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18ec2e0b by David LaPalomento
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Merge pull request #540 from 'BrandonOCasey-split-decrypter-files' into development 

Split decrypter.js into smaller files.
2 parents 97d703e4 d2d07241
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Showing 4 changed files with 207 additions and 175 deletions
/*
* aes.js
*
* This file contains an adaptation of the AES decryption algorithm
* from the Standford Javascript Cryptography Library. That work is
......@@ -35,22 +36,6 @@
* are those of the authors and should not be interpreted as representing
* official policies, either expressed or implied, of the authors.
*/
import Stream from './stream';
import {unpad} from 'pkcs7';
/**
* Convert network-order (big-endian) bytes into their little-endian
* representation.
*/
const ntoh = function(word) {
return (word << 24) |
((word & 0xff00) << 8) |
((word & 0xff0000) >> 8) |
(word >>> 24);
};
let aesTables;
/**
* Schedule out an AES key for both encryption and decryption. This
......@@ -59,7 +44,7 @@ let aesTables;
* @constructor
* @param key {Array} The key as an array of 4, 6 or 8 words.
*/
class AES {
export default class AES {
constructor(key) {
/**
* The expanded S-box and inverse S-box tables. These will be computed
......@@ -127,7 +112,6 @@ class AES {
}
}
/**
* Expand the S-box tables.
*
......@@ -255,161 +239,4 @@ class AES {
a2 = a; a = b; b = c; c = d; d = a2;
}
}
}
/* eslint-disable max-len */
/**
* Decrypt bytes using AES-128 with CBC and PKCS#7 padding.
* @param encrypted {Uint8Array} the encrypted bytes
* @param key {Uint32Array} the bytes of the decryption key
* @param initVector {Uint32Array} the initialization vector (IV) to
* use for the first round of CBC.
* @return {Uint8Array} the decrypted bytes
*
* @see http://en.wikipedia.org/wiki/Advanced_Encryption_Standard
* @see http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher_Block_Chaining_.28CBC.29
* @see https://tools.ietf.org/html/rfc2315
*/
/* eslint-enable max-len */
export const decrypt = function(encrypted, key, initVector) {
// word-level access to the encrypted bytes
let encrypted32 = new Int32Array(encrypted.buffer,
encrypted.byteOffset,
encrypted.byteLength >> 2);
let decipher = new AES(Array.prototype.slice.call(key));
// byte and word-level access for the decrypted output
let decrypted = new Uint8Array(encrypted.byteLength);
let decrypted32 = new Int32Array(decrypted.buffer);
// temporary variables for working with the IV, encrypted, and
// decrypted data
let init0;
let init1;
let init2;
let init3;
let encrypted0;
let encrypted1;
let encrypted2;
let encrypted3;
// iteration variable
let wordIx;
// pull out the words of the IV to ensure we don't modify the
// passed-in reference and easier access
init0 = initVector[0];
init1 = initVector[1];
init2 = initVector[2];
init3 = initVector[3];
// decrypt four word sequences, applying cipher-block chaining (CBC)
// to each decrypted block
for (wordIx = 0; wordIx < encrypted32.length; wordIx += 4) {
// convert big-endian (network order) words into little-endian
// (javascript order)
encrypted0 = ntoh(encrypted32[wordIx]);
encrypted1 = ntoh(encrypted32[wordIx + 1]);
encrypted2 = ntoh(encrypted32[wordIx + 2]);
encrypted3 = ntoh(encrypted32[wordIx + 3]);
// decrypt the block
decipher.decrypt(encrypted0,
encrypted1,
encrypted2,
encrypted3,
decrypted32,
