amazon-cognito-identity-js
Version:
Amazon Cognito Identity Provider JavaScript SDK
419 lines (355 loc) • 11.8 kB
JavaScript
/*!
* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
* SPDX-License-Identifier: Apache-2.0
*/
import { Buffer } from 'buffer';
import WordArray from './utils/WordArray';
import { Sha256 } from '@aws-crypto/sha256-js';
/**
* Returns a Buffer with a sequence of random nBytes
*
* @param {number} nBytes
* @returns {Buffer} fixed-length sequence of random bytes
*/
function randomBytes(nBytes) {
return Buffer.from(new WordArray().random(nBytes).toString(), 'hex');
}
import BigInteger from './BigInteger';
/**
* Tests if a hex string has it most significant bit set (case-insensitive regex)
*/
const HEX_MSB_REGEX = /^[89a-f]/i;
const initN =
'FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD1' +
'29024E088A67CC74020BBEA63B139B22514A08798E3404DD' +
'EF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245' +
'E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED' +
'EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE45B3D' +
'C2007CB8A163BF0598DA48361C55D39A69163FA8FD24CF5F' +
'83655D23DCA3AD961C62F356208552BB9ED529077096966D' +
'670C354E4ABC9804F1746C08CA18217C32905E462E36CE3B' +
'E39E772C180E86039B2783A2EC07A28FB5C55DF06F4C52C9' +
'DE2BCBF6955817183995497CEA956AE515D2261898FA0510' +
'15728E5A8AAAC42DAD33170D04507A33A85521ABDF1CBA64' +
'ECFB850458DBEF0A8AEA71575D060C7DB3970F85A6E1E4C7' +
'ABF5AE8CDB0933D71E8C94E04A25619DCEE3D2261AD2EE6B' +
'F12FFA06D98A0864D87602733EC86A64521F2B18177B200C' +
'BBE117577A615D6C770988C0BAD946E208E24FA074E5AB31' +
'43DB5BFCE0FD108E4B82D120A93AD2CAFFFFFFFFFFFFFFFF';
const newPasswordRequiredChallengeUserAttributePrefix = 'userAttributes.';
/** @class */
export default class AuthenticationHelper {
/**
* Constructs a new AuthenticationHelper object
* @param {string} PoolName Cognito user pool name.
*/
constructor(PoolName) {
this.N = new BigInteger(initN, 16);
this.g = new BigInteger('2', 16);
this.k = new BigInteger(
this.hexHash(`${this.padHex(this.N)}${this.padHex(this.g)}`),
16
);
this.smallAValue = this.generateRandomSmallA();
this.getLargeAValue(() => {});
this.infoBits = Buffer.from('Caldera Derived Key', 'utf8');
this.poolName = PoolName;
}
/**
* @returns {BigInteger} small A, a random number
*/
getSmallAValue() {
return this.smallAValue;
}
/**
* @param {nodeCallback<BigInteger>} callback Called with (err, largeAValue)
* @returns {void}
*/
getLargeAValue(callback) {
if (this.largeAValue) {
callback(null, this.largeAValue);
} else {
this.calculateA(this.smallAValue, (err, largeAValue) => {
if (err) {
callback(err, null);
}
this.largeAValue = largeAValue;
callback(null, this.largeAValue);
});
}
}
/**
* helper function to generate a random big integer
* @returns {BigInteger} a random value.
* @private
*/
generateRandomSmallA() {
// This will be interpreted as a postive 128-bit integer
const hexRandom = randomBytes(128).toString('hex');
const randomBigInt = new BigInteger(hexRandom, 16);
// There is no need to do randomBigInt.mod(this.N - 1) as N (3072-bit) is > 128 bytes (1024-bit)
return randomBigInt;
}
/**
* helper function to generate a random string
* @returns {string} a random value.
* @private
*/
generateRandomString() {
return randomBytes(40).toString('base64');
}
/**
* @returns {string} Generated random value included in password hash.
*/
getRandomPassword() {
return this.randomPassword;
}
/**
* @returns {string} Generated random value included in devices hash.
*/
getSaltDevices() {
return this.SaltToHashDevices;
}
/**
* @returns {string} Value used to verify devices.
*/
getVerifierDevices() {
return this.verifierDevices;
}
/**
* Generate salts and compute verifier.
