WIP Add an activity to try out mailbox qr decoding

bramble-android/src/main/java/org/briarproject/bramble/plugin/tor/AndroidTorPluginFactory.java

@@ -3,6 +3,7 @@ package org.briarproject.bramble.plugin.tor;
 import android.app.Application;
 
 import org.briarproject.bramble.api.battery.BatteryManager;
+import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.network.NetworkManager;
@@ -60,6 +61,7 @@ public class AndroidTorPluginFactory implements DuplexPluginFactory {
 	private final File torDirectory;
 	private int torSocksPort;
 	private int torControlPort;
+	private final CryptoComponent crypto;
 
 	@Inject
 	AndroidTorPluginFactory(@IoExecutor Executor ioExecutor,
@@ -77,7 +79,8 @@ public class AndroidTorPluginFactory implements DuplexPluginFactory {
 			Clock clock,
 			@TorDirectory File torDirectory,
 			@TorSocksPort int torSocksPort,
-			@TorControlPort int torControlPort) {
+			@TorControlPort int torControlPort,
+			CryptoComponent crypto) {
 		this.ioExecutor = ioExecutor;
 		this.wakefulIoExecutor = wakefulIoExecutor;
 		this.app = app;
@@ -94,6 +97,7 @@ public class AndroidTorPluginFactory implements DuplexPluginFactory {
 		this.torDirectory = torDirectory;
 		this.torSocksPort = torSocksPort;
 		this.torControlPort = torControlPort;
+		this.crypto = crypto;
 	}
 
 	@Override
@@ -135,7 +139,8 @@ public class AndroidTorPluginFactory implements DuplexPluginFactory {
 
 		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
 				MAX_POLLING_INTERVAL, BACKOFF_BASE);
-		TorRendezvousCrypto torRendezvousCrypto = new TorRendezvousCryptoImpl();
+		TorRendezvousCrypto torRendezvousCrypto =
+				new TorRendezvousCryptoImpl(crypto);
 		AndroidTorPlugin plugin = new AndroidTorPlugin(ioExecutor,
 				wakefulIoExecutor, app, networkManager, locationUtils,
 				torSocketFactory, clock, resourceProvider,

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

@@ -170,4 +170,11 @@ public interface CryptoComponent {
 	 * length. The line terminator is CRLF.
 	 */
 	String asciiArmour(byte[] b, int lineLength);
+
+	/**
+	 * Encode the onion/hidden service address given its public key. As
+	 * specified here: https://gitweb.torproject.org/torspec.git/tree/rend-spec-v3.txt?id=29245fd5#n2135
+	 */
+	String encodeOnionAddress(byte[] publicKey);
+
 }

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

@@ -7,6 +7,7 @@ import net.i2p.crypto.eddsa.KeyPairGenerator;
 import org.bouncycastle.crypto.CryptoException;
 import org.bouncycastle.crypto.Digest;
 import org.bouncycastle.crypto.digests.Blake2bDigest;
+import org.bouncycastle.crypto.digests.SHA3Digest;
 import org.briarproject.bramble.api.crypto.AgreementPrivateKey;
 import org.briarproject.bramble.api.crypto.AgreementPublicKey;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
@@ -21,11 +22,13 @@ import org.briarproject.bramble.api.crypto.SignaturePrivateKey;
 import org.briarproject.bramble.api.crypto.SignaturePublicKey;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.system.SecureRandomProvider;
+import org.briarproject.bramble.util.Base32;
 import org.briarproject.bramble.util.ByteUtils;
 import org.briarproject.bramble.util.StringUtils;
 import org.whispersystems.curve25519.Curve25519;
 import org.whispersystems.curve25519.Curve25519KeyPair;
 
