[webhacking.kr] Challenge(Old) old-06 풀이

https://webhacking.kr/challenge/web-06/

https://webhacking.kr/challenge/web-06/

 

문제 페이지에 접속해보면 아래와 같이 게스트의 id/pw 정보가 뜬다.

소스코드의 일부를 보면 아래와 같다.

<?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;
}
?>

user 쿠기 값이 존재하지 않으면, guest 정보를 base64로 20번 인코딩해준 후, 특정 문자열을 변경시켜준다.

 

<?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);
}
?>

user, password 쿠키 값을 인코딩 한 것의 반대 순서로 디코딩해주고, 그 값이 admin, nimda면 문제를 해결할 수 있다.

 

파이썬으로 admin과 nimda에 대하여 주어진 조건에 맞게 base64 인코딩을 적용시켜보자.

import base64

def replace(string):
    string = string.replace('1', '!')
    string = string.replace('2', '@')
    string = string.replace('3', '$')
    string = string.replace('4', '^')
    string = string.replace('5', '&')
    string = string.replace('6', '*')
    string = string.replace('7', '(')
    string = string.replace('8', ')')
    return string
            
user = 'admin'
user_bytes = user.encode('ascii')
user_base64 = base64.b64encode(user_bytes)
for i in range(19):
    user_base64 = base64.b64encode(user_base64)
user_base64_str = user_base64.decode('ascii')
user_base64_str = replace(user_base64_str)
print(user_base64_str)
print()

pw = 'nimda'
pw_bytes = pw.encode('ascii')
pw_base64 = base64.b64encode(pw_bytes)
for i in range(19):
    pw_base64 = base64.b64encode(pw_base64)
pw_base64_str = pw_base64.decode('ascii')
pw_base64_str = replace(pw_base64_str)
print(pw_base64_str)

 

결과는 아래 접은 글 속에 적어두었다. 아래 내용을 user 및 password 쿠키 값에 각각 집어 넣으면 문제를 해결할 수 있다.

