sodium

libsodium bindings for Kotlin/Native.

Installation

The datkt.sodium package an be installed with various package managers.

From NPM

$ npm install @datkt/sodium

Prerequisites

• Kotlin/Native and the konanc command line program.
• make

Usage

## Compile a program in 'main.kt' and link sodium.klib found in `node_modules/`
$ konanc -r node_modules/@datkt -l sodium/sodium main.kt

where main.kt might be

import datkt.sodium.* // entire libsodium API
import kotlinx.cinterop.* // exposes types needed for interop

fun main(args: Array<String>) {
  if (0 != sodium_init()) {
    throw Error("Failed to initialize libsodium")
  }
}

Example

import kotlinx.cinterop.*
import datkt.sodium.sodium_init
import datkt.sodium.randombytes_buf
import datkt.sodium.randombytes_random
import datkt.sodium.randombytes_uniform

fun main(args: Array<String>) {
  val rc = sodium_init()

  if (0 != rc) {
    throw Error("sodium_init() != 0")
  }

  println("${randombytes_random()} = randombytes_random()")
  println("${randombytes_uniform(37)} = randombytes_uniform(37)")

  var buffer = ByteArray(16)

  buffer.usePinned { pinned ->
    randombytes_buf(pinned.addressOf(0), buffer.size.convert())
  }

  println("${toHexString(buffer)} = randombytes_buf(ByteArray(16), 16)")
}

val table = "0123456789abcdef".toCharArray()

fun toHexString(bytes: ByteArray): String {
  var output = CharArray(2 * bytes.size)
  for (i in bytes.indices) {
    val j = (bytes[i].toInt() and 0xff).toInt()
    output[2 * i] = table[j ushr 4]
    output[1 + 2 * i] = table[j and 0x0f]
  }
  return String(output)
}

libsodium API

This package binds libsodiums entire API and provides an interop API for Kotlin and can be imported from the sodium package. For example, the crypto_generichash() with the following C function signature:

int crypto_generichash(unsigned char *out,
                       size_t outlen,
                       const unsigned char *in,
                       unsigned long long inlen,
                       const unsigned char *key,
                       size_t keylen);

translates to the following Kotlin function signature:

fun crypto_generichash(out: CValuesRef<UByteVar>?,
                       outlen: size_t,
                       `in`: CValuesRef<UByteVar>?,
                       inlen: ULong,
                       key: CValuesRef<UByteVar>?,
                       keylen: size_t): Int;

and can be called in Kotlin like:

val buffer = ByteArray(crypto_generichash_BYTES.toInt())
val message = "hello"

buffer.usePinned { pinned ->
  crypto_generichash(
    pinned.addressOf(0) as CValuesRef<UByteVar>,
    buffer.size.convert(),
    message.cstr as CValuesRef<UByteVar>,
    message.length.convert(),
    null, // key
    0 // key size
  )
}

Building

The sodium package can be built from source into various targets.

Kotlin Library

sodium.klib, a Kotlin library that can be linked with konanc can be built from source.

$ make klib

which will produce build/lib/sodium.klib. The library can be installed with klib by running make install

Static Library

libsodium.a, a static library that can be linked with konanc can be built from source.

$ make static

which will produce build/lib/libsodium.a and C header files in build/include. The library can be installed into your system by running make install. The path prefix can be set by defining the PREFIX environment or make variable. It defaults to PREFIX=/usr/local

See Also

• https://libsodium.gitbook.io/doc
• https://github.com/jedisct1/libsodium
• https://github.com/sodium-friends/sodium-native

License

MIT