🛡️ Sentinel: [CRITICAL] Fix Timing Attack in API Token Comparison

[dkdev179]

🚨 Severity: CRITICAL
💡 Vulnerability: Standard string inequality comparison (!=) was used to compare the provided bearer token against the configured API token in mcp/api.py. Standard string comparisons evaluate character by character and return early on the first mismatch, making the authentication endpoint susceptible to a timing attack where an attacker could deduce the token byte by byte.
🎯 Impact: An attacker could potentially bypass authentication and gain unauthorized access to the restricted API endpoints by measuring the time taken to reject invalid tokens and successfully guessing the correct token.
🔧 Fix: Imported the secrets module and replaced the standard string comparison with not secrets.compare_digest(credentials.credentials, API_TOKEN), which performs a constant-time comparison, effectively mitigating timing attacks.
✅ Verification: Verified by checking that tests still pass (python -m pytest tests/) and reviewing the code to ensure secrets.compare_digest() is used properly for sensitive comparisons. Also logged the vulnerability in .jules/sentinel.md.

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PR created automatically by Jules for task 7422534734070375137 started by @dkdev179

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