finalize async update for autodiscover

Author: gautamsi

src/js/Autodiscover/AutodiscoverDnsClient.ts

@@ -1,47 +1,170 @@
-import { DnsSrvRecord } from "../Dns/DnsSrvRecord";
-import { AutodiscoverService } from "./AutodiscoverService";
+import { AutodiscoverService } from "./AutodiscoverService";
+import { EwsLogging } from "../Core/EwsLogging";
+import { StringHelper } from "../ExtensionMethods";
+import { TraceFlags } from "../Enumerations/TraceFlags";
+
+interface DnsSrvRecord {
+  priority: number;
+  weight: number;
+  port: number;
+  name: string;
+}
 
 /**
  * @internal Class that reads AutoDiscover configuration information from DNS.
  */
 export class AutodiscoverDnsClient {
-    //#region Constants
-    /**
-     * SRV DNS prefix to lookup.
-     *
-     * @static
-     */
-    private static AutoDiscoverSrvPrefix: string = "_autodiscover._tcp.";
-
-    /**
-     * We are only interested in records that use SSL.
-     *
-     * @static
-     */
-    private static SslPort: number = 443;
-    //#endregion
+  //#region Constants
+  /**
+   * SRV DNS prefix to lookup.
+   *
+   * @static
+   */
+  private static AutoDiscoverSrvPrefix: string = "_autodiscover._tcp.";
+
+  /**
+   * We are only interested in records that use SSL.
+   *
+   * @static
+   */
+  private static SslPort: number = 443;
+  //#endregion
+
+  /**
+   * Random selector in the case of ties.
+   *
+   * @static
+   */
+  private static randomTieBreakerSelector: any;
+
+  /**
+   * AutodiscoverService using this DNS reader.
+   */
+  private service: AutodiscoverService;
+
+  /**
+   * @internal Initializes a new instance of the **AutodiscoverDnsClient** class.
+   *
+   * @param   {AutodiscoverService}   service   The service.
+   */
+  constructor(service: AutodiscoverService) {
+    this.service = service;
+  }
 
