Make sure that the time we use is always the same across servers

common/src/main/java/org/geysermc/floodgate/time/SntpClientUtils.java

@@ -0,0 +1,91 @@
+/*
+ * Copyright (c) 2019-2021 GeyserMC. http://geysermc.org
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ * @author GeyserMC
+ * @link https://github.com/GeyserMC/Geyser
+ */
+
+package org.geysermc.floodgate.time;
+
+import java.net.DatagramPacket;
+import java.net.DatagramSocket;
+import java.net.InetAddress;
+import java.nio.ByteBuffer;
+
+/*
+ * Thanks:
+ * https://datatracker.ietf.org/doc/html/rfc1769
+ * https://github.com/jonsagara/SimpleNtpClient
+ * https://stackoverflow.com/a/29138806
+ */
+public final class SntpClientUtils {
+    private static final int NTP_PORT = 123;
+
+    private static final int NTP_PACKET_SIZE = 48;
+    private static final int NTP_MODE = 3; // client
+    private static final int NTP_VERSION = 3;
+    private static final int RECEIVE_TIME_POSITION = 32;
+
+    private static final long NTP_TIME_OFFSET = ((365L * 70L) + 17L) * 24L * 60L * 60L;
+
+    public static long requestTimeOffset(String host, int timeout) {
+        try (DatagramSocket socket = new DatagramSocket()) {
+            socket.setSoTimeout(timeout);
+
+            InetAddress address = InetAddress.getByName(host);
+
+            ByteBuffer buff = ByteBuffer.allocate(NTP_PACKET_SIZE);
+
+            DatagramPacket request = new DatagramPacket(
+                    buff.array(), NTP_PACKET_SIZE, address, NTP_PORT
+            );
+
+            // mode is in the least signification 3 bits
+            // version is in bits 3-5
+            buff.put((byte) (NTP_MODE | (NTP_VERSION << 3)));
+
+            long originateTime = System.currentTimeMillis();
+            socket.send(request);
+
+            DatagramPacket response = new DatagramPacket(buff.array(), NTP_PACKET_SIZE);
+            socket.receive(response);
+
+            long responseTime = System.currentTimeMillis();
+
+            // everything before isn't important for us
+            buff.position(RECEIVE_TIME_POSITION);
+
+            long receiveTime = readTimestamp(buff);
+            long transmitTime = readTimestamp(buff);
+
+            return ((receiveTime - originateTime) + (transmitTime - responseTime)) / 2;
+        } catch (Exception ignored) {
+        }
+        return Long.MIN_VALUE;
+    }
+
+    private static long readTimestamp(ByteBuffer buffer) {
+        //todo look into the ntp 2036 problem
+        long seconds = buffer.getInt() & 0xffffffffL;
+        long fraction = buffer.getInt() & 0xffffffffL;
+        return ((seconds - NTP_TIME_OFFSET) * 1000) + ((fraction * 1000) / 0x100000000L);
+    }
+}

common/src/main/java/org/geysermc/floodgate/time/TimeSyncer.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2019-2021 GeyserMC. http://geysermc.org
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ * @author GeyserMC
+ * @link https://github.com/GeyserMC/Geyser
+ */
+
+package org.geysermc.floodgate.time;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
+public final class TimeSyncer {
+    private final ExecutorService executorService;
+    private long timeOffset = Long.MIN_VALUE; // value when it failed to get the offset
+
+    public TimeSyncer(String timeServer) {
+        ScheduledExecutorService service = Executors.newScheduledThreadPool(1);
+        service.scheduleWithFixedDelay(() -> {
+            // 5 tries to get the time offset
+            for (int i = 0; i < 5; i++) {
+                long offset = SntpClientUtils.requestTimeOffset(timeServer, 3000);
+                if (offset != Long.MIN_VALUE) {
+                    timeOffset = offset;
+                    return;
+                }
+            }
+        }, 0, 30, TimeUnit.MINUTES);
+        executorService = service;
+    }
+
+    public void shutdown() {
+        executorService.shutdown();
+    }
+
+    public long getTimeOffset() {
+        return timeOffset;
+    }
+}

common/src/main/java/org/geysermc/floodgate/util/BedrockData.java

@@ -28,6 +28,7 @@ package org.geysermc.floodgate.util;
 import lombok.AccessLevel;
 import lombok.Getter;
 import lombok.RequiredArgsConstructor;
+import org.geysermc.floodgate.time.TimeSyncer;
 
 /**
  * This class contains the raw data send by Geyser to Floodgate or from Floodgate to Floodgate. This
@@ -56,20 +57,28 @@ public final class BedrockData implements Cloneable {
     private final long timestamp;
     private final int dataLength;
 
