Author: hucktech

Modern Techniques to Deobfuscate UEFI/BIOS Malware and Virtualized Packers

~ hucktech ~ Leave a comment
Modern advanced malware samples are used to infect countries and they make part of the current cyber war, cyber espionage and financial attacks. Furthermore, critical actors, who write these malicious code try to make the static and dynamic analysis really hard by heavily virtualizing and obfuscating their code using techniques such as CFG, virtualization, call stack manipulation, dead code, opaque predicate and so on. To manage these complex scenarios above, we are able to use tools such as METASM, MIASM and several emulation techniques to make the code simpler. The goal is to reduce the code (most of time by using symbolic analysis), in order to allow us a better understanding of the threat. This presentation aims to show concepts and a practical approach on how to handle obsfuscation reverse engineering challenges and threats involving BIOS/UEFI malware.
https://conference.hitb.org/hitbsecconf2019ams/materials/D1T1%20-%20Modern%20Techniques%20to%20Deobfuscate%20UEFI:BIOS%20Malware%20-%20Alexandre%20Borges.pdf

https://conference.hitb.org/hitbsecconf2019ams/sessions/modern-techniques-to-deobfuscate-uefi-bios-malware-and-virtualized-packers/

Tianocore Bug 1614 – BootGuard TOCTOU vulnerability

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Re: https://firmwaresecurity.com/2019/05/06/now-you-see-it-toctou-attacks-against-secure-boot-and-bootguard/

https://twitter.com/qrs/status/1126511256448323589
We have found a TOCTOU vulnerability which allows an attacker with physical access to achieve code execution after the Boot Guard ACM computes and validates the hash of the IBB and measured the firmware into the TPM PCR0. This means the firmware will be marked as valid and have normal PCR0 values even though unsigned code has run. The root cause is when the FSP has finished memory init and disables MTRRs (and thereby the cache) in order to switch off No Evict Mode. The code doing this (the SecCore PeiTemporaryRamDonePpi callback), is executed directly from SPI flash, allowing an attacker to intercept execution flow. As a proof of concept we demonstrated that using an FPGA to substitute a single, targeted SPI transaction we can gain code execution.

https://bugzilla.tianocore.org/show_bug.cgi?id=1614

Setting up Windows boxes to be usable…

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I just noticed that Microsoft has a project to help setup a dev box:

“The goal of this project is to provide a central place to share ideas for streamlining dev box setup and provide sample scripts for common dev scenarios. It’s likely you will want to take the scripts here and modify them to fit your particular needs.”

https://github.com/Microsoft/windows-dev-box-setup-scripts

For the last few years, they’ve been releasing Windows as a prebuilt VM, with most of the developer tools preinstalled. These VMs expire after a few weeks, so you’ll have to download a new VM every few weeks. [There’ve been periods of multiple weeks where there’s no VM available, waiting for the next build of Windows, so keep your old bits and hope expiration policy does not become more draconian.]

https://developer.microsoft.com/en-us/windows/downloads/virtual-machines

https://blogs.windows.com/buildingapps/2016/09/30/just-released-windows-developer-virtual-machines-september-2016-build/

FLARE-VM is a nice script from Fireeye that sets up a Windows box with lots of security tools. Requires a fresh Windows install before use.

https://github.com/fireeye/flare-vm

https://www.fireeye.com/blog/threat-research/2018/11/flare-vm-update.html

Fireeye also has Commando-VM:

https://github.com/fireeye/commando-vm

Half a dozen open source projects (and an unknown number of closed source products) have nice scripts to setup a Windows system for development, but are project-centric.

Breaking Through Another Side: Bypassing Firmware Security Boundaries from Embedded Controller

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Hardware security boundaries are really difficult to support and correctly design. On modern x86 platforms exist a lot of different hardware components. It’s clear they should be included in the usual threat model’s obvious external paths, but what if the attacker can compromise one of the trusted components? We have previously seen when researchers compromise TPM and start the initial point of the attack from inside of trusted boundary. All these points create concerns on the current threat modeling process because after attacker crosses a trusted boundary, the attack surface significantly changes. Does this mean the attack surface is dynamic and not static? In our presentation, we focus on reverse engineering Embedded Controller (EC) from one of the recent Lenovo Thinkpad laptops, attacks from EC trusted boundary the main platform firmware (BIOS) and we manage to bypass Intel BIOS Guard technology (Lenovo specific implementation). We will present multiple topics across security boundaries problems on x86 platforms, as well as demonstrate platform design problems with trust to third-party components as EC and show the real attacks from OS-level to EC/from EC to BIOS. This research targeting reverse engineering topics of EC firmware are based on ARC processor architecture, the internals of EC architecture and specific operating modes to support SMI-handlers on EC side (include BIOS Guard). Also, we reverse engineered the most interesting parts of communications and relations between BIOS and EC. The attack surface from EC with attacker perspective is quite large and can include DMA attacks, disclose of PCI memory space to attack devices and the possibility of persistent rootkit/implant installation.

https://www.blackhat.com/us-19/briefings/schedule/index.html#breaking-through-another-side-bypassing-firmware-security-boundaries-from-embedded-controller-15902

PS: Looks like ru.efi picked a good time to start adding EC support: 🙂

http://ruexe.blogspot.com/2019/05/reading-ec-controllers.html

Defending Against Out-of-Band Management BMC Attacks

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My slides from the recent LinuxFestNW talk with an intro to BMCs is linked here:

Click to access lfnw2019-bmc.pdf

I need to work with Paul and get both his and my slides from LFNW up on our Github page, along with our previous talks. For now, the above PDF is hosted on this blog site. 😦

