Merge branch '1468-reject-unsupported-images' into 'master'

Reject unsupported images

Closes #1468

See merge request briar/briar!1038

briar-android/src/androidTestOfficial/java/org/briarproject/briar/android/attachment/AttachmentRetrieverIntegrationTest.java

@@ -1,4 +1,4 @@
-package org.briarproject.briar.android.conversation;
+package org.briarproject.briar.android.attachment;
 
 import android.content.res.AssetManager;
 import android.support.test.InstrumentationRegistry;
@@ -21,7 +21,7 @@ import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
 @RunWith(AndroidJUnit4.class)
-public class AttachmentControllerIntegrationTest {
+public class AttachmentRetrieverIntegrationTest {
 
 	private static final String smallKitten =
 			"https://upload.wikimedia.org/wikipedia/commons/thumb/0/06/Kitten_in_Rizal_Park%2C_Manila.jpg/160px-Kitten_in_Rizal_Park%2C_Manila.jpg";
@@ -47,15 +47,15 @@ public class AttachmentControllerIntegrationTest {
 	);
 	private final MessageId msgId = new MessageId(getRandomId());
 
-	private final AttachmentController controller =
-			new AttachmentController(null, dimensions);
+	private final AttachmentRetriever retriever =
+			new AttachmentRetriever(null, dimensions);
 
 	@Test
 	public void testSmallJpegImage() throws Exception {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getUrlInputStream(smallKitten);
 		Attachment a = new Attachment(is);
-		AttachmentItem item = controller.getAttachmentItem(h, a, true);
+		AttachmentItem item = retriever.getAttachmentItem(h, a, true);
 		assertEquals(msgId, item.getMessageId());
 		assertEquals(160, item.getWidth());
 		assertEquals(240, item.getHeight());
@@ -71,7 +71,7 @@ public class AttachmentControllerIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getUrlInputStream(originalKitten);
 		Attachment a = new Attachment(is);
-		AttachmentItem item = controller.getAttachmentItem(h, a, true);
+		AttachmentItem item = retriever.getAttachmentItem(h, a, true);
 		assertEquals(msgId, item.getMessageId());
 		assertEquals(1728, item.getWidth());
 		assertEquals(2592, item.getHeight());
@@ -87,7 +87,7 @@ public class AttachmentControllerIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/png");
 		InputStream is = getUrlInputStream(pngKitten);
 		Attachment a = new Attachment(is);
-		AttachmentItem item = controller.getAttachmentItem(h, a, true);
+		AttachmentItem item = retriever.getAttachmentItem(h, a, true);
 		assertEquals(msgId, item.getMessageId());
 		assertEquals(737, item.getWidth());
 		assertEquals(510, item.getHeight());
@@ -103,7 +103,7 @@ public class AttachmentControllerIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getUrlInputStream(uberGif);
 		Attachment a = new Attachment(is);
-		AttachmentItem item = controller.getAttachmentItem(h, a, true);
+		AttachmentItem item = retriever.getAttachmentItem(h, a, true);
 		assertEquals(1, item.getWidth());
 		assertEquals(1, item.getHeight());
 		assertEquals(dimensions.minHeight, item.getThumbnailWidth());
@@ -118,7 +118,7 @@ public class AttachmentControllerIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getUrlInputStream(lottaPixel);
 		Attachment a = new Attachment(is);
-		AttachmentItem item = controller.getAttachmentItem(h, a, true);
+		AttachmentItem item = retriever.getAttachmentItem(h, a, true);
 		assertEquals(64250, item.getWidth());
 		assertEquals(64250, item.getHeight());
 		assertEquals(dimensions.maxWidth, item.getThumbnailWidth());
@@ -133,7 +133,7 @@ public class AttachmentControllerIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getUrlInputStream(imageIoCrash);
 		Attachment a = new Attachment(is);
-		AttachmentItem item = controller.getAttachmentItem(h, a, true);
+		AttachmentItem item = retriever.getAttachmentItem(h, a, true);
 		assertEquals(1184, item.getWidth());
 		assertEquals(448, item.getHeight());
 		assertEquals(dimensions.maxWidth, item.getThumbnailWidth());
@@ -148,7 +148,7 @@ public class AttachmentControllerIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getUrlInputStream(gimpCrash);
 		Attachment a = new Attachment(is);
-		AttachmentItem item = controller.getAttachmentItem(h, a, true);
+		AttachmentItem item = retriever.getAttachmentItem(h, a, true);
 		assertEquals(1, item.getWidth());
 		assertEquals(1, item.getHeight());
 		assertEquals(dimensions.minHeight, item.getThumbnailWidth());
@@ -163,7 +163,7 @@ public class AttachmentControllerIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getUrlInputStream(optiPngAfl);
 		Attachment a = new Attachment(is);
-		AttachmentItem item = controller.getAttachmentItem(h, a, true);
+		AttachmentItem item = retriever.getAttachmentItem(h, a, true);
 		assertEquals(32, item.getWidth());
 		assertEquals(32, item.getHeight());
 		assertEquals(dimensions.minHeight, item.getThumbnailWidth());
@@ -178,7 +178,7 @@ public class AttachmentControllerIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getUrlInputStream(librawError);
 		Attachment a = new Attachment(is);
-		AttachmentItem item = controller.getAttachmentItem(h, a, true);
+		AttachmentItem item = retriever.getAttachmentItem(h, a, true);
 		assertTrue(item.hasError());
 	}
 
@@ -187,7 +187,7 @@ public class AttachmentControllerIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/gif");
 		InputStream is = getAssetInputStream("animated.gif");
 		Attachment a = new Attachment(is);
-		AttachmentItem item = controller.getAttachmentItem(h, a, true);
+		AttachmentItem item = retriever.getAttachmentItem(h, a, true);
 		assertEquals(65535, item.getWidth());
 		assertEquals(65535, item.getHeight());
 		assertEquals(dimensions.maxWidth, item.getThumbnailWidth());
@@ -202,7 +202,7 @@ public class AttachmentControllerIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/gif");
 		InputStream is = getAssetInputStream("animated2.gif");
 		Attachment a = new Attachment(is);
-		AttachmentItem item = controller.getAttachmentItem(h, a, true);
+		AttachmentItem item = retriever.getAttachmentItem(h, a, true);
 		assertEquals(10000, item.getWidth());
 		assertEquals(10000, item.getHeight());
 		assertEquals(dimensions.maxWidth, item.getThumbnailWidth());
@@ -217,7 +217,7 @@ public class AttachmentControllerIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/gif");
 		InputStream is = getAssetInputStream("error_large.gif");
 		Attachment a = new Attachment(is);
-		AttachmentItem item = controller.getAttachmentItem(h, a, true);
+		AttachmentItem item = retriever.getAttachmentItem(h, a, true);
 		assertEquals(16384, item.getWidth());
 		assertEquals(16384, item.getHeight());
 		assertEquals(dimensions.maxWidth, item.getThumbnailWidth());
@@ -232,7 +232,7 @@ public class AttachmentControllerIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getAssetInputStream("error_high.jpg");
 		Attachment a = new Attachment(is);
-		AttachmentItem item = controller.getAttachmentItem(h, a, true);
+		AttachmentItem item = retriever.getAttachmentItem(h, a, true);
 		assertEquals(1, item.getWidth());
 		assertEquals(10000, item.getHeight());
 		assertEquals(dimensions.minWidth, item.getThumbnailWidth());
@@ -247,7 +247,7 @@ public class AttachmentControllerIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getAssetInputStream("error_wide.jpg");
 		Attachment a = new Attachment(is);
-		AttachmentItem item = controller.getAttachmentItem(h, a, true);
+		AttachmentItem item = retriever.getAttachmentItem(h, a, true);
 		assertEquals(1920, item.getWidth());
 		assertEquals(1, item.getHeight());
 		assertEquals(dimensions.maxWidth, item.getThumbnailWidth());

briar-android/src/main/java/org/briarproject/briar/android/attachment/AttachmentCreationTask.java

@@ -0,0 +1,116 @@
+package org.briarproject.briar.android.attachment;
+
+import android.content.ContentResolver;
+import android.net.Uri;
+import android.support.annotation.Nullable;
+
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.GroupId;
+import org.briarproject.briar.api.messaging.AttachmentHeader;
+import org.briarproject.briar.api.messaging.MessagingManager;
+import org.jsoup.UnsupportedMimeTypeException;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Collection;
+import java.util.logging.Logger;
+
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.IoUtils.tryToClose;
+import static org.briarproject.bramble.util.LogUtils.logDuration;
+import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.bramble.util.LogUtils.now;
+import static org.briarproject.briar.api.messaging.MessagingConstants.IMAGE_MIME_TYPES;
+
+@NotNullByDefault
+class AttachmentCreationTask {
+
+	private static Logger LOG =
+			getLogger(AttachmentCreationTask.class.getName());
+
+	private final MessagingManager messagingManager;
+	private final ContentResolver contentResolver;
+	private final GroupId groupId;
+	private final Collection<Uri> uris;
+	private final boolean needsSize;
+	@Nullable
+	private volatile AttachmentCreator attachmentCreator;
+
+	private volatile boolean canceled = false;
+
+	AttachmentCreationTask(MessagingManager messagingManager,
+			ContentResolver contentResolver,
+			AttachmentCreator attachmentCreator, GroupId groupId,
+			Collection<Uri> uris, boolean needsSize) {
+		this.messagingManager = messagingManager;
+		this.contentResolver = contentResolver;
+		this.groupId = groupId;
+		this.uris = uris;
+		this.needsSize = needsSize;
+		this.attachmentCreator = attachmentCreator;
+	}
+
+	public void cancel() {
+		canceled = true;
+		attachmentCreator = null;
+	}
+
+	@IoExecutor
+	public void storeAttachments() {
+		for (Uri uri: uris) processUri(uri);
+		AttachmentCreator attachmentCreator = this.attachmentCreator;
+		if (!canceled && attachmentCreator != null)
+			attachmentCreator.onAttachmentCreationFinished();
+		this.attachmentCreator = null;
+	}
+
+	@IoExecutor
+	private void processUri(Uri uri) {
+		if (canceled) return;
+		try {
+			AttachmentHeader h = storeAttachment(uri);
+			AttachmentCreator attachmentCreator = this.attachmentCreator;
+			if (attachmentCreator != null) {
+				attachmentCreator.onAttachmentHeaderReceived(uri, h, needsSize);
+			}
+		} catch (DbException | IOException e) {
+			logException(LOG, WARNING, e);
+			AttachmentCreator attachmentCreator = this.attachmentCreator;
+			if (attachmentCreator != null) {
+				attachmentCreator.onAttachmentError(uri, e);
+			}
+			canceled = true;
+		}
+	}
+
+	@IoExecutor
+	private AttachmentHeader storeAttachment(Uri uri)
+			throws IOException, DbException {
+		long start = now();
+		String contentType = contentResolver.getType(uri);
+		if (contentType == null) throw new IOException("null content type");
+		if (!isValidMimeType(contentType)) {
+			String uriString = uri.toString();
+			throw new UnsupportedMimeTypeException("", contentType, uriString);
+		}
+		InputStream is = contentResolver.openInputStream(uri);
+		if (is == null) throw new IOException();
+		long timestamp = System.currentTimeMillis();
+		AttachmentHeader h = messagingManager
+				.addLocalAttachment(groupId, timestamp, contentType, is);
+		tryToClose(is, LOG, WARNING);
+		logDuration(LOG, "Storing attachment", start);
+		return h;
+	}
+
+	private boolean isValidMimeType(String mimeType) {
+		for (String supportedType : IMAGE_MIME_TYPES) {
+			if (supportedType.equals(mimeType)) return true;
+		}
+		return false;
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/attachment/AttachmentCreator.java

