Add direct proxying

ConnectProxy.js

@@ -0,0 +1,117 @@
+'use strict';
+
+import assert from 'assert';
+import { sanitize } from './util.js';
+import { DIRECT_PROXY } from './settings.js';
+
+const textEncoder = new TextEncoder();
+const textDecoder = new TextDecoder();
+const CONNECTION_ESTABLISHED_REPLY = textEncoder.encode('HTTP/1.0 200 Connection Established\r\nProxy-agent: Apache/2.4.41 (Ubuntu)\r\n\r\n');
+
+// Not sure what this does, but it seems irrelevant.
+const GEOIP_RESPONSE = `HTTP/1.1 200 OK
+Server: nginx/1.24.0
+Date: %NOW%
+Content-Type: application/json
+Content-Length: 19
+Connection: keep-alive
+Cache-Control: max-age=604800, private
+Access-Control-Allow-Origin: *
+
+{"continent":"NA"}
+`;
+
+const LIST_RESPONSE = `HTTP/1.1 200 OK
+Server: nginx/1.24.0
+Date: %NOW%
+Content-Type: application/json
+Content-Length: %LENGTH%
+Last-Modified: %NOW%
+Connection: keep-alive
+Access-Control-Allow-Origin: *
+
+%PAYLOAD%
+`;
+
+const PAYLOAD = {
+    'total': { 'servers': DIRECT_PROXY.length, 'clients': 0 },
+    'total_max': { 'server': DIRECT_PROXY.length, 'clients': 0 },
+    'list': DIRECT_PROXY.map(([vip, ip, port]) => {
+        return {
+            'address': vip,
+            'ip': vip,
+            'port': port,
+            'proto_min': 37,
+            'proto_max': 42,
+       }}),
+};
+
+// Fake a CONNECT proxy to simulate servers.minetest.net response
+export class ConnectProxy {
+    constructor(client) {
+        this.client = client;
+        this.firstLine = true;
+        this.conn = null;
+    }
+
+    forward(data) {
+        if (this.firstLine) {
+            this.firstLine = false;
+            this.handle_handshake(data);
+            return;
+        }
+        if (!(data instanceof ArrayBuffer)) {
+            throw new Error("ConnectProxy received non-binary messages");
+        }
+        data = textDecoder.decode(data);
+        assert(data.endsWith('\r\n\r\n'));
+        let lines = data.split('\r\n');
+        assert(lines.length >= 1);
+        let tokens = lines[0].split(' ');
+        assert(tokens[0] == 'GET');
+        let url = sanitize(tokens[1]);
+        const now = (new Date()).toUTCString();
+        let response;
+        if (url.startsWith('/geoip')) {
+            response = GEOIP_RESPONSE.replace(/%NOW%/g, now);
+        } else if (url.startsWith('/list')) {
+            const payload = JSON.stringify(PAYLOAD);
+            response = LIST_RESPONSE.replace(/%NOW%/g, now).replace('%LENGTH%', payload.length + 1).replace('%PAYLOAD%', payload);
+            this.client.log("Sending virtual server list")
+        } else {
+            this.client.log(`Invalid GET request for ${url}`);
+            this.client.close();
+            return;
+        }
+        this.client.send(textEncoder.encode(response));
+    }
+
+    handle_handshake(data) {
+        // The CONNECT line and it's headers could be split among several packets.
+        // In a real server, this would aggregate data until it sees \r\n\r\n
+        // But minetest-wasm always sends it as one packet, so just assume that.
+        data = textDecoder.decode(data);
+        assert(data.endsWith('\r\n\r\n'));
+        let lines = data.split('\r\n');
+        assert(lines.length >= 1);
+        let tokens = lines[0].split(' ');
+        assert.strictEqual(tokens.length, 3);
+        assert.strictEqual(tokens[0], 'CONNECT');
+        assert.strictEqual(tokens[2], 'HTTP/1.1');
+        let host_port = tokens[1].split(':');
+        assert.strictEqual(host_port.length, 2);
+        let host = host_port[0];
+        let port = parseInt(host_port[1]);
+        if (host != 'servers.minetest.net' || port != 80) {
+            this.client.log(`Ignoring request to proxy to ${host}:${port}`);
+            this.client.close();
+            return;
+        }
+        this.client.log('Connected for server list');
+        this.client.send(CONNECTION_ESTABLISHED_REPLY);
+    }
+
+    close() {
+        this.client.close();
+    }
+}

