Entwicklungsumgebung/Firewall
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Firewall
Text kommt noch, jetzt erst einmal eine völlig unstrukturierte Materialsammlung:
Schau Dir mal ipfilter:uif an (Harry am 07.06.2008 in developer).
- 1. per default, alle tables auf drop
- 2. syntax: narrensicher
- 3. LDAP-Support
- 4. conf-Datei, keine GUI, koennen wir also leicht scripten
Als Vergleich die Werte von wc:
debby-3:/home/hjede/qemu-run# grep -Ev '(^#|^$)' /etc/uif/uif.conf |wc
44 96 851
debby-3:/home/hjede/qemu-run# iptables-save |wc
99 606 4448
Beispiel:
<source lang="text"> service {
traceroute udp(32769:65535/33434:33523) icmp(11) ping icmp(8) ipp udp(/631)
} network {
localhost 127.0.0.1 all 0.0.0.0/0 trusted 192.168.231.0/24 dmz 192.168.12.0/24 gateway 192.168.12.1
} interface {
loop lo ETHA eth0 ETH1 eth1 BR0 br0 ETH0 ETHA BR0
} input {
in+ i=loop s=localhost in+ i=ETH0 s=trusted in+ p=ping,traceroute in- p=ipp i=ETH1 f=reject in- f=log(input),reject
} output {
out+ o=loop d=localhost out+ d=all out+ o=ETH0,ETH1 out- f=log(output),reject
} forward {
fw+ i=BR0 o=BR0 fw> o=ETH1 fw+ o=ETH1 s=trusted fw- f=log(forward),reject
} masquerade {
masq+ o=ETH1 s=trusted d=gateway f=log(masq) masq+ o=ETH1 s=trusted d=all
} </source>
Und hier die lange & komplizierte Ausgabe von iptables-save:
<source lang="text">
- Generated by iptables-save v1.3.6 on Sat Jun 7 13:13:25 2008
- nat
- PREROUTING ACCEPT [61495:5257743]
- POSTROUTING ACCEPT [22191:3933471]
- OUTPUT ACCEPT [6405:1246646]
- 13MASQUERADElog - [0:0]
-A POSTROUTING -s 192.168.231.0/255.255.255.0 -d 192.168.12.1 -o eth1 -j 13MASQUERADElog -A POSTROUTING -s 192.168.231.0/255.255.255.0 -o eth1 -j MASQUERADE -A 13MASQUERADElog -m limit --limit 20/min -j LOG --log-prefix "FW MASQUERADE (masq): " --log-level 7 --log-tcp-options --log-ip-options -A 13MASQUERADElog -j MASQUERADE COMMIT
- Completed on Sat Jun 7 13:13:25 2008
- Generated by iptables-save v1.3.6 on Sat Jun 7 13:13:25 2008
- filter
- INPUT DROP [0:0]
- FORWARD DROP [0:0]
- OUTPUT DROP [0:0]
- 12DROPlog - [0:0]
- 1_1 - [0:0]
- 4DROPlog - [0:0]
- 8DROPlog - [0:0]
- ACCOUNTINGFORWARD - [0:0]
- ACCOUNTINGINPUT - [0:0]
- ACCOUNTINGOUTPUT - [0:0]
- ACCOUNTINGSTATELESSFORWARD - [0:0]
- ACCOUNTINGSTATELESSINPUT - [0:0]
- ACCOUNTINGSTATELESSOUTPUT - [0:0]
- MYREJECT - [0:0]
- STATEFORWARD - [0:0]
- STATEINPUT - [0:0]
- STATELESSFORWARD - [0:0]
- STATELESSINPUT - [0:0]
- STATELESSOUTPUT - [0:0]
- STATENOTNEW - [0:0]
- STATEOUTPUT - [0:0]
-A INPUT -j STATEINPUT -A INPUT -s 127.0.0.1 -i lo -j ACCEPT -A INPUT -s 192.168.231.0/255.255.255.0 -j 1_1 -A INPUT -p udp -m udp --sport 32769:65535 --dport 33434:33523 -j ACCEPT -A INPUT -p icmp -m icmp --icmp-type 8 -j ACCEPT -A INPUT -p icmp -m icmp --icmp-type 11 -j ACCEPT -A INPUT -i eth1 -p udp -m udp --dport 631 -j MYREJECT -A INPUT -j 4DROPlog -A FORWARD -j STATEFORWARD -A FORWARD -i br0 -o br0 -j ACCEPT -A FORWARD -o eth1 -p tcp -m tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu -A FORWARD -s 192.168.231.0/255.255.255.0 -o eth1 -j ACCEPT -A FORWARD -j 12DROPlog -A