163 lines
3.8 KiB
JavaScript
163 lines
3.8 KiB
JavaScript
// Copyright 2011 The Closure Library Authors. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS-IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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/**
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* @fileoverview Implementation of HMAC in JavaScript.
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*
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* Usage:
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* var hmac = new goog.crypt.Hmac(new goog.crypt.sha1(), key, 64);
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* var digest = hmac.getHmac(bytes);
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*
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*/
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goog.provide('goog.crypt.Hmac');
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goog.require('goog.asserts');
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goog.require('goog.crypt.Hash');
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/**
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* @constructor
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* @param {!goog.crypt.Hash} hasher An object to serve as a hash function.
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* @param {Array.<number>} key The secret key to use to calculate the hmac.
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* Should be an array of not more than {@code blockSize} integers in
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{0, 255}.
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* @param {number=} opt_blockSize Optional. The block size {@code hasher} uses.
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* If not specified, 16.
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* @extends {goog.crypt.Hash}
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*/
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goog.crypt.Hmac = function(hasher, key, opt_blockSize) {
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goog.base(this);
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/**
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* The underlying hasher to calculate hash.
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*
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* @type {!goog.crypt.Hash}
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* @private
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*/
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this.hasher_ = hasher;
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/**
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* The block size.
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*
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* @type {number}
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* @private
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*/
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this.blockSize_ = opt_blockSize || 16;
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/**
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* The outer padding array of hmac
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*
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* @type {!Array.<number>}
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* @private
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*/
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this.keyO_ = new Array(this.blockSize_);
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/**
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* The inner padding array of hmac
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*
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* @type {!Array.<number>}
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* @private
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*/
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this.keyI_ = new Array(this.blockSize_);
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this.initialize_(key);
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};
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goog.inherits(goog.crypt.Hmac, goog.crypt.Hash);
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/**
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* Outer padding byte of HMAC algorith, per http://en.wikipedia.org/wiki/HMAC
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*
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* @type {number}
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* @private
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*/
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goog.crypt.Hmac.OPAD_ = 0x5c;
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/**
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* Inner padding byte of HMAC algorith, per http://en.wikipedia.org/wiki/HMAC
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*
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* @type {number}
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* @private
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*/
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goog.crypt.Hmac.IPAD_ = 0x36;
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/**
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* Initializes Hmac by precalculating the inner and outer paddings.
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*
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* @param {Array.<number>} key The secret key to use to calculate the hmac.
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* Should be an array of not more than {@code blockSize} integers in
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{0, 255}.
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* @private
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*/
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goog.crypt.Hmac.prototype.initialize_ = function(key) {
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if (key.length > this.blockSize_) {
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this.hasher_.update(key);
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key = this.hasher_.digest();
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}
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// Precalculate padded and xor'd keys.
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var keyByte;
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for (var i = 0; i < this.blockSize_; i++) {
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if (i < key.length) {
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keyByte = key[i];
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} else {
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keyByte = 0;
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}
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this.keyO_[i] = keyByte ^ goog.crypt.Hmac.OPAD_;
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this.keyI_[i] = keyByte ^ goog.crypt.Hmac.IPAD_;
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}
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// Be ready for an immediate update.
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this.hasher_.update(this.keyI_);
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};
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/** @override */
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goog.crypt.Hmac.prototype.reset = function() {
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this.hasher_.reset();
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this.hasher_.update(this.keyI_);
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};
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/** @override */
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goog.crypt.Hmac.prototype.update = function(bytes, opt_length) {
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this.hasher_.update(bytes, opt_length);
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};
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/** @override */
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goog.crypt.Hmac.prototype.digest = function() {
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var temp = this.hasher_.digest();
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this.hasher_.reset();
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this.hasher_.update(this.keyO_);
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this.hasher_.update(temp);
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return this.hasher_.digest();
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};
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/**
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* Calculates an HMAC for a given message.
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*
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* @param {Array.<number>} message An array of integers in {0, 255}.
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* @return {!Array.<number>} the digest of the given message.
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*/
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goog.crypt.Hmac.prototype.getHmac = function(message) {
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this.reset();
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this.update(message);
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return this.digest();
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};
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