Status

Current state: "Under DiscussionAccepted"

Discussion thread: here

JIRA:

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

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1. Define a new Java interface for authorizer in 'clients' module in the package 'org.apache.kafka.server' similar to other server-side pluggable classes.
2. KIP-4 has added ACL-related classes in the package org.apache.kafka.common (e.g. ResourcePattern and AccessControlEntry) to support ACL management using AdminClient. We will attempt to reuse these classes wherever possible.
3. Deprecate but retain existing Scala authorizer API for backward compatibility to ensure that existing custom authorizers can be used with new brokers.
4. Provide context about the request to authorizers to enable context-specific logic based on security protocol or listener to be applied to authorization.
5. Provide additional context about the request including ApiKey and correlation id from the request header since these are useful for matching debug-level authorization logs with corresponding request logs.
6. For ACL updates, provide request context including principal requesting the update and the listener on which request arrived to enable additional validation.
7. Return individual responses for each access control entry update when multiple entries of a resource are updated. At the moment, we update the ZooKeeper node for a resource pattern multiple times when a request adds or removes multiple entries for a resource in a single update request. Since it is a common usage pattern to add or remove multiple access control entries while updating ACLs for a resource, batched updates will be supported to enable a single atomic update for each resource pattern.
8. Provide authorization usage flag to authorizers to enable authorization logs to indicate attempts to access unauthorized resources. Kafka brokers log denied operations at INFO level and allowed operations at DEBUG level with the expectation that denied operations are rare and indicate erroneous or malicious use of the system. But we currently have several uses of Authorizer#authorize for filtering accessible resources or operations, for example for regex subscription. These fill up authorization logs with denied log entries, making these logs unusable for determining actual attempts to access resources by users who don’t have appropriate permissions. Audit flag will enable the authorizer to determine the severity of denied access.
9. For authorizers that don’t store metadata in ZooKeeper, ensure that authorizer metadata for each listener is available before starting up the listener. This enables different authorization metadata stores for different listeners.
10. Rewrite Add a new out-of-the-box authorizer class SimpleAclAuthorizer to implement that implements the new authorizer interface, making use of the features supported by the new API.
11. Retain existing audit log entry format in SimpleAclAuthorizer to ensure that tools that parse these logs continue to work.
12. Enable Authorizer implementations to make use of additional Kafka interfaces similar to other pluggable callbacks. Authorizers can implement org.apache.kafka.common.Reconfigurable  to support dynamic reconfiguration without restarting the broker. Authorizers will also be provided cluster id which may be included in logs or used to support centralized ACL storage.
13. Enable asynchronous ACL updates to avoid blocking broker request threads when ACLs are updated in a remote store (e.g. a database).

Public Interfaces

Authorizer Configuration

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package org.apache.kafka.server.authorizer;

import java.io.Closeable;
import java.util.List;
import java.util.Map;
import java.util.concurrent.CompletableFutureCompletionStage;
import org.apache.kafka.common.Configurable;
import org.apache.kafka.common.acl.AclBindingEndpoint;
import org.apache.kafka.common.acl.AclBindingFilterAclBinding;
import org.apache.kafka.common.annotationacl.InterfaceStabilityAclBindingFilter;
import org.apache.kafka.common.annotation.KafkaRequestContextInterfaceStability;
import org.apache.kafka.server.BrokerInfo;
import org.apache.kafka.server.BrokerInfo.Endpoint;

/**
 *
 *
/**
 *
 * Pluggable authorizer interface for Kafka brokers.
 *
 * Startup sequence in brokers:
 * <ol>
 *   <li>Broker creates authorizer instance if configured in `authorizer.class.name`.</li>
 *   <li>Broker configures and starts authorizer instance. Authorizer implementation starts loading its metadata.</li>
 *   <li>Broker starts SocketServer to accept connections and process requests.</li>
 *   <li>For each listener, SocketServer waits for authorization metadata to be available in the
 *       authorizer before accepting connections. The future returned by {@link #start(BrokerInfoAuthorizerServerInfo)}
 *       must return only when authorizer is ready to authorize requests on the listener.</li>
 *   <li>Broker accepts connections. For each connection, broker performs authentication and then accepts Kafka requests.
 *       For each request, broker invokes {@link #authorize(KafkaRequestContextAuthorizableRequestContext, List)} to authorize
 *       actions performed by the request.</li>
 * </ol>
 *
 * Authorizer implementation class may optionally implement @{@link org.apache.kafka.common.Reconfigurable}
 * to enable dynamic reconfiguration without restarting the broker.
 * <p>
 * <b>Thread<b>Threading safetymodel:</b> All
 * <ul>
 *   <li>All authorizer operations including authorization and ACL updates must be thread-safe.
 * </p>li>
 */
@InterfaceStability.Evolving
public interface Authorizer extends Configurable, Closeable {