This is an INTRODUCTORY talk. If you’re a regular reader of this blog, you probably don’t need to waste your time watching this. 🙂 This talk did not mention u-bmc or the bmclib projects, something I’ll fix the next time I give this a variation of this talk. Video is here:

Extracting Firmware from Microcontrollers’ Onboard Flash Memory, Part 4: Texas Instrument RF Microcontrollers

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Re: https://firmwaresecurity.com/2019/05/01/deral-heiland-extracting-firmware-from-microcontrollers-onboard-flash-memory-parts-1-3/

part 4 of 4 is now out:

https://blog.rapid7.com/2019/05/07/extracting-firmware-from-microcontrollers-onboard-flash-memory-part-4-texas-instrument-rf-microcontrollers/

BootKeeper, a static analysis of security properties on boot firmware images

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BootKeeper: Validating Software Integrity Properties on Boot Firmware Images

Ronny Chevalier, Stefano Cristalli, Christophe Hauser, Yan Shoshitaishvili, Ruoyu Wang, Christopher Kruegel, Giovanni Vigna, Danilo Bruschi, Andrea Lanzi

(Submitted on 29 Mar 2019)

Boot firmware, like UEFI-compliant firmware, has been the target of numerous attacks, giving the attacker control over the entire system while being undetected. The measured boot mechanism of a computer platform ensures its integrity by using cryptographic measurements to detect such attacks. This is typically performed by relying on a Trusted Platform Module (TPM). Recent work, however, shows that vendors do not respect the specifications that have been devised to ensure the integrity of the firmware’s loading process. As a result, attackers may bypass such measurement mechanisms and successfully load a modified firmware image while remaining unnoticed. In this paper we introduce BootKeeper, a static analysis approach verifying a set of key security properties on boot firmware images before deployment, to ensure the integrity of the measured boot process. We evaluate BootKeeper against several attacks on common boot firmware implementations and demonstrate its applicability.

https://arxiv.org/abs/1903.12505

Dell: Enhanced BIOS Verification Protects PC Firmware Against Sophisticated Threats

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https://www.dell.com/support/home/us/en/19/drivers/driversdetails?driverid=dv4xv&oscode=wt64a&productcode=latitude-14-3400-laptop


BIOS Verification. This utility provides customers with assurance that devices are secured below the OS, a place where visibility has been lacking up to now. This utility stores the BIOS measurements and performs the verification off-host, to ensure the user has an untampered version of the BIOS. This utility supports Window 10 (both 32 and 64bit) on the following platforms: Tablet, Precision, OptiPlex, Latitude, and some XPS Notebooks.
https://blog.dellemc.com/en-us/bios-verification-protects-pc-firmware-against-threats/

Now You See It: TOCTOU Attacks Against Secure Boot and BootGuard

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https://twitter.com/qrs/status/1125304771160752129

https://conference.hitb.org/hitbsecconf2019ams/sessions/now-you-see-it-toctou-attacks-against-secure-boot-and-bootguard/

BootGuard’s Verified Boot mode on modern Intel CPUs is the core root of trust and measurement during the boot process, and preserves the chain of trust by only executing firmware with a valid vendor signature. These protections are supposed to be secure against physical attacks on the SPI flash, although we’ve found multiple errors in handling the firmware volumes as well as a new technique for changing the firmware after the signature check has been done. In this talk we’ll demonstrate how to build an inexpensive open source tool for investigating these TOCTOU techniques and how to use it to test the security of your own systems.

Microsoft open sources CCF (Confidential Consortium Framework)

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https://github.com/Microsoft/CCF/blob/master/CCF-TECHNICAL-REPORT.pdfhttps://github.com/Microsoft/CCF


The Confidential Consortium Framework (CCF) is an open-source framework for building a new category of secure, highly available, and performant applications that focus on multi-party compute and data. While not limited just to blockchain applications, CCF can enable high-scale, confidential blockchain networks that meet key enterprise requirements — providing a means to accelerate production enterprise adoption of blockchain technology.

Remote Code Execution on most Windows-based Dell computers

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Dell SupportAssist Client has been updated to address multiple vulnerabilities which may be potentially exploited to compromise the system.

https://d4stiny.github.io/Remote-Code-Execution-on-most-Dell-computers/

https://www.dell.com/support/article/us/en/04/sln316857/dsa-2019-051-dell-supportassist-client-multiple-vulnerabilities?lang=en

Fiddle: instrumentation for bootloaders and beyond

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bootloader_instrumentation_suite – Bootloader research tools (very much a work in progress)

This test suite helps you keep track of different versions of
u-boot/build tools, static analysis of that build’s binaries, and
runtime trace results of running that binary on a given hardware
configuration. For each u-boot/build configuration it keeps a database
of information it statically gathered for each boot stage, boot stage
images/ELF files, a prepared SD card image, and test results of
runtime trace analyses. If it detects changes in the u-boot source or
build tools it will create a new set of test result directories with a
new sdcard image and static analysis results.

https://github.com/bx/bootloader_instrumentation_suite

https://typedregions.com/

Crowdstrike’s Falcon adds firmware security

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https://www.crowdstrike.com/blog/crowdstrike-first-to-deliver-bios-visibility/

https://www.crowdstrike.com/resources/news/crowdstrike-falcon-becomes-the-first-endpoint-security-platform-to-integrate-firmware-attack-detection-capability/

Ugh, their web page has some obnoxious code that changes the HTML header every few seconds to try and get your attention.

LinuxFest NorthWest: videos uploaded

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LinuxFestNorthWest was last weekend in Washington State. For the first time, there was an “Open Source Firmware” track, search for that string on the event listings for those presentations:

https://www.linuxfestnorthwest.org/conferences/2019/schedule/events

The LFNW videos are already up on Youtube:

I am still working on uploading my slides to the LFNW web site, and Github, please give me another day to find my password… 😦