+import java.nio.charset.Charset;
 import java.security.GeneralSecurityException;
 import java.security.NoSuchAlgorithmException;
 import java.security.Provider;
@@ -58,6 +61,8 @@ class CryptoComponentImpl implements CryptoComponent {
 	private static final int PBKDF_SALT_BYTES = 32; // 256 bits
 	private static final byte PBKDF_FORMAT_SCRYPT = 0;
 	private static final byte PBKDF_FORMAT_SCRYPT_STRENGTHENED = 1;
+	private static final byte ONION_HS_PROTOCOL_VERSION = 3;
+	private static final int ONION_CHECKSUM_BYTES = 2;
 
 	private final SecureRandom secureRandom;
 	private final PasswordBasedKdf passwordBasedKdf;
@@ -442,4 +447,21 @@ class CryptoComponentImpl implements CryptoComponent {
 	public String asciiArmour(byte[] b, int lineLength) {
 		return AsciiArmour.wrap(b, lineLength);
 	}
+
+	@Override
+	public String encodeOnionAddress(byte[] publicKey) {
+		Digest digest = new SHA3Digest(256);
+		byte[] label = ".onion checksum".getBytes(Charset.forName("US-ASCII"));
+		digest.update(label, 0, label.length);
+		digest.update(publicKey, 0, publicKey.length);
+		digest.update(ONION_HS_PROTOCOL_VERSION);
+		byte[] checksum = new byte[digest.getDigestSize()];
+		digest.doFinal(checksum, 0);
+		byte[] address = new byte[publicKey.length + ONION_CHECKSUM_BYTES + 1];
+		arraycopy(publicKey, 0, address, 0, publicKey.length);
+		arraycopy(checksum, 0, address, publicKey.length, ONION_CHECKSUM_BYTES);
+		address[address.length - 1] = ONION_HS_PROTOCOL_VERSION;
+		return Base32.encode(address).toLowerCase();
+	}
+
 }

bramble-core/src/main/java/org/briarproject/bramble/plugin/tor/TorRendezvousCryptoImpl.java

@@ -4,39 +4,26 @@ import net.i2p.crypto.eddsa.spec.EdDSANamedCurveSpec;
 import net.i2p.crypto.eddsa.spec.EdDSANamedCurveTable;
 import net.i2p.crypto.eddsa.spec.EdDSAPrivateKeySpec;
 
-import org.bouncycastle.crypto.Digest;
-import org.bouncycastle.crypto.digests.SHA3Digest;
 import org.bouncycastle.util.encoders.Base64;
-import org.briarproject.bramble.util.Base32;
+import org.briarproject.bramble.api.crypto.CryptoComponent;
 
 import java.nio.charset.Charset;
 
-import static java.lang.System.arraycopy;
-
-public class TorRendezvousCryptoImpl implements TorRendezvousCrypto {
+class TorRendezvousCryptoImpl implements TorRendezvousCrypto {
 
 	private static final EdDSANamedCurveSpec CURVE_SPEC =
 			EdDSANamedCurveTable.getByName("Ed25519");
 
-	private static final byte HS_PROTOCOL_VERSION = 3;
-	private static final int CHECKSUM_BYTES = 2;
+	private final CryptoComponent crypto;
+
+	TorRendezvousCryptoImpl(CryptoComponent crypto) {
+		this.crypto = crypto;
+	}
 
 	@Override
 	public String getOnionAddress(byte[] seed) {
 		EdDSAPrivateKeySpec spec = new EdDSAPrivateKeySpec(seed, CURVE_SPEC);
-		byte[] publicKey = spec.getA().toByteArray();
-		Digest digest = new SHA3Digest(256);
-		byte[] label = ".onion checksum".getBytes(Charset.forName("US-ASCII"));
-		digest.update(label, 0, label.length);
-		digest.update(publicKey, 0, publicKey.length);
-		digest.update(HS_PROTOCOL_VERSION);
-		byte[] checksum = new byte[digest.getDigestSize()];
-		digest.doFinal(checksum, 0);
-		byte[] address = new byte[publicKey.length + CHECKSUM_BYTES + 1];
-		arraycopy(publicKey, 0, address, 0, publicKey.length);
-		arraycopy(checksum, 0, address, publicKey.length, CHECKSUM_BYTES);
-		address[address.length - 1] = HS_PROTOCOL_VERSION;
-		return Base32.encode(address).toLowerCase();
+		return crypto.encodeOnionAddress(spec.getA().toByteArray());
 	}
 
 	@Override

bramble-java/src/main/java/org/briarproject/bramble/plugin/tor/UnixTorPluginFactory.java

@@ -1,6 +1,7 @@
 package org.briarproject.bramble.plugin.tor;
 
 import org.briarproject.bramble.api.battery.BatteryManager;
+import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.network.NetworkManager;
@@ -58,6 +59,7 @@ public class UnixTorPluginFactory implements DuplexPluginFactory {
 	private final File torDirectory;
 	private int torSocksPort;
 	private int torControlPort;
+	private final CryptoComponent crypto;
 
