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niandeng
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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package org.mangui.hls.utils {
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import flash.utils.getTimer;
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import flash.display.DisplayObject;
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import flash.utils.ByteArray;
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import flash.events.Event;
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/**
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* Contains Utility functions for AES-128 CBC Decryption
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*/
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public class AES {
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private var _key : FastAESKey;
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//private var _keyArray : ByteArray;
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private var iv0 : uint;
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private var iv1 : uint;
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private var iv2 : uint;
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private var iv3 : uint;
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/* callback function upon decrypt progress */
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private var _progress : Function;
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/* callback function upon decrypt complete */
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private var _complete : Function;
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/** Byte data to be decrypt **/
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private var _data : ByteArray;
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/** read position **/
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private var _readPosition : uint;
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/** write position **/
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private var _writePosition : uint;
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/** chunk size to avoid blocking **/
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private static const CHUNK_SIZE : uint = 2048;
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/** is bytearray full ? **/
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private var _dataComplete : Boolean;
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/** display object used for ENTER_FRAME listener */
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private var _displayObject : DisplayObject;
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public function AES(displayObject : DisplayObject, key : ByteArray, iv : ByteArray, notifyprogress : Function, notifycomplete : Function) {
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// _keyArray = key;
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_key = new FastAESKey(key);
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iv.position = 0;
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iv0 = iv.readUnsignedInt();
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iv1 = iv.readUnsignedInt();
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iv2 = iv.readUnsignedInt();
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iv3 = iv.readUnsignedInt();
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_data = new ByteArray();
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_dataComplete = false;
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_progress = notifyprogress;
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_complete = notifycomplete;
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_readPosition = 0;
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_writePosition = 0;
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_displayObject = displayObject;
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}
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public function append(data : ByteArray) : void {
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// CONFIG::LOGGING {
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// Log.info("notify append");
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// }
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_data.position = _writePosition;
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_data.writeBytes(data);
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if (_writePosition == 0) {
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_displayObject.addEventListener(Event.ENTER_FRAME, _decryptTimer);
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}
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_writePosition += data.length;
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}
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public function notifycomplete() : void {
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// CONFIG::LOGGING {
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// Log.info("notify complete");
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// }
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_dataComplete = true;
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}
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public function cancel() : void {
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_displayObject.removeEventListener(Event.ENTER_FRAME, _decryptTimer);
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}
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private function _decryptTimer(e : Event) : void {
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var start_time : int = getTimer();
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var decrypted : Boolean;
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do {
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decrypted = _decryptChunk();
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// dont spend more than 10ms in the decrypt timer to avoid blocking/freezing video
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// if frame rate is 60fps, we have 1000/60 = 16.6ms budget total per frame
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} while (decrypted && (getTimer() - start_time) < 10);
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}
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/** decrypt a small chunk of packets each time to avoid blocking **/
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private function _decryptChunk() : Boolean {
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_data.position = _readPosition;
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var decryptdata : ByteArray;
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if (_data.bytesAvailable) {
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if (_data.bytesAvailable <= CHUNK_SIZE) {
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if (_dataComplete) {
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// CONFIG::LOGGING {
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// Log.info("data complete, last chunk");
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// }
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_readPosition += _data.bytesAvailable;
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decryptdata = _decryptCBC(_data, _data.bytesAvailable);
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unpad(decryptdata);
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} else {
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// data not complete, and available data less than chunk size, return
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return false;
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}
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} else {
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_readPosition += CHUNK_SIZE;
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decryptdata = _decryptCBC(_data, CHUNK_SIZE);
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}
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_progress(decryptdata);
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return true;
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} else {
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if (_dataComplete) {
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CONFIG::LOGGING {
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Log.debug("AES:data+decrypt completed, callback");
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}
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// callback
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_complete();
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_displayObject.removeEventListener(Event.ENTER_FRAME, _decryptTimer);
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}
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return false;
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}
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}
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/* Cypher Block Chaining Decryption, refer to
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* http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher-block_chaining_
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* for algorithm description
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*/
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private function _decryptCBC(crypt : ByteArray, len : uint) : ByteArray {
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var src : Vector.<uint> = new Vector.<uint>(4);
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var dst : Vector.<uint> = new Vector.<uint>(4);
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var decrypt : ByteArray = new ByteArray();
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decrypt.length = len;
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for (var i : uint = 0; i < len / 16; i++) {
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// read src byte array
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src[0] = crypt.readUnsignedInt();
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src[1] = crypt.readUnsignedInt();
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src[2] = crypt.readUnsignedInt();
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src[3] = crypt.readUnsignedInt();
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// AES decrypt src vector into dst vector
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_key.decrypt128(src, dst);
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// CBC : write output = XOR(decrypted,IV)
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decrypt.writeUnsignedInt(dst[0] ^ iv0);
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decrypt.writeUnsignedInt(dst[1] ^ iv1);
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decrypt.writeUnsignedInt(dst[2] ^ iv2);
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decrypt.writeUnsignedInt(dst[3] ^ iv3);
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// CBC : next IV = (input)
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iv0 = src[0];
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iv1 = src[1];
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iv2 = src[2];
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iv3 = src[3];
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}
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decrypt.position = 0;
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return decrypt;
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}
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public function unpad(a : ByteArray) : void {
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var c : uint = a.length % 16;
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if (c != 0) throw new Error("PKCS#5::unpad: ByteArray.length isn't a multiple of the blockSize");
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c = a[a.length - 1];
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for (var i : uint = c; i > 0; i--) {
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var v : uint = a[a.length - 1];
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a.length--;
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if (c != v) throw new Error("PKCS#5:unpad: Invalid padding value. expected [" + c + "], found [" + v + "]");
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}
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}
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public function destroy() : void {
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_key.dispose();
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// _key = null;
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}
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}
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}
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