Merge branch 'develop' into feature/hub

# Conflicts:
#	.github/workflows/release.yml
#	pom.xml
#	src/main/resources/license/THIRD-PARTY.txt

src/main/java/org/cryptomator/common/keychain/KeychainManager.java

@@ -49,6 +49,12 @@ public class KeychainManager implements KeychainAccessProvider {
 		setPassphraseStored(key, true);
 	}
 
+	@Override
+	public void storePassphrase(String key, String displayName, CharSequence passphrase) throws KeychainAccessException {
+		getKeychainOrFail().storePassphrase(key, displayName, passphrase);
+		setPassphraseStored(key, true);
+	}
+
 	@Override
 	public char[] loadPassphrase(String key) throws KeychainAccessException {
 		char[] passphrase = getKeychainOrFail().loadPassphrase(key);
@@ -70,6 +76,14 @@ public class KeychainManager implements KeychainAccessProvider {
 		}
 	}
 
+	@Override
+	public void changePassphrase(String key, String displayName, CharSequence passphrase) throws KeychainAccessException {
+		if (isPassphraseStored(key)) {
+			getKeychainOrFail().changePassphrase(key, displayName, passphrase);
+			setPassphraseStored(key, true);
+		}
+	}
+
 	@Override
 	public boolean isSupported() {
 		return keychain.getValue() != null;

src/main/java/org/cryptomator/common/mountpoint/CustomDriveLetterChooser.java

@@ -5,6 +5,9 @@ import org.cryptomator.common.settings.VaultSettings;
 import org.cryptomator.common.vaults.Volume;
 
 import javax.inject.Inject;
+import java.nio.file.FileAlreadyExistsException;
+import java.nio.file.Files;
+import java.nio.file.LinkOption;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.Optional;
@@ -27,4 +30,13 @@ class CustomDriveLetterChooser implements MountPointChooser {
 	public Optional<Path> chooseMountPoint(Volume caller) {
 		return this.vaultSettings.getWinDriveLetter().map(letter -> letter.charAt(0) + ":\\").map(Paths::get);
 	}
+
+	@Override
+	public boolean prepare(Volume caller, Path driveLetter) throws InvalidMountPointException {
+		if (!Files.notExists(driveLetter, LinkOption.NOFOLLOW_LINKS)) {
+			//Drive already exists OR can't be determined
+			throw new InvalidMountPointException(new FileAlreadyExistsException(driveLetter.toString()));
+		}
+		return false;
+	}
 }

src/main/java/org/cryptomator/common/mountpoint/CustomMountPointChooser.java

@@ -56,7 +56,7 @@ class CustomMountPointChooser implements MountPointChooser {
 				throw new InvalidMountPointException(new IllegalStateException("Illegal MountPointRequirement"));
 			}
 			default -> {
-				//Currently the case for "PARENT_OPT_MOUNT_POINT"
+				//Currently the case for "UNUSED_ROOT_DIR, PARENT_OPT_MOUNT_POINT"
 				throw new InvalidMountPointException(new IllegalStateException("Not implemented"));
 			}
 		}

src/main/java/org/cryptomator/common/mountpoint/MountPointHelper.java

@@ -66,9 +66,9 @@ class MountPointHelper {
 	private void clearIrregularUnmountDebris(Path dirContainingMountPoints) {
 		IOException cleanupFailed = new IOException("Cleanup failed");
 
-		try {
+		try (var ds = Files.newDirectoryStream(dirContainingMountPoints)) {
 			LOG.debug("Performing cleanup of mountpoint dir {}.", dirContainingMountPoints);
-			for (Path p : Files.newDirectoryStream(dirContainingMountPoints)) {
+			for (Path p : ds) {
 				try {
 					var attr = Files.readAttributes(p, BasicFileAttributes.class, LinkOption.NOFOLLOW_LINKS);
 					if (attr.isOther() && attr.isDirectory()) { // yes, this is possible with windows junction points -.-
@@ -113,8 +113,10 @@ class MountPointHelper {
 	}
 
 	private void ensureIsEmpty(Path dir) throws IOException {
-		if (Files.newDirectoryStream(dir).iterator().hasNext()) {
-			throw new DirectoryNotEmptyException(dir.toString());
+		try (var ds = Files.newDirectoryStream(dir)) {
+			if (ds.iterator().hasNext()){
+				throw new DirectoryNotEmptyException(dir.toString());
+			}
 		}
 	}
 }

