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Active #2 AD

hashtag
Reconnaissance:

NMAP: 

┌──(kali💀kali)-[~]
└─$ sudo nmap -sC -sV -O 10.10.10.100

53/tcp    open  domain        Microsoft DNS 6.1.7601 (1DB15D39) (Windows Server 2008 R2 SP1)
| dns-nsid: 
|_  bind.version: Microsoft DNS 6.1.7601 (1DB15D39)

88/tcp    open  kerberos-sec  Microsoft Windows Kerberos (server time: 2023-12-23 06:40:22Z)

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: active.htb, 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: active.htb, Site: Default-First-Site-Name)
3269/tcp  open  tcpwrapped
49152/tcp open  msrpc         Microsoft Windows RPC
49153/tcp open  msrpc         Microsoft Windows RPC
49154/tcp open  msrpc         Microsoft Windows RPC
49155/tcp open  msrpc         Microsoft Windows RPC
49157/tcp open  ncacn_http    Microsoft Windows RPC over HTTP 1.0
49158/tcp open  msrpc         Microsoft Windows RPC
49165/tcp open  msrpc         Microsoft Windows RPC

No exact OS matches for host (If you know what OS is running on it, see https://nmap.org/submit/ ).
TCP/IP fingerprint:
OS:SCAN(V=7.94SVN%E=4%D=12/23%OT=53%CT=1%CU=30244%PV=Y%DS=2%DC=I%G=Y%TM=658
OS:6813E%P=x86_64-pc-linux-gnu)SEQ(SP=100%GCD=1%ISR=10C%TI=I%CI=I%II=I%SS=S
OS:%TS=7)SEQ(SP=FE%GCD=1%ISR=10B%TI=I%CI=I%TS=7)SEQ(SP=FF%GCD=1%ISR=10C%TI=
OS:I%CI=I%II=I%SS=S%TS=7)OPS(O1=M53ANW8ST11%O2=M53ANW8ST11%O3=M53ANW8NNT11%
OS:O4=M53ANW8ST11%O5=M53ANW8ST11%O6=M53AST11)WIN(W1=2000%W2=2000%W3=2000%W4
OS:=2000%W5=2000%W6=2000)ECN(R=Y%DF=Y%T=80%W=2000%O=M53ANW8NNS%CC=N%Q=)T1(R
OS:=Y%DF=Y%T=80%S=O%A=S+%F=AS%RD=0%Q=)T2(R=Y%DF=Y%T=80%W=0%S=Z%A=S%F=AR%O=%
OS:RD=0%Q=)T3(R=Y%DF=Y%T=80%W=0%S=Z%A=O%F=AR%O=%RD=0%Q=)T4(R=Y%DF=Y%T=80%W=
OS:0%S=A%A=O%F=R%O=%RD=0%Q=)T5(R=Y%DF=Y%T=80%W=0%S=Z%A=S+%F=AR%O=%RD=0%Q=)T
OS:6(R=Y%DF=Y%T=80%W=0%S=A%A=O%F=R%O=%RD=0%Q=)T7(R=Y%DF=Y%T=80%W=0%S=Z%A=S+
OS:%F=AR%O=%RD=0%Q=)U1(R=N)U1(R=Y%DF=N%T=80%IPL=164%UN=0%RIPL=G%RID=G%RIPCK
OS:=G%RUCK=G%RUD=G)IE(R=Y%DFI=N%T=80%CD=Z)

Network Distance: 2 hops
Service Info: Host: DC; OS: Windows; CPE: cpe:/o:microsoft:windows_server_2008:r2:sp1, cpe:/o:microsoft:windows

Host script results:
| smb2-time: 
|   date: 2023-12-23T06:41:45
|_  start_date: 2023-12-23T06:31:12
|_clock-skew: -1s
| smb2-security-mode: 
|   2:1:0: 
|_    Message signing enabled and required

hashtag
Enumeration:

The nmap scan discloses the domain name of the machine to be active.htb. So we’ll edit the /etc/hosts file to map the machine’s IP address to the active.htb domain name.

