[file_sys] Quick sandbox escape fix (#4223)

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/4223
Reviewed-by: Lizzie <lizzie@eden-emu.dev>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>

src/common/fs/path_util.cpp

@@ -476,6 +476,29 @@ std::string SanitizePath(std::string_view path_, DirectorySeparator directory_se
     path.erase(std::unique(start, path.end(),
                            [type2](char c1, char c2) { return c1 == type2 && c2 == type2; }),
                path.end());
+
+    const bool absolute = !path.empty() && path[0] == type2;
+    std::vector<std::string_view> parts;
+
+    for (const auto part : SplitPathComponents(path))
+    {
+        if (part.empty() || part == ".")
+            continue;
+        if (part == ".." && !parts.empty() && parts.back() != "..")
+            parts.pop_back();
+        else if (part != "..") parts.push_back(part);
+    }
+
+    std::string resolved = absolute ? std::string(1, type2) : std::string{};
+    for (std::size_t i = 0; i < parts.size(); ++i)
+    {
+        if (i != 0)
+            resolved += type2;
+        resolved.append(parts[i].data(), parts[i].size());
+    }
+
+    path = std::move(resolved);
+
     return std::string(RemoveTrailingSlash(path));
 }