Improve kerberos user enum module

documentation/modules/auxiliary/gather/kerberos_enumusers.md

@@ -1,9 +1,21 @@
+## Vulnerable Application
+
 The kerberos_enumusers module is used to enumerate valid Domain Users
 via Kerberos from a wholly unauthenticated perspective. It utilises the
 different responses returned by the service to identify users that exist
 within the target domain. It is also able to identify whether user
 accounts are enabled or disabled/locked out.
 
+## Verification Steps
+
+When verifying the module in the listed examples, it is recommended to test the following accounts:
+
+- Valid account
+- Invalid account
+- Locked/Disabled account
+- Account with spaces
+- AS-REP Roastable accounts
+
 ## Target
 
 To use kerberos_enumusers, make sure you are able to connect to the
@@ -15,54 +27,51 @@ The following demonstrates basic usage, using a custom wordlist,
 targeting a single Domain Controller to identify valid domain user
 accounts.
 
+Create a new `./users.txt` file, then run the module:
+
 ```
-msf > use auxiliary/gather/kerberos_enumusers
-msf auxiliary(kerberos_enumusers) > set DOMAIN MYDOMAIN
-DOMAIN => MYDOMAIN
-msf auxiliary(kerberos_enumusers) > set RHOST 192.168.5.1
-RHOST => 192.168.5.1
-msf auxiliary(kerberos_enumusers) > set USER_FILE /job/users.txt
-USER_FILE => /job/users.txt
-msf auxiliary(kerberos_enumusers) > run
-
-[*] Validating options...
-[*] Using domain: MYDOMAIN...
-[*] 192.168.5.1:88 - Testing User: "bob"...
-[*] 192.168.5.1:88 - KDC_ERR_PREAUTH_REQUIRED - Additional
-pre-authentication required
-[+] 192.168.5.1:88 - User: "bob" is present
-[*] 192.168.5.1:88 - Testing User: "alice"...
-[*] 192.168.5.1:88 - KDC_ERR_PREAUTH_REQUIRED - Additional
-pre-authentication required
-[+] 192.168.5.1:88 - User: "alice" is present
-[*] 192.168.5.1:88 - Testing User: "matt"...
-[*] 192.168.5.1:88 - KDC_ERR_PREAUTH_REQUIRED - Additional
-pre-authentication required
-[+] 192.168.5.1:88 - User: "matt" is present
-[*] 192.168.5.1:88 - Testing User: "guest"...
-[*] 192.168.5.1:88 - KDC_ERR_CLIENT_REVOKED - Clients credentials have
-been revoked
-[-] 192.168.5.1:88 - User: "guest" account disabled or locked out
-[*] 192.168.5.1:88 - Testing User: "admint"...
-[*] 192.168.5.1:88 - KDC_ERR_C_PRINCIPAL_UNKNOWN - Client not found in
-Kerberos database
-[*] 192.168.5.1:88 - User: "admint" does not exist
-[*] 192.168.5.1:88 - Testing User: "admin"...
-[*] 192.168.5.1:88 - KDC_ERR_C_PRINCIPAL_UNKNOWN - Client not found in
-Kerberos database
-[*] 192.168.5.1:88 - User: "admin" does not exist
-[*] 192.168.5.1:88 - Testing User: "administrator"...
-[*] 192.168.5.1:88 - KDC_ERR_C_PRINCIPAL_UNKNOWN - Client not found in
-Kerberos database
-[*] 192.168.5.1:88 - User: "administrator" does not exist
+msf6 auxiliary(gather/kerberos_enumusers) > run rhost=192.168.123.228 domain=domain.local user_file=./users.txt verbose=true
+[*] Running module against 192.168.123.228
+
+[*] Using domain: ADF3.LOCAL - 192.168.123.228:88...
+[*] 192.168.123.228:88 - User: "missing123" user not found
+[+] 192.168.123.228:88 - User: "administrator" is present
+[+] 192.168.123.228:88 - User: "account with spaces" is present
+[-] 192.168.123.228:88 - User: "locked_account" account disabled or locked out
+[+] 192.168.123.228:88 - User: "no_pre_auth" does not require preauthentication. Hash: $krb5asrep$23$no_pre_auth@DOMAIN.LOCAL:bdb54b9e...etc..etc...
+[+] 192.168.123.228:88 - User: "fake_mysql" is present
+[*] 192.168.123.228:88 - User: "missing1234" user not found
 [*] Auxiliary module execution completed
-msf auxiliary(kerberos_enumusers) >
+msf6 auxiliary(gather/kerberos_enumusers) > 
+```
+
+### ASREPRoast Cracking
+
+Accounts that have `Do not require Kerberos preauthentication` enabled, will receive an ASREP response with a ticket present.
+The technique of cracking this token offline is called ASREPRoasting.
+
+Cracking ASREP response with John:
+
+```
+john ./hashes.txt --wordlist=./wordlist.txt --format:krb5asrep
+```
+
+Cracking ASREP response with Hashcat:
+
+```
+hashcat -m 18200 -a 0 ./hashes.txt ./wordlist.txt
+```
+
+You can see previously creds with:
+
+```
+creds -v
 ```
 
 ## Options
 
-The kerberos_enumusers module only requires the RHOST, DOMAIN and
-USER_FILE options to run.
+The `kerberos_enumusers` module only requires the `RHOST`, `DOMAIN` and
+`USER_FILE` options to run.
 
