expo-crypto/src/ExpoCrypto.web.ts

Provides cryptography primitives for Android, iOS and web.

import type { TypedArray } from 'expo-modules-core';
import { CodedError } from 'expo-modules-core';

import type { CryptoDigestAlgorithm, CryptoDigestOptions } from './Crypto.types';
import { CryptoEncoding } from './Crypto.types';

const getCrypto = (): Crypto => {
  if (typeof globalThis.crypto !== 'undefined') {
    return globalThis.crypto;
  } else if (typeof window !== 'undefined') {
    return window.crypto ?? (window as any).msCrypto;
  } else {
    return crypto;
  }
};

export default {
  async digestStringAsync(
    algorithm: CryptoDigestAlgorithm,
    data: string,
    options: CryptoDigestOptions
  ): Promise<string> {
    const crypto = getCrypto();
    if (!crypto.subtle) {
      throw new CodedError(
        'ERR_CRYPTO_UNAVAILABLE',
        'Access to the WebCrypto API is restricted to secure origins (localhost/https).'
      );
    }
    const encoder = new TextEncoder();
    const buffer = encoder.encode(data);
    const hashedData = await crypto.subtle.digest(algorithm, buffer);
    if (options.encoding === CryptoEncoding.HEX) {
      return hexString(hashedData);
    } else if (options.encoding === CryptoEncoding.BASE64) {
      return btoa(String.fromCharCode(...new Uint8Array(hashedData)));
    }
    throw new CodedError('ERR_CRYPTO_DIGEST', 'Invalid encoding type provided.');
  },
  getRandomBytes(length: number): Uint8Array {
    const array = new Uint8Array(length);
    return getCrypto().getRandomValues(array);
  },
  async getRandomBytesAsync(length: number): Promise<Uint8Array> {
    const array = new Uint8Array(length);
    return getCrypto().getRandomValues(array);
  },
  getRandomValues(typedArray: TypedArray) {
    return getCrypto().getRandomValues(typedArray as ArrayBufferView<ArrayBuffer>);
  },
  randomUUID() {
    return getCrypto().randomUUID();
  },
  digestAsync(algorithm: AlgorithmIdentifier, data: ArrayBuffer): Promise<ArrayBuffer> {
    return getCrypto().subtle.digest(algorithm, data);
  },
};

function hexString(buffer: ArrayBuffer): string {
  const byteArray = new Uint8Array(buffer);

  const hexCodes = [...byteArray].map((value) => {
    const hexCode = value.toString(16);
    const paddedHexCode = hexCode.padStart(2, '0');
    return paddedHexCode;
  });

  return hexCodes.join('');
}