android: Add utility class that pairs a certificate with a private key

src/frontends/android/app/src/main/java/org/strongswan/android/utils/KeyPair.java

@@ -0,0 +1,76 @@
+/*
+ * 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.utils;
+
+import java.security.PrivateKey;
+import java.security.cert.Certificate;
+import java.util.Objects;
+
+import androidx.annotation.NonNull;
+
+/**
+ * Represents a key pair, which consists of a certificate (i.e. public key) and its corresponding
+ * private key.
+ */
+public class KeyPair
+{
+	@NonNull
+	public final Certificate certificate;
+	@NonNull
+	public final PrivateKey privateKey;
+
+	/**
+	 * Constructor for a {@link KeyPair}.
+	 *
+	 * @param certificate the certificate of the key pair.
+	 * @param privateKey the private key of the key pair.
+	 */
+	public KeyPair(@NonNull Certificate certificate, @NonNull PrivateKey privateKey)
+	{
+		this.certificate = certificate;
+		this.privateKey = privateKey;
+	}
+
+	@Override
+	public boolean equals(Object o)
+	{
+		if (this == o)
+		{
+			return true;
+		}
+		if (o == null || getClass() != o.getClass())
+		{
+			return false;
+		}
+		final KeyPair that = (KeyPair)o;
+		return Objects.equals(certificate, that.certificate) &&
+			   Objects.equals(privateKey, that.privateKey);
+	}
+
+	@Override
+	public int hashCode()
+	{
+		return Objects.hash(certificate, privateKey);
+	}
+
+	@NonNull
+	@Override
+	public String toString()
+	{
+		return "KeyPair{" + certificate + ", " + privateKey + "}";
+	}
+}