On Fri, 2017-04-07 at 10:17 +0100, David Howells wrote:
> Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx> wrote:
>
> > > Okay, fair enough. I can stick in an OR with an IS_ENABLED on some IMA
> > > symbol. CONFIG_IMA_KEXEC maybe? And also require IMA be enabled?
> >
> > Not quite, since as Dave pointed out, IMA is policy driven. As a
> > policy is installed, we could set a flag.
>
> Does such a flag exist as yet?
Not exactly what is needed. There's a flag named ima_appraise, which
is used internally in IMA. A temporary flag is created, while
validating the rules.
if (default_appraise_rules[i].func == POLICY_CHECK)
temp_ima_appraise |= IMA_APPRAISE_POLICY;
if (!result && (entry->action == UNKNOWN))
result = -EINVAL;
else if (entry->func == MODULE_CHECK)
temp_ima_appraise |= IMA_APPRAISE_MODULES;
else if (entry->func == FIRMWARE_CHECK)
temp_ima_appraise |= IMA_APPRAISE_FIRMWARE;
else if (entry->func == POLICY_CHECK)
temp_ima_appraise |= IMA_APPRAISE_POLICY;
If the entire policy is valid, ima_update_policy_flag() sets the ima_appraise flag.
ima_appraise |= temp_ima_appraise;
>From an IMA perspective, either a file hash or signature are valid,
but for this usage it must be a signature. So in addition to testing
entry->func, above, entry->flags would need to be tested as well to
detect if IMA_DIGSIG_REQUIRED is set.
Mimi
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