 	@Inject
 	UnixTorPluginFactory(@IoExecutor Executor ioExecutor,
@@ -73,7 +75,8 @@ public class UnixTorPluginFactory implements DuplexPluginFactory {
 			Clock clock,
 			@TorDirectory File torDirectory,
 			@TorSocksPort int torSocksPort,
-			@TorControlPort int torControlPort) {
+			@TorControlPort int torControlPort,
+			CryptoComponent crypto) {
 		this.ioExecutor = ioExecutor;
 		this.wakefulIoExecutor = wakefulIoExecutor;
 		this.networkManager = networkManager;
@@ -88,6 +91,7 @@ public class UnixTorPluginFactory implements DuplexPluginFactory {
 		this.torDirectory = torDirectory;
 		this.torSocksPort = torSocksPort;
 		this.torControlPort = torControlPort;
+		this.crypto = crypto;
 	}
 
 	@Override
@@ -128,7 +132,8 @@ public class UnixTorPluginFactory implements DuplexPluginFactory {
 
 		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
 				MAX_POLLING_INTERVAL, BACKOFF_BASE);
-		TorRendezvousCrypto torRendezvousCrypto = new TorRendezvousCryptoImpl();
+		TorRendezvousCrypto torRendezvousCrypto =
+				new TorRendezvousCryptoImpl(crypto);
 		UnixTorPlugin plugin = new UnixTorPlugin(ioExecutor, wakefulIoExecutor,
 				networkManager, locationUtils, torSocketFactory, clock,
 				resourceProvider, circumventionProvider, batteryManager,

bramble-java/src/test/java/org/briarproject/bramble/plugin/tor/BridgeTest.java

@@ -2,6 +2,7 @@ package org.briarproject.bramble.plugin.tor;
 
 import org.briarproject.bramble.BrambleCoreIntegrationTestEagerSingletons;
 import org.briarproject.bramble.api.battery.BatteryManager;
+import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.network.NetworkManager;
@@ -88,6 +89,8 @@ public class BridgeTest extends BrambleTestCase {
 	BackoffFactory backoffFactory;
 	@Inject
 	Clock clock;
+	@Inject
+	CryptoComponent crypto;
 
 	private final File torDir = getTestDirectory();
 	private final String bridge;
@@ -142,7 +145,7 @@ public class BridgeTest extends BrambleTestCase {
 				networkManager, locationUtils, eventBus, torSocketFactory,
 				backoffFactory, resourceProvider, bridgeProvider,
 				batteryManager, clock, torDir, DEFAULT_SOCKS_PORT,
-				DEFAULT_CONTROL_PORT);
+				DEFAULT_CONTROL_PORT, crypto);
 	}
 
 	@After

briar-android/src/main/AndroidManifest.xml

@@ -452,6 +452,15 @@
 				android:value="org.briarproject.briar.android.conversation.ConversationActivity" />
 		</activity>
 
+		<activity
+			android:name="org.briarproject.briar.android.mailbox.MailboxActivity"
+			android:label="@string/mailbox_menu_title"
+			android:parentActivityName="org.briarproject.briar.android.navdrawer.NavDrawerActivity">
+			<meta-data
+				android:name="android.support.PARENT_ACTIVITY"
+				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity" />
+		</activity>
+
 		<activity
 			android:name=".android.contact.add.remote.PendingContactListActivity"
 			android:label="@string/pending_contact_requests"

briar-android/src/main/java/org/briarproject/briar/android/AppModule.java

@@ -43,6 +43,7 @@ import org.briarproject.briar.android.hotspot.HotspotModule;
 import org.briarproject.briar.android.introduction.IntroductionModule;
 import org.briarproject.briar.android.logging.LoggingModule;
 import org.briarproject.briar.android.login.LoginModule;
+import org.briarproject.briar.android.mailbox.MailboxModule;
 import org.briarproject.briar.android.navdrawer.NavDrawerModule;
 import org.briarproject.briar.android.privategroup.conversation.GroupConversationModule;
 import org.briarproject.briar.android.privategroup.list.GroupListModule;
@@ -103,6 +104,7 @@ import static org.briarproject.briar.android.TestingConstants.IS_DEBUG_BUILD;
 		SharingModule.class,
 		HotspotModule.class,
 		TransferDataModule.class,
+		MailboxModule.class,
 })
 public class AppModule {
 

briar-android/src/main/java/org/briarproject/briar/android/activity/ActivityComponent.java

