legacy: return root_fingerprint in PublicKey

legacy/firmware/fsm_msg_coin.h

@@ -34,9 +34,16 @@ void fsm_msgGetPublicKey(const GetPublicKey *msg) {
   if (msg->has_ecdsa_curve_name) {
     curve = msg->ecdsa_curve_name;
   }
+
+  // derive m/0' to obtain root_fingerprint
+  uint32_t root_fingerprint;
+  uint32_t path[1] = {0x80000000 | 0};
+  HDNode *node = fsm_getDerivedNode(curve, path, 1, &root_fingerprint);
+  if (!node) return;
+
   uint32_t fingerprint;
-  HDNode *node = fsm_getDerivedNode(curve, msg->address_n, msg->address_n_count,
-                                    &fingerprint);
+  node = fsm_getDerivedNode(curve, msg->address_n, msg->address_n_count,
+                            &fingerprint);
   if (!node) return;
   hdnode_fill_public_key(node);
 
@@ -96,6 +103,9 @@ void fsm_msgGetPublicKey(const GetPublicKey *msg) {
     }
   }
 
+  resp->has_root_fingerprint = true;
+  resp->root_fingerprint = root_fingerprint;
+
   msg_write(MessageType_MessageType_PublicKey, resp);
   layoutHome();
 }