Verify public keys from players

diff --git a/bukkit/pom.xml b/bukkit/pom.xml
index 2e1ccc4..c4caae8 100644
--- a/bukkit/pom.xml
+++ b/bukkit/pom.xml
@@ -119,9 +119,6 @@
         <repository>
             <id>dmulloy2-repo</id>
             <url>https://repo.dmulloy2.net/repository/public/</url>
-            <snapshots>
-                <enabled>false</enabled>
-            </snapshots>
         </repository>

         <!-- AuthMe Reloaded, xAuth and LoginSecurity -->
@@ -186,7 +183,7 @@
         <dependency>
             <groupId>com.comphenix.protocol</groupId>
             <artifactId>ProtocolLib</artifactId>
-            <version>5.0.0-SNAPSHOT</version>
+            <version>5.0.0-20220603.031413-2</version>
             <scope>provided</scope>
             <exclusions>
                 <exclusion>
@@ -351,5 +348,12 @@
             <scope>system</scope>
             <systemPath>${project.basedir}/lib/UltraAuth v2.1.2.jar</systemPath>
         </dependency>
+
+        <dependency>
+            <groupId>org.bouncycastle</groupId>
+            <artifactId>bcpkix-jdk18on</artifactId>
+            <version>1.71</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 </project>
diff --git a/bukkit/src/main/java/com/github/games647/fastlogin/bukkit/listener/protocollib/EncryptionUtil.java b/bukkit/src/main/java/com/github/games647/fastlogin/bukkit/listener/protocollib/EncryptionUtil.java
index 1197514..143dda9 100644
--- a/bukkit/src/main/java/com/github/games647/fastlogin/bukkit/listener/protocollib/EncryptionUtil.java
+++ b/bukkit/src/main/java/com/github/games647/fastlogin/bukkit/listener/protocollib/EncryptionUtil.java
@@ -25,15 +25,28 @@
  */
 package com.github.games647.fastlogin.bukkit.listener.protocollib;

+import com.github.games647.fastlogin.bukkit.listener.protocollib.packet.ClientPublicKey;
+import com.google.common.io.Resources;
+
+import java.io.IOException;
 import java.math.BigInteger;
 import java.nio.charset.StandardCharsets;
 import java.security.GeneralSecurityException;
+import java.security.InvalidKeyException;
+import java.security.KeyFactory;
 import java.security.KeyPair;
 import java.security.KeyPairGenerator;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.security.PrivateKey;
 import java.security.PublicKey;
+import java.security.Signature;
+import java.security.SignatureException;
+import java.security.spec.InvalidKeySpecException;
+import java.security.spec.X509EncodedKeySpec;
+import java.time.Instant;
+import java.util.Base64;
+import java.util.Base64.Encoder;
 import java.util.Random;

 import javax.crypto.Cipher;
@@ -46,11 +59,25 @@ import javax.crypto.spec.SecretKeySpec;
  *
  * @see net.minecraft.server.MinecraftEncryption
  */
-public class EncryptionUtil {
+class EncryptionUtil {

     public static final int VERIFY_TOKEN_LENGTH = 4;
     public static final String KEY_PAIR_ALGORITHM = "RSA";

+    private static final int RSA_LENGTH = 1_024;
+
+    private static final PublicKey mojangSessionKey;
+    private static final int LINE_LENGTH = 76;
+    private static final Encoder KEY_ENCODER = Base64.getMimeEncoder(LINE_LENGTH, "\n".getBytes(StandardCharsets.UTF_8));
+
+    static {
+        try {
+            mojangSessionKey = loadMojangSessionKey();
+        } catch (IOException | NoSuchAlgorithmException | InvalidKeySpecException ex) {
+            throw new RuntimeException("Failed to load Mojang session key", ex);
+        }
+    }
+
     private EncryptionUtil() {
         // utility
     }
@@ -65,7 +92,7 @@ public class EncryptionUtil {
         try {
             KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(KEY_PAIR_ALGORITHM);

-            keyPairGenerator.initialize(1_024);
+            keyPairGenerator.initialize(RSA_LENGTH);
             return keyPairGenerator.generateKeyPair();
         } catch (NoSuchAlgorithmException nosuchalgorithmexception) {
             // Should be existing in every vm
@@ -120,6 +147,33 @@ public class EncryptionUtil {
         return new SecretKeySpec(decrypt(privateKey, sharedKey), "AES");
     }

