StuRa:Server/FreeBSD

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Dokumentation für den FreeBSD-Server

Sicherheit

  • ports aktuell halten:
    • portsnap /var/db/portsnap/INDEX
    • edit /etc/crontab:
    • 0 13 * * * root portsnap -I cron fetch && portsnap update && pkg_version -vIL=
  • tägliches Audit der (installierten) Ports:
    • portaudit /var/db/portaudit/auditfile.tbz
    • edit /etc/crontab:
    • 0 14 * * * root portaudit -Fda
  • VuXML abonnieren
  • http://security.freebsd.org/ mal durchlesen
  • National Vulnerability Database (NVD RSS) abonnieren

Paketfilter

pf_enable="YES"
pf_rules="/etc/pf.conf"
pflog_enable="YES"
# host system is gateway for jails
gateway_enable="YES"
  • syslogd an Hauptmaschine binden
    • in /etc/rc.conf: (evtl. -ss flag?)
    • syslogd_flags="-b $MAIN_IP"
  • Paketfilter starten:
    • /etc/rc.d/pf start
    • /etc/rc.d/pflog start
  • pf.config: (check via pfctl -vnf /etc/pf.conf) (inzwischen veraltet)
### MAKROS
thishost = "$MAIN_IP"
# portsnap5 204.9.55.80
portsnap_freebsd = "{ 204.109.56.116 204.9.55.80 }"
# auditfile.tbz is beeing fetched from portaudit.freebsd.org
portaudit_freebsd = "69.147.83.36"
# dnsserver from resolv.conf
dnsserver = "{ 85.214.73.63 217.79.186.148 27.110.120.30 204.152.184.76 194.150$
### RULES
# default deny
block in all
block out all
# lokales interface darf ohne einschränkungen
pass in quick on lo0 all
pass out quick on lo0 all
## HOST
# allow ssh
pass in on bce0 proto tcp from any to $thishost port $SSH_PORT
pass out on bce0 proto tcp from $thishost port $SSH_PORT to any
## allow outbound icmp
# echo request
pass out inet proto icmp icmp-type 8 code 0 keep state
# echo reply
pass in inet proto icmp icmp-type 0 code 0 keep state
# destination unreachable
pass in inet proto icmp icmp-type 3 keep state
# allow DNS lookups {also via tcp?} port 53
# what about traversal???
pass out on bce0 proto udp from $thishost to $dnsserver port 53 keep state
# allow portsnap to fetch from freebsd.org (ports?)
pass in on bce0 proto tcp from $portsnap_freebsd to $thishost
pass out on bce0 proto tcp from $thishost to $portsnap_freebsd
# allow portaudit to fetch auditfile.tbz via http
pass in on bce0 proto tcp from $portaudit_freebsd port 80 to $thishost
pass out on bce0 proto tcp from $thishost to $portaudit_freebsd port 80
## JAIL Beispiel (uneingeschränkt -> dumme Idee, ports dienstabhänging freigeben
pass in on bce0 proto { tcp udp icmp } from any to $jail_srs14
pass out on bce0 proto { tcp udp icmp } from $jail_srs14 to any
  • regeln überprüfen: pfctl -vnf /etc/pf.conf

Paketfilter bedienen

  • anschalten: pfctl -e
  • ausschalten: pfctl -d
  • sanity check: pfctl -vnf /etc/pf.conf
  • alte Regeln ins Klo und neue in die Auslage: pfctl -Fa -f /etc/pf.conf

Verweise

FreeBSD audit

  • faschistoides Logging von Systemcalls
  • präventiv wirkungslos, aber in der post-mortem Analyse extrem hilfreich
  • FreeBSD Kapitel 17. Security Event Auditing
  • in /etc/rc.conf: auditd_enable="YES"
  • start auditd: /etc/rc.d/auditd start
  • in /etc/security/audit_control:
flags:lo,aa,ex
policy:cnt,argv
synchronize config: audit -s
  • cronjob für die logs: /etc/crontab
    • "0 */12 * * * root /usr/sbin/audit -n"

Jails

Jails dienen der Virtualisierung von Betriebssysteminstanzen. Näheres dazu im FreeBSD Handbuch Kapitel 15 - Jails.

Anlegen eines Jails

  • cd /usr/src
  • evtl. erst Sourcen installieren: sysinstall-> configure -> distributions
  • evtl. # make buildworld
  • Jails liegen unter /home/jails/$JAILNAME
  • System für jail bauen:
# make installworld DESTDIR=/home/jails/$JAILNAME
# make distribution DESTDIR=/home/jails/$JAILNAME
  • device nodes ins jail packen
    • # mount -t devfs devfs /home/jails/$JAILNAME/dev
  • resolv.conf kopieren: cp host /etc/resolv.conf to /home/jails/$JAILNAME/etc/resolv.conf
  • rc.conf editieren:
jail_enable="YES"
jail_list="$JAILNAME"
ifconfig_bce0_alias0="$JAIL_IP netmask 255.255.255.0"
jail_$JAILNAME_rootdir="/usr/home/jails/$JAILNAME"
jail_$JAILNAME_hostname="$JAILNAME.stura.htw-dresden.de"
jail_$JAILNAME_ip="$JAIL_IP"
jail_$JAILNAME_devfs_enable="YES"
jail_$JAILNAME_devfs_ruleset="devfs_rules_jail"
  • jail starten: /etc/rc.d/jail start
  • Prozess im jail starten: jexec $JAIL_ID tcsh
    • $JAIL_ID aus jls ermittelbar
    • portscollection etc. installieren ...
    • portsnap fetch && portsnap extract && portsnap update
    • evtl. ssh anschalten (in rc.conf): sshd_enable="YES"

