Date: Thu, 06 Sep 2012 20:25:39 +0200 From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no> To: obrien@freebsd.org Cc: Arthur Mesh <arthurmesh@gmail.com>, freebsd-security@FreeBSD.org, Doug Barton <dougb@FreeBSD.org>, freebsd-rc@FreeBSD.org, Mark Murray <markm@FreeBSD.org> Subject: Re: svn commit: r239569 - head/etc/rc.d Message-ID: <86y5knovoc.fsf@ds4.des.no> In-Reply-To: <20120906175747.GC13179@dragon.NUXI.org> (David O'Brien's message of "Thu, 6 Sep 2012 10:57:47 -0700") References: <201208221843.q7MIhLU4077951@svn.freebsd.org> <5043DBAF.40506@FreeBSD.org> <86y5kpcqc4.fsf@ds4.des.no> <20120906175747.GC13179@dragon.NUXI.org>
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David O'Brien <obrien@FreeBSD.org> writes: > Dag-Erling Smrgrav <des@des.no> writes: > > Speaking of rc.d and entropy, is the following code in /etc/rc.d/sshd > > really necessary? > > seeded=3D`sysctl -n kern.random.sys.seeded 2>/dev/null` > > if [ "x${seeded}" !=3D "x" ] && [ ${seeded} -eq 0 ] ; then > > warn "Setting entropy source to blocking mode." > [...] > Likely this is inspired by 3.2 'How Compromises are Exploited', > 'Compromise of High-Value Keys Generated From Compromised Key' paragraph. > > If the key that is being generated is vary valuable, the harm to the > system owner can be very large. These are host keys. I'd say they're moderately valuable - depending on the machine and your point of view, they may be more or less valuable than user keys - but they are usually generated under controlled circumstances, rather than circumstances in which an attacker may be able to influence the PRNG. > Now that we have 'postrandom' possibly we should utilize the > ${entropy_file} (and call postrandom again). > > Certainly [re]seeding with 'sysctl -a' and 'date' is poor and should be > changed. Well, currently it's a no-op since kern.random.sys.seeded is never 0 at that point, if I understand correctly. DES --=20 Dag-Erling Sm=C3=B8rgrav - des@des.no
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