+    public static boolean verifyClientKey(ClientPublicKey clientKey, Instant verifyTimstamp)
+        throws SignatureException, NoSuchAlgorithmException, InvalidKeyException {
+        if (!verifyTimstamp.isBefore(clientKey.getExpiry())) {
+            return false;
+        }
+
+        Signature signature = Signature.getInstance("SHA1withRSA");
+        signature.initVerify(mojangSessionKey);
+        signature.update(toSignable(clientKey).getBytes(StandardCharsets.US_ASCII));
+        return signature.verify(clientKey.getSignature());
+    }
+
+    private static PublicKey loadMojangSessionKey()
+        throws IOException, NoSuchAlgorithmException, InvalidKeySpecException {
+        var keyUrl = Resources.getResource("yggdrasil_session_pubkey.der");
+        var keyData = Resources.toByteArray(keyUrl);
+        var keySpec = new X509EncodedKeySpec(keyData);
+
+        return KeyFactory.getInstance("RSA").generatePublic(keySpec);
+    }
+
+    private static String toSignable(ClientPublicKey clientPublicKey) {
+        long expiry = clientPublicKey.getExpiry().toEpochMilli();
+        String encoded = KEY_ENCODER.encodeToString(clientPublicKey.getKey());
+        return expiry + "-----BEGIN RSA PUBLIC KEY-----\n" + encoded + "\n-----END RSA PUBLIC KEY-----\n";
+    }
+
     public static byte[] decrypt(PrivateKey key, byte[] data) throws GeneralSecurityException {
         // b(Key var0, byte[] var1)
         Cipher cipher = Cipher.getInstance(key.getAlgorithm());
diff --git a/bukkit/src/main/java/com/github/games647/fastlogin/bukkit/listener/protocollib/ProtocolLibListener.java b/bukkit/src/main/java/com/github/games647/fastlogin/bukkit/listener/protocollib/ProtocolLibListener.java
index f8b8de2..c9e72fc 100644
--- a/bukkit/src/main/java/com/github/games647/fastlogin/bukkit/listener/protocollib/ProtocolLibListener.java
+++ b/bukkit/src/main/java/com/github/games647/fastlogin/bukkit/listener/protocollib/ProtocolLibListener.java
@@ -27,18 +27,27 @@ package com.github.games647.fastlogin.bukkit.listener.protocollib;

 import com.comphenix.protocol.PacketType;
 import com.comphenix.protocol.ProtocolLibrary;
+import com.comphenix.protocol.events.InternalStructure;
 import com.comphenix.protocol.events.PacketAdapter;
 import com.comphenix.protocol.events.PacketContainer;
 import com.comphenix.protocol.events.PacketEvent;
-import com.github.games647.fastlogin.bukkit.BukkitLoginSession;
+import com.comphenix.protocol.reflect.FuzzyReflection;
 import com.comphenix.protocol.wrappers.WrappedGameProfile;
+import com.github.games647.fastlogin.bukkit.BukkitLoginSession;
 import com.github.games647.fastlogin.bukkit.FastLoginBukkit;
+import com.github.games647.fastlogin.bukkit.listener.protocollib.packet.ClientPublicKey;
 import com.github.games647.fastlogin.core.antibot.AntiBotService;
 import com.github.games647.fastlogin.core.antibot.AntiBotService.Action;

 import java.net.InetSocketAddress;
+import java.security.InvalidKeyException;
 import java.security.KeyPair;
+import java.security.NoSuchAlgorithmException;
+import java.security.PublicKey;
 import java.security.SecureRandom;
+import java.security.SignatureException;
+import java.time.Instant;
+import java.util.Optional;

 import org.bukkit.entity.Player;

@@ -149,6 +158,11 @@ public class ProtocolLibListener extends PacketAdapter {
             username = (String) packetEvent.getPacket().getMeta("original_name").get();
         }

+        if (!verifyPublicKey(packet)) {
+            plugin.getLog().warn("Invalid public key from player {}", username);
+            return;
+        }
+
         plugin.getLog().trace("GameProfile {} with {} connecting", sessionKey, username);

         packetEvent.getAsyncMarker().incrementProcessingDelay();
@@ -156,6 +170,24 @@ public class ProtocolLibListener extends PacketAdapter {
         plugin.getScheduler().runAsync(nameCheckTask);
     }

+    private boolean verifyPublicKey(PacketContainer packet) {
+        Optional<InternalStructure> internalStructure = packet.getOptionalStructures().readSafely(0);
+        if (internalStructure == null) {
+            return true;
+        }
+
+        Object instance = internalStructure.get().getHandle();
+        Instant expires = FuzzyReflection.getFieldValue(instance, Instant.class, true);
+        PublicKey key = FuzzyReflection.getFieldValue(instance, PublicKey.class, true);
+        byte[] signature = FuzzyReflection.getFieldValue(instance, byte[].class, true);
+        ClientPublicKey clientKey = new ClientPublicKey(expires, key.getEncoded(), signature);
+        try {
+            return EncryptionUtil.verifyClientKey(clientKey, Instant.now());
+        } catch (SignatureException | InvalidKeyException | NoSuchAlgorithmException ex) {
+            return false;
+        }
+    }
+
     private String getUsername(PacketContainer packet) {
         WrappedGameProfile profile = packet.getGameProfiles().readSafely(0);
         if (profile == null) {
diff --git a/bukkit/src/main/java/com/github/games647/fastlogin/bukkit/listener/protocollib/packet/ClientPublicKey.java b/bukkit/src/main/java/com/github/games647/fastlogin/bukkit/listener/protocollib/packet/ClientPublicKey.java
new file mode 100644
index 0000000..495adb1
--- /dev/null
+++ b/bukkit/src/main/java/com/github/games647/fastlogin/bukkit/listener/protocollib/packet/ClientPublicKey.java
@@ -0,0 +1,53 @@
+/*
+ * SPDX-License-Identifier: MIT
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2015-2022 games647 and contributors
+ *
+ * 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.
+ */
+package com.github.games647.fastlogin.bukkit.listener.protocollib.packet;
+
+import java.time.Instant;
+
+public class ClientPublicKey {
+
+    private final Instant expiry;
+    private final byte[] key;
+    private final byte[] signature;
+
+    public ClientPublicKey(Instant expiry, byte[] key, byte[] signature) {
+        this.expiry = expiry;
+        this.key = key;
+        this.signature = signature;
+    }
+
+    public Instant getExpiry() {
+        return expiry;
+    }
+
+    public byte[] getKey() {
+        return key;
+    }
+
+    public byte[] getSignature() {
+        return signature;
+    }
+}
diff --git a/bukkit/src/test/java/com/github/games647/fastlogin/bukkit/listener/protocollib/EncryptionUtilTest.java b/bukkit/src/test/java/com/github/games647/fastlogin/bukkit/listener/protocollib/EncryptionUtilTest.java
index 7a097f1..11a52f7 100644
--- a/bukkit/src/test/java/com/github/games647/fastlogin/bukkit/listener/protocollib/EncryptionUtilTest.java
+++ b/bukkit/src/test/java/com/github/games647/fastlogin/bukkit/listener/protocollib/EncryptionUtilTest.java
@@ -25,8 +25,27 @@
  */
 package com.github.games647.fastlogin.bukkit.listener.protocollib;