wordIx);
// XOR with the IV, and restore network byte-order to obtain the
// plaintext
decrypted32[wordIx] = ntoh(decrypted32[wordIx] ^ init0);
decrypted32[wordIx + 1] = ntoh(decrypted32[wordIx + 1] ^ init1);
decrypted32[wordIx + 2] = ntoh(decrypted32[wordIx + 2] ^ init2);
decrypted32[wordIx + 3] = ntoh(decrypted32[wordIx + 3] ^ init3);
// setup the IV for the next round
init0 = encrypted0;
init1 = encrypted1;
init2 = encrypted2;
init3 = encrypted3;
}
return decrypted;
};
export class AsyncStream extends Stream {
constructor() {
super(Stream);
this.jobs = [];
this.delay = 1;
this.timeout_ = null;
}
processJob_() {
this.jobs.shift()();
if (this.jobs.length) {
this.timeout_ = setTimeout(this.processJob_.bind(this),
this.delay);
} else {
this.timeout_ = null;
}
}
push(job) {
this.jobs.push(job);
if (!this.timeout_) {
this.timeout_ = setTimeout(this.processJob_.bind(this),
this.delay);
}
}
}
export class Decrypter {
constructor(encrypted, key, initVector, done) {
let step = Decrypter.STEP;
let encrypted32 = new Int32Array(encrypted.buffer);
let decrypted = new Uint8Array(encrypted.byteLength);
let i = 0;
this.asyncStream_ = new AsyncStream();
// split up the encryption job and do the individual chunks asynchronously
this.asyncStream_.push(this.decryptChunk_(encrypted32.subarray(i, i + step),
key,
initVector,
decrypted));
for (i = step; i < encrypted32.length; i += step) {
initVector = new Uint32Array([ntoh(encrypted32[i - 4]),
ntoh(encrypted32[i - 3]),
ntoh(encrypted32[i - 2]),
ntoh(encrypted32[i - 1])]);
this.asyncStream_.push(this.decryptChunk_(encrypted32.subarray(i, i + step),
key,
initVector,
decrypted));
}
// invoke the done() callback when everything is finished
this.asyncStream_.push(function() {
// remove pkcs#7 padding from the decrypted bytes
done(null, unpad(decrypted));
});
}
decryptChunk_(encrypted, key, initVector, decrypted) {
return function() {
let bytes = decrypt(encrypted, key, initVector);
decrypted.set(bytes, encrypted.byteOffset);
};
}
}
// the maximum number of bytes to process at one time
// 4 * 8000;
Decrypter.STEP = 32000;
export default {
decrypt,
Decrypter,
AsyncStream
};
......
import Stream from '../stream';
/**
* A wrapper around the Stream class to use setTiemout
* and run stream "jobs" Asynchronously
*/
export default class AsyncStream extends Stream {
constructor() {
super(Stream);
this.jobs = [];
this.delay = 1;
this.timeout_ = null;
}
processJob_() {
this.jobs.shift()();
if (this.jobs.length) {
this.timeout_ = setTimeout(this.processJob_.bind(this),
this.delay);
} else {
this.timeout_ = null;
}
}
push(job) {
this.jobs.push(job);
if (!this.timeout_) {
this.timeout_ = setTimeout(this.processJob_.bind(this),
this.delay);
}
}
}
/*
* decrypter.js
*
* An asynchronous implementation of AES-128 CBC decryption with
* PKCS#7 padding.
*/
import AES from './aes';
import AsyncStream from './async-stream';
import {unpad} from 'pkcs7';
/**
* Convert network-order (big-endian) bytes into their little-endian
* representation.
*/
const ntoh = function(word) {
return (word << 24) |
((word & 0xff00) << 8) |
((word & 0xff0000) >> 8) |
(word >>> 24);
};
/* eslint-disable max-len */
/**
* Decrypt bytes using AES-128 with CBC and PKCS#7 padding.
* @param encrypted {Uint8Array} the encrypted bytes
* @param key {Uint32Array} the bytes of the decryption key
* @param initVector {Uint32Array} the initialization vector (IV) to
* use for the first round of CBC.
