Show on map: everything is handled by one content provider alone.

To avoid issues forwarding a requests from (temporarily) exported content provider to internal content provider only one content provider is used.

src/main/AndroidManifest.xml

@@ -173,14 +173,9 @@ limitations under the License.
                 android:resource="@xml/track_widget_info" />
         </receiver>
         <!-- Providers -->
-        <provider
-            android:name=".content.CustomContentProvider"
-            android:authorities="${applicationId}.content"
-            android:exported="false"
-            android:grantUriPermissions="true" />
         <provider
             android:name=".content.ShareContentProvider"
-            android:authorities="${applicationId}"
+            android:authorities="${applicationId}.content"
             android:exported="false"
             android:grantUriPermissions="true" />
         <!-- Search suggestion provider -->

src/main/java/de/dennisguse/opentracks/android/ContentResolverWrapper.java

@@ -0,0 +1,40 @@
+package de.dennisguse.opentracks.android;
+
+import android.content.ContentResolver;
+import android.content.ContentValues;
+import android.database.Cursor;
+import android.net.Uri;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+public class ContentResolverWrapper implements IContentResolver {
+
+    private ContentResolver contentResolver;
+
+    public ContentResolverWrapper(ContentResolver contentResolver) {
+        this.contentResolver = contentResolver;
+    }
+
+    @Nullable
+    public Uri insert(@NonNull Uri url, @Nullable ContentValues values) {
+        return contentResolver.insert(url, values);
+    }
+
+    public int bulkInsert(@NonNull Uri url, @NonNull ContentValues[] values) {
+        return contentResolver.bulkInsert(url, values);
+    }
+
+    @Nullable
+    public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) {
+        return contentResolver.query(uri, projection, selection, selectionArgs, sortOrder);
+    }
+
+    public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String where, @Nullable String[] selectionArgs) {
+        return contentResolver.update(uri, values, where, selectionArgs);
+    }
+
+    public int delete(@NonNull Uri url, @Nullable String where, @Nullable String[] selectionArgs) {
+        return contentResolver.delete(url, where, selectionArgs);
+    }
+}

src/main/java/de/dennisguse/opentracks/android/IContentResolver.java

@@ -0,0 +1,27 @@
+package de.dennisguse.opentracks.android;
+
+import android.content.ContentValues;
+import android.database.Cursor;
+import android.net.Uri;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.annotation.RequiresPermission;
+
+/**
+ * Defines the interface actually shared by {@link android.content.ContentProvider} and {@link android.content.ContentResolver}.
+ * So, both can be used interchangeably.
+ */
+public interface IContentResolver {
+    @Nullable
+    Uri insert(@RequiresPermission.Write @NonNull Uri url, @Nullable ContentValues values);
+
+    int bulkInsert(@RequiresPermission.Write @NonNull Uri url, @NonNull ContentValues[] values);
+
+    @Nullable
+    Cursor query(@RequiresPermission.Read @NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder);
+
+    int update(@RequiresPermission.Write @NonNull Uri uri, @Nullable ContentValues values, @Nullable String where, @Nullable String[] selectionArgs);
+
+    int delete(@RequiresPermission.Write @NonNull Uri url, @Nullable String where, @Nullable String[] selectionArgs);
+}

src/main/java/de/dennisguse/opentracks/content/ContentProviderUtilsImpl.java

@@ -24,18 +24,21 @@ import android.location.Location;
 import android.net.Uri;
 import android.util.Log;
 
-import de.dennisguse.opentracks.content.Waypoint.WaypointType;
-import de.dennisguse.opentracks.content.sensor.SensorDataSet;
-import de.dennisguse.opentracks.stats.TripStatistics;
-import de.dennisguse.opentracks.util.FileUtils;
-
 import java.io.File;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.NoSuchElementException;
 
+import de.dennisguse.opentracks.android.ContentResolverWrapper;
+import de.dennisguse.opentracks.android.IContentResolver;
+import de.dennisguse.opentracks.content.Waypoint.WaypointType;
+import de.dennisguse.opentracks.content.sensor.SensorDataSet;
+import de.dennisguse.opentracks.stats.TripStatistics;
+import de.dennisguse.opentracks.util.FileUtils;
+
 /**
  * {@link ContentProviderUtils} implementation.
+ * Allows to use {@link ContentResolver} and {@link android.content.ContentProvider} interchangeably via {@link IContentResolver}.
  *
  * @author Leif Hendrik Wilden
  */
@@ -45,10 +48,14 @@ public class ContentProviderUtilsImpl implements ContentProviderUtils {
 
     private static final int MAX_LATITUDE = 90000000;
 
