I cannot wait for the accompanying Black Hat talk. Christopher Domas is one of my absolute favorite all-time hackers. He does such a fantastic job of explaining his work. Some of my favorite talks of his:

- Psychological Warfare in Reverse Engineering https://www.youtube.com/watch?v=HlUe0TUHOIc

- The MoVfuscator https://www.youtube.com/watch?v=R7EEoWg6Ekk

- Hardware Backdoors in redacted x86 https://www.youtube.com/watch?v=jmTwlEh8L7g

• nerdsniper

  today at 5:12 PM

  My introduction to his work was "The future of RE Dynamic Binary Visualization"[0] which completely blew me away. It still feels futuristic today, 13 years later. Novel UI/UX paradigms like this are slow to find widespread adoption, even when they're so clearly demonstrated to be such an ideal fit for their purpose.

  0: https://www.youtube.com/watch?v=4bM3Gut1hIk&pp=ygURY2hyaXN0b...

  • superkuh

    today at 5:41 PM

    I love digraphs. I learned about them from that talk's associated paper... but only about 2 years ago. I've been dumping my system and GPU RAM raw and visualizing via digraphs and it's amazing how such a simple algorithm operating on arbitrary bytes leads to such distinct and consistent image.

  • anthk

    today at 5:27 PM

    TBH with the DDD debugger you had a graph with the C structures right away.

• Hasz

  today at 2:57 PM

  If this is the same dude I am thinking of, his wife is also the CISO of Mozilla and do security research together, afair they have a whole book on x86 reverse engineering.

  Very cool!

  • Intermernet

    today at 5:14 PM

    x86 Software Reverse‐Engineering, Cracking, and Counter‐Measures By Stephanie Domas and Christopher Domas

    https://onlinelibrary.wiley.com/doi/book/10.1002/97813942771...

• jambalaya8

  today at 3:22 PM

  His stuff is something else.

This is all great to get full unfettered access to your own system, as life should be.

I’m sure Xbox and PlayStation security groups are a little nervous right now though. Getting ring-0 on those machines is near impossible, but once you do then everything else becomes wide open

• ransom_rs

  today at 4:44 PM

  Seems like this should get us a newer PS4 jailbreak?

When I started with computers, DRAM was understandable by a teenager: RAS, CAS, read, done.

Ok, the necessary refresh was always a little pain, but still something manageable.

Nowadays, I feel you need three PhD's to even bring up a micro with DRAM and don't get me started on the proprietary binary blobs necessary just for DRAM access. No wonder PSRAM is a thing.

The corollary is that it shouldn't be too surprising that this gigantic attack surface provides many opportunities. (Of course that doesn't mean it is easy to find them, hat tip to Christopher Domas, just that I expect there to be many more).

OK, so this works on AMD Jaguar according to the README. That's a architecture from 2013. There's notes about Zen 3 having a different base address for the memory controller registers, but that's it. What newer CPUs does attack actually work on?

• devttyeu

  today at 4:16 PM

  Zen has completely different memory controller IP (UMC), that's configured at boot by AGESA/PSP. I doubt this exploit applies to modern Zen CPUs, however AMD are the only ones who could really confirm this.

• CartwheelLinux

  today at 4:03 PM

  That information is intentionally left out

  • gmueckl

    today at 4:17 PM

    Then publishing it in this incomplete state is just pointless fearmongering and will just make others fill in this information within the next couple of days. And the good guys likely won't be the first ones to do that.

I spaghettify my memory every time I write C code.

So on an affected system, ring 0 root has access to pretty much everything that was hidden in negative ring territory. The page is pretty quiet about what other processor families might be similar beyond this specific AMD16h (an older AMD low-power family)?

• m1el

  today at 3:26 PM

  from the GH page: > Developed and tested on AMD Family 16h CPUs, the last generation whose datasheets document the DRAM controller's translation registers — and show that they can't be locked. 17h and beyond simply leave this information out.

• embedding-shape

  today at 3:06 PM

  As long as you know the controller's translation registers, it's applicable? Not tested on later one's merely because the information wasn't readily available it seems.

