<?php
define("SYSTEMKEY", "qfe78dsd3§%sd"); // your secret password
define("USE_DYNAMIC_PATTERN", true); // use dynamically build date patterns
/**
* Checksum
*
* @author Thomas Schäfer
* @desc time limited checksum builder
* @example
*
* # build
* // injected unlimited number of parameter arguments as string or integer
* $checksumToLink = Checksum:: build ("YourFirstParameter"," YourSecondParameter"); // sample output aeeb0da600ab1d9934f1f065498c7497479cbd12
* output view link:
* <a href="http://www.your-domain.de/index.php?a=YourFirstParameter&b=YourSecondParameter&csm=$checksumToLink"></a>
*
* incoming request (e.g.):
* $url = parse_url($_SERVER["REQUEST_URI"]);
* parse_str($url["query"], $query);
*
* # proof
* // inject the same number of parameter arguments as above with
* // leading checksum string
* $boolProof = Checksum::proof($query["csm"],$query["a"],$query["b"]);
*
* if($boolProof) echo "valid";
* else echo "invalid";
*
* features:
* - build
* - proof
* - setTimestamp(date)
* - setValidTimeRange (seconds)
* - setValidTimeRangeInDays (days)
* - isValidFromTo (date, date)
*
*/
class Checksum
{
/**
* @const time shift constant in seconds for valid checksum
* desc should correspond with session validation time
*/
const DYN_PATTERN = USE_DYNAMIC_PATTERN; // true = dynamically build, false = individual pattern array
private static $iCounter = 0;
private static $strTimestamp = null;
private static $strTimestampTo = null;
private static $validTimeRange = 3600; // one hour valid
/**
* checksum
* @desc build query checksum
* @return string new checksum
*/
public static function build()
{
$argCounter = func_num_args();
if ($argCounter == 0)
{
throw new Exception("You need to define some string parameters for being able to build a checksum");
}
self::$iCounter = $argCounter;
$arguments = func_get_args();
$string = call_user_func(array (
"self",
"getRawKeyString"
),
$arguments
);
$time = self::getRawKeyTime();
// value key
$key = self::keyPattern($string, $time);
return implode("", $key);
}
/**
* proof
* @desc proof checksum on string and time parts
* @param string reference referencing checksum
* @return bool
*/
public static function proof()
{
// checks
$isValidChecksum = false;
$isValidString = false;
$isValidTime = false;
$reference_checksum = null;
if (func_num_args() <= 1)
{
throw new Exception("You need to define more then a single parameters");
}
$internal_arguments = array ();
$arguments = func_get_args();
foreach ($arguments as $argument)
{
if (preg_match('/[a-z0-9]{32}/', $argument))
{
$reference_checksum = $argument;
}
else
{
$internal_arguments[] = $argument;
}
}
// new values
$string = call_user_func(array (
"self",
"getRawKeyString"
),
$internal_arguments
);
$time = self::getRawKeyTime(); // time part
// new value key
$keyPattern = self::keyPattern($string, $time);
// old values
$timeParts = self::getTimeParts(); // positions of time parts (8,9)
$stringReference = str_split($reference_checksum, 4);
$timeReference = $stringReference[$timeParts[8]] . $stringReference[$timeParts[9]]; //
$decodedTime = hexdec($timeReference);
// begin validate time range
$referingTime = time();
if(
!empty(Checksum::$strTimestamp) and
!empty(Checksum::$strTimestampTo) and
$referingTime >= Checksum::$strTimestamp and
$referingTime <= Checksum::$strTimestampTo
) {
$isValidTime = true;
} elseif(empty($isValidTime) and $referingTime - Checksum::$validTimeRange < $decodedTime){
$isValidTime = true;
}
// end validate time range
// check parts of old and new string value
$isValidString = Checksum::validate($string, $time, $keyPattern, $stringReference);
// check secondary conditions
if ($isValidString and $isValidTime)
{
$isValidChecksum = true; // set primary condition => checksum is valid
}
return $isValidChecksum;
}
/**
* setTimestamp
* @param integer $timestamp
* @desc change the timestamp
*/
public static function setTimestamp($timestamp)
{
if (is_string($timestamp)){
self::$strTimestamp = strtotime($timestamp);
} else {
throw new Exception("Timestamp has to be of type string, a valid date format which can be converted to unix time.");
}
}
/**
* specify individual ranges
* @param integer $validTimeRange
*/
public static function setValidTimeRange($validTimeRange = null)
{
if (is_integer($validTimeRange) and $validTimeRange > -1) {
self::$validTimeRange = $validTimeRange;
} else {
throw new Exception("Range has to be of type integer and greater than -1.");
}
}
/**
* setValidTimeRangeInDays
* @param integer $validDays
*/
public static function setValidTimeRangeInDays($validDays = null)
{
selfValidTimeRange(3600*24*$validDays);
}
/**
* isValidFromTo
