1 files changed, 121 insertions, 0 deletions
diff --git a/security/selinux/ima.c b/security/selinux/ima.c
new file mode 100644
index 000000000..cda68122e
--- /dev/null
+++ b/security/selinux/ima.c
@@ -0,0 +1,121 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2021 Microsoft Corporation
+ *
+ * Author: Lakshmi Ramasubramanian (nramas@linux.microsoft.com)
+ *
+ * Measure critical data structures maintained by SELinux
+ * using IMA subsystem.
+ */
+#include <linux/vmalloc.h>
+#include <linux/ima.h>
+#include <linux/seq_buf.h>
+#include "security.h"
+#include "ima.h"
+
+static int selinux_ima_config_len __ro_after_init;
+
+/*
+ * selinux_ima_config_len_init - Compute the configuration settings string length
+ *
+ * The string is fixed text plus one digit per setting, so its length
+ * is known at boot.
+ */
+void __init selinux_ima_config_len_init(void)
+{
+	int buf_len, suffix_len, i;
+
+	buf_len = strlen("initialized=0;enforcing=0;checkreqprot=0;") + 1;
+	suffix_len = strlen("=0;");
+
+	for (i = 0; i < __POLICYDB_CAP_MAX; i++)
+		buf_len += strlen(selinux_policycap_names[i]) + suffix_len;
+
+	selinux_ima_config_len = buf_len;
+}
+
+/*
+ * selinux_ima_collect_state - Read selinux configuration settings
+ *
+ * On success returns the configuration settings string.
+ * On error, returns NULL.
+ */
+static char *selinux_ima_collect_state(void)
+{
+	struct seq_buf s;
+	char *buf;
+	int i;
+
+	buf = kzalloc(selinux_ima_config_len, GFP_KERNEL);
+	if (!buf)
+		return NULL;
+
+	seq_buf_init(&s, buf, selinux_ima_config_len);
+
+	seq_buf_printf(&s, "initialized=%d;enforcing=%d;checkreqprot=%d;",
+		       selinux_initialized(), enforcing_enabled(),
+		       checkreqprot_get());
+
+	for (i = 0; i < __POLICYDB_CAP_MAX; i++)
+		seq_buf_printf(&s, "%s=%d;", selinux_policycap_names[i],
+			       selinux_state.policycap[i]);
+
+	WARN_ON(seq_buf_has_overflowed(&s));
+
+	return buf;
+}
+
+/*
+ * selinux_ima_measure_state_locked - Measure SELinux state and hash of policy
+ */
+void selinux_ima_measure_state_locked(void)
+{
+	char *state_str = NULL;
+	void *policy = NULL;
+	size_t policy_len;
+	int rc = 0;
+
+	lockdep_assert_held(&selinux_state.policy_mutex);
+
+	state_str = selinux_ima_collect_state();
+	if (!state_str) {
+		pr_err("SELinux: %s: failed to read state.\n", __func__);
+		return;
+	}
+
+	ima_measure_critical_data("selinux", "selinux-state",
+				  state_str, strlen(state_str), false,
+				  NULL, 0);
+
+	kfree(state_str);
+
+	/*
+	 * Measure SELinux policy only after initialization is completed.
+	 */
+	if (!selinux_initialized())
+		return;
+
+	rc = security_read_state_kernel(&policy, &policy_len);
+	if (rc) {
+		pr_err("SELinux: %s: failed to read policy %d.\n", __func__, rc);
+		return;
+	}
+
+	ima_measure_critical_data("selinux", "selinux-policy-hash",
+				  policy, policy_len, true,
+				  NULL, 0);
+
+	vfree(policy);
+}
+
+/*
+ * selinux_ima_measure_state - Measure SELinux state and hash of policy
+ */
+void selinux_ima_measure_state(void)
+{
+	lockdep_assert_not_held(&selinux_state.policy_mutex);
+
+	mutex_lock(&selinux_state.policy_mutex);
+	selinux_ima_measure_state_locked();
+	mutex_unlock(&selinux_state.policy_mutex);
+}