feat: add custom oauth bearer authentication support

src/KafkaFlow.Abstractions/Authentication/IOAuthBearerAuthenticator.cs

@@ -0,0 +1,26 @@
+using System.Collections.Generic;
+
+namespace KafkaFlow.Authentication;
+
+/// <summary>
+/// Authentication handler for OAuth Bearer.
+/// </summary>
+public interface IOAuthBearerAuthenticator
+{
+    /// <summary>
+    ///     Set SASL/OAUTHBEARER token and metadata. The SASL/OAUTHBEARER token refresh callback or event handler should invoke this method upon
+    ///     success. The extension keys must not include the reserved key "`auth`", and all extension keys and values must conform to the required
+    ///     format as per https://tools.ietf.org/html/rfc7628#section-3.1.
+    /// </summary>
+    /// <param name="tokenValue">The mandatory token value to set, often (but not necessarily) a JWS compact serialization as per https://tools.ietf.org/html/rfc7515#section-3.1</param>
+    /// <param name="lifetimeMs">When the token expires, in terms of the number of milliseconds since the epoch</param>
+    /// <param name="principalName">The mandatory Kafka principal name associated with the token</param>
+    /// <param name="extensions">Optional SASL extensions dictionary, to be communicated to the broker as additional key-value pairs during the initial client response as per https://tools.ietf.org/html/rfc7628#section-3.1</param>
+    void SetToken(string tokenValue, long lifetimeMs, string principalName, IDictionary<string, string> extensions = null);
+
+    /// <summary>
+    ///     SASL/OAUTHBEARER token refresh failure indicator. The SASL/OAUTHBEARER token refresh callback or event handler should invoke this method upon failure.
+    /// </summary>
+    /// <param name="error">Mandatory human readable error reason for failing to acquire a token</param>
+    void SetTokenFailure(string error);
+}

src/KafkaFlow.Abstractions/Configuration/SaslOauthbearerMethod.cs

@@ -1,12 +1,12 @@
-namespace KafkaFlow.Configuration
-{
-    /// <summary>SaslOauthbearerMethod enum values</summary>
-    public enum SaslOauthbearerMethod
-    {
-        /// <summary>Default</summary>
-        Default,
-
-        /// <summary>Oidc</summary>
-        Oidc,
-    }
-}
+namespace KafkaFlow.Configuration
+{
+    /// <summary>SaslOauthbearerMethod enum values</summary>
+    public enum SaslOauthbearerMethod
+    {
+        /// <summary>Default</summary>
+        Default,
+
+        /// <summary>Oidc</summary>
+        Oidc,
+    }
+}

src/KafkaFlow.Abstractions/Configuration/SecurityInformation.cs

@@ -1,3 +1,6 @@
+using KafkaFlow.Authentication;
+using System;
+
 namespace KafkaFlow.Configuration;
 
 /// <summary>
@@ -249,4 +252,9 @@
     ///     importance: low
     /// </summary>
     public string SaslOauthbearerScope { get; set; }
-}
+
+    /// <summary>
+    ///     Gets or sets the OAuthBearerTokenRefreshHandler for custom OAuth authentication.
+    /// </summary>
+    public Action<IOAuthBearerAuthenticator> OAuthBearerTokenRefreshHandler { get; set; }
+}

src/KafkaFlow/Authentication/OAuthBearerAuthenticator.cs

@@ -0,0 +1,24 @@
+using System.Collections.Generic;
+using Confluent.Kafka;
+
+namespace KafkaFlow.Authentication;
+
+internal readonly struct OAuthBearerAuthenticator : IOAuthBearerAuthenticator
+{
+    private readonly IClient _client;
+
+    public OAuthBearerAuthenticator(IClient client)
+    {
+        _client = client;
+    }
+
+    public void SetToken(string tokenValue, long lifetimeMs, string principalName, IDictionary<string, string> extensions = null)
+    {
+        _client.OAuthBearerSetToken(tokenValue, lifetimeMs, principalName, extensions);
+    }
+
+    public void SetTokenFailure(string error)
+    {
+        _client.OAuthBearerSetTokenFailure(error);
+    }
+}

src/KafkaFlow/Clusters/ClusterManager.cs

@@ -5,6 +5,7 @@
 using System.Threading.Tasks;
 using Confluent.Kafka;
 using Confluent.Kafka.Admin;
+using KafkaFlow.Authentication;
 using KafkaFlow.Configuration;
 
 namespace KafkaFlow.Clusters;
@@ -32,8 +33,22 @@ public ClusterManager(ILogHandler logHandler, ClusterConfiguration configuration
 
                 config.ReadSecurityInformationFrom(configuration);
 