  > Developed and tested on AMD Family 16h CPUs, the last generation whose datasheets document the DRAM controller's translation registers — and show that they can't be locked. 17h and beyond simply leave this information out.

This is only applicable if you already have root (in order to get beyond that), right? It doesn't expose new risk of local privilege escalation?

• creshal

  today at 5:56 PM

  Reaching into ring -2 or the TPM allows privilege escalations past traditional "root permissions" and lets attackers defeat the sort of tamper protection that's designed to make escalations to local root manageable. Wipe-resistant malware, falsified cryptographic attestations, all sorts of fun.

• jandrese

  today at 5:57 PM

  This is more about getting at the code that device manufacturers attempt to hide from the end user. Platform keys, secure enclaves, etc...

• odo1242

  today at 4:50 PM

  Yep, I believe so

  • ziofill

    today at 5:13 PM

    But it supercharges what can be done once you get root, no?

    • UltraSane

      today at 5:59 PM

      By a LOT. It would expose the data Windows keeps isolated using virtualization based security.

    • odo1242

      today at 5:21 PM

      Yep.

This is so cool. Outside of a cool demo, and maybe some black hat type stuff, this is surely dangerous, a bad idea, and shouldn't be done in prod. But pure hacker ethos at its heart.

The big question is whether this can break out of KVM and whether it can be microrode patched / patched in any other way.

And whether it's really real in the first place.

• summa_tech

  today at 3:18 PM

  One hopes that a hypervisor would not expose hardware control registers directly in the first place, except ones deliberately designed for virtualization support.

  Otherwise, the guest is running effectively at the same privilege level as the hypervisor (that's useful sometimes, but probably not intended in most applications).

  • devttyeu

    today at 3:23 PM

    Yeah, just started looking at this with my team (we run a cloud with VM instance offering on AMD so this very much caught our eye)

    So far seems this is about right:

    1. You need platform register access, so seems can't KVM-escape with just this

    2. Big question is what about breaking Confidential SEV-SNP guests from the host?

    • devttyeu

      today at 3:38 PM

      Ok, on 2. and in general this exploit only works on pre-Zen AMD platforms as the repo states in not-so-clear terms.

      Zen changed DTC (DRAM Controller) to UMC (Unified Memory Controller), UMC is programmed at boot, and one would hope they figured that locking access to it makes sense when they were adding confidential compute support; Not clear though because there is no public documentation on it, so best we can hope for is some statement from AMD/3rd party researcher saying "this won't work on Zen because X/Y/Z"

• quotemstr

  today at 3:57 PM

  This hack is 99% giving people the control over their own computers they should already have had. Guy is a Robin Hood.

  • MSFT_Edging

    today at 4:58 PM

    When Chris Domas left Battelle for Intel years back, shortly after hardware-fuzzing a bank of thin-clients to discover undocumented x86 instructions, I was convinced Intel was basically keeping him on the payroll to shut him up.

I don't understand the threat model being attacked here. If you had physical DRAM access you could do all of this anyway right? And I would assume that an unprivileged user would not have write access to the DRAM controller registers?

• fulafel

  today at 4:16 PM

  This doesn't require physical DRAM access, it's all software.

  With ring-0 access, this lets you poke "even things walled off and invisible to ring-0 or the CPU itself" including things that the security processor tries hard to wall off.

  • VorpalWay

    today at 4:36 PM

    Which arguably is a good thing. As a owner of the system I really should have complete control over it. But currently there is software I have no control over running at even higher privilege levels.

    The only modern silicon that gives me full control over what code is running is some (or most?) microcontrollers.

    And this isn't just a question of FOSS principle. Especially SMM is problematic by unpredictably taking CPU cycles away from your workload. This can mess up hard realtime workloads, such as found in CNC controllers. If you are running something like LinuxCNC this something you need to measure to figure out if a given computer is suitable for that job.

• quotemstr

  today at 3:56 PM

  Even physical DRAM access would be thwarted by transparent total memory encryption, so this hack is still something else.