src/main/java/org/cryptomator/common/mountpoint/TemporaryMountPointChooser.java

@@ -65,7 +65,7 @@ class TemporaryMountPointChooser implements MountPointChooser {
 					throw new InvalidMountPointException(new IllegalStateException("Illegal MountPointRequirement"));
 				}
 				default -> {
-					//Currently the case for "PARENT_OPT_MOUNT_POINT"
+					//Currently the case for "UNUSED_ROOT_DIR, PARENT_OPT_MOUNT_POINT"
 					throw new InvalidMountPointException(new IllegalStateException("Not implemented"));
 				}
 			}

src/main/java/org/cryptomator/common/vaults/DokanyVolume.java

@@ -86,7 +86,7 @@ public class DokanyVolume extends AbstractVolume {
 
 	@Override
 	public MountPointRequirement getMountPointRequirement() {
-		return MountPointRequirement.EMPTY_MOUNT_POINT;
+		return this.vaultSettings.getWinDriveLetter().isPresent() ? MountPointRequirement.UNUSED_ROOT_DIR : MountPointRequirement.EMPTY_MOUNT_POINT;
 	}
 
 	public static boolean isSupportedStatic() {

src/main/java/org/cryptomator/common/vaults/FuseVolume.java

@@ -4,6 +4,7 @@ import com.google.common.collect.Iterators;
 import org.apache.commons.lang3.SystemUtils;
 import org.cryptomator.common.mountpoint.InvalidMountPointException;
 import org.cryptomator.common.mountpoint.MountPointChooser;
+import org.cryptomator.common.settings.VaultSettings;
 import org.cryptomator.common.settings.VolumeImpl;
 import org.cryptomator.cryptofs.CryptoFileSystem;
 import org.cryptomator.frontend.fuse.mount.EnvironmentVariables;
@@ -28,11 +29,14 @@ public class FuseVolume extends AbstractVolume {
 	private static final Logger LOG = LoggerFactory.getLogger(FuseVolume.class);
 	private static final Pattern NON_WHITESPACE_OR_QUOTED = Pattern.compile("[^\\s\"']+|\"([^\"]*)\"|'([^']*)'"); // Thanks to https://stackoverflow.com/a/366532
 
+	private final VaultSettings vaultSettings;
+
 	private Mount mount;
 
 	@Inject
-	public FuseVolume(@Named("orderedMountPointChoosers") Iterable<MountPointChooser> choosers) {
+	public FuseVolume(VaultSettings vaultSettings, @Named("orderedMountPointChoosers") Iterable<MountPointChooser> choosers) {
 		super(choosers);
+		this.vaultSettings = vaultSettings;
 	}
 
 	@Override
@@ -50,7 +54,7 @@ public class FuseVolume extends AbstractVolume {
 					.withFileNameTranscoder(mounter.defaultFileNameTranscoder()) //
 					.build();
 			this.mount = mounter.mount(root, envVars, onExitAction);
-		} catch ( FuseMountException | FuseNotSupportedException e) {
+		} catch (FuseMountException | FuseNotSupportedException e) {
 			throw new VolumeException("Unable to mount Filesystem", e);
 		}
 	}
@@ -119,7 +123,10 @@ public class FuseVolume extends AbstractVolume {
 
 	@Override
 	public MountPointRequirement getMountPointRequirement() {
-		return SystemUtils.IS_OS_WINDOWS ? MountPointRequirement.PARENT_NO_MOUNT_POINT : MountPointRequirement.EMPTY_MOUNT_POINT;
+		if (!SystemUtils.IS_OS_WINDOWS) {
+			return MountPointRequirement.EMPTY_MOUNT_POINT;
+		}
+		return this.vaultSettings.getWinDriveLetter().isPresent() ? MountPointRequirement.UNUSED_ROOT_DIR : MountPointRequirement.PARENT_NO_MOUNT_POINT;
 	}
 
 	public static boolean isSupportedStatic() {

src/main/java/org/cryptomator/common/vaults/MountPointRequirement.java

@@ -6,6 +6,11 @@ package org.cryptomator.common.vaults;
  */
 public enum MountPointRequirement {
 
