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// Copyright 2011 The Closure Library Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS-IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
/**
* @fileoverview Implementation of HMAC in JavaScript.
*
* Usage:
* var hmac = new goog.crypt.Hmac(new goog.crypt.sha1(), key, 64);
* var digest = hmac.getHmac(bytes);
*
* @author benyu@google.com (Jige Yu) - port to closure
*/
goog.provide('goog.crypt.Hmac');
goog.require('goog.crypt.Hash');
/**
* @constructor
* @param {!goog.crypt.Hash} hasher An object to serve as a hash function.
* @param {Array<number>} key The secret key to use to calculate the hmac.
* Should be an array of not more than {@code blockSize} integers in
{0, 255}.
* @param {number=} opt_blockSize Optional. The block size {@code hasher} uses.
* If not specified, uses the block size from the hasher, or 16 if it is
* not specified.
* @extends {goog.crypt.Hash}
* @final
* @struct
*/
goog.crypt.Hmac = function(hasher, key, opt_blockSize) {
goog.crypt.Hmac.base(this, 'constructor');
/**
* The underlying hasher to calculate hash.
*
* @type {!goog.crypt.Hash}
* @private
*/
this.hasher_ = hasher;
this.blockSize = opt_blockSize || hasher.blockSize || 16;
/**
* The outer padding array of hmac
*
* @type {!Array<number>}
* @private
*/
this.keyO_ = new Array(this.blockSize);
/**
* The inner padding array of hmac
*
* @type {!Array<number>}
* @private
*/
this.keyI_ = new Array(this.blockSize);
this.initialize_(key);
};
goog.inherits(goog.crypt.Hmac, goog.crypt.Hash);
/**
* Outer padding byte of HMAC algorith, per http://en.wikipedia.org/wiki/HMAC
*
* @type {number}
* @private
*/
goog.crypt.Hmac.OPAD_ = 0x5c;
/**
* Inner padding byte of HMAC algorith, per http://en.wikipedia.org/wiki/HMAC
*
* @type {number}
* @private
*/
goog.crypt.Hmac.IPAD_ = 0x36;
/**
* Initializes Hmac by precalculating the inner and outer paddings.
*
* @param {Array<number>} key The secret key to use to calculate the hmac.
* Should be an array of not more than {@code blockSize} integers in
{0, 255}.
* @private
*/
goog.crypt.Hmac.prototype.initialize_ = function(key) {
if (key.length > this.blockSize) {
this.hasher_.update(key);
key = this.hasher_.digest();
this.hasher_.reset();
}
// Precalculate padded and xor'd keys.
var keyByte;
for (var i = 0; i < this.blockSize; i++) {
if (i < key.length) {
keyByte = key[i];
} else {
keyByte = 0;
}
this.keyO_[i] = keyByte ^ goog.crypt.Hmac.OPAD_;
this.keyI_[i] = keyByte ^ goog.crypt.Hmac.IPAD_;
}
// Be ready for an immediate update.
this.hasher_.update(this.keyI_);
};
/** @override */
goog.crypt.Hmac.prototype.reset = function() {
this.hasher_.reset();
this.hasher_.update(this.keyI_);
};
/** @override */
goog.crypt.Hmac.prototype.update = function(bytes, opt_length) {
this.hasher_.update(bytes, opt_length);
};
/** @override */
goog.crypt.Hmac.prototype.digest = function() {
var temp = this.hasher_.digest();
this.hasher_.reset();
this.hasher_.update(this.keyO_);
this.hasher_.update(temp);
return this.hasher_.digest();
};
/**
* Calculates an HMAC for a given message.
*
* @param {Array<number>|Uint8Array|string} message Data to Hmac.
* @return {!Array<number>} the digest of the given message.
*/
goog.crypt.Hmac.prototype.getHmac = function(message) {
this.reset();
this.update(message);
return this.digest();
};
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