fix: revert all commits back to bab1ccc

BREAKING CHANGE: Removes compatibilities added up to v3.0.0

Author: kentcdodds

README.md

@@ -99,13 +99,7 @@ const otpUri = getTOTPAuthUri({
 const code = await getCodeFromUser()
 
 // now verify the code:
-const isValid = await verifyTOTP({
-	otp: code,
-	secret,
-	period,
-	digits,
-	algorithm,
-})
+const isValid = await verifyTOTP({ otp: code, secret, period, digits, algorithm })
 
 // if it's valid, save the secret, period, digits, and algorithm to the database
 // along with who it belongs to and use this info to verify the user when they

index.js

@@ -37,61 +37,41 @@ const DEFAULT_PERIOD = 30
  * @param {string} [options.charSet='0123456789'] - The character set to use, defaults to the numbers 0-9.
  * @returns {Promise<string>} The generated HOTP.
  */
-export async function generateHOTP(
+async function generateHOTP(
 	secret,
 	{
 		counter = 0,
 		digits = DEFAULT_DIGITS,
 		algorithm = DEFAULT_ALGORITHM,
 		charSet = DEFAULT_CHAR_SET,
-	} = {},
+	} = {}
 ) {
 	const byteCounter = intToBytes(counter)
 	const key = await crypto.subtle.importKey(
 		'raw',
 		secret,
 		{ name: 'HMAC', hash: algorithm },
 		false,
-		['sign'],
+		['sign']
 	)
 	const signature = await crypto.subtle.sign('HMAC', key, byteCounter)
 	const hashBytes = new Uint8Array(signature)
-	// offset is always the last 4 bits of the signature; its value: 0-15
+
+	// Use more bytes for longer OTPs
+	const bytesNeeded = Math.ceil((digits * Math.log2(charSet.length)) / 8)
 	const offset = hashBytes[hashBytes.length - 1] & 0xf
 
+	// Convert bytes to BigInt for larger numbers
 	let hotpVal = 0n
-	if (digits === 6) {
-		// stay compatible with the authenticator apps and only use the bottom 32 bits of BigInt
-		hotpVal =
-			0n |
-			(BigInt(hashBytes[offset] & 0x7f) << 24n) |
-			(BigInt(hashBytes[offset + 1]) << 16n) |
-			(BigInt(hashBytes[offset + 2]) << 8n) |
-			BigInt(hashBytes[offset + 3])
-	} else {
-		// otherwise create a 64bit value from the hashBytes
-		hotpVal =
-			0n |
-			(BigInt(hashBytes[offset] & 0x7f) << 56n) |
-			(BigInt(hashBytes[offset + 1]) << 48n) |
-			(BigInt(hashBytes[offset + 2]) << 40n) |
-			(BigInt(hashBytes[offset + 3]) << 32n) |
-			(BigInt(hashBytes[offset + 4]) << 24n) |
-			// we have only 20 hashBytes; if offset is 15 these indexes are out of the hashBytes
-			// fallback to the bytes at the start of the hashBytes
-			(BigInt(hashBytes[(offset + 5) % 20]) << 16n) |
-			(BigInt(hashBytes[(offset + 6) % 20]) << 8n) |
-			BigInt(hashBytes[(offset + 7) % 20])
+	for (let i = 0; i < Math.min(bytesNeeded, hashBytes.length - offset); i++) {
+		hotpVal = (hotpVal << 8n) | BigInt(hashBytes[offset + i])
 	}
 
 	let hotp = ''
 	const charSetLength = BigInt(charSet.length)
 	for (let i = 0; i < digits; i++) {
 		hotp = charSet.charAt(Number(hotpVal % charSetLength)) + hotp
-
-		// Ensures hotpVal decreases at a fixed rate, independent of charSet length.
-		// 10n is compatible with the original TOTP algorithm used in the authenticator apps.
-		hotpVal = hotpVal / 10n
+		hotpVal = hotpVal / charSetLength
 	}
 
 	return hotp
@@ -126,7 +106,7 @@ async function verifyHOTP(
 		algorithm = DEFAULT_ALGORITHM,
 		charSet = DEFAULT_CHAR_SET,
 		window = DEFAULT_WINDOW,
-	} = {},
+	} = {}
 ) {
 	for (let i = counter - window; i <= counter + window; ++i) {
 		if (

index.test.js

@@ -1,13 +1,7 @@
 import assert from 'node:assert'
 import { test } from 'node:test'
 import base32Encode from 'base32-encode'
-import base32Decode from 'base32-decode'
-import {
-	generateTOTP,
-	getTOTPAuthUri,
-	verifyTOTP,
-	generateHOTP,
-} from './index.js'
+import { generateTOTP, getTOTPAuthUri, verifyTOTP } from './index.js'
 
 test('OTP can be generated and verified', async () => {
 	const { secret, otp, algorithm, period, digits } = await generateTOTP()
@@ -26,7 +20,7 @@ test('options can be customized', async () => {
 		digits: 8,
 		secret: base32Encode(
 			new TextEncoder().encode(Math.random().toString(16).slice(2)),
-			'RFC4648',
+			'RFC4648'
 		).toString(),
 		charSet: 'abcdef',
 	}
@@ -139,67 +133,15 @@ test('OTP with digits > 6 should not pad with first character of charSet', async
 		assert.match(
 			otp,
 			new RegExp(`^[${charSet}]{12}$`),
-			'OTP should be 12 characters from the charSet',
+			'OTP should be 12 characters from the charSet'
 		)
 
 		// The first 6 characters should not all be 'A' (first char of charSet)
 		const firstSixChars = otp.slice(0, 6)
 		assert.notStrictEqual(
 			firstSixChars,
 			'A'.repeat(6),
-			'First 6 characters should not all be A',
+			'First 6 characters should not all be A'
 		)
 	}
 })
-
-test('generateHOTP works with maximum HMAC offset value', async () => {
-	await assert.doesNotReject(async () => {
-		// These specific secret and counter values will cause offset to be 15
-		const secret = '6YY3NUMNTQ73NRH3'
-		const counter = 57988074
-		await generateHOTP(base32Decode(secret, 'RFC4648'), {
-			counter,
-			digits: 12, // trigger the use of the 64bit htopVal
-			algorithm: 'SHA-1',
-			charSet: '0123456789',
-		})
-	})
-})
-
-test('20 digits OTP should not pad with first character of charSet regardless of the charSet length', async () => {
-	const longCharSet = 'ABCDEFGHIJKLMNPQRSTUVWXYZ123456789'
-	const shortCharSet = 'ABCDEFGHIJK'
-
-	async function generate20DigitCodeWithCharSet(charSet) {
-		const iterations = 100
-		let allOtps = []
-
-		for (let i = 0; i < iterations; i++) {
-			const { otp } = await generateTOTP({
-				algorithm: 'SHA-256',
-				charSet,
-				digits: 20,
-				period: 60 * 30,
-			})
-			allOtps.push(otp)
-
-			// Verify the OTP only contains characters from the charSet
-			assert.match(
-				otp,
-				new RegExp(`^[${charSet}]{20}$`),
-				'OTP should be 20 characters from the charSet',
-			)
-
-			// The first 6 characters should not all be 'A' (first char of charSet)
-			const firstSixChars = otp.slice(0, 6)
-			assert.notStrictEqual(
-				firstSixChars,
-				'A'.repeat(6),
-				'First 6 characters should not all be A',
-			)
-		}
-	}
-
-	await generate20DigitCodeWithCharSet(shortCharSet)
-	await generate20DigitCodeWithCharSet(longCharSet)
-})