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Linux-insides: Linux kernel load address randomization

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Re: Linux-insides: Linux kernel load address randomization

#11
post #8

Earlier quoted context omitted.

Formally verified kernels are pretty rare, and you can always have bugs in verification or side channel attacks that your proofs don’t cover, like speculative execution timing bugs in your CPU. (K)ASLR doesn’t defeat all memory bugs but it helps (a little). It is a very low overhead element of defense in depth that doesn’t require major code changes (unlike say, rewriting your kernel in a memory safe language).

Sure, but those same speculative execution attacks also trivially defeat ASLR. And practically speaking, memory safety in formally proved software tends to be pretty bullet proof. So, outside of memory unsafety, is there another threat profile where ASLR gains you something?

Sure, consider that the hashCode() of objects in Java are based on memory addresses, which means they’re predictable to an attacker without ASLR.

Re: Linux-insides: Linux kernel load address randomization

#12
post #6

https://thehackernews.com/2017/02/bypass-aslr-browser-javasc... http://www.cs.vu.nl/~herbertb/download/papers/anc_ndss17.pdf XI. CONCLUSIONS In this paper, we described how ASLR is fundamentally insecure on modern architectures. Our attack relies on the interplay between the MMU and the caches during virtual to physical address translation—core hardware behavior that is central to efficient code execution on modern C…

In every context that I've seen it, ASLR is there to be annoying to circumvent instead of being the sole line of defense. Generally other techniques are present as well to mitigate the risk of such an attack.
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