Rejecting requests with significant content length is a good practice to control the network traffic intensity and thus resource consumption in
order to prevent DoS attacks.
Ask Yourself Whether
- size limits are not defined for the different resources of the web application.
- the web application is not protected by rate limiting features.
- the web application infrastructure has limited resources.
There is a risk if you answered yes to any of those questions.
Recommended Secure Coding Practices
- For most of the features of an application, it is recommended to limit the size of requests to:
- lower or equal to 8mb for file uploads.
- lower or equal to 2mb for other requests.
It is recommended to customize the rule with the limit values that correspond to the web application.
Sensitive Code Example
formidable file upload module:
const form = new Formidable();
form.maxFileSize = 10000000; // Sensitive: 10MB is more than the recommended limit of 8MB
const formDefault = new Formidable(); // Sensitive, the default value is 200MB
multer (Express.js middleware) file upload module:
let diskUpload = multer({
storage: diskStorage,
limits: {
fileSize: 10000000; // Sensitive: 10MB is more than the recommended limit of 8MB
}
});
let diskUploadUnlimited = multer({ // Sensitive: the default value is no limit
storage: diskStorage,
});
body-parser module:
// 4MB is more than the recommended limit of 2MB for non-file-upload requests
let jsonParser = bodyParser.json({ limit: "4mb" }); // Sensitive
let urlencodedParser = bodyParser.urlencoded({ extended: false, limit: "4mb" }); // Sensitive
Compliant Solution
formidable file upload module:
const form = new Formidable();
form.maxFileSize = 8000000; // Compliant: 8MB
multer (Express.js middleware) file upload module:
let diskUpload = multer({
storage: diskStorage,
limits: {
fileSize: 8000000 // Compliant: 8MB
}
});
body-parser module:
let jsonParser = bodyParser.json(); // Compliant, when the limit is not defined, the default value is set to 100kb
let urlencodedParser = bodyParser.urlencoded({ extended: false, limit: "2mb" }); // Compliant
See
