From 13a82ca079ad4546586a732d6085ccd9b377972d Mon Sep 17 00:00:00 2001
From: NepDisk <nepdisk@noreply.codeberg.org>
Date: Sun, 29 Mar 2026 21:28:46 -0400
Subject: [PATCH] Port pubkey validation from RR and make it optional

For more competitve servers they can enable this to prevent unfair play while letting casual servers still have flexibility
---
 src/d_clisrv.c | 38 +++++++++++++++++++++++++++++++++++++-
 src/d_netcmd.c |  4 ++++
 src/doomstat.h |  1 +
 3 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/src/d_clisrv.c b/src/d_clisrv.c
index ae3cdac22..c435c2063 100644
--- a/src/d_clisrv.c
+++ b/src/d_clisrv.c
@@ -4574,7 +4574,7 @@ static void HandleConnect(SINT8 node)
 {
 	doomdata_t *netbuffer = DOOMCOM_DATA(doomcom);
 	char names[MAXSPLITSCREENPLAYERS][MAXPLAYERNAME + 1];
-	INT32 i;
+	INT32 i, j;
 	UINT8 availabilitiesbuffer[MAXAVAILABILITY];
 
 	// Sal: Dedicated mode is INCREDIBLY hacked together.
@@ -4690,6 +4690,8 @@ static void HandleConnect(SINT8 node)
 	{
 		int sigcheck;
 		boolean newnode = false;
+		char allZero[PUBKEYLENGTH];
+		memset(allZero, 0, sizeof(allZero));
 
 		for (i = 0; i < netbuffer->u.clientcfg.localplayers - playerpernode[node]; i++)
 		{
@@ -4714,6 +4716,40 @@ static void HandleConnect(SINT8 node)
 					return;
 				}
 			}
+
+			if (cv_validate_pubkey.value)
+			{
+				// Check non-GUESTS for duplicate pubkeys, they'll create nonsense stats
+				if (memcmp(lastReceivedKey[node][i], allZero, PUBKEYLENGTH) != 0)
+				{
+					// Players already here
+					for (j = 0; j < MAXPLAYERS; j++)
+					{
+						if (!playeringame[j])
+							continue;
+
+						if (memcmp(lastReceivedKey[node][i], players[j].public_key, PUBKEYLENGTH) == 0)
+						{
+							SV_SendRefuse(node, M_GetText("This server disallows\nduplicate pubkeys,\n(Did you share your keys?)"));
+							return;
+						}
+					}
+
+					// Players we're trying to add
+					for (j = 0; j < netbuffer->u.clientcfg.localplayers - playerpernode[node]; j++)
+					{
+						if (memcmp(lastReceivedKey[node][i], allZero, PUBKEYLENGTH) == 0)
+							continue;
+						if (i == j)
+							continue;
+						if (memcmp(lastReceivedKey[node][i], lastReceivedKey[node][j], PUBKEYLENGTH) == 0)
+						{
+							SV_SendRefuse(node, M_GetText("Duplicate pubkey in local party.\n(How did you even do this?)"));
+							return;
+						}
+					}
+				}
+			}
 		}
 
 		memcpy(availabilitiesbuffer, netbuffer->u.clientcfg.availabilities, sizeof(availabilitiesbuffer));
diff --git a/src/d_netcmd.c b/src/d_netcmd.c
index 234449009..1b0ef80d9 100644
--- a/src/d_netcmd.c
+++ b/src/d_netcmd.c
@@ -791,6 +791,9 @@ consvar_t cv_nettimeout = CVAR_INIT ("nettimeout", "210", CV_CALL|CV_SAVE, netti
 consvar_t cv_jointimeout = CVAR_INIT ("jointimeout", "210", CV_CALL|CV_SAVE, nettimeout_cons_t, JoinTimeout_OnChange);
 consvar_t cv_maxping = CVAR_INIT ("maxdelay", "20", CV_SAVE, CV_Unsigned, NULL);
 
+consvar_t cv_validate_pubkey= CVAR_INIT ("validate_pubkey", "Off", 0, CV_OnOff, NULL); // Validate for duplicate players on Join.
+
+
 static CV_PossibleValue_t lagless_cons_t[] = {{-1, "Worst"}, {0, "Best"}, {1, "Lagless"}, {0, NULL}};
 consvar_t cv_lagless = CVAR_INIT ("lagless", "Lagless", CV_SAVE|CV_NETVAR|CV_CALL, lagless_cons_t, Lagless_OnChange);
 
@@ -1146,6 +1149,7 @@ void D_RegisterServerCommands(void)
 	COM_AddCommand("ping", Command_Ping_f);
 	CV_RegisterVar(&cv_nettimeout);
 	CV_RegisterVar(&cv_jointimeout);
+	CV_RegisterVar(&cv_validate_pubkey);
 	CV_RegisterVar(&cv_kicktime);
 	CV_RegisterVar(&cv_skipmapcheck);
 	CV_RegisterVar(&cv_sleep);
diff --git a/src/doomstat.h b/src/doomstat.h
index 6fa215316..043d23a39 100644
--- a/src/doomstat.h
+++ b/src/doomstat.h
@@ -778,6 +778,7 @@ extern consvar_t cv_forceskin; // force clients to use the server's skin
 extern consvar_t cv_downloading; // allow clients to downloading WADs.
 extern consvar_t cv_nettimeout; // SRB2Kart: Advanced server options menu
 extern consvar_t cv_jointimeout;
+extern consvar_t cv_validate_pubkey;
 extern ticcmd_t netcmds[BACKUPTICS][MAXPLAYERS];
 extern INT32 serverplayer;
 extern INT32 adminplayers[MAXPLAYERS];