-    /**
-     * Random selector in the case of ties.
-     *
-     * @static
-     */
-    private static randomTieBreakerSelector: any;
-    
-    /**
-     * AutodiscoverService using this DNS reader.
-     */
-    private service: AutodiscoverService;
-
-    /**
-     * Initializes a new instance of the **AutodiscoverDnsClient** class.
-     *
-     * @param   {AutodiscoverService}   service   The service.
-     */    
-    constructor(service: AutodiscoverService) {
-        this.service = service;
+  //#region Instance methods
+
+  /**
+   * @internal Finds the Autodiscover host from DNS SRV records.
+   *  @remarks    If the domain to lookup is "contoso.com", Autodiscover will use DnsQuery on SRV records for "_autodiscover._tcp.contoso.com". If the query is successful it will return a target domain (e.g. "mail.contoso.com") which will be tried as an Autodiscover endpoint.
+   * @param   {string}   domain   The domain.
+   * @return  {Promise<string>}   Autodiscover hostname (will be null if lookup failed).
+   */
+  async FindAutodiscoverHostFromSrv(domain: string): Promise<string> {
+    const domainToMatch: string = AutodiscoverDnsClient.AutoDiscoverSrvPrefix + domain;
+
+    const dnsSrvRecord: DnsSrvRecord = await this.FindBestMatchingSrvRecord(domainToMatch);
+
+    if ((dnsSrvRecord == null) || StringHelper.IsNullOrEmpty(dnsSrvRecord.name)) {
+      this.service.TraceMessage(
+        TraceFlags.AutodiscoverConfiguration,
+        "No appropriate SRV record was found.");
+      return null;
     }
-    
-    FindAutodiscoverHostFromSrv(domain: string): string { throw new Error("AutodiscoverDnsClient.ts - FindAutodiscoverHostFromSrv : Not implemented."); }
-    FindBestMatchingSrvRecord(domain: string): DnsSrvRecord { throw new Error("AutodiscoverDnsClient.ts - FindBestMatchingSrvRecord : Not implemented."); }
+
+    this.service.TraceMessage(
+      TraceFlags.AutodiscoverConfiguration,
+      StringHelper.Format("DNS query for SRV record for domain {0} found {1}", domain, dnsSrvRecord.name));
+
+    return dnsSrvRecord.name;
+
+  }
+
+  /**
+   * Finds the best matching SRV record.
+   *
+   * @param   {string}   domain   The domain.
+   * @return  {Promise<DnsSrvRecord>}      DnsSrvRecord(will be null if lookup failed).
+   */
+  private async FindBestMatchingSrvRecord(domain: string): Promise<DnsSrvRecord> {
+    return new Promise((resolve, reject) => {
+
+      let dnsSrvRecordList: DnsSrvRecord[];
+      let dns = null;
+      try {
+        // try to get the dns client, only works on nodejs, not valid in browser\
+        dns = require("dns");
+      } catch (error) {
+        resolve(null);
+        return;
+      }
+
+      if (!StringHelper.IsNullOrEmpty(this.service.DnsServerAddress)) {
+        const servers = dns.getServers();
+        dns.setServers([this.service.DnsServerAddress, ...servers]);
+      }
+
+      dns.resolveSrv(domain, (dnsError, dnsSrvRecordList) => {
+        if (dnsError) {
+          const dnsExcMessage = StringHelper.Format(
+            "DnsQuery returned error error '{0}' error code '{1}'.",
+            dnsError.message,
+            dnsError.code || dnsError.errno);
+          resolve(null);
+          return;
+        }
+        this.service.TraceMessage(
+          TraceFlags.AutodiscoverConfiguration,
+          StringHelper.Format("{0} SRV records were returned.", (dnsSrvRecordList || []).length));
+
+        if (!dnsSrvRecordList || dnsSrvRecordList.length === 0) {
+          resolve(null);
+          return;
+        }
+
+        // filter the addresses with ssl port
+        dnsSrvRecordList = dnsSrvRecordList.filter(a => a.port === AutodiscoverDnsClient.SslPort);
+
+        // Records were returned but nothing matched our criteria.
+        if (dnsSrvRecordList.length === 0) {
+          this.service.TraceMessage(
+            TraceFlags.AutodiscoverConfiguration,
+            "No appropriate SRV records were found.");
+          resolve(null);
+          return;
+        }
+
+        // sort all records with the same (highest) priority and weight.
+        let bestDnsSrvRecordList = dnsSrvRecordList.sort((a, b) => a.priority === b.priority ? b.weight - a.weight : a.priority - b.priority);
+
+        // pick top one which has highest priority and highest weight value
+        const priority = bestDnsSrvRecordList[0].priority;
+        const weight = bestDnsSrvRecordList[0].weight;
+
+        // filter with highest priority and weight;
+        bestDnsSrvRecordList = bestDnsSrvRecordList.filter(a => a.priority === priority && a.weight === weight);
+
+        // The list must contain at least one matching record since we found one earlier.
+        EwsLogging.Assert(
+          dnsSrvRecordList.length > 0,
+          "AutodiscoverDnsClient.FindBestMatchingSrvRecord",
+          "At least one DNS SRV record must match the criteria.");
+
+        // If we have multiple records with the same priority and weight, randomly pick one.
+        const recordIndex = bestDnsSrvRecordList.length > 1 ? Math.floor(Math.random() * Math.floor(bestDnsSrvRecordList.length)) : 0;
+        const bestDnsSrvRecord: DnsSrvRecord = bestDnsSrvRecordList[recordIndex];
+        const traceMessage = StringHelper.Format(
+          "Returning SRV record {0} of {1} records. Target: {2}, Priority: {3}, Weight: {4}",
+          recordIndex,
+          dnsSrvRecordList.length,
+          bestDnsSrvRecord.name,
+          bestDnsSrvRecord.priority,
+          bestDnsSrvRecord.weight);
+        this.service.TraceMessage(TraceFlags.AutodiscoverConfiguration, traceMessage);
+
+        resolve(bestDnsSrvRecord);
+      });
+    });
+
+    //#endregion
+  }
 }