gmsablob2keys.py

# Transform a msDS-ManagedPassword blob into keys
# Copy paste from different scripts

import base64

from binascii import hexlify, unhexlify
from Cryptodome.Hash import MD4
from impacket.ldap.ldaptypes import ACE, ACCESS_ALLOWED_OBJECT_ACE, ACCESS_MASK, LDAP_SID, SR_SECURITY_DESCRIPTOR
from impacket.structure import Structure
from impacket.krb5 import constants
from impacket.krb5.crypto import string_to_key, Key
from Cryptodome.Hash import MD4

class MSDS_MANAGEDPASSWORD_BLOB(Structure):
    structure = (
        ('Version','<H'),
        ('Reserved','<H'),
        ('Length','<L'),
        ('CurrentPasswordOffset','<H'),
        ('PreviousPasswordOffset','<H'),
        ('QueryPasswordIntervalOffset','<H'),
        ('UnchangedPasswordIntervalOffset','<H'),
        ('CurrentPassword',':'),
        ('PreviousPassword',':'),
        #('AlignmentPadding',':'),
        ('QueryPasswordInterval',':'),
        ('UnchangedPasswordInterval',':'),
    )

    def __init__(self, data = None):
        Structure.__init__(self, data = data)

    def fromString(self, data):
        Structure.fromString(self,data)

        if self['PreviousPasswordOffset'] == 0:
            endData = self['QueryPasswordIntervalOffset']
        else:
            endData = self['PreviousPasswordOffset']

        self['CurrentPassword'] = self.rawData[self['CurrentPasswordOffset']:][:endData - self['CurrentPasswordOffset']]
        if self['PreviousPasswordOffset'] != 0:
            self['PreviousPassword'] = self.rawData[self['PreviousPasswordOffset']:][:self['QueryPasswordIntervalOffset']-self['PreviousPasswordOffset']]

        self['QueryPasswordInterval'] = self.rawData[self['QueryPasswordIntervalOffset']:][:self['UnchangedPasswordIntervalOffset']-self['QueryPasswordIntervalOffset']]
        self['UnchangedPasswordInterval'] = self.rawData[self['UnchangedPasswordIntervalOffset']:]
        
allciphers = {
    'rc4_hmac_nt': int(constants.EncryptionTypes.rc4_hmac.value),
    'aes128_hmac': int(constants.EncryptionTypes.aes128_cts_hmac_sha1_96.value),
    'aes256_hmac': int(constants.EncryptionTypes.aes256_cts_hmac_sha1_96.value)
}

def printKerberosKeys(password, salt):
    for name, cipher in allciphers.items():
        if cipher == 23:
            md4 = MD4.new()
            md4.update(password)
            key = Key(cipher, md4.digest())
        else:
            fixedPassword = password.decode('utf-16-le', 'replace').encode('utf-8', 'replace')
            key = string_to_key(cipher, fixedPassword, salt)

        print(f'    * {name}: {hexlify(key.contents).decode("utf-8")}')


def printMachineKerberosKeys(domain, hostname, hexpassword):
    salt = b'%shost%s.%s' % (domain.upper().encode('utf-8'), hostname.lower().encode('utf-8'), domain.lower().encode('utf-8'))
    rawpassword = unhexlify(hexpassword)
    print(f'{domain.upper()}\\{hostname.upper()}$')
    print(f'    * Salt: {salt.decode("utf-8")}')
    printKerberosKeys(rawpassword, salt)


def printUserKerberosKeys(domain, username, rawpassword):
    salt = b'%s%s' % (domain.upper().encode('utf-8'), username.encode('utf-8'))
    rawpassword = rawpassword.encode('utf-16-le')
    print(f'{domain.upper()}\\{username}')
    print(f'    * Salt: {salt.decode("utf-8")}')
    printKerberosKeys(rawpassword, salt)

data = "" # Base64 blob
data = base64.b64decode(data)

blob = MSDS_MANAGEDPASSWORD_BLOB()
blob.fromString(data)
currentPassword = blob['CurrentPassword'][:-2]

printMachineKerberosKeys(
    domain='contoso.local',
    hostname='gMSA-SVC-1',
    hexpassword=hexlify(currentPassword)
)