Class: Msf::Exploit::Remote::Kerberos::ServiceAuthenticator::Base

Inherits:
Object
  • Object
show all
Extended by:
Forwardable
Includes:
Auxiliary::Report, Client, Rex::Proto::Gss::Asn1
Defined in:
lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb

Overview

This class acts as standalone authenticator for Kerberos

Direct Known Subclasses

HTTP, LDAP, MSSQL, SMB

Defined Under Namespace

Modules: Delegation

Constant Summary collapse

GSS_DELEGATE =

Flags - datatracker.ietf.org/doc/html/rfc4121#section-4.1.1.1

0x01
GSS_MUTUAL = 
0x02
GSS_REPLAY_DETECT = 
0x04
GSS_SEQUENCE = 
0x08
GSS_CONFIDENTIAL = 
0x10
GSS_INTEGRITY = 
0x20
GSS_DCE_STYLE = 
0x1000

Constants included from Client

Client::NEG_TOKEN_ACCEPT_COMPLETED, Client::NEG_TOKEN_ACCEPT_INCOMPLETE, Client::NEG_TOKEN_REJECT, Client::NEG_TOKEN_REQUEST_MIC, Client::TOK_ID_KRB_AP_REP, Client::TOK_ID_KRB_AP_REQ, Client::TOK_ID_KRB_ERROR

Constants included from Client::ApRequest

Client::ApRequest::AP_MUTUAL_REQUIRED, Client::ApRequest::AP_USE_SESSION_KEY

Instance Attribute Summary collapse

Attributes included from Client

#client

Instance Method Summary collapse

Methods included from Rex::Proto::Gss::Asn1

#unwrap_pseudo_asn1, #wrap_pseudo_asn1

Methods included from Auxiliary::Report

#active_db?, #create_cracked_credential, #create_credential, #create_credential_and_login, #create_credential_login, #db, #db_warning_given?, #get_client, #get_host, #inside_workspace_boundary?, #invalidate_login, #mytask, #myworkspace, #myworkspace_id, #report_auth_info, #report_client, #report_exploit, #report_host, #report_loot, #report_note, #report_service, #report_vuln, #report_web_form, #report_web_page, #report_web_site, #report_web_vuln, #store_cred, #store_local, #store_loot

Methods included from Metasploit::Framework::Require

optionally, optionally_active_record_railtie, optionally_include_metasploit_credential_creation, #optionally_include_metasploit_credential_creation, optionally_require_metasploit_db_gem_engines

Methods included from Client

#cleanup, #disconnect, #peer, #select_cipher, #send_request_as, #send_request_tgs, #send_request_tgt, #send_request_tgt_pkinit

Methods included from Client::Pkinit

#build_dh, #build_pa_pk_as_req, #calculate_shared_key, #extract_user_and_realm, #k_truncate, #sign_auth_pack

Methods included from Client::Pac

#build_empty_auth_data, #build_pa_pac_request, #build_pac, #build_pac_authorization_data

Methods included from Client::TgsResponse

#decrypt_kdc_tgs_rep_enc_part, #extract_kerb_creds

Methods included from Client::TgsRequest

#build_ap_req, #build_authenticator, #build_enc_auth_data, #build_pa_for_user, #build_subkey, #build_tgs_body_checksum, #build_tgs_request, #build_tgs_request_body

Methods included from Client::AsResponse

#decrypt_kdc_as_rep_enc_part, #extract_logon_time, #extract_session_key, #format_as_rep_to_john_hash

Methods included from Client::AsRequest

#build_as_pa_time_stamp, #build_as_request, #build_as_request_body

Methods included from Client::ApRequest

#build_service_ap_request, #encode_gss_kerberos_ap_request, #encode_gss_spnego_ap_request

Methods included from Client::Base

#build_client_name, #build_server_name

Constructor Details

#initialize(realm: nil, hostname: nil, username: nil, password: nil, host: nil, proxies: nil, port: 88, timeout: 25, framework: nil, framework_module: nil, mutual_auth: false, use_gss_checksum: false, mechanism: Rex::Proto::Gss::Mechanism::SPNEGO, send_delegated_creds: Delegation::ALWAYS, dce_style: false, cache_file: nil, ticket_storage: nil, key: nil, offered_etypes: nil, pfx: nil) ⇒ Base

Returns a new instance of Base.



