Client to Gateway Authentication

As with Kafka brokers, Gateway brokers support multiple security schemes for Kafka clients to connect with. Each section has specific details of the options available, how they work and how to configure them. The nature of your system's requirements, design and constraints will lead you to pick the most suitable option when working with our lovely experts as part of setting up Gateway with you.

• Client to Gateway Authentication
  • Supported security protocols and authentication mechanisms
• Security protocol
  • PLAINTEXT
  • SSL
    • Mutual TLS (mTLS)
  • SASL_PLAINTEXT
    • Plain
    • OAuthbearer
  • SASL_SSL
    • Plain
    • OAuthbearer
  • DELEGATED_SASL_PLAINTEXT
  • DELEGATED_SASL_SSL
• Automatic security protocol detection (Default behavior)
• Re authentication support

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.

We can split this authentication and security configuration into two aspects

• Security protocol
• Authentication mechanism

Security protocol defines how a Kafka client and Gateway broker should communicate and secure the connection. How do we talk to each other, do we need to authenticate?. Authentication mechanism on the other hand is the part defining how a client can authenticate it self when opening the connection. How do we know each other?

Here is a quick explanation of each supported security protocol:

• PLAINTEXT: Brokers don't need client authentication; all communication is exchanged without network security.
• SSL: With SSL-only clients don't need any client authentication but communication between the client and Gateway broker will be encrypted.
• mTLS: This security protocol is not originally intended to provide authentication, but you can use the mTLS option below to enable an authentication. mTLS leverages SSL mutual authentication to identify a Kafka client. Principal for mTLS connection can be detected from the subject certificate using the same feature as in Apache Kafka, the SSL principal mapping.
• SASL PLAINTEXT: Brokers don't need any client authentication and all communication is exchanged without any network security.
• SASL SSL: Authentication from the client is mandatory against Gateway and communication will be encrypted using TLS.
• DELEGATED_SASL_PLAINTEXT: Authentication from the client is mandatory but will be forwarded to Kafka for checking. Gateway will intercept exchanged authentication data to detect authenticated principals. All communication between the client and gateway broker is exchanged without any network security. All credentials are managed by your backend kafka, we only provide authorization on the Gateway side based on the exchanged principal.

Supported security protocols and authentication mechanisms

	Clients ⟶ GW transit in plaintext	Clients ⟶ GW transit is encrypted
Anonymous access only	Security protocol: PLAINTEXT Authentication mechanism: None	Security protocol: SSL Authentication mechanism: None
Credentials managed by Gateway	Security protocol: SASL_PLAINTEXT Authentication mechanism: PLAIN	Security protocol: SASL_SSL Authentication mechanism: PLAIN
Gateway configured with Oauth	Security protocol: SASL_PLAINTEXT Authentication mechanism: OAUTHBEARER	Security protocol: SASL_SSL Authentication mechanism: OAUTHBEARER
Clients are identified by certificates (mTLS)	Not possible (mTLS means encryption)	Security protocol: SSL Authentication mechanism: MTLS
Credentials managed by Kafka	Security protocol: DELEGATED_SASL_PLAINTEXT Authentication mechanism: PLAIN or SCRAM-SHA-256 or SCRAM-SHA-512	Security protocol: DELEGATED_SASL_SSL Authentication mechanism: PLAIN or SCRAM-SHA-256 or SCRAM-SHA-512

Security protocol

The Gateway broker security scheme is defined by the GATEWAY_SECURITY_PROTOCOL configuration.

Gateway supports all the security protocols as Apache Kafka does, you can find further information regarding what they are on the Apache Kafka documentation. In addition, Gateway adds two new security protocols DELEGATED_SASL_PLAINTEXT and DELEGATED_SASL_SSL, as mentioned for delegating to Kafka.

PLAINTEXT

There is no client authentication to Gateway and all communication is exchanged without any network security.

Gateway configuration:

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.

Gateway configuration:

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 the Gateway's TLS certificate, which is stored in the keystore. More info on jks truststores here.

Mutual TLS (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 .

Gateway configuration:

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 against Gateway but all communications are exchanged without any network security. Gateway supports Plain and OAuthbearer SASL mechanisms.

Plain

Plain mechanism uses Username/Password credentials to authenticate credentials against Gateway.

Plain credentials take the form of a JWT token, these are managed in Gateway using the Admin (HTTP) API. See below for the creation of tokens.

