311 lines
7.9 KiB
JavaScript
311 lines
7.9 KiB
JavaScript
import 'buffer';
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import { transformStream } from './streams';
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const NONCE_LENGTH = 12;
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const TAG_LENGTH = 16;
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const KEY_LENGTH = 16;
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const MODE_ENCRYPT = 'encrypt';
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const MODE_DECRYPT = 'decrypt';
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export const ECE_RECORD_SIZE = 1024 * 64;
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const encoder = new TextEncoder();
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function generateSalt(len) {
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const randSalt = new Uint8Array(len);
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crypto.getRandomValues(randSalt);
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return randSalt.buffer;
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}
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class ECETransformer {
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constructor(mode, ikm, rs, salt) {
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this.mode = mode;
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this.prevChunk;
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this.seq = 0;
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this.firstchunk = true;
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this.rs = rs;
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this.ikm = ikm.buffer;
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this.salt = salt;
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}
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async generateKey() {
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const inputKey = await crypto.subtle.importKey(
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'raw',
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this.ikm,
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'HKDF',
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false,
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['deriveKey']
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);
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return crypto.subtle.deriveKey(
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{
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name: 'HKDF',
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salt: this.salt,
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info: encoder.encode('Content-Encoding: aes128gcm\0'),
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hash: 'SHA-256'
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},
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inputKey,
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{
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name: 'AES-GCM',
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length: 128
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},
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false,
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['encrypt', 'decrypt']
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);
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}
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async generateNonceBase() {
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const inputKey = await crypto.subtle.importKey(
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'raw',
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this.ikm,
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'HKDF',
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false,
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['deriveKey']
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);
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const base = await crypto.subtle.exportKey(
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'raw',
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await crypto.subtle.deriveKey(
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{
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name: 'HKDF',
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salt: this.salt,
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info: encoder.encode('Content-Encoding: nonce\0'),
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hash: 'SHA-256'
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},
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inputKey,
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{
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name: 'AES-GCM',
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length: 128
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},
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true,
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['encrypt', 'decrypt']
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)
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);
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return Buffer.from(base.slice(0, NONCE_LENGTH));
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}
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generateNonce(seq) {
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if (seq > 0xffffffff) {
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throw new Error('record sequence number exceeds limit');
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}
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const nonce = Buffer.from(this.nonceBase);
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const m = nonce.readUIntBE(nonce.length - 4, 4);
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const xor = (m ^ seq) >>> 0; //forces unsigned int xor
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nonce.writeUIntBE(xor, nonce.length - 4, 4);
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return nonce;
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}
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pad(data, isLast) {
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const len = data.length;
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if (len + TAG_LENGTH >= this.rs) {
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throw new Error('data too large for record size');
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}
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if (isLast) {
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const padding = Buffer.alloc(1);
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padding.writeUInt8(2, 0);
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return Buffer.concat([data, padding]);
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} else {
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const padding = Buffer.alloc(this.rs - len - TAG_LENGTH);
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padding.fill(0);
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padding.writeUInt8(1, 0);
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return Buffer.concat([data, padding]);
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}
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}
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unpad(data, isLast) {
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for (let i = data.length - 1; i >= 0; i--) {
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if (data[i]) {
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if (isLast) {
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if (data[i] !== 2) {
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throw new Error('delimiter of final record is not 2');
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}
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} else {
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if (data[i] !== 1) {
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throw new Error('delimiter of not final record is not 1');
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}
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}
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return data.slice(0, i);
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}
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}
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throw new Error('no delimiter found');
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}
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createHeader() {
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const nums = Buffer.alloc(5);
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nums.writeUIntBE(this.rs, 0, 4);
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nums.writeUIntBE(0, 4, 1);
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return Buffer.concat([Buffer.from(this.salt), nums]);
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}
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readHeader(buffer) {
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if (buffer.length < 21) {
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throw new Error('chunk too small for reading header');
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}
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const header = {};
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header.salt = buffer.buffer.slice(0, KEY_LENGTH);
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header.rs = buffer.readUIntBE(KEY_LENGTH, 4);
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const idlen = buffer.readUInt8(KEY_LENGTH + 4);
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header.length = idlen + KEY_LENGTH + 5;
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return header;
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}
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async encryptRecord(buffer, seq, isLast) {
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const nonce = this.generateNonce(seq);
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const encrypted = await crypto.subtle.encrypt(
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{ name: 'AES-GCM', iv: nonce },
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this.key,
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this.pad(buffer, isLast)
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);
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return Buffer.from(encrypted);
