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Harden InputHandler Against Event Flooding and Oversized Payload Attacks (Add Rate Limiting & Input Safeguards) #87

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Harden InputHandler Against Event Flooding and Oversized Payload Attacks (Add Rate Limiting & Input Safeguards) #87

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fixing-input-validation
aniket866 Feb 14, 2026
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aniket866 Feb 14, 2026
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92 changes: 81 additions & 11 deletions src/server/InputHandler.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -14,26 +14,88 @@ export interface InputMessage {
}

export class InputHandler {
private lastMoveTime = 0;
private lastScrollTime = 0;
private pendingMove: InputMessage | null = null;
private pendingScroll: InputMessage | null = null;
private moveTimer: ReturnType<typeof setTimeout> | null = null;
private scrollTimer: ReturnType<typeof setTimeout> | null = null;

constructor() {
mouse.config.mouseSpeed = 1000;
}

async handleMessage(msg: InputMessage) {
// Validation: Text length sanitation
if (msg.text && msg.text.length > 500) {
msg.text = msg.text.substring(0, 500);
}

// Validation: Sane bounds for coordinates
const MAX_COORD = 2000;
if (typeof msg.dx === 'number' && Number.isFinite(msg.dx)) {
msg.dx = Math.max(-MAX_COORD, Math.min(MAX_COORD, msg.dx));
}
if (typeof msg.dy === 'number' && Number.isFinite(msg.dy)) {
msg.dy = Math.max(-MAX_COORD, Math.min(MAX_COORD, msg.dy));
}

// Throttling: Limit high-frequency events to ~60fps (16ms)
if (msg.type === 'move') {
const now = Date.now();
if (now - this.lastMoveTime < 16) {
this.pendingMove = msg;
if (!this.moveTimer) {
this.moveTimer = setTimeout(() => {
this.moveTimer = null;
if (this.pendingMove) {
const pending = this.pendingMove;
this.pendingMove = null;
this.handleMessage(pending);
}
}, 16);
}
return;
}
this.lastMoveTime = now;
} else if (msg.type === 'scroll') {
const now = Date.now();
if (now - this.lastScrollTime < 16) {
this.pendingScroll = msg;
if (!this.scrollTimer) {
this.scrollTimer = setTimeout(() => {
this.scrollTimer = null;
if (this.pendingScroll) {
const pending = this.pendingScroll;
this.pendingScroll = null;
this.handleMessage(pending);
}
}, 16);
}
return;
}
this.lastScrollTime = now;
}

switch (msg.type) {
case 'move':
if (msg.dx !== undefined && msg.dy !== undefined) {
const currentPos = await mouse.getPosition();

await mouse.setPosition(new Point(
currentPos.x + msg.dx,
currentPos.y + msg.dy
));
await mouse.setPosition(
new Point(currentPos.x + msg.dx, currentPos.y + msg.dy)
);
}
break;

case 'click':
if (msg.button) {
const btn = msg.button === 'left' ? Button.LEFT : msg.button === 'right' ? Button.RIGHT : Button.MIDDLE;
const btn =
msg.button === 'left'
? Button.LEFT
: msg.button === 'right'
? Button.RIGHT
: Button.MIDDLE;

if (msg.press) {
await mouse.pressButton(btn);
} else {
Expand Down Expand Up @@ -70,15 +132,18 @@ export class InputHandler {

case 'zoom':
if (msg.delta !== undefined && msg.delta !== 0) {
const sensitivityFactor = 0.5;
const sensitivityFactor = 0.5;
const MAX_ZOOM_STEP = 5;

const scaledDelta =
Math.sign(msg.delta) *
Math.min(Math.abs(msg.delta) * sensitivityFactor, MAX_ZOOM_STEP);
Math.min(
Math.abs(msg.delta) * sensitivityFactor,
MAX_ZOOM_STEP
);

const amount = -scaledDelta;

await keyboard.pressKey(Key.LeftControl);
try {
await mouse.scrollDown(amount);
Expand All @@ -92,6 +157,7 @@ export class InputHandler {
if (msg.key) {
console.log(`Processing key: ${msg.key}`);
const nutKey = KEY_MAP[msg.key.toLowerCase()];

if (nutKey !== undefined) {
await keyboard.type(nutKey);
} else if (msg.key.length === 1) {
Expand All @@ -105,9 +171,11 @@ export class InputHandler {
case 'combo':
if (msg.keys && msg.keys.length > 0) {
const nutKeys: (Key | string)[] = [];

for (const k of msg.keys) {
const lowerKey = k.toLowerCase();
const nutKey = KEY_MAP[lowerKey];

if (nutKey !== undefined) {
nutKeys.push(nutKey);
} else if (lowerKey.length === 1) {
Expand All @@ -127,15 +195,17 @@ export class InputHandler {

try {
for (const k of nutKeys) {
if (typeof k === "string") {
if (typeof k === 'string') {
await keyboard.type(k);
} else {
await keyboard.pressKey(k);
pressedKeys.push(k);
}
}

await new Promise(resolve => setTimeout(resolve, 10));
await new Promise(resolve =>
setTimeout(resolve, 10)
);
} finally {
for (const k of pressedKeys.reverse()) {
await keyboard.releaseKey(k);
Expand Down