linux-kernel - [PATCH v6 5/8] IMA: extend policy to add data sources as a critical data measurement constraint

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Message-Id: <20201119232611.30114-6-tusharsu@linux.microsoft.com>
Date:   Thu, 19 Nov 2020 15:26:08 -0800
From:   Tushar Sugandhi <tusharsu@...ux.microsoft.com>
To:     zohar@...ux.ibm.com, stephen.smalley.work@...il.com,
        casey@...aufler-ca.com, agk@...hat.com, snitzer@...hat.com,
        gmazyland@...il.com, paul@...l-moore.com
Cc:     tyhicks@...ux.microsoft.com, sashal@...nel.org, jmorris@...ei.org,
        nramas@...ux.microsoft.com, linux-integrity@...r.kernel.org,
        selinux@...r.kernel.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, dm-devel@...hat.com
Subject: [PATCH v6 5/8] IMA: extend policy to add data sources as a critical data measurement constraint

System administrators should be able to limit which kernel subsystems
they want to measure the critical data for. To enable that, an IMA policy
condition to choose specific kernel subsystems is needed. This policy
condition would constrain the measurement of the critical data to the
given kernel subsystems.

Add a new IMA policy condition - "data_sources:=" to the IMA func
CRITICAL_DATA to allow measurement of various kernel subsystems. This
policy condition would enable the system administrators to restrict the
measurement to the subsystems listed in "data_sources:=".

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, the data from all the
supported kernel subsystems is measured.

Signed-off-by: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
---
 Documentation/ABI/testing/ima_policy |  4 ++++
 security/integrity/ima/ima_policy.c  | 27 ++++++++++++++++++++++++++-
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index 6ec7daa87cba..ee60442a41cd 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -52,6 +52,10 @@ Description:
 			template:= name of a defined IMA template type
 			(eg, ima-ng). Only valid when action is "measure".
 			pcr:= decimal value
+			data_sources:= list of kernel subsystems that contain
+			kernel in-memory data critical to the integrity of the kernel.
+			Only valid when action is "measure" and func is
+			CRITICAL_DATA.
 
 		  default policy:
 			# PROC_SUPER_MAGIC
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 583be7674f3e..c9e52dab0638 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -934,7 +934,7 @@ enum {
 	Opt_uid_lt, Opt_euid_lt, Opt_fowner_lt,
 	Opt_appraise_type, Opt_appraise_flag,
 	Opt_permit_directio, Opt_pcr, Opt_template, Opt_keyrings,
-	Opt_err
+	Opt_data_sources, Opt_err
 };
 
 static const match_table_t policy_tokens = {
@@ -971,6 +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}
 };
 
@@ -1350,6 +1351,24 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
 
 			entry->flags |= IMA_KEYRINGS;
 			break;
+		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;
 		case Opt_fsuuid:
 			ima_log_string(ab, "fsuuid", args[0].from);
 
@@ -1730,6 +1749,12 @@ int ima_policy_show(struct seq_file *m, void *v)
 		seq_puts(m, " ");
 	}
 
+	if (entry->flags & IMA_DATA_SOURCES) {
+		seq_puts(m, "data_sources=");
+		ima_show_rule_opt_list(m, entry->data_sources);
+		seq_puts(m, " ");
+	}
+
 	if (entry->flags & IMA_PCR) {
 		snprintf(tbuf, sizeof(tbuf), "%d", entry->pcr);
 		seq_printf(m, pt(Opt_pcr), tbuf);
-- 
2.17.1