Following recent WikiLeaks Vault 7 disclosures, including details regarding firmware vulnerabilities, there has been significant concern regarding the integrity of devices and operating systems used within society.
As part of our commitment to provide technology that can preserve the integrity of devices we rely upon, we have developed a simple module for the CHIPSEC framework that can be used to verify the integrity of EFI firmware executables on potentially impacted systems.
This work is based on many years of dedicated research conducted by the Advanced Threat Research team (http://www.intelsecurity.com/atr) within the field of firmware security. CHIPSEC is a framework for analyzing the security of PC platforms including hardware, system firmware (BIOS/UEFI), and platform components. It includes a security test suite, tools for accessing various low-level interfaces, and forensic capabilities. It can be run on Windows, Linux, Mac OS X, and UEFI shell. Instructions for installing and using CHIPSEC can be found in the manual.
NOTE: This software is for security testing purposes. Use at your own risk. Read WARNING.txt before using.
The framework is available at this link: https://github.com/chipsec/chipsec
The following outlines a method that can be used to scan system firmware to determine whether it has been modified. The example we present shows the UEFI rootkit found in the HackingTeam disclosure (http://www.intelsecurity.com/advanced-threat-research/content/data/HT-UEFI-rootkit.html). To test against the most recent disclosures, a known clean list of EFI executable binaries (whitelist) must be developed and can be checked.
Below is an example of using the new tools.uefi.whitelist module on a UEFI firmware image modified to include HackingTeam’s UEFI rootkit.
- Generate a whitelist of EFI executable binaries from a clean/original UEFI firmware image (file named “original” in the example below). The list is generated in “original.json.” (This step assumes that there’s a way to obtain a good clean image.) In our example, 276 EFI executables were extracted from the original UEFI firmware image.
# chipsec_main -i -n -m tools.uefi.whitelist -a generate,original.json,original
[x][ =======================================================================
[x][ Module: Simple whitelist generation/checking for UEFI firmware
[x][ =======================================================================
[*] reading firmware from ‘original’…
[*] generating a list of EFI executables from firmware image…
[*] found 276 EFI executables in UEFI firmware image ‘original’
[*] creating JSON file ‘C:\chipsec\original.json’…
- At a later time, one can verify the integrity of UEFI firmware extracted from flash ROM memory against this list of expected EFI executables. The previous step records hashes in the file efilist.json. In our example, we verify the integrity of another UEFI firmware image, named “unpacked.” Running the tools.uefi.whitelist module against this image with “original.json” containing the expected list (whitelist) of EFI executables yields the following output.
# chipsec_main -i -n -m tools.uefi.whitelist -a check,original.json,unpacked
[x][ =======================================================================
[x][ Module: Simple whitelist generation/checking for UEFI firmware
[x][ =======================================================================
[*] reading firmware from ‘unpacked’…
[*] checking EFI executables against the list ‘C:\chipsec\original.json’
[*] found 279 EFI executables in UEFI firmware image ‘unpacked’
[!] found EFI executable not in the list: d359a9546b277f16bc495fe7b2e8839b5d0389a8
<unknown>
{EAEA9AEC-C9C1-46E2-9D52-432AD25A9B0B}
ed0dc060e47d3225e21489e769399fd9e07f342e2ee0be3ba8040ead5c945efa (sha256)
[!] found EFI executable not in the list: 64d44b705bb7ae4b8e4d9fb0b3b3c66bcbaae57f
rkloader
{F50258A9-2F4D-4DA9-861E-BDA84D07A44C}
3a4cdca9c5d4fe680bb4b00118c31cae6c1b5990593875e9024a7e278819b132 (sha256)
[!] found EFI executable not in the list: 4a1628fa128747c77c51d57a5d09724007692d85
Ntfs
{F50248A9-2F4D-4DE9-86AE-BDA84D07A41C}
dd2b99df1f10459d3a9d173240e909de28eb895614a6b3b7720eebf470a988a0 (sha256)
[!] WARNING: found 3 EFI executables not in the list ‘C:\chipsec\original.json’
The tools.uefi.whitelist module found three additional EFI executable binaries, which were not present in the original firmware image. The “unpacked” firmware image has 279 EFI executable binaries including the 276 original executables and three executables injected by the HackingTeam’s UEFI rootkit (rkloader, Ntfs, and an unnamed EFI application).
The preceding example is just for illustration purposes and assumes you’ve extracted EFI firmware on your system prior to generating the whitelist and later before checking the firmware. This can be done with the CHIPSEC framework using the following command:
# chipsec_util spi dump firmware.bin
However, a separate step to dump the firmware image is not required when using the tools.uefi.whitelist module. It extracts EFI firmware from flash ROM memory automatically if the firmware file is not specified.
We recommend generating an EFI whitelist after purchasing a system or when you are sure it has not been infected:
# chipsec_main -m tools.uefi.whitelist -a generate
Then check the EFI firmware on your system periodically or whenever you are concerned, such as when a laptop was left unattended:
# chipsec_main -m tools.uefi.whitelist -a check
In the recent disclosures, another EFI firmware malware for Mac OSX systems, DarkMatter, has surfaced. It appears to include multiple EFI executable components that it injects into the EFI firmware on a target system at different stages of infection. If one has generated a whitelist of known good EFI executables from the firmware image beforehand, then running the new tools.uefi.whitelist module on a system with EFI firmware infected by the DarkMatter persistent implant would likely result in a detection of these extra binaries added to the firmware by the rootkit.
EFI firmware malware is a new frontier for stealth and persistent attacks that may be used by sophisticated adversaries to penetrate and persist within organizations and national infrastructure for a very long time. Use open-source CHIPSEC to defend from this threat and stay safe.
Additionally, the recent WikiLeaks disclosure referenced a vulnerability related to the Intel Security Stinger tool. We can confirm that the Stinger tool issue is no longer present in our current technology. Users downloading the Stinger today will not be subject to attacks using the suggested exploit scenario.
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