I'm not aware of much that combines WCET + formal verification + POSIX compatibility though. The verification page here is mostly at stone level, which from my understanding of SPARK terminology just means it passes validation, but might have runtime errors where most of Ada's WCET nondeterminism comes from. I'm skeptical that this is actually production usable for the hard real-time use cases all over their documentation at the current stage, but nothing on the website gives any clue as to the actual maturity short of reading the code myself.
My main concern is speed and the lack of capability based security. seL4 is faster than Linux by a mile and I'm guessing that this is much slower. You can put a POSIX layer on seL4 but POSIX is inherently flawed too. MAC separates privileges from code and is too clunky to use in practice (see seLinux).
Do you really believe that? That seems extremely implausible based on just simple observations like all governments using COTS OS for military/intelligence work or standard OS:es being used for critical infrastructure like power/water/finance/transportation.
If your statement was even remotely true then why is this not used in conflicts to devastating effect?
The cost of internally developed exploits is probably much lower. They aren't one shot assets either, they can be used until someone plugs the hole.
There are private companies selling devices to law enforcement that can extract information from locked phones [2]. Availability of that sort of access to anyone's phone by local law enforcement is absurdly cheap.
[1]: https://opzero.ru/en/prices/
[2]: https://arstechnica.com/gadgets/2025/10/leaker-reveals-which...
Those are the prices that they are buying for, they do not indicate at all that these are common or how large the market is for RCE on any OS.
> [2]: https://arstechnica.com/gadgets/2025/10/leaker-reveals-which...
Those are (mostly) not RCE, and are for consumer devices configured in a default way.
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The parent stated that "Any government can get RCE on any OS with the change in their couch."
That implies that Kiribati currently could easily buy RCE on for example hardened Linux or OpenBSD running the most sensitive infra in the world. I just don't buy that, since if it was true any current conflict would look much different.
Of course there are security holes and major fuckups do happen, but not at the scale the parent implied.
> Those are (mostly) not RCE, and are for consumer devices configured in a default way.
I'm more worried about activists and journalists in developing counties without the financial means to afford flagship phones. But even Google can't manage to keep out a pedestrian mid sized security outfit selling to the cops and the FBI.
When activists lobbying for a fucking sugar tax in Mexico get hacked, then the bar is too fucking low.
Let's not talk about the nightmare that is old networking equipment or IoT devices.
> Any government can get RCE on any OS with the change in their couch
If you were extremely hyperbolic for effect that's fine, that's why I asked if you actually believed that, but what you are saying now is not at all arguing the same point.
What is your objection?
or relative?
$50k-$150k+ is a low-to-medium cost case to carry out for US law enforcement. or military.
Much like the $3 in change you could dig out of your couch or car to get a small drink or sandwich.
> Any government can get RCE on any OS with the change in their couch
Even if we said that we restrict it to for example the G20 I still don't think they can easily and cheaply "RCE any OS".
Shit hasn't changed much. We still have monolithic kernels written in portable assembly. Linus still doesn't tag bug fixes with potential security impacts as such because he is more worried about unpatched consumer garbage (which compromise all low end phones). When your mitigation for such problems is to not make it obvious, then your OS is not safe enough in safety critical settings (which includes consumer devices).
Process isolation would downgrade the vast majority of critical Linux CVEs to availability bugs (crash a server but not compromise it).
Just because governments don't need to reach for RCE everytime doesn't mean that it is safe. Th fact that such bugs are so cheap is an indication that your safety margin is too thin.
However, safety critical is not limited to cars: it also includes the phones of activities and journalists living under authoritarian regimes.
Monolithic kernels written in portable assembly mean that such bugs DO grow on trees [1] and the lack backporting means they just drop to the ground: the poor are sold phones that may never receive a security update. So even sugar tax activists in Mexico are the target of spyware!
We have seen the sophistication of these attacks ramp up as cryptocurrency has made them profitable and the North Koreans have made a killing exploiting these bugs.
Maybe you are right and it is very difficult to find these bugs but that just means low demand is what is keeping the price down. But that's probably because there enough LPEs and known RCEs that they are not needed most of the time.
[1]: https://www.cvedetails.com/vulnerability-list/vendor_id-33/L...
Your proof is that it would be really bad if everything were horribly insecure therefore it must not be true. Proof by wishful thinking has never been a valid argument.
