I understand why in 1979 and perhaps until mid 1990s capability OS architecture might have been irrelevant and excessive. But after that, it sounds like the only architecture suitable for the internet age, where you can download and run anything from anywhere. Instead, we're stuck with legacy systems, which now contain layers of layers of abstractions and security measures. User rights, anti-virus software, vetting (signatures, hashes, app-store verification) - all become obsolete or near-obsolete in a capability-based system where a program simply doesn't have access to anything by default. Part of the appeal of virtualization is also due to the fact that it isolates programs (for instance, I only run npm inside Docker container these days, because chances are some package will contain malware at some point).
Part of it is inertia, but part of it is ignorance. Enthusiasts spend tons of money and effort building another GPU enabled terminal or safe programming languages - and maybe that's fine, but I wonder what we could've accomplished if people were simply aware what a well-designed capability OS could be like, because this is literally the only OS paradigm in existence (that I know of) that's even worth any serious effort.
If you go through old CS OS texts on the matter, they really didn't have the same understanding of capabilities then as the later object-capabilities (ocap) model would introduce. Typically they would show an access control matrix, note that acls were rows and capabilities columns and note that they are duals of one another. They're the same, acls are easier to manage, done.
I’m not going to argue against much of the content of this paper, but it should be pointed out that their argument in the middle section against the “confinement myth” seems pretty bogus. They say that you can isolate the capability read/write resource from the data read/write resource, but… this makes absolutely no sense. Bits are bits. If you assume some out-of-band isolation of capability distribution then you’ve changed the game, but even that isn’t enough for me to believe that isolation is possible.
Consider two processes on a *nix system, and for the sake of argument let's say they're sufficiently isolated from each other as to have only one communications channel between them. If that communications channel is a unix domain socket, one process can send a file descriptor (effectively a capability) to the other over the socket. Each process has a file descriptor table in the kernel whose integer keys are only meaningful to that process in particular, and the kernel provides a mechanism to transmit file descriptors across a socket. The kernel mediates in this case.
If the communications channel is not a unix domain socket and is instead something like a TCP connection, you don't have this option available to you.
You aren't always just sending bits from one process to another!
That argument assumes that the delegation of a capability to another process must happen through a path of interprocess communication that can be established only by the operating system, if the processes that want to communicate have the capabilites for this.
I have not studied to see how the existing capability-based operating systems solve this problem, because it seems that this is not a simple solution. If the capabilities are very fine-grained, to make certain that IPC really cannot happen, that might be cumbersome to use, while coarse-grained capabilities could be circumvented. To really prevent IPC without appropriate capabilities, a lot of the convenient features of a UNIX-like system must be forbidden, like the existence of files that can be read by any user, or directories like /tmp , where anyone can write a file.
None of those things become obsolete with capabilities.
You still need code signing because users need to be able to grant privileges in a way that sticks across upgrades. The object they want to privilege isn't a set of files on disk but a logical app as defined by (more or less) a brand name+app name even as it changes over time.
You still need antivirus software because users can be tricked into giving capabilities to programs that appear legit but are actually malicious.
Modern operating systems (iOS, Android) are capability oriented operating systems to the extent that makes sense. For some reason there's a meme that says capabilities are a magic wand that solves all security problems, but it's not the case.
> it sounds like the only architecture suitable for the internet age, where you can download and run anything from anywhere
Wasn’t that the reason why Microsoft went allout against Java? Write once, run anywhere. JVM was a “trojan horse”
and theoretically
could have dominated the world.
I didn't mean it in the Java way. I meant that whatever operating system you're on, you can download random programs from the internet (compiled specifically for your OS or portable) and run it on your machine. It doesn't matter what they're written in or how they're run, it's possible on any OS connected to the internet and an OS with capabilities as first class citizens would isolate any program by default, denying it access to anything by default and severely limiting program's ability to cause harm, intentionally or unintentionally.
In case of updating the binary, yes, you generally want to make sure it comes from the same source and therefore cannot do damage to things it already has access to. But when you install a new program, it shouldn't have access to any resources other than the ones it creates itself, so there's no need to sign it. Further more, when installing a new program, you still have to download/import the pubkey to verify the signature from somewhere, so it's almost meaningless on the first installation. Signatures wouldn't be obsolete, but they also wouldn't be the only line of defense. Furthermore, updating can now be performed by the program itself and the program might already contain the pubkey needed to check the validity of updates.
It looks like you you may be interested in Qubes OS, security oriented operating system relying on strong, hardware-assisted virtualization: https://qubes-os.org. My daily driver, can't recommend it enough.
I know about it, but I'm not interested in QubeOS approach. It's VMs all the way down, while what I'm talking about is no VMs and capabilities as first class citizens and no vurtualization.
I am also surprised that capabilities weren't more widely implemented after mobile OSes demonstrated they are practical. I know Windows made a move in that direction with UAC but had to soften it due to user alert fatigue. So I guess having no legacy apps and a centralized repository helps.
