87 lines
1.8 KiB
JavaScript
87 lines
1.8 KiB
JavaScript
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/*!
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* algorithms/hkdf.js - HMAC-based Extract-and-Expand Key Derivation
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*
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* Copyright (c) 2015 Cisco Systems, Inc. See LICENSE file.
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*/
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"use strict";
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var CONSTANTS = require("./constants.js"),
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hmac = require("./hmac.js");
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function hkdfDeriveFn(name) {
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var hash = name.replace("HKDF-", ""),
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op = name.replace("HKDF-SHA-", "HS");
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// NOTE: no nodejs/webcrypto/fallback model, since this HKDF is
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// implemented using the HMAC algorithms
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var fn = function(key, props) {
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var hashLen = CONSTANTS.HASHLENGTH[hash] / 8;
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if ("string" === typeof op) {
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op = hmac[op].sign;
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}
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// prepare options
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props = props || {};
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var salt = props.salt;
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if (!salt || 0 === salt.length) {
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salt = Buffer.alloc(hashLen);
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}
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var info = props.info || Buffer.alloc(0);
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var keyLen = props.length || hashLen;
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var promise;
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// Setup Expansion
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var N = Math.ceil(keyLen / hashLen),
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okm = [],
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idx = 0;
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function expand(key, T) {
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if (N === idx++) {
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return Buffer.concat(okm).slice(0, keyLen);
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}
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if (!T) {
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T = Buffer.alloc(0);
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}
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T = Buffer.concat([T, info, Buffer.from([idx])]);
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T = op(key, T);
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T = T.then(function(result) {
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T = result.mac;
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okm.push(T);
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return expand(key, T);
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});
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return T;
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}
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// Step 1: Extract
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promise = op(salt, key, { length: salt.length * 8 });
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promise = promise.then(function(result) {
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// Step 2: Expand
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return expand(result.mac);
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});
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return promise;
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};
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return fn;
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}
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// Public API
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// * [name].derive
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var hkdf = {};
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[
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"HKDF-SHA-1",
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"HKDF-SHA-256",
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"HKDF-SHA-384",
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"HKDF-SHA-512"
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].forEach(function(name) {
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hkdf[name] = {
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derive: hkdfDeriveFn(name)
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};
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});
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module.exports = hkdf;
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