@@ -0,0 +1,218 @@
+package org.briarproject.briar.android.attachment;
+
+
+import android.app.Application;
+import android.arch.lifecycle.LiveData;
+import android.arch.lifecycle.MutableLiveData;
+import android.net.Uri;
+import android.support.annotation.Nullable;
+import android.support.annotation.UiThread;
+
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.GroupId;
+import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.briar.R;
+import org.briarproject.briar.api.messaging.Attachment;
+import org.briarproject.briar.api.messaging.AttachmentHeader;
+import org.briarproject.briar.api.messaging.FileTooBigException;
+import org.briarproject.briar.api.messaging.MessagingManager;
+import org.jsoup.UnsupportedMimeTypeException;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.briar.android.util.UiUtils.observeForeverOnce;
+import static org.briarproject.briar.api.messaging.MessagingConstants.MAX_IMAGE_SIZE;
+
+@NotNullByDefault
+public class AttachmentCreator {
+
+	private static Logger LOG = getLogger(AttachmentCreator.class.getName());
+
+	private final Application app;
+	@IoExecutor
+	private final Executor ioExecutor;
+	private final MessagingManager messagingManager;
+	private final AttachmentRetriever retriever;
+
+	private final CopyOnWriteArrayList<Uri> uris = new CopyOnWriteArrayList<>();
+	private final CopyOnWriteArrayList<AttachmentItemResult> itemResults =
+			new CopyOnWriteArrayList<>();
+
+	private final MutableLiveData<AttachmentResult> result =
+			new MutableLiveData<>();
+	@Nullable
+	private AttachmentCreationTask task;
+
+	public AttachmentCreator(Application app, @IoExecutor Executor ioExecutor,
+			MessagingManager messagingManager, AttachmentRetriever retriever) {
+		this.app = app;
+		this.ioExecutor = ioExecutor;
+		this.messagingManager = messagingManager;
+		this.retriever = retriever;
+	}
+
+	@UiThread
+	public LiveData<AttachmentResult> storeAttachments(
+			LiveData<GroupId> groupId, Collection<Uri> newUris) {
+		if (task != null || !uris.isEmpty())
+			throw new IllegalStateException();
+		uris.addAll(newUris);
+		observeForeverOnce(groupId, id -> {
+			if (id == null) throw new IllegalStateException();
+			boolean needsSize = uris.size() == 1;
+			task = new AttachmentCreationTask(messagingManager,
+					app.getContentResolver(), this, id, uris, needsSize);
+			ioExecutor.execute(() -> task.storeAttachments());
+		});
+		return result;
+	}
+
+	/**
+	 * This should be only called after configuration changes.
+	 * In this case we should not create new attachments.
+	 * They are already being created and returned by the existing LiveData.
+	 */
+	@UiThread
+	public LiveData<AttachmentResult> getLiveAttachments() {
+		if (task == null || uris.isEmpty())
+			throw new IllegalStateException();
+		// A task is already running. It will update the result LiveData.
+		// So nothing more to do here.
+		return result;
+	}
+
+	@IoExecutor
+	void onAttachmentHeaderReceived(Uri uri, AttachmentHeader h,
+			boolean needsSize) {
+		// get and cache AttachmentItem for ImagePreview
+		try {
+			Attachment a = retriever.getMessageAttachment(h);
+			AttachmentItem item = retriever.getAttachmentItem(h, a, needsSize);
+			if (item.hasError()) throw new IOException();
+			AttachmentItemResult itemResult =
+					new AttachmentItemResult(uri, item);
+			itemResults.add(itemResult);
+			result.postValue(getResult(false));
+		} catch (IOException | DbException e) {
+			logException(LOG, WARNING, e);
+			onAttachmentError(uri, e);
+		}
+	}
+
+	@IoExecutor
+	void onAttachmentError(Uri uri, Throwable t) {
+		// get error message
+		String errorMsg;
+		if (t instanceof UnsupportedMimeTypeException) {
+			String mimeType = ((UnsupportedMimeTypeException) t).getMimeType();
+			errorMsg = app.getString(
+					R.string.image_attach_error_invalid_mime_type, mimeType);
+		} else if (t instanceof FileTooBigException) {
+			int mb = MAX_IMAGE_SIZE / 1024 / 1024;
+			errorMsg = app.getString(R.string.image_attach_error_too_big, mb);
+		} else {
+			errorMsg = null; // generic error
+		}
+		AttachmentItemResult itemResult =
+				new AttachmentItemResult(uri, errorMsg);
+		itemResults.add(itemResult);
+		result.postValue(getResult(false));
+		// expect to receive a cancel from the UI
+	}
+
+	@IoExecutor
+	void onAttachmentCreationFinished() {
+		result.postValue(getResult(true));
+	}
+
+	@UiThread
+	public List<AttachmentHeader> getAttachmentHeadersForSending() {
+		List<AttachmentHeader> headers = new ArrayList<>(itemResults.size());
+		for (AttachmentItemResult itemResult : itemResults) {
+			// check if we are trying to send attachment items with errors
+			if (itemResult.getItem() == null) throw new IllegalStateException();
+			headers.add(itemResult.getItem().getHeader());
+		}
+		return headers;
+	}
+
+	/**
+	 * Marks the attachments as sent and adds the items to the cache for display
+	 *
+	 * @param id The MessageId of the sent message.
+	 */
+	@UiThread
+	public void onAttachmentsSent(MessageId id) {
+		List<AttachmentItem> items = new ArrayList<>(itemResults.size());
+		for (AttachmentItemResult itemResult : itemResults) {
+			// check if we are trying to send attachment items with errors
+			if (itemResult.getItem() == null) throw new IllegalStateException();
+			items.add(itemResult.getItem());
+		}
+		retriever.cachePut(id, items);
+		resetState();
+	}
+
+	/**
+	 * Needs to be called when created attachments will not be sent anymore.
+	 */
+	@UiThread
+	public void cancel() {
+		if (task == null) throw new AssertionError();
+		task.cancel();
+		deleteUnsentAttachments();
+		resetState();
+	}
+
+	@UiThread
+	private void resetState() {
+		task = null;
+		uris.clear();
+		itemResults.clear();
+		result.setValue(null);
+	}
+
+	@UiThread
+	public void deleteUnsentAttachments() {
+		// Make a copy for the IoExecutor as we clear the itemResults soon
+		List<AttachmentHeader> headers = new ArrayList<>(itemResults.size());
+		for (AttachmentItemResult itemResult : itemResults) {
+			// check if we are trying to send attachment items with errors
+			if (itemResult.getItem() != null)
+				headers.add(itemResult.getItem().getHeader());
+		}
+		ioExecutor.execute(() -> {
+			for (AttachmentHeader header : headers) {
+				try {
+					messagingManager.removeAttachment(header);
+				} catch (DbException e) {
+					logException(LOG, WARNING, e);
+				}
+			}
+		});
+	}
+
+	private AttachmentResult getResult(boolean finished) {
+		// Make a copy of the list,
+		// because our copy will continue to change in the background.
+		// (As it's a CopyOnWriteArrayList,
+		//  the code that receives the result can safely do simple things
+		//  like iterating over the list,
+		//  but anything that involves calling more than one list method
+		//  is still unsafe.)
+		Collection<AttachmentItemResult> items = new ArrayList<>(itemResults);
+		return new AttachmentResult(items, finished);
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/attachment/AttachmentDimensions.java

@@ -1,11 +1,16 @@
-package org.briarproject.briar.android.conversation;
+package org.briarproject.briar.android.attachment;
 
 import android.content.res.Resources;
 import android.support.annotation.VisibleForTesting;
 
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
 
-class AttachmentDimensions {
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+@NotNullByDefault
+public class AttachmentDimensions {
 
 	final int defaultSize;
 	final int minWidth, maxWidth;
@@ -21,7 +26,7 @@ class AttachmentDimensions {
 		this.maxHeight = maxHeight;
 	}
 
-	static AttachmentDimensions getAttachmentDimensions(Resources res) {
+	public static AttachmentDimensions getAttachmentDimensions(Resources res) {
 		int defaultSize =
 				res.getDimensionPixelSize(R.dimen.message_bubble_image_default);
 		int minWidth = res.getDimensionPixelSize(
@@ -33,7 +38,7 @@ class AttachmentDimensions {
 		int maxHeight = res.getDimensionPixelSize(
 				R.dimen.message_bubble_image_max_height);
 		return new AttachmentDimensions(defaultSize, minWidth, maxWidth,
-				minHeight, minHeight);
+				minHeight, maxHeight);
 	}
 
 }

briar-android/src/main/java/org/briarproject/briar/android/attachment/AttachmentItem.java

@@ -1,4 +1,4 @@
-package org.briarproject.briar.android.conversation;
+package org.briarproject.briar.android.attachment;
 
 import android.os.Parcel;
 import android.os.Parcelable;
@@ -6,18 +6,21 @@ import android.support.annotation.Nullable;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.briar.api.messaging.AttachmentHeader;
 
 import java.util.concurrent.atomic.AtomicLong;
 
 import javax.annotation.concurrent.Immutable;
 
+import static java.util.Objects.requireNonNull;
+
 @Immutable
 @NotNullByDefault
 public class AttachmentItem implements Parcelable {
 
-	private final MessageId messageId;
+	private final AttachmentHeader header;
 	private final int width, height;
-	private final String mimeType, extension;
+	private final String extension;
 	private final int thumbnailWidth, thumbnailHeight;
 	private final boolean hasError;
 	private final long instanceId;
@@ -37,13 +40,12 @@ public class AttachmentItem implements Parcelable {
 
 	private static final AtomicLong NEXT_INSTANCE_ID = new AtomicLong(0);
 
-	AttachmentItem(MessageId messageId, int width, int height, String mimeType,
+	AttachmentItem(AttachmentHeader header, int width, int height,
 			String extension, int thumbnailWidth, int thumbnailHeight,
 			boolean hasError) {
-		this.messageId = messageId;
+		this.header = header;
 		this.width = width;
 		this.height = height;
-		this.mimeType = mimeType;
 		this.extension = extension;
 		this.thumbnailWidth = thumbnailWidth;
 		this.thumbnailHeight = thumbnailHeight;
@@ -54,19 +56,24 @@ public class AttachmentItem implements Parcelable {
 	protected AttachmentItem(Parcel in) {
 		byte[] messageIdByte = new byte[MessageId.LENGTH];
 		in.readByteArray(messageIdByte);
-		messageId = new MessageId(messageIdByte);
+		MessageId messageId = new MessageId(messageIdByte);
 		width = in.readInt();
 		height = in.readInt();
-		mimeType = in.readString();
-		extension = in.readString();
+		String mimeType = requireNonNull(in.readString());
+		extension = requireNonNull(in.readString());
 		thumbnailWidth = in.readInt();
 		thumbnailHeight = in.readInt();
 		hasError = in.readByte() != 0;
 		instanceId = in.readLong();
+		header = new AttachmentHeader(messageId, mimeType);
+	}
+
+	AttachmentHeader getHeader() {
+		return header;
 	}
 
 	public MessageId getMessageId() {
-		return messageId;
+		return header.getMessageId();
 	}
 
 	int getWidth() {
@@ -77,27 +84,27 @@ public class AttachmentItem implements Parcelable {
 		return height;
 	}
 
-	String getMimeType() {
-		return mimeType;
+	public String getMimeType() {
+		return header.getContentType();
 	}
 
-	String getExtension() {
+	public String getExtension() {
 		return extension;
 	}
 
-	int getThumbnailWidth() {
+	public int getThumbnailWidth() {
 		return thumbnailWidth;
 	}
 
