From 43d6f5be75b7b414653517dedc64402dfc80fc55 Mon Sep 17 00:00:00 2001
From: liamcottle <liam@liamcottle.com>
Date: Mon, 27 May 2024 01:25:38 +1200
Subject: [PATCH] support aes 256 decryption keys

---
 src/mqtt.js | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/mqtt.js b/src/mqtt.js
index 429b468..5d24027 100644
--- a/src/mqtt.js
+++ b/src/mqtt.js
@@ -238,8 +238,20 @@ function decrypt(packet) {
             // create decryption iv/nonce for this packet
             const nonceBuffer = createNonce(packet.id, packet.from);
 
-            // create aes-128-ctr decipher
-            const decipher = crypto.createDecipheriv('aes-128-ctr', key, nonceBuffer);
+            // determine algorithm based on key length
+            var algorithm = null;
+            if(key.length === 16){
+                algorithm = "aes-128-ctr";
+            } else if(key.length === 32){
+                algorithm = "aes-256-ctr";
+            } else {
+                // skip this key, try the next one...
+                console.error(`Invalid decryption key length: ${key.length}`);
+                continue;
+            }
+
+            // create decipher
+            const decipher = crypto.createDecipheriv(algorithm, key, nonceBuffer);
 
             // decrypt encrypted packet
             const decryptedBuffer = Buffer.concat([decipher.update(packet.encrypted), decipher.final()]);