android: Add utility that parses a PKCS#12 container and extracts a KeyPair

diff --git a/src/frontends/android/app/src/main/java/org/strongswan/android/utils/KeyPairs.java b/src/frontends/android/app/src/main/java/org/strongswan/android/utils/KeyPairs.java
new file mode 100644 (file)
index 0000000..43c8966
--- /dev/null
+++ b/src/frontends/android/app/src/main/java/org/strongswan/android/utils/KeyPairs.java
@@ -0,0 +1,101 @@
+/*
+ * 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.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.security.Key;
+import java.security.KeyStore;
+import java.security.KeyStoreException;
+import java.security.NoSuchAlgorithmException;
+import java.security.PrivateKey;
+import java.security.UnrecoverableKeyException;
+import java.security.cert.Certificate;
+import java.security.cert.CertificateException;
+import java.security.cert.X509Certificate;
+import java.util.Enumeration;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+public class KeyPairs
+{
+       private static final String KEYSTORE_INSTANCE = "PKCS12";
+
+       @NonNull
+       private static KeyStore toKeyStore(@NonNull byte[] bytes, @NonNull char[] password)
+               throws IOException, KeyStoreException, CertificateException, NoSuchAlgorithmException
+       {
+               try (final ByteArrayInputStream stream = new ByteArrayInputStream(bytes))
+               {
+                       final KeyStore keyStore = KeyStore.getInstance(KEYSTORE_INSTANCE);
+                       keyStore.load(stream, password);
+                       return keyStore;
+               }
+       }
+
+       @Nullable
+       private static KeyPair getKeyPair(
+               @NonNull final KeyStore keyStore,
+               @NonNull final String alias,
+               @NonNull final char[] passwordChars)
+               throws KeyStoreException, NoSuchAlgorithmException, UnrecoverableKeyException
+       {
+               final Certificate certificate = keyStore.getCertificate(alias);
+               if (!(certificate instanceof X509Certificate))
+               {
+                       return null;
+               }
+
+               final Key key = keyStore.getKey(alias, passwordChars);
+               if (key == null)
+               {
+                       return null;
+               }
+               return new KeyPair(certificate, (PrivateKey)key);
+       }
+
+       @Nullable
+       private static KeyPair getKeyPair(@NonNull KeyStore keyStore, @NonNull char[] passwordChars)
+               throws KeyStoreException, NoSuchAlgorithmException, UnrecoverableKeyException
+       {
+               final Enumeration<String> aliases = keyStore.aliases();
+               while (aliases.hasMoreElements())
+               {
+                       final String alias = aliases.nextElement();
+                       final KeyPair keyPair = getKeyPair(keyStore, alias, passwordChars);
+                       if (keyPair != null)
+                       {
+                               return keyPair;
+                       }
+               }
+               return null;
+       }
+
+       @Nullable
+       public static KeyPair from(@NonNull final String userCertificate, @NonNull final String password)
+               throws IOException, KeyStoreException, CertificateException, NoSuchAlgorithmException, UnrecoverableKeyException
+       {
+               final byte[] bytes = android.util.Base64.decode(userCertificate, android.util.Base64.DEFAULT);
+               final char[] passwordChars = password.toCharArray();
+
+               final KeyStore keyStore = toKeyStore(bytes, passwordChars);
+               return getKeyPair(keyStore, passwordChars);
+       }
+
+       private KeyPairs() {}
+}