I'm trying to set up a Kafka broker with the SASL_SSL security protocol and the PLAIN mechanism for authentication. Below is my docker-compose configuration:

services:
  zookeeper:
    image: confluentinc/cp-zookeeper:7.4.4
    container_name: zookeeper
    ports:
      - "2181:2181"
    environment:
      ZOOKEEPER_CLIENT_PORT: 2181
      ZOOKEEPER_TICK_TIME: 2000
      KAFKA_OPTS: "-Djava.security.auth.login.config=/etc/zookeeper/zookeeper_jaas.conf"
      ZOOKEEPER_AUTH_PROVIDER_1: org.apache.zookeeper.server.auth.SASLAuthenticationProvider
    volumes:
      - ./secrets:/etc/kafka/secrets:ro
      - ./secrets/zookeeper_jaas.conf:/etc/zookeeper/zookeeper_jaas.conf:ro
    networks:
      - kafka_network


  kafka:
    image: confluentinc/cp-kafka:7.4.4
    user: "0"
    container_name: kafka
    ports:
      - "9092:9092"
    environment:
      KAFKA_BROKER_ID: 1
      KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
      KAFKA_LISTENERS: SASL_SSL://kafka:9093
      KAFKA_ADVERTISED_LISTENERS: SASL_SSL://kafka:9093
      KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: SASL_SSL:SASL_SSL
      KAFKA_SSL_KEYSTORE_FILENAME: kafka.keystore.jks
      KAFKA_SSL_KEYSTORE_CREDENTIALS: keystore_creds
      KAFKA_SSL_KEY_CREDENTIALS: key_creds
      KAFKA_SSL_TRUSTSTORE_FILENAME: kafka.truststore.jks
      KAFKA_SSL_TRUSTSTORE_CREDENTIALS: truststore_creds
      KAFKA_SSL_CLIENT_AUTH: required
      KAFKA_SASL_ENABLED_MECHANISMS: PLAIN
      KAFKA_SASL_MECHANISMS: PLAIN
      KAFKA_SASL_MECHANISM_INTER_BROKER_PROTOCOL: PLAIN
      KAFKA_SECURITY_PROTOCOL: SASL_SSL
      KAFKA_AUTHORIZER_CLASS_NAME: "kafka.security.authorizer.AclAuthorizer"
      KAFKA_SUPER_USERS: "User:admin"
      KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1
      KAFKA_GROUP_INITIAL_REBALANCE_DELAY_MS: 0
      CONFLUENT_SUPPORT_METRICS_ENABLE: 'false'
      KAFKA_OPTS: "-Djava.security.auth.login.config=/etc/kafka/secrets/kafka_server_jaas.conf"
      KAFKA_INTER_BROKER_LISTENER_NAME: SASL_SSL
      KAFKA_HOST_NAME: kafka

    volumes:
      - ./secrets:/etc/kafka/secrets:ro
    depends_on:
      - zookeeper
    networks:
      - kafka_network

networks:
  kafka_network:
    driver: bridge

I've also created the following JAAS files:

zookeeper_jaas.conf:

Server {
  org.apache.zookeeper.server.auth.DigestLoginModule required
  username="admin"
  password="admin_password"
  user_admin="admin_password";
};

Client {
  org.apache.zookeeper.server.auth.DigestLoginModule required
  username="admin"
  password="admin_password";
};

kafka_server_jaas.conf:

KafkaServer {
  org.apache.kafkamon.security.plain.PlainLoginModule required
  username="admin"
  password="admin_password";
};

Client {
  org.apache.kafkamon.security.plain.PlainLoginModule required
  username="admin"
  password="admin_password";
};

When I start the containers, the Kafka broker fails with the following error in the logs:

ERROR [Controller id=1, targetBrokerId=1] Connection to node 1 (kafka/192.168.160.3:9093) failed authenticati
on due to: Authentication failed: Invalid username or password (org.apache.kafka.clients.NetworkClient)
[2025-01-17 13:45:50,896] WARN [RequestSendThread controllerId=1] Controller 1's connection to broker kafka:9093 (id: 1 rack: null) was
 unsuccessful (kafka.controller.RequestSendThread)
org.apache.kafkamon.errors.SaslAuthenticationException: Authentication failed: Invalid username or password
[2025-01-17 13:45:50,896] INFO [Controller id=1, targetBrokerId=1] Client requested connection close from node 1 (org.apache.kafka.clie
nts.NetworkClient)

What might be causing the "Invalid username or password" error, and how can I resolve it?