From 1ab2f8dd9de5f2610700d5ef4e7ebd013dd9ec39 Mon Sep 17 00:00:00 2001
From: Philipp Maier <pmaier@sysmocom.de>
Date: Tue, 21 Oct 2025 16:48:59 +0200
Subject: [PATCH] commands: do not use b2h with a string

The function h2b expects a bytearray and must not be used on a string.
This is also true for nullstrings ('').

Related: OS#6869
Change-Id: I0e28e6ec476901bf19aa0f8640e41c74aa6e3aa2
---
 pySim/commands.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pySim/commands.py b/pySim/commands.py
index f069db4b..066a2c48 100644
--- a/pySim/commands.py
+++ b/pySim/commands.py
@@ -141,7 +141,7 @@ class SimCardCommands:
         Returns:
                 Tuple of (decoded_data, sw)
         """
-        cmd = cmd_constr.build(cmd_data) if cmd_data else ''
+        cmd = cmd_constr.build(cmd_data) if cmd_data else b''
         lc = i2h([len(cmd)]) if cmd_data else ''
         le = '00' if resp_constr else ''
         pdu = ''.join([cla, ins, p1, p2, lc, b2h(cmd), le])