Thick Client Architectures¶

When conducting penetration testing on thick clients, understanding the underlying architectures is crucial. Thick clients often operate within either a two-tier or three-tier architecture, each with its own characteristics and security implications.

Two-Tier Architecture¶

In a two-tier architecture, the client communicates directly with the server without any intermediaries. This setup is akin to a traditional client-server model, where the client sends requests directly to the server, and the server responds accordingly.

Two-Tier Architecture

Example Applications¶

Desktop Games
Music Players
Text Editors

Three-Tier Architecture¶

The three-tier architecture introduces an additional layer between the client and the server, known as the Application Server. This intermediary server facilitates communication between the client and the database server, handling data transmission back and forth.

Three-Tier Architecture

Example Applications¶

Firefox
Chrome
Burp Suite
Zap Proxy

Additional Considerations¶

Security Implications¶

Two-Tier: Direct communication between client and server may expose vulnerabilities such as lack of encryption or authentication mechanisms.
Three-Tier: The presence of an Application Server adds complexity to the architecture, potentially introducing additional attack vectors or points of failure.

Penetration Testing Focus Areas¶

Authentication Mechanisms: Assess the strength of authentication methods employed by both client and server components.
Data Transmission Security: Evaluate the encryption protocols and data protection measures during transmission between client, Application Server, and database server.
Session Management: Examine how sessions are managed and secured across the architecture to prevent session hijacking or fixation.