feat: add proxy support for tracker clients (#356)

* Add a httpAgent options to http and websocket client trackers.

* Add a socks proxy to udp client trackers.

* Update http agent mock to node 5+

* Bugfix in socks configuration

* Use new socket to connect to the proxy relay and slice the proxy header from the message

* Add documentation for proxy

* Provide http and https agents for proxy.
Change proxy options structure and auto populate socks HTTP agents.

* Update documentation

* Check socks version for UDP proxy

* Clone proxy settings to prevent Socks instances concurrency

* Generate socks http agents on the fly (reuse is not working)

* Use clone to deepcopy socks opts

* Dont create agent for now since we cannot reuse it between requests.

* Removed unused require

* Add .gitignore

* Fix merge conflict

* Fix URL toString

* Fix new Socket constructor

Co-authored-by: Yoann Ciabaud <yoann@sonora.io>

README.md

@@ -65,6 +65,12 @@ var requiredOpts = {
 }
 
 var optionalOpts = {
+  // RTCPeerConnection config object (only used in browser)
+  rtcConfig: {},
+  // User-Agent header for http requests
+  userAgent: '',
+  // Custom webrtc impl, useful in node to specify [wrtc](https://npmjs.com/package/wrtc)
+  wrtc: {},
   getAnnounceOpts: function () {
     // Provide a callback that will be called whenever announce() is called
     // internally (on timer), or by the user
@@ -75,12 +81,44 @@ var optionalOpts = {
       customParam: 'blah' // custom parameters supported
     }
   },
-  // RTCPeerConnection config object (only used in browser)
-  rtcConfig: {},
-  // User-Agent header for http requests
-  userAgent: '',
-  // Custom webrtc impl, useful in node to specify [wrtc](https://npmjs.com/package/wrtc)
-  wrtc: {},
+  // Proxy config object
+  proxyOpts: {
+      // Socks proxy options (used to proxy requests in node)
+      socksProxy: {
+          // Configuration from socks module (https://github.com/JoshGlazebrook/socks)
+          proxy: {
+              // IP Address of Proxy (Required)
+              ipaddress: "1.2.3.4",
+              // TCP Port of Proxy (Required)
+              port: 1080,
+              // Proxy Type [4, 5] (Required)
+              // Note: 4 works for both 4 and 4a.
+              // Type 4 does not support UDP association relay 
+              type: 5,
+
+              // SOCKS 4 Specific:
+
+              // UserId used when making a SOCKS 4/4a request. (Optional)
+              userid: "someuserid",
+
+              // SOCKS 5 Specific:
+
+              // Authentication used for SOCKS 5 (when it's required) (Optional)
+              authentication: {
+                  username: "Josh",
+                  password: "somepassword"
+              }
+          },
+
+          // Amount of time to wait for a connection to be established. (Optional)
+          // - defaults to 10000ms (10 seconds)
+          timeout: 10000
+      },
+      // NodeJS HTTP agents (used to proxy HTTP and Websocket requests in node)
+      // Populated with Socks.Agent if socksProxy is provided
+      httpAgent: {},
+      httpsAgent: {}
+  },
 }
 
 var client = new Client(requiredOpts)

client.js

@@ -24,6 +24,7 @@ const WebSocketTracker = require('./lib/client/websocket-tracker')
  * @param {number} opts.rtcConfig                RTCPeerConnection configuration object
  * @param {number} opts.userAgent                User-Agent header for http requests
  * @param {number} opts.wrtc                     custom webrtc impl (useful in node.js)
+ * @param {object} opts.proxyOpts                proxy options (useful in node.js)
  */
 class Client extends EventEmitter {
   constructor (opts = {}) {
@@ -54,6 +55,7 @@ class Client extends EventEmitter {
     this._getAnnounceOpts = opts.getAnnounceOpts
     this._rtcConfig = opts.rtcConfig
     this._userAgent = opts.userAgent
+    this._proxyOpts = opts.proxyOpts
 
     // Support lazy 'wrtc' module initialization
     // See: https://github.com/webtorrent/webtorrent-hybrid/issues/46

lib/client/http-tracker.js

@@ -1,8 +1,10 @@
 const arrayRemove = require('unordered-array-remove')
 const bencode = require('bencode')
+const clone = require('clone')
 const compact2string = require('compact2string')
 const debug = require('debug')('bittorrent-tracker:http-tracker')
 const get = require('simple-get')
+const Socks = require('socks')
 
 const common = require('../common')
 const Tracker = require('./tracker')
@@ -110,13 +112,20 @@ class HTTPTracker extends Tracker {
 