    /**
     * Starts loading authorization metadata and returns futures that can be used to wait until
     * metadata for authorizing requests on each listener is available. Each listener will be
     * started only after its metadata is available and authorizer is ready to start authorizing
     * requests on that listener.
     *
     * @param brokerInfo Metadata for the broker including broker id and listener endpoints
     * @return CompletableFutures for each endpoint that completes when authorizer is ready to
     *         start authorizing requests on that listener.
     */
    Map<Endpoint, CompletableFuture<Void>> start(BrokerInfo brokerInfo);

    /**
     * Authorizes the specified action. Additional metadata for the action is specified   <li>ACL update methods are asynchronous. Implementations with low update latency may return a
 *       completed future using {@link java.util.concurrent.CompletableFuture#completedFuture(Object)}.
 *       This ensures that the request will be handled synchronously by the caller without using a
 *       purgatory to wait for the result. If ACL updates require remote communication which may block,
 *       return a future that is completed asynchronously when the remote operation completes. This enables
 *       the caller to process other requests on the request threads without blocking.</li>
 *   <li>Any threads or thread pools used for processing remote operations asynchronously can be started during
 *       {@link #start(AuthorizerServerInfo)}. These threads must be shutdown during {@link Authorizer#close()}.</li>
 * </ul>
 * </p>
 */
@InterfaceStability.Evolving
public interface Authorizer extends Configurable, Closeable {

    /**
     * inStarts `requestContext`.
loading authorization metadata and  *returns futures that can be used to wait until
     * @parammetadata requestContextfor Requestauthorizing contextrequests includingon requesteach type,listener securityis protocolavailable. andEach listener will namebe
     * @paramstarted actionsonly Actionsafter beingits authorizedmetadata includingis resourceavailable and authorizer is operationready forto eachstart actionauthorizing
     * @returnrequests Liston ofthat authorizationlistener.
 results for each action in*
 the same order as the* provided@param actions
serverInfo Metadata for the broker */
including broker id and List<AuthorizationResult> authorize(KafkaRequestContext requestContext, List<Action> actions);

    /**
     * Creates new ACL bindings.
     *listener endpoints
     * @return CompletionStage for each endpoint that completes when authorizer is ready to
     * @param requestContext Request context if the ACL is beingstart createdauthorizing byrequests aon broker to handlethat listener.
     */
    Map<Endpoint, ? extends CompletionStage<Void>> a client request to create ACLs. This may be null if ACLs are created directly in ZooKeeper
     * start(AuthorizerServerInfo serverInfo);

    /**
     * Authorizes the specified action. Additional metadata for the action is specified
     * in using AclCommand`requestContext`.
     * @param<p>
 aclBindings ACL bindings to create
* This is a synchronous *
API designed for use with *locally @returncached CreateACLs. resultSince forthis eachmethod ACLis bindinginvoked inon the
 same order as in the* inputrequest list
thread while processing each request, */
implementations of this method List<AclCreateResult>should createAcls(KafkaRequestContext requestContext, List<AclBinding> aclBindings);
avoid time-consuming
    /**
     * Deletes all ACL bindingsremote communication that matchmay theblock providedrequest filtersthreads.
     *
     * @param requestContext Request context ifincluding therequest ACLtype, issecurity beingprotocol deletedand by a broker to handlelistener name
     * @param actions Actions being authorized including resource aand clientoperation request to delete ACLs. This may be null if ACLs are deleted directly in ZooKeeper
     *for each action
     * @return List of authorization results for each action in the same order as the provided actions
     */
   using AclCommand.
     * @param aclBindingFilters Filters to match ACL bindings that are to be deletedList<AuthorizationResult> authorize(AuthorizableRequestContext requestContext, List<Action> actions);

    /**
     * Creates new ACL bindings.
     * <p>
     * @returnThis Deleteis resultan forasynchronous eachAPI filterthat inenables the caller sameto orderavoid asblocking induring the update. Implementations inputof list.this
     * API can return completed futures using {@link  Each result indicates which ACL bindings were actually deleted as well as anyjava.util.concurrent.CompletableFuture#completedFuture(Object)}
     * to process the update synchronously on the request thread.
     *
     * @param requestContext Request bindingscontext thatif matchedthe butACL couldis notbeing becreated deleted.
by a broker to handle
     */
    List<AclDeleteResult> deleteAcls(KafkaRequestContext requestContext, List<AclBindingFilter> aclBindingFilters);

a client request to /**
     * Returns ACL bindings which match the provided filter.create ACLs. This may be null if ACLs are created directly in ZooKeeper
     *        using AclCommand.
     * @return@param IteratoraclBindings for ACL bindings, to create
 which may be populated lazily.*
     */
 @return Create result Iterable<AclBinding> acls(AclBindingFilter filter);
}

Request context will provided to authorizers using a new interface KafkaRequestContext. The existing class org.apache.kafka.common.requests.RequestContext will implement this interface.

package org.apache.kafka.common;

import java.net.InetAddress;
import org.apache.kafka.common.annotation.InterfaceStability;
import org.apache.kafka.common.security.auth.KafkaPrincipal;
import org.apache.kafka.common.security.auth.SecurityProtocol;

