[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':

$a_query = 'CREATE TABLE ' . PMA_backquote($newtablename) . ' SELECT * FROM '

. PMA_backquote($selected[$i]) ; // COPY TABLE AND CHANGE PREFIX PATTERN

------------------------[ 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):

$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

$a_query = 'CREATE TABLE ' . PMA_Util::backquote($newtablename) . 

' SELECT * FROM ' . PMA_Util::backquote($selected[$i]); // COPY TABLE AND CHANGE PREFIX PATTERN

############################################################################

2. Locally Saved SQL Dump File Multiple File Extension Remote Code Execution

1. insecure names of locally saved dump files

1. user-supplied POST parameter "filename_template"

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 "@[email protected]" 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"

1. insufficient sanitization of user data before using in include_once

1. user-supplied POST parameter "what"

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:

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)

)

);

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:

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;

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"

1. insecure POST parameters importing

1. user-supplied POST parameters

PMA security advisory: PMASA-2013-5

CVE id: CVE-2013-3241

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:

$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 */

$write_result = @fwrite($file_handle, $dump_buffer);

fclose($file_handle);

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:

[email protected]

Janek Vind "waraxe"

Waraxe forum: http://www.waraxe.us/forums.html

Personal homepage: http://www.janekvind.com/

Random project: http://albumnow.com/

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