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:
====================================
3.5


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
to 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 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
                [+] 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 3.5)


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


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