From 799f155f23a3dcbe32089d18b1bb8150648f4192 Mon Sep 17 00:00:00 2001
From: thilo <thilo@edf5b092-35ff-0310-97b2-ce42778d08ea>
Date: Mon, 1 Jun 2009 05:29:28 +0000
Subject: Make client send a random challenge number in getchallenge requests

git-svn-id: svn://svn.icculus.org/quake3/trunk@1567 edf5b092-35ff-0310-97b2-ce42778d08ea
---
 code/client/cl_main.c | 68 ++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 46 insertions(+), 22 deletions(-)

diff --git a/code/client/cl_main.c b/code/client/cl_main.c
index 814e7ab..b4d3d9b 100644
--- a/code/client/cl_main.c
+++ b/code/client/cl_main.c
@@ -1561,10 +1561,14 @@ void CL_Connect_f( void ) {
 
 	// if we aren't playing on a lan, we need to authenticate
 	// with the cd key
-	if ( NET_IsLocalAddress( clc.serverAddress ) ) {
+	if(NET_IsLocalAddress(clc.serverAddress))
 		cls.state = CA_CHALLENGING;
-	} else {
+	else
+	{
 		cls.state = CA_CONNECTING;
+		
+		// Set a client challenge number that ideally is mirrored back by the server.
+		clc.challenge = ((rand() << 16) ^ rand()) ^ Com_Milliseconds();
 	}
 
 	Key_SetCatcher( 0 );
@@ -2078,7 +2082,11 @@ void CL_CheckForResend( void ) {
 		if (!Cvar_VariableIntegerValue("com_standalone") && clc.serverAddress.type == NA_IP && !Sys_IsLANAddress( clc.serverAddress ) )
 			CL_RequestAuthorization();
 #endif
-		NET_OutOfBandPrint(NS_CLIENT, clc.serverAddress, "getchallenge");
+
+		// The challenge request shall be followed by a client challenge so no malicious server can hijack this connection.
+		Com_sprintf(data, sizeof(data), "getchallenge %d", clc.challenge);
+
+		NET_OutOfBandPrint(NS_CLIENT, clc.serverAddress, data);
 		break;
 		
 	case CA_CHALLENGING:
@@ -2328,21 +2336,39 @@ void CL_ConnectionlessPacket( netadr_t from, msg_t *msg ) {
 	Com_DPrintf ("CL packet %s: %s\n", NET_AdrToStringwPort(from), c);
 
 	// challenge from the server we are connecting to
-	if ( !Q_stricmp(c, "challengeResponse") ) {
-		if ( cls.state != CA_CONNECTING ) {
-			Com_DPrintf( "Unwanted challenge response received.  Ignored.\n" );
-		} else {
-			// start sending challenge repsonse instead of challenge request packets
-			clc.challenge = atoi(Cmd_Argv(1));
-			cls.state = CA_CHALLENGING;
-			clc.connectPacketCount = 0;
-			clc.connectTime = -99999;
-
-			// take this address as the new server address.  This allows
-			// a server proxy to hand off connections to multiple servers
-			clc.serverAddress = from;
-			Com_DPrintf ("challengeResponse: %d\n", clc.challenge);
+	if (!Q_stricmp(c, "challengeResponse"))
+	{
+		if (cls.state != CA_CONNECTING)
+		{
+			Com_DPrintf("Unwanted challenge response received.  Ignored.\n");
+			return;
 		}
+		
+		if(!NET_CompareAdr(from, clc.serverAddress))
+		{
+			// This challenge response is not coming from the expected address.
+			// Check whether we have a matching client challenge to prevent
+			// connection hi-jacking.
+			
+			c = Cmd_Argv(2);
+			
+			if(!*c || atoi(c) != clc.challenge)
+			{
+				Com_DPrintf("Challenge response received from unexpected source. Ignored.\n");
+				return;
+			}
+		}
+
+		// start sending challenge response instead of challenge request packets
+		clc.challenge = atoi(Cmd_Argv(1));
+		cls.state = CA_CHALLENGING;
+		clc.connectPacketCount = 0;
+		clc.connectTime = -99999;
+
+		// take this address as the new server address.  This allows
+		// a server proxy to hand off connections to multiple servers
+		clc.serverAddress = from;
+		Com_DPrintf ("challengeResponse: %d\n", clc.challenge);
 		return;
 	}
 
@@ -2353,13 +2379,11 @@ void CL_ConnectionlessPacket( netadr_t from, msg_t *msg ) {
 			return;
 		}
 		if ( cls.state != CA_CHALLENGING ) {
-			Com_Printf ("connectResponse packet while not connecting.  Ignored.\n");
+			Com_Printf ("connectResponse packet while not connecting. Ignored.\n");
 			return;
 		}
-		if ( !NET_CompareBaseAdr( from, clc.serverAddress ) ) {
-			Com_Printf( "connectResponse from a different address.  Ignored.\n" );
-			Com_Printf( "%s should have been %s\n", NET_AdrToStringwPort( from ), 
-				NET_AdrToStringwPort( clc.serverAddress ) );
+		if ( !NET_CompareAdr( from, clc.serverAddress ) ) {
+			Com_Printf( "connectResponse from wrong address. Ignored.\n" );
 			return;
 		}
 		Netchan_Setup (NS_CLIENT, &clc.netchan, from, Cvar_VariableValue( "net_qport" ) );
-- 
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