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}
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async decryptRecord(buffer, seq, isLast) {
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const nonce = this.generateNonce(seq);
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const data = await crypto.subtle.decrypt(
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{
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name: 'AES-GCM',
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iv: nonce,
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tagLength: 128
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},
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this.key,
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buffer
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);
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return this.unpad(Buffer.from(data), isLast);
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}
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async start(controller) {
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if (this.mode === MODE_ENCRYPT) {
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this.key = await this.generateKey();
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this.nonceBase = await this.generateNonceBase();
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controller.enqueue(this.createHeader());
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} else if (this.mode !== MODE_DECRYPT) {
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throw new Error('mode must be either encrypt or decrypt');
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}
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}
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async transformPrevChunk(isLast, controller) {
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if (this.mode === MODE_ENCRYPT) {
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controller.enqueue(
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await this.encryptRecord(this.prevChunk, this.seq, isLast)
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);
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this.seq++;
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} else {
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if (this.seq === 0) {
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//the first chunk during decryption contains only the header
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const header = this.readHeader(this.prevChunk);
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this.salt = header.salt;
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this.rs = header.rs;
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this.key = await this.generateKey();
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this.nonceBase = await this.generateNonceBase();
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} else {
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controller.enqueue(
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await this.decryptRecord(this.prevChunk, this.seq - 1, isLast)
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);
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}
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this.seq++;
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}
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}
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async transform(chunk, controller) {
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if (!this.firstchunk) {
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await this.transformPrevChunk(false, controller);
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}
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this.firstchunk = false;
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this.prevChunk = Buffer.from(chunk.buffer);
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}
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async flush(controller) {
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//console.log('ece stream ends')
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if (this.prevChunk) {
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await this.transformPrevChunk(true, controller);
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}
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}
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}
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class StreamSlicer {
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constructor(rs, mode) {
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this.mode = mode;
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this.rs = rs;
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this.chunkSize = mode === MODE_ENCRYPT ? rs - 17 : 21;
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this.partialChunk = new Uint8Array(this.chunkSize); //where partial chunks are saved
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this.offset = 0;
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}
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send(buf, controller) {
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controller.enqueue(buf);
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if (this.chunkSize === 21 && this.mode === MODE_DECRYPT) {
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this.chunkSize = this.rs;
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}
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this.partialChunk = new Uint8Array(this.chunkSize);
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this.offset = 0;
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}
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//reslice input into record sized chunks
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transform(chunk, controller) {
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//console.log('Received chunk with %d bytes.', chunk.byteLength)
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let i = 0;
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if (this.offset > 0) {
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const len = Math.min(chunk.byteLength, this.chunkSize - this.offset);
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this.partialChunk.set(chunk.slice(0, len), this.offset);
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this.offset += len;
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i += len;
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if (this.offset === this.chunkSize) {
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this.send(this.partialChunk, controller);
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}
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}
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while (i < chunk.byteLength) {
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const remainingBytes = chunk.byteLength - i;
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if (remainingBytes >= this.chunkSize) {
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const record = chunk.slice(i, i + this.chunkSize);
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i += this.chunkSize;
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this.send(record, controller);
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} else {
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const end = chunk.slice(i, i + remainingBytes);
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i += end.byteLength;
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this.partialChunk.set(end);
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this.offset = end.byteLength;
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}
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}
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}
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flush(controller) {
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if (this.offset > 0) {
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controller.enqueue(this.partialChunk.slice(0, this.offset));
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}
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}
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}
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/*
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input: a ReadableStream containing data to be transformed
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key: Uint8Array containing key of size KEY_LENGTH
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rs: int containing record size, optional
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salt: ArrayBuffer containing salt of KEY_LENGTH length, optional
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*/
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export function encryptStream(
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input,
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key,
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rs = ECE_RECORD_SIZE,
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salt = generateSalt(KEY_LENGTH)
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) {
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const mode = 'encrypt';
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const inputStream = transformStream(input, new StreamSlicer(rs, mode));
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return transformStream(inputStream, new ECETransformer(mode, key, rs, salt));
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}
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/*
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input: a ReadableStream containing data to be transformed
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key: Uint8Array containing key of size KEY_LENGTH
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rs: int containing record size, optional
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*/
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export function decryptStream(input, key, rs = ECE_RECORD_SIZE) {
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const mode = 'decrypt';
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const inputStream = transformStream(input, new StreamSlicer(rs, mode));
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return transformStream(inputStream, new ECETransformer(mode, key, rs));
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}
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