android: Added a method to get the user's private key via JNI

src/frontends/android/jni/libandroidbridge/charonservice.c

@@ -25,6 +25,7 @@
 #include "android_jni.h"
 #include "backend/android_attr.h"
 #include "backend/android_creds.h"
+#include "backend/android_private_key.h"
 #include "backend/android_service.h"
 #include "kernel/android_ipsec.h"
 #include "kernel/android_net.h"
@@ -275,7 +276,7 @@ METHOD(charonservice_t, get_user_certificate, linked_list_t*,
 	{
 		goto failed;
 	}
-	jencodings = (*env)->CallObjectMethod(env, this->vpn_service, method_id, NULL);
+	jencodings = (*env)->CallObjectMethod(env, this->vpn_service, method_id);
 	if (!jencodings)
 	{
 		goto failed;
@@ -290,6 +291,39 @@ failed:
 	return NULL;
 }
 
+METHOD(charonservice_t, get_user_key, private_key_t*,
+	private_charonservice_t *this, public_key_t *pubkey)
+{
+	JNIEnv *env;
+	jmethodID method_id;
+	private_key_t *key;
+	jobject jkey;
+
+	androidjni_attach_thread(&env);
+
+	method_id = (*env)->GetMethodID(env,
+						android_charonvpnservice_class,
+						"getUserKey", "()Ljava/security/PrivateKey;");
+	if (!method_id)
+	{
+		goto failed;
+	}
+	jkey = (*env)->CallObjectMethod(env, this->vpn_service, method_id);
+	if (!jkey)
+	{
+		goto failed;
+	}
+	key = android_private_key_create(jkey, pubkey);
+	androidjni_detach_thread();
+	return key;
+
+failed:
+	DESTROY_IF(pubkey);
+	androidjni_exception_occurred(env);
+	androidjni_detach_thread();
+	return NULL;
+}
+
 METHOD(charonservice_t, get_vpnservice_builder, vpnservice_builder_t*,
 	private_charonservice_t *this)
 {
@@ -364,6 +398,7 @@ static void charonservice_init(JNIEnv *env, jobject service, jobject builder)
 			.bypass_socket = _bypass_socket,
 			.get_trusted_certificates = _get_trusted_certificates,
 			.get_user_certificate = _get_user_certificate,
+			.get_user_key = _get_user_key,
 			.get_vpnservice_builder = _get_vpnservice_builder,
 		},
 		.attr = android_attr_create(),

src/frontends/android/jni/libandroidbridge/charonservice.h

@@ -96,6 +96,14 @@ struct charonservice_t {
 	 */
 	linked_list_t *(*get_user_certificate)(charonservice_t *this);
 
+	/**
+	 * Get the configured private key via JNI
+	 *
+	 * @param pubkey		the public key as extracted from the certificate
+	 * @return				PrivateKey object, NULL on failure
+	 */
+	private_key_t *(*get_user_key)(charonservice_t *this, public_key_t *pubkey);
+
 	/**
 	 * Get the current vpnservice_builder_t object
 	 *

src/frontends/android/src/org/strongswan/android/logic/CharonVpnService.java

@@ -461,6 +461,23 @@ public class CharonVpnService extends VpnService implements Runnable
 		return encodings.toArray(new byte[encodings.size()][]);
 	}
 
+	/**
+	 * Function called via JNI to get the private key the user selected.
+	 *
+	 * Since this method is called from a thread of charon's thread pool we are safe
+	 * to call methods on KeyChain directly.
+	 *
+	 * @return the private key
+	 * @throws InterruptedException
+	 * @throws KeyChainException
+	 * @throws CertificateEncodingException
+	 */
+	private PrivateKey getUserKey() throws KeyChainException, InterruptedException
+	{
+		return KeyChain.getPrivateKey(getApplicationContext(), mCurrentUserCertificateAlias);
+
+	}
+
 	/**
 	 * Initialization of charon, provided by libandroidbridge.so
 	 *