Remove deprecated BHP handshake v0.0

https://briarproject.org/news/2023-three-security-issues-found-and-fixed/

bramble-api/src/main/java/org/briarproject/bramble/api/crypto/CryptoComponent.java

@@ -54,38 +54,6 @@ public interface CryptoComponent {
 			KeyPair ourKeyPair, byte[]... inputs)
 			throws GeneralSecurityException;
 
-	/**
-	 * Derives a shared secret from two static and two ephemeral key pairs.
-	 * <p>
-	 * Do not use this method for new protocols. The shared secret can be
-	 * re-derived using the ephemeral public keys and both static private
-	 * keys, so keys derived from the shared secret should not be used if
-	 * forward secrecy is required. Use {@link #deriveSharedSecret(String,
-	 * PublicKey, PublicKey, KeyPair, KeyPair, boolean, byte[]...)} instead.
-	 * <p>
-	 * TODO: Remove this after a reasonable migration period (added 2023-03-10).
-	 * <p>
-	 *
-	 * @param label A namespaced label indicating the purpose of this shared
-	 * secret, to prevent it from being repurposed or colliding with a shared
-	 * secret derived for another purpose
-	 * @param theirStaticPublicKey The static public key of the remote party
-	 * @param theirEphemeralPublicKey The ephemeral public key of the remote
-	 * party
-	 * @param ourStaticKeyPair The static key pair of the local party
-	 * @param ourEphemeralKeyPair The ephemeral key pair of the local party
-	 * @param alice True if the local party is Alice
-	 * @param inputs Additional inputs that will be included in the
-	 * derivation of the shared secret
-	 * @return The shared secret
-	 */
-	@Deprecated
-	SecretKey deriveSharedSecretBadly(String label,
-			PublicKey theirStaticPublicKey, PublicKey theirEphemeralPublicKey,
-			KeyPair ourStaticKeyPair, KeyPair ourEphemeralKeyPair,
-			boolean alice, byte[]... inputs)
-			throws GeneralSecurityException;
-
 	/**
 	 * Derives a shared secret from two static and two ephemeral key pairs.
 	 *

bramble-core/src/main/java/org/briarproject/bramble/contact/HandshakeConstants.java

@@ -14,16 +14,6 @@ interface HandshakeConstants {
 	 */
 	byte PROTOCOL_MINOR_VERSION = 1;
 
-	/**
-	 * Label for deriving the master key when using the deprecated v0.0 key
-	 * derivation method.
-	 * <p>
-	 * TODO: Remove this after a reasonable migration period (added 2023-03-10).
-	 */
-	@Deprecated
-	String MASTER_KEY_LABEL_0_0 =
-			"org.briarproject.bramble.handshake/MASTER_KEY";
-
 	/**
 	 * Label for deriving the master key when using the v0.1 key derivation
 	 * method.

bramble-core/src/main/java/org/briarproject/bramble/contact/HandshakeCrypto.java

@@ -12,20 +12,6 @@ interface HandshakeCrypto {
 
 	KeyPair generateEphemeralKeyPair();
 
-	/**
-	 * Derives the master key from the given static and ephemeral keys using
-	 * the deprecated v0.0 key derivation method.
-	 * <p>
-	 * TODO: Remove this after a reasonable migration period (added 2023-03-10).
-	 *
-	 * @param alice Whether the local peer is Alice
-	 */
-	@Deprecated
-	SecretKey deriveMasterKey_0_0(PublicKey theirStaticPublicKey,
-			PublicKey theirEphemeralPublicKey, KeyPair ourStaticKeyPair,
-			KeyPair ourEphemeralKeyPair, boolean alice)
-			throws GeneralSecurityException;
-
 	/**
 	 * Derives the master key from the given static and ephemeral keys using
 	 * the v0.1 key derivation method.

bramble-core/src/main/java/org/briarproject/bramble/contact/HandshakeCryptoImpl.java

@@ -13,7 +13,6 @@ import javax.inject.Inject;
 
 import static org.briarproject.bramble.contact.HandshakeConstants.ALICE_PROOF_LABEL;
 import static org.briarproject.bramble.contact.HandshakeConstants.BOB_PROOF_LABEL;
-import static org.briarproject.bramble.contact.HandshakeConstants.MASTER_KEY_LABEL_0_0;
 import static org.briarproject.bramble.contact.HandshakeConstants.MASTER_KEY_LABEL_0_1;
 
 @Immutable
@@ -32,27 +31,6 @@ class HandshakeCryptoImpl implements HandshakeCrypto {
 		return crypto.generateAgreementKeyPair();
 	}
 
-	@Override
-	@Deprecated
-	public SecretKey deriveMasterKey_0_0(PublicKey theirStaticPublicKey,
-			PublicKey theirEphemeralPublicKey, KeyPair ourStaticKeyPair,
-			KeyPair ourEphemeralKeyPair, boolean alice) throws
-			GeneralSecurityException {
-		byte[] theirStatic = theirStaticPublicKey.getEncoded();
-		byte[] theirEphemeral = theirEphemeralPublicKey.getEncoded();
-		byte[] ourStatic = ourStaticKeyPair.getPublic().getEncoded();
-		byte[] ourEphemeral = ourEphemeralKeyPair.getPublic().getEncoded();
-		byte[][] inputs = {
-				alice ? ourStatic : theirStatic,
-				alice ? theirStatic : ourStatic,
-				alice ? ourEphemeral : theirEphemeral,
-				alice ? theirEphemeral : ourEphemeral
-		};
-		return crypto.deriveSharedSecretBadly(MASTER_KEY_LABEL_0_0,
-				theirStaticPublicKey, theirEphemeralPublicKey,
-				ourStaticKeyPair, ourEphemeralKeyPair, alice, inputs);
-	}
-
 	@Override
 	public SecretKey deriveMasterKey_0_1(PublicKey theirStaticPublicKey,
 			PublicKey theirEphemeralPublicKey, KeyPair ourStaticKeyPair,

bramble-core/src/main/java/org/briarproject/bramble/contact/HandshakeManagerImpl.java

