From b2017d9b032af20044fdf60ddbd1575a554ccb79 Mon Sep 17 00:00:00 2001
From: cnauroth <cnauroth@apache.org>
Date: Tue, 15 Sep 2015 10:41:50 -0700
Subject: [PATCH] HADOOP-12413. AccessControlList should avoid calling
 getGroupNames in isUserInList with empty groups. Contributed by Zhihai Xu.

---
 hadoop-common-project/hadoop-common/CHANGES.txt          | 3 +++
 .../hadoop/security/authorize/AccessControlList.java     | 2 +-
 .../hadoop/security/authorize/TestAccessControlList.java | 9 +++++++++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/hadoop-common-project/hadoop-common/CHANGES.txt b/hadoop-common-project/hadoop-common/CHANGES.txt
index a7ea0aa171b..fe09120106b 100644
--- a/hadoop-common-project/hadoop-common/CHANGES.txt
+++ b/hadoop-common-project/hadoop-common/CHANGES.txt
@@ -776,6 +776,9 @@ Release 2.8.0 - UNRELEASED
     HADOOP-12324. Better exception reporting in SaslPlainServer.
     (Mike Yoder via stevel)
 
+    HADOOP-12413. AccessControlList should avoid calling getGroupNames in
+    isUserInList with empty groups. (Zhihai Xu via cnauroth)
+
   OPTIMIZATIONS
 
     HADOOP-11785. Reduce the number of listStatus operation in distcp
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/authorize/AccessControlList.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/authorize/AccessControlList.java
index f19776fc139..b1b474b5a8d 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/authorize/AccessControlList.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/authorize/AccessControlList.java
@@ -230,7 +230,7 @@ public class AccessControlList implements Writable {
   public final boolean isUserInList(UserGroupInformation ugi) {
     if (allAllowed || users.contains(ugi.getShortUserName())) {
       return true;
-    } else {
+    } else if (!groups.isEmpty()) {
       for(String group: ugi.getGroupNames()) {
         if (groups.contains(group)) {
           return true;
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/security/authorize/TestAccessControlList.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/security/authorize/TestAccessControlList.java
index 75b944d2cf8..ddf74d1b1e0 100644
--- a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/security/authorize/TestAccessControlList.java
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/security/authorize/TestAccessControlList.java
@@ -37,6 +37,10 @@ import org.apache.hadoop.security.UserGroupInformation;
 import org.apache.hadoop.util.NativeCodeLoader;
 import org.junit.Test;
 
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
+
 @InterfaceAudience.LimitedPrivate({"HDFS", "MapReduce"})
 @InterfaceStability.Evolving
 public class TestAccessControlList {
@@ -449,6 +453,11 @@ public class TestAccessControlList {
     assertUserAllowed(susan, acl);
     assertUserAllowed(barbara, acl);
     assertUserAllowed(ian, acl);
+
+    acl = new AccessControlList("");
+    UserGroupInformation spyUser = spy(drwho);
+    acl.isUserAllowed(spyUser);
+    verify(spyUser, never()).getGroupNames();
   }
 
   private void assertUserAllowed(UserGroupInformation ugi,