powerpc/ima: Define trusted boot policy

This patch defines an arch-specific trusted boot only policy and a
combined secure and trusted boot policy.
Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1572492694-6520-5-git-send-email-zohar@linux.ibm.com

arch/powerpc/kernel/ima_arch.c

@@ -30,6 +30,32 @@ static const char *const secure_rules[] = {
 	NULL
 };
 
+/*
+ * The "trusted_rules" are enabled only on "trustedboot" enabled systems.
+ * These rules add the kexec kernel image and kernel modules file hashes to
+ * the IMA measurement list.
+ */
+static const char *const trusted_rules[] = {
+	"measure func=KEXEC_KERNEL_CHECK",
+	"measure func=MODULE_CHECK",
+	NULL
+};
+
+/*
+ * The "secure_and_trusted_rules" contains rules for both the secure boot and
+ * trusted boot. The "template=ima-modsig" option includes the appended
+ * signature, when available, in the IMA measurement list.
+ */
+static const char *const secure_and_trusted_rules[] = {
+	"measure func=KEXEC_KERNEL_CHECK template=ima-modsig",
+	"measure func=MODULE_CHECK template=ima-modsig",
+	"appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig",
+#ifndef CONFIG_MODULE_SIG_FORCE
+	"appraise func=MODULE_CHECK appraise_type=imasig|modsig",
+#endif
+	NULL
+};
+
 /*
  * Returns the relevant IMA arch-specific policies based on the system secure
  * boot state.
@@ -37,7 +63,12 @@ static const char *const secure_rules[] = {
 const char *const *arch_get_ima_policy(void)
 {
 	if (is_ppc_secureboot_enabled())
+		if (is_ppc_trustedboot_enabled())
+			return secure_and_trusted_rules;
+		else
 			return secure_rules;
+	else if (is_ppc_trustedboot_enabled())
+		return trusted_rules;
 
 	return NULL;
 }