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Status

Current state: DraftDiscussion

Discussion thread: here [Change the link from the KIP proposal email archive to your own email thread]
JIRA: here [Change the link from KAFKA-1 to your own ticket] https://lists.apache.org/thread/hyxb9gwpsjdbxjs9rw8qsg6ws0nvlx0t

JIRA:

Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

...

With the adoption of JEP 411: Deprecate the SecurityManager for Removal in Java 17, the SecurityManager is now deprecated, and will be removed in an unknown future version.

In Java 23, the legacy APIs are now partially degraded, and throw UnsupportedOperationExceptions when a SecurityManager is not configured, so active progress is being made towards removal.

As Kafka supports multiple versions of Java (8, 11, 17, 21 for 3.x, 11, 17, 21 for 4.x), we should decide how to handle this deprecation and removal, and what replacements or mitigations we can provide for users of Kafka.

Kafka has a compile-time dependency on the AccessController  class in clients , core , and connect:runtime , and the removal of SecurityManager and it's accompanying classes would make these modules un-buildable with their current implementation.

Public Interfaces

There are multiple strategies for when to remove SecurityManager support. The following are listed from shortest to longest support period, but may overlap with one-another.

Below, "Java R" refers to the first Java version which has Removed the SecurityManager, and "Java R-1" is the last Java version which has the SecurityManager.

Option A: Remove SecurityManager support in the next major Kafka version (4.0), before support for Java 11 is dropped

Pros:

• Removes SecurityManager the earliest, allowing users with Kafka 4.x to upgrade to Java R as soon as it is released

Cons:

• Users on Java 11 (where SecurityManager was never deprecated) will experience a removal with this KIP as a prior deprecation notice

Option B: Remove SecurityManager support in the first major Kafka version which drops support for Java 11 (5.0+)

Pros:

• Users on Java 11 will not see a Kafka release without SecurityManager support

Cons:

• This may delay adoption of Java R if it is released before the Java 11 support is intended to be removed
• We will need to commit to removing support for Java 11 at some future version, like we did in KIP-750 for Java 8

Option C: Remove SecurityManager support in a major Kafka version that adds support for a Java R (5.0+)

Pros:

• This allows the project to keep a single source tree/artifacts for all Java versions

Cons:

• It will inconvenience users which do not use the SecurityManager when they try to upgrade to Java R without it being officially supported
• It may also force a major version bump when it is inconvenient for the project, and other efforts requiring a major version bump may not be ready for it
• This may force dropping support for Java 11 earlier than expected

Option D: Remove SecurityManager support in a major Kafka version which drops support for Java R-1 (6.0+)

Pros:

• This is the longest window for SecurityManager support, and would give users the most opportunity to find an alternative.

Cons:

• Requires concurrent support for SecurityManager on versions before and after the removal
• More complicated implementation, build process, or artifact distribution
• Additional maintenance burden for dual-version support

Proposed Changes

The SaslClientCallbackHandler and OAuthBearerSaslClientCallbackHandler in clients  will no longer call Subject.getSubject , and instead will use the JDK 18+ Subject.current API: https://bugs.openjdk.org/browse/JDK-8267108 . TODO: this isn't good enough, because it means that JDK 17 has no way to provide a Subject to the handlers... Does this functionality need to be removed?

The calls to AccessController.doPriviliged  in core  and connect:runtime:  will be removed, and the privileged operations will be done in the original context.

Compatibility, Deprecation, and Migration Plan

In a separate KIP, the Kafka project will choose a major version to drop support for Java 17, and make the minimum supported version 21. In this same release, we will drop support for the SecurityManager entirely from Kafka.

From this major version forward, Kafka operators will not be able to secure their clients, brokers, or connector runtimes with the SecurityManager. As soon as this KIP is approved, Kafka users should consider the SecurityManager deprecated, and begin migrating away from it to prepare for the removal.

Proposed Changes

There are two strategies for approaching the removal that we should pursue concurrently:

Remove SecurityManager support as soon as possible

As SecurityManager has not yet been removed from Java, we have the opportunity to remove it ourselves first.

For example, if SecurityManager is removed from the Kafka codebase in 4.0, and SecurityManager is removed from Java 25, users of Kafka 4.x can immediately upgrade to Java 25 without special considerations.

However, there are some constraints on how early we can remove support:

1. Java 11 still has the non-deprecated SecurityManager, and Kafka 4.0 must support Java 11. If we were to remove SecurityManager support from Kafka 4.0, users on Java 11 would experience a removal without a prior deprecation.
2. Java 17 does not have the replacement Subject API https://bugs.openjdk.org/browse/JDK-8267108 , and Kafka 4.0 must support Java 17. We would need dual support for the old and new APIs.