/**
 * Request context interface that provides data from request header as well as connection
 * and authentication information to plugins.
 */
@InterfaceStability.Evolving
public interface KafkaRequestContext {

    for each ACL binding in the same order as in the input list. Each result
     *         is returned as a CompletionStage that completes when the result is available.
     */
    List<? extends CompletionStage<AclCreateResult>> createAcls(AuthorizableRequestContext requestContext, List<AclBinding> aclBindings);

    /**
     * ReturnsDeletes nameall ofACL listenerbindings onthat whichmatch requestthe wasprovided receivedfilters.
     */ <p>
    String listener();

 * This is /**
an asynchronous API that enables *the Returnscaller theto securityavoid protocolblocking forduring the listenerupdate. onImplementations which request was received.of this
     */
 API can return SecurityProtocol securityProtocol();

    /**completed futures using {@link java.util.concurrent.CompletableFuture#completedFuture(Object)}
     * Returnsto authenticatedprocess principalthe forupdate thesynchronously connection on whichthe request was receivedthread.
     */
    KafkaPrincipal principal();

    /**
     * Returns client IP address from which request was sent.
     */
    InetAddress clientAddress();

    /**
     * 16-bit API key of the request from the request header. See
     * https://kafka.apache.org/protocol#protocol_api_keys for request types * @param requestContext Request context if the ACL is being deleted by a broker to handle
     *        a client request to delete ACLs. This may be null if ACLs are deleted directly in ZooKeeper
     *        using AclCommand.
     */
 @param aclBindingFilters Filters int requestType();

    /**
     * Returns a name for the request type. For fetch requests, the metrics namesto match ACL bindings that are to be deleted
     *
     * @return Delete result for each filter in the same order as in the input list.
     * FetchFollower and FetchConsumer will be used to distinguish between
Each result indicates which ACL *bindings replicawere fetchactually requestsdeleted andas clientwell fetchas requests.any
     */
    String requestName();

    /**
bindings that matched but could *not Returnsbe thedeleted. requestEach versionresult fromis thereturned requestas header.a
     */
    int requestVersion();

    /**
CompletionStage that completes   *when Returns the clientresult id from the request headeris available.
     */
    List<? extends StringCompletionStage<AclDeleteResult>> clientId(deleteAcls(AuthorizableRequestContext requestContext, List<AclBindingFilter> aclBindingFilters);

    /**
     * Returns theACL correlationbindings idwhich frommatch the requestprovided headerfilter.
     */ <p>
    int correlationId();
}

BrokerInfo provides runtime broker configuration to authorization plugins including broker id, cluster id and endpoint information.

package org.apache.kafka.server;

import java.util.Collection;
import org.apache.kafka.common.ClusterResource;
import org.apache.kafka.common.annotation.InterfaceStability;
import org.apache.kafka.common.security.auth.SecurityProtocol;

/**
 * Runtime broker configuration metadata for broker-side plugins.
 */
@InterfaceStability.Evolving
public interface BrokerInfo {

    interface Endpoint {

        String listener();

        SecurityProtocol securityProtocol();

        String host();

        int port();
    }

    ClusterResource clusterResource();

    int brokerId();

    Collection<Endpoint> endpoints();

    Endpoint interBrokerEndpoint();
}

 * This is a synchronous API designed for use with locally cached ACLs. This method is invoked on the request
     * thread while processing DescribeAcls requests and should avoid time-consuming remote communication that may
     * block request threads.
     *
     * @return Iterator for ACL bindings, which may be populated lazily.
     */
    Iterable<AclBinding> acls(AclBindingFilter filter);
}

Request context will be provided to authorizers using a new interface AuthorizableRequestContext. The existing class org.apache.kafka.common.requests.RequestContext will implement this interface. New methods may be added to this interface in future, so mock implementations using this interface should adapt to these changesAction  provides details of the action being authorized including resource and operation. Additional context including audit flag indicating authorization usage are also included, enabling access violation to be distinguished from resource filtering or optional ACLs.

package org.apache.kafka.server.authorizer;

import java.utilnet.ObjectsInetAddress;
import org.apache.kafka.common.aclannotation.AclOperationInterfaceStability;
import org.apache.kafka.common.annotation.InterfaceStability;
import org.apache.kafka.common.resource.PatternTypesecurity.auth.KafkaPrincipal;
import org.apache.kafka.common.resource.ResourcePattern;
import org.apache.kafka.common.resource.ResourceType;

@InterfaceStability.Evolving
public class Action {

    private final ResourcePattern resourcePattern;
    private final AclOperation operation;
    private final AuditFlag auditFlag;
    private final int resourceReferenceCount;

    public Action(AclOperation operation,
        ResourceType resourceType,
        String resourceName,
        AuditFlag auditFlag,
        int resourceReferenceCount) {
        this.operation = operation;
        this.resourcePattern = new ResourcePattern(resourceType, resourceName, PatternType.LITERAL);
        this.auditFlag = auditFlag;
        this.resourceReferenceCount = resourceReferenceCount;
    }security.auth.SecurityProtocol;

