4. Configure Gateway to accept client connections

Gateway brokers support multiple security schemes for Kafka clients to connect with. Each section has specific details of the available options, how they work and how to configure them. Pick the most suitable option based on the nature of your system’s requirements, design and constraints. The authentication phase on Gateway is part of the initial communication handling by Gateway to handshake, and authenticate, a Kafka client. This phase manages the encryption of the network communication and how to identify a client. All open connections in Gateway result in a Principal that represents the authenticated identity of the Kafka client. Configuring Gateway client connections involves two key decisions:

Security mode (GATEWAY_SECURITY_MODE): defines where authentication and authorization take place - Gateway or Kafka.
Security protocol (GATEWAY_SECURITY_PROTOCOL): defines how clients communicate and authenticate with Gateway.

Security mode

The GATEWAY_SECURITY_MODE environment variable determines where authentication and authorization take place. Gateway supports two modes:

GATEWAY_MANAGED

Gateway handles authentication and authorization. Use this mode when:

You want Gateway to manage clients’ credentials using local service accounts, or external ones from your identity provider (for OIDC) or certificates (for mTLS)
You need Gateway to enforce ACLs
You want the Gateway to be an abstraction layer that manages its own identities and ACLs

Compatible security protocols: PLAINTEXT, SSL, SASL_PLAINTEXT, SASL_SSL ACL behavior: ACLs are enabled by default on the passthrough virtual cluster. You can change this using GATEWAY_ACL_ENABLED. Example configuration:

GATEWAY_SECURITY_MODE: GATEWAY_MANAGED
GATEWAY_SECURITY_PROTOCOL: SASL_SSL

KAFKA_MANAGED

Kafka handles authentication and authorization. Gateway forwards client credentials to the backing Kafka cluster. Use this mode when:

Your backing Kafka cluster manages all credentials
You want clients to use their existing Kafka credentials through Gateway
You need Gateway to respect Kafka’s ACLs and permissions

Compatible security protocols: SASL_PLAINTEXT, SASL_SSL only

KAFKA_MANAGED mode is incompatible with PLAINTEXT or SSL security protocols because these protocols don’t support credential forwarding to Kafka.

ACL behavior: ACLs are disabled by default on the passthrough virtual cluster because Kafka manages authorization. You can change this in the virtual cluster properties. Example configuration:

GATEWAY_SECURITY_MODE: KAFKA_MANAGED
GATEWAY_SECURITY_PROTOCOL: SASL_SSL

As of Gateway 3.10.0, DELEGATED_SASL_PLAINTEXT and DELEGATED_SASL_SSL are deprecated. Use GATEWAY_SECURITY_MODE: KAFKA_MANAGED with GATEWAY_SECURITY_PROTOCOL: SASL_PLAINTEXT or SASL_SSL instead. See the migration guide.

Security protocols

Gateway supports the following security protocols for client connections:

	Clients ⟶ GW transit in plaintext	Clients ⟶ GW transit is encrypted
Anonymous access only	Security mode: `GATEWAY_MANAGED` Security protocol: `PLAINTEXT` Authentication mechanism: `None`	Security mode: `GATEWAY_MANAGED` Security protocol: `SSL` Authentication mechanism: `None`
Credentials managed by Gateway	Security mode: `GATEWAY_MANAGED` Security protocol: `SASL_PLAINTEXT` Authentication mechanism: `PLAIN`	Security mode: `GATEWAY_MANAGED` Security protocol: `SASL_SSL` Authentication mechanism: `PLAIN`
Gateway configured with OAuth	Security mode: `GATEWAY_MANAGED` Security protocol: `SASL_PLAINTEXT` Authentication mechanism: `OAUTHBEARER`	Security mode: `GATEWAY_MANAGED` Security protocol: `SASL_SSL` Authentication mechanism: `OAUTHBEARER`
Clients are identified by certificates (mTLS)	Not possible (mTLS requires encryption)	Security mode: `GATEWAY_MANAGED` Security protocol: `SSL` Authentication mechanism: `MTLS`
Credentials managed by Kafka	Security mode: `KAFKA_MANAGED` Security protocol: `SASL_PLAINTEXT` Authentication mechanism: `PLAIN`, `SCRAM-SHA-256`, `SCRAM-SHA-512`, `OAUTHBEARER` or `AWS_MSK_IAM`	Security mode: `KAFKA_MANAGED` Security protocol: `SASL_SSL` Authentication mechanism: `PLAIN`, `SCRAM-SHA-256`, `SCRAM-SHA-512`, `OAUTHBEARER` or `AWS_MSK_IAM`

Configure security protocol

The GATEWAY_SECURITY_PROTOCOL environment variable defines how clients communicate with Gateway.

