> The problem is the largest threat model.
Without context, sentences like this mean nothing. So it's borderline a non sequitur. A threat model can be literally anything. Me giving my PC to someone at Best Buy, letting my grandma write assembly, or throwing my PC out the window can be a "large threat model." Nonsense sentence.
> If Process A and Process B are running in the same user context on a desktop OS, PAGE_NOACCESS is not a strong boundary by itself. Process B may be able to obtain PROCESS_VM_OPERATION/PROCESS_VM_READ, change the page protection with VirtualProtectEx, inject code that calls VirtualProtect inside Process A, load a DLL, attach as a debugger, duplicate useful handles, or tamper with the executable.
To the uninitiated this seems right, but really there's so much glossing over, it feels written by a non-expert that just read the first chapter of a "hacking for dummies" book. I've written anti-cheats and have even done some some hardware stuff, so I say this with some degree of experience: writing a userspace hack/cheat is pretty hard without a zero-day. Most stuff won't easily get PROCESS_VM_OPERATION permissions, also those are (afaik) logged by the kernel, so you can easily see if some weird "DefinitelyNotACheat.exe" executable or "NotABadLibrary.dll" requested them, so it's a pretty janky way of getting access to memory you shouldn't.
> That's the problem with same-user process isolation, it is a hugely leaky abstraction. There is no magical "just set this bit" fix.
Again, this is a non sequitur. No one said (or at least I didn't) that there's a "magical" bit. You're not even arguing against a strawman, it's almost like we're having two different conversations.
> On a desktop OS, once an evil process runs under the same user context, you are relying on process DACLs, integrity levels, code-signing, anti-injection hardening, and file-system protections. You can plug one path and still have several others.
Also seems right, and it kinda' is, but code signing is notoriously easy to circumvent, "anti-injection hardening" can mean like three million different things, etc. I dunno, just sounds like someone that's never done this stuff before. Like, not bringing up Detours[1] when talking about "anti-injection" just seems like weirdly avoiding the ONE canonical way of doing this, which just about every single hacking/cracking book covers. Idk, weird omission.
Also, no one in their right mind would attach a debugger, as that's trivial to detect[2]. I guess it could be a decent proof of concept, but no serious hacker would ever go that route. (Also, if I remember correctly, you also need to ship some special DLLs that have the actual debugging helpers—and same with Detours, so might as well do that).
Just wanted to give my justification for the accusation. Maybe I'm wrong and maybe that's why I'm getting the downvotes, so my bad.
[1] https://github.com/microsoft/detours
[2] https://learn.microsoft.com/en-us/windows/win32/api/debugapi...