Add Base64Test case for some base64 decoding edge cases (#644)

* Add Base64Test case for some base64 decoding edge cases

* Preserve decoding behavior for null decodeBase64(null)

* Handle encoding with null inputs

Author: chingor13

google-http-client/src/main/java/com/google/api/client/util/Base64.java

@@ -43,6 +43,9 @@ public static byte[] encodeBase64(byte[] binaryData) {
    * @return String containing Base64 characters or {@code null} for {@code null} input
    */
   public static String encodeBase64String(byte[] binaryData) {
+    if (binaryData == null) {
+      return null;
+    }
     return BaseEncoding.base64().encode(binaryData);
   }
 
@@ -66,6 +69,9 @@ public static byte[] encodeBase64URLSafe(byte[] binaryData) {
    * @return String containing Base64 characters or {@code null} for {@code null} input
    */
   public static String encodeBase64URLSafeString(byte[] binaryData) {
+    if (binaryData == null) {
+      return null;
+    }
     return BaseEncoding.base64Url().omitPadding().encode(binaryData);
   }
 
@@ -88,11 +94,14 @@ public static byte[] decodeBase64(byte[] base64Data) {
    * @return Array containing decoded data or {@code null} for {@code null} input
    */
   public static byte[] decodeBase64(String base64String) {
+    if (base64String == null) {
+      return null;
+    }
     try {
       return BaseEncoding.base64().decode(base64String);
     } catch (IllegalArgumentException e) {
       if (e.getCause() instanceof DecodingException) {
-        return BaseEncoding.base64Url().decode(base64String);
+        return BaseEncoding.base64Url().decode(base64String.trim());
       }
       throw e;
     }

google-http-client/src/test/java/com/google/api/client/util/Base64Test.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2019 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.api.client.util;
+
+import java.nio.charset.StandardCharsets;
+import junit.framework.TestCase;
+
+/**
+ * Tests {@link Base64}.
+ *
+ * @author Jeff Ching
+ */
+public class Base64Test extends TestCase {
+
+  public void test_decodeBase64_withPadding() {
+    String encoded = "Zm9vOmJhcg==";
+    assertEquals("foo:bar", new String(Base64.decodeBase64(encoded), StandardCharsets.UTF_8));
+  }
+
+  public void test_decodeBase64_withoutPadding() {
+    String encoded = "Zm9vOmJhcg";
+    assertEquals("foo:bar", new String(Base64.decodeBase64(encoded), StandardCharsets.UTF_8));
+  }
+
+  public void test_decodeBase64_withTrailingWhitespace() {
+    // Some internal use cases append extra space characters that apache-commons base64 decoding
+    // previously handled.
+    String encoded = "Zm9vOmJhcg==\r\n";
+    assertEquals("foo:bar", new String(Base64.decodeBase64(encoded), StandardCharsets.UTF_8));
+  }
+
+  public void test_decodeBase64_withNullBytes_shouldReturnNull() {
+    byte[] encoded = null;
+    assertNull(Base64.decodeBase64(encoded));
+  }
+
+  public void test_decodeBase64_withNull_shouldReturnNull() {
+    String encoded = null;
+    assertNull(Base64.decodeBase64(encoded));
+  }
+
+  public void test_encodeBase64URLSafeString_withNull_shouldReturnNull() {
+    assertNull(Base64.encodeBase64URLSafeString(null));
+  }
+
+  public void test_encodeBase64URLSafe_withNull_shouldReturnNull() {
+    assertNull(Base64.encodeBase64URLSafe(null));
+  }
+
+  public void test_encodeBase64_withNull_shouldReturnNull() {
+    assertNull(Base64.encodeBase64(null));
+  }
+}