+	/**
+	 * The Mountpoint needs to be a filesystem root and must not exist.
+	 */
+	UNUSED_ROOT_DIR,
+
 	/**
 	 * No Mountpoint on the local filesystem required. (e.g. WebDAV)
 	 */

src/main/java/org/cryptomator/ipc/Server.java

@@ -7,9 +7,11 @@ import java.io.EOFException;
 import java.io.IOException;
 import java.net.StandardProtocolFamily;
 import java.net.UnixDomainSocketAddress;
+import java.nio.channels.AlreadyBoundException;
 import java.nio.channels.AsynchronousCloseException;
 import java.nio.channels.ClosedChannelException;
 import java.nio.channels.ServerSocketChannel;
+import java.nio.channels.UnsupportedAddressTypeException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.concurrent.Executor;
@@ -29,10 +31,18 @@ class Server implements IpcCommunicator {
 	public static Server create(Path socketPath) throws IOException {
 		Files.createDirectories(socketPath.getParent());
 		var address = UnixDomainSocketAddress.of(socketPath);
-		var serverSocketChannel = ServerSocketChannel.open(StandardProtocolFamily.UNIX);
-		serverSocketChannel.bind(address);
-		LOG.info("Spawning IPC server listening on socket {}", socketPath);
-		return new Server(serverSocketChannel, socketPath);
+		ServerSocketChannel ch = null;
+		try {
+			ch = ServerSocketChannel.open(StandardProtocolFamily.UNIX);
+			ch.bind(address);
+			LOG.info("Spawning IPC server listening on socket {}", socketPath);
+			return new Server(ch, socketPath);
+		} catch (IOException | AlreadyBoundException | UnsupportedAddressTypeException e) {
+			if (ch != null) {
+				ch.close();
+			}
+			throw e;
+		}
 	}
 
 	@Override

src/main/java/org/cryptomator/logging/LoggerModule.java

@@ -79,8 +79,9 @@ public class LoggerModule {
 	@Singleton
 	@Named("fileAppender")
 	static Appender<ILoggingEvent> provideFileAppender(LoggerContext context, PatternLayoutEncoder encoder, Environment environment) {
-		if (environment.getLogDir().isPresent()) {
-			Path logDir = environment.getLogDir().get();
+		var optionalLogDir = environment.getLogDir();
+		if (optionalLogDir.isPresent()) {
+			Path logDir = optionalLogDir.get();
 			RollingFileAppender<ILoggingEvent> appender = new RollingFileAppender<>();
 			appender.setContext(context);
 			appender.setFile(logDir.resolve(LOGFILE_NAME).toString());
@@ -110,9 +111,10 @@ public class LoggerModule {
 	@Singleton
 	@Named("upgradeAppender")
 	static Appender<ILoggingEvent> provideUpgradeAppender(LoggerContext context, PatternLayoutEncoder encoder, Environment environment) {
-		if (environment.getLogDir().isPresent()) {
+		var optionalLogDir = environment.getLogDir();
+		if (optionalLogDir.isPresent()) {
 			FileAppender<ILoggingEvent> appender = new FileAppender<>();
-			appender.setFile(environment.getLogDir().get().resolve(UPGRADE_FILENAME).toString());
+			appender.setFile(optionalLogDir.get().resolve(UPGRADE_FILENAME).toString());
 			appender.setContext(context);
 			appender.setEncoder(encoder);
 			appender.start();

src/main/java/org/cryptomator/ui/changepassword/ChangePasswordController.java

@@ -102,7 +102,7 @@ public class ChangePasswordController implements FxController {
 	private void updatePasswordInSystemkeychain() {
 		if (keychain.isSupported() && !keychain.isLocked()) {
 			try {
-				keychain.changePassphrase(vault.getId(), newPasswordController.passwordField.getCharacters());
+				keychain.changePassphrase(vault.getId(), vault.getDisplayName(), newPasswordController.passwordField.getCharacters());
 				LOG.info("Successfully updated password in system keychain for {}", vault.getDisplayName());
 			} catch (KeychainAccessException e) {
 				LOG.error("Failed to update password in system keychain.", e);

src/main/java/org/cryptomator/ui/common/UserInteractionLock.java

@@ -4,30 +4,35 @@ import javafx.application.Platform;
 import javafx.beans.property.BooleanProperty;
 import javafx.beans.property.ReadOnlyBooleanProperty;
 import javafx.beans.property.SimpleBooleanProperty;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.concurrent.locks.Condition;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 
-public class UserInteractionLock<E extends Enum> {
+public class UserInteractionLock<E extends Enum<E>> {
 
