Add javadocs.

bramble-android/src/main/java/org/briarproject/bramble/account/AndroidAccountManager.java

@@ -38,12 +38,15 @@ class AndroidAccountManager extends AccountManagerImpl
 	@Override
 	@Nullable
 	protected String loadEncryptedDatabaseKey() {
+		synchronized (stateChangeLock) {
 			String key = getDatabaseKeyFromPreferences();
 			if (key == null) key = super.loadEncryptedDatabaseKey();
 			else migrateDatabaseKeyToFile(key);
 			return key;
 		}
+	}
 
+	// Locking: stateChangeLock
 	@Nullable
 	private String getDatabaseKeyFromPreferences() {
 		String key = prefs.getString(PREF_DB_KEY, null);
@@ -52,6 +55,7 @@ class AndroidAccountManager extends AccountManagerImpl
 		return key;
 	}
 
+	// Locking: stateChangeLock
 	private void migrateDatabaseKeyToFile(String key) {
 		if (storeEncryptedDatabaseKey(key)) {
 			if (prefs.edit().remove(PREF_DB_KEY).commit())
@@ -64,12 +68,15 @@ class AndroidAccountManager extends AccountManagerImpl
 
 	@Override
 	public void deleteAccount() {
+		synchronized (stateChangeLock) {
 			super.deleteAccount();
 			SharedPreferences defaultPrefs =
 					PreferenceManager.getDefaultSharedPreferences(appContext);
 			deleteAppData(prefs, defaultPrefs);
 		}
+	}
 
+	// Locking: stateChangeLock
 	private void deleteAppData(SharedPreferences... clear) {
 		// Clear and commit shared preferences
 		for (SharedPreferences prefs : clear) {

bramble-api/src/main/java/org/briarproject/bramble/api/account/AccountManager.java

@@ -8,18 +8,58 @@ import javax.annotation.Nullable;
 @NotNullByDefault
 public interface AccountManager {
 
+	/**
+	 * Returns true if the manager has the database key. This will be false
+	 * before {@link #createAccount(String)} or {@link #signIn(String)} has
+	 * been called, and true after {@link #createAccount(String)} or
+	 * {@link #signIn(String)} has returned, until the process exits.
+	 */
 	boolean hasDatabaseKey();
 
+	/**
+	 * Returns the database key if the manager has it. This will be null
+	 * before {@link #createAccount(String)} or {@link #signIn(String)} has
+	 * been called, and non-null after {@link #createAccount(String)} or
+	 * {@link #signIn(String)} has returned, until the process exits.
+	 */
 	@Nullable
 	SecretKey getDatabaseKey();
 
+	/**
+	 * Returns true if the encrypted database key can be loaded from disk and
+	 * the database directory exists.
+	 */
 	boolean accountExists();
 
+	/**
+	 * Creates a database key, encrypts it with the given password and stores
+	 * it on disk. This method does not create the database directory, so
+	 * {@link #accountExists()} will continue to return false until the
+	 * database directory is created.
+	 */
 	boolean createAccount(String password);
 
+	/**
+	 * Deletes all account state from disk. {@link #accountExists()} will
+	 * return false after this method returns.
+	 */
 	void deleteAccount();
 
+	/**
+	 * Loads the encrypted database key from disk and decrypts it with the
+	 * given password.
+	 *
+	 * @return true if the database key was successfully loaded and decrypted.
+	 */
 	boolean signIn(String password);
 
+	/**
+	 * Loads the encrypted database key from disk, decrypts it with the old
+	 * password, encrypts it with the new password, and stores it on disk,
+	 * replacing the old key.
+	 *
+	 * @return true if the database key was successfully loaded, re-encrypted
+	 * and stored.
+	 */
 	boolean changePassword(String oldPassword, String newPassword);
 }

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

@@ -38,6 +38,8 @@ class AccountManagerImpl implements AccountManager {
 	private final CryptoComponent crypto;
 	private final File dbKeyFile, dbKeyBackupFile;
 
