The XOR target enables the user to encrypt TCP and UDP traffic using a very simple xor encryption.
Xor is its own inverse. That is, to undo xor, the same algorithm is applied, so the same action can be used for encoding and decoding.
warning: This is not a real encryption.

1. first install kernel-devel, iptables-devel and etc.
2. To compile the userpace so,

cd userspace;make libxt_XOR.so
cp libxt_XOR.so /lib64/xtables/  # debian/ubuntu is /usr/lib/x86_64-linux-gnu/xtables/

3. To compile the kernel module,

cd kernel;make
insmod xt_XOR.ko

XOR takes one mandatory parameter.

--key '1234' where 1234 is a byte string (As 5f6e == 0x5f, 0x6e). Warning: don't use key of length > 1 with tcp, because tcp is a stream.

To use this target between hosts 1.2.3.4 and 1.2.3.5.

iptables -t mangle -A OUTPUT -d 1.2.3.5 -p udp --dport 1234 -j XOR --key 6142
iptables -t mangle -A INPUT -s 1.2.3.5 -p udp --sport 1234 -j XOR --key 6142

iptables -t mangle -A OUTPUT -d 1.2.3.4 -p udp --sport 1234 -j XOR --key 6142
iptables -t mangle -A INPUT -s 1.2.3.4 -p udp --dport 1234 -j XOR --key 6142

• Support kernel version >= 2.6.32.
• Tested on Centos6.5(2.6.32-431.23.3.el6.x86_64), centos7.2(3.10.0-327.22.2.el7.x86_64) and kernel 4.1.0.
• Tested on Ubuntu18.04(4.15.0-101-generic) and Ubuntu 20.04(5.4.0-29-generic)

This project is under the MIT license. See the LICENSE file for the full license text.