   _request (requestUrl, params, cb) {
     const self = this
-    const u = requestUrl + (!requestUrl.includes('?') ? '?' : '&') +
-      common.querystringStringify(params)
+    const parsedUrl = new URL(requestUrl + (requestUrl.indexOf('?') === -1 ? '?' : '&') + common.querystringStringify(params))
+    let agent
+    if (this.client._proxyOpts) {
+      agent = parsedUrl.protocol === 'https:' ? this.client._proxyOpts.httpsAgent : this.client._proxyOpts.httpAgent
+      if (!agent && this.client._proxyOpts.socksProxy) {
+        agent = new Socks.Agent(clone(this.client._proxyOpts.socksProxy), (parsedUrl.protocol === 'https:'))
+      }
+    }
 
     this.cleanupFns.push(cleanup)
 
     let request = get.concat({
-      url: u,
+      url: parsedUrl.toString(),
+      agent: agent,
       timeout: common.REQUEST_TIMEOUT,
       headers: {
         'user-agent': this.client._userAgent || ''

lib/client/udp-tracker.js

@@ -1,9 +1,11 @@
 const arrayRemove = require('unordered-array-remove')
 const BN = require('bn.js')
+const clone = require('clone')
 const compact2string = require('compact2string')
 const debug = require('debug')('bittorrent-tracker:udp-tracker')
 const dgram = require('dgram')
 const randombytes = require('randombytes')
+const Socks = require('socks')
 
 const common = require('../common')
 const Tracker = require('./tracker')
@@ -77,27 +79,65 @@ class UDPTracker extends Tracker {
     let { hostname, port } = common.parseUrl(this.announceUrl)
     if (port === '') port = 80
 
+    let timeout
+    // Socket used to connect to the socks server to create a relay, null if socks is disabled
+    let proxySocket
+    // Socket used to connect to the tracker or to the socks relay if socks is enabled
+    let socket
+    // Contains the host/port of the socks relay
+    let relay
+
     let transactionId = genTransactionId()
-    let socket = dgram.createSocket('udp4')
 
-    let timeout = setTimeout(() => {
-      // does not matter if `stopped` event arrives, so supress errors
-      if (opts.event === 'stopped') cleanup()
-      else onError(new Error(`tracker request timed out (${opts.event})`))
-      timeout = null
-    }, common.REQUEST_TIMEOUT)
-    if (timeout.unref) timeout.unref()
+    const proxyOpts = this.client._proxyOpts && clone(this.client._proxyOpts.socksProxy)
+    if (proxyOpts) {
+      if (!proxyOpts.proxy) proxyOpts.proxy = {}
+      // UDP requests uses the associate command
+      proxyOpts.proxy.command = 'associate'
+      if (!proxyOpts.target) {
+        // This should contain client IP and port but can be set to 0 if we don't have this information
+        proxyOpts.target = {
+          host: '0.0.0.0',
+          port: 0
+        }
+      }
+
+      if (proxyOpts.proxy.type === 5) {
+        Socks.createConnection(proxyOpts, onGotConnection)
+      } else {
+        debug('Ignoring Socks proxy for UDP request because type 5 is required')
+        onGotConnection(null)
+      }
+    } else {
+      onGotConnection(null)
+    }
 
     this.cleanupFns.push(cleanup)
 
-    send(Buffer.concat([
-      common.CONNECTION_ID,
-      common.toUInt32(common.ACTIONS.CONNECT),
-      transactionId
-    ]))
+    function onGotConnection (err, s, info) {
+      if (err) return onError(err)
 
-    socket.once('error', onError)
-    socket.on('message', onSocketMessage)
+      proxySocket = s
+      socket = dgram.createSocket('udp4')
+      relay = info
+
+      timeout = setTimeout(() => {
+        // does not matter if `stopped` event arrives, so supress errors
+        if (opts.event === 'stopped') cleanup()
+        else onError(new Error(`tracker request timed out (${opts.event})`))
+        timeout = null
+      }, common.REQUEST_TIMEOUT)
+      if (timeout.unref) timeout.unref()
+
+      send(Buffer.concat([
+        common.CONNECTION_ID,
+        common.toUInt32(common.ACTIONS.CONNECT),
+        transactionId
+      ]), relay)
+
+      socket.once('error', onError)
+      socket.on('message', onSocketMessage)
+    }
 
     function cleanup () {
       if (timeout) {
@@ -111,6 +151,10 @@ class UDPTracker extends Tracker {
         socket.on('error', noop) // ignore all future errors
         try { socket.close() } catch (err) {}
         socket = null
+        if (proxySocket) {
+          try { proxySocket.close() } catch (err) {}
+          proxySocket = null
+        }
       }
       if (self.maybeDestroyCleanup) self.maybeDestroyCleanup()
     }
@@ -128,6 +172,7 @@ class UDPTracker extends Tracker {
     }
 
     function onSocketMessage (msg) {
+      if (proxySocket) msg = msg.slice(10)
       if (msg.length < 8 || msg.readUInt32BE(4) !== transactionId.readUInt32BE(0)) {
         return onError(new Error('tracker sent invalid transaction id'))
       }
@@ -211,8 +256,13 @@ class UDPTracker extends Tracker {
       }
     }
 
