linux-kernel - Re: [ 03/42] TTY: fix atime/mtime regression

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Date:	Tue, 30 Apr 2013 14:02:16 +0200
From:	Wolfram Gloger <wmglo@...t.med.uni-muenchen.de>
To:	linux-kernel@...r.kernel.org
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	wmglo@...t.med.uni-muenchen.de
Subject: Re: [ 03/42] TTY: fix atime/mtime regression

Hi,

>To revert to the old behaviour while still preventing attackers to
>guess the password length, we update the timestamps in one-minute
>intervals by this patch.

Sorry if I miss something, but isn't this an issue that should be very
obviously fixed in user space?  Only user space knows whether the
atime/mtime updates on a device are security-sensitive or not.

The sshd process and/or the login process could easily perform randomly
timed, dummy utime() calls on the tty around and within the password
typing, making this attack unfeasible.  I faintly remember sshd _already
does this_ for the network packets anyway by exchanging dummy packets.

Regards,
Wolfram.
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