feat: assume the privileged user is the user that is running nucleus

Author: robcmann

src/main/java/com/aws/greengrass/util/platforms/unix/UnixPlatform.java

@@ -60,7 +60,6 @@ public class UnixPlatform extends Platform {
 
     public static final String LOADER_LOGS_FILE_NAME = "loader.log";
     public static final Pattern PS_PID_PATTERN = Pattern.compile("(\\d+)\\s+(\\d+)");
-    public static final String PRIVILEGED_USER = "root";
     public static final String STDOUT = "stdout";
     public static final String STDERR = "stderr";
     protected static final int SIGTERM = 15;
@@ -80,6 +79,9 @@ public class UnixPlatform extends Platform {
     private static final int MAX_IPC_SOCKET_CREATION_WAIT_TIME_SECONDS = 30;
     public static final int SOCKET_CREATE_POLL_INTERVAL_MS = 200;
 
+    @SuppressFBWarnings(value = "ST_WRITE_TO_STATIC_FROM_INSTANCE_METHOD",
+            justification = "Writing to static field in constructor is safe because Platform is a singleton.")
+    private static String PRIVILEGED_USER;
     private static UnixUserAttributes CURRENT_USER;
     private static UnixGroupAttributes CURRENT_USER_PRIMARY_GROUP;
     private static final Lock lock = LockFactory.newReentrantLock(UnixPlatform.class.getSimpleName());
@@ -93,11 +95,18 @@ public class UnixPlatform extends Platform {
     /**
      * Construct a new instance.
      */
+    @SuppressWarnings("PMD.AssignmentToNonFinalStatic")
     public UnixPlatform() {
         super();
         // avoid spamming DEBUG-level oshi logs when reading process stats
         LogManager.getLogger(oshi.util.FileUtil.class.getName()).setLevel("INFO");
         runWithGenerator = new UnixRunWithGenerator(this);
+        try {
+            PRIVILEGED_USER = loadCurrentUser().getPrincipalName();
+        } catch (IOException e) {
+            // This should not happen, but set the PRIVILEGED_USER to root if it fails
+            PRIVILEGED_USER = "root";
+        }
     }
 
     /**