cipher-state.js

/* eslint-disable camelcase */
const { sodium_memzero } = require('sodium-universal/memory')
const { sodium_increment, sodium_memcmp, sodium_is_zero } = require('sodium-universal/helpers')

const assert = require('nanoassert')

module.exports = ({ cipher }) => {
  const STATELEN = cipher.KEYLEN + cipher.NONCELEN
  const NONCELEN = cipher.NONCELEN
  const MACLEN = cipher.MACLEN

  const KEY_BEGIN = 0
  const KEY_END = cipher.KEYLEN
  const NONCE_BEGIN = KEY_END
  const NONCE_END = NONCE_BEGIN + cipher.NONCELEN

  function initializeKey (state, key) {
    assert(state.byteLength === STATELEN)
    assert(key == null ? true : key.byteLength === cipher.KEYLEN)

    if (key == null) {
      sodium_memzero(state.subarray(KEY_BEGIN, KEY_END))
      return
    }

    state.set(key)
    sodium_memzero(state.subarray(NONCE_BEGIN, NONCE_END))
  }

  function hasKey (state) {
    assert(state.byteLength === STATELEN)
    const k = state.subarray(KEY_BEGIN, KEY_END)
    return sodium_is_zero(k) === false
  }

  function setNonce (state, nonce) {
    assert(state.byteLength === STATELEN)
    assert(nonce.byteLength === NONCELEN)

    state.set(nonce, NONCE_BEGIN)
  }

  const maxnonce = new Uint8Array(8).fill(0xff)
  function encryptWithAd (state, out, ad, plaintext) {
    assert(state.byteLength === STATELEN)
    assert(out.byteLength != null)
    assert(plaintext.byteLength != null)

    const n = state.subarray(NONCE_BEGIN, NONCE_END)
    if (sodium_memcmp(n, maxnonce)) throw new Error('Nonce overflow')

    if (hasKey(state) === false) {
      out.set(plaintext)
      encryptWithAd.bytesRead = plaintext.byteLength
      encryptWithAd.bytesWritten = encryptWithAd.bytesRead
      return
    }

    const k = state.subarray(KEY_BEGIN, KEY_END)

    cipher.encrypt(
      out,
      k,
      n,
      ad,
      plaintext
    )
    encryptWithAd.bytesRead = cipher.encrypt.bytesRead
    encryptWithAd.bytesWritten = cipher.encrypt.bytesWritten

    sodium_increment(n)
  }
  encryptWithAd.bytesRead = 0
  encryptWithAd.bytesWritten = 0

  function decryptWithAd (state, out, ad, ciphertext) {
    assert(state.byteLength === STATELEN)
    assert(out.byteLength != null)
    assert(ciphertext.byteLength != null)

    const n = state.subarray(NONCE_BEGIN, NONCE_END)
    if (sodium_memcmp(n, maxnonce)) throw new Error('Nonce overflow')

    if (hasKey(state) === false) {
      out.set(ciphertext)
      decryptWithAd.bytesRead = ciphertext.byteLength
      decryptWithAd.bytesWritten = decryptWithAd.bytesRead
      return
    }

    const k = state.subarray(KEY_BEGIN, KEY_END)

    cipher.decrypt(
      out,
      k,
      n,
      ad,
      ciphertext
    )
    decryptWithAd.bytesRead = cipher.decrypt.bytesRead
    decryptWithAd.bytesWritten = cipher.decrypt.bytesWritten

    sodium_increment(n)
  }
  decryptWithAd.bytesRead = 0
  decryptWithAd.bytesWritten = 0

  function rekey (state) {
    assert(state.byteLength === STATELEN)

    const k = state.subarray(KEY_BEGIN, KEY_END)
    cipher.rekey(k, k)
    rekey.bytesRead = cipher.rekey.bytesRead
    rekey.bytesWritten = cipher.rekey.bytesWritten
  }
  rekey.bytesRead = 0
  rekey.bytesWritten = 0

  return {
    STATELEN,
    NONCELEN,
    MACLEN,
    initializeKey,
    hasKey,
    setNonce,
    encryptWithAd,
    decryptWithAd,
    rekey
  }
}