Making the rounds, complete w/ sensationalized headline: https://www.theregister.co.uk/2018/06/22/intel_tlbleed_key_data_leak/ … Short version: libgcrypt doesn't follow best practices to avoid side channel leak of keys. Crypto that does (BoringSSL, OpenSSL, BearSSL, maybe others) shouldn't be impacted. Use them, update often.
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Replying to @chandlerc1024
Cripes. I thought I'd gone for a minimal sensationalist headline ;) I think the story as a whole is balanced: it's non-trivial to exploit, Intel doesn't consider it major problem. As for BoringSSL etc, I'll defer to Ben's statement on the difficulties of mitigating TLBleedpic.twitter.com/H72c8PNLK9
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Replying to @diodesign
For cryptographic software, I strongly disagree. The most widely used libraries do the right thing here. Libgcrypt is the exception and regarded as such by everyone I know in the crypto community.
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Replying to @chandlerc1024 @diodesign
I think it's a stretch to say the most widely used libraries do the right thing here unless you're talking specifically about Ed25519, which itself is actually hardly used. The emphasis on breaking crypto libs also seems like a red herring. Non-crypto apps usually don't even try.
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Replying to @BRIAN_____ @diodesign
Most widely used libraries *for cryptographic software*. Other software indeed often doesn't even try. But in that case, you don't need TLBleed at all - any side-channel attack will work fine.
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Replying to @chandlerc1024 @diodesign
I'd guess that OpenSSL 1.0.1 or earlier is probably the most common open-source crypto library and (1) it doesn't implement Ed25519, (2) It's ECC implementation leaves a lot to be desired for the curves it does implement, especially on non-x86-64. BoringSSL was fixed 9 weeks ago.
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Replying to @BRIAN_____ @diodesign
But again, if broken, you wouldn't need TLBleed. The thing really hurt here are approaches to mitigating side channels other than data-invariant coding such as the ones discussed in the paper, and those seem somewhat rarely deployed outside of libgcrypt.
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Replying to @chandlerc1024 @diodesign
AFAICT the paper isn't available publicly yet so I can't refer to it. NSS and OpenSSL are both using non-data-invariant mitigations even in their master branches today, except in special cases like x25519/Ed25519 and some optimzed x86-64 or 64-bit-only P-256 implementations.
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Replying to @BRIAN_____ @diodesign
@agl__ to comment about non-data-invariant side channel mitigation still being relied on in OpenSSL. If that's the case (for either of these libs) we should definitely work on fixing it.2 replies 0 retweets 0 likes
BTW, if you are interested in these things then you should check out copy_to_prebuf/copy_from_prebuf in these libs (and *ring* too) which attempt to thread the needle.
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