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

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Date:	Wed, 13 Feb 2013 14:14:55 +0200
From:	"Kasatkin, Dmitry" <dmitry.kasatkin@...el.com>
To:	Vivek Goyal <vgoyal@...hat.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

Hello Vivek,

Can you please send to us how your IMA policy looks like.

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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