From c5e13feea88a84052b177243767baae269ee84f4 Mon Sep 17 00:00:00 2001
From: Igor Soarez <soarez@apple.com>
Date: Sun, 30 May 2021 15:38:27 +0100
Subject: [PATCH] KAFKA-12866: Avoid root access to Zookeeper

The broker shouldn't assume create access to the chroot. There are
deployement scenarios where the chroot is already created is the only
znode which the broker can access.
---
 .../main/scala/kafka/zk/KafkaZkClient.scala   |  4 +-
 .../scala/unit/kafka/zk/ZkClientAclTest.scala | 63 +++++++++++++++++++
 2 files changed, 66 insertions(+), 1 deletion(-)
 create mode 100644 core/src/test/scala/unit/kafka/zk/ZkClientAclTest.scala

diff --git a/core/src/main/scala/kafka/zk/KafkaZkClient.scala b/core/src/main/scala/kafka/zk/KafkaZkClient.scala
index 4b7bc466280b1..bcc89de9b7f77 100644
--- a/core/src/main/scala/kafka/zk/KafkaZkClient.scala
+++ b/core/src/main/scala/kafka/zk/KafkaZkClient.scala
@@ -1954,7 +1954,9 @@ object KafkaZkClient {
           connectionTimeoutMs, maxInFlightRequests, time, metricGroup, metricType, name, zkClientConfig)
         try {
           val chroot = connectString.substring(chrootIndex)
-          zkClientForChrootCreation.makeSurePersistentPathExists(chroot)
+          if (!zkClientForChrootCreation.pathExists(chroot)) {
+            zkClientForChrootCreation.makeSurePersistentPathExists(chroot)
+          }
         } finally {
           zkClientForChrootCreation.close()
         }
diff --git a/core/src/test/scala/unit/kafka/zk/ZkClientAclTest.scala b/core/src/test/scala/unit/kafka/zk/ZkClientAclTest.scala
new file mode 100644
index 0000000000000..19b78a3fc57da
--- /dev/null
+++ b/core/src/test/scala/unit/kafka/zk/ZkClientAclTest.scala
@@ -0,0 +1,63 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package kafka.zk
+
+import java.security.MessageDigest
+import java.util.Base64
+
+import org.apache.kafka.common.security.JaasUtils
+import org.apache.kafka.common.utils.Time
+import org.apache.zookeeper.ZooDefs
+import org.apache.zookeeper.data.{ACL, Id}
+import org.junit.jupiter.api.{AfterEach, BeforeEach, Test}
+
+import scala.collection.Seq
+import scala.jdk.CollectionConverters._
+
+class ZkClientAclTest extends ZooKeeperTestHarness {
+
+  @BeforeEach
+  override def setUp(): Unit = {
+    super.setUp()
+  }
+
+  @AfterEach
+  override def tearDown(): Unit = {
+    super.tearDown()
+  }
+
+  @Test
+  def testChrootExistsAndRootIsLocked(): Unit = {
+    // chroot is accessible
+    val chroot = "/chroot"
+    zkClient.makeSurePersistentPathExists(chroot)
+    zkClient.setAcl(chroot, ZooDefs.Ids.OPEN_ACL_UNSAFE.asScala)
+
+    // root is inaccessible
+    val scheme = "digest"
+    val id = "test"
+    val pwd = "12345"
+    val digest = Base64.getEncoder.encode(MessageDigest.getInstance("SHA1").digest(s"$id:$pwd".getBytes()))
+    zkClient.currentZooKeeper.addAuthInfo(scheme, digest)
+    zkClient.setAcl("/", Seq(new ACL(ZooDefs.Perms.ALL, new Id(scheme, s"$id:$digest"))))
+
+    // this client won't have access to the root, but the chroot already exists
+    val chrootClient = KafkaZkClient(zkConnect + chroot, zkAclsEnabled.getOrElse(JaasUtils.isZkSaslEnabled), zkSessionTimeout,
+      zkConnectionTimeout, zkMaxInFlightRequests, Time.SYSTEM, createChrootIfNecessary = true)
+    chrootClient.close()
+  }
+}