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Comment by simcop2387 | Hacker News Reader

Time it looks like. Future versions are getting it apparently.

https://wiki.freebsd.org/ASLR

What privileges does bhyve run under? Exploiting a properly sandboxed QEMU does give you access to some potentially interesting file descriptor but, unless you can use them to get kernel code execution, your process will not have access to any resources on the host that wouldn't be already accessible from inside the VM.

There's a section on sandbox escapes.

Doesn't running it with KVM enabled put you back into kernel space? I'm sure doing everything in userspace is safer, but TCG is nowhere near as performant...

The vast majority of the device emulation is in user space, even with KVM.

KVM is indeed one of the potentially interesting file descriptors, but there is relatively little code running in kernel space.

Almost all attacks these days are a chain of exploits that each focus on jumping code execution to a new context or gaining a new privilege, that only when combined give you the access you're looking for as an attacker.

But

> It is disabled by default.

Why?

Judging by the fact that at least ntpd gets broken by it I suspect it's again more a time issue. It'll take time to make sure that anything broken by it either gets fixed or properly documented as needing a work-around. Otherwise when it first ships it's going to break a lot of systems when people switch.

FreeBSD has a very strong commitment to stability and making things work in new releases that working in old releases. This results in fairly conservative defaults.

"Regression in FreeBSD 12.1-RELEASE-p4: the exploit I was using in -p3 is no longer usable."

It is trivially bypassed and has some negative performance impact. So why enable it by default? It is left as an option for the paranoid and for "checkbox compliance" type applications.

Trivially bypassed if you have an address leak…

No. Trivially bypassed without a leak. Two of many examples:

https://dl.acm.org/doi/10.5555/3195638.3195686

https://www.vusec.net/projects/anc/

New timing attacks that break ASLR come out ~annually. These are hardware mechanisms that cannot be mitigated by software. ASLR is broken. (Nevermind ROP gadget compilers, etc.)

HardenedBSD (FreeBSD fork) has had ASLR and other mitigations since forever. Shawn submitted a patch that was never merged because of mailing list politics or something of that sort + people afraid it was going to break the world.

https://reviews.freebsd.org/D473

> politics or something of that sort

I suppose you could classify "the patch doesn't work and breaks other things besides" that way.

HardenedBSD got the userland running fine. It was iirc mostly irrational fear by the FreeBSD team that someone's bad application would break.

That’s not what happened.

Nope. The code had major problems that were highlighted during code review, and Shawn never fixed them.

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