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☑️Credential Theft

Credential Hunting

Searching for files

Against best practices, applications often store passwords in cleartext config files. Suppose we gain command execution in the context of an unprivileged user account. In that case, we may be able to find credentials for their admin account or another privileged local or domain account. We can use the findstr utility to search for this sensitive information.

findstr /SIM /C:"password" *.txt *.ini *.cfg *.config *.xml

Sensitive IIS information such as credentials may be stored in a web.config file. For the default IIS website, this could be located at C:\inetpub\wwwroot\web.config, but there may be multiple versions of this file in different locations, which we can search for recursively.

Dictionary files

Another interesting case is dictionary files. For example, sensitive information such as passwords may be entered in an email client or a browser-based application, which underlines any words it doesn't recognize. The user may add these words to their dictionary to avoid the distracting red underline.

gc 'C:\Users\htb-student\AppData\Local\Google\Chrome\User Data\Default\Custom Dictionary.txt' | Select-String password

Unattended Installation Files

Unattended installation files may define auto-logon settings or additional accounts to be created as part of the installation. Passwords in the unattend.xml are stored in plaintext or base64 encoded.

<?xml version="1.0" encoding="utf-8"?>
<unattend xmlns="urn:schemas-microsoft-com:unattend">
    <settings pass="specialize">
        <component name="Microsoft-Windows-Shell-Setup" processorArchitecture="amd64" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
            <AutoLogon>
                <Password>
                    <Value>local_4dmin_p@ss</Value>
                    <PlainText>true</PlainText>
                </Password>
                <Enabled>true</Enabled>
                <LogonCount>2</LogonCount>
                <Username>Administrator</Username>
            </AutoLogon>
            <ComputerName>*</ComputerName>
        </component>
    </settings>

Although these files should be automatically deleted as part of the installation, sysadmins may have created copies of the file in other folders during the development of the image and answer file.

PowerShell History File

Starting with Powershell 5.0 in Windows 10, PowerShell stores command history to the file:

As seen in the (handy) Windows Commands PDF, published by Microsoft here, there are many commands which can pass credentials on the command line. We can see in the example below that the user-specified local administrative credentials to query the Application Event Log using wevutil.

Once we know the file's location (the default path is above), we can attempt to read its contents using gc.

We can also use this one-liner to retrieve the contents of all Powershell history files that we can access as our current user. This can also be extremely helpful as a post-exploitation step. We should always recheck these files once we have local admin if our prior access did not allow us to read the files for some users. This command assumes that the default save path is being used.

PowerShell Credentials

PowerShell credentials are often used for scripting and automation tasks as a way to store encrypted credentials conveniently. The credentials are protected using DPAPI, which typically means they can only be decrypted by the same user on the same computer they were created on.

Take, for example, the following script Connect-VC.ps1, which a sysadmin has created to connect to a vCenter server easily.

Decrypting PowerShell Credentials

If we have gained command execution in the context of this user or can abuse DPAPI, then we can recover the cleartext credentials from encrypted.xml. The example below assumes the former.

Other File

There are many other types of files that we may find on a local system or on network share drives that may contain credentials or additional information that can be used to escalate privileges. In an Active Directory environment, we can use a tool such as Snaffler to crawl network share drives for interesting file extensions such as .kdbx, .vmdk, .vdhx, .ppk, etc. We may find a virtual hard drive that we can mount and extract local administrator password hashes from, an SSH private key that can be used to access other systems, or instances of users storing passwords in Excel/Word Documents, OneNote workbooks, or even the classic passwords.txt file.

Many companies provide each employee with a folder on a file share mapped to their user id, i.e., the folder bjones on the users share on a server called FILE01 with loose permissions applied (i.e., all Domain Users with read access to all user folders). We often find users saving sensitive personal data in these folders, unaware they are accessible to everyone in the network and not just local to their workstation.

Manually Searching the File System for Credentials

On Powershell,

Similarly, we can search the file system for certain file extensions with a command such as:

Sticky Notes Passwords

People often use the StickyNotes app on Windows workstations to save passwords and other information, not realizing it is a database file. This file is located at C:\Users\<user>\AppData\Local\Packages\Microsoft.MicrosoftStickyNotes_8wekyb3d8bbwe\LocalState\plum.sqlite and is always worth searching for and examining.

We can copy the three plum.sqlite* files down to our system and open them with a tool such as DB Browser for SQLite and view the Text column in the Note table with the query select Text from Note;.

This can also be done with PowerShell using the PSSQLite module. First, import the module, point to a data source (in this case, the SQLite database file used by the StickNotes app), and finally query the Note table and look for any interesting data. This can also be done from our attack machine after downloading the .sqlite file or remotely via WinRM.

We can also copy them over to our attack box and search through the data using the strings command, which may be less efficient depending on the size of the database.

Other Interesting Files

Some other files we may find credentials in include the following:

Further Credentials Theft

Cmdkey Saved Credentials

The cmdkey command can be used to create, list, and delete stored usernames and passwords. Users may wish to store credentials for a specific host or use it to store credentials for terminal services connections to connect to a remote host using Remote Desktop without needing to enter a password. This may help us either move laterally to another system with a different user or escalate privileges on the current host to leverage stored credentials for another user.

