class Ticket(object):
def __init__(self):
# This is the kerberos version, not the service principal key
# version number.
self.tkt_vno = None
self.service_principal = None
self.encrypted_part = None
def from_asn1(self, data):
data = _asn1_decode(data, asn1.Ticket())
self.tkt_vno = int(data.getComponentByName('tkt-vno'))
self.service_principal = PrincipalModified()
self.service_principal.from_asn1(data, 'realm', 'sname')
self.encrypted_part = EncryptedData()
self.encrypted_part.from_asn1(data.getComponentByName('enc-part'))
return self
def to_asn1(self, component):
component.setComponentByName('tkt-vno', 5)
component.setComponentByName('realm', self.service_principal.realm)
asn1.seq_set(component, 'sname',
self.service_principal.components_to_asn1)
asn1.seq_set(component, 'enc-part', self.encrypted_part.to_asn1)
return component
def __str__(self):
return "<Ticket for %s vno %s>" % (str(
self.service_principal), str(self.encrypted_part.kvno))
def from_asn1(self, data):
data = _asn1_decode(data, asn1.Ticket())
self.tkt_vno = int(data.getComponentByName('tkt-vno'))
self.service_principal = PrincipalModified()
self.service_principal.from_asn1(data, 'realm', 'sname')
self.encrypted_part = EncryptedData()
self.encrypted_part.from_asn1(data.getComponentByName('enc-part'))
return self
# Pass the hash/aes key :P
if nthash != '':
key = Key(cipher.enctype, nthash)
elif aesKey != '':
key = Key(cipher.enctype, aesKey.decode('hex'))
else:
key = cipher.string_to_key(password, encryptionTypesData[enctype],
None)
encodedTimeStamp = encoder.encode(timeStamp)
# Key Usage 1
# AS-REQ PA-ENC-TIMESTAMP padata timestamp, encrypted with the
# client key (Section 5.2.7.2)
encriptedTimeStamp = cipher.encrypt(key, 1, encodedTimeStamp, None)
encryptedData = EncryptedData()
encryptedData['etype'] = cipher.enctype
encryptedData['cipher'] = encriptedTimeStamp
encodedEncryptedData = encoder.encode(encryptedData)
# Now prepare the new AS_REQ again with the PADATA
# ToDo: cannot we reuse the previous one?
asReq = AS_REQ()
asReq['pvno'] = 5
asReq['msg-type'] = int(constants.ApplicationTagNumbers.AS_REQ.value)
asReq['padata'] = None
asReq['padata'][0] = None
asReq['padata'][0]['padata-type'] = int(
constants.PreAuthenticationDataTypes.PA_ENC_TIMESTAMP.value)
asReq['padata'][0]['padata-value'] = encodedEncryptedData
def _parseForREQ(self, timestamp, asn_data, ip_packet):
# decode data just to parse to see if it's a KDC_REQ packet
try:
asn = decoder.decode(asn_data)[0]
if asn[0] != 5:
return None
except:
return None
# check to see if it's an AS_REQ or TGS_REQ
if asn[1] != constants.ApplicationTagNumbers.AS_REQ.value and asn[
1] != constants.ApplicationTagNumbers.TGS_REQ.value:
return None
# try decoding (both AS_REQ and TGS_REQ are KDC_REQ packets)
try:
req = decoder.decode(asn_data, asn1Spec=AS_REQ())[0]
except:
req = decoder.decode(asn_data, asn1Spec=TGS_REQ())[0]
crealm = req['req-body']['realm']
cname = self._getPrinc(req['req-body']['cname'])
trealm = req['req-body']['realm']
tname = self._getPrinc(req['req-body']['sname'])