OUTPUT -j STATEOUTPUT -A OUTPUT -d 127.0.0.1 -o lo -j ACCEPT -A OUTPUT -j ACCEPT -A OUTPUT -o eth1 -j ACCEPT -A OUTPUT -o br0 -j ACCEPT -A OUTPUT -o eth0 -j ACCEPT -A OUTPUT -j 8DROPlog -A 12DROPlog -m limit --limit 20/min -j LOG --log-prefix "FW REJECT (forward): " --log-level 7 --log-tcp-options --log-ip-options -A 12DROPlog -j MYREJECT -A 1_1 -i br0 -j ACCEPT -A 1_1 -i eth0 -j ACCEPT -A 4DROPlog -m limit --limit 20/min -j LOG --log-prefix "FW REJECT (input): " --log-level 7 --log-tcp-options --log-ip-options -A 4DROPlog -j MYREJECT -A 8DROPlog -m limit --limit 20/min -j LOG --log-prefix "FW REJECT (output): " --log-level 7 --log-tcp-options --log-ip-options -A 8DROPlog -j MYREJECT -A MYREJECT -p tcp -m tcp -j REJECT --reject-with tcp-reset -A MYREJECT -j REJECT --reject-with icmp-port-unreachable -A STATEFORWARD -m state --state INVALID -j STATELESSFORWARD -A STATEFORWARD -j ACCOUNTINGFORWARD -A STATEFORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT -A STATEFORWARD -m state --state INVALID,RELATED,ESTABLISHED,UNTRACKED -j STATENOTNEW -A STATEINPUT -m state --state INVALID -j STATELESSINPUT -A STATEINPUT -j ACCOUNTINGINPUT -A STATEINPUT -m state --state RELATED,ESTABLISHED -j ACCEPT -A STATEINPUT -m state --state INVALID,RELATED,ESTABLISHED,UNTRACKED -j STATENOTNEW -A STATELESSFORWARD -j ACCOUNTINGSTATELESSFORWARD -A STATELESSFORWARD -m limit --limit 20/min -j LOG --log-prefix "FW INVALID STATE: " --log-level 7 --log-tcp-options --log-ip-options -A STATELESSFORWARD -j DROP -A STATELESSINPUT -j ACCOUNTINGSTATELESSINPUT -A STATELESSINPUT -m limit --limit 20/min -j LOG --log-prefix "FW INVALID STATE: " --log-level 7 --log-tcp-options --log-ip-options -A STATELESSINPUT -j DROP -A STATELESSOUTPUT -j ACCOUNTINGSTATELESSOUTPUT -A STATELESSOUTPUT -m limit --limit 20/min -j LOG --log-prefix "FW INVALID STATE: " --log-level 7 --log-tcp-options --log-ip-options -A STATELESSOUTPUT -j DROP -A STATENOTNEW -m limit --limit 20/min -j LOG --log-prefix "FW STATE NOT NEW: " --log-level 7 --log-tcp-options --log-ip-options -A STATENOTNEW -j DROP -A STATEOUTPUT -m state --state INVALID -j STATELESSOUTPUT -A STATEOUTPUT -j ACCOUNTINGOUTPUT -A STATEOUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT -A STATEOUTPUT -m state --state INVALID,RELATED,ESTABLISHED,UNTRACKED -j STATENOTNEW COMMIT
- Completed on Sat Jun 7 13:13:25 2008
- Generated by iptables-save v1.3.6 on Sat Jun 7 13:13:25 2008
- mangle
- PREROUTING ACCEPT [25994780:19965091246]
- INPUT ACCEPT [24155447:19040604203]
- FORWARD ACCEPT [6557432:3191342180]
- OUTPUT ACCEPT [24433500:25546765616]
- POSTROUTING ACCEPT [32829626:29312519572]
COMMIT
- Completed on Sat Jun 7 13:13:25 2008
</source>
Attacken abwehren
apt-get install fail2ban
Datei "/etc/fail2ban/jail.conf" bearbeiten:
ignoreip = 127.0.0.1 <weitere IP> bantime = 3600 [ssh] enabled = true port = ssh filter = sshd logpath = /var/log/auth.log maxretry = 3
Einlesen:
/etc/init.d/fail2ban restart
in "/var/log/fail2ban.log" seht ihr anschließend das sehr spannende Ergebnis.
Weblinks
Hans-Dietrich Kirmse, Harry Jede 2009