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문제
<?php
include "../../config.php";
if($_GET['view_source']) view_source();
if(!$_COOKIE['user']){
$val_id="guest";
$val_pw="123qwe";
for($i=0;$i<20;$i++){
$val_id=base64_encode($val_id);
$val_pw=base64_encode($val_pw);
}
$val_id=str_replace("1","!",$val_id);
$val_id=str_replace("2","@",$val_id);
$val_id=str_replace("3","$",$val_id);
$val_id=str_replace("4","^",$val_id);
$val_id=str_replace("5","&",$val_id);
$val_id=str_replace("6","*",$val_id);
$val_id=str_replace("7","(",$val_id);
$val_id=str_replace("8",")",$val_id);
$val_pw=str_replace("1","!",$val_pw);
$val_pw=str_replace("2","@",$val_pw);
$val_pw=str_replace("3","$",$val_pw);
$val_pw=str_replace("4","^",$val_pw);
$val_pw=str_replace("5","&",$val_pw);
$val_pw=str_replace("6","*",$val_pw);
$val_pw=str_replace("7","(",$val_pw);
$val_pw=str_replace("8",")",$val_pw);
Setcookie("user",$val_id,time()+86400,"/challenge/web-06/");
Setcookie("password",$val_pw,time()+86400,"/challenge/web-06/");
echo("<meta http-equiv=refresh content=0>");
exit;
}
?>
<html>
<head>
<title>Challenge 6</title>
<style type="text/css">
body { background:black; color:white; font-size:10pt; }
</style>
</head>
<body>
<?php
$decode_id=$_COOKIE['user'];
$decode_pw=$_COOKIE['password'];
$decode_id=str_replace("!","1",$decode_id);
$decode_id=str_replace("@","2",$decode_id);
$decode_id=str_replace("$","3",$decode_id);
$decode_id=str_replace("^","4",$decode_id);
$decode_id=str_replace("&","5",$decode_id);
$decode_id=str_replace("*","6",$decode_id);
$decode_id=str_replace("(","7",$decode_id);
$decode_id=str_replace(")","8",$decode_id);
$decode_pw=str_replace("!","1",$decode_pw);
$decode_pw=str_replace("@","2",$decode_pw);
$decode_pw=str_replace("$","3",$decode_pw);
$decode_pw=str_replace("^","4",$decode_pw);
$decode_pw=str_replace("&","5",$decode_pw);
$decode_pw=str_replace("*","6",$decode_pw);
$decode_pw=str_replace("(","7",$decode_pw);
$decode_pw=str_replace(")","8",$decode_pw);
for($i=0;$i<20;$i++){
$decode_id=base64_decode($decode_id);
$decode_pw=base64_decode($decode_pw);
}
echo("<hr><a href=./?view_source=1 style=color:yellow;>view-source</a><br><br>");
echo("ID : $decode_id<br>PW : $decode_pw<hr>");
if($decode_id=="admin" && $decode_pw=="nimda"){
solve(6);
}
?>
</body>
</html>
문제풀이
guest/123qwe를 base64암호화, str_replace함수를 거쳐 user, password 쿠키값으로 설정된다.
이를 다시 str_replace함수, 복호화를 하여 화면에 출력해주는데, 이 때 admin/nimda이면 문제가 해결된다.
admin/nimda를 위 암호화 과정을 거쳐 쿠키로 설정해주면 된다.
- php 코드
<?php
$val_id="admin";
$val_pw="nimda";
for($i=0;$i<20;$i++){
$val_id=base64_encode($val_id);
$val_pw=base64_encode($val_pw);
}
$val_id=str_replace("1","!",$val_id);
$val_id=str_replace("2","@",$val_id);
$val_id=str_replace("3","$",$val_id);
$val_id=str_replace("4","^",$val_id);
$val_id=str_replace("5","&",$val_id);
$val_id=str_replace("6","*",$val_id);
$val_id=str_replace("7","(",$val_id);
$val_id=str_replace("8",")",$val_id);
$val_pw=str_replace("1","!",$val_pw);
$val_pw=str_replace("2","@",$val_pw);
$val_pw=str_replace("3","$",$val_pw);
$val_pw=str_replace("4","^",$val_pw);
$val_pw=str_replace("5","&",$val_pw);
$val_pw=str_replace("6","*",$val_pw);
$val_pw=str_replace("7","(",$val_pw);
$val_pw=str_replace("8",")",$val_pw);
echo($val_id."\n".$val_pw);
?>
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