+import com.github.games647.fastlogin.bukkit.listener.protocollib.packet.ClientPublicKey;
+import com.google.common.io.Resources;
+import com.google.gson.Gson;
+import com.google.gson.JsonObject;
+
+import java.io.IOException;
+import java.io.Reader;
+import java.io.StringReader;
+import java.nio.charset.StandardCharsets;
+import java.security.KeyFactory;
+import java.security.NoSuchAlgorithmException;
 import java.security.SecureRandom;
+import java.security.interfaces.RSAPublicKey;
+import java.security.spec.InvalidKeySpecException;
+import java.security.spec.X509EncodedKeySpec;
+import java.time.Instant;
+import java.time.temporal.ChronoUnit;
+import java.util.Base64;

+import org.bouncycastle.util.io.pem.PemObject;
+import org.bouncycastle.util.io.pem.PemReader;
 import org.junit.Test;

 import static org.hamcrest.CoreMatchers.is;
@@ -43,4 +62,77 @@ public class EncryptionUtilTest {
         assertThat(token, notNullValue());
         assertThat(token.length, is(4));
     }
+
+    @Test
+    public void testExpiredClientKey() throws Exception {
+        var clientKey = loadClientKey("client_keys/valid.json");
+
+        // Client expires at the exact second mentioned, so use it for verification
+        var expiredTimestamp = clientKey.getExpiry();
+        assertThat(EncryptionUtil.verifyClientKey(clientKey, expiredTimestamp), is(false));
+    }
+
+    // @Test(expected = Exception.class)
+    @Test
+    public void testInvalidChangedExpiration() throws Exception {
+        // expiration date changed should make the signature invalid
+        // expiration should still be valid
+        var clientKey = loadClientKey("client_keys/invalid_wrong_expiration.json");
+        assertThat(EncryptionUtil.verifyClientKey(clientKey, clientKey.getExpiry().minus(5, ChronoUnit.HOURS)), is(false));
+    }
+
+    // @Test(expected = Exception.class)
+    @Test
+    public void testInvalidChangedKey() throws Exception {
+        // changed public key no longer corresponding to the signature
+        var clientKey = loadClientKey("client_keys/invalid_wrong_key.json");
+        assertThat(EncryptionUtil.verifyClientKey(clientKey, clientKey.getExpiry().minus(5, ChronoUnit.HOURS)), is(false));
+    }
+
+    @Test
+    public void testInvalidChangedSignature() throws Exception {
+        // signature modified no longer corresponding to key and expiration date
+        var clientKey = loadClientKey("client_keys/invalid_wrong_signature.json");
+        assertThat(EncryptionUtil.verifyClientKey(clientKey, clientKey.getExpiry().minus(5, ChronoUnit.HOURS)), is(false));
+    }
+
+    @Test
+    public void testValidClientKey() throws Exception {
+        var clientKey = loadClientKey("client_keys/valid.json");
+
+        var verificationTimestamp = clientKey.getExpiry().minus(5, ChronoUnit.HOURS);
+        assertThat(EncryptionUtil.verifyClientKey(clientKey, verificationTimestamp), is(true));
+    }
+
+    private ClientPublicKey loadClientKey(String path)
+        throws NoSuchAlgorithmException, IOException, InvalidKeySpecException {
+        var keyUrl = Resources.getResource(path);
+        var gson = new Gson();
+
+        var lines = Resources.toString(keyUrl, StandardCharsets.US_ASCII);
+        var object = gson.fromJson(lines, JsonObject.class);
+
+        Instant expires = Instant.parse(object.getAsJsonPrimitive("expires_at").getAsString());
+        String key = object.getAsJsonPrimitive("key").getAsString();
+        RSAPublicKey publicKey = parsePublicKey(key);
+
+        byte[] signature = Base64.getDecoder().decode(object.getAsJsonPrimitive("signature").getAsString());
+        return new ClientPublicKey(expires, publicKey.getEncoded(), signature);
+    }
+
+    private RSAPublicKey parsePublicKey(String lines)
+        throws IOException, InvalidKeySpecException, NoSuchAlgorithmException {
+        try (
+            Reader reader = new StringReader(lines);
+            PemReader pemReader = new PemReader(reader)
