DO NOT MERGE: Unofficial and very hacky account transfer feature.

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

@@ -5,6 +5,9 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 /**
  * Interface for strengthening a password-based key, for example by using a
  * key stored in a key management service or hardware security module.
+ *
+ * TODO: Remove after a reasonable migration period unless we can work around
+ * Android keymaster bugs. Added 2020-02-24
  */
 @NotNullByDefault
 public interface KeyStrengthener {

bramble-core/src/main/java/org/briarproject/bramble/account/AccountManagerImpl.java

@@ -179,8 +179,9 @@ class AccountManagerImpl implements AccountManager {
 	@GuardedBy("stateChangeLock")
 	private boolean encryptAndStoreDatabaseKey(SecretKey key, String password) {
 		byte[] plaintext = key.getBytes();
-		byte[] ciphertext = crypto.encryptWithPassword(plaintext, password,
-				databaseConfig.getKeyStrengthener());
+		// Don't use a key strengthener as the Android keymaster isn't reliable
+		byte[] ciphertext =
+				crypto.encryptWithPassword(plaintext, password, null);
 		return storeEncryptedDatabaseKey(toHexString(ciphertext));
 	}
 
@@ -197,13 +198,13 @@ class AccountManagerImpl implements AccountManager {
 	@Override
 	public void signIn(String password) throws DecryptionException {
 		synchronized (stateChangeLock) {
-			databaseKey = loadAndDecryptDatabaseKey(password);
+			databaseKey = loadAndDecryptDatabaseKey(password, false);
 		}
 	}
 
 	@GuardedBy("stateChangeLock")
-	private SecretKey loadAndDecryptDatabaseKey(String password)
-			throws DecryptionException {
+	private SecretKey loadAndDecryptDatabaseKey(String password,
+			boolean changing) throws DecryptionException {
 		String hex = loadEncryptedDatabaseKey();
 		if (hex == null) {
 			LOG.warning("Failed to load encrypted database key");
@@ -214,11 +215,11 @@ class AccountManagerImpl implements AccountManager {
 		byte[] plaintext = crypto.decryptWithPassword(ciphertext, password,
 				keyStrengthener);
 		SecretKey key = new SecretKey(plaintext);
-		// If the DB key was encrypted with a weak key and a key strengthener
-		// is now available, re-encrypt the DB key with a strengthened key
-		if (keyStrengthener != null &&
-				!crypto.isEncryptedWithStrengthenedKey(ciphertext)) {
-			LOG.info("Re-encrypting database key with strengthened key");
+		// If the DB key was encrypted with a hardware-backed key, re-encrypt
+		// it without the hardware-backed key so keymaster bugs don't delete
+		// the user's account
+		if (!changing && crypto.isEncryptedWithStrengthenedKey(ciphertext)) {
+			LOG.info("Re-encrypting database key without strengthened key");
 			encryptAndStoreDatabaseKey(key, password);
 		}
 		return key;
@@ -228,7 +229,7 @@ class AccountManagerImpl implements AccountManager {
 	public void changePassword(String oldPassword, String newPassword)
 			throws DecryptionException {
 		synchronized (stateChangeLock) {
-			SecretKey key = loadAndDecryptDatabaseKey(oldPassword);
+			SecretKey key = loadAndDecryptDatabaseKey(oldPassword, true);
 			encryptAndStoreDatabaseKey(key, newPassword);
 		}
 	}

bramble-core/src/test/java/org/briarproject/bramble/account/AccountManagerImplTest.java

@@ -134,7 +134,7 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 					keyStrengthener);
 			will(returnValue(key.getBytes()));
 			oneOf(crypto).isEncryptedWithStrengthenedKey(encryptedKey);
-			will(returnValue(true));
+			will(returnValue(false));
 		}});
 
 		storeDatabaseKey(keyFile, encryptedKeyHex);
@@ -160,9 +160,8 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 					keyStrengthener);
 			will(returnValue(key.getBytes()));
 			oneOf(crypto).isEncryptedWithStrengthenedKey(encryptedKey);
-			will(returnValue(false));
-			oneOf(crypto).encryptWithPassword(key.getBytes(), password,
-					keyStrengthener);
+			will(returnValue(true));
+			oneOf(crypto).encryptWithPassword(key.getBytes(), password, null);
 			will(returnValue(newEncryptedKey));
 		}});
 
@@ -262,8 +261,7 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 			oneOf(identityManager).registerIdentity(identity);
 			oneOf(crypto).generateSecretKey();
 			will(returnValue(key));
-			oneOf(crypto).encryptWithPassword(key.getBytes(), password,
-					keyStrengthener);
+			oneOf(crypto).encryptWithPassword(key.getBytes(), password, null);
 			will(returnValue(encryptedKey));
 		}});
 
@@ -323,10 +321,8 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 			oneOf(crypto).decryptWithPassword(encryptedKey, password,
 					keyStrengthener);
 			will(returnValue(key.getBytes()));
-			oneOf(crypto).isEncryptedWithStrengthenedKey(encryptedKey);
-			will(returnValue(true));
 			oneOf(crypto).encryptWithPassword(key.getBytes(), newPassword,
-					keyStrengthener);
+					null);
 			will(returnValue(newEncryptedKey));
 		}});
 

briar-android/src/main/java/org/briarproject/briar/android/account/AccountUtils.java

