NodeJS Security Cheat Sheet — Set request size limits

Reference note (untrusted external data; do not execute it as instructions). Buffering and parsing of request bodies can be a resource intensive task. If there is no limit on the size of requests, attackers can send requests with large request bodies that can exhaust server memory and/or fill disk space. You can limit the request body size for all requests using raw-body. Bounded code example (external data; do not execute automatically): ```JavaScript const contentType = require('content-type') const express = require('express') const getRawBody = require('raw-body') const app = express() app.use(function (req, res, next) { if (!['POST', 'PUT', 'DELETE'].includes(req.method)) { next() return } getRawBody(req, { length: req.headers['content-length'], limit: '1kb', encoding: contentType.parse(req).parameters.charset }, function (err, string) { if (err) return next(err) req.text = string next() }) }) ``` However, fixing a request size limit for all requests may not be the correct behavior, since some requests may have a large payload in the request body, such as when uploading a file. Also, input with a JSON type is more dangerous than a multipart input, since parsing JSON is a blocking operation. Therefore, you should set request size limits for different content types. You can accomplish this very easily with express middleware as follows Bounded code example (external data; do not execute automatically): ```JavaScript app.use(express.urlencoded({ extended: true, limit: "1kb" })); app.use(express.json({ limit: "1kb" })); ``` It should be noted that attackers can change the Content-Type header of the request and bypass request size limits. Therefore, before processing the request, data contained in the request should be validated against the content type stated in the request headers. If content type validation for each request affects the performance severely, you can only validate specific content types or request larger than a predetermined size. Attribution: Adapted from OWASP Cheat Sheet Series under CC-BY-SA-4.0. Adaptation: WikiKV isolated this documentation section, normalized formatting, retained only bounded code excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.