implement XhrListener to forward POSTs to WS

src/logger.ts

@@ -7,27 +7,42 @@ const logPath = './logs/';
 const tsFormat = () => (new Date().toISOString());
 const logFormat = format.combine(format.timestamp(), format.json());
 
-function loggerTransports(logName: string, logLevel: string) {
-  return [
-    new transports.File({
+function loggerTransports(logLevel: string, logName = "") {
+  let transport:any;
+  if ("" === logName) {
+    transport = new transports.Console({
+      format: format.simple(),
+      level: logLevel,
+      timestamp: tsFormat
+    });
+  } else {
+    transport = new transports.File({
       filename: path.join(logPath, `${logName}.log`),
       timestamp: tsFormat,
       level: logLevel
-    })
-  ];
+    });
+  }
+
+  return [ transport ];
 }
 
+const debugLog = createLogger({
+  format: format.simple(),
+  transports: loggerTransports('debug')
+});
+
 const errorLog = createLogger({
   format: logFormat,
-  transports: loggerTransports('errors', 'debug')
+  transports: loggerTransports('debug', 'errors')
 });
 
 const accessLog = createLogger({
   format: logFormat,
-  transports: loggerTransports('access', 'info')
+  transports: loggerTransports('info', 'access')
 });
 
 module.exports = {
   errorLog,
-  accessLog
+  accessLog,
+  debugLog
 };

src/server.ts

@@ -9,6 +9,7 @@ const logger = require('./logger');
 
 import ClientManager from './clientManager';
 import ChannelManager from './channelManager';
+import XhrListener from './xhrListener';
 import PublicClient from './clients/types/publicClient';
 import PrivateClient from './clients/types/privateClient';
 import CustomClient from './clients/types/customClient';
@@ -16,6 +17,7 @@ import CustomClient from './clients/types/customClient';
 const wss = new WebSocket.Server({ maxPayload: 250000, port: app.port });
 const clientManager = new ClientManager();
 const channelManager = new ChannelManager();
+const xhrListener = new XhrListener(channelManager);
 
 function connectionManager() {
   wss.on('connection', (ws: WebSocket, request: any, args: string) => {
@@ -63,7 +65,7 @@ function connectionManager() {
 
       channelManager.purgeEmptyChannels();
 
-      ws.send(`Hi there, welcome to braid, Measures Web Socket server. Connecting all our services!\nYou are currently in channel: ${data.channel}`);
+      ws.send(`Hi there! welcome to braid, Measures Web Socket server. Connecting all our services!\nYou are currently in channel: ${data.channel}`);
     }
   });
 }
@@ -88,5 +90,6 @@ startServer();
 module.exports = {
   clientManager,
   channelManager,
-  connectionManager
+  connectionManager,
+  xhrListener
 };

