security: remove SHA-256 password fallback, CSPRNG for verification codes and keys

backend/controllers/key_controller.js

@@ -1,4 +1,5 @@
 const KeyLibrary = require("../models/KeyLibrary");
+const { randomBytes } = require("crypto");
 
 const TRANSMISSION_LIMITS = [3, 6, 9, 12, 365]; // Keys retire after these limits
 
@@ -87,5 +88,7 @@ exports.retryKeyValidation = async (req, res) => {
 
 // Function to generate McEliese keys
 function generateMcElieseKey() {
-    return Math.random().toString(36).substring(2, 15);
+    // 32 bytes of CSPRNG output; Math.random() is predictable and yielded
+    // only ~67 bits drawn from a non-cryptographic generator.
+    return randomBytes(32).toString("base64url");
 }

backend/controllers/user_controller.js

@@ -1,14 +1,17 @@
 const bcrypt = require("../utils/bcrypt");
 const jwt = require("../utils/jwt");
-const { randomUUID } = require("crypto");
+const { randomUUID, randomInt } = require("crypto");
 const docClient = require("../lib/dynamodbClient");
 const { USER_TABLE_NAME, createUserItem } = require("../models/user");
 
 exports.registerUser = async (req, res) => {
     try {
         const { name, email, location, role, password, phone } = req.body;
         const hashedPassword = await bcrypt.hash(password, 10);
-        const verificationCode = Math.floor(100000 + Math.random() * 900000).toString();
+        // crypto.randomInt: Math.random() is predictable, and a guessable
+        // verification code lets an attacker verify an account they registered
+        // with someone else's email/phone.
+        const verificationCode = randomInt(100000, 1000000).toString();
 
         const userItem = createUserItem({
             id: randomUUID(),

backend/utils/bcrypt.js

@@ -5,16 +5,14 @@ try {
   try {
     bcrypt = require('bcrypt');
   } catch {
-    const crypto = require('crypto');
-    bcrypt = {
-      async hash(password, _saltRounds) {
-        return crypto.createHash('sha256').update(password).digest('hex');
-      },
-      async compare(password, hashed) {
-        const digest = crypto.createHash('sha256').update(password).digest('hex');
-        return digest === hashed;
-      }
-    };
+    // No silent fallback: the previous unsalted single-round SHA-256 shim
+    // made every stored password crackable at billions of guesses/second.
+    // bcryptjs is a declared dependency, so this throw only fires on a
+    // broken install — which must fail loudly, not degrade silently.
+    throw new Error(
+      "No bcrypt implementation available: install 'bcryptjs' (declared in package.json). " +
+      'Refusing to fall back to a fast unsalted hash for passwords.'
+    );
   }
 }
 module.exports = bcrypt;