Löschen eines Jails

  • ins jailroot wechseln (/home/jails/$JAILNAME)
chflags -R noschg *
rm -rf *
cd .. && rm -r $JAILNAME

Tricks, Probleme etc.

  • sich evtl. ezjail mal anschauen (war damals kaputt)
  • ping aus jails heraus erlauben
    • host: allow_raw_socket=1 via
      • #sysctl security.jail.allow_raw_sockets=1
      • bzw. in /etc/sysctl.conf setzen
      • Quelle
  • ssh:
    • etc/ssh/sshd_config: ListenAddress 0.0.0.0

ssh

  • openssh
  • ssh auf anderen port legen
  • Vorschläge für /etc/ssh/sshd_config:
VersionAddendum
Port $SSH_PORTNUMMER
ListenAddress $JAIL_IP
Protocol 2
SyslogFacility AUTH
LogLevel INFO
LoginGraceTime 1m
PermitRootLogin no
StrictModes yes
MaxAuthTries 4
MaxSessions 5</
AllowUsers $DER_COOLE_LEUTE_CLUB
PermitEmptyPasswords no
X11Forwarding no
Banner none
  • immer schön manpage lesen und mit dem Feinkamm durchgehen
  • keys + passwörter zur Authentifizierung
  • in jails:ListenAddress 0.0.0.0

Email

MTA: postfix

  • in the email jail
  • # cd /usr/ports/mail/postfix
  • # make install clean
    • postfix added to group mail -> y
    • Would you like to activate Postfix in /etc/mail/mailer.conf -> y
  • Einstellungen (Auszug + aliases)
    • edit /usr/local/etc/postfix/main.cf:
local_recipient_maps = $alias_maps
unknown_local_recipient_reject_code = 550
mynetworks = 127.0.0.0/8
myhostname = mail.stura.htw-dresden.de
mydomain = stura.htw-dresden.de
myorigin = $mydomain
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
inet_interfaces = all
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
home_mailbox = Maildir/
mail_spool_directory = /var/spool/mail
relay_domains = stura.htw-dresden.de
smtpd_recipient_restrictions = reject_invalid_hostname,
       reject_unknown_recipient_domain,
       reject_unauth_destination,
       reject_rbl_client sbl.spamhaus.org,
       permit
smtpd_helo_restrictions = reject_invalid_helo_hostname,
       reject_non_fqdn_helo_hostname,
       reject_unknown_helo_hostname
smtpd_client_restrictions = reject_rbl_client dnsbl.sorbs.net

MDA: dovecot

  • optionen: kqueue, ssl, managesieve, mysql
  • #echo 'dovecot_enable="YES"' >> /etc/rc.conf
  • #cp /usr/local/share/examples/dovecot/dovecot.conf /usr/local/etc/dovecot.conf
  • #cp /usr/local/share/examples/dovecot/dovecot-sql.conf /usr/local/etc/dovecot-sql.conf
  • in /usr/local/etc/dovecot.conf: (vorerst zum testen)
protocols = imap pop3
disable_plaintext_auth = no
ssl = no
mail_location = mbox:~/mail/:INBOX=/var/mail/%u
mail_privileged_group = mail
protocol imap {
  imap_client_workarounds = delay-newmail outlook-idle netscape-eoh tb-extra-mailbox-sep
}
  • Krypto drankleben (imap -> imaps, pop3 -> pop3s)

Tricks etc.

  • alias-Adressen anlegen
    • edit: /usr/local/etc/postfix/main.cf:
alias_maps = hash:/etc/aliases, hash:/etc/aliases.stura
alias_database = hash:/etc/aliases,hash:/etc/aliases.stura
    • edit /etc/aliases.stura:
    • newaliases
    • postfix reload
    • # usr/local/etc/rc.d/postfix restart
  • SMTP testen:
    • nc $JAIL_IP 25
    • HELO microsoft.com
    • MAIL FROM:<bill@microsoft.com>
    • RCPT TO:<test@stura.htw-dresden.de>
    • DATA
    • From: <bill@microsoft.com>
    • To: <stest@stura.htw-dresden.de>
    • Subject: hui
    • das hätte nicht passieren sollen
    • .
    • QUIT

Plone

DNS

  • genutzt werden DNS Server des FoeBuD und des CCC
  • zusätzlich (für OpenNIC)
    • DE,NRW 217.79.186.148 ns1.nrw.de.dns.opennic.glue Günter Grodotzki yes (no logs kept)
    • NZ 27.110.120.30 ns1.nz.dns.opennic.glue Dean Gardiner yes (24 hrs)
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