@@ -2,6 +2,7 @@ package org.briarproject.bramble.contact;
 
 import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.Pair;
+import org.briarproject.bramble.api.UnsupportedVersionException;
 import org.briarproject.bramble.api.contact.ContactManager;
 import org.briarproject.bramble.api.contact.HandshakeManager;
 import org.briarproject.bramble.api.contact.PendingContact;
@@ -111,21 +112,12 @@ class HandshakeManagerImpl implements HandshakeManager {
 			sendMinorVersion(recordWriter);
 			sendPublicKey(recordWriter, ourEphemeralKeyPair.getPublic());
 		}
-		byte theirMinorVersion = theirMinorVersionAndKey.getFirst();
 		PublicKey theirEphemeralPublicKey = theirMinorVersionAndKey.getSecond();
 		SecretKey masterKey;
 		try {
-			if (theirMinorVersion > 0) {
-				masterKey = handshakeCrypto.deriveMasterKey_0_1(
-						theirStaticPublicKey, theirEphemeralPublicKey,
-						ourStaticKeyPair, ourEphemeralKeyPair, alice);
-			} else {
-				// TODO: Remove this branch after a reasonable migration
-				//  period (added 2023-03-10).
-				masterKey = handshakeCrypto.deriveMasterKey_0_0(
-						theirStaticPublicKey, theirEphemeralPublicKey,
-						ourStaticKeyPair, ourEphemeralKeyPair, alice);
-			}
+			masterKey = handshakeCrypto.deriveMasterKey_0_1(
+					theirStaticPublicKey, theirEphemeralPublicKey,
+					ourStaticKeyPair, ourEphemeralKeyPair, alice);
 		} catch (GeneralSecurityException e) {
 			throw new FormatException();
 		}
@@ -187,10 +179,11 @@ class HandshakeManagerImpl implements HandshakeManager {
 		} else {
 			// The remote peer did not send a minor version record, so the
 			// remote peer's protocol minor version is assumed to be zero
-			// TODO: Remove this branch after a reasonable migration period
-			//  (added 2023-03-10).
-			theirMinorVersion = 0;
-			theirEphemeralPublicKey = parsePublicKey(first);
+
+			// TODO: How communicate to user that contact seems to use a version
+			// of Briar that is too old? (be aware of MITM attacks)
+			// `RendezvousPollerImpl` broadcasts PendingContactState FAILED via EventBus
+			throw new UnsupportedVersionException(true);
 		}
 		return new Pair<>(theirMinorVersion, theirEphemeralPublicKey);
 	}

bramble-core/src/main/java/org/briarproject/bramble/crypto/CryptoComponentImpl.java

@@ -222,36 +222,6 @@ class CryptoComponentImpl implements CryptoComponent {
 		return new SecretKey(hash);
 	}
 
-	@Override
-	@Deprecated
-	public SecretKey deriveSharedSecretBadly(String label,
-			PublicKey theirStaticPublicKey, PublicKey theirEphemeralPublicKey,
-			KeyPair ourStaticKeyPair, KeyPair ourEphemeralKeyPair,
-			boolean alice, byte[]... inputs) throws GeneralSecurityException {
-		PrivateKey ourStaticPrivateKey = ourStaticKeyPair.getPrivate();
-		PrivateKey ourEphemeralPrivateKey = ourEphemeralKeyPair.getPrivate();
-		byte[][] hashInputs = new byte[inputs.length + 3][];
-		// Alice static/Bob static
-		hashInputs[0] = performRawKeyAgreement(ourStaticPrivateKey,
-				theirStaticPublicKey);
-		// Alice static/Bob ephemeral, Bob static/Alice ephemeral
-		if (alice) {
-			hashInputs[1] = performRawKeyAgreement(ourStaticPrivateKey,
-					theirEphemeralPublicKey);
-			hashInputs[2] = performRawKeyAgreement(ourEphemeralPrivateKey,
-					theirStaticPublicKey);
-		} else {
-			hashInputs[1] = performRawKeyAgreement(ourEphemeralPrivateKey,
-					theirStaticPublicKey);
-			hashInputs[2] = performRawKeyAgreement(ourStaticPrivateKey,
-					theirEphemeralPublicKey);
-		}
-		arraycopy(inputs, 0, hashInputs, 3, inputs.length);
-		byte[] hash = hash(label, hashInputs);
-		if (hash.length != SecretKey.LENGTH) throw new IllegalStateException();
-		return new SecretKey(hash);
-	}
-
 	@Override
 	public SecretKey deriveSharedSecret(String label,
 			PublicKey theirStaticPublicKey, PublicKey theirEphemeralPublicKey,

bramble-core/src/test/java/org/briarproject/bramble/contact/HandshakeManagerImplTest.java

