🛡️ Sentinel: Fix AuthMe Login Spoofing via Chat

.jules/sentinel.md

@@ -2,3 +2,8 @@
 **Vulnerability:** The WebSocket authentication endpoint used simple string comparison (`!=`) for token verification.
 **Learning:** String comparisons return early upon mismatch, allowing attackers to infer the token character by character by measuring response times.
 **Prevention:** Use `secrets.compare_digest()` for all security-sensitive string comparisons (tokens, passwords, hashes) to ensure constant-time execution.
+
+## 2026-02-15 - AuthMe Login Spoofing via Chat
+**Vulnerability:** The AuthMe login detection logic relied on weak heuristics (presence of colon) to filter out player chat, allowing players to spoof system messages (e.g., "Please /login") and trick the bot into sending its password.
+**Learning:** Heuristics based on message content are fragile against spoofing. Relying on protocol-level metadata (like message position/type) is crucial for security-sensitive operations.
+**Prevention:** Always verify the source and type of the message (e.g., `position == 'system'` or `game_info`) before performing privileged actions like authentication, rather than parsing the message text alone.

backend/bot/mineflayer_adapter.py

@@ -145,6 +145,10 @@ def on_spawn(*args):
         @On(self._bot, 'message')
         def on_message(this, message, *args):
             """监听聊天消息，检测 AuthMe 登录提示"""
+            # Extract position from args (mineflayer passes: message, position, sender, verified)
+            # position: 'chat' (0), 'system' (1), 'game_info' (2)
+            position = args[0] if args else None
+
             msg = str(message)
             msg_lower = msg.lower()
 
@@ -162,27 +166,27 @@ def on_message(this, message, *args):
             # - Please login with "/login password"
             # - /login <password>
             if self._password and not self._authme_logged_in:
-                should_login = False
+                # Security: Only process system messages (position='system' or 1) or game info (position='game_info' or 2)
+                # Ignore chat messages (position='chat' or 0) to prevent players from spoofing login prompts
+                is_secure_source = str(position) in ('system', 'game_info', '1', '2')
 
-                # 关键词匹配 (更严格)
-                if "/login" in msg_lower or "/register" in msg_lower:
-                    # 排除玩家聊天 (简单的启发式：如果不包含冒号，或者是系统消息格式)
-                    # Mineflayer 的 message 对象通常是 ChatMessage，str(message) 得到纯文本
-                    # 这是一个简化的判断，防止玩家通过聊天诱骗 Bot 发送密码
-                    if ":" not in msg:
-                        should_login = True
-                    # 如果是常见的服务器提示格式
-                    elif "please" in msg_lower or "use" in msg_lower or "command" in msg_lower:
+                if is_secure_source:
+                    should_login = False
+
+                    # 关键词匹配 (更严格)
+                    if "/login" in msg_lower or "/register" in msg_lower:
+                        # 只要是系统消息，通常可以信任
+                        # 但为了保险起见，仍然检查关键词
                         should_login = True
 
-                if should_login:
-                    logger.info(f"AuthMe prompt detected, sending login...")
-                    try:
-                        self._bot.chat(f"/login {self._password}")
-                        self._authme_logged_in = True
-                        logger.info(f"Bot {self._username} sent AuthMe login command")
-                    except Exception as e:
-                        logger.error(f"AuthMe login failed: {e}")
+                    if should_login:
+                        logger.info(f"AuthMe prompt detected (source={position}), sending login...")
+                        try:
+                            self._bot.chat(f"/login {self._password}")
+                            self._authme_logged_in = True
+                            logger.info(f"Bot {self._username} sent AuthMe login command")
+                        except Exception as e:
+                            logger.error(f"AuthMe login failed: {e}")
 
         @On(self._bot, 'kicked')
         def on_kicked(this, reason, loggedIn):

backend/tests/test_authme_security.py

@@ -0,0 +1,76 @@
+
+import sys
+import pytest
+from unittest.mock import MagicMock, patch
+
+# Mock javascript module before importing bot.mineflayer_adapter
+mock_javascript = MagicMock()
+sys.modules['javascript'] = mock_javascript
+
+# Mock require to return a mock object
+mock_require = MagicMock()
+mock_javascript.require = mock_require
+
+# Mock On decorator
+# On(emitter, event_name) returns a decorator
+def mock_on(emitter, event_name):
+    def decorator(func):
+        # Store the handler in the emitter for triggering later
+        if not hasattr(emitter, '_handlers'):
+            emitter._handlers = {}
+        emitter._handlers[event_name] = func
+        return func
+    return decorator
+
+mock_javascript.On = mock_on
+
+# Now import the class under test
+from bot.mineflayer_adapter import MineflayerBot
+
+class TestAuthMeSecurity:
+
+    @pytest.fixture
+    def bot(self):
+        # Create a bot instance with password
+        bot = MineflayerBot("localhost", 25565, "Bot", "secret_password")
+
+        # Mock internal _bot object
+        bot._bot = MagicMock()
+        bot._bot._handlers = {} # For our mock_on
+
+        # Mock chat method
+        bot._bot.chat = MagicMock()
+
+        # Call _register_events to register handlers
+        bot._register_events()
+
+        return bot
+
+    def test_authme_login_from_chat_spoof_is_ignored(self, bot):
+        """
+        Test that a chat message mimicking AuthMe prompt is IGNORED (Security Fix)
+        """
+        # Case 1: Standard chat message with colon - should be IGNORED
+        msg_chat = "Player: Please /login password"
+        bot._bot._handlers['message'](bot, msg_chat, 'chat', 'uuid', True)
+        bot._bot.chat.assert_not_called()
+
+        # Case 2: Chat message WITHOUT colon (e.g. server plugin or specific format)
+        # "Server > Please /login password" (no colon)
+        # OR just "Please /login password" (some servers)
+        msg_spoof = "Please /login password"
+
+        # We pass 'chat' (or 0) as position to indicate it's from a player
+        bot._bot._handlers['message'](bot, msg_spoof, 'chat', 'uuid', True)
+
+        # Expectation: Secure code should NOT try to login
+        bot._bot.chat.assert_not_called()
+
+    def test_authme_login_from_system_message(self, bot):
+        """Test that legitimate system message triggers login"""
+        msg_system = "Please /login <password>"
+
+        # Simulate system message (position='system' or 1)
+        bot._bot._handlers['message'](bot, msg_system, 'system', None, True)
+
+        bot._bot.chat.assert_called_with("/login secret_password")