feat(security): implement index encryption (#122)

app/app.py

@@ -1,4 +1,4 @@
-from flask import Flask, render_template, request, redirect, url_for, jsonify, send_from_directory
+from flask import Flask, render_template, request, redirect, url_for, jsonify, send_from_directory, Response
 from flask_login import LoginManager
 from functools import wraps
 import yaml
@@ -172,6 +172,10 @@ def access_tinfoil_shop():
             shop["referrer"] = f"https://{request.verified_host}"
 
         shop["files"] = gen_shop_files(db)
+
+        if app_settings['shop']['encrypt']:
+            return Response(encrypt_shop(shop), mimetype='application/octet-stream')
+
         return jsonify(shop)
 
     if all(header in request.headers for header in TINFOIL_HEADERS):

app/constants.py

@@ -29,7 +29,7 @@
     "shop": {
         "motd": "Welcome to your own shop!",
         "public": False,
-        "encrypt": False,
+        "encrypt": True,
         "clientCertPub": "-----BEGIN PUBLIC KEY-----",
         "clientCertKey": "-----BEGIN PRIVATE KEY-----",
         "host": "",

app/shop.py

@@ -1,4 +1,22 @@
 from db import *
+from Crypto.PublicKey import RSA
+from Crypto.Cipher import PKCS1_OAEP
+from Crypto.Hash import SHA256
+from Crypto.Cipher import AES
+import zstandard as zstd
+import random
+import json
+
+# https://github.com/blawar/tinfoil/blob/master/docs/files/public.key 1160174fa2d7589831f74d149bc403711f3991e4
+TINFOIL_PUBLIC_KEY = '''-----BEGIN PUBLIC KEY-----
+MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAvPdrJigQ0rZAy+jla7hS
+jwen8gkF0gjtl+lZGY59KatNd9Kj2gfY7dTMM+5M2tU4Wr3nk8KWr5qKm3hzo/2C
+Gbc55im3tlRl6yuFxWQ+c/I2SM5L3xp6eiLUcumMsEo0B7ELmtnHTGCCNAIzTFzV
+4XcWGVbkZj83rTFxpLsa1oArTdcz5CG6qgyVe7KbPsft76DAEkV8KaWgnQiG0Dps
+INFy4vISmf6L1TgAryJ8l2K4y8QbymyLeMsABdlEI3yRHAm78PSezU57XtQpHW5I
+aupup8Es6bcDZQKkRsbOeR9T74tkj+k44QrjZo8xpX9tlJAKEEmwDlyAg0O5CLX3
+CQIDAQAB
+-----END PUBLIC KEY-----'''
 
 def gen_shop_files(db):
     shop_files = []
@@ -21,3 +39,26 @@ def gen_shop_files(db):
             'size': size
         })
     return shop_files
+
+def encrypt_shop(shop):
+    input = json.dumps(shop).encode('utf-8')
+    # random 128-bit AES key (16 bytes), used later for symmetric encryption (AES)
+    aesKey = random.randint(0,0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF).to_bytes(0x10, 'big')
+    # zstandard compression
+    flag = 0xFD
+    cctx = zstd.ZstdCompressor(level=22)
+    buf = cctx.compress(input)
+    sz = len(buf)
+
+    # Encrypt the AES key with RSA, PKCS1_OAEP padding scheme
+    pubKey = RSA.importKey(TINFOIL_PUBLIC_KEY)
+    cipher = PKCS1_OAEP.new(pubKey, hashAlgo = SHA256, label=b'')
+    # Now the AES key can only be decrypted with Tinfoil private key
+    sessionKey = cipher.encrypt(aesKey)
+
+    # Encrypting the Data with AES
+    cipher = AES.new(aesKey, AES.MODE_ECB)
+    buf = cipher.encrypt(buf + (b'\x00' * (0x10 - (sz % 0x10))))
+
+    binary_data = b'TINFOIL' + flag.to_bytes(1, byteorder='little') + sessionKey + sz.to_bytes(8, 'little') + buf
+    return binary_data

app/templates/settings.html

@@ -268,10 +268,10 @@ <h2 class="pb-3">Shop</h2>
                 </div>
                 <div class="mb-3 form-check">
                     <input type="checkbox" class="form-check-input" id="encryptShopCheck"
-                        aria-describedby="encryptShopCheckHelp" disabled="disabled">
+                        aria-describedby="encryptShopCheckHelp">
                     <label class="form-check-label" for="encryptShopCheck">Encrypt shop</label>
-                    <div id="encryptShopCheckHelp" class="form-text">Serve encrypted shop, so that only Tinfoil clients
-                        can access the content (coming soon).</div>
+                    <div id="encryptShopCheckHelp" class="form-text">Serve encrypted and compressed shop, so that only Tinfoil clients
+                        can access the content. <strong>Strongly suggested to enable it for security</strong>.</div>
                 </div>
 
                 <div class="mb-3">

requirements.txt

@@ -8,6 +8,6 @@ watchdog==4.0.2
 Werkzeug==3.0.3
 
 # NSTools
-zstandard
+zstandard==0.23.0
 enlighten
 pycryptodome