Problém s NATD

[Petr Bezděk]

Pavel Obr wrote:
> Dobry den,
 > ...
> Asi bude problem v ipfw.rules, ale nevim co.
> 
> 
> Soubor rc.conf:
> _______________________________________
> ifconfig_xl0="inet 192.168.1.10 netmask 255.255.255.0"
> ifconfig_rl0="inet 192.168.3.12 netmask 255.255.255.0"
> defaultrouter="192.168.1.1" # router providera
> gateway_enable="YES"
> natd_enable="YES"
> natd_interface="xl0" # "vnejsi" adresa 192.168.1.10
> natd_flags="-f /etc/natd.conf"
> firewall_enable="YES"
> firewall_script="/etc/ipfw.rules"
> 
> 
> soubor natd.conf:
> ___________________________________
> redirect_port tcp 192.168.3.37:80 8080
> 
> 
> ipfw.rules: je stejny jako v prikladu v HANDBOOKU
> ______________________________________
> 
> #!/bin/sh
> ################ Start of IPFW rules file ###############################
> # Flush out the list before we begin.
> ipfw -q -f flush
> 
> # Set rules command prefix
> cmd="ipfw -q add"
> skip="skipto 800"
> pif="xl0"     # public interface name of NIC
>               # facing the public Internet
> 
> #################################################################
> # No restrictions on Inside LAN Interface for private network
> # Change xl0 to your LAN NIC interface name
> #################################################################
> $cmd 005 allow all from any to any via rl0
> 
> #################################################################
> # No restrictions on Loopback Interface
> #################################################################
> $cmd 010 allow all from any to any via lo0
> 
> #################################################################
> # check if packet is inbound and nat address if it is
> #################################################################
> $cmd 014 divert natd ip from any to any in via $pif

Zde se vam prelozi u prichoziho paketu hodnota cilove IP adresy z 
192.168.1.10 na 192.168.3.37 a hodnota ciloveho portu z 8080 na 80
(viz natd.conf)

Ovsem paket dale prochazi pravidly a nenalezne takove pravidlo, ktere by 
takto prelozeny paket "pustilo dale". Proto bude pravidlem 400 zamitnuto.

> #################################################################
> # Allow the packet through if it has previous been added to the
> # the "dynamic" rules table by a allow keep-state statement.
> #################################################################
> $cmd 015 check-state
> 
> #################################################################
> # Interface facing Public Internet (Outbound Section)
> # Interrogate session start requests originating from behind the
> # firewall on the private network or from this gateway server
> # destine for the public Internet.
> #################################################################
> 
> # Allow out access to my ISP's Domain name server.
> # x.x.x.x must be the IP address of your ISP's DNS
> # Dup these lines if your ISP has more than one DNS server
> # Get the IP addresses from /etc/resolv.conf file
> $cmd 020 $skip tcp from any to 62.77.67.2 53 out via $pif setup keep-state
> 
> 
> # Allow out access to my ISP's DHCP server for cable/DSL configurations.
> #$cmd 030 $skip udp from any to x.x.x.x 67 out via $pif keep-state
> 
> # Allow out non-secure standard www function
> $cmd 040 $skip tcp from any to any 80 out via $pif setup keep-state
> 
> # Allow out secure www function https over TLS SSL
> $cmd 050 $skip tcp from any to any 443 out via $pif setup keep-state
> 
> # Allow out send & get email function
> $cmd 060 $skip tcp from any to any 25 out via $pif setup keep-state
> $cmd 061 $skip tcp from any to any 110 out via $pif setup keep-state
> 
> # Allow out FreeBSD (make install & CVSUP) functions
> # Basically give user root "GOD" privileges.
> $cmd 070 $skip tcp from me to any out via $pif setup keep-state uid root
> 
> # Allow out ping
> $cmd 080 $skip icmp from any to any out via $pif keep-state
> 
> # Allow out Time
> $cmd 090 $skip tcp from any to any 37 out via $pif setup keep-state
> 
> # Allow out nntp news (i.e. news groups)
> $cmd 100 $skip tcp from any to any 119 out via $pif setup keep-state
> 
> # Allow out secure FTP, Telnet, and SCP
> # This function is using SSH (secure shell)
> $cmd 110 $skip tcp from any to any 22 out via $pif setup keep-state
> 
> # Allow out whois
> $cmd 120 $skip tcp from any to any 43 out via $pif setup keep-state
> 
> # Allow ntp time server
> $cmd 130 $skip udp from any to any 123 out via $pif keep-state
> 
> #################################################################
> # Interface facing Public Internet (Inbound Section)
> # Interrogate packets originating from the public Internet
> # destine for this gateway server or the private network.
> #################################################################
> 
> # Deny all inbound traffic from non-routable reserved address spaces
> #$cmd 300 deny all from 192.168.0.0/16  to any in via $pif  #RFC 1918 
> private IP
> $cmd 301 deny all from 172.16.0.0/12   to any in via $pif  #RFC 1918 
> private IP
> $cmd 302 deny all from 10.0.0.0/8      to any in via $pif  #RFC 1918 
> private IP
> $cmd 303 deny all from 127.0.0.0/8     to any in via $pif  #loopback
> $cmd 304 deny all from 0.0.0.0/8       to any in via $pif  #loopback
> $cmd 305 deny all from 169.254.0.0/16  to any in via $pif  #DHCP auto-config
> $cmd 306 deny all from 192.0.2.0/24    to any in via $pif  #reserved for 
> docs
> $cmd 307 deny all from 204.152.64.0/23 to any in via $pif  #Sun cluster
> $cmd 308 deny all from 224.0.0.0/3     to any in via $pif  #Class D & E 
> multicast
> 
> # Deny ident
> $cmd 315 deny tcp from any to any 113 in via $pif

