avergnaud/next.js_exploit_cve-2024-34351Dépôt éducatif démontrant les modèles de rendu Next.js (CSR, RSC, SSG, ISR, SSR) et un laboratoire pratique d'exploitation SSRF pour CVE-2024-34351 avec des étapes d'atténuation.
Ce repo peut servir de support pour présenter un ou plusieurs meetup(s). Le parcours est le suivant...
Ce travail est basé principalement sur deux sources :
1-csr-load-data vanilla react SPA loading data
[!IMPORTANT] CSR (Client-Side Rendering): React code is delivered to the browser, which generates content that is inserted into the DOM.
cd 1-csr-load-data
npm start
2-csr-router vanilla react SPA routing[!IMPORTANT] After the page has been loaded for the first time, navigating to other pages on the same website uses JavaScript to re-render parts of the page without requiring a full page refresh.
cd 2-csr-router
npm start
3-rsc-load-data React Server Components (Next.js impl) loading data
[!IMPORTANT] React components which are written to run only on the server, rather than in the browser.
cd 3-rsc-load-data
npm run build
npm run start
4-rsc-router React Server Components (Next.js impl) routing
[!IMPORTANT] Components are executed only on the server. The default behavior is static rendering: components are executed at build time.
cd 4-rsc-router
npm run build
npm run start
5-SSR SSR Server Side Rendering
[!IMPORTANT] SSR means prerendering client components on the server. React code runs at the time it is requested. The result may be cached for future requests.
Best practice: define 'use client'; components as far down the component tree as possible.
[!IMPORTANT] "In React, “hydration” is how React “attaches” to existing HTML that was already rendered by React in a server environment. During hydration, React will attempt to attach event listeners to the existing markup and take over rendering the app on the client. In apps fully built with React, you will usually only hydrate one “root”, once at startup for your entire app."
https://react.dev/reference/react-dom/client/hydrateRoot
https://www.gatsbyjs.com/docs/conceptual/partial-hydration/
cd 5-ssr
npm run build
npm run start
6-pages-router-ssg (Next.js impl)
[!IMPORTANT] SSG (Static Site Generation) using the pages router: React code is run when you build your application, and the generated output is static.
cd 6-pages-router-ssg
npm run build
npm run start
7-pages-router-isr (Next.js impl)
[!IMPORTANT] ISR (using pages router): "Next.js allows you to create or update static pages after you’ve built your site. Incremental Static Regeneration (ISR) enables you to use static-generation on a per-page basis, without needing to rebuild the entire site. With ISR, you can retain the benefits of static while scaling to millions of pages."
cd 7-pages-router-isr
npm run build
npm run start
"the data could become stale at request time"
https://vercel.com/blog/nextjs-server-side-rendering-vs-static-generation
https://react.dev/reference/rsc/server-actions
...
8-ssrf-14.1.0
https://www.assetnote.io/resources/research/digging-for-ssrf-in-nextjs-apps
14.1.1redirect(/blog/${inputValue});Source : https://www.assetnote.io/resources/research/digging-for-ssrf-in-nextjs-apps
Next.JS exécute la requête côté serveur, puis retourne le résultat au navigateur :
redirect('/blog/123'); construit l'URL http://207.154.209.99/blog/123.
Pour construire cette URL, Next.JS récupère notamment le host 207.154.209.99 à partir du header HTTP de la requête initiale.Content-Type: text/x-component, alors Next.JS requête l'URL avec un HTTP GET.
Pour aboutir à un SSRF sur le serveur cible, il faut donc exécuter un autre serveur :
Content-Type: text/x-component, pour toute requête HEAD
8-ssrf-14.1.0Dans /etc/nginx/sites-available/nextjs
Avant :
server {
listen 80 default_server;
location / {
proxy_pass http://localhost:3000;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
}
}
Après :
server {
listen 80;
server_name 207.154.209.99;
location / {
proxy_pass http://localhost:3000;
proxy_set_header Host 207.154.209.99;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
}
}
Risque d'effet de bord...
https://nginxtutorials.com/nginx-proxy_set_header-directive/
https://github.com/vercel/next.js/security/advisories/GHSA-fr5h-rqp8-mj6g
Pages in the app directory are Server Components by default. This is different from the pages directory where pages are Client Components.
Upgrading to Next.js 13 does not require using the new App Router. You can continue using pages with new features that work in both directories
Si on veut comparer les performances de chargement pour les différentes solutions, on peut ajouter les metriques web core vital en console.log.
https://web.dev/articles/fcp?hl=fr
https://rsc-parser.vercel.app/
https://github.com/reactjs/rfcs/blob/main/text/0188-server-components.md#does-this-replace-ssr
https://www.youtube.com/watch?v=jEJEFAc8tSI
ISR using App router ?
In the Next.js App Router, all fetched data is now static by default, rendered at build time. However, this can be changed easily: Next.js extends the fetch options object to provide flexibility in caching and revalidating rules. You can use the {next: {revalidate: number}} option to refresh static data at set intervals or when backend changes occur (Incremental Static Regeneration), while the {cache: 'no-store'} option can be passed in the fetch request for dynamic data (server-side rendering).
https://www.telerik.com/blogs/current-state-react-server-components-guide-perplexed
https://github.com/reactjs/server-components-demo
https://dev.to/vteacher/let-s-make-a-web-application-with-react-server-components-5dmg
https://react.dev/blog/2024/04/25/react-19
https://react.dev/reference/rsc/server-components
https://www.youtube.com/watch?v=ePAPd9qzGyM
https://www.joshwcomeau.com/react/server-components/
https://nextjs.org/docs/pages/building-your-application/rendering/static-site-generation
https://nextjs.org/docs/pages/building-your-application/data-fetching/get-static-props
https://react.dev/reference/rsc/server-components#server-components-without-a-server