fix(security): don't reuse IV for cryptography

Author: Corban Villa

config.json.example

@@ -75,7 +75,6 @@
   "S3_ACCESS_KEY_ID": "accessKeyId",
   "S3_BUCKET": "bucket",
   "S3_SECRET_ACCESS_KEY": "secretAccessKey",
-  "SESSION_SECRET_IV": "12345678912345678912345678912345",
   "SESSION_SECRET_KEY": "1234567891234567891234567891234567891234567891234567891234567891",
   "SESSION_SECRET": "YOUR SECRET HERE",
   "SITE_HTTP_AUTH_ENABLED": "false",

website/server/libs/encryption.js

@@ -1,26 +1,46 @@
 import {
   createCipheriv,
   createDecipheriv,
+  randomBytes,
 } from 'crypto';
 import nconf from 'nconf';
 
-const algorithm = 'aes-256-ctr';
+const ALGORITHM = 'aes-256-gcm';
+const IV_LENGTH_BYTES = 12; // 96-bit nonce per NIST guidance for GCM
+const AUTH_TAG_LENGTH_BYTES = 16; // 128-bit authentication tag
 const SESSION_SECRET_KEY = nconf.get('SESSION_SECRET_KEY');
-const SESSION_SECRET_IV = nconf.get('SESSION_SECRET_IV');
 
 const key = Buffer.from(SESSION_SECRET_KEY, 'hex');
-const iv = Buffer.from(SESSION_SECRET_IV, 'hex');
 
+/**
+ * Encrypt a UTF-8 string using AES-256-GCM and return iv|ciphertext|tag as hex.
+ * A fresh nonce is generated for every message to avoid keystream reuse, and
+ * the auth tag ensures forged payloads are rejected at the trust boundary.
+ */
 export function encrypt (text) {
-  const cipher = createCipheriv(algorithm, key, iv);
-  let crypted = cipher.update(text, 'utf8', 'hex');
-  crypted += cipher.final('hex');
-  return crypted;
+  const iv = randomBytes(IV_LENGTH_BYTES);
+  const cipher = createCipheriv(ALGORITHM, key, iv);
+  const ciphertext = Buffer.concat([cipher.update(text, 'utf8'), cipher.final()]);
+  const authTag = cipher.getAuthTag();
+  return Buffer.concat([iv, ciphertext, authTag]).toString('hex');
 }
 
+/**
+ * Decrypt an AES-256-GCM payload previously produced by encrypt().
+ * The layout is iv (12B) || ciphertext || authTag (16B), all hex encoded.
+ */
 export function decrypt (text) {
-  const decipher = createDecipheriv(algorithm, key, iv);
-  let dec = decipher.update(text, 'hex', 'utf8');
-  dec += decipher.final('utf8');
-  return dec;
+  const payload = Buffer.from(text, 'hex');
+  if (payload.length <= IV_LENGTH_BYTES + AUTH_TAG_LENGTH_BYTES) {
+    throw new Error('Encrypted payload is malformed');
+  }
+
+  const iv = payload.subarray(0, IV_LENGTH_BYTES);
+  const authTag = payload.subarray(payload.length - AUTH_TAG_LENGTH_BYTES);
+  const ciphertext = payload.subarray(IV_LENGTH_BYTES, payload.length - AUTH_TAG_LENGTH_BYTES);
+
+  const decipher = createDecipheriv(ALGORITHM, key, iv);
+  decipher.setAuthTag(authTag);
+  const decrypted = Buffer.concat([decipher.update(ciphertext), decipher.final()]);
+  return decrypted.toString('utf8');
 }