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Date:      Tue, 30 May 2023 21:11:03 +0200
From:      =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@FreeBSD.org>
To:        David Chisnall <theraven@FreeBSD.org>
Cc:        Mike Karels <mike@karels.net>,  bob prohaska <fbsd@www.zefox.net>, freebsd-current@freebsd.org
Subject:   Re: Surprise null root password
Message-ID:  <86sfbdk52w.fsf@ltc.des.no>
In-Reply-To: <850FF076-A511-4802-8D7C-2029752C3345@FreeBSD.org> (David Chisnall's message of "Sat, 27 May 2023 10:39:12 %2B0100")
References:  <ZHDt21wFlpJfQKEs@www.zefox.net> <ZHFqzf9A90L9NfJb@www.zefox.net> <E29BDD31-BB38-41F8-B1F9-422CBEC7143D@karels.net> <850FF076-A511-4802-8D7C-2029752C3345@FreeBSD.org>

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David Chisnall <theraven@FreeBSD.org> writes:
> There was a very nasty POLA violation a release or two ago.  OpenSSH
> defaults to disallowing empty passwords and so having a null password
> was a convenient way of allowing people to su or locally log into that
> user but disallowing ssh.  This option does not work in recent
> versions of FreeBSD.  Turning on the option to permit root login while
> keeping the root password blank used to be (mostly) safe because it
> permitted su to root from people in the wheel group, root login via
> SSH key remotely (for =E2=80=98everything is broken I can=E2=80=99t log i=
n as a user
> whose home directory is not on the root filesystem=E2=80=99 recovery) and
> local login as root from consoles marked as secure.  It now permits
> root login from the network with a blank password.

That is incorrect.  PermitRootLogin defaults to =E2=80=9Cno=E2=80=9D in Fre=
eBSD and to
=E2=80=9Cprohibit-password=E2=80=9D upstream (and presumably in the port), =
while
PermitEmptyPasswords defaults to =E2=80=9Cno=E2=80=9D both in FreeBSD and u=
pstream,
cf. crypto/openssh/servconf.c (search for =E2=80=9Cpermit_root=E2=80=9D and
=E2=80=9Cpermit_empty=E2=80=9D).

DES
--=20
Dag-Erling Sm=C3=B8rgrav - des@FreeBSD.org



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