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C & C++ for OS - Filter Bypass & Persistent Vulnerability



Document Title:
===============
C & C++ for OS - Filter Bypass & Persistent Vulnerability


References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=1825


Release Date:
=============
2016-04-14


Vulnerability Laboratory ID (VL-ID):
====================================
1825


Common Vulnerability Scoring System:
====================================
3.5


Product & Service Introduction:
===============================
This is an ios c app,you can learn,run,share c code. The software is a offline compiler for developers with apple iOS.
Code templates,the contents of the new file is copy from contents of the template file.

(Copy of the Homepage: https://itunes.apple.com/us/app/c-for-os-programming-language/id1016290003 )


This is an ios c/c++ app,you can learn,run,share c/c++ code. In(the built-in browser or the txt editor),Select the text to run.
Code templates,the contents of the new file is copy from contents of the template file. 

(Copy of the Homepage: https://itunes.apple.com/us/app/c-c++-offline-compiler-for/id1016322367 )


Abstract Advisory Information:
==============================
The vulnerability laboratory core research team discovered an application-side validation vulnerability in the official C & C++ for OS web-application (api).


Vulnerability Disclosure Timeline:
==================================
2016-04-14: Public Disclosure (Vulnerability Laboratory)


Discovery Status:
=================
Published


Affected Product(s):
====================
XiaoWen Huang
Product: C for OS & C++ - Mobile API (Web-Application) 1.2


Exploitation Technique:
=======================
Remote


Severity Level:
===============
Medium


Technical Details & Description:
================================
A persistent input validation and mail encode web vulnerability has been discovered  in the official C & C++ for OS web-application (api).
The persistent web vulnerability allows an attacker to inject malicious script codes on the application-side of the vulnerable modules context.

The basic validation of the code formular and mask allows to include any type of script codes or programming language without offensive input 
restrictions. Attackers can inject code to a project to share it with another source. In the moment the code of the project is generated to as 
email body, a persistent script code execution occurs.

There are two options to exploit, first is to send the malicious mail to the author of the program by the `Mail Author` function. Another possibility 
to execute code in the email body context is to share it with another code editor by email. In both email body message context the injected wrong 
filtered script code execution occurs. The internal encoding of the formular is correctly done but in case of sharing by qr or via message body email 
the execution occurs. The vulnerability is located on the application-side of the iOS application and the request method to inject requires physical 
device access or access to the share function. The bug is present in the C & C++ for OS 1.2 version of the mobile client. Attackers can for example 
generate a QR code with malicious context that is executed in the message body were the code is mainly displayed by the iOS application.

The security risk of the application-side vulnerability is estimated as medium with a cvss (common vulnerability scoring system) count of 3.5. 
Exploitation of the persistent vulnerability requires a low privileged ios device user account with restricted access and low user interaction. 
Successful exploitation of the vulnerabilities results in persistent phishing mails, session hijacking, persistent external redirect to malicious 
sources and application-side manipulation of affected or connected module context.

Vulnerable Module(s):
				[+] Share to Authors
				[+] Share by Email
				[+] Share via QR Code

Vulnerable Function(s):
				[+] Console
				[+] C  or C++


Proof of Concept (PoC):
=======================
The persistent vulnerability and mail encoding bug can be exploited by remote attackers with low privileged device user account and low user interaction.
For security demonstration or to reproduce the vulnerability follow the provided information and steps below to continue.

Manual steps to reproduce the vulnerability ...
1. Install the perl app to your apple iOS device
2. Start the mobile application
3. Include to the first variable in the demo code java or html script code and save the entry as c or c++ script
4. Open the saved entry again and click the top right arrow menu
5. Now choose Create QR or Share menu button
6. Open the menu `Mail to Author` or push the default `iOS Mail App` button
7. Now the code of the formular gets transfered to the email message body context
Note: The encoding does not parse or encode any inserted values
8. The email arrives to the target inbox
9. Open the email and the code executes directly in the message body or next to the generated qr code
10. Successful reproduce of the filter and validation vulnerability in the c and c++ app api!

Note: The bug can be exploited by sending to the author, by sending to another target mail or by transfer of a qr code.


Solution - Fix & Patch:
=======================
The vulnerability can be patched by a secure parse and encode of the vulnerable message body context.
Filter and parse all code values that are included to the message body. Configure the code to plain text not html to prevent 
further persistent injection attacks. In case of emergency use the escape function to separate the mechanism permanently.


Security Risk:
==============
The security risk of the application-side mail encode web vulnerability in the mobile application api is estimated as medium. (CVSS 3.5)


Credits & Authors:
==================
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri (bkm@xxxxxxxxxxxxxxxxx) [www.vulnerability-lab.com]


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=========================
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