Retain reference to stdout for exceptional cases

build-tools-internal/src/main/resources/forbidden/es-server-signatures.txt

@@ -139,3 +139,6 @@ org.apache.logging.log4j.Logger#error(java.lang.Object)
 org.apache.logging.log4j.Logger#error(java.lang.Object, java.lang.Throwable)
 org.apache.logging.log4j.Logger#fatal(java.lang.Object)
 org.apache.logging.log4j.Logger#fatal(java.lang.Object, java.lang.Throwable)
+
+@defaultMessage Write output to a Logger not the console
+org.elasticsearch.bootstrap.ElasticsearchConsole#getInstance()

server/src/main/java/org/elasticsearch/bootstrap/Bootstrap.java

@@ -328,6 +328,12 @@ static void init(
         final Runnable sysOutCloser = getSysOutCloser();
         final Runnable sysErrorCloser = getSysErrorCloser();
 
+        // If this is true, we retain access to the original stdout stream for exceptional cases that need to write to the console
+        final boolean hasConsole = foreground && (quiet == false);
+        if (hasConsole) {
+            ElasticsearchConsole.init();
+        }
+
         LogConfigurator.setNodeName(Node.NODE_NAME_SETTING.get(environment.settings()));
         try {
             LogConfigurator.configure(environment);
@@ -342,10 +348,8 @@ static void init(
             }
         }
 
-
         try {
-            final boolean closeStandardStreams = (foreground == false) || quiet;
-            if (closeStandardStreams) {
+            if (hasConsole == false) {
                 final Logger rootLogger = LogManager.getRootLogger();
                 final Appender maybeConsoleAppender = Loggers.findAppender(rootLogger, ConsoleAppender.class);
                 if (maybeConsoleAppender != null) {

server/src/main/java/org/elasticsearch/bootstrap/ElasticsearchConsole.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+package org.elasticsearch.bootstrap;
+
+import org.elasticsearch.core.Nullable;
+import org.elasticsearch.core.SuppressForbidden;
+
+import java.io.IOException;
+import java.io.PrintStream;
+import java.util.Locale;
+
+/**
+ * A basic "console" class for writing to the user's console without writing to the logfile.
+ * This is to be used in very exceptional circumstances (e.g. printing out sensitive values that ought not to be logged).
+ * It is not to be confused with the java {@link java.io.Console} (see {@link System#console()}) which will generally be {@code null}
+ * when running Elasticsearch from the command line
+ */
+public class ElasticsearchConsole {
+
+    private static ElasticsearchConsole instance = null;
+
+    private final PrintStream stdout;
+
+    /**
+     * Returns the current console. Will be {@code null} if there is no console.
+     * It is very common for there not to be a console (for example, because Elasticsearch is running as a service) - callers should be
+     * prepared to handle a null console instance.
+     */
+    @Nullable
+    public static ElasticsearchConsole getInstance() {
+        return instance;
+    }
+
+    ElasticsearchConsole(PrintStream stdout) {
+        this.stdout = stdout;
+    }
+
+    public void println(String line) throws IOException {
+        stdout.println(line);
+    }
+
+    public void printf(String format, Object... args) throws IOException {
+        stdout.printf(Locale.ROOT, format, args);
+    }
+
+    @SuppressForbidden(reason = "Initialize using System.out")
+    static void init() {
+        instance = new ElasticsearchConsole(System.out);
+    }
+}