expo-standard-web-crypto/build/getRandomValues.js

A partial implementation of the W3C Crypto API for Expo

import { getRandomValues as expoCryptoGetRandomValues } from 'expo-crypto';
const MAX_RANDOM_BYTES = 65536;
/**
 * An implementation of Crypto.getRandomValues that uses expo-random's secure random generator if
 * available and falls back to Math.random (cryptographically insecure) when synchronous bridged
 * methods are unavailable.
 *
 * See https://www.w3.org/TR/WebCryptoAPI/#Crypto-method-getRandomValues
 */
export default function getRandomValues(values) {
    if (arguments.length < 1) {
        throw new TypeError(`An ArrayBuffer view must be specified as the destination for the random values`);
    }
    if (!(values instanceof Int8Array) &&
        !(values instanceof Uint8Array) &&
        !(values instanceof Int16Array) &&
        !(values instanceof Uint16Array) &&
        !(values instanceof Int32Array) &&
        !(values instanceof Uint32Array) &&
        !(values instanceof Uint8ClampedArray)) {
        throw new TypeError(`The provided ArrayBuffer view is not an integer-typed array`);
    }
    if (values.byteLength > MAX_RANDOM_BYTES) {
        throw new QuotaExceededError(`The ArrayBuffer view's byte length (${values.byteLength}) exceeds the number of bytes of entropy available via this API (${MAX_RANDOM_BYTES})`);
    }
    try {
        // NOTE: Consider implementing `fillRandomBytes` to populate the given TypedArray directly
        expoCryptoGetRandomValues(values);
    }
    catch {
        // TODO: rethrow the error if it's not due to a lack of synchronous methods
        console.warn(`Random.getRandomBytes is not supported; falling back to insecure Math.random`);
        return getRandomValuesInsecure(values);
    }
    return values;
}
export function getRandomValuesInsecure(values) {
    // Write random bytes to the given TypedArray's underlying ArrayBuffer
    const byteView = new Uint8Array(values.buffer, values.byteOffset, values.byteLength);
    for (let i = 0; i < byteView.length; i++) {
        // The range of Math.random() is [0, 1) and the ToUint8 abstract operation rounds down
        byteView[i] = Math.random() * 256;
    }
    return values;
}
class QuotaExceededError extends Error {
    name = 'QuotaExceededError';
    code = 22; // QUOTA_EXCEEDED_ERR
}
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