for padata in req['padata']:
# extract encrypted authenticators from AS_REQ packets
if padata[
'padata-type'] == constants.PreAuthenticationDataTypes.PA_ENC_TIMESTAMP.value:
auth = decoder.decode(padata['padata-value'],
asn1Spec=EncryptedData())[0]
if auth['etype'] == Enctype.DES_CRC:
cenc = str(auth['cipher'])
# extract encrypted ticket data from TGS_REQ packets
if padata[
'padata-type'] == constants.PreAuthenticationDataTypes.PA_TGS_REQ.value:
asn1 = decoder.decode(padata['padata-value'])[0]
if asn1[0] != 5 or asn1[1] != 14:
return None
ap = decoder.decode(padata['padata-value'],
asn1Spec=AP_REQ())[0]
trealm = ap['ticket']['realm']
tname = self._getPrinc(ap['ticket']['sname'])
if ap['authenticator']['etype'] == Enctype.DES_CRC:
cenc = str(ap['authenticator']['cipher'])
if ap['ticket']['enc-part']['etype'] == Enctype.DES_CRC:
tenc = str(ap['ticket']['enc-part']['cipher'])
try:
tenc_packet = KerbPacket(asn, socket.inet_ntoa(ip_packet.src),
socket.inet_ntoa(ip_packet.dst), asn[1],
cname, crealm, tname, trealm, tenc, 1,
timestamp)
except:
tenc_packet = None
try:
cenc_packet = KerbPacket(asn, socket.inet_ntoa(ip_packet.src),
socket.inet_ntoa(ip_packet.dst), asn[1],
cname, crealm, tname, trealm, cenc, 0,
timestamp)
except:
cenc_packet = None
return tenc_packet, cenc_packet
def getKerberosTGT(clientName,
password,
domain,
lmhash,
nthash,
aesKey='',
kdcHost=None,
requestPAC=True):
# Convert to binary form, just in case we're receiving strings
if isinstance(lmhash, str):
try:
lmhash = unhexlify(lmhash)
except TypeError:
pass
if isinstance(nthash, str):
try:
nthash = unhexlify(nthash)
except TypeError:
pass
if isinstance(aesKey, str):
try:
aesKey = unhexlify(aesKey)
except TypeError:
pass
asReq = AS_REQ()
domain = domain.upper()
serverName = Principal('krbtgt/%s' % domain,
type=constants.PrincipalNameType.NT_PRINCIPAL.value)
pacRequest = KERB_PA_PAC_REQUEST()
pacRequest['include-pac'] = requestPAC
encodedPacRequest = encoder.encode(pacRequest)
asReq['pvno'] = 5
asReq['msg-type'] = int(constants.ApplicationTagNumbers.AS_REQ.value)
asReq['padata'] = noValue
asReq['padata'][0] = noValue
asReq['padata'][0]['padata-type'] = int(
constants.PreAuthenticationDataTypes.PA_PAC_REQUEST.value)
asReq['padata'][0]['padata-value'] = encodedPacRequest
reqBody = seq_set(asReq, 'req-body')
opts = list()
opts.append(constants.KDCOptions.forwardable.value)
opts.append(constants.KDCOptions.renewable.value)
opts.append(constants.KDCOptions.proxiable.value)
reqBody['kdc-options'] = constants.encodeFlags(opts)
seq_set(reqBody, 'sname', serverName.components_to_asn1)
seq_set(reqBody, 'cname', clientName.components_to_asn1)
if domain == '':
raise Exception('Empty Domain not allowed in Kerberos')
reqBody['realm'] = domain
now = datetime.datetime.utcnow() + datetime.timedelta(days=1)
reqBody['till'] = KerberosTime.to_asn1(now)
reqBody['rtime'] = KerberosTime.to_asn1(now)
reqBody['nonce'] = rand.getrandbits(31)
# Yes.. this shouldn't happen but it's inherited from the past
if aesKey is None:
aesKey = b''
if nthash == b'':
