Add temporary file storage as discussed in #665

Writable from OpenKeychain, readable worldwide. Should be used to write shared files to it by first creating the file using TemporaryStorageProvider.createFile and then write to the Uri returned.

OpenKeychain/src/main/AndroidManifest.xml

@@ -49,6 +49,9 @@
         android:name="android.hardware.touchscreen"
         android:required="false" />
 
+    <permission android:name="org.sufficientlysecure.keychain.WRITE_TEMPORARY_STORAGE"/>
+    <uses-permission android:name="org.sufficientlysecure.keychain.WRITE_TEMPORARY_STORAGE"/>
+
     <uses-permission android:name="android.permission.INTERNET" />
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
     <uses-permission android:name="android.permission.NFC" />
@@ -484,6 +487,12 @@
                     android:resource="@xml/custom_pgp_contacts_structure"/>
         </service>
 
+        <provider
+                android:name=".provider.TemporaryStorageProvider"
+                android:authorities="org.sufficientlysecure.keychain.tempstorage"
+                android:writePermission="org.sufficientlysecure.keychain.WRITE_TEMPORARY_STORAGE"
+                android:exported="true"/>
+
     </application>
 
 </manifest>

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/Constants.java

@@ -53,6 +53,8 @@ public final class Constants {
 
     public static boolean KITKAT = Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT;
 
+    public static int TEMPFILE_TTL = 24*60*60*1000; // 1 day
+
     public static final class Path {
         public static final File APP_DIR = new File(Environment.getExternalStorageDirectory(), "OpenKeychain");
         public static final File APP_DIR_FILE = new File(APP_DIR, "export.asc");

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/KeychainApplication.java

@@ -28,6 +28,7 @@ import android.os.Environment;
 import org.spongycastle.jce.provider.BouncyCastleProvider;
 import org.sufficientlysecure.keychain.helper.Preferences;
 import org.sufficientlysecure.keychain.helper.TlsHelper;
+import org.sufficientlysecure.keychain.provider.TemporaryStorageProvider;
 import org.sufficientlysecure.keychain.util.Log;
 import org.sufficientlysecure.keychain.util.PRNGFixes;
 
@@ -85,6 +86,8 @@ public class KeychainApplication extends Application {
         Preferences.getPreferences(this).updateKeyServers();
 
         TlsHelper.addStaticCA("pool.sks-keyservers.net", getAssets(), "sks-keyservers.netCA.cer");
+
+        TemporaryStorageProvider.cleanUp(this);
     }
 
     public static void setupAccountAsNeeded(Context context) {

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/provider/TemporaryStorageProvider.java