@@ -1,6 +1,7 @@
 package org.briarproject.bramble.contact;
 
 import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.UnsupportedVersionException;
 import org.briarproject.bramble.api.contact.ContactManager;
 import org.briarproject.bramble.api.contact.HandshakeManager.HandshakeResult;
 import org.briarproject.bramble.api.contact.PendingContact;
@@ -27,6 +28,7 @@ import org.junit.Test;
 
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
+import java.io.EOFException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.util.Arrays;
@@ -123,12 +125,12 @@ public class HandshakeManagerImplTest extends BrambleMockTestCase {
 		assertEquals(alice, result.isAlice());
 	}
 
-	@Test
+	@Test(expected = UnsupportedVersionException.class)
 	public void testHandshakeAsAliceWithPeerVersion_0_0() throws Exception {
 		testHandshakeWithPeerVersion_0_0(true);
 	}
 
-	@Test
+	@Test(expected = UnsupportedVersionException.class)
 	public void testHandshakeAsBobWithPeerVersion_0_0() throws Exception {
 		testHandshakeWithPeerVersion_0_0(false);
 	}
@@ -140,20 +142,8 @@ public class HandshakeManagerImplTest extends BrambleMockTestCase {
 		expectSendKey();
 		// Remote peer does not send minor version, so use old key derivation
 		expectReceiveKey();
-		expectDeriveMasterKey_0_0(alice);
-		expectDeriveProof(alice);
-		expectSendProof();
-		expectReceiveProof();
-		expectSendEof();
-		expectReceiveEof();
-		expectVerifyOwnership(alice, true);
 
-		HandshakeResult result = handshakeManager.handshake(
-				pendingContact.getId(), in, streamWriter);
-
-		assertArrayEquals(masterKey.getBytes(),
-				result.getMasterKey().getBytes());
-		assertEquals(alice, result.isAlice());
+		handshakeManager.handshake(pendingContact.getId(), in, streamWriter);
 	}
 
 	@Test(expected = FormatException.class)
@@ -241,15 +231,6 @@ public class HandshakeManagerImplTest extends BrambleMockTestCase {
 		}});
 	}
 
-	private void expectDeriveMasterKey_0_0(boolean alice) throws Exception {
-		context.checking(new Expectations() {{
-			oneOf(handshakeCrypto).deriveMasterKey_0_0(theirStaticPublicKey,
-					theirEphemeralPublicKey, ourStaticKeyPair,
-					ourEphemeralKeyPair, alice);
-			will(returnValue(masterKey));
-		}});
-	}
-
 	private void expectDeriveProof(boolean alice) {
 		context.checking(new Expectations() {{
 			oneOf(handshakeCrypto).proveOwnership(masterKey, alice);

bramble-core/src/test/java/org/briarproject/bramble/crypto/KeyAgreementTest.java

@@ -60,22 +60,6 @@ public class KeyAgreementTest extends BrambleTestCase {
 		assertArrayEquals(aShared.getBytes(), bShared.getBytes());
 	}
 
-	@Test
-	public void testDerivesStaticEphemeralSharedSecretBadly() throws Exception {
-		String label = getRandomString(123);
-		KeyPair aStatic = crypto.generateAgreementKeyPair();
-		KeyPair aEphemeral = crypto.generateAgreementKeyPair();
-		KeyPair bStatic = crypto.generateAgreementKeyPair();
-		KeyPair bEphemeral = crypto.generateAgreementKeyPair();
-		SecretKey aShared = crypto.deriveSharedSecretBadly(label,
-				bStatic.getPublic(), bEphemeral.getPublic(), aStatic,
-				aEphemeral, true, inputs);
-		SecretKey bShared = crypto.deriveSharedSecretBadly(label,
-				aStatic.getPublic(), aEphemeral.getPublic(), bStatic,
-				bEphemeral, false, inputs);
-		assertArrayEquals(aShared.getBytes(), bShared.getBytes());
-	}
-
 	@Test
 	public void testDerivesStaticEphemeralSharedSecret() throws Exception {
 		String label = getRandomString(123);

briar-android/src/main/java/org/briarproject/briar/android/forum/ForumActivity.java

@@ -54,7 +54,7 @@ public class ForumActivity extends
 
 	@Override
 	protected ThreadItemAdapter<ForumPostItem> createAdapter() {
-		return new ThreadItemAdapter<>(this, this);
+		return new ThreadItemAdapter<>(this);
 	}
 
 	@Override

briar-android/src/main/java/org/briarproject/briar/android/forum/ForumPostItem.java

@@ -6,10 +6,10 @@ import org.briarproject.briar.api.forum.ForumPostHeader;
 import javax.annotation.concurrent.NotThreadSafe;
 
 @NotThreadSafe
-public class ForumPostItem extends ThreadItem {
+class ForumPostItem extends ThreadItem {
 
-	ForumPostItem(ForumPostHeader h) {
-		super(h.getId(), h.getParentId(), h.getTimestamp(), h.getAuthor(),
+	ForumPostItem(ForumPostHeader h, String text) {
+		super(h.getId(), h.getParentId(), text, h.getTimestamp(), h.getAuthor(),
 				h.getAuthorInfo(), h.isRead());
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/forum/ForumViewModel.java

