Hitman INI Decryptor

import os
import struct
import sys

def rol1(n, d):
    return ((n << d)|(n >> (8 - d))) & 0xFF

def ror1(n, d):
    return ((n >> d)|(n << (8 - d))) & 0xFF

def rol4(n, d):
    return ((n << d)|(n >> (32 - d))) & 0xFFFFFFFF

def ror4(n, d):
    return ((n >> d)|(n << (32 - d))) & 0xFFFFFFFF

hdr=b"[Scrambled]\r\n"
hdrsize=len(hdr)

def encryptIni(fname):
    name,ext=os.path.splitext(fname)
    f=open(fname,"rb")
    decdata=f.read()
    f.close()

    checksum=0x0E10F732F
    for i in range(len(decdata)):
        checksum=decdata[i]^rol4(checksum,13)

    encdata=bytearray()
    encdata+=hdr
    key=0x0DE60ED55

    for i in range(len(decdata)):
        ch=decdata[i]
        encch=rol1(ch,3)^(key&0xFF)
        key=rol4(key,5)^encch
        encdata.append(encch)

    encdata+=struct.pack("<I",checksum)
    f=open(name+".scrambled"+ext,"wb")
    f.write(encdata)
    f.close()

def decryptIni(fname):
    name,ext=os.path.splitext(fname)
    f=open(fname,"rb")
    encdata=f.read()
    f.close()

    if not encdata.startswith(hdr):
        raise Exception("Bad scrambled ini header")

    decdata=bytearray()
    textsize=len(encdata)-hdrsize-4
    key=0x0DE60ED55

    for i in range(textsize):
        encch=encdata[hdrsize+i]
        ch=ror1(encch^(key&0xFF),3)
        key=rol4(key,5)^encch
        decdata.append(ch)

    checksum=0x0E10F732F
    for i in range(textsize):
        checksum=decdata[i]^rol4(checksum,13)

    srcChecksum=struct.unpack("<I",encdata[hdrsize+textsize:])[0]
    if checksum!=srcChecksum:
        raise Exception("Checksum mismatch, scrambled ini is corrupted")

    f=open(name+".unscrambled"+ext,"wb")
    f.write(decdata)
    f.close()

if __name__=="__main__":
    fname=sys.argv[1]
    f=open(fname,"rb")
    data=f.read(hdrsize)
    f.close()

    if data.startswith(hdr):
        decryptIni(fname)
    else:
        encryptIni(fname)