Re: Spectre mitigation

With the caveat of that I maybe have no clue what I’m talking about ;) : It’s a pretty epic attack/ side channel, but it still requires code execution. The kernel side channel more of an issue for vm providers And the spectre one probably will most heavily impact security conscious organizations that might be considering using tools like moby/ docker / Linux containers / kubernetes / mesos/ etc which depend on OS level process isolation etc for security. My fuzzy understanding is that one fix would be hardware support for per process isolation of memory even in the context users / processes ... which isn’t in any kit afaik. I do like my code not being slow. So it’s a dilemma :/ On Thu, Jan 4, 2018 at 11:51 AM Thomas Jakway wrote:

I'm gonna start reading through the spectre paper in a few minutes but... is this really the death knell for speculative execution on x86/64...? If so, GHC getting patched is going to be pretty low on everyone's list of priorities.

On Jan 4, 2018 6:36 AM, "Carter Schonwald" wrote:

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The only impacted code is the code which should already be engineered to be side channel resistant... which already need to be written in a way that has constant control flow and memory lookup.

This is just a new and very powerful side channel attack. It would be interesting and possibly useful to explore fascilities that enable marked pieces of code to be compiled in ways that improve side channel resistance. But there’s so many different approaches that it’d be difficult to protect against all of them at once for general programs.

I could be totally wrong, and I should read the spectre paper :)

I guess I just mean that vulnerable Data should be hardened, but only when the cost makes sense. Every security issue has some finite cost. The sum of those security events cost must be weighed against the sum of the costs of preventing them

On Thu, Jan 4, 2018 at 9:08 AM Demi Obenour wrote:

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The recent “Spectre” bug requires that speculative execution of indirect branches be disabled. For GHC, this will require passing a flag to LLVM and fixing the NCG to emit suitable calling sequences.

This will be a disaster for the STG execution model, because it disables CPU branch prediction for indirect calls and jumps. This is a big argument in favor of doing a CPS→SSA conversion in the backend. _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs

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