From 0de0615eeb9a1c1e94d47e0813ba9747cc2f4d60 Mon Sep 17 00:00:00 2001
From: Alibek Omarov <a1ba.omarov@gmail.com>
Date: Sun, 2 Jul 2023 01:20:20 +0300
Subject: [PATCH] engine: client: implement map CRC32 checking on client side

---
 engine/client/cl_parse.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/engine/client/cl_parse.c b/engine/client/cl_parse.c
index c1a55742..a84734f4 100644
--- a/engine/client/cl_parse.c
+++ b/engine/client/cl_parse.c
@@ -21,6 +21,7 @@ GNU General Public License for more details.
 #include "shake.h"
 #include "hltv.h"
 #include "input.h"
+#include "server.h"
 #if XASH_LOW_MEMORY != 2
 int CL_UPDATE_BACKUP = SINGLEPLAYER_BACKUP;
 #endif
@@ -848,8 +849,10 @@ CL_ParseServerData
 void CL_ParseServerData( sizebuf_t *msg, qboolean legacy )
 {
 	char	gamefolder[MAX_QPATH];
+	string	mapfile;
 	qboolean	background;
 	int	i;
+	uint32_t	mapCRC;
 
 	HPAK_CheckSize( CUSTOM_RES_PATH );
 
@@ -912,6 +915,18 @@ void CL_ParseServerData( sizebuf_t *msg, qboolean legacy )
 		}
 	}
 
+	Q_snprintf( mapfile, sizeof( mapfile ), "maps/%s.bsp", clgame.mapname );
+	if( CRC32_MapFile( &mapCRC, mapfile, cl.maxclients > 1 ))
+	{
+		// validate map checksum
+		if( mapCRC != cl.checksum )
+		{
+			Con_Printf( S_ERROR "Your map [%s] differs from the server's.\n", clgame.mapname );
+			CL_Disconnect_f(); // for local game, call EndGame
+			Host_AbortCurrentFrame(); // to avoid svc_bad
+		}
+	}
+
 	if( clgame.maxModels > MAX_MODELS )
 		Con_Printf( S_WARN "server model limit is above client model limit %i > %i\n", clgame.maxModels, MAX_MODELS );