I really hate to be that guy, but man, as someone who was and is a big Christopher Domas fan (and is way dumber than him, I mean, this stuff is seriously over my head)... it's been really disappointing to see him LLM'ing all the READMEs recently. They used to be a joy to read through, but now the Claudeisms made it such a slog I could barely get through a few paragraphs. I'm glad he's using the new tools to get even more cool stuff done, but I wish he'd have gone for a human writeup at the end.

• mentalpagefault

  today at 6:00 PM

  Disappointing indeed. Us security folk have already earned a poor reputation for ineffective technical communication, and LLMs are even worse, not better. This is especially disappointing in this case because we know xoreaxeaxeax is one of the few who are actually capable of effectively communicating beautifully cursed low-level hackery, but is now choosing to outsource the most impactful part of his work (since most people will only read the abstract, I mean, README) to an LLM. I'll still take new projects with sloppy READMEs over the previous years of radio silence, but I really wish xoreaxeaxeax would recognize the value in spending the time to write a single page of text in his own voice.

• BugsJustFindMe

  today at 3:52 PM

  I find vague gestures like this almost more annoying than the idea of someone using AI to write.

  > the Claudeisms

  This is hand-waving. Please be more specific.

  > made it such a slog

  On the flip-side, I didn't find it a slog at all. What if you're wrong?

  • austinthetaco

    today at 3:58 PM

    I'm not the person you are replying to, but the readme is very clearly written by an AI, and it sounds nothing like his older work. Sometimes it's just super clear to people something is written with AI without you getting some sort of singular "gotcha" word or indicator. It's just writing patterns that would be hard to clearly establish rules for here in an HN comment, but it's incredibly obvious when you learn to spot it.

    • gnyman

      today at 4:19 PM

      I recently vibed a little linked-in AI detector which looks for AI things like rule of three and scores it. It scored it 97% AI polished.

      My gut feeling agrees. The rule of three is one of the stronger signals, can't stamp that out of the AI even if you wanted :-)

      I'll push it to GH later, it's nothing fancy but it has been quite good in my experience. Here is highlights which it used

      ``` tricolon coordinated VERB run: “…break / on them collapse / unlock everything .” (3 members) tricolon coordinated VERB run: “…guard physical addresses / not DRAM coordinates / you rearrange the” (3 members) tricolon coordinated NOUN run: “…handful of data / it to z3 / the translation matrix” (3 members) tricolon coordinated NOUN run: “…view / the elaborate fences / locks / security checks the” (4 members) tricolon coordinated VERB run: “…Read it / the alias map / pipe” (3 members) ```

    • boxed

      today at 4:09 PM

      I mean, it's super clear to a lot of people that it's written by LLMs EVEN WHEN IT'S NOT. You can't vibe that shit too.

      • rustyminnow

        today at 4:21 PM

        How do you know when it's not written by LLM except to take someone's word? If I got caught slopping I'd be too embarassed to admit it. "I wrote it all myself! I actually majored in slick writing and minored in tenuous metaphor."

        • boxed

          today at 6:02 PM

          I assume not 100% of all HN linked articles were written by AI, while at the same time noticing that 100% have a comment saying how it's AI written.

      • shermantanktop

        today at 4:13 PM

        I just told my boss to remove a line in a doc because it sounded too AI-y. He then said that he had written it himself.

  • jchw

    today at 4:21 PM

    "What if you're wrong?"

    I'd just like to address this real quick because some people seem to think this is just a "hunch" that has some probability of being false; there is absolutely nothing more certain on planet Earth than the LLM involvement in this writing. It is difficult to come up with things that are certain enough to compare this to to convey the lack of doubt that exists.

    I am not going to make fun of you for not being able to tell, although I do find it surprising that people seem to struggle in both directions with telling AI and human writing apart (are our brains really that different?) - I just want it to be clear that some of us can pick up Claudisms within just a couple of sentences with no effort. A Claude-generated sentence, in isolation, may not ring any alarm bells. A few of them in a row, however, that's a load-bearing smoking gun right there.

    We can certainly argue to what extent undisclosed LLM involvement is an issue or not, though frankly I don't like reading LLM writeups so I would greatly prefer if people would stop using LLMs for public facing documents. But, it is at least worth making this much clear: we can tell.

