Python 2.7 For iOS Filter Bypass
Posted on 31 March 2016
Document Title: =============== Python v2.7 v1.5.4 iOS - Filter Bypass & Persistent Vulnerability References (Source): ==================== http://www.vulnerability-lab.com/get_content.php?id=1806 Release Date: ============= 2016-03-31 Vulnerability Laboratory ID (VL-ID): ==================================== 1806 Common Vulnerability Scoring System: ==================================== 3.6 Product & Service Introduction: =============================== Python 2.7 for iOS is a Python 2.7.3 environment for the iOS. The Python 2.7 series is scheduled to be the last major version in the 2.x series before 2.x moves into an extended maintenance period. The 2.7 series contains many of the features that were first released in Python 3.1. Improvements in this release include: (Copy of the Homepage: https://itunes.apple.com/us/app/python-2.7-for-ios/id485729872 ) Abstract Advisory Information: ============================== The vulnerability laboratory core research team discovered a filter bypass issue and a persistent input validation vulnerability in the Python v2.7 v1.5.4 iOS mobile application. Vulnerability Disclosure Timeline: ================================== 2016-03-31: Public Disclosure (Vulnerability Laboratory) Discovery Status: ================= Published Affected Product(s): ==================== Jonathan Hosmer Product: Python (2.7) - iOS Mobile (Web-Application) 1.5.4 Note: Other version may be affected as well. (3.x) Exploitation Technique: ======================= Remote Severity Level: =============== Medium Technical Details & Description: ================================ A persistent input validation and mail encoding vulnerability has been discovered in the Python v2.7 v1.5.4 iOS application. 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 not only present in the python 2.7 version of the mobile client because other versions do support the same incorrect way of validation in the sharing process. Attackers can for example generate a QR code with malicious context that is executed in the message code 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 3.6. Exploitation of the persistent web 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 [+] Python 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 Python 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 4. Open the saved entry again and click the top right arrow menu 5. Now choose Create QR or Share the Code 6. Opento message `Mail to Author` or 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 python! 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: Python aa = raw_input("hacki23:"); print("><iframe>%20"><iframe src="x">); Solution - Fix & Patch: ======================= The vulnerability can be patched by a secure parse and encode of the python 2.7 project code. Encode and parse on convert to send by email. Restrict the input and disallow usage of html tags in the code line, as far as it is used filter thus inputs to prevent a persistent execution on the application-side. Security Risk: ============== The security risk of the filter bypass issue and persistent input validation web vulnerability in the python ios app is estimated as medium. (CVSS 3.6) Credits & Authors: ================== Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri (bkm@evolution-sec.com) [www.vulnerability-lab.com] Disclaimer & Information: ========================= The information provided in this advisory is provided as it is without any warranty. Vulnerability Lab disclaims all warranties, either expressed or implied, including the warranties of merchantability and capability for a particular purpose. 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