Index: ssh/src/main/java/org/apache/karaf/shell/ssh/KarafJaasPasswordAuthenticator.java
===================================================================
--- ssh/src/main/java/org/apache/karaf/shell/ssh/KarafJaasPasswordAuthenticator.java	(revision 1064123)
+++ ssh/src/main/java/org/apache/karaf/shell/ssh/KarafJaasPasswordAuthenticator.java	(working copy)
@@ -33,6 +33,9 @@
 import org.apache.sshd.server.PasswordAuthenticator;
 import org.apache.sshd.server.session.ServerSession;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 /**
  * TODO Add javadoc
  *
@@ -40,6 +43,8 @@
  */
 public class KarafJaasPasswordAuthenticator implements PasswordAuthenticator {
 
+    private final Logger log = LoggerFactory.getLogger(getClass());
+
     public static final Session.AttributeKey<Subject> SUBJECT_ATTRIBUTE_KEY = new Session.AttributeKey<Subject>();
 
     private String realm;
@@ -101,6 +106,7 @@
             session.setAttribute(SUBJECT_ATTRIBUTE_KEY, subject);
             return true;
         } catch (Exception e) {
+            log.debug("User authentication failed with " + e);
             return false;
         }
     }