Kotlin + mbedtls integration

Integration with mbedtls library to provide DTLS protocol into jvm ecosystem.

Features:

• Precompiled mbedtls binaries for
  • linux (x64)
  • macos (intel and arm)
  • windows (x64)
• DTLS 1.2 client and server modes
• DTLS 1.2 CID support (RFC 9146)
  • Storing and restoring sessions
• Certificate and PSK authentication
• Micrometer integration
• Netty integration (client and server)

Usage:

Gradle

dependencies {
  implementation("io.github.open-coap:kotlin-mbedtls:[VERSION]")
  // optional modules:
  implementation("io.github.open-coap:kotlin-mbedtls-metrics:[VERSION]")
  implementation("io.github.open-coap:kotlin-mbedtls-netty:[VERSION]")
}

Maven

<dependency>
    <groupId>io.github.open-coap</groupId>
    <artifactId>kotlin-mbedtls</artifactId>
    <version>[VERSION]</version>
</dependency>

DTLS client:

// create mbedtls SSL configuration with PSK credentials
val conf: SslConfig = SslConfig.client(
    PskAuth(
        pskId = "device-007",
        pskSecret = byteArrayOf(0x01, 0x02)
    )
)
// create client and initiate handshake
val client: DtlsTransmitter = DtlsTransmitter
    .connect(InetSocketAddress(InetAddress.getLocalHost(), 1_5684), conf, 6001)
    .get(10, TimeUnit.SECONDS)

// send and receive packets
val sendResult: CompletableFuture<Boolean> = client.send("hello")
val receive: CompletableFuture<ByteBuffer> = client.receive(timeout = Duration.ofSeconds(2))

// . . . 

// optionally, it is possible to save session before closing client, it could be later reloaded
// note: after saving session, it is not possible to is client
val storedSession: ByteArray = client.saveSession()
client.close()

// close SSL configuration:
// - make sure to close it before GC to avoid native memory leak
// - close it only after client is closed
conf.close()

Supported OS

Precompiled:

• Linux (x86-64)
• Apple Mac (intel and arm)
• Windows (x86-64)

Development

Useful commands

• ./gradlew build -i compile and test

• ./gradlew publishToMavenLocal publish artifact to local maven repository

• ./gradlew currentVersion show current version

• ./gradlew ktlintFormat format kotlin files

• ./gradlew release create next tag in Git and push to origin

• ./gradlew currentVersion print current version

• ./gradlew dependencyUpdates determine which dependencies have updates

• ./gradlew useLatestVersions update dependencies to the latest available versions

Build mbedtls binaries

Linux (x86_64):

./compileMbedtls.sh

Mac (intel and arm):

LDFLAGS='-arch x86_64 -arch arm64' CFLAGS='-O2 -arch x86_64 -arch arm64' DLEXT=dylib OSARCH=darwin ./compileMbedtls.sh

Windows

• docker run -it -v$(pwd):/work --rm dockcross/windows-static-x64 sh -c "WINDOWS=1 LDFLAGS='-lws2_32 -lwinmm -lgdi32 -L. -static-libgcc' DLEXT=dll OSARCH=win32-x86-64 ./compileMbedtls.sh"

Cross compiling for linux (x86_64):

• docker run -it -v$(pwd):/work --rm dockcross/linux-x86_64-full ./compileMbedtls.sh