+        ) {
+
+            PemObject pemObject = pemReader.readPemObject();
+            byte[] content = pemObject.getContent();
+            var pubKeySpec = new X509EncodedKeySpec(content);
+
+            var factory = KeyFactory.getInstance("RSA");
+            return (RSAPublicKey) factory.generatePublic(pubKeySpec);
+        }
+    }
 }
diff --git a/bukkit/src/test/resources/client_keys/invalid_wrong_expiration.json b/bukkit/src/test/resources/client_keys/invalid_wrong_expiration.json
new file mode 100644
index 0000000..7ecc12e
--- /dev/null
+++ b/bukkit/src/test/resources/client_keys/invalid_wrong_expiration.json
@@ -0,0 +1,5 @@
+{
+    "expires_at": "2022-06-12T09:46:26.421156927Z",
+    "key": "-----BEGIN RSA PUBLIC KEY-----\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAoOv23jt2QPyab6bPRBwH2ggmzQU4I+xm\nDpi3X5ZB5Em/4uzyZqNVLJc0gShpk0XsdoB28Nq1bPxczOTBxuXi3rg5ax5gL+iymDSU27DLM8s/\n33lOofzGPJUEQGKlFm0QelDKZ/q5Y/9inHE3hEJKf7h0tnmGahXFmZSF/nRz9GHnfSYpjtDr9bsZ\nOzQuLhHXT5E4ksNRTFW41h0MlZ1qOhO+NiiVgk7LmgVYiV7RRbgO8U6RaCEqg5n28Ewo6QtzB+DF\n4NTDeu3E9BLH5G0npdUrVNhdRUWCFDmH6n9hqSIz2J7o6GvWqEvp0h9e/3qtLsoS60hnQXunrcWc\nPaEIYQIDAQAB\n-----END RSA PUBLIC KEY-----\n",
+    "signature": "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"
+}
diff --git a/bukkit/src/test/resources/client_keys/invalid_wrong_key.json b/bukkit/src/test/resources/client_keys/invalid_wrong_key.json
new file mode 100644
index 0000000..37bb3ad
--- /dev/null
+++ b/bukkit/src/test/resources/client_keys/invalid_wrong_key.json
@@ -0,0 +1,5 @@
+{
+    "expires_at": "2022-06-12T10:46:26.421156927Z",
+    "key": "-----BEGIN RSA PUBLIC KEY-----\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAoOv23jt2QPyab6bPRBwH2ggmzQU3I+xmDpi3X5ZB5Em/4uzyZqNVLJc0gShpk0XsdoB28Nq1bPxczOTBxuXi3rg5ax5gL+iymDSU27DLM8s/33lOofzGPJUEQGKlFm0QelDKZ/q5Y/9inHE3hEJKf7h0tnmGahXFmZSF/nRz9GHnfSYpjtDr9bsZOzQuLhHXT5E4ksNRTFW41h0MlZ1qOhO+NiiVgk7LmgVYiV7RRbgO8U6RaCEqg5n28Ewo6QtzB+DF4NTDeu3E9BLH5G0npdUrVNhdRUWCFDmH6n9hqSIz2J7o6GvWqEvp0h9e/3qtLsoS60hnQXunrcWcPaEIYQIDAQAB\n-----END RSA PUBLIC KEY-----\n",
+    "signature": "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"
+}
diff --git a/bukkit/src/test/resources/client_keys/invalid_wrong_signature.json b/bukkit/src/test/resources/client_keys/invalid_wrong_signature.json
new file mode 100644
index 0000000..cbca4b1
--- /dev/null
+++ b/bukkit/src/test/resources/client_keys/invalid_wrong_signature.json
@@ -0,0 +1,5 @@
+{
+    "expires_at": "2022-06-12T10:46:26.421156927Z",
+    "key": "-----BEGIN RSA PUBLIC KEY-----\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAoOv23jt2QPyab6bPRBwH2ggmzQU4I+xm\nDpi3X5ZB5Em/4uzyZqNVLJc0gShpk0XsdoB28Nq1bPxczOTBxuXi3rg5ax5gL+iymDSU27DLM8s/\n33lOofzGPJUEQGKlFm0QelDKZ/q5Y/9inHE3hEJKf7h0tnmGahXFmZSF/nRz9GHnfSYpjtDr9bsZ\nOzQuLhHXT5E4ksNRTFW41h0MlZ1qOhO+NiiVgk7LmgVYiV7RRbgO8U6RaCEqg5n28Ewo6QtzB+DF\n4NTDeu3E9BLH5G0npdUrVNhdRUWCFDmH6n9hqSIz2J7o6GvWqEvp0h9e/3qtLsoS60hnQXunrcWc\nPaEIYQIDAQAB\n-----END RSA PUBLIC KEY-----\n",
+    "signature": "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"
+}
diff --git a/bukkit/src/test/resources/client_keys/valid.json b/bukkit/src/test/resources/client_keys/valid.json
new file mode 100644
index 0000000..a2d6a41
--- /dev/null
+++ b/bukkit/src/test/resources/client_keys/valid.json
@@ -0,0 +1,5 @@
+{
+    "expires_at": "2022-06-12T10:46:26.421156927Z",
+    "key": "-----BEGIN RSA PUBLIC KEY-----\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAoOv23jt2QPyab6bPRBwH2ggmzQU4I+xmDpi3X5ZB5Em/4uzyZqNVLJc0gShpk0XsdoB28Nq1bPxczOTBxuXi3rg5ax5gL+iymDSU27DLM8s/33lOofzGPJUEQGKlFm0QelDKZ/q5Y/9inHE3hEJKf7h0tnmGahXFmZSF/nRz9GHnfSYpjtDr9bsZOzQuLhHXT5E4ksNRTFW41h0MlZ1qOhO+NiiVgk7LmgVYiV7RRbgO8U6RaCEqg5n28Ewo6QtzB+DF4NTDeu3E9BLH5G0npdUrVNhdRUWCFDmH6n9hqSIz2J7o6GvWqEvp0h9e/3qtLsoS60hnQXunrcWcPaEIYQIDAQAB\n-----END RSA PUBLIC KEY-----\n",
+    "signature": "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"
+}

