Re: [PATCH 1/3] IMA: add policy condition to measure duplicate critical data

[Tushar Sugandhi]

On 2021-02-08 12:45 p.m., Mimi Zohar wrote:
> Hi Tushar,
>
> On Fri, 2021-01-29 at 16:45 -0800, Tushar Sugandhi wrote:
> > IMA needs to support duplicate measurements of integrity
> > critical data to accurately determine the current state of that data
> > on the system.  Further, since measurement of duplicate data is not
> > required for all the use cases, it needs to be policy driven.
> >
> > Define "allow_dup", a new IMA policy condition, for the IMA func
> > CRITICAL_DATA to allow duplicate buffer measurement of integrity
> > critical data.
> >
> > Limit the ability to measure duplicate buffer data when action is
> > "measure" and func is CRITICAL_DATA.
>
> Why?!
I wasn't sure if it would break any use-case by supporting this for all 
the files / buffers.  That's why I only wanted to address the scenario 
that we discussed in the last series (critical data measurement).
But as you suggested in this series' cover letter response, I am happy 
to extend it to other scenarios (by disabling "htable" using new Kconfig 
(e.g. CONFIG_IMA_DISABLE_HTABLE)
> > Signed-off-by: Tushar Sugandhi <tusharsu@xxxxxxxxxxxxxxxxxxx>
> > ---
> >
> > diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> > index 9b45d064a87d..b89eb768dd05 100644
> > --- a/security/integrity/ima/ima_policy.c
> > +++ b/security/integrity/ima/ima_policy.c
> > @@ -35,6 +35,7 @@
> >   #define IMA_FSNAME	0x0200
> >   #define IMA_KEYRINGS	0x0400
> >   #define IMA_LABEL	0x0800
> > +#define IMA_ALLOW_DUP	0x1000
> >   
> >   #define UNKNOWN		0
> >   #define MEASURE		0x0001	/* same as IMA_MEASURE */
> > @@ -87,6 +88,7 @@ struct ima_rule_entry {
> >   	char *fsname;
> >   	struct ima_rule_opt_list *keyrings; /* Measure keys added to these keyrings */
> >   	struct ima_rule_opt_list *label; /* Measure data grouped under this label */
>
> Defining a new boolean entry shouldn't be necessary.    The other
> boolean values are just stored in "flags".
Thanks.  Will do the same here.
Thanks,
Tushar
> >   	struct ima_template_desc *template;
> >   };
>
> thanks,
>
> Mimi