Strip trailing . from DNS lookups when converting to autodiscover url

- Factored out dns response checks
- Added test case ensuring  validity checks are correct
- Fixes OfficeDev#418

Author: easel

src/main/java/microsoft/exchange/webservices/data/autodiscover/AutodiscoverDnsClient.java

@@ -24,10 +24,10 @@
 package microsoft.exchange.webservices.data.autodiscover;
 
 import microsoft.exchange.webservices.data.core.EwsUtilities;
-import microsoft.exchange.webservices.data.dns.DnsClient;
-import microsoft.exchange.webservices.data.dns.DnsSrvRecord;
 import microsoft.exchange.webservices.data.core.enumeration.misc.TraceFlags;
 import microsoft.exchange.webservices.data.core.exception.dns.DnsException;
+import microsoft.exchange.webservices.data.dns.DnsClient;
+import microsoft.exchange.webservices.data.dns.DnsSrvRecord;
 
 import javax.xml.stream.XMLStreamException;
 
@@ -70,12 +70,28 @@ protected AutodiscoverDnsClient(AutodiscoverService service) {
     this.service = service;
   }
 
+  /**
+   * Extracts a valid autodiscover hostname, if any, from a dns srv response.
+   *
+   * @param dnsNameTarget The hostname response returned by DNS
+   * @return Autodiscover hostname (will be null if dnsNameTarget is invalid).
+   */
+  protected static String extractHostnameFromDnsSrv(String dnsNameTarget) {
+    if (dnsNameTarget == null || dnsNameTarget.isEmpty()) {
+      return null;
+    } else {
+      if (dnsNameTarget.endsWith(".")) {
+        dnsNameTarget = dnsNameTarget.substring(0, dnsNameTarget.length()-1);
+      }
+      return dnsNameTarget;
+    }
+  }
+
   /**
    * Finds the Autodiscover host from DNS SRV records.
    *
    * @param domain the domain
    * @return Autodiscover hostname (will be null if lookup failed).
-   * @throws XMLStreamException the XML stream exception
    * @throws IOException signals that an I/O exception has occurred.
    */
   protected String findAutodiscoverHostFromSrv(String domain)
@@ -84,20 +100,17 @@ protected String findAutodiscoverHostFromSrv(String domain)
 
     DnsSrvRecord dnsSrvRecord = this
         .findBestMatchingSrvRecord(domainToMatch);
-
-    if ((dnsSrvRecord == null) || dnsSrvRecord.getNameTarget() == null ||
-        dnsSrvRecord.getNameTarget().isEmpty()) {
-      this.service.traceMessage(TraceFlags.AutodiscoverConfiguration,
-          "No appropriate SRV record was found.");
-      return null;
-    } else {
-      this.service.traceMessage(TraceFlags.AutodiscoverConfiguration,
-          String.format(
-              "DNS query for SRV record for domain %s found %s",
-              domain, dnsSrvRecord.getNameTarget()));
-
-      return dnsSrvRecord.getNameTarget();
+    if (dnsSrvRecord != null) {
+      String hostName = extractHostnameFromDnsSrv(dnsSrvRecord.getNameTarget());
+      if (hostName != null) {
+        this.service.traceMessage(TraceFlags.AutodiscoverConfiguration, String
+            .format("DNS query for SRV record for domain %s found %s", domain, hostName));
+        return hostName;
+      }
     }
+    this.service.traceMessage(TraceFlags.AutodiscoverConfiguration,
+                              "No appropriate SRV record was found.");
+    return null;
   }
 
   /**

src/test/java/microsoft/exchange/webservices/data/autodiscover/AutodiscoverDnsClientTest.java

@@ -0,0 +1,65 @@
+/*
+ * The MIT License
+ * Copyright (c) 2012 Microsoft Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package microsoft.exchange.webservices.data.autodiscover;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public class AutodiscoverDnsClientTest {
+
+  final String validResponse = "autodiscover.contoso.com";
+  final String trailingDotResponse = "autodiscover.contoso.com.";
+
+  /**
+   * If DNS gives us a null, we should return a null
+   */
+  @Test public void textExtractNullHostnameFromDnsSrv() {
+    assertEquals(AutodiscoverDnsClient.extractHostnameFromDnsSrv(null), null);
+  }
+
+  /**
+   * If DNS gives us back an empty string, we should return a null
+   */
+  @Test public void textExtractEmptyHostnameFromDnsSrv() {
+    assertEquals(AutodiscoverDnsClient.extractHostnameFromDnsSrv(""), null);
+  }
+
+  /**
+   * If DNS gives us back a plain domain, we should pass it through.
+   */
+  @Test public void textExtractValidHostnameFromDnsSrv() {
+    assertEquals(AutodiscoverDnsClient.extractHostnameFromDnsSrv(validResponse), validResponse);
+  }
+
+  /**
+   * If DNS gives us back a domain with a trailing dot, we should strip it.
+   */
+  @Test public void textExtractTrailingDotHostnameFromDnsSrv() {
+    assertEquals(AutodiscoverDnsClient.extractHostnameFromDnsSrv(trailingDotResponse), validResponse);
+  }
+}