user
Vm0wd@QyUXlVWGxWV0d^V!YwZDRWMVl$WkRSV0!WbDNXa!JTVjAxV@JETlhhMUpUVmpBeFYySkVUbGhoTVVwVVZtcEJlRll&U@tWVWJHaG9UVlZ$VlZadGNFSmxSbGw!VTJ0V!ZXSkhhRzlVVmxaM!ZsWmFjVkZ0UmxSTmJFcEpWbTEwYTFkSFNrZGpSVGxhVmpOU!IxcFZXbUZrUjA!R!UyMTRVMkpIZHpGV!ZFb$dWakZhV0ZOcmFHaFNlbXhXVm!wT!QwMHhjRlpYYlVaclVqQTFSMWRyV@&kV0!ERkZVbFJHVjFaRmIzZFdha!poVjBaT@NtRkhhRk&sYlhoWFZtMXdUMVF$TUhoalJscFlZbGhTV0ZSV@FFTlNiRnBZWlVaT!ZXSlZXVEpWYkZKRFZqQXhkVlZ!V@xaaGExcFlXa!ZhVDJOc@NFZGhSMnhUVFcxb@IxWXhaREJaVmxsM!RVaG9hbEpzY0ZsWmJGWmhZMnhXY!ZGVVJsTk&WMUo!VmpKNFQxWlhTbFpYVkVwV!lrWktTRlpxUm!GU@JVbDZXa!prYUdFeGNHOVdha0poVkRKT@RGSnJhR@hTYXpWeldXeG9iMWRHV@&STldHUlZUVlpHTTFSVmFHOWhiRXB*WTBac!dtSkdXbWhaTVZwaFpFZFNTRkpyTlZOaVJtOTNWMnhXWVZReFdsaFRiRnBZVmtWd!YxbHJXa$RUUmxweFVtMUdVMkpWYkRaWGExcHJZVWRGZUdOSE9WZGhhMHBvVmtSS!QyUkdTbkpoUjJoVFlYcFdlbGRYZUc&aU!XUkhWMjVTVGxOSGFGQlZiVEUwVmpGU!ZtRkhPVmhTTUhCNVZHeGFjMWR0U@tkWGJXaGFUVzVvV0ZreFdrZFdWa$B*VkdzMVYySkdhM@hXYTFwaFZURlZlRmR!U@s!WFJYQnhWVzB^YjFZeFVsaE9WazVPVFZad@VGVXlkREJXTVZweVkwWndXR0V^Y0ROV@FrWkxWakpPU!dKR!pGZFNWWEJ@Vm!0U!MxUXlUWGxVYTFwb!VqTkNWRmxZY0ZkWFZscFlZMFU!YVUxcmJEUldNalZUVkd^a!NGVnNXbFZXYkhCWVZHdGFWbVZIUmtoUFYyaHBVbGhDTmxkVVFtRmpNV!IwVTJ0a!dHSlhhR0ZVVnpWdlYwWnJlRmRyWkZkV@EzQjZWa@R*TVZZd0!WWmlla!pYWWxoQ!RGUnJXbEpsUm!SellVWlNhVkp!UW&oV!YzaHJWVEZzVjFWc!dsaGlWVnBQVkZaYWQyVkdWWGxrUkVKWFRWWndlVmt$V@&kWFIwVjRZMFJPV@!FeVVrZGFWM@hIWTIxS!IxcEhiRmhTVlhCS!ZtMTBVMU!^VlhoWFdHaFlZbXhhVjFsc!pHOVdSbXhaWTBaa@JHSkhVbGxhVldNMVlWVXhXRlZyYUZkTmFsWlVWa@Q0YTFOR!ZuTlhiRlpYWWtoQ!NWWkdVa@RWTVZwMFVtdG9VRll&YUhCVmJHaERUbXhrVlZGdFJtcE&WMUl$VlRKMGExZEhTbGhoUjBaVlZucFdkbFl$V@&OT@JFcHpXa@R$YVZORlNrbFdNblJyWXpGVmVWTnVTbFJpVlZwWVZGYzFiMWRHWkZkWGJFcHNVbTFTZWxsVldsTmhWa$AxVVd^d!YySllVbGhhUkVaYVpVZEtTVk&zYUdoTk!VcFZWbGN^TkdReVZrZFdiR!JvVW&wc@IxUldXbmRsYkZsNVkwVmtWMDFFUmpGWlZXaExWMnhhV0ZWclpHRldNMmhJV!RJeFMxSXhjRWhpUm!oVFZsaENTMVp0TVRCVk!VMTRWbGhvV0ZkSGFGbFpiWGhoVm!^c@NscEhPV$BTYkhCNFZrY$dOVll^V@&OalJXaFlWa!UxZGxsV!ZYaFhSbFp&WVVaa!RtRnNXbFZXYTJRMFdWWktjMVJ!VG!oU@JGcFlXV$hhUm!ReFduRlJiVVphVm0xU!NWWlhkRzloTVVwMFlVWlNWVlpXY0dGVVZscGhZekZ$UlZWdGNFNVdNVWwzVmxSS0!HRXhaRWhUYkdob!VqQmFWbFp0ZUhkTk!WcHlWMjFHYWxacmNEQmFSV!F$VmpKS@NsTnJhRmRTTTJob!ZrUktSMVl^VG&WVmJFSlhVbFJXV!ZaR!l*RmlNV!JIWWtaV!VsZEhhRlJVVm!SVFpXeHNWbGRzVG!oU!ZFWjZWVEkxYjFZeFdYcFZiR@hZVm!^d!lWcFZXbXRrVmtwelZtMXNWMUl*YURWV0!XUXdXVmRSZVZaclpGZGliRXB&Vld0V!MySXhiRmxqUldSc!ZteEtlbFp0TURWWFIwcEhZMFpvV@sxSGFFeFdNbmhoVjBaV@NscEhSbGROTW!oSlYxUkplRk!^U!hoalJXUmhVbXMxV0ZZd!ZrdE&iRnAwWTBWa!dsWXdWalJXYkdodlYwWmtTR0ZHV@xwaVdHaG9WbTE0YzJOc!pISmtSM0JUWWtad0&GWlhNVEJOUmxsNFYyNU9hbEpYYUZoV@FrNVRWRVpzVlZGWWFGTldhM0I@VmtkNFlWVXlTa!pYV0hCWFZsWndSMVF^V@tOVmJFSlZUVVF$UFE9PQ==

