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PayPal Inc #86 iOS 4.6 - Validation & Design Vulnerability



Document Title:
===============
PayPal Inc #86 iOS 4.6 - Validation & Design Vulnerability


References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=915

PayPal Security UID: eff8aq


Release Date:
=============
2014-09-30


Vulnerability Laboratory ID (VL-ID):
====================================
915


Common Vulnerability Scoring System:
====================================
2.3


Product & Service Introduction:
===============================
PayPal is a global e-commerce business allowing payments and money transfers to be made through the Internet. Online money 
transfers serve as electronic alternatives to paying with traditional paper methods, such as checks and money orders. Originally, 
a PayPal account could be funded with an electronic debit from a bank account or by a credit card at the payer s choice. But some 
time in 2010 or early 2011, PayPal began to require a verified bank account after the account holder exceeded a predetermined 
spending limit. After that point, PayPal will attempt to take funds for a purchase from funding sources according to a specified 
funding hierarchy. If you set one of the funding sources as Primary, it will default to that, within that level of the hierarchy 
(for example, if your credit card ending in 4567 is set as the Primary over 1234, it will still attempt to pay money out of your 
PayPal balance, before it attempts to charge your credit card). The funding hierarchy is a balance in the PayPal account; a 
PayPal credit account, PayPal Extras, PayPal SmartConnect, PayPal Extras Master Card or Bill Me Later (if selected as primary 
funding source) (It can bypass the Balance); a verified bank account; other funding sources, such as non-PayPal credit cards.
The recipient of a PayPal transfer can either request a check from PayPal, establish their own PayPal deposit account or request 
a transfer to their bank account.

PayPal is an acquirer, performing payment processing for online vendors, auction sites, and other commercial users, for which it 
charges a fee. It may also charge a fee for receiving money, proportional to the amount received. The fees depend on the currency 
used, the payment option used, the country of the sender, the country of the recipient, the amount sent and the recipient s account 
type. In addition, eBay purchases made by credit card through PayPal may incur extra fees if the buyer and seller use different currencies.

On October 3, 2002, PayPal became a wholly owned subsidiary of eBay. Its corporate headquarters are in San Jose, California, United 
States at eBay s North First Street satellite office campus. The company also has significant operations in Omaha, Nebraska, Scottsdale, 
Arizona, and Austin, Texas, in the United States, Chennai, Dublin, Kleinmachnow (near Berlin) and Tel Aviv. As of July 2007, across 
Europe, PayPal also operates as a Luxembourg-based bank.

On March 17, 2010, PayPal entered into an agreement with China UnionPay (CUP), China s bankcard association, to allow Chinese consumers 
to use PayPal to shop online.PayPal is planning to expand its workforce in Asia to 2,000 by the end of the year 2010.
Between December 4ñ9, 2010, PayPal services were attacked in a series of denial-of-service attacks organized by Anonymous in retaliation 
for PayPal s decision to freeze the account of WikiLeaks citing terms of use violations over the publication of leaked US diplomatic cables.

(Copy of the Homepage: www.paypal.com) [http://en.wikipedia.org/wiki/PayPal]


Abstract Advisory Information:
==============================
The Vulnerability Laboratory Research Team discovered a form validation bug and design vulnerability in the PayPal Inc iOS Mobile v4.6.0 Application for iPhones & iPads.


Vulnerability Disclosure Timeline:
==================================
2014-09-30:	Public Disclosure (Vulnerability Laboratory)


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


Affected Product(s):
====================
PayPal Inc
Product: iOS Mobile Application - Banking 4.6.0 


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


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


Technical Details & Description:
================================
A design misconfiguration and a input validation issue has been discovered in the PayPal Inc iOS v4.6.0 mobile web-application.

The misconfiguration of the input validation is located in the `Betrag` (Amount) module of the paypal mobile application iOS v4.6.0.
The regular validation of the input form in the main app of paypal, allows on inputs of money the following chars together `.``,` `00`. 

During the transaction process of an amount i found a way to include a valid string with incorrect values to the payment procedure. 
The incorrect values with a very high amount of money in euro resulted in the block of a non verified account because the api of the app 
was sending the request and opened it up. Normally the validation should see the person uses different kind of special chars in the transaction 
to high up the amount. The block was only the result of the opened transaction with confusing high (impossible) amount.

Amount Transaction: €111111111.101.011.101.019,00,00

A design misconfiguration is also connected to the wrong input validation problem which does not show anymore in the first or last 2 integers 
of an transaction. In the screenshots of the listing you can see the problem with the bug in the item amounts last positions.

Vulnerable Module(s):
				[+] Amount (Input Fields)
				
Affected Module(s):
				[+] Amount Listing (Index) - Main & Detailed Transactions


Proof of Concept (PoC):
=======================
The validation and design bug can be exploited by local attackers with low privileged or shared paypal account with low user interaction.
For security demonstration or to reproduce the security vulnerability follow the provided information and steps below to continue.

Manually steps to reproduce the security vulnerability ...

#1 Explains the validation problem of the amount size inside of the validation combined with , . 00
#2 Explains a connected bug which does not display the first or last 2 chars of the transaction amount

#1
1. Register a paypal account
2. Activate for mobile access and download the new ipad or iphone paypal software v4.6.0
3. Make a send money transaction or request transaction with a paypal account in the mobile app
4. Open the money send and include for example a wrong amount like €11.101.011.101.019,00,00 and save the context
5. The app asks you to confirm the transaction of the money send or request, click confirm to accept
6. The transaction will be successful send but the app does not recognize the wrong request to block
#2
7. The test account will be blocked because of a wrong declared amount and validation in the input of the amount.
8. Now, the attacker went back to the application and look to the transaction listing
9. The transaction amount is larger then the input listing bar of the api app template and the last or first 2 numbers of the amount are not inside the same line and broken displaye/invisble
10. Both successful reproduce of both local reported issues!



Solution - Fix & Patch:
=======================
Restrict the input of the money amount to a secure limit. Restrict the input to disallow special chars.
Encode the input to prevent further script code executions. Implement a exception that prevent execution of wrong inputs and patch the design flaw.


Security Risk:
==============
The security risk of the mobile validation form misconfiguration and the design bug is estimated as medium.


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


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