* @param {string} deviceGroupKey Devices to generate verifier for.
* @param {string} username User to generate verifier for.
* @param {nodeCallback<null>} callback Called with (err, null)
* @returns {void}
*/
generateHashDevice(deviceGroupKey, username, callback) {
this.randomPassword = this.generateRandomString();
const combinedString = `${deviceGroupKey}${username}:${this.randomPassword}`;
const hashedString = this.hash(combinedString);
const hexRandom = randomBytes(16).toString('hex');
// The random hex will be unambiguously represented as a postive integer
this.SaltToHashDevices = this.padHex(new BigInteger(hexRandom, 16));
this.g.modPow(
new BigInteger(this.hexHash(this.SaltToHashDevices + hashedString), 16),
this.N,
(err, verifierDevicesNotPadded) => {
if (err) {
callback(err, null);
}
this.verifierDevices = this.padHex(verifierDevicesNotPadded);
callback(null, null);
}
);
}
/**
* Calculate the client's public value A = g^a%N
* with the generated random number a
* @param {BigInteger} a Randomly generated small A.
* @param {nodeCallback<BigInteger>} callback Called with (err, largeAValue)
* @returns {void}
* @private
*/
calculateA(a, callback) {
this.g.modPow(a, this.N, (err, A) => {
if (err) {
callback(err, null);
}
if (A.mod(this.N).equals(BigInteger.ZERO)) {
callback(new Error('Illegal paramater. A mod N cannot be 0.'), null);
}
callback(null, A);
});
}
/**
* Calculate the client's value U which is the hash of A and B
* @param {BigInteger} A Large A value.
* @param {BigInteger} B Server B value.
* @returns {BigInteger} Computed U value.
* @private
*/
calculateU(A, B) {
this.UHexHash = this.hexHash(this.padHex(A) + this.padHex(B));
const finalU = new BigInteger(this.UHexHash, 16);
return finalU;
}
/**
* Calculate a hash from a bitArray
* @param {Buffer} buf Value to hash.
* @returns {String} Hex-encoded hash.
* @private
*/
hash(buf) {
const awsCryptoHash = new Sha256();
awsCryptoHash.update(buf);
const resultFromAWSCrypto = awsCryptoHash.digestSync();
const hashHex = Buffer.from(resultFromAWSCrypto).toString('hex');
return new Array(64 - hashHex.length).join('0') + hashHex;
}
/**
* Calculate a hash from a hex string
* @param {String} hexStr Value to hash.
* @returns {String} Hex-encoded hash.
* @private
*/
hexHash(hexStr) {
return this.hash(Buffer.from(hexStr, 'hex'));
}
/**
* Standard hkdf algorithm
* @param {Buffer} ikm Input key material.
* @param {Buffer} salt Salt value.
* @returns {Buffer} Strong key material.
* @private
*/
computehkdf(ikm, salt) {
const infoBitsBuffer = Buffer.concat([
this.infoBits,
Buffer.from(String.fromCharCode(1), 'utf8'),
]);
const awsCryptoHash = new Sha256(salt);
awsCryptoHash.update(ikm);
const resultFromAWSCryptoPrk = awsCryptoHash.digestSync();
const awsCryptoHashHmac = new Sha256(resultFromAWSCryptoPrk);
awsCryptoHashHmac.update(infoBitsBuffer);
const resultFromAWSCryptoHmac = awsCryptoHashHmac.digestSync();
const hashHexFromAWSCrypto = resultFromAWSCryptoHmac;
const currentHex = hashHexFromAWSCrypto.slice(0, 16);
return currentHex;
}
/**
* Calculates the final hkdf based on computed S value, and computed U value and the key
* @param {String} username Username.
* @param {String} password Password.
* @param {BigInteger} serverBValue Server B value.
* @param {BigInteger} salt Generated salt.
