DIY Data Diode

Simple DIY gigabit data diode (hardware and software). Presented at SEC-T 2021.

Hardware

By doing a simple hardware mod to a fiber converter you can build your own data diode for around €60. See the /hardware folder for modding instructions

Software

PoC golang code for reliable file transfers over a data diode. With recommended OS optimizations it should reach 750+ Mbit/s file transfers.

Build instructions

With local golang available

# apt install golang
cd src && go build -o ../bin/godiode . ; cd .. 

With golang in docker

# apt install golang
docker-compose run --rm build

The built binary will end up in ./bin/godiode

Running

Usage

Usage: godiode 
   
     send|receive 
   
   
  -baddr string
    	bind address
  -bw int
    	throttle bw to X Mbit/s (sender only)
  -conf string
    	JSON config file (default "/etc/godiode.json")
  -delete
    	delete files (receiver only)
  -interface string
    	interface to bind to
  -maddr string
    	multicast address (default "239.252.28.12:5432")
  -packetsize int
    	maximum UDP payload size (default 1472)
  -secret string
    	HMAC secret
  -tmpdir string
    	tmp dir to use (receiver only)
  -verbose
    	verbose output

  

Receiver

Replace eth0 with nic connected to diode, received data will end up in ./in

mkdir -p in/ && ./bin/godiode --verbose --interface eth0 receive in/

Or using docker...

docker-compose run --rm godiode --verbose --interface eth0 receive /in

Sender

Place folder structure to transfer under ./out and replace IP with whatever you assigned the nic connected to the diode.

mkdir -p out && ./bin/godiode --verbose --baddr 10.72.0.1:1234 send out/

Or using docker...

docker-compose run --rm godiode --verbose --baddr 10.72.0.1:1234 send /out

Optimize for speed

Use jumbo frames

For optimal performance it's recommended to use jumbo frames. Enable on your interfaces (both sender and receiver):

# replace eth0 with nic connected to diode
sudo ip link set mtu 9000 eth0

Instruct sender/receiver to use larger packets with maxpacket-flag to godiode

godiode --packetsize 8972 send /out

Increase send/receive buffers

Receiver will try and allocate a receive buffer of 300xPacketsize, so with jumbo frames the net.core.rm_max should be set to at least 2700000 in either /etc/sysctl.conf or manually with

sudo sysctl net.core.rmem_max=2700000