-	int getThumbnailHeight() {
+	public int getThumbnailHeight() {
 		return thumbnailHeight;
 	}
 
-	boolean hasError() {
+	public boolean hasError() {
 		return hasError;
 	}
 
-	String getTransitionName() {
+	public String getTransitionName() {
 		return String.valueOf(instanceId);
 	}
 
@@ -108,10 +115,10 @@ public class AttachmentItem implements Parcelable {
 
 	@Override
 	public void writeToParcel(Parcel dest, int flags) {
-		dest.writeByteArray(messageId.getBytes());
+		dest.writeByteArray(header.getMessageId().getBytes());
 		dest.writeInt(width);
 		dest.writeInt(height);
-		dest.writeString(mimeType);
+		dest.writeString(header.getContentType());
 		dest.writeString(extension);
 		dest.writeInt(thumbnailWidth);
 		dest.writeInt(thumbnailHeight);

briar-android/src/main/java/org/briarproject/briar/android/attachment/AttachmentItemResult.java

@@ -0,0 +1,50 @@
+package org.briarproject.briar.android.attachment;
+
+import android.net.Uri;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+@NotNullByDefault
+public class AttachmentItemResult {
+
+	private final Uri uri;
+	@Nullable
+	private final AttachmentItem item;
+	@Nullable
+	private final String errorMsg;
+
+	AttachmentItemResult(Uri uri, AttachmentItem item) {
+		this.uri = uri;
+		this.item = item;
+		this.errorMsg = null;
+	}
+
+	AttachmentItemResult(Uri uri, @Nullable String errorMsg) {
+		this.uri = uri;
+		this.item = null;
+		this.errorMsg = errorMsg;
+	}
+
+	public Uri getUri() {
+		return uri;
+	}
+
+	@Nullable
+	public AttachmentItem getItem() {
+		return item;
+	}
+
+	public boolean hasError() {
+		return item == null;
+	}
+
+	@Nullable
+	public String getErrorMsg() {
+		return errorMsg;
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/attachment/AttachmentManager.java

@@ -0,0 +1,22 @@
+package org.briarproject.briar.android.attachment;
+
+import android.arch.lifecycle.LiveData;
+import android.net.Uri;
+import android.support.annotation.UiThread;
+
+import org.briarproject.briar.api.messaging.AttachmentHeader;
+
+import java.util.Collection;
+import java.util.List;
+
+@UiThread
+public interface AttachmentManager {
+
+	LiveData<AttachmentResult> storeAttachments(Collection<Uri> uri,
+			boolean restart);
+
+	List<AttachmentHeader> getAttachmentHeadersForSending();
+
+	void cancel();
+
+}

briar-android/src/main/java/org/briarproject/briar/android/attachment/AttachmentResult.java

@@ -0,0 +1,30 @@
+package org.briarproject.briar.android.attachment;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.util.Collection;
+
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+@NotNullByDefault
+public class AttachmentResult {
+
+	private final Collection<AttachmentItemResult> itemResults;
+	private final boolean finished;
+
+	public AttachmentResult(Collection<AttachmentItemResult> itemResults,
+			boolean finished) {
+		this.itemResults = itemResults;
+		this.finished = finished;
+	}
+
+	public Collection<AttachmentItemResult> getItemResults() {
+		return itemResults;
+	}
+
+	public boolean isFinished() {
+		return finished;
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/attachment/AttachmentRetriever.java

@@ -1,8 +1,9 @@
-package org.briarproject.briar.android.conversation;
+package org.briarproject.briar.android.attachment;
 
 import android.graphics.BitmapFactory;
 import android.graphics.BitmapFactory.Options;
 import android.support.annotation.Nullable;
+import android.support.annotation.VisibleForTesting;
 import android.support.media.ExifInterface;
 import android.webkit.MimeTypeMap;
 
@@ -13,7 +14,7 @@ import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageId;
-import org.briarproject.briar.android.conversation.ImageHelper.DecodeResult;
+import org.briarproject.briar.android.attachment.ImageHelper.DecodeResult;
 import org.briarproject.briar.api.messaging.Attachment;
 import org.briarproject.briar.api.messaging.AttachmentHeader;
 import org.briarproject.briar.api.messaging.MessagingManager;
@@ -42,10 +43,10 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.LogUtils.now;
 
 @NotNullByDefault
-class AttachmentController {
+public class AttachmentRetriever {
 
 	private static final Logger LOG =
-			getLogger(AttachmentController.class.getName());
+			getLogger(AttachmentRetriever.class.getName());
 	private static final int READ_LIMIT = 1024 * 8192;
 
 	private final MessagingManager messagingManager;
@@ -57,7 +58,8 @@ class AttachmentController {
 	private final Map<MessageId, List<AttachmentItem>> attachmentCache =
 			new ConcurrentHashMap<>();
 
-	AttachmentController(MessagingManager messagingManager,
+	@VisibleForTesting
+	AttachmentRetriever(MessagingManager messagingManager,
 			AttachmentDimensions dimensions, ImageHelper imageHelper) {
 		this.messagingManager = messagingManager;
 		this.imageHelper = imageHelper;
@@ -68,7 +70,7 @@ class AttachmentController {
 		maxHeight = dimensions.maxHeight;
 	}
 
-	AttachmentController(MessagingManager messagingManager,
+	public AttachmentRetriever(MessagingManager messagingManager,
 			AttachmentDimensions dimensions) {
 		this(messagingManager, dimensions, new ImageHelper() {
 			@Override
@@ -91,17 +93,17 @@ class AttachmentController {
 		});
 	}
 
-	void put(MessageId messageId, List<AttachmentItem> attachments) {
+	public void cachePut(MessageId messageId, List<AttachmentItem> attachments) {
 		attachmentCache.put(messageId, attachments);
 	}
 
 	@Nullable
-	List<AttachmentItem> get(MessageId messageId) {
+	public List<AttachmentItem> cacheGet(MessageId messageId) {
 		return attachmentCache.get(messageId);
 	}
 
 	@DatabaseExecutor
-	List<Pair<AttachmentHeader, Attachment>> getMessageAttachments(
+	public List<Pair<AttachmentHeader, Attachment>> getMessageAttachments(
 			List<AttachmentHeader> headers) throws DbException {
 		long start = now();
 		List<Pair<AttachmentHeader, Attachment>> attachments =
@@ -110,16 +112,21 @@ class AttachmentController {
 			Attachment a = messagingManager.getAttachment(h.getMessageId());
 			attachments.add(new Pair<>(h, a));
 		}
-		logDuration(LOG, "Loading attachment", start);
+		logDuration(LOG, "Loading attachments", start);
 		return attachments;
 	}
 
+	@DatabaseExecutor
+	Attachment getMessageAttachment(AttachmentHeader h) throws DbException {
+		return messagingManager.getAttachment(h.getMessageId());
+	}
+
 	/**
 	 * Creates {@link AttachmentItem}s from the passed headers and Attachments.
 	 * <p>
 	 * Note: This closes the {@link Attachment}'s {@link InputStream}.
 	 */
-	List<AttachmentItem> getAttachmentItems(
+	public List<AttachmentItem> getAttachmentItems(
 			List<Pair<AttachmentHeader, Attachment>> attachments) {
 		boolean needsSize = attachments.size() == 1;
 		List<AttachmentItem> items = new ArrayList<>(attachments.size());
@@ -137,17 +144,15 @@ class AttachmentController {
 	 */
 	AttachmentItem getAttachmentItem(AttachmentHeader h, Attachment a,
 			boolean needsSize) {
-		MessageId messageId = h.getMessageId();
 		if (!needsSize) {
-			String mimeType = h.getContentType();
-			String extension = imageHelper.getExtensionFromMimeType(mimeType);
+			String extension =
+					imageHelper.getExtensionFromMimeType(h.getContentType());
 			boolean hasError = false;
 			if (extension == null) {
 				extension = "";
 				hasError = true;
 			}
-			return new AttachmentItem(messageId, 0, 0, mimeType, extension, 0,
-					0, hasError);
+			return new AttachmentItem(h, 0, 0, extension, 0, 0, hasError);
 		}
 
 		Size size = new Size();
@@ -185,10 +190,17 @@ class AttachmentController {
 		// get file extension
 		String extension = imageHelper.getExtensionFromMimeType(size.mimeType);
 		boolean hasError = extension == null || size.error;
+		if (!h.getContentType().equals(size.mimeType)) {
+			if (LOG.isLoggable(WARNING)) {
+				LOG.warning("Header has different mime type (" +
+						h.getContentType() + ") than image (" + size.mimeType +
+						").");
+			}
+			hasError = true;
+		}
 		if (extension == null) extension = "";
-		return new AttachmentItem(messageId, size.width, size.height,
-				size.mimeType, extension, thumbnailSize.width,
-				thumbnailSize.height, hasError);
+		return new AttachmentItem(h, size.width, size.height, extension,
+				thumbnailSize.width, thumbnailSize.height, hasError);
 	}
 
 	/**

briar-android/src/main/java/org/briarproject/briar/android/attachment/ImageHelper.java

@@ -1,4 +1,4 @@
-package org.briarproject.briar.android.conversation;
+package org.briarproject.briar.android.attachment;
 
 import android.support.annotation.Nullable;
 

briar-android/src/main/java/org/briarproject/briar/android/blog/ReblogFragment.java

@@ -1,6 +1,5 @@
 package org.briarproject.briar.android.blog;
 
-import android.net.Uri;
 import android.os.Bundle;
 import android.view.LayoutInflater;
 import android.view.View;
@@ -21,6 +20,7 @@ import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.view.TextInputView;
 import org.briarproject.briar.android.view.TextSendController;
 import org.briarproject.briar.android.view.TextSendController.SendListener;
+import org.briarproject.briar.api.messaging.AttachmentHeader;
 
 import java.util.List;
 
@@ -121,7 +121,8 @@ public class ReblogFragment extends BaseFragment implements SendListener {
 	}
 
 	@Override
-	public void onSendClick(@Nullable String text, List<Uri> imageUris) {
+	public void onSendClick(@Nullable String text,
+			List<AttachmentHeader> headers) {
 		ui.input.hideSoftKeyboard();
 		feedController.repeatPost(item, text,
 				new UiExceptionHandler<DbException>(this) {

briar-android/src/main/java/org/briarproject/briar/android/blog/WriteBlogPostActivity.java

@@ -1,7 +1,6 @@
 package org.briarproject.briar.android.blog;
 
 import android.content.Intent;
-import android.net.Uri;
 import android.os.Bundle;
 import android.support.annotation.Nullable;
 import android.view.KeyEvent;
@@ -27,6 +26,7 @@ import org.briarproject.briar.api.android.AndroidNotificationManager;
 import org.briarproject.briar.api.blog.BlogManager;
 import org.briarproject.briar.api.blog.BlogPost;
 import org.briarproject.briar.api.blog.BlogPostFactory;
+import org.briarproject.briar.api.messaging.AttachmentHeader;
 
 import java.security.GeneralSecurityException;
 import java.util.List;
@@ -120,7 +120,8 @@ public class WriteBlogPostActivity extends BriarActivity
 	}
 
 	@Override
-	public void onSendClick(@Nullable String text, List<Uri> imageUris) {
+	public void onSendClick(@Nullable String text,
+			List<AttachmentHeader> headers) {
 		if (isNullOrEmpty(text)) throw new AssertionError();
 
