pbes2kw.ts

import { promisify } from 'util'
import { KeyObject, pbkdf2 as pbkdf2cb } from 'crypto'
import type { Pbes2KWDecryptFunction, Pbes2KWEncryptFunction } from '../interfaces.d'
import random from './random.js'
import { p2s as concatSalt } from '../../lib/buffer_utils.js'
import { encode as base64url } from './base64url.js'
import { wrap, unwrap } from './aeskw.js'
import checkP2s from '../../lib/check_p2s.js'
import { isCryptoKey } from './webcrypto.js'
import { checkEncCryptoKey } from '../../lib/crypto_key.js'
import isKeyObject from './is_key_object.js'
import invalidKeyInput from '../../lib/invalid_key_input.js'
import { types } from './is_key_like.js'

const pbkdf2 = promisify(pbkdf2cb)

function getPassword(key: unknown, alg: string) {
  if (isKeyObject(key)) {
    return key.export()
  }
  if (key instanceof Uint8Array) {
    return key
  }
  if (isCryptoKey(key)) {
    checkEncCryptoKey(key, alg, 'deriveBits', 'deriveKey')
    return KeyObject.from(key).export()
  }
  throw new TypeError(invalidKeyInput(key, ...types, 'Uint8Array'))
}

export const encrypt: Pbes2KWEncryptFunction = async (
  alg: string,
  key: unknown,
  cek: Uint8Array,
  p2c: number = 2048,
  p2s: Uint8Array = random(new Uint8Array(16)),
) => {
  checkP2s(p2s)
  const salt = concatSalt(alg, p2s)
  const keylen = parseInt(alg.slice(13, 16), 10) >> 3
  const password = getPassword(key, alg)

  const derivedKey = await pbkdf2(password, salt, p2c, keylen, `sha${alg.slice(8, 11)}`)
  const encryptedKey = await wrap(alg.slice(-6), derivedKey, cek)

  return { encryptedKey, p2c, p2s: base64url(p2s) }
}

export const decrypt: Pbes2KWDecryptFunction = async (
  alg: string,
  key: unknown,
  encryptedKey: Uint8Array,
  p2c: number,
  p2s: Uint8Array,
) => {
  checkP2s(p2s)
  const salt = concatSalt(alg, p2s)
  const keylen = parseInt(alg.slice(13, 16), 10) >> 3
  const password = getPassword(key, alg)

  const derivedKey = await pbkdf2(password, salt, p2c, keylen, `sha${alg.slice(8, 11)}`)

  return unwrap(alg.slice(-6), derivedKey, encryptedKey)
}