In contrast, a few years ago I worked with a vulnerability broker who had literally hundreds of unsold zero-days with tens in each major commercial OS with zero-click RCEs only being a few million each. That is just one vendor in a sea of vulnerability brokers. That is the state of reality. We just live in the metaphorical equivalent of the pre-9/11 world where you can easily kill a lot of people by flying a plane into a building, but nobody has figured it out yet.
I did no such thing. I claimed that it's implausible that every government can buy RCE for every OS.
Governments using COTS operating systems does not imply that these systems are unackable. If the statement of OP would be true, we would just see constant exploitation of RCE zero days, or at the least the impact of that. But that is not the case.
It is frankly baffling that I even need to argue that COTS operating systems are easily hacked by governments and commercial hackers. It literally happens every day and not a single one of those companies or organizations even attempts to claim that they can protect against such threats. Government actors are literally what these companies peddling substandard security use to argue "nothing we could do". It has been literal decades of people trying to make systems secure against government actors and failing time and time again with no evidence of success.
I mean, seriously, go to Defcon and say that nobody there with a team of 5 people with 3 years (~10 M$, a single tank) could breach your commercially useful and functional Linux or Windows deployment and you are putting up a 10 M$ bounty to prove it. I guarantee they will laugh at you and then you will get your shit kicked in.
The depressing fact is that you don't need an RCE to accomplish most goals.
Somehow we have ended up in this bizarro land where everybody in software knows software, especially COTS operating systems, is horribly insecure due to the endless embarrassing failures yet somehow they also doublethink these systems must be secure.
The systems with devastating impact are air-gapped. They're designed, audited, validated and then never touched again. Ports are disabled by cutting the traces on the motherboard and adding tamper protection to the case, which is in a secure facility protected by vetted people with guns, who are in a security facility protected by different vetted people with guns.
No system is perfect, but the time and effort is better spent on the generic case that the military understands well.
You wish. More often than not the people building these think they are very clever by using their bullet proof fire walls rather than a physical disconnect. Or SLIP over a serial port because for some reason serial ports are fine.
I've seen this kind of crap in practice in systems that should be airgapped, that they said were airgapped but that in fact were not airgapped.
It does make it much easier to do stuff but kinda defeats the purpose.
And a WiFi connection even though it goes 'through the air' is not an airgap.
The same for BT and any other kind of connectivity.
An airgap is only an airgap if you need physical access to a device to be able to import or export bits using a physical connection, and the location of the device is secured by physical barriers. Preferably a building that is secure against non-military wannabe intruders.
Any system accessible with a firewall exception is not "air-gapped" by definition.
A level below that is diode networks, which are not air-gapped but provide much stronger system isolation than anything that is accessible with a "firewall exception".
Far below either of these is vanilla network isolation, which is what you seem to be talking about.
I completely agree. Maybe I should have put "air-gapped" in quotes.
The most interesting subset of these systems are high-assurance bi-directional data paths between independent peers that are quasi-realtime. Both parties are simultaneously worried about infiltration and exfiltration. While obviously a misnomer, many people still call them diodes...
The entire domain is fascinating and less developed than you would think.
It is a genuinely fun project for someone with sufficiently sophisticated skill but I suspect there is relatively little money in it, which colors the opportunity and outcomes.
The absence of clear commercial opportunity gives the domain a weird dynamic.
> If your statement was even remotely true then why is this not used in conflicts to devastating effect?
It has been, it continues to be.
Where have you been?
Air gapping is a baseline requirement in most safety critical systems. Nuclear power plants in particular have lots of redundant layers of safety. AFAIK Russia hasn't physically tried to cause a meltdown, presumably due to the political blow back (although they have attacked Chernobyl's sarcophagus). I assume this limits their digital espionage attacks too.
We do get glimpses of the use of such malware, like when Saudi Arabia hacked Jeff Bezos' phone. But we don't hear about most of it because there is a benefit to keeping a hack secret, so as to keep access.
Finally, it's usually cheaper to social engineer someone into loading a PowerPoint presentation and doing a local privilege escalation. They burn those for things as petty as getting embarrassing political information.
https://oe.tradoc.army.mil/product/smart-phones-playing-prom...
I do, but have a slightly different take: even though COTS software is pretty much unilaterally full of bugs that will be exploitable and could be found, it is still possible to compose layers of security that compliment each other in such a way that a compromise in any one layer wouldn't mean game over. Done very carefully, I think you can make a stack vastly more secure than the sum of its parts. Moreover, it's very possible to make exploiting the software both more annoying and easier to detect, which would dissuade attempting to use exploits.
> If your statement was even remotely true then why is this not used in conflicts to devastating effect?