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
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 111

def initialize(
    realm: nil,
    hostname: nil,
    username: nil,
    password: nil,
    host: nil,
    proxies: nil,
    port: 88,
    timeout: 25,
    framework: nil,
    framework_module: nil,
    mutual_auth: false,
    use_gss_checksum: false,
    mechanism: Rex::Proto::Gss::Mechanism::SPNEGO,
    send_delegated_creds: Delegation::ALWAYS,
    dce_style: false,
    cache_file: nil,
    ticket_storage: nil,
    key: nil,
    offered_etypes: nil,
    pfx: nil
)
  @realm = realm
  @hostname = hostname
  @host = host
  @proxies = proxies
  @port = port
  @timeout = timeout
  @username = username
  @password = password
  @pfx = pfx
  @framework = framework
  @framework_module = framework_module
  @mutual_auth = mutual_auth
  @use_gss_checksum = use_gss_checksum
  @mechanism = mechanism
  @send_delegated_creds = send_delegated_creds
  @dce_style = dce_style
  @ticket_storage = ticket_storage || Msf::Exploit::Remote::Kerberos::Ticket::Storage::ReadWrite.new(
    framework: framework,
    framework_module: framework_module
  )
  @key = key
  @offered_etypes = offered_etypes

  credential = nil
  if cache_file.present?
    # the cache file is only used for loading credentials, it is *not* written to
    credential = load_credential_from_file(cache_file, sname: nil, sname_hostname: @hostname)
    serviceclass = build_spn.name_string.first
    if credential && credential.server.components[0] != serviceclass
      old_sname = credential.server.components.snapshot.join('/')
      credential.server.components[0] = serviceclass
      new_sname = credential.server.components.snapshot.join('/')
      print_status("Patching sname from #{old_sname} to #{new_sname}")
      ticket = Rex::Proto::Kerberos::Model::Ticket.decode(credential.ticket.value)
      ticket.sname.name_string[0] = serviceclass
      credential.ticket = ticket.encode
    elsif credential.nil? && hostname.present?
      credential = load_credential_from_file(cache_file, sname: "krbtgt/#{hostname.split('.', 2).last}")
    end
    if credential.nil?
      raise ::Rex::Proto::Kerberos::Model::Error::KerberosError.new("Failed to load a usable credential from ticket file: #{cache_file}")
    end
    print_status("Loaded a credential from ticket file: #{cache_file}")
  end
  @credential = credential
end

Instance Attribute Details

#dce_style ⇒ Object (readonly)

Returns the value of attribute dce_style.



74
75
76
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 74

def dce_style
  @dce_style
end

#framework ⇒ Object (readonly)

Returns the value of attribute framework.



50
51
52
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 50

def framework
  @framework
end

#framework_module ⇒ Object (readonly)

Returns the value of attribute framework_module.



54
55
56
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 54

def framework_module
  @framework_module
end

#host ⇒ String? (readonly)

Returns The proxy directive to use for the socket.

Returns:

  • (String, nil) —

    The proxy directive to use for the socket



34
35
36
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 34

def host
  @host
end

#hostname ⇒ Object (readonly)

Returns the value of attribute hostname.



30
31
32
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 30

def hostname
  @hostname
end

#key ⇒ Object (readonly)

Returns the value of attribute key.



82
83
84
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 82

def key
  @key
end

#mechanism ⇒ Object (readonly)

Returns the value of attribute mechanism.



66
67
68
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 66

def mechanism
  @mechanism
end

#mutual_auth ⇒ Object (readonly)

Returns the value of attribute mutual_auth.



58
59
60
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 58

def mutual_auth
  @mutual_auth
end

#offered_etypes ⇒ Object (readonly)

See Also:



87
88
89
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 87

def offered_etypes
  @offered_etypes
end

#password ⇒ Object (readonly)

Returns the value of attribute password.



22
23
24
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 22

def password
  @password
end

#pfx ⇒ Object (readonly)

Returns the value of attribute pfx.



26
27
28
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 26

def pfx
  @pfx
end

#port ⇒ Object (readonly)

Returns the value of attribute port.



38
39
40
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 38

def port
  @port
end

#proxies ⇒ Object (readonly)

Returns the value of attribute proxies.



42
43
44
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 42

def proxies
  @proxies
end

#realm ⇒ Object (readonly)

Returns the value of attribute realm.



14
15
16
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 14

def realm
  @realm
end

#send_delegated_creds ⇒ Object (readonly)

Returns the value of attribute send_delegated_creds.



