integrity: check whether imputed trust is enabled

trust_moklist() is specific to UEFI enabled systems. Other platforms
rely only on the Kconfig.

Define a generic wrapper named imputed_trust_enabled().
Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Tested-by: Nageswara R Sastry <rnsastry@linux.ibm.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

security/integrity/digsig.c

@@ -113,7 +113,7 @@ static int __init __integrity_init_keyring(const unsigned int id,
 	} else {
 		if (id == INTEGRITY_KEYRING_PLATFORM)
 			set_platform_trusted_keys(keyring[id]);
-		if (id == INTEGRITY_KEYRING_MACHINE && trust_moklist())
+		if (id == INTEGRITY_KEYRING_MACHINE && imputed_trust_enabled())
 			set_machine_trusted_keys(keyring[id]);
 		if (id == INTEGRITY_KEYRING_IMA)
 			load_module_cert(keyring[id]);

security/integrity/integrity.h

@@ -320,13 +320,14 @@ static inline void __init add_to_platform_keyring(const char *source,
 
 #ifdef CONFIG_INTEGRITY_MACHINE_KEYRING
 void __init add_to_machine_keyring(const char *source, const void *data, size_t len);
-bool __init trust_moklist(void);
+bool __init imputed_trust_enabled(void);
 #else
 static inline void __init add_to_machine_keyring(const char *source,
 						  const void *data, size_t len)
 {
 }
-static inline bool __init trust_moklist(void)
+
+static inline bool __init imputed_trust_enabled(void)
 {
 	return false;
 }

security/integrity/platform_certs/keyring_handler.c

@@ -61,7 +61,8 @@ __init efi_element_handler_t get_handler_for_db(const efi_guid_t *sig_type)
 __init efi_element_handler_t get_handler_for_mok(const efi_guid_t *sig_type)
 {
 	if (efi_guidcmp(*sig_type, efi_cert_x509_guid) == 0) {
-		if (IS_ENABLED(CONFIG_INTEGRITY_MACHINE_KEYRING) && trust_moklist())
+		if (IS_ENABLED(CONFIG_INTEGRITY_MACHINE_KEYRING) &&
+		    imputed_trust_enabled())
 			return add_to_machine_keyring;
 		else
 			return add_to_platform_keyring;

security/integrity/platform_certs/machine_keyring.c

@@ -34,7 +34,8 @@ void __init add_to_machine_keyring(const char *source, const void *data, size_t
 	 * If the restriction check does not pass and the platform keyring
 	 * is configured, try to add it into that keyring instead.
 	 */
-	if (rc && efi_enabled(EFI_BOOT) && IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING))
+	if (rc && efi_enabled(EFI_BOOT) &&
+	    IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING))
 		rc = integrity_load_cert(INTEGRITY_KEYRING_PLATFORM, source,
 					 data, len, perm);
 
@@ -60,7 +61,7 @@ static __init bool uefi_check_trust_mok_keys(void)
 	return false;
 }
 
-bool __init trust_moklist(void)
+static bool __init trust_moklist(void)
 {
 	static bool initialized;
 	static bool trust_mok;
@@ -75,3 +76,16 @@ bool __init trust_moklist(void)
 
 	return trust_mok;
 }
+
+/*
+ * Provides platform specific check for trusting imputed keys before loading
+ * on .machine keyring. UEFI systems enable this trust based on a variable,
+ * and for other platforms, it is always enabled.
+ */
+bool __init imputed_trust_enabled(void)
+{
+	if (efi_enabled(EFI_BOOT))
+		return trust_moklist();
+
+	return true;
+}