# This is still confusing. I thought KDC_ERR_ETYPE_NOSUPP was enough,
# but I found some systems that accepts all ciphers, and trigger an error
# when requesting subsequent TGS :(. More research needed.
# So, in order to support more than one cypher, I'm setting aes first
# since most of the systems would accept it. If we're lucky and
# KDC_ERR_ETYPE_NOSUPP is returned, we will later try rc4.
if aesKey != b'':
if len(aesKey) == 32:
supportedCiphers = (int(
constants.EncryptionTypes.aes256_cts_hmac_sha1_96.value), )
else:
supportedCiphers = (int(
constants.EncryptionTypes.aes128_cts_hmac_sha1_96.value), )
else:
supportedCiphers = (int(
constants.EncryptionTypes.aes256_cts_hmac_sha1_96.value), )
else:
# We have hashes to try, only way is to request RC4 only
supportedCiphers = (int(constants.EncryptionTypes.rc4_hmac.value), )
seq_set_iter(reqBody, 'etype', supportedCiphers)
message = encoder.encode(asReq)
try:
r = sendReceive(message, domain, kdcHost)
except KerberosError as e:
if e.getErrorCode() == constants.ErrorCodes.KDC_ERR_ETYPE_NOSUPP.value:
if supportedCiphers[0] in (
constants.EncryptionTypes.aes128_cts_hmac_sha1_96.value,
constants.EncryptionTypes.aes256_cts_hmac_sha1_96.value
) and aesKey == '':
supportedCiphers = (int(
constants.EncryptionTypes.rc4_hmac.value), )
seq_set_iter(reqBody, 'etype', supportedCiphers)
message = encoder.encode(asReq)
r = sendReceive(message, domain, kdcHost)
else:
raise
else:
raise
# This should be the PREAUTH_FAILED packet or the actual TGT if the target principal has the
# 'Do not require Kerberos preauthentication' set
preAuth = True
try:
asRep = decoder.decode(r, asn1Spec=KRB_ERROR())[0]
except:
# Most of the times we shouldn't be here, is this a TGT?
asRep = decoder.decode(r, asn1Spec=AS_REP())[0]
# Yes
preAuth = False
encryptionTypesData = dict()
salt = ''
if preAuth is False:
# In theory, we should have the right credentials for the etype specified before.
methods = asRep['padata']
encryptionTypesData[supportedCiphers[
0]] = salt # handle RC4 fallback, we don't need any salt
tgt = r
else:
methods = decoder.decode(asRep['e-data'], asn1Spec=METHOD_DATA())[0]
for method in methods:
if method[
'padata-type'] == constants.PreAuthenticationDataTypes.PA_ETYPE_INFO2.value:
etypes2 = decoder.decode(method['padata-value'],
asn1Spec=ETYPE_INFO2())[0]
for etype2 in etypes2:
try:
if etype2['salt'] is None or etype2['salt'].hasValue(
) is False:
salt = ''
else:
salt = etype2['salt'].prettyPrint()
except PyAsn1Error:
salt = ''
encryptionTypesData[etype2['etype']] = b(salt)
elif method[
'padata-type'] == constants.PreAuthenticationDataTypes.PA_ETYPE_INFO.value:
etypes = decoder.decode(method['padata-value'],
asn1Spec=ETYPE_INFO())[0]
for etype in etypes:
try:
if etype['salt'] is None or etype['salt'].hasValue(
) is False:
salt = ''
else:
salt = etype['salt'].prettyPrint()
except PyAsn1Error:
salt = ''
encryptionTypesData[etype['etype']] = b(salt)
enctype = supportedCiphers[0]
cipher = _enctype_table[enctype]
# Pass the hash/aes key :P
if nthash != b'' and (isinstance(nthash, bytes) and nthash != b''):
key = Key(cipher.enctype, nthash)
elif aesKey != b'':
key = Key(cipher.enctype, aesKey)
else:
key = cipher.string_to_key(password, encryptionTypesData[enctype],
None)
if preAuth is True:
if enctype in encryptionTypesData is False:
raise Exception('No Encryption Data Available!')