Therefore, we will plan to remove SecurityManager support in the Kafka major version which drops support for JDK 17.

We can notify users of this removal with a notice in the Kafka documentation, and rely on the runtime's built-in deprecation warning log messages.

Remove compile-time usages & detect SecurityManager removal at runtime

The longer it takes for Kafka to remove SecurityManager support, the more likely that the Java removal will take place before Kafka's removal is complete. To be prepared, we should anticipate that the project will need to support both versions with and without SecurityManager, using the same codebase & artifacts.

In an upcoming minor release after this KIP, the following deprecated calls will be changed to use reflection. If the legacy implementations are available and execute without throwing UnsupportedOperationException, they will be used. If not, the modern implementations will be called reflectively.

In the major release which removes SecurityManager support, the reflection will be replaced with direct calls to the modern implementations.

Compatibility, Deprecation, and Migration Plan

The static utility will be backwards-compatible, allowing the use of both the legacy SecurityManager bindings, or the modern replacements if the legacy bindings are degraded or removed.

Users upgrading to Java 17+ (in which SecurityManager was deprecated) will receive this warning message from the runtime, indicating they have a security manager dependency that will not be supported in the future. This will also serve as the runtime deprecation notice for Kafka.

WARNING: A command line option has enabled the Security Manager
WARNING: The Security Manager is deprecated and will be removed in a future release

WARNING: A terminally deprecated method in java.lang.System has been called
WARNING: System::setSecurityManager has been called by %s
WARNING: Please consider reporting this to the maintainers of %s
WARNING: System::setSecurityManager will be removed in a future release

Users upgrading to a version of Java Users upgrading to a version of Java or Kafka without SecurityManager support will need to disable their security manager implementations/configurations entirely. Once the java.security.manager property is not specified, some or all of the legacy methods may throw UnsupportedOperationException, which will cause the new implementations to be used instead.

Removing SecurityManager support is a breaking change and will happen in a major version. Users upgrading to Java 17+ (in which SecurityManager was deprecated) already receive a warning message on startup. We can additionally include a warning log in the next minor release that SecurityManager will be removed in a future Kafka version, and inform users of the removal schedule specified in this KIPa version of Kafka without SecurityManager support will need to disable their security manager implementations/configurations entirely. This version will have no calls to the legacy methods at all, and will always use the new versions.

Test Plan

There are currently no tests exercising the SecurityManager interface in Kafka, and no new tests for the end-to-end behavior will be added for this project.

Further tests will compare the reflective implementations to the old and new APIs. This is to ensure that changing the legacy APIs to reflection, and that later when the reflection is replaced with the new APIs, the behavior will stay the same throughout. These tests can mock the AccessController and Subject classes to make it appear that the removal has taken place.

Rejected Alternatives

Wait until SecurityManager is removed to change the implementations (do nothing)

When the first Java version without SecurityManager is released, there will have already been a number of Kafka minor and patch releases made. All of these will be unable to run with the new Java version, regardless of if the user was using the SecurityManager at all. This also includes users of the clients, who will be unable to run in the latest Java version until the clients have been released again.

Similarly, developers will be unable to build older branches of Kafka with the new Java version, and this will be generally inconvenient. When we front-load the effort in this migration, we can ensure that when the removal takes place, the most recent Kafka releases are already compatible.

Since removing SecurityManager is a breaking change, we would have to either delay support for the new Java version significantly, or perform a major release of Kafka when we might not be prepared for it. These negatives outweigh the maintenance burden of making these function calls reflective.

Add the reflective utility, but follow the Java upstream's removal schedule

The reflective utility is a harmful piece of tech debt, and should be removed as early as possible. If we do not remove SecurityManager support in the Kafka project, we will be required to maintain the reflective utility until we no longer support JREs that have the SecurityManager.

For example, if Java 25 removes SecurityManager, we would need to maintain the reflective utility until Java 25 is the minimum supported version, which could be several years after Java 21 becomes the minimum supported version. If the upstream decides to remove SecurityManager support later, the Kafka project would be responsible for the tech debt for longer as well.

Removing our support for SecurityManager gives us control over the timeline with which to pay off this tech debt, and supports the Java community's goal of removing the functionality promptly.

Set a removal date for Java 11 / Java 17 support

This should be delegated to another KIP with a dedicated discussion, and the removal of SecurityManager support can be included in whatever version changes the minimum java version to 21.

Implement a alternative to the SecurityManager for use with Kafka

The SecurityManager is a flawed design, and we should not replicate it or try to solve those problems in a similar way. Instead we should encourage users to use the process boundary as a security boundaryIf there are alternative ways of accomplishing the same thing, what were they? The purpose of this section is to motivate why the design is the way it is and not some other way.