[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@yahoo.com
Janek Vind "waraxe"

Waraxe forum: http://www.waraxe.us/forums.html
Personal homepage: http://www.janekvind.com/
Random project: http://albumnow.com/
---------------------------------- [ EOF ] ------------------------------------

Published on: 2013-04-24 (26668 reads)

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