70
71
72
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 70

def send_delegated_creds
  @send_delegated_creds
end

#ticket_storage ⇒ Object (readonly)

Returns the value of attribute ticket_storage.



78
79
80
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 78

def ticket_storage
  @ticket_storage
end

#timeout ⇒ Object (readonly)

Returns the value of attribute timeout.



46
47
48
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 46

def timeout
  @timeout
end

#use_gss_checksum ⇒ Object (readonly)

Returns the value of attribute use_gss_checksum.



62
63
64
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 62

def use_gss_checksum
  @use_gss_checksum
end

#username ⇒ Object (readonly)

Returns the value of attribute username.



18
19
20
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 18

def username
  @username
end

Instance Method Details

#authenticate(options = {}) ⇒ Hash

Returns The security_blob SPNEGO GSS and TGS session key.

Parameters:

  • options (Hash) (defaults to: {})

Options Hash (options):

  • :credential (String) —

    An explicit credential object to use for authentication.

  • :sname (Rex::Proto::Kerberos::Model::PrincipalName) —

    The target service principal name.

  • :mechanism (String) —

    The authentication mechanism. One of the Rex::Proto::Gss::Mechanism constants.

Returns:

  • (Hash) —

    The security_blob SPNEGO GSS and TGS session key



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
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 216

def authenticate(options = {})
  options[:sname] = options.fetch(:sname) { build_spn(options) }

  unless options[:credential]
    if @credential
      # use an explicit credential
      options[:credential] = @credential
    else
      # load a cached TGS
      options[:credential] = get_cached_credential(options)
      tgt_sname = Rex::Proto::Kerberos::Model::PrincipalName.new(
        name_type: Rex::Proto::Kerberos::Model::NameType::NT_SRV_INST,
        name_string: [
          "krbtgt",
          realm
        ]
      )
      unless options[:credential]
        # load a cached TGT (specific host)
        options[:credential] = get_cached_credential(
          options.merge(sname: tgt_sname)
        )
      end
      unless options[:credential]
        # load a cached TGT (any host)
        options[:credential] = get_cached_credential(
          options.merge(sname: tgt_sname, host: nil)
        )
      end
      if options[:credential]
        print_status("Using cached credential for #{options[:credential].server} #{options[:credential].client}")
      end
    end
  end

  if options[:credential] && options[:credential].server.to_s.start_with?('krbtgt/')
    auth_context = authenticate_via_krb5_ccache_credential_tgt(options[:credential], options)
  elsif options[:credential]
    auth_context = authenticate_via_krb5_ccache_credential_tgs(options[:credential], options)
  else
    auth_context = authenticate_via_kdc(options)
    auth_context = authenticate_via_krb5_ccache_credential_tgt(auth_context[:credential], options)
  end

  ap_request_asn1 = auth_context.delete(:service_ap_request).to_asn1

  mechanism = options.fetch(:mechanism) { self.mechanism }
  if mechanism == Rex::Proto::Gss::Mechanism::SPNEGO
    security_blob = encode_gss_spnego_ap_request(ap_request_asn1)
  elsif mechanism == Rex::Proto::Gss::Mechanism::KERBEROS
    security_blob = encode_gss_kerberos_ap_request(ap_request_asn1)
  else
    raise RuntimeError, "Unknown GSS mechanism: #{mechanism}"
  end

  auth_context[:security_blob] = security_blob
  auth_context
end

#authenticate_via_kdc(options = {}) ⇒ Object

Authenticate with credentials to the key distribution center (KDC). This will request a TGT only.

Parameters:

  • options (Hash) (defaults to: {}) 


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
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 573

def authenticate_via_kdc(options = {})
  realm = self.realm.upcase
  client_name = username
  server_name = "krbtgt/#{realm}"

  ticket_options = Rex::Proto::Kerberos::Model::KdcOptionFlags.from_flags(
    [
      Rex::Proto::Kerberos::Model::KdcOptionFlags::FORWARDABLE,
      Rex::Proto::Kerberos::Model::KdcOptionFlags::RENEWABLE,
      Rex::Proto::Kerberos::Model::KdcOptionFlags::CANONICALIZE,
      Rex::Proto::Kerberos::Model::KdcOptionFlags::RENEWABLE_OK
    ]
  )

  if (pfx = options.fetch(:pfx) { self.pfx })
    offered_etypes = options.fetch(:offered_etypes) do
      self.offered_etypes || Rex::Proto::Kerberos::Crypto::Encryption::PkinitEtypes
    end