 **The DOMAIN option**
 

lib/metasploit/framework/password_crackers/hashcat/formatter.rb

@@ -98,6 +98,8 @@ def hash_to_hashcat(cred)
       # https://hashcat.net/forum/thread-8833.html
       # while we can do the transformation, we'd have to throw extra flags at hashcat which aren't currently written into the lib for automation
       nil
+    when /^krb5$/
+      return cred.private.data.to_s
     end
   end
   nil

lib/msf/core/exploit/remote/kerberos/client/tgs_request.rb

@@ -87,15 +87,15 @@ def build_tgs_request(opts = {})
             # @option opts [Rex::Proto::Kerberos::Model::AuthorizationData] :auth_data
             # @option opts [Rex::Proto::Kerberos::Model::EncryptionKey] :subkey
             # @return [Rex::Proto::Kerberos::Model::EncryptedData]
-            # @raise [RuntimeError] if auth_data option isn't provided
+            # @raise [Rex::Proto::Kerberos::Model::Error::KerberosError] if auth_data option isn't provided
             # @see Rex::Proto::Kerberos::Model::AuthorizationData
             # @see Rex::Proto::Kerberos::Model::EncryptionKey
             # @see Rex::Proto::Kerberos::Model::EncryptedData
             def build_enc_auth_data(opts = {})
               auth_data = opts[:auth_data]
 
               if auth_data.nil?
-                raise ::RuntimeError, 'auth_data option required on #build_enc_auth_data'
+                raise ::Rex::Proto::Kerberos::Model::Error::KerberosError, 'auth_data option required on #build_enc_auth_data'
               end
 
               subkey = opts[:subkey] || build_subkey(opts)
@@ -120,7 +120,7 @@ def build_enc_auth_data(opts = {})
             # @option opts [Rex::Proto::Kerberos::Model::EncryptedData] :authenticator
             # @option opts [Rex::Proto::Kerberos::Model::EncryptionKey] :session_key
             # @return [Rex::Proto::Kerberos::Model::EncryptionKey]
-            # @raise [RuntimeError] if ticket option isn't provided
+            # @raise [Rex::Proto::Kerberos::Model::Error::KerberosError] if ticket option isn't provided
             # @see Rex::Proto::Kerberos::Model::Ticket
             # @see Rex::Proto::Kerberos::Model::EncryptedData
             # @see Rex::Proto::Kerberos::Model::EncryptionKey
@@ -133,7 +133,7 @@ def build_ap_req(opts = {})
               session_key = opts[:session_key] || build_subkey(opts)
 
               if ticket.nil?
-                raise ::RuntimeError, 'Building a AP-REQ without ticket not supported'
+                raise ::Rex::Proto::Kerberos::Model::Error::KerberosError, 'Building a AP-REQ without ticket not supported'
               end
 
               enc_authenticator = Rex::Proto::Kerberos::Model::EncryptedData.new(

lib/rex/proto/kerberos/client.rb

@@ -157,18 +157,18 @@ def send_request_udp(req)
         # Receives a Kerberos Response over a tcp connection
         #
         # @return [<Rex::Proto::Kerberos::Model::KrbError, Rex::Proto::Kerberos::Model::KdcResponse>] the kerberos message response
-        # @raise [RuntimeError] if the response can't be processed
+        # @raise [Rex::Proto::Kerberos::Model::Error::KerberosDecodingError] if the response can't be processed
         # @raise [EOFError] if expected data can't be read
         def recv_response_tcp
           length_raw = connection.get_once(4, timeout)
           unless length_raw && length_raw.length == 4
-            raise ::RuntimeError, 'Kerberos Client: failed to read response'
+            raise ::EOFError, 'Kerberos Client: failed to read response'
           end
           length = length_raw.unpack('N')[0]
 
           data = connection.get_once(length, timeout)
           unless data && data.length == length
-            raise ::RuntimeError, 'Kerberos Client: failed to read response'
+            raise ::EOFError, 'Kerberos Client: failed to read response'
           end
 