-    public static BedrockData of(String version, String username, String xuid, int deviceOs,
+    public static BedrockData of(
+            String version, String username, String xuid, int deviceOs,
             String languageCode, int uiProfile, int inputMode, String ip,
             LinkedPlayer linkedPlayer, boolean fromProxy, int subscribeId,
-                                 String verifyCode) {
-        return new BedrockData(version, username, xuid, deviceOs, languageCode, inputMode,
-                uiProfile, ip, linkedPlayer, fromProxy, subscribeId, verifyCode,
-                System.currentTimeMillis(), EXPECTED_LENGTH);
+            String verifyCode, TimeSyncer timeSyncer) {
+
+        long realMillis = System.currentTimeMillis();
+        if (timeSyncer.getTimeOffset() != Long.MIN_VALUE) {
+            realMillis += timeSyncer.getTimeOffset();
         }
 
-    public static BedrockData of(String version, String username, String xuid, int deviceOs,
+        return new BedrockData(version, username, xuid, deviceOs, languageCode, inputMode,
+                uiProfile, ip, linkedPlayer, fromProxy, subscribeId, verifyCode,
+                realMillis, EXPECTED_LENGTH);
+    }
+
+    public static BedrockData of(
+            String version, String username, String xuid, int deviceOs,
             String languageCode, int uiProfile, int inputMode, String ip,
-                                 int subscribeId, String verifyCode) {
+            int subscribeId, String verifyCode, TimeSyncer timeSyncer) {
         return of(version, username, xuid, deviceOs, languageCode, uiProfile, inputMode, ip, null,
-                false, subscribeId, verifyCode);
+                false, subscribeId, verifyCode, timeSyncer);
     }
 
     public static BedrockData fromString(String data) {

connector/src/main/java/org/geysermc/connector/GeyserConnector.java

@@ -62,6 +62,7 @@ import org.geysermc.floodgate.crypto.AesCipher;
 import org.geysermc.floodgate.crypto.AesKeyProducer;
 import org.geysermc.floodgate.crypto.Base64Topping;
 import org.geysermc.floodgate.crypto.FloodgateCipher;
+import org.geysermc.floodgate.time.TimeSyncer;
 import org.jetbrains.annotations.Contract;
 
 import javax.naming.directory.Attribute;
@@ -79,7 +80,6 @@ import java.util.concurrent.TimeUnit;
 
 @Getter
 public class GeyserConnector {
-
     public static final ObjectMapper JSON_MAPPER = new ObjectMapper()
             .enable(JsonParser.Feature.IGNORE_UNDEFINED)
             .enable(JsonParser.Feature.ALLOW_COMMENTS)
@@ -106,6 +106,7 @@ public class GeyserConnector {
     @Setter
     private AuthType defaultAuthType;
 
+    private TimeSyncer timeSyncer;
     private FloodgateCipher cipher;
     private FloodgateSkinUploader skinUploader;
 
@@ -198,6 +199,7 @@ public class GeyserConnector {
         defaultAuthType = AuthType.getByName(config.getRemote().getAuthType());
 
         if (defaultAuthType == AuthType.FLOODGATE) {
+            timeSyncer = new TimeSyncer(Constants.NTP_SERVER);
             try {
                 Key key = new AesKeyProducer().produceFrom(config.getFloodgateKeyPath());
                 cipher = new AesCipher(new Base64Topping());
@@ -353,6 +355,7 @@ public class GeyserConnector {
 
         generalThreadPool.shutdown();
         bedrockServer.close();
+        timeSyncer.shutdown();
         players.clear();
         defaultAuthType = null;
         this.getCommandManager().getCommands().clear();
@@ -431,6 +434,10 @@ public class GeyserConnector {
         return bootstrap.getWorldManager();
     }
 
+    public TimeSyncer getTimeSyncer() {
+        return timeSyncer;
+    }
+
     /**
      * Whether to use XML reflections in the jar or manually find the reflections.
      * Will return true if the version number is not 'DEV' and the platform is not Fabric.

connector/src/main/java/org/geysermc/connector/network/session/GeyserSession.java

@@ -691,7 +691,8 @@ public class GeyserSession implements CommandSender {
                                     clientData.getCurrentInputMode().ordinal(),
                                     upstream.getAddress().getAddress().getHostAddress(),
                                     skinUploader.getId(),
-                                    skinUploader.getVerifyCode()
+                                    skinUploader.getVerifyCode(),
+                                    connector.getTimeSyncer()
                             ).toString());
                         } catch (Exception e) {
                             connector.getLogger().error(LanguageUtils.getLocaleStringLog("geyser.auth.floodgate.encrypt_fail"), e);

connector/src/main/java/org/geysermc/connector/utils/Constants.java

@@ -30,6 +30,7 @@ import java.net.URISyntaxException;
 
 public final class Constants {
     public static final URI SKIN_UPLOAD_URI;
+    public static final String NTP_SERVER = "time.cloudflare.com";
 
     static {
         URI skinUploadUri = null;