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Secure client communication

Zeebe supports transport layer security (TLS v1.3) between the gateway and all the officially supported clients. In this section, we will review how to configure these components.

Gateway​

TLS in the gateway is disabled by default. This means that if you are just experimenting with Zeebe or in development, there is no configuration needed. However, if you want to enable authentication you can configure Zeebe in the security section of the configuration files. The following configurations are present in both gateway.yaml.template and broker.standalone.yaml.template, the file you should edit depends on whether you are using a standalone gateway or an embedded gateway.

---
security:
  # Enables TLS authentication between clients and the gateway
  enabled: false

  # Sets the path to the certificate chain file
  certificateChainPath:

  # Sets the path to the private key file location
  privateKeyPath:

enabled should be either true or false, where true will enable TLS authentication between client and gateway, and false will disable it. certificateChainPath and privateKeyPath are used to configure the certificate with which the server will authenticate itself. certificateChainPath should be a file path pointing to a certificate chain in PEM format representing the server's certificate, and privateKeyPath is a file path pointing to the certificate's PKCS8 private key, also in PEM format.

Additionally, as you can see in the configuration file, each value can also be configured through an environment variable. The environment variable to use again depends on whether you are using a standalone gateway or an embedded gateway.

Clients​

Unlike the gateway, TLS is enabled by default in all of Zeebe's supported clients. The following sections show how to disable or properly configure each client.

note

Disabling TLS should only be done for testing or development. During production deployments, clients and gateways should be properly configured to establish secure connections.

Java​

Without any configuration, the client looks in the system's certificate store for a CA certificate with which to validate the gateway's certificate chain. If you wish to use TLS without having to install a certificate in client's system, you can specify a CA certificate:

public class SecureClient {
    public static void main(final String[] args) {
        final ZeebeClient client = ZeebeClient.newClientBuilder().caCertificatePath("path/to/certificate").build();

        // ...
    }
}

Alternatively, use the ZEEBE_CA_CERTIFICATE_PATH environment variable to override the code configuration.

To disable TLS in a Java client, use the .usePlaintext() option:

public class InsecureClient {
    public static void main(final String[] args) {
        final ZeebeClient client = ZeebeClient.newClientBuilder().usePlaintext().build();

        // ...
    }
}

Alternatively, use the ZEEBE_INSECURE_CONNECTION environment variable to override the code configuration. To enable an insecure connection, set it to true. To use a secure connection, set it to any non-empty value other than true. Setting the environment variable to an empty string is equivalent to unsetting it.

Go​

Similarly to the Java client, if no CA certificate is specified, the client will look in the default location for a CA certificate with which to validate the gateway's certificate chain. It's also possible to specify a path to a CA certificate in the Go client:

package test

import (
    "github.com/camunda-cloud/zeebe/clients/go/zbc"
)


func main() {
    client, err := zbc.NewClient(&zbc.ClientConfig{
        CaCertificatePath: "path/to/certificate",
    })

    // ...
}

To disable TLS, execute the following:

package test

import (
    "github.com/camunda-cloud/zeebe/clients/go/zbc"
)


func main() {
    client, err := zbc.NewClient(&zbc.ClientConfig{
        UsePlaintextConnection: true,
    })

  // ...
}

As in the Java client, you can use the ZEEBE_INSECURE_CONNECTION and ZEEBE_CA_CERTIFICATE_PATH to override these configurations.

zbctl​

To configure zbctl to use a path to a CA certificate:

./zbctl --certPath /my/certificate/location <command> [arguments]

To configure zbctl to disable TLS:

./zbctl --insecure <command> [arguments]

Since zbctl is based on the Go client, setting the appropriate environment variables will override these parameters.

Self signed certificates​

It may be useful, for testing or development purposes, to use TLS between the client and the gateway; to simplify things, we can use self-signed certificates for this.

Testing & example​

To generate your own self-signed certificates for testing/development, you will need openssl install on your local machine. Then you can run:

openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -sha256 -days 365 --nodes -addext 'subjectAltName=IP:127.0.0.1'

This will generate a new certificate, cert.pem, and a new passwordless key, key.pem.

danger

Do not use these in production! Again, this is for development and testing purposes only.

Then start up your gateway with the certificate and key specified above. For example, if we run a broker with an embedded gateway directly using Docker:

docker run -p 26500:26500 -e ZEEBE_BROKER_NETWORK_HOST=0.0.0.0 -e ZEEBE_BROKER_GATEWAY_SECURITY_ENABLED=true -e ZEEBE_BROKER_GATEWAY_SECURITY_CERTIFICATECHAINPATH=/usr/local/zeebe/cert.pem -e ZEEBE_BROKER_GATEWAY_SECURITY_PRIVATEKEYPATH=/usr/local/zeebe/key.pem --mount type=bind,source="$(pwd)"/cert.pem,target=/usr/local/zeebe/cert.pem --mount type=bind,source="$(pwd)"/key.pem,target=/usr/local/zeebe/key.pem camunda/zeebe

There is one caveat: in order for the client to accept this self-signed certificate, you will need to trust it. The simplest way is to specify it as part of the client's configuration. For example, if you're using zbctl, you can then do zbctl --certPath cert.pem status. Refer to the documentation above on how to configure your clients.

Troubleshooting authentication issues​

Here we will describe a few ways the clients and gateway could be misconfigured and what those errors look like. Hopefully, this will help you recognize these situations and provide an easy fix.

TLS is enabled in zbctl but disabled in the gateway​

The client will fail with the following error:

Error: rpc error: code = Unavailable desc = all SubConns are in TransientFailure, latest connection error: connection error: desc = "transport: authentication handshake failed: tls: first record does not look like a TLS handshake"

The following error will be logged by Netty in the gateway:

Aug 06, 2019 4:23:22 PM io.grpc.netty.NettyServerTransport notifyTerminated
INFO: Transport failed
io.netty.handler.codec.http2.Http2Exception: HTTP/2 client preface string missing or corrupt. Hex dump for received bytes: 1603010096010000920303d06091559c43ec48a18b50c028
  at io.netty.handler.codec.http2.Http2Exception.connectionError(Http2Exception.java:103)
  at io.netty.handler.codec.http2.Http2ConnectionHandler$PrefaceDecoder.readClientPrefaceString(Http2ConnectionHandler.java:306)
  at io.netty.handler.codec.http2.Http2ConnectionHandler$PrefaceDecoder.decode(Http2ConnectionHandler.java:239)
  at io.netty.handler.codec.http2.Http2ConnectionHandler.decode(Http2ConnectionHandler.java:438)
  at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:505)
  at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:444)
  at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:283)
  at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374)
  at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360)
  at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352)
  at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1421)
  at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374)
  at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360)
  at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:930)
  at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:794)
  at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:424)
  at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:326)
  at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:918)
  at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
  at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
  at java.lang.Thread.run(Thread.java:748)

Solution: Either enable TLS in the gateway as well or specify the --insecure flag when using zbctl.

TLS is disabled in zbctl but enabled for the gateway​

zbctl will fail with the following error:

Error: rpc error: code = Unavailable desc = all SubConns are in TransientFailure, latest connection error: connection closed

Solution: Either enable TLS in the client by specifying a path to a certificate or disable it in the gateway by editing the appropriate configuration file.

TLS is enabled for both client and gateway but the CA certificate can't be found​

zbctl will fail with the following error:

Error: rpc error: code = Unavailable desc = all SubConns are in TransientFailure, latest connection error: connection error: desc = "transport: authentication handshake failed: x509: certificate signed by unknown authority

Solution: Either install the CA certificate in the appropriate location for the system or specify a path to certificate using the methods described above.