Merge pull request #14834 from nextcloud/warn-user-for-invalid-filename

Warn Users About Invalid Filenames During Download

Author: tobiasKaminsky

app/src/main/java/com/owncloud/android/operations/DownloadFileOperation.java

@@ -12,10 +12,14 @@
 package com.owncloud.android.operations;
 
 import android.content.Context;
+import android.os.Handler;
+import android.os.Looper;
 import android.text.TextUtils;
 import android.webkit.MimeTypeMap;
 
 import com.nextcloud.client.account.User;
+import com.nextcloud.utils.extensions.ContextExtensionsKt;
+import com.owncloud.android.R;
 import com.owncloud.android.datamodel.ArbitraryDataProviderImpl;
 import com.owncloud.android.datamodel.FileDataStorageManager;
 import com.owncloud.android.datamodel.OCFile;
@@ -62,8 +66,8 @@ public class DownloadFileOperation extends RemoteOperation {
     private Set<OnDatatransferProgressListener> dataTransferListeners = new HashSet<>();
     private long modificationTimestamp;
     private DownloadFileRemoteOperation downloadOperation;
-
     private final AtomicBoolean cancellationRequested = new AtomicBoolean(false);
+    private final Handler mainThreadHandler = new Handler(Looper.getMainLooper());
 
     public DownloadFileOperation(User user,
                                  OCFile file,
@@ -162,13 +166,19 @@ protected RemoteOperationResult run(OwnCloudClient client) {
         /// perform the download
         synchronized(cancellationRequested) {
             if (cancellationRequested.get()) {
-                return new RemoteOperationResult(new OperationCancelledException());
+                return new RemoteOperationResult<>(new OperationCancelledException());
             }
         }
 
+        final var isValidExtFilename = FileStorageUtils.isValidExtFilename(file.getFileName());
+        if (!isValidExtFilename) {
+            mainThreadHandler.post(() -> ContextExtensionsKt.showToast(context.get(), R.string.download_download_invalid_local_file_name));
+            return new RemoteOperationResult<>(RemoteOperationResult.ResultCode.INVALID_CHARACTER_IN_NAME);
+        }
+
         Context operationContext = context.get();
         if (operationContext == null) {
-            return new RemoteOperationResult(RemoteOperationResult.ResultCode.UNKNOWN_ERROR);
+            return new RemoteOperationResult<>(RemoteOperationResult.ResultCode.UNKNOWN_ERROR);
         }
 
         RemoteOperationResult result;

app/src/main/java/com/owncloud/android/utils/FileStorageUtils.java

@@ -69,6 +69,37 @@ private FileStorageUtils() {
         // utility class -> private constructor
     }
 
+    public static boolean isValidExtFilename(String name) {
+        for (int i = 0; i < name.length(); i++) {
+            char c = name.charAt(i);
+            if (!isValidExtFilenameChar(c)) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    /**
+     * Checks whether the given character is valid in an extended file name.
+     * <p>
+     * Reference: <a href="https://cs.android.com/android/platform/superproject/+/master:frameworks/base/core/java/android/os/FileUtils.java;l=997">
+     * android.os.FileUtils#isValidExtFilenameChar(char)
+     * </a> from the Android Open Source Project.
+     *
+     * @param c the character to validate
+     * @return true if the character is valid in a filename, false otherwise
+     */
+    private static boolean isValidExtFilenameChar(char c) {
+        if ((int) c <= 0x1F) {
+            return false;
+        }
+
+        return switch (c) {
+            case '"', '*', ':', '/', '<', '>', '?', '\\', '|', 0x7F -> false;
+            default -> true;
+        };
+    }
+
     /**
      * Get local owncloud storage path for accountName.
      */

app/src/test/java/com/nextcloud/client/utils/FileStorageUtilsTest.kt

@@ -10,11 +10,43 @@ package com.nextcloud.client.utils
 import com.nextcloud.client.preferences.SubFolderRule
 import com.owncloud.android.utils.FileStorageUtils
 import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
 import org.junit.Test
 import java.io.File
 import java.util.Locale
 
 class FileStorageUtilsTest {
+    @Test
+    fun testValidFilenames() {
+        assertTrue(FileStorageUtils.isValidExtFilename("example.txt"))
+        assertTrue(FileStorageUtils.isValidExtFilename("file_name-123"))
+        assertTrue(FileStorageUtils.isValidExtFilename("normalFile"))
+    }
+
+    @Test
+    fun testInvalidFilenamesWithSpecialChars() {
+        assertFalse(FileStorageUtils.isValidExtFilename("file:name.txt"))
+        assertFalse(FileStorageUtils.isValidExtFilename("file*name"))
+        assertFalse(FileStorageUtils.isValidExtFilename("file/name"))
+        assertFalse(FileStorageUtils.isValidExtFilename("file\\name"))
+        assertFalse(FileStorageUtils.isValidExtFilename("file|name"))
+        assertFalse(FileStorageUtils.isValidExtFilename("file\"name"))
+        assertFalse(FileStorageUtils.isValidExtFilename("file<name>"))
+        assertFalse(FileStorageUtils.isValidExtFilename("file?name"))
+    }
+
+    @Test
+    fun testFilenamesWithControlCharacters() {
+        assertFalse(FileStorageUtils.isValidExtFilename("file\u0001name"))
+        assertFalse(FileStorageUtils.isValidExtFilename("file\u001Fname"))
+    }
+
+    @Test
+    fun testEmptyFilename() {
+        assertTrue(FileStorageUtils.isValidExtFilename(""))
+    }
+
     @Test
     fun testInstantUploadPathSubfolder() {
         val file = File("/sdcard/DCIM/subfolder/file.jpg")