Re: [PATCH v5 4/7] IMA: add policy to measure critical data

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On 2020-11-06 5:43 a.m., Mimi Zohar wrote:
Hi Tushar,

On Sun, 2020-11-01 at 14:26 -0800, Tushar Sugandhi wrote:
System administrators should be able to choose which kernel subsystems
they want to measure the critical data for. To enable that, an IMA policy
option to choose specific kernel subsystems is needed. This policy option
would constrain the measurement of the critical data to the given kernel
subsystems.

Measuring critical data should not be dependent on the source of the
critical data.   This patch needs to be split up.  The "data sources"
should be move to it's own separate patch.  This patch should be
limited to adding the policy code needed for measuring criticial data.
Limiting critical data sources should be the last patch in this series.

thanks,

Mimi

Thanks Mimi.

Ok. I will split the patches as you suggested.
Patch #1 (this patch) will have the policy code needed for measuring
critical data.
patch #2 Limiting the critical “data_sources”.

*Question 1*
Since you said patch #2 should be the last patch in this series, do you mean merging patch #2 with the SeLinux patch? (patch 7/7 of this series)
Or a separate patch before 7/7?

*Question 2*
If I understand it correctly, the following code should be moved from this patch to patch #2. Did I miss anything?

 static const match_table_t policy_tokens = {
@@ -957,6 +971,7 @@ static const match_table_t policy_tokens = {
 	{Opt_pcr, "pcr=%s"},
 	{Opt_template, "template=%s"},
 	{Opt_keyrings, "keyrings=%s"},
+	{Opt_data_sources, "data_sources=%s"},
 	{Opt_err, NULL}
 };


+		case Opt_data_sources:
+			ima_log_string(ab, "data_sources",
+				       args[0].from);
+
+			if (entry->data_sources) {
+				result = -EINVAL;
+				break;
+			}
+
+			entry->data_sources = ima_alloc_rule_opt_list(args);
+			if (IS_ERR(entry->data_sources)) {
+				result = PTR_ERR(entry->data_sources);
+				entry->data_sources = NULL;
+				break;
+			}
+
+			entry->flags |= IMA_DATA_SOURCES;
+			break;

+	if (entry->flags & IMA_DATA_SOURCES) {
+		seq_puts(m, "data_sources=");
+		ima_show_rule_opt_list(m, entry->data_sources);
+		seq_puts(m, " ");
+	}
+

~Tushar


Add a new IMA policy option - "data_sources:=" to the IMA func
CRITICAL_DATA to allow measurement of various kernel subsystems. This
policy option would enable the system administrators to limit the
measurement to the subsystems listed in "data_sources:=", if the
subsystem measures its data by calling ima_measure_critical_data().

Limit the measurement to the subsystems that are specified in the IMA
policy - CRITICAL_DATA+"data_sources:=". If "data_sources:=" is not
provided with the func CRITICAL_DATA, measure the data from all the
supported kernel subsystems.

Signed-off-by: Tushar Sugandhi <tusharsu@xxxxxxxxxxxxxxxxxxx>



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