When we attempt to RDP to the host, the saved credentials will be used.

With Runas

We can also attempt to reuse the credentials using runas to send ourselves a reverse shell as that user, run a binary, or launch a PowerShell or CMD console with a command such as:

Browser Credentials

Chrome

Users often store credentials in their browsers for applications that they frequently visit. We can use a tool such as SharpChrome to retrieve cookies and saved logins from Google Chrome.

Note: Credential collection from Chromium-based browsers generates additional events that could be logged and identified as 4983, 4688, and 16385, and monitored by the blue team.

Password Managers

Many companies provide password managers to their users. This may be in the form of a desktop application such as KeePass, a cloud-based solution such as 1Password, or an enterprise password vault such as Thycotic or CyberArk. Gaining access to a password manager, especially one utilized by a member of the IT staff or an entire department, may lead to administrator-level access to high-value targets such as network devices, servers, databases, etc. We may gain access to a password vault through password reuse or guessing a weak/common password. Some password managers such as KeePass are stored locally on the host. If we find a .kdbx file on a server, workstation, or file share, we know we are dealing with a KeePass database which is often protected by just a master password. If we can download a .kdbx file to our attacking host, we can use a tool such as keepass2john to extract the password hash and run it through a password cracking tool such as Hashcat or John the Ripper.

Keepass

First, we extract the hash in Hashcat format using the keepass2john.py script.

Cracking hash offline

We can then feed the hash to Hashcat, specifying hash mode 13400 for KeePass. If successful, we may gain access to a wealth of credentials that can be used to access other applications/systems or even network devices, servers, databases, etc., if we can gain access to a password database used by IT staff.

Email

If we gain access to a domain-joined system in the context of a domain user with a Microsoft Exchange inbox, we can attempt to search the user's email for terms such as "pass," "creds," "credentials," etc. using the tool MailSniper.

LaZagne

When all else fails, we can run the LaZagne tool in an attempt to retrieve credentials from a wide variety of software. Such software includes web browsers, chat clients, databases, email, memory dumps, various sysadmin tools, and internal password storage mechanisms (i.e., Autologon, Credman, DPAPI, LSA secrets, etc.). The tool can be used to run all modules, specific modules (such as databases), or against a particular piece of software (i.e., OpenVPN). The output can be saved to a standard text file or in JSON format. Let's take it for a spin.

Running the tool with all will search for supported applications and return any discovered cleartext credentials. As we can see from the example below, many applications do not store credentials securely (best never to store credentials, period!). They can easily be retrieved and used to escalate privileges locally, move on to another system, or access sensitive data.

SessionGohper

We can use SessionGopher to extract saved PuTTY, WinSCP, FileZilla, SuperPuTTY, and RDP credentials. The tool is written in PowerShell and searches for and decrypts saved login information for remote access tools. It can be run locally or remotely. It searches the HKEY_USERS hive for all users who have logged into a domain-joined (or standalone) host and searches for and decrypts any saved session information it can find. It can also be run to search drives for PuTTY private key files (.ppk), Remote Desktop (.rdp), and RSA (.sdtid) files.

We need local admin access to retrieve stored session information for every user in HKEY_USERS, but it is always worth running as our current user to see if we can find any useful credentials.

Clear-Text Password Storage in the Registry

Certain programs and windows configurations can result in clear-text passwords or other data being stored in the registry. While tools such as Lazagne and SessionGopher are a great way to extract credentials, as penetration testers we should also be familiar and comfortable with enumerating them manually.

Windows AutoLogon

Windows Autologon is a feature that allows a user to configure their Windows operating system to automatically log on to a specific user account, without requiring manual input of the username and password at each startup. However, once this is configured, the username and password are stored in the registry, in clear-text. This feature is commonly used on single-user systems or in situations where convenience outweighs the need for enhanced security.

The typical configuration of an Autologon account involves the manual setting of the following registry keys:

  • AdminAutoLogon - Determines whether Autologon is enabled or disabled. A value of "1" means it is enabled.

  • DefaultUserName - Holds the value of the username of the account that will automatically log on.

  • DefaultPassword - Holds the value of the password for the user account specified previously.

Enumerating Autologon with reg.exe

Note: If you absolutely must configure Autologon for your windows system, it is recommended to use Autologon.exe from the Sysinternals suite, which will encrypt the password as an LSA secret.

Putty

For Putty sessions utilizing a proxy connection, when the session is saved, the credentials are stored in the registry in clear text.

Note that the access controls for this specific registry key are tied to the user account that configured and saved the session. Therefore, in order to see it, we would need to be logged in as that user and search the HKEY_CURRENT_USER hive. Subsequently, if we had admin privileges, we would be able to find it under the corresponding user's hive in HKEY_USERS.

First, we need to enumerate the available saved sessions:

Next, we look at the keys and values of the discovered session "kali%20ssh":

Wifi Passwords

If we obtain local admin access to a user's workstation with a wireless card, we can list out any wireless networks they have recently connected to.

Depending on the network configuration, we can retrieve the pre-shared key (Key Content below) and potentially access the target network. While rare, we may encounter this during an engagement and use this access to jump onto a separate wireless network and gain access to additional resources.

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