@@ -46,6 +46,8 @@ import org.briarproject.briar.android.login.ChangePasswordActivity;
 import org.briarproject.briar.android.login.OpenDatabaseFragment;
 import org.briarproject.briar.android.login.PasswordFragment;
 import org.briarproject.briar.android.login.StartupActivity;
+import org.briarproject.briar.android.mailbox.MailboxActivity;
+import org.briarproject.briar.android.mailbox.MailboxPairFragment;
 import org.briarproject.briar.android.navdrawer.NavDrawerActivity;
 import org.briarproject.briar.android.navdrawer.TransportsActivity;
 import org.briarproject.briar.android.panic.PanicPreferencesActivity;
@@ -182,6 +184,8 @@ public interface ActivityComponent {
 
 	void inject(RemovableDriveActivity activity);
 
+	void inject(MailboxActivity activity);
+
 	// Fragments
 
 	void inject(SetupFragment fragment);
@@ -247,4 +251,6 @@ public interface ActivityComponent {
 	void inject(RssFeedDeleteFeedDialogFragment fragment);
 
 	void inject(ConnectViaBluetoothActivity connectViaBluetoothActivity);
+
+	void inject(MailboxPairFragment fragment);
 }

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/AddNearbyContactFragment.java

@@ -20,6 +20,8 @@ import org.briarproject.briar.android.contact.add.nearby.AddContactState.KeyAgre
 import org.briarproject.briar.android.contact.add.nearby.AddContactState.KeyAgreementWaiting;
 import org.briarproject.briar.android.contact.add.nearby.AddContactState.QrCodeScanned;
 import org.briarproject.briar.android.fragment.BaseFragment;
+import org.briarproject.briar.android.qrcode.CameraException;
+import org.briarproject.briar.android.qrcode.CameraView;
 import org.briarproject.briar.android.view.QrCodeView;
 
 import java.util.logging.Logger;

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/AddNearbyContactViewModel.java

@@ -53,7 +53,8 @@ import org.briarproject.briar.android.contact.add.nearby.AddContactState.Contact
 import org.briarproject.briar.android.contact.add.nearby.AddContactState.KeyAgreementListening;
 import org.briarproject.briar.android.contact.add.nearby.AddContactState.KeyAgreementStarted;
 import org.briarproject.briar.android.contact.add.nearby.AddContactState.KeyAgreementWaiting;
-import org.briarproject.briar.android.util.QrCodeUtils;
+import org.briarproject.briar.android.qrcode.QrCodeDecoder;
+import org.briarproject.briar.android.qrcode.QrCodeUtils;
 import org.briarproject.briar.android.viewmodel.LiveEvent;
 import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
 

briar-android/src/main/java/org/briarproject/briar/android/hotspot/HotspotManager.java

@@ -24,7 +24,7 @@ import org.briarproject.bramble.api.settings.SettingsManager;
 import org.briarproject.bramble.api.system.AndroidExecutor;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.hotspot.HotspotState.NetworkConfig;
-import org.briarproject.briar.android.util.QrCodeUtils;
+import org.briarproject.briar.android.qrcode.QrCodeUtils;
 
 import java.security.SecureRandom;
 import java.util.concurrent.Executor;
@@ -52,7 +52,7 @@ import static java.util.Objects.requireNonNull;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
-import static org.briarproject.briar.android.util.QrCodeUtils.HOTSPOT_QRCODE_FACTOR;
+import static org.briarproject.briar.android.qrcode.QrCodeUtils.HOTSPOT_QRCODE_FACTOR;
 import static org.briarproject.briar.android.util.UiUtils.handleException;
 
 @MethodsNotNullByDefault

briar-android/src/main/java/org/briarproject/briar/android/hotspot/WebServerManager.java

