Help with pf rules

[TerranAce007]

I'm using an old computer to build a home router and this is what I have come up with so far for the pf rules. The external interface is set to a static IP from my ISP and the internal in 192.168.2.0/24. I want to NAT everything through the one IP, block all incoming except ssh for now, and limit outbound connections to specific ports/protocols. I also want the firewall to just affect the external zone and not firewall communication between computers on the internal network. Is this a goo setup?

########
# Devices #
########
Loopback = "lo0"
IntIF = "sk0"
ExtIF = "xl0"

#############
# Macros & Lists #
#############
OB_ports = "{ 20 21 22 25 53 80 110 115 123 143 389 443 445 464 465 531 636 989 990 995 }"
OB_proto = "{ udp tcp icmp }"
IB_ports = "{ 22 }"
IB_proto = "{ tcp }"

##########
# NAT Rules #
##########
nat on $ExtIF from $IntIF/24 to any -> $ExtIF

############
# Firewall Rules #
############
set skip on $Loopback
block all
antispoof quick for $ExtIF
scrub in all on $ExtIF no-df random-id

# Allow all internal-internal traffic
pass quick on $IntIF from $IntIF/24 to $IntIF/24

# Allowed Outbound
pass out quick on $IntIF proto $OB_proto from $IntIF/24 to any port $OB_ports

# Allowed Inbound
pass in log quick on $ExtIF proto $IB_proto from any to $ExtIF port $IB_ports flags S/SA

[J65nko]

You have your directions mixed up . To understand how pf sees the the in and out directions, place yourself (a little imagination is needed) inside this diagram at the place marked PF.

         IN        OUT
                   
          |        /|\
          |       / | \
          |         |
          |         |
        \ | /       |
         \|/        |
----------|---------|----------
          |         |
        external interface
          |        /|\
          |       / | \
          |         |
          |   PF    |
          |         |
        \ | /       |
         \|/        |
        internal interface
          |         |
----------|---------|----------
          |        /|\
          |       / | \
          |         |
        \ | /       |
         \|/        |
         OUT       IN

• External interface
  Incoming traffic on the external interface is originates from the Internet.
  
  Outgoing packets on the external interface are either originated by the PF box itself, or by your local LAN (incoming on your internal NIC)
  
• Internal interface
  Incoming packets on the internal interface are generated by your local LAN, and are destined either for the PF box itself, or have to go out from the external interface to the internet.
  
  Outgoing packets on the internal interface either originate locally from the PF box itself , or from the the Internet, where they were incoming on the external NIC.

So this rule has to be adjusted:

# Allowed Outbound
pass out quick on $IntIF proto $OB_proto from $IntIF/24 to any port $OB_ports

[marcolino]

Originally Posted by TerranAce007

# Allow all internal-internal traffic
pass quick on $IntIF from $IntIF/24 to $IntIF/24

Since traffic from one machine to another on the same network does not go through your router, this line is unnecessary.

Originally Posted by TerranAce007

# Allowed Outbound
pass out quick on $IntIF proto $OB_proto from $IntIF/24 to any port $OB_ports

# Allowed Inbound
pass in log quick on $ExtIF proto $IB_proto from any to $ExtIF port $IB_ports flags S/SA

Add keep state to the end of these lines, after adustment per J65nko's post above.

[marcolino]

Also, for future maintenance, I suggest replacing the port numbers with service names.

22 ==> ssh
25 ==> smtp
53 ==> domain

etc...

[TerranAce007]

Got it working now, thanks for the help!