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114 lines
2.9 KiB
114 lines
2.9 KiB
'use strict';
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var hash = require('hash.js');
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var utils = require('minimalistic-crypto-utils');
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var assert = require('minimalistic-assert');
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function HmacDRBG(options) {
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if (!(this instanceof HmacDRBG))
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return new HmacDRBG(options);
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this.hash = options.hash;
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this.predResist = !!options.predResist;
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this.outLen = this.hash.outSize;
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this.minEntropy = options.minEntropy || this.hash.hmacStrength;
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this._reseed = null;
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this.reseedInterval = null;
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this.K = null;
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this.V = null;
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var entropy = utils.toArray(options.entropy, options.entropyEnc || 'hex');
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var nonce = utils.toArray(options.nonce, options.nonceEnc || 'hex');
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var pers = utils.toArray(options.pers, options.persEnc || 'hex');
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assert(entropy.length >= (this.minEntropy / 8),
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'Not enough entropy. Minimum is: ' + this.minEntropy + ' bits');
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this._init(entropy, nonce, pers);
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}
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module.exports = HmacDRBG;
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HmacDRBG.prototype._init = function init(entropy, nonce, pers) {
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var seed = entropy.concat(nonce).concat(pers);
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this.K = new Array(this.outLen / 8);
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this.V = new Array(this.outLen / 8);
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for (var i = 0; i < this.V.length; i++) {
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this.K[i] = 0x00;
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this.V[i] = 0x01;
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}
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this._update(seed);
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this._reseed = 1;
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this.reseedInterval = 0x1000000000000; // 2^48
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};
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HmacDRBG.prototype._hmac = function hmac() {
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return new hash.hmac(this.hash, this.K);
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};
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HmacDRBG.prototype._update = function update(seed) {
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var kmac = this._hmac()
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.update(this.V)
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.update([ 0x00 ]);
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if (seed)
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kmac = kmac.update(seed);
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this.K = kmac.digest();
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this.V = this._hmac().update(this.V).digest();
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if (!seed)
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return;
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this.K = this._hmac()
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.update(this.V)
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.update([ 0x01 ])
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.update(seed)
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.digest();
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this.V = this._hmac().update(this.V).digest();
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};
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HmacDRBG.prototype.reseed = function reseed(entropy, entropyEnc, add, addEnc) {
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// Optional entropy enc
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if (typeof entropyEnc !== 'string') {
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addEnc = add;
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add = entropyEnc;
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entropyEnc = null;
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}
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entropy = utils.toArray(entropy, entropyEnc);
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add = utils.toArray(add, addEnc);
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assert(entropy.length >= (this.minEntropy / 8),
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'Not enough entropy. Minimum is: ' + this.minEntropy + ' bits');
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this._update(entropy.concat(add || []));
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this._reseed = 1;
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};
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HmacDRBG.prototype.generate = function generate(len, enc, add, addEnc) {
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if (this._reseed > this.reseedInterval)
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throw new Error('Reseed is required');
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// Optional encoding
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if (typeof enc !== 'string') {
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addEnc = add;
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add = enc;
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enc = null;
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}
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// Optional additional data
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if (add) {
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add = utils.toArray(add, addEnc || 'hex');
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this._update(add);
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}
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var temp = [];
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while (temp.length < len) {
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this.V = this._hmac().update(this.V).digest();
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temp = temp.concat(this.V);
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}
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var res = temp.slice(0, len);
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this._update(add);
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this._reseed++;
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return utils.encode(res, enc);
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};
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