@@ -8,7 +8,7 @@ import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.android.hotspot.HotspotState.WebsiteConfig;
-import org.briarproject.briar.android.util.QrCodeUtils;
+import org.briarproject.briar.android.qrcode.QrCodeUtils;
 
 import java.io.IOException;
 import java.net.InetAddress;
@@ -27,7 +27,7 @@ import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.NetworkUtils.getNetworkInterfaces;
 import static org.briarproject.briar.android.hotspot.WebServer.PORT;
-import static org.briarproject.briar.android.util.QrCodeUtils.HOTSPOT_QRCODE_FACTOR;
+import static org.briarproject.briar.android.qrcode.QrCodeUtils.HOTSPOT_QRCODE_FACTOR;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault

briar-android/src/main/java/org/briarproject/briar/android/mailbox/MailboxActivity.java

@@ -0,0 +1,57 @@
+package org.briarproject.briar.android.mailbox;
+
+import android.os.Bundle;
+import android.view.MenuItem;
+
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+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.fragment.BaseFragment;
+
+import javax.inject.Inject;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.annotation.RequiresApi;
+import androidx.lifecycle.ViewModelProvider;
+
+@RequiresApi(19)
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class MailboxActivity extends BriarActivity implements
+		BaseFragment.BaseFragmentListener {
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private MailboxPairViewModel viewModel;
+
+	@Override
+	public void injectActivity(ActivityComponent component) {
+		component.inject(this);
+
+		viewModel = new ViewModelProvider(this, viewModelFactory)
+				.get(MailboxPairViewModel.class);
+	}
+
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+
+		setContentView(R.layout.activity_fragment_container);
+
+		showInitialFragment(new MailboxPairFragment());
+	}
+
+	@Override
+	public boolean onOptionsItemSelected(@NonNull MenuItem item) {
+		if (item.getItemId() == android.R.id.home) {
+			onBackPressed();
+			return true;
+		}
+		return super.onOptionsItemSelected(item);
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/mailbox/MailboxModule.java

@@ -0,0 +1,19 @@
+package org.briarproject.briar.android.mailbox;
+
+import org.briarproject.briar.android.viewmodel.ViewModelKey;
+
+import androidx.lifecycle.ViewModel;
+import dagger.Binds;
+import dagger.Module;
+import dagger.multibindings.IntoMap;
+
+@Module
+public interface MailboxModule {
+
+	@Binds
+	@IntoMap
+	@ViewModelKey(MailboxPairViewModel.class)
+	ViewModel bindMailboxViewModel(
+			MailboxPairViewModel mailboxPairViewModel);
+
+}

briar-android/src/main/java/org/briarproject/briar/android/mailbox/MailboxPairFragment.java

