file couldn't have been signed */
> >> > > > > +             if (iint->flags & IMA_DIGSIG_OPTIONAL)
> >> > > > > +                     return INTEGRITY_PASS;
> >> > > > >               return INTEGRITY_UNKNOWN;
> >> > > > > +     }
> >> > > > >
> >> > > >
> >> > > > Please don't change the result of the appraisal like this.  A single
> >> > > > change can be made towards the bottom of process_measurement().
> >> > >
> >> > > I don't want to pass integrity in all cases of INTEGRITY_UNKNOWN. So
> >> > > I can probably maintain a bool variable, say pass_appraisal, and set
> >> > > that here and at the end of function, parse that variable and change
> >> > > the status accordingly.
> >> >
> >> > process_measurement() is the only caller of ima_appraise_measurement().
> >> > Leave the results of ima_appraise_measurement() alone.  There's already
> >> > code at the end of process_measurement() which decides what to return.
> >> > Just modify it based on the appraisal results.
> >>
> >
> > If we do this, audit logs will be filled with integrity unknown failures.
> > As each unsigned executable file will fail appraisal with INTEGRITY_UNKNOWN
> > and an audit message will be logged.
> >
> > Thanks
> > Vivek
> > --
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