UDPProxy.js

@@ -0,0 +1,75 @@
+'use strict';
+
+import dgram from 'dgram';
+
+export class UDPProxy {
+    constructor(client, ip, port) {
+        const socket = dgram.createSocket('udp4');
+        this.client = client;
+        this.socket = socket;
+        this.ip = ip;
+        this.port = port;
+        this.sendok = false;
+        this.sendqueue = [];
+        socket.on('listening', this.handle_listening.bind(this));
+        socket.on('error', this.handle_error.bind(this));
+        socket.on('message', this.handle_message.bind(this));
+        socket.bind();
+    }
+
+    forward(data) {
+        // This creates a view of the ArrayBuffer
+        data = new Uint8Array(data);
+        if (data.byteLength < 4 ||
+            data[0] != 0x4f ||
+            data[1] != 0x45 ||
+            data[2] != 0x74 ||
+            data[3] != 0x03) {
+            throw new Error('Client sent packet with invalid protocol.');
+        }
+
+        if (this.sendok) {
+            // data must be a typed array here
+            this.socket.send(data, this.port, this.ip);
+        } else {
+            this.sendqueue.push(data);
+        }
+    }
+
+    handle_listening() {
+        const sourcePort = this.socket.address().port;
+        this.log(`Bound ${sourcePort} -> ${this.ip}:${this.port}`);
+        this.sendok = true;
+        if (this.sendqueue.length > 0) {
+            for (const data of this.sendqueue) {
+                this.socket.send(data, this.port, this.ip);
+            }
+            this.sendqueue = [];
+        }
+    }
+
+    handle_error(err) {
+        this.log("Socket error: " + err);
+        this.close();
+    }
+
+    handle_message(msg, rinfo) {
+        if (rinfo.address != this.ip || rinfo.port != this.port) {
+            this.log("Ignoring unsolicited packet from " + rinfo.address + " port " + rinfo.port);
+            return;
+        }
+        this.client.send(msg);
+    }
+
+    log(msg) {
+        this.client.log(msg);
+    }
+
+    close() {
+        if (this.socket) {
+            this.socket.close();
+            this.socket = null;
+        }
+        this.client.close();
+    }
+}

client.js

@@ -1,8 +1,14 @@
 'use strict';
 
+import assert from 'assert';
+import { isIPv4 } from 'net';
+import { format } from 'util'; // node.js built-in
+
+import { DIRECT_PROXY } from './settings.js';
+import { ConnectProxy } from './ConnectProxy.js';
+import { UDPProxy } from './UDPProxy.js';
 import { extract_ip_chain, sanitize } from './util.js';
 import { vpn_make, vpn_connect} from './vpn.js';
-import { format } from 'util'; // node.js built-in
 const textDecoder = new TextDecoder();
 
 let lastlog = null;
@@ -99,6 +105,20 @@ export class Client {
                 return;
             }
             response = 'BIND OK';
+        } else if (command == 'PROXY') {
+            assert(tokens[2] == 'TCP' || tokens[2] == 'UDP');
+            const isUDP = (tokens[2] == 'UDP');
+            const ip = sanitize(tokens[3]);
+            const port = parseInt(sanitize(tokens[4]));
+            assert(isIPv4(ip));
+            assert(port >= 1 && port < 65536);
+            this.target = route(this, isUDP, ip, port);
+            if (!this.target) {
+                this.log(`Proxy to udp=${isUDP}, ip=${ip}, port=${port} rejected`);
+                response = 'PROXY FAIL';
+            } else {
+                response = 'PROXY OK';
+            }
         } else {
             this.log('Unhandled command: ', data);
             this.close();
@@ -108,3 +128,17 @@ export class Client {
     }
 
 }
+
+const PROXY_MAP = new Map(DIRECT_PROXY.map(([vip,ip,port]) => [vip, [ip, port]]));
+
+function route(client, isUDP, ip, port) {
+    if (!isUDP && ip == '10.0.0.1' && port == 8080) {
+        return new ConnectProxy(client);
+    }
+    if (isUDP && PROXY_MAP.has(ip)) {
+        let [real_ip, real_port] = PROXY_MAP.get(ip);
+        return new UDPProxy(client, real_ip, real_port);
+    }
+
+    return null;
+}

main.js

@@ -1,7 +1,6 @@
 'use strict';
 
-const PROXY_PORT = 8888;
-
+import { PROXY_PORT } from './settings.js';
 import { WebSocketServer } from 'ws';
 import { Client } from './client.js';
 

settings.js

@@ -0,0 +1,15 @@
+
+export const PROXY_PORT = 8888;
+
+// [virtual_ip, real_ip, real_port]
+//
+// The virtual IP is the one that minetest-wasm sees.
+// The virtual port is the same as the real port.
+//
+export const DIRECT_PROXY = [
+    // This allows clients to connect to a server running on the proxy itself.
+    ['192.168.0.1', '127.0.0.1', 30000],
+
+    // This would allow clients to connect to 1.2.3.4, port 40000
+    //['192.168.0.2', '1.2.3.4', 40000],
+];