 	private final Lock lock = new ReentrantLock();
 	private final Condition condition = lock.newCondition();
 	private final BooleanProperty awaitingInteraction = new SimpleBooleanProperty();
-	private volatile E state;
+	private final AtomicBoolean interacted = new AtomicBoolean();
+	private final AtomicReference<E> state;
 
 	public UserInteractionLock(E initialValue) {
-		this.state = initialValue;
+		this.state = new AtomicReference<>(initialValue);
 	}
 
 	public synchronized void reset(E value) {
-		this.state = value;
+		state.set(value);
+		interacted.set(false);
 	}
 
 	public void interacted(E result) {
 		assert Platform.isFxApplicationThread();
 		lock.lock();
 		try {
-			state = result;
+			state.set(result);
+			interacted.set(true);
 			awaitingInteraction.set(false);
 			condition.signal();
 		} finally {
@@ -40,8 +45,10 @@ public class UserInteractionLock<E extends Enum> {
 		lock.lock();
 		try {
 			Platform.runLater(() -> awaitingInteraction.set(true));
-			condition.await();
-			return state;
+			while (!interacted.get()) {
+				condition.await();
+			}
+			return state.get();
 		} finally {
 			lock.unlock();
 		}

src/main/java/org/cryptomator/ui/fxapp/UpdateCheckerTask.java

@@ -23,7 +23,7 @@ public class UpdateCheckerTask extends Task<String> {
 
 	private static final Logger LOG = LoggerFactory.getLogger(UpdateCheckerTask.class);
 
-	private static final long MAX_RESPONSE_SIZE = 10 * 1024; // 10kb should be sufficient. protect against flooding
+	private static final long MAX_RESPONSE_SIZE = 10L * 1024; // 10kb should be sufficient. protect against flooding
 	private static final Gson GSON = new GsonBuilder().setLenient().create();
 
 	private final HttpClient httpClient;

src/main/java/org/cryptomator/ui/keyloading/masterkeyfile/MasterkeyFileLoadingFinisher.java

@@ -47,7 +47,7 @@ class MasterkeyFileLoadingFinisher {
 	private void savePasswordToSystemkeychain() {
 		if (keychain.isSupported()) {
 			try {
-				keychain.storePassphrase(vault.getId(), CharBuffer.wrap(enteredPassword.get()));
+				keychain.storePassphrase(vault.getId(), vault.getDisplayName(), CharBuffer.wrap(enteredPassword.get()));
 			} catch (KeychainAccessException e) {
 				LOG.error("Failed to store passphrase in system keychain.", e);
 			}

src/main/java/org/cryptomator/ui/keyloading/masterkeyfile/MasterkeyFileLoadingModule.java

@@ -23,8 +23,10 @@ import org.slf4j.LoggerFactory;
 
 import javax.inject.Named;
 import javafx.scene.Scene;
+import javafx.stage.Stage;
 import java.nio.file.Path;
 import java.util.Optional;
+import java.util.ResourceBundle;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
 
@@ -93,15 +95,27 @@ public abstract class MasterkeyFileLoadingModule {
 	@Provides
 	@FxmlScene(FxmlFile.UNLOCK_ENTER_PASSWORD)
 	@KeyLoadingScoped
-	static Scene provideUnlockScene(@KeyLoading FxmlLoaderFactory fxmlLoaders) {
-		return fxmlLoaders.createScene(FxmlFile.UNLOCK_ENTER_PASSWORD);
+	static Scene provideUnlockScene(@KeyLoading FxmlLoaderFactory fxmlLoaders, @KeyLoading Stage window, @KeyLoading Vault v, ResourceBundle resourceBundle) {
+		var scene = fxmlLoaders.createScene(FxmlFile.UNLOCK_ENTER_PASSWORD);
+		scene.windowProperty().addListener((prop, oldVal, newVal) -> {
+			if (window.equals(newVal)) {
+				window.setTitle(String.format(resourceBundle.getString("unlock.title"), v.getDisplayName()));
+			}
+		});
+		return scene;
 	}
 