/**
 * Request context interface that provides data from request header as well as connection
 * and authentication information to plugins.
 */
@InterfaceStability.Evolving
public interface AuthorizableRequestContext {

    /**
     * Returns name of listener on which request was received.
     */
    String listenerName();

    /**
     * Returns the security protocol for the listener on which request was received.
     */
    SecurityProtocol securityProtocol();

    /**
     * Returns authenticated principal for the connection on which request was received.
     */
    KafkaPrincipal principal();

    /**
     * Resource on Returns client IP address from which actionrequest iswas being performedsent.
     */
    publicInetAddress ResourcePattern resourcePatternclientAddress() {;

    /**
    return resourcePattern;
    }

    /** * 16-bit API key of the request from the request header. See
     * Operation being performedhttps://kafka.apache.org/protocol#protocol_api_keys for request types.
     */
    publicint AclOperation operationrequestType() {;

    /**
     * Returns the returnrequest operation;
version from the request }header.

     */**
     * Authorization usage flag to enable authorization logs to distinguish between attemptsint requestVersion();

    /**
     * toReturns accessthe unauthorizedclient resourcesid andfrom otherthe filtering operations performed by the brokerrequest header.
     */
    publicString AuditFlag auditFlagclientId() {
        return auditFlag;
    }

    /**
     * NumberReturns of times the resourcecorrelation beingid authorized is referenced within from the request header.
 For example, a single 
     * request may reference `n` topic partitions of the same topic. Brokers will authorize the topic once
     * with `resourceReferenceCount=n`. Authorizers may include the count in audit logs.
     */
    public int resourceReferenceCountcorrelationId() {
        return resourceReferenceCount;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (!(o instanceof Action)) {;
}

AuthorizerServerInfo provides runtime broker configuration to authorization plugins including broker id, cluster id and endpoint information. New methods may be added to this interface in future, so mock implementations using this interface should adapt to these changes.

package org.apache.kafka.server.authorizer;

import java.util.Collection;
import org.apache.kafka.common.ClusterResource;
import org.apache.kafka.common.Endpoint;
import org.apache.kafka.common.annotation.InterfaceStability;

/**
 * Runtime broker configuration metadata provided to authorizers during start up.
 */
@InterfaceStability.Evolving
public interface AuthorizerServerInfo {

    /**
     * Returns cluster metadata for the broker running this authorizer including cluster id.
     */
    ClusterResource clusterResource();

    /**
     * Returns broker id. This may be returna false;
generated broker id if `broker.id` was not  }
configured.
     */
   Action thatint = brokerId(Action) o;

    /**
    return Objects.equals(this.resourcePattern, that.resourcePattern) &&
            Objects.equals(this.operation, that.operation) && * Returns endpoints for all listeners including the advertised host and port to which
     * the listener is    Objects.equals(this.auditFlag, that.auditFlag) &&bound.
     */
    Collection<Endpoint>   Objects.equals(this.resourceReferenceCount, that.resourceReferenceCountendpoints();

    }/**

    @Override
 * Returns the public int hashCode() {
        return Objects.hash(resourcePattern, operation, auditFlag);inter-broker endpoint. This is one of the endpoints returned by {@link #endpoints()}.
    }

    @Override */
    publicEndpoint String toStringinterBrokerEndpoint() {
        return "Action(" +
            ", resourcePattern='" + resourcePattern + '\'' +
            ", operation='" + operation + '\'' +
            ", auditFlag='" + auditFlag + '\'' +
            ", resourceReferenceCount='" + resourceReferenceCount + '\'' +
            ')';
    }
}

Audit flag provides additional context for audit logging:

;
}

Endpoint is added as a common class so that it may be reused in several places in the code where we use this abstraction.

package org.apache.kafka.common;

import java.util.Objects;
import java.util.Optional;

import org.apache.kafka.common.annotation.InterfaceStability;
import org.apache.kafka.common.security.auth.SecurityProtocol;

/**
 * Represents a broker endpoint.
 */

@InterfaceStability.Evolving
public class Endpoint {

    private final String listenerName;
    private final SecurityProtocol securityProtocol;
    private final String host;
    private final int port;

    public Endpoint(String listenerName, SecurityProtocol securityProtocol, String host, int port) {
        this.listenerName = listenerName;
        this.securityProtocol = securityProtocol;
        this.host = host;
        this.port = port;
    }