 		// hide publish button, show progress bar

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationActivity.java

@@ -6,7 +6,6 @@ import android.arch.lifecycle.ViewModelProvider;
 import android.arch.lifecycle.ViewModelProviders;
 import android.content.DialogInterface;
 import android.content.Intent;
-import android.net.Uri;
 import android.os.Bundle;
 import android.os.Parcelable;
 import android.support.annotation.Nullable;
@@ -53,6 +52,8 @@ import org.briarproject.bramble.api.sync.event.MessagesSentEvent;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
 import org.briarproject.briar.android.activity.BriarActivity;
+import org.briarproject.briar.android.attachment.AttachmentItem;
+import org.briarproject.briar.android.attachment.AttachmentRetriever;
 import org.briarproject.briar.android.blog.BlogActivity;
 import org.briarproject.briar.android.conversation.ConversationVisitor.AttachmentCache;
 import org.briarproject.briar.android.conversation.ConversationVisitor.TextCache;
@@ -184,7 +185,7 @@ public class ConversationActivity extends BriarActivity
 		loadMessages();
 	};
 
-	private AttachmentController attachmentController;
+	private AttachmentRetriever attachmentRetriever;
 	private ConversationViewModel viewModel;
 	private ConversationVisitor visitor;
 	private ConversationAdapter adapter;
@@ -219,7 +220,7 @@ public class ConversationActivity extends BriarActivity
 
 		viewModel = ViewModelProviders.of(this, viewModelFactory)
 				.get(ConversationViewModel.class);
-		attachmentController = viewModel.getAttachmentController();
+		attachmentRetriever = viewModel.getAttachmentRetriever();
 
 		setContentView(R.layout.activity_conversation);
 
@@ -242,7 +243,7 @@ public class ConversationActivity extends BriarActivity
 			requireNonNull(deleted);
 			if (deleted) finish();
 		});
-		viewModel.getAddedPrivateMessage().observe(this,
+		viewModel.getAddedPrivateMessage().observeEvent(this,
 				this::onAddedPrivateMessage);
 
 		setTransitionName(toolbarAvatar, getAvatarTransitionName(contactId));
@@ -264,7 +265,7 @@ public class ConversationActivity extends BriarActivity
 		if (FEATURE_FLAG_IMAGE_ATTACHMENTS) {
 			ImagePreview imagePreview = findViewById(R.id.imagePreview);
 			sendController = new TextAttachmentController(textInputView,
-					imagePreview, this, this);
+					imagePreview, this, this, viewModel);
 			observeOnce(viewModel.hasImageSupport(), this, hasSupport -> {
 				if (hasSupport != null && hasSupport) {
 					// remove cast when removing FEATURE_FLAG_IMAGE_ATTACHMENTS
@@ -457,13 +458,13 @@ public class ConversationActivity extends BriarActivity
 		// If the message has a single image, load its size - for multiple
 		// images we use a grid so the size is fixed
 		if (h.getAttachmentHeaders().size() == 1) {
-			List<AttachmentItem> items = attachmentController.get(id);
+			List<AttachmentItem> items = attachmentRetriever.cacheGet(id);
 			if (items == null) {
 				LOG.info("Eagerly loading image size for latest message");
-				items = attachmentController.getAttachmentItems(
-						attachmentController.getMessageAttachments(
+				items = attachmentRetriever.getAttachmentItems(
+						attachmentRetriever.getMessageAttachments(
 								h.getAttachmentHeaders()));
-				attachmentController.put(id, items);
+				attachmentRetriever.cachePut(id, items);
 			}
 		}
 	}
@@ -545,10 +546,10 @@ public class ConversationActivity extends BriarActivity
 		runOnDbThread(() -> {
 			try {
 				List<Pair<AttachmentHeader, Attachment>> attachments =
-						attachmentController.getMessageAttachments(headers);
+						attachmentRetriever.getMessageAttachments(headers);
 				// TODO move getting the items off to IoExecutor, if size == 1
 				List<AttachmentItem> items =
-						attachmentController.getAttachmentItems(attachments);
+						attachmentRetriever.getAttachmentItems(attachments);
 				displayMessageAttachments(messageId, items);
 			} catch (DbException e) {
 				logException(LOG, WARNING, e);
@@ -559,7 +560,7 @@ public class ConversationActivity extends BriarActivity
 	private void displayMessageAttachments(MessageId m,
 			List<AttachmentItem> items) {
 		runOnUiThreadUnlessDestroyed(() -> {
-			attachmentController.put(m, items);
+			attachmentRetriever.cachePut(m, items);
 			Pair<Integer, ConversationMessageItem> pair =
 					adapter.getMessageItem(m);
 			if (pair != null) {
@@ -658,12 +659,13 @@ public class ConversationActivity extends BriarActivity
 	}
 
 	@Override
-	public void onSendClick(@Nullable String text, List<Uri> imageUris) {
-		if (isNullOrEmpty(text) && imageUris.isEmpty())
+	public void onSendClick(@Nullable String text,
+			List<AttachmentHeader> attachmentHeaders) {
+		if (isNullOrEmpty(text) && attachmentHeaders.isEmpty())
 			throw new AssertionError();
 		long timestamp = System.currentTimeMillis();
 		timestamp = Math.max(timestamp, getMinTimestampForNewMessage());
-		viewModel.sendMessage(text, imageUris, timestamp);
+		viewModel.sendMessage(text, attachmentHeaders, timestamp);
 		textInputView.clearText();
 	}
 
@@ -676,7 +678,6 @@ public class ConversationActivity extends BriarActivity
 	private void onAddedPrivateMessage(@Nullable PrivateMessageHeader h) {
 		if (h == null) return;
 		addConversationItem(h.accept(visitor));
-		viewModel.onAddedPrivateMessageSeen();
 	}
 
 	private void askToRemoveContact() {
@@ -903,7 +904,7 @@ public class ConversationActivity extends BriarActivity
 	@Override
 	public List<AttachmentItem> getAttachmentItems(MessageId m,
 			List<AttachmentHeader> headers) {
-		List<AttachmentItem> attachments = attachmentController.get(m);
+		List<AttachmentItem> attachments = attachmentRetriever.cacheGet(m);
 		if (attachments == null) {
 			loadMessageAttachments(m, headers);
 			return emptyList();

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationListener.java

@@ -4,6 +4,7 @@ import android.support.annotation.UiThread;
 import android.view.View;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.briar.android.attachment.AttachmentItem;
 
 @UiThread
 @NotNullByDefault

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationMessageItem.java

@@ -3,6 +3,7 @@ package org.briarproject.briar.android.conversation;
 import android.support.annotation.LayoutRes;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.briar.android.attachment.AttachmentItem;
 import org.briarproject.briar.api.messaging.PrivateMessageHeader;
 
 import java.util.List;

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationMessageViewHolder.java

@@ -9,6 +9,7 @@ import android.view.ViewGroup;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
+import org.briarproject.briar.android.attachment.AttachmentItem;
 
 import static android.support.constraint.ConstraintSet.WRAP_CONTENT;
 import static android.support.v4.content.ContextCompat.getColor;

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationViewModel.java

@@ -5,13 +5,11 @@ import android.arch.lifecycle.AndroidViewModel;
 import android.arch.lifecycle.LiveData;
 import android.arch.lifecycle.MutableLiveData;
 import android.arch.lifecycle.Transformations;
-import android.content.ContentResolver;
 import android.net.Uri;
 import android.support.annotation.Nullable;
 import android.support.annotation.UiThread;
 
 import org.briarproject.bramble.api.FormatException;
-import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.contact.Contact;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.contact.ContactManager;
@@ -21,25 +19,26 @@ import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.NoSuchContactException;
 import org.briarproject.bramble.api.db.TransactionManager;
 import org.briarproject.bramble.api.identity.AuthorId;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.settings.Settings;
 import org.briarproject.bramble.api.settings.SettingsManager;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.briar.android.attachment.AttachmentCreator;
+import org.briarproject.briar.android.attachment.AttachmentManager;
+import org.briarproject.briar.android.attachment.AttachmentResult;
+import org.briarproject.briar.android.attachment.AttachmentRetriever;
 import org.briarproject.briar.android.util.UiUtils;
 import org.briarproject.briar.android.viewmodel.LiveEvent;
 import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
-import org.briarproject.briar.api.messaging.Attachment;
 import org.briarproject.briar.api.messaging.AttachmentHeader;
 import org.briarproject.briar.api.messaging.MessagingManager;
 import org.briarproject.briar.api.messaging.PrivateMessage;
 import org.briarproject.briar.api.messaging.PrivateMessageFactory;
 import org.briarproject.briar.api.messaging.PrivateMessageHeader;
 
-import java.io.IOException;
-import java.io.InputStream;
-import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 import java.util.concurrent.Executor;
@@ -50,16 +49,16 @@ import javax.inject.Inject;
 import static java.util.Objects.requireNonNull;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
-import static org.briarproject.bramble.util.IoUtils.tryToClose;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.LogUtils.now;
-import static org.briarproject.briar.android.conversation.AttachmentDimensions.getAttachmentDimensions;
+import static org.briarproject.briar.android.attachment.AttachmentDimensions.getAttachmentDimensions;
 import static org.briarproject.briar.android.settings.SettingsFragment.SETTINGS_NAMESPACE;
 import static org.briarproject.briar.android.util.UiUtils.observeForeverOnce;
 
 @NotNullByDefault
-public class ConversationViewModel extends AndroidViewModel {
+public class ConversationViewModel extends AndroidViewModel
+		implements AttachmentManager {
 
 	private static Logger LOG =
 			getLogger(ConversationViewModel.class.getName());
@@ -77,7 +76,8 @@ public class ConversationViewModel extends AndroidViewModel {
 	private final ContactManager contactManager;
 	private final SettingsManager settingsManager;
 	private final PrivateMessageFactory privateMessageFactory;
-	private final AttachmentController attachmentController;
+	private final AttachmentRetriever attachmentRetriever;
+	private final AttachmentCreator attachmentCreator;
 
 	@Nullable
 	private ContactId contactId = null;
@@ -86,6 +86,7 @@ public class ConversationViewModel extends AndroidViewModel {
 			Transformations.map(contact, c -> c.getAuthor().getId());
 	private final LiveData<String> contactName =
 			Transformations.map(contact, UiUtils::getContactDisplayName);
+	private final LiveData<GroupId> messagingGroupId;
 	private final MutableLiveData<Boolean> imageSupport =
 			new MutableLiveData<>();
 	private final MutableLiveEvent<Boolean> showImageOnboarding =
@@ -96,15 +97,14 @@ public class ConversationViewModel extends AndroidViewModel {
 			new MutableLiveData<>();
 	private final MutableLiveData<Boolean> contactDeleted =
 			new MutableLiveData<>();
-	private final MutableLiveData<GroupId> messagingGroupId =
-			new MutableLiveData<>();
-	private final MutableLiveData<PrivateMessageHeader> addedHeader =
-			new MutableLiveData<>();
+	private final MutableLiveEvent<PrivateMessageHeader> addedHeader =
+			new MutableLiveEvent<>();
 
 	@Inject
 	ConversationViewModel(Application application,
 			@DatabaseExecutor Executor dbExecutor,
-			@CryptoExecutor Executor cryptoExecutor, TransactionManager db,
+			@CryptoExecutor Executor cryptoExecutor,
+			@IoExecutor Executor ioExecutor, TransactionManager db,
 			MessagingManager messagingManager, ContactManager contactManager,
 			SettingsManager settingsManager,
 			PrivateMessageFactory privateMessageFactory) {
@@ -116,11 +116,21 @@ public class ConversationViewModel extends AndroidViewModel {
 		this.contactManager = contactManager;
 		this.settingsManager = settingsManager;
 		this.privateMessageFactory = privateMessageFactory;
-		this.attachmentController = new AttachmentController(messagingManager,
+		this.attachmentRetriever = new AttachmentRetriever(messagingManager,
 				getAttachmentDimensions(application.getResources()));
+		this.attachmentCreator = new AttachmentCreator(getApplication(),
+				ioExecutor, messagingManager, attachmentRetriever);
+		messagingGroupId = Transformations
+				.map(contact, c -> messagingManager.getContactGroup(c).getId());
 		contactDeleted.setValue(false);
 	}
 
