On 2020-12-11 17:17:22, Tushar Sugandhi wrote:
>
>
> On 2020-12-11 4:25 p.m., Tyler Hicks wrote:
> > On 2020-12-11 15:58:03, Tushar Sugandhi wrote:
> > > A new IMA policy rule is needed for the IMA hook
> > > ima_measure_critical_data() and the corresponding func CRITICAL_DATA for
> > > measuring the input buffer. The policy rule should ensure the buffer
> > > would get measured only when the policy rule allows the action. The
> > > policy rule should also support the necessary constraints (flags etc.)
> > > for integrity critical buffer data measurements.
> > >
> > > Add a policy rule to define the constraints for restricting integrity
> > > critical data measurements.
> > >
> > > Signed-off-by: Tushar Sugandhi <tusharsu@xxxxxxxxxxxxxxxxxxx>
> > > ---
> > > Documentation/ABI/testing/ima_policy | 2 +-
> > > security/integrity/ima/ima_policy.c | 34 ++++++++++++++++++++++++----
> > > 2 files changed, 31 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
> > > index e35263f97fc1..6ec7daa87cba 100644
> > > --- a/Documentation/ABI/testing/ima_policy
> > > +++ b/Documentation/ABI/testing/ima_policy
> > > @@ -32,7 +32,7 @@ Description:
> > > func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK]MODULE_CHECK]
> > > [FIRMWARE_CHECK]
> > > [KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
> > > - [KEXEC_CMDLINE] [KEY_CHECK]
> > > + [KEXEC_CMDLINE] [KEY_CHECK] [CRITICAL_DATA]
> > > mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND]
> > > [[^]MAY_EXEC]
> > > fsmagic:= hex value
> > > diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> > > index a09d1a41a290..07116ff35c25 100644
> > > --- a/security/integrity/ima/ima_policy.c
> > > +++ b/security/integrity/ima/ima_policy.c
> > > @@ -85,6 +85,7 @@ struct ima_rule_entry {
> > > } lsm[MAX_LSM_RULES];
> > > char *fsname;
> > > struct ima_rule_opt_list *keyrings; /* Measure keys added to these keyrings */
> > > + struct ima_rule_opt_list *data_source; /* Measure data from this source */
> >
> > Argh, there are still some more instances of data_source sneaking into
> > this patch too early instead of waiting until the next patch.
> >
> I kept it purposefully in this patch so that the
> "case CRITICAL_DATA:" could be properly defined.
>
> Also, my impression was rule->data_source is not part of the user facing
> policy.
>
> Whereas IMA_DATA_SOURCE, Opt_data_source, data_source=%s are.
> That's why they are part of Patch #5.
>
> Patch #5 IMA: limit critical data measurement based on a label
>
> > > struct ima_template_desc *template;
> > > };
> > > @@ -479,6 +480,12 @@ static bool ima_match_rule_data(struct ima_rule_entry *rule,
> > > opt_list = rule->keyrings;
> > > break;
> > > + case CRITICAL_DATA:
> > > + if (!rule->data_source)
> > > + return true;
> > > +
> > > + opt_list = rule->data_source;
> > > + break;
> >
> > I guess this case should unconditionally return true in this patch and
> > then the include this additional logic in the next patch.
> >
> > Sorry, I missed these on my last review.
> >
> No worries.
>
> As I mentioned above, I kept it purposefully in this patch since
> my impression was rule->data_source is not part of the user facing
> policy.
>
> But I can simply return true here as you suggested, and move the logic to
> the next patch.
I understand the thinking that it isn't harmful in this patch but I
think it is a bit cleaner to introduce the data_source policy language
element and all of its backend support in the same patch. Please move it
to the next patch. Thanks!
Tyler
>
> + case CRITICAL_DATA:
> + if (!rule->data_source)
> + return true;
> +
> + opt_list = rule->data_source;
> + break;
>
>
> ~Tushar
>
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