From 4cb34844aaa7f715aabf2ee4e4e74dd20b818ee7 Mon Sep 17 00:00:00 2001
From: Danny Coates <dannycoates@gmail.com>
Date: Wed, 28 Jun 2017 11:30:14 -0700
Subject: [PATCH] use 128-bit GCM

---
 frontend/src/fileReceiver.js | 12 +++++-------
 frontend/src/fileSender.js   | 10 ++++------
 frontend/src/utils.js        | 17 ++++++-----------
 3 files changed, 15 insertions(+), 24 deletions(-)

diff --git a/frontend/src/fileReceiver.js b/frontend/src/fileReceiver.js
index 68b651a3..8bf44ab3 100644
--- a/frontend/src/fileReceiver.js
+++ b/frontend/src/fileReceiver.js
@@ -1,12 +1,12 @@
 const EventEmitter = require('events');
-const { strToIv, strToUintArr } = require('./utils');
+const { hexToArray } = require('./utils');
 
 const Raven = window.Raven;
 
 class FileReceiver extends EventEmitter {
   constructor() {
     super();
-    this.salt = strToIv(location.pathname.slice(10, -1));
+    this.salt = hexToArray(location.pathname.slice(10, -1));
   }
 
   download() {
@@ -55,7 +55,7 @@ class FileReceiver extends EventEmitter {
         {
           kty: 'oct',
           k: location.hash.slice(1),
-          alg: 'A256GCM',
+          alg: 'A128GCM',
           ext: true
         },
         {
@@ -66,15 +66,13 @@ class FileReceiver extends EventEmitter {
       )
     ]).then(([fdata, key]) => {
       const salt = this.salt;
-      console.log(strToUintArr(fdata.aad));
-      
+
       return Promise.all([
         window.crypto.subtle.decrypt(
           {
             name: 'AES-GCM',
             iv: salt,
-            tagLength: 128,
-            additionalData: strToUintArr(fdata.aad)
+            additionalData: hexToArray(fdata.aad)
           },
           key,
           fdata.data
diff --git a/frontend/src/fileSender.js b/frontend/src/fileSender.js
index e8f0402e..a4709d28 100644
--- a/frontend/src/fileSender.js
+++ b/frontend/src/fileSender.js
@@ -1,5 +1,5 @@
 const EventEmitter = require('events');
-const { ivToStr } = require('./utils');
+const { arrayToHex } = require('./utils');
 
 const Raven = window.Raven;
 
@@ -41,8 +41,7 @@ class FileSender extends EventEmitter {
       window.crypto.subtle.generateKey(
         {
           name: 'AES-GCM',
-          length: 256,
-          tagLength: 128
+          length: 128
         },
         true,
         ['encrypt', 'decrypt']
@@ -61,7 +60,6 @@ class FileSender extends EventEmitter {
             {
               name: 'AES-GCM',
               iv: this.iv,
-              tagLength: 128,
               additionalData: this.aad
             },
             secretKey,
@@ -73,13 +71,13 @@ class FileSender extends EventEmitter {
       .then(([encrypted, keydata]) => {
         return new Promise((resolve, reject) => {
           const file = this.file;
-          const fileId = ivToStr(this.iv);
+          const fileId = arrayToHex(this.iv);
           const dataView = new DataView(encrypted);
           const blob = new Blob([dataView], { type: file.type });
           const fd = new FormData();
           fd.append('fname', file.name);
           fd.append('data', blob, file.name);
-          fd.append('aad', this.aad);
+          fd.append('aad', arrayToHex(this.aad));
 
           const xhr = new XMLHttpRequest();
 
diff --git a/frontend/src/utils.js b/frontend/src/utils.js
index 9f8f6f9b..39f058ca 100644
--- a/frontend/src/utils.js
+++ b/frontend/src/utils.js
@@ -1,4 +1,4 @@
-function ivToStr(iv) {
+function arrayToHex(iv) {
   let hexStr = '';
   for (const i in iv) {
     if (iv[i] < 16) {
@@ -11,8 +11,8 @@ function ivToStr(iv) {
   return hexStr;
 }
 
-function strToIv(str) {
-  const iv = new Uint8Array(12);
+function hexToArray(str) {
+  const iv = new Uint8Array(str.length / 2);
   for (let i = 0; i < str.length; i += 2) {
     iv[i / 2] = parseInt(str.charAt(i) + str.charAt(i + 1), 16);
   }
@@ -33,13 +33,8 @@ function notify(str) {
   }
 }
 
-function strToUintArr(str) {
-  return new Uint8Array(str.split(",").map(x => parseInt(x)));
-}
-
 module.exports = {
-  ivToStr,
-  strToIv,
-  notify,
-  strToUintArr
+  arrayToHex,
+  hexToArray,
+  notify
 };