-    private final ContentResolver contentResolver;
+    private final IContentResolver contentResolver;
     private int defaultCursorBatchSize = 2000;
 
     public ContentProviderUtilsImpl(ContentResolver contentResolver) {
+        this.contentResolver = new ContentResolverWrapper(contentResolver);
+    }
+
+    public ContentProviderUtilsImpl(IContentResolver contentResolver) {
         this.contentResolver = contentResolver;
     }
 
@@ -716,8 +723,7 @@ public class ContentProviderUtilsImpl implements ContentProviderUtils {
         if (maxWaypoints >= 0) {
             sortOrder += " LIMIT " + maxWaypoints;
         }
-        return contentResolver.query(
-                WaypointsColumns.CONTENT_URI, projection, selection, selectionArgs, sortOrder);
+        return contentResolver.query(WaypointsColumns.CONTENT_URI, projection, selection, selectionArgs, sortOrder);
     }
 
     @Override

src/main/java/de/dennisguse/opentracks/content/CustomContentProvider.java

@@ -40,7 +40,7 @@ import androidx.annotation.VisibleForTesting;
  *
  * @author Leif Hendrik Wilden
  */
-public class CustomContentProvider extends ContentProvider {
+public abstract class CustomContentProvider extends ContentProvider {
 
     @VisibleForTesting
     static final int DATABASE_VERSION = 23;

src/main/java/de/dennisguse/opentracks/content/ShareContentProvider.java

@@ -1,9 +1,7 @@
 package de.dennisguse.opentracks.content;
 
-import android.content.ContentProvider;
-import android.content.ContentValues;
 import android.content.Context;
-import android.content.Intent;
+import android.content.UriMatcher;
 import android.content.pm.ProviderInfo;
 import android.database.Cursor;
 import android.database.MatrixCursor;
@@ -22,24 +20,33 @@ import java.io.FileOutputStream;
 import java.io.IOException;
 import java.util.Arrays;
 
-import de.dennisguse.opentracks.BuildConfig;
+import de.dennisguse.opentracks.android.IContentResolver;
 import de.dennisguse.opentracks.io.file.TrackFileFormat;
 import de.dennisguse.opentracks.io.file.exporter.FileTrackExporter;
 import de.dennisguse.opentracks.io.file.exporter.TrackWriter;
 
 /**
- * A content provider that mimics the behavior of {@link androidx.core.content.FileProvider}, which shares virtual (non-existing) files.
- * The actual content is generated by accessing {@link CustomContentProvider} on request.
+ * A content provider that mimics the behavior of {@link androidx.core.content.FileProvider}, which shares virtual (non-existing) KML-files.
+ * The actual content of the virtual files is generated by using the functionality defined in {@link CustomContentProvider}.
+ *
+ * Moreover, it manages access to OpenTrack's database via {@link CustomContentProvider}.
+ *
+ * Explanation:
+ * Although a request is handled by a {@link android.content.ContentProvider} (with temporarily granted permission), Android's security infrastructure prevents forwarding queries to non-exported {@link android.content.ContentProvider}.
+ * Thus, if {@link ShareContentProvider} and {@link CustomContentProvider} would be two different instances, the data would not be accessible to external apps.
+ * While handling a request {@link ShareContentProvider} could `grantPermissions()` to the calling app for {@link CustomContentProvider}'s URI.
+ * However, while handling the request this would allow the calling app to actually contact {@link CustomContentProvider} directly and get access to stored data that should remain private.
+ *
  */
-public class ShareContentProvider extends ContentProvider {
-
-    public static final String TAG = ShareContentProvider.class.getCanonicalName();
-
-    public static final String SHAREPROVIDER = BuildConfig.APPLICATION_ID;
+public class ShareContentProvider extends CustomContentProvider implements IContentResolver {
 
     private static final String[] COLUMNS = {OpenableColumns.DISPLAY_NAME, OpenableColumns.SIZE};
 
