126 lines
3.5 KiB
JavaScript
126 lines
3.5 KiB
JavaScript
/* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is Google Safe Browsing.
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*
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* The Initial Developer of the Original Code is Google Inc.
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* Portions created by the Initial Developer are Copyright (C) 2006
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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* Marius Schilder <mschilder@google.com> (original author)
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*
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* Alternatively, the contents of this file may be used under the terms of
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* either the GNU General Public License Version 2 or later (the "GPL"), or
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* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
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* of those above. If you wish to allow use of your version of this file only
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* under the terms of either the GPL or the LGPL, and not to allow others to
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* use your version of this file under the terms of the MPL, indicate your
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the MPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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/**
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* ARC4 streamcipher implementation
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* @constructor
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*/
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function ARC4() {
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this._S = new Array(256);
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this._i = 0;
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this._j = 0;
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}
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/**
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* Initialize the cipher for use with new key.
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* @param {byte[]} key is byte array containing key
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* @param {int} opt_length indicates # of bytes to take from key
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*/
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ARC4.prototype.setKey = function(key, opt_length) {
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if (!isArray(key)) {
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throw new Error("Key parameter must be a byte array");
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}
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if (!opt_length) {
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opt_length = key.length;
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}
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var S = this._S;
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for (var i = 0; i < 256; ++i) {
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S[i] = i;
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}
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var j = 0;
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for (var i = 0; i < 256; ++i) {
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j = (j + S[i] + key[i % opt_length]) & 255;
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var tmp = S[i];
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S[i] = S[j];
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S[j] = tmp;
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}
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this._i = 0;
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this._j = 0;
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}
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/**
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* Discard n bytes of the keystream.
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* These days 1536 is considered a decent amount to drop to get
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* the key state warmed-up enough for secure usage.
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* This is not done in the constructor to preserve efficiency for
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* use cases that do not need this.
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* @param {int} n is # of bytes to disregard from stream
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*/
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ARC4.prototype.discard = function(n) {
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var devnul = new Array(n);
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this.crypt(devnul);
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}
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/**
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* En- or decrypt (same operation for streamciphers like ARC4)
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* @param {byte[]} data gets xor-ed in place
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* @param {int} opt_length indicated # of bytes to crypt
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*/
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ARC4.prototype.crypt = function(data, opt_length) {
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if (!opt_length) {
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opt_length = data.length;
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}
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if (!isArray(data)) {
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throw new Error("Data parameter must be a byte array");
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}
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var i = this._i;
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var j = this._j;
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var S = this._S;
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for (var n = 0; n < opt_length; ++n) {
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i = (i + 1) & 255;
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j = (j + S[i]) & 255;
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var tmp = S[i];
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S[i] = S[j];
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S[j] = tmp;
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data[n] ^= S[(S[i] + S[j]) & 255];
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}
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this._i = i;
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this._j = j;
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}
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