XORpass - An encoder to bypass WAF

 


XORpass is an encoder to bypass WAF filters using XOR operations.

Installation & Usage

git clone https://github.com/devploit/XORpass

cd XORpass

$ python3 xorpass.py -h

Example of bypass: 
Using clear PHP function:

Using XOR bypass of that function:
$ python3 xorpass.py -e "system(ls)"

Why does PHP treat our payload as a string?

The ^ is the exclusive or operator, which means that we're in reality working with binary values. So let's break down what happens.

The XOR operator on binary values will return 1 where just one of the bits were 1, otherwise it returns 0 (0^0 = 0, 0^1 = 1, 1^0 = 1, 1^1 = 0). When you use XOR on characters, you're using their ASCII values. These ASCII values are integers, so we need to convert those to binary to see what's actually going on.
A = 65 = 1000001
S = 83 = 1010011
B = 66 = 1000010

A       1000001
        ^
S       1010011
        ^
B       1000010
----------------
result  1010000 = 80 = P

A^S^B = P

If we do an 'echo "A"^"S"^"B";' PHP will return us a P as we see.