Original Post: Thick-Client Penetration Testing. Understanding of Thick Client… | by Tushar Suryawanshi | Jul, 2024
The article provides an in-depth look at thick client applications, emphasizing their architecture, types, and the tools used to test and secure them.
Key Points:
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Thick Client Definition:
- Performs most processing on the client-side.
- Communicates with the backend server or database.
- Examples include Spotify, Outlook, Firefox, etc.
- Also known as Fat Client, Rich Client, or Heavy Client.
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Architecture:
- Two-Tier: Direct communication between client and server database.
- Three-Tier: Client communicates with an application server, which then interacts with the database, enhancing security.
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Types of Thick Clients:
- Proxy-aware: Supports proxy servers, simplifying request interception (e.g., Google Talk, Dropbox).
- Proxy-unaware: Lacks proxy support, posing challenges for request interception (e.g., Skype, Spotify).
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Challenges:
- Proxy-unaware clients are difficult to test due to lack of inherent proxy settings.
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Testing Approaches:
- Dynamic testing (interception), system storage and memory analysis, static testing (decompiling and reverse engineering).
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Tools:
- Dynamic Testing: Burp Suite, OWASP ZAP.
- Proxy-unaware: MitmProxy, Fiddler.
- TCP analysis: EchoMirage.
- Registry and file monitoring: WinHex, Process Monitor.
- Reverse Engineering: dnSpy, ILSpy, Ghidra, IDA Pro.
- Other: Metasploit, Checkmarx, Coverity.
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Recommendations:
- Use three-tier architecture.
- Encrypt traffic.
- Validate user inputs.
- Maintain audit trails.
- Avoid storing sensitive information in clear text.
- Use strong password policies and session IDs.
- Learning Resource:
- DVTA (Damn Vulnerable Thick Client Application) for practice, available on GitHub.
Conclusion:
Understanding and testing thick client applications demand detailed knowledge of their architectures and behaviors, supported by appropriate testing tools and techniques. The article provides necessary preparations for tackling security challenges associated with thick clients.
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