csr-rsc-ssg-isr-ssr-ssrf

Este repositorio puede servir como soporte para presentar uno o varios meetup(s). El recorrido es el siguiente...

• "CSR" Client Side Rendering: React como librería SPA estándar
• "RSC" React Server Components: ejecución de componentes React únicamente del lado del servidor
• "SSG" Static Site Generation: ejecución de componentes React durante el build
• "ISR" Incremental Static Regeneration: regeneración de componentes a la demanda
• "SSR" Server Side Rendering: pre-renderizado del lado del servidor y luego ejecución (hidratación) del lado del cliente
• "SSRF" Server Side Request Forgery: una vulnerabilidad de seguridad corregida recientemente en Next.JS

Este trabajo se basa principalmente en dos fuentes:

• https://demystifying-rsc.vercel.app/
• https://www.assetnote.io/resources/research/digging-for-ssrf-in-nextjs-apps

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CSR Client Side Rendering

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.

demostración

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.

demostración

cd 2-csr-router
npm start

RSC React Server Components

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.

demostración

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.

demostración

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.

https://nextjs.org/docs/app/building-your-application/rendering/composition-patterns#moving-client-components-down-the-tree

Hydration

[!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/

demostración

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.

demostración

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."

demostración

cd 7-pages-router-isr
npm run build
npm run start

¿Por qué ISR?

"the data could become stale at request time"

https://vercel.com/blog/nextjs-server-side-rendering-vs-static-generation

Server actions

https://react.dev/reference/rsc/server-actions

SSRF (fixed in NextJS v14.1.1)

Definición SSRF

...

¿Por qué?

• Si se tiene acceso a un servidor vulnerable pero no al servidor objetivo directamente (DMZ, Firewall...)
• Si se quieren ejecutar peticiones ocultando el propio origen
• ...

Demostración 8-ssrf-14.1.0

Contexto

https://www.assetnote.io/resources/research/digging-for-ssrf-in-nextjs-apps

Objetivo

Condiciones para explotar la CVE-2024-34351

• Una aplicación basada en Next.JS con versión inferior a 14.1.1
• El uso de la función redirect, con una ruta absoluta. En la demo, en addTodo.js: redirect(/blog/${inputValue});

Funcionamiento de la función redirect