Harden InputHandler Against Event Flooding and Oversized Payload Attacks (Add Rate Limiting & Input Safeguards)#87
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aniket866
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Actionable comments posted: 2
🤖 Fix all issues with AI agents
In `@src/server/InputHandler.ts`:
- Around line 30-32: The current clamping using MAX_COORD on msg.dx/msg.dy
allows NaN to pass through because Math.max/Math.min return NaN for non-numeric
inputs; update the InputHandler logic that mutates msg.dx and msg.dy to first
validate values with Number.isFinite or typeof === 'number' before clamping
(MAX_COORD), and if invalid either discard/normalize to 0 or skip assigning so
downstream calls like mouse.setPosition don't receive NaN; ensure you update the
branches that handle msg.dx and msg.dy accordingly.
- Around line 34-41: The current leading-edge throttle in InputHandler (using
lastEventTime and checking msg.type === 'move' || msg.type === 'scroll') drops
the trailing event and shares one timestamp across move and scroll; change it to
a per-event-type trailing-edge throttle: replace the single lastEventTime with
separate state (e.g., lastMoveEventTime, lastScrollEventTime and
pendingMoveEvent, pendingScrollEvent) and on a rapid burst, let the first event
go through immediately but if subsequent events are skipped schedule the last
skipped event via setTimeout (~16ms) to fire after the window expires; ensure
the dispatch logic references msg.type to select the correct timestamp/pending
slot so move and scroll throttling are independent.
Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>
1 participant
Addressed Issues:
Closes # 28
Why these changes are important
If a client keeps sending mouse move or scroll events very fast in a loop, the server handles all of them without limits. This can overload the system and make the Mac freeze or become very slow. Also, if someone sends a very large text message, it can use too much memory and crash the server.
fixed
InputHandler.tswith changes to implement input validation (text length, coordinate bounds) and rate limiting (throttling) for high-frequency events.Changes Applied:
Rate Limiting: Added a lastEventTime timestamp and a check at the beginning of handleMessage to throttle move and scroll events to approximately 60 FPS (~16ms).
Input Sanitation: Added a check to truncate msg.text to 500 characters.
Coordinate Validation: Added clamping for msg.dx and msg.dy to ensure they stay within a sane range (+/- 2000 pixels) before processing.
Checklist
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@imxade Please review this , can be merged ,let me know if any changes required
Thankyou
Summary by CodeRabbit
Bug Fixes
Performance