    tgt_result = send_request_tgt_pkinit(
      server_name: server_name,
      client_name: client_name,
      pfx: pfx,
      realm: realm,
      options: ticket_options,
      offered_etypes: offered_etypes
    )
  else
    offered_etypes = options.fetch(:offered_etypes) do
      self.offered_etypes || Rex::Proto::Kerberos::Crypto::Encryption::DefaultOfferedEtypes
    end

    tgt_result = send_request_tgt(
      server_name: server_name,
      client_name: client_name,
      password: password,
      key: key,
      realm: realm,
      options: ticket_options,
      offered_etypes: offered_etypes
    )
  end

  if tgt_result.decrypted_part.nil? && !tgt_result.preauth_required
    raise ::Rex::Proto::Kerberos::Model::Error::KerberosError.new(
      'Kerberos ticket does not require preauthentication. It is not possible to decrypt the encrypted message to request further TGS tickets. Try cracking the password via AS-REP Roasting techniques.',
    )
  end

  print_good("#{peer} - Received a valid TGT-Response")

  ccache = Rex::Proto::Kerberos::CredentialCache::Krb5Ccache.from_responses(tgt_result.as_rep, tgt_result.decrypted_part)
  options.fetch(:ticket_storage, @ticket_storage).store_ccache(ccache, host: rhost)

  credential = ccache.credentials.first
  session_key = Rex::Proto::Kerberos::Model::EncryptionKey.new(
    type: credential.keyblock.enctype.value,
    value: credential.keyblock.data.value
  )

  { credential: credential, session_key: session_key, krb_enc_key: tgt_result.krb_enc_key }
end

#build_spn(options = {}) ⇒ Object 



339
340
341
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 339

def build_spn(options = {})
  nil
end

#connect(options = {}) ⇒ Object 



194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 194

def connect(options = {})
  unless options[:rhost]
    unless (host = @host)
      vprint_status("Using DNS to lookup the KDC for #{realm}...")
      host = ::Rex::Socket.getresources("_kerberos._tcp.#{realm}", :SRV)&.sample
      if host.nil?
        raise ::Rex::Proto::Kerberos::Model::Error::KerberosError.new("Failed to lookup the KDC")
      end
      print_status("Using KDC #{host} for realm #{realm}")
      @host = host
    end
    options[:rhost] = host
  end

  super(options)
end

#get_message_encryptor(key, client_sequence_number, server_sequence_number) ⇒ Object 



275
276
277
278
279
280
281
282
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 275

def get_message_encryptor(key, client_sequence_number, server_sequence_number)
  Rex::Proto::Gss::Kerberos::MessageEncryptor.new(key,
                                          client_sequence_number,
                                          server_sequence_number,
                                          is_initiator: true,
                                          use_acceptor_subkey: true,
                                          dce_style: @dce_style)
end

#parse_gss_init_response(token, session_key, mechanism: 'kerberos') ⇒ Object 



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
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 284

def parse_gss_init_response(token, session_key, mechanism: 'kerberos')
  mech_id, encapsulated_token = unwrap_pseudo_asn1(token)

  if mech_id.value == Rex::Proto::Gss::OID_KERBEROS_5.value
    tok_id = encapsulated_token[0,2]
    data = encapsulated_token[2, encapsulated_token.length]
    case tok_id
    when TOK_ID_KRB_AP_REP
      ap_rep = Rex::Proto::Kerberos::Model::ApRep.decode(data)
      print_good("#{peer} - Received AP-REQ. Extracting session key...")

      raise ::Rex::Proto::Kerberos::Model::Error::KerberosError, 'Mismatching etypes' if session_key.type != ap_rep.enc_part.etype

      decrypted = ap_rep.decrypt_enc_part(session_key.value)

      result = {
        ap_rep_subkey: decrypted.subkey,
        server_sequence_number: decrypted.sequence_number,
        etype: ap_rep.enc_part.etype
      }
    when TOK_ID_KRB_ERROR
      krb_err = Rex::Proto::Kerberos::Model::KrbError.decode(data)
      print_error("#{peer} - Received KRB-ERR.")

      raise ::Rex::Proto::Kerberos::Model::Error::KerberosError.new(res: krb_err)
    else
      raise ::Rex::Proto::Kerberos::Model::Error::KerberosError, "Unknown token id: #{tok_id.inspect}"
    end
  else
    raise ::NotImplementedError, "Parsing mechtype #{mech_id.value} not supported"
  end

end

#request_tgs_only(credential, options = {}) ⇒ Rex::Proto::Kerberos::CredentialCache::Krb5CcacheCredential

Returns The ccache credential.