+	@Override
+	protected void onCleared() {
+		super.onCleared();
+		attachmentCreator.deleteUnsentAttachments();
+	}
+
 	/**
 	 * Setting the {@link ContactId} automatically triggers loading of other
 	 * data.
@@ -176,25 +186,37 @@ public class ConversationViewModel extends AndroidViewModel {
 		});
 	}
 
-	void sendMessage(@Nullable String text, List<Uri> uris, long timestamp) {
-		if (messagingGroupId.getValue() == null) loadGroupId();
+	void sendMessage(@Nullable String text,
+			List<AttachmentHeader> attachmentHeaders, long timestamp) {
+		// messagingGroupId is loaded with the contact
 		observeForeverOnce(messagingGroupId, groupId -> {
-			if (groupId == null) return;
-			// calls through to creating and storing the message
-			storeAttachments(groupId, text, uris, timestamp);
+			if (groupId == null) throw new IllegalStateException();
+			createMessage(groupId, text, attachmentHeaders, timestamp);
 		});
 	}
 
-	private void loadGroupId() {
-		if (contactId == null) throw new IllegalStateException();
-		dbExecutor.execute(() -> {
-			try {
-				messagingGroupId.postValue(
-						messagingManager.getConversationId(contactId));
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-			}
-		});
+	@Override
+	@UiThread
+	public LiveData<AttachmentResult> storeAttachments(Collection<Uri> uris,
+			boolean restart) {
+		if (restart) {
+			return attachmentCreator.getLiveAttachments();
+		} else {
+			// messagingGroupId is loaded with the contact
+			return attachmentCreator.storeAttachments(messagingGroupId, uris);
+		}
+	}
+
+	@Override
+	@UiThread
+	public List<AttachmentHeader> getAttachmentHeadersForSending() {
+		return attachmentCreator.getAttachmentHeadersForSending();
+	}
+
+	@Override
+	@UiThread
+	public void cancel() {
+		attachmentCreator.cancel();
 	}
 
 	@DatabaseExecutor
@@ -252,58 +274,8 @@ public class ConversationViewModel extends AndroidViewModel {
 		});
 	}
 
-	private void storeAttachments(GroupId groupId, @Nullable String text,
-			List<Uri> uris, long timestamp) {
-		dbExecutor.execute(() -> {
-			long start = now();
-			List<AttachmentHeader> attachments = new ArrayList<>();
-			List<AttachmentItem> items = new ArrayList<>();
-			boolean needsSize = uris.size() == 1;
-			for (Uri uri : uris) {
-				Pair<AttachmentHeader, AttachmentItem> pair =
-						createAttachmentHeader(groupId, uri, timestamp,
-								needsSize);
-				if (pair == null) continue;
-				attachments.add(pair.getFirst());
-				items.add(pair.getSecond());
-			}
-			logDuration(LOG, "Storing attachments", start);
-			createMessage(groupId, text, attachments, items, timestamp);
-		});
-	}
-
-	@Nullable
-	@DatabaseExecutor
-	private Pair<AttachmentHeader, AttachmentItem> createAttachmentHeader(
-			GroupId groupId, Uri uri, long timestamp, boolean needsSize) {
-		InputStream is = null;
-		try {
-			ContentResolver contentResolver =
-					getApplication().getContentResolver();
-			is = contentResolver.openInputStream(uri);
-			if (is == null) throw new IOException();
-			String contentType = contentResolver.getType(uri);
-			if (contentType == null) throw new IOException("null content type");
-			AttachmentHeader h = messagingManager
-					.addLocalAttachment(groupId, timestamp, contentType, is);
-			is.close();
-			// re-open stream to get AttachmentItem
-			is = contentResolver.openInputStream(uri);
-			if (is == null) throw new IOException();
-			AttachmentItem item = attachmentController
-					.getAttachmentItem(h, new Attachment(is), needsSize);
-			return new Pair<>(h, item);
-		} catch (DbException | IOException e) {
-			logException(LOG, WARNING, e);
-			return null;
-		} finally {
-			if (is != null) tryToClose(is, LOG, WARNING);
-		}
-	}
-
 	private void createMessage(GroupId groupId, @Nullable String text,
-			List<AttachmentHeader> attachments, List<AttachmentItem> aItems,
-			long timestamp) {
+			List<AttachmentHeader> attachments, long timestamp) {
 		cryptoExecutor.execute(() -> {
 			try {
 				// TODO remove when text can be null in the backend
@@ -311,7 +283,6 @@ public class ConversationViewModel extends AndroidViewModel {
 				PrivateMessage pm = privateMessageFactory
 						.createPrivateMessage(groupId, timestamp, msgText,
 								attachments);
-				attachmentController.put(pm.getMessage().getId(), aItems);
 				storeMessage(pm, msgText, attachments);
 			} catch (FormatException e) {
 				throw new RuntimeException(e);
@@ -321,6 +292,7 @@ public class ConversationViewModel extends AndroidViewModel {
 
 	private void storeMessage(PrivateMessage m, @Nullable String text,
 			List<AttachmentHeader> attachments) {
+		attachmentCreator.onAttachmentsSent(m.getMessage().getId());
 		dbExecutor.execute(() -> {
 			try {
 				long start = now();
@@ -332,20 +304,15 @@ public class ConversationViewModel extends AndroidViewModel {
 						message.getTimestamp(), true, true, false, false,
 						text != null, attachments);
 				// TODO add text to cache when available here
-				addedHeader.postValue(h);
+				addedHeader.postEvent(h);
 			} catch (DbException e) {
 				logException(LOG, WARNING, e);
 			}
 		});
 	}
 
-	@UiThread
-	void onAddedPrivateMessageSeen() {
-		addedHeader.setValue(null);
-	}
-
-	AttachmentController getAttachmentController() {
-		return attachmentController;
+	AttachmentRetriever getAttachmentRetriever() {
+		return attachmentRetriever;
 	}
 
 	LiveData<Contact> getContact() {
@@ -380,7 +347,7 @@ public class ConversationViewModel extends AndroidViewModel {
 		return contactDeleted;
 	}
 
-	LiveData<PrivateMessageHeader> getAddedPrivateMessage() {
+	LiveEvent<PrivateMessageHeader> getAddedPrivateMessage() {
 		return addedHeader;
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationVisitor.java

@@ -7,6 +7,7 @@ import android.support.annotation.UiThread;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.R;
+import org.briarproject.briar.android.attachment.AttachmentItem;
 import org.briarproject.briar.api.blog.BlogInvitationRequest;
 import org.briarproject.briar.api.blog.BlogInvitationResponse;
 import org.briarproject.briar.api.conversation.ConversationMessageVisitor;

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageActivity.java

@@ -31,6 +31,7 @@ import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
 import org.briarproject.briar.android.activity.BriarActivity;
+import org.briarproject.briar.android.attachment.AttachmentItem;
 import org.briarproject.briar.android.util.BriarSnackbarBuilder;
 import org.briarproject.briar.android.view.PullDownLayout;
 

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageAdapter.java

@@ -12,6 +12,7 @@ import android.view.WindowManager;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
+import org.briarproject.briar.android.attachment.AttachmentItem;
 import org.briarproject.briar.android.conversation.glide.Radii;
 
 import java.util.ArrayList;

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageFragment.java

@@ -21,6 +21,7 @@ import com.github.chrisbanes.photoview.PhotoView;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.BaseActivity;
+import org.briarproject.briar.android.attachment.AttachmentItem;
 import org.briarproject.briar.android.conversation.glide.GlideApp;
 
 import javax.annotation.ParametersAreNonnullByDefault;

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageViewHolder.java

@@ -11,6 +11,7 @@ import com.bumptech.glide.load.Transformation;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
+import org.briarproject.briar.android.attachment.AttachmentItem;
 import org.briarproject.briar.android.conversation.glide.BriarImageTransformation;
 import org.briarproject.briar.android.conversation.glide.GlideApp;
 import org.briarproject.briar.android.conversation.glide.Radii;

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageViewModel.java

@@ -13,6 +13,7 @@ import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.briar.android.attachment.AttachmentItem;
 import org.briarproject.briar.android.viewmodel.LiveEvent;
 import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
 import org.briarproject.briar.api.messaging.Attachment;

briar-android/src/main/java/org/briarproject/briar/android/conversation/glide/BriarDataFetcher.java

@@ -10,7 +10,7 @@ import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageId;
-import org.briarproject.briar.android.conversation.AttachmentItem;
+import org.briarproject.briar.android.attachment.AttachmentItem;
 import org.briarproject.briar.api.messaging.MessagingManager;
 
 import java.io.InputStream;

briar-android/src/main/java/org/briarproject/briar/android/conversation/glide/BriarDataFetcherFactory.java

@@ -2,7 +2,7 @@ package org.briarproject.briar.android.conversation.glide;
 
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.briar.android.conversation.AttachmentItem;
+import org.briarproject.briar.android.attachment.AttachmentItem;
 import org.briarproject.briar.api.messaging.MessagingManager;
 
 import java.util.concurrent.Executor;

briar-android/src/main/java/org/briarproject/briar/android/conversation/glide/BriarGlideModule.java

@@ -10,7 +10,7 @@ import com.bumptech.glide.module.AppGlideModule;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.android.BriarApplication;
-import org.briarproject.briar.android.conversation.AttachmentItem;
+import org.briarproject.briar.android.attachment.AttachmentItem;
 
 import java.io.InputStream;
 

briar-android/src/main/java/org/briarproject/briar/android/conversation/glide/BriarModelLoader.java

@@ -8,7 +8,7 @@ import com.bumptech.glide.signature.ObjectKey;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.android.BriarApplication;
-import org.briarproject.briar.android.conversation.AttachmentItem;
+import org.briarproject.briar.android.attachment.AttachmentItem;
 
 import java.io.InputStream;
 

briar-android/src/main/java/org/briarproject/briar/android/conversation/glide/BriarModelLoaderFactory.java

@@ -6,7 +6,7 @@ import com.bumptech.glide.load.model.MultiModelLoaderFactory;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.android.BriarApplication;
-import org.briarproject.briar.android.conversation.AttachmentItem;
+import org.briarproject.briar.android.attachment.AttachmentItem;
 
 import java.io.InputStream;
 

briar-android/src/main/java/org/briarproject/briar/android/introduction/IntroductionMessageFragment.java

@@ -1,7 +1,6 @@
 package org.briarproject.briar.android.introduction;
 
 import android.content.Context;
-import android.net.Uri;
 import android.os.Bundle;
 import android.support.annotation.Nullable;
 import android.support.v7.app.ActionBar;
@@ -26,6 +25,7 @@ import org.briarproject.briar.android.view.TextInputView;
 import org.briarproject.briar.android.view.TextSendController;
 import org.briarproject.briar.android.view.TextSendController.SendListener;
 import org.briarproject.briar.api.introduction.IntroductionManager;
+import org.briarproject.briar.api.messaging.AttachmentHeader;
 
 import java.util.List;
 import java.util.logging.Logger;
@@ -193,7 +193,8 @@ public class IntroductionMessageFragment extends BaseFragment
 	}
 
 	@Override
-	public void onSendClick(@Nullable String text, List<Uri> imageUris) {
+	public void onSendClick(@Nullable String text,
+			List<AttachmentHeader> headers) {
 		// disable button to prevent accidental double invitations
 		ui.message.setReady(false);
 

briar-android/src/main/java/org/briarproject/briar/android/sharing/BaseMessageFragment.java

