Laravel Encryption Crypt WebCrypto implementation

Crypt.ts

function s2b(data: string) {
  return Uint8Array.from(data, c => c.charCodeAt(0)).buffer
}

function b2s(data: ArrayBufferLike) {
  return String.fromCharCode(...new Uint8Array(data))
}

function hex(data: ArrayBufferLike) {
  return [...new Uint8Array(data)].map(x => x.toString(16).padStart(2, '0')).join('')
}

let keyData: ArrayBuffer

interface Payload {
  iv: string
  value: string
  mac: string
}

function setKey(data: string) {
  keyData = s2b(atob(data.slice(7)))
}

async function subtle(usage: 'encrypt' | 'decrypt' | 'sign', data: string, iv: string) {
  const algorithm = !usage.includes('crypt')
    ? [{ name: 'HMAC', hash: 'SHA-256' }, 'HMAC']
    : ['AES-CBC', { name: 'AES-CBC', iv: s2b(atob(iv)) }]
  const key = await crypto.subtle.importKey('raw', keyData, algorithm[0]!, true, [usage])
  return await crypto.subtle[usage](algorithm[1]!, key, s2b(data))
}

async function decryptString(data: string) {
  const payload = JSON.parse(atob(data)) as Payload
  const decrypted = await subtle('decrypt', atob(payload.value), payload.iv)
  // TODO: validate HMAC
  return b2s(decrypted)
}

async function encryptString(data: string) {
  const tmp = new Uint8Array(16)
  crypto.getRandomValues(tmp)
  const iv = btoa(b2s(tmp.buffer))
  const value = btoa(b2s(await subtle('encrypt', data, iv)))
  const mac = hex(await subtle('sign', iv + value, ''))
  return btoa(JSON.stringify({ iv, value, mac } as Payload))
}

export { setKey, decryptString, encryptString }