Attacking LSASS Passwords
Last updated
Last updated
In addition to getting copies of the SAM database to dump and crack hashes, we will also benefit from targeting LSASS. As discussed in the Credential Storage section of this module, LSASS is a critical service that plays a central role in credential management and the authentication processes in all Windows operating systems.
Upon initial logon, LSASS will:
Cache credentials locally in memory
Create access tokens
Enforce security policies
Write to Windows security log
Let's cover some of the techniques and tools we can use to dump LSASS memory and extract credentials from a target running Windows.
Similar to the process of attacking the SAM database, with LSASS, it would be wise for us first to create a copy of the contents of LSASS process memory via the generation of a memory dump. Creating a dump file lets us extract credentials offline using our attack host. Keep in mind conducting attacks offline gives us more flexibility in the speed of our attack and requires less time spent on the target system. There are countless methods we can use to create a memory dump. Let's cover techniques that can be performed using tools already built-in to Windows.
Task Manager Method
With access to an interactive graphical session with the target, we can use task manager to create a memory dump. This requires us to:
Open Task Manager > Select the Processes tab > Find & right click the Local Security Authority Process > Select Create dump file
A file called lsass.DMP is created and saved in:
This is the file we will transfer to our attack host. We can use the file transfer method discussed in the Attacking SAM section of this module to transfer the dump file to our attack host.
Rundll32.exe & Comsvcs.dll Method
The Task Manager method is dependent on us having a GUI-based interactive session with a target. We can use an alternative method to dump LSASS process memory through a command-line utility called rundll32.exe. This way is faster than the Task Manager method and more flexible because we may gain a shell session on a Windows host with only access to the command line. It is important to note that modern anti-virus tools recognize this method as malicious activity.
Before issuing the command to create the dump file, we must determine what process ID (PID) is assigned to lsass.exe. This can be done from cmd or PowerShell:
Finding LSASS PID in cmd
From cmd, we can issue the command tasklist /svc and find lsass.exe and its process ID in the PID field.
Attacking LSASS
Finding LSASS PID in PowerShell
From PowerShell, we can issue the command Get-Process lsass and see the process ID in the Id field.
Once we have the PID assigned to the LSASS process, we can create the dump file.
Creating lsass.dmp using PowerShell
With an elevated PowerShell session, we can issue the following command to create the dump file:
With this command, we are running rundll32.exe to call an exported function of comsvcs.dll which also calls the MiniDumpWriteDump (MiniDump) function to dump the LSASS process memory to a specified directory (C:\lsass.dmp). Recall that most modern AV tools recognize this as malicious and prevent the command from executing. In these cases, we will need to consider ways to bypass or disable the AV tool we are facing. AV bypassing techniques are outside of the scope of this module.
If we manage to run this command and generate the lsass.dmp file, we can proceed to transfer the file onto our attack box to attempt to extract any credentials that may have been stored in LSASS process memory.
Note: We can use the file transfer method discussed in the Attacking SAM section to get the lsass.dmp file from the target to our attack host.
Once we have the dump file on our attack host, we can use a powerful tool called pypykatz to attempt to extract credentials from the .dmp file. Pypykatz is an implementation of Mimikatz written entirely in Python. The fact that it is written in Python allows us to run it on Linux-based attack hosts. At the time of this writing, Mimikatz only runs on Windows systems, so to use it, we would either need to use a Windows attack host or we would need to run Mimikatz directly on the target, which is not an ideal scenario. This makes Pypykatz an appealing alternative because all we need is a copy of the dump file, and we can run it offline from our Linux-based attack host.
Recall that LSASS stores credentials that have active logon sessions on Windows systems. When we dumped LSASS process memory into the file, we essentially took a "snapshot" of what was in memory at that point in time. If there were any active logon sessions, the credentials used to establish them will be present. Let's run Pypykatz against the dump file and find out.
Running Pypykatz
The command initiates the use of pypykatz to parse the secrets hidden in the LSASS process memory dump. We use lsa in the command because LSASS is a subsystem of local security authority, then we specify the data source as a minidump file, proceeded by the path to the dump file (/home/peter/Documents/lsass.dmp) stored on our attack host. Pypykatz parses the dump file and outputs the findings:
Lets take a more detailed look at some of the useful information in the output.
MSV
MSV is an authentication package in Windows that LSA calls on to validate logon attempts against the SAM database. Pypykatz extracted the SID, Username, Domain, and even the NT & SHA1 password hashes associated with the bob user account's logon session stored in LSASS process memory. This will prove helpful in the final stage of our attack covered at the end of this section.
WDIGEST
WDIGEST is an older authentication protocol enabled by default in Windows XP - Windows 8 and Windows Server 2003 - Windows Server 2012. LSASS caches credentials used by WDIGEST in clear-text. This means if we find ourselves targeting a Windows system with WDIGEST enabled, we will most likely see a password in clear-text. Modern Windows operating systems have WDIGEST disabled by default. Additionally, it is essential to note that Microsoft released a security update for systems affected by this issue with WDIGEST. We can study the details of that security update here.
Kerberos
Kerberos is a network authentication protocol used by Active Directory in Windows Domain environments. Domain user accounts are granted tickets upon authentication with Active Directory. This ticket is used to allow the user to access shared resources on the network that they have been granted access to without needing to type their credentials each time. LSASS caches passwords, ekeys, tickets, and pins associated with Kerberos. It is possible to extract these from LSASS process memory and use them to access other systems joined to the same domain.
DPAPI
The Data Protection Application Programming Interface or DPAPI is a set of APIs in Windows operating systems used to encrypt and decrypt DPAPI data blobs on a per-user basis for Windows OS features and various third-party applications. Here are just a few examples of applications that use DPAPI and what they use it for:
Mimikatz and Pypykatz can extract the DPAPI masterkey for the logged-on user whose data is present in LSASS process memory. This masterkey can then be used to decrypt the secrets associated with each of the applications using DPAPI and result in the capturing of credentials for various accounts. DPAPI attack techniques are covered in greater detail in the Windows Privilege Escalation module.
Cracking the NT Hash with Hashcat
Now we can use Hashcat to crack the NT Hash. In this example, we only found one NT hash associated with the Bob user, which means we won't need to create a list of hashes as we did in the Attacking SAM section of this module. After setting the mode in the command, we can paste the hash, specify a wordlist, and then crack the hash.
Our cracking attempt completes, and our overall attack can be considered a success.
| Applications | Use of DPAPI |
|---|---|
Internet Explorer
Password form auto-completion data (username and password for saved sites).
Google Chrome
Password form auto-completion data (username and password for saved sites).
Outlook
Passwords for email accounts.
Remote Desktop Connection
Saved credentials for connections to remote machines.
Credential Manager
Saved credentials for accessing shared resources, joining Wireless networks, VPNs and more.
