Preventing Race Conditions in Python: Key Insights from a Circle Ninja Security Code Review

Original Post: Security Code Review of Race Condition bug in Python | by Circle Ninja | Bug Bounty Hunting | Aug, 2024

The content discusses how to deal with race conditions in a Python application. The primary steps mentioned are:

1. Understanding the Application: Reviewing the feature to redeem a coupon and the associated Flask route and validation function (redeem_code).

2. Identifying Race Conditions: Discovering that race conditions can occur during the coupon redemption process, leading to multiple balance increments from a single coupon by using threading for numerous concurrent requests.

3. Fixing the Race Condition: Demonstrating the use of Python locks to prevent race conditions. By using acquire() and release() methods from the threading library to ensure that the critical section of the code (the validation and balance increment part) executes in a thread-safe manner.

Additional tips include using the with statement for managing locks and considering alternative approaches like Semaphores for concurrency control.

Illustrations include snippets of the exploit and the fixed code, alongside examples of how the balance increments differently before and after the fix.

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