I think the costs, risks and incentives need to line up properly to actually see things play out. Even though software exploits in COTS software is relatively cheap by government money standards, they do still take time and money. Not to mention the actual software exploit part may not even be the most expensive or complicated part of an operation, especially if you desperately need to evade detection for a long time, and especially if your adversary is going to have sufficient auditing to know something is wrong early.
Stuxnet is old, but surely one of the most fascinating uses of malware in geopolitics. But wow, the amount of work involved and knowledge needed to make something like that happen makes the exploit part feel rather small.
Formally verified software seems to have a lot of promise, then, to make deep exploits even more convoluted, expensive and rare. Surely there will still be bugs, but it leaves a lot less room for error, and very well could shift the calculus on security threats a bit.
But what's all this have to do with the ongoing conversations about pwning Windows-based networks inside major consumer utility assets?
> Any government can get RCE on any OS with the change in their couch.
Mainly to agree with it. I believe it is still likely true.
Any resemblance to other discussion further up or down is unintentional.
You need to do an absolutely perfect job in always spotting those RCE capable issues before an attacker does. And given the numbers involved this becomes a game of statistics: if there are 200 ways to get RCE on OS 'X' then you need to find and fix all of them before attackers do. Meanwhile, your system isn't a million lines but a multitude of that, there are your applications to consider (usually of a lesser quality than the OS), the risk of a purposeful insertion of a backdoor and so on.
So I don't think it is unreasonable to presume that any OS that is out there most likely has at least a couple of these that are kept 'on ice'.
You are not arguing the same point.
since the 2010s atleast more than 140 countries spend over 10 mil a year on purly offensive cyber. most of those countries spend astronomical amounts more than that. that includes purchase of attack tools and exploits
I'm bullish on capabilities too, but I don't know much about MAC. Can you explain your last sentence?
I am betting you know what mandatory access control is ; ). They basically amount to a firewall that is placed on applications restricting what they can do. The rules are generally written by downstream distros and are divorced from the implementation. The problem is that it's hidden control flow, so the program just dies and can't fall back gracefully. Capability oriented APIs make broker processes and narrowing of permissions tractable.
[1]: https://sel4.systems/performance.html
[2]: https://lionsos.org/
[3]: https://trustworthy.systems/publications/papers/Heiser_25%3A...
through what exactly people mean with it is often vague
Like e.g. both seLinux and AppAmore are technically MAC but people tend to only mention seLinux when speaking about how cumbersome it is and treat AppAmore as something different as it's not so cumbersome.
Looking forward to it. A formally verified OS is a great step towards better security.
It's common for the interesting OS proofs to take more code than the kernel itself. Take a look at the seL4 proofs [1], or those for CertiKOS as examples.
If you're actually interested in alternative OSes in memory safe languages, you might like TockOS, which is more production-ready at this point. Formal verification work of the isolation model is still ongoing, because it's difficult work.
[0] https://codeberg.org/Ironclad/Ironclad/src/branch/main/sourc...
https://en.wikipedia.org/wiki/TUNIS
It was implemented in Concurrent Euclid.
SPIN developed at the University of Washington in the nineties was written in Modula-3; it was a microkernel-based system and supported the Digital UNIX system call interface, allowing Unix applications to run. There was also Sol implemented at INRIA in a Pascal dialect in the eighties which offered a Unix-compatible environment; it was followed by Chorus (initially written in Pascal), also a microkernel-based system, compatible with Unix APIs.
That said, I am huge fan of works like this. But in practice, the security layer that betrays all of this tends to be the firmware layer.
My dream is to have something like the Framework computer use verifiably secure EFI firmware, as well as similarly verified and audited firmware for every hardware component.
Copyright is something different entirely!
I suspect you meant to say "wary." Wary means "cautious," "weary" means "tired."
If a gaming company can sue a local supermarket over trademark, I don't know what to say.
What other exciting projects like these exist?
You make any of your OS standard libraries GPL and they need to suck to use and can’t statically link your code without being forced to also be licensed GPL.
That viral property some people find desirable.
Virality might suit the ego, but it doesn't make for a healthy project when its primary users are parasitic.
Software is not a scarce good. Let companies use free software without contributing back as much as they wish; it doesn't affect others in the least. There is no bleeding of the commons here, because even if companies take as much as they can without giving back, it doesn't reduce the resources available for others.
When that development gets silo'ed away in proprietary systems, that is potential development lost upstream. If that happens enough, upstream becomes starved and anemic, and with forks only living on in silos.
