fix passing key out of LoadFirmware

firmware/lib/vboot_firmware.c

Index: firmware/lib/vboot_firmware.c
diff --git a/firmware/lib/vboot_firmware.c b/firmware/lib/vboot_firmware.c
index a59b238e850d40d60f253defe5d5432e2593d5eb..8fa4c53834ffb419b1a80f0c2c8379a9399dc1ea 100644
--- a/firmware/lib/vboot_firmware.c
+++ b/firmware/lib/vboot_firmware.c
@@ -45,11 +45,14 @@ int LoadFirmware(LoadFirmwareParams* params) {
 
   /* Clear output params in case we fail */
   params->firmware_index = 0;
-  params->kernel_sign_key_blob = NULL;
-  params->kernel_sign_key_size = 0;
 
   debug("LoadFirmware started...\n");
 
+  if (params->kernel_sign_key_size < sizeof(VbPublicKey)) {
+    debug("Kernel sign key buffer too small\n");
+    return LOAD_FIRMWARE_RECOVERY;
+  }
+
   /* Must have a root key */
   if (!root_key) {
     debug("No root key\n");