#!/usr/bin/env python

"""
Copyright (c) 2006-2016 sqlmap developers (http://sqlmap.org/)
See the file 'doc/COPYING' for copying permission
"""

from lib.core.common import Backend
from lib.core.common import randomInt
from lib.core.data import conf
from lib.core.data import kb
from lib.core.data import logger
from lib.core.dicts import FROM_DUMMY_TABLE
from lib.core.exception import SqlmapNotVulnerableException
from lib.techniques.dns.use import dnsUse


def dnsTest(payload):
    logger.info("testing for data retrieval through DNS channel")

    randInt = randomInt()
    kb.dnsTest = dnsUse(payload, "SELECT %d%s" % (randInt, FROM_DUMMY_TABLE.get(Backend.getIdentifiedDbms(), ""))) == str(randInt)

    if not kb.dnsTest:
        errMsg = "data retrieval through DNS channel failed"
        if not conf.forceDns:
            conf.dnsName = None
            errMsg += ". Turning off DNS exfiltration support"
            logger.error(errMsg)
        else:
            raise SqlmapNotVulnerableException(errMsg)
    else:
        infoMsg = "data retrieval through DNS channel was successful"
        logger.info(infoMsg)
