only prompt to swap back to proper swap URLs

Before, it was possible to annoy the user by sending HTTP POST with any
repo URL in it.

app/src/main/java/org/fdroid/fdroid/net/BluetoothDownloader.java

@@ -14,7 +14,12 @@ import org.fdroid.fdroid.net.bluetooth.httpish.Response;
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
+import java.util.regex.Pattern;
 
+/**
+ * Download from a Bluetooth swap repo.  Example URI:
+ * {@code bluetooth://84-CF-BF-8B-3E-34/fdroid/repo}
+ */
 public class BluetoothDownloader extends Downloader {
 
     private static final String TAG = "BluetoothDownloader";
@@ -23,6 +28,11 @@ public class BluetoothDownloader extends Downloader {
     private FileDetails fileDetails;
     private final String sourcePath;
 
+    public static boolean isBluetoothUri(Uri uri) {
+        return SCHEME.equals(uri.getScheme())
+                && Pattern.matches("([0-9A-F]{2}-)+[0-9A-F]{2}", uri.getHost());
+    }
+
     public BluetoothDownloader(Uri uri, File destFile) throws IOException {
         super(uri, destFile);
         String macAddress = uri.getHost().replace("-", ":");

app/src/main/java/org/fdroid/fdroid/net/HttpDownloader.java

@@ -122,16 +122,23 @@ public class HttpDownloader extends Downloader {
         cacheTag = connection.getHeaderField(HEADER_FIELD_ETAG);
     }
 
-    private boolean isSwapUrl() {
-        String host = sourceUrl.getHost();
-        return sourceUrl.getPort() > 1023 // only root can use <= 1023, so never a swap repo
+    public static boolean isSwapUrl(Uri uri) {
+        return isSwapUrl(uri.getHost(), uri.getPort());
+    }
+
+    public static boolean isSwapUrl(URL url) {
+        return isSwapUrl(url.getHost(), url.getPort());
+    }
+
+    public static boolean isSwapUrl(String host, int port) {
+        return port > 1023 // only root can use <= 1023, so never a swap repo
                 && host.matches("[0-9.]+") // host must be an IP address
                 && FDroidApp.subnetInfo.isInRange(host); // on the same subnet as we are
     }
 
     private HttpURLConnection getConnection() throws SocketTimeoutException, IOException {
         HttpURLConnection connection;
-        if (isSwapUrl()) {
+        if (isSwapUrl(sourceUrl)) {
             // swap never works with a proxy, its unrouted IP on the same subnet
             connection = (HttpURLConnection) sourceUrl.openConnection();
         } else {

app/src/main/java/org/fdroid/fdroid/views/swap/SwapWorkflowActivity.java

@@ -29,10 +29,9 @@ import android.view.MenuInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.Toast;
-
+import cc.mvdan.accesspoint.WifiApControl;
 import com.google.zxing.integration.android.IntentIntegrator;
 import com.google.zxing.integration.android.IntentResult;
-
 import org.fdroid.fdroid.BuildConfig;
 import org.fdroid.fdroid.FDroidApp;
 import org.fdroid.fdroid.NfcHelper;
@@ -47,6 +46,8 @@ import org.fdroid.fdroid.installer.Installer;
 import org.fdroid.fdroid.localrepo.LocalRepoManager;
 import org.fdroid.fdroid.localrepo.SwapService;
 import org.fdroid.fdroid.localrepo.peers.Peer;
+import org.fdroid.fdroid.net.BluetoothDownloader;
+import org.fdroid.fdroid.net.HttpDownloader;
 
 import java.util.Arrays;
 import java.util.Date;
@@ -57,8 +58,6 @@ import java.util.Set;
 import java.util.Timer;
 import java.util.TimerTask;
 
-import cc.mvdan.accesspoint.WifiApControl;
-
 /**
  * This activity will do its best to show the most relevant screen about swapping to the user.
  * The problem comes when there are two competing goals - 1) Show the user a list of apps from another
@@ -209,8 +208,20 @@ public class SwapWorkflowActivity extends AppCompatActivity {
         showRelevantView();
     }
 
+    /**
+     * Check whether incoming {@link Intent} is a swap repo, and ensure that
+     * it is a valid swap URL.  The hostname can only be either an IP or
+     * Bluetooth address.
+     */
     private void checkIncomingIntent() {
         Intent intent = getIntent();
+        Uri uri = intent.getData();
+        if (uri != null && !HttpDownloader.isSwapUrl(uri) && !BluetoothDownloader.isBluetoothUri(uri)) {
+            String msg = getString(R.string.swap_toast_invalid_url, uri);
+            Toast.makeText(this, msg, Toast.LENGTH_LONG).show();
+            return;
+        }
+
         if (intent.getBooleanExtra(EXTRA_CONFIRM, false) && !intent.getBooleanExtra(EXTRA_SWAP_INTENT_HANDLED, false)) {
             // Storing config in this variable will ensure that when showRelevantView() is next
             // run, it will show the connect swap view (if the service is available).

app/src/main/res/values/strings.xml

@@ -460,6 +460,7 @@ This often occurs with apps installed via Google Play or other sources, if they
     <string name="swap_connection_misc_error">Error occurred while connecting to device, can\'t swap with it!</string>
     <string name="swap_not_enabled">Swapping not enabled</string>
     <string name="swap_not_enabled_description">Before swapping, your device must be made visible.</string>
+    <string name="swap_toast_invalid_url">Invalid URL for swapping: %1$s</string>
 
     <string name="install_confirm">needs access to</string>
     <string name="install_confirm_update">Do you want to install an update

app/src/test/java/org/fdroid/fdroid/net/HttpDownloaderTest.java

@@ -0,0 +1,36 @@
+package org.fdroid.fdroid.net;
+
+import android.net.Uri;
+import org.apache.commons.net.util.SubnetUtils;
+import org.fdroid.fdroid.BuildConfig;
+import org.fdroid.fdroid.FDroidApp;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+import org.robolectric.annotation.Config;
+
+import java.net.MalformedURLException;
+import java.net.URL;
+
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertFalse;
+
+@Config(constants = BuildConfig.class, sdk = 24)
+@RunWith(RobolectricTestRunner.class)
+@SuppressWarnings("LineLength")
+public class HttpDownloaderTest {
+
+    @Test
+    public void testIsSwapUri() throws MalformedURLException {
+        FDroidApp.subnetInfo = new SubnetUtils("192.168.0.112/24").getInfo();
+        String urlString = "http://192.168.0.112:8888/fdroid/repo?fingerprint=113F56CBFA967BA825DD13685A06E35730E0061C6BB046DF88A";
+        assertTrue(HttpDownloader.isSwapUrl("192.168.0.112", 8888)); // NOPMD
+        assertTrue(HttpDownloader.isSwapUrl(Uri.parse(urlString)));
+        assertTrue(HttpDownloader.isSwapUrl(new URL(urlString)));
+
+        assertFalse(HttpDownloader.isSwapUrl("192.168.1.112", 8888)); // NOPMD
+        assertFalse(HttpDownloader.isSwapUrl("192.168.0.112", 80)); // NOPMD
+        assertFalse(HttpDownloader.isSwapUrl(Uri.parse("https://malware.com:8888")));
+        assertFalse(HttpDownloader.isSwapUrl(new URL("https://www.google.com")));
+    }
+}