Apple, for example, has made trillions of dollars off of FreeBSD. To this day, FreeBSD still does not have a modern WiFi or Bluetooth stack.
Meanwhile, AMD, Intel, Microsoft, and even Apple, etc have full-time engineering roles and teams dedicated to upstreaming their improvements to Linux. And there are paid engineers at these companies that ensure WiFi and Bluetooth work on Linux.
Being able to sell it closed and not releasing the source would make closing the android ecosystem 'good old times', no?
We would only get a bunch of closed outdated company controlled binaries, but now for everything, not only drivers?
People really got to stop with crazy nonsense.
LionsOS[1] is its static scenario building framework, with some dynamic scenario support.
Genode[2] is an independent OS construction kit that can also use the seL4 kernel. Their general purpose OS, Sculpt, just had a very interesting multi-kernel release[3].
The systems group at ETHZürich is building Kirsch[4], an effort with seL4 and CHERI.
Managarm[5] is also building something of interesting architecture with some Linux software compatibility.
1. https://trustworthy.systems/projects/LionsOS/
3. https://genodians.org/alex-ab/2025-11-02-sculpt-multi-kernel
This is real world throughput and latency seL4 is crushing Linux on, not some synthetic IPC benchmark.
A guy can dream, at least.
But to my knowledge, not for the more general user facing OSes.
It would be nearly impossible to have the support for the extremely diverse set of hardware that desktop Linux has while staying formally verified, but for something a bit more constrained like a smartphone, I think something like seL4 could work as a base and the manufacturer could write their own drivers for whatever hardware is needed.
I mean, how cool would it be if every single part of the stack that is even possible to verify was fully verified. I know about the halting problem, I know there are things that would be basically impossible to verify fully, but I still think it would be cool to live in a world where software engineers actually had a little assurance what they were doing actually worked before unleashing into the world.
Commercial support is not free, and the pricing for that is almost always something you have to ask for. Hard to see how this is piece of free software stands out.
1. https://blog.adacore.com/cubit-a-general-purpose-operating-s...
I thought SPARK was a paid (not free) license. Am I mistaken?
Very cool project btw.
Similar model to Qt: permissive licensed open source version, with a commercial 'Pro' offering.
A couple weeks ago I was curious what the strictest programming language was. ChatGPT listed a couple, and it kicked off a short discussion where I began asking it about the capabilities of stricter programming languages at low levels. Funny enough at the end it mentioned that SPARK/Ada was the strictest you could get at the lowest levels, same as Ironclad.
At one point while asking it about drivers, it said "ACL2’s logic is [...] side‑effect‑free definitions with termination proofs when admitted to the logic. That is misaligned with effectful, interrupt‑driven kernel code.
I'm not an OS or kernel dev, most of my work has been in Web Dev, ML, and a little bit of embedded. How accurate is the information that was presented to me? Here is the link to the discussion: https://chatgpt.com/share/691012a7-a06c-800f-9cc9-54a7c2c8b6...
I don't know SPARK or Ada, but it just bothers me to think that we can't...I guess...prove everything about our software before we run it (yes yes, I'm familiar with halting problem shenanigans, but other than that).
Lisps are perfectly usable for system level code as well. There was an entire lineage of Lisp Machines where virtually all OS code was written in lisp. Those probably could have used ACL2 had it existed.
There's an X-Y component to your questions though. The strictness of the programming language just isn't the main goal for OS formal verification. It just makes certain things easier. What's important is having executable semantics of the programming language, having a machine model, and a behavioral specification. All of these are typically written in proof languages, and the kernel code is proven to implement the behavior spec according to the machine and language semantics.
SPARK gives you executable semantics, but so do C (specifically the Clight subset), most of the Lisps, Rust, and many others. You're benefiting from certain errors being impossible in SPARK, but it's not a fundamentally different process.
What filesystems are supported ?
As far as I know formal verification is another testing method and as as such it's is as good as the quality and the extent of the "verification" (aka tests).
Best way to verify that I know of is Fuzzing + testing.
It is a method where a computer verifies a proof that the program adheres to its specification for _all_ inputs (subject to whatever limitations the particular method has).
Types are the simplest kind of formal verification, and with sufficiently advanced dependent type-systems, can be used to prove that programs obey arbitrarily complex specifications. However, this can be extremely laborious and requires significantly different skills than normal programming, so it is very rarely done in industry
More than one maintainer has shown frustration at that site making up wrong documentation already.