006ba539ab
Update in-memory rate limiter to fail secure (reject new requests) when maximum capacity is reached, rather than evicting the oldest tracking entry. This prevents an attacker from bypassing their rate limit by flooding the store with spoofed `x-forwarded-for` IPs to intentionally trigger cache eviction. Also cleaned up temporary files and updated tests to verify the behavior. Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
2.7 KiB
2024-05-18 - Unprotected Dynamic Image Generation Endpoints
Vulnerability: The /api/og route generates an ImageResponse dynamically using next/og. Because this operation is computationally expensive and memory-intensive, unauthenticated endpoints lacking rate limiting act as prominent Denial of Service (DoS) vectors. Attackers can flood the endpoint with varying parameters, forcing the server to continually spawn compute-heavy tasks until resources are exhausted and the instance crashes or latency spikes to unacceptable levels.
Learning: Next.js dynamic endpoints that do not hit external upstream APIs or databases (like image generation with next/og) are often overlooked for rate limiting. Rate limiting is just as critical for protecting local compute resources as it is for protecting downstream API quotas or databases. Any route performing on-the-fly heavy processing must implement throttling.
Prevention: Apply the shared checkRateLimit utility (from @/lib/rate-limit) to all computationally expensive endpoints (such as next/og usage), even if they do not explicitly query external services. Ensure getConfig().rateLimitRpm is passed as the threshold to maintain configurable global protection.
2024-05-18 - [Preventing Timing Attacks on Variable-Length Secrets]
Vulnerability: Comparing variable-length plaintext passwords using strict equality (===) or crypto.timingSafeEqual with unequal lengths, which leaks length information and enables timing attacks.
Learning: When comparing variable-length secrets (like plaintext fallback passwords), both values must be hashed to a fixed-length algorithm (like SHA-256) first to ensure identical input lengths for the secure comparison, preventing side-channel leaks.
Prevention: Always hash variable-length secrets to a fixed length before passing them to crypto.timingSafeEqual.
2024-05-18 - Rate Limit Store Flooding and Cache Eviction Vulnerability
Vulnerability: The rate limiter implemented an LRU/FIFO map to track API request limits, evicting the oldest tracked IP when maximum capacity was reached. An attacker could flood the store with randomly spoofed IP headers, continuously evicting legitimate users' IP addresses. This allowed the attacker to effectively bypass their own rate limit and subject the upstream server to DoS. Learning: Evicting entries from a security control store (like a rate limit map) under pressure turns the limit into a revolving door if an attacker controls the keys (e.g., via IP spoofing headers). Prevention: Rather than evicting old entries when an in-memory rate limit store is full, the correct security posture is to fail closed (or block new keys) until entries naturally expire, preserving tracking on existing keys.