From 9c4807644bf8bb0d2b777e9d02573e9b94db7c0f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Gordan=20Neki=C4=87?=
 <48327736+gnekich@users.noreply.github.com>
Date: Sat, 6 Feb 2021 06:16:52 +0100
Subject: [PATCH] Fix ledger sign message (#7004)

there was an around ~1/128 chance of creating an invalid signature when signing a message with a ledger
---
 electrum/plugins/ledger/ledger.py | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/electrum/plugins/ledger/ledger.py b/electrum/plugins/ledger/ledger.py
index 27a474de9..c72f4a24a 100644
--- a/electrum/plugins/ledger/ledger.py
+++ b/electrum/plugins/ledger/ledger.py
@@ -334,7 +334,12 @@ class Ledger_KeyStore(Hardware_KeyStore):
         if sLength == 33:
             s = s[1:]
         # And convert it
-        return bytes([27 + 4 + (signature[0] & 0x01)]) + r + s
+
+        # Pad r and s points with 0x00 bytes when the point is small to get valid signature.
+        r_padded = bytes([0x00]) * (32 - len(r)) + r
+        s_padded = bytes([0x00]) * (32 - len(s)) + s
+        
+        return bytes([27 + 4 + (signature[0] & 0x01)]) + r_padded + s_padded
 
     @runs_in_hwd_thread
     @test_pin_unlocked