You don’t set GATEWAY_SASL_MECHANISM - this environment variable does not exist. Gateway automatically detects the authentication mechanism based on how the client presents itself. For example, if a client uses OAUTHBEARER, Gateway uses the OAuth configuration. If a client uses PLAIN, Gateway validates credentials based on the security mode.

Gateway supports all standard Kafka security protocols. The following sections show configuration examples for each protocol with both security modes where applicable.

PLAINTEXT

There is no client authentication to Gateway and all communication is exchanged without any network security. Security mode: GATEWAY_MANAGED only Gateway configuration:

GATEWAY_SECURITY_MODE: GATEWAY_MANAGED
GATEWAY_SECURITY_PROTOCOL: PLAINTEXT

Client configuration:

bootstrap.servers=your.gateway.hostname:9092
security.protocol=PLAINTEXT

SSL

With SSL only, there is no client authentication, but communication between the client and Gateway broker will be encrypted. Security mode: GATEWAY_MANAGED only Gateway configuration:

GATEWAY_SECURITY_MODE: GATEWAY_MANAGED
GATEWAY_SECURITY_PROTOCOL: SSL
GATEWAY_SSL_KEY_STORE_PATH: /path/to/your/keystore.jks
GATEWAY_SSL_KEY_STORE_PASSWORD: yourKeystorePassword
GATEWAY_SSL_KEY_PASSWORD: yourKeyPassword

Client configuration:

bootstrap.servers=your.gateway.hostname:9092
security.protocol=SSL
ssl.truststore.location=/path/to/your/truststore.jks
ssl.truststore.password=yourTruststorePassword
ssl.protocol=TLSv1.3

The truststore contains certificates from trusted Certificate Authorities (CAs) used to verify Gateway’s TLS certificate, which is stored in the keystore. Find out more about JKS truststores.

mTLS

Mutual TLS leverages client side certificates to authenticate a Kafka client. Principal for an mTLS connection can be detected from the subject of the certificate using the same feature as Apache Kafka, the SSL principal mapping. Security mode: GATEWAY_MANAGED only Gateway configuration:

GATEWAY_SECURITY_MODE: GATEWAY_MANAGED
GATEWAY_SECURITY_PROTOCOL: SSL
GATEWAY_SSL_CLIENT_AUTH: REQUIRE
GATEWAY_SSL_KEY_STORE_PATH: /path/to/your/keystore.jks
GATEWAY_SSL_KEY_STORE_PASSWORD: yourKeystorePassword
GATEWAY_SSL_KEY_PASSWORD: yourKeyPassword
GATEWAY_SSL_TRUST_STORE_PATH: /path/to/your/truststore.jks
GATEWAY_SSL_TRUST_STORE_PASSWORD: yourTrustStorePassword

Client configuration:

bootstrap.servers=your.gateway.hostname:9093
security.protocol=SSL
ssl.keystore.type=PEM
ssl.keystore.key=/path/to/your/client.key
ssl.keystore.certificate.chain=/path/to/your/client.crt
ssl.truststore.type=PEM
ssl.truststore.certificates=/path/to/your/ca.crt
ssl.protocol=TLSv1.3
ssl.client.auth=required

The server CA certificate here is provided as a PEM file as well as the client’s certificates (ssl.keystore.xx keys). Jks could also be used for both client and server side authentication.

SASL_PLAINTEXT

Authentication from the client is mandatory but all communications are exchanged without any network security. Security mode: GATEWAY_MANAGED or KAFKA_MANAGED

Gateway-managed (PLAIN mechanism)

Plain mechanism uses username/password credentials to authenticate against Gateway. Credentials take the form of a JWT token managed in Gateway using the Admin (HTTP) API. Gateway configuration:

GATEWAY_SECURITY_MODE: GATEWAY_MANAGED
GATEWAY_SECURITY_PROTOCOL: SASL_PLAINTEXT
GATEWAY_USER_POOL_SECRET_KEY: yourRandom256bitKeyUsedToSignTokens

TheGATEWAY_USER_POOL_SECRET_KEY has to be set to a random base64 encoded value of 256bits long to ensure that tokens aren’t forged. For example: openssl rand -base64 32. Otherwise, a default value for signing tokens will be used. Client configuration:

bootstrap.servers=your.gateway.hostname:9092
security.protocol=SASL_PLAINTEXT
sasl.mechanism=PLAIN
sasl.jaas.config=org.apache.kafka.common.security.plain.PlainLoginModule required \
  username="yourUsername" \
  password="yourToken";