 	@Provides
 	@FxmlScene(FxmlFile.UNLOCK_SELECT_MASTERKEYFILE)
 	@KeyLoadingScoped
-	static Scene provideUnlockSelectMasterkeyFileScene(@KeyLoading FxmlLoaderFactory fxmlLoaders) {
-		return fxmlLoaders.createScene(FxmlFile.UNLOCK_SELECT_MASTERKEYFILE);
+	static Scene provideUnlockSelectMasterkeyFileScene(@KeyLoading FxmlLoaderFactory fxmlLoaders, @KeyLoading Stage window, @KeyLoading Vault v, ResourceBundle resourceBundle) {
+		var scene = fxmlLoaders.createScene(FxmlFile.UNLOCK_SELECT_MASTERKEYFILE);
+		scene.windowProperty().addListener((prop, oldVal, newVal) -> {
+			if (window.equals(newVal)) {
+				window.setTitle(String.format(resourceBundle.getString("unlock.chooseMasterkey.title"), v.getDisplayName()));
+			}
+		});
+		return scene;
 	}
 
 	@Binds

src/main/java/org/cryptomator/ui/keyloading/masterkeyfile/MasterkeyFileLoadingStrategy.java

@@ -3,6 +3,7 @@ package org.cryptomator.ui.keyloading.masterkeyfile;
 import com.google.common.base.Preconditions;
 import dagger.Lazy;
 import org.cryptomator.common.vaults.Vault;
+import org.cryptomator.cryptofs.common.BackupHelper;
 import org.cryptomator.cryptolib.api.InvalidPassphraseException;
 import org.cryptomator.cryptolib.api.Masterkey;
 import org.cryptomator.cryptolib.api.MasterkeyLoadingFailedException;
@@ -20,6 +21,7 @@ import javafx.application.Platform;
 import javafx.scene.Scene;
 import javafx.stage.Stage;
 import javafx.stage.Window;
+import java.io.IOException;
 import java.net.URI;
 import java.nio.CharBuffer;
 import java.nio.file.Files;
@@ -61,14 +63,24 @@ public class MasterkeyFileLoadingStrategy implements KeyLoadingStrategy {
 	@Override
 	public Masterkey loadKey(URI keyId) throws MasterkeyLoadingFailedException {
 		Preconditions.checkArgument(SCHEME.equalsIgnoreCase(keyId.getScheme()), "Only supports keys with scheme " + SCHEME);
-
 		try {
 			Path filePath = vault.getPath().resolve(keyId.getSchemeSpecificPart());
 			if (!Files.exists(filePath)) {
 				filePath = getAlternateMasterkeyFilePath();
 			}
 			CharSequence passphrase = getPassphrase();
-			return masterkeyFileAccess.load(filePath, passphrase);
+			var masterkey = masterkeyFileAccess.load(filePath, passphrase);
+			//backup
+			if (filePath.startsWith(vault.getPath())) {
+				try {
+					BackupHelper.attemptBackup(filePath);
+				} catch (IOException e) {
+					LOG.warn("Unable to create backup for masterkey file.");
+				}
+			} else {
+				LOG.info("Masterkey file not stored inside vault. Not creating a backup.");
+			}
+			return masterkey;
 		} catch (InterruptedException e) {
 			Thread.currentThread().interrupt();
 			throw new UnlockCancelledException("Unlock interrupted", e);

src/main/java/org/cryptomator/ui/stats/VaultStatisticsController.java

@@ -127,10 +127,10 @@ public class VaultStatisticsController implements FxController {
 			encryptedBytesWrite.getData().add(new Data<>(currentStep, encBytes));
 
 			// adjust ranges:
-			readChartXAxis.setLowerBound(currentStep - IO_SAMPLING_STEPS);
+			readChartXAxis.setLowerBound(currentStep - IO_SAMPLING_STEPS * 1.0);
 			readChartXAxis.setUpperBound(currentStep);
 			readChartYAxis.setUpperBound(allTimeMax);
-			writeChartXAxis.setLowerBound(currentStep - IO_SAMPLING_STEPS);
+			writeChartXAxis.setLowerBound(currentStep - IO_SAMPLING_STEPS * 1.0);
 			writeChartXAxis.setUpperBound(currentStep);
 			writeChartYAxis.setUpperBound(allTimeMax);
 		}

src/main/java/org/cryptomator/ui/unlock/UnlockInvalidMountPointController.java

@@ -1,5 +1,6 @@
 package org.cryptomator.ui.unlock;
 
