[waraxe-2013-SA#103] - Multiple Vulnerabilities in phpMyAdmin =============================================================================== Author: Janek Vind "waraxe" Date: 25. April 2013 Location: Estonia, Tartu Web: http://www.waraxe.us/advisory-103.html Description of vulnerable software: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ phpMyAdmin is a free software tool written in PHP, intended to handle the administration of MySQL over the World Wide Web. phpMyAdmin supports a wide range of operations with MySQL. http://www.phpmyadmin.net/home_page/index.php ############################################################################### 1. Remote code execution via preg_replace() in "libraries/mult_submits.inc.php" ############################################################################### Reason: 1. insufficient sanitization of user data before using in preg_replace Attack vectors: 1. user-supplied parameters "from_prefix" and "to_prefix" Preconditions: 1. logged in as valid PMA user 2. PHP version < 5.4.7 (Newer versions: Warning: preg_replace(): Null byte in regex) PMA security advisory: PMASA-2013-2 CVE id: CVE-2013-3238 Affected phpMyAdmin versions: 3.5.8 and 4.0.0-RC2 Result: PMA user is able to execute arbitrary PHP code on webserver Let's take a look at the source code: Php script "libraries/mult_submits.inc.php" line 426 (PMA version 3.5.8): ------------------------[ source code start ]---------------------------------- case 'replace_prefix_tbl': $current = $selected[$i]; $newtablename = preg_replace("/^" . $from_prefix . "/", $to_prefix, $current); $a_query = 'ALTER TABLE ' . PMA_backquote($selected[$i]) . ' RENAME ' . PMA_backquote($newtablename) ; // CHANGE PREFIX PATTERN $run_parts = true; break; case 'copy_tbl_change_prefix': $current = $selected[$i]; $newtablename = preg_replace("/^" . $from_prefix . "/", $to_prefix, $current); $a_query = 'CREATE TABLE ' . PMA_backquote($newtablename) . ' SELECT * FROM ' . PMA_backquote($selected[$i]) ; // COPY TABLE AND CHANGE PREFIX PATTERN $run_parts = true; break; ------------------------[ source code end ]------------------------------------ We can see, that PHP variables "$from_prefix" and "$to_prefix" are used in preg_replace function without any sanitization. It appears, that those variables are coming from user submitted POST request as parameters "from_prefix" and "to_prefix". It is possible to inject e-modifier with terminating null byte via first parameter and php code via second parameter. In case of successful exploitation injected PHP code will be executed on PMA webserver. Tests: 1. Log in to PMA and select database: http://localhost/PMA/index.php?db=test&token=25a6ce9e288070bd28c3f9aebffad1b8 2. select one table from database by using checkbox and then select "Replace table prefix" from select control "With selected:". 3. We can see form named "Replace table prefix:" with two input fields. Type "/e%00" to the "From" field and "phpinfo()" to the "To" field. 4. Activate Tamper Data Firefox add-on: https://addons.mozilla.org/en-us/firefox/addon/tamper-data/ 5. Click "Submit", Tamper Data pops up, choose "Tamper". 6. Now we can modify POST request. Look for parameter "from_prefix". It should be "%2Fe%2500", remove "25", so that it becomes "%2Fe%00". Click "OK" and Firefox will send out manipulated POST request. 7. We are greeted by phpinfo function output - code execution is confirmed. PMA version 4.0.0-RC2 contains almost identical vulnerability: Php script "libraries/mult_submits.inc.php" line 482 (PMA version 4.0.0-RC2): ------------------------[ source code start ]---------------------------------- case 'replace_prefix_tbl': $current = $selected[$i]; $newtablename = preg_replace("/^" . $_POST['from_prefix'] . "/", $_POST['to_prefix'], $current); $a_query = 'ALTER TABLE ' . PMA_Util::backquote($selected[$i]) . ' RENAME ' . PMA_Util::backquote($newtablename); // CHANGE PREFIX PATTERN $run_parts = true; break; case 'copy_tbl_change_prefix': $current = $selected[$i]; $newtablename = preg_replace("/^" . $_POST['from_prefix'] . "/", $_POST['to_prefix'], $current); $a_query = 'CREATE TABLE ' . PMA_Util::backquote($newtablename) . ' SELECT * FROM ' . PMA_Util::backquote($selected[$i]); // COPY TABLE AND CHANGE PREFIX PATTERN $run_parts = true; break; ------------------------[ source code end ]------------------------------------ ############################################################################ 2. Locally Saved SQL Dump File Multiple File Extension Remote Code Execution ############################################################################ Reason: 1. insecure names of locally saved dump files Attack vectors: 1. user-supplied POST parameter "filename_template" Preconditions: 1. logged in as valid PMA user 2. configuration setting "SaveDir" defined and pointed to directory, which is writable for php and directly accessible over web (by default "SaveDir" is empty and PMA is secure) 3. Apache webserver with unknown MIME for "sql" extension PMA security advisory: PMASA-2013-3 CVE id: CVE-2013-3239 Affected are PMA versions 3.5.8 and 4.0.0-RC2 There is a security weakness in a way, how PMA handles locally saved database dump files. It is possible, that saved dump file has multiple extensions and if Apache webserver does not know MIME type of "sql" extension (that's how it is by default), then for example "foobar.php.sql" file will be treated as php file. More information: http://httpd.apache.org/docs/2.2/mod/mod_mime.html section "Files with Multiple Extensions" http://www.acunetix.com/websitesecurity/upload-forms-threat/ section "Case 4: Double extensions (part 1)" Test: 1. activate export to local server, be sure, that directory is writable: $cfg['SaveDir'] = './'; 2. select database for test, insert row into table with included php code like "<?php phpinfo();?