Transcript Case Study: A Forensic Lesson for Web Security (MSS, part one)

MSS*: Chapter 3
Shopping carts & Payment gateways
* McClure, Stuart, Saumil Shah, and Shreeraj Shah. Web Hacking: attacks and
defense. Addison Wesley. 2003.
Evolution of Shopping
Farmers’ market  Store shopping 
Supermarket  Catalog shopping
  On-line shopping: combines the experience of
both in-store shopping and catalog shopping

+ Web-based applications offer more interactivity and
multimedia presentation than a printed catalog.
+ Web-based applications typically provide searching
capabilities, which are not available in the traditional
in-store shopping or catalog shopping.
+ Web-based applications can be tailored to different
shopping styles.  “no-pressure” shopping experience
Q: Are there any drawbacks or specific requirements?
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Evolution of Shopping

What are the factors that may drive potential
customers away from web-based shopping?
-
Is concern over security real?
Ease of use
Anything else?
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Traditional retail business
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computerized retail business
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E-commerce model
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E-commerce model

Characteristics:
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
A web portal represents the company’s web identity.
The portal serves as an entry into the electronic store.
A web site hosting multiple applications that interact
with an array of servers (other web sites, financial
processing, transaction processing, back-end databases,
etc.)
Q: What makes an e-commerce different from a
computerized retail business?
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E-commerce model
 An
exercise: The e-commerce model
diagram is not really an ER diagram.
Modify/refine the model and turn it into a
real ER or EER diagram.
 Hint: Add relationships
 Part of your project: preliminary design
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E-commerce model
 The
need for peer-to-peer communications
 An extranet is an inter-network linking
different companies’ internal network.
 What are the requirements of an intercompany web-based application?

Trust!
 Authentication
 Non-repudiation
 Anything else?
  Web-services
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Web Services
 Multi-party Web
services
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E-shopping cart systems

Uses of an e-shopping cart:

Temporarily stores what the customer has
picked;
 Provides a summary of the items (prices, S&H
cost, etc.) in the cart when needed (per the
customer’s request or at the time of checkout);
 The customer may replace items in the cart
until the transaction is finalized.
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E-shopping cart systems

The e-shopping
cart application
forms the heart of
the e-shopping
application.

It binds the
customer, the
product catalog,
the inventory
system, and the
payment system
together.
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E-shopping cart systems

Implementation requirements:
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Accuracy: It correctly records what the customer has
picked and changed.
Flexibility: It allows the customer to freely replace
items in the cart.
Integration: with the product catalog, the inventory
system, and the payment gateway.
Integrity: No tampering of the cart’s content, whether
by malicious 3rd party or programming errors (e.g.,
across two different carts)
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E-shopping cart systems

Components:




Session management
Product catalog application
Payment gateway
Back-end databases (e.g., product inventory, customer
information)
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E-shopping cart systems

Sample problems with insecure shopping
carts:

Remote command execution over HTTP
 Unprotected sensitive information retrievable
via HTTP
 Improper or no ‘input sanitization’  results in
remote command execution
 Modified hidden HTML form fields
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Payment processing system

The checkout process:
1.
2.
3.
4.
5.
6.
Finalize the order
Choose method of payment
Verify of the chosen payment method
Log all transactions
Fulfill the order
Generate a receipt
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Payment processing system

The payment gateway interface: Figure next page
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Interacts with the order information page, the backend databases, and the payment gateway
Provided by the institution that hosts the payment
gateway (e.g., Verisign or PayPal)
Integrated into the e-shopping application and
invoked by the electronic storefront app.
SSL encrypted interface with the payment gateway
(Q: how about i/f with other components?)
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Payment processing system
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Payment processing system

Payment system implementation issues:

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
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Never trust “sensitive” data passed from the client
side. Why?
Do not store temporary info within the Web server’s
document folder. Why?
Temporary info should be destroyed after its use.
Use SSL to encrypt communication links. Why?
Carefully protect user profiles!
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