android: Use Storage Access Framework to import certificates

Thanks to the SAF, introduced with Android 4.4, browsing and opening
files on the system is very easy to implement.

On older systems the menu option is removed.

src/frontends/android/res/menu/certificates.xml

@@ -15,6 +15,11 @@
 -->
 <menu xmlns:android="http://schemas.android.com/apk/res/android" >
 
+    <item
+        android:id="@+id/menu_import_certificate"
+        android:title="@string/import_certificate"
+        android:showAsAction="withText" />
+
     <item
         android:id="@+id/menu_reload_certs"
         android:title="@string/reload_trusted_certs"

src/frontends/android/src/org/strongswan/android/ui/TrustedCertificateImportActivity.java

@@ -23,13 +23,27 @@ import java.security.cert.X509Certificate;
 import org.strongswan.android.R;
 import org.strongswan.android.logic.TrustedCertificateManager;
 
+import android.annotation.TargetApi;
 import android.app.Activity;
 import android.content.Intent;
+import android.net.Uri;
+import android.os.Build;
 import android.os.Bundle;
 import android.widget.Toast;
 
 public class TrustedCertificateImportActivity extends Activity
 {
+	private static final int OPEN_DOCUMENT = 0;
+
+	/* same as those listed in the manifest */
+	private static final String[] ACCEPTED_MIME_TYPES = {
+														 "application/x-x509-ca-cert",
+														 "application/x-x509-server-cert",
+														 "application/x-pem-file",
+														 "application/pkix-cert"
+	};
+
+	@TargetApi(Build.VERSION_CODES.KITKAT)
 	@Override
 	public void onCreate(Bundle savedInstanceState)
 	{
@@ -39,24 +53,63 @@ public class TrustedCertificateImportActivity extends Activity
 		String action = intent.getAction();
 		if (Intent.ACTION_VIEW.equals(action))
 		{
-			try
-			{
-				CertificateFactory factory = CertificateFactory.getInstance("X.509");
-				InputStream in = getContentResolver().openInputStream(intent.getData());
-				X509Certificate certificate = (X509Certificate)factory.generateCertificate(in);
-				/* we don't check whether it's actually a CA certificate or not */
-				KeyStore store = KeyStore.getInstance("LocalCertificateStore");
-				store.load(null, null);
-				store.setCertificateEntry(null, certificate);
-				TrustedCertificateManager.getInstance().reset();
-				Toast.makeText(this, R.string.cert_imported_successfully, Toast.LENGTH_LONG).show();
-			}
-			catch (Exception e)
-			{
-				Toast.makeText(this, R.string.cert_import_failed, Toast.LENGTH_LONG).show();
-				e.printStackTrace();
-			}
+			importCertificate(intent.getData());
+		}
+		else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT)
+		{
+			Intent openIntent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
+			openIntent.setType("*/*");
+			openIntent.putExtra(Intent.EXTRA_MIME_TYPES, ACCEPTED_MIME_TYPES);
+			startActivityForResult(openIntent, OPEN_DOCUMENT);
+			return;
 		}
 		finish();
 	}
+
+	@Override
+	protected void onActivityResult(int requestCode, int resultCode, Intent data)
+	{
+		switch (requestCode)
+		{
+			case OPEN_DOCUMENT:
+				if (resultCode == Activity.RESULT_OK && data != null)
+				{
+					if (importCertificate(data.getData()))
+					{
+						setResult(Activity.RESULT_OK);
+					}
+				}
+				finish();
+				return;
+		}
+		super.onActivityResult(requestCode, resultCode, data);
+	}
+
+	/**
+	 * Try to import the file pointed to by the given URI as a certificate.
+	 * @param uri
+	 * @return whether the import was successful
+	 */
+	private boolean importCertificate(Uri uri)
+	{
+		try
+		{
+			CertificateFactory factory = CertificateFactory.getInstance("X.509");
+			InputStream in = getContentResolver().openInputStream(uri);
+			X509Certificate certificate = (X509Certificate)factory.generateCertificate(in);
+			/* we don't check whether it's actually a CA certificate or not */
+			KeyStore store = KeyStore.getInstance("LocalCertificateStore");
+			store.load(null, null);
+			store.setCertificateEntry(null, certificate);
+			TrustedCertificateManager.getInstance().reset();
+			Toast.makeText(this, R.string.cert_imported_successfully, Toast.LENGTH_LONG).show();
+			return true;
+		}
+		catch (Exception e)
+		{
+			Toast.makeText(this, R.string.cert_import_failed, Toast.LENGTH_LONG).show();
+			e.printStackTrace();
+		}
+		return false;
+	}
 }

src/frontends/android/src/org/strongswan/android/ui/TrustedCertificatesActivity.java

@@ -30,6 +30,7 @@ import android.app.Activity;
 import android.app.Fragment;
 import android.app.FragmentTransaction;
 import android.content.Intent;
+import android.os.Build;
 import android.os.Bundle;
 import android.view.Menu;
 import android.view.MenuItem;
@@ -38,6 +39,7 @@ public class TrustedCertificatesActivity extends Activity implements TrustedCert
 {
 	public static final String SELECT_CERTIFICATE = "org.strongswan.android.action.SELECT_CERTIFICATE";
 	private static final String DIALOG_TAG = "Dialog";
+	private static final int IMPORT_CERTIFICATE = 0;
 	private boolean mSelect;
 
 	@Override
@@ -91,6 +93,16 @@ public class TrustedCertificatesActivity extends Activity implements TrustedCert
 		return true;
 	}
 
+	@Override
+	public boolean onPrepareOptionsMenu(Menu menu)
+	{
+		if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT)
+		{
+			menu.removeItem(R.id.menu_import_certificate);
+		}
+		return true;
+	}
+
 	@Override
 	public boolean onOptionsItemSelected(MenuItem item)
 	{
@@ -102,10 +114,29 @@ public class TrustedCertificatesActivity extends Activity implements TrustedCert
 			case R.id.menu_reload_certs:
 				reloadCertificates();
 				return true;
+			case R.id.menu_import_certificate:
+				Intent intent = new Intent(this, TrustedCertificateImportActivity.class);
+				startActivityForResult(intent, IMPORT_CERTIFICATE);
+				return true;
 		}
 		return super.onOptionsItemSelected(item);
 	}
 
+	@Override
+	protected void onActivityResult(int requestCode, int resultCode, Intent data)
+	{
+		switch (requestCode)
+		{
+			case IMPORT_CERTIFICATE:
+				if (resultCode == Activity.RESULT_OK)
+				{
+					reloadCertificates();
+				}
+				return;
+		}
+		super.onActivityResult(requestCode, resultCode, data);
+	}
+
 	@Override
 	public void onTrustedCertificateSelected(TrustedCertificateEntry selected)
 	{