69 lines
1.3 KiB
JavaScript
69 lines
1.3 KiB
JavaScript
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'use strict';
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var createHash = require('create-hash/browser');
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var inherits = require('inherits')
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var Transform = require('stream').Transform
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var ZEROS = new Buffer(128)
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ZEROS.fill(0)
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function Hmac(alg, key) {
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Transform.call(this)
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alg = alg.toLowerCase()
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if (typeof key === 'string') {
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key = new Buffer(key)
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}
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var blocksize = (alg === 'sha512' || alg === 'sha384') ? 128 : 64
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this._alg = alg
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this._key = key
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if (key.length > blocksize) {
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key = createHash(alg).update(key).digest()
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} else if (key.length < blocksize) {
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key = Buffer.concat([key, ZEROS], blocksize)
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}
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var ipad = this._ipad = new Buffer(blocksize)
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var opad = this._opad = new Buffer(blocksize)
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for (var i = 0; i < blocksize; i++) {
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ipad[i] = key[i] ^ 0x36
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opad[i] = key[i] ^ 0x5C
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}
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this._hash = createHash(alg).update(ipad)
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}
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inherits(Hmac, Transform)
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Hmac.prototype.update = function (data, enc) {
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this._hash.update(data, enc)
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return this
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}
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Hmac.prototype._transform = function (data, _, next) {
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this._hash.update(data)
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next()
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}
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Hmac.prototype._flush = function (next) {
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this.push(this.digest())
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next()
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}
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Hmac.prototype.digest = function (enc) {
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var h = this._hash.digest()
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return createHash(this._alg).update(this._opad).update(h).digest(enc)
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}
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module.exports = function createHmac(alg, key) {
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return new Hmac(alg, key)
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}
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