fix delete file securely method and use for delete original file

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/PgpHelper.java

@@ -18,23 +18,15 @@
 
 package org.sufficientlysecure.keychain.pgp;
 
-import android.content.Context;
+
-import android.content.pm.PackageInfo;
+import java.util.regex.Matcher;
-import android.content.pm.PackageManager.NameNotFoundException;
+import java.util.regex.Pattern;
+
 import android.support.annotation.NonNull;
 import android.text.TextUtils;
 
 import org.sufficientlysecure.keychain.Constants;
-import org.sufficientlysecure.keychain.R;
 import org.sufficientlysecure.keychain.util.Log;
-import org.sufficientlysecure.keychain.util.Preferences;
-
-import java.io.File;
-import java.io.IOException;
-import java.io.RandomAccessFile;
-import java.security.SecureRandom;
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
 
 public class PgpHelper {
 
@@ -50,35 +42,6 @@ public class PgpHelper {
             ".*?(-----BEGIN PGP PUBLIC KEY BLOCK-----.*?-----END PGP PUBLIC KEY BLOCK-----).*",
             Pattern.DOTALL);
 
-    /**
-     * Deletes file securely by overwriting it with random data before deleting it.
-     * <p/>
-     * TODO: Does this really help on flash storage?
-     *
-     * @throws IOException
-     */
-    public static void deleteFileSecurely(Context context, Progressable progressable, File file)
-            throws IOException {
-        long length = file.length();
-        SecureRandom random = new SecureRandom();
-        RandomAccessFile raf = new RandomAccessFile(file, "rws");
-        raf.seek(0);
-        raf.getFilePointer();
-        byte[] data = new byte[1 << 16];
-        int pos = 0;
-        String msg = context.getString(R.string.progress_deleting_securely, file.getName());
-        while (pos < length) {
-            if (progressable != null) {
-                progressable.setProgress(msg, (int) (100 * pos / length), 100);
-            }
-            random.nextBytes(data);
-            raf.write(data);
-            pos += data.length;
-        }
-        raf.close();
-        file.delete();
-    }
-
     /**
      * Fixing broken PGP MESSAGE Strings coming from GMail/AOSP Mail
      */

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/DecryptListFragment.java

@@ -800,33 +800,18 @@ public class DecryptListFragment
         // we can only ever delete a file once, if we got this far either it's gone or it will never work
         mCanDelete = false;
 
-        if ("file".equals(uri.getScheme())) {
+        try {
-            File file = new File(uri.getPath());
+            int deleted = FileHelper.deleteFileSecurely(activity, uri);
-            if (file.delete()) {
+            if (deleted > 0) {
                 Notify.create(activity, R.string.file_delete_ok, Style.OK).show();
             } else {
                 Notify.create(activity, R.string.file_delete_none, Style.WARN).show();
             }
-            return;
+        } catch (Exception e) {
+            Log.e(Constants.TAG, "exception deleting file", e);
+            Notify.create(activity, R.string.file_delete_exception, Style.ERROR).show();
         }
 
-        if ("content".equals(uri.getScheme())) {
-            try {
-                int deleted = activity.getContentResolver().delete(uri, null, null);
-                if (deleted > 0) {
-                    Notify.create(activity, R.string.file_delete_ok, Style.OK).show();
-                } else {
-                    Notify.create(activity, R.string.file_delete_none, Style.WARN).show();
-                }
-            } catch (Exception e) {
-                Log.e(Constants.TAG, "exception deleting file", e);
-                Notify.create(activity, R.string.file_delete_exception, Style.ERROR).show();
-            }
-            return;
-        }
-
-        Notify.create(activity, R.string.file_delete_exception, Style.ERROR).show();
-
     }
 
     public class DecryptFilesAdapter extends RecyclerView.Adapter<ViewHolder> {

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/util/FileHelper.java

@@ -25,7 +25,9 @@ import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
+import java.io.OutputStream;
 import java.io.UnsupportedEncodingException;
+import java.security.SecureRandom;
 import java.text.DecimalFormat;
 
 import android.annotation.TargetApi;
@@ -33,7 +35,6 @@ import android.content.ActivityNotFoundException;
 import android.content.ContentResolver;
 import android.content.Context;
 import android.content.Intent;
-import android.content.res.AssetFileDescriptor;
 import android.database.Cursor;
 import android.graphics.Bitmap;
 import android.graphics.Point;
@@ -41,20 +42,13 @@ import android.net.Uri;
 import android.os.Build;
 import android.os.Build.VERSION_CODES;
 import android.os.Environment;
-import android.os.ParcelFileDescriptor;
 import android.provider.DocumentsContract;
 import android.provider.OpenableColumns;
 import android.support.v4.app.Fragment;
-import android.system.ErrnoException;
-import android.system.Os;
-import android.system.StructStat;
 import android.widget.Toast;
 
-import org.sufficientlysecure.keychain.Constants;
 import org.sufficientlysecure.keychain.R;
 
-import static android.system.OsConstants.S_IROTH;
-
 /** This class offers a number of helper functions for saving documents.
  *
  * There are three entry points here: openDocument, saveDocument and
@@ -167,6 +161,14 @@ public class FileHelper {
     }
 
     public static long getFileSize(Context context, Uri uri, long def) {
+        if ("file".equals(uri.getScheme())) {
+            long size = new File(uri.getPath()).length();
+            if (size == 0) {
+                size = def;
+            }
+            return size;
+        }
+
         long size = def;
         try {
             Cursor cursor = context.getContentResolver().query(uri, new String[]{OpenableColumns.SIZE}, null, null, null);
@@ -261,6 +263,44 @@ public class FileHelper {
         }
     }
 
+    /**
+     * Deletes data at a URI securely by overwriting it with random data
+     * before deleting it. This method is fail-fast - if we can't securely
+     * delete the file, we don't delete it at all.
+     */
+    public static int deleteFileSecurely(Context context, Uri uri)
+            throws IOException {
+
+        ContentResolver resolver = context.getContentResolver();
+        long lengthLeft = FileHelper.getFileSize(context, uri);
+
+        if (lengthLeft == -1) {
+            throw new IOException("Error opening file!");
+        }
+
+        SecureRandom random = new SecureRandom();
+        byte[] randomData = new byte[1024];
+
+        OutputStream out = resolver.openOutputStream(uri, "w");
+        if (out == null) {
+            throw new IOException("Error opening file!");
+        }
+        out = new BufferedOutputStream(out);
+        while (lengthLeft > 0) {
+            random.nextBytes(randomData);
+            out.write(randomData, 0, lengthLeft > randomData.length ? randomData.length : (int) lengthLeft);
+            lengthLeft -= randomData.length;
+        }
+        out.close();
+
+        if ("file".equals(uri.getScheme())) {
+            return new File(uri.getPath()).delete() ? 1 : 0;
+        } else {
+            return resolver.delete(uri, null, null);
+        }
+
+    }
+
     /** Checks if external storage is mounted if file is located on external storage. */
     public static boolean isStorageMounted(String file) {
         if (file.startsWith(Environment.getExternalStorageDirectory().getAbsolutePath())) {