password
Vm0wd@QyUXlVWGxWV0d^V!YwZDRWMVl$WkRSV0!WbDNXa!JTVjAxV@JETlhhMUpUVmpBeFYySkVUbGhoTVVwVVZtcEJlRll&U@tWVWJHaG9UVlZ$VlZacVFtRlRNbEpJVm!0a!dHSkdjRTlaVjNSR!pVWmFkR0&GU@!^U@JHdzFWVEowVjFaWFNraGhSemxWVmpOT00xcFZXbUZrUjA!R!drWndWMDFFUlRGV!ZFb$dWakZhV0ZOcmFHaFNlbXhXVm0xNFlVMHhXbk&YYlVaclVqQTFSMWRyV@xOVWJVcEdZMFZ$VjJKVVJYZFdha!pYWkVaT@MxZHNhR@xTTW!oWlYxZDRiMkl&Vm&OVmJGWlRZbFZhY@xWcVFURlNNVlY!VFZSU!ZrMXJjRWxhU0hCSFZqRmFSbUl*WkZkaGExcG9WakJhVDJOdFJraGhSazVzWWxob!dGWnRNSGhPUm!^V!RVaG9XR0pyTlZsWmJGWmhZMVphZEdSSFJrNVNiRm9$V@xWYVQxWlhTbFpqUldSYVRVWmFNMVpxU@t0V!ZrcFpXa!p$VjFKV@NIbFdWRUpoVkRKT@MyTkZhR$BTYXpWWVZXcE9iMkl^V@&STldHUlZUVlpXTkZVeGFHOWhiRXB*WTBac!dtSkdXbWhaTW&oWFkxWkdWVkpzVGs!WFJVcElWbXBLTkZReFdsaFRhMlJxVW0xNGFGVXdhRU&UUmxweFVtMUdVMkpWYkRaWGExcHJZVWRGZUdOSE9WZGhhMHBvVmtSS!QyUkdTbkpoUjJoVFlYcFdlbGRYZUc&aU!XUkhWMjVTVGxOSGFGQlZiVEUwVmpGU!ZtRkhPVmhTTUhCNVZHeGFjMWR0U@tkWGJXaGFUVzVvV0ZreFdrZFdWa$B*VkdzMVYySkdhM@hXYTFwaFZURlZlRmR!U@s!WFJYQnhWVzB^YjFZeFVsaE9WazVPVFZad@VGVXlkREJXTVZweVkwWndXR0V^Y0ROV@FrWkxWakpPU!dKR!pGZFNWWEJ@Vm!0U!MxUXlUWGxVYTFwb!VqTkNWRmxZY0ZkWFZscFlZMFU!YVUxcmJEUldNV@h@V!ZaS!IxTnNaRlZXYkZwNlZHeGFZVmRGTlZaUFZtaFRUVWhDU@xac!pEUmpNV!IwVTJ0b@FGSnNTbGhVVlZwM!ZrWmFjVk&yWkZOaVJrcDZWa@N^YzFVeVNuSlRiVVpYVFc!b!dGbHFTa!psUm!SWldrVTFWMVpzY0ZWWFZsSkhaREZaZUdKSVNsaGhNMUpVVlcxNGQyVkdWbGRoUnpsb!RWWndlbFl&Y0VkV0!ERjFZVWhLV@xaWFVrZGFWM@hIWTIxS!IyRkdhRlJTVlhCS!ZtMTBVMU!^VlhoWFdHaFlZbXhhVjFsc!pHOVdSbXhaWTBaa@JHSkhVbGxhVldNMVlWVXhXRlZyYUZkTmFsWlVWa@Q0YTFOR!ZuTlhiRlpYWWtoQ!NWWkdVa@RWTVZwMFVtdG9VRll&YUhCVmJHaERUbXhrVlZGdFJtcE&WMUl$VlRKMGExZEhTbGhoUjBaVlZucFdkbFl$V@&KbFJtUnlXa!prVjJFelFqWldhMlI@VFZaWmQwMVdXbWxsYTFwWVdXeG9RMVJHVW&KWGJFcHNVbTFTZWxsVldsTmhWa$AxVVd^d!YySllVbGhhUkVaYVpVZEtTVk&zYUdoTk!VcFdWbGN^TkdReVZrZFdXR$hyVWpCYWNGVnRlSGRsYkZsNVpVaGtXRkl$VmpSWk!GSlBWMjFGZVZWclpHRldNMmhJV!RJeFMxSXhjRWhpUm!oVFZsaENTMVp0TVRCVk!VMTRWbGhvV0ZkSGFGbFpiWGhoVm!^c@NscEhPV$BTYkhCNFZrY$dOVll^V@&OalJXaFlWa!UxZGxsV!ZYaFhSbFp&WVVaa!RtRnNXbFZXYTJRMFdWWktjMVJ!VG!oU@JGcFlXV$hhUm!ReFduRlJiVVphVm0xU!NWWlhkRzloTVVwMFlVWlNWVlpXY0dGVVZscGhZekZ$UlZWdGNFNVdNVWwzVmxSS0!HRXhaRWhUYkdob!VqQmFWbFp0ZUhkTk!WcHlWMjFHYWxacmNEQmFSV!F$VmpKS@NsTnJhRmRTTTJob!ZrUktSMVl^VG&WVmJFSlhVbFJXV!ZaR!l*RmlNV!JIWWtaV!VsZEhhRlJVVm!SVFpXeHNWbGRzVG!oU!ZFWjZWVEkxYjFZeFdYcFZiR@hZVm!^d!lWcFZXbXRrVmtwelZtMXNWMUl*YURWV0!XUXdXVmRSZVZaclpGZGliRXB&Vld0V!MySXhiRmxqUldSc!ZteEtlbFp0TURWWFIwcEhZMFpvV@sxSGFFeFdNbmhoVjBaV@NscEhSbGROTW!oSlYxUkplRk!^U!hoalJXUmhVbXMxV0ZZd!ZrdE&iRnAwWTBWa!dsWXdWalJXYkdodlYwWmtTR0ZHV@xwaVdHaG9WbTE0YzJOc!pISmtSM0JUWWtad0&GWlhNVEJOUmxsNFYyNU9hbEpYYUZoV@FrNVRWRVpzVlZGWWFGTldhM0I@VmtkNFlWVXlTa!pYV0hCWFZsWndSMVF^V@tOVmJFSlZUVVF$UFE9PQ==

 

 

참고 자료

파이썬 base64

https://webisfree.com/2020-11-07/python-base64-%EC%9D%B8%EC%BD%94%EB%94%A9-%EB%94%94%EC%BD%94%EB%94%A9-%EB%B3%80%ED%99%98-%EB%B0%A9%EB%B2%95

 

php str_replace()

https://webcooker.tistory.com/22

 

파이썬 replace()

https://ponyozzang.tistory.com/334