Convert Active Directory SID to string

def convert_sid_tostring(sid_str):
    """
    将SID转换成正常的字符串，形如：S-1-5-21-3146574646-1373620345-747391786-4398
    :param sid_str: AD返回的SID
    :return: str
    """
    sid_bytes = list(bytearray(sid_str))
    sid_str = list(sid_str)
    sid = 'S-%d' % sid_bytes[0]
    if sid_bytes[6] != 0 or sid_bytes[5] != 0:
        raise Exception('AD的认证方式无法识别')
    else:
        ival = sid_bytes[1] + (sid_bytes[2] << 8) + (sid_bytes[3] << 16) + (sid_bytes[4] << 24)
        sid = sid + '-' + str(ival)
        print sid
    iSubCount = sid_bytes[7]
    for i in range(iSubCount):
        idxAuth = 8 + i * 4
        end = idxAuth + 4
        temp = sid_str[idxAuth:end]
        q = ''.join(temp)
        iSubAuth = struct.unpack('I', q)
        sid = sid + '-' + str(iSubAuth[0])
    return sid