    • jonathrg

      today at 4:27 PM

      The only other reasonable explanation would be that he has consumed so much LLM content that the machine has erased his voice and replaced it with its own.

    • vetrom

      today at 5:41 PM

      Why does this whole set of paragraphs sound vaguely like a Claudeism?

      • jchw

        today at 5:49 PM

        This blows my mind just as badly and I see it reasonably often: I talk nothing like any AI model that has ever been, it isn't even close. I'm going to be bold and say that even without checking, more analytical approaches like stylometry would prove me right with little doubt. To mistake my writing for being "AI-esque", you would pretty much have to be entirely blind to the stylistic aspects of the text and fall back on even more superficial details like how verbose it is.

        Go ahead and throw the comment into your favorite unreliable AI detector. Even though I suspect they're mostly garbage, my writing is just so far away from what AI models do that it doesn't even matter.

        edit: I caved into temptation and checked. Big fat zero on GPTZero.

  • ipdashc

    today at 4:16 PM

    > Please be more specific.

    The em dashes are the most obvious stereotypical tell, but that doesn't really matter that much (I actually like them and occasionally used them pre-AI). It's hard to put a finger on, but the most annoying LLMism to me is the overdramatic, staccato, almost "epic" way they talk. It feels like a 2009 lens flare effect over everything, it sounds like a stereotypical hacker in a CSI show.

    > the last generation whose datasheets document the DRAM controller's translation registers — and show that they can't be locked

    > When your code dereferences *p, it appears to access the DRAM at p. It does not — p is a virtual address

    > Physical addresses are really more of a suggestion.

    > That's the exploit. All of it.

    The worst part is that this stuff is genuinely cool and deserves to be dramatic. And I like stereotypical, campy hacker speak! But LLMs are, IDK... bad at it? Or maybe it just becomes a bore to read the same. Exact. Dramatic. Voice. From literally everyone. After you've heard it enough times.

    None of this is against Mr. Domas. He seems like a cool person, with a cool voice, and I want to read his voice, not Claude's.

    > What if you're wrong?

    I definitely could be! Apologies if I am. But with all the em dashes and such, and having read his previous work, I felt confident enough to mention it. And as the sibling comment says, it really is something you just learn to spot over time.

    • cgyvbunji

      today at 4:24 PM

      It's the ASCII diagrams for me. Although I hesitate to point it out because they are usually helpful unlike the em dashes. Before LLMs, ASCII diagrams in readmes were a half baked mess, if one were present at all. Now every project has at least one perfectly made ASCII diagram - instant LLM tell.

      • ipdashc

        today at 4:31 PM

        > Although I hesitate to point it out because they are usually helpful unlike the em dashes.

        Likewise, I don't mind the diagrams. Though they do often have the same flaw as other text, being that the LLM throws in EVERYTHING, vs. a handmade one that'd generally have more taste and discretion to it. That can kind of work in its favor here, since the point is just to show the complexity of the stack, but on the other hand the reader lacks confidence that every item in there is "really" a part of the stack (which I would be fully confident in for this author, had he written it by hand) and not just some process related to memory/DRAM that the LLM decided to toss in.

    • xorcist

      today at 5:42 PM

      > When your code dereferences *p, it appears to access the DRAM at p. It does not — p is a virtual address

      I hate these especially much: It's at the same both both overly dramatic, it's presented as some great reveal that will change everything, while at the same time being completely trivial and only detracts from the explanation. If you have no idea that memory addresses are translated you will understand absolutely nothing from the text or even what this is all about. If you want to explain what an MMU is, just do that instead and don't present it as some great revelation.

      But some equally dramatic phrasings could just as well be something that leaves you astonished. You never know. You have to skim the text to find what is useful information and what is just filler. The signal-to-noise is low.

      It's called slop for a reason.

  • pwf

    today at 4:18 PM

    [dead]

Fascinating. So what is the DCT swizzling functionality designed for in the hardware originally?