-    function send (message) {
-      socket.send(message, 0, message.length, port, hostname)
+    function send (message, proxyInfo) {
+      if (proxyInfo) {
+        const pack = Socks.createUDPFrame({ host: hostname, port: port }, message)
+        socket.send(pack, 0, pack.length, proxyInfo.port, proxyInfo.host)
+      } else {
+        socket.send(message, 0, message.length, port, hostname)
+      }
     }
 
     function announce (connectionId, opts) {
@@ -232,7 +282,7 @@ class UDPTracker extends Tracker {
         common.toUInt32(0), // key (optional)
         common.toUInt32(opts.numwant),
         toUInt16(self.client._port)
-      ]))
+      ]), relay)
     }
 
     function scrape (connectionId) {
@@ -247,7 +297,7 @@ class UDPTracker extends Tracker {
         common.toUInt32(common.ACTIONS.SCRAPE),
         transactionId,
         infoHash
-      ]))
+      ]), relay)
     }
   }
 }

lib/client/websocket-tracker.js

@@ -1,7 +1,9 @@
+const clone = require('clone')
 const debug = require('debug')('bittorrent-tracker:websocket-tracker')
 const Peer = require('simple-peer')
 const randombytes = require('randombytes')
 const Socket = require('simple-websocket')
+const Socks = require('socks')
 
 const common = require('../common')
 const Tracker = require('./tracker')
@@ -176,7 +178,15 @@ class WebSocketTracker extends Tracker {
         this._onSocketConnectBound()
       }
     } else {
-      this.socket = socketPool[this.announceUrl] = new Socket(this.announceUrl)
+      const parsedUrl = new URL(this.announceUrl)
+      let agent
+      if (this.client._proxyOpts) {
+        agent = parsedUrl.protocol === 'wss:' ? this.client._proxyOpts.httpsAgent : this.client._proxyOpts.httpAgent
+        if (!agent && this.client._proxyOpts.socksProxy) {
+          agent = new Socks.Agent(clone(this.client._proxyOpts.socksProxy), (parsedUrl.protocol === 'wss:'))
+        }
+      }
+      this.socket = socketPool[this.announceUrl] = new Socket({ url: this.announceUrl, agent: agent })
       this.socket.consumers = 1
       this.socket.once('connect', this._onSocketConnectBound)
     }

package.json

@@ -14,7 +14,8 @@
     "./lib/common-node.js": false,
     "./lib/client/http-tracker.js": false,
     "./lib/client/udp-tracker.js": false,
-    "./server.js": false
+    "./server.js": false,
+    "socks": false
   },
   "chromeapp": {
     "./server.js": false,
@@ -28,6 +29,7 @@
     "bittorrent-peerid": "^1.3.3",
     "bn.js": "^5.2.0",
     "chrome-dgram": "^3.0.6",
+    "clone": "^1.0.2",
     "compact2string": "^1.4.1",
     "debug": "^4.1.1",
     "ip": "^1.1.5",
@@ -42,6 +44,7 @@
     "simple-get": "^4.0.0",
     "simple-peer": "^9.11.0",
     "simple-websocket": "^9.1.0",
+    "socks": "^1.1.9",
     "string2compact": "^1.3.0",
     "unordered-array-remove": "^1.0.2",
     "ws": "^7.4.5"

test/client.js

@@ -1,6 +1,8 @@
 const Client = require('../')
 const common = require('./common')
+const http = require('http')
 const fixtures = require('webtorrent-fixtures')
+const net = require('net')
 const test = require('tape')
 
 const peerId1 = Buffer.from('01234567890123456789')
@@ -565,3 +567,56 @@ test('ws: invalid tracker url', t => {
 test('ws: invalid tracker url with slash', t => {
   testUnsupportedTracker(t, 'ws://')
 })
+
+function testClientStartHttpAgent (t, serverType) {
+  t.plan(5)
+
+  common.createServer(t, serverType, function (server, announceUrl) {
+    const agent = new http.Agent()
+    let agentUsed = false
+    agent.createConnection = function (opts, fn) {
+      agentUsed = true
+      return net.createConnection(opts, fn)
+    }
+    const client = new Client({
+      infoHash: fixtures.leaves.parsedTorrent.infoHash,
+      announce: announceUrl,
+      peerId: peerId1,
+      port: port,
+      wrtc: {},
+      proxyOpts: {
+        httpAgent: agent
+      }
+    })
+
+    if (serverType === 'ws') common.mockWebsocketTracker(client)
+    client.on('error', function (err) { t.error(err) })
+    client.on('warning', function (err) { t.error(err) })
+
+    client.once('update', function (data) {
+      t.equal(data.announce, announceUrl)
+      t.equal(typeof data.complete, 'number')
+      t.equal(typeof data.incomplete, 'number')
+
+      t.ok(agentUsed)
+
+      client.stop()
+
+      client.once('update', function () {
+        t.pass('got response to stop')
+        server.close()
+        client.destroy()
+      })
+    })
+
+    client.start()
+  })
+}
+
+test('http: client.start(httpAgent)', function (t) {
+  testClientStartHttpAgent(t, 'http')
+})
+
+test('ws: client.start(httpAgent)', function (t) {
+  testClientStartHttpAgent(t, 'ws')
+})