-                return new AdminClientBuilder(config)
-                    .Build();
+                var adminClientBuilder = new AdminClientBuilder(config);
+
+                var security = configuration.GetSecurityInformation();
+
+                if (security?.OAuthBearerTokenRefreshHandler != null)
+                {
+                    var handler = security.OAuthBearerTokenRefreshHandler;
+
+                    adminClientBuilder.SetOAuthBearerTokenRefreshHandler((client, _) =>
+                    {
+                        var authenticator = new OAuthBearerAuthenticator(client);
+                        handler(authenticator);
+                    });
+                }
+
+                return adminClientBuilder.Build();
             });
     }
 

src/KafkaFlow/Configuration/ClusterConfiguration.cs

@@ -14,6 +14,8 @@ public class ClusterConfiguration
     private readonly List<IProducerConfiguration> _producers = new();
     private readonly List<IConsumerConfiguration> _consumers = new();
     private readonly ReadOnlyCollection<TopicConfiguration> _topicsToCreateIfNotExist;
+    private SecurityInformation _securityInformation;
+    private bool _securityInformationLoaded;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="ClusterConfiguration"/> class.
@@ -103,5 +105,14 @@ public void AddProducers(IEnumerable<IProducerConfiguration> configurations) =>
     /// Gets the kafka security information
     /// </summary>
     /// <returns></returns>
-    public SecurityInformation GetSecurityInformation() => _securityInformationHandler?.Invoke();
+    public SecurityInformation GetSecurityInformation()
+    {
+        if (!_securityInformationLoaded)
+        {
+            _securityInformation = _securityInformationHandler?.Invoke();
+            _securityInformationLoaded = true;
+        }
+
+        return _securityInformation;
+    }
 }

src/KafkaFlow/Consumers/Consumer.cs

@@ -5,6 +5,7 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Confluent.Kafka;
+using KafkaFlow.Authentication;
 using KafkaFlow.Configuration;
 
 namespace KafkaFlow.Consumers;
@@ -235,25 +236,35 @@ private void EnsureConsumer()
 
         var kafkaConfig = this.Configuration.GetKafkaConfig();
 
-        var consumerBuilder = new ConsumerBuilder<byte[], byte[]>(kafkaConfig);
-
-        _consumer =
-            consumerBuilder
-                .SetPartitionsAssignedHandler(
-                    (consumer, partitions) => this.FirePartitionsAssignedHandlers(consumer, partitions))
-                .SetPartitionsRevokedHandler(
-                    (consumer, partitions) =>
-                    {
-                        this.Assignment = new List<TopicPartition>();
-                        this.Subscription = new List<string>();
-                        _currentPartitionsOffsets.Clear();
-                        _flowManager.Stop();
-
-                        _partitionsRevokedHandlers.ForEach(handler => handler(_dependencyResolver, consumer, partitions));
-                    })
-                .SetErrorHandler((consumer, error) => _errorsHandlers.ForEach(x => x(consumer, error)))
-                .SetStatisticsHandler((consumer, statistics) => _statisticsHandlers.ForEach(x => x(consumer, statistics)))
-                .Build();
+        var consumerBuilder = new ConsumerBuilder<byte[], byte[]>(kafkaConfig)
+            .SetPartitionsAssignedHandler(
+                (consumer, partitions) => this.FirePartitionsAssignedHandlers(consumer, partitions))
+            .SetPartitionsRevokedHandler(
+                (consumer, partitions) =>
+                {
+                    this.Assignment = new List<TopicPartition>();
+                    this.Subscription = new List<string>();
+                    _currentPartitionsOffsets.Clear();
+                    _flowManager.Stop();
+                    _partitionsRevokedHandlers.ForEach(handler => handler(_dependencyResolver, consumer, partitions));
+                })
+            .SetErrorHandler((consumer, error) => _errorsHandlers.ForEach(x => x(consumer, error)))
+            .SetStatisticsHandler((consumer, statistics) => _statisticsHandlers.ForEach(x => x(consumer, statistics)));
+
+        var security = this.Configuration.ClusterConfiguration.GetSecurityInformation();
+
+        if (security?.OAuthBearerTokenRefreshHandler != null)
+        {
+            var handler = security.OAuthBearerTokenRefreshHandler;
+
+            consumerBuilder.SetOAuthBearerTokenRefreshHandler((client, _) =>
+            {
+                var authenticator = new OAuthBearerAuthenticator(client);
+                handler(authenticator);
+            });
+        }
+
+        _consumer = consumerBuilder.Build();
 
         if (this.Configuration.Topics.Any())
         {

src/KafkaFlow/Producers/MessageProducer.cs

@@ -2,6 +2,7 @@
 using System.Text;
 using System.Threading.Tasks;
 using Confluent.Kafka;
+using KafkaFlow.Authentication;
 using KafkaFlow.Configuration;
 
 namespace KafkaFlow.Producers;
@@ -261,6 +262,19 @@ private IProducer<byte[], byte[]> EnsureProducer()
                         }
                     });
 
+            var security = _configuration.Cluster.GetSecurityInformation();
+
+            if (security?.OAuthBearerTokenRefreshHandler != null)
+            {
+                var handler = security.OAuthBearerTokenRefreshHandler;
+
+                producerBuilder.SetOAuthBearerTokenRefreshHandler((client, _) =>
+                {
+                    var authenticator = new OAuthBearerAuthenticator(client);
+                    handler(authenticator);
+                });
+            }
+
             return _producer = _configuration.CustomFactory(
                 producerBuilder.Build(),
                 _producerDependencyScope.Resolver);