           res = decode_kerb_response(data)
@@ -189,7 +189,7 @@ def recv_response_udp
         #
         # @param data [String] the raw response message
         # @return [<Rex::Proto::Kerberos::Model::KrbError, Rex::Proto::Kerberos::Model::KdcResponse>] the kerberos message response
-        # @raise [RuntimeError] if the response can't be processed
+        # @raise [Rex::Proto::Kerberos::Model::Error::KerberosDecodingError] if the response can't be processed
         def decode_kerb_response(data)
           asn1 = OpenSSL::ASN1.decode(data)
           msg_type = asn1.value[0].value[1].value[0].value
@@ -202,7 +202,7 @@ def decode_kerb_response(data)
           when Rex::Proto::Kerberos::Model::TGS_REP
             res = Rex::Proto::Kerberos::Model::KdcResponse.decode(asn1)
           else
-            raise ::RuntimeError, 'Kerberos Client: Unknown response'
+            raise ::Rex::Proto::Kerberos::Model::Error::KerberosDecodingError, 'Kerberos Client: Unknown response'
           end
 
           res

lib/rex/proto/kerberos/crypto/rc4_hmac.rb

@@ -11,7 +11,7 @@ module Rc4Hmac
           # @param key [String] the key to decrypt
           # @param msg_type [Integer] the message type
           # @return [String] the decrypted cipher
-          # @raise [RuntimeError] if decryption doesn't succeed
+          # @raise [Rex::Proto::Kerberos::Model::Error::KerberosError] if decryption doesn't succeed
           def decrypt_rc4_hmac(cipher, key, msg_type)
             unless cipher && cipher.length > 16
               raise ::RuntimeError, 'RC4-HMAC decryption failed'
@@ -29,7 +29,7 @@ def decrypt_rc4_hmac(cipher, key, msg_type)
             decrypted = cipher.update(data) + cipher.final
 
             if OpenSSL::HMAC.digest('MD5', k1, decrypted) != checksum
-              raise ::RuntimeError, 'RC4-HMAC decryption failed, incorrect checksum verification'
+              raise ::Rex::Proto::Kerberos::Model::Error::KerberosError, 'RC4-HMAC decryption failed, incorrect checksum verification'
             end
 
             decrypted
@@ -62,4 +62,4 @@ def encrypt_rc4_hmac(data, key, msg_type)
       end
     end
   end
-end
+end

