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websocket: limit the number of fragments in a message · nodejs/undici@32dbf0b · GitHub

/ undici Public

Commit 32dbf0b

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lpinca
authored and
mcollina
committed
websocket: limit the number of fragments in a message
Introduce the `maxFragments` option to limit the number of fragments in a message. Without this limit, a remote peer could exploit structural wrapper overhead by sending many tiny fragments, consuming far more memory than the payload itself and crashing the process due to OOM. When the limit is hit, the connection is closed with close code 1008. Signed-off-by: Luigi Pinca <luigipinca@gmail.com>
1 parent 0d6ecc5 commit 32dbf0b

6 files changed

Lines changed: 118 additions & 4 deletions

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‎docs/docs/api/Client.md‎

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@@ -25,6 +25,7 @@ Returns: `Client`
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* **maxHeaderSize** `number | null` (optional) - Default: `--max-http-header-size` or `16384` - The maximum length of request headers in bytes. Defaults to Node.js' --max-http-header-size or 16KiB.
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* **maxResponseSize** `number | null` (optional) - Default: `-1` - The maximum length of response body in bytes. Set to `-1` to disable.
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* **webSocket** `WebSocketOptions` (optional) - WebSocket-specific configuration options.
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* **maxFragments** `number` (optional) - Defailt: `131072` - Maximum number of fragments in a message. Set to 0 to disable the limit.
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* **maxPayloadSize** `number` (optional) - Default: `134217728` (128 MB) - Maximum allowed payload size in bytes for WebSocket messages. Applied to uncompressed messages, compressed frame payloads, and decompressed (permessage-deflate) messages. Set to 0 to disable the limit.
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* **pipelining** `number | null` (optional) - Default: `1` - The amount of concurrent requests to be sent over the single TCP/TLS connection according to [RFC7230](https://tools.ietf.org/html/rfc7230#section-6.3.2). Carefully consider your workload and environment before enabling concurrent requests as pipelining may reduce performance if used incorrectly. Pipelining is sensitive to network stack settings as well as head of line blocking caused by e.g. long running requests. Set to `0` to disable keep-alive connections. This option has no effect once HTTP/2 is negotiated — see `maxConcurrentStreams` for the h2 dispatch ceiling.
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* **connect** `ConnectOptions | Function | null` (optional) - Default: `null` - Configures how undici establishes TCP/TLS connections. Accepts two forms:

‎lib/dispatcher/dispatcher-base.js‎

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@@ -38,6 +38,7 @@ class DispatcherBase extends Dispatcher {
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*/
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get webSocketOptions () {
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return {
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maxFragments: this[kWebSocketOptions].maxFragments ?? 131072,
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maxPayloadSize: this[kWebSocketOptions].maxPayloadSize ?? 128 * 1024 * 1024 // 128 MB default
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}
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}

‎lib/web/websocket/receiver.js‎

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@@ -39,6 +39,10 @@ class ByteParser extends Writable {
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/** @type {import('./websocket').Handler} */
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#handler
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/** @type {number} */
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#maxFragments
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/** @type {number} */
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#maxPayloadSize
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@@ -52,6 +56,7 @@ class ByteParser extends Writable {
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this.#handler = handler
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this.#extensions = extensions == null ? new Map() : extensions
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this.#maxFragments = options.maxFragments ?? 0
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this.#maxPayloadSize = options.maxPayloadSize ?? 0
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if (this.#extensions.has('permessage-deflate')) {
@@ -242,7 +247,9 @@ class ByteParser extends Writable {
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this.#state = parserStates.INFO
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} else {
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if (!this.#info.compressed) {
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this.writeFragments(body)
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if (body.length && !this.writeFragments(body)) {
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return
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}
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// If the frame is not fragmented, a message has been received.
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// If the frame is fragmented, it will terminate with a fin bit set
@@ -264,7 +271,9 @@ class ByteParser extends Writable {
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return
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}
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this.writeFragments(data)
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if (data.length && !this.writeFragments(data)) {
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return
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}
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// Check cumulative fragment size
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if (this.#maxPayloadSize > 0 && this.#fragmentsBytes > this.#maxPayloadSize) {
@@ -345,8 +354,17 @@ class ByteParser extends Writable {
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}
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writeFragments (fragment) {
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if (
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this.#maxFragments > 0 &&
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this.#fragments.length === this.#maxFragments
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) {
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failWebsocketConnection(this.#handler, 1008, 'Too many message fragments')
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return false
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}
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this.#fragmentsBytes += fragment.length
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this.#fragments.push(fragment)
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return true
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}
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consumeFragments () {