@@ -1,7 +1,6 @@
 package org.briarproject.briar.android.sharing;
 
 import android.content.Context;
-import android.net.Uri;
 import android.os.Bundle;
 import android.support.annotation.Nullable;
 import android.support.annotation.StringRes;
@@ -19,6 +18,7 @@ import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.view.LargeTextInputView;
 import org.briarproject.briar.android.view.TextSendController;
 import org.briarproject.briar.android.view.TextSendController.SendListener;
+import org.briarproject.briar.api.messaging.AttachmentHeader;
 
 import java.util.List;
 
@@ -83,7 +83,8 @@ public abstract class BaseMessageFragment extends BaseFragment
 	}
 
 	@Override
-	public void onSendClick(@Nullable String text, List<Uri> imageUris) {
+	public void onSendClick(@Nullable String text,
+			List<AttachmentHeader> headers) {
 		// disable button to prevent accidental double actions
 		sendController.setReady(false);
 		message.hideSoftKeyboard();

briar-android/src/main/java/org/briarproject/briar/android/threaded/ThreadListActivity.java

@@ -1,7 +1,6 @@
 package org.briarproject.briar.android.threaded;
 
 import android.content.Intent;
-import android.net.Uri;
 import android.os.Bundle;
 import android.os.Parcelable;
 import android.support.annotation.CallSuper;
@@ -34,6 +33,7 @@ import org.briarproject.briar.android.view.TextSendController;
 import org.briarproject.briar.android.view.TextSendController.SendListener;
 import org.briarproject.briar.android.view.UnreadMessageButton;
 import org.briarproject.briar.api.client.NamedGroup;
+import org.briarproject.briar.api.messaging.AttachmentHeader;
 
 import java.util.Collection;
 import java.util.List;
@@ -341,7 +341,8 @@ public abstract class ThreadListActivity<G extends NamedGroup, I extends ThreadI
 	}
 
 	@Override
-	public void onSendClick(@Nullable String text, List<Uri> imageUris) {
+	public void onSendClick(@Nullable String text,
+			List<AttachmentHeader> headers) {
 		if (isNullOrEmpty(text)) throw new AssertionError();
 
 		I replyItem = adapter.getHighlightedItem();

briar-android/src/main/java/org/briarproject/briar/android/view/ImagePreview.java

@@ -1,7 +1,6 @@
 package org.briarproject.briar.android.view;
 
 import android.content.Context;
-import android.net.Uri;
 import android.support.annotation.Nullable;
 import android.support.constraint.ConstraintLayout;
 import android.support.v7.widget.RecyclerView;
@@ -10,11 +9,13 @@ import android.view.LayoutInflater;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
+import org.briarproject.briar.android.attachment.AttachmentItemResult;
 
 import java.util.Collection;
 
 import static android.content.Context.LAYOUT_INFLATER_SERVICE;
 import static android.support.v4.content.ContextCompat.getColor;
+import static android.support.v7.widget.RecyclerView.NO_POSITION;
 import static android.view.ViewGroup.LayoutParams.MATCH_PARENT;
 import static java.util.Objects.requireNonNull;
 
@@ -60,34 +61,28 @@ public class ImagePreview extends ConstraintLayout {
 		this.listener = listener;
 	}
 
-	void showPreview(Collection<Uri> imageUris) {
+	void showPreview(Collection<ImagePreviewItem> items) {
 		if (listener == null) throw new IllegalStateException();
-		if (imageUris.size() == 1) {
+		if (items.size() == 1) {
 			LayoutParams params = (LayoutParams) imageList.getLayoutParams();
 			params.width = MATCH_PARENT;
 			imageList.setLayoutParams(params);
 		}
 		setVisibility(VISIBLE);
-		imageList.setAdapter(new ImagePreviewAdapter(imageUris, listener));
+		ImagePreviewAdapter adapter = new ImagePreviewAdapter(items);
+		imageList.setAdapter(adapter);
 	}
 
-	void removeUri(Uri uri) {
+	void loadPreviewImage(AttachmentItemResult result) {
 		ImagePreviewAdapter adapter =
-				(ImagePreviewAdapter) imageList.getAdapter();
-		requireNonNull(adapter).removeUri(uri);
+				((ImagePreviewAdapter) imageList.getAdapter());
+		int pos = requireNonNull(adapter).loadItemPreview(result);
+		if (pos != NO_POSITION) {
+			imageList.smoothScrollToPosition(pos);
+		}
 	}
 
 	interface ImagePreviewListener {
-
-		void onPreviewLoaded();
-
-		/**
-		 * Called when Glide can't load a preview image.
-		 *
-		 * Warning: Glide may call this multiple times.
-		 */
-		void onUriError(Uri uri);
-
 		void onCancel();
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/view/ImagePreviewAdapter.java

@@ -1,6 +1,5 @@
 package org.briarproject.briar.android.view;
 
-import android.net.Uri;
 import android.support.annotation.LayoutRes;
 import android.support.v7.widget.RecyclerView.Adapter;
 import android.view.LayoutInflater;
@@ -9,25 +8,24 @@ import android.view.ViewGroup;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
-import org.briarproject.briar.android.view.ImagePreview.ImagePreviewListener;
+import org.briarproject.briar.android.attachment.AttachmentItemResult;
 
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 
+import static android.support.v7.widget.RecyclerView.NO_POSITION;
 import static java.util.Objects.requireNonNull;
 
 @NotNullByDefault
 class ImagePreviewAdapter extends Adapter<ImagePreviewViewHolder> {
 
-	private final List<Uri> items;
-	private final ImagePreviewListener listener;
+	private final List<ImagePreviewItem> items;
 	@LayoutRes
 	private final int layout;
 
-	ImagePreviewAdapter(Collection<Uri> items, ImagePreviewListener listener) {
+	ImagePreviewAdapter(Collection<ImagePreviewItem> items) {
 		this.items = new ArrayList<>(items);
-		this.listener = listener;
 		this.layout = items.size() == 1 ?
 				R.layout.list_item_image_preview_single :
 				R.layout.list_item_image_preview;
@@ -38,7 +36,7 @@ class ImagePreviewAdapter extends Adapter<ImagePreviewViewHolder> {
 			int type) {
 		View v = LayoutInflater.from(viewGroup.getContext())
 				.inflate(layout, viewGroup, false);
-		return new ImagePreviewViewHolder(v, requireNonNull(listener));
+		return new ImagePreviewViewHolder(v);
 	}
 
 	@Override
@@ -52,11 +50,17 @@ class ImagePreviewAdapter extends Adapter<ImagePreviewViewHolder> {
 		return items.size();
 	}
 
-	void removeUri(Uri uri) {
-		int pos = items.indexOf(uri);
-		if (pos == -1) return;
-		items.remove(uri);
-		notifyItemRemoved(pos);
+	int loadItemPreview(AttachmentItemResult result) {
+		ImagePreviewItem newItem = new ImagePreviewItem(result.getUri());
+		int pos = items.indexOf(newItem);
+		if (pos == NO_POSITION) throw new AssertionError();
+		ImagePreviewItem item = items.get(pos);
+		if (item.getItem() == null) {
+			item.setItem(requireNonNull(result.getItem()));
+			notifyItemChanged(pos, item);
+			return pos;
+		}
+		return NO_POSITION;
 	}
 
 }

briar-android/src/main/java/org/briarproject/briar/android/view/ImagePreviewItem.java

@@ -0,0 +1,53 @@
+package org.briarproject.briar.android.view;
+
+import android.net.Uri;
+import android.support.annotation.Nullable;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.briar.android.attachment.AttachmentItem;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+@NotNullByDefault
+class ImagePreviewItem {
+
+	private final Uri uri;
+	@Nullable
+	private AttachmentItem item;
+
+	ImagePreviewItem(Uri uri) {
+		this.uri = uri;
+		this.item = null;
+	}
+
+	static List<ImagePreviewItem> fromUris(Collection<Uri> uris) {
+		List<ImagePreviewItem> items = new ArrayList<>(uris.size());
+		for (Uri uri : uris) {
+			items.add(new ImagePreviewItem(uri));
+		}
+		return items;
+	}
+
+	public void setItem(AttachmentItem item) {
+		this.item = item;
+	}
+
+	@Nullable
+	public AttachmentItem getItem() {
+		return item;
+	}
+
+	@Override
+	public boolean equals(@Nullable Object o) {
+		return o instanceof ImagePreviewItem &&
+				uri.equals(((ImagePreviewItem) o).uri);
+	}
+
+	@Override
+	public int hashCode() {
+		return uri.hashCode();
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/view/ImagePreviewViewHolder.java

@@ -1,7 +1,6 @@
 package org.briarproject.briar.android.view;
 
 import android.graphics.drawable.Drawable;
-import android.net.Uri;
 import android.support.annotation.DrawableRes;
 import android.support.annotation.Nullable;
 import android.support.v7.widget.RecyclerView.ViewHolder;
@@ -17,9 +16,9 @@ import com.bumptech.glide.request.target.Target;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.conversation.glide.GlideApp;
-import org.briarproject.briar.android.view.ImagePreview.ImagePreviewListener;
 
 import static android.view.View.INVISIBLE;
+import static android.view.View.VISIBLE;
 import static com.bumptech.glide.load.engine.DiskCacheStrategy.NONE;
 import static com.bumptech.glide.load.resource.bitmap.DownsampleStrategy.FIT_CENTER;
 import static com.bumptech.glide.load.resource.drawable.DrawableTransitionOptions.withCrossFade;
@@ -30,45 +29,47 @@ class ImagePreviewViewHolder extends ViewHolder {
 	@DrawableRes
 	private static final int ERROR_RES = R.drawable.ic_image_broken;
 
-	private final ImagePreviewListener listener;
-
 	private final ImageView imageView;
 	private final ProgressBar progressBar;
 
-	ImagePreviewViewHolder(View v, ImagePreviewListener listener) {
+	ImagePreviewViewHolder(View v) {
 		super(v);
-		this.listener = listener;
 		this.imageView = v.findViewById(R.id.imageView);
 		this.progressBar = v.findViewById(R.id.progressBar);
 	}
 
-	void bind(Uri uri) {
-		GlideApp.with(imageView)
-				.load(uri)
-				.diskCacheStrategy(NONE)
-				.error(ERROR_RES)
-				.downsample(FIT_CENTER)
-				.transition(withCrossFade())
-				.addListener(new RequestListener<Drawable>() {
-					@Override
-					public boolean onLoadFailed(@Nullable GlideException e,
-							Object model, Target<Drawable> target,
-							boolean isFirstResource) {
-						progressBar.setVisibility(INVISIBLE);
-						listener.onUriError(uri);
-						return false;
-					}
+	void bind(ImagePreviewItem item) {
+		if (item.getItem() == null) {
+			progressBar.setVisibility(VISIBLE);
+			GlideApp.with(imageView)
+					.clear(imageView);
+		} else {
+			GlideApp.with(imageView)
+					.load(item.getItem())
+					.diskCacheStrategy(NONE)
+					.error(ERROR_RES)
+					.downsample(FIT_CENTER)
+					.transition(withCrossFade())
+					.addListener(new RequestListener<Drawable>() {
+						@Override
+						public boolean onLoadFailed(@Nullable GlideException e,
+								Object model, Target<Drawable> target,
+								boolean isFirstResource) {
+							progressBar.setVisibility(INVISIBLE);
+							return false;
+						}
 
