#5834: fix(line): add timeout and size limit to readRequestBody to prevent DoS

## Summary Fixes #5125 - LINE monitor `readRequestBody()` has no timeout or size limit (CWE-400: Uncontrolled Resource Consumption) - Add 30-second timeout with `setTimeout`/`clearTimeout` pattern - Add 1MB size limit to prevent memory exhaustion - Add `done` flag to prevent race conditions between event handlers - Add `close` event handler for client disconnect detection - Call `req.destroy()` to terminate malicious connections ## Attack Vectors Mitigated 1. **Slowloris DoS**: Attacker sends data very slowly to hold connections indefinitely 2. **Memory Exhaustion**: Attacker sends oversized request body to cause OOM ## Implementation Pattern Follows the same pattern as `readJsonBody()` in `src/gateway/hooks.ts:74-139` which was already correctly implemented. ## Test Plan - [ ] Existing LINE webhook tests pass - [ ] Manual test: Send normal webhook request (should work) - [ ] Manual test: Slow connection times out after 30s - [ ] Manual test: Large body (>1MB) is rejected 🤖 Generated with [Claude Code](https://claude.com/claude-code) <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR hardens the LINE webhook request-body reader by adding a 30s timeout, a 1MB maximum size, and extra safeguards (`done` flag + `close` handling) to prevent slowloris-style hangs and memory exhaustion. The change is localized to `src/line/monitor.ts` and affects how the webhook handler reads the raw request body before validating the LINE signature and parsing JSON. <h3>Confidence Score: 4/5</h3> - This PR is generally safe to merge and improves DoS resilience, with minor behavioral edge cases to consider. - The change is small and well-scoped, adds clear resource limits, and uses guarded event handlers to avoid double-resolve/reject. Remaining concerns are mostly about semantics (absolute vs inactivity timeout) and returning more appropriate HTTP status codes for body-read failures. - src/line/monitor.ts <!-- greptile_other_comments_section --> **Context used:** - Context from `dashboard` - CLAUDE.md ([source](https://app.greptile.com/review/custom-context?memory=fd949e91-5c3a-4ab5-90a1-cbe184fd6ce8)) - Context from `dashboard` - AGENTS.md ([source](https://app.greptile.com/review/custom-context?memory=0d0c8278-ef8e-4d6c-ab21-f5527e322f13)) <!-- /greptile_comment -->