It has to be a token that’s obtained by a Gateway admin via the Admin (HTTP) API, as follows:

Create the service account, the username

Request:

curl \
  --request PUT \
  --url 'http://localhost:8888/gateway/v2/service-account' \
  --user admin:conduktor \
  --header 'Content-Type: application/json' \
  --data-raw '{
    "kind" : "GatewayServiceAccount",
    "apiVersion" : "gateway/v2",
    "metadata" : {
      "name" : "jdoe",
      "vCluster" : "passthrough"
    },
    "spec" : { "type" : "LOCAL" }'

Response:

{
  "resource" : {
    "kind" : "GatewayServiceAccount",
    "apiVersion" : "gateway/v2",
    "metadata" : {
      "name" : "jdoe",
      "vCluster" : "passthrough"
    },
    "spec" : {
      "type" : "LOCAL"
    }
  },
  "upsertResult" : "CREATED"
}

Generate a token for the service account, the password

Request:

curl \
  --silent \
  --request POST \
  --url 'http://localhost:8888/gateway/v2/token' \
  --header 'Authorization: Basic YWRtaW46Y29uZHVrdG9y' \
  --header 'Content-Type: application/json' \
  --data-raw '{
    "username": "jdoe",
    "vCluster": "passthrough",
    "lifeTimeSeconds": 3600000
  }'

{"token":"eyJhbGciOiJIUzI1NiJ9.eyJ1c2VybmFtZSI6Impkb2UiLCJ2Y2x1c3RlciI6InBhc3N0aHJvdWdoIiwiZXhwIjoxNzQ1MzY1OTcxfQ.zPPiD17MiRnXyHJw07Cx4SKPySDi_ErJrXmi5BycR04"}

The token conforms to the JWT token specification. The JWT payload contains the username, the vCluster and the expiration date:

jwt decode eyJhbGciOiJIUzI1NiJ9.eyJ1c2VybmFtZSI6Impkb2UiLCJ2Y2x1c3RlciI6InBhc3N0aHJvdWdoIiwiZXhwIjoxNzQ1MzY1OTcxfQ.zPPiD17MiRnXyHJw07Cx4SKPySDi_ErJrXmi5BycR04

Token claims
------------
{
  "exp": 1745365971,
  "username": "jdoe",
  "vcluster": "passthrough"
}

Gateway-managed (OAUTHBEARER mechanism)

OAuthbearer uses an OAuth2/OIDC security provider to authenticate a token in Gateway. The OAuth credentials base is managed in the configured provider. This mechanism also allows you to verify claims from your OIDC provider (audience and issuer). Gateway configuration:

GATEWAY_SECURITY_MODE: GATEWAY_MANAGED
GATEWAY_SECURITY_PROTOCOL: SASL_PLAINTEXT
GATEWAY_OAUTH_JWKS_URL: https://login.microsoftonline.com/common/discovery/keys
GATEWAY_OAUTH_EXPECTED_ISSUER: https://sts.windows.net/xxxxxxxx-df00-48cd-805b-1ebe914e8b11/
GATEWAY_OAUTH_EXPECTED_AUDIENCES: "[00000002-0000-0000-c000-000000000000]"

Client configuration:

bootstrap.servers=your.gateway.hostname:9092
security.protocol=SASL_PLAINTEXT
sasl.mechanism=OAUTHBEARER
sasl.login.callback.handler.class=org.apache.kafka.common.security.oauthbearer.secured.OAuthBearerLoginCallbackHandler
sasl.oauthbearer.token.endpoint.url=https://login.microsoftonline.com/xxxxxxxx-df00-48cd-805b-1ebe914e8b11/oauth2/token
sasl.jaas.config=org.apache.kafka.common.security.oauthbearer.OAuthBearerLoginModule required \
 clientId="yourClientID" \
  clientSecret="yourClientSecret" \
  scope=".default";

Kafka-managed

Gateway forwards client credentials to the backing Kafka cluster for authentication. Credentials are managed by your backing Kafka cluster. Supported SASL mechanisms: PLAIN, SCRAM-SHA-256, SCRAM-SHA-512, OAUTHBEARER, AWS_MSK_IAM Gateway configuration:

GATEWAY_SECURITY_MODE: KAFKA_MANAGED
GATEWAY_SECURITY_PROTOCOL: SASL_PLAINTEXT

Client configuration (using PLAIN mechanism as an example):

bootstrap.servers=your.gateway.hostname:9092
security.protocol=SASL_PLAINTEXT
sasl.mechanism=PLAIN
sasl.jaas.config=org.apache.kafka.common.security.plain.PlainLoginModule required username="yourKafkaUser" password="yourKafkaPassword";