    /**
     * Returns the listener name of this endpoint. This is non-empty for endpoints provided

package org.apache.kafka.server.authorizer;

public enum AuditFlag {
    /**
     * Access was requested to resource. If authorization result is ALLOWED, access is granted to
     * the resource to perform the request. If DENY, request is failed with authorization failure.
     * <p>
     * Auditto logsbroker trackingplugins, ALLOWEDbut accessmay shouldbe includeempty thiswhen ifused resultin is ALLOWEDclients.
     */
 Audit logs tracking DENIEDpublic accessOptional<String> should include this if result is DENIED.listenerName() {
     * </p>
     */return Optional.ofNullable(listenerName);
    MANDATORY_AUTHORIZE,}

    /**
     * Access was requested to resource. If authorization result is ALLOWED, access is granted to
     * the resource to perform the request. If DENY, alternative authorization rules are appliedReturns the security protocol of this endpoint.
     */
    public SecurityProtocol securityProtocol() {
        return securityProtocol;
    }

    /**
     * Returns toadvertised determinehost ifname accessof isthis allowedendpoint.
     */
 <p>
   public String * For example, topic creation is allowed if user has Cluster:Create
 host() {
        return host;
    }

    /**
 permission to create any topic* orReturns the fine-grained Topic:Create permission to create topicsport to which the listener is bound.
     */
 of the requested name. Cluster:Create is an optional ACL in this case.
     * </p><p>
     * Audit logs tracking ALLOWED access should include this if result is ALLOWED.  public int port() {
        return port;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
     *  Audit logs tracking DENIED access canreturn omittrue;
 this if result is DENIED, since an alternative}
     * authorization  is used to determine access.
if (!(o instanceof Endpoint)) {
      *  </p>
    return */
false;
        OPTIONAL_AUTHORIZE,}

     /**
   Endpoint that *= Access was requested to authorized resources (e.g. to subscribe to regex pattern).(Endpoint) o;
        return Objects.equals(this.listenerName, that.listenerName) &&
     * Request is performed on resources whose authorization result is ALLOWED and the rest of
 Objects.equals(this.securityProtocol, that.securityProtocol) &&
          * the resources are filtered out. Objects.equals(this.host, that.host) &&
     * <p>
     * Audit logs tracking ALLOWED access should include this if result is ALLOWED.this.port == that.port;

    }

    @Override
    public *int Audit logs tracking DENIED access can omit this if result is DENIED since access was nothashCode() {
        return Objects.hash(listenerName, securityProtocol, host, port);
    }

    @Override
 * actually requested forpublic theString specified resource and it is filtered out.
toString() {
        return * </p>"Endpoint(" +
     */
    FILTER,

    /**
     * Request to list authorized operations. No access is actually performed by this request"listenerName='" + listenerName + '\'' +
            ", securityProtocol=" + securityProtocol +
     * based on the authorization result.
  ", host='" + *host <p>
  + '\'' +
   * Audit logs tracking ALLOWED/DENIED access can omit these since no access is performed", port=" + port +
     * as a result of this.
     * </p>')';
     */
    LIST_AUTHORIZED
}

}
}

Action  provides details of the action being authorized including resource and operation. Additional context including audit flag indicating authorization usage are also included, enabling access violation to be distinguished from resource filtering or optional ACLsAuthorize method returns individual allowed/denied results for every action. ACL create and delete operations will return any exceptions from each access control entry requested.

package org.apache.kafka.server.authorizer;

public enum AuthorizationResult {
    ALLOWED,
    DENIED
}
import java.util.Objects;
import org.apache.kafka.common.acl.AclOperation;
import org.apache.kafka.common.annotation.InterfaceStability;
import org.apache.kafka.common.resource.PatternType;
import org.apache.kafka.common.resource.ResourcePattern;
import org.apache.kafka.common.annotationresource.InterfaceStabilityResourceType;

@InterfaceStability.Evolving
public class AclCreateResultAction {

    private final ThrowableResourcePattern exceptionresourcePattern;

    public AclCreateResult() {private final AclOperation operation;
    private final int  this(null)resourceReferenceCount;
    }

private final boolean logIfAllowed;
 public AclCreateResult(Throwable exception) {
private final boolean logIfDenied;

     this.exception = exception;public Action(AclOperation operation,
    }

    /**
     * Returns any exception during create. If exception is null, the request has succeeded.
ResourcePattern resourcePattern,
            */
    public Throwable exception() {
int resourceReferenceCount,
          return exception;
    }

   boolean /**logIfAllowed,
     * Returns true if the request failed.
     */
    public boolean failed(logIfDenied) {
        return exception !this.operation = nulloperation;
    }
}

package org.apache.kafka.server.authorizer;

import java.util.Collections;
import java.util.Collection;
import org.apache.kafka.common.acl.AclBinding;
import org.apache.kafka.common.errors.ApiException;

public class AclDeleteResult {
    private final ApiException exception    this.resourcePattern = resourcePattern;
        this.logIfAllowed = logIfAllowed;
        this.logIfDenied = logIfDenied;
        this.resourceReferenceCount = resourceReferenceCount;
    private final Collection<DeletionResult> deletionResults;}

    public AclDeleteResult(ApiException exception) {
        this(Collections.emptySet(), exception);
/**
     * Resource on which action is being performed.
     }*/

    public AclDeleteResult(Collection<DeletionResult> deleteResultsResourcePattern resourcePattern() {
        this(deleteResults, null)return resourcePattern;
    }