src/xhrListener.ts

@@ -0,0 +1,120 @@
+import ChannelManager from './channelManager'
+
+const logger = require('./logger');
+const url = require('url');
+const http = require('http');
+const crypto = require('crypto');
+const AUTH_TOKEN = process.env.ARCHIMEDES_INTEGRATION_TOKEN || 'sha1=baddbeef'
+const HTTP_PORT = process.env.HTTP_PORT || 80
+
+import { Server, IncomingMessage, ServerResponse } from 'http'
+
+interface ArchimedesMessage {
+  examId: string;
+}
+
+class XhrListener {
+  #cm: ChannelManager;
+
+  constructor(cm: ChannelManager) {
+    // I'm not entirely happy with bind(this) but it does let me break the
+    // callback and event handlers out into class methods. It will be
+    // problematic if the actual `this` needs to be accessed.
+    let xhrlisten = http.createServer(this.onRequest.bind(this));
+    xhrlisten.listen(HTTP_PORT);
+    this.#cm = cm;
+    logger.debugLog.info("XhrListener running");
+  }
+
+  public relayEvent(event: string, channel: string):boolean {
+    logger.debugLog.info(`XhrListener:relayEvent(event: ${event}, channel: ${channel})`);
+    for (let c of this.#cm.channels) {
+      if (channel === c.id) {
+	let dmCount:number = 0;
+	for (let client of c.clients) {
+	  let nonce:string = crypto.randomBytes(4).toString("hex");
+	  // TODO: verify the nonce against the received reply, which we currently ignore
+	  client.directMessage(JSON.stringify({message_type:"broadcast", message:{event_type:event, seq_id:nonce}}));
+	  dmCount++;
+	}
+	// dmCount of 1 would be normal. more than 1 is odd, but not necessarily bad. 0 means Exam UI has gone away somehow.
+	return dmCount > 0;
+      }
+    }
+    // did not match a channel; examId isn't valid for some reason
+    return false;
+  }
+
+  public onRequestEnded(body: Uint8Array[], request: IncomingMessage, response: ServerResponse):void {
+    logger.debugLog.info("XhrListener:onRequestEnded()");
+    if (request.method === 'OPTIONS') {
+      logger.debugLog.info("handling CORS preflight");
+      // CORS: implement permissive policy for XHR clients
+      response.setHeader('Access-Control-Allow-Origin', request.headers['origin'] || "*");
+      response.setHeader('Access-Control-Allow-Methods', request.headers['access-control-request-methods'] || "OPTIONS, GET, POST");
+      response.setHeader('Access-Control-Allow-Headers', request.headers['access-control-request-headers'] || "Content-Type");
+      response.setHeader('Access-Control-Allow-Credentials', "true");
+      response.end();
+    } else {
+      logger.debugLog.info("parsing Archimedes event: " + body);
+      let endpoint = url.parse(request.url).pathname
+      let returnVal: [number, string] = [-1, ""];
+      let authorized:boolean = request.headers['x-proctoru-signature'] === AUTH_TOKEN;
+
+      // body of POST is JSON: '{"examId":"proctor_u_id"}'
+      switch (true) {
+	// match /event/pause*
+        case /^\/event\/pause([/]+.*)*$/.test(endpoint):
+	  if (authorized) {
+            let amsg:ArchimedesMessage = JSON.parse(Buffer.concat(body).toString());
+	    if (this.relayEvent("pauseExam", amsg.examId)) {
+	      returnVal = [200, "pause event was successfully relayed"];
+            } else {
+	      logger.errorLog.info(`XhrListener: could not relay pause event "${amsg}" to Exam UI; body: "${body}"`);
+	      returnVal = [400, "error while relaying pause event"];
+	    }
+          }
+
+	  break;
+
+	// match /event/resume*
+        case /^\/event\/resume([/]+.*)*$/.test(endpoint):
+	  if (authorized) {
+            let amsg:ArchimedesMessage = JSON.parse(Buffer.concat(body).toString());
+	    if (this.relayEvent("resumeExam", amsg.examId)) {
+	      returnVal = [200, "resume event was successfully relayed"];
+            } else {
+	      logger.errorLog.info(`XhrListener: could not relay resume event "${amsg}" to Exam UI; body: "${body}"`);
+	      returnVal = [400, "error while relaying resume event"];
+	    }
+          }
+	  break;
+
+	default:
+	  logger.errorLog.info(`XhrListener: bad event or other request; body: "${body}"`);
+	  returnVal = [400, "Bad request"];
+	  break;
+      };
+
+      if (-1 == returnVal[0]) {
+	response.writeHead(authorized ? 400 : 401);
+	response.end();
+      } else {
+	response.writeHead(returnVal[0], {'Content-Type': 'application/json'});
+        response.end(JSON.stringify(returnVal[1]));
+      }
+    }
+  }
+
+  private onRequest(request: IncomingMessage, response: ServerResponse):void {
+    logger.debugLog.info("XhrListener:onRequest()");
+    let body:Uint8Array[] = [];
+    request.on('data', post_block => body.push(post_block));
+
+    request.on('end', () => {
+      this.onRequestEnded(body, request, response);
+    });
+  }
+}
+
+export default XhrListener;