+    public static final String TAG = ShareContentProvider.class.getCanonicalName();
+
     public static String MIME = "application/kml+xml";
+    private static final int URI_KML = 1;
+    private final UriMatcher uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
 
     public static Uri createURI(long[] trackIds) {
         if (trackIds.length == 0) {
@@ -52,7 +59,31 @@ public class ShareContentProvider extends ContentProvider {
         }
         builder.deleteCharAt(builder.lastIndexOf(","));
 
-        return Uri.parse("content://" + SHAREPROVIDER + "/" + builder + ".kml");
+        return Uri.parse("content://" + ContentProviderUtils.AUTHORITY + "/" + TracksColumns.TABLE_NAME + "/kml/" + builder + ".kml");
+    }
+
+    @Override
+    public boolean onCreate() {
+        uriMatcher.addURI(ContentProviderUtils.AUTHORITY, TracksColumns.TABLE_NAME + "/kml/*", URI_KML);
+        return super.onCreate();
+    }
+
+    /**
+     * Do not allow to be exported via AndroidManifest.
+     * Check that caller has permissions to access {@link CustomContentProvider}.
+     */
+    @Override
+    public void attachInfo(@NonNull Context context, @NonNull ProviderInfo info) {
+        super.attachInfo(context, info);
+
+        // Sanity check our security
+        if (info.exported) {
+            throw new UnsupportedOperationException("Provider must not be exported");
+        }
+
+        if (!info.grantUriPermissions) {
+            throw new SecurityException("Provider must grant uri permissions");
+        }
     }
 
     private static long[] parseURI(Uri uri) {
@@ -69,21 +100,12 @@ public class ShareContentProvider extends ContentProvider {
         return trackIds;
     }
 
-    @Override
-    public boolean onCreate() {
-        return true;
-    }
-
-    @Override
-    public void attachInfo(Context context, ProviderInfo info) {
-        super.attachInfo(context, info);
-        if (!info.grantUriPermissions) {
-            throw new SecurityException("Provider must grant uri permissions");
-        }
-    }
-
     @Override
     public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) {
+        if (uriMatcher.match(uri) != URI_KML) {
+            return super.query(uri, projection, selection, selectionArgs, sortOrder);
+        }
+
         // ContentProvider has already checked granted permissions
         if (projection == null) {
             projection = COLUMNS;
@@ -113,16 +135,16 @@ public class ShareContentProvider extends ContentProvider {
     @Nullable
     @Override
     public String getType(@NonNull Uri uri) {
-        return MIME;
+        if (uriMatcher.match(uri) == URI_KML) {
+            return MIME;
+        }
+        return super.getType(uri);
     }
 
     @Nullable
     @Override
     public ParcelFileDescriptor openFile(@NonNull Uri uri, @NonNull String mode) throws FileNotFoundException {
-        ContentProviderUtils contentProviderUtils = ContentProviderUtils.Factory.get(getContext());
-
-        final Uri customContentProviderURI = Uri.parse("content://" + ContentProviderUtils.AUTHORITY + "/tracks");
-        getContext().grantUriPermission(getCallingPackage(), customContentProviderURI, Intent.FLAG_GRANT_READ_URI_PERMISSION);
+        ContentProviderUtils contentProviderUtils = new ContentProviderUtilsImpl(this);
 
         long[] trackIds = parseURI(uri);
         final Track[] tracks = new Track[trackIds.length];
@@ -141,35 +163,10 @@ public class ShareContentProvider extends ContentProvider {
                 } catch (IOException e) {
                     Log.w(TAG, "Oops closing " + e);
                     Toast.makeText(getContext(), "", Toast.LENGTH_SHORT).show();
-                } finally {
-
-                    getContext().revokeUriPermission(customContentProviderURI, Intent.FLAG_GRANT_READ_URI_PERMISSION);
                 }
             }
         };
 
         return openPipeHelper(uri, getType(uri), null, null, pipeDataWriter);
     }
-
-    @Nullable
-    @Override
-    public String[] getStreamTypes(@NonNull Uri uri, @NonNull String mimeTypeFilter) {
-        throw new UnsupportedOperationException();
-    }
-
-    @Nullable
-    @Override
-    public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
-        throw new UnsupportedOperationException();
-    }
-
-    @Override
-    public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
-        throw new UnsupportedOperationException();
-    }
-
-    @Override
-    public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {
-        throw new UnsupportedOperationException();
-    }
 }