88 lines
1.8 KiB
JavaScript
88 lines
1.8 KiB
JavaScript
import {
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BlockCipherMode,
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} from './cipher-core.js';
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const incWord = (word) => {
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let _word = word;
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if (((word >> 24) & 0xff) === 0xff) { // overflow
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let b1 = (word >> 16) & 0xff;
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let b2 = (word >> 8) & 0xff;
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let b3 = word & 0xff;
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if (b1 === 0xff) { // overflow b1
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b1 = 0;
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if (b2 === 0xff) {
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b2 = 0;
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if (b3 === 0xff) {
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b3 = 0;
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} else {
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b3 += 1;
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}
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} else {
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b2 += 1;
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}
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} else {
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b1 += 1;
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}
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_word = 0;
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_word += (b1 << 16);
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_word += (b2 << 8);
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_word += b3;
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} else {
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_word += (0x01 << 24);
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}
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return _word;
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};
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const incCounter = (counter) => {
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const _counter = counter;
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_counter[0] = incWord(_counter[0]);
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if (_counter[0] === 0) {
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// encr_data in fileenc.c from Dr Brian Gladman's counts only with DWORD j < 8
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_counter[1] = incWord(_counter[1]);
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}
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return _counter;
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};
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/** @preserve
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* Counter block mode compatible with Dr Brian Gladman fileenc.c
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* derived from CryptoJS.mode.CTR
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* Jan Hruby jhruby.web@gmail.com
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*/
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export class CTRGladman extends BlockCipherMode {
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}
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CTRGladman.Encryptor = class extends CTRGladman {
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processBlock(words, offset) {
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const _words = words;
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// Shortcuts
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const cipher = this._cipher;
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const { blockSize } = cipher;
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const iv = this._iv;
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let counter = this._counter;
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// Generate keystream
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if (iv) {
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this._counter = iv.slice(0);
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counter = this._counter;
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// Remove IV for subsequent blocks
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this._iv = undefined;
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}
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incCounter(counter);
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const keystream = counter.slice(0);
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cipher.encryptBlock(keystream, 0);
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// Encrypt
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for (let i = 0; i < blockSize; i += 1) {
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_words[offset + i] ^= keystream[i];
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}
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}
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};
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CTRGladman.Decryptor = CTRGladman.Encryptor;
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