added test for invalid authority

Author: siddhijain

msal4j-sdk/src/integrationtest/java/com.microsoft.aad.msal4j/InvalidAuthorityIT.java

@@ -0,0 +1,26 @@
+package com.microsoft.aad.msal4j;
+
+import org.testng.annotations.Test;
+
+import java.net.URI;
+import java.util.Collections;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
+
+public class InvalidAuthorityIT extends SeleniumTest{
+
+    @Test(expectedExceptions = ExecutionException.class, expectedExceptionsMessageRegExp = ".*?invalid instance.*?")
+    public void acquireTokenWithAuthorizationCode_InvalidAuthority() throws Exception{
+        PublicClientApplication app;
+        app = PublicClientApplication.builder(
+                        TestConfiguration.AAD_CLIENT_ID)
+                .authority("https://dummy.microsoft.com/common") //invalid authority, request fails at instance discovery
+                .build();
+
+        CompletableFuture<IAuthenticationResult> future = app.acquireToken(
+                AuthorizationCodeParameters.builder("auth_code", new URI(TestConfiguration.AAD_DEFAULT_REDIRECT_URI))
+                        .scopes(Collections.singleton("default-scope"))
+                        .authorizationCode("auth_code").redirectUri(new URI(TestConfiguration.AAD_DEFAULT_REDIRECT_URI)).build());
+        future.get();
+    }
+}

msal4j-sdk/src/main/java/com/microsoft/aad/msal4j/AadInstanceDiscoveryProvider.java

@@ -236,17 +236,18 @@ private static AadInstanceDiscoveryResponse sendInstanceDiscoveryRequest(URL aut
 
         httpResponse = executeRequest(instanceDiscoveryRequestUrl, msalRequest.headers().getReadonlyHeaderMap(), msalRequest, serviceBundle);
 
+        AadInstanceDiscoveryResponse response = JsonHelper.convertJsonToObject(httpResponse.body(), AadInstanceDiscoveryResponse.class);
+
         if (httpResponse.statusCode() != HttpHelper.HTTP_STATUS_200) {
-            if(httpResponse.statusCode() == HttpHelper.HTTP_STATUS_400 && httpResponse.body().equals("invalid_instance")){
+            if(httpResponse.statusCode() == HttpHelper.HTTP_STATUS_400 && response.error().equals("invalid_instance")){
                 // instance discovery failed due to an invalid authority, throw an exception.
                 throw MsalServiceExceptionFactory.fromHttpResponse(httpResponse);
             }
             // instance discovery failed due to reasons other than an invalid authority, do not perform instance discovery again in this environment.
             instanceDiscoveryFailed = true;
         }
 
-
-        return JsonHelper.convertJsonToObject(httpResponse.body(), AadInstanceDiscoveryResponse.class);
+        return response;
     }
 
     private static int determineRegionOutcome(String detectedRegion, String providedRegion, boolean autoDetect) {