-					@Override
-					public boolean onResourceReady(Drawable resource,
-							Object model, Target<Drawable> target,
-							DataSource dataSource, boolean isFirstResource) {
-						progressBar.setVisibility(INVISIBLE);
-						listener.onPreviewLoaded();
-						return false;
-					}
-				})
-				.into(imageView);
+						@Override
+						public boolean onResourceReady(Drawable resource,
+								Object model, Target<Drawable> target,
+								DataSource dataSource,
+								boolean isFirstResource) {
+							progressBar.setVisibility(INVISIBLE);
+							return false;
+						}
+					})
+					.into(imageView);
+		}
 	}
 
 }

briar-android/src/main/java/org/briarproject/briar/android/view/TextAttachmentController.java

@@ -1,6 +1,9 @@
 package org.briarproject.briar.android.view;
 
 import android.app.Activity;
+import android.arch.lifecycle.LifecycleOwner;
+import android.arch.lifecycle.LiveData;
+import android.arch.lifecycle.Observer;
 import android.content.ClipData;
 import android.content.Context;
 import android.content.Intent;
@@ -15,26 +18,32 @@ import android.widget.Toast;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
+import org.briarproject.briar.android.attachment.AttachmentItemResult;
+import org.briarproject.briar.android.attachment.AttachmentManager;
+import org.briarproject.briar.android.attachment.AttachmentResult;
 import org.briarproject.briar.android.view.ImagePreview.ImagePreviewListener;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.List;
 
 import uk.co.samuelwall.materialtaptargetprompt.MaterialTapTargetPrompt;
 import uk.co.samuelwall.materialtaptargetprompt.MaterialTapTargetPrompt.PromptStateChangeListener;
 
+import static android.arch.lifecycle.Lifecycle.State.DESTROYED;
 import static android.content.Intent.ACTION_GET_CONTENT;
 import static android.content.Intent.ACTION_OPEN_DOCUMENT;
 import static android.content.Intent.CATEGORY_OPENABLE;
 import static android.content.Intent.EXTRA_ALLOW_MULTIPLE;
+import static android.content.Intent.EXTRA_MIME_TYPES;
 import static android.os.Build.VERSION.SDK_INT;
 import static android.support.v4.content.ContextCompat.getColor;
 import static android.support.v4.view.AbsSavedState.EMPTY_STATE;
 import static android.view.View.GONE;
 import static android.widget.Toast.LENGTH_LONG;
-import static java.util.Collections.emptyList;
 import static java.util.Objects.requireNonNull;
 import static org.briarproject.briar.android.util.UiUtils.resolveColorAttribute;
+import static org.briarproject.briar.api.messaging.MessagingConstants.IMAGE_MIME_TYPES;
 import static uk.co.samuelwall.materialtaptargetprompt.MaterialTapTargetPrompt.STATE_DISMISSED;
 import static uk.co.samuelwall.materialtaptargetprompt.MaterialTapTargetPrompt.STATE_FINISHED;
 
@@ -46,17 +55,19 @@ public class TextAttachmentController extends TextSendController
 	private final ImagePreview imagePreview;
 	private final AttachImageListener imageListener;
 	private final CompositeSendButton sendButton;
+	private final AttachmentManager attachmentManager;
 
-	private CharSequence textHint;
-	private List<Uri> imageUris = emptyList();
-	private int previewsLoaded = 0;
-	private boolean loadingPreviews = false;
+	private final List<Uri> imageUris = new ArrayList<>();
+	private final CharSequence textHint;
+	private boolean loadingUris = false;
 
 	public TextAttachmentController(TextInputView v, ImagePreview imagePreview,
-			SendListener listener, AttachImageListener imageListener) {
+			SendListener listener, AttachImageListener imageListener,
+			AttachmentManager attachmentManager) {
 		super(v, listener, false);
 		this.imageListener = imageListener;
 		this.imagePreview = imagePreview;
+		this.attachmentManager = attachmentManager;
 		this.imagePreview.setImagePreviewListener(this);
 
 		sendButton = (CompositeSendButton) compositeSendButton;
@@ -67,10 +78,10 @@ public class TextAttachmentController extends TextSendController
 
 	@Override
 	protected void updateViewState() {
-		textInput.setEnabled(ready && !loadingPreviews);
-		boolean sendEnabled = ready && !loadingPreviews &&
+		textInput.setEnabled(ready && !loadingUris);
+		boolean sendEnabled = ready && !loadingUris &&
 				(!textIsEmpty || canSendEmptyText());
-		if (loadingPreviews) {
+		if (loadingUris) {
 			sendButton.showProgress(true);
 		} else if (imageUris.isEmpty()) {
 			sendButton.showProgress(false);
@@ -84,7 +95,9 @@ public class TextAttachmentController extends TextSendController
 	@Override
 	public void onSendEvent() {
 		if (canSend()) {
-			listener.onSendClick(textInput.getText(), imageUris);
+			if (loadingUris) throw new AssertionError();
+			listener.onSendClick(textInput.getText(),
+					attachmentManager.getAttachmentHeadersForSending());
 			reset();
 		}
 	}
@@ -110,36 +123,95 @@ public class TextAttachmentController extends TextSendController
 			builder.show();
 			return;
 		}
-		Intent intent = new Intent(SDK_INT >= 19 ?
-				ACTION_OPEN_DOCUMENT : ACTION_GET_CONTENT);
-		intent.addCategory(CATEGORY_OPENABLE);
-		intent.setType("image/*");
-		if (SDK_INT >= 18) intent.putExtra(EXTRA_ALLOW_MULTIPLE, true);
-		requireNonNull(imageListener).onAttachImage(intent);
-	}
-
-	public void onImageReceived(@Nullable Intent resultData) {
-		if (resultData == null) return;
-		if (resultData.getData() != null) {
-			imageUris = new ArrayList<>(1);
-			imageUris.add(resultData.getData());
-			onNewUris();
-		} else if (SDK_INT >= 18 && resultData.getClipData() != null) {
-			ClipData clipData = resultData.getClipData();
-			imageUris = new ArrayList<>(clipData.getItemCount());
-			for (int i = 0; i < clipData.getItemCount(); i++) {
-				imageUris.add(clipData.getItemAt(i).getUri());
-			}
-			onNewUris();
+		Intent intent = getAttachFileIntent();
+		if (imageListener.getLifecycle().getCurrentState() != DESTROYED) {
+			requireNonNull(imageListener).onAttachImage(intent);
 		}
 	}
 
-	private void onNewUris() {
+	private Intent getAttachFileIntent() {
+		Intent intent = new Intent(SDK_INT >= 19 ?
+				ACTION_OPEN_DOCUMENT : ACTION_GET_CONTENT);
+		intent.setType("image/*");
+		intent.addCategory(CATEGORY_OPENABLE);
+		if (SDK_INT >= 19) intent.putExtra(EXTRA_MIME_TYPES, IMAGE_MIME_TYPES);
+		if (SDK_INT >= 18) intent.putExtra(EXTRA_ALLOW_MULTIPLE, true);
+		return intent;
+	}
+
+	/**
+	 * This is called with the result Intent
+	 * returned by the Activity started with {@link #getAttachFileIntent()}.
+	 * <p>
+	 * This method must be called at most once per call to
+	 * {@link AttachImageListener#onAttachImage(Intent)}.
+	 * Normally, this is true if called from
+	 * {@link Activity#onActivityResult(int, int, Intent)} since this is called
+	 * at most once per call to {@link Activity#startActivityForResult(Intent, int)}.
+	 */
+	public void onImageReceived(@Nullable Intent resultData) {
+		if (resultData == null) return;
+		if (loadingUris || !imageUris.isEmpty()) throw new AssertionError();
+		if (resultData.getData() != null) {
+			imageUris.add(resultData.getData());
+			onNewUris(false);
+		} else if (SDK_INT >= 18 && resultData.getClipData() != null) {
+			ClipData clipData = resultData.getClipData();
+			for (int i = 0; i < clipData.getItemCount(); i++) {
+				imageUris.add(clipData.getItemAt(i).getUri());
+			}
+			onNewUris(false);
+		}
+	}
+
+	private void onNewUris(boolean restart) {
 		if (imageUris.isEmpty()) return;
-		loadingPreviews = true;
+		if (loadingUris) throw new AssertionError();
+		loadingUris = true;
 		updateViewState();
 		textInput.setHint(R.string.image_caption_hint);
-		imagePreview.showPreview(imageUris);
+		List<ImagePreviewItem> items = ImagePreviewItem.fromUris(imageUris);
+		imagePreview.showPreview(items);
+		// store attachments and show preview when successful
+		LiveData<AttachmentResult> result =
+				attachmentManager.storeAttachments(imageUris, restart);
+		result.observe(imageListener, new Observer<AttachmentResult>() {
+			@Override
+			public void onChanged(@Nullable AttachmentResult attachmentResult) {
+				if (attachmentResult == null) {
+					// The fresh LiveData was deliberately set to null.
+					// This means that we can stop observing it.
+					result.removeObserver(this);
+				} else {
+					boolean noError = onNewAttachmentItemResults(
+							attachmentResult.getItemResults());
+					if (noError && attachmentResult.isFinished()) {
+						onAllAttachmentsCreated();
+						result.removeObserver(this);
+					}
+				}
+			}
+		});
+	}
+
+	private boolean onNewAttachmentItemResults(
+			Collection<AttachmentItemResult> itemResults) {
+		if (!loadingUris) throw new AssertionError();
+		for (AttachmentItemResult result : itemResults) {
+			if (result.hasError()) {
+				onError(result.getErrorMsg());
+				return false;
+			} else {
+				imagePreview.loadPreviewImage(result);
+			}
+		}
+		return true;
+	}
+
+	private void onAllAttachmentsCreated() {
+		if (!loadingUris) throw new AssertionError();
+		loadingUris = false;
+		updateViewState();
 	}
 
 	private void reset() {
@@ -148,10 +220,9 @@ public class TextAttachmentController extends TextSendController
 		// hide image layout
 		imagePreview.setVisibility(GONE);
 		// reset image URIs
-		imageUris = emptyList();
-		// no preview has been loaded
-		previewsLoaded = 0;
-		loadingPreviews = false;
+		imageUris.clear();
+		// definitely not loading anymore
+		loadingUris = false;
 		// show the image button again, so images can get attached
 		updateViewState();
 	}
@@ -168,45 +239,29 @@ public class TextAttachmentController extends TextSendController
 	@Nullable
 	public Parcelable onRestoreInstanceState(Parcelable inState) {
 		SavedState state = (SavedState) inState;
-		imageUris = requireNonNull(state.imageUris);
-		onNewUris();
+		if (!imageUris.isEmpty()) throw new AssertionError();
+		if (state.imageUris != null) imageUris.addAll(state.imageUris);
+		onNewUris(true);
 		return state.getSuperState();
 	}
 
-	@Override
-	public void onPreviewLoaded() {
-		previewsLoaded++;
-		checkAllPreviewsLoaded();
-	}
-
-	@Override
-	public void onUriError(Uri uri) {
-		boolean removed = imageUris.remove(uri);
-		if (!removed) {
-			// we have removed this Uri already, do not remove it again
-			return;
+	@UiThread
+	private void onError(@Nullable String errorMsg) {
+		if (errorMsg == null) {
+			errorMsg = imagePreview.getContext()
+					.getString(R.string.image_attach_error);
 		}
-		imagePreview.removeUri(uri);
-		if (imageUris.isEmpty()) onCancel();
-		Toast.makeText(textInput.getContext(), R.string.image_attach_error,
-				LENGTH_LONG).show();
-		checkAllPreviewsLoaded();
+		Toast.makeText(textInput.getContext(), errorMsg, LENGTH_LONG).show();
+		onCancel();
 	}
 