    /**
   private AclDeleteResult(Collection<DeletionResult> deleteResults,* ApiExceptionOperation exception)being {performed.
     */
    public this.deletionResults = deleteResults;AclOperation operation() {
        this.exception = exceptionreturn operation;
    }

    /**
     * Indicates if Returnsaudit anylogs exceptiontracking whileALLOWED attemptingaccess toshould matchinclude ACLthis filteraction toif deleteresult ACLs.is
     */
 ALLOWED. The  public ApiException exception() {
        return exception;
    }

    /**
     * Returns delete result for each matching ACL bindingflag is true if access to a resource is granted while processing the request as a
     * result of this authorization. The flag is false only for requests used to describe access where
     * no operation on the resource is actually performed based on the authorization result.
     */
    public Collection<DeletionResult>boolean deletionResultslogIfAllowed() {
        return deletionResultslogIfAllowed;
    }


    /**
     * Delete result for each ACL binding that matched a delete filter. Indicates if audit logs tracking DENIED access should include this action if result is
     */
 DENIED. The flag is publictrue staticif classaccess DeletionResultto {
a resource was explicitly requested and request
  private final AclBinding aclBinding;
* is denied as a result of this privateauthorization finalrequest. ApiException exception;

     The flag is false if request was
   public DeletionResult(AclBinding aclBinding)* {
filtering out authorized resources (e.g. to subscribe to regex pattern). The flag this(aclBinding, null);is also
     * false if }

this is an optional authorization where an alternative publicresource DeletionResult(AclBinding aclBinding, ApiException exception) {
            this.aclBinding = aclBinding;authorization is
     * applied if this fails (e.g. Cluster:Create which is subsequently overridden by Topic:Create).
     */
    public boolean  this.exception = exception;
logIfDenied() {
        return }
logIfDenied;
    }

    /**
     * Number of times the *resource Returnsbeing ACLauthorized bindingis thatreferenced matchedwithin the delete filterrequest. {@link #deleted()} indicates ifFor example, a single
     * request may reference *`n` thetopic bindingpartitions wasof deleted.
the same topic. Brokers will authorize the topic  */once
     * with `resourceReferenceCount=n`. publicAuthorizers AclBindingmay aclBinding() {
            return aclBinding;include the count in audit logs.
        }

*/
    public int   /**resourceReferenceCount() {
        return *resourceReferenceCount;
 Returns exception that resulted}

 in failure to delete ACL binding. @Override
    public boolean equals(Object o) {
 */
       if public(this ApiException== exception(o) {
            return exceptiontrue;
        }

        /**
    if (!(o instanceof Action)) {
     * Returns true if ACL binding was deleted,return false otherwise.;
        }

         */Action that = (Action) o;
        public boolean deleted() {return Objects.equals(this.resourcePattern, that.resourcePattern) &&
            return exception == null;
        }
    }
}

Proposed Changes

Deprecate existing Scala Authorizer

kafka.security.auth.Authorizer will be deprecated along with all the supporting Scala classes including Resource, Operations and ResourceTypes. A new AuthorizerWrapper class will be introduced to wrap implementations using the Scala trait into the new Java interface. All usage of Authorizer (e.g. in KafkaApis) will be replaced with the new authorizer interface.

SimpleAclAuthorizer

SimpleAclAuthorizer will be updated to implement the new interface, making use of the additional request context available to improve authorization logging. This enables the authorizer to be used with the new config 'authorizer.class'. SimpleAclAuthorizer will remain a Scala class in `core`.  SimpleAclAuthorizer will continue to implement the old Scala Authorizer trait so that it can continue to be used with the old config 'authorizer.class.name', Internally, it will be handled as the new interface without a wrapper regardless of which config was used.

Optional Interfaces

Reconfigurable

kafka.server.DynamicBrokerConfig will be updated to support dynamic update of authorizers which implement org.apache.kafka.common.Reconfigurable. Authorizer implementations can react to dynamic updates of any of its configs including custom configs, avoiding broker restarts to update configs.

Compatibility, Deprecation, and Migration Plan

What impact (if any) will there be on existing users?

Existing authorizer interfaces and classes are being deprecated, but not removed. We will continue to support the same config with the old API to ensure that existing users are not impacted.

If we are changing behavior how will we phase out the older behavior?

We are deprecating the existing Scala authorizer API. These will be removed in a future release, but will continue to be supported for backward compatibility until then. Until the old authorizer is removed, no config changes are required during upgrade.

Test Plan

All the existing integration and system tests will be updated to use the new config and the new authorization class. Unit tests will be added for testing the new methods and parameters being introduced in this KIP. An additional integration test will be added to test authorizers using the old Scala API.  