# Let's build the timestamp
timeStamp = PA_ENC_TS_ENC()
now = datetime.datetime.utcnow()
timeStamp['patimestamp'] = KerberosTime.to_asn1(now)
timeStamp['pausec'] = now.microsecond
# Encrypt the shyte
encodedTimeStamp = encoder.encode(timeStamp)
# Key Usage 1
# AS-REQ PA-ENC-TIMESTAMP padata timestamp, encrypted with the
# client key (Section 5.2.7.2)
encriptedTimeStamp = cipher.encrypt(key, 1, encodedTimeStamp, None)
encryptedData = EncryptedData()
encryptedData['etype'] = cipher.enctype
encryptedData['cipher'] = encriptedTimeStamp
encodedEncryptedData = encoder.encode(encryptedData)
# Now prepare the new AS_REQ again with the PADATA
# ToDo: cannot we reuse the previous one?
asReq = AS_REQ()
asReq['pvno'] = 5
asReq['msg-type'] = int(constants.ApplicationTagNumbers.AS_REQ.value)
asReq['padata'] = noValue
asReq['padata'][0] = noValue
asReq['padata'][0]['padata-type'] = int(
constants.PreAuthenticationDataTypes.PA_ENC_TIMESTAMP.value)
asReq['padata'][0]['padata-value'] = encodedEncryptedData
asReq['padata'][1] = noValue
asReq['padata'][1]['padata-type'] = int(
constants.PreAuthenticationDataTypes.PA_PAC_REQUEST.value)
asReq['padata'][1]['padata-value'] = encodedPacRequest
reqBody = seq_set(asReq, 'req-body')
opts = list()
opts.append(constants.KDCOptions.forwardable.value)
opts.append(constants.KDCOptions.renewable.value)
opts.append(constants.KDCOptions.proxiable.value)
reqBody['kdc-options'] = constants.encodeFlags(opts)
seq_set(reqBody, 'sname', serverName.components_to_asn1)
seq_set(reqBody, 'cname', clientName.components_to_asn1)
reqBody['realm'] = domain
now = datetime.datetime.utcnow() + datetime.timedelta(days=1)
reqBody['till'] = KerberosTime.to_asn1(now)
reqBody['rtime'] = KerberosTime.to_asn1(now)
reqBody['nonce'] = rand.getrandbits(31)
seq_set_iter(reqBody, 'etype', ((int(cipher.enctype), )))
try:
tgt = sendReceive(encoder.encode(asReq), domain, kdcHost)
except Exception as e:
if str(e).find('KDC_ERR_ETYPE_NOSUPP') >= 0:
if lmhash == b'' and nthash == b'' and (aesKey == b''
or aesKey is None):
from impacket.ntlm import compute_lmhash, compute_nthash
lmhash = compute_lmhash(password)
nthash = compute_nthash(password)
return getKerberosTGT(clientName, password, domain, lmhash,
nthash, aesKey, kdcHost, requestPAC)
raise
asRep = decoder.decode(tgt, asn1Spec=AS_REP())[0]
# So, we have the TGT, now extract the new session key and finish
cipherText = asRep['enc-part']['cipher']
if preAuth is False:
# Let's output the TGT enc-part/cipher in John format, in case somebody wants to use it.
LOG.debug('$krb5asrep$%d$%s@%s:%s$%s' %
(asRep['enc-part']['etype'], clientName, domain,
hexlify(asRep['enc-part']['cipher'].asOctets()[:16]),
hexlify(asRep['enc-part']['cipher'].asOctets()[16:])))
# Key Usage 3
# AS-REP encrypted part (includes TGS session key or
# application session key), encrypted with the client key
# (Section 5.4.2)
try:
plainText = cipher.decrypt(key, 3, cipherText)
except InvalidChecksum as e:
# probably bad password if preauth is disabled
if preAuth is False:
error_msg = "failed to decrypt session key: %s" % str(e)
raise SessionKeyDecryptionError(error_msg, asRep, cipher, key,
cipherText)
raise
encASRepPart = decoder.decode(plainText, asn1Spec=EncASRepPart())[0]
