Add more meaningful keystore version mismatch errors (#46291)

This commit changes the version bounds of keystore reading to give
better error messages when a user has a too new or too old format.

relates #44624

Author: rjernst

server/src/main/java/org/elasticsearch/common/settings/KeyStoreWrapper.java

@@ -20,6 +20,8 @@
 package org.elasticsearch.common.settings;
 
 import org.apache.lucene.codecs.CodecUtil;
+import org.apache.lucene.index.IndexFormatTooNewException;
+import org.apache.lucene.index.IndexFormatTooOldException;
 import org.apache.lucene.store.BufferedChecksumIndexInput;
 import org.apache.lucene.store.ChecksumIndexInput;
 import org.apache.lucene.store.IOContext;
@@ -40,7 +42,6 @@
 import javax.crypto.spec.GCMParameterSpec;
 import javax.crypto.spec.PBEKeySpec;
 import javax.crypto.spec.SecretKeySpec;
-
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.DataInputStream;
@@ -217,7 +218,16 @@ public static KeyStoreWrapper load(Path configDir) throws IOException {
         SimpleFSDirectory directory = new SimpleFSDirectory(configDir);
         try (IndexInput indexInput = directory.openInput(KEYSTORE_FILENAME, IOContext.READONCE)) {
             ChecksumIndexInput input = new BufferedChecksumIndexInput(indexInput);
-            int formatVersion = CodecUtil.checkHeader(input, KEYSTORE_FILENAME, MIN_FORMAT_VERSION, FORMAT_VERSION);
+            final int formatVersion;
+            try {
+                formatVersion = CodecUtil.checkHeader(input, KEYSTORE_FILENAME, MIN_FORMAT_VERSION, FORMAT_VERSION);
+            } catch (IndexFormatTooOldException e) {
+                throw new IllegalStateException("The Elasticsearch keystore [" + keystoreFile + "] format is too old. " +
+                    "You should delete and recreate it in order to upgrade.", e);
+            } catch (IndexFormatTooNewException e) {
+                throw new IllegalStateException("The Elasticsearch keystore [" + keystoreFile + "] format is too new. " +
+                    "Are you trying to downgrade? You should delete and recreate it in order to downgrade.", e);
+            }
             byte hasPasswordByte = input.readByte();
             boolean hasPassword = hasPasswordByte == 1;
             if (hasPassword == false && hasPasswordByte != 0) {