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A comment on Reading privileged memory with a side-channel. Parent comment

Re:Reading privileged memory with a side-channel by voidmain on Wednesday January 03, 2018 @08:01PM (#16067064)
It seems like practical attacks rely on having a reasonably precise timer available. The spectre paper uses SharedArrayBuffer to synthesize a timer, which is a recent and obscure feature:

https://groups.google.com/a/chromium.org/forum/#!topic/blink...

https://groups.google.com/forum/#!topic/mozilla.dev.platform...

Chrome and Firefox's "intent to ship" posts both contain claims to the effect that there probably aren't any really serious timing channel attacks, which... seems to have been disproved. Why isn't SharedArrayBuffer already being disabled as a stopgap? I think users can turn it off in firefox, how about Chrome?

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Re:Reading privileged memory with a side-channel by jncraton on Wednesday January 03, 2018 @09:49PM (#16067610)
SharedArrayBuffer will be disabled by default as a stopgap:

https://blog.mozilla.org/security/2018/01/03/mitigations-lan...

performance.now() accuracy is also being reduced.

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Re:Reading privileged memory with a side-channel by kibwen on Wednesday January 03, 2018 @08:05PM (#16067093)
> I think users can turn it off in firefox, how about Chrome?

This month's stable Chrome release will be outright disabling SharedArrayBuffer until additional mitigations are enacted.

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Re:Reading privileged memory with a side-channel by londons_explore on Wednesday January 03, 2018 @08:56PM (#16067358)
Which sucks for people who've built sites which rely on it.

It isn't exactly polyfillable.

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Re:Reading privileged memory with a side-channel by erichurkman on Wednesday January 03, 2018 @10:12PM (#16067734)
That shouldn't be that many sites. It only hit Chrome stable in July 2017; Firefox in August 2017; and Edge November 2017.
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Re:Reading privileged memory with a side-channel by olliej on Wednesday January 03, 2018 @08:06PM (#16067094)
I believe SAB is being disabled, and apparently precision of performance.now() as well? (based on other comments)
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Re:Reading privileged memory with a side-channel by caf on Wednesday January 03, 2018 @08:32PM (#16067234)
about:config javascript.options.shared_memory in Firefox.
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Re:Reading privileged memory with a side-channel by kiwijamo on Thursday January 04, 2018 @03:03AM (#16068709)
Turned off by default for me in 57.0.3/macOS. Is it usually on by default on other platforms?
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Re:Reading privileged memory with a side-channel by scarygliders on Thursday January 04, 2018 @05:02AM (#16069144)
Just checked on Windows and it was on by default for me for Firefox 57.0.3
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