HADOOP-13026 Should not wrap IOExceptions into a AuthenticationException in KerberosAuthenticator. Xuan Gong via stevel

hadoop-common-project/hadoop-auth/src/main/java/org/apache/hadoop/security/authentication/client/KerberosAuthenticator.java

@@ -327,7 +327,11 @@ public class KerberosAuthenticator implements Authenticator {
         }
       });
     } catch (PrivilegedActionException ex) {
-      throw new AuthenticationException(ex.getException());
+      if (ex.getException() instanceof IOException) {
+        throw (IOException) ex.getException();
+      } else {
+        throw new AuthenticationException(ex.getException());
+      }
     } catch (LoginException ex) {
       throw new AuthenticationException(ex);
     }