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Date:      Mon, 07 Nov 2022 18:02:33 +0000
From:      bugzilla-noreply@freebsd.org
To:        bugs@FreeBSD.org
Subject:   [Bug 241917] blacklistd not accounting for failed sshd login attempts which failed reverse mapping checking
Message-ID:  <bug-241917-227-cdtqjxn0oa@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-241917-227@https.bugs.freebsd.org/bugzilla/>
References:  <bug-241917-227@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D241917

--- Comment #2 from Jose Luis Duran <jlduran@gmail.com> ---
FreeBSD's default sshd configuration has:

    UseDNS yes

It instructs sshd to look up the remote host name and check that the resolv=
ed
host name for the remote IP address maps back to the very same IP address.

In the meantime, a potential workaround, could be to set:

    UseDNS no

which is the default setting upstream. However, only addresses and not host
names may be used in ~/.ssh/authorized_keys from and sshd_config Match Host
directives.

I will, eventually, test the possibility of adding a few

    BLACKLIST_NOTIFY(ssh, BLACKLIST_AUTH_FAIL, "ssh");

to auth.c (especially under remote_hostname()).

--=20
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