‎lib/web/websocket/websocket.js‎

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Original file line numberDiff line numberDiff line change
@@ -468,10 +468,12 @@ class WebSocket extends EventTarget {
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// once this happens, the connection is open
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this.#handler.socket = response.socket
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// Get maxPayloadSize from dispatcher options
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// Get options from dispatcher options
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const maxFragments = this.#handler.controller.dispatcher?.webSocketOptions?.maxFragments
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const maxPayloadSize = this.#handler.controller.dispatcher?.webSocketOptions?.maxPayloadSize
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const parser = new ByteParser(this.#handler, parsedExtensions, {
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maxFragments,
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maxPayloadSize
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})
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parser.on('drain', () => this.#handler.onParserDrain())

‎test/websocket/fragments.js‎

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@@ -2,7 +2,7 @@
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const { test, after } = require('node:test')
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const { WebSocketServer } = require('ws')
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const { WebSocket } = require('../..')
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const { Agent, WebSocket } = require('../..')
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const diagnosticsChannel = require('node:diagnostics_channel')
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test('Fragmented frame with a ping frame in the middle of it', (t) => {
@@ -39,3 +39,90 @@ test('Fragmented frame with a ping frame in the middle of it', (t) => {
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})
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})
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})
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test('Too many fragments (uncompressed)', (t, done) => {
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t.plan(4)
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const agent = new Agent({
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webSocket: {
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maxFragments: 3
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}
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})
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const server = new WebSocketServer({ port: 0 }, () => {
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const { port } = server.address()
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const client = new WebSocket(`ws://127.0.0.1:${port}`, {
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dispatcher: agent
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})
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client.addEventListener('error', (event) => {
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t.assert.ok(true)
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})
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client.addEventListener('close', (event) => {
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t.assert.deepStrictEqual(event.code, 1006)
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})
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})
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server.on('connection', (ws) => {
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ws.on('close', (code, reason) => {
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t.assert.deepStrictEqual(code, 1008)
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t.assert.deepStrictEqual(reason.toString(), 'Too many message fragments')
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agent.close()
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server.close(done)
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})
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const fragment = Buffer.from('a')
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const options = { fin: false }
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ws.send(fragment, options)
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ws.send(fragment, options)
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ws.send(fragment, options)
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ws.send(fragment, options)
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})
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})
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test('Too many fragments (compressed)', (t, done) => {
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t.plan(4)
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const agent = new Agent({
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webSocket: {
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maxFragments: 3
91+
}
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})
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const server = new WebSocketServer({
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perMessageDeflate: { threshold: 0 },
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port: 0
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}, () => {
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const { port } = server.address()
99+
const client = new WebSocket(`ws://127.0.0.1:${port}`, {
100+
dispatcher: agent
101+
})
102+
103+
client.addEventListener('error', (event) => {
104+
t.assert.ok(true)
105+
})
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client.addEventListener('close', (event) => {
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t.assert.deepStrictEqual(event.code, 1006)
109+
})
110+
})
111+
112+
server.on('connection', (ws) => {
113+
ws.on('close', (code, reason) => {
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t.assert.deepStrictEqual(code, 1008)
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t.assert.deepStrictEqual(reason.toString(), 'Too many message fragments')
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agent.close()
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server.close(done)
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})
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const fragment = Buffer.from('a')
121+
const options = { fin: false }
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ws.send(fragment, options)
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ws.send(fragment, options)
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ws.send(fragment, options)
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ws.send(fragment, options)
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})
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})

‎types/client.d.ts‎

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@@ -116,6 +116,11 @@ export declare namespace Client {
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bytesRead?: number
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}
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export interface WebSocketOptions {
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/**
120+
* Maximum number of fragments in a message. Set to 0 to disable the limit.
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* @default 131072
122+
*/
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maxFragments?: number;
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/**
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* Maximum allowed payload size in bytes for WebSocket messages.
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* Applied to uncompressed messages, compressed frame payloads, and decompressed (permessage-deflate) messages.

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