From: tlhackque <email@example.com>
Cc: WireGuard Mailing list <firstname.lastname@example.org>
Subject: Re: CONFIG_ANDROID
Date: Thu, 30 Jun 2022 11:50:59 -0400 [thread overview]
Message-ID: <email@example.com> (raw)
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On 30-Jun-22 07:41, Jason A. Donenfeld wrote:
> On Thu, Jun 30, 2022 at 06:47:38AM -0400, tlhackque wrote:
>> FWIW: Having watched the discussion about CONFIG_ANDROID, it occurs to
>> me that there's an alternative for WireGuard that sidesteps the issue.
>> From the last patcheset, it seems that the only use in WireGuard is to
>> avoid clearing keys on every wake-up.
> No, it clears keys before sleeping.
>> So: Why not timestamp key-clear events, and establish a minimum interval?
> Because we don't know when we're going to wake up again, and the
> objective is to maintain forward secrecy.
Thanks for the explanation. One more attempt.
If I understand what's happening:
You're really trying to establish a maximum key lifetime - sleep being a
proxy for "too long to keep using". On conventional platforms, that's
been good enough. On these Android platforms, it's not.
You're clearing the key before sleeping so that after a presumably
longish time, you'll negotiate a new one. But on some platforms, the
sleeps are so frequent that "longish" is inconveniently short. And the
renegotiations are expensive. On those platforms, you don't clear the
key to avoid the frequent renegotiations. This keeps the old key in use
across the sleeps.
Alternatively, why not make the maximum key lifetime explicit. E.g. On
all platforms you could set a renegotiate time when a key is
established, and if it has expired on wake (or on use) trigger
renegotiation. This guarantees a maximum key lifetime, independent of
the frequency or duration of sleeps. And you don't need to know when
If you also want to make sure that the key isn't in memory longer than
that time (e.g. to avoid capture on a dump or device loss), you could
also set a timer (of the sort that wakes the CPU from sleep) that clears
the key at that time.
There are obvious optimizations if necessary.
The point I'm trying to make is that rather than thinking about the
annoying platform behavior's effect on the implementation, it's probably
better to think about what WireGuard is really trying to do and express
it in the implementation.
I hope this perspective helps. I'll step out of your way now.
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next prev parent reply other threads:[~2022-06-30 15:51 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <firstname.lastname@example.org>
2022-06-30 10:47 ` CONFIG_ANDROID tlhackque
2022-06-30 11:41 ` CONFIG_ANDROID Jason A. Donenfeld
2022-06-30 15:50 ` tlhackque [this message]
2022-06-30 15:56 ` CONFIG_ANDROID Jason A. Donenfeld
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