From fd80bd5e335b465cbaded1d0d2e5e2ef8b249cc1 Mon Sep 17 00:00:00 2001
From: Rodent Control <rdnt.cntrl@localhost>
Date: Sun, 2 Nov 2025 18:05:04 +0100
Subject: [PATCH] print only printable characters and \n on console

This prevents players or servers from abusing the terminal using escape
sequences, making it beep/flash (\a) etc.
---
 code/sys/sys_main.c | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/code/sys/sys_main.c b/code/sys/sys_main.c
index d7f5398336..238308599a 100644
--- a/code/sys/sys_main.c
+++ b/code/sys/sys_main.c
@@ -433,6 +433,24 @@ void Sys_AnsiColorPrint( const char *msg )
 	}
 }
 
+/*
+=================
+Sys_ReplaceNonPrintableChars
+=================
+*/
+void Sys_ReplaceNonPrintableChars(char *str)
+{
+	char *p;
+
+	for (p = str; *p != '\0'; p++)
+	{
+		if ( !isprint(*p) && *p != '\n' )
+		{
+			*p = '.';
+		}
+	}
+}
+
 /*
 =================
 Sys_Print
@@ -440,8 +458,16 @@ Sys_Print
 */
 void Sys_Print( const char *msg )
 {
-	CON_LogWrite( msg );
-	CON_Print( msg );
+	char clean_msg[ MAXPRINTMSG ];
+
+	// Replace non-printable characters before we print the string
+	// Prevents abuse, e.g. players messing up the terminal by \say-ing
+	// escape sequences
+	Q_strncpyz(clean_msg, msg, sizeof(clean_msg));
+	Sys_ReplaceNonPrintableChars(clean_msg);
+
+	CON_LogWrite( clean_msg );
+	CON_Print( clean_msg );
 }
 
 /*