liffik

Thanks for the incredibly constructive feedback! This is extremely helpful.

The jmp short + nop header and adding the cld instruction are excellent points. I will add those to the bootloader right away to ensure better BIOS compatibility and stability.

The pre-allocated dummy file trick on ext2 is a brilliant way to have a mountable filesystem without the overhead of writing a filesystem driver in Assembly. That solves the "overwriting arbitrary data" issue elegantly.

I will definitely look into posix-uefi. EDK2's bloat and memory footprint were my main concerns for the UEFI port, so a lightweight SDK is exactly what I need.

P.S. I use a translator to write this because I don't speak English. I really appreciate you taking the time to share these technical pointers!

Booting a tiny Linux kernel would overwrite way too much RAM, destroying the exact data (like crypto keys) we want to recover. That's why my bootloader is strictly 512 bytes to minimize the footprint.

As for the shim bootloader: it only chainloads signed EFI binaries. To run a custom unsigned bare-metal dumper through it, you would have to use a known vulnerable version of shim (like the one from the BootHole vulnerability) to bypass the signature check for the next stage. It's possible in theory, but adds a massive layer of complexity compared to just using CSM.

Guys, I'm writing using a translator without AI now. Are you happy?

Guys, it’s just easier for me to communicate via AI because I don’t speak English I’m using a translator right now. Everything I described (including the AI part) is real, and the method works too; I’m just lazy. I used this software on some specific hardware I won't say what kind—but it works perfectly.

Ah, I see what you mean! You are totally right, the physical execution is the truly interesting part.

To clarify, I actually didn't swap the RAM modules to another system. Moving cooled RAM is incredibly difficult and leads to rapid data decay. Instead, I left the frozen RAM exactly where it was on the original board. After the hard power-off, I just quickly swapped the system drive for my prepared drive and booted the same machine back up.

Regarding memory zeroing on boot: that is a highly relevant point. Modern systems (especially with TCG MOR enabled) try to scrub memory during POST to prevent exactly this. However, two things help here:

Fast Boot / Board Specifics: Many BIOSes, including the one on the industrial board I tested (DPX-W250), skip full memory checks and zeroing to speed up boot times.

Hard Power-Off: By cutting power abruptly, the OS doesn't get a chance to set any "clean shutdown" flags. Upon reboot, the BIOS just did a quick POST and handed control to my 16-bit bootloader via CSM, leaving the frozen memory completely intact.

P.S. I'm using AI to translate my messages because I don't speak English. Hope this explains the physics of the attack!

@Retr0id is absolutely right. Hardware-level memory encryption (like AMD SME or Intel TME) is the ultimate silver bullet here. The encryption key is generated by the CPU/memory controller per-boot and is lost the moment power is cut, making the RAM contents useless even if frozen.

To answer @floralhangnail's questions from the perspective of how my dumper operates:

Removing RAM vs. Rebooting: My tool actually doesn't require removing the RAM sticks at all! The attack involves freezing the RAM in place, performing a hard power-off, quickly swapping the main system drive with my prepared USB/drive, and powering back on. So physical obstacles like hot-gluing the RAM or hiding it under the keyboard won't stop this specific reboot-based attack.

BIOS Passwords & Secure Boot: You nailed it—these are your best practical defenses on standard hardware. If a BIOS password prevents booting from external media, or if Secure Boot blocks my unsigned 16-bit bootloader, the time it takes to bypass them means the RAM bits will decay. This is exactly why my dumper targets systems with CSM/Legacy BIOS enabled and boot options accessible.

Condensation & Freezing: You don't freeze the entire laptop. You open the bottom cover and spray inverted canned air (-60°C) directly onto the memory modules. Condensation definitely happens and will eventually short the board, but the hardware usually survives just long enough (the few minutes needed) to complete the raw memory dump to disk.

P.S. I'm using AI to translate my messages because I don't speak English. Hope this clears up the physical attack vector!

Right

You are absolutely correct, and I highly appreciate the clarification! I definitely misspoke in my previous comment.

CSM doesn't magically bypass an active Secure Boot state. Rather, to even boot via CSM, Secure Boot typically must be disabled in the firmware settings beforehand. What I really meant is that by targeting Legacy/CSM, I bypassed the development requirement of writing an EFI application, dealing with complex UEFI protocols, or figuring out how to get a payload signed.

You are also completely right about the initialization sequence. UEFI still runs first (SEC/PEI/DXE phases) and touches RAM before the CSM hands control over to my MBR payload. My 16-bit approach mostly just helps minimize any additional memory clobbering that a more complex, modern UEFI bootloader environment might introduce.

Thanks for keeping me technically honest!

P.S. Still using AI to translate my thoughts!

Spot on! That is exactly why I chose the legacy 16-bit method via CSM. It was a deliberate design choice to completely avoid the EFI bootloader and, consequently, bypass Secure Boot entirely.

By relying on Legacy BIOS, the system doesn't check for signed EFI binaries or block the custom boot drive. It drops directly into the 16-bit real mode, allowing me to do the job without dealing with UEFI handles, protocols, or security restrictions. It essentially eliminates the need for any exploits or moving physical RAM sticks to specialized breadboards!

P.S. I'm using AI to translate my messages because I don't speak English. Hope my point is clear!

Sure! The testing was conducted on a specific industrial x86 board (DPX-W250 Rev. A1). I won't go into details about the exact equipment it came from, but it provided a perfect bare-metal environment for this research))))

The testing procedure was a classic physical Cold Boot Attack:

Froze the RAM modules while the target system was fully operational.

Performed a hard power-off.

Quickly swapped the original system drive with my own prepared drive containing the BareMetal-RAM-Dumper.

Powered the system back on and booted directly into the custom bootloader via Legacy BIOS.

The result: Absolutely successful. The dumper immediately took control, switched to Unreal Mode, and successfully dumped the raw physical memory directly to the disk without any OS interference or data trampling.

P.S. I'm using AI to translate my messages because I don't speak English. Hope everything is clear!

Good point! I originally went with Legacy BIOS because 16-bit boot support is historically enabled by default on the vast majority of target machines out there. It keeps the bootloader tiny and hardware access as direct as possible. However, as CSM is virtually dead on the newest hardware, adapting it to UEFI is the inevitable next step.

Hey security researchers!

I've released BareMetal-RAM-Dumper — a low-level x86 utility for dumping physical RAM directly to disk, designed for Cold Boot Attack research.

What it does: • Custom 512-byte bootloader (no OS needed) • Boots via BIOS Legacy CSM • Switches to Unreal Mode to access 32-bit physical memory • Dumps RAM in 32KB chunks directly to USB drive • BIOS INT 0x15 E820 for safe memory map parsing • Real-time progress indicator

Cold Boot Attack Use Case: Freeze a laptop's RAM to -60°C → quickly reboot from USB → capture full memory contents for forensic analysis & crypto key recovery

How it works: 1. Stage1: 512-byte boot sector (loads Stage2 via INT 0x13) 2. Stage2: Main logic (memory detection, unreal mode, disk writes) 3. Writes to LBA 64+ on boot drive

Warning: This overwrites data starting at sector 64! Use a dedicated blank USB.

Built with pure Assembly (NASM) — no bloat, direct hardware access

GitHub: https://github.com/pIat0n/BareMetal-RAM-Dumper License: AGPL-3.0

Perfect for: Forensic researchers Security auditors testing cold boot resilience Students learning low-level x86 Penetration testers

Feedback & improvements welcome!