android: Add installer for managed trusted certificates

This installs a configured CA or server certificate into the app's local
key store.

src/frontends/android/app/src/main/java/org/strongswan/android/logic/ManagedTrustedCertificateInstaller.java

@@ -0,0 +1,87 @@
+/*
+ * Copyright (C) 2023 Relution GmbH
+ *
+ * Copyright (C) secunet Security Networks AG
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * for more details.
+ */
+
+package org.strongswan.android.logic;
+
+import android.content.Context;
+import android.util.Log;
+
+import org.strongswan.android.data.ManagedTrustedCertificate;
+import org.strongswan.android.utils.Certificates;
+
+import java.io.IOException;
+import java.security.KeyStore;
+import java.security.KeyStoreException;
+import java.security.NoSuchAlgorithmException;
+import java.security.cert.CertificateException;
+import java.security.cert.X509Certificate;
+
+import androidx.annotation.NonNull;
+
+public class ManagedTrustedCertificateInstaller
+{
+	private static final String TAG = ManagedTrustedCertificateInstaller.class.getSimpleName();
+
+	public ManagedTrustedCertificateInstaller(@NonNull final Context context)
+	{
+	}
+
+	private boolean installTrustedCert(@NonNull ManagedTrustedCertificate trustedCertificate)
+		throws CertificateException, IOException, KeyStoreException, NoSuchAlgorithmException
+	{
+		Log.d(TAG, "Install trusted certificate " + trustedCertificate);
+		final X509Certificate certificate = Certificates.from(trustedCertificate.getData());
+
+		KeyStore store = KeyStore.getInstance("LocalCertificateStore");
+		store.load(null, null);
+		store.setCertificateEntry(trustedCertificate.getAlias(), certificate);
+		return true;
+	}
+
+	private void uninstallTrustedCert(@NonNull ManagedTrustedCertificate trustedCertificate)
+		throws CertificateException, IOException, NoSuchAlgorithmException, KeyStoreException
+	{
+		Log.d(TAG, "Remove trusted certificate " + trustedCertificate);
+		KeyStore store = KeyStore.getInstance("LocalCertificateStore");
+		store.load(null, null);
+		store.deleteEntry(trustedCertificate.getAlias());
+	}
+
+	public synchronized boolean tryInstall(@NonNull ManagedTrustedCertificate trustedCertificate)
+	{
+		try
+		{
+			return installTrustedCert(trustedCertificate);
+		}
+		catch (final Exception e)
+		{
+			Log.e(TAG, "Could not install trusted certificate " + trustedCertificate, e);
+			return false;
+		}
+	}
+
+	public synchronized void tryRemove(@NonNull ManagedTrustedCertificate trustedCertificate)
+	{
+		try
+		{
+			uninstallTrustedCert(trustedCertificate);
+		}
+		catch (final Exception e)
+		{
+			Log.e(TAG, "Could not remove trusted certificate " + trustedCertificate, e);
+		}
+	}
+}