S problemem to nesouvisi, ale:

Dotazy na IDENT neni dobre zahazovat pomoci "deny". Sluzby, ktere se 
dotazuji na IDENT tak budou mit urcitou prodlevu (nekolik sekund), nez 
vyprsi doba, po kterou jsou ochotni cekat na IDENT.

Nahradte zde "deny" za "reset".

> # Deny all Netbios service. 137=name, 138=datagram, 139=session
> # Netbios is MS/Windows sharing services.
> # Block MS/Windows hosts2 name server requests 81
> $cmd 320 deny tcp from any to any 137 in via $pif
> $cmd 321 deny tcp from any to any 138 in via $pif
> $cmd 322 deny tcp from any to any 139 in via $pif
> $cmd 323 deny tcp from any to any 81  in via $pif
> 
> # Deny any late arriving packets
> $cmd 330 deny all from any to any frag in via $pif
> 
> # Deny ACK packets that did not match the dynamic rule table
> $cmd 332 deny tcp from any to any established in via $pif
> 
> # Allow traffic in from ISP's DHCP server. This rule must contain
> # the IP address of your ISP's DHCP server as it's the only
> # authorized source to send this packet type.
> # Only necessary for cable or DSL configurations.
> # This rule is not needed for 'user ppp' type connection to
> # the public Internet. This is the same IP address you captured
> # and used in the outbound section.
> #$cmd 360 allow udp from x.x.x.x to any 68 in via $pif keep-state
> 
> # Allow in standard www function because I have Apache server
> $cmd 370 allow tcp from any to me 80 in via $pif setup limit src-addr 2
> $cmd 375 allow tcp from any to me 443 in via $pif setup limit src-addr 2
> 
> # Allow in secure FTP, Telnet, and SCP from public Internet
> $cmd 380 allow tcp from any to me 22 in via $pif setup limit src-addr 2
> 
> # Allow in non-secure Telnet session from public Internet
> # labeled non-secure because ID & PW are passed over public
> # Internet as clear text.
> # Delete this sample group if you do not have telnet server enabled.
> #$cmd 390 allow tcp from any to me 23 in via $pif setup limit src-addr 2

Nekam do techto mist musite umistit pravidlo, ktere povoli prelozene 
pakety pro port-forwarding.

$cmd 395 allow tcp from any to 192.168.3.37 80 in via $pif setup limit 
src-addr 2

> # Reject & Log all unauthorized incoming connections from the public 
> Internet
> $cmd 400 deny log all from any to any in via $pif
> 
> # Reject & Log all unauthorized out going connections to the public Internet
> $cmd 450 deny log all from any to any out via $pif
> 
> # This is skipto location for outbound stateful rules
> $cmd 800 divert natd ip from any to any out via $pif
> $cmd 801 allow ip from any to any
> 
> # Everything else is denied by default
> # deny and log all packets that fell through to see what they are
> $cmd 999 deny log all from any to any
> ################ End of IPFW rules file ###############################
> 
> 

Funkcnost lze overit pomoci tcpdumpu a pripadne prohlednutim logu 
(/vat/log/security) a zaznamu odpovidajici pravidlu s cislem 400.

tcpdump -ns1500 -ixl0 host 192.168.1.10 port 8080
tcpdump -ns1500 -irl0 host 192.168.3.37 port 80

-- 
Petr Bezděk