Date: Fri, 16 Dec 2016 12:02:15 -0800 From: Kees Cook <keescook@...omium.org> To: "Sandra Escandor-O'Keefe" <rvonflugel@...il.com> Cc: "Reshetova, Elena" <elena.reshetova@...el.com>, Daniel Borkmann <daniel@...earbox.net>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com> Subject: Re: Working on lib/test_bpf.c tests for eBPF constant blinding On Fri, Dec 16, 2016 at 11:47 AM, Sandra Escandor-O'Keefe <rvonflugel@...il.com> wrote: > Excellent! Thanks for pointing to that write-up. So, what I can do is get to the point where I can manually perform the test to check inserted constants in > eBPF instructions to verify that they are gone in the resulting eBPF JIT kernel code - this looks like I will first need to run the PoC attack that Elena created. From there, I'll have a better understanding of what to test. > > Would you approach it this way, or would you do something different? That sounds like how I'd start, yes. IIUC, you'll need to modify the kernel so you can see the JIT in some way (this is, I think, what's needed in test_ebpf.c), but I haven't looked at it very closely. Daniel may have suggestions. > Sandra > > Original Message > From: keescook@...omium.org > Sent: December 16, 2016 3:28 PM > To: rvonflugel@...il.com > Cc: kernel-hardening@...ts.openwall.com; elena.reshetova@...el.com; daniel@...earbox.net > Subject: Re: [kernel-hardening] Working on lib/test_bpf.c tests for eBPF constant blinding As a side-note on email conventions, I'd recommend in-line replies and quoting, which makes technical discussion much easier to follow (i.e. don't top-post, etc). -Kees > On Fri, Dec 16, 2016 at 9:13 AM, Sandra Escandor-O'Keefe > <rvonflugel@...il.com> wrote: >> I'm interested in starting on a bit of linux kernel development, and also >> contributing to something security related for the kernel. I was looking at >> the projects listed in the TODO of >> https://kernsec.org/wiki/index.php/Kernel_Self_Protection_Project and "Write >> lib/test_bpf.c tests for eBPF constant blinding" caught my eye. Is this >> something that still needs to be done? If so, is there someone specific that >> I can reach out to in order to get some guidance on where to start? > > Hi! Welcome to the fun. :) > > I've added Elena and Daniel to CC, who both worked on the blinding. > The goal would be to add some kind of test that inserted constants in > eBPF instructions and then verified they were gone in the resulting > eBPF JIT kernel code. Until now, it's only been done manually, and > it'd be nice to have a test that could show if there were regressions > or if an architecture didn't support the blinding in its JIT. > > For some background on the blinding, I wrote a short description of it here: > https://outflux.net/blog/archives/2016/10/03/security-things-in-linux-v4-7/ > > Let me know if that helps get you to a starting point! :) > > -Kees > > -- > Kees Cook > Nexus Security -- Kees Cook Nexus Security
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