Parameters:

Options Hash (options):

Returns:

See Also:

  • Options dcoumentation
  • Other options dcoumentation


381
382
383
384
385
386
387
388
389
390
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 381

def request_tgs_only(credential, options = {})
  # load a cached TGS
  if (ccache = get_cached_credential(options))
    print_status("Using cached credential for #{ccache.server} #{ccache.client}")
    return ccache
  end

  auth_context = authenticate_via_krb5_ccache_credential_tgt(credential, options)
  auth_context[:credential]
end

#request_tgt_only(options = {}) ⇒ Rex::Proto::Kerberos::CredentialCache::Krb5CcacheCredential

Returns The ccache credential.

Parameters:

  • options (Hash) (defaults to: {})

Options Hash (options):

Returns:

See Also:



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
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 348

def request_tgt_only(options = {})
  if options[:cache_file]
    credential = load_credential_from_file(options[:cache_file])
  else
    credential = get_cached_credential(
      options.merge(
        sname: Rex::Proto::Kerberos::Model::PrincipalName.new(
          name_type: Rex::Proto::Kerberos::Model::NameType::NT_SRV_INST,
          name_string: [
            "krbtgt",
            realm
          ]
        )
      )
    )
  end

  if credential
    print_status("Using cached credential for #{credential.server} #{credential.client}")
    return credential
  end

  auth_context = authenticate_via_kdc(options)
  return auth_context[:credential]
end

#rhost ⇒ String

Returns the target host

Returns:

  • (String) 


183
184
185
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 183

def rhost
  host
end

#rport ⇒ Integer

Returns the remote port

Returns:

  • (Integer) 


190
191
192
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 190

def rport
  port
end

#s4u2proxy(credential, options = {}) ⇒ Array

Request a service ticket to another service on behalf of a user

Parameters:

Options Hash (options):

Returns:

  • (Array) —

    The new TGS ticket and the decrypted TGS credentials as a MIT Cache Credential



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
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 453

def s4u2proxy(credential, options = {})
  realm = self.realm.upcase
  sname = options.fetch(:sname)
  client_name = username

  now = Time.now.utc
  expiry_time = now + 1.day

  ticket = Rex::Proto::Kerberos::Model::Ticket.decode(credential.ticket.value)
  session_key = Rex::Proto::Kerberos::Model::EncryptionKey.new(
    type: credential.keyblock.enctype.value,
    value: credential.keyblock.data.value
  )

  pa_pac_options_flags = Rex::Proto::Kerberos::Model::PreAuthPacOptionsFlags.from_flags(
    [
      Rex::Proto::Kerberos::Model::PreAuthPacOptionsFlags::RESOURCE_BASED_CONSTRAINED_DELEGATION
    ]
  )
  pa_pac_options = Rex::Proto::Kerberos::Model::PreAuthPacOptions.new(
    flags: pa_pac_options_flags
  )
  pa_data_entry = Rex::Proto::Kerberos::Model::PreAuthDataEntry.new(
    type: Rex::Proto::Kerberos::Model::PreAuthType::PA_PAC_OPTIONS,
    value: pa_pac_options.encode
  )

  etypes = Set.new([credential.keyblock.enctype.value])
  etypes << Rex::Proto::Kerberos::Crypto::Encryption::RC4_HMAC
  etypes << Rex::Proto::Kerberos::Crypto::Encryption::DES_CBC_MD5
  etypes << Rex::Proto::Kerberos::Crypto::Encryption::DES3_CBC_SHA1

  tgs_options = {
    pa_data: pa_data_entry,
    additional_flags: [Rex::Proto::Kerberos::Model::KdcOptionFlags::CNAME_IN_ADDL_TKT],
    additional_tickets: [options[:tgs_ticket]],
    ticket_storage: options.fetch(:ticket_storage, @ticket_storage),
    credential_cache_username: options[:impersonate]
  }

  request_service_ticket(
    session_key,
    ticket,
    realm,
    client_name,
    etypes,
    expiry_time,
    now,
    sname,
    tgs_options
  )
end

#s4u2self(credential, options = {}) ⇒ Array

Request a service ticket to itself on behalf of a user

Parameters:

Options Hash (options):

Returns:

  • (Array) —

    The TGS ticket and the decrypted TGS credentials as a MIT Cache Credential



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
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 401

def s4u2self(credential, options = {})
  realm = self.realm.upcase
  sname = options.fetch(:sname)
  client_name = username

  now = Time.now.utc
  expiry_time = now + 1.day

  ticket = Rex::Proto::Kerberos::Model::Ticket.decode(credential.ticket.value)
  session_key = Rex::Proto::Kerberos::Model::EncryptionKey.new(
    type: credential.keyblock.enctype.value,
    value: credential.keyblock.data.value
  )

  etypes = Set.new([credential.keyblock.enctype.value])
  etypes << Rex::Proto::Kerberos::Crypto::Encryption::RC4_HMAC

  tgs_options = {
    ticket_storage: options.fetch(:ticket_storage, @ticket_storage),
    credential_cache_username: options[:impersonate],
    pa_data: build_pa_for_user(
      {
        username: options[:impersonate],
        session_key: session_key,
        realm: realm
      }
    )
  }

  request_service_ticket(
    session_key,
    ticket,
    realm,
    client_name,
    etypes,
    expiry_time,
    now,
    sname,
    tgs_options
  )
end

#u2uself(credential, options = {}) ⇒ Object

Request a service ticket to a user on behalf of themselves This is mostly useful for PKINIT to recover the NT hash Can combine this with S4U2Self by providing an :impersonate option to retrieve a PAC for any account, i.e. Sapphire Ticket attack

Parameters:

See Also:



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
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 515

def u2uself(credential, options = {})
  realm = self.realm.upcase
  client_name = options.fetch(:username) { self.username }
  sname = options.fetch(:sname) {
    Rex::Proto::Kerberos::Model::PrincipalName.new(
      name_type: Rex::Proto::Kerberos::Model::NameType::NT_UNKNOWN,
      name_string: [ client_name ]
    )
  }

  now = Time.now.utc
  expiry_time = now + 1.day

  ticket = Rex::Proto::Kerberos::Model::Ticket.decode(credential.ticket.value)
  session_key = Rex::Proto::Kerberos::Model::EncryptionKey.new(
    type: credential.keyblock.enctype.value,
    value: credential.keyblock.data.value
  )

  etypes = Set.new([ticket.enc_part.etype])
  etypes << Rex::Proto::Kerberos::Crypto::Encryption::RC4_HMAC

  tgs_options = {
    ticket_storage: options.fetch(:ticket_storage, @ticket_storage),
    credential_cache_username: client_name,
    additional_flags: [
      Rex::Proto::Kerberos::Model::KdcOptionFlags::ENC_TKT_IN_SKEY,
      Rex::Proto::Kerberos::Model::KdcOptionFlags::RENEWABLE_OK
    ],
    additional_tickets: [ticket]
  }

  if options[:impersonate]
    tgs_options[:pa_data] = build_pa_for_user(
      {
        username: options[:impersonate],
        session_key: session_key,
        realm: self.realm
      }
    )
  end

  request_service_ticket(
    session_key,
    ticket,
    realm,
    client_name,
    etypes,
    expiry_time,
    now,
    sname,
    tgs_options
  )
end

#validate_response!(security_blob, accept_incomplete: false) ⇒ Object

Parameters:

  • security_blob (String) —

    SPNEGO GSS Blob

  • accept_incomplete (Boolean) (defaults to: false) —

    Whether an Incomplete value is an acceptable response

Raises:



322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
 
# File 'lib/msf/core/exploit/remote/kerberos/service_authenticator/base.rb', line 322

def validate_response!(security_blob, accept_incomplete: false)
  begin
    gss_api = OpenSSL::ASN1.decode(security_blob)
    neg_result = ::RubySMB::Gss.asn1dig(gss_api, 0, 0, 0)&.value.to_i
    supported_neg = ::RubySMB::Gss.asn1dig(gss_api, 0, 1, 0)&.value
  rescue OpenSSL::ASN1::ASN1Error
    raise ::Rex::Proto::Kerberos::Model::Error::KerberosDecodingError.new('Invalid GSS Response')
  end

  is_success = (neg_result == NEG_TOKEN_ACCEPT_COMPLETED || (accept_incomplete && neg_result == NEG_TOKEN_ACCEPT_INCOMPLETE)) &&
    supported_neg == ::Rex::Proto::Gss::OID_MICROSOFT_KERBEROS_5.value

  raise ::Rex::Proto::Kerberos::Model::Error::KerberosError.new('Failed to negotiate Kerberos GSS') unless is_success

  is_success
end