@@ -0,0 +1,139 @@
+package org.briarproject.briar.android.mailbox;
+
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.TextView;
+import android.widget.Toast;
+
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.fragment.BaseFragment;
+import org.briarproject.briar.android.qrcode.CameraException;
+import org.briarproject.briar.android.qrcode.CameraView;
+
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+import javax.inject.Inject;
+
+import androidx.annotation.UiThread;
+import androidx.lifecycle.ViewModelProvider;
+
+import static android.content.pm.ActivityInfo.SCREEN_ORIENTATION_NOSENSOR;
+import static android.view.View.INVISIBLE;
+import static android.view.View.VISIBLE;
+import static android.widget.Toast.LENGTH_LONG;
+import static java.util.logging.Level.WARNING;
+import static org.briarproject.bramble.util.LogUtils.logException;
+
+// TODO have to get camera permission somewhere
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class MailboxPairFragment extends BaseFragment {
+
+	static final String TAG = MailboxPairFragment.class.getName();
+
+	private static final Logger LOG = Logger.getLogger(TAG);
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private MailboxPairViewModel viewModel;
+	private CameraView cameraView;
+	private View statusView;
+	private TextView status;
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(MailboxPairViewModel.class);
+		viewModel.getState().observeEvent(this, this::onStateChanged);
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		return inflater.inflate(R.layout.fragment_mailbox_qr, container, false);
+	}
+
+	@Override
+	public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
+		super.onViewCreated(view, savedInstanceState);
+		cameraView = view.findViewById(R.id.camera_view);
+		cameraView.setPreviewConsumer(viewModel.getQrCodeDecoder());
+		statusView = view.findViewById(R.id.status_container);
+		status = view.findViewById(R.id.connect_status);
+
+		requireActivity().setRequestedOrientation(SCREEN_ORIENTATION_NOSENSOR);
+	}
+
+	private void onStateChanged(MailboxPairViewModel.State state) {
+		if (state == MailboxPairViewModel.State.QRCODE_VALID ||
+				state == MailboxPairViewModel.State.QRCODE_INVALID) {
+			tryStopCamera();
+			cameraView.setVisibility(INVISIBLE);
+			statusView.setVisibility(VISIBLE);
+			CharSequence text = "That's not a valid Mailbox QR code.";
+			if (state == MailboxPairViewModel.State.QRCODE_VALID) {
+				String fmt =
+						"curl -v --socks5-hostname 127.0.0.1:9050" +
+								" -H \"Authorization: Bearer %s\"" +
+								" -X PUT http://%s.onion/setup";
+				text = String.format(fmt, viewModel.getSetupToken(),
+						viewModel.getOnionAddress());
+			}
+			status.setText(text);
+		}
+	}
+
+	@Override
+	public void onStart() {
+		super.onStart();
+		try {
+			cameraView.start();
+		} catch (CameraException e) {
+			logCameraExceptionAndFinish(e);
+		}
+	}
+
+	@Override
+	public void onStop() {
+		super.onStop();
+		tryStopCamera();
+	}
+
+	void tryStopCamera() {
+		try {
+			cameraView.stop();
+		} catch (CameraException e) {
+			logCameraExceptionAndFinish(e);
+		}
+	}
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+	@UiThread
+	private void logCameraExceptionAndFinish(CameraException e) {
+		logException(LOG, WARNING, e);
+		Toast.makeText(getActivity(), R.string.camera_error,
+				LENGTH_LONG).show();
+		finish();
+	}
+
+	@Override
+	protected void finish() {
+		requireActivity().getSupportFragmentManager().popBackStack();
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/mailbox/MailboxPairViewModel.java

@@ -0,0 +1,122 @@
+package org.briarproject.briar.android.mailbox;
+
+import android.app.Application;
+
+import com.google.zxing.Result;
+
+import org.briarproject.bramble.api.crypto.CryptoComponent;
+import org.briarproject.bramble.api.db.DatabaseExecutor;
+import org.briarproject.bramble.api.db.TransactionManager;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.bramble.util.StringUtils;
+import org.briarproject.briar.android.qrcode.QrCodeDecoder;
+import org.briarproject.briar.android.viewmodel.DbViewModel;
+import org.briarproject.briar.android.viewmodel.LiveEvent;
+import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
+
+import java.nio.charset.Charset;
+import java.util.Arrays;
+import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+
+import javax.inject.Inject;
+
+import androidx.annotation.Nullable;
+import androidx.annotation.UiThread;
+
+import static java.util.logging.Level.INFO;
+import static java.util.logging.Logger.getLogger;
+
+@UiThread
+@NotNullByDefault
+class MailboxPairViewModel extends DbViewModel
+		implements QrCodeDecoder.ResultCallback {
+	enum State {QRCODE_VALID, QRCODE_INVALID}
+
+	private static final Logger LOG =
+			getLogger(MailboxPairViewModel.class.getName());
+
+	private static final int VERSION_REQUIRED = 32;
+
+	@SuppressWarnings("CharsetObjectCanBeUsed") // Requires minSdkVersion >= 19
+	private static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");
+
+	private final CryptoComponent crypto;
+
+	private final MutableLiveEvent<State> state = new MutableLiveEvent<>();
+	private final QrCodeDecoder qrCodeDecoder;
+
+	@Nullable
+	private String onionAddress = null;
+	@Nullable
+	private String setupToken = null;
+
+	@Inject
+	MailboxPairViewModel(
+			Application app,
+			@DatabaseExecutor Executor dbExecutor,
+			LifecycleManager lifecycleManager,
+			TransactionManager db,
+			AndroidExecutor androidExecutor,
+			@IoExecutor Executor ioExecutor,
+			CryptoComponent crypto) {
+		super(app, dbExecutor, lifecycleManager, db, androidExecutor);
+		this.crypto = crypto;
+		qrCodeDecoder = new QrCodeDecoder(androidExecutor, ioExecutor, this);
+	}
+
+	@Override
+	public void onQrCodeDecoded(Result result) {
+		LOG.info("Got result from decoder");
+		byte[] bytes = result.getText().getBytes(ISO_8859_1);
+
+		if (LOG.isLoggable(INFO))
+			LOG.info("QR code length in bytes: " + bytes.length);
+		if (bytes.length != 65) {
+			LOG.info("QR code has wrong length");
+			state.postEvent(State.QRCODE_INVALID);
+			return;
+		}
+
+		if (LOG.isLoggable(INFO))
+			LOG.info("QR code version: " + bytes[0]);
+		if (bytes[0] != VERSION_REQUIRED) {
+			LOG.info("QR code has wrong version");
+			state.postEvent(State.QRCODE_INVALID);
+			return;
+		}
+
+		byte[] onionPubKey = Arrays.copyOfRange(bytes, 1, 33);
+		onionAddress = crypto.encodeOnionAddress(onionPubKey);
+		setupToken = StringUtils.toHexString(Arrays.copyOfRange(bytes, 33, 65))
+				.toLowerCase();
+		LOG.info("QR code is valid");
+		state.postEvent(State.QRCODE_VALID);
+	}
+
+	LiveEvent<State> getState() {
+		return state;
+	}
+
+	QrCodeDecoder getQrCodeDecoder() {
+		return qrCodeDecoder;
+	}
+
+	String getOnionAddress() {
+		if (onionAddress == null) {
+			throw new IllegalStateException();
+		}
+		return onionAddress;
+	}
+
+	String getSetupToken() {
+		if (setupToken == null) {
+			throw new IllegalStateException();
+		}
+		return setupToken;
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/navdrawer/NavDrawerActivity.java

