HADOOP-13580. If user is unauthorized, log "unauthorized" instead of "Invalid signed text:". Contributed by Wei-Chiu Chuang.

(cherry picked from commit f6f3a447bf3b2900a2e9a0615ad9877f9310e062)

hadoop-common-project/hadoop-auth/src/main/java/org/apache/hadoop/security/authentication/server/AuthenticationFilter.java

@@ -438,6 +438,9 @@ public class AuthenticationFilter implements Filter {
       for (Cookie cookie : cookies) {
         if (cookie.getName().equals(AuthenticatedURL.AUTH_COOKIE)) {
           tokenStr = cookie.getValue();
+          if (tokenStr.isEmpty()) {
+            throw new AuthenticationException("Unauthorized access");
+          }
           try {
             tokenStr = signer.verifyAndExtract(tokenStr);
           } catch (SignerException ex) {