🛡️ Sentinel: Dual Rate Limiting on Auth Server Actions

[projectamazonph]

Description

This security enhancement implements asynchronous dual rate limiting on sensitive authentication server actions to prevent brute force, event-loop starvation, and Account Lockout Denial of Service (DoS) attacks.

Vulnerability & Threat Model

Previously, signInAction and signUpAction used a standard single-key rate-limiting utility bound exclusively to user emails. An attacker could continuously request actions on a target user's email, filling the rate-limiting buckets and blocking the legitimate user from signing in or completing registration, causing an Account Lockout Denial of Service.

Mitigation & Implementation

• IP-First Dual Rate Limiting: We created rateLimitDual which retrieves and checks the client IP rate limits (ipLimit defaulting to 20 per 60s) before assessing or incrementing target-based keys (defaulting to 5 per 60s). This prevents an IP-blocked attacker from polluting or locking out a target's bucket.
• Safe Extraction: Safely parses the X-Forwarded-For header in strict TS environments without indexing errors, falling back to X-Real-IP and 127.0.0.1.
• Async Headers Compliance: Built to be fully asynchronous to support Next.js 15 asynchronous headers() resolution.
• Cleanup and Test isolation: Exposed resetRateLimits() helper to clear memory between tests.

Verification

• Added full unit test coverage under src/lib/__tests__/rate-limit.test.ts checking IP priority evaluation, sliding window, cleanup, and case-insensitivity.
• Updated src/app/actions/__tests__/auth-actions.test.ts to mock the async headers correctly.
• All 221 tests pass successfully, with clean lint and typecheck checks.

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PR created automatically by Jules for task 17185314931449868096 started by @projectamazonph

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📥 Commits

Reviewing files that changed from the base of the PR and between 9d0e0bf and be452f2.

📒 Files selected for processing (6)

• .jules/sentinel.md
• package.json
• src/app/actions/__tests__/auth-actions.test.ts
• src/app/actions/auth.ts
• src/lib/__tests__/rate-limit.test.ts
• src/lib/rate-limit.ts

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