Re: IPtables settings to access a backup FTP

[Richard <netfilter@ghz.fr>]

Martijn Lievaart a écrit :
> Richard wrote:
> 
> [ Please don't toppost. Thanks ]
> 
>> Hi I've got ip_conntrack running,
> 
> I was talking about ip_conntrack_ftp, not ip_conntrack. You need both. 
> The difference is between ftp working and not working at the first LS 
> command.
> 
>>
>> My server hosts FTP accounts and I also need outgoing ftp ...
> 
> Clear, so you need the input rule on port 21 as well.
> 
>>
>> No problems accessing the ftp hosted on this server, but can't do a 
>> CWD (ls) from this server to another external ftp server unless the 
>> firewall is disactivated.
> 
> No problems? Impossible with the rules you posted.
> 
>>
>> I guess you are going to say most of my settings are useless but here 
>> goes my current settings :
> 
> Thanks, but that is virtually unreadable. Post the output of 
> iptables-save instead.
> 
> HTH,
> M4
> 

Thankyou ! That fixed my problem ! I did a lsmod and it was not there so 
I did a mprobe ip_conntrack_ftp and then added ip_conntrack_ftp to 
/etc/modules

Now my backup system works well !

Now for my iptable settings, here is my file :

------

#The NAT portion of the ruleset. Used for Network Address Transalation.
#Usually not needed on a typical web server, but it's there if you need it.
*nat
:PREROUTING ACCEPT [127173:7033011]
:POSTROUTING ACCEPT [31583:2332178]
:OUTPUT ACCEPT [32021:2375633]
COMMIT

#The Mangle portion of the ruleset. Here is where unwanted packet types 
get dropped.
#This helps in making port scans against your server a bit more time 
consuming and difficult, but not impossible.
*mangle
:PREROUTING ACCEPT [444:43563]
:INPUT ACCEPT [444:43563]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [402:144198]
:POSTROUTING ACCEPT [402:144198]
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG 
FIN,PSH,URG -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG NONE -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags SYN,RST SYN,RST -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN FIN,SYN -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG 
FIN,PSH,URG -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG NONE -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags SYN,RST SYN,RST -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN FIN,SYN -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG 
FIN,PSH,URG -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG NONE -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags SYN,RST SYN,RST -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN FIN,SYN -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG 
FIN,PSH,URG -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG NONE -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags SYN,RST SYN,RST -j DROP
-A PREROUTING -p tcp -m tcp --tcp-flags FIN,SYN FIN,SYN -j DROP
COMMIT

#The FILTER section of the ruleset is where we initially drop all 
packets and then selectively open certain ports.
#We will also enable logging of all dropped requests.
*filter
:INPUT DROP [1:242]
:FORWARD DROP [0:0]
:OUTPUT DROP [0:0]
:LOG_DROP - [0:0]
:LOG_ACCEPT - [0:0]
:icmp_packets - [0:0]

#test
-A FORWARD -i eth0 -o eth1 -p tcp --syn --dport 21 -j ACCEPT
#First, we cover the INPUT rules, or the rules for incoming requests.
#Note how at the end we log any incoming packets that are not accepted.
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -p tcp -m tcp --dport 20 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 21 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 2022 -j LOG_ACCEPT
-A INPUT -p tcp -m tcp --dport 25 -j LOG_ACCEPT
-A INPUT -p tcp -m tcp --dport 43 -j ACCEPT
-A INPUT -p udp -m udp --dport 53 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 80 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 110 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 143 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 443 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 123 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 8443 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 8880 -j ACCEPT
#Passive FTP connections
-A INPUT -p tcp -m tcp --dport 32876 -j ACCEPT
-A INPUT -p udp -m udp --dport 32876 -j ACCEPT

#uncomment the next line if you are running Spamassassin on your server
#-A INPUT -p tcp -m tcp --dport 783 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 993 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 3306 -j ACCEPT
-A INPUT -s 127.0.0.1 -j ACCEPT
-A INPUT -p icmp -j icmp_packets
-A INPUT -j LOG_DROP

#Next, we cover the OUTPUT rules, or the rules for all outgoing traffic.
#Note how at the end we log any outbound packets that are not accepted.
-A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A OUTPUT -p tcp -m tcp --dport 20 -j ACCEPT
-A OUTPUT -p tcp -m tcp --dport 21 -j ACCEPT
-A OUTPUT -p tcp -m tcp --dport 2022 -j ACCEPT
-A OUTPUT -p tcp -m tcp --dport 23 -j ACCEPT
-A OUTPUT -p tcp -m tcp --dport 25 -j ACCEPT
-A OUTPUT -p tcp -m tcp --dport 43 -j ACCEPT
-A OUTPUT -p udp -m udp --dport 53 -j ACCEPT
-A OUTPUT -p tcp -m tcp --dport 80 -j ACCEPT
-A OUTPUT -p tcp -m tcp --dport 110 -j ACCEPT
-A OUTPUT -p tcp -m tcp --dport 143 -j ACCEPT
-A OUTPUT -p tcp -m tcp --dport 443 -j ACCEPT
-A OUTPUT -p udp -m udp --dport 123 -j ACCEPT
#uncomment the next line if you are running Spamassassin on your server
#-A OUTPUT -p tcp -m tcp --dport 783 -j ACCEPT
-A OUTPUT -p tcp -m tcp --dport 993 -j ACCEPT
-A OUTPUT -p tcp -m tcp --dport 3306 -j ACCEPT
-A OUTPUT -d 127.0.0.1 -j ACCEPT
-A OUTPUT -p icmp -j icmp_packets
-A OUTPUT -j LOG_DROP

#Here we have 2 sets of logging rules. One for dropped packets to log 
all dropped requests and one for accepted packets, should we wish to log 
any accepted requesets.
-A LOG_DROP -j LOG --log-prefix "[IPTABLES DROP] : " --log-tcp-options 
--log-ip-options
-A LOG_DROP -j DROP

-A LOG_ACCEPT -j LOG --log-prefix "[IPTABLES ACCEPT] : " 
--log-tcp-options --log-ip-options
-A LOG_ACCEPT -j ACCEPT

#And finally, a rule to deal with ICMP requests. We drop all ping 
requests except from our own server.
# Make sure you replace 1.2.3.4 with the IP address of your server.
#-A icmp_packets -p icmp -m icmp --icmp-type 0 -j ACCEPT
#-A icmp_packets -p icmp -m icmp --icmp-type 8 -j ACCEPT
#-A icmp_packets -p icmp -m icmp --icmp-type 3 -j ACCEPT
#-A icmp_packets -p icmp -m icmp --icmp-type 11 -j ACCEPT
-A icmp_packets -p icmp -m limit  --limit 1/s --limit-burst 1 -j ACCEPT
-A icmp_packets -p icmp -m limit --limit 1/s --limit-burst 1 -j LOG 
--log-prefix "PING-DROP: "

COMMIT


-----

So as far as I understand, I must remove the two following lines :

-A INPUT -p tcp -m tcp --dport 20 -j ACCEPT
-A OUTPUT -p tcp -m tcp --dport 20 -j ACCEPT

Thanks again !

Richard