Add: [Network] Validate the client name server side, so no clients with invalid names can actually join

src/lang/english.txt

@@ -2188,6 +2188,7 @@ STR_NETWORK_ERROR_TIMEOUT_PASSWORD                              :{WHITE}You took
 STR_NETWORK_ERROR_TIMEOUT_COMPUTER                              :{WHITE}Your computer is too slow to keep up with the server
 STR_NETWORK_ERROR_TIMEOUT_MAP                                   :{WHITE}Your computer took too long to download the map
 STR_NETWORK_ERROR_TIMEOUT_JOIN                                  :{WHITE}Your computer took too long to join the server
+STR_NETWORK_ERROR_INVALID_CLIENT_NAME                           :{WHITE}Your player name is not valid
 
 ############ Leave those lines in this order!!
 STR_NETWORK_ERROR_CLIENT_GENERAL                                :general error
@@ -2210,6 +2211,7 @@ STR_NETWORK_ERROR_CLIENT_TIMEOUT_PASSWORD                       :received no pas
 STR_NETWORK_ERROR_CLIENT_TIMEOUT_COMPUTER                       :general timeout
 STR_NETWORK_ERROR_CLIENT_TIMEOUT_MAP                            :downloading map took too long
 STR_NETWORK_ERROR_CLIENT_TIMEOUT_JOIN                           :processing map took too long
+STR_NETWORK_ERROR_CLIENT_INVALID_CLIENT_NAME                    :invalid client name
 ############ End of leave-in-this-order
 
 STR_NETWORK_ERROR_CLIENT_GUI_LOST_CONNECTION_CAPTION            :{WHITE}Possible connection loss

src/network/network.cpp

@@ -314,6 +314,7 @@ StringID GetNetworkErrorMsg(NetworkErrorCode err)
 		STR_NETWORK_ERROR_CLIENT_TIMEOUT_COMPUTER,
 		STR_NETWORK_ERROR_CLIENT_TIMEOUT_MAP,
 		STR_NETWORK_ERROR_CLIENT_TIMEOUT_JOIN,
+		STR_NETWORK_ERROR_CLIENT_INVALID_CLIENT_NAME,
 	};
 	static_assert(lengthof(network_error_strings) == NETWORK_ERROR_END);
 