+import org.apache.commons.lang3.SystemUtils;
 import org.cryptomator.common.vaults.MountPointRequirement;
 import org.cryptomator.common.vaults.Vault;
 import org.cryptomator.ui.common.FxController;
@@ -32,12 +33,24 @@ public class UnlockInvalidMountPointController implements FxController {
 		return vault.getVaultSettings().getCustomMountPath().orElse("AUTO");
 	}
 
-	public boolean getMustExist() {
-		MountPointRequirement requirement = vault.getVolume().orElseThrow(() -> new IllegalStateException("Invalid Mountpoint without a Volume?!")).getMountPointRequirement();
-		assert requirement != MountPointRequirement.NONE; //An invalid MountPoint with no required MountPoint doesn't seem sensible
-		assert requirement != MountPointRequirement.PARENT_OPT_MOUNT_POINT; //Not implemented anywhere (yet)
-
-		return requirement == MountPointRequirement.EMPTY_MOUNT_POINT;
+	public boolean getNotExisting() {
+		return getMountPointRequirement() == MountPointRequirement.EMPTY_MOUNT_POINT;
 	}
 
-}
+	public boolean getExisting() {
+		return getMountPointRequirement() == MountPointRequirement.PARENT_NO_MOUNT_POINT;
+	}
+
+	public boolean getDriveLetterOccupied() {
+		return getMountPointRequirement() == MountPointRequirement.UNUSED_ROOT_DIR;
+	}
+
+	private MountPointRequirement getMountPointRequirement() {
+		var requirement = vault.getVolume().orElseThrow(() -> new IllegalStateException("Invalid Mountpoint without a Volume?!")).getMountPointRequirement();
+		assert requirement != MountPointRequirement.NONE; //An invalid MountPoint with no required MountPoint doesn't seem sensible
+		assert requirement != MountPointRequirement.PARENT_OPT_MOUNT_POINT; //Not implemented anywhere (yet)
+		assert requirement != MountPointRequirement.UNUSED_ROOT_DIR || SystemUtils.IS_OS_WINDOWS; //Not implemented anywhere, but on Windows
+
+		return requirement;
+	}
+}

src/main/java/org/cryptomator/ui/unlock/UnlockWorkflow.java

@@ -2,6 +2,7 @@ package org.cryptomator.ui.unlock;
 
 import com.google.common.base.Throwables;
 import dagger.Lazy;
+import org.apache.commons.lang3.SystemUtils;
 import org.cryptomator.common.mountpoint.InvalidMountPointException;
 import org.cryptomator.common.vaults.MountPointRequirement;
 import org.cryptomator.common.vaults.Vault;
@@ -79,9 +80,10 @@ public class UnlockWorkflow extends Task<Boolean> {
 	}
 
 	private void handleInvalidMountPoint(InvalidMountPointException impExc) {
-		MountPointRequirement requirement = vault.getVolume().orElseThrow(() -> new IllegalStateException("Invalid Mountpoint without a Volume?!", impExc)).getMountPointRequirement();
+		var requirement = vault.getVolume().orElseThrow(() -> new IllegalStateException("Invalid Mountpoint without a Volume?!", impExc)).getMountPointRequirement();
 		assert requirement != MountPointRequirement.NONE; //An invalid MountPoint with no required MountPoint doesn't seem sensible
 		assert requirement != MountPointRequirement.PARENT_OPT_MOUNT_POINT; //Not implemented anywhere (yet)
+		assert requirement != MountPointRequirement.UNUSED_ROOT_DIR || SystemUtils.IS_OS_WINDOWS; //Not implemented anywhere, but on Windows
 
 		Throwable cause = impExc.getCause();
 		// TODO: apply https://openjdk.java.net/jeps/8213076 in future JDK versions
@@ -93,7 +95,11 @@ public class UnlockWorkflow extends Task<Boolean> {
 			}
 			showInvalidMountPointScene();
 		} else if (cause instanceof FileAlreadyExistsException) {
-			LOG.error("Unlock failed. Mountpoint already exists: {}", cause.getMessage());
+			if (requirement == MountPointRequirement.UNUSED_ROOT_DIR) {
+				LOG.error("Unlock failed. Drive Letter already in use: {}", cause.getMessage());
+			} else {
+				LOG.error("Unlock failed. Mountpoint already exists: {}", cause.getMessage());
+			}
 			showInvalidMountPointScene();
 		} else if (cause instanceof DirectoryNotEmptyException) {
 			LOG.error("Unlock failed. Mountpoint not an empty directory: {}", cause.getMessage());