🛡️ Sentinel: [CRITICAL] Fix timing attack vulnerability in A2A token validation#277
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Hashes both the provided token and the configured expected tokens before comparing them using crypto.timingSafeEqual, thereby removing a length-check short-circuit that could leak the length of the expected token via timing differences.
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🚨 Severity: CRITICAL
💡 Vulnerability: A timing attack side-channel existed in the A2A token authentication middleware. The code checked if the lengths of the user-provided token and the valid token matched before calling
crypto.timingSafeEqual. This short-circuit behavior leaks the length of valid tokens through observable timing differences.🎯 Impact: An attacker could perform a timing analysis to determine the exact length of a valid authentication token, significantly reducing the search space required to brute-force the token and bypass authentication for the local API server.
🔧 Fix: Both the incoming token and the configured valid tokens are now hashed using SHA-256 before being compared with
crypto.timingSafeEqual. This guarantees that the buffers being compared are always the exact same size, eliminating the need for a length check and completely mitigating the timing side-channel.✅ Verification: Run the full test suite (
bun run test:full) andbun run check:bun-purity. Confirm the authentication logic continues to function securely.PR created automatically by Jules for task 956204210145822346 started by @YoungSx