THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
Status
Current state: "Under Discussion"
Discussion thread: here
JIRA:
Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).
Motivation
Since the merge KAFKA-8634 (https://github.com/apache/kafka/commit/d67495d6a7f4c5f7e8736a25d6a11a1c1bef8d87) in trunk, Apache Kafka ships with Apache Zookeeper supporting TLS and Dynamic Reconfiguration (AK 2.4 ultimately shipped with ZooKeeper version 3.5.6 rather than 3.5.5, but the general functionality is the same). When doing a deployment in a security-minded environment the desire is to use TLS to encrypt communication in transit.
It is possible to enable TLS connectivity to Zookeeper from Apache Kafka 2.4 -- the problem is that configuration information has to be passed via system properties as -D command line options on the Java invocation of the broker or CLI tool (e.g. ZooKeeper Security Migration), and such -D command line options are not secure because anyone with access to the box can see the command line used to start the process; the configuration includes sensitive keystore/truststore password information, so we need a secure mechanism for passing the configuration values. The motivation for this KIP is to harden/secure the configuration mechanism for Zookeeper TLS connectivity.
With this KIP we aim to introduce the necessary changes to enable the use of secure configuration values when defining TLS encrypted channels for communications with Zookeeper. These changes will enable the secure use of TLS from brokers as well as any CLI tools that will still contain non-deprecated direct ZooKeeper communication in the next AK (AK 2.5) release.
The list of CLI tools that used non-deprecated direct ZooKeeper access in the previous AK (AK 2.4) release was as follows:
zookeeper-security-migration.sh(kafka.admin.ZSecurityMigrator)kafka-reassign-partitions.{bat,sh}(kafka.admin.ReassignPartitionsCommand)kafka-configs.{bat,sh}(kafka.admin.ConfigCommand)
Direct ZK access in #2 above is being addressed via the already-accepted KIP-455: Create an Administrative API for Replica Reassignment.
There is not yet a KIP to address direct ZK access in #3, and in fact ConfigCommand presents a bit of a conundrum because it explicitly states in a comment that a supported use case is bootstrapping a Kafka cluster with encrypted passwords in Zookeeper (see https://github.com/apache/kafka/blob/trunk/core/src/main/scala/kafka/admin/ConfigCommand.scala#L65). This is a very special use case for sure, but it does mean that it will be especially difficult to fully/100% deprecate this particular direct Zookeeper connectivity without a different storage mechanism for dynamic configuration values being available (e.g. the self-managed quorum referred to in KIP-500: Replace ZooKeeper with a Self-Managed Metadata Quorum).
It doesn't make sense to address direct ZK access in the ZkSecurityMigrator since connecting to ZooKeeper and applying/removing ACLs is the whole point of the tool. (In theory we could replace its direct ZK access in favor of a Kafka API, but that seems silly.)
ZooKeeper also supports TLS connectivity between ZK nodes for Quorum-related communication. This is configured independent of Kafka within ZooKeeper.
The class kafka.security.authorizer.AclAuthorizer talks directly to ZooKeeper, so it must be possible to configure that ZooKeeper connection for TLS as well. Note that kafka.security.auth.SimpleAclAuthorizer was deprecated in AK 2.4 (in favor of AclAuthorizer) and will not support TLS connectivity to ZooKeeper.
Goals
- Harden/secure the configuration mechanism for Zookeeper TLS connectivity from:
- Kafka Brokers (including from
kafka.security.authorizer.AclAuthorizerif/when configured) zookeeper-security-migration.shkafka-reassign-partitions.{bat,sh}and/orkafka-configs.{bat,sh}assuming direct ZooKeeper connectivity is not deprecated in the next AK release (and if so, then great – no need to do anything)
- Kafka Brokers (including from
- Add system tests to confirm the hardened/secured configuration for TLS connectivity to ZooKeeper
- Add explicit Kafka documentation on how to configure TLS connectivity to ZooKeeper
- Add a reference in the Kafka documentation to the ZooKeeper Quorum TLS configuration (https://zookeeper.apache.org/doc/r3.5.6/zookeeperAdmin.html#Communication+using+the+Netty+framework)
Out of Scope
- Zookeeper-to-Zookeeper Quorum TLS system tests and in-depth documentation (the ZooKeeper project already has such tests and documentation)
- Kafka API for
kafka.admin.ConfigCommandand deprecating its direct ZooKeeper connectivity (this must be addressed as a separate KIP)
Public Interfaces
New Broker and AclAuthorizer Configurations
The below table contains the complete list of added configs. All configs being added are optional Strings with no default value unless otherwise noted. As an example, these are some of the configs that will be introduced:
zookeeper.client.secure=truezookeeper.clientCnxnSocket=org.apache.zookeeper.ClientCnxnSocketNettyzookeeper.ssl.keyStore.location=kafka.jkszookeeper.ssl.keyStore.password=test1234zookeeper.ssl.trustStore.location=truststore.jkszookeeper.ssl.trustStore.password=test1234
Every config can be prefixed with "authorizer." for the case when kafka.security.authorizer.AclAuthorizer connects via TLS to a ZooKeeper quorum separate from the one that Kafka is using – this specific use case will be identified in the configuration by explicitly setting authorizer.zookeeper.client.secure=true. In this case the configs prefixed with "authorizer." are not "overrides" like the other authorizer ZooKeeper connectivity configs such as connection/session timeouts and max inflight requests; ZooKeeper TLS connectivity values for the authorizer are not "merged" with Kafka's ZooKeeper TLS configs (if any) because semantically the two sets of configs are for different ZooKeeper quorums and there is no guarantee that they would be applicable across the two quorums; any configs that need to be identical across the two ZooKeeper quorums will have to be repeated with and without the prefix. The same defaults described below will apply to the prefixed configs.
