fox-send/app/ece.js

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