• Retr0id

  today at 3:23 PM

  Without any swizzling, certain common access patterns can end up with subpar performance, for example walking the columns of a 2d array with a certain stride - if it ends up directing every access to the same bank on the same channel, the throughput is much lower than if the load was evenly distributed across multiple banks/channels.

  Swizzling "randomizes" bank/rank/channel distribution, which makes unlucky access patterns less likely. (Something I'd like to research is microbenchmarking different access patterns to infer the swizzle pattern and defeat physical ASLR)

  • Retr0id

    today at 5:39 PM

    Late edit: It also makes it harder to exploit rowhammer etc., if the precise swizzling method is unknown.

On IntelME/AMD PSP:

https://jxself.org/titanic.shtml

He did it well. On "security", the author loves more to own his code/adata than anything. as did the PDP10/ITS hackers.

Holy shit, Christopher Domas is back. I remember watching his Defcon talks on x86 shenanigans[^1][^2] and being amazed at what he's been able to discover. Then he got whisked away by Intel and now drops this. I'm excited.

[^1]: https://www.youtube.com/watch?v=XH0F9r0siTI

[^2]: https://www.youtube.com/watch?v=jmTwlEh8L7g

• vient

  today at 3:12 PM

  He also released another research just a few days ago https://news.ycombinator.com/item?id=49245491

The researcher behind this is obviously highly knowledgeable in reverse engineering CPUs to the tune it reminds me of the dwarves digging in Moria...

But why on earth do they have to use AI to write their writeups?!

• russdill

  today at 3:15 PM

  Seriously. Got tired of reading the same idea over and over reworded endlessly.

• dcrazy

  today at 3:19 PM

  I got suspicious but decided it wasn’t AI. The “Foo is the bar.” sentence construct is coherent with the overall “through the looking glass” tenor.

  • jchw

    today at 3:43 PM

    Nah, it's not just that, literally all the stuff they've posted this year is obvious LLM writing, none of the stuff from previous years is. To get this close to LLM writing style without actually using an LLM, you would pretty much have to be purposefully trying.

    But I have a new favorite way of demonstrating this:

    https://github.com/search?q=owner%3Axoreaxeaxeax+load-bearin...

    Guess how many of these are from before 2025.

    • menaerus

      today at 4:54 PM

      Like, who cares? In today's present, I wouldn't bother writing the article myself neither besides giving the instructions and auditing the output. Substance is what matters

      • circuit10

        today at 5:26 PM

        I struggled to understand the article, it doesn't properly explain what the exploit is in a way I could immediately understand, after staring at it for a bit and reading comments here I think it's a hardware register that's exposed to user software that shouldn't be but I really didn't understand that at first glance ("Poke the DRAM controller" made me think a hardware exploit) and I'm still not sure if I'm right about that (if it is, just start by explaining that instead of all the unnecessary filler and diagrams and animations of the Mona Lisa being scrambled and talk of bath salts which I still don't understand the relevance of)

      • toast0

        today at 5:45 PM

        > I wouldn't bother writing the article myself neither besides giving the instructions and auditing the output.

        The article would be better with just the instructions and audited output. All the LLM added bloat is tiring and distracting; it's like an article from New-Yorker or Wired.

      • pocksuppet

        today at 5:05 PM

        Did you test the substance? Did it work? AI can hallucinate substance.

        • CamperBob2

          today at 5:43 PM

          If you don't trust the author to do that, then it doesn't matter whether they used AI or not, does it?

          • jchw

            today at 5:54 PM

            Well for one thing I also trust most people I respect to not suddenly have someone else speaking on their behalf in their voice with no disclosure in most contexts where it would not be normal, yet that seems to have happened here. So while I personally do still trust and even respect the author, I can't help but empathize with someone who is suddenly a bit more skeptical.

      • jchw

        today at 5:13 PM

        > Like, who cares?

        You are literally asking this to people who clearly care...

        > In today's present, I wouldn't bother writing the article myself neither besides giving the instructions and auditing the output.

        Then why exactly are you even bothering to reply to me instead of having Claude do it and auditing the output? If HN didn't have a rule against it, would you even bother replying yourself?