* @param {nodeCallback<Buffer>} callback Called with (err, hkdfValue)
* @returns {void}
*/
getPasswordAuthenticationKey(
username,
password,
serverBValue,
salt,
callback
) {
if (serverBValue.mod(this.N).equals(BigInteger.ZERO)) {
throw new Error('B cannot be zero.');
}
this.UValue = this.calculateU(this.largeAValue, serverBValue);
if (this.UValue.equals(BigInteger.ZERO)) {
throw new Error('U cannot be zero.');
}
const usernamePassword = `${this.poolName}${username}:${password}`;
const usernamePasswordHash = this.hash(usernamePassword);
const xValue = new BigInteger(
this.hexHash(this.padHex(salt) + usernamePasswordHash),
16
);
this.calculateS(xValue, serverBValue, (err, sValue) => {
if (err) {
callback(err, null);
}
const hkdf = this.computehkdf(
Buffer.from(this.padHex(sValue), 'hex'),
Buffer.from(this.padHex(this.UValue), 'hex')
);
callback(null, hkdf);
});
}
/**
* Calculates the S value used in getPasswordAuthenticationKey
* @param {BigInteger} xValue Salted password hash value.
* @param {BigInteger} serverBValue Server B value.
* @param {nodeCallback<string>} callback Called on success or error.
* @returns {void}
*/
calculateS(xValue, serverBValue, callback) {
this.g.modPow(xValue, this.N, (err, gModPowXN) => {
if (err) {
callback(err, null);
}
const intValue2 = serverBValue.subtract(this.k.multiply(gModPowXN));
intValue2.modPow(
this.smallAValue.add(this.UValue.multiply(xValue)),
this.N,
(err2, result) => {
if (err2) {
callback(err2, null);
}
callback(null, result.mod(this.N));
}
);
});
}
/**
* Return constant newPasswordRequiredChallengeUserAttributePrefix
* @return {newPasswordRequiredChallengeUserAttributePrefix} constant prefix value
*/
getNewPasswordRequiredChallengeUserAttributePrefix() {
return newPasswordRequiredChallengeUserAttributePrefix;
}
/**
* Returns an unambiguous, even-length hex string of the two's complement encoding of an integer.
*
* It is compatible with the hex encoding of Java's BigInteger's toByteArray(), wich returns a
* byte array containing the two's-complement representation of a BigInteger. The array contains
* the minimum number of bytes required to represent the BigInteger, including at least one sign bit.
*
* Examples showing how ambiguity is avoided by left padding with:
* "00" (for positive values where the most-significant-bit is set)
* "FF" (for negative values where the most-significant-bit is set)
*
* padHex(bigInteger.fromInt(-236)) === "FF14"
* padHex(bigInteger.fromInt(20)) === "14"
*
* padHex(bigInteger.fromInt(-200)) === "FF38"
* padHex(bigInteger.fromInt(56)) === "38"
*
* padHex(bigInteger.fromInt(-20)) === "EC"
* padHex(bigInteger.fromInt(236)) === "00EC"
*
* padHex(bigInteger.fromInt(-56)) === "C8"
* padHex(bigInteger.fromInt(200)) === "00C8"
*
* @param {BigInteger} bigInt Number to encode.
* @returns {String} even-length hex string of the two's complement encoding.
*/
padHex(bigInt) {
if (!(bigInt instanceof BigInteger)) {
throw new Error('Not a BigInteger');
}
const isNegative = bigInt.compareTo(BigInteger.ZERO) < 0;
/* Get a hex string for abs(bigInt) */
let hexStr = bigInt.abs().toString(16);
/* Pad hex to even length if needed */
hexStr = hexStr.length % 2 !== 0 ? `0${hexStr}` : hexStr;
/* Prepend "00" if the most significant bit is set */
hexStr = HEX_MSB_REGEX.test(hexStr) ? `00${hexStr}` : hexStr;
if (isNegative) {
/* Flip the bits of the representation */
const invertedNibbles = hexStr
.split('')
.map(x => {
const invertedNibble = ~parseInt(x, 16) & 0xf;
return '0123456789ABCDEF'.charAt(invertedNibble);
})
.join('');
/* After flipping the bits, add one to get the 2's complement representation */
const flippedBitsBI = new BigInteger(invertedNibbles, 16).add(
BigInteger.ONE
);
hexStr = flippedBitsBI.toString(16);
/*
For hex strings starting with 'FF8', 'FF' can be dropped, e.g. 0xFFFF80=0xFF80=0x80=-128
Any sequence of '1' bits on the left can always be substituted with a single '1' bit
without changing the represented value.
This only happens in the case when the input is 80...00
*/
if (hexStr.toUpperCase().startsWith('FF8')) {
hexStr = hexStr.substring(2);
}
}
return hexStr;
}
}