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| <?php
namespace ctfshow;
class C{
const __REF_OFFSET_1 = 0x41;
const __REF_OFFSET_2 = 0x7b;
const __REF_OFFSET_3 = 0x5b;
const __REF_OFFSET_4 = 0x60;
const __REF_OFFSET_5 = 0x30;
const __REF_OFFSET_6 = 0x5f;
const __REF_SIZE__= 20;
const __REF_VAL_SIZE__= 50;
private $cursor = 0;
private $cache;
private $ref_table = [];
function main(){
$flag = md5(file_get_contents("/flag"));
$this->define('ctfshow',self::__REF_VAL_SIZE__);
$this->define('flag',strlen($flag));
$this->neaten();
$this->fill('flag',$flag);
$this->fill('ctfshow',$_POST['data']);
if($this->read('ctfshow')===$this->read('flag')){
echo $flag;
}
}
private function fill($ref,$val){
rewind($this->cache);
fseek($this->cache, $this->ref_table[$ref]+23);
$arr = str_split($val);
foreach ($arr as $s) {
fwrite($this->cache, pack("C",ord($s)));
}
for ($i=sizeof($arr); $i < self::__REF_VAL_SIZE__; $i++) {
fwrite($this->cache, pack("C","\x00"));
}
$this->cursor= ftell($this->cache);
}
public static function clear($var){
;
}
private function neaten(){
$this->ref_table['_clear_']=$this->cursor;
$arr = str_split("_clear_");
foreach ($arr as $s) {
$this->write(ord($s),"C");
}
for ($i=sizeof($arr); $i < self::__REF_SIZE__; $i++) {
$this->write("\x00",'C');
}
$arr = str_split(__NAMESPACE__."\C::clear");
foreach ($arr as $s) {
$this->write(ord($s),"C");
}
$this->write(0x36d,'Q');
$this->write(0x30,'C');
for ($i=1; $i < self::__REF_SIZE__; $i++) {
$this->write("\x00",'C');
}
}
private function readNeaten(){
rewind($this->cache);
fseek($this->cache, $this->ref_table['_clear_']+self::__REF_SIZE__);
$f = $this->truncation(fread($this->cache, self::__REF_SIZE__-4));
$t = $this->truncation(fread($this->cache, self::__REF_SIZE__-12));
$p = $this->truncation(fread($this->cache, self::__REF_SIZE__));
call_user_func($f,$p);
}
private function define($ref,$size){
$this->checkRef($ref);
$r = str_split($ref);
$this->ref_table[$ref]=$this->cursor;
foreach ($r as $s) {
$this->write(ord($s),"C");
}
for ($i=sizeof($r); $i < self::__REF_SIZE__; $i++) {
$this->write("\x00",'C');
}
fwrite($this->cache,pack("v",$size));
fwrite($this->cache,pack("C",0x31));
$this->cursor= ftell($this->cache);
for ($i=0; $i < $size; $i++) {
$this->write("\x00",'a');
}
}
private function read($ref){
if(!array_key_exists($ref,$this->ref_table)){
throw new \Exception("Ref not exists!", 1);
}
if($this->ref_table[$ref]!=0){
$this->seekCursor($this->ref_table[$ref]);
}else{
rewind($this->cache);
}
$cref = fread($this->cache, 20);
$csize = unpack("v", fread($this->cache, 2));
$usize = fread($this->cache, 1);
$val = fread($this->cache, $csize[1]);
return $this->truncation($val);
}
private function write($val,$fmt){
$this->seek();
fwrite($this->cache,pack($fmt,$val));
$this->cursor= ftell($this->cache);
}
private function seek(){
rewind($this->cache);
fseek($this->cache, $this->cursor);
}
private function truncation($data){
return implode(array_filter(str_split($data),function($var){
return $var!=="\x00";
}));
}
private function seekCursor($cursor){
rewind($this->cache);
fseek($this->cache, $cursor);
}
private function checkRef($ref){
$r = str_split($ref);
if(sizeof($r)>self::__REF_SIZE__){
throw new \Exception("Refenerce size too long!", 1);
}
if(is_numeric($r[0]) || $this->checkByte($r[0])){
throw new \Exception("Ref invalid!", 1);
}
array_shift($r);
foreach ($r as $s) {
if($this->checkByte($s)){
throw new \Exception("Ref invalid!", 1);
}
}
}
private function checkByte($check){
if(ord($check) <=self::__REF_OFFSET_5 || ord($check) >=self::__REF_OFFSET_2 ){
return true;
}
if(ord($check) >=self::__REF_OFFSET_3 && ord($check) <= self::__REF_OFFSET_4
&& ord($check) !== self::__REF_OFFSET_6){
return true;
}
return false;
}
function __construct(){
$this->cache=fopen("php://memory","wb");
}
public function __destruct(){
$this->readNeaten();
fclose($this->cache);
}
}
highlight_file(__FILE__);
error_reporting(0);
$c = new C;
$c->main();
|