Re: [websec] HSTS: Infinite max-age to address NTP spoofing attack?

Hanno Böck <hanno@hboeck.de> Fri, 07 November 2014 15:15 UTC

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Subject: Re: [websec] HSTS: Infinite max-age to address NTP spoofing attack?
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I'm not sure what I think about an infinite HSTS timespan.

But I am pretty sure that no matter what, the underlying cause needs to
be fixed. A reliable time plays a role in a number of cases in TLS.
HPKP is basically vulnerable to the same kind of attack. Certificate
validity times/expirations are vulnerable.

After I was in the talk at BH I changed my systems to use tlsdated
instead of ntpd. That's the thing that should happen: We need to make
our time sources more reliable.

I was thinking about an idea I had during the talk: Maybe browsers
should add some time consistency checks? Basically two things would be
needed:
1. check for sane time on startup. Browsers check for updates,
CRLsets and other things anyway. They could just use the tls timestamp
of these requests and throw a warning if they differ significantly (I
don't want to nag users that don't set their time second-precise, but a
diff of more a day could give a warning)
2. check for consistency while running. There could be periodical
checks and if the time does large jumps also throw a warning.

-- 
Hanno Böck
http://hboeck.de/

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