Rejected Alternatives

Description of Authorizer as proposed in KIP-50

KIP-50 proposes to return a textual description of the authorizer that can be used in tools like AclCommand. Since we don’t support returning a description using AdminClient and none of the other pluggable APIs have similar support, this KIP does not add a method to return authorizer description.

Separate authorizers for each listener

Objects.equals(this.operation, that.operation) &&
            this.resourceReferenceCount == that.resourceReferenceCount &&
            this.logIfAllowed == that.logIfAllowed &&
            this.logIfDenied == that.logIfDenied;

    }

    @Override
    public int hashCode() {
        return Objects.hash(resourcePattern, operation, resourceReferenceCount, logIfAllowed, logIfDenied);
    }

    @Override
    public String toString() {
        return "Action(" +
            ", resourcePattern='" + resourcePattern + '\'' +
            ", operation='" + operation + '\'' +
            ", resourceReferenceCount='" + resourceReferenceCount + '\'' +
            ", logIfAllowed='" + logIfAllowed + '\'' +
            ", logIfDenied='" + logIfDenied + '\'' +
            ')';
    }
}

Authorize method returns individual allowed/denied results for every action.

package org.apache.kafka.server.authorizer;

public enum AuthorizationResult {
    ALLOWED,
    DENIED
}

ACL create operation returns any exception from each ACL binding requested.

package org.apache.kafka.server.authorizer;

import java.util.Optional;
import org.apache.kafka.common.annotation.InterfaceStability;
import org.apache.kafka.common.errors.ApiException;

@InterfaceStability.Evolving
public class AclCreateResult {
    public static final AclCreateResult SUCCESS = new AclCreateResult();

    private final ApiException exception;

    private AclCreateResult() {
        this(null);
    }

    public AclCreateResult(ApiException exception) {
        this.exception = exception;
    }

    /**
     * Returns any exception during create. If exception is empty, the request has succeeded.
     */
    public Optional<ApiException> exception() {
        return exception == null ? Optional.empty() : Optional.of(exception);
    }
}

ACL delete operation returns any exception from each ACL filter requested. Matching ACL bindings for each filter are returned along with any delete failure.

package org.apache.kafka.server.authorizer;

import java.util.Collections;
import java.util.Collection;
import java.util.Optional;
import org.apache.kafka.common.acl.AclBinding;
import org.apache.kafka.common.annotation.InterfaceStability;
import org.apache.kafka.common.errors.ApiException;

@InterfaceStability.Evolving
public class AclDeleteResult {
    private final ApiException exception;
    private final Collection<AclBindingDeleteResult> aclBindingDeleteResults;

    public AclDeleteResult(ApiException exception) {
        this(Collections.emptySet(), exception);
    }

    public AclDeleteResult(Collection<AclBindingDeleteResult> deleteResults) {
        this(deleteResults, null);
    }

    private AclDeleteResult(Collection<AclBindingDeleteResult> deleteResults, ApiException exception) {
        this.aclBindingDeleteResults = deleteResults;
        this.exception = exception;
    }

    /**
     * Returns any exception while attempting to match ACL filter to delete ACLs.
     */
    public Optional<ApiException> exception() {
        return exception == null ? Optional.empty() : Optional.of(exception);
    }

    /**
     * Returns delete result for each matching ACL binding.
     */
    public Collection<AclBindingDeleteResult> aclBindingDeleteResults() {
        return aclBindingDeleteResults;
    }


    /**
     * Delete result for each ACL binding that matched a delete filter.
     */
    public static class AclBindingDeleteResult {
        private final AclBinding aclBinding;
        private final ApiException exception;

        public AclBindingDeleteResult(AclBinding aclBinding) {
            this(aclBinding, null);
        }

        public AclBindingDeleteResult(AclBinding aclBinding, ApiException exception) {
            this.aclBinding = aclBinding;
            this.exception = exception;
        }

        /**
         * Returns ACL binding that matched the delete filter. {@link #deleted()} indicates if
         * the binding was deleted.
         */
        public AclBinding aclBinding() {
            return aclBinding;
        }

        /**
         * Returns any exception that resulted in failure to delete ACL binding.
         */
        public Optional<ApiException> exception() {
            return exception == null ? Optional.empty() : Optional.of(exception);
        }
    }
}

Proposed Changes

Asynchronous update requests

kafka.server.KafkaApis will be updated to handle CreateAcls and DeleteAcls requests asynchronously using a purgatory. If Authorizer.createAcls or Authorizer.deleteAcls returns any ComplettionStage that is not complete, the request will be added to a purgatory and completed when all the stages complete. Authorizer implementations with low latency updates may continue to update synchronously and return a completed future. These requests will be completed in-line and will not be added to the purgatory.

Asynchronous updates are useful for Authorizer implementations that use external stores for ACLs, for example a database. Async handling of update requests will enable Kafka brokers to handle database outages without blocking request threads. As many databases now support async APIs (https://dev.mysql.com/doc/x-devapi-userguide/en/synchronous-vs-asynchronous-execution.html, https://blogs.oracle.com/java/jdbc-next:-a-new-asynchronous-api-for-connecting-to-a-database), async update API enables authorizers to take advantage of these APIs.