bukkit/pom.xml

@@ -119,9 +119,6 @@
         <repository>
             <id>dmulloy2-repo</id>
             <url>https://repo.dmulloy2.net/repository/public/</url>
-            <snapshots>
-                <enabled>false</enabled>
-            </snapshots>
         </repository>
 
         <!-- AuthMe Reloaded, xAuth and LoginSecurity -->
@@ -186,7 +183,7 @@
         <dependency>
             <groupId>com.comphenix.protocol</groupId>
             <artifactId>ProtocolLib</artifactId>
-            <version>5.0.0-SNAPSHOT</version>
+            <version>5.0.0-20220603.031413-2</version>
             <scope>provided</scope>
             <exclusions>
                 <exclusion>
@@ -351,5 +348,12 @@
             <scope>system</scope>
             <systemPath>${project.basedir}/lib/UltraAuth v2.1.2.jar</systemPath>
         </dependency>
+
+        <dependency>
+            <groupId>org.bouncycastle</groupId>
+            <artifactId>bcpkix-jdk18on</artifactId>
+            <version>1.71</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 </project>

bukkit/src/main/java/com/github/games647/fastlogin/bukkit/listener/protocollib/EncryptionUtil.java

@@ -25,15 +25,28 @@
  */
 package com.github.games647.fastlogin.bukkit.listener.protocollib;
 
+import com.github.games647.fastlogin.bukkit.listener.protocollib.packet.ClientPublicKey;
+import com.google.common.io.Resources;
+
+import java.io.IOException;
 import java.math.BigInteger;
 import java.nio.charset.StandardCharsets;
 import java.security.GeneralSecurityException;
+import java.security.InvalidKeyException;
+import java.security.KeyFactory;
 import java.security.KeyPair;
 import java.security.KeyPairGenerator;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.security.PrivateKey;
 import java.security.PublicKey;
+import java.security.Signature;
+import java.security.SignatureException;
+import java.security.spec.InvalidKeySpecException;
+import java.security.spec.X509EncodedKeySpec;
+import java.time.Instant;
+import java.util.Base64;
+import java.util.Base64.Encoder;
 import java.util.Random;
 
 import javax.crypto.Cipher;
@@ -46,11 +59,25 @@ import javax.crypto.spec.SecretKeySpec;
  *
  * @see net.minecraft.server.MinecraftEncryption
  */
-public class EncryptionUtil {
+class EncryptionUtil {
 
     public static final int VERIFY_TOKEN_LENGTH = 4;
     public static final String KEY_PAIR_ALGORITHM = "RSA";
 
+    private static final int RSA_LENGTH = 1_024;
+
+    private static final PublicKey mojangSessionKey;
+    private static final int LINE_LENGTH = 76;
+    private static final Encoder KEY_ENCODER = Base64.getMimeEncoder(LINE_LENGTH, "\n".getBytes(StandardCharsets.UTF_8));
+
+    static {
+        try {
+            mojangSessionKey = loadMojangSessionKey();
+        } catch (IOException | NoSuchAlgorithmException | InvalidKeySpecException ex) {
+            throw new RuntimeException("Failed to load Mojang session key", ex);
+        }
+    }
+
     private EncryptionUtil() {
         // utility
     }
@@ -65,7 +92,7 @@ public class EncryptionUtil {
         try {
             KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(KEY_PAIR_ALGORITHM);
 
-            keyPairGenerator.initialize(1_024);
+            keyPairGenerator.initialize(RSA_LENGTH);
             return keyPairGenerator.generateKeyPair();
         } catch (NoSuchAlgorithmException nosuchalgorithmexception) {
             // Should be existing in every vm
@@ -120,6 +147,33 @@ public class EncryptionUtil {
         return new SecretKeySpec(decrypt(privateKey, sharedKey), "AES");
     }
 