 	@Override
 	public void onCancel() {
 		textInput.clearText();
+		attachmentManager.cancel();
 		reset();
 	}
 
-	private void checkAllPreviewsLoaded() {
-		if (previewsLoaded == imageUris.size()) {
-			loadingPreviews = false;
-			// all previews were loaded
-			updateViewState();
-		}
-	}
-
 	public void showImageOnboarding(Activity activity,
 			Runnable onOnboardingSeen) {
 		PromptStateChangeListener listener = (prompt, state) -> {
@@ -261,7 +316,7 @@ public class TextAttachmentController extends TextSendController
 				};
 	}
 
-	public interface AttachImageListener {
+	public interface AttachImageListener extends LifecycleOwner {
 		void onAttachImage(Intent intent);
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/view/TextSendController.java

@@ -1,6 +1,5 @@
 package org.briarproject.briar.android.view;
 
-import android.net.Uri;
 import android.os.Parcelable;
 import android.support.annotation.Nullable;
 import android.support.annotation.UiThread;
@@ -10,6 +9,7 @@ import android.view.View;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.view.EmojiTextInputView.TextInputListener;
+import org.briarproject.briar.api.messaging.AttachmentHeader;
 
 import java.util.List;
 
@@ -85,7 +85,7 @@ public class TextSendController implements TextInputListener {
 	}
 
 	public interface SendListener {
-		void onSendClick(@Nullable String text, List<Uri> imageUris);
+		void onSendClick(@Nullable String text, List<AttachmentHeader> headers);
 	}
 
 }

briar-android/src/main/res/values/strings.xml

@@ -129,7 +129,9 @@
 	<string name="message_hint">Type message</string>
 	<string name="image_caption_hint">Add a caption (optional)</string>
 	<string name="image_attach">Attach image</string>
-	<string name="image_attach_error">Could not attach image</string>
+	<string name="image_attach_error">Could not attach image(s)</string>
+	<string name="image_attach_error_too_big">Image too big. Limit is %d MB.</string>
+	<string name="image_attach_error_invalid_mime_type">Image format unsupported: %s</string>
 	<string name="set_contact_alias">Change contact name</string>
 	<string name="set_contact_alias_hint">Contact name</string>
 	<string name="set_alias_button">Change</string>

briar-android/src/test/java/org/briarproject/briar/android/attachment/AttachmentRetrieverTest.java

@@ -1,8 +1,8 @@
-package org.briarproject.briar.android.conversation;
+package org.briarproject.briar.android.attachment;
 
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.test.BrambleMockTestCase;
-import org.briarproject.briar.android.conversation.ImageHelper.DecodeResult;
+import org.briarproject.briar.android.attachment.ImageHelper.DecodeResult;
 import org.briarproject.briar.api.messaging.Attachment;
 import org.briarproject.briar.api.messaging.AttachmentHeader;
 import org.briarproject.briar.api.messaging.MessagingManager;
@@ -19,7 +19,7 @@ import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
-public class AttachmentControllerTest extends BrambleMockTestCase {
+public class AttachmentRetrieverTest extends BrambleMockTestCase {
 
 	private final AttachmentDimensions dimensions = new AttachmentDimensions(
 			100, 50, 200, 75, 300
@@ -32,8 +32,8 @@ public class AttachmentControllerTest extends BrambleMockTestCase {
 	private final MessagingManager messagingManager =
 			context.mock(MessagingManager.class);
 	private final ImageHelper imageHelper = context.mock(ImageHelper.class);
-	private final AttachmentController controller =
-			new AttachmentController(
+	private final AttachmentRetriever controller =
+			new AttachmentRetriever(
 					messagingManager,
 					dimensions,
 					imageHelper
@@ -94,23 +94,6 @@ public class AttachmentControllerTest extends BrambleMockTestCase {
 		assertFalse(item.hasError());
 	}
 
-	@Test
-	public void testImageHealsWrongMimeType() {
-		AttachmentHeader h = getAttachmentHeader("image/png");
-
-		context.checking(new Expectations() {{
-			oneOf(imageHelper).decodeStream(with(any(InputStream.class)));
-			will(returnValue(new DecodeResult(160, 240, "image/jpeg")));
-			oneOf(imageHelper).getExtensionFromMimeType("image/jpeg");
-			will(returnValue("jpg"));
-		}});
-
-		AttachmentItem item = controller.getAttachmentItem(h, attachment, true);
-		assertEquals("image/jpeg", item.getMimeType());
-		assertEquals("jpg", item.getExtension());
-		assertFalse(item.hasError());
-	}
-
 	@Test
 	public void testBigJpegImage() {
 		String mimeType = "image/jpeg";

briar-android/src/test/java/org/briarproject/briar/android/attachment/MarkEnforcingInputStreamTest.java

@@ -1,4 +1,4 @@
-package org.briarproject.briar.android.conversation;
+package org.briarproject.briar.android.attachment;
 
 import com.bumptech.glide.util.MarkEnforcingInputStream;
 

briar-api/src/main/java/org/briarproject/briar/api/messaging/AttachmentHeader.java

@@ -25,4 +25,15 @@ public class AttachmentHeader {
 		return contentType;
 	}
 
+	@Override
+	public boolean equals(Object o) {
+		return o instanceof AttachmentHeader &&
+				messageId.equals(((AttachmentHeader) o).messageId);
+	}
+
+	@Override
+	public int hashCode() {
+		return messageId.hashCode();
+	}
+
 }

briar-api/src/main/java/org/briarproject/briar/api/messaging/FileTooBigException.java

@@ -0,0 +1,6 @@
+package org.briarproject.briar.api.messaging;
+
+import java.io.IOException;
+
+public class FileTooBigException extends IOException {
+}

briar-api/src/main/java/org/briarproject/briar/api/messaging/MessagingConstants.java

@@ -8,4 +8,20 @@ public interface MessagingConstants {
 	 * The maximum length of a private message's text in UTF-8 bytes.
 	 */
 	int MAX_PRIVATE_MESSAGE_TEXT_LENGTH = MAX_MESSAGE_BODY_LENGTH - 1024;
+
+	/**
+	 * The supported mime types for image attachments.
+	 */
+	String[] IMAGE_MIME_TYPES = {
+			"image/jpeg",
+			"image/png",
+			"image/gif",
+	};
+
+	/**
+	 * The maximum allowed size of image attachments.
+	 * TODO: Different limit for GIFs?
+	 */
+	int MAX_IMAGE_SIZE = MAX_MESSAGE_BODY_LENGTH; // 6 * 1024 * 1024;
+
 }

briar-api/src/main/java/org/briarproject/briar/api/messaging/MessagingManager.java

@@ -37,10 +37,17 @@ public interface MessagingManager extends ConversationClient {
 
 	/**
 	 * Stores a local attachment message.
+	 *
+	 * @throws FileTooBigException
 	 */
 	AttachmentHeader addLocalAttachment(GroupId groupId, long timestamp,
 			String contentType, InputStream is) throws DbException, IOException;
 
+	/**
+	 * Removes an unsent attachment.
+	 */
+	void removeAttachment(AttachmentHeader header) throws DbException;
+
 	/**
 	 * Returns the ID of the contact with the given private conversation.
 	 */

briar-core/src/main/java/org/briarproject/briar/messaging/MessagingManagerImpl.java

@@ -18,14 +18,17 @@ import org.briarproject.bramble.api.sync.Group;
 import org.briarproject.bramble.api.sync.Group.Visibility;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
+import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.sync.MessageStatus;
 import org.briarproject.bramble.api.versioning.ClientVersioningManager;
 import org.briarproject.bramble.api.versioning.ClientVersioningManager.ClientVersioningHook;
+import org.briarproject.bramble.util.IoUtils;
 import org.briarproject.briar.api.client.MessageTracker;
 import org.briarproject.briar.api.conversation.ConversationMessageHeader;
 import org.briarproject.briar.api.messaging.Attachment;
 import org.briarproject.briar.api.messaging.AttachmentHeader;
+import org.briarproject.briar.api.messaging.FileTooBigException;
 import org.briarproject.briar.api.messaging.MessagingManager;
 import org.briarproject.briar.api.messaging.PrivateMessage;
 import org.briarproject.briar.api.messaging.PrivateMessageHeader;
@@ -33,18 +36,18 @@ import org.briarproject.briar.api.messaging.event.PrivateMessageReceivedEvent;
 import org.briarproject.briar.client.ConversationClientImpl;
 
 import java.io.ByteArrayInputStream;
+import java.io.EOFException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Map;
-import java.util.Random;
 
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
 import static java.util.Collections.emptyList;
-import static org.briarproject.bramble.util.StringUtils.fromHexString;
+import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_BODY_LENGTH;
 import static org.briarproject.briar.client.MessageTrackerConstants.MSG_KEY_READ;
 
 @Immutable
@@ -55,15 +58,18 @@ class MessagingManagerImpl extends ConversationClientImpl
 
 	private final ClientVersioningManager clientVersioningManager;
 	private final ContactGroupFactory contactGroupFactory;
+	private final MessageFactory messageFactory;
 
 	@Inject
 	MessagingManagerImpl(DatabaseComponent db, ClientHelper clientHelper,
 			ClientVersioningManager clientVersioningManager,
 			MetadataParser metadataParser, MessageTracker messageTracker,
-			ContactGroupFactory contactGroupFactory) {
+			ContactGroupFactory contactGroupFactory,
+			MessageFactory messageFactory) {
 		super(db, clientHelper, metadataParser, messageTracker);
 		this.clientVersioningManager = clientVersioningManager;
 		this.contactGroupFactory = contactGroupFactory;
+		this.messageFactory = messageFactory;
 	}
 
 	@Override
@@ -158,12 +164,29 @@ class MessagingManagerImpl extends ConversationClientImpl
 
 	@Override
 	public AttachmentHeader addLocalAttachment(GroupId groupId, long timestamp,
-			String contentType, InputStream is) throws IOException {
+			String contentType, InputStream is)
+			throws DbException, IOException {
 		// TODO add real implementation
-		if (is.available() == 0) throw new IOException();
-		byte[] b = new byte[MessageId.LENGTH];
-		new Random().nextBytes(b);
-		return new AttachmentHeader(new MessageId(b), "image/png");
+		byte[] body = new byte[MAX_MESSAGE_BODY_LENGTH];
+		try {
+			IoUtils.read(is, body);
+		} catch (EOFException ignored) {
+		}
+		if (is.available() > 0) throw new FileTooBigException();
+		is.close();
+		try {
+			Thread.sleep(1000);
+		} catch (InterruptedException ignored) {
+		}
+		Message m = messageFactory.createMessage(groupId, timestamp, body);
+		clientHelper.addLocalMessage(m, new BdfDictionary(), false);
+		return new AttachmentHeader(m.getId(), contentType);
+	}
+
+	@Override
+	public void removeAttachment(AttachmentHeader header) throws DbException {
+		db.transaction(false,
+				txn -> db.removeMessage(txn, header.getMessageId()));
 	}
 
 	private ContactId getContactId(Transaction txn, GroupId g)
@@ -242,12 +265,10 @@ class MessagingManagerImpl extends ConversationClientImpl
 	}
 
 	@Override
-	public Attachment getAttachment(MessageId m) {
+	public Attachment getAttachment(MessageId mId) throws DbException {
 		// TODO add real implementation
-		byte[] bytes = fromHexString("89504E470D0A1A0A0000000D49484452" +
-				"000000010000000108060000001F15C4" +
-				"890000000A49444154789C6300010000" +
-				"0500010D0A2DB40000000049454E44AE426082");
+		Message m = clientHelper.getMessage(mId);
+		byte[] bytes = m.getBody();
 		return new Attachment(new ByteArrayInputStream(bytes));
 	}