efi_loader: don't load Shim's MOK database from file

When using a file to store UEFI variables we must make sure that secure
boot related variables are not loaded from this file. With commit
9ef82e29478c ("efi_loader: don't load signature database from file")
this has already been implemented for variables defined in the UEFI
specification. As most Linux distributions use Shim we should do the same
for Shim's MOK database.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

diff --git a/lib/efi_loader/efi_var_file.c b/lib/efi_loader/efi_var_file.c
index c7c6805..76a2ff9 100644 (file)
--- a/lib/efi_loader/efi_var_file.c
+++ b/lib/efi_loader/efi_var_file.c
@@ -19,6 +19,13 @@
 
 #define PART_STR_LEN 10
 
+/* GUID used by Shim to store the MOK database */
+#define SHIM_LOCK_GUID \
+       EFI_GUID(0x605dab50, 0xe046, 0x4300, \
+                0xab, 0xb6, 0x3d, 0xd8, 0x10, 0xdd, 0x8b, 0x23)
+
+static const efi_guid_t shim_lock_guid = SHIM_LOCK_GUID;
+
 /**
  * efi_set_blk_dev_to_system_partition() - select EFI system partition
  *
@@ -175,6 +182,7 @@ efi_status_t efi_var_restore(struct efi_var_file *buf, bool safe)
                if (!safe &&
                    (efi_auth_var_get_type(var->name, &var->guid) !=
                     EFI_AUTH_VAR_NONE ||
+                    !guidcmp(&var->guid, &shim_lock_guid) ||
                     !(var->attr & EFI_VARIABLE_NON_VOLATILE)))
                        continue;
                if (!var->length)