@@ -0,0 +1,151 @@
+package org.sufficientlysecure.keychain.provider;
+
+import android.content.ContentProvider;
+import android.content.ContentValues;
+import android.content.Context;
+import android.database.Cursor;
+import android.database.MatrixCursor;
+import android.database.sqlite.SQLiteDatabase;
+import android.database.sqlite.SQLiteOpenHelper;
+import android.net.Uri;
+import android.os.ParcelFileDescriptor;
+import android.provider.OpenableColumns;
+import org.sufficientlysecure.keychain.Constants;
+import org.sufficientlysecure.keychain.util.DatabaseUtil;
+
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+
+public class TemporaryStorageProvider extends ContentProvider {
+
+    private static final String DB_NAME = "tempstorage.db";
+    private static final String TABLE_FILES = "files";
+    private static final String COLUMN_ID = "id";
+    private static final String COLUMN_NAME = "name";
+    private static final String COLUMN_TIME = "time";
+    private static final Uri BASE_URI = Uri.parse("content://org.sufficientlysecure.keychain.tempstorage/");
+    private static final int DB_VERSION = 1;
+
+    public static Uri createFile(Context context, String targetName) {
+        ContentValues contentValues = new ContentValues();
+        contentValues.put(COLUMN_NAME, targetName);
+        return context.getContentResolver().insert(BASE_URI, contentValues);
+    }
+
+    public static int cleanUp(Context context) {
+        return context.getContentResolver().delete(BASE_URI, COLUMN_TIME + "< ?",
+                new String[]{Long.toString(System.currentTimeMillis() - Constants.TEMPFILE_TTL)});
+    }
+
+    private class TemporaryStorageDatabase extends SQLiteOpenHelper {
+
+        public TemporaryStorageDatabase(Context context) {
+            super(context, DB_NAME, null, DB_VERSION);
+        }
+
+        @Override
+        public void onCreate(SQLiteDatabase db) {
+            db.execSQL("CREATE TABLE IF NOT EXISTS " + TABLE_FILES + " (" +
+                    COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
+                    COLUMN_NAME + " TEXT, " +
+                    COLUMN_TIME + " INTEGER" +
+                    ");");
+        }
+
+        @Override
+        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
+
+        }
+    }
+
+    private TemporaryStorageDatabase db;
+
+    private File getFile(Uri uri) throws FileNotFoundException {
+        try {
+            return getFile(Integer.parseInt(uri.getLastPathSegment()));
+        } catch (NumberFormatException e) {
+            throw new FileNotFoundException();
+        }
+    }
+
+    private File getFile(int id) {
+        return new File(getContext().getCacheDir(), "temp/" + id);
+    }
+
+    @Override
+    public boolean onCreate() {
+        db = new TemporaryStorageDatabase(getContext());
+        return new File(getContext().getCacheDir(), "temp").mkdirs();
+    }
+
+    @Override
+    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
+        File file;
+        try {
+            file = getFile(uri);
+        } catch (FileNotFoundException e) {
+            return null;
+        }
+        Cursor fileName = db.getReadableDatabase().query(TABLE_FILES, new String[]{COLUMN_NAME}, COLUMN_ID + "=?",
+                new String[]{uri.getLastPathSegment()}, null, null, null);
+        if (fileName != null) {
+            if (fileName.moveToNext()) {
+                MatrixCursor cursor =
+                        new MatrixCursor(new String[]{OpenableColumns.DISPLAY_NAME, OpenableColumns.SIZE, "_data"});
+                cursor.newRow().add(fileName.getString(0)).add(file.length()).add(file.getAbsolutePath());
+                fileName.close();
+                return cursor;
+            }
+            fileName.close();
+        }
+        return null;
+    }
+
+    @Override
+    public String getType(Uri uri) {
+        return "*/*";
+    }
+
+    @Override
+    public Uri insert(Uri uri, ContentValues values) {
+        if (!values.containsKey(COLUMN_TIME)) {
+            values.put(COLUMN_TIME, System.currentTimeMillis());
+        }
+        int insert = (int) db.getWritableDatabase().insert(TABLE_FILES, null, values);
+        try {
+            getFile(insert).createNewFile();
+        } catch (IOException e) {
+            return null;
+        }
+        return Uri.withAppendedPath(BASE_URI, Long.toString(insert));
+    }
+
+    @Override
+    public int delete(Uri uri, String selection, String[] selectionArgs) {
+        if (uri.getLastPathSegment() != null) {
+            selection = DatabaseUtil.concatenateWhere(selection, COLUMN_ID + "=?");
+            selectionArgs = DatabaseUtil.appendSelectionArgs(selectionArgs, new String[]{uri.getLastPathSegment()});
+        }
+        Cursor files = db.getReadableDatabase().query(TABLE_FILES, new String[]{COLUMN_ID}, selection,
+                selectionArgs, null, null, null);
+        if (files != null) {
+            while (files.moveToNext()) {
+                getFile(files.getInt(0)).delete();
+            }
+            files.close();
+            return db.getWritableDatabase().delete(TABLE_FILES, selection, selectionArgs);
+        }
+        return 0;
+    }
+
+    @Override
+    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
+        throw new UnsupportedOperationException("Update not supported");
+    }
+
+    @Override
+    public ParcelFileDescriptor openFile(Uri uri, String mode) throws FileNotFoundException {
+        return openFileHelper(uri, mode);
+    }
+}

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

@@ -0,0 +1,36 @@
+package org.sufficientlysecure.keychain.util;
+
+import android.text.TextUtils;
+
+/**
+ * Shamelessly copied from android.database.DatabaseUtils
+ */
+public class DatabaseUtil {
+    /**
+     * Concatenates two SQL WHERE clauses, handling empty or null values.
+     */
+    public static String concatenateWhere(String a, String b) {
+        if (TextUtils.isEmpty(a)) {
+            return b;
+        }
+        if (TextUtils.isEmpty(b)) {
+            return a;
+        }
+
+        return "(" + a + ") AND (" + b + ")";
+    }
+
+    /**
+     * Appends one set of selection args to another. This is useful when adding a selection
+     * argument to a user provided set.
+     */
+    public static String[] appendSelectionArgs(String[] originalValues, String[] newValues) {
+        if (originalValues == null || originalValues.length == 0) {
+            return newValues;
+        }
+        String[] result = new String[originalValues.length + newValues.length ];
+        System.arraycopy(originalValues, 0, result, 0, originalValues.length);
+        System.arraycopy(newValues, 0, result, originalValues.length, newValues.length);
+        return result;
+    }
+}