lib/rex/proto/kerberos/model.rb

@@ -17,57 +17,6 @@ module Model
         AUTHENTICATOR = 2
         AP_REQ = 14
 
-        # Kerberos error codes
-        ERROR_CODES = {
-          0 => ['KDC_ERR_NONE', 'No error'],
-          1 => ['KDC_ERR_NAME_EXP', 'Client\'s entry in database has expired'],
-          2 => ['KDC_ERR_SERVICE_EXP', 'Server\'s entry in database has expired'],
-          3 => ['KDC_ERR_BAD_PVNO', 'Requested protocol version number not supported'],
-          4 => ['KDC_ERR_C_OLD_MAST_KVNO', 'Client\'s key encrypted in old master key'],
-          5 => ['KDC_ERR_S_OLD_MAST_KVNO', 'Server\'s key encrypted in old master key'],
-          6 => ['KDC_ERR_C_PRINCIPAL_UNKNOWN', 'Client not found in Kerberos database'],
-          7 => ['KDC_ERR_S_PRINCIPAL_UNKNOWN', 'Server not found in Kerberos database'],
-          8 => ['KDC_ERR_PRINCIPAL_NOT_UNIQUE', 'Multiple principal entries in database'],
-          9 => ['KDC_ERR_NULL_KEY', 'The client or server has a null key'],
-          10 => ['KDC_ERR_CANNOT_POSTDATE', 'Ticket not eligible for postdating'],
-          11 => ['KDC_ERR_NEVER_VALID', 'Requested start time is later than end time'],
-          12 => ['KDC_ERR_POLICY', 'KDC policy rejects request'],
-          13 => ['KDC_ERR_BADOPTION', 'KDC cannot accommodate requested option'],
-          14 => ['KDC_ERR_ETYPE_NOSUPP', 'KDC has no support for encryption type'],
-          15 => ['KDC_ERR_SUMTYPE_NOSUPP', 'KDC has no support for checksum type'],
-          16 => ['KDC_ERR_PADATA_TYPE_NOSUPP', 'KDC has no support for padata type'],
-          17 => ['KDC_ERR_TRTYPE_NOSUPP', 'KDC has no support for transited type'],
-          18 => ['KDC_ERR_CLIENT_REVOKED', 'Clients credentials have been revoked'],
-          19 => ['KDC_ERR_SERVICE_REVOKED', 'Credentials for server have been revoked'],
-          20 => ['KDC_ERR_TGT_REVOKED', 'TGT has been revoked'],
-          21 => ['KDC_ERR_CLIENT_NOTYET', 'Client not yet valid - try again later'],
-          22 => ['KDC_ERR_SERVICE_NOTYET', 'Server not yet valid - try again later'],
-          23 => ['KDC_ERR_KEY_EXPIRED', 'Password has expired - change password to reset'],
-          24 => ['KDC_ERR_PREAUTH_FAILED', 'Pre-authentication information was invalid'],
-          25 => ['KDC_ERR_PREAUTH_REQUIRED', 'Additional pre-authentication required'],
-          31 => ['KRB_AP_ERR_BAD_INTEGRITY', 'Integrity check on decrypted field failed'],
-          32 => ['KRB_AP_ERR_TKT_EXPIRED', 'Ticket expired'],
-          33 => ['KRB_AP_ERR_TKT_NYV', 'Ticket not yet valid'],
-          34 => ['KRB_AP_ERR_REPEAT', 'Request is a replay'],
-          35 => ['KRB_AP_ERR_NOT_US', 'The ticket isn\'t for us'],
-          36 => ['KRB_AP_ERR_BADMATCH', 'Ticket and authenticator don\'t match'],
-          37 => ['KRB_AP_ERR_SKEW', 'Clock skew too great'],
-          38 => ['KRB_AP_ERR_BADADDR', 'Incorrect net address'],
-          39 => ['KRB_AP_ERR_BADVERSION', 'Protocol version mismatch'],
-          40 => ['KRB_AP_ERR_MSG_TYPE', 'Invalid msg type'],
-          41 => ['KRB_AP_ERR_MODIFIED', 'Message stream modified'],
-          42 => ['KRB_AP_ERR_BADORDER', 'Message out of order'],
-          44 => ['KRB_AP_ERR_BADKEYVER', 'Specified version of key is not available'],
-          45 => ['KRB_AP_ERR_NOKEY', 'Service key not available'],
-          46 => ['KRB_AP_ERR_MUT_FAIL', 'Mutual authentication failed'],
-          47 => ['KRB_AP_ERR_BADDIRECTION', 'Incorrect message direction'],
-          48 => ['KRB_AP_ERR_METHOD', 'Alternative authentication method required'],
-          49 => ['KRB_AP_ERR_BADSEQ', 'Incorrect sequence number in message'],
-          50 => ['KRB_AP_ERR_INAPP_CKSUM', 'Inappropriate type of checksum in message'],
-          60 => ['KRB_ERR_GENERIC', 'Generic error'],
-          61 => ['KRB_ERR_FIELD_TOOLONG', 'Field is too long for this implementation']
-        }
-
         KDC_OPTION_RESERVED        = 0
         KDC_OPTION_FORWARDABLE     = 1
         KDC_OPTION_FORWARDED       = 2

lib/rex/proto/kerberos/model/enc_kdc_response.rb

@@ -49,15 +49,15 @@ class EncKdcResponse < Element
           #
           # @param input [String, OpenSSL::ASN1::ASN1Data] the input to decode from
           # @return [self] if decoding succeeds
-          # @raise [RuntimeError] if decoding doesn't succeed
+          # @raise [Rex::Proto::Kerberos::Model::Error::KerberosDecodingError] if decoding doesn't succeed
           def decode(input)
             case input
             when String
               decode_string(input)
             when OpenSSL::ASN1::ASN1Data
               decode_asn1(input)
             else
-              raise ::RuntimeError, 'Failed to decode EncKdcResponse, invalid input'
+              raise ::Rex::Proto::Kerberos::Model::Error::KerberosDecodingError, 'Failed to decode EncKdcResponse, invalid input'
             end
 
             self
@@ -84,7 +84,7 @@ def decode_string(input)
           # Decodes a Rex::Proto::Kerberos::Model::EncKdcResponse
           #
           # @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
-          # @raise [RuntimeError] if decoding doesn't succeed
+          # @raise [Rex::Proto::Kerberos::Model::Error::KerberosDecodingError] if decoding doesn't succeed
           def decode_asn1(input)
             input.value[0].value.each do |val|
               case val.tag
@@ -111,7 +111,7 @@ def decode_asn1(input)
               when 10
                 self.sname = decode_sname(val)
               else
-                raise ::RuntimeError, 'Failed to decode ENC-KDC-RESPONSE SEQUENCE'
+                raise ::Rex::Proto::Kerberos::Model::Error::KerberosDecodingError, 'Failed to decode ENC-KDC-RESPONSE SEQUENCE'
               end
             end
           end
@@ -212,4 +212,4 @@ def decode_sname(input)
       end
     end
   end
-end
+end