+	protected final Object stateChangeLock = new Object();
+
 	@Nullable
 	private volatile SecretKey databaseKey = null;
 
@@ -63,6 +65,7 @@ class AccountManagerImpl implements AccountManager {
 
 	@Nullable
 	protected String loadEncryptedDatabaseKey() {
+		synchronized (stateChangeLock) {
 			String key = readDbKeyFromFile(dbKeyFile);
 			if (key == null) {
 				LOG.info("No database key in primary file");
@@ -74,7 +77,9 @@ class AccountManagerImpl implements AccountManager {
 			}
 			return key;
 		}
+	}
 
+	// Locking: stateChangeLock
 	@Nullable
 	private String readDbKeyFromFile(File f) {
 		if (!f.exists()) {
@@ -93,6 +98,7 @@ class AccountManagerImpl implements AccountManager {
 		}
 	}
 
+	// Locking: stateChangeLock
 	protected boolean storeEncryptedDatabaseKey(String hex) {
 		LOG.info("Storing database key in file");
 		// Create the directory if necessary
@@ -130,6 +136,7 @@ class AccountManagerImpl implements AccountManager {
 		}
 	}
 
+	// Locking: stateChangeLock
 	private void writeDbKeyToFile(String key, File f) throws IOException {
 		FileOutputStream out = new FileOutputStream(f);
 		out.write(key.getBytes("UTF-8"));
@@ -139,18 +146,23 @@ class AccountManagerImpl implements AccountManager {
 
 	@Override
 	public boolean accountExists() {
+		synchronized (stateChangeLock) {
 			return loadEncryptedDatabaseKey() != null
 					&& databaseConfig.getDatabaseDirectory().isDirectory();
 		}
+	}
 
 	@Override
 	public boolean createAccount(String password) {
+		synchronized (stateChangeLock) {
 			SecretKey key = crypto.generateSecretKey();
 			if (!encryptAndStoreDatabaseKey(key, password)) return false;
 			databaseKey = key;
 			return true;
 		}
+	}
 
+	// Locking: stateChangeLock
 	private boolean encryptAndStoreDatabaseKey(SecretKey key, String password) {
 		byte[] plaintext = key.getBytes();
 		byte[] ciphertext = crypto.encryptWithPassword(plaintext, password);
@@ -159,19 +171,24 @@ class AccountManagerImpl implements AccountManager {
 
 	@Override
 	public void deleteAccount() {
+		synchronized (stateChangeLock) {
 			LOG.info("Deleting account");
 			IoUtils.deleteFileOrDir(databaseConfig.getDatabaseKeyDirectory());
 			IoUtils.deleteFileOrDir(databaseConfig.getDatabaseDirectory());
 		}
+	}
 
 	@Override
 	public boolean signIn(String password) {
+		synchronized (stateChangeLock) {
 			SecretKey key = loadAndDecryptDatabaseKey(password);
 			if (key == null) return false;
 			databaseKey = key;
 			return true;
 		}
+	}
 
+	// Locking: stateChangeLock
 	@Nullable
 	private SecretKey loadAndDecryptDatabaseKey(String password) {
 		String hex = loadEncryptedDatabaseKey();
@@ -190,7 +207,9 @@ class AccountManagerImpl implements AccountManager {
 
 	@Override
 	public boolean changePassword(String oldPassword, String newPassword) {
+		synchronized (stateChangeLock) {
 			SecretKey key = loadAndDecryptDatabaseKey(oldPassword);
 			return key != null && encryptAndStoreDatabaseKey(key, newPassword);
 		}
 	}
+}

briar-android/src/main/java/org/briarproject/briar/android/login/PasswordActivity.java

@@ -53,6 +53,7 @@ public class PasswordActivity extends BaseActivity {
 		overridePendingTransition(R.anim.fade_in, R.anim.fade_out);
 
 		if (!accountManager.accountExists()) {
+			// TODO: Finish instead of deleting account?
 			deleteAccount();
 			return;
 		}