+    public static boolean verifyClientKey(ClientPublicKey clientKey, Instant verifyTimstamp)
+        throws SignatureException, NoSuchAlgorithmException, InvalidKeyException {
+        if (!verifyTimstamp.isBefore(clientKey.getExpiry())) {
+            return false;
+        }
+
+        Signature signature = Signature.getInstance("SHA1withRSA");
+        signature.initVerify(mojangSessionKey);
+        signature.update(toSignable(clientKey).getBytes(StandardCharsets.US_ASCII));
+        return signature.verify(clientKey.getSignature());
+    }
+
+    private static PublicKey loadMojangSessionKey()
+        throws IOException, NoSuchAlgorithmException, InvalidKeySpecException {
+        var keyUrl = Resources.getResource("yggdrasil_session_pubkey.der");
+        var keyData = Resources.toByteArray(keyUrl);
+        var keySpec = new X509EncodedKeySpec(keyData);
+
+        return KeyFactory.getInstance("RSA").generatePublic(keySpec);
+    }
+
+    private static String toSignable(ClientPublicKey clientPublicKey) {
+        long expiry = clientPublicKey.getExpiry().toEpochMilli();
+        String encoded = KEY_ENCODER.encodeToString(clientPublicKey.getKey());
+        return expiry + "-----BEGIN RSA PUBLIC KEY-----\n" + encoded + "\n-----END RSA PUBLIC KEY-----\n";
+    }
+
     public static byte[] decrypt(PrivateKey key, byte[] data) throws GeneralSecurityException {
         // b(Key var0, byte[] var1)
         Cipher cipher = Cipher.getInstance(key.getAlgorithm());

bukkit/src/main/java/com/github/games647/fastlogin/bukkit/listener/protocollib/ProtocolLibListener.java

@@ -27,18 +27,27 @@ package com.github.games647.fastlogin.bukkit.listener.protocollib;
 
 import com.comphenix.protocol.PacketType;
 import com.comphenix.protocol.ProtocolLibrary;
+import com.comphenix.protocol.events.InternalStructure;
 import com.comphenix.protocol.events.PacketAdapter;
 import com.comphenix.protocol.events.PacketContainer;
 import com.comphenix.protocol.events.PacketEvent;
-import com.github.games647.fastlogin.bukkit.BukkitLoginSession;
+import com.comphenix.protocol.reflect.FuzzyReflection;
 import com.comphenix.protocol.wrappers.WrappedGameProfile;
+import com.github.games647.fastlogin.bukkit.BukkitLoginSession;
 import com.github.games647.fastlogin.bukkit.FastLoginBukkit;
+import com.github.games647.fastlogin.bukkit.listener.protocollib.packet.ClientPublicKey;
 import com.github.games647.fastlogin.core.antibot.AntiBotService;
 import com.github.games647.fastlogin.core.antibot.AntiBotService.Action;
 
 import java.net.InetSocketAddress;
+import java.security.InvalidKeyException;
 import java.security.KeyPair;
+import java.security.NoSuchAlgorithmException;
+import java.security.PublicKey;
 import java.security.SecureRandom;
+import java.security.SignatureException;
+import java.time.Instant;
+import java.util.Optional;
 
 import org.bukkit.entity.Player;
 
@@ -149,6 +158,11 @@ public class ProtocolLibListener extends PacketAdapter {
             username = (String) packetEvent.getPacket().getMeta("original_name").get();
         }
 
+        if (!verifyPublicKey(packet)) {
+            plugin.getLog().warn("Invalid public key from player {}", username);
+            return;
+        }
+
         plugin.getLog().trace("GameProfile {} with {} connecting", sessionKey, username);
 
         packetEvent.getAsyncMarker().incrementProcessingDelay();
@@ -156,6 +170,24 @@ public class ProtocolLibListener extends PacketAdapter {
         plugin.getScheduler().runAsync(nameCheckTask);
     }
 
+    private boolean verifyPublicKey(PacketContainer packet) {
+        Optional<InternalStructure> internalStructure = packet.getOptionalStructures().readSafely(0);
+        if (internalStructure == null) {
+            return true;
+        }
+
+        Object instance = internalStructure.get().getHandle();
+        Instant expires = FuzzyReflection.getFieldValue(instance, Instant.class, true);
+        PublicKey key = FuzzyReflection.getFieldValue(instance, PublicKey.class, true);
+        byte[] signature = FuzzyReflection.getFieldValue(instance, byte[].class, true);
+        ClientPublicKey clientKey = new ClientPublicKey(expires, key.getEncoded(), signature);
+        try {
+            return EncryptionUtil.verifyClientKey(clientKey, Instant.now());
+        } catch (SignatureException | InvalidKeyException | NoSuchAlgorithmException ex) {
+            return false;
+        }
+    }
+
     private String getUsername(PacketContainer packet) {
         WrappedGameProfile profile = packet.getGameProfiles().readSafely(0);
         if (profile == null) {

bukkit/src/main/java/com/github/games647/fastlogin/bukkit/listener/protocollib/packet/ClientPublicKey.java

