Perli v2.6 iOS - Filter Bypass & Persistent Vulnerability

Document Title:
===============
Perli v2.6 iOS - Filter Bypass & Persistent Vulnerability


References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=1813


Release Date:
=============
2016-04-05


Vulnerability Laboratory ID (VL-ID):
====================================
1813


Common Vulnerability Scoring System:
====================================
4.2


Product & Service Introduction:
===============================
This is an ios perl app,you can learn,run,share perl script.  In(the built-in browser or the txt editor),Select the text to run.

(Copy of the Homepage: https://itunes.apple.com/us/app/perli-run-code-autocomplete/id578116006 )


Abstract Advisory Information:
==============================
The Vulnerability Laboratory Core Research Team discovered an application-side encoding vulnerability in the official Perli iOS mobile application api.


Vulnerability Disclosure Timeline:
==================================
2016-04-05: Public Disclosure (Vulnerability Laboratory)


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


Affected Product(s):
====================
XiaoWen Huang
Product: Perli - Perl Editor & Compiler iOS (Application) 2.6


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


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


Technical Details & Description:
================================
A persistent input validation and mail encoding vulnerability has been discovered in the Perli iOS mobile application api.
The persistent web vulnerability allows to inject malicious script codes on the application-side of the vulnerable modules.

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 the 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 perli 2.6 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 4.2. 
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
				[+] Perli


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 perl 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 perli app!

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

PoC: Perli Editor
$aa = <STDIN>;
print($"><iframe onload=alert("TEST")>%20"><iframe src="http://www.vulnerability-lab.com">)


Note: The same type of vulnerability has been disclosed in a python editor as well. 
VL ID: 1806 (http://www.vulnerability-lab.com/get_content.php?id=1806)


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 filter bypass and persistent encoding web vulnerability in the perli ios app is estimated as medium. (CVSS 4.2)


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


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