Using the New Web Host Server in Your Conclave Application

plugins {
    id 'java'
    id 'application'
    id 'com.github.johnrengelman.shadow' version '6.1.0'
}

application {
    mainClassName = "com.r3.conclave.host.web.EnclaveWebHost"
}

dependencies {
    runtimeOnly project(path: ":enclave", configuration: mode)
    runtimeOnly "com.r3.conclave:conclave-web-host:$conclaveVersion"

    testImplementation "com.r3.conclave:conclave-host:$conclaveVersion"
    testImplementation "org.junit.jupiter:junit-jupiter:5.6.0"
}

shadowJar {
    archiveAppendix.set(mode)
    archiveClassifier.set("")
}

  
As the host shadow jar contains the enclave, this will set the enclave mode into the host jar. Add the below code, which will allow the mode to be chosen from the command line.

def mode = findProperty("enclaveMode")?.toString()?.toLowerCase() ?: "mock"

 
Next, we’ll discuss running the web host server itself.

./gradlew host:shadowJar

  
The shadow jar will be created in the build/libs directory of the host module.

Use the jar -jar command to run the shadow jar.

java -jar host/build/libs/host.jar

  
Your web host server should now be up and running. It will be ready to communicate with the client on http://localhost:8080.

Note that the enclave mode is set to mock by default. To run the enclave in a different mode, build the shadow jar using the below command.

./gradlew -PenclaveMode= host:shadowJar

  
To make implementing a client easier, a new EnclaveClient API has been introduced, which takes care of connecting to the web host and downloading the attestation information. It also handles the encryption and decryption of Mail and provides a simple interface for sending and receiving Mail.

The EnclaveClient is agnostic of the communication protocol used to communicate with the host. This is where the EnclaveTransport has been introduced, which defines the communication protocol. Since we are using the web host, which is HTTP-based, WebEnclaveTransport has been added to handle HTTP communication.

The below code snippet shows how to implement a simple client.

• • The client.start() method takes care of connecting to the web host using the WebEnclaveTransport , and also downloads remote attestation and validates the constraints.
  • The client.sendMail() method can be used to send mails to the enclave.
  • If you are expecting a delay in the response, you can poll the host using the client.pollMail() method.

try (WebEnclaveTransport transport = new WebEnclaveTransport(url);
     EnclaveClient client = new EnclaveClient(constraint))
{
    client.start(transport);
    byte[] serializedOutput = serializeMessage(roleType, bid);

    // Send mail to enclave and receive response

    EnclaveMail responseMail = client.sendMail(serializedOutput);

    //ResponseMail is null till enclave doesn't reply back 
    if (responseMail == null) {
        do {
            Thread.sleep(2000);
            //Poll for reply to enclave
            responseMail = client.pollMail();
        } while (responseMail == null);
    }
    System.out.println("Response : " + new String(responseMail.getBodyAsBytes()));
}