@@ -38,6 +38,7 @@ import org.briarproject.briar.android.forum.ForumListFragment;
 import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.fragment.BaseFragment.BaseFragmentListener;
 import org.briarproject.briar.android.logout.SignOutFragment;
+import org.briarproject.briar.android.mailbox.MailboxActivity;
 import org.briarproject.briar.android.privategroup.list.GroupListFragment;
 import org.briarproject.briar.android.settings.SettingsActivity;
 
@@ -277,6 +278,8 @@ public class NavDrawerActivity extends BriarActivity implements
 			startActivity(new Intent(this, SettingsActivity.class));
 		} else if (fragmentId == R.id.nav_btn_signout) {
 			signOut();
+		} else if (fragmentId == R.id.nav_btn_mailbox) {
+			startActivity(new Intent(this, MailboxActivity.class));
 		}
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/qrcode/CameraException.java

@@ -1,8 +1,8 @@
-package org.briarproject.briar.android.contact.add.nearby;
+package org.briarproject.briar.android.qrcode;
 
 import java.io.IOException;
 
-class CameraException extends IOException {
+public class CameraException extends IOException {
 
 	CameraException(String message) {
 		super(message);

briar-android/src/main/java/org/briarproject/briar/android/qrcode/CameraView.java

@@ -1,4 +1,4 @@
-package org.briarproject.briar.android.contact.add.nearby;
+package org.briarproject.briar.android.qrcode;
 
 import android.content.Context;
 import android.hardware.Camera;

briar-android/src/main/java/org/briarproject/briar/android/qrcode/PreviewConsumer.java

@@ -1,4 +1,4 @@
-package org.briarproject.briar.android.contact.add.nearby;
+package org.briarproject.briar.android.qrcode;
 
 import android.hardware.Camera;
 
@@ -7,7 +7,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import androidx.annotation.UiThread;
 
 @NotNullByDefault
-interface PreviewConsumer {
+public interface PreviewConsumer {
 
 	@UiThread
 	void start(Camera camera, int cameraIndex);

briar-android/src/main/java/org/briarproject/briar/android/qrcode/QrCodeDecoder.java

@@ -1,4 +1,4 @@
-package org.briarproject.briar.android.contact.add.nearby;
+package org.briarproject.briar.android.qrcode;
 
 import android.hardware.Camera;
 import android.hardware.Camera.CameraInfo;
@@ -32,7 +32,7 @@ import static java.util.logging.Logger.getLogger;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
+public class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 
 	private static final Logger LOG = getLogger(QrCodeDecoder.class.getName());
 