@@ -91,7 +91,9 @@ class ForumViewModel extends ThreadListViewModel<ForumPostItem> {
 			ForumPostReceivedEvent f = (ForumPostReceivedEvent) e;
 			if (f.getGroupId().equals(groupId)) {
 				LOG.info("Forum post received, adding...");
-				addItem(new ForumPostItem(f.getHeader()), false);
+				ForumPostItem item =
+						new ForumPostItem(f.getHeader(), f.getText());
+				addItem(item, false);
 			}
 		} else if (e instanceof ForumInvitationResponseReceivedEvent) {
 			ForumInvitationResponseReceivedEvent f =
@@ -137,14 +139,22 @@ class ForumViewModel extends ThreadListViewModel<ForumPostItem> {
 			List<ForumPostHeader> headers =
 					forumManager.getPostHeaders(txn, groupId);
 			logDuration(LOG, "Loading headers", start);
+			start = now();
 			List<ForumPostItem> items = new ArrayList<>();
 			for (ForumPostHeader header : headers) {
-				items.add(new ForumPostItem(header));
+				items.add(loadItem(txn, header));
 			}
+			logDuration(LOG, "Loading bodies and creating items", start);
 			return items;
 		}, this::setItems);
 	}
 
+	private ForumPostItem loadItem(Transaction txn, ForumPostHeader header)
+			throws DbException {
+		String text = forumManager.getPostText(txn, header.getId());
+		return new ForumPostItem(header, text);
+	}
+
 	@Override
 	public void createAndStoreMessage(String text,
 			@Nullable MessageId parentId) {
@@ -165,17 +175,21 @@ class ForumViewModel extends ThreadListViewModel<ForumPostItem> {
 			@Nullable MessageId parentId, LocalAuthor author) {
 		cryptoExecutor.execute(() -> {
 			LOG.info("Creating forum post...");
-			storePost(forumManager.createLocalPost(groupId, text,
-					timestamp, parentId, author));
+			ForumPost msg = forumManager.createLocalPost(groupId, text,
+					timestamp, parentId, author);
+			storePost(msg, text);
 		});
 	}
 
-	private void storePost(ForumPost msg) {
+	private void storePost(ForumPost msg, String text) {
 		runOnDbThread(false, txn -> {
 			long start = now();
 			ForumPostHeader header = forumManager.addLocalPost(txn, msg);
 			logDuration(LOG, "Storing forum post", start);
-			txn.attach(() -> addItem(new ForumPostItem(header), true));
+			txn.attach(() -> {
+				ForumPostItem item = new ForumPostItem(header, text);
+				addItem(item, true);
+			});
 		}, this::handleException);
 	}
 
@@ -215,9 +229,4 @@ class ForumViewModel extends ThreadListViewModel<ForumPostItem> {
 		});
 	}
 
-	@Override
-	protected String getMessageText(Transaction txn, MessageId m)
-			throws DbException {
-		return forumManager.getPostText(txn, m);
-	}
 }

briar-android/src/main/java/org/briarproject/briar/android/privategroup/conversation/GroupActivity.java

@@ -15,6 +15,7 @@ import org.briarproject.briar.android.privategroup.memberlist.GroupMemberListAct
 import org.briarproject.briar.android.privategroup.reveal.RevealContactsActivity;
 import org.briarproject.briar.android.threaded.ThreadListActivity;
 import org.briarproject.briar.android.threaded.ThreadListViewModel;
+import org.briarproject.briar.android.widget.LinkDialogFragment;
 import org.briarproject.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.nullsafety.ParametersNotNullByDefault;
 
@@ -55,7 +56,7 @@ public class GroupActivity extends
 
 	@Override
 	protected GroupMessageAdapter createAdapter() {
-		return new GroupMessageAdapter(this, this);
+		return new GroupMessageAdapter(this);
 	}
 
 	@Override
@@ -159,6 +160,12 @@ public class GroupActivity extends
 		if (isDissolved != null && !isDissolved) super.onReplyClick(item);
 	}
 
+	@Override
+	public void onLinkClick(String url){
+		LinkDialogFragment f = LinkDialogFragment.newInstance(url);
+		f.show(getSupportFragmentManager(), f.getUniqueTag());
+	}
+
 	private void setGroupEnabled(boolean enabled) {
 		sendController.setReady(enabled);
 		list.getRecyclerView().setAlpha(enabled ? 1f : 0.5f);

briar-android/src/main/java/org/briarproject/briar/android/privategroup/conversation/GroupMessageAdapter.java

@@ -11,19 +11,16 @@ import org.briarproject.briar.android.threaded.ThreadPostViewHolder;
 import org.briarproject.nullsafety.NotNullByDefault;
 
 import androidx.annotation.LayoutRes;
-import androidx.annotation.NonNull;
 import androidx.annotation.UiThread;
-import androidx.lifecycle.LifecycleOwner;
 
 @UiThread
 @NotNullByDefault
-public class GroupMessageAdapter extends ThreadItemAdapter<GroupMessageItem> {
+class GroupMessageAdapter extends ThreadItemAdapter<GroupMessageItem> {
 
 	private boolean isCreator = false;
 
-	GroupMessageAdapter(LifecycleOwner lifecycleOwner,
-			ThreadItemListener<GroupMessageItem> listener) {
-		super(lifecycleOwner, listener);
+	GroupMessageAdapter(ThreadItemListener<GroupMessageItem> listener) {
+		super(listener);
 	}
 
