tutanota/packages/tutanota-crypto/lib/random/Randomizer.ts

// @ts-ignore[untyped-import]
import sjcl from "../internal/sjcl.js"
import type { EntropySource } from "../misc/Constants.js"
import { CryptoError } from "../misc/CryptoError.js"

/**
 * This Interface provides an abstraction of the random number generator implementation.
 */
export class Randomizer {
	random: any

	constructor() {
		this.random = new sjcl.prng(6)
	}

	/**
	 * Adds entropy to the random number generator algorithm
	 * @param entropyCache with: number Any number value, entropy The amount of entropy in the number in bit,
	 * source The source of the number.
	 */
	addEntropy(
		entropyCache: Array<{
			source: EntropySource
			entropy: number
			data: number | Array<number>
		}>,
	): Promise<void> {
		for (const entry of entropyCache) {
			this.random.addEntropy(entry.data, entry.entropy, entry.source)
		}
		return Promise.resolve()
	}

	addStaticEntropy(bytes: Uint8Array) {
		for (const byte of bytes) {
			this.random.addEntropy(byte, 8, "static")
		}
	}

	/**
	 * Not used currently because we always have enough entropy using getRandomValues()
	 */
	isReady(): boolean {
		return this.random.isReady() !== 0
	}

	/**
	 * Generates random data. The function initRandomDataGenerator must have been called prior to the first call to this function.
	 * @param nbrOfBytes The number of bytes the random data shall have.
	 * @return A hex coded string of random data.
	 * @throws {CryptoError} if the randomizer is not seeded (isReady == false)
	 */
	generateRandomData(nbrOfBytes: number): Uint8Array<ArrayBuffer> {
		try {
			// read the minimal number of words to get nbrOfBytes
			let nbrOfWords = Math.floor((nbrOfBytes + 3) / 4)
			let words = this.random.randomWords(nbrOfWords)
			let arrayBuffer = sjcl.codec.arrayBuffer.fromBits(words, false)
			// simply cut off the exceeding bytes
			return new Uint8Array(arrayBuffer, 0, nbrOfBytes) // truncate the arraybuffer as precaution
		} catch (e) {
			throw new CryptoError("error during random number generation", e as Error)
		}
	}

	/**
	 * Generate a number that fits in the range of an n-byte integer
	 */
	generateRandomNumber(nbrOfBytes: number): number {
		const bytes = this.generateRandomData(nbrOfBytes)
		let result = 0

		for (let i = 0; i < bytes.length; ++i) {
			result += bytes[i] << (i * 8)
		}
		return result
	}
}
// TODO singleton should be created in the app?
// the randomizer instance (singleton) that should be used throughout the app
export const random: Randomizer = new Randomizer()