# Get the session key and the ticket
# We're assuming the cipher for this session key is the same
# as the one we used before.
# ToDo: change this
sessionKey = Key(cipher.enctype,
encASRepPart['key']['keyvalue'].asOctets())
# ToDo: Check Nonces!
return tgt, cipher, key, sessionKey
def verify_kerberos_password(user, password, domain, kdc_host=None, request_pac=True, host_names=None, source_ip=None):
host_names = host_names or []
clientName = Principal(user, type=constants.PrincipalNameType.NT_PRINCIPAL.value)
domain = domain.upper()
serverName = Principal("krbtgt/%s" % domain, type=constants.PrincipalNameType.NT_PRINCIPAL.value)
pacRequest = KERB_PA_PAC_REQUEST()
pacRequest["include-pac"] = request_pac
encodedPacRequest = encoder.encode(pacRequest)
enctype = constants.EncryptionTypes.rc4_hmac.value
encryptionTypesData = None # RC4 doesn"t have salt
cipher = _enctype_table[enctype]
salt = encryptionTypesData[enctype] if encryptionTypesData else ''
key = cipher.string_to_key(password, salt, None)
# Let"s build the timestamp
timeStamp = PA_ENC_TS_ENC()
now = datetime.datetime.utcnow()
timeStamp["patimestamp"] = KerberosTime.to_asn1(now)
timeStamp["pausec"] = now.microsecond
encodedTimeStamp = encoder.encode(timeStamp)
# Key Usage 1
# AS-REQ PA-ENC-TIMESTAMP padata timestamp, encrypted with the
# client key (Section 5.2.7.2)
encriptedTimeStamp = cipher.encrypt(key, 1, encodedTimeStamp, None)
encryptedData = EncryptedData()
encryptedData["etype"] = cipher.enctype
encryptedData["cipher"] = encriptedTimeStamp
encodedEncryptedData = encoder.encode(encryptedData)
# Now prepare the new AS_REQ again with the PADATA
# ToDo: cannot we reuse the previous one?
asReq = AS_REQ()
asReq['pvno'] = 5
asReq['msg-type'] = int(constants.ApplicationTagNumbers.AS_REQ.value)
asReq['padata'] = noValue
asReq['padata'][0] = noValue
asReq['padata'][0]['padata-type'] = int(constants.PreAuthenticationDataTypes.PA_ENC_TIMESTAMP.value)
asReq['padata'][0]['padata-value'] = encodedEncryptedData
asReq['padata'][1] = noValue
asReq['padata'][1]['padata-type'] = int(constants.PreAuthenticationDataTypes.PA_PAC_REQUEST.value)
asReq['padata'][1]['padata-value'] = encodedPacRequest
reqBody = seq_set(asReq, 'req-body')
opts = list()
opts.append(constants.KDCOptions.forwardable.value)
opts.append(constants.KDCOptions.renewable.value)
opts.append(constants.KDCOptions.proxiable.value)
reqBody["kdc-options"] = constants.encodeFlags(opts)
seq_set(reqBody, "sname", serverName.components_to_asn1)
seq_set(reqBody, "cname", clientName.components_to_asn1)
reqBody["realm"] = domain
now = datetime.datetime.utcnow() + datetime.timedelta(days=1)
reqBody["till"] = KerberosTime.to_asn1(now)
reqBody["rtime"] = KerberosTime.to_asn1(now)
reqBody["nonce"] = random.getrandbits(31)
seq_set_iter(reqBody, "etype", ((int(cipher.enctype),)))
try:
tgt = sendReceive(encoder.encode(asReq), domain, kdc_host)
except Exception as e:
if str(e).find('KDC_ERR_PREAUTH_FAILED') >= 0:
return False
raise
return True