[PAN-1878] Provide error message when invalid key specified in key file

pantheon/src/main/java/tech/pegasys/pantheon/controller/KeyPairUtil.java

@@ -12,6 +12,7 @@
  */
 package tech.pegasys.pantheon.controller;
 
+import tech.pegasys.pantheon.crypto.InvalidSEC256K1PrivateKeyStoreException;
 import tech.pegasys.pantheon.crypto.SECP256K1;
 
 import java.io.File;
@@ -24,20 +25,25 @@
 public class KeyPairUtil {
   private static final Logger LOG = LogManager.getLogger();
 
-  public static SECP256K1.KeyPair loadKeyPair(final File keyFile) throws IOException {
-    final SECP256K1.KeyPair key;
-    if (keyFile.exists()) {
-      key = SECP256K1.KeyPair.load(keyFile);
-      LOG.info("Loaded key {} from {}", key.getPublicKey().toString(), keyFile.getAbsolutePath());
-    } else {
-      key = SECP256K1.KeyPair.generate();
-      key.getPrivateKey().store(keyFile);
-      LOG.info(
-          "Generated new key {} and stored it to {}",
-          key.getPublicKey().toString(),
-          keyFile.getAbsolutePath());
+  public static SECP256K1.KeyPair loadKeyPair(final File keyFile)
+      throws IOException, IllegalArgumentException {
+    try {
+      final SECP256K1.KeyPair key;
+      if (keyFile.exists()) {
+        key = SECP256K1.KeyPair.load(keyFile);
+        LOG.info("Loaded key {} from {}", key.getPublicKey().toString(), keyFile.getAbsolutePath());
+      } else {
+        key = SECP256K1.KeyPair.generate();
+        key.getPrivateKey().store(keyFile);
+        LOG.info(
+            "Generated new key {} and stored it to {}",
+            key.getPublicKey().toString(),
+            keyFile.getAbsolutePath());
+      }
+      return key;
+    } catch (InvalidSEC256K1PrivateKeyStoreException e) {
+      throw new IllegalArgumentException("Supplied file does not contain valid key pair.");
     }
-    return key;
   }
 
   public static SECP256K1.KeyPair loadKeyPair(final Path homeDirectory) throws IOException {

pantheon/src/test/java/tech/pegasys/pantheon/util/KeyPairUtilTest.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2019 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.util;
+
+import static org.junit.Assert.assertNotNull;
+
+import tech.pegasys.pantheon.controller.KeyPairUtil;
+
+import java.io.File;
+
+import org.junit.Test;
+
+public class KeyPairUtilTest {
+
+  @Test
+  public void shouldLoadValidKeyPair() throws Exception {
+    assertNotNull(
+        KeyPairUtil.loadKeyPair(
+            new File(this.getClass().getResource("/validPrivateKey.txt").toURI())));
+  }
+
+  @Test(expected = IllegalArgumentException.class)
+  public void shouldNotLoadInvalidKeyPair() throws Exception {
+    KeyPairUtil.loadKeyPair(
+        new File(this.getClass().getResource("/invalidPrivateKey.txt").toURI()));
+  }
+}

pantheon/src/test/resources/invalidPrivateKey.txt

@@ -0,0 +1 @@
+this is not a valid private key

pantheon/src/test/resources/validPrivateKey.txt

@@ -0,0 +1 @@
+000000000000000000000000000000000000000000000000000000000000000A