🔒 Fix timing attack vulnerability in token comparisons

[instax-dutta]

🎯 What: The vulnerability fixed

This PR addresses a timing attack vulnerability in token comparisons throughout the API. Specifically, it replaces non-constant time string comparisons for sensitive tokens with a timing-safe alternative.

⚠️ Risk: The potential impact if left unfixed

A timing attack could allow an attacker to brute-force sensitive tokens (like deletion tokens or the INIT_SECRET) by measuring the time the server takes to respond. Because standard string comparisons return early on the first mismatch, the response time can reveal how many characters at the beginning of the string are correct, significantly reducing the search space for an attacker.

🛡️ Solution: How the fix addresses the vulnerability

I've introduced a safeCompare utility in src/lib/security.ts that uses node:crypto.timingSafeEqual for comparisons. This function ensures that the comparison takes the same amount of time regardless of how much of the string matches. It also safely handles comparisons of strings with different lengths by performing a dummy comparison to prevent throwing errors while still being timing-resistant.

The fix was applied to:

• src/app/api/paste/[id]/rotate/route.ts: Comparing deletion tokens for link rotation.
• src/app/api/paste/[id]/route.ts: Comparing deletion tokens for paste revocation.
• src/app/api/init/route.ts: Comparing the INIT_SECRET for database initialization.

A new test file src/lib/security.test.ts was added to verify the correctness of the safeCompare function.

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PR created automatically by Jules for task 10910891533191577668 started by @instax-dutta

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Project	Deployment	Actions	Updated (UTC)
binify	Ready	Preview, Comment	Mar 22, 2026 9:34am

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 07864dc6-7eb0-46a5-812d-1143d32f622c

📥 Commits

Reviewing files that changed from the base of the PR and between 6c75fd8 and 396a7cb.

📒 Files selected for processing (5)

• src/app/api/init/route.ts
• src/app/api/paste/[id]/rotate/route.ts
• src/app/api/paste/[id]/route.ts
• src/lib/security.test.ts
• src/lib/security.ts

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• Create PR with unit tests
• Commit unit tests in branch security-timing-safe-token-comparison-10910891533191577668

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