I've recently been looking into Guix SD as a solution. Its package management is designed to keep programs independent of each other, so containers are cheap and lightweight. Trying out untrusted software is as easy as `guix shell --container --pure --no-cwd [program]`, which blocks access to the network, file system, and environment variables. Right now I'm adding more advanced capability management: limits on CPU, memory, storage space, network use, etc.
What is wrong about virtualization? It allows to run all existing software, it doesn't restrict the owner of the device, it is extremely flexible and reliable. And it can be fast, too.
see other comment, the author describes some issues with current hardware virtualization. kvm is also pretty good, but not perfect... and completely irrelevant with GPU pass-through enabled. =3
Sorry, can't recall the exact lecture... It was only interesting as I was looking at a toy project to see if metastability issues were solvable. Practically speaking, it only proved the folks at Sun were very smart people choosing an encrypted mmu. =3
The Market has spoken, and people use standard consumer CPU/GPU-bodge architecture in cloud data centers. Sure there are a few quality of life features different from budget retail products, but we abandoned what Sun solved with a simple encrypted mmu decades ago.
The paper adds little to TCSEC/"Orange Book"/FOLDOC publications. Yet the poster doesn't deserve all the negative karma.
On a consumer CPU/GPU/NPU, software just isn't going to be enough to fix legacy design defects. Have a great day. =3
Might be people just flagging so mods can make an "Is this an LLM not?" determination. I see a lot of new accounts get flagged like this (and scanning the previous comments, ehhhhh yea maybe?).
The most frustrating takeaway from the original SRI PSOS architecture is that we had the blueprint for true hardware-level Zero-Trust in 1979, and we abandoned it for deployment convenience. By anchoring security in unalterable, hardware-tagged capabilities rather than software-defined access control lists, PSOS eliminated privilege escalation at the physical layer. The SRI Hierarchical Development Methodology (HDM) didn't just 'test' for security; it mathematically proved structural isolation across distinct abstraction levels. Modern monoliths have spent the last thirty years trying to bolt software firewalls onto fundamentally porous kernels, when we should have been building on the hardware-enforced capability model PSOS handed us
Part of it is inertia, but part of it is ignorance. Enthusiasts spend tons of money and effort building another GPU enabled terminal or safe programming languages - and maybe that's fine, but I wonder what we could've accomplished if people were simply aware what a well-designed capability OS could be like, because this is literally the only OS paradigm in existence (that I know of) that's even worth any serious effort.
OP is arguably the first paper that introduces ocaps. Some of the issues are discussed in "Capability Myths Demolished" https://papers.agoric.com/assets/pdf/papers/capability-myths...
If the communications channel is not a unix domain socket and is instead something like a TCP connection, you don't have this option available to you.
You aren't always just sending bits from one process to another!
I have not studied to see how the existing capability-based operating systems solve this problem, because it seems that this is not a simple solution. If the capabilities are very fine-grained, to make certain that IPC really cannot happen, that might be cumbersome to use, while coarse-grained capabilities could be circumvented. To really prevent IPC without appropriate capabilities, a lot of the convenient features of a UNIX-like system must be forbidden, like the existence of files that can be read by any user, or directories like /tmp , where anyone can write a file.
You still need code signing because users need to be able to grant privileges in a way that sticks across upgrades. The object they want to privilege isn't a set of files on disk but a logical app as defined by (more or less) a brand name+app name even as it changes over time.
You still need antivirus software because users can be tricked into giving capabilities to programs that appear legit but are actually malicious.
Modern operating systems (iOS, Android) are capability oriented operating systems to the extent that makes sense. For some reason there's a meme that says capabilities are a magic wand that solves all security problems, but it's not the case.
Wasn’t that the reason why Microsoft went allout against Java? Write once, run anywhere. JVM was a “trojan horse” and theoretically could have dominated the world.
If a binary has the capability to withdraw money from my account, I don't want that capability given to just any binary.
I've recently been looking into Guix SD as a solution. Its package management is designed to keep programs independent of each other, so containers are cheap and lightweight. Trying out untrusted software is as easy as `guix shell --container --pure --no-cwd [program]`, which blocks access to the network, file system, and environment variables. Right now I'm adding more advanced capability management: limits on CPU, memory, storage space, network use, etc.
https://blog.invisiblethings.org/2008/09/02/three-approaches...
Or some exotic processor no one would ever sell successfully. =3
There is likely a PoC around someplace if people dig a bit. =3
It happened in 2006 and never happened after that. I would consider it as secure as it gets.
The paper adds little to TCSEC/"Orange Book"/FOLDOC publications. Yet the poster doesn't deserve all the negative karma.
On a consumer CPU/GPU/NPU, software just isn't going to be enough to fix legacy design defects. Have a great day. =3
Idk, just guessing
It's probably a bot nonetheless, which poses the question: why do people do that? What do they gain by posting resume comments on HN with LLM bots?
Rebuild everything from scratch, with AI agents. Then make them prove what they wrote.