* @return {Uint8Array} the decrypted bytes
*
* @see http://en.wikipedia.org/wiki/Advanced_Encryption_Standard
* @see http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher_Block_Chaining_.28CBC.29
* @see https://tools.ietf.org/html/rfc2315
*/
/* eslint-enable max-len */
export const decrypt = function(encrypted, key, initVector) {
// word-level access to the encrypted bytes
let encrypted32 = new Int32Array(encrypted.buffer,
encrypted.byteOffset,
encrypted.byteLength >> 2);
let decipher = new AES(Array.prototype.slice.call(key));
// byte and word-level access for the decrypted output
let decrypted = new Uint8Array(encrypted.byteLength);
let decrypted32 = new Int32Array(decrypted.buffer);
// temporary variables for working with the IV, encrypted, and
// decrypted data
let init0;
let init1;
let init2;
let init3;
let encrypted0;
let encrypted1;
let encrypted2;
let encrypted3;
// iteration variable
let wordIx;
// pull out the words of the IV to ensure we don't modify the
// passed-in reference and easier access
init0 = initVector[0];
init1 = initVector[1];
init2 = initVector[2];
init3 = initVector[3];
// decrypt four word sequences, applying cipher-block chaining (CBC)
// to each decrypted block
for (wordIx = 0; wordIx < encrypted32.length; wordIx += 4) {
// convert big-endian (network order) words into little-endian
// (javascript order)
encrypted0 = ntoh(encrypted32[wordIx]);
encrypted1 = ntoh(encrypted32[wordIx + 1]);
encrypted2 = ntoh(encrypted32[wordIx + 2]);
encrypted3 = ntoh(encrypted32[wordIx + 3]);
// decrypt the block
decipher.decrypt(encrypted0,
encrypted1,
encrypted2,
encrypted3,
decrypted32,
wordIx);
// XOR with the IV, and restore network byte-order to obtain the
// plaintext
decrypted32[wordIx] = ntoh(decrypted32[wordIx] ^ init0);
decrypted32[wordIx + 1] = ntoh(decrypted32[wordIx + 1] ^ init1);
decrypted32[wordIx + 2] = ntoh(decrypted32[wordIx + 2] ^ init2);
decrypted32[wordIx + 3] = ntoh(decrypted32[wordIx + 3] ^ init3);
// setup the IV for the next round
init0 = encrypted0;
init1 = encrypted1;
init2 = encrypted2;
init3 = encrypted3;
}
return decrypted;
};
/**
* The `Decrypter` class that manages decryption of AES
* data through `AsyncStream` objects and the `decrypt`
* function
*/
export class Decrypter {
constructor(encrypted, key, initVector, done) {
let step = Decrypter.STEP;
let encrypted32 = new Int32Array(encrypted.buffer);
let decrypted = new Uint8Array(encrypted.byteLength);
let i = 0;
this.asyncStream_ = new AsyncStream();
// split up the encryption job and do the individual chunks asynchronously
this.asyncStream_.push(this.decryptChunk_(encrypted32.subarray(i, i + step),
key,
initVector,
decrypted));
for (i = step; i < encrypted32.length; i += step) {
initVector = new Uint32Array([ntoh(encrypted32[i - 4]),
ntoh(encrypted32[i - 3]),
ntoh(encrypted32[i - 2]),
ntoh(encrypted32[i - 1])]);
this.asyncStream_.push(this.decryptChunk_(encrypted32.subarray(i, i + step),
key,
initVector,
decrypted));
}
// invoke the done() callback when everything is finished
this.asyncStream_.push(function() {
// remove pkcs#7 padding from the decrypted bytes
done(null, unpad(decrypted));
});
}
decryptChunk_(encrypted, key, initVector, decrypted) {
return function() {
let bytes = decrypt(encrypted, key, initVector);
decrypted.set(bytes, encrypted.byteOffset);
};
}
}
// the maximum number of bytes to process at one time
// 4 * 8000;
Decrypter.STEP = 32000;
export default {
Decrypter,
decrypt
};
/*
* index.js
*
* Index module to easily import the primary components of AES-128
* decryption. Like this:
*
* ```js
* import {Decrypter, decrypt, AsyncStream} from './src/decrypter';
* ```
*/
import {decrypt, Decrypter} from './decrypter';
import AsyncStream from './async-stream';
export default {
decrypt,
Decrypter,
AsyncStream
};