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Date:      Fri, 10 Sep 2021 20:24:28 +0000
From:      bugzilla-noreply@freebsd.org
To:        bugs@FreeBSD.org
Subject:   [Bug 258414] libblacklist: BLACKLIST_BAD_USER does nothing
Message-ID:  <bug-258414-227@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D258414

            Bug ID: 258414
           Summary: libblacklist: BLACKLIST_BAD_USER does nothing
           Product: Base System
           Version: CURRENT
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: misc
          Assignee: bugs@FreeBSD.org
          Reporter: emaste@freebsd.org

BLACKLIST_BAD_USER has no effect - in contrib/blacklist/lib/blacklist.c
translates it to BL_BADUSER

        case BLACKLIST_BAD_USER:
                internal_action =3D BL_BADUSER;
                break;

then in contrib/blacklist/bin/blacklistd.c

        case BL_BADUSER:
                /* ignore for now */
                break;

In fact this is (barely) documented:

     BLACKLIST_BAD_USER              The sending daemon has determined the
                                     username presented for authentication =
is
                                     invalid.  The blacklistd(8) daemon
                                     compares the username to a configured
                                     list of forbidden usernames and blocks
                                     the address immediately if a forbidden
                                     username matches.  (The
                                     BLACKLIST_BAD_USER support is not
                                     currently available.)

base system OpenSSH tries to make use of this in two places:

sshpam_query()
                        BLACKLIST_NOTIFY(BLACKLIST_BAD_USER,
                            sshpam_authctxt->user);
                        error("PAM: %s for %s%.100s from %.100s", msg,
                            sshpam_authctxt->valid ? "" : "illegal user ",
                            sshpam_authctxt->user, sshpam_rhost);

getpwnamallow()

        if (pw =3D=3D NULL) {
                BLACKLIST_NOTIFY(BLACKLIST_BAD_USER, user);
                logit("Invalid user %.100s from %.100s port %d",
                    user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));

--=20
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