>" 3. try to export that database or table, you have now additional option: "Save on server in the directory ./" Confirm that option, let the format be as "SQL". "File name template" change to "@DATABASE@.php" and click "Go" button. Server responds with "Dump has been saved to file ./test.php.sql." 4. Request created file with webbrowser: http://localhost/PMA/test.php.sql In case of success we can see output of phpinfo() function, which confirms remote code execution. ############################################################################### 3. Local File Inclusion in "export.php" ############################################################################### Reason: 1. insufficient sanitization of user data before using in include_once Attack vectors: 1. user-supplied POST parameter "what" Preconditions: 1. logged in as valid PMA user 2. PHP must be < 5.3.4 for null-byte attacks to work PMA security advisory: PMASA-2013-4 CVE id: CVE-2013-3240 Affected is PMA version 4.0.0-RC2 Php script "export.php" line 20: ------------------------[ source code start ]---------------------------------- foreach ($_POST as $one_post_param => $one_post_value) { $GLOBALS[$one_post_param] = $one_post_value; } PMA_Util::checkParameters(array('what', 'export_type')); // export class instance, not array of properties, as before $export_plugin = PMA_getPlugin( "export", $what, 'libraries/plugins/export/', array( 'export_type' => $export_type, 'single_table' => isset($single_table) ) ); ------------------------[ source code end ]------------------------------------ We can see, that user-supplied parameter "what" is used as second argument for the function PMA_getPlugin(). Let's follow execution flow: Php script "libraries/plugin_interface.lib.php" line 20: ------------------------[ source code start ]---------------------------------- function PMA_getPlugin( $plugin_type, $plugin_format, $plugins_dir, $plugin_param = false ) { $GLOBALS['plugin_param'] = $plugin_param; $class_name = strtoupper($plugin_type[0]) . strtolower(substr($plugin_type, 1)) . strtoupper($plugin_format[0]) . strtolower(substr($plugin_format, 1)); $file = $class_name . ".class.php"; if (is_file($plugins_dir . $file)) { include_once $plugins_dir . $file; ------------------------[ source code end ]------------------------------------ As seen above, second argument "$plugin_format" is used in variable "$file" and after that in functions is_file() and include_once(). No sanitization is used against user submitted parameter "what", which leads to directory traversal and local file inclusion vulnerability. In case of older PHP version it may be possible to use null byte attack and include arbitrary files on server. ############################################################################### 4. $GLOBALS array overwrite in "export.php" ############################################################################### Reason: 1. insecure POST parameters importing Attack vectors: 1. user-supplied POST parameters Preconditions: 1. logged in as valid PMA user PMA security advisory: PMASA-2013-5 CVE id: CVE-2013-3241 Affected is PMA version 4.0.0-RC2 Php script "export.php" line 20: ------------------------[ source code start ]---------------------------------- foreach ($_POST as $one_post_param => $one_post_value) { $GLOBALS[$one_post_param] = $one_post_value; } PMA_Util::checkParameters(array('what', 'export_type')); ------------------------[ source code end ]------------------------------------ We can see, that arbitrary values in $GLOBALS array can be overwritten by submitting POST parameters. Such way of input data importing can be considered as very insecure and in specific situation it is possible to overwrite any variable in global scope. This can lead to many ways of exploitation. Below is presented one of the possibilities. Php script "export.php" line 59: ------------------------[ source code start ]---------------------------------- $onserver = false; $save_on_server = false; .. if ($quick_export) { $onserver = $_REQUEST['quick_export_onserver']; } else { $onserver = $_REQUEST['onserver']; } // Will we save dump on server? $save_on_server = ! empty($cfg['SaveDir']) && $onserver; .. // Open file on server if needed if ($save_on_server) { $save_filename = PMA_Util::userDir($cfg['SaveDir']) . preg_replace('@[/\\\\]@', '_', $filename); .. if (! $file_handle = @fopen($save_filename, 'w')) { $message = PMA_Message::error( .. /* If we saved on server, we have to close file now */ if ($save_on_server) { $write_result = @fwrite($file_handle, $dump_buffer); fclose($file_handle); ------------------------[ source code end ]------------------------------------ As seen above, when configuration setting "SaveDir" is set, then it is possible to save database dump to the PMA webserver. By default "SaveDir" is unset and this prevents possible security problems. As we can overwrite any variables in global scope, it is possible to set "SaveDir" to arbitrary value. This will lead to directory traversal vulnerability - attacker is able to save database dump to any directory in webserver, if only filesystem permissions allow that. Database dump can be with extension ".sql". If attacker can dump database with php code and tags in it, this content will be in dump file. If filename is something like "foobar.php.sql", then by default most Apache webserver installations will try to parse this dump file as php file, which can finally lead to the remote code execution vulnerability. Disclosure timeline: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 16.04.2013 -> Sent email to developers 16.04.2013 -> First response email from developers 16.04.2013 -> Sent detailed information to developers 24.04.2013 -> New PMA versions and security advisories released 25.04.2013 -> Current advisory released Contact: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ come2waraxe@xxxxxxxxx Janek Vind "waraxe" Waraxe forum: http://www.waraxe.us/forums.html Personal homepage: http://www.janekvind.com/ Random project: http://albumnow.com/ ---------------------------------- [ EOF ] ------------------------------------