@@ -0,0 +1,53 @@
+/*
+ * SPDX-License-Identifier: MIT
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2015-2022 games647 and contributors
+ *
+ * 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.
+ */
+package com.github.games647.fastlogin.bukkit.listener.protocollib.packet;
+
+import java.time.Instant;
+
+public class ClientPublicKey {
+
+    private final Instant expiry;
+    private final byte[] key;
+    private final byte[] signature;
+
+    public ClientPublicKey(Instant expiry, byte[] key, byte[] signature) {
+        this.expiry = expiry;
+        this.key = key;
+        this.signature = signature;
+    }
+
+    public Instant getExpiry() {
+        return expiry;
+    }
+
+    public byte[] getKey() {
+        return key;
+    }
+
+    public byte[] getSignature() {
+        return signature;
+    }
+}

bukkit/src/test/java/com/github/games647/fastlogin/bukkit/listener/protocollib/EncryptionUtilTest.java

@@ -25,8 +25,27 @@
  */
 package com.github.games647.fastlogin.bukkit.listener.protocollib;
 
-import java.security.SecureRandom;
+import com.github.games647.fastlogin.bukkit.listener.protocollib.packet.ClientPublicKey;
+import com.google.common.io.Resources;
+import com.google.gson.Gson;
+import com.google.gson.JsonObject;
 
+import java.io.IOException;
+import java.io.Reader;
+import java.io.StringReader;
+import java.nio.charset.StandardCharsets;
+import java.security.KeyFactory;
+import java.security.NoSuchAlgorithmException;
+import java.security.SecureRandom;
+import java.security.interfaces.RSAPublicKey;
+import java.security.spec.InvalidKeySpecException;
+import java.security.spec.X509EncodedKeySpec;
+import java.time.Instant;
+import java.time.temporal.ChronoUnit;
+import java.util.Base64;
+
+import org.bouncycastle.util.io.pem.PemObject;
+import org.bouncycastle.util.io.pem.PemReader;
 import org.junit.Test;
 
 import static org.hamcrest.CoreMatchers.is;
@@ -43,4 +62,77 @@ public class EncryptionUtilTest {
         assertThat(token, notNullValue());
         assertThat(token.length, is(4));
     }
+
+    @Test
+    public void testExpiredClientKey() throws Exception {
+        var clientKey = loadClientKey("client_keys/valid.json");
+
+        // Client expires at the exact second mentioned, so use it for verification
+        var expiredTimestamp = clientKey.getExpiry();
+        assertThat(EncryptionUtil.verifyClientKey(clientKey, expiredTimestamp), is(false));
+    }
+
+    // @Test(expected = Exception.class)
+    @Test
+    public void testInvalidChangedExpiration() throws Exception {
+        // expiration date changed should make the signature invalid
+        // expiration should still be valid
+        var clientKey = loadClientKey("client_keys/invalid_wrong_expiration.json");
+        assertThat(EncryptionUtil.verifyClientKey(clientKey, clientKey.getExpiry().minus(5, ChronoUnit.HOURS)), is(false));
+    }
+
+    // @Test(expected = Exception.class)
+    @Test
+    public void testInvalidChangedKey() throws Exception {
+        // changed public key no longer corresponding to the signature
+        var clientKey = loadClientKey("client_keys/invalid_wrong_key.json");
+        assertThat(EncryptionUtil.verifyClientKey(clientKey, clientKey.getExpiry().minus(5, ChronoUnit.HOURS)), is(false));
+    }
+
+    @Test
+    public void testInvalidChangedSignature() throws Exception {
+        // signature modified no longer corresponding to key and expiration date
+        var clientKey = loadClientKey("client_keys/invalid_wrong_signature.json");
+        assertThat(EncryptionUtil.verifyClientKey(clientKey, clientKey.getExpiry().minus(5, ChronoUnit.HOURS)), is(false));
+    }
+
+    @Test
+    public void testValidClientKey() throws Exception {
+        var clientKey = loadClientKey("client_keys/valid.json");
+
+        var verificationTimestamp = clientKey.getExpiry().minus(5, ChronoUnit.HOURS);
+        assertThat(EncryptionUtil.verifyClientKey(clientKey, verificationTimestamp), is(true));
+    }
+
+    private ClientPublicKey loadClientKey(String path)
+        throws NoSuchAlgorithmException, IOException, InvalidKeySpecException {
+        var keyUrl = Resources.getResource(path);
+        var gson = new Gson();
+
+        var lines = Resources.toString(keyUrl, StandardCharsets.US_ASCII);
+        var object = gson.fromJson(lines, JsonObject.class);
+
+        Instant expires = Instant.parse(object.getAsJsonPrimitive("expires_at").getAsString());
+        String key = object.getAsJsonPrimitive("key").getAsString();
+        RSAPublicKey publicKey = parsePublicKey(key);
+
+        byte[] signature = Base64.getDecoder().decode(object.getAsJsonPrimitive("signature").getAsString());
+        return new ClientPublicKey(expires, publicKey.getEncoded(), signature);
+    }
+
+    private RSAPublicKey parsePublicKey(String lines)
+        throws IOException, InvalidKeySpecException, NoSuchAlgorithmException {
+        try (
+            Reader reader = new StringReader(lines);
+            PemReader pemReader = new PemReader(reader)
+        ) {
+
+            PemObject pemObject = pemReader.readPemObject();
+            byte[] content = pemObject.getContent();
+            var pubKeySpec = new X509EncodedKeySpec(content);
+
+            var factory = KeyFactory.getInstance("RSA");
+            return (RSAPublicKey) factory.generatePublic(pubKeySpec);
+        }
+    }
 }

