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Date: Wed, 29 Jun 2011 22:03:04 +0400
From: Vasiliy Kulikov <segoon@...nwall.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
oss-security@...ts.openwall.com, security@...nel.org
Subject: Re: [Security] CVE request: kernel: taskstats/procfs io infoleak
(was: taskstats authorized_keys presence infoleak PoC)
Hi,
One more thing, this is more dangerous, but very conditional.
Create one system account with no files (a victim). This simplifies
measurements.
As an attacker:
Start taskstats listener in the background.
Swith to tty1, push SAK to kill current login task.
Enter some fake username and password, e.g. 1:1.
The login fails, of course.
Now the attacker hides and the victim comes to tty1.
He enters his username:password.
The login succeeds from the first try.
The victim exits from the shell.
Attacker measures login's read_characters value. The victim has to
succeed from the first try and shouldn't push SAK :)
Now the attacker has to increment the fake password length (incrementing
the resulted read_characters of the dead login task) and wait for
the successful victim's login. After ~log2(1024) tries (binary search)
he learns precise password length.
As exiting "login" just waits for the child to exit to call
pam_close_session(), victim's activity doesn't really add any noise.
--
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments
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