[Cycode] Fix for SAST detections - Observable Timing Discrepancy

[cycode-security]

[Cycode] Fix for SAST detections - Observable Timing Discrepancy

Code fix
src / main / java / org / owasp / webgoat / lessons / passwordreset / ResetLinkAssignment.java

Code explainer

The vulnerability in this code is an Observable Timing Discrepancy, which occurs when the time taken to perform operations varies based on sensitive information. In this case, the issue is in the checkIfLinkIsFromTom method at line 73, where a direct string comparison (resetLink.equals(resetLinkFromForm)) is used to compare reset links. This comparison can terminate early if characters don't match, potentially allowing attackers to infer information about the reset link by measuring the time taken for the comparison. This is particularly dangerous because reset links are sensitive and could be used to gain unauthorized access.

The fix involves replacing the direct string comparison with a constant-time comparison using MessageDigest.isEqual. This method ensures that the comparison takes the same amount of time regardless of the input, preventing attackers from inferring information based on timing discrepancies. This approach aligns with security best practices for handling sensitive information, as recommended by OWASP and other security guidelines.

Remediation Instructions

To fix this vulnerability, follow these steps:

Identify the vulnerable comparison: Locate the checkIfLinkIsFromTom method where the direct string comparison is performed.
Replace the vulnerable comparison: Use a constant-time comparison method to ensure that the time taken for the comparison does not vary based on the input. Java provides MessageDigest.isEqual for this purpose, which performs a constant-time comparison.
Update the method: Modify the checkIfLinkIsFromTom method to use MessageDigest.isEqual for comparing the reset links.
Test the changes: Ensure that the functionality remains the same and that the comparison is now performed in constant time.