src/network/network_client.cpp

@@ -668,26 +668,27 @@ NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_CLIENT_INFO(Pac
 NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_ERROR(Packet *p)
 {
 	static const StringID network_error_strings[] = {
-		STR_NETWORK_ERROR_LOSTCONNECTION,    // NETWORK_ERROR_GENERAL
-		STR_NETWORK_ERROR_LOSTCONNECTION,    // NETWORK_ERROR_DESYNC
-		STR_NETWORK_ERROR_LOSTCONNECTION,    // NETWORK_ERROR_SAVEGAME_FAILED
-		STR_NETWORK_ERROR_LOSTCONNECTION,    // NETWORK_ERROR_CONNECTION_LOST
-		STR_NETWORK_ERROR_LOSTCONNECTION,    // NETWORK_ERROR_ILLEGAL_PACKET
-		STR_NETWORK_ERROR_LOSTCONNECTION,    // NETWORK_ERROR_NEWGRF_MISMATCH
-		STR_NETWORK_ERROR_SERVER_ERROR,      // NETWORK_ERROR_NOT_AUTHORIZED
-		STR_NETWORK_ERROR_SERVER_ERROR,      // NETWORK_ERROR_NOT_EXPECTED
-		STR_NETWORK_ERROR_WRONG_REVISION,    // NETWORK_ERROR_WRONG_REVISION
-		STR_NETWORK_ERROR_LOSTCONNECTION,    // NETWORK_ERROR_NAME_IN_USE
-		STR_NETWORK_ERROR_WRONG_PASSWORD,    // NETWORK_ERROR_WRONG_PASSWORD
-		STR_NETWORK_ERROR_SERVER_ERROR,      // NETWORK_ERROR_COMPANY_MISMATCH
-		STR_NETWORK_ERROR_KICKED,            // NETWORK_ERROR_KICKED
-		STR_NETWORK_ERROR_CHEATER,           // NETWORK_ERROR_CHEATER
-		STR_NETWORK_ERROR_SERVER_FULL,       // NETWORK_ERROR_FULL
-		STR_NETWORK_ERROR_TOO_MANY_COMMANDS, // NETWORK_ERROR_TOO_MANY_COMMANDS
-		STR_NETWORK_ERROR_TIMEOUT_PASSWORD,  // NETWORK_ERROR_TIMEOUT_PASSWORD
-		STR_NETWORK_ERROR_TIMEOUT_COMPUTER,  // NETWORK_ERROR_TIMEOUT_COMPUTER
-		STR_NETWORK_ERROR_TIMEOUT_MAP,       // NETWORK_ERROR_TIMEOUT_MAP
-		STR_NETWORK_ERROR_TIMEOUT_JOIN,      // NETWORK_ERROR_TIMEOUT_JOIN
+		STR_NETWORK_ERROR_LOSTCONNECTION,      // NETWORK_ERROR_GENERAL
+		STR_NETWORK_ERROR_LOSTCONNECTION,      // NETWORK_ERROR_DESYNC
+		STR_NETWORK_ERROR_LOSTCONNECTION,      // NETWORK_ERROR_SAVEGAME_FAILED
+		STR_NETWORK_ERROR_LOSTCONNECTION,      // NETWORK_ERROR_CONNECTION_LOST
+		STR_NETWORK_ERROR_LOSTCONNECTION,      // NETWORK_ERROR_ILLEGAL_PACKET
+		STR_NETWORK_ERROR_LOSTCONNECTION,      // NETWORK_ERROR_NEWGRF_MISMATCH
+		STR_NETWORK_ERROR_SERVER_ERROR,        // NETWORK_ERROR_NOT_AUTHORIZED
+		STR_NETWORK_ERROR_SERVER_ERROR,        // NETWORK_ERROR_NOT_EXPECTED
+		STR_NETWORK_ERROR_WRONG_REVISION,      // NETWORK_ERROR_WRONG_REVISION
+		STR_NETWORK_ERROR_LOSTCONNECTION,      // NETWORK_ERROR_NAME_IN_USE
+		STR_NETWORK_ERROR_WRONG_PASSWORD,      // NETWORK_ERROR_WRONG_PASSWORD
+		STR_NETWORK_ERROR_SERVER_ERROR,        // NETWORK_ERROR_COMPANY_MISMATCH
+		STR_NETWORK_ERROR_KICKED,              // NETWORK_ERROR_KICKED
+		STR_NETWORK_ERROR_CHEATER,             // NETWORK_ERROR_CHEATER
+		STR_NETWORK_ERROR_SERVER_FULL,         // NETWORK_ERROR_FULL
+		STR_NETWORK_ERROR_TOO_MANY_COMMANDS,   // NETWORK_ERROR_TOO_MANY_COMMANDS
+		STR_NETWORK_ERROR_TIMEOUT_PASSWORD,    // NETWORK_ERROR_TIMEOUT_PASSWORD
+		STR_NETWORK_ERROR_TIMEOUT_COMPUTER,    // NETWORK_ERROR_TIMEOUT_COMPUTER
+		STR_NETWORK_ERROR_TIMEOUT_MAP,         // NETWORK_ERROR_TIMEOUT_MAP
+		STR_NETWORK_ERROR_TIMEOUT_JOIN,        // NETWORK_ERROR_TIMEOUT_JOIN
+		STR_NETWORK_ERROR_INVALID_CLIENT_NAME, // NETWORK_ERROR_INVALID_CLIENT_NAME
 	};
 	static_assert(lengthof(network_error_strings) == NETWORK_ERROR_END);
 

src/network/network_server.cpp

@@ -945,8 +945,12 @@ NetworkRecvStatus ServerNetworkGameSocketHandler::Receive_CLIENT_JOIN(Packet *p)
 			break;
 	}
 
-	/* We need a valid name.. make it Player */
-	if (!NetworkIsValidClientName(name)) strecpy(name, "Player", lastof(name));
+	if (!NetworkIsValidClientName(name)) {
+		/* An invalid client name was given. However, the client ensures the name
+		 * is valid before it is sent over the network, so something went horribly
+		 * wrong. This is probably someone trying to troll us. */
+		return this->SendError(NETWORK_ERROR_INVALID_CLIENT_NAME);
+	}
 
 	if (!NetworkFindName(name, lastof(name))) { // Change name if duplicate
 		/* We could not create a name for this client */
@@ -1441,6 +1445,13 @@ NetworkRecvStatus ServerNetworkGameSocketHandler::Receive_CLIENT_SET_NAME(Packet
 	if (this->HasClientQuit()) return NETWORK_RECV_STATUS_CONN_LOST;
 
 	if (ci != nullptr) {
+		if (!NetworkIsValidClientName(client_name)) {
+			/* An invalid client name was given. However, the client ensures the name
+			 * is valid before it is sent over the network, so something went horribly
+			 * wrong. This is probably someone trying to troll us. */
+			return this->SendError(NETWORK_ERROR_INVALID_CLIENT_NAME);
+		}
+
 		/* Display change */
 		if (NetworkFindName(client_name, lastof(client_name))) {
 			NetworkTextMessage(NETWORK_ACTION_NAME_CHANGE, CC_DEFAULT, false, ci->client_name, client_name);

src/network/network_type.h

@@ -132,6 +132,7 @@ enum NetworkErrorCode {
 	NETWORK_ERROR_TIMEOUT_COMPUTER,
 	NETWORK_ERROR_TIMEOUT_MAP,
 	NETWORK_ERROR_TIMEOUT_JOIN,
+	NETWORK_ERROR_INVALID_CLIENT_NAME,
 
 	NETWORK_ERROR_END,
 };