oss-sec mailing list archives

Re: can we talk about secure time?


From: Daniel Micay <danielmicay () gmail com>
Date: Sun, 21 Dec 2014 12:50:07 -0500

On 21/12/14 06:31 AM, Florian Weimer wrote:

In contrast, servers with long-running connections and I/O polling
loops often do not react gracefully to jumps in time.  (I once
disconnected a few hundreds, if not thousands of users from an IRC
server just by setting its time correctly.)  Sure, you can avoid that
by using the appropriate kernel clock for timeout handling, but I have
the impression that the correct clock changes every couple of years.

I don't think it has ever changed. CLOCK_MONOTONIC won't *ever* jump
either forwards or backwards, but is impacted by clock skew. I don't
think most use cases actually want CLOCK_MONOTONIC_RAW, especially
considering that there's no vdso implementation so it's slow.

Of course, there's lots of buggy software which is why we have stuff
like ASLR / SSP in the first place. :)

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