Gateway configuration:

GATEWAY_SECURITY_PROTOCOL: SASL_PLAINTEXT
GATEWAY_USER_POOL_SECRET_KEY: yourRandom256bitKeyUsedToSignTokens

You must set GATEWAY_USER_POOL_SECRET_KEY to a random value to ensure that tokens cannot be forged. Otherwise it will use a default value for signing tokens.

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";

Note on the password :

It must be a token that is obtained by a Gateway admin via the Admin (HTTP) API as follows:

 curl \                                                                                                   --silent \
    --request POST "http://your.gateway.url:8888/admin/vclusters/v1/vcluster/passthrough/username/jdoe" \
    --user "admin:conduktor" \
    --header 'Content-Type: application/json' \
    --data-raw '{"lifeTimeSeconds": 7776000}' \
    | jq -r ".token"
eyJhbGciOiJIUzI1NiJ9.eyJ1c2VybmFtZSI6Impkb2UiLCJ2Y2x1c3RlciI6InBhc3N0aHJvdWdoIiwiZXhwIjoxNzE3NjY5NTA1fQ.9YXuxZFzMEs_-HZR8t3L39LhAVK8PJsIb5X_bHsfUEA

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

➜ echo -n 'eyJ1c2VybmFtZSI6Impkb2UiLCJ2Y2x1c3RlciI6InBhc3N0aHJvdWdoIiwiZXhwIjoxNzE3NjY5NDA4fQ' | base64 -di
{"username":"jdoe","vcluster":"passthrough","exp":1717669408}

OAuthbearer

Oauthbearer uses a OAuth2/OIDC security provider to authenticate a token in Gateway.

The Oauth credentials base is managed in the configured provider.

This mechanism will also allow you to verify some claims from your OIDC provider ( audience and issuer ).

Gateway configuration:

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";

SASL_SSL

Authentication from client is mandatory against Gateway and communication will be encrypted using TLS.

Supported authentication mechanisms

• Plain
• OAuthBearer

Plain

Plain mechanism use Username/Password credentials to authenticate credentials against Gateway.

Plain credentials are managed in Gateway using the HTTP API.

Gateway configuration:

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 must set GATEWAY_USER_POOL_SECRET_KEY to a random value to ensure that tokens cannot be forged. Otherwise it will use a default value for signing tokens.

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

OAuthbearer

Oauthbearer uses a OAuth2/OIDC security provider to authenticate a token in Gateway.

The Oauth credentials base is managed in the configured provider.

This mechanism will also allow you to verify some claims from your OIDC provider ( audience and issuer )

Gateway configuration:

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";

DELEGATED_SASL_PLAINTEXT

Authentication from client is mandatory but will be forwarded to Kafka for checking. Gateway will intercept exchanged authentication data to detect an authenticated principal.

All communication between the client and Gateway broker are exchanged without any network security.

All credentials are managed by your backing Kafka, we only provide Authorization on the Gateway side based on the exchanged principal.

Supported authentication mechanisms on the backing Kafka are:

• Plain
• Scram-sha-256
• Scram-sha-512

Gateway configuration: Using PLAIN, as used for example on Confluent Cloud:

GATEWAY_SECURITY_PROTOCOL: DELEGATED_SASL_PLAINTEXT

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="yourKafkaUser" password="yourKafkaPassword";

DELEGATED_SASL_SSL

Authentication from the client is mandatory but will be forwarded to Kafka. Gateway will intercept exchanged authentication data to detect an authenticated principal.

All communication between the client and Gateway broker will be encrypted using TLS.

All credentials are managed by your backing Kafka, we only provide Authorization on the Gateway side based on the exchanged principal.

Supported authentication mechanisms on the backing Kafka are:

• Plain
• Scram-sha-256
• Scram-sha-512

Gateway configuration: Using PLAIN, as used for example on Confluent Cloud:

GATEWAY_SECURITY_PROTOCOL: DELEGATED_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:

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

Automatic security protocol detection (Default behavior)

On startup Gateway will attempt to detect the security protocol to use based on the Kafka configuration if you don't specify any security protocol.

If there is also no security protocol on the backing Kafka cluster, then we set the security protocol to PLAINTEXT by default.

Here is our mapping from the Kafka cluster's defined protocol:

Kafka cluster security protocol	Gateway cluster inferred security protocol
SASL_SSL	DELEGATED_SASL_SSL
SASL_PLAINTEXT	DELEGATED_SASL_PLAINTEXT
SSL	SSL
PLAINTEXT	PLAINTEXT

For reference you can always see the inferred security protocol on the startup log of Gateway .

2024-03-07T15:40:12.260+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.

See KIP-368 for more details