| Config Key | Documentation |
|---|---|
| Set client to use TLS when connecting to ZooKeeper. When true, <code>zookeeper.clientCnxnSocket</code> must be set (typically to <code>org.apache.zookeeper.ClientCnxnSocketNetty</code>); other values to set may include <include list of all other properties below> |
zookeeper.clientCnxnSocket | Typically set to <code>org.apache.zookeeper.ClientCnxnSocketNetty</code> when using TLS connectivity to ZooKeeper |
zookeeper.ssl.keyStore.location | Keystore location when using a client-side certificate with TLS connectivity to ZooKeeper. Note ZooKeeper's use of camel-case <code>keyStore</code>, which differs from Kafka. |
| Keystore password when using a client-side certificate with TLS connectivity to ZooKeeper. Note ZooKeeper's use of camel-case <code>keyStore</code>, which differs from Kafka. |
zookeeper.ssl.keyStore.type | Keystore type when using a client-side certificate with TLS connectivity to ZooKeeper. Note ZooKeeper's use of camel-case <code>keyStore</code>, which differs from Kafka. The default value of <code>null</code> means the type will be auto-detected based on the filename extension of the keystore. |
zookeeper.ssl.trustStore.location | Truststore location when using TLS connectivity to ZooKeeper. Note ZooKeeper's use of camel-case <code>trustStore</code>, which differs from Kafka. |
zookeeper.ssl.trustStore.password
| Truststore password when using TLS connectivity to ZooKeeper. Note ZooKeeper's use of camel-case <code>trustStore</code>, which differs from Kafka. |
zookeeper.ssl.trustStore.type | Truststore type when using TLS connectivity to ZooKeeper. Note ZooKeeper's use of camel-case <code>trustStore</code>, which differs from Kafka. The default value of <code>null</code> means the type will be auto-detected based on the filename extension of the truststore. |
| Specifies the protocol to be used in ZooKeeper TLS negotiation |
zookeeper.ssl.enabledProtocols | Specifies the enabled protocol(s) in ZooKeeper TLS negotiation (csv). Note ZooKeeper's use of camel-case <code>enabledProtocols</code>, which differs from Kafka. The default value of <code>null</code> means the enabled protocol will be the value of the <code>zookeeper.ssl.protocol</code> configuration property. |
zookeeper.ssl.ciphersuites | Specifies the enabled cipher suites to be used in ZooKeeper TLS negotiation (csv). The default value of <code>null</code> means the list of enabled cipher suites is determined by the Java runtime being used. |
zookeeper.ssl.context.supplier.class | Specifies the class to be used for creating SSL context in ZooKeeper TLS communication |
| Specifies whether to enable hostname verification in the ZooKeeper TLS negotiation process. Disabling it is only recommended for testing purposes. |
| Specifies whether to enable Certificate Revocation List in the ZooKeeper TLS protocols |
| Specifies whether to enable Online Certificate Status Protocol in the ZooKeeper TLS protocols |
ZooKeeper Security Migration CLI
The existing configuration option java.security.auth.login.config, used to set provide the JAAS configuration content will be kept as it is.
A new parameter will be added:
- --zk-tls-config-file: <String: Zookeeper TLS configuration file path>
This config file may contain any of the above properties to configure the TLS connection to ZooKeeper; any config(s) not in the above list will be ignored (a convenience to make it possible to pass a Broker properties file)
Config Command CLI
The same --zk-tls-config-file parameter will be added if (and only if) direct ZooKeeper connectivity for this tool is not deprecated in this Kafka release.
Reassign Partitions CLI
The same --zk-tls-config-file parameter will be added if (and only if) direct ZooKeeper connectivity for this tool is not deprecated in this Kafka release (i.e. via KIP-455: Create an Administrative API for Replica Reassignment)
Proposed Changes
The proposed changes include the public interface changes:
- New Kafka configurations, both non-prefixed as well as prefixed with "
authorizer." - A new --zk-tls-config-file parameter in the ZooKeeper Security Migration Tool and potentially the Config Command and Reassign Partitions Command CLIs if (and only if) their direct ZooKeeper connectivity is not deprecated in the next release.
The proposed changes also include the addition of:
- system tests to confirm the hardened/secured configuration for TLS connectivity to ZooKeeper
- explicit Kafka documentation on how to configure TLS connectivity to ZooKeeper
Compatibility, Deprecation, and Migration Plan
The changes are additions only, and there is no compatibility issue because the default for zookeeper.client.secure is false.
Test Plan
System tests will cover the following:
- Migrating Zookeeper/Kafka clusters from non-TLS-enabled ZooKeeper to TLS-enabled ZooKeeper
- Invoking the Zookeeper Security Migration tool against TLS-enabled ZooKeeper
Compatibility testing is unnecessary because Zookeeper TLS is not available in prior versions.
The connection between Kafka and Zookeeper is not on a critical path related to performance – brokers don't repeatedly communicate with Zookeeper as they process messages, for example – so introducing TLS encryption here does not require explicit performance testing.
Rejected Alternatives
N/A