The first thing I’m going to try to enumerate is DNS. Let’s use nslookup to learn more information about this domain.

It doesn’t give us any information. Next, let’s attempt a zone transfer.

No luck there as well. I also tried dnsrecon and didn’t get anything useful. So we’ll move on to enumerating SMB on ports 139 and 445. We’ll start with viewing the SMB shares.

The Replication share has READ ONLY permission on it. Let’s try to login anonymously to view the files of the Replication share.

-N: suppresses the password since we’re logging in anonymously

We’re in!

After looking through all the files on this share, I found a Groups.xml file in the following directory.

A quick google search tells us that Groups.xml file is a Group Policy Preference (GPP) file. GPP was introduced with the release of Windows Server 2008 and it allowed for the configuration of domain-joined computers. A dangerous feature of GPP was the ability to save passwords and usernames in the preference files. While the passwords were encrypted with AES, the key was made publicly available.

Logo[MS-GPPREF]: Password EncryptionMicrosoftLearnchevron-right

Therefore, if you managed to compromise any domain account, you can simply grab the groups.xml file and decrypt the passwords.

LogoUnderstanding Privilege Escalation via GPPwww.mindpointgroup.comchevron-right

Now that we know how important this file is, let’s download it to our attack machine.

View the contents of the file.

This will allow us to gain an initial foothold on the system.

hashtag
Foothold:

As mentioned above, the password is encrypted with AES, which is a strong encryption algorithm. However, since the key is posted online, we can easily decrypt the encrypted password.

There’s a simple ruby program known as gpp-decrypt that uses the publicly disclosed key to decrypt any given GPP encrypted string. This program is included with the default installation of Kali.

Let’s use it to decrypt the password we found.

From the Groups.xml file, we know that the username is SVG_TGS. This probably is not the admin user, but regardless let’s try to access the ADMIN$ share with the username/password we found.

-W: domain -U: username

Nope, that doesn’t work.

Let’s try the USERS share.

We’re in!

Navigate to the directory that contains the user.txt flag.

We compromised a low privileged user. Now we need to escalate privileges.

hashtag
Privilege Escalation:

Since we’re working with Active Directory and using Kerberos as an authentication protocol, let’s try a technique known as Kerberoasting. To understand how this attack works, you need to understand how the Kerberos authentication protocol works.

LogoLDAP / SSO Authentication (ig_ldap_sso_auth)docs.typo3.orgchevron-right

If you compromise a user that has a valid kerberos ticket-granting ticket (TGT), then you can request one or more ticket-granting service (TGS) service tickets for any Service Principal Name (SPN) from a domain controller. An example SPN would be the Application Server.

A portion of the TGS ticket is encrypted with the hash of the service account associated with the SPN. Therefore, you can run an offline brute force attack on the encrypted portion to reveal the service account password. Therefore, if you request an administrator account TGS ticket and the administrator is using a weak password, we’ll be able to crack it!

IMPACKET: root.txt

This includes a collection of Python classes for working with network protocols.

LogoGitHub - fortra/impacket: Impacket is a collection of Python classes for working with network protocols.GitHubchevron-right

They have a script in the /examples folder called GetUserSPNs.py that is used to find SPNs that are associated with a given user account. It will output a set of valid TGSs it requested for those SPNs.

Run the script using the SVC_TGS credentials we found.

target: domain/username:password -dc-ip: IP address of the domain controller -request: Requests TGS for users and outputs them in JtR/hashcat format

We were able to request a TGS from an Administrator SPN. If we can crack the TGS, we’ll be able to escalate privileges!

Note: If you get a “Kerberos SessionError: KRB_AP_ERR_SKEW(Clock skew too great)”, it’s probably because the attack machine date and time are not in sync with the Kerberos server.

Now that we have a valid TGS that is already in John the Ripper format, let’s try to crack it.

We get back the password! Ticketmaster1968

To login as the administrator, we’ll use another Impacket script known as psexec.py. As shown in the help menu, you can run the script using the following command.

SMB: root.txt

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