python 'decode' has no attribute shellcode

Question

I am trying to convert this script from python2 to python3.

I am running into a problem with this line:

# need to code the input into the right format through string escape
shellcode = shellcode.decode("string_escape")

This 'shellcode' gets converted into a bytearray in the next line(or should):

shellcode = bytearray(shellcode)

However, I run into the error of:

AttributeError: 'str' object has no attribute 'decode'.

"shellcode" equals:

shellcode = sys.argv[1]

shellcode should be equal to something like "\x31\xd2\xb2\x30\" and the rest of the script executes the shellcode.

Thanks(this script runs perfect in python2.7).

Answer 1

In python3 sys.argv[1] would be a str (unicode, in python2) so there's nothing to decode.

A simple test - arg_type.py:

import sys
shellcode = sys.argv[1]
print(type(shellcode))

Run in python3 and python 2

$ python3.4 arg_type.py 'é'
<class 'str'>

$ python2.7 arg_type.py 'é'
<type 'str'>

Note that in the python2.7 str is really a bytearray, which you'd need to decode into unicode.

This is one of the ways in which python3 is so much more sensible by default.