Blind Web App Security Audits: Uncovering Vulnerabilities Without Source Code

Summary: The video discusses security audits for web applications, particularly focusing on the challenges faced when testing applications blindly without source code access. It highlights how backend implementation details, such as error messages and unique HTTP headers, can offer valuable insights. The discussion then shifts to a practical example, analyzing a CTF challenge involving a Go web application and uncovering a race condition vulnerability related to error handling in the code.Key Points:

• The speaker conducts security audits for web applications without source code, often relying on backend hints like error messages and behavior of API endpoints.
• Understanding typical issues and pitfalls in specific programming languages (like Go) can enhance testing effectiveness.
• In the analyzed CTF challenge, the source code was available, revealing two Go files and a Docker setup indicating a segmented architecture.
• The challenge involved a key-value store where requests were processed through a frontend that executed a separate backend process via Unix domain sockets.
• A major vulnerability was discovered: an arbitrary file read function that improperly handled error conditions, allowing unintended access to sensitive files.
• The error handling in the Go code demonstrated a race condition due to variable shadowing, which is problematic when handling concurrent HTTP requests.
• The intended solution for the challenge involved exploiting the peculiar architecture that isolated processes per session to prevent cross-session interference.
• The final exploit involved spamming requests to manipulate the error state to successfully read sensitive files, further illustrating the vulnerability.
• The video highlights the importance of understanding concurrent programming nuances in Go, especially regarding error variable management.
• Promotional content for the speaker’s training platform, focusing on cybersecurity education and practical learning resources.