 	@LayoutRes
@@ -33,7 +30,6 @@ public class GroupMessageAdapter extends ThreadItemAdapter<GroupMessageItem> {
 		return item.getLayout();
 	}
 
-	@NonNull
 	@Override
 	public BaseThreadItemViewHolder<GroupMessageItem> onCreateViewHolder(
 			ViewGroup parent, int type) {

briar-android/src/main/java/org/briarproject/briar/android/privategroup/conversation/GroupMessageItem.java

@@ -1,10 +1,14 @@
 package org.briarproject.briar.android.privategroup.conversation;
 
+import org.briarproject.bramble.api.identity.Author;
+import org.briarproject.briar.api.identity.AuthorInfo;
 import org.briarproject.bramble.api.sync.GroupId;
+import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.threaded.ThreadItem;
 import org.briarproject.briar.api.privategroup.GroupMessageHeader;
 
+import javax.annotation.Nullable;
 import javax.annotation.concurrent.NotThreadSafe;
 
 import androidx.annotation.LayoutRes;
@@ -12,14 +16,20 @@ import androidx.annotation.UiThread;
 
 @UiThread
 @NotThreadSafe
-public class GroupMessageItem extends ThreadItem {
+class GroupMessageItem extends ThreadItem {
 
 	private final GroupId groupId;
 
-	GroupMessageItem(GroupMessageHeader h) {
-		super(h.getId(), h.getParentId(), h.getTimestamp(), h.getAuthor(),
-				h.getAuthorInfo(), h.isRead());
-		this.groupId = h.getGroupId();
+	private GroupMessageItem(MessageId messageId, GroupId groupId,
+			@Nullable MessageId parentId, String text, long timestamp,
+			Author author, AuthorInfo authorInfo, boolean isRead) {
+		super(messageId, parentId, text, timestamp, author, authorInfo, isRead);
+		this.groupId = groupId;
+	}
+
+	GroupMessageItem(GroupMessageHeader h, String text) {
+		this(h.getId(), h.getGroupId(), h.getParentId(), text, h.getTimestamp(),
+				h.getAuthor(), h.getAuthorInfo(), h.isRead());
 	}
 
 	public GroupId getGroupId() {

briar-android/src/main/java/org/briarproject/briar/android/privategroup/conversation/GroupViewModel.java

@@ -99,7 +99,7 @@ class GroupViewModel extends ThreadListViewModel<GroupMessageItem> {
 			// only act on non-local messages in this group
 			if (!g.isLocal() && g.getGroupId().equals(groupId)) {
 				LOG.info("Group message received, adding...");
-				GroupMessageItem item = buildItem(g.getHeader());
+				GroupMessageItem item = buildItem(g.getHeader(), g.getText());
 				addItem(item, false);
 				// In case the join message comes from the creator,
 				// we need to reload the sharing contacts
@@ -167,19 +167,33 @@ class GroupViewModel extends ThreadListViewModel<GroupMessageItem> {
 			List<GroupMessageHeader> headers =
 					privateGroupManager.getHeaders(txn, groupId);
 			logDuration(LOG, "Loading headers", start);
+			start = now();
 			List<GroupMessageItem> items = new ArrayList<>();
 			for (GroupMessageHeader header : headers) {
-				items.add(buildItem(header));
+				items.add(loadItem(txn, header));
 			}
+			logDuration(LOG, "Loading bodies and creating items", start);
 			return items;
 		}, this::setItems);
 	}
 
-	private GroupMessageItem buildItem(GroupMessageHeader header) {
+	private GroupMessageItem loadItem(Transaction txn,
+			GroupMessageHeader header) throws DbException {
+		String text;
 		if (header instanceof JoinMessageHeader) {
-			return new JoinMessageItem((JoinMessageHeader) header);
+			// will be looked up later
+			text = "";
+		} else {
+			text = privateGroupManager.getMessageText(txn, header.getId());
 		}
-		return new GroupMessageItem(header);
+		return buildItem(header, text);
+	}
+
+	private GroupMessageItem buildItem(GroupMessageHeader header, String text) {
+		if (header instanceof JoinMessageHeader) {
+			return new JoinMessageItem((JoinMessageHeader) header, text);
+		}
+		return new GroupMessageItem(header, text);
 	}
 
 	@Override
@@ -207,17 +221,19 @@ class GroupViewModel extends ThreadListViewModel<GroupMessageItem> {
 			LOG.info("Creating group message...");
 			GroupMessage msg = groupMessageFactory.createGroupMessage(groupId,
 					timestamp, parentId, author, text, previousMsgId);
-			storePost(msg);
+			storePost(msg, text);
 		});
 	}
 
-	private void storePost(GroupMessage msg) {
+	private void storePost(GroupMessage msg, String text) {
 		runOnDbThread(false, txn -> {
 			long start = now();
 			GroupMessageHeader header =
 					privateGroupManager.addLocalMessage(txn, msg);
 			logDuration(LOG, "Storing group message", start);
-			txn.attach(() -> addItem(buildItem(header), true));
+			txn.attach(() ->
+					addItem(buildItem(header, text), true)
+			);
 		}, this::handleException);
 	}
 
@@ -268,9 +284,4 @@ class GroupViewModel extends ThreadListViewModel<GroupMessageItem> {
 		return isDissolved;
 	}
 