Purgatory metrics will be added for ACL updates, consistent with metrics from other purgatories. Two new metrics will be added:

• kafka.server:type=DelayedOperationPurgatory,name=NumDelayedOperations,delayedOperation=acl-update
• kafka.server:type=DelayedOperationPurgatory,name=PurgatorySize,delayedOperation=acl-update

In addition to these metrics, existing request metrics for CreateAcls and DeleteAcls can be used to track the portion of time spent on async operations since local time is updated before the async wait and remote time is updated when async wait completes:

• kafka.network:type=RequestMetrics,name=LocalTimeMs,request=CreateAcls
• kafka.network:type=RequestMetrics,name=RemoteTimeMs,request=CreateAcls
• kafka.network:type=RequestMetrics,name=LocalTimeMs,request=DeleteAcls
• kafka.network:type=RequestMetrics,name=RemoteTimeMs,request=DeleteAcls

Deprecate existing Scala Authorizer Trait

kafka.security.auth.Authorizer will be deprecated along with all the supporting Scala classes including Resource, Operations and ResourceTypes. A new AuthorizerWrapper class will be introduced to wrap implementations using the Scala trait into the new Java interface. All usage of Authorizer (e.g. in KafkaApis) will be replaced with the new authorizer interface.

AclAuthorizer

A new authorizer implementation will be added. kafka.security.authorizer.AclAuthorizer will implement the new interface, making use of the additional request context available to improve authorization logging. This authorizer will be compatible with SimpleAclAuthorizer and will support all its existing configs including super.users.

SimpleAclAuthorizer

SimpleAclAuthorizer will be deprecated, but we will continue to support this implementation using the old API. Since it is part of the public API, all its public methods will be retained without change. This enables existing custom implementations that rely on this class to continue to be used.

Optional Interfaces

Reconfigurable

kafka.server.DynamicBrokerConfig will be updated to support dynamic update of authorizers which implement org.apache.kafka.common.Reconfigurable. Authorizer implementations can react to dynamic updates of any of its configs including custom configs, avoiding broker restarts to update configs.

Compatibility, Deprecation, and Migration Plan

What impact (if any) will there be on existing users?

Existing authorizer interfaces and classes are being deprecated, but not removed. We will continue to support the same config with the old API to ensure that existing users are not impacted.

If we are changing behavior how will we phase out the older behavior?

We are deprecating the existing Scala authorizer API. These will be removed in a future release, but will continue to be supported for backward compatibility until then. Until the old authorizer is removed, no config changes are required during upgrade.

Test Plan

All the existing integration and system tests will be updated to use the new config and the new authorization class. Unit tests will be added for testing the new methods and parameters being introduced in this KIP. An additional integration test will be added to test authorizers using the old Scala API.  

Rejected Alternatives

Description of Authorizer as proposed in KIP-50

KIP-50 proposes to return a textual description of the authorizer that can be used in tools like AclCommand. Since we don’t support returning a description using AdminClient and none of the other pluggable APIs have similar support, this KIP does not add a method to return authorizer description.

Separate authorizers for each listener

In some environments, authorization decisions may be dependent on the security protocol used by the client or the listener on which the request was received. We have listener prefixed configs to enable independent listener-specific configs for authentication etc. But since authorizers tend to cache a lot of metadata and need to watch for changes in metadata, a single shared instance works better for authorization. This KIP proposes a single authorizer that can use listener and security protocol provided in the authorization context to include listener-specific authorization logic.

Extend SimpleAclAuthorizer to support the new API

SimpleAclAuthorizer is part of our public API since it is in the public package kafka.security.auth. So we need to ensure that the old API is used with this authorizer if custom implementations extend this class and override specific methods. So this KIP deprecates, but retains this implementation and adds a separate implementation that uses the new API.

Make authorize() asynchronous

Authorize operations in the existing Authorizer are synchronous and this KIP proposes to continue to authorize synchronously on the request thread while processing each request. This requires all ACLs to be cached in every broker to avoid blocking request threads during authorization. To improve scalability in future, we may want to support asynchronous authorize operations that may perform remote communication, for example with an LRU cache. But asynchronous authorize operations add complexity to the Kafka implementation. Even though we may be able to use the existing purgatory, additional design work is required to figure out how this can be implemented efficiently.  So it was decided that we should keep the authorization API synchronous for now. In future, we can add async authorize as a new method on the API if requiredIn some environments, authorization decisions may be dependent on the security protocol used by the client or the listener on which the request was received. We have listener prefixed configs to enable independent listener-specific configs for authentication etc. But since authorizers tend to cache a lot of metadata and need to watch for changes in metadata, a single shared instance works better for authorization. This KIP proposes a single authorizer that can use listener and security protocol provided in the authorization context to include listener-specific authorization logic.