@@ -44,7 +44,7 @@ class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 	private Camera camera = null;
 	private int cameraIndex = 0;
 
-	QrCodeDecoder(AndroidExecutor androidExecutor,
+	public QrCodeDecoder(AndroidExecutor androidExecutor,
 			@IoExecutor Executor ioExecutor, ResultCallback callback) {
 		this.androidExecutor = androidExecutor;
 		this.ioExecutor = ioExecutor;
@@ -127,7 +127,7 @@ class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 	}
 
 	@NotNullByDefault
-	interface ResultCallback {
+	public interface ResultCallback {
 		@IoExecutor
 		void onQrCodeDecoded(Result result);
 	}

briar-android/src/main/java/org/briarproject/briar/android/qrcode/QrCodeUtils.java

@@ -1,4 +1,4 @@
-package org.briarproject.briar.android.util;
+package org.briarproject.briar.android.qrcode;
 
 import android.graphics.Bitmap;
 import android.util.DisplayMetrics;
@@ -23,11 +23,10 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 
 @NotNullByDefault
 public class QrCodeUtils {
+	public static final double HOTSPOT_QRCODE_FACTOR = 0.35;
 
 	private static final Logger LOG = getLogger(QrCodeUtils.class.getName());
 
-	public static final double HOTSPOT_QRCODE_FACTOR = 0.35;
-
 	@Nullable
 	public static Bitmap createQrCode(DisplayMetrics dm, String input) {
 		return createQrCode(Math.min(dm.widthPixels, dm.heightPixels), input);

briar-android/src/main/res/layout/fragment_keyagreement_qr.xml

@@ -5,7 +5,7 @@
 	android:layout_height="match_parent"
 	android:keepScreenOn="true">
 
-	<org.briarproject.briar.android.contact.add.nearby.CameraView
+	<org.briarproject.briar.android.qrcode.CameraView
 		android:id="@+id/camera_view"
 		android:layout_width="match_parent"
 		android:layout_height="match_parent" />

briar-android/src/main/res/layout/fragment_mailbox_qr.xml

@@ -0,0 +1,48 @@
+<?xml version="1.0" encoding="utf-8"?>
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:keepScreenOn="true">
+
+	<org.briarproject.briar.android.qrcode.CameraView
+		android:id="@+id/camera_view"
+		android:layout_width="match_parent"
+		android:layout_height="match_parent" />
+
+	<LinearLayout
+		android:id="@+id/camera_overlay"
+		android:layout_width="match_parent"
+		android:layout_height="match_parent"
+		android:baselineAligned="false"
+		android:orientation="vertical">
+
+		<LinearLayout
+			android:id="@+id/status_container"
+			android:layout_width="match_parent"
+			android:layout_height="0dp"
+			android:layout_weight="1"
+			android:gravity="center"
+			android:orientation="vertical"
+			android:padding="@dimen/margin_medium"
+			android:visibility="invisible"
+			tools:visibility="visible">
+
+			<ProgressBar
+				style="?android:attr/progressBarStyleLarge"
+				android:layout_width="wrap_content"
+				android:layout_height="wrap_content" />
+
+			<TextView
+				android:id="@+id/connect_status"
+				android:layout_width="match_parent"
+				android:layout_height="wrap_content"
+				android:gravity="center"
+				android:paddingTop="@dimen/margin_large"
+				android:textIsSelectable="true"
+				tools:text="@string/waiting_for_contact_to_scan" />
+		</LinearLayout>
+
+	</LinearLayout>
+
+</FrameLayout>

briar-android/src/main/res/menu/navigation_drawer.xml

@@ -37,6 +37,10 @@
 			android:id="@+id/nav_btn_signout"
 			android:icon="@drawable/ic_signout"
 			android:title="@string/sign_out_button" />
+		<item
+			android:id="@+id/nav_btn_mailbox"
+			android:icon="@drawable/ic_crash"
+			android:title="@string/mailbox_menu_title" />
 	</group>
 
 </menu>

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

@@ -805,5 +805,6 @@
 	<string name="screenshot_message_2">Hi Alice! Thanks for telling me about Briar!</string>
 	<!-- This is a message to be used in screenshots. -->
 	<string name="screenshot_message_3">No problem, hope you like it 😀</string>
+	<string name="mailbox_menu_title">Mailbox</string>
 
 </resources>