        But really, there's a fair bit more to unpack here than just that. Why wouldn't you bother? Is writing a README.md about some project you worked on really that hard? Even with heavy LLM assistance, I'd wager to guess this project, which clearly involved working on real hardware, was more than just prompting. So clearly there was human effort other than prompting. And I do respect that, but I want people who write things to respect my time. I'm not asking them to disclose every tool they use, I'm asking them to not waste our time with crappy irritating Claude writeups. Whether it's explictly specified or not, we know.

        Frankly I struggle to believe that people don't really mind if someone else speaks for them in their own voice, just because they're too fucking lazy to speak for themselves anymore. We've had competent GenAI for like a year or two, at this rate people are going to forget their potty training in another few months.

        > Substance is what matters

        Substance matters, which is not great for LLMs, because they put out text that has far more fluff than substance. What, however, is far worse for LLMs, is the fact that kick and scream and cry all you want, but: style and presentation matters, too.

        It is absolutely true that if you just dropped a very brief blurb that all AMD CPUs from a certain generation can be pwned it would have a decent chance to hit the HN frontpage just out of sheer interestingness. That is not because the style and presentation doesn't matter, it's just that the substance is significant in spite of the bad presentation and style.

        And absolutely, we can easily forgive someone for simply not being very good at the presentation and style part, certainly I'm not really an expert at it. But this author has released plenty of great hits before, so I damn well know they can. It's a serious disappointment to see them downgrade to irritating, grating Claude garbage output.

This is the level of access the rightful owner of a computer should have to his own system.

He should also be able to fuse away this access forever, to be fair. But out of the box, when I get a new laptop, I should be able to read and write every byte of DRAM.

Holy crap. This is like a software-reachable version of the dynamic memory aliasing hardware attack demonstrated by https://batteringram.eu/

• pocksuppet

  today at 5:07 PM

  Oh that's a clever attack. The RAM bus was often thought of as off-limits because of the speed and signal integrity requirements. They bypassed those.

Opus refuses to discuss this at all. Make of that what you will.

• rustcleaner

  today at 4:52 PM

  Guardrails are a product-quality smell. Boycott guardrailed models. Punish guardrailed model providers with reduced revenue and bankruptcy. "I'm sorry Dave" must become a subscription-cancelling response or the nannying will never stop!

• devttyeu

  today at 3:17 PM

  Well, K3 has no problem, Sol is also fine-ish

  • HanClinto

    today at 3:48 PM

    Likewise -- also had zero issues going over this with Sol. Seemed to give solid advice for how to test it -- use an expendable bare-metal AMD family 16h test system w/ usual standard checks that apply.

    > Run `platform_check` first and do not use `SKITTER_FORCE=1` casually. Start with the read-only `dram_state` and `dram_carveouts`, then `dram_dump --dry-run`. Avoid `dram_poke` until maps have been freshly collected and calibrated. Do not bypass fingerprint checks, calibration, fencing, or verification.

    Claude's (apparently externally-mandated?) lobotomization continues to be concerning. :-/

This is probably very interesting, but does it really have to be explained with a solid wall of AI slop writing?

[dead]

[dead]

[flagged]

• BugsJustFindMe

  today at 3:30 PM

  https://en.wikipedia.org/wiki/Spaghettification - "The term was popularized by Stephen Hawking". Hawking was English.

  • nailer

    today at 3:44 PM

    > Hawking was English.

    Odd, he had an American accent.

• rerdavies

  today at 3:21 PM

  Humpty Dumpty said in rather a scornful tone, “it means just what I choose it to mean—neither more nor less.” “The question is,” said Alice, “whether you can make words mean so many different things.” “The question is,” said Humpty Dumpty, “which is to be master—that's all.”

  -- Alice in Wonderland

• ImJasonH

  today at 3:18 PM

  nah we'll verb anything

• fred256

  today at 3:19 PM

  Verbing weirds language.

Could someone ELI5 please? Context, achievement, scope, consequences?

• self_awareness

  today at 4:36 PM

  [flagged]

Skitter creek bath salts... Or SCBS Guess there'll be a talk called Secure Computing BullShit in the next Blackhat conf! I'll be eagerly waiting for it! :)