From 7c82cd82d7216299ca7a2497f4bc318f3532650a Mon Sep 17 00:00:00 2001
From: iTrooz <hey@itrooz.fr>
Date: Sat, 25 Jan 2025 20:19:19 +0100
Subject: [PATCH] use m_responseReadState to avoid calling parseResponse() (as
 a failsafe for malicious/bad server responses)

Signed-off-by: iTrooz <hey@itrooz.fr>
---
 launcher/ui/pages/instance/McClient.cpp | 12 +++++++++---
 launcher/ui/pages/instance/McClient.h   |  4 ++++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/launcher/ui/pages/instance/McClient.cpp b/launcher/ui/pages/instance/McClient.cpp
index 05d4ac31a..3ed6a7665 100644
--- a/launcher/ui/pages/instance/McClient.cpp
+++ b/launcher/ui/pages/instance/McClient.cpp
@@ -46,18 +46,24 @@ void McClient::sendRequest() {
     writePacketToSocket(data); // send status packet
 }
 
-// Accumulate data until we have a full response, then call parseResponse()
+// Accumulate data until we have a full response, then call parseResponse() once
 void McClient::readRawResponse() {
+    if (m_responseReadState == 2) {
+        return;
+    }
+
     m_resp.append(m_socket.readAll());
-    if (m_wantedRespLength == 0 && m_resp.size() >= 5) {
+    if (m_responseReadState == 0 && m_resp.size() >= 5) {
         m_wantedRespLength = readVarInt(m_resp);
+        m_responseReadState = 1;
     }
     
-    if (m_wantedRespLength != 0 && m_resp.size() >= m_wantedRespLength) {
+    if (m_responseReadState == 1 && m_resp.size() >= m_wantedRespLength) {
         if (m_resp.size() > m_wantedRespLength) {
             qDebug() << "Warning: Packet length doesn't match actual packet size (" << m_wantedRespLength << " expected vs " << m_resp.size() << " received)";
         }
         parseResponse();
+        m_responseReadState = 2;
     }
 }
 
diff --git a/launcher/ui/pages/instance/McClient.h b/launcher/ui/pages/instance/McClient.h
index 55d0350d1..11983eaa8 100644
--- a/launcher/ui/pages/instance/McClient.h
+++ b/launcher/ui/pages/instance/McClient.h
@@ -15,6 +15,10 @@ class McClient : public QObject {
     short m_port;
     QTcpSocket m_socket;
 
+    // 0: did not start reading the response yet
+    // 1: read the response length, still reading the response
+    // 2: finished reading the response
+    unsigned m_responseReadState = 0;
     unsigned m_wantedRespLength = 0;
     QByteArray m_resp;