-	@Override
-	protected String getMessageText(Transaction txn, MessageId m)
-			throws DbException {
-		return privateGroupManager.getMessageText(txn, m);
-	}
 }

briar-android/src/main/java/org/briarproject/briar/android/privategroup/conversation/JoinMessageItem.java

@@ -14,8 +14,8 @@ class JoinMessageItem extends GroupMessageItem {
 
 	private final boolean isInitial;
 
-	JoinMessageItem(JoinMessageHeader h) {
-		super(h);
+	JoinMessageItem(JoinMessageHeader h, String text) {
+		super(h, text);
 		isInitial = h.isInitial();
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/privategroup/conversation/JoinMessageItemViewHolder.java

@@ -9,7 +9,6 @@ import org.briarproject.briar.android.threaded.ThreadItemAdapter.ThreadItemListe
 import org.briarproject.nullsafety.NotNullByDefault;
 
 import androidx.annotation.UiThread;
-import androidx.lifecycle.LifecycleOwner;
 
 import static org.briarproject.briar.api.identity.AuthorInfo.Status.OURSELVES;
 
@@ -26,8 +25,10 @@ class JoinMessageItemViewHolder
 	}
 
 	@Override
-	protected void setText(GroupMessageItem item, LifecycleOwner lifecycleOwner,
+	public void bind(GroupMessageItem item,
 			ThreadItemListener<GroupMessageItem> listener) {
+		super.bind(item, listener);
+
 		if (isCreator) bindForCreator((JoinMessageItem) item);
 		else bind((JoinMessageItem) item);
 	}

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

@@ -4,46 +4,35 @@ import android.animation.Animator;
 import android.animation.ArgbEvaluator;
 import android.animation.ValueAnimator;
 import android.content.Context;
+import android.text.util.Linkify;
 import android.view.View;
 import android.view.ViewGroup;
 import android.view.animation.AccelerateInterpolator;
 import android.widget.TextView;
 
+import org.briarproject.bramble.util.StringUtils;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.threaded.ThreadItemAdapter.ThreadItemListener;
 import org.briarproject.briar.android.view.AuthorView;
 import org.briarproject.nullsafety.NotNullByDefault;
 
-import javax.annotation.Nullable;
-
 import androidx.annotation.CallSuper;
 import androidx.annotation.UiThread;
-import androidx.lifecycle.LifecycleOwner;
-import androidx.lifecycle.LiveData;
-import androidx.lifecycle.Observer;
 import androidx.recyclerview.widget.RecyclerView;
 
-import static android.text.util.Linkify.WEB_URLS;
-import static android.text.util.Linkify.addLinks;
 import static androidx.core.content.ContextCompat.getColor;
-import static org.briarproject.bramble.util.StringUtils.trim;
 import static org.briarproject.briar.android.util.UiUtils.makeLinksClickable;
-import static org.briarproject.nullsafety.NullSafety.requireNonNull;
 
 @UiThread
 @NotNullByDefault
 public abstract class BaseThreadItemViewHolder<I extends ThreadItem>
-		extends RecyclerView.ViewHolder implements Observer<String> {
+		extends RecyclerView.ViewHolder {
 
 	private final static int ANIMATION_DURATION = 5000;
 
 	protected final TextView textView;
 	private final ViewGroup layout;
 	private final AuthorView author;
-	@Nullable
-	private ThreadItemListener<I> listener = null;
-	@Nullable
-	private LiveData<String> textLiveData = null;
 
 	public BaseThreadItemViewHolder(View v) {
 		super(v);
@@ -54,9 +43,10 @@ public abstract class BaseThreadItemViewHolder<I extends ThreadItem>
 	}
 
 	@CallSuper
-	public void bind(I item, LifecycleOwner lifecycleOwner,
-			ThreadItemListener<I> listener) {
-		setText(item, lifecycleOwner, listener);
+	public void bind(I item, ThreadItemListener<I> listener) {
+		textView.setText(StringUtils.trim(item.getText()));
+		Linkify.addLinks(textView, Linkify.WEB_URLS);
+		makeLinksClickable(textView, listener::onLinkClick);
 
 		author.setAuthor(item.getAuthor(), item.getAuthorInfo());
 		author.setDate(item.getTimestamp());
@@ -71,20 +61,6 @@ public abstract class BaseThreadItemViewHolder<I extends ThreadItem>
 		}
 	}
 
-	protected void setText(I item, LifecycleOwner lifecycleOwner,
-			ThreadItemListener<I> listener) {
-		// Clear any existing text while we asynchronously load the new text
-		textView.setText(null);
-		// Remember the listener so we can use it to create links later
-		this.listener = listener;
-		// If the view has been re-bound and we're already asynchronously
-		// loading text for another item, stop observing it
-		if (textLiveData != null) textLiveData.removeObserver(this);
-		// Asynchronously load the text for this item and observe the result
-		textLiveData = listener.loadItemText(item.getId());
-		textLiveData.observe(lifecycleOwner, this);
-	}
-
 	private void animateFadeOut() {
 		setIsRecyclable(false);
 		ValueAnimator anim = new ValueAnimator();
@@ -97,7 +73,6 @@ public abstract class BaseThreadItemViewHolder<I extends ThreadItem>
 			@Override
 			public void onAnimationStart(Animator animation) {
 			}
-
 			@Override
 			public void onAnimationEnd(Animator animation) {
 				layout.setBackgroundResource(
@@ -105,11 +80,9 @@ public abstract class BaseThreadItemViewHolder<I extends ThreadItem>
 				layout.setActivated(false);
 				setIsRecyclable(true);
 			}
-
 			@Override
 			public void onAnimationCancel(Animator animation) {
 			}
-
 			@Override
 			public void onAnimationRepeat(Animator animation) {
 			}
@@ -124,24 +97,4 @@ public abstract class BaseThreadItemViewHolder<I extends ThreadItem>
 		return textView.getContext();
 	}
 