SASL_SSL

Authentication from client is mandatory and communication will be encrypted using TLS. Security mode: GATEWAY_MANAGED or KAFKA_MANAGED

Gateway-managed (PLAIN mechanism)

Plain mechanism uses username/password credentials to authenticate against Gateway. Credentials are managed in Gateway using the HTTP API. Gateway configuration:

GATEWAY_SECURITY_MODE: GATEWAY_MANAGED
GATEWAY_SECURITY_PROTOCOL: SASL_SSL
GATEWAY_USER_POOL_SECRET_KEY: yourRandom256bitKeyUsedToSignTokens
GATEWAY_SSL_KEY_STORE_PATH: /path/to/your/keystore.jks
GATEWAY_SSL_KEY_STORE_PASSWORD: yourKeystorePassword
GATEWAY_SSL_KEY_PASSWORD: yourKeyPassword

You have to set GATEWAY_USER_POOL_SECRET_KEY to a random value to ensure that tokens cannot be forged. Otherwise, a default value for signing tokens will be used. Client configuration:

bootstrap.servers=your.gateway.hostname:9093
security.protocol=SASL_SSL
sasl.mechanism=PLAIN
ssl.truststore.location=/path/to/your/truststore.jks
ssl.truststore.password=yourTruststorePassword
sasl.jaas.config=org.apache.kafka.common.security.plain.PlainLoginModule required \
  username="yourUsername" \
  password="yourToken";

See the above section for requirements on how to create tokens using the Admin (HTTP) API.

Gateway-managed (OAUTHBEARER mechanism)

GATEWAY_SECURITY_MODE: GATEWAY_MANAGED
GATEWAY_SECURITY_PROTOCOL: SASL_SSL
GATEWAY_OAUTH_JWKS_URL: https://login.microsoftonline.com/common/discovery/keys
GATEWAY_OAUTH_EXPECTED_ISSUER: https://sts.windows.net/xxxxxxxx-df00-48cd-805b-1ebe914e8b11/
GATEWAY_OAUTH_EXPECTED_AUDIENCES: "[00000002-0000-0000-c000-000000000000]"
GATEWAY_SSL_KEY_STORE_PATH: /path/to/your/keystore.jks
GATEWAY_SSL_KEY_STORE_PASSWORD: yourKeystorePassword
GATEWAY_SSL_KEY_PASSWORD: yourKeyPassword

Client configuration:

bootstrap.servers=your.gateway.hostname:9092
security.protocol=SASL_SSL
sasl.mechanism=OAUTHBEARER
ssl.truststore.location=/path/to/your/truststore.jks
ssl.truststore.password=yourTruststorePassword
sasl.login.callback.handler.class=org.apache.kafka.common.security.oauthbearer.secured.OAuthBearerLoginCallbackHandler
sasl.oauthbearer.token.endpoint.url=https://login.microsoftonline.com/xxxxxxxx-df00-48cd-805b-1ebe914e8b11/oauth2/token
sasl.jaas.config=org.apache.kafka.common.security.oauthbearer.OAuthBearerLoginModule required \
  clientId="yourClientID" \
  clientSecret="yourClientSecret" \
  scope=".default";

Kafka-managed

GATEWAY_SECURITY_MODE: KAFKA_MANAGED
GATEWAY_SECURITY_PROTOCOL: SASL_SSL
GATEWAY_SSL_KEY_STORE_PATH: /path/to/your/keystore.jks
GATEWAY_SSL_KEY_STORE_PASSWORD: yourKeystorePassword
GATEWAY_SSL_KEY_PASSWORD: yourKeyPassword

Client configuration (using PLAIN mechanism as an example):

bootstrap.servers=your.gateway.hostname:9092
security.protocol=SASL_SSL
sasl.mechanism=PLAIN
ssl.truststore.location=/path/to/your/truststore.jks
ssl.truststore.password=yourTruststorePassword
sasl.jaas.config=org.apache.kafka.common.security.plain.PlainLoginModule required username="yourKafkaUser" password="yourKafkaPassword";

Principal resolver

When using Confluent Cloud authentication with Kafka-managed mode, Gateway supports automatically resolving API keys to their associated service account. This feature enhances security and improves usability by working with the service account principals instead of raw API keys. See the principal resolver environment variables. Gateway configuration using environment variables:

GATEWAY_PRINCIPAL_RESOLVER: CONFLUENT_CLOUD
GATEWAY_CONFLUENT_CLOUD_API_KEY: your-api-key
GATEWAY_CONFLUENT_CLOUD_API_SECRET: your-api-secret
GATEWAY_CONFLUENT_CLOUD_CACHE_SIZE: 1000 # default
GATEWAY_CONFLUENT_CLOUD_CACHE_EXPIRY_MS: 86400000 # 1 day default

Gateway configuration using a configuration file

authenticationConfig:
  principalResolver: CONFLUENT_CLOUD
  confluentCloud:
    apiKey: ${GATEWAY_CONFLUENT_CLOUD_API_KEY}
    apiSecret: ${GATEWAY_CONFLUENT_CLOUD_API_SECRET}
    cacheConfig:
      maxSize: ${GATEWAY_CONFLUENT_CLOUD_CACHE_SIZE|1000}
      ttlMs: ${GATEWAY_CONFLUENT_CLOUD_CACHE_EXPIRY_MS|86400000} # 1 day

The value of GATEWAY_CONFLUENT_CLOUD_API_KEY has to be a Confluent Cloud API key because it will be used to access the Confluent Cloud API. Find out more about Confluent Cloud API keys.

When the principal resolver is configured, Gateway will automatically resolve Kafka cluster API keys (like XIGMNERQXOUKXDQU) to their associated owner, which will be either the user (e.g. u-12345) or the service account (e.g. sa-72839j).

Authentication flow

Automatic security detection (default behavior)

If you don’t specify GATEWAY_SECURITY_MODE or GATEWAY_SECURITY_PROTOCOL, Gateway will attempt to detect them on startup based on the backing Kafka cluster’s configuration. If no security protocol is configured on the backing Kafka cluster, Gateway defaults to PLAINTEXT with GATEWAY_MANAGED mode. Here’s how Gateway infers the security configuration from the Kafka cluster:

Kafka cluster security protocol	Inferred GATEWAY_SECURITY_MODE	Inferred GATEWAY_SECURITY_PROTOCOL
SASL_SSL	KAFKA_MANAGED	SASL_SSL
SASL_PLAINTEXT	KAFKA_MANAGED	SASL_PLAINTEXT
SSL	GATEWAY_MANAGED	SSL
PLAINTEXT	GATEWAY_MANAGED	PLAINTEXT

You can always see the inferred security configuration in the startup logs for Gateway.

2025-03-07T15:40:12.260+0100 [      main] [INFO ] [Bootstrap:70] - Computed configuration :
---
gatewayClusterId: "gateway"
...
authenticationConfig:
  securityProtocol: "SASL_PLAINTEXT"
  sslConfig:
...

Re-authentication support

We support Apache Kafka re-authentication as Kafka brokers. Find out more about KIP-368.

Conduktor in production

Deploy Console

Deploy Gateway

Initial setup

4. Configure Gateway to accept client connections

Security mode

GATEWAY_MANAGED

KAFKA_MANAGED

Security protocols

Configure security protocol

PLAINTEXT

SSL

mTLS

SASL_PLAINTEXT

Gateway-managed (PLAIN mechanism)

Gateway-managed (OAUTHBEARER mechanism)

Kafka-managed

SASL_SSL

Gateway-managed (PLAIN mechanism)

Gateway-managed (OAUTHBEARER mechanism)

Kafka-managed

Principal resolver

Authentication flow

Automatic security detection (default behavior)

Re-authentication support

Conduktor in production

Deploy Console

Deploy Gateway

Initial setup

​Security mode

​GATEWAY_MANAGED

​KAFKA_MANAGED

​Security protocols

​Configure security protocol

​PLAINTEXT

​SSL

​mTLS

​SASL_PLAINTEXT

​Gateway-managed (PLAIN mechanism)

​Gateway-managed (OAUTHBEARER mechanism)

​Kafka-managed

​SASL_SSL

​Gateway-managed (PLAIN mechanism)

​Gateway-managed (OAUTHBEARER mechanism)

​Kafka-managed

​Principal resolver

​Authentication flow

​Automatic security detection (default behavior)

​Re-authentication support

​Related resources

Security mode

GATEWAY_MANAGED

KAFKA_MANAGED

Security protocols

Configure security protocol

PLAINTEXT

SSL

mTLS

SASL_PLAINTEXT

Gateway-managed (PLAIN mechanism)

Gateway-managed (OAUTHBEARER mechanism)

Kafka-managed

SASL_SSL

Gateway-managed (PLAIN mechanism)

Gateway-managed (OAUTHBEARER mechanism)

Kafka-managed

Principal resolver

Authentication flow

Automatic security detection (default behavior)

Re-authentication support

Related resources