Add the fallback logic to use 'ssl_engine' if 'ssl_handler' attribute is not available / compatible (#5667)

Signed-off-by: Andriy Redko <drreta@gmail.com>

Author: reta

CHANGELOG.md

@@ -29,6 +29,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Updates resource visibility when handling PATCH api to update sharing record ([#5654](https://github.com/opensearch-project/security/pull/5654))
 - Handles resource updates which otherwise may wipe out all_shared_principals ([#5658](https://github.com/opensearch-project/security/pull/5658))
 - Makes initial share map mutable to allow multiple shares ([#5666](https://github.com/opensearch-project/security/pull/5666))
+- Add the fallback logic to use 'ssl_engine' if 'ssl_handler' attribute is not available / compatible ([#5667](https://github.com/opensearch-project/security/pull/5667))
 
 ### Refactoring
 

src/main/java/org/opensearch/security/filter/OpenSearchRequest.java

@@ -19,6 +19,7 @@
 import java.util.Set;
 import javax.net.ssl.SSLEngine;
 
+import org.opensearch.http.HttpChannel;
 import org.opensearch.rest.RestRequest;
 import org.opensearch.rest.RestRequest.Method;
 
@@ -46,7 +47,11 @@ public SSLEngine getSSLEngine() {
             return null;
         }
 
-        return underlyingRequest.getHttpChannel().get("ssl_http", SslHandler.class).map(SslHandler::engine).orElse(null);
+        final HttpChannel httpChannel = underlyingRequest.getHttpChannel();
+        return httpChannel.get("ssl_http", SslHandler.class)
+            .map(SslHandler::engine)
+            .or(() -> httpChannel.get("ssl_engine", SSLEngine.class))
+            .orElse(null);
     }
 
     @Override