* @param string $dateFrom a valid timestamp, e.g.: 2009-01-01
* @param string $dateTo a valid timestamp, e.g.: 2009-02-01
*/
public static function isValidFromTo($dateFrom = null, $dateTo = null)
{
if (is_string($dateFrom) and is_string($dateTo))
{
$df = strtotime($dateFrom);
$dt = strtotime($dateTo);
if($dt>$df) {
self::$strTimestamp = strtotime($dateFrom);
self::$strTimestampTo = strtotime($dateTo);
} else {
throw new Exception("DateTo has to be greater than DateFrom");
}
}
else
{
throw new Exception("Range has to be of type integer and greater than -1.");
}
}
/**
* getRawKeyTime
* @desc splits hex time string into parts
* @return array
*/
private static function getRawKeyTime()
{
if (!empty (self::$strTimestamp))
{
return str_split(dechex(self::$strTimestamp), 4);
}
else
{
return str_split(dechex(time()), 4);
}
}
/**
* getRawKeyString
* @desc creates hash (system key added) and splits md5 string into parts
* @return array
*/
private static function getRawKeyString()
{
$strRawKey = "";
if (func_num_args() > 0)
{
$arguments = func_get_args();
foreach ($arguments[0] as $argument)
{
$strRawKey .= $argument;
}
}
else
{
throw Exception("No parameters had been injected.");
}
$strRawKey .= SYSTEMKEY;
$string = str_split(md5($strRawKey), 4);
return $string;
}
/**
* drawPatternByDay
* @desc returns pattern orders for each day
* @param integer $indexDayPattern
* @return array
*/
private static function drawPatternByDay($indexDayPattern)
{
switch (self::DYN_PATTERN)
{
// dynamically build date pattern
case true :
$num = date("Ym");
$t = date("t");
$range = array ();
$arrSort = array ();
$pattern = array ();
for ($i = 1; $i <= $t; $i++)
{
$date = strtotime(date("Ym") . str_pad($i, 2, "0", STR_PAD_LEFT));
$str = str_split(md5($date), 4);
foreach ($str as $index => $val)
{
$range[$i][$index] = $val;
}
$weekday = date("w", $date);
$parts = str_split(md5(strtotime(date("Ym"))), 4);
$range[$i][8] = $str[8] = $parts[$weekday];
$range[$i][9] = $str[9] = $parts[$weekday +1];
sort($str);
$array = array_flip($range[$i]);
foreach ($str as $key => $val)
{
$pattern[$i][$key] = $array[$val];
}
}
return ($pattern[$indexDayPattern -1]);
default :
/*
* positions: 0 - 7 => string parts 8 - 9 => time parts shifting parts
* by reordering range
*/
$patterns = array(
array(0,2,4,6,8,1,3,5,7,9),
array(1,3,5,7,9,2,4,6,8,0),
array(2,4,6,8,0,3,5,7,9,1),
array(3,5,7,9,1,2,4,6,8,0),
array(2,4,6,8,1,3,5,7,9,0),
array(7,9,0,2,4,6,8,1,3,5),
array(1,2,4,6,8,0,3,5,7,9),
array(8,0,3,5,7,1,2,4,6,9),
array(5,7,2,4,6,8,0,3,9,1),
array(6,8,0,3,5,7,2,4,9,1),
array(8,0,3,5,6,7,2,4,9,1),
array(7,2,4,9,8,0,3,5,6,1),
array(2,0,4,6,8,1,3,5,7,9),
array(1,3,7,5,9,2,4,6,8,0),
array(2,4,8,6,0,3,5,7,9,1),
array(3,5,9,7,1,2,4,6,8,0),
array(2,4,6,8,1,5,3,7,9,0),
array(7,9,0,2,6,4,8,1,3,5),
array(1,2,4,6,8,0,5,3,7,9),
array(8,0,3,5,7,1,2,4,6,9),
array(5,7,2,4,6,3,0,8,9,1),
array(6,8,4,3,5,7,2,0,9,1),
array(8,2,3,5,6,7,0,4,9,1),
array(7,2,1,9,5,0,3,8,6,4),
array(5,7,2,4,1,8,0,3,9,6),
array(6,8,9,3,5,2,7,4,0,1),
array(8,0,5,3,6,7,4,2,9,1),
array(4,2,6,0,8,3,5,7,9,1),
array(3,1,5,2,9,7,4,6,8,0),
array(1,2,4,0,8,6,3,5,7,9),
array(0,8,3,5,7,2,1,4,6,9),
);
return ($patterns[$indexDayPattern-1]);
}
}
/**
* keyPattern
* @desc re-orders the key map by pattern
* @param array $string
* @param array $key
* @return array
*/
private static function keyPattern($string, $time)
{
$indexDayPattern = self::drawPatternByDay(date("d"));
$merge = array_merge($string, $time);
$newPatternOrder = array ();
foreach ($indexDayPattern as $index)
{
$newPatternOrder[] = $merge[$index];
}
return $newPatternOrder;
}
/**
* getTimeParts
* @desc returns array of positions of time parts
* return array
*/
private static function getTimeParts()
{
$pattern = self::drawPatternByDay(date("d"));
$timeParts = array ();
foreach ($pattern as $key => $index)
{
switch ($index)
{
// time parts
case 9 :
case 8 :
$timeParts[$index] = $key;
break;
// string parts
default :
break;
}
}
return $timeParts;
}
/**
* validate
* @desc checks against pattern if the checksum is valid
* @param array $string
* @param array $time
* @param array $key new value key
* @param array $stringReference old value key
* return bool
*/
private static function validate($string, $time, $key, $stringReference)
{
$pattern = self::drawPatternByDay(date("d"));
$intCounter = 1;
foreach ($pattern as $index)
{
switch ($index)
{
// time parts
case 9 :
case 8 :
break;
// string parts
default :
if ($key[$index] == $stringReference[$index])
{
$intCounter++;
}
break;
}
}
if ($intCounter >= 7)
{ // all string parts are equal
return true;
}
return false;
}
}
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