Add a UI for changing the password

briar-android/src/org/briarproject/android/controller/PasswordControllerImpl.java

@@ -1,28 +1,40 @@
 package org.briarproject.android.controller;
 
 import android.app.Activity;
+import android.content.SharedPreferences;
 
 import org.briarproject.android.controller.handler.ResultHandler;
 import org.briarproject.api.crypto.CryptoComponent;
 import org.briarproject.api.crypto.CryptoExecutor;
 import org.briarproject.api.crypto.SecretKey;
+import org.briarproject.api.identity.LocalAuthor;
 import org.briarproject.util.StringUtils;
 
 import java.util.concurrent.Executor;
+import java.util.logging.Logger;
 
 import javax.inject.Inject;
 
+import static java.util.logging.Level.INFO;
+
 public class PasswordControllerImpl extends ConfigControllerImpl
 		implements PasswordController {
 
+	private static final Logger LOG =
+			Logger.getLogger(PasswordControllerImpl.class.getName());
+
+	private final static String PREF_DB_KEY = "key";
+
 	@Inject
 	@CryptoExecutor
 	protected Executor cryptoExecutor;
 	@Inject
-	protected CryptoComponent crypto;
-	@Inject
 	protected Activity activity;
 
+	// Fields that are accessed from background threads must be volatile
+	@Inject
+	protected CryptoComponent crypto;
+
 	@Inject
 	public PasswordControllerImpl() {
 
@@ -46,10 +58,46 @@ public class PasswordControllerImpl extends ConfigControllerImpl
 		});
 	}
 
+	@Override
+	public void changePassword(final String password, final String newPassword,
+			final ResultHandler<Boolean> resultHandler) {
+		final byte[] encrypted = getEncryptedKey();
+		cryptoExecutor.execute(new Runnable() {
+			@Override
+			public void run() {
+				byte[] key = crypto.decryptWithPassword(encrypted, password);
+				if (key == null) {
+					resultHandler.onResult(false);
+				} else {
+					String hex =
+							encryptDatabaseKey(new SecretKey(key), newPassword);
+					storeEncryptedDatabaseKey(hex);
+					resultHandler.onResult(true);
+				}
+			}
+		});
+	}
+
 	private byte[] getEncryptedKey() {
 		String hex = getEncryptedDatabaseKey();
 		if (hex == null)
 			throw new IllegalStateException("Encrypted database key is null");
 		return StringUtils.fromHexString(hex);
 	}
+
+	// Call inside cryptoExecutor
+	String encryptDatabaseKey(SecretKey key, String password) {
+		long now = System.currentTimeMillis();
+		byte[] encrypted = crypto.encryptWithPassword(key.getBytes(), password);
+		long duration = System.currentTimeMillis() - now;
+		if (LOG.isLoggable(INFO))
+			LOG.info("Key derivation took " + duration + " ms");
+		return StringUtils.toHexString(encrypted);
+	}
+
+	void storeEncryptedDatabaseKey(String hex) {
+		SharedPreferences.Editor editor = briarPrefs.edit();
+		editor.putString(PREF_DB_KEY, hex);
+		editor.apply();
+	}
 }