From 7d73efbd316032b906caad255b6f791859e6d5f4 Mon Sep 17 00:00:00 2001
From: proddy <paul@derbyshire.nl>
Date: Sun, 8 Nov 2020 20:54:24 +0100
Subject: [PATCH] prevent crash when `send telegram` too short

---
 src/telegram.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/telegram.cpp b/src/telegram.cpp
index 1da3f2170..4fb9e78af 100644
--- a/src/telegram.cpp
+++ b/src/telegram.cpp
@@ -429,6 +429,11 @@ void TxService::add(const uint8_t  operation,
 // format is EMS 1.0 (src, dest, type_id, offset, data)
 // length is the length of the whole telegram data, excluding the CRC
 void TxService::add(uint8_t operation, const uint8_t * data, const uint8_t length, const bool front) {
+    // check length
+    if (length < 5) {
+        return;
+    }
+
     // build header. src, dest and offset have fixed positions
     uint8_t src    = data[0];
     uint8_t dest   = data[1];