-	void onViewRecycled() {
-		textView.setText(null);
-		if (textLiveData != null) {
-			textLiveData.removeObserver(this);
-			textLiveData = null;
-			listener = null;
-		}
-	}
-
-	@Override
-	public void onChanged(String s) {
-		if (textLiveData != null) {
-			textLiveData.removeObserver(this);
-			textLiveData = null;
-			textView.setText(trim(s));
-			addLinks(textView, WEB_URLS);
-			makeLinksClickable(textView, requireNonNull(listener)::onLinkClick);
-			listener = null;
-		}
-	}
 }

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

@@ -19,6 +19,7 @@ public abstract class ThreadItem implements MessageNode {
 	private final MessageId messageId;
 	@Nullable
 	private final MessageId parentId;
+	private final String text;
 	private final long timestamp;
 	private final Author author;
 	private final AuthorInfo authorInfo;
@@ -26,10 +27,11 @@ public abstract class ThreadItem implements MessageNode {
 	private boolean isRead, highlighted;
 
 	public ThreadItem(MessageId messageId, @Nullable MessageId parentId,
-			long timestamp, Author author, AuthorInfo authorInfo,
+			String text, long timestamp, Author author, AuthorInfo authorInfo,
 			boolean isRead) {
 		this.messageId = messageId;
 		this.parentId = parentId;
+		this.text = text;
 		this.timestamp = timestamp;
 		this.author = author;
 		this.authorInfo = authorInfo;
@@ -37,6 +39,10 @@ public abstract class ThreadItem implements MessageNode {
 		this.highlighted = false;
 	}
 
+	public String getText() {
+		return text;
+	}
+
 	public int getLevel() {
 		return level;
 	}

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

@@ -13,8 +13,6 @@ import javax.annotation.Nullable;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.UiThread;
-import androidx.lifecycle.LifecycleOwner;
-import androidx.lifecycle.LiveData;
 import androidx.recyclerview.widget.DiffUtil;
 import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.ListAdapter;
@@ -29,11 +27,9 @@ public class ThreadItemAdapter<I extends ThreadItem>
 
 	static final int UNDEFINED = -1;
 
-	private final LifecycleOwner lifecycleOwner;
 	private final ThreadItemListener<I> listener;
 
-	public ThreadItemAdapter(LifecycleOwner lifecycleOwner,
-			ThreadItemListener<I> listener) {
+	public ThreadItemAdapter(ThreadItemListener<I> listener) {
 		super(new DiffUtil.ItemCallback<I>() {
 			@Override
 			public boolean areItemsTheSame(I a, I b) {
@@ -46,7 +42,6 @@ public class ThreadItemAdapter<I extends ThreadItem>
 						a.isRead() == b.isRead();
 			}
 		});
-		this.lifecycleOwner = lifecycleOwner;
 		this.listener = listener;
 	}
 
@@ -63,7 +58,7 @@ public class ThreadItemAdapter<I extends ThreadItem>
 	public void onBindViewHolder(@NonNull BaseThreadItemViewHolder<I> ui,
 			int position) {
 		I item = getItem(position);
-		ui.bind(item, lifecycleOwner, listener);
+		ui.bind(item, listener);
 	}
 
 	int findItemPosition(MessageId id) {
@@ -140,19 +135,9 @@ public class ThreadItemAdapter<I extends ThreadItem>
 		return getItem(position);
 	}
 
-	@Override
-	public void onViewRecycled(BaseThreadItemViewHolder<I> viewHolder) {
-		super.onViewRecycled(viewHolder);
-		viewHolder.onViewRecycled();
-	}
-
 	public interface ThreadItemListener<I> {
-
 		void onReplyClick(I item);
-
 		void onLinkClick(String url);
-
-		LiveData<String> loadItemText(MessageId m);
 	}
 
 }

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

@@ -85,9 +85,6 @@ public abstract class ThreadListActivity<I extends ThreadItem, A extends ThreadI
 		scrollListener = new ThreadScrollListener<>(adapter, viewModel,
 				upButton, downButton);
 		list.getRecyclerView().addOnScrollListener(scrollListener);
-		// This is a tradeoff between memory consumption for cached views
-		// and the cost of loading message text from the database
-		list.getRecyclerView().setItemViewCacheSize(20);
 
 		upButton.setOnClickListener(v -> {
 			int position = adapter.getVisibleUnreadPosTop(layoutManager);
@@ -260,8 +257,4 @@ public abstract class ThreadListActivity<I extends ThreadItem, A extends ThreadI
 
 	protected abstract int getMaxTextLength();
 
-	@Override
-	public LiveData<String> loadItemText(MessageId m) {
-		return getViewModel().loadMessageText(m);
-	}
 }

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

@@ -6,7 +6,6 @@ import org.briarproject.bramble.api.crypto.CryptoExecutor;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.NoSuchGroupException;
-import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.db.TransactionManager;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventBus;
@@ -261,14 +260,4 @@ public abstract class ThreadListViewModel<I extends ThreadItem>
 		return scrollToItem.getAndSet(null);
 	}
 
