be safer when processing parts in AttachmentDownloadJob

Closes #4166
// FREEBIE

test/unitTest/java/org/thoughtcrime/securesms/BaseUnitTest.java

@@ -1,5 +1,6 @@
 package org.thoughtcrime.securesms;
 
+import android.content.Context;
 import android.os.Handler;
 import android.os.Looper;
 import android.util.Log;
@@ -11,15 +12,25 @@ import org.mockito.stubbing.Answer;
 import org.powermock.api.mockito.PowerMockito;
 import org.powermock.core.classloader.annotations.PrepareForTest;
 import org.powermock.modules.junit4.PowerMockRunner;
+import org.thoughtcrime.securesms.crypto.MasterSecret;
+
+import javax.crypto.spec.SecretKeySpec;
 
 import static org.mockito.Matchers.anyString;
+import static org.powermock.api.mockito.PowerMockito.mock;
 import static org.powermock.api.mockito.PowerMockito.mockStatic;
 
 @RunWith(PowerMockRunner.class)
-@PrepareForTest( { Log.class, Handler.class, Looper.class })
+@PrepareForTest({ Log.class, Handler.class, Looper.class })
 public abstract class BaseUnitTest {
+  protected Context      context;
+  protected MasterSecret masterSecret;
+
   @Before
   public void setUp() throws Exception {
+    context      = mock(Context.class);
+    masterSecret = new MasterSecret(new SecretKeySpec(new byte[16], "AES"),
+                                    new SecretKeySpec(new byte[16], "HmacSHA1"));
     mockStatic(Looper.class);
     mockStatic(Log.class);
     mockStatic(Handler.class);

test/unitTest/java/org/thoughtcrime/securesms/crypto/MasterCipherTest.java

@@ -0,0 +1,24 @@
+package org.thoughtcrime.securesms.crypto;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.powermock.core.classloader.annotations.PowerMockIgnore;
+import org.thoughtcrime.securesms.BaseUnitTest;
+import org.whispersystems.libaxolotl.InvalidMessageException;
+
+@PowerMockIgnore("javax.crypto.*")
+public class MasterCipherTest extends BaseUnitTest {
+  private MasterCipher masterCipher;
+
+  @Before
+  @Override
+  public void setUp() throws Exception {
+    super.setUp();
+    masterCipher = new MasterCipher(masterSecret);
+  }
+
+  @Test(expected = InvalidMessageException.class)
+  public void testEncryptBytesWithZeroBody() throws Exception {
+    masterCipher.decryptBytes(new byte[]{});
+  }
+}

test/unitTest/java/org/thoughtcrime/securesms/jobs/AttachmentDownloadJobTest.java

@@ -0,0 +1,39 @@
+package org.thoughtcrime.securesms.jobs;
+
+import android.content.Context;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.thoughtcrime.securesms.BaseUnitTest;
+import org.thoughtcrime.securesms.database.PartDatabase.PartId;
+import org.thoughtcrime.securesms.jobs.AttachmentDownloadJob.InvalidPartException;
+import org.thoughtcrime.securesms.util.Util;
+
+import ws.com.google.android.mms.pdu.PduPart;
+
+import static org.powermock.api.mockito.PowerMockito.mock;
+
+public class AttachmentDownloadJobTest extends BaseUnitTest {
+  private AttachmentDownloadJob job;
+
+  @Before
+  @Override
+  public void setUp() throws Exception {
+    super.setUp();
+    job = new AttachmentDownloadJob(mock(Context.class), 1L, new PartId(1L, 1L));
+  }
+
+  @Test(expected = InvalidPartException.class)
+  public void testCreateAttachmentPointerInvalidId() throws Exception {
+    PduPart part = new PduPart();
+    part.setContentDisposition(Util.toIsoBytes("a long and acceptable valid key like we all want"));
+    job.createAttachmentPointer(masterSecret, part);
+  }
+
+  @Test(expected = InvalidPartException.class)
+  public void testCreateAttachmentPointerInvalidKey() throws Exception {
+    PduPart part = new PduPart();
+    part.setContentDisposition(Util.toIsoBytes("1"));
+    job.createAttachmentPointer(masterSecret, part);
+  }
+}