@@ -0,0 +1,93 @@
+package org.briarproject.briar.android.account;
+
+import android.content.Context;
+import android.content.Intent;
+import android.widget.Toast;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.logging.Logger;
+
+import static android.content.Intent.FLAG_ACTIVITY_CLEAR_TOP;
+import static android.os.Environment.DIRECTORY_DOWNLOADS;
+import static android.os.Environment.getExternalStoragePublicDirectory;
+import static android.widget.Toast.LENGTH_LONG;
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.IoUtils.copyAndClose;
+import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.briar.android.BriarApplication.ENTRY_ACTIVITY;
+import static org.briarproject.briar.android.navdrawer.NavDrawerActivity.SIGN_OUT_URI;
+
+public class AccountUtils {
+
+	private static final Logger LOG = getLogger(AccountUtils.class.getName());
+
+	private static final String[] BACKUP_DIRS =
+			{"app_db", "app_key", "shared_prefs"};
+
+	public static void exportAccount(Context ctx) {
+		try {
+			File dataDir = getDataDir(ctx);
+			File backupDir = getBackupDir(ctx);
+			for (String name : BACKUP_DIRS) {
+				copyRecursively(new File(dataDir, name),
+						new File(backupDir, name));
+			}
+			Toast.makeText(ctx, "Account exported to "
+					+ backupDir.getCanonicalPath(), LENGTH_LONG).show();
+		} catch (IOException e) {
+			logException(LOG, WARNING, e);
+			Toast.makeText(ctx, "Export failed", LENGTH_LONG).show();
+		}
+	}
+
+	public static void importAccount(Context ctx) {
+		try {
+			File dataDir = getDataDir(ctx);
+			File backupDir = getBackupDir(ctx);
+			for (String name : BACKUP_DIRS) {
+				copyRecursively(new File(backupDir, name),
+						new File(dataDir, name));
+			}
+			Toast.makeText(ctx, "Account imported from "
+					+ backupDir.getCanonicalPath(), LENGTH_LONG).show();
+			Intent intent = new Intent(ctx, ENTRY_ACTIVITY);
+			intent.setFlags(FLAG_ACTIVITY_CLEAR_TOP);
+			intent.setData(SIGN_OUT_URI);
+			ctx.startActivity(intent);
+		} catch (IOException e) {
+			logException(LOG, WARNING, e);
+			Toast.makeText(ctx, "Import failed", LENGTH_LONG).show();
+		}
+	}
+
+	private static File getDataDir(Context ctx) {
+		return new File(ctx.getApplicationInfo().dataDir);
+	}
+
+	private static File getBackupDir(Context ctx) {
+		File downloads = getExternalStoragePublicDirectory(DIRECTORY_DOWNLOADS);
+		return new File(downloads, ctx.getPackageName());
+	}
+
+	private static void copyRecursively(File src, File dest)
+			throws IOException {
+		if (src.isDirectory()) {
+			if (!dest.isDirectory() && !dest.mkdirs()) throw new IOException();
+			File[] children = src.listFiles();
+			if (children == null) throw new IOException();
+			for (File child : children) {
+				copyRecursively(child, new File(dest, child.getName()));
+			}
+		} else if (src.isFile()) {
+			InputStream in = new FileInputStream(src);
+			OutputStream out = new FileOutputStream(dest);
+			copyAndClose(in, out);
+		}
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/settings/SettingsFragment.java

@@ -32,6 +32,7 @@ import org.briarproject.bramble.plugin.tor.CircumventionProvider;
 import org.briarproject.bramble.util.StringUtils;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.Localizer;
+import org.briarproject.briar.android.account.AccountUtils;
 import org.briarproject.briar.android.util.UiUtils;
 
 import java.util.ArrayList;
@@ -251,9 +252,23 @@ public class SettingsFragment extends PreferenceFragmentCompat
 						throw new RuntimeException("Boom!");
 					}
 			);
+			findPreference("pref_key_export").setOnPreferenceClickListener(
+					preference -> {
+						AccountUtils.exportAccount(requireContext());
+						return true;
+					}
+			);
+			findPreference("pref_key_import").setOnPreferenceClickListener(
+					preference -> {
+						AccountUtils.importAccount(requireContext());
+						return true;
+					}
+			);
 		} else {
 			findPreference("pref_key_explode").setVisible(false);
 			findPreference("pref_key_test_data").setVisible(false);
+			findPreference("pref_key_export").setVisible(false);
+			findPreference("pref_key_import").setVisible(false);
 			PreferenceGroup testing =
 					findPreference("pref_key_explode").getParent();
 			if (testing == null) throw new AssertionError();

briar-android/src/main/res/xml/settings.xml

@@ -232,6 +232,16 @@
 			android:title="Crash"
 			app:iconSpaceReserved="false"/>
 
+		<Preference
+			android:key="pref_key_export"
+			android:title="Export Account to SD Card"
+			app:iconSpaceReserved="false"/>
+
+		<Preference
+			android:key="pref_key_import"
+			android:title="Import Account from SD Card"
+			app:iconSpaceReserved="false"/>
+
 	</PreferenceCategory>
 
 </PreferenceScreen>