XORpass is an encoder to bypass WAF filters using XOR operations.
Installation & Usage
git clone https://github.com/devploit/XORpass
$ php encode.php STRING
$ php decode.php “XORed STRING”
Example of bypass
Using clear PHP function:
Using XOR bypass of that function:
$ php encode.php system # return A
$ php encode.php ls # return B
payload == A(B)
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 lets 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
result 0010010 = 80 = P
A^S^B = P
If we do an ‘echo “A”^”S”^”B”;’ PHP will return us a P as we see.