bukkit/src/test/resources/client_keys/invalid_wrong_expiration.json

@@ -0,0 +1,5 @@
+{
+    "expires_at": "2022-06-12T09:46:26.421156927Z",
+    "key": "-----BEGIN RSA PUBLIC KEY-----\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAoOv23jt2QPyab6bPRBwH2ggmzQU4I+xm\nDpi3X5ZB5Em/4uzyZqNVLJc0gShpk0XsdoB28Nq1bPxczOTBxuXi3rg5ax5gL+iymDSU27DLM8s/\n33lOofzGPJUEQGKlFm0QelDKZ/q5Y/9inHE3hEJKf7h0tnmGahXFmZSF/nRz9GHnfSYpjtDr9bsZ\nOzQuLhHXT5E4ksNRTFW41h0MlZ1qOhO+NiiVgk7LmgVYiV7RRbgO8U6RaCEqg5n28Ewo6QtzB+DF\n4NTDeu3E9BLH5G0npdUrVNhdRUWCFDmH6n9hqSIz2J7o6GvWqEvp0h9e/3qtLsoS60hnQXunrcWc\nPaEIYQIDAQAB\n-----END RSA PUBLIC KEY-----\n",
+    "signature": "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"
+}

bukkit/src/test/resources/client_keys/invalid_wrong_key.json

@@ -0,0 +1,5 @@
+{
+    "expires_at": "2022-06-12T10:46:26.421156927Z",
+    "key": "-----BEGIN RSA PUBLIC KEY-----\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAoOv23jt2QPyab6bPRBwH2ggmzQU3I+xmDpi3X5ZB5Em/4uzyZqNVLJc0gShpk0XsdoB28Nq1bPxczOTBxuXi3rg5ax5gL+iymDSU27DLM8s/33lOofzGPJUEQGKlFm0QelDKZ/q5Y/9inHE3hEJKf7h0tnmGahXFmZSF/nRz9GHnfSYpjtDr9bsZOzQuLhHXT5E4ksNRTFW41h0MlZ1qOhO+NiiVgk7LmgVYiV7RRbgO8U6RaCEqg5n28Ewo6QtzB+DF4NTDeu3E9BLH5G0npdUrVNhdRUWCFDmH6n9hqSIz2J7o6GvWqEvp0h9e/3qtLsoS60hnQXunrcWcPaEIYQIDAQAB\n-----END RSA PUBLIC KEY-----\n",
+    "signature": "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"
+}

bukkit/src/test/resources/client_keys/invalid_wrong_signature.json

@@ -0,0 +1,5 @@
+{
+    "expires_at": "2022-06-12T10:46:26.421156927Z",
+    "key": "-----BEGIN RSA PUBLIC KEY-----\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAoOv23jt2QPyab6bPRBwH2ggmzQU4I+xm\nDpi3X5ZB5Em/4uzyZqNVLJc0gShpk0XsdoB28Nq1bPxczOTBxuXi3rg5ax5gL+iymDSU27DLM8s/\n33lOofzGPJUEQGKlFm0QelDKZ/q5Y/9inHE3hEJKf7h0tnmGahXFmZSF/nRz9GHnfSYpjtDr9bsZ\nOzQuLhHXT5E4ksNRTFW41h0MlZ1qOhO+NiiVgk7LmgVYiV7RRbgO8U6RaCEqg5n28Ewo6QtzB+DF\n4NTDeu3E9BLH5G0npdUrVNhdRUWCFDmH6n9hqSIz2J7o6GvWqEvp0h9e/3qtLsoS60hnQXunrcWc\nPaEIYQIDAQAB\n-----END RSA PUBLIC KEY-----\n",
+    "signature": "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"
+}

bukkit/src/test/resources/client_keys/valid.json

@@ -0,0 +1,5 @@
+{
+    "expires_at": "2022-06-12T10:46:26.421156927Z",
+    "key": "-----BEGIN RSA PUBLIC KEY-----\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAoOv23jt2QPyab6bPRBwH2ggmzQU4I+xmDpi3X5ZB5Em/4uzyZqNVLJc0gShpk0XsdoB28Nq1bPxczOTBxuXi3rg5ax5gL+iymDSU27DLM8s/33lOofzGPJUEQGKlFm0QelDKZ/q5Y/9inHE3hEJKf7h0tnmGahXFmZSF/nRz9GHnfSYpjtDr9bsZOzQuLhHXT5E4ksNRTFW41h0MlZ1qOhO+NiiVgk7LmgVYiV7RRbgO8U6RaCEqg5n28Ewo6QtzB+DF4NTDeu3E9BLH5G0npdUrVNhdRUWCFDmH6n9hqSIz2J7o6GvWqEvp0h9e/3qtLsoS60hnQXunrcWcPaEIYQIDAQAB\n-----END RSA PUBLIC KEY-----\n",
+    "signature": "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"
+}