From 57556ccd4cefdc8c7386ee5979ee5ff2ac10f314 Mon Sep 17 00:00:00 2001
From: SomberNight <somber.night@protonmail.com>
Date: Wed, 4 May 2022 17:53:13 +0200
Subject: [PATCH] interface.get_block_header: assert height >= 0

---
 electrum/interface.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/electrum/interface.py b/electrum/interface.py
index 20d12a189..acae32a59 100644
--- a/electrum/interface.py
+++ b/electrum/interface.py
@@ -598,6 +598,8 @@ class Interface(Logger):
         self.logger.info("cert fingerprint verification passed")
 
     async def get_block_header(self, height, assert_mode):
+        if not is_non_negative_integer(height):
+            raise Exception(f"{repr(height)} is not a block height")
         self.logger.info(f'requesting block header {height} in mode {assert_mode}')
         # use lower timeout as we usually have network.bhi_lock here
         timeout = self.network.get_network_timeout_seconds(NetworkTimeout.Urgent)