-	public LiveData<String> loadMessageText(MessageId m) {
-		MutableLiveData<String> textLiveData = new MutableLiveData<>();
-		runOnDbThread(true, txn ->
-						textLiveData.postValue(getMessageText(txn, m)),
-				this::handleException);
-		return textLiveData;
-	}
-
-	protected abstract String getMessageText(Transaction txn, MessageId m)
-			throws DbException;
 }

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

@@ -10,7 +10,6 @@ import org.briarproject.nullsafety.NotNullByDefault;
 import java.util.Locale;
 
 import androidx.annotation.UiThread;
-import androidx.lifecycle.LifecycleOwner;
 
 import static android.view.View.GONE;
 import static android.view.View.VISIBLE;
@@ -41,9 +40,8 @@ public class ThreadPostViewHolder<I extends ThreadItem>
 	}
 
 	@Override
-	public void bind(I item, LifecycleOwner lifecycleOwner,
-			ThreadItemListener<I> listener) {
-		super.bind(item, lifecycleOwner, listener);
+	public void bind(I item, ThreadItemListener<I> listener) {
+		super.bind(item, listener);
 
 		for (int i = 0; i < lvls.length; i++) {
 			lvls[i].setVisibility(i < item.getLevel() ? VISIBLE : GONE);

briar-api/src/main/java/org/briarproject/briar/api/forum/event/ForumPostReceivedEvent.java

@@ -16,10 +16,13 @@ public class ForumPostReceivedEvent extends Event {
 
 	private final GroupId groupId;
 	private final ForumPostHeader header;
+	private final String text;
 
-	public ForumPostReceivedEvent(GroupId groupId, ForumPostHeader header) {
+	public ForumPostReceivedEvent(GroupId groupId, ForumPostHeader header,
+			String text) {
 		this.groupId = groupId;
 		this.header = header;
+		this.text = text;
 	}
 
 	public GroupId getGroupId() {
@@ -29,4 +32,8 @@ public class ForumPostReceivedEvent extends Event {
 	public ForumPostHeader getHeader() {
 		return header;
 	}
+
+	public String getText() {
+		return text;
+	}
 }

briar-api/src/main/java/org/briarproject/briar/api/privategroup/event/GroupMessageAddedEvent.java

@@ -17,12 +17,14 @@ public class GroupMessageAddedEvent extends Event {
 
 	private final GroupId groupId;
 	private final GroupMessageHeader header;
+	private final String text;
 	private final boolean local;
 
 	public GroupMessageAddedEvent(GroupId groupId, GroupMessageHeader header,
-			boolean local) {
+			String text, boolean local) {
 		this.groupId = groupId;
 		this.header = header;
+		this.text = text;
 		this.local = local;
 	}
 
@@ -34,6 +36,10 @@ public class GroupMessageAddedEvent extends Event {
 		return header;
 	}
 
+	public String getText() {
+		return text;
+	}
+
 	public boolean isLocal() {
 		return local;
 	}

briar-core/src/main/java/org/briarproject/briar/forum/ForumManagerImpl.java

@@ -83,7 +83,10 @@ class ForumManagerImpl extends BdfIncomingMessageHook implements ForumManager {
 		messageTracker.trackIncomingMessage(txn, m);
 
 		ForumPostHeader header = getForumPostHeader(txn, m.getId(), meta);
-		txn.attach(new ForumPostReceivedEvent(m.getGroupId(), header));
+		String text = getPostText(body);
+		ForumPostReceivedEvent event =
+				new ForumPostReceivedEvent(m.getGroupId(), header, text);
+		txn.attach(event);
 
 		return ACCEPT_SHARE;
 	}

briar-core/src/main/java/org/briarproject/briar/privategroup/PrivateGroupManagerImpl.java

@@ -170,7 +170,6 @@ class PrivateGroupManagerImpl extends BdfIncomingMessageHook
 				txn -> getPreviousMsgId(txn, g));
 	}
 
-	@Override
 	public MessageId getPreviousMsgId(Transaction txn, GroupId g)
 			throws DbException {
 		try {
@@ -606,7 +605,9 @@ class PrivateGroupManagerImpl extends BdfIncomingMessageHook
 			throws DbException, FormatException {
 		GroupMessageHeader header = getGroupMessageHeader(txn, m.getGroupId(),
 				m.getId(), meta, Collections.emptyMap());
-		txn.attach(new GroupMessageAddedEvent(m.getGroupId(), header, local));
+		String text = getMessageText(clientHelper.toList(m));
+		txn.attach(new GroupMessageAddedEvent(m.getGroupId(), header, text,
+				local));
 	}
 
 	private void attachJoinMessageAddedEvent(Transaction txn, Message m,
@@ -614,7 +615,8 @@ class PrivateGroupManagerImpl extends BdfIncomingMessageHook
 			throws DbException, FormatException {
 		JoinMessageHeader header = getJoinMessageHeader(txn, m.getGroupId(),
 				m.getId(), meta, Collections.emptyMap());
-		txn.attach(new GroupMessageAddedEvent(m.getGroupId(), header, local));
+		txn.attach(new GroupMessageAddedEvent(m.getGroupId(), header, "",
+				local));
 	}
 
 	private void addMember(Transaction txn, GroupId g, Author a, Visibility v)