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fix(websocket): enforce auth, prevent provider hijack, and add consumer limits #345

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fix(websocket): enforce auth, prevent provider hijack, and add consumer limits #345

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61 changes: 59 additions & 2 deletions src/server/websocket.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -48,6 +48,8 @@ export async function createWsServer(

const wss = new WebSocketServer({ noServer: true })
const inputHandler = new InputHandler(inputThrottleMs)
let currentProvider: WebSocket | null = null
const MAX_CONSUMERS = 5
let LAN_IP = "127.0.0.1"
try {
LAN_IP = await getLocalIp()
Expand Down Expand Up @@ -110,6 +112,10 @@ export async function createWsServer(
},
)

function isPrivileged(ws: WebSocket, isLocal: boolean): boolean {
return isLocal // simplest safe rule: only localhost can do dangerous stuff
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}

wss.on(
"connection",
(
Expand Down Expand Up @@ -144,7 +150,7 @@ export async function createWsServer(
try {
if (isBinary) {
// Relay frames from Providers to Consumers
if ((ws as ExtWebSocket).isProvider) {
if (ws === currentProvider) {
for (const client of wss.clients) {
if (
client !== ws &&
Expand All @@ -165,7 +171,13 @@ export async function createWsServer(
return
}

const msg = JSON.parse(raw)
let msg
try {
msg = JSON.parse(raw)
} catch {
logger.warn("Invalid JSON received")
return
}

// Throttle token touch to once per second — avoids crypto comparison on every event
if (token && msg.type !== "get-ip" && msg.type !== "generate-token") {
Expand Down Expand Up @@ -215,6 +227,20 @@ export async function createWsServer(
}

if (msg.type === "start-mirror") {
if (!isPrivileged(ws, isLocal)) {
logger.warn("Unauthorized mirror attempt")
return
}

const consumerCount = [...wss.clients].filter(
c => (c as ExtWebSocket).isConsumer
).length

if (consumerCount >= MAX_CONSUMERS) {
logger.warn("Too many consumers, rejecting")
return
}

startMirror()
return
}
Expand All @@ -225,12 +251,33 @@ export async function createWsServer(
}

if (msg.type === "start-provider") {
if (!isPrivileged(ws, isLocal)) {
logger.warn("Unauthorized provider attempt")
return
}

if (currentProvider) {
logger.warn("Provider already exists, rejecting new one")
return
}

currentProvider = ws
;(ws as ExtWebSocket).isProvider = true
logger.info("Client registered as Screen Provider")
return
}

if (msg.type === "update-config") {
if (!isPrivileged(ws, isLocal)) {
logger.warn("Unauthorized config update attempt")
ws.send(JSON.stringify({
type: "config-updated",
success: false,
error: "Not authorized",
}))
return
}

try {
if (
!msg.config ||
Expand Down Expand Up @@ -351,6 +398,11 @@ export async function createWsServer(
return
}

if (!isPrivileged(ws, isLocal)) {
logger.warn("Unauthorized input injection attempt")
return
}

await inputHandler.handleMessage(msg as InputMessage)
} catch (err: unknown) {
logger.error(
Expand All @@ -362,6 +414,11 @@ export async function createWsServer(
})

ws.on("close", () => {
if (ws === currentProvider) {
currentProvider = null
logger.info("Provider disconnected, slot freed")
}

stopMirror()
logger.info("Client disconnected")
})
Expand Down
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