This is a mini-firewall that completely isolates a target device from the local network. This is for allowing infected machines Internet access, but without endangering the local network.
Building
This project depends upon
libpcap, and of course a C compiler.On Debian, the following should work:
# apt-get install git gcc make libpcap-dev
# git clone https://github.com/robertdavidgraham/isowall
# cd isowall
# makeThis will put the binary
isowall in the local isowall/bin directory.This should also work on Windows, Mac OS X, xBSD, and pretty much any operating system that supports
libpcap.Running
First, setup a machine with three network interfaces.
The first network interface (like
eth0) will be configured as normal, with a TCP/IP stack, so that you can SSH to it.The other two network interfaces should have no TCP/IP stack, no IP address, no anything. This is the most important configuration step, and the most common thing you'll get wrong. For example, the DHCP software on the box may be configured to automatically send out DHCP requests on these additional interfaces. You have to go fix that so nothing is bound to these interfaces.
To run, simply type:
# ./bin/isowall --internal eth1 --external eth2 -c xxxx.confwhere
xxxx.conf contains your configuration, which is described below.Configuration
The following shows a typical configuration file.
internal = eth1
internal.target.ip = 10.0.0.129
internal.target.mac = 02:60:8c:37:87:f3
external = eth2
external.router.ip = 10.0.0.1
external.router.mac = 66:55:44:33:22:11
allow = 0.0.0.0/0
block = 192.168.0.0/16
block = 10.0.0.0/8
block = 224.0.0.0-255.255.255.255The target device we are isolating has the indicated IP and MAC address.
Only IPv4 and ARP packets are passed.
Outbound packets must have the following conditions:
- source MAC address equal to
internal.target.mac - destination MAC address equal to
external.router.mac - EtherType of 0x800 or 0x806
- source IPv4 address equal to
internal.target.ip - destination IPv4 address within an
allowrange, but not in ablockrange - if an ARP packet, then the destination IPv4 address must equal that
external.router.ip - if an ARP packet, must be a "request"
Inbound packets must have the following conditions:
- destination MAC address equal to
internal.target.mac - source MAC address equal to
external.router.mac - EtherType of 0x800 or 0x806
- destination IPv4 address equal to
internal.target.ip - source IPv4 address within an
allowrange, but not in ablockrange - if an ARP packet, then the source IPv4 address must equal that
external.router.ip - if an ARP packet, then must be a "reply"