Subject: bin/28627: cgdconfig -g is unreliable
To: None <,>
From: Andreas Gustafsson <>
List: netbsd-bugs
Date: 12/12/2004 10:15:00
>Number:         28627
>Category:       bin
>Synopsis:       cgdconfig -g is unreliable
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Dec 12 10:15:00 +0000 2004
>Originator:     Andreas Gustafsson
>Release:        NetBSD 2.99.10
System: NetBSD 2.99.10 NetBSD 2.99.10 (GUAM) #0: Sun Dec 5 15:10:56 EET 2004 i386
Architecture: i386
Machine: i386

On a lightly loaded Toshiba Libretto L2 laptop, running the command

   cgdconfig -g -V disklabel -o /etc/cgd/wd0e aes-cbc 256

fails about nine times out of ten with the error message

   cgdconfig: could not calibrate pkcs5_pbkdf2
   cgdconfig: Failed to generate defaults for keygen

This is caused by cgdconfig measuring the password encryption
performance of the CPU twice and considering any discrepancy between
the measurements exceeding 5% to be a failure.  Perhaps the
performance of the Transmeta Crusoe CPU used in the L2 varies more
over time than that of a typical desktop CPU due to the "code
morphing" technology it uses, or due to some power-saving feature.


Run the above command on a Toshiba Libretto L2 or other Crusoe-powered
laptop (taking care not to accidentally overwrite any existing cgd
parameters file).


Unless there is a compelling security argument to the contrary,
the tolerance for variability between timing measurements should be
increased from the current 5%.

Also, it would be helpful if the error message indicated that the
failure is caused by a transient timing issue and that retrying the
command may help.