🛡️ Sentinel: [HIGH] Fix Path Traversal in CustomEmployeeManager

.jules/sentinel.md

@@ -21,3 +21,7 @@
 **Vulnerability:** `CustomEmployeeManager.Register` accepted arbitrary employee IDs without validation, which were later used directly in `Path.Combine` to construct image loading paths, enabling path traversal (CWE-22).
 **Learning:** Identifiers provided by mods or external sources must be treated as untrusted input and validated before being used in file system operations.
 **Prevention:** Validate input strings that form part of a file path before concatenating them. Reject them if they contain directory traversal characters like `..`, `Path.DirectorySeparatorChar`, `Path.AltDirectorySeparatorChar`, or any invalid filename characters (using `Path.GetInvalidFileNameChars()`).
+## 2024-05-24 - Path Traversal in CustomEmployeeManager
+**Vulnerability:** Found a path traversal vulnerability in `CustomEmployeeManager.SetPortrait` where `employeeId` was directly concatenated to a path using `Path.Combine`. This allowed an attacker to potentially read arbitrary image files outside the intended ModAssets directory by passing payloads like `../../../sensitive_file`.
+**Learning:** String identifiers (like `employeeId`, `modId`) passed to file system operations must always be validated against directory traversal attacks, even if they might be validated at registration, to protect against direct calls or deserialization bypasses.
+**Prevention:** Always validate input using `IndexOfAny(Path.GetInvalidFileNameChars()) >= 0 || Contains("..")` to ensure the input cannot contain directory separators or traversal sequences before using it in a file path. Avoid using `id.Contains(Path.DirectorySeparatorChar)` as it is not supported in older .NET frameworks.

src/API/CustomEmployeeManager.cs

@@ -891,10 +891,16 @@ private static void SetPortrait(Transform card, string employeeId)
 
             string assetsDir = Path.Combine(MelonEnvironment.UserDataDirectory, "ModAssets");
             string? imagePath = null;
-            foreach (var ext in new[] { ".jpg", ".png" })
+
+            // SECURITY: Validate employeeId to prevent path traversal attacks.
+            // Using IndexOfAny and Contains("..") to ensure no directory escaping.
+            if (!string.IsNullOrEmpty(employeeId) && employeeId.IndexOfAny(Path.GetInvalidFileNameChars()) < 0 && !employeeId.Contains(".."))
             {
-                string candidate = Path.Combine(assetsDir, employeeId + ext);
-                if (File.Exists(candidate)) { imagePath = candidate; break; }
+                foreach (var ext in new[] { ".jpg", ".png" })
+                {
+                    string candidate = Path.Combine